DOT/FAA/AR-05/16 

Office of Aviation Research 

Washington, D.C. 20591

Contaminated Billet Study 

September 2005 

Final Report 

This document is available to the U.S. public 

through the National Technical Information 

Service (NTIS), Springfield, VA 22161. 

U.S. Department of Transportation 

Federal Aviation Administration
NOTICE 

This document is disseminated under the sponsorship of the U.S. 

Department of Transportation in the interest of information exchange. The 

United States Government assumes no liability for the contents or use 

thereof. The United States Government does not endorse products or 

manufacturers. Trade or manufacturers names appear herein solely 

because they are considered essential to the objective of this report. This 

document does not constitute FAA certification policy. Consult your local 

FAA aircraft certification office as to its use. 

This report is available at the Federal Aviation Administration William J. 

Hughes Technical Center’s Full-Text Technical Reports page: 

actlibrary.tc.faa.gov in Adobe Acrobat portable document format (PDF). 
 Technical Report Documentation Page

1. Report No.

DOT/FAA/AR-05/16

2. Government Accession No. 3. Recipient's Catalog No.

 4. Title and Subtitle 

CONTAMINATED BILLET STUDY 

5. Report Date 

September 2005

6. Performing Organization Code

7. Author(s)

Lisa Brasche1, Thomas Chiou1, Bruce Thompson1, Kevin Smith2, Bill Meeker1, 

Frank Margetan1

, Paul Panetta1, Rick Chenail2, Fredrick Galli2, Jeff Umbach2, Dave 

Raulerson2

, Andrei Degtyar2, Jon Bartos3, Dave Copley3, Bob McElligott3, Pat 

Howard3

,

,

 and Manohar Bashyam3

8. Performing Organization Report No. 

 

9. Performing Organization Name and Address

Iowa State University1 Pratt & Whitney2

Center for Nondestructive Evaluation East Hartford, CT 

Ames, IA 50011 

10. Work Unit No. (TRAIS)

General Electric Aircraft Engines3

Cincinnati, OH

11. Contract or Grant No.

DTFA0398FIA029

12. Sponsoring Agency Name and Address

U.S. Department of Transportation 

Federal Aviation Administration

13. Type of Report and Period Covered

Final Report

Office of Aviation Research 

Washington, DC 20591

14. Sponsoring Agency Code

ANE-110

15. Supplementary Notes

The FAA William J. Hughes Technical Center Technical Monitor was Cu Nguyen. 

16. Abstract

During the Engine Titanium Consortium (ETC) Phase I program, the existence of a contaminated heat of titanium billet was 

made known to ETC and the Federal Aviation Administration. During processing of the billet, for a nonaerospace customer, a 

power outage led to a vacuum leak and resulted in numerous natural hard alpha defects. Because of the unique opportunity 

offered by the over 60 natural defects, an assessment was made that determined the defects were typical of those found in rotor

grade material. The material was purchased for use in nondestructive evaluation and lifing studies. The 12 billets were inspected 

using multizone and conventional inspection with a subset of the heat inspected using a phased array method. Upon analysis of 

the inspection data, 10 of the 64 indications were selected for detailed metallographic characterization. The ten defects were

serially sectioned at 5-mil increments, and the metallographic data was used to construct solid models for use in probability of 

detection studies. Several billets were also used in reproducibility and noise studies. Results of the inspection, defect 

characterization, and solid model generation are provided in this report along with use of the data in preliminary probability of 

detection calculations. 

17. Key Words 

Titanium billet, Hard alpha, Ultrasonic inspection, Probability 

of detection

18. Distribution Statement 

This document is available to the public through the National 

Technical Information Service (NTIS), Springfield, Virginia 

22161.

19. Security Classif. (of this report)

 Unclassified 

20. Security Classif. (of this page)

 Unclassified

21. No. of Pages

 237

22. Price

Form DOT F1700.7 (8-72) Reproduction of completed page authorized 
TABLE OF CONTENTS 

Page 

EXECUTIVE SUMMARY xi 

1. INTRODUCTION 1 

1.1 Purpose 1 

1.2 Background 1 

1.3 Program Objectives 3 

1.4 Related Activities and Documents 4 

2. APPROACH 4 

2.1 Initial Assessment of Heat 5 

2.2 Inspection Summary 11 

2.3 Description of Multizone Inspection 12 

2.4 Defect Characterization 15 

3. DISCUSSION OF RESULTS 23 

3.1 Inspection of the Contaminated Heat 23 

3.2 Phased Array Inspection of the CBS Billets 31 

3.3 Defect Characterization 36 

3.4 Generation of Geometrical Data for Use in PoD Calculations 40 

3.4.1 Geometrical Modeling 42 

3.4.2 Ultrasonic Modeling 47 

3.4.3 Error Analyses 49 

3.5 Utilization of Data for PoD Analysis 53 

3.6 Noise Analysis Studies 53 

3.7 Reproducibility Studies Using the CBS Billets 63 

3.7.1 Reproducibility Studies—Rolls-Royce 63 

3.7.2 Reproducibility Studies—ETC 67 

3.8 Misses Assessment 77 

3.9 Disposition of CBS Materials 82 

4. CONCLUSIONS 90 

5. REFERENCES 91 

iii
APPENDICES 

A—Literature Survey Completed by AlliedSignal in Phase I—Engine Titanium 

Consortium Program 

 B—Defect Characterization Protocol

 C—Inspection Results for Contaminated Billet 

D—Ultrasonic C-Scan Results for Indications Selected for Use in Probability of 

Detection Studies 

 E—Defect Characterization Data

 F—Reconstruction of Hard Alpha Defects Using Metallographic Sectioning Data

 G—Ultrasonic Modeling of Hard Alpha Defects 

iv
LIST OF FIGURES 

Figure Page 

1 Manufacturing Cycle for Critical Rotating Components 2 

2 Comparison of Typical Conversion Process Used to Produce Rotor-Grade Billets 

and the Conversion Process Used to Produce the CBS Billets 6 

3 Photomacrograph Documents Removal of Indication From Billet Sample 6 

4 Cylindrical Slug Taken From Billet B3W1 Was Cross-Sectioned Approximately 

0.3′′ Below the Plane of the Photomacrograph Shown in Figure 3 7 

5 Electron Microprobe Backscattered Electron Image of Defect Taken From Billet 

B3W1 9 

6 Microprobe Results in Medium Nitrogen 9 

7 Electron Microprobe Shows Areas of Highest Nitrogen Content 10 

8 Location of Billets Within the Ignot, Which Came From the Bottom Half of 

the Ingot 11 

9 Spherically Focused Transducer, Offset 1/6 of Billet Radius to Produce 45o 

Longitudinal Wave 12 

10 Multizone Concept That Uses Bicylindrical Transducers Designed to Focus 

Within 1′′ Zones From Billet Surface to 1/2′′ Beyond Center 12 

11 Ultrasonic and Metallographic Analysis Steps Used to Characterize the Defects 15 

12 Orientation of Sectioning Plane With Respect to Inspection Direction 16 

13 Section Planes for Practice Defect 17 

14 Microprobe Measurement Points for Practice Defect 18 

15 Results for Nitrogen Scan Perpendicular (Transverse 1) to the Long Axis of the 

Defect With Zero Located at the Defect Core 20 

16 Results for Nitrogen Scan Parallel to the Long Axis of the Defect With Zero 

Located at the End of the Defect Core 21 

17 (a) Results for Oxygen Scan Perpendicular to the Long Axis (Transverse 1) of the 

Defect With Zero Located at the Defect Core and (b) Results for Oxygen Scan 

Parallel to the Long Axis of the Defect With Zero Located at the End of the 

Defect Core 22 

v
18 Results for Ammonium Bifluoride and Kroll’s Etchants 23 

19 Venn Diagram Showing the Number of Indications Detected per Inspection 

Method 24 

20 Example of Inspection Results for Billet B1AW1 26 

21 Example of C-Scan Used in Selection of Defects for Further Characterization 27 

22 Distribution of Amplitude Expressed as %FSH and SNR Results 29 

23 Amplitude and SNR Results as a Function of Depth 30 

24 Comparison of Single-Focus Transducer and Phased Array 31 

25 Seven-Element Annular Array Developed for the CBS Evaluation 32 

26 Setup Used in Billet Inspection 33 

27 Comparison of Amplitude and SNR for Phased Array and Multizone Inspection 

of CBS Billets 36 

28 Process Used for Ultrasonic Characterization of the Indications 37 

29 Ultrasonic Characterization for B3W3 Indication B 38 

30 Ultrasonic Characterization at Cube State Prior to Metallographic Sectioning of 

B3W3 Indication B 38 

31 Selected Metallographic Sections for Sample B3W3-B 39 

32 Microprobe Results for Section 5 (Approximately 20 mils) in Defect B3W3-B 39 

33 Microprobe Results for Section 11 (Approximately 65 mils) in Defect B3W3-B 40 

34 Peak Amplitudes of Inclusion and Void With and Without the Hard Alpha Shells 

for Different Inclusion Diameters 42 

35 Polishes 8-13 of the Realigned and Reduced Cross-Section Images Used to 

Reconstruct Defect B1AW2-X 43 

36 Stacking Orientation of the Metallographs of Hard Alpha Defect B1AW2-X 43 

37 Example of More Complicated Void Connections 44 

38 Raw vs NURB Void Boundary Trace Projection: Right Void of B1AW2-X 45 

39 Three Angle Views of the Surface Model for Defect B1AW2-X 46 

vi
40 Actual Dimensions of Defect B1AW2-X 46 

41 Example of Flaw Illumination By Ultrasonic Beam 47 

42 Block Orientation for Experimental Ultrasonic Measurements 48 

43 Comparison of Ultrasonic C-Scan Results, Model and Experiment 48 

44 Decibel Amplitude Errors at 0- (peak), 40-, and 80-mils Scan Offset for All Six 

Sides of Defect B1AW2-X 50 

45 Structural Plateaus in Defect B2W2-C’s Geometric Model 50 

46 Comparison Between Model and Experiment: dB Error of Peak Amplitude vs 

Log of Projected Flaw Area 51 

47 Decibel Model Errors vs the Scan Offsets for Cases of Five Defects 52 

48 Distribution of dB Model Errors of Peak Amplitudes in the Optimal Orientation 52 

49 Summary of dB Model Errors of Peak Amplitudes in Optimal Orientation 53 

50 C-Scan Image of 11′′ Section of Billet B3W3 54 

51 Sample Sectioning Plan for Noise Studies 55 

52 Macrostructure Results for High- and Low-Noise Samples 56 

53 Microstructure of High- and Low-Noise Samples 56 

54 Velocity Results for High- and Low-Noise Samples 57 

55 Attenuation and FOM Results for High- and Low-Noise Samples 58 

56 Steps Required to Validate Theory of Noise Models 59 

57 Electron Backscatter Kikuchi Diffraction Results for High-Noise Samples 60 

58 Electron Backscatter Kikuchi Diffraction Results for Low-Noise Samples 61 

59 Two-Point Correlation From High- and Low-Noise Regions of the Samples 62 

60 Comparison of Predicted and Observed Values of Backscattering Coefficient 63 

61 Amplitude Data for Various Transducers Used in the Rolls-Royce Study 67 

62 Variability Analysis for Amplitude From Multizone Inspection 73 

63 Variability Analysis for Amplitude From Conventional Inspection 73 

vii
64 Comparison of Multizone and Conventional Inspection Variability 74 

65 Reproducibility Results for Indication B1BW1A-B From Field Studies 74 

66 Factors Evaluated During Reproducibility Study 75 

67 Main Effects Plot and Interactions Plot 76 

68 Comparison of SNR for Laboratory Design of Equipment and Round-Robin 

Field Study 77 

69 C-Scan of Indications D and C From Billet Segment B3W1BB Also Detected in 

Prior Inspections 79 

70 C-Scan and Waveform Results for Indication B of Billet Segment B3W1BB 80 

71 C-Scan and Waveform Results for New Indication Found in Billet Segment 

B1BW3CB 81 

72 C-Scan and Waveform Results for New Indication Found in Billet Segment 

B1BW3CB Using 10-MHz Phased Array Inspection 82 

73 C-Scan Results for Indication B1BW1-G Used in HIP-to-Heal Sample 89 

viii
LIST OF TABLES 

Table Page 

1 Concentration Measurements for B3W1 8 

2 Results of Point Microprobe Measurements for Practice Defect 19 

3 Summary of Inspection Parameters for Each of the Inspection Methods 24 

4 Tabulation of the Ten Indications Selected for Detailed Characterization and 

Reconstruction 28 

5 Zoning Arrangement for Phased Array Inspection of CBS 6′′ Diameter Billet 34 

6 Signal to Noise and Amplitude Data From Phased Array Inspection 35 

7 Billets Used in Rolls-Royce Reproducibility Study 64 

8 Tabulation of Detections in Rolls-Royce Reproducibility Study 65 

9 Transducers Used in Rolls-Royce Comparison Study 65 

10 Amplitude Data From Transducer Comparison Study 66 

11 Summary of Prior Ultrasonic Inspection Results for Billets Selected for 

Reproducibility Study 68 

12 Test Matrix Used for Reproducibility Study 69 

13 Summary of Conventional Indications Recorded as False Calls in Billet B1BW1A 70 

14 Summary of Statistics of Multizone Reproducibility Study 70 

15 Summary of Amplitude Statistics for Conventional Inspection 71 

16 Summary of Signal Minus Noise Statistics for Conventional Inspection 71 

17 Percent Efficiency of Multizone Inspection During Reproducibility Studies 72 

18 Percent Efficiency of Conventional Inspection During Reproducibility Studies 72 

19 Results of Full Factorial Experiment Performed in Laboratory Environment 76 

20 Mults Used in the Misses Assessment 78 

21 Listing of Samples Remaining From Original Billet Material 83 

22 Inspection Amplitudes and SNR for Indication B1BW1-G Used in HIP-to-Heal 

Sample 89 

ix
LIST OF ACRONYMS 

1D One-dimensional 

2D Two-dimensional 

3D Three-dimensional 

AANC Airworthiness Assurance Nondestructive Inspection Validation Center 

Al Aluminum 

C Carbon 

CA Conventional angle 

CBS Contaminated Billet Study 

CHM Cold hearth melting 

CL Conventional longitudinal 

ETC Engine Titanium Consortium 

FAA Federal Aviation Administration 

FATS Focussed Array Transducer System 

FBH Flat-bottom hole 

FOM Figure of merit 

FSH Full-screen height 

GE General Electric Aircraft Engines 

HIP Hot isostatic press 

ISU Iowa State University 

MZ Multizone 

N Nitrogen 

NURBS Nonuniform rational b-splines 

OD Outside diameter 

PC Personal computer 

PoD Probability of detection 

POP Pulse-on-position 

RAM Random access memory 

RF Radio frequency 

ROI Region of interest 

SNR Signal-to-noise ratio 

Ti Titanium 

TRMD Turbine Rotor Materials Design 

V Vanadium 

VAR Vacuum arc remelting 

WORM Write-once-read-many 

x
EXECUTIVE SUMMARY

During the Engine Titanium Consortium (ETC) Phase I program, the existence of a 

contaminated heat of titanium billet was made known to ETC and the Federal Aviation 

Administration. During processing of the billet for a nonaerospace customer, a power outage led 

to a vacuum leak and resulted in numerous natural hard alpha defects. Because of the unique 

opportunity offered by over 60 natural defects, an assessment was made that determined the 

defects were typical of those found in rotor grade material. The material was purchased for use 

in nondestructive evaluation and lifing studies. The 12 billets were inspected using multizone 

and conventional inspection with a subset of the heat inspected using a phased array method. 

Upon analysis of the inspection data, 10 of the 64 indications were selected for detailed 

metallographic characterization. The ten defects were serially sectioned at 5-mil increments, and 

the metallographic data was used to construct solid models for use in probability of detection 

studies. Several billets were also used in reproducibility and noise studies. The results of the 

inspection, defect characterization, and solid model generation are provided in this report along 

with use of the data in preliminary probability of detection (PoD) calculations. The following 

primary conclusions were arrived at: 

• More than two times as many indications were found with multizone inspection than with 

the dual probe (longitudinal and angle inspection) conventional inspection. Detection 

occurred over the full depth of the billet for both methods. Conventional inspection 

detection was not correlated to the multizone amplitudes, i.e., the conventional misses 

occurred over the range of amplitudes. 

• Phased array inspection was demonstrated to have similar capability to the multizone 

results with the advantage of simpler fixturing. 

• In chemical analysis studies of the defects, the nitrogen concentration was found to drop 

to less than 1% within 10 mils from the defect center (center of the voiding). The 

implications of these results are that the nugget and diffusion zone contribute little to the 

detection of the defect. Ultrasonic response is dominated by the presence of cracks and 

voiding. 

• Defect characterization of ten defects provides detailed understanding of hard alpha 

defects for use by metallurgists, life management, design, and inspection personnel. The 

data also provides input for PoD calculations and for use in model validation. 

• Using the solid model results, the sizes of the defects were tabulated and used in 

subsequent PoD calculations. Preliminary results indicate inconsistencies between PoD 

calculations generated from prior data and the recent Contaminated Billet Study 

characterization. Additional effort is underway to extend the PoD calculations to include 

the full dataset of 60 indications and to further understand the input to prior PoD 

calculations. 

• Several reproducibility studies were performed using a subset of the billets. Variability 

of amplitude response up to 10 dB was found for both conventional and multizone 

xi
methods. Inspection setup and transducer alignment were identified as key contributors 

to the variability. 

• Of the ten hard alpha defects selected for metallographic sectioning, seven were not 

detected by conventional inspection. All of the missed defects were very large, having 

hard alpha core areas in the 15,000 to 100,000 square mils of range. 

xii
1. INTRODUCTION.

1.1 PURPOSE.

The safety of jet engines is dependent on the use of inspection technology for the detection of 

critical defects and accurate quantification of the performance of the various inspection methods 

for use in design and lifing calculations. Typically, the performance is quantified through the 

use of statistical tools and is reported as a probability of detection (PoD). However, the accuracy 

of the PoD results is dependent on having a significant number of data points for a given flaw 

type for use in the calculations. 

The major flaw type of concern in titanium alloys used in production of jet engines is hard alpha 

defects that are caused by nitrogen and/or oxygen impurities in the metal. The hard alpha 

defects are often accompanied by cracks and voids, which may be located using present 

ultrasonic and eddy-current inspection procedures. Subsurface hard alpha defects that are found 

in production are almost always accompanied by cracks or voids. These hard alpha regions, 

being more brittle than nominal material, generally crack prior to surrounding material, thereby 

acting as a fatigue crack origin. 

Naturally occurring hard alpha defects in rotor grade material have been reported at occurrences 

of less than one per million pounds. Therefore, their availability for study and evaluation is 

limited. In February 1995, while performing a routine inspection for a nonaerospace customer, a 

titanium supplier found multiple indications with conventional ultrasonic inspection. Upon 

sectioning two of the indications, hard alpha was confirmed, and the existence of the heat was 

made known to the Engine Titanium Consortium (ETC). Because of the opportunity this heat 

offered, ETC proposed to the Federal Aviation Administration (FAA) William J. Hughes 

Technical Center to purchase the heat for inspection, processing, and life management studies as 

part of the ETC research and for use by the FAA Turbine Rotor Materials Design (TRMD) 

program performed by Southwest Research Institute. The program became known as the 

Contaminated Billet Study (CBS) and has provided a unique opportunity for study by both the 

inspection and the lifing communities. 

Through use of the heat for various inspection studies and subsequent metallographic and 

chemical analysis, a considerable amount was learned about the physical properties and 

detectability of this defect type. The inspection results, subsequent sectioning, and use of this 

heat for PoD studies are the subject of this report. 

1.2 BACKGROUND.

Hard alpha defects are also know as high interstitial defects [1] and are defined as an 

interstitially stabilized alpha phase region of substantially higher hardness than the surrounding 

material, arising from very high local nitrogen, oxygen, or carbon concentrations that increase 

the beta transus and produce the high hardness, often brittle, alpha phase. Also commonly called 

a type I defect, low-density inclusion, or hard alpha, the defects are often associated with voids 

and cracks. Defects may occur because of the inadvertent use of burned sponge or contaminated 

raw stock, improperly processed electrodes, or vacuum leaks. Because of the deleterious effect 

1
of these defects on the fatigue life of titanium alloys, any billet or forging found to contain a 

defect is removed from use in critical rotating components. Manufacture of rotating components 

of jet engines involves a multiple-step process that is designed to arrive at optimal material and 

mechanical properties. A schematic of the typical process is shown in figure 1. Raw materials 

are selected to ensure cleanliness of the final product. They are consolidated into a compact, 

used in preparation of the final ingot. Typical ingot diameters are 24′′ or greater and are 

fabricated using either triple vacuum arc remelting (VAR) or cold hearth melting (CHM) 

followed by a VAR step. Ingots are visually inspected for indications of surface contamination 

before further processing to billet. Conversion of ingot to billet typically involves the use of Vdie or rotary Gesellschaft fur Maschinenbau-und-fertigungstechnik processes to reduce the billet 

diameter to the appropriate size and arrive at acceptable microstructural conditions (i.e., grain 

size and alpha/beta ratios). After billet conversion, the surface is prepared for inspection and the 

billet is inspected with immersion ultrasonic inspection. If hard alpha defects are found, the 

entire heat in which any hard alpha defect occurs will be downgraded from premium quality and 

is no longer acceptable for use in critical rotating components. Those billets found acceptable 

will be cut into sections of appropriate length for a given forging design known as mults. The 

mults are then forged into a sonic shape for ultrasonic inspection. If no defects are found, the 

sonic-shaped component will be machined to final shape and then will be typically inspected 

with fluorescent penetrant inspection and surface etching, e.g., blue etch anodize, prior to 

entering service. 

Raw 

materials 

3VAR or CHM

Inspection

Inspection

Ingot to billet processing

Forged shape

Finished part

Raw 

materials 

3VAR or CHM

Inspection

Inspection

Ingot to billet processing

Forged shape

Finished part

FIGURE 1. MANUFACTURING CYCLE FOR CRITICAL ROTATING COMPONENTS 

2
The FAA and the aviation industry have placed much attention on the occurrence and detection 

of hard alpha defects since the 1989 Sioux City accident [2]. The FAA established an internal 

team to review the production, use, and management of titanium components and published the 

results of their efforts in the Titanium Rotating Component Review Team Report [3]. 

Recommendations included improvements for the inspection of titanium, which led to the 

establishment of the Engine Titanium Consortium. After the incident, the Jet Engine Titanium 

Quality Committee was formed under the auspices of the FAA, with membership including all 

the U.S. and European aircraft engine producers, for the purpose of rapid dissemination of 

titanium alloy melt-related defect issues and data and included activities leading to Advisory 

Circular (AC) 33.15-1, “Manufacturing Process of Premium Quality Titanium Alloy Rotating 

Engine Components” [1]. To address life management related issues, the Rotor Integrity 

Subcommittee was established through the auspices of the Aerospace Industries Association. 

Through cooperative efforts with the FAA, AC 33.14-1, “Damage Tolerance for High Energy 

Turbine Engine Rotors [4],” was also generated. A companion research program known as the 

Turbine Rotor Materials Design was initiated at Southwest Research Institute to support the 

needs of the lifing community. 

In 1995, the ETC held its first of three open forums to place the results of the program in the 

public domain. At the meeting, the existence of a contaminated heat of Ti-6Al-4V was made 

known to the ETC team. An initial inspection indicated multiple defects, and a preliminary 

destructive analysis confirmed the existence of hard alpha defects. The ETC team requested 

approval from the FAA to purchase the heat of material for use by the ETC and TRMD research 

programs. A research program was put in place to use the material to improve the understanding 

of detectability of hard alpha and to provide quantitative data for use in inspection and lifing 

decisions. 

1.3 PROGRAM OBJECTIVES.

The program objectives were: 

• to provide a quantitative assessment of various ultrasonic approaches to billet inspection. 

• to provide basic knowledge and data to improve the detection of hard alpha by 

developing an understanding of the acoustic, physical, and chemical properties of hard 

alpha defects. 

• to provide reference samples containing naturally occurring hard alpha defects for 

evaluation of future inspection techniques, validation of PoD and ultrasonic 

methodologies, and support of technology transfer to titanium billet suppliers. 

• to support the development of a probabilistically based, damage tolerance design code to 

augment the current safe-life philosophy for life management of commercial aircraft 

turbine engine rotors components. 

3
1.4 RELATED ACTIVITIES AND DOCUMENTS.

The ETC was established in 1993 and included Iowa State University (ISU), General Electric 

Aircraft Engines (GE), Honeywell Engine Systems & Services, and Pratt & Whitney in a 

partnership to perform research that contributes to improvements in flight safety. The Phase I 

program, which was completed in 1998, led to improvements in production inspection of 

titanium billet [5], improved physics models for ultrasonics [6 and 7], and a feasibility study for 

phased array for ultrasonic inspection of billets [8]. In-service inspection efforts led to a 

commercially available portable scanner [9] and eddy-current probes [10] as well as improved 

probe designs [11] and eddy-current probe design tools [12]. Considerable progress was also 

made in developing a new approach [13] to quantifying inspection performance as reported in 

the FAA report DOT/FAA/AR-01/96, “A Methodology for the Assessment of the Capability of 

Inspection Systems for Detection of Subsurface Flaws in Engine Components” [14]. As part of 

the Phase I program, a literature survey was completed that detailed the defect types that occur in 

titanium billet. A summary of the results of that survey are provided in appendix A. 

A companion research program [15], TRMD, was funded by the FAA with the objective to 

develop a probabilistically based damage tolerance design code to augment the current safe-life 

approach for life management of commercial aircraft gas turbine rotors and disks. Initial 

application of the code focused on melt-related hard alpha anomalies in titanium. Tests were 

also performed to determine the mechanical properties of hard alpha and titanium disk alloys, 

and a forging code was developed to predict the shape and orientation of hard alpha anomalies 

during processing. The probabilistic damage tolerance code that was developed for low-cycle 

fatigue of titanium rotors and disks containing hard alpha anomalies is called Design Assessment 

of Reliability With INspection (DARWIN®). It was developed by Southwest Research Institute 

in collaboration with Honeywell, formerly AlliedSignal Engines; GE; Pratt & Whitney; and 

Rolls-Royce Allison. Included in the TRMD program were efforts to validate deformation codes 

used in forging design and optimization. The objective of that portion of the program [16] was 

to develop a finite element microcode to simulate the deformation of a hard alpha inclusion 

during forming processes. Several of the CBS indications were provided to the TRMD program 

for use in validation of the deformation code and for use in generating material properties data 

with the results provided in FAA reports [16] and presentations. 

2. APPROACH. 

The approach for this research effort included the following steps, with details provided in 

sections 2.1-2.4. 

• Determination of cause of the hard alpha defects in the available heat and suitability for 

further study 

• Inspection of heat using multizone (MZ), conventional, and phased array inspection 

methods 

• Analysis of inspection data and distribution of indications for further PoD and forging 

studies 

4
• Detailed ultrasonic characterization of ten defects selected for use in PoD studies 

• Metallographic sectioning with chemical analysis of the ten defects 

• Coordination with the TRMD program in their use of three defects used for forging 

studies 

• Use of metallographic section data to reconstruct the defect morphologies and subsequent 

PoD analysis 

2.1 INITIAL ASSESSMENT OF HEAT. 

In February 1995, the FAA-funded programs, the ETC and TRMD, were made aware of the 

existence of a contaminated heat of Ti-6Al-4V. The contaminated heat, number 883588-02, 

occurred as the result of a loss of power during melting. Following completion of the double 

VAR processing, the ingot was split in two and converted to the final billet diameter of 6′′. The 

forging process is detailed in figure 2. Note that this is not the standard practice for rotor-grade 

materials, which are typically either triple VAR or CHM/VAR processed and rotary forged from 

ingot to final billet geometry. However, the original customer did not intend to use the material 

for aerospace applications, hence, the difference in processing. The supplier indicated that this 

heat was formulated from 72% revert, 28% sponge, and was chamber-welded. The primary 

ingot was piggy-back melted; the first electrode was melted uneventfully. Partway into the 

second melt, a total melt shop power outage occurred. The power outage shutdown the vacuum 

pumps, and a pressure spike occurred before the furnace was backfilled with argon. After power 

returned, melting was resumed to complete the primary ingot. The primary ingot was inverted 

and remelted to complete the processing. The initial inspection of the heat was completed using 

conventional 5-MHz transducers in two wave modes, longitudinal and refracted shear, which led 

to the detection of multiple indications. Based on the ultrasonic results, the heat was 

dispositioned for further commercial use. To ensure that the defect types were typical of hard 

alpha defects found in rotor-quality materials, an assessment was made with input from the ETC 

and TRMD teams along with representatives from the metallurgy staff at the original equipment 

manufacturers (OEM). Based on the chemical analysis and metallographic sectioning of the 

initial defects, it was determined that these defects were representative and, therefore, 

appropriate for further study, as described in the paragraphs below. 

To determine the appropriateness of the material for further study, a chemical and 

metallographic analysis was performed on two of the indications, one of which is shown in 

figure 3. The bulk composition consisted of C-0.02, N-0.014, Fe-0.18, Al-5.56, V-4.10, O-0.18, 

and Y-<50 parts per million, within the range of typical Ti-6Al-4V. The purpose of the study 

was to characterize the inclusion as a typical hard alpha inclusion, compared to inclusions 

previously removed from billet product or from forged components. As reported by Bogan [17], 

the inclusion was a hard, brittle, cracked, and voided hard alpha, containing up to 12.6% nitrogen 

and surrounded by a diffusion zone and could be considered typical of those encountered in 

billet and forged products. Microprobe data showed that the highest nitrogen areas contained 

approximately 1.5%-2.0% vanadium with approximately 0.1%-0.9% aluminum. 

5
Typical Process

• 36′′ dia. ingot

• Heat 2100 ° F

20′′ RCS

• Heat 1750 ° F

16′′ RCS

• Heat 1975 ° F

13′′ RCS H 2O quench from dies

• Heat 1750 ° F

9′′ Octagon

• Heat 1750 ° F

GFM Forge to 6.375′′ dia.

Bar turn to size 6′′ dia. 

RCS - Round corners square

OCT - octagon shape 

CBS Process

36′′ dia. ingot, 78′′ length

• Heat 2100 ° F

Upset forge to 50′′ length,

Rotate 90, draw to 32′′ x 42′′

• Heat 2100 ° F

27′′x 38”

• Heat 1750 ° F

18.375′′ x 35.375′′

Grind to 18′′ x 35′′

Ship to customer

• Further processing at customer to 6.4′′ x 28.7′′; 

hard alpha detection; returned to RMI

• Flame cut

B1 in half, slit in thirds

B2 slit in thirds

B3 slit in thirds

Produced 12 pcs @ 6.4′′ x 9.5′′

• Heat 1750 ° F

6′′ RCS

• Heat 1750 ° F

6.5′′ OCT

Bar turn to size 6′′ dia.

FIGURE 2. COMPARISON OF TYPICAL CONVERSION PROCESS USED TO PRODUCE 

ROTOR-GRADE BILLETS AND THE CONVERSION PROCESS USED TO 

PRODUCE THE CBS BILLETS 

(Note: the original customer for this material was not an aerospace customer.) 

FIGURE 3. PHOTOMACROGRAPH DOCUMENTS REMOVAL OF INDICATION 

FROM BILLET SAMPLE 

(Note the two indications visible in this sample were taken from B3W1. The indications were 

located at 0.875′′ and 1.15′′ from the billet surface.) 

6
The presence of alloy content at the core of the inclusion indicates that the defect formation 

occurred in the alloyed state. The presence of oxygen in reduced nitrogen areas and the general 

absence of carbon all suggest an air leak type of hard alpha formation. An optical micrograph of 

the indication is shown in figure 4. The cylindrical slug was cross-sectioned approximately 0.3′′

below the plane of the photomacrograph shown in figure 3. The 25X magnification 

photomicrograph maintains orientation between top and bottom views with the billet center 

shown to the right. The core of the inclusion (stabilized alpha with cracks and voids) is seen to 

be approximately 0.10′′ in cross-sectional dimension with a diffusion zone extending to 0.20′′

radially by approximately 0.12′′ tangentially. Microprobe measurements were used to complete 

the analysis of B3W1 and are tabulated in table 1. The results of the microprobe analysis of this 

indication are shown in figures 5 through 7. 

FIGURE 4. CYLINDRICAL SLUG TAKEN FROM BILLET B3W1 WAS CROSSSECTIONED APPROXIMATELY 0.3′′ BELOW THE PLANE OF THE 

PHOTOMACROGRAPH SHOWN IN FIGURE 3 

(The 25X magnification photomicrograph shown here maintains orientation between top and 

bottom views with the billet center shown to the right.) 

7
TABLE 1. CONCENTRATION MEASUREMENTS FOR B3W1 

Point Ti Al V O C N

6 86.47 0.06 1.48 <ML <ML 12.1

7 85.68 0.42 2.88 0.1 <ML 11.4

8 87.36 0.35 1.99 <ML <ML 12.6

9 86.69 0.14 1.56 <ML <ML 12.0

10 85.98 0.57 1.86 <ML <ML 11.6

11 87.85 0.87 2.14 <ML <ML 10.2

12 86.55 0.48 2.11 <ML <ML 11.7

13 87.24 0.43 1.87 <ML <ML 11.3

14 86.89 0.19 1.67 <ML <ML 11.8

15 89.92 0.98 2.03 0.4 <ML 7.4

16 86.41 0.48 1.79 <ML <ML 11.9

17 86.92 0.85 2.85 <ML <ML 10.9

18 87.46 0.29 1.65 <ML <ML 11.8

19 86.81 0.33 1.64 <ML <ML 11.5

20 86.93 0.09 1.43 <ML <ML 12.2

21 87.38 0.07 1.32 <ML <ML 12.1

22 86.87 0.11 1.43 <ML <ML 12.3

23 89.14 1.17 2.45 <ML <ML 7.9

24 91.58 0.75 2.86 <ML <ML 7.0

25 90.08 0.71 2.15 <ML <ML 7.5

26 93.23 0.79 2.21 <ML <ML 5.6

27 91.13 0.78 2.01 0.2 <ML 6.7

28 89.87 1.18 2.84 <ML <ML 6.6

29 90.24 6.02 3.86 <ML <ML 1.3

30 89.89 6.25 2.53 <ML <ML 1.6

31 89.85 5.21 2.36 <ML <ML 2.1

32 90.25 4.83 2.21 0.4 <ML 3

33 90.37 1.15 2.15 0.1 <ML 6.4

34 90.76 2.61 2.08 <ML <ML 4.3

35 90.81 5.57 2.56 <ML <ML 1.7

36 88.94 4.16 2.58 0.9 <ML 4.4

37 90.03 4.81 2.48 <ML <ML 3.4

38 90.08 4.59 2.26 <ML <ML 3

39 90.77 3.04 1.98 <ML <ML 4

40 90.72 1.68 1.98 <ML <ML 5.8

41 91.24 5.95 2.06 0.2 <ML 1.3

42 91.78 3.67 1.98 0.2 <ML 3.2

43 89.02 7.89 2.88 <ML <ML 1

44 89.02 6.69 2.95 1.2 <ML 1.3

45 98.74 3.83 2.15 0.5 <ML 2.8

46 89.72 2.94 2.65 <ML <ML 4.7

47 91.12 6.86 2.29 <ML <ML 1.4

48 90.68 4.45 2.22 <ML <ML 3.3

49 92.58 1.54 1.64 <ML <ML 4.7

50 98.96 7.17 2.39 <ML <ML 0.6

51 98.66 6.44 2.59 <ML <ML 1.1

52 91.44 6.98 2.45 <ML <ML 0.5

53 91.71 7.17 2.15 <ML <ML 0.3

54 91.31 6.73 2.44 0.3 <ML 0.7

55 92.06 4.53 1.98 <ML <ML 2

56 90.85 4.69 1.96 0.5 <ML 2.6

57 90.11 5.45 2.58 0.7 <ML 1.7

58 91.38 6.41 2.34 <ML <ML 0.8

59 91.17 6.45 2.30 <ML <ML 0.8

60 98.96 6.53 2.50 <ML <ML 0.6

61 91.05 6.78 2.86 <ML <ML 0.4

62 91.06 6.22 2.89 <ML <ML 0.8

63 92.18 6.82 2.09 <ML <ML 0.5

64 91.94 7.05 2.10 <ML <ML <ML

<ML - less than measuraable levels

O, C, N levels are not absolute concentrations but are relative to an average 

baseline value taken well away from the void area

Points correspond to locations marked in figures 4 through 7. 

8
FIGURE 5. ELECTRON MICROPROBE BACKSCATTERED ELECTRON IMAGE OF 

DEFECT TAKEN FROM BILLET B3W1 

(Numbers indicate location of microprobe measurements. Billet center is to right of image.) 

FIGURE 6. MICROPROBE RESULTS IN MEDIUM NITROGEN 

(Range from 3.0% nitrogen at point 32 to 6.4% at point 33.) 

9
FIGURE 7. ELECTRON MICROPROBE SHOWS AREAS OF HIGHEST 

NITROGEN CONTENT 

(The range of nitrogen content is from 7.4% N at point 15 up to 12.6% at point 8. 

The average nitrogen content in this area is 11.2%. Also note cracking in this 

area of the sample. The original micrograph was at 400X magnification.) 

In addition to microprobe analysis, microhardness measurements were also made. The Knoop 

500-gram microhardness ranged from a high of 805 (Rc 63) in the central core nugget, gradually 

decreasing to a value of 313 (Rc 30) in the normal microstructure. In May 1995, a joint 

ETC/TRMD assessment was made even though the heat was double VAR, the hard alpha defect 

was representative of typical defects found in triple VAR rotor-grade material. The ETC 

purchased the heat on behalf of the FAA for use in the inspection and lifing and deformation 

modeling programs. 

The purchase included 6325 pounds of heat, representing half of the heat. The heat was 

converted into twelve 6′′ diameter billets ranging from 87′′ to 131′′ in length. The location of the 

billets within the original ingot is shown in figure 8. The billet designations are listed first 

(B3W1, B3W2, etc.) followed by the length of the billet in inches. The number of indications 

detected by each of the inspection methods is listed for multizone, conventional longitudinal 

(CL), and conventional angle (CA). Four additional multizones were found upon detailed 

analysis of the data by ETC personnel that were not found (i.e., missed) by the production 

inspection analysis. The number of indications found in each billet by the original inspection 

and by the additional analysis (+ n) performed by ETC is indicated in figure 8. 

10
B1AW3

Len = 111”

MZ = 5 + 2

CL = 2

CA = 2

B1AW2

Len = 117”

MZ = 6 + 1

CL = 4

CA = 3

B1AW1

Len = 112.5”

MZ = 5

CL = 1

CA = 3 

B1BW3

Len = 107.5

MZ = 4

CL = 0

CA = 0

B1BW2

Len = 100.5”

MZ = 5

CL = 4 

CA = 2

B1BW1

Len = 104”

MZ = 8

CL = 3

CA = 4

B2W3

Len = 131”

MZ = 3

CL = 0

CA = 1

B2W2

Len = 123”

MZ = 3 + 1

CL = 0

CA = 0

B2W1

Len = 133”

MZ = 4

CL = 2

CA = 3

B3W3

Len = 124.5”

MZ = 4

CL = 2

CA = 3

B3W2

Len = 119.5”

MZ = 8

CL = 2

CA = 3

B3W1

Len = 117”

MZ = 4

CL = 3

CA = 3

B1AW3

Len = 111”

MZ = 5 + 2

CL = 2

CA = 2

B1AW2

Len = 117”

MZ = 6 + 1

CL = 4

CA = 3

B1AW1

Len = 112.5”

MZ = 5

CL = 1

CA = 3 

B1BW3

Len = 107.5

MZ = 4

CL = 0

CA = 0

B1BW2

Len = 100.5”

MZ = 5

CL = 4 

CA = 2

B1BW1

Len = 104”

MZ = 8

CL = 3

CA = 4

B2W3

Len = 131”

MZ = 3

CL = 0

CA = 1

B2W2

Len = 123”

MZ = 3 + 1

CL = 0

CA = 0

B2W1

Len = 133”

MZ = 4

CL = 2

CA = 3

B3W3

Len = 124.5”

MZ = 4

CL = 2

CA = 3

B3W2

Len = 119.5”

MZ = 8

CL = 2

CA = 3

B3W1

Len = 117”

MZ = 4

CL = 3

CA = 3

FIGURE 8. LOCATION OF BILLETS WITHIN THE IGNOT, WHICH CAME FROM 

THE BOTTOM HALF OF THE INGOT 

2.2 INSPECTION SUMMARY. 

To fully characterize the heat and provide necessary data for PoD estimates, three inspection 

techniques were used: 

1. Conventional dual transducer inspection: a 5-MHz longitudinal, cylindrically focused 

transducer at normal incidence (element size was 1′′ by 0.5′′ with an inspection water 

path of 3.5′′ and a focal length of 8′′) and a 5-MHz refracted longitudinal, spherically 

focused transducer (diameter of 0.75′′ and water path of 3.5′′) at an incident angle of 9.6o 

to produce a 45o longitudinal wave. The refracted angle was accomplished by offseting 

the transducer by 1/6 of the billet radius. The setup for the refracted longitudinal 

inspection is shown in figure 9. Note, the original inspection used refracted shear rather 

than refracted longitudinal. 

2. Multizone inspection: 5-MHz bicylindrical focus, five zones. The multizone approach is 

based on the use of a bicylindrically focused transducer, which is designed to focus at 1′′

zones, as shown conceptually in figure 10. Additional details of the multizone inspection 

process are provided in section 2.3. 

3. Phased array inspection: 10-MHz center element for near-surface inspection, 5-MHz 

outer elements (seven) for the other four zones. Additional details of the phased array 

inspection are provided in section 3.2. 

11
Incident angle 9.6°

Refracted 

longitudinal angle 

45°

Incident angle 9.6°

Refracted 

longitudinal angle 

45°

FIGURE 9. SPHERICALLY FOCUSED TRANSDUCER, OFFSET 1/6 OF 

BILLET RADIUS TO PRODUCE 45o LONGITUDINAL WAVE 

Bicylindrical focused transducers -

FIGURE 10. MULTIZONE CONCEPT THAT USES BICYLINDRICAL TRANSDUCERS 

DESIGNED TO FOCUS WITHIN 1′′ ZONES FROM BILLET SURFACE TO 

1/2′′ BEYOND CENTER 

2.3 DESCRIPTION OF MULTIZONE INSPECTION. 

The multizone system is a real-time, personal computer (PC)-based platform that employs 

custom built analog electronics using up to eight parallel (nonmultiplexed) channels, each with a 

remote pulser/receiver matched to the ultrasonic transducer. Scanned helically, the billet is 

divided into concentric zones with a focused transducer used to acquire peak-detected C-scan 

image data for each zone. The depth of each zone is established by the depth of focus of that 

transducer. C-scan image data from all channels are displayed simultaneously on a 1024 x 1280 

cathode ray tube, which scrolls as the inspection advances along the billet length. At the time of 

the CBS inspection, the data were written to optical storage upon completion of the inspection. 

Custom postscan analysis software was developed to detect flaws using signal-to-noise-based 

algorithms as well as amplitude rejection. 

Motivation in the design of the multizone system was the use of focused transducers to overcome 

material noise and therefore improve detection. However, multiple compound focused 

transducers were required to inspect the billet volume to uniform sensitivity. The transducers 

were fitted with dual curvature lenses to produce a diffraction-limited symmetrical focus. This 

12
configuration provided more uniform sensitivity versus depth for a given scan rate. The 

inspection zones were determined by the transducer focal zone parameters, i.e., diameter, d, and 

focal length, F. Each transducer inspects a depth of material roughly equal to the -3 dB depth of 

field εz and at a spatial sampling rate at least one-half the -6 dB beam diameter εx. 

εz = 3.6λ[F/d]

2

c1/c2 

εx = 1.03 λ[F/d]

The value c1 is the sound velocity in water (0.058 in/μsec), c2 is the sound velocity in titanium 

(0.243 in/μsec), and λ is the wavelength (0.049 in. in titanium at 5 MHz). A typical multizone 

transducer produces 5 MHz, F/8.0 beams that are approximately 0.1′′ diameter and 0.8′′ depth of 

field for titanium. At deeper depths, larger F numbers are used due to the limitation in element 

diameters produced by commercial vendors. By increasing the transducer size and depth in the 

material of its focal zone, overlapping foci are produced to uniformly inspect the billet volume, 

as shown in figure 10. 

The ultrasonic instrument used custom analog electronics with up to eight parallel, 

nonmultiplexed channels. The parallel, nonmultiplexed architecture was used to eliminate any 

unattenuated sound that might interfere with a given channel’s signal. A multiplexed solution 

also introduces possible speed limitations. Each transducer has its own remote pulser/receiver, 

which is matched to that specific transducer. The user can set various parameters for each 

channel such as attenuation, signal gate delay and width, and triggering rate. The data generated 

for each channel/zone is an analog, peak-to-peak C-scan voltage ranging from 0 to 10 volts, 

which is sent to the computer for display and storage. 

The recommended computer configuration considered state of the art at the time of the CBS 

study was an Intel-based PC (e.g., 486, Pentium, etc.) with a large amount of random access 

memory (RAM) (64 MB or larger is recommended) running MSDOS and Windows. The RAM 

permits storage of data from all eight channels in memory as it is acquired. This eliminates timeconsuming disk accesses during acquisition. Standard data acquisition boards were used for 

digital handshaking signals between the computer and the electronics and for digitization of the 

analog C-scan data. A 21′′ 1280 x 1024 resolution color monitor allowed all eight channels to be 

displayed simultaneously during acquisition. The archival storage requirement was achieved 

using a write-once-read-many (WORM) optical disk for archiving the image data. 

For inspection, the billet was immersed in a water tank and rotated about its axis. The maximum 

billet rotation speed was approximately 30 revolutions per minute. The transducers, aligned 

normal to the billet surface, were mounted on a stage or follower that rides on a track over the 

tank. As the billet rotates, the follower moves axially along the billet length and the material is 

inspected in a helical pattern. An axial encoder was mounted on the follower and was used to 

report axial position of the transducers during the scan. A rotary encoder was coupled to an 

adapter that is attached to the end of the billet using double-sided adhesive. The encoder 

generated a once-per-revolution index or home pulse, which was used by the computer 

acquisition software to determine the 0° location on the billet. The rotary encoder also generated 

13
a 2048 pulse-per-revolution signal. This signal provided a position-dependent trigger for the 

ultrasonic transducers known as a pulse-on-position or POP pulse. The POP signal was used by 

the electronics to synchronize the triggering of the transducers for all eight channels to the billet 

rotation. Each channel divided down the 2048 master POP to the sample rate required to inspect 

the particular zone. 

Outer zones with larger radii required more samples than inner zones to fully inspect the 

material. The sample count for a given zone was a function of the zone circumference and the 

beam diameter εx of the transducer. While transducers covering the larger radii zones fire more 

often than their smaller radii counterparts, all transducers fire simultaneously when they do 

trigger. This greatly minimized the possibility of any unattenuated sound from any channel 

interfering with the signal from any other channel. 

Prior to inspection, the user must start the acquisition software on the computer. Based on the 

billet material and diameter, the operator is instructed on how to configure the electronics. 

Parameters such as attenuation, signal gate delay and width, and POP rate were set using 

thumbwheel switches on the electronics for the required number of channels. Information such 

as operator ID, billet length, and identification numbers must be entered into the software as 

well. Once the electronics are configured and the acquisition software is running, the rotary 

encoder begins triggering the electronics. The electronics fire the transducers and produce 

analog C-scan data values. These analog signals, along with axial position information, are sent 

to the PC acquisition software for storage in RAM and display. Upon scan completion, the user 

is given the opportunity to enter any comments about the scan. The data are then transferred 

from computer memory to disk and later archived to the WORM optical disk for permanent 

storage. 

The implementation of digital data acquisition allows postscan analysis, which is not possible 

with any current conventional billet inspection system. A typical multizone inspection on a 

single billet can generate 30 MB or more of ultrasonic image data. These data can include flaw 

signals obscured by an acoustic noise level that varies both circumferentially and axially along 

the billet. An image analysis software package was developed to aid the operators in finding 

indications. This package, which runs on the system PC, provides a Microsoft Windows-based 

graphical user interface for displaying and manipulating the inspection results. Using data 

analysis tools such as maximum value axial cross sections and image magnification, the operator 

is able to locate signals that are above the local acoustic noise and display them at high 

resolution. The operator can then isolate potential rejectable signals and a surrounding area of 

homogeneous noise for each indication. Using those two regions-of-interest (ROI), the operator 

can calculate the signal-to-noise ratio (SNR) for each indication where SNR is defined as 

nn

ns

P

P SNR

μ

μ

 - 

 - = 

where Ps is the maximum value of the signal ROI, Pn is the third highest (to exclude electrical 

noise spikes) value in the noise ROI, and mn is the mean of noise ROI. Material acceptance 

criterion based on both peak amplitude and SNR are applied to the indication to make the accept 

14
or reject decision. The PC can quickly review 30+ MB of data, allowing the task to be 

completed before the billet is removed from the tank. Since the scan positional information is 

stored along with the image data, the operator can return the transducer to the location on the 

billet where an indication exists to verify its location and mark the billet for sectioning to remove 

the material surrounding the indication. The multizone inspection system and postinspection 

data analysis described here are representative of the approach used in inspection of the CBS 

billets. 

2.4 DEFECT CHARACTERIZATION.

The contaminated billet material offered an unprecedented opportunity for analysis of hard alpha 

defects. Defect characterization data combined with the ultrasonic inspection data provided 

improved understanding of the relationship between flaw morphology and detectability. A full 

protocol was developed for the defect characterization and is provided in appendix B. 

Characterization included ultrasonic measurements in several configurations, followed by 

metallographic sectioning. Digital images were recorded for each of the defect slices for use in 

the three-dimensional (3D) reconstruction of the flaws. Microprobe measurements were made 

on selected slices in each indication. Figure 11 provides a flow chart of the characterization 

steps. 

Section to approx. 6” mult

• 5MHz inspection using 

bicyclindrical transducer 

focused in zone of 

indication 

Section to 3” cube

• 5MHz waveforms

Section to 1” cube

• 25 MHz c-scan

• CT imaging

Metallographic sectioning 

5 mil slices at 50X

Two slices

• Microprobe

• Grain orientation imaging

• Rayleigh wave maps 

3D Reconstruction 

and solid model 

development

Section to approx. 6” mult

• 5MHz inspection using 

bicyclindrical transducer 

focused in zone of 

indication 

Section to 3” cube

• 5MHz waveforms

Section to 1” cube

• 25 MHz c-scan

• CT imaging

Metallographic sectioning 

5 mil slices at 50X

Two slices

• Microprobe

• Grain orientation imaging

• Rayleigh wave maps 

3D Reconstruction 

and solid model 

development

FIGURE 11. ULTRASONIC AND METALLOGRAPHIC ANALYSIS STEPS USED TO 

CHARACTERIZE THE DEFECTS 

It was anticipated that pores and cracks would dominate the signals from hard alpha inclusions; 

therefore, a complete characterization of their morphology was the highest priority. To 

accurately predict the ultrasonic response of such irregularly shaped objects, definition of the 

surface to a resolution less than the ultrasonic wavelength is needed. At 5 MHz, the longitudinal 

ultrasonic wavelength is approximately 1.2 mm (0.048 in.) in titanium. Ideally, one would like 

the resolution to be about 10% of this, 120 μm (0.005 in.). Thus, 0.005′′ was selected as the 

distance between sectioning planes. The sectioning planes should contain the direction of 

insonification, i.e., the sample can be sectioned in either the axial-radial plane or the 

circumferential-radial plane. Axial circumferential sectioning is not recommended, since there 

would be the possibility that a thin crack, which might have contributed strongly to the 

ultrasonic response, would fall between the planes. Furthermore, such sectioning would make it 

difficult to locate the positions of sharp concentration steps. The axial-radial plane was selected 

as the sectioning plane, as shown in figure 12, to minimize the number of polishes required. 

15
Plane 1

5 mils 

between 

sectioning 

planes

Sample block will be 

polished in the 

orientation shown. 

Plane 1 to start at 

diffusion zone and 

continue through “n” 

planes until diffusion 

zone no longer 

evident in 

micrograph

Sample block with 1” 

envelope around 

defect as indicated by 

c-scan image in billet 

scan

Plane 1

5 mils 

between 

sectioning 

planes

5 mils 

between 

sectioning 

planes

Sample block will be 

polished in the 

orientation shown. 

Plane 1 to start at 

diffusion zone and 

continue through “n” 

planes until diffusion 

zone no longer 

evident in 

micrograph

Sample block with 1” 

envelope around 

defect as indicated by 

c-scan image in billet 

scan

FIGURE 12. ORIENTATION OF SECTIONING PLANE WITH RESPECT TO 

INSPECTION DIRECTION 

A practice defect was selected for developing and testing the characterization protocols. The 

defect was taken from billet B3W1. Note that the sectioning process used for this defect did not 

follow the orientation with respect to the billet axis as used with the other ten CBS indications. 

The purpose of characterization of this defect was to arrive at the etchants and microprobe 

processes. Five successive sections were made, as shown in figure 13. Note the change from 

diffusion zone to voiding as the sectioning progressed through the defect. The fifth section was 

used to evaluate the microprobe process. The sample was analyzed for titanium, aluminum, 

vanadium, nitrogen, and oxygen. Carbon could not be analyzed because the mounting material 

used required carbon coating of the sample. All analyses were performed at an accelerating 

voltage of 10 kV and a beam current of approximately 60 nA. A point analysis was used for the 

general survey, while selected area raster analyses at 4000X magnification were employed for 

the concentration profiles. The following analyses were performed: 

• A general survey of approximately 25 points in and around the defect. Locations, which 

included primarily alpha phase, were chosen whenever possible for the point 

measurements. 

• Two transverse concentration profiles ranging from ±50 mils of the defect center. 

• One longitudinal concentration profile ranging from the defect center to 300 mils into the 

alloy. 

16
FIGURE 13. SECTION PLANES FOR PRACTICE DEFECT 

17
Figure 14 shows the location of 25 point scans and 3 line scans completed on the practice defect. 

The results for the 25 points are tabulated in table 2. The results for the nitrogen line scans are 

shown in figures 15 (transverse scan) and 16 (longitudinal scan). Figure 17 provides the results 

for the oxygen scans. The scans show that the variation in nitrogen concentration was much 

more prominent transversely across the defect (see figure 15) than parallel to (in the plane of) the 

defect (see figure 16). This is consistent with the metallographic appearance and indicates that 

both the defect and the surrounding diffusion zone are flattened and elongated. In the diffusion 

zone there were no points where the composition changed abruptly. Note that within 10 mils of 

the defect center, the nitrogen concentration has dropped to less than 1 percent nitrogen. The 

ETC team was interested in understanding the concentration profile that determines whether 

there are significant ultrasonic impedance differences that will impact the inspection response. 

Based on the microprobe results and the need to understand the concentration profile, the 

decision was made to confine future microprobe analyses to line scans. 

.

.

.

.

. .

. .

. .

.

.

. . . . 8

1000 μm ~ 40mils

.

2

1

3

4

5

6

7

9 11 10

12

.

19 . 18

17

20

15 16 .

21

22

23

24

25

13

14

.

.

ETC Contaminated Billet Study - “Practice” Hard Alpha Titanium Defect

Optical image of defect. Numbers and arrows indicate approximate locations of point analyses and line scans.

Transverse No. 1 Transverse No. 2

Longitudinal

FIGURE 14. MICROPROBE MEASUREMENT POINTS FOR PRACTICE DEFECT 

In addition to arriving at the measurement process for microprobe analysis, a comparison of 

etchants was completed using the practice defect. A comparison was made to determine which 

etchant provided the best micrographs for hard alpha core/diffusion zone studies. Two etchants 

were compared, ammonium bifluoride and krolls etchant, as shown in figure 18. Note the more 

prominent indication of the diffusion zone in figure 18(a). Based on these results, the decision 

was made to use ammonium bifluoride in the defect characterization studies. 

18
TABLE 2. RESULTS OF POINT MICROPROBE MEASUREMENTS FOR 

PRACTICE DEFECT 

Point No. Titanium Aluminum Vanadium Oxygen Nitrogen 

0 (Center) 88.1 1.1 1.2 <0.1 8.6 

1 89.8 5.6 1.9 0.3 1.4 

2 89.6 6.9 2.0 0.3 0.6 

3 88.1 5.8 2.2 0.3 1.5 

4 86.9 5.2 2.0 0.3 2.1 

5 86.8 3.7 1.4 0.3 2.9 

6 86.6 5.9 1.7 0.3 1.3 

7 84.2 7.0 1.8 0.3 0.6 

8 85.1 5.6 1.8 0.3 2.0 

9 86.2 5.7 2.0 0.3 1.5 

10 85.2 5.9 1.7 0.3 0.9 

11 85.4 5.8 1.9 0.3 1.1 

12 89.2 6.7 1.6 0.3 0.7 

13 87.8 5.3 1.7 0.3 1.2 

14 88.6 4.9 2.0 0.3 1.3 

15 85.8 5.0 1.7 0.3 1.9 

16 86.3 4.9 1.8 0.3 1.5 

17 86.2 6.3 1.9 0.3 0.9 

18 84.3 6.4 1.8 0.3 0.9 

19 83.8 6.0 2.0 0.3 1.2 

20 85.2 7.1 1.6 0.3 0.3 

21 83.9 7.0 1.6 0.3 0.4 

22 84.8 6.7 1.7 0.3 0.4 

23 85.0 7.2 1.6 0.3 0.4 

24 83.2 7.3 1.7 0.3 0.5 

25 85.7 7.2 1.7 0.3 0.2 

All concentrations shown in weight percent. The location of the points is provided in figure 14.

19
LOCATION 

(mils) 

NITROGEN 

(weight %) 

 LOCATION 

(mils) 

NITROGEN 

(weight %) 

-50 0.3 0 7.3 

-50 0 1 4.3 

-45 0.3 1 3.3 

-40 0.1 2 1.9 

-40 0.2 2 2.6 

-35 0.3 3 1.9 

-35 0.2 4 1.0 

-30 0.5 4 1.1 

-30 0.4 5 1.3 

-25 0.1 5 1.6 

-25 0.5 6 0.8 

-20 0.6 6 0.8 

-20 0.1 7 1.0 

-15 0.8 8 1.2 

-15 0.8 8 0.9 

-10 1.0 10 1.1 

-10 0.8 10 0.7 

-8 1.3 11 0.8 

-6 1.3 15 0.7 

-5 0.7 15 0.7 

-5 1.2 20 0.7 

-3 3.4 20 0.8 

-3 1.0 25 0.3 

-2 5.5 25 0.1 

-1 5.9 30 0 

-1 2.8 35 0.1 

0 6.5 40 0.2 

 40 0.2 

 45 0.2 

 45 0.2 

 50 0.2 

 50 0.2 

B

B

B B

B B

B

BB

B

B B

B

BB

B

B

B B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

BB B

B

B

B

B B B B

B

B

B B B B BB B

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

-50 -40 -30 -20 -10 0 10 20 30 40 50

B NITROGEN

LOCATION (mils)

FIGURE 15. RESULTS FOR NITROGEN SCAN PERPENDICULAR (TRANSVERSE 1) TO 

THE LONG AXIS OF THE DEFECT WITH ZERO LOCATED AT THE DEFECT CORE 

(The location of the scan is provided in figure 14.) 

20
LOCATION 

(mils) 

NITROGEN 

(weight %) 

1 2.1 

2 1.2 

5 1.7 

7 0.9 

10 0.9 

15 0.6 

20 0.7 

25 0.8 

30 0.4 

35 0.8 

40 0.1 

45 0.1 

50 0.4 

60 0.7 

70 0.7 

80 0.6 

90 0.2 

100 0.2 

120 0.4 

140 0.8 

160 0.1 

200 0.2 

300 0.2 

B

B

B

B B

B

B

B

B

B

B B

B

B B

B

B B

B

B

B

B

0

0.5

1

1.5

2

2.5

0 50 100 150 200 250 300

B NITROGEN

LOCATION (mils)

FIGURE 16. RESULTS FOR NITROGEN SCAN PARALLEL TO THE LONG AXIS OF 

THE DEFECT WITH ZERO LOCATED AT THE END OF THE DEFECT CORE 

(The location of the scan is provided in figure 14.) 

21
B

B

B

B

B

B

B

B

B B

B B

B

B

B BB

B B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B B

B

B

B

B

B

B B

B

B

B

B

B

B

B

B B

B

B B

B

B

B BB

B

B

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

-50 -40 -30 -20 -10 0 10 20 30 40 50

B

LOCATION (mils)

OXYGEN

(a) 

BB B

B B

B

B B

B

B

B

B

B

B

B

B

B B

B

B B

B

B

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0 50 100 150 200 250 300

B

LOCATION (mils)

OXYGEN

(b) 

FIGURE 17. (a) RESULTS FOR OXYGEN SCAN PERPENDICULAR TO THE LONG AXIS 

(TRANSVERSE 1) OF THE DEFECT WITH ZERO LOCATED AT THE DEFECT CORE 

AND (b) RESULTS FOR OXYGEN SCAN PARALLEL TO THE LONG AXIS OF THE 

DEFECT WITH ZERO LOCATED AT THE END OF THE DEFECT CORE 

(The location of the scans is provided in figure 14.) 

22
(a)

(b)

FIGURE 18. RESULTS FOR (a) AMMONIUM BIFLUORIDE AND 

(b) KROLL’S ETCHANTS 

3. DISCUSSION OF RESULTS. 

3.1 INSPECTION OF THE CONTAMINATED HEAT. 

The full heat was inspected at the billet supplier in September 1995 using the conventional dualtransducer inspection and multizone inspection methods. Modifications to hardware and 

software were made to the multizone system to also enable digital data collection for the two 

conventional inspection methods (CL and CA). This allowed amplitude and SNR analysis using 

the same software as for the multizone data. Setup parameters are summarized in table 3. A 

summary of the number of indications found for each method, with the exception of phased 

array, is shown in the figure 19. Note that the metallurgical review criteria for conventional 

inspection implies that indications in the CBS inspection with an amplitude greater than 45% 

would require cutup to determine if the response was from a rejectable defect. Therefore, in the 

evaluation of this heat, any conventional signals with an amplitude greater than 45% were 

included as indications. 

23
TABLE 3. SUMMARY OF INSPECTION PARAMETERS FOR EACH OF THE 

INSPECTION METHODS 

Multizone 

Conventional Longitudinal 

(CL) 

Conventional Refracted 

Longitudinal 

(CA) 

Transducer 

description 

5-MHz, 

bicylindrical 

focused 

probes 

(4 zones) 

5-MHz cylindrically 

focused transducer element 

size 1′′ x 0.5′′ with an 

inspection water path of 

3.5′′ and a focal length of 8′′

5-MHz spherically 

focused transducer, 

diameter of 0.75′′ and 

water path of 3.5′′ 

Calibration #2 FBH #3 FBH 0.02′′ diameter hole 

Index per revolution 0.042′′ 0.042′′ 0.042′′

Rejection amplitude* 70% 70% 70% 

Rejection S/N 2.5 Signals greater than 3 dB 

above noise, but not less 

than 30% FSH, are subject 

to metallurgical review 

Signals greater than 3 

dB above noise, but not 

less than 30% FSH, are 

subject to metallurgical 

review 

*Inspection is set up such that response to calibration target, e.g., #2 or #3 flat-bottom hole (FBH), is equivalent to 

 80% full-screen height (FSH). Rejection occurs when signal response exceeds 70% FSH. 

Multizone

60 indications

Conv.

normal

Conv.

angle

4

19

8

4 additional

indications

FIGURE 19. VENN DIAGRAM SHOWING THE NUMBER OF INDICATIONS 

DETECTED PER INSPECTION METHOD 

24
The 12 CBS billets were previously inspected for the initial customer in November 1994, and the 

results were provided to the ETC as part of the purchase. In the initial inspection, precautions 

were not taken to prevent saturation of the ultrasonic signal. To enable capture of digital data 

using approved multizone and conventional inspection methods and to ensure that saturation of 

the signals did not occur, the complete heat was reinspected in September 1995. 

Billet maps were generated for each of the billets and were used in comparisons and to guide 

selection of indications for the various studies described in section 3. Figure 20 provides the 

inspection results for one of the billets as an example. The complete set is provided in 

appendix C. These maps summarize the inspection results for each of the billets. The billet ID 

is provided in the upper left corner of each sheet. Below this is a summary of results. In the first 

column, indications were identified alphabetically with the left most indication beginning with 

A. The second column lists the distance from the end of the billet. Indication depths are 

provided in the next six columns of figure 20 for each of the inspection times (September 1995 

and November 1994) and inspection methods (conventional normal, conventional longitudinal, 

multizone). Graphical representations, referred to as billet maps, provide the amplitude response 

and SNR for each of the indications, as was determined during each of the inspections. The SNR 

values quoted were computed in accordance with the multizone definition and calculated using 

digitally recorded C-scan data for both the multizone and conventional inspection methods. 

C-scan images were also generated for each of the indications and estimates made of the 

indication size. An example of the C-scan results is shown in figure 21. The billet ID and 

indication ID are listed (e.g., B3W3-B) along with the zone in which the indication was found. 

Inches from top indicates the axial location of the defect within the billet. The amplitude, SNR, 

and depth are tabulated from the billet maps (see figure 20). The axial and circumferential 

lengths were estimated using the indication sizes from the C-scan images. The estimates of the 

axial length were straight-forward. The estimates of the circumferential length were based on 

the formula x = 2πrθ, where θ was the circumferential extent of the image in pixels divided by 

the total number of pixels in a 360° revolution. No correction was made for the effects of beam 

size. 

The C-scan images were reviewed to select 10 representative defects for use in the 

metallographic cutups to support PoD studies. The initial review led to the characterization of 

the indications into three categories: low amplitude, small spatial extent; high amplitude, small 

spatial extent; and high amplitude, large spatial extent. The C-scan results for the indications 

selected for use in the metallographic studies are provided in appendix D. A summary of the 

PoD indications is provided in table 4. Defects were also selected by the TRMD program for use 

in forging studies. The results of that program are provided in separate reports [15 and 16]. 

25
B1AW1

September 1995 Inspection November 1994 Inspection

Multizone Conv. Normal Conv. Angle Multizone Conv. Normal Conv. Angle

Stamped I.D.Inches from top Depth Depth Depth Depth Depth Depth

A 3.3 0.2 0.3

B 25.9 0.6 0.6 0.6 0.5 0.5

C 66.4 1.6 1.8 1.6 1.6

D 92.7 1.7 1.8

E 95.2 0.6 0.6 0.7 0.5 0.5

Conventional Normal Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "C" 42%

1.91snr

Conventional Angle Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "B" 42%

2.62snr "C" 28%

1.85snr

 "E" 55%

4.44snr

Conventional Normal Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"B" 45% "E" 70%

Multizone Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "A" >100%

6.5snr "B">100%

4.8 snr "C" 95%

4.06snr "D" 62%

3.4snr

 "E" 89%

4.2snr

Conventional Angle Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"B" 70% "E" >100%

Additional indication reported on Nov 1994

Multizone, 12" from top, 0.94" deep,

amplitude 53%, 2.11 SNR (not rejectable)

Multizone Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"A" 190%

12.24snr "B" 201%

4.36 snr "C" 83%

5.47 snr "D" 73%

4.65 snr

"E" 127%

4.47 snr

Original billet 

length: 112.5"

FIGURE 20. EXAMPLE OF INSPECTION RESULTS FOR BILLET B1AW1 

(Results for all 12 billets are provided in appendix C.) 

26
Billet ID: B3We-B 

Zone: 1 

Inches from top: 51 

Amplitude 

(%) SNR 

Depth 

(in) 

Axial Length 

(in) 

Racial Length 

(in) 

Multizone 120 5.74 0.8 0.7152 0.2160 

Conventional 

Longitudinal 

50 2.39 1.0 

Conventional 

Angle 

60 4.37 1.0 

Billet Length: 124.5 

FIGURE 21. EXAMPLE OF C-SCAN USED IN SELECTION OF DEFECTS FOR 

FURTHER CHARACTERIZATION 

(The complete set of defects used in the metallographic studies is provided in appendix D.) 

27
TABLE 4. TABULATION OF THE TEN INDICATIONS SELECTED FOR DETAILED 

CHARACTERIZATION AND RECONSTRUCTION 

Inspection Results 

Sample Indication ID 

Multizone 

Amplitude 

SNR 

Conventional 

Longitudinal 

Amplitude 

SNR 

Conventional 

Angle 

Amplitude 

SNR 

Depth 

(inches)

PoD-1 B3W3-B MZ=120%, 5.74 CL=50%, 2.39 CA=60%, 4.37 0.8 

PoD-2 B1BW3-C MZ=127%, 6.67 CL=miss CA=miss 0.5 

PoD-3 B1BW3-D MZ=74%, 5.06 CL=miss CA=miss 1.5 

PoD-4 B1AW3-E MZ=47%, 2.52 CL=miss CA=miss 1.6 

PoD-5 B1AW3-D MZ=101%, 4.49 CL=miss CA=miss 1.1 

PoD-6 B1AW3-A MZ=142%, 5.02 CL=50%, 2.92 CA=60%, 2.48 0.7 

PoD-7 B2W2-C MZ=74%, 4.09 CL=miss CA=miss 0.2 

PoD-8 B1AW2-D MZ=134%, 5.46 CL=50% 2.61 CA=miss 0.7 

PoD-8X B1AW2-X* MZ=94%, 5.05 CL=miss CA=miss 0.5 

PoD-9 B1AW2-B MZ=225%, 21.7 CL=miss CA=miss 0.2 

*Indication B1AW2-X was found near the originally selected indication, B1AW2-D and further sectioned for 

evaluation completing the set of ten indications. 

Analysis of the inspection results included consideration of the amplitude and SNR. Figure 22 

shows the distribution of amplitude and SNR for the indications. Note that no correlation was 

found between the multizone response and the conventional inspection results, i.e., indications 

detected by the conventional methods occurred over the same range of amplitude and SNR as the 

multizone inspection results. However, as reported earlier, more indications were found with 

multizone than with the conventional detection methods. Analysis of the indication response as 

a function of depth is plotted in figure 23. Note that detections occurred for all three methods at 

all inspection depths. 

28
0

50

100

150

200

250

300

350

400

450

500

Amplitude

Multizone Amp (%)

Conv. Normal Amp (%)

Conv. Angle Amp (%)

0

5

10

15

20

25

30

SNR

Multizone SNR

Conv. Normal SNR

Conv. Angle SNR

FIGURE 22. DISTRIBUTION OF AMPLITUDE EXPRESSED AS %FSH (TOP) AND SNR 

RESULTS (BOTTOM) 

29
0

100

200

300

400

500

0123

Depth (inches)

Amplitude (%FSH)

Multizone

Conv. Normal

Conv. Angle

0

10

20

30

0 0.5 1 1.5 2 2.5

Depth (inches)

Signal to Noise Ratio

3

Multizone

Conv. Normal

Conv. Angle

FIGURE 23. AMPLITUDE (TOP) AND SNR (BOTTOM) 

RESULTS AS A FUNCTION OF DEPTH 

30
3.2 PHASED ARRAY INSPECTION OF THE CBS BILLETS.

As part of the ETC Phase I program, a feasibility study [8, 18, 19, and 20] of phased array 

ultrasonics was completed. This technology enables a single transducer, made up of discrete 

elements, to be focused electronically. The variable focusing capability allows zoned 

inspections to be performed on-the-fly. The original objectives were 

• to review the commercially available phased array equipment and identify a source for 

the evaluation process. 

• to evaluate the performance of the phased array transducer relative to conventional and 

multizone transducers. 

• to access feasibility for implementing a phased array approach in a production 

environment. 

The CBS material offered an excellent opportunity for a feasibility demonstration of the phased 

array approach. While the effort of this program provided a preliminary assessment, it was 

recognized that advances in system design, transducer design, and data analysis had occurred 

since the time of the work represented here. Nevertheless, these results provide an indication of 

the state of the technology in the mid 1990s. At the time of the program (1995), two phased 

array suppliers were identified with Structural Integrity Associates (SIA) selected to provide 

hardware and software for the feasibility study. The SIA phased array instrumentation is 

referred to as the Focussed Array Transducer System (FATS). The system has seven ultrasonic 

channels and is, therefore, limited to seven separate phased elements. This is sufficient for the 

simple annular array transducer designed for billet inspection. With advances in computational 

speed and capability, today’s phased array systems typically include 128 channels, which may 

offer further flexibility in optimizing billet inspection. Figure 24 depicts a conventional singlezone setup versus the phased array multiple-zone setup. The most obvious difference between 

the two zoned inspection approaches is the requirement for either one transducer (phased array) 

or multiple transducers located at several positions along the billet, as shown in figure 10. 

FIGURE 24. COMPARISON OF SINGLE-FOCUS TRANSDUCER (LEFT) AND 

PHASED ARRAY (RIGHT) 

(Note that phased array concept allows inspection at 

multiple depths using a single transducer.) 

31
Phased array technology involves using transducers with several (~5-7) elements to many (>100) 

elements. Each element has all the characteristics of a conventional single-element transducer 

except typically the shape. Conventional immersion transducers are typically circular with a flat, 

spherically or cylindrically focused face. Phased array transducers typically are configured in 

linear, annular, or two-dimensional (2D) configurations. Annular array transducers also come in 

one-dimensional (1D) and 2D forms. Though the focusing capability is axisymmetric for the 

simpler annular array, it is still considered a 1D array and is the approach evaluated in this 

program. Figure 25 depicts a simple annular transducer with seven concentric elements. 

Whereas a 2D annular may have five concentric rings, the rings themselves may be, for example, 

segmented into four segments for a total of 20 elements. More recent developments [21] have 

included specialized probes with up to 128 elements arranged as a sectorial annular array. This 

configuration will permit variable focusing and beam steering unlike the earlier 1D version 

evaluated in this program that only permitted variable focusing. The transducer was designed to 

operate at 5 MHz, the same frequency used in the conventional and multizone billet inspection. 

A 10-MHz center element was selected to provide improved near-surface resolution. 

Seven-Element 

Circular Array 

Transducer 

FIGURE 25. SEVEN-ELEMENT ANNULAR ARRAY DEVELOPED FOR 

THE CBS EVALUATION 

Phased array transducers are designed and fabricated similar to conventional transducers based 

on a desired characteristic resonant frequency and focusing requirements. The discretization of 

the transducer produces separate elements that respond independently. Controlling the 

excitation of the electronic delay (phasing) mechanism for the individual elements provides for 

the variable focusing capability. Typically, at least one dimension of the elements in the array is 

very small, resulting in a highly divergent beam characteristic for that direction. The phasing 

and integration of the individual beams from each element produce the resultant beam. The 

overall beam will have a natural focus like a conventional transducer. For some cases in which a 

concave lens is mounted on the face of the transducer, the transducer takes on a new focus due to 

the lens. This is referred to as the geometric focus, which defines where the transducer will 

focus when all the elements are in phase. 

32
The phasing process is implemented by controlling the timing of pulsing and receiving of each 

element relative to the other elements. By choosing the timing appropriately, the effective focus 

is either moved in or out relative to the geometric focus. Fundamentally, there is a maximum of 

a quarter wavelength limit relative to how much of a phase difference can be introduced between 

any two elements. For spherical focusing with an annular array transducer, the maximum delay 

would be between the center element and the outer most element. Note that all the elements are 

not typically used to create all the focal zones. Where possible, the elements are used to 

maintain a constant focal length/aperture ratio in an attempt to keep the beam spot size within the 

focal zones relatively constant. This leads to the observation, which is often confusing, that 

there is not a direct relationship between the number of elements and the number of focal zones. 

The phasing of the elements creates the focal zones, so the greater the control of phasing, the 

greater the number of focal zones. Another aspect of the ultrasonic inspection of contoured 

surfaces is the use of a mirror with a contour to counteract the distortion introduced by the 

inspection surface, i.e., the cylindrical surface of the billet. The mirror is designed for a specific 

curvature to produce a beam profile comparable to that of the beam going through a flat surface. 

Figure 26 shows the phased array billet inspection arrangement with the curvature-correcting 

mirror used in the ETC Phase I program. 

Holding fixture

Curvature correcting mirror

Sevenelement 

annular array

FIGURE 26. SETUP USED IN BILLET INSPECTION 

(Note mirror design is optimized for a given billet diameter extending the 

number of billet sizes for which a single transducer can be used.) 

A lens and mirror was designed to produce a zoning arrangement for the 6′′ diameter material, as 

described in table 5. Though the first and second zone do not have a -3 dB overlap, there is a 

-6 dB overlap and an SNR at this depth of about 25:1. Table 5 lists the zoning scheme and the 

elements involved in achieving the focal characteristics for each of the zones. 

33
TABLE 5. ZONING ARRANGEMENT FOR PHASED ARRAY INSPECTION OF 

CBS 6′′ DIAMETER BILLET 

Zone -6 dB -3 dB Center +3 dB +6 dB Elements 

1 0.1 0.2 0.4 0.9 1.2 1 

2 1.1 1.2 1.4 2.1 2.25 2-3 

3 1.45 1.55 1.9 2.2 2.4 2-4 

4 1.9 2.0 2.2 2.5 2.6 2-5 

5 2.2 2.3 2.7 3.3 3.5 2-6 

To enable C-scan data acquisition using FATS at supplier B, fixturing and cabling were 

fabricated. The fixturing was to adapt the FATS transducer to the ultrasonic tank bridge. The 

cabling interfaced with the existing encoders used by multizone for the purpose of data 

registration. A calibration standard specific to the FATS zoning scheme was also fabricated. 

The location and size of the zones in FATS are interrelated. This dependency is only a limitation 

of the FATS analog design and not phased array technology. A design with more control of the 

time delays promotes an ability to optimize the zoning arrangement. Other instruments are 

currently available using more flexible designs with digital capability. 

The primary interfacing issues were access to the encoder signals to generate C-scan data with 

position synchronization, hardware interfacing to the FATS transducer fixturing, and cable 

lengths and grounding. The cabling and grounding issues were not resolved during the first five 

billet scans (B1BW1, B1AW3, B2W3, B1BW3, and B2W2), therefore, analysis of this data was 

not possible. B3W1B, B1AW1, and B1AW2 were run next and a rescan was performed for 

B1BW1 from 36′′ to 84′′. B1AW1 and B1AW2 had to be run in two separate scans since the 

billets were too long to permit scanning with the shorter cable lengths and had to be turned endto-end to complete the scan. Amplitude and SNR were calculated for comparison to the 

multizone inspection results and are plotted in figure 27 with similar performance found between 

the two approaches. The data plotted in figure 27 is limited to zones 2 through 5 since zone 1 of 

the phased array transducer used the 10-MHz center element. A tabulation of the amplitude and 

SNR for the indications from the phased array inspection is provided in table 6. 

This preliminary evaluation suggests that phased array technology could be an alternate solution 

for the zoned billet inspection requirements, given the data in figure 27, with the following 

advantages noted: 

• Requires only a lens and mirror change for each billet diameter versus potentially a 

different set of transducers, reducing the overall cost. 

• Complexity of the fixturing is reduced significantly over multiple discrete transducers. 

• Setup is simpler since only one transducer is involved. 

Other factors such as capital equipment costs, system reliability, operator training, and 

equipment durability are unknown at this time. 

34
TABLE 6. SIGNAL TO NOISE AND AMPLITUDE DATA FROM 

PHASED ARRAY INSPECTION 

Billet ID Defect ID SNR 

Amplitude 

(%) 

Depth 

(inches) 

Position From Top 

(inches) 

B1AW1 A 4.3 56 0.2 3.3 

B1AW1 B 4.06 75 0.6 25.9 

B1AW1 C 12.53 179 1.6 66.4 

B1AW1 D 5.66 99 1.7 92.7 

B1AW1 E 3.07 76 0.6 95.2 

B1AW2 A 12.15 253 0.3 42.5 

B1AW2 B 5.93 101 0.2 72.0 

B1AW2 C 6.31 113 0.8 89.0 

B1AW2 D 5.4 94 0.7 98.0 

B1AW2 E 6.87 179 1.3 104.0 

B1AW2 F 4.5 142 1.1 114.4 

B1AW2 X 2.92 61 0.5 98.7 

B1AW3 A 3.82 69 0.7 60 

B1AW3 B 2.54 86 0.9 63 

B1AW3 C 11 357 1.5 79 

B1AW3 D 3.78 98 1.1 94.8 

B1AW3 E 2.06 47 1.6 106 

B1AW3 Y 3.24 99 1.3 77 

B1AW3 Z 3.47 90 1.3 81 

B1BW1 A 5.08 225 2.2 21.8 

B1BW1 B 10.12 179 1.7 28.5 

B1BW1 C 6.43 113 0.6 44.8 

B1BW1 D 4.22 94 1 49 

B1BW1 F 14.47 357 1.1 67.8 

B1BW1 G 6.68 142 1.5 81 

B1BW1 H 6.18 82 0.4 99.5 

B1BW3 A 3.24 94 1.3 22 

B1BW3 B 3.45 61 1.1 43.5 

B1BW3 C 5.66 73 0.5 66 

B1BW3 D 4.36 99 1.5 86 

B2W2 B 3.99 66 0.6 14 

B2W2 D 2.37 76 0.6 55 

B2W2 X 2.04 36 0.55 57 

B2W3 A 6.12 80 0.2 20.1 

B2W3 B 3.27 160 2.3 27.8 

B2W3 C 3.3 58 2 31 

B3W1B A 8.57 357 2 68.8 

B3W1B B 3.8 179 2.2 84.8 

B3W1B C 2.78 142 2.3 102.5 

B3W1B D 2.36 127 1.9 104.3 

Note: Not all billets were inspected with the phased array setup. 

35
FIGURE 27. COMPARISON OF AMPLITUDE (TOP) AND SNR (BOTTOM) FOR PHASED 

ARRAY AND MULTIZONE INSPECTION OF CBS BILLETS 

0

10

20

30

0 10 20 3

Multizone SNR

Phased array SN

0

R

0

10

20

30

0 10 20 3

Multizone SNR

Phased array SN

0

R

0

100

200

300

400

500

0 100 200 300 400 500

Multizone amplitude - %FSH

Phased array (FATS) amplitude - % FSH

0

100

200

300

400

500

0 100 200 300 400 500

Multizone amplitude - %FSH

3.3 DEFECT CHARACTERIZATION.

As listed in table 4, ten defects were selected for detailed characterization and reconstruction for 

use in PoD studies. Ultrasonic results from the billet supplier were reviewed to determine the 

location of the defect. Mults were sectioned from the billets such that the desired indication was 

positioned in the center of the mult, providing the needed material envelope to begin the 

ultrasonic characterization. The characterization process included a 5-MHz multizone zone 

inspection at the depth of the indication. The mult was then sectioned from the billet leaving a 

1.0′′ envelope of material surrounding the indication where possible. The sample containing the 

indication was referred to as the 3′′ cube. A 5-MHz scout inspection was done on the 3′′ cube to 

guide further sectioning. Only depth information was collected during this process. The 3′′ cube 

was then sectioned so that approximately 0.500′′ of material envelope surrounded the indication 

where possible. The sample containing the indication was referred to as the 1′′ cube. The 1′′

36
cube was then ultrasonically characterized with a 25-MHz, F10 transducer focused on the 

indication. The cube was scanned at a 0.010′′ index with a 100-MHz sampling rate, both C-scan 

and waveform data were collected. The process is depicted in figure 28. After completion of the 

ultrasonic characterization, the sample was shipped to the metallography team for sectioning, 

micrograph capture, and microprobe analysis. The results for the first indication are discussed in 

detail below with the results for all ten indications provided in appendix E. 

5 MHz Multizone

C-scan & waveform

data collected

Indication sectioned

from Mult. 1.0” envelope

surrounds indication

5 MHz inspection

depth information only

Indication sectioned 

from 3” cube. 0.5” envelope

surrounds indication

25 MHz characterization

of 1.0” cube. C-scan, waveform

and depth data collected. Cube

begins metallography process

Billet Serial

Number/

Side 5

Billet Serial

Number/

Side 5

Billet Serial

Number/

Side 5

6

5

4 2

Sides

5

4

6

2

Sides

5 MHz Multizone

C-scan & waveform

data collected

Indication sectioned

from Mult. 1.0” envelope

surrounds indication

5 MHz inspection

depth information only

Indication sectioned 

from 3” cube. 0.5” envelope

surrounds indication

25 MHz characterization

of 1.0” cube. C-scan, waveform

and depth data collected. Cube

begins metallography process

Billet Serial

Number/

Side 5

Billet Serial

Number/

Side 5

Billet Serial

Number/

Side 5

6

5

4 2

Sides

5

4

6

2

Sides

FIGURE 28. PROCESS USED FOR ULTRASONIC CHARACTERIZATION OF 

THE INDICATIONS 

The first of the indications came from billet B3W3. Indication B was sectioned from the billet at 

the axial position of 51.0′′. Initial characterization and sectioning was completed at GE with the 

results shown in figure 29. The sample was then shipped to ISU for detailed ultrasonic 

characterization. The results are shown for side 4 in figure 30. After completion of the 

ultrasonic measurements in the 1′′ cube, the samples were shipped to Pratt & Whitney for 

sectioning, capture of the digital micrographs, and microprobe analysis. For indication B3W3-B, 

21 sections were required to polish through the indication. The results for several of the slices 

are shown in figure 31. Four sections were selected as representative of the defect. The first 

section shows the initial occurrence of diffusion zone and serves as the section from which other 

sections are measured. In the third section, taken at 15 mils, the occurrence of voiding is noted 

with more expansive voiding present in the 60-mil section. The last section occurred at 95 mils 

and shows the last remnants of diffusion zone for this sample. Note that for the 60-mil section, 

over 35 micrographs were taken and digitally pasted to generate the montage shown in figure 31. 

In some of the more extended defects, the number of micrographs required to fully capture the 

defect in a given section plane exceeded 120, generating copious amounts of metallographic 

data. 

For indication B3W3-B, microprobe measurements were made after the fifth and eleventh 

sections and are provided in figures 32 and 33 respectively. Full tabulations of the data are 

provided in appendix E. Note that the concentration is highest in the core and drops rapidly 

away from the core. Even within the areas where the microstructure is distributed, i.e., area that 

would typically be classified as diffusion zone, the concentration is already at less than 1 wt% 

nitrogen. Given the narrow region over which the high nitrogen concentration occurs, the impact 

of the nitrogen on ultrasonic response is minimal (see related figure and discussion in section 

3.4). 

37
Mult inspection parameters: 

Transducer - 

Index - 0.010 

Data Acquisition Rate -0.010 

Inspection Sensitivity -#2 FBH at 80 - 90% in Titanium

Inspection Range -

Sampling Rate - 100 MHz 

Depth Axial Length Amplitude Signal-to-Noise Ratio

0.8 0.8 ” 127% 

25 MHz inspection parameters 

Transducer - 25 MHz, F10 - focal point positioned at indication depth

Index - 0.010 

Data Acquisition Rate -0.010 

Inspection sensitivity -

Inspection range -C - B-scan entire volume 

Sampling Rate - 200 MHz 

Side Depth Axial Length Amplitude % Sensitivity, dB

1 0.444′′ 0.8′′ 66 60

2 0.496′′ 0.8′′ 93 60

3 0.453′′ 0.8′′ 76 60

4 0.399′′ 0.8′′ 96 60

5 0.460′′ 0.8′′ 73 74

6 0.435′′ 0.8′′ 79 72

View is from Side 1, the side which 

was polished. Sides 5 and 6 represent 

the axial ends with Side 5 having the 

serial number. Sides 2 and 4 

represent the hoop direction (the 

circumferential plane) 

Side 6

Side 5

Side 4

Side 2

Mult inspection parameters: 

Transducer - Zone 1, 6′′ diameter, 5MHz 

Index - 0.010 

Data Acquisition Rate -0.010 

Inspection Sensitivity -#2 FBH at 80 - 90% in Titanium

Inspection Range -0.2′′ to 0.8′′

Sampling Rate - 100 MHz 

Depth Axial Length Amplitude Signal-to-Noise Ratio

0.8 0.8 ” 127% 5.7 

25 MHz inspection parameters 

Transducer - 25 MHz, F10 - focal point positioned at indication depth

Index - 0.010 

Data Acquisition Rate -0.010 

Inspection sensitivity -#2 FBH at 84% at 

Inspection range -C - scan , Between Front and Back/ 48d

Sampling Rate - 200 MHz 

Side Depth Axial Length Amplitude % Sensitivity, dB

1 66 60

2 93 60

3 76 60

4 96 60

5 73 74

6 79 72

View is from Side 1, the side which 

was polished. Sides 5 and 6 represent 

the axial ends with Side 5 having the 

serial number. Sides 2 and 4 

represent the hoop direction (the 

circumferential plane) 

Side 6

Side 5

Side 4

Side 2

Side 6

Side 5

Side 4

Side 2

FIGURE 29. ULTRASONIC CHARACTERIZATION FOR B3W3 INDICATION B Side 5 Side 6

ISU 5 MHz 51 by 171 @10 mils

GE 25 MHz 100 by 170 

Side 6

Side 5

FIGURE 30. ULTRASONIC CHARACTERIZATION AT CUBE STATE PRIOR TO 

METALLOGRAPHIC SECTIONING OF B3W3 INDICATION B 

(Results are shown for side 2 at 5 MHz (top) and 25 MHz (bottom).) 

38
90 mils – Twenty-first section

First section

15 mils – Third section

60 mils - Fourteenth section 

FIGURE 31. SELECTED METALLOGRAPHIC SECTIONS FOR SAMPLE B3W3-B 

(The montages shown here were generated from a series of 3′′ x 5′′ micrographs taken at 

100X magnification that were digitally pasted to form the image for the full indication.) 

B3W3 - B

0

2

4

6

8

10

-50 -40 -30 -20 -10 0 10 20 30 40 50

Distance (mils)

Wt% Nitrogen

Scan 1

Scan 2

Scan 3

Scan 1

Scan 2

Scan 3

FIGURE 32. MICROPROBE RESULTS FOR SECTION 5 

(APPROXIMATELY 20 mils) IN DEFECT B3W3-B 

(Three scans were made, as shown on the micrograph. The results are plotted for 

nitrogen concentration as a function of distance from the core. Note that the 

longitudinal scan (scan 3) extended away from the indication with nitrogen 

levels at nominal levels out to 400 mils (data not plotted past 50 mils).) 

39
Scan 1 Scan 2 Scan 3

B3W3 - B

0

2

4

6

8

10

12

-50 -40 -30 -20 -10 0 10 20 30 40 50

Distance (mils)

Wt% Nitrogen

Scan 1

Scan 2

Scan 3

FIGURE 33. MICROPROBE RESULTS FOR SECTION 11 

(APPROXIMATELY 65 mils) IN DEFECT B3W3-B 

(Three scans were made, as shown on the micrograph. The results are plotted for 

nitrogen concentration as a function of distance from the center of the core.) 

Complete defect characterization results for each of the ten indications is provided in appendix 

E. Specific highlights for each individual indication are provided in summary form to conclude 

appendix E. The defect characterization was completed with a dual purpose: (1) to improve the 

detailed understanding of hard alpha defects for use by metallurgists, life management, design, 

and inspection personnel and (2) to provide input into PoD calculations and, in particular, for use 

in model validation, as discussed in the following. 

3.4 GENERATION OF GEOMETRICAL DATA FOR USE IN PoD CALCULATIONS. 

PoD plays an important role in estimates of engine life, which requires an understanding of the 

relationship between detectability and flaw size. Many factors impact the detectability of a 

given flaw including the size, shape, and orientation of the flaw; the chemical composition of the 

defect; the location in the component (depth); and the geometry/part factors (curvature, surface 

finish), all of which should be taken into account in the design of the inspection. The efforts of 

this program were to provide basic knowledge to improve the detection of hard alpha by 

developing an understanding of the acoustic, physical, and chemical properties of hard alpha and 

incorporating those into PoD considerations. In meeting these objectives, the following steps 

were accomplished: 

• Quantify the ultrasonic response. 

• Quantify the defect descriptors, including the shape and distribution of voids, the general 

microstructural variations associated with core and diffusion zones, and the relationship 

of these to chemical composition. 

• Develop and verify a model for predicting the ultrasonic response in terms of defect 

descriptors. 

• Use this information to access and improve detection reliability. 

40
In the past, PoD studies normally required statistical analysis of large amounts of experimental 

data. However, the rare occurrence of naturally occurring hard alpha defects and the difficulty 

of manufacturing realistic synthetic flaws have made data acquisition very difficult. To get 

around this obstacle, a new approach has recently emerged using ultrasonic models to accurately 

calculate the flaw responses. These require, as input parameters, geometrical models containing 

the spatial and material descriptions of the flaws. By using models in this way, one was able to 

examine the effect of flaw morphology on the ultrasonic signals in a reasonable time frame and 

to extract a more extensive knowledge base from the limited naturally occurring flaws. In 

addition, a variety of inspection scenarios can be simulated rapidly to generate the necessary data 

for PoD evaluation. The efforts of the ETC Phase I program advanced this new approach with 

the CBS providing an unprecedented opportunity to gain extensive knowledge on naturally 

occurring hard alpha defects. As was previously stated, ten of the indications were chosen as 

representative sample defects for these studies, and various experimental data have been 

obtained by ultrasonic, metallurgical, and chemical analyses to determine the detailed 

morphology and composition of these defects. 

During the early stages of the CBS, it was assumed that the ultrasonic response of the hard alpha 

defect came from the whole hard alpha region consisting of diffusion zone, hard alpha nuggets, 

and the void/crack components. Effort was focused on improving the capability in geometric 

and ultrasonic modeling for the entire hard alpha defect, including each of the subregions. A 

number of software building blocks were developed [22 and 23]. Based on metallographic data 

of real hard alpha defects, solid geometric models of subregions treated initially as if they had 

uniform acoustic properties were developed. Various methods to determine and extract the flaw 

boundary on the metallographs were also developed (see appendix F). The ultrasonic response 

was derived from the Thompson-Gray measurement model framework using the Born 

Approximation [24]. The Born inclusion model was thoroughly tested using output of the solid 

models and several data sets of synthetic hard alpha inclusions of known size and properties [22 

and 24]. 

As results of the microprobe/chemical analyses became available during the program, ETC 

gained a much better understanding of the microstructures of the hard alpha defects. The 

microprobe/chemical analyses revealed that the nitrogen concentrations are only high in thin 

layers up to approximately 10 mils around the void components of the hard alpha defects (see 

figures 32 and 33). At the edges of these regions, there is a sharp transition to much lower 

levels, characteristic of the diffusion zone. This localized nitrogen concentration led to a profile 

of acoustic properties that peaks around the void boundary and rapidly decreases to the baseline 

of the normal titanium moving away from the voids. This has important ultrasonic implications. 

It is well known that regions of slowly varying acoustic properties produce only weak ultrasonic 

signals, whereas sharp boundaries produce strong signals. Since rapid changes only occur near 

the voids, this suggests that the voids and the near-void region in which nitrogen is high, will 

produce the majority of the ultrasonic response. Based on this finding, a new material model 

was developed to estimate the acoustic properties throughout the titanium alloys, including the 

hard alpha regions [25]. The essential feature of that work was the study of the effects of hard 

alpha layers, i.e., the core and diffusion zones, on the ultrasonic responses in the presence and 

absence of voids/cracks. The major results of that study are summarized in the following 

paragraph. 

41
To obtain an accurate benchmark to test the Born inclusion model for such nonuniform property 

profiles, an exact solution for a spherical-shaped inclusion with varying properties was derived 

from the classic Ying-Truell result [26]. For a spherical hard alpha inclusion, this new exact 

solution approximates the nonuniform material profile piecewise by a number of concentric 

spherical shells of uniform properties. The simulation result showed that the contribution of 

these thin layers to the total ultrasonic response of the hard alpha defects, compared with those 

from the void components, is insignificant. Figure 34 compares the peak amplitudes of the 

inclusion and void, with or without the hard alpha shell, for different inclusion diameters 

(in terms of FBH numbers). For either inclusion or void, the amplitudes only change slightly 

with hard alpha shells included. Based on this study, effort was focused only on the void 

components in the subsequent modeling work. In the geometric model development, this shifted 

attention from the earlier solid models of full hard alpha regions to the surface models of the 

void components. However, it should be pointed out that the basic theory of nonuniform rational 

b-splines (NURBS) developed in the solid model case still hold for the newer surface model 

(see appendix G). 

0.00E+00

1.00E-03

2.00E-03

3.00E-03

4.00E-03

5.00E-03

6.00E-03

0 1 2 3 4 5 6 7 8 9 10 11

Flaw Diameter in FBH Number (#1=1/64 in.)

Peak-Peak Amplitude

inclusion wl h-a shell

void wl 30mils h-a shell

inclusion wlout h-a shell

void wl out h-a shell

void wl stretched 90mils h-a

shell

FIGURE 34. PEAK AMPLITUDES OF INCLUSION AND VOID WITH AND WITHOUT 

THE HARD ALPHA SHELLS FOR DIFFERENT INCLUSION DIAMETERS 

3.4.1 Geometrical Modeling. 

To generate the necessary flaw surface data for each of the ten hard alpha defects, a multistep 

process was required. Here, defect B1AW2-X is used as an example to illustrate the various 

steps. Detailed results of the other nine defects are provided in appendix E. To obtain the 

necessary information from the hard alpha defects for geometrical reconstruction, the exact 

locations of the defects in the billets were first identified ultrasonically. As detailed previously, 

small blocks of 1- to 2-inch dimensions containing these defects were then cut from the billets, 

followed by both 5-MHz and high-frequency ultrasonic scans taken from each of the six sides. 

42
These scans included volumetric A-scans and C-scans, which will be compared later with the 

ultrasonic model predictions. Prior to the destructive sectioning, on the two opposite sides of the 

cube block along the original billet axial direction, microscopic fiducial marks were drilled into 

the cube block parallel to the sectioning direction. These fiducial marks served as the common 

alignment reference for later stack up of the metallographs for reconstruction. The sectioning 

process was carried out by successive polishing of the block surface at small increments from 2 

to 10 mils. After each polishing session, the cross sections were photographed through an 

optical microscope to form the metallographs. Next, the metallographs were realigned by using 

the fiducial marks and other features on the metallographs. These submetallographs provided 

the main data bases for building the geometrical models. Figure 35 shows polishes 8-13 of the 

realigned and reduced cross-section images used to reconstruct defect B1AW2-X, depicting the 

complicated geometry of the void structures. Figure 36 illustrates the orientation and stack-up 

sequence of these metallographic images. 

Polish 11

Polish 10

Polish 9

Polish 8

Polish 12

Polish 13

R

L S1 S2

R

R

R

R

R

L

L

L

L

L

L

S2

Polish 11

Polish 10

Polish 9

Polish 8

Polish 12

Polish 13

R

L S1 S2

R

R

R

R

R

L

L

L

L

L

L

S2

FIGURE 35. POLISHES 8-13 OF THE REALIGNED AND REDUCED CROSS-SECTION 

IMAGES USED TO RECONSTRUCT DEFECT B1AW2-X 

(Each image is of 256 gray-scale level, 1000(H) by 500(V) pixels in size. 

The dimension scale is 135 pixels = 10 mils.) 

Y

Z

Polish 8

Polish 13

X

Polish 8

Polish 9

stack-up sequence

(polish in from side 2 of the cube)

Y

Z

Polish 8

Polish 13

X

Polish 9

stack-up sequence

(polish in from side 2 of the cube)

Polish 8

FIGURE 36. STACKING ORIENTATION OF THE METALLOGRAPHS OF 

HARD ALPHA DEFECT B1AW2-X 

43
The most important step of the process is to identify the void parts and to determine their 

connectivities, i.e., the blue prints showing how corresponding void cross-section boundaries on 

adjacent metallographs are connected. The labels associated with each void cross section (L, R, 

S1, and S2) in figure 36 are the simplest connections among the ten selected hard alpha defects. 

Figure 37 shows an example of one of the more complicated voiding structures from defect 

B1BW3-C. The connectivity trees shown in figures 36 and 37 were generated for each of the ten 

defects. 

B1BW3-C Connectivity Tree 

Using Re-Aligned Sub-Micrographs

10

9

7

29

17

14/10.0........43........ 7..

12/9.0...........38...26.27.

34

7

7

8

12

14

17(71)

15

10/8.0 ..........31... 13

18(75)

08/7.0...........24.......

8

09/7.1..........28.....................................11................................15(62).........................................................19(80)..............20(85)21(88)22(91)23(94)24(98)

07/6.1...........22.............................................. 7(cover 11-14)

........................... ....11(47)12(50)......13(53)14(56)

9 6 10

11 12

13 14

7

(covers 13)

8

9 6 10 19

20

21

22

23

25(102)

24 26(106)27(109)

11/8.1...........35........................28(112)............................................29(118)........................................... .................30(121)...6...10...20. 21.22. . 25..26 27 ..............................................................................................................................31(124;cover 6,10) 32(128;cover 20-22) 

..............................................................................................................................................................................................33(132;cover 26-27)

14

15

16(67)

16

8 19 18

30 28

13/9.1..........40............................... 34(135) .............................29...................................35(140).......................30...........................23. 24. 25 ...33

9 31 32 23 24

25

33

28

14

15

16

8 31 32

17

35 19 9 18

10

9

7

29

17

14/10.0........43........ 7..

12/9.0...........38...26.27.

34

7

7

8

12

14

17(71)

15

10/8.0 ..........31... 13

18(75)

08/7.0...........24.......

8

09/7.1..........28.....................................11................................15(62).........................................................19(80)..............20(85)21(88)22(91)23(94)24(98)

07/6.1...........22.............................................. 7(cover 11-14)

........................... ....11(47)12(50)......13(53)14(56)

9 6 10

11 12

13 14

7

(covers 13)

8

9 6 10 19

20

21

22

23

25(102)

24 26(106)27(109)

11/8.1...........35........................28(112)............................................29(118)........................................... .................30(121)...6...10...20. 21.22. . 25..26 27 ..............................................................................................................................31(124;cover 6,10) 32(128;cover 20-22) 

..............................................................................................................................................................................................33(132;cover 26-27)

14

15

16(67)

16

8 19 18

30 28

13/9.1..........40............................... 34(135) .............................29...................................35(140).......................30...........................23. 24. 25 ...33

9 31 32 23 24

25

33

28

14

15

16

8 31 32

17

35 19 9 18

FIGURE 37. EXAMPLE OF MORE COMPLICATED VOID CONNECTIONS 

(Results are shown for slices 7 through 10 of indication B1BW3-C. Numbers used 

to track voids between slices are shown in yellow.) 

The other important step is to accurately and efficiently determine the enormous number of 

boundaries from these void cross sections. To automate this step, several edge detection 

techniques were applied from image-processing tools, including the regional growth technique 

discussed in appendix F. However, none of these techniques were found to adequately handle 

the complexity of the void boundary structures. Therefore, it was decided that tracing the 

boundary manually by using a screen locator was the most suitable method for this task. 

Before the 3D surface models of the void parts could be reconstructed, all cross-section 

boundary traces of each void part must be parameterized. Using the manually traced data as 

input, this parameterization involved 2D interpolation of these cross-section boundaries using 

the NURBS technique. Figure 38 compares several boundary trace projections of the right void 

44
of B1AW2-X, showing both the manually traced and the NURBS interpolated data. It is seen 

that NURBS works very well in tracking the rather complicated manually traced boundaries. 

Using the connectivity plan (figure 36) and the parameterized 2D cross-section boundary data 

(figure 38), the 3D surface model of a void part can then be built by interpolating the 

corresponding points on all cross-section boundary traces of the same void part. (See appendix F 

for details.) Three angle views of the 3D surface model for defect B1AW2-X are shown in 

figures 39 and 40, showing its physical dimensions. 

120

140

160

180

200

220

240

260

280

300

320

500 550 600 650 700 750 800 850

X in pixels

Y in pixels

NURB pol 8 R

raw pol 8 R

NURB pol 9 R 

raw pol 9 R

NURB pol 10 R

raw pol 10 R

NURB pol 11 R

raw pol 11 R

URB pol 12 R

raw pol 12 R

NURB pol 12.5 R

raw pol 12.5 R

R

Polish 9

120

140

160

180

200

220

240

260

280

300

320

500 550 600 650 700 750 800 850

X in pixels

Y in pixels

NURB pol 8 R

raw pol 8 R

NURB pol 9 R 

raw pol 9 R

NURB pol 10 R

raw pol 10 R

NURB pol 11 R

raw pol 11 R

URB pol 12 R

raw pol 12 R

120

140

160

180

200

220

240

260

280

300

320

500 550 600 650 700 750 800 850

X in pixels

Y in pixels

NURB pol 8 R

raw pol 8 R

NURB pol 9 R 

raw pol 9 R

NURB pol 10 R

raw pol 10 R

NURB pol 11 R

raw pol 11 R

URB pol 12 R

raw pol 12 R

NURB pol 12.5 R

raw pol 12.5 R

R

Polish 9

FIGURE 38. RAW VS NURB VOID BOUNDARY TRACE PROJECTION: RIGHT 

VOID OF B1AW2-X 

In this particular model, 3702 spatial coordinate points were used to construct 7388 triangular 

facets on the discrete defect surface. The size of the defect is about 52 x 18 x 34 mils, with the 

52-mil dimension at a slight tilt from the original billet axis. The size of the triangular facets 

was maintained around one-tenth of the ultrasonic wavelength at the upper quarter of the 

frequency spectrum. This size ratio was selected to ensure the convergence of the ultrasonic 

model calculations. 

45
Y 

Z 

X 

FIGURE 39. THREE ANGLE VIEWS OF THE SURFACE MODEL FOR 

DEFECT B1AW2-X 

34 mils 

(Z)

52 mils (X) 

(X)

FIGURE 40. ACTUAL DIMENSIONS OF DEFECT B1AW2-X 

(The dimension in Y direction is 18 mils.) 

To construct a geometric surface of an irregular shape that is representative of a typical hard 

alpha defect, cross-section boundaries of the defect must be available in adjacent micrographs. 

When this requirement was not met, supplemental boundary patches were derived from 

neighboring micrographs. Every identifiable void cross section, shown as a dark area in the 

micrograph, is numbered on each micrograph for use in the reconstruction. The other situation 

in which patches are needed is when extreme shape change occurs between two adjacent 

boundary cross sections. The middle ground patches make the transition of the shape change 

smoother so that a geometrically feasible model can be constructed. Polish 12.5 in figure 38 

depicts one such example. Many other patches were used in much more complicated connective 

structure of the other hard alpha defect reconstructions (appendix F). 

46
3.4.2 Ultrasonic Modeling. 

In this section, the ultrasonic modeling results of defect B1AW2-X are described using a 

multifacet Kirchhoff model. For details of this and other ultrasonic models, the reader is referred 

to appendix G. 

After the geometrical surface model consisting of multiple triangular facets was created as 

described above, a global beam tracking routine needs to be performed so that proper coordinate 

information of the illuminated defect surface can be provided to the ultrasonic models. Given an 

origin source (beam), the objective was to determine which facets on the surface of the model 

would be illuminated with how much incident amplitude, the area covered by the source (beam 

radius), and the direction in which the beam is propagating. This was done by using a forward 

ray-tracing technique. Figure 41 demonstrates the beam-tracking analysis completed on a void, 

where the beam coverage (size) of the flaw, as indicated by the central white region, was reduced 

for purposes of illustration. 

FIGURE 41. EXAMPLE OF FLAW ILLUMINATION BY ULTRASONIC BEAM 

The illuminated geometric information then serves as input to the ultrasonic model to calculate 

the flaw signals. As described previously, the morphology of hard alpha defects is complicated. 

Exact models capable of predicting the ultrasonic responses of real defects with such complexity 

are not available. If exact models were available, current technology does not provide sufficient 

and accurate morphological data. Thus, modeling efforts were focused on the use of 

approximations to reduce the complexity. An approximate ultrasonic model using the highfrequency Kirchhoff approximation has proven to be successful for modeling hard alpha defects 

[23]. The Kirchhoff model is particularly suitable for making use of the multifaceted data of the 

defect surfaces provided by the geometric model. Following previous ultrasonic model 

development [24 and 27], the new void model was also derived from the Thompson-Gray 

measurement framework [28] and the Auld’s reciprocity formulation [29]. The unique feature 

of this approach was that radio frequency waveforms (A-scans) were calculated directly and can 

be compared with the actual measurement on an absolute level. Figure 42 shows the coordinate 

system defining the orientation of the cube containing the defect, and figure 43 displays the 

C-scan comparisons between the model and experiment for defect B1AW2-X. It can be seen 

that the agreement in both peak amplitude and image shape are very good with the largest 

difference only being 5.7 dB. 

47
X

Z

Side 2 (front)

Side 1 (top)

Side 5 

(right)

Y

Side 3 (bottom)

Side 6 

(left)

Side 4 (back)

X

Z

Side 2 (front)

Side 1 (top)

Side 5 

(right)

Y

Side 3 (bottom)

Side 6 

(left)

Side 4 (back)

FIGURE 42. BLOCK ORIENTATION FOR EXPERIMENTAL 

ULTRASONIC MEASUREMENTS 

(Sides 5 and 6 are in the billet axial direction. Sides 1 and 3 are 

in the original direction of billet (beam) inspection.) 

Side 1

Model Experiment

31(H) x 31(V) @10 mils, 6dB

peak amplitude @6dB=398 mv

deviation=-11% or -1.0 dB 

100(H) x 30(V) @10 mils, 6dB

peak amplitude @6dB=448 mv

Side 2

31(H) x 31(V) @10 mils, 0dB

peak amplitude @0dB=498 mv

deviation=94% or 5.7 dB 

100(H) x 30(V) @10 mils, 0dB

peak amplitude @0dB=257 mv

Side 3

31(H) x 31(V) @10 mils, 6dB

peak amplitude @6dB=461 mv

deviation=-7.2% or -0.6 dB 

100(H) x 30(V) @10 mils, 6dB

peak amplitude @6dB=430 mv

Side 4

31(H) x 31(V) @10 mils, 0dB

peak amplitude @0dB=175 mv

deviation=-29% or -2.9 dB 

100(H) x 30(V) @10 mils, 0dB

peak amplitude @0dB=244 mv

100(H) x 30(V) @10 mils, 0dB

peak amplitude@0dB = 374 mv

31(H) x 31(V) @10 mils, 0dB

peak amplitude@0dB = 309 mv

deviation=-17% or -1.7 dB

Side 5

100(H) x 30(V) @10 mils, 0dB

peak amplitude@0dB = 450 mv

31(H) x 31(V) @10 mils, 0dB

peak amplitude@0dB = 403 mv

deviation=-10% or -1.0 dB

Side 6

Side 1

Model Experiment

31(H) x 31(V) @10 mils, 6dB

peak amplitude @6dB=398 mv

deviation=-11% or -1.0 dB 

100(H) x 30(V) @10 mils, 6dB

peak amplitude @6dB=448 mv

Side 2

31(H) x 31(V) @10 mils, 0dB

peak amplitude @0dB=498 mv

deviation=94% or 5.7 dB 

100(H) x 30(V) @10 mils, 0dB

peak amplitude @0dB=257 mv

Side 3

31(H) x 31(V) @10 mils, 6dB

peak amplitude @6dB=461 mv

deviation=-7.2% or -0.6 dB 

100(H) x 30(V) @10 mils, 6dB

peak amplitude @6dB=430 mv

Side 4

31(H) x 31(V) @10 mils, 0dB

peak amplitude @0dB=175 mv

deviation=-29% or -2.9 dB 

100(H) x 30(V) @10 mils, 0dB

peak amplitude @0dB=244 mv

100(H) x 30(V) @10 mils, 0dB

peak amplitude@0dB = 374 mv

31(H) x 31(V) @10 mils, 0dB

peak amplitude@0dB = 309 mv

deviation=-17% or -1.7 dB

Side 5

100(H) x 30(V) @10 mils, 0dB

peak amplitude@0dB = 450 mv

31(H) x 31(V) @10 mils, 0dB

peak amplitude@0dB = 403 mv

deviation=-10% or -1.0 dB

Side 6

FIGURE 43. COMPARISON OF ULTRASONIC C-SCAN RESULTS, 

MODEL AND EXPERIMENT 

48
3.4.3 Error Analyses. 

As described in section 3.4, the characterization and modeling of each of the hard alpha defects 

is a multistep process. There are at least five potentially significant error sources that occur in 

the process. 

• Ultrasonic measurement error may occur during ultrasonic data acquisition from the 

blocks. Even in a carefully controlled laboratory setting, a 10% daily fluctuation (0.8 

dB) in the measurement is not unusual. 

• The procedure for sectioning and capturing micrographs, material pullout, nonuniform 

etching, and insufficient light exposure can lead to incorrect interpretation of the crosssection images and lead to micrograph production error. 

• Micrograph alignment errors are introduced when spatial registrations of information 

from successive sections with respect to a common reference cannot be maintained. In 

some cases, severe misalignments in the raw data of more than one gross size of the 

defect were experienced, and corrections had to be made in the reconstruction. 

• Discretization error of the geometric model arises due to the sparse spacing between the 

micrographs. Although the spacing of 5 mils is the smallest currently affordable, it 

implies a resolution in the polishing direction that is 30 times worse than that of the 

micrograph image. In fact, rapid shape changes in a defect’s cross-section boundary 

were often observed from neighboring micrographs. It is evident that important 

geometric information on these shape changes has been lost in most cases. 

• Ultrasonic model error exists in both theory and numerical implementation. Other than 

the approximation made in the model, the omission of the hard alpha layer can cause 

additional deviations. 

Geometric and ultrasonic modeling were completed for all ten hard alpha defects selected for 

detailed analysis, namely, B3W3-B, B1BW3-C, B1BW3-D, B1AW3-E, B1AW3-D, B1AW3-A, 

B2W2-C, B1AW2-D, and B1AW2-B, of which some results have been presented in references 

22, 23, and 27. The shape and size of these hard alpha defects differ widely from each other, 

ranging from a large elongated cigar shape (B1BW3-C) of size 1404 (axial) by 171 by 59 mils to 

a small four-piece pancake (B1AW2-X) of size 52 by 18 by 34 mils. 

An error analysis of the model results was performed over the five major error sources identified 

above. Since a statistical flaw rejection is based on peak amplitude thresholding, the main 

assessment focused on the accuracy of model peak amplitude in the C-scan images. The other 

important indicator is the degree of matching of the C-scan image shape between the experiment 

and model. As a first cut, the degree of C-scan matching was determined from the amplitudes at 

peak position and two sets of four neighboring positions in the scan grid at 40 and 80 mils offset, 

respectively. 

49
It is interesting to see that the model predictions for inspections from sides 2 and 4, whose planes 

are parallel to the micrograph planes, seem to have larger errors than those with incidence 

through the perpendicular sides 1, 3, 5, and 6, as illustrated in figure 44, for the cases of defect 

B1AW2-X. This was largely due to the lack of information in between the sparse micrograph 

data and the possible misalignment of the micrographs. The lack of information is particularly 

problematic, given that the exact starting and ending locations and shapes of a single defect or 

defect branches were usually unknown, and would have to be deduced from the nearest 

micrographs. At these defect locations, the construction algorithms of the geometric model 

tended to conservatively create flat plateaus that cause the ultrasonic model to predict incorrect 

specular responses. These structural plateaus are clearly depicted in figure 45 from the 

geometric model of defect B2W2-C. It should be emphasized, however, that these difficulties do 

not occur for the insonification through side 1, corresponding to the actual (radial) inspection 

direction in the billet. Indeed, that was one of the motivations in determining the orientation of 

the polishing direction, as shown in figure 12. 

Scan Sides of Cube Block

20*log(Model Vpp/Exp Vpp)

-10 -5 0 5 10

Side 1 Side 3 Side 2 Side 4 Side 5 Side 6

0 offset (peak)

40 mils offset

80 mils offset

FIGURE 44. DECIBEL AMPLITUDE ERRORS AT 0- (PEAK), 40-, AND 80-mil SCAN 

OFFSET FOR ALL SIX SIDES OF DEFECT B1AW2-X 

Cross-section micrograph planes

FIGURE 45. STRUCTURAL PLATEAUS IN DEFECT B2W2-C’S GEOMETRIC MODEL 

50
In most cases, the model error increases with the defect cross-section area (figure 46). This 

appears to be the accumulated effect of the geometric model errors, which in turn originated 

from the insufficient micrograph data. Similarly, the size of model deviations increases with the 

scan offset from the peak position, as shown in figure 47. This is an indication of C-scan image 

mismatch. The boxes in figure 47 indicate the position of the middle 50% of the data, and the 

line inside the box is the median of the responses. The whiskers show the range of the data, 

except for one extreme outlier, which is shown as a short horizontal line. When restricting 

attention to the experimental data in the original billet scan direction, the accuracy of the 

combined geometric and ultrasonic models is very much in line with variability found in current 

industrial inspection. This is evident from the upper graph in figure 48, which shows that in the 

optimal direction, except for one minor exception, the model deviations of the peak amplitudes 

in the original billet inspection directions are all within ±6 dB bounds. This is typical of ranges 

of ultrasonic field reproducibility, but twice the described reproducibility range of ±3 dB. In 

fact, as figure 49 shows, more than 50% of the deviations of the peak are well below 3 dB, well 

above the expectation. Data is also provided for the nonoptimal direction, i.e., the direction in 

which more variability exists from the metallographic reconstruction process. Even in this case, 

agreement is still reasonable, as shown in the lower portion of figure 48. 

DB error vs.log(area) for offset distance=0

log(Area)

20*log(Model Predicted Vpp/Experiment Vpp

6 81 7 90 1 1 1 2

-15 -10 -5 0 5 10 15 20 25 30

B3W3-B

B1BW3-C

B1BW3-D

B1AW3-E

B1AW3-D

B1AW3-A

B2W2-C

B1AW2-D

B1AW2-B

B1AW2-X

regression line

0 line

DB error vs.log(area) for offset distance=0

log(Area)

20*log(Model Predicted Vpp/Experiment Vpp

6 81 7 90 1 1 1 2

-15 -10 -5 0 5 10 15 20 25 30

B3W3-B

B1BW3-C

B1BW3-D

B1AW3-E

B1AW3-D

B1AW3-A

B2W2-C

B1AW2-D

B1AW2-B

B1AW2-X

regression line

0 line

FIGURE 46. COMPARISON BETWEEN MODEL AND EXPERIMENT: dB ERROR OF 

PEAK AMPLITUDE VS LOG OF PROJECTED FLAW AREA 

51
-10 0 10 20

0 40 80

Offset Distance in mils

20*log(Model Vpp/Exp Vpp)

25%

50%

75%

FIGURE 47. DECIBEL MODEL ERRORS VS THE SCAN OFFSETS FOR CASES 

OF FIVE DEFECTS 

(This is a graphical depiction of the errors with 50% of the points falling within the green area.) 

-8

-6

-4

-2

0

2

4

6

8

B3W3-B B1BW3-C B1BW3-D B1AW3-E B1AW3-D B1AW3-A B2W2-C B1AW2-D B1AW2-X

Billet ID

Model Deviation in dB -4.00

0.00

4.00

8.00

12.00

16.00

B3W3-B B1BW3-C B1BW3-D B1AW3-E B1AW3-A B2W2-C B1AW2-D B1AW2-B B1AW2-X

Billet ID

Model Deviation in dB

FIGURE 48. DISTRIBUTION OF dB MODEL ERRORS OF PEAK AMPLITUDES IN THE 

OPTIMAL ORIENTATION 

(Original billet scan direction; sides 1 and 3 shown in upper plot. 

Distribution of dB model errors of peak amplitudes in the nonoptimal orientation 

(orthogonal to original billet scan direction; sides 2 and 4) shown in lower plot.) 

52
53

41

6

0

10

20

30

40

50

60

< 3 dB 3-6 dB > 6 dB

Model Deviation Range in dB

Proportion in Percentage

FIGURE 49. SUMMARY OF dB MODEL ERRORS OF PEAK AMPLITUDES IN OPTIMAL 

ORIENTATION (Original billet scan direction; sides 1 and 3) 

3.5 UTILIZATION OF DATA FOR PoD ANALYSIS. 

Improving knowledge of PoD was a major motivation for the CBS, as was discussed in 

section 1.1. The data described in this report significantly expands the information upon which 

PoD estimates can be made, particularly in light of the fact that the CBS provided the highest 

fidelity data available defining the responses of naturally occurring hard alpha inclusions. 

Significant efforts have been made to estimate PoD from this data. However, a number of 

complexities have been encountered during the analysis, which indicate that traditional 

techniques are not appropriate for the analysis of this data [30]. Alternate approaches for PoD 

analysis of the data are being developed. The results of the PoD analysis will be issued in a 

separate report. 

3.6 NOISE ANALYSIS STUDIES. 

A key element in the detection of a defect is the SNR, which was the focus of a short study 

within the CBS program. The purpose of this study was to gain a better understanding of the 

physical phenomena that control noise levels—information that could be used to guide future 

efforts to modify processing to reduce noise. An 11′′ section of billet, B3W3, was characterized 

for further sectioning and study [31 and 32]. A multizone transducer (serial no. 015261; 5 MHz, 

1′′ diameter, focused 1.55′′ deep in a 6′′ billet at a 3′′ water path) and a Sonix scanner with a 

rotating turntable were used for the initial characterization. The inspection water path was 3′′, 

and three time gates were set, each having a duration of 4 microseconds. These gates were 

centered 8.2, 16.4, and 24.6 microseconds after the onset of the front surface echo, respectively, 

so they were centered about 1′′, 2′′, and 3′′ deep in the billet. The C-scan images in figure 50 

display the gated-peak noise voltage at each point in the scan for the three time gates. Red is 

53
high voltage, blue/violet is low voltage, with dark red coloration indicating that the voltage takes 

up 100% of the vertical oscilloscope scale (with no distance amplitude corrections for focusing). 

Since the third time gate is well beyond the focal zone, all noise values there are well below 

100%, and no red colors are seen in the third image. The horizontal axis is a rotation angle from 

0o to 360o (or, equivalently, 18.8′′ of length along the billet circumference), and the vertical axis 

is 11′′ of travel along the billet axis. The vertical dimension has been stretched so that in the 

image, the 18.8′′ (horizontal) circumferential length and the 11′′ (vertical) axial length are about 

in the proper proportion at the billet surface. Thus, one can imagine that the image simply wraps 

around the billet circumference without distortion. There is a dark blue feature in each image, 

which is associated with a mask made of multiple layers of duct tape (trapping some air) that was 

placed on the outside of the billet. This mask was used to orient the image to the actual billet 

surface. 

(a)

(b)

(c)

FIGURE 50. C-SCAN IMAGE OF 11′′ SECTION OF BILLET B3W3 

(Red = high noise; violet = low noise. Gate centered (a) at 1′′ deep, (b) 2′′ deep, and (c) 3′′ deep.) 

54
Noise banding, which had been observed since the application of multizone inspection to 

titanium billets in the late 1980s and early 1990s, is quite evident. In the top two images, the 

average noise level in the high-noise regions (red) is about twice that of the low-noise regions 

(blue). For the top two images, different regions of metal are being inspected as the billet 

rotates, so the variations seen result from variations of the microstructure with position. Note 

that the third time gate is centered near the billet axis, so the same central tube of material is 

being insonified at all inspection angles. Thus, the variations seen in the third image partially 

result from the dependence on beam propagation direction of the scattering from a fixed metal 

region. Based on the characterization, a sectioning plan was developed to generate samples from 

the high- and low-noise regions, as shown in figure 51. 

“High Noise”

Region

“Low Noise”

Region

Gated Peak Noise in a 4-μs-wide gate centered 1” deep

Billet Axis

Three coupons from each region 2.5 x 5 x 6 cm3

2.5 cm

5 cm

Coupons 6 cm thick

along billet axis.

CL Mid OD

“High Noise”

Region

“Low Noise”

Region

Gated Peak Noise in a 4-μs-wide gate centered 1” deep

“High Noise”

Region

“Low Noise”

Region

Gated Peak Noise in a 4-μs-wide gate centered 1” deep

Billet Axis

Three coupons from each region 2.5 x 5 x 6 cm3

2.5 cm

5 cm

Coupons 6 cm thick

along billet axis.

CL Mid OD

FIGURE 51. SAMPLE SECTIONING PLAN FOR NOISE STUDIES 

Measurements made on the noise samples included microstructural analysis, ultrasonic 

characterization (velocity and backscatter noise), and grain orientation imaging. The results of 

the macrostructural characterization of the high- and low-noise samples are shown in figure 52. 

Highly elongated macrograins are seen with orientations that are significantly different in the 

high- and low-noise regions. More detail is provided by the micrographs in figure 53. For the 

samples taken from the outside diameter (OD) in both the high- and low-noise regions, 

micrographs were made under both normal illumination (right-hand image) and under crossed 

polarizers (left-hand and middle images). Metallographs were made on each of three orthogonal 

faces of the samples and assembled and shown to give a 3D representation of the structure under 

different magnification and illumination. As was seen from the macrographs, an elongated 

structure appears in both the high- and low-noise regions, but with quite different orientations. 

Generally speaking, the role of the radial and hoop directions seem to be interchanged. 

55
Radial 1 mm

Hoop

Axial

High Noise Low Noise

1 mm

High Noise Low Noise

Radial 1 mm

Hoop

Axial

High Noise Low Noise

1 mm

High Noise Low Noise

FIGURE 52. MACROSTRUCTURE RESULTS FOR HIGH- AND LOW-NOISE SAMPLES 

66

66

μm

μm

66

66 μ

μm

m

260 μm

260 μm

66

66

μm

μm

66

66

μm

μm

66

66 μ

μm

m

66

66 μ

μm

m

260 μm

260 μm

260 μm260 μm

260 μm260 μm

66

66

μm

μm

66

66 μ

μm

m

260 μm

260 μm

66

66

μm

μm

66

66

μm

μm

66

66 μ

μm

m

66

66 μ

μm

m

260 μm

260 μm

260 μm260 μm

260 μm260 μm

Axial Hoop

Radial

High Noise (OD)

Low Noise (OD)

Outside Diameter Sample

Macrostructure Intermediate Microstructure

Note:

Secondary elongation: hoop

Note:

Secondary elongation: radial

FIGURE 53. MICROSTRUCTURE OF HIGH- AND LOW-NOISE SAMPLES 

(For each sample, the left and center images were taken under crossed polarizes to indicate 

regions of correlated orientation while the right image was taken under normal illumination.) 

56
When ultrasound propagates in the radial direction, as would be the case during a billet 

inspection, it will be incident on the large faces of the macrostructural elements in the high-noise 

sample, whereas it will be propagating parallel to the large faces in the low-noise sample. At an 

intuitive level, it is not surprising that the noise is greater in the former case. It is interesting to 

note that at a high magnification under normal illumination, these differences are not evident. 

Figure 54 shows the results of velocity measurements made on these samples. In the high-noise 

OD sample, the longitudinal velocity in the hoop direction is the greatest, while in the radial 

direction, it is the smallest. These roles are reversed in the low-noise OD sample. Because of 

the anisotropy of the single crystal elastic constants of titanium, such results are generally 

indicative of preferred orientation. This is consistent with the previous observations. The 

changes in the orientation of the macrostructures from high- to low-noise regions is presumably 

a consequence of different deformations that occurred in these regions. Since deformation 

processing is well known to create texture in titanium, as a result of slip on particular 

crystallographic planes, the existence of different textures in regions with different deformationcontrolled macrostructures is not surprising. 

0.614

0.618

0.622

0.626

0.630

0.634

0123

L-Wave Speed (cm/μs)

OD Mid CL

Axial 

Radial 

Hoop 

4

Low Noise 

0.614

0.618

0.622

0.626

0.630

0.634

0123

L-Wave Speed (cm/μs)

OD Mid CL

Axial 

Radial 

Hoop 

High Noise 

4

FIGURE 54. VELOCITY RESULTS FOR HIGH- AND LOW-NOISE SAMPLES 

57
Figure 55 presents the results of measurements of attenuation and the backscattering figure of 

merit (FOM) on these same samples. The FOM is a measure of the material’s capacity to create 

noise and can be considered a material property. A careful discussion of this quantity, and its 

influence on the inspection of titanium, can be found in reports on the fundamental studies of 

titanium billet of ETC Phase I. As would be expected, the FOM for radial propagation is greater 

in the high-noise region than in the low-noise region. As was observed for the velocity, there 

appears to be a total reversal of the behaviors in the radial and hoop directions for the two 

samples. The same is observed for the attenuation. This interchange in properties between the 

radial and hoop directions in the two samples is consistent with the micrographs shown in 

figure 55. 

0.00

0.10

0.20

0.30

0.40

0 2 4 6 8 10 12 14 16

Frequency (MHz)

Attenuation (N/cm)

Radial

Hoop

Axial High Noise (OD)

0.00

0.02

0.04

0.06

0.08

0.10

0 5 10 15 20

Frequency (MHz)

FOM (1/cm1/2)

Radial

Hoop

Axial

High Noise (OD)

0.00

0.02

0.04

0.06

0.08

0.10

0 5 10 15 20

Frequency (MHz)

FOM (1/cm1/2)

Radial

Hoop

Axial

Low Noise (OD)

0.00

0.10

0.20

0.30

0.40

0 2 4 6 8 10 12 14 1

Frequency (MHz)

Attenuation (N/cm

Radial

Hoop

Axial Low Noise (OD)

6

FIGURE 55. ATTENUATION AND FOM RESULTS FOR HIGH- AND 

LOW-NOISE SAMPLES 

It should be noted that figure 55 indicates that regions of high attenuation exhibit low 

backscattering and vice versa. This is consistent with previous observations made on titanium as 

a part of the fundamental studies efforts. 

The above discussions provide a qualitative explanation of the differences in noise properties in 

the high- and low-noise regions. As a part of the fundamental studies, a theory was developed to 

explain the relationship of microstructure to noise, which was conducted to see if that theory 

would explain the observed noise behavior. The theory will not be described here other than to 

indicate that its central element is the degree to which the crystallographic orientations of nearby 

crystallites are correlated. Since the crystallites are elastically anisotropic, orientation 

58
correlations imply correlations in the local elastic properties that control the backscattering. 

Figure 56 summarizes the steps needed to test the quantitative theory relating microstructure to 

noise. Using Electron Backscatter Kikuchi Diffraction measurements, as implemented in an 

orientation-imaging microscope, an image of the variation of crystallite orientations as a function 

of position is formed. Combining this information with knowledge of the single crystal elastic 

constants allows images to be made of the local values of the elastic constants. From such 

images, one can compute a quantity known as the two-point correlation of elastic constants. 

This serves as an input parameter to the theoretical prediction of the backscattered ultrasonic 

noise. 

1. Electron Backscatter Kikuchi Diffraction (EBSD)

• Euler angles as a function of position.

2. Calculate CII I = 1,2,3 

3. Calculate <δCII(x,y)δCII(x’,y’)>

4. Input into theory to predict backscattered noise

Axial

C22 Hoop

C11

Radial

C33

Axial

C22 Hoop

C11

Radial

C33

Theory Validation

Measure <δCII(r)δCII(r’)> using

Orientation Imaging Microscopy (OIM)

OIM Data

FIGURE 56. STEPS REQUIRED TO VALIDATE THEORY OF NOISE MODELS 

Figures 57 and 58 show the results of the orientation imaging for the high- and low-noise 

samples. The first image shows a pseudocolor map in which changes in color simply indicate 

changes in orientation, i.e., grain boundaries. The next three maps show the spatial variation of 

particular elastic constants. The elongated structures that were observed in the macrographs and 

micrographs are again observed, but now in a way that can provide direct input to theories 

predicting the noise levels. Figure 59 provides an example of the two-point correlations of 

elastic constants that are inferred from this data. This has a much greater extent in the axial 

direction, consistent with the elongation of the macrostructure in that direction. 

59
High Noise 

Hoop Face 

175

150 CIJ

Axial (C

(GPa)

22)

Radial (C33)

C22 (157 GPa) C33 (157 GPa)

C11 (158 GPa)

85 μm

High Noise 

Hoop Face 

175

150 CIJ

Axial (C

(GPa)

22)

Radial (C33)

Axial (C22)

Radial (C33)

C22 (157 GPa) C33 (157 GPa)

C11 (158 GPa)

85 μm

FIGURE 57. ELECTRON BACKSCATTER KIKUCHI DIFFRACTION RESULTS FOR 

HIGH-NOISE SAMPLES 

60
175

150

CIJ (GPa)

C22 

156 GPa

C33 

159 GPa

C11 

155 GPa

Low Noise

Radial Face

Axial (C22)

Hoop (C11)

200 μm

175

150

CIJ (GPa)

C22 

156 GPa

C33 

159 GPa

C11 

155 GPa

Low Noise

Radial Face

Axial (C22)

Hoop (C11)

Axial (C22)

Hoop (C11)

200 μm

FIGURE 58. ELECTRON BACKSCATTER KIKUCHI DIFFRACTION RESULTS FOR 

LOW-NOISE SAMPLES 

61
High Noise

Low Noise

-0.2

0

0.2

0.4

0.6

0.8

1

0 100 200 300 400

Distance (μm)

<

δ

C22(r)

δ

C22(r')>

Hoop Face

Radial Direction

Axial Direction

-0.2

0

0.2

0.4

0.6

0.8

1

0 100 200 300 400

Distance (μm)

<

δ

C22(r)

δ

C22(r')>

Hoop Direction

Axial Direction

Radial Face

FIGURE 59. TWO-POINT CORRELATION FROM HIGH- AND LOW-NOISE REGIONS 

OF THE SAMPLES 

Figure 60 presents a comparison of theoretical predictions of the backscattering coefficient, 

based on the orientation-imaging data as discussed above, to the experimental observations that 

were reported in figure 55. Note here that η

1/2 is identical to the FOM. The agreement between 

theory and experiment is clearly excellent. This suggests that a good understanding of the 

relationship of backscattering to micro- and macrostructure is now in hand. Such information 

will be of significant value in guiding the design of improved alloys with lower backscattered 

noise. This understanding may also provide insight into the development of improved 

techniques to detect the microtexture zones that have been associated with dwell time fatigue. 

62
Theory Validation

0.00

0.02

0.04

0.06

0.08

0.10

0 5 10 15 20

Frequency (MHz)

FOM (1/cm1/2)

Radial

Hoop

Axial

High Noise (OD)

0.00

0.02

0.04

0.06

0.08

0.10

0 5 10 15 20

Frequency (MHz)

FOM (1/cm1/2)

Radial

Hoop

Axial

Low Noise (OD)

FIGURE 60. COMPARISON OF PREDICTED AND OBSERVED VALUES OF 

BACKSCATTERING COEFFICIENT 

3.7 REPRODUCIBILITY STUDIES USING THE CBS BILLETS. 

3.7.1 Reproducibility Studies—Rolls-Royce. 

Because of the unique opportunities offered by the CBS billets, Rolls-Royce requested access to 

a portion of the heat for use in comparison studies of multizone and conventional inspection. 

The work [33] performed by Rolls-Royce in cooperation with billet supplier A had three 

objectives: 

• Determination of defect detectability differences between conventional inspection (RollsRoyce procedure) and multizone at the same level of inspection sensitivity 

63
• Assessment of the performance of multizone in normal operation taking advantage of 

reduced noise level capability 

• Assessment of the frequency dependency of suspected type 1 defects related to FBH 

targets 

Three billets were selected that included two billets with the maximum number of indications 

found by multizone and one billet with indications found by multizone but no indications found 

using the conventional inspection. Table 7 shows the detections for the three billets selected. 

The conventional inspection procedure followed RPS 707 (QCTP 6317), which included using a 

#3 FBH calibration reference set at 80% FSH and distance-amplitude correction. Stop-on-defect 

was used with an alarm set at 10% above noise, which led to an alarm setting of 35% in the CBS 

material. A 5-MHz cylindrical focused transducer with an 8′′ focal length and dimensions of 

1.5′′ by 0.75′′ was focused at the surface. Back-wall echo was monitored and an index of 50% of 

the minimum beam width was used. 

TABLE 7. BILLETS USED IN ROLLS-ROYCE REPRODUCIBILITY STUDY 

Number of Indications From Sept. 1995 Inspection 

Billet Identification Conventional Normal Multizone 

B1BW1 3 8 

B1BW3 0 4 

B3W2 2 8 

The three billets were shipped to the billet supplier (supplier A) for inspection. Upon their 

arrival, the surface was belt polished, which complicated the comparison of the inspection data 

before and after polishing. The number of detections for each of the inspections is provided in 

table 8. At this facility, only the amplitude response was used to determine the multizone 

detections. They did not use the SNR responses. Note that billet B1BW1 was not inspected 

using multizone in September 1994. Other variations in inspection are provided as footnotes to 

the table. In their analysis of the data, Rolls-Royce reported a variation between separate 

multizone inspections. These variations were attributed to difficulties in setup and were similar 

to that found in a later reproducibility study performed by ETC, as described below. 

As part of the Rolls-Royce studies, a comparison was made of multizone when calibrated to a 

#2 and #3 FBH sensitivity. The first three multizone inspections were performed using a 

protocol similar to AMS 2826 and were calibrated using a #2 FBH standard. The results are 

shown in the first three multizone columns of table 8. The last column in table 8 shows the 

results for the #3 FBH inspection. The inspection was achieved by using the same inspection 

setup parameters established for a #2 FBH but decreasing the gain for each channel by 7 dB to 

simulate a #3 FBH sensitivity. The detectability was best, i.e., more indications were found, 

with the #2 FBH inspection. 

64
TABLE 8. TABULATION OF DETECTIONS IN ROLLS-ROYCE 

REPRODUCIBILITY STUDY 

Conventional Normala Inspection Multizone 

Billet 

Identification 

RPS 707 

Jan. 1996b

Supplier B 

Sept. 1995 

Supplier B 

Nov. 1994b

Supplier A

Jan. 1996 

Supplier B 

Sept. 1995

Supplier B 

Nov. 1994 

Supplier A

No. 3 

Jan. 1996 

B1BW1 6 3 5 8 8 NA 4c

B1BW3 0 0 0 4 4 4 4 

B3W2 5d 2 4 6d 8 4e 6 

a Conventional inspections used a different transducer and setup, as described above. 

b Stop-on-defect was used for these two inspection runs. 

c All eight indications were detected, but only four were above the 35% threshold. 

d A section of the billet was removed that contained indication H. Indication C was not detected with multizone in 

the supplier A study but was detected in a prior supplier B September 1995 inspection. 

e

 A section of this billet containing three defects was not scanned in November 1994. 

The final part of the Rolls-Royce study was a comparison of various frequency cylindrical 

focused transducers as listed in table 9. Amplitude data for each of the indications are provided 

in table 10 and plotted in figure 61. For these results, the 5-MHz conventional inspection 

provided higher amplitudes than the 7.5- and 10-MHz inspections compared to the response 

from a #2 FBH. Comparable S/N data were not available but may contribute to overall 

improvements in detection [34 and 35]. The variability between supplier B and supplier A data 

are also evident in these results as is the improved amplitude when calibrating to a #2 FBH 

compared to the #3 FBH setup. Various factors contribute to the variability including flaw 

morphology and depth, transducer, and inspection setup. For these data sets, the surface finish 

was also different between supplier B and supplier A inspections, i.e., the billets underwent a 

polishing step that changed the surface condition between the two inspection locations. 

TABLE 9. TRANSDUCERS USED IN ROLLS-ROYCE COMPARISON STUDY 

Type Frequency 

Focal Length 

(inches) 

Meccasonics 5 MHz 8 

Harisonic 7.5 MHz 4 

Harisonic 10 MHz 4 

Harisonic 10 MHz 12 

65
TABLE 10. AMPLITUDE DATA FROM TRANSDUCER COMPARISON STUDY 

Conventional #3FBH Multizone 

Supplier B 

September 

1995 Supplier A January 1996 

Supplier B 

September 

1995 

Supplier A 

January 1996 

#2 FBH 

(%) 

5 MHz 

(%) 

7.5 MHz

(%) 

10 MHz

(%) 

10 MHz

(%) 

#2 FBH 

(%) 

#2 FBH 

(%) 

#3 FBH

(%) 

B1BW1 

A 81 40 25 63 72 19 

B 100 60 30 25 113 152 38 

C 70 126 100 112 112 142 114 56 

D 56 56 28 

E 50 30 30 20 69 55 31 

F 179 251 178 251 200 450 322 174 

G 100 126 100 95 100 213 219 101 

H 127 74 33 

B1BW3 

A 113 102 45 

B 160 122 68 

C 127 73 36 

D 74 124 48 

B3W2 

A 355 251 200 178 357 287 128 

B 200 158 126 126 113 338 151 

C 201 

D 80 200 126 80 75 127 154 58 

E 74 158 112 65 75 213 184 87 

F 160 122 52 

G 158 141 80 90 142 260 116 

H 253 

66
0%

100%

200%

300%

400%

500%

600%

B1

BW

1

A B C D E F G H B1

BW

3

A B C D B3

W2

A B C D E F G H

Supplier B - 5 MHz Supplier A – 5 MHz Supplier A - 7.5 MHz

Supplier A - 10 MHz Supplier A - 10 MHz Supplier B - # 2FBH - MZ

Supplier A - #2 FBH - MZ Supplier A - #3 FBH - MZ

FIGURE 61. AMPLITUDE DATA FOR VARIOUS TRANSDUCERS USED IN THE 

ROLLS-ROYCE STUDY 

Given these results, the following conclusions were found: 

• Multizone demonstrated a better level of detectability than RPS 707 conventional 

ultrasonic inspection. 

• Variation in process capability between separate multizone inspections (suppler B 

compared to suppler A) was noted. Process variation is believed to be attributable to the 

setup problem. 

• At conventional inspection sensitivity, i.e., #3 FBH, multizone demonstrated a better 

level of detectability than the conventional ultrasonic inspection used in this study. At 

the same alarm level, the detectability was approximately the same. 

• Defect indication response in titanium billet is consistently diminished as transducer 

frequency is increased from 5 MHz to 10 MHz. 

3.7.2 Reproducibility Studies—ETC. 

Motivated by the results of the Rolls-Royce study, two billets from the CBS heat were selected, 

B2W3 131′′ long and B1BW1A 72′′ long, for use in an ETC study of reproducibility [36]. Note 

that B1BW1A was cut from billet B1BW1, which was originally 104′′ long. Table 11 

summarizes the results of previous multizone and conventional inspections for the two billets. 

67
TABLE 11. SUMMARY OF PRIOR ULTRASONIC INSPECTION RESULTS FOR BILLETS 

SELECTED FOR REPRODUCIBILITY STUDY 

Conventional 

November 1994 

Conventional 

September 1995 

Multizone 

November 

1994 

Multizone 

September 

1995 

Indication 

Axial 

Location 

(inches) 

Depth 

(inches) 

Ampl. 

(%) SNR 

Ampl. 

(%) SNR 

Normal

Ampl. 

(%) 

Angle 

Ampl. 

(%) 

Normal

Ampl. 

(%) 

Angle

Ampl. 

(%) 

B1BW1A 

A 21.8 2.2 nt nt 63 2.96 nr nr nr 68 

B 28.5 1.7 nt nt 113 5.67 70 30 nr nr 

C 44.8 0.6 nt nt 142 8.09 70 >100 70 >100 

D 49.0 1.0 nt nt 56 2.79 nr nr nr nr 

E 61.3 0.9 nt nt 69 3.05 30 >100 nr nr 

F 67.8 1.1 nt nt 450 26.6 >100 70 179 >100 

B2W3 

A 20.1 0.2 >100 6.54 107 6.81 nr nr nr nr 

B 27.8 2.3 49 2.9 72 3.54 nr nr nr 72 

C 31.0 2.0 nr nr 50 2.59 40** 60** nr nr 

** Amplitudes reported for indication at correct axial location but at 0.25′′ to 0.5′′ depth may be a false call. 

nt = Not Tested nr = Not Reported 

A text matrix that included an inspection at three locations, using five sets of multizone 

transducers and six sets of conventional transducers with multiple inspectors at each location, is 

shown in table 12. The multizone inspection followed the GE specification. This included 

directions to inspect at the calibration gain (#2 FBH) with a repeat, with the gain reduced by 12 

dB if saturated indications occurred. The encoder adapter was removed and reattached between 

operators. The operators were asked to record amplitude and SNRs for rejectable indications 

along with the noise level. The conventional test matrix was similar to the multizone with the 

exception that the inspection with multiple transducer sets was to be performed at two locations. 

The multizone test matrix led to 15 inspection opportunities for each of the 9 indications. The 

test matrix generated for the conventional inspection differed from the multizone test matrix 

because the multiple transducer sets were used at two locations, resulting in 21 inspection runs. 

The conventional transducer set consisted of two transducers, one for normal incidence and one 

for angle beam inspection. The normal incidence transducers used were 5 MHz cylindrically 

focused, with element dimensions 1′′ by 0.5′′ or 1′′ by 0.75′′. The transducers used for angle 

beam included both types used for normal beam inspection, as well as a spherically focused, 

0.75′′ diameter, 5-MHz model. The inspection was in accordance with an engine manufacturer’s 

approved procedure, using approved inspectors and calibration standards. The angle beam 

68
inspection used an offset of 1/6 of the billet radius, producing a refracted longitudinal wave at 

45o from the surface normal, as described in figure 9. 

TABLE 12. TEST MATRIX USED FOR REPRODUCIBILITY STUDY 

Location Transducer Set Operators 

Multizone Inspection Matrix 

Z 1 A, B, C 

Z 2 A, B, C 

Z 3 A, B, C 

Y 4 D, E, F 

X 5 H, I, J 

Conventional Inspection Matrix 

W 6 J, K, L 

W 7 J, K, L 

W 8 J, K, L 

V 9 M, N, O 

V 10 M, N, O 

V 11 M, N, O 

U 12 P, Q, R 

Instructions were given to evaluate and report all rejectable indications and to re-evaluate any 

saturated indications at a reduced gain level, reporting the amplitude and gain adjustment. 

Reports were requested of the noise level, the attenuation difference from the calibration 

standard, and the applied attenuation correction. Copies of strip chart recordings were requested 

if used during the conventional inspections (note: strip chart that recording is not a requirement 

but is used by some suppliers—one of the three suppliers provided strip charts). 

The results were derived from the written inspection reports. For the supplier who used strip 

chart recording, the strip charts were reviewed for consistency with the reports. Any indication 

reported on either normal incidence, angle beam, or both, which corresponded with a previously 

reported indication (see table 11), was counted as a find. In four instances, indications were 

reported that did not correspond to any known indication. Each was reported on only 1 of the 21 

inspection runs and had an amplitude of either 10% or 15% above the reported noise level (reject 

level was 10% above noise). These four indications were recorded as false calls during the 

conventional inspection and are listed in table 13. Note that these presumed false calls were all 

reported from the same inspection location. 

69
TABLE 13. SUMMARY OF CONVENTIONAL INDICATIONS RECORDED AS FALSE 

CALLS IN BILLET B1BW1A 

Axial Location 

(inches) 

Depth 

(inches) 

Angle or 

Normal 

Amplitude 

(%) 

Signal Minus Noise 

(%) 

6.25 3.00 angle 40 15 

37.5 3.50 normal 50 15 

39.25 3.25 normal 50 10 

54.25 3.25 normal 50 10 

The summary statistics for the multizone inspection data that are presented in table 14 show the 

reported signal amplitudes and SNR statistics. 

TABLE 14. SUMMARY OF STATISTICS OF MULTIZONE REPRODUCIBILITY STUDY 

Amplitude Statistics 

(15 Runs) 

S/N Statistics 

(15 Runs) 

Indication Rejections Min. Max. Mean Std. Dev. Min. Max. Mean Std. Dev.

B1BW1AA 15 50 92 65.33 12.00 3.3 4.52 3.89 0.413 

B1BW1AB 15 58 152 103.07 26.67 4.07 10.88 7.02 1.866 

B1BW1AC 15 98 200 138.47 33.54 6.69 12.29 9.42 1.467 

B1BW1AD 9 40 77 56.07 13.60 1.91 3.36 2.65 0.346 

B1BW1AE 15 44 100 69.67 12.82 2.18 4.16 3.22 0.663 

B1BW1AF 15 200 560 349.07 118.68 10.09 45.34 18.42 11.133 

B2W3A 15 53 140 77.93 27.42 3.33 9.58 6.36 1.752 

B2W3B 15 41 116 67.33 22.88 2.79 5.48 4.09 0.950 

B2W3C 11 23 68 42.60 14.74 1.74 4.18 3.16 0.775 

The summary statistics for the conventional inspection that are presented in tables 15 and 16 

tabulate the amplitude and signal minus noise, respectively. The signal minus noise data are 

shown to allow comparison with the typical reject criterion of 10% above noise for the 

conventional inspection. For each of the two tables, statistics of maximum, minimum, mean, and 

standard deviation are shown for each indication. These were calculated from only the finds 

information for each indication. 

70
TABLE 15. SUMMARY OF AMPLITUDE STATISTICS FOR CONVENTIONAL 

INSPECTION 

Finds Normal Incidence Amplitude Angle Incidence Amplitude 

Indication Total 

Normal 

Incidence 

Angle 

Beam 

Min.

(%) 

Max.

(%) 

Mean

(%) 

Std. 

Dev.

(%) 

Min.

(%) 

Max. 

(%) 

Mean

(%) 

Std. 

Dev.

(%) 

B1BW1AA 18 7 18 40 65 49 8 35 65 47 10 

B1BW1AB 18 17 17 30 90 58 13 30 90 46 19 

B1BW1AC 20 20 7 50 134 79 23 30 55 45 11 

B1BW1AD 0 0 0 

B1BW1AE 1 1 0 40 40 40 0 

B1BW1AF 21 21 9 113 401 190 83 60 142 88 28 

B2W3A 0 0 0 

B2W3B 0 0 0 

B2W3C 9 0 9 30 80 46 14 

TABLE 16. SUMMARY OF SIGNAL MINUS NOISE STATISTICS FOR 

CONVENTIONAL INSPECTION 

Finds 

Normal Incidence Signal 

Minus Noise 

Angle Incidence Signal 

Minus Noise 

Indication Total 

Normal 

Incidence 

Angle 

Beam 

Min.

(%) 

Max.

(%) 

Mean

(%) 

Std. 

Dev.

(%) 

Min.

(%) 

Max. 

(%) 

Mean

(%) 

Std. 

Dev.

(%) 

B1BW1AA 18 7 18 10 30 16 7 10 45 26 10 

B1BW1AB 18 17 17 10 70 28 16 10 65 24 18 

B1BW1AC 20 20 7 15 89 48 20 10 35 25 11 

B1BW1AD 0 0 0 

B1BW1AE 1 1 0 20 20 20 0 

B1BW1AF 21 21 9 85 324 150 63 35 117 66 28 

B2W3A 0 0 0 

B2W3B 0 0 0 

B2W3C 9 0 9 10 55 24 13 

A review of the data shows that one of the indications (B1BW1A indication F) was rejected on 

all 21 inspection runs. This was also the highest amplitude indication on both the multizone and 

conventional tests. Three of the indications were not rejected on any conventional inspection 

run. The remaining five indications were rejected between runs 1 and 20. The reported 

amplitudes of indication F found on all runs varied between 113% and 401% in longitudinal 

mode, showing a degree of variation similar to that observed by the multizone inspection, as 

shown by the data in table 14. 

71
The fraction of opportunities [36] that resulted in detections, which will be referred to here as 

percent efficiency for conciseness, are shown in table 17 for both the multizone and conventional 

inspections conducted in the reproducibility study. 

TABLE 17. PERCENT EFFICIENCY OF MULTIZONE INSPECTION DURING 

REPRODUCIBILITY STUDIES 

Billet ID Indication ID Opportunities Detections Percent Efficiency 

B1BW1A A 

B 

C 

D 

E 

F 

15 

15 

15 

15 

15 

15 

15 

15 

15 

9 

15 

15 

100 

100 

100 

60 

100 

100 

B2W3 A 

B 

C 

15 

15 

15 

15 

15 

11 

100 

100 

73 

All Indications 135 125 92.5 

TABLE 18. PERCENT EFFICIENCY OF CONVENTIONAL INSPECTION DURING 

REPRODUCIBILITY STUDIES 

Billet ID Indication ID Opportunities Detections Percent Efficiency 

B1BW1A A 

B 

C 

D 

E 

F 

21 

21 

21 

21 

21 

21 

18 

18 

20 

0 

1 

21 

86 

86 

96 

0 

1 

100 

B2W3 A 

B 

C 

21 

21 

21 

0 

0 

0 

0 

0 

0 

All Indications 189 87 46 

Comparison of these results shows that the ratio of the percent efficiency for conventional and 

multizone inspections during the reproducibility studies was 49.7%; a value that is very close to 

the ratio of 51.7% during the overall CBS based on the 31 conventional finds and the 60 

multizone finds, as shown in figure 19. 

The data was analyzed further for statistical comparison. Separate variability comparisons were 

made of the amplitude for the multizone (figure 62) and conventional (figure 63) inspections. 

Figure 64 plots all the data on a single graph. Note that similar variability was found between 

the two methods. 

72
log(Equivalent FBH Size)

log(Percent Screen Height)

0.2 0.3 0.4 0.5 0.6

1.0 1.5 2.0 2.5

Site 3

Site 2

Site 1

ETC Reproducibility Study ETC Reproducibility Study 

log (Signal) versus log (Size) log (Signal) versus log (Size) 10 dB ~ 4σ

log(Equivalent FBH Size)

log(Percent Screen Height)

0.2 0.3 0.4 0.5 0.6

1.0 1.5 2.0 2.5

Site 3

Site 2

Site 1

ETC Reproducibility Study ETC Reproducibility Study 

log (Signal) versus log (Size) log (Signal) versus log (Size) 10 dB ~ 4σ

FIGURE 62. VARIABILITY ANALYSIS FOR AMPLITUDE FROM 

MULTIZONE INSPECTION 

(Approximately 10 dB variation was found.) 

Copley Conventional study

1.2 1.4 1.6 1.8 2.0 2.2 2.4

0.5

1.0

1.5

2.0

2.5

3.0

10 dB 

C-Normal

C-Angular

ETC Reproducibility Study ETC Reproducibility Study – Conventional Inspection Conventional Inspection

log (Signal) versus log (Size) log (Signal) versus log (Size)

log size (average of amplitude over target) 

log signal (percent screen height) 

FIGURE 63. VARIABILITY ANALYSIS FOR AMPLITUDE FROM 

CONVENTIONAL INSPECTION 

(Approximately 10 dB variation was found. Data shown for both normal and 

angular inspection modes.) 

73
Copley

1.5 2.0 2.5

0.5

1.0

1.5

2.0

2.5

3.0

10 dB 

ETC Reproducibility Study ETC Reproducibility Study

log (Signal) versus log (Size) log (Signal) versus log (Size)

log size (average of amplitude over target) 

log signal (percent screen height) 

C-Normal

C-Angular

Multizone

FIGURE 64. COMPARISON OF MULTIZONE AND CONVENTIONAL 

INSPECTION VARIABILITY 

Typical results for a single indication are shown in figure 65. Indication B1BW1A-B was 

selected and the results were plotted. Each group represents three operators and the same 

location and using the same transducers. 

0.00

2.00

4.00

6.00

8.00

10.00

12.00

12345

GROUP

SNR

0.00

2.00

4.00

6.00

8.00

10.00

12.00

12345

GROUP

SNR

FIGURE 65. REPRODUCIBILITY RESULTS FOR INDICATION B1BW1A-B FROM 

FIELD STUDIES 

74
Based on these results, a laboratory study was designed to assess the factors that could lead to 

such variability with a concentration on factors that affect the SNR. The factors evaluated in the 

laboratory study included transducer, water path, and transducer alignment, as shown in 

figure 66. Other potential causes not considered included instrumentation, sampling/line 

spacing, SNR algorithm, and gate position. 

Transducer

Inclusion

Transducer Focal Length Water Path Length Transducer Alignment

Sound beam

FIGURE 66. FACTORS EVALUATED DURING REPRODUCIBILITY STUDY 

A full factorial study was planned, which included the following: 

• Transducer: 2 levels (NDT Systems, Panametrics) 

• Water Path: 3 levels (2.6′′, 3.0′′, and 3.4′′) 

• Alignment: 3 levels (-1.5o, 0o, and +1.5o) 

• 20 runs total (3 x 3 x 2 plus two duplicates) 

The results are provided in table 19 with the main effects and interactions plots presented in 

figure 67. No significant interactions were found between the factors; therefore, each could be 

evaluated separately. 

75
TABLE 19. RESULTS OF FULL FACTORIAL EXPERIMENT PERFORMED IN 

LABORATORY ENVIRONMENT 

Run Transducer Angle Waterpath SNR 

1 -1 -1 -1 4.79 

2 -1 0 -1 5.23 transducer: -1 NDT Systems 

3 -1 1 -1 11.79 +1 Panametrics 

4 -1 -1 0 4.23 

5 -1 0 0 4.54 angle: -1 -1.5 degrees 

6 -1 1 0 11.71 0 0 degrees 

7 -1 -1 1 3.65 +1 +1.5 degrees 

8 -1 0 1 4.94 

9 -1 1 1 10.93 waterpath: -1 2.6 inches 

10 1 -1 -1 4.68 0 3.0 inches 

11 1 0 -1 5.26 +1 3.4 inches 

12 1 1 -1 11.96 

13 1 -1 0 5.03 

14 1 0 0 5.92 

15 1 1 0 11.82 

16 1 -1 1 3.58 

17 1 0 1 5.2 

18 1 1 1 11.89 

19 1 0 0 5.32 

20 1 0 0 5.11 

 (a) (b) 

FIGURE 67. (a) MAIN EFFECTS PLOT AND (b) INTERACTIONS PLOT 

As a final step in the analysis, a comparison was made of the field and laboratory results, as 

shown in figure 68, indicating that similar variations were found between the two studies. 

76
0

2

4

6

8

10

12

14

DOE

Results

Signal-to-noise ratio

Round 

Robin

(all data)

0

2

4

6

8

10

12

14

DOE

Results

Signal-to-noise ratio

Round 

Robin

(all data)

FIGURE 68. COMPARISON OF SNR FOR LABORATORY DESIGN OF EQUIPMENT AND 

ROUND-ROBIN FIELD STUDY 

The following conclusions were reported [36]: 

• Variability was found to be similar for the conventional and multizone inspections, even 

though more indications were found with multizone. The ratio of percentage efficiency 

for conventional and multizone was 49.7%. 

• Primary sources of variability were transducer, transducer alignment, and water path 

distance, with the greatest contributor believed to be the transducer alignment. 

• Factors deemed less significant were instrumentation, sampling, the SNR algorithm as 

implemented in the multizone software, and gate position (which can affect zone 1). 

3.8 MISSES ASSESSMENT.

A critical aspect of any inspection method is an understanding of those defects, which may be 

missed. In an effort to assess the occurrence of defects that were not detected with the ultrasonic 

methods described in section 3.1, two separate efforts were undertaken to determine if misses 

existed. Three mults, approximately 51′′ long, were selected for further reduction and 

subsequent inspection. The mults were shipped to Braeburn Steel for reduction to 1.5′′ bar. The 

bars were hot-rolled, straightened, and centerless ground to a surface finish of 63 root mean 

square prior to inspection in a typical bar inspection facility. The bars were inspected at 10 MHz 

at the WestPenn Testlabs using their TestTec bar inspection facility with calibration set at a 

sensitivity of #1.5 FBH. The three mults selected for the study were B1AW2A, B1AW3A, and 

B2W2D. Note that the B1AW2A mult contained an indication that was detected during an 

77
earlier inspection. This mult was selected to be compared to an indication-free material. An 

inspection of the bars did not lead to rejectable indications because of high-noise conditions. 

This was the case for the bars from all three mults, including B1AW2A, which contained a 

known indication with 134% FSH and 13.6 SNR, as recorded during the multizone inspection. 

Given the noise conditions of the bars, using the bars for misses assessment was deemed 

inconclusive. 

The second effort to assess misses involved inspection of mults to a higher sensitivity using 

phased array inspection. Eleven mults of various lengths were selected and are listed in table 20. 

An annular array probe with a 10-MHz center element surrounded by a 7.5-MHz operating 

frequency in the outer rings was used for the evaluation. Seven overlapping zones were used at 

0.6′′ increments at a sensitivity of #2 FBH. Several of the mults had indications detected during 

prior inspections, as indicated in the final column of table 20. The presence of all prior 

indications was confirmed using the phased array method. As an example, figures 69 and 70 

show the results for indications B, C, and D of billet segment B3W1BB. Note that indications C 

and D were found in multiple zones. 

TABLE 20. MULTS USED IN THE MISSES ASSESSMENT 

Billet 

Segment 

ID 

Mult 

Length Inspection Results 

B3W3CA 32′′ Confirmed presence of indication D. No new indications. 

B3W3C 36′′ Confirmed presence of indication C. No new indications. 

B3W3A 35′′ Confirmed presence of indication A. No new indications. 

B2W1C 29′′ Confirmed presence of indication D. No new indications. 

B2W1CA 36′′ No new indications. 

B3W1BB 34′′ Confirmed presence of indications B, C, and D. No new 

indications. 

B1AW1B 32′′ Confirmed presence of indications D and E. No new indications. 

B3W2CA 36′′ Confirmed presence of indication F. No new indications. 

B1BW3CB 14′′ One new indication found. 

B1BW3C 13′′ No new indications. 

B1BW3A 12′′ No new indications. 

78
2”

4”

Zone 4

Zone 5

Indication D

Indication C

ne 4

zone 4

ns

Indication D

Indication C

2”

4”

Zone 4

Zone 5

Indication D

Indication C

ne 4

zone 4

ns

Indication D

Indication C

FIGURE 69. C-SCAN OF INDICATIONS D AND C FROM BILLET SEGMENT B3W1BB 

ALSO DETECTED IN PRIOR INSPECTIONS 

(Note that both indications were detected in zones 4 and 5. 

Waveforms from zone 4 are also shown for both indications (lower).) 

79
12.5”

Zone 5

Indication B

FIGURE 70. C-SCAN AND WAVEFORM RESULTS FOR INDICATION B OF 

BILLET SEGMENT B3W1BB 

As indicated in table 20, only one new indication was identified. The indication was found in 

billet segment B1BW3CB with an amplitude of 95% of a #2 FBH. Figure 71 shows the C-scan 

and waveform results taken with the phased array setup. After completion of the high-sensitivity 

phased array inspection (7.5 MHz), the sample was shipped to the GE Quality Technology 

Center (QTC) for multizone inspection. The GE-QTC staff reinspected the mult using 

production multizone probes and probes fabricated by Corporate Research and Development. A 

34% amplitude was reported (based on 80% calibration for a #2 FBH), which is not rejectable. 

An offset of 0.1′′ was used both axially and circumferentially. The axial offset resulted in no 

change. The circumferential offset increased the amplitude to 60%, which is below the reject 

threshold. These results are indicative of the variability that is present in billet inspection and 

point to the importance of flaw morphology and inspection setup to the detection of flaws. The 

sample was also inspected with a higher-frequency (10 MHz) phased array probe. The results 

from the inspection are shown in figure 72. Given the strong ultrasonic response from multiple 

inspections, the decision was made to destructively characterize the indication. 

80
B1BW3CB; indication at ~1.2′′ depth; ~95% of #2 FBH 

FIGURE 71. C-SCAN AND WAVEFORM RESULTS FOR NEW INDICATION FOUND IN 

BILLET SEGMENT B1BW3CB 

81
10 MHz phased array inspection results

FIGURE 72. C-SCAN AND WAVEFORM RESULTS FOR NEW INDICATION FOUND IN 

BILLET SEGMENT B1BW3CB USING 10-MHz PHASED ARRAY INSPECTION 

3.9 DISPOSITION OF CBS MATERIALS. 

Included in the program objectives was the goal to provide reference samples containing 

naturally occurring hard alpha defects for evaluation of future inspection techniques, validation 

of PoD and ultrasonic methodologies, and support of technology transfer to titanium billet 

suppliers. A number of samples remain and are incorporated into the FAA sample library, which 

is managed by the Airworthiness Assurance Nondestructive Inspection Validation Center 

(AANC) at Sandia National Laboratories. Table 21 provides a description of the billet materials 

and indicates those sections that were transitioned for future public domain access. Column 1 

contains the original billet ID number. Column 2 contains the indication designator. Column 3 

contains the current billet segment ID designator. Columns 4 and 5 provide location information 

for the indications with inspection amplitude and SNR for each of the three inspection methods 

contained in columns 6 through 11. Column 12 provides the disposition of the material. Those 

items that are included in the AANC sample library are indicated. 

82
TABLE 21. LISTING OF SAMPLES REMAINING FROM ORIGINAL BILLET MATERIA

Original Billet ID 

Indication 

ID 

Current Billet 

Segment ID 

Inches 

From Top Depth 

MZ 

SNR 

MZ 

Amp 

(%) 

CL 

SNR 

CL 

Amp 

(%) 

CA 

SNR 

CA 

Amp 

(%) Dispo

B1AW1 A B1AW1A 3.3 0.2 12.14 190 NA NA NA NA 

80′′ mult inco

library with I

B1AW1 B B1AW1A 25.9 0.6 4.36 201 NA NA 2.62 42 

80′′ mult inco

library with I

B1AW1 C B1AW1A 66.4 1.6 5.47 83 1.91 42 1.85 28 

80′′ mult inco

library with I

B1AW1 D B1AW1B 92.7 1.7 4.65 73 NA NA NA NA 

32′′ mult inco

library with I

B1AW1 E B1AW1B 95.2 0.6 4.47 127 NA NA 4.44 55 

32′′ mult inco

library with I

B1AW2 A 

B1AW2A - 

bar 42.5 0.3 13.59 134 NA NA NA NA 

Material from 

1.5′′ bar, inco

library with I

B1AW2 B 

no remaining 

pieces 72.0 0.2 21.7 225 NA NA NA NA 

ETC defect c

B1AW2 C B1AW2C 89.0 0.8 16.29 213 2.49 65 3.2 >100 

14′′ mult inco

library with I

B1AW2 D 

no remaining 

pieces 98.0 0.7 5.46 134 2.61 50 NA NA 

ETC defect c

B1AW2 E B1AW2E 104.0 1.3 4.29 160 3.2 >100 2.92 >100 

14′′ mult inco

library with I

B1AW2 F B1AW2E 114.4 1.1 12.8 268 5.15 94 4.52 86 

14′′ mult inco

library with I

B1AW2 X no remaining 

pieces 

98.7 0.5 5.05 94 NA NA NA NA ETC defect c

B1AW3 none B1AW3A - 

bar 

51 Material from 

2′′ bar, incorp

library with E

83
TABLE 21. LISTING OF SAMPLES REMAINING FROM ORIGINAL BILLET MATERIAL (Co

Original Billet ID 

Indication 

ID 

Current Billet 

Segment ID 

Inches From 

Top Depth 

MZ 

SNR 

MZ 

Amp 

(%) 

CL 

SNR 

CL 

Amp 

(%) 

CA 

SNR 

CA 

Amp 

(%) Dispo

B1AW3 A no remaining 

pieces 

60.0 0.7 5.02 142 2.92 50 2.48 60 ETC defect c

B1AW3 B B1AW3AA 63.0 0.9 2.05 69 NA NA NA NA 18′′ mult inco

library with I

B1AW3 C B1AW3AB 79.0 1.5 11.79 253 2.69 62 5.7 >100 20′′ mult inco

library with I

B1AW3 D no remaining 

pieces 

94.8 1.1 4.49 101 NA NA NA NA ETC defect c

B1AW3 E no remaining 

pieces 

106.0 1.6 2.52 47 NA NA NA NA ETC defect c

B1AW3 Y B1AW3AB 77 1.3 5.05 99 NA NA NA NA 20′′ mult inco

library with I

B1AW3 Z B1AW3AB 81 1.3 3.48 77 NA NA NA NA 20′′ mult inco

library with I

B1AW3 none B1AW3AC 14′′ mult inco

library with Iremnants afteindication 

B1BW1 A B1BW1A 21.8 2.2 2.96 63 NA NA 4.12 68 74′′ mult to b

sample librar

B1BW1 B B1BW1A 28.5 1.7 5.67 113 NA NA NA NA 74′′ mult to b

sample librar

B1BW1 C B1BW1A 44.8 0.6 8.09 142 2.96 70 5.36 >100% 74′′ mult to b

sample librar

B1BW1 D B1BW1A 49.0 1.0 2.79 56 NA NA NA NA 74′′ mult to b

sample librar

84
85

TABLE 21. LISTING OF SAMPLES REMAINING FROM ORIGINAL BILLET MATERIAL (Co

Original Billet ID 

Indication 

ID 

Current Billet 

Segment ID 

Inches From 

Top Depth 

MZ 

SNR 

MZ 

Amp 

(%) 

CL 

SNR 

CL 

Amp 

(%) 

CA 

SNR 

CA 

Amp 

(%) Dispo

B1BW1 E B1BW1A 61.3 0.9 3.05 69 NA NA NA NA 74′′ mult to b

sample librar

B1BW1 F B1BW1A 67.8 1.1 26.6 450 4.6 179 5.6 >100% 74′′ mult to b

sample librar

B1BW1 G B1BW1B 81.0 1.5 8.28 213 2.85 100 3.39 80 HIP to heal s

segment 

B1BW1 H B1BW1C 99.5 0.4 6.56 127 NA NA NA NA 14′′ mult to b

sample librar

B1BW2B A B1BW2B 1.1 1.2 13.27 179 5.54 118 NA NA 86′′ mult inco

library with I

B1BW2B B B1BW2B 17.4 0.3 15.74 160 6.00 108 NA NA 86′′ mult inco

library with I

B1BW2B C B1BW2B 43.2 0.3 7.55 113 NA NA NA NA 86′′ mult inco

library with I

B1BW2B D B1BW2B 51.2 1.6 11.38 160 2.31 46 4.14 116 86′′ mult inco

library with I

B1BW2B E B1BW2B 65.0 1.5 8.38 142 2.57 108 5.42 101 86′′ mult inco

library with I

B1BW3 none B1BW3A 12′′ mult inco

library with I

B1BW3 A B1BW3AA 22.0 1.3 3.92 113 NA NA NA NA Forged to pan

inspection stu

B1BW3 B B1BW3AB 43.5 1.1 7.56 160 NA NA NA NA Provided to T

study—with 2

into sample liB1BW3AB 
86

TABLE 21. LISTING OF SAMPLES REMAINING FROM ORIGINAL BILLET MATERIAL (Co

Original Billet ID 

Indication 

ID 

Current Billet 

Segment ID 

Inches From 

Top Depth 

MZ 

SNR 

MZ 

Amp 

(%) 

CL 

SNR 

CL 

Amp 

(%) 

CA 

SNR 

CA 

Amp 

(%) Dispo

B1BW3 C no remaining 

pieces 

66.0 0.5 6.67 127 NA NA NA NA ETC defect c

B1BW3 D B1BW3CA 86.0 1.5 5.06 74 NA NA NA NA ETC defect c

with 10′′ piec

sample librar

B1BW3 none B1BW3CB 14′′ mult inco

library with I

B1BW3 none B1BW3C 13′′ mult inco

library with I

B2W1 A 10.7 0.5 11.35 142 3.46 60 4.59 90 9′′ mult incor

library with I

B2W1 B 24.5 1.3 11.05 151 3.59 85 2.76 60 attenuation stB2W1 C B2W1B 65.0 0.9 6.67 127 NA NA 22.35 60 Forged to pan

inspection stu

B2W1 D B2W1C 69.5 0.5 6.46 87 NA NA NA NA 29′′ mult inco

library with I

B2W2 none B2W1CA 36′′ mult inco

library with I

B2W2 A Visible end 

burst, 

indication 

marked as 

A; ultrasonic 

inspection 

not feasible 

B2W2 B B2W2B 14.0 0.6 6.55 107 NA NA NA NA 10′′ mult inco

library with I
87

TABLE 21. LISTING OF SAMPLES REMAINING FROM ORIGINAL BILLET MATERIAL (Co

Original Billet ID 

Indication 

ID 

Current Billet 

Segment ID 

Inches From 

Top Depth 

MZ 

SNR 

MZ 

Amp 

(%) 

CL 

SNR 

CL 

Amp 

(%) 

CA 

SNR 

CA 

Amp 

(%) Dispo

B2W2 C no remaining 

pieces 

22.4 0.2 4.09 74 NA NA NA NA ETC defect c

B2W2 D B2W2C 55.0 0.6 4.46 113 NA NA NA NA 25′′ mult inco

library with I

B2W2 none B2W2D Material from 

to 2′′ bar, inc

library with I

B2W2 X B2W2C 57 0.55 4.97 61 NA NA NA NA 25′′ mult inco

library with I

B2W3 A B2W3B 20.1 0.2 6.81 107 NA NA 3.78 72 18′′ mult inco

library with I

B2W3 B B2W3B 27.8 2.3 3.54 72 NA NA NA NA 18′′ mult inco

library with I

B2W3 C B2W3B 31.0 2.0 2.59 50 NA NA NA NA 18′′ mult inco

library with I

B3W1B A 68.8 2.0 4.8 84 1.36 35 3.96 55 Attenuation sB3W1B B B3W1BB 84.8 2.2 2.45 73 NA NA NA NA 34′′ mult inco

library with I

B3W1B C B3W1BB 102.5 2.3 3.52 99 1.95 40 1.91 35 34′′ mult inco

library with I

B3W1B D B3W1BB 104.3 1.9 9.52 134 2.65 50 4.91 70 34′′ mult inco

library with I

B3W2 A B3W2A 1.9 0.7 12.25 357 NA NA NA NA 11′′ mult inco

library with I

B3W2 B B3W2A 3.3 0.3 8.39 113 NA NA 5.11 >100 11′′ mult inco

library with I
88

TABLE 21. LISTING OF SAMPLES REMAINING FROM ORIGINAL BILLET MATERIAL (Co

Original Billet ID 

Indication 

ID 

Current Billet 

Segment ID 

Inches From 

Top Depth 

MZ 

SNR 

MZ 

Amp 

(%) 

CL 

SNR 

CL 

Amp 

(%) 

CA 

SNR 

CA 

Amp 

(%) Dispo

B3W2 C B3W2A 8.7 2.1 8.32 201 NA NA NA NA 11′′ mult inco

library with I

B3W2 D 16.9 1.5 5.06 127 3.0 60 3.05 54 Part of B3W2B3W2 E 40.0 1.3 12.53 213 4.47 74 NA NA Provided to T

study—remn

provided to sB3W3CB 

B3W2 F B3W2CA 85.5 0.2 6.83 160 NA NA NA NA 36′′ mult inco

library with I

B3W2 G B3W2CB 113.0 1.3 5.88 142 NA NA 5.74 84 Provided to T

study—remn

4.5′′, and 11′′ 

into sample liB3W2CB 

B3W3 A 12.3 0.6 7.65 113 NA NA 3.96 80 35′′ mult inco

library with I

B3W3 B no remaining 

pieces 

51.0 0.8 5.74 120 2.39 50 4.37 60 ETC defect c

B3W3 C B3W3C 67.6 2.9 8.99 127 3.08 >100 3.67 85 36′′ mult inco

library with I

B3W3 D B3W3CA 109.6 0.9 8.93 142 NA NA NA NA 32′′ mult inco

library with I

B3W3 none B3W3CB 6′′ mult incor

library with I
Among the samples that are included in the library is the hot isostatic press (HIP)-to-heal 

sample. In an effort to evaluate the effect or reducing and eliminating the cracks and voids 

normally associated with hard alpha inclusions on detectability of hard alpha, an indication was 

selected and a mult removed from the billet. Indication B1BW1-G was selected, and a 16′′

section was removed. The details of the inspection are provided in table 22, and the results are 

shown in figure 73. The indication was detected using all three methods during the field 

inspection. After sectioning, the mult was inspected using the multizone system at GE prior to 

and after the HIPping process. No indications were found after the HIPping process. These 

results point to the enhanced detectability of hard alpha in the presence of cracks and voiding. 

The sample also provides an excellent resource for the evaluation of future inspection 

improvements. 

TABLE 22. INSPECTION AMPLITUDES AND SNR FOR INDICATION B1BW1-G USED 

IN HIP-TO-HEAL SAMPLE 

Inspection location 

MZ Amplitude and 

SNR 

Conventional Normal 

Amplitude and SNR 

Conventional Angle 

and SNR 

Field inspection 213% - 8.3 SNR 100% - 2.9 SNR 80% - 3.4 SNR 

Laboratory inspection 125% - 7.4 SNR 

After HIPping No indication detected

FIGURE 73. C-SCAN RESULTS FOR INDICATION B1BW1-G USED IN 

HIP-TO-HEAL SAMPLE 

(Note: the indication was detectable in zones 2 and 3 during the original field inspection.) 

89
4. CONCLUSIONS. 

Hard alpha defects are defined as an interstitially stabilized alpha phase region of substantially 

higher hardness than surrounding material, arising from very high local nitrogen, oxygen, or 

carbon concentrations that produce the high hardness, often brittle, alpha phase. Defects may 

occur because of the inadvertent use of burned sponge or contaminated raw stock, improperly 

processed electrodes, or vacuum leaks. If hard alpha defects are found, the entire heat in which 

any hard alpha defect occurs will be downgraded from premium quality and is no longer 

acceptable for use in critical rotating components. The occurrence of hard alpha defects is rare 

and detailed study has not been possible. In 1995, the existence of a contaminated heat of 

material was made known to the Engine Titanium Consortium. The heat was purchased and 

inspected using multizone and conventional inspection methods. Sixty indications were detected 

using the multizone method with four misses, compared to 30 detections with conventional 

inspection. Ten of the defects were selected for detailed characterization. Metallographic 

characterization of the defects was accomplished using optical microscopy at 5-mil intervals. 

The optical micrographs were digitally recorded for subsequent reconstruction leading to solid 

models representing the cracking and voiding of the ten defects. The Contaminated Billet Study 

(CBS) material offers an unprecedented opportunity to evaluate naturally occurring hard alpha 

defects and understand the factors related to their detectability. The following primary 

conclusions were found: 

• More than twice as many indications were found with multizone inspection than with the 

dual probe (longitudinal and angle inspection) conventional inspection. Detection 

occurred over the full depth of the billet for both methods. Conventional inspection 

detection was not correlated to the multizone amplitudes, i.e., the conventional misses 

occurred over the range of amplitudes. 

• Phased array inspection was demonstrated to have similar capability to the multizone 

results with the advantage of simpler fixturing. 

• In chemical analysis studies of the defects, the nitrogen concentration was found to drop 

to less than 1% within 10 mils from the defect center (center of the voiding). The 

implications of these results are that the nugget and diffusion zone contribute little to the 

detection of the defect. Ultrasonic response is dominated by the presence of cracks and 

voiding. 

• Defect characterization of ten defects provided detailed hard alpha defect data for 

metallurgists, life management, design, and inspection personnel. The data also provided 

input for probability of detection (PoD) calculations and was used in model validation. 

• Of the ten hard alpha defects selected for metallographic sectioning, seven were not 

detected by conventional inspection. All of the missed defects had hard alpha core areas 

in the 15,000 to 100,000-square-mil range. 

90
• Using the solid model results, the sizes of the defects were tabulated and used in 

subsequent PoD calculations. The preliminary results indicated inconsistencies between 

PoD calculations generated from prior data and the recent CBS characterization. 

• Several reproducibility studies were performed using a subset of the billets. Variability 

of up to 10 dB was found for both methods. Inspection setup and transducer alignment 

were identified as key contributors to the variability. 

5. REFERENCES. 

1. FAA Advisory Circular 33.15-1, “Manufacturing Process of Premium Quality Titanium 

Alloy Rotating Engine Components,” September 22, 1998. 

2. “United Airlines Flight 232 McDonnell Douglas DC-10-10 Sioux Gateway Airport, 

Sioux City, Iowa,” July 19, 1989, NTSB Report Number, AAR-90-06, November 1, 

1990. 

3. J.R. Costa, R.E. Gonzalez, R.E. Guyotte, D.P. Salvano, T. Swift, and R.J. Koenig (chair), 

“Titanium Rotating Components Review Team Report,” Federal Aviation 

Administration, Aircraft Certification Service, Engine and Propeller Directorate, Boston, 

MA, December 14, 1990. 

4. FAA Advisory Circular AC 33.14-1, “Damage Tolerance for High Energy Turbine 

Engine Rotors,” January 8, 2001. 

5. Howard, P., Copley, D., and Gilmore, R., “Transducer Design for High Sensitivity 

Ultrasonic Inspection of Titanium,” in Rev. of Prog. in QNDE, Vol.16A, D.O. Thompson 

and D.E. Chimenti, eds., Plenum, New York, 1997, pp. 893-900. 

6. Gray, T.A., “Application of Measurement Models to Specification of Ultrasonic 

Inspections,” in Rev. of Prog. in QNDE, Vol.16B, D.O. Thompson and D.E. Chimenti, 

eds., Plenum, New York, 1997, pp. 2061-2068. 

7. Thompson, R.B., Margetan, F.J., Yalda, I., Chiou, C.-P., and Panetta, P.D., “Coupling 

Microstructure Outputs of Process Models to Ultrasonic Inspectability Predictions,” in 

Rev. of Prog. in QNDE, Vol.17B, D.O. Thompson and D.E. Chimenti, eds., Plenum, New 

York, 1998, pp. 1847-1853. 

8. Umbach, J.A. and Roberts, R.A., “Ultrasonic Phased Array Transducers-Model and 

Experiment,” presented at ASNT Fall Conference, October 1997. 

9. K. Smith and L. Brasche, “Successful Implementation of FAA Research Addressing the 

Disk Inspection Initiative,” in Proceedings of the 5th Annual FAA/NASA/DOD Aging 

Aircraft Conference, on CD, 2003. 

91
10. Filkins, R.J., Fulton, J.P., Patton, T.C. and Young, J.D., “Recent Advances and 

Implementations of Flexible Eddy Current Probe Technology,” in Rev. of Prog. in 

QNDE, Vol.17B, D.O. Thompson and D.E. Chimenti, eds., Plenum, New York, 1998, 

pp. 1809-1816.

11. Amos, J.M. and Chao, J.C., “Optimization of a Wide-Field Eddy Current Probe Using a 

Boundary Element Method Based Model,” in Rev. of Prog. in QNDE, Vol.17A, D.O. 

Thompson and D.E. Chimenti, eds., Plenum, New York, 1998, pp. 275-282. 

12. Chao, J.C., Nakagawa, N., Raulerson, D.A., and Moulder, J.C., “Boundary Element 

Method Based Probe Design Model Validation,” in Rev. of Prog. in QNDE, Vol.16A, 

D.O. Thompson and D.E. Chimenti, eds., Plenum, New York, 1997, pp. 967-972. 

13. Meeker, W.Q., Chan, V., Thompson, R.B., and Chiou, C.-P., “A Methodology for 

Predicting Probability of Detection for Ultrasonic Testing,” in Rev. of Prog. in QNDE, 

Vol.20B, D.O. Thompson and D.E. Chimenti, eds., AIP, Melville, NY, 2001, pp. 1972-

1978. 

14. “A Methodology for the Assessment of the Capability of Inspection Systems for 

Detection of Subsurface Flaws in Engine Components,” FAA Report DOT/FAA/AR01/96, September 2002. 

15. G.R. Leverant, R.C. McClung, Y.-T. Wu, H.R. Millwater, D.S. Riha, M.P. Enright, G.G. 

Chell, K.S. Chan, P.C. McKeighan, M. Gorelik, C. Fischer, D. Lehmann, K. Green, J. 

Bartos, N. Howard, and S. Srivatsa, “Turbine Rotor Material Design,” FAA Report 

DOT/FAA/AR-00/64, December 2000. 

16. S. Srivatsa, “Turbine Rotor Material Design—Task 2, Effect of Forging on Defect 

Morphology,” Southwest Research Institute, December 11, 2002. 

17. W.W. Bogan, “Metallurgical Evaluation: RMI 2XVAR Ti64 Heat 883588 Hard Alpha,” 

Internal ETC Letter Report, April 27, 1995. 

18. Smith, K.D., “Zoned Ultrasonic Inspection of Titanium Billet Using Phased Array 

Transducers,” Engine Titanium Consortium Open Forum Proceedings, February 1995. 

19. Mucciardi, T., “Phased Array Inspection of Titanium Billets,” Engine Titanium 

Consortium Open Forum Proceedings, May 1996. 

20. Umbach, J. and Roberts, R. “Focussed Array Transducer for Billet Inspection: Model and 

Experiment,” Engine Titanium Consortium Open Forum Proceedings, November 1997. 

21. Lacroix, B., Lupien, V., Duffy, T., Kinney, A., Khandelwal, P., and Wasan, H.S., 

“Phased-Array Ultrasonic System for Inspection of Titanium Billets,” Review of Progress 

92
in Quantitative Nondestructive Evaluation, D.O. Thompson and D.E. Chimenti, eds., 

Vol. 21A, p. 861, 2002. 

22. B. Boyd, C.-P. Chiou, R.B. Thompson, and J. Oliver, “Development of Geometrical 

Models of Hard Alpha Inclusions for Ultrasonic Analysis in Titanium Alloys,” Review of 

Progress in Quantitative Nondestructive Evaluation, D.O. Thompson and D.E. Chimenti, 

eds., Vol. 17A, 1998, pp. 823-830. 

23. C.-P. Chiou, B. Boyd, R.B. Thompson, and J. Oliver, “Geometrical and Ultrasonic 

Modeling of Hard Alpha Defect Components in Titanium Alloys,” Review of Progress in 

Quantitative Nondestructive Evaluation, D.O. Thompson and D.E. Chimenti, eds., Vol. 

18B, 1999, pp. 1829-1836. 

24. C.-P. Chiou, F.J. Margetan, and R. B. Thompson, “Modeling of Ultrasonic Signals from 

Weak Inclusions,” Review of Progress in Quantitative Nondestructive Evaluation, D.O. 

Thompson and D.E. Chimenti, eds., Vol. 15A, 1996, pp. 49-55. 

25. C.-P. Chiou and R.B. Thompson, “A Comparative Study of Ultrasonic Models for Hard 

Alpha Defects in Titanium Alloys,” Presented in Review of Progress in Quantitative 

Nondestructive Evaluation, July 30, 1999. 

26. C.F. Ying and R. Truell, “Scattering of a Plane Longitudinal Wave by a Spherical 

Obstacle in an Isotropically Elastic Solid,” Journal of Applied Physics, Vol. 27, No. 9, 

1956, pp. 1086-1097. 

27. C.-P. Chiou, F.J. Margetan, R.B. Thompson, and Brian Boyd, “Development of 

Ultrasonic Model for Hard Alpha Inclusions in Titanium Alloys,” Review of Progress in 

Quantitative Nondestructive Evaluation, D.O. Thompson and D.E. Chimenti, eds., Vol. 

16B, p. 1529, 1997. 

28. R.B. Thompson and T.A. Gray, “A Model Relating Ultrasonic Scattering Measurements 

Through Liquid-Solid Interfaces to Unbounded Medium Scattering Amplitudes,” Journal 

of Acoustical Society of America, 74 (4), 1983, pp. 1279-1290. 

29. B.A. Auld, “General Electromechanical Reciprocity Relations Applied to the Calculation 

of Elastic Wave Scattering Coefficients,” Wave Motion, 1, 1979, pp. 3-10. 

30. Thompson, R.B., Meeker, W.Q., Chiou, C.-P., Brasche, L., Burkel, D., and Sturges, D.J., 

“Issues in the Determination of Default POD for Hard Alpha Inclusions in Titanium 

Rotating Components for Aircraft Engines,” Review of Progress in Quantitative 

Nondestructive Evaluation, Vol. 23B, D.O. Thompson and D.E. Chimenti, eds., AIP, NY, 

p. 1587-1594, 2004. 

31. P.D. Panetta, R.B. Thompson, and F.J. Margetan, “Use of Electron Backscatter 

Diffraction in Understanding Texture and the Mechanisms of Backscattered Noise 

93
Generation in Titanium Alloys,” in Rev. of Prog. in QNDE, Vol. 17A, D.O. Thompson 

and D.E. Chimenti, eds., Plenum, New York, 1998, p. 89-96. 

32. Panetta, P.D., Thompson, R.B., Margetan, F.J., and Yalda, I., “Ultrasonic Microstructural 

Characterization and Modeling of Attenuation in Ti-17 and Ti-6Al-4V Alloys,” 

Nondestructive Evaluation and Materials Properties, O. Buck and P. Liaw, eds., TMS, 

Warrendale, OH, 1998. 

33. Gooding, C. and Biddulph, J., “Ultrasonic Inspection of Titanium Alloy Billet From RMI 

Contaminated Heat #883588,” Engine Titanium Consortium Open Forum Proceedings, 

May 1996. 

34. Margetan, F.J., Yalda, I.M., and Thompson, R.B., “Estimating Ultrasonic Signal-to-Noise 

Ratios for Inspections of Cylindrical Billets,” Review of Progress in Quantitative 

Nondestructive Evaluation, D.O. Thompson and D.E. Chimenti, eds., Vol. 13B, p. 1737, 

1994. 

35. Howard, P.J. and Gilmore, R.S., “Ultrasonic C-Scan Imaging for Hard Alpha Flaw 

Detection and Characterization,” Review of Progress in Quantitative Nondestructive 

Evaluation, D.O. Thompson and D.E. Chimenti, eds., Vol. 13B, p. 763, 1994. 

36. Copley, D., “Billet Inspection Reproducibility Study: ETC Open Forum Proceedings,” 

Houston, Texas, 1997. 

94
APPENDIX A—LITERATURE SURVEY COMPLETED BY ALLIEDSIGNAL IN 

PHASE I: ENGINE TITANIUM CONSORTIUM PROGRAM 

A-1
A REVIEW OF THE ORIGIN AND CHARACTER OF INGOT DEFECTS 

THAT MAY OCCUR IN AEROSPACE TITANIUM ALLOYS AND 

NDE METHODS FOR THEIR DETECTION 

James A. Hall, Janet Wade, Lloyd Schaefer, Andy Kinney 

Materials and Process Engineering 

and 

Valerie Peters 

Component Investigation 

AlliedSignal Engines 

June 1997 updated February 2003 

1. ABSTRACT 

In support of the Federal Aviation Administration’s (FAA) Engine Titanium Consortium (ETC), 

this paper discusses the origin and characteristics of titanium melt related defects, provides a 

brief synopsis of experiments conducted to date relating to the evaluation and/or control of melt 

related defects, the potential nondestructive evaluation (NDE) methods for detecting such 

defects, and contains literature search references pertaining to these subjects. The report is 

divided into three sections: 

Section 1 of this report contains discussions of Type I defects, high-density inclusions, Type II 

defects, ingot porosity, and alloy segregation with their definitions, causes and characteristics. 

Brief synopses of several published experiments relating to sources of nitride inclusions, defect 

removal, nitride seed development, effect of defects on fatigue properties, and alpha segregation 

are also included. Forging or conversion related defects are not included in this report. 

Section 2 addresses surface and volumetric NDE methods appropriate for detecting and 

characterizing titanium melt related defects. Image and signal analysis techniques for these 

methods are identified and discussed as well as various means of measuring NDE methods 

probability of detection (POD). 

Section 3 comments on the utility of the literature review and recommendations for future work. 

2. ACKNOWLEDGMENT 

This material is based upon work performed as a part of the Engine Titanium Consortium 

operated by Iowa State University for the FAA New England Engine and Propeller Directorate 

and the FAA Technical Center under Grant Number 94-G-048. 

3. INTRODUCTION 

As a part of the Fundamental Studies in Titanium Task of the ETC, a literature review was 

undertaken. The literature review had the following purposes: 

• Provide the latest information about the formation of various defect types 

• Detail any known preventative measures for these types of defects 

A-2
• Provide information regarding the effect of microstructure and macrostructure of the 

parent material on detectability 

• Catalog data on the material properties 

• Provide background information on NDE methods developed by other researchers 

appropriate to titanium inspection 

The intent is to provide data for the formulation of approaches to the various defect detection 

problems in various material forms. The available literature was reviewed from the NERAC and 

NOTICE databases. Additional information was also gathered from other available sources such 

as the following: non-proprietary information solicited from members of the ETC, various 

domestic producers of titanium, and the Jet Engine Titanium Quality Committee; QNDE 

proceedings; and other open literature journals. The synopses provided below are only a 

sampling and should not be interpreted as being complete, nor inclusive of all key work. 

4. INGOT DEFECTS, DEFINITION, ORIGINS and CHARACTERISTICS 

4.1 TYPE I DEFECTS [A-1 to A-5] 

Type I defects are also known as high interstitial defects (HID), interstitial rich inclusions or low 

density inclusions (LDI). They are recognized as alpha rich particles interstitially stabilized with 

nitrogen, oxygen or carbon, or some combinations of these. Their metal alloy content may range 

from very nearly all titanium to nominal alloy content of the host heat or even of a different 

alloy. 

The embryo form of these defects have a much higher melting point than titanium or Ti alloys 

and must be consumed by dissolution into the melt. Depending on the relative size and densities 

of Type I defects, large heavy defects may survive multiple vacuum arc remelt (VAR) 

processing and smaller lighter defects may survive cold hearth melting (CHM). The defects are 

substantially harder than the surrounding matrix and may impair fatigue resistance and ductility. 

The defects are difficult to detect unless associated with voids or cracking from thermomechanical working. The term LDI arose from this void association, however, the alpha-rich 

phase itself is not of “low density.” Of course, creation of a defect during melting as described 

below, will negate some, or all, of the dissolution opportunities offered by melting. 

4.2 SOURCES OF TYPE I DEFECTS 

4.2.1 BURNED SPONGE, REACTOR VESSEL BURNING [A-2 and A-5] 

Type I defects, originating from this source are attributed to the entry of air into the reaction 

vessel or vacuum distillation chamber during sponge production. If in a confined volume, air 

reacts with the titanium sponge, which consumes oxygen (O2) first, and then the nitrogen (N2). 

Nitrogen rich defects resist dissolution in the liquid titanium. 

Visual Appearance: Regions of high nitrogen content titanium, when removed from the reactor 

vessel appear much like the titanium metal, only much more friable. It seldom is golden in color 

A-3
as the near stoichiometric TiN intermetallic would be and therefore it is not easy to visually 

separate them from the normal particles. 

Metallurgical Characteristics: the metallic alloy content will be considerably less than that of the 

host alloy and the hardness will be significantly higher. Voids may be associated with the larger 

variety of these defects. 

Location in Ingot: Large defects are heavier than the liquid and will tend to concentrate in the 

bottom 1/3 of the ingot. Smaller (if not dissolved) defects, may be more uniformly distributed. 

Defects in this family reflect an out-of-control process and may appear in all heats incorporating 

the culprit sponge lot, and have a size distribution only slightly different than that of the sponge, 

reduced slightly in size by melting dissolution. 

4.2.2 BURNED SPONGE, OTHER [A-5] 

Type I defects are attributed to burned sponge caused by the following: 

• Fires or flashing which may occur during extraction of sponge from the reactor or 

vacuum distillation chamber 

• Downstream processes, such as crushing the chip to sponge 

• Drying, in the case of leached sponge 

• Sponge may experience combustion during blending and compacting of the electrode 

Visual Appearance: In most cases the burned sponge is discolored and visually separable. The 

refractory particle is brittle and easily crushed. As these causes will affect entire lots of sponge 

production, a visual examination of selected samples of each lot is often used as a quality control 

process and finding of HID embryos will disqualify the entire lot from rotor grade applications. 

However this inspection is ineffective in screening out down stream defect sources from events, 

such as combustion during the blending operation. 

4.2.3 BURNED BULK SCRAP [A-5] 

• Torch cutting. Type I defects may be attributed to torch cutting in preparation of bulk 

scrap for fabrication. Part of the process detail involves combustion of titanium and in 

the tight confines of the cutting zone, nitrogen combustion is possible. Furthermore, 

residual organic material may contribute to carbon stabilization in this region. 

• Infoliated ends of mill scrap may contain high O2 and/or N2 levels and should be avoided 

for rotor grade material as they are not easily cleaned. 

Metallurgical characteristics: The defect will have normal metallic alloy content of the scrap 

source. It is unlikely to have cracks or voids unless associated with conversion or forging 

operations. Size varies but shape will likely be irregular. 

A-4
4.2.4 BURNED CHIPS AND TURNINGS [A-5]. 

Burned chips and turnings may be another source of HID formers. If burned in a restricted 

volume, they may become highly contaminated with nitrogen (or carbon in the case of 

machining chips burned during the machining operation itself or prior to the cleaning step in the 

chip processing line), therefore they are refractory. The shape and size of chip (high surface to 

volume ratio) leads to rapid dissolution during melting and are less likely to be serious HID 

sources in multiple melted ingot, e.g., double or triple VAR, fabricated from electrodes 

contaminated by them. 

4.2.5 INADEQUATE SHIELDING OF WELDS DURING ELECTRODE FABRICATION 

[A-2 and A-5] 

Type I defects may be attributed to inadequate shielding of welds during electrode fabrication 

which can result in nitrogen rich weld metal. Defects may be attributed to the use of metal-inert 

gas (MIG) welding, if the welding process is not shielded well enough to exclude contamination. 

Welding of sponge electrodes with plasma torches produces a wide gradient of metallic content 

as the host being welded contains sponge particles, pure metallic additions, and master alloy 

particles. The use of chamber welding and specially shielded weld enclosures is necessary to 

assure absence of contaminated welds. 

Visual Appearance: They are sometimes discolored with the characteristic gold color of TiN. 

Visual inspection of the welds after the electrode is fabricated often will reveal indications of 

poor shielding although this is not fool proof as over welding contaminated welds will destroy 

the visual evidence. 

Metallurgical Characteristics: HIDs from this source may contain metallic alloying elements in 

the range from unalloyed titanium to that of the host alloy. It will be harder than the host alloy 

because of the interstitial content. Any cracking associated with the HID will come from 

deformation processing at either billet or forging stages. However, this type of defect may 

survive the melting and conversion processes without developing cracks. 

Location in Ingot: This type of HID will be heavier than the liquid titanium and tend to sink to 

the bottom of the liquid pool. In multiple melting operations, each melt ingot will concentrate 

the HIDs in the bottom 1/3 of its length. Each melt will reduce the HID size depending on the 

pool depth, the alloy melting temperature, and the practice for electrode inversion between melts. 

It is a good practice to disallow welding in preparation of the final melt electrode because any 

HID embryo will have only one chance to dissolve. 

A-5
4.2.6 VAR FURNACE LEAKS [A-2, A-4, and A-5] 

Type I defects attributed to air leaks are most commonly associated with leaks in sliding seals 

(the ram feed through in most VAR furnace designs). This rarely occurs. Such condition is 

evidenced by a pressure increase in the furnace, unless a rapid increase in leak rate is also 

experienced. This may be dampened by high pumping capacity. 

Visual Appearance: The defect will be rather large and may appear associated with a hole in the 

remaining wafer after hot top which may appear much like a torch cut surface. 

Metallurgical Characteristics: The defect will be harder than the matrix and have the metallic 

composition of the host ingot with a higher alpha content when occurring in alpha-beta alloys. 

The defect is unlikely to have cracks or voids except those associated with deformation 

processing. They may be large. 

Location in Ingot: The defect will be localized near the top of the ingot produced when the leak 

occurred but may survive subsequent melting and wind up in the next ingot at a position 

depending on the electrode inversion practice used. 

4.2.7 INEFFECTIVE HOUSEKEEPING [A-5] 

Type I defects are often attributed to splatter and other melt condensate deposits within the 

furnace enclosure (furnace head and ancillary devices and chambers). These will be finely 

divided and will oxidize (nitride) when such hot particles are exposed to air - this is generally 

associated with opening the furnace and exposing the virgin alloy splatter to the atmosphere. 

Subsequent melting may see these particles fall in the molten pool and survive by rapidly sinking 

to the bottom or sides - most common when the pool is shallow such as at the arc strike or in the 

hot top operation. This sort of defect may occur in VAR as well as CHM operations. 

Metallurgical Characteristics: The origin of the source may have come from another heat of 

material, therefore the metallic composition could be anything. In this case the HID will be 

harder than the matrix, and due to the possibility of inter-alloy mixing, there may be a very 

different microstructure. The defect is unlikely to have voids or cracks associated with them. 

They are likely to be regularly shaped but not exclusively. They are likely to be smaller than the 

first 6 HIDs described above. 

Location in Ingot: The defects tend to be concentrated near the top or the bottom of the final 

melt because of the shallow pool existing in these locations. For the deeper pool situations in 

steady state melting, their survival is problematic and limited to the regions near the ingot 

surface. With some alloys the final melt is performed entirely with a shallow pool to avoid melt 

segregation and, in this case, these defects may occur anywhere in the ingot. The defect is not 

likely to be as refractory as the other HID’s and is not likely to survive multiple melting. 

A-6
4.2.8 RESIDUAL BURNED MATERIAL FROM FIRST INGOT SURFACE[A-5] 

Recent experience has shown that residual magnesium or sodium in the sponge will vaporize 

during the first melt of a sponge electrode. The condensate from this vaporization forms on the 

crucible surface and is effectively transferred to the ingot surface as it subsequently fills the 

crucible. When the crucible is stripped from this first melt ingot, which will become an electrode 

for the next VAR, under certain conditions these metal deposits will ignite and burn with enough 

heat released to oxidize the rather porous ingot surface forming oxide and nitride rich titanium. 

These areas are refractory and may not melt during the subsequent two or three VAR steps. 

Metallurgical Characteristics: These particles start out rather large and pancake shaped and may 

be free of initial voids. Their composition may be near that of the base alloy. But they may also 

be rich in the high vapor pressure alloying elements such as aluminum. They may have almost 

any size or shape as these features will be modulated some by subsequent melts. Depending on 

both the size and initial interstitial content, these defects may or may not crack during 

deformation processing so we cannot count on having cracks or voids to aid UT detection. They 

will be oxygen and nitrogen stabilized but not stabilized with carbon. 

Location in Ingot: These defects are most likely to find their way to the bottom part of each 

subsequent melt if they are refractory enough to survive the liquid metal exposure and the 

thermal shock of transfer across the arc zone. If the electrode inversion practice is such that the 

bottom of the first melt becomes the top of the second and inversion occurs again to make the 

third VAR ingot, it is possible that part of the final electrode will melt through the HID 

containing material during the hot-topping operation. Therefore, such defects will have no deep 

pool into which to sink. Accordingly, there is a possibility that the hot-topped region may 

contain hard alpha defects. Generally speaking, this material is all lost in top cropping for other 

reasons so we seldom, if ever find such defects near the top of the billet made of rotor grade 

triple VAR ingot. 

Prevention: Take precautions to avoid the environment conducive to the burning described 

above. With the anticipation that not always will the operation be able to avoid ignition of the 

inevitable deposit (even vacuum distilled sponge contains sufficient volatile residuals to cause a 

light case of this problem) by observing the crucible stripping operation operators can identify 

the potential problem areas and take measure to eliminate them from the process stream. 

4.3 HIGH DENSITY INCLUSIONS [A-2, A-3, and A-5] 

High-density inclusions include refractory metals (W, Mo, Ta, and Nb) or refractory metal 

carbides. The main sources of these defects are scrap and poor housekeeping. Carbide and 

tungsten particles have often been traced to machine turnings cut with carbide tools and nonconsumable welding electrodes, respectively. Refractory metals have higher melting points and 

densities than titanium and tend to sink to the liquid-metal interface at the bottom of the molten 

pool and to a lesser extent on the outer 25% of the radius. 

A-7
Another source of high-density inclusions is ineffective housekeeping associated with equipment 

repair, such as TIG welding. Without proper house cleaning, inadvertent inclusion of a 

Thoriated Tungsten welding electrode scrap may result. Similarly, even very small tungsten 

metal pieces, such as incandescent light bulb filaments have been shown to survive multiple 

VAR of titanium alloys [A-6] 

Master alloy additions of refractory metals, such as Molybdenum, are formulated to reduce the 

melting point so that they will completely dissolve or melt, but there is history of these sorts of 

particles surviving. Recent, known, events have been attributed to use of coarse master alloy 

particles in formulating the ingot. The key to avoiding such occurrences is to make sure that the 

alloy additions are small enough particle size to assure dissolution in multiply melted material. 

4.4 TYPE II DEFECTS [A-2, A-3, and A-5] 

Type II defects are also known as soft alpha segregates. These defects are found in alloys 

containing aluminum. Type II defects are often called High Aluminum Defects (HAD) because 

of the significantly higher than normal aluminum content they exhibit. Another name often used 

to describe this sort of defect is “chicken tracks” which reflects their appearance in billet slices. 

Cause: Type II alpha defects are associated with ingot pipe and void formation. As shrinkage 

pipe forms in a hot titanium alloy ingot, aluminum (or any other relatively volatile alloying 

element at the high temperature involved) evaporates rapidly from the hottest surfaces of the 

void, filling it with metallic vapor which condenses on cooler surfaces of the void as the ingot 

cools. As a result, the interior surface of the void will be coated with aluminum and/or other 

volatile elements, and just below the surface, the microstructure will be slightly depleted in these 

elements. Subsequent forging of the ingot or intermediate mill product, in the production of 

billet and bar, will cause the voids to close, but the temperature and time combination is 

insufficient to result in serious homogenization. 

Visual Appearance: Areas enriched or depleted with aluminum will often be found to outline 

portions of the original void/pipe surface and appear as Type II segregation. The result of 

forging the voids closed is a rather irregularly shaped zone of aluminum rich alloy (the name of 

chicken tracks is descriptive here) often with an alpha lean zone immediately adjacent. They 

appear as light and dark etching zones, respectively, in the macrostructure of product. 

Metallurgical Characteristics: The aluminum content of the defect is usually somewhat higher 

than that of the matrix and the vanadium content may be lower in Ti Al-V alloys. However, it is 

not uncommon to find an associated area which is slightly lower in aluminum content and higher 

in vanadium that the matrix. The defect is a form of localized alpha segregation but, unlike a 

Type I defects, is quite ductile with a hardness usually not much greater than that of the matrix. 

The segregates tend to be relatively long, thin and very irregular. Small defects do not seem to 

have a pronounced effect on mechanical properties of annealed alloys. 

Detection: When these defects are anodized, some develop a characteristic blue color. 

However, areas depleted in aluminum tend to etch lighter on anodizing. These areas and have 

A-8
been incorrectly referred to as beta segregation. They present only a small difference in elastic 

properties so UT inspection is not likely to detect Type II defects, especially the smaller ones. 

Prevention: Good hot topping practices that minimize the area removed during billet cropping 

for macroexamination. A good billet slice inspection and cropping practice will virtually 

eliminate these defects associated with healed pipe. However, it is possible to create them with 

aggressive billet conversion practice and these are difficult to detect. The best practice is to 

avoid their creation by process control in the mill. 

4.5 INGOT POROSITY 

There are two primary types of ingot porosity: gas porosity and shrinkage porosity. 

Gas porosity in VAR ingots has often been found associated with residual chloride salts in the 

sponge. Salts have essentially no solubility in the solid metal but form vapor bubbles in the 

liquid phase which have been found to account for the following defects: 

• Unhealed pipe in billet 

• Blisters observed in Ti-8Mn sheet 

• Weld porosity 

• Porosity in blended elemental powder metallurgy products 

Gas porosity in Plasma Arc Melted (PAM) ingots is usually associated with entrapped inert gas 

used in the melting operations. Subsequent VAR ought to remove these, and PAM + VAR ingot, 

produced normally, will be free of gas porosity. 

Shrinkage porosity can be found throughout the ingot and in the pipe section. Porosity in the 

pipe section results from metal shrinkage and is also associated with creation of Type II defects. 

They can be largely avoided by good hot topping practices. High melt rates have been found to 

produce more ingot porosity than slow rates (better melt degassing occurs at the slow rates and 

the shallower pools experience less shrinkage on freezing). 

Shrinkage porosity is unlikely to survive ingot conversion practices and should not be confused 

with strain induced porosity created during the conversion process itself. The latter often results 

in “clean” porosity which is often seen during UT inspection of the billet when sophisticated 

means, like multi-zone inspection, are applied. 

4.6 ALLOY SEGREGATION [A-2, A-5, and A-7] 

Alloy segregation can be influenced by several factors including, primarily, the alloying 

elements added and their amounts; solidification conditions, including temperature gradients; 

power interruptions or other perturbations of steady state conditions; hot topping procedure; and 

the homogeneity of the starting material. 

Segregation is most conveniently discussed in terms of the general categories of 

macrosegregation and microsegregation. 

A-9
Macrosegregation is generally characterized by alloying element composition differences 

measurable over a long range such as top to bottom, or center to outside of the ingot, or its 

primary converted products, such as billet. The causes for this can be lumped generally into 

three categories: 

• Inhomogeneity of starting material or electrode so that the composition of the last to melt 

dominates the composition of the top of the VAR ingot 

• Effects of directional solidification, given homogeneous electrodes, in which the melting 

point suppressers will concentrate in the liquid and be richest in the last to solidify, which 

means that the top of the VAR ingot and the centerline will likely be rich in these 

elements. The opposite is true of melting point raisers. 

• Vaporization and re-condensation, on crucible walls, of high vapor pressure elements, 

such as aluminum. As the ingot lengthens when more electrode is consumed, these 

elements will be entrapped in the ingot surface creating an aluminum rich zone at the 

ingot surface. During conversion, these are lost due to intermediate conditioning, but 

remelted electrodes are then inhomogeneous as the greatest amount of condensate is seen 

towards the end of the melt (top of the crucible). This occurs because there is much more 

time for the vaporization/condensation cycle to occur. These are often avoided by proper 

electrode formulation compensation or electrode inversion practices and, in the last case, 

splash ring avoidance or remelt procedures. 

Microsegregation, as distinguished from inclusions with refractory characteristics, usually results 

from liquid/solid partitioning during solidification much as for the macrosegregation. Its 

manifestation will be localized in areas where concentrations of partitioned melting point 

suppressers in the liquid, at the liquid-solid interface, is subjected to accelerated solidification, 

such as a rapid reduction in heat input. Also, where the solidification conditions favor the 

formation of a dendritic liquid/solid interface there is a micro partitioning of liquid formers. The 

interdendritic zones, being the last to solidify, will entrap extraordinarily high amounts of 

melting point suppressers that are mostly beta forming elements. The manifestation of this is a 

local area with its beta transus temperature much lower than its immediate surroundings. Near 

transus heat treatments will expose these areas as very lean or absent of primary alpha after a 

subtransus thermal exposure and are called beta flecks. The controls which can minimize the 

occurrence of such segregation include avoidance of power interruptions or abrupt negative 

changes in power level, maintenance of high thermal gradients in the liquid at the solid/liquid 

interface, and adherence to the Tiller [A-8] model for the conditions that favor the formation of 

planar interfaces. These include, establishing high temperature gradients in the liquid, low 

interface velocity, and effectively removing the build up of solute in the liquid at the interface. 

There are some other liquid phase formers which segregate but do not form beta flecks because 

subsequent solid state transformations result in discrete precipitates. The most common amongst 

these is silicon, which can, if large amounts are in the alloy and the proper solidification 

conditions are not present, result in bands of higher than normal concentration of discrete silicide 

precipitates. There is considerable controversy regarding the impact these bands have on 

properties, but there is no disagreement that there is no harm in avoiding them and this is the safe 

thing to do. 

A-10
The beta flecks, in an alpha-beta heat treated microstructure, can reduce the fatigue properties 

due to microstructural discontinuities which produce elastic property discontinuities as was 

found in low cycle fatigue testing of the high strength alloy Ti-5Al-2Sn-2Zr-4Cr-4Mo (Ti-17) 

alloy. 

4.7 SYNOPSES OF EXPERIMENTAL WORK 

This section contains synopses of several articles which were associated with or related to defect 

removal, sources of nitride inclusions, nitride seed development, and the effect of defects on 

fatigue properties. 

4.7.1 NITRIDE INCLUSIONS IN TITANIUM INGOTS: A STUDY OF POSSIBLE 

SOURCES IN THE PRODUCTION OF MAGNESIUM-REDUCED SPONGE (1973) [A-1] 

Purpose: The objective of this experiment was to demonstrate how impurities may be introduced 

into titanium sponge during manufacture by the magnesium reduction process and to determine 

under what conditions they contribute to the formation of defect-forming impurity clusters that 

persist through the ingot melting cycle. 

Conclusions: When contaminated by an air leak during the distillation cycle or when made from 

air contaminated magnesium, a large variation in nitrogen content was found in the magnesiumreduced titanium sponge. TiN and Ti2N were found in the highest-nitrogen regions. The 

observed nitrides were not in the form of hard, high-density particles. However, the friable 

pieces, powder pockets or loose powder may be compressed during electrode pressing and 

subsequently sintered, during melting, from the heat of the arc to produce higher-density 

particles. These higher density particles can survive arc melting. 

Color and texture are not reliable criteria for spotting these sort of defects during sponge 

inspection. During both the reduction cycle and the distillation cycle, air-burned and nitrided 

sponge may change its color and texture. The sponge particles act as nuclei for sponge growth 

and may be found partially or completely clad by newly formed sponge. 

It is not clear that HIDs with these physical characteristics have been unambiguously identified 

in any multiple melted VAR heat but the possibility for their existence, none-the-less exists 

[A-5]. 

4.7.2 ALPHA SEGREGATION IN TITANIUM ALLOYS [A-9] 

Purpose: An experiment was conducted by creating an artificial “pipe” to show that Type II 

(alpha segregation) defects form in pipe cavities and is a result of non-uniform evaporation and 

redeposition of relatively volatile alloying elements such as aluminum. 

Experiment/Conclusions: An ultrasonically sound Ti-6Al-4V square billet was heated to 1700°F 

and the corners were severely pressed in such a way as to deliberately create center bursts which 

would be detectable by UT inspection. After the internally cracked billet was, cooled and 

conditioned followed by UT verification of the internal cracking, the piece was reheated to 

A-11
2050°F for six hours and forged to heal the internal cracks. Ultrasonic inspection showed no 

remaining defects and slices cut from areas previously showing sonic indications showed the 

characteristics of Type II alpha segregation. 

4.7.3 REMOVAL OF DEFECTS FROM TITANIUM ALLOYS WITH ELECTRON BEAM 

COLD HEARTH REFINING [A-2] 

Purpose: An experiment was conducted to evaluate the EBCHM process for removal of defect 

particles from liquid titanium to prevent inclusion formation in ingots. 

Experiment/Conclusions: Various materials including carbide tool chips, nitrided sponge, and 

flame-cut titanium scrap were used as seed in sub-scale EBCHR experiments. 

All of the tungsten carbide tool bit seeds were located in the hearth skull using x-ray inspection 

after melting of a tungsten carbide tool bit seeded electrode which was fabricated from Ti-6Al4V scrap. The hearth skull was then remelted several times to show the dissolution rate of HDI’s 

to be roughly 20 microns/sec. 

An ingot was produced which contained Type I defects and was then used as melt stock for 

EBCHM. The material was melted twice in the hearth and cast into an ingot. One defect was 

detected in the ingot and was attributed to a large transient in the process in which a piece of the 

electrode fell into the front end of the hearth at the same time that a high voltage arc extinguished 

the electron beams. The large flow of metal washed over the piece of electrode in the hearth and 

carried the defect over the lip into the ingot mold. Hearth and baffle design modifications have 

since been incorporated into production equipment to avoid this sort of occurrence [A-6]. 

To understand the behavior of HID’s, an experiment was run by seeding Ti-6Al-4V bars with 

cutting slag and nitrided sponge. Though HID’s are sometimes believed to be less dense than the 

liquid surrounding them, their density is actually greater than the liquid and they sink. The 

analysis is still in progress, however, the seeds that were located were all beneath the surface of 

the liquid down to the solid-liquid interface. It was shown that HID’s settle rapidly to the solidliquid interface and then process to dissolve at a rate determined by the temperature at that 

interface. 

EBCHM and PCHM have been sufficiently well developed that now they have been 

incorporated into the permitted processes for producing rotor grade billet for certain OEMs. 

Substantiating this has been a record of hard alpha inclusions, found in rotor grade billet made 

from ingots the incorporate these cold hearth melting methods, is equivalent to triple VAR. 

There is no doubt that this process is matter-of-fact and approaching maturity [A-6]. 

4.7.4 DEVELOPMENT OF SEEDS FOR REPRODUCIBLE LDI’S IN TITANIUM 

MELTING TESTS [A-10] 

Purpose: The paper discussed the manufacture and evaluation of artificial HID formers (seeds). 

A-12
Experiment/Conclusions: Sponge particles were nitrided in a furnace containing flowing 

nitrogen at partial pressure less than one atmosphere to produce a uniform gold color with an of 

average 12 to 15% nitrogen. The particles were crushed and 200 of the particles were dispersed 

uniformly throughout the sponge compacts and triple VAR melted. The ingots were processed 

to an inspectable product and UT inspection to a #2 FBH detected 9 HID’s. Although larger, the 

defects exhibited a similar microstructural appearance, nitrogen content, and microhardness 

value to that of a natural HID. 

While these seeds do help with experiments designed to understand the survivability of nitrogen 

stabilized sponge in the VAR process, they are clearly not realistic in that they are purely sponge 

source, have been crushed to irregular shapes, and probably do not contain the internal porosity 

generally associated with actual burned sponge. As a result, their apparent density will be higher 

than actual defects and the lack of internal porosity reduces their detectability. Also the nitrogen 

content is higher, therefore their refractory nature will be more severe than any of the actual 

burned sponge. Any conclusions drawn by use of such nitrided and crushed sponge will clearly 

indicate survivability in VAR processes much greater than expected for realistic defects but fails 

to address the near neutral density particle that has a greater chance of surviving a cold hearth 

melt by virtue of their not sinking to the skull [A-5]. 

4.7.5 ELECTRON BEAM MELTED IN-SPEC TITANIUM REMELT ELECTRODES [A-4] 

Purpose: This paper discussed a recycle system to incorporate both alloy and oxygen correction 

during the Electron Beam (EB) melt instead of during the first Vacuum Arc Remitting (VAR) 

melt. Electrodes whose chemistries have been fully correct during the EB melt are called “inspec” electrodes and require only one consumable VAR melt to meet specification requirements. 

EB melting, commonly called EBCHM (Electron Beam Cold Hearth Melting) is used as a 

method for consolidating titanium machine turnings into electrodes suitable for consumable 

VAR. The residence time of the large water-cooled copper hearth used in EB melting effectively 

removes high-density contaminants, such as carbide tool bits and refractory metals. The water 

cooled copper hearth of the EBCHM process affords the molten titanium additional exposure to 

the effects of furnace vacuum electron beam superheat and this additional residence time may 

help reduce or eliminate Type I defects. In a US Bureau of Mines study A-5] entitled, “Type I 

defects: their causes and methods of elimination,” skull melting was identified as a melting 

process capable of dissolving Type I defects. 

Conclusions: The first attempts at EB melting an aggregate blend of machine turnings, sponge, 

85-15 Al-V master alloy, and aluminum were less than completely successful. When the initial 

“in-spec” electrodes were EBCH melted, using a series of conventional master alloy particles 

crushed to various sizes including the standard size range, master alloy segregation occurred. To 

solve this segregation problem, a master alloy lot, in which the geometry of the individual 

particles more closely matched the geometry of the machine turning scrap, was used. By 

blending components selected for both size and geometrical consistency, segregation during 

feeding was eliminated. This indicates that to get homogeneous ingots, the master alloy cannot 

all sink into the skull at the early stages of melting. Increasing the surface-to-volume ratio of the 

master alloy particles, as was done, helps to accomplish this objective [A-5]. Although not 

addressed by the authors, EBCHM processes will tend to vaporize volatile elements such as 

A-13
aluminum so enriched feed materials will be necessary to achieve in-specification chemistry. 

Furthermore, the final resting point for the vaporized metal creates a situation with condensate 

that will need attention in order to avoid introduction of additional defects and/or local zones of 

chemical inhomogeneity [A-6]. 

4.7.6 MELTING OF NITRIDE SEEDED Ti 6-4 ALLOY INGOTS [A-11] 

Purpose: Purpose of the paper is to evaluate the capability of the ISM (Induction Slag Melting) 

and CVAR (Consumable Electrode Vacuum Arc Melting) processes as a method of dissolving 

hard alpha defects introduced by contaminated input materials. Two parallel experiments were 

performed. One experiment used titanium sponge manufactured in a small-scale laboratory 

facility while the other used commercially available sponge. Non-contaminated control ingots 

and contaminated ingots were made from each set of sponge material using both melting 

processes. 

Conclusions: Alpha formers were somewhat more readily dissolved during the ISM process than 

during the CVAR process. This was believed to be a result of a somewhat longer residence time 

in the molten state and the induction stirring furnaces which may serve to buoy up nitride 

particles and increase their residence time in the melt as compared to the CVAR process. During 

CVAR melting high nitrogen areas in the consumable electrode appear to sinter to high density 

either in the electrode behind the arc or during melting and passage through the arc. The 

particles fragment during passage through the arc or in the molten pool to result in more, but 

smaller, defects, which are believed to be more difficult to dissolve in the molten pool due to 

their high sintered densities. 

The ISM process will also generate a bit more superheat and a few degrees of temperature is 

very effective in dissolving refractory particles. Temperature is much more important than time, 

as the amount of dissolution is related to the square root of time, while it is related to an 

exponential with temperature [A-5]. The statement regarding the concurrent sintering and 

fragmentation of nitrided particles during passage through the arc in a VAR process is a bit 

puzzling and not totally consistent with observations of nitrided sponge related HIDs [A-5]. 

Smaller seeds that have a higher surface to volume ratio also dissolve more rapidly. It is not 

clear that the nitrogen content, and therefore melting temperature, will be affected by any of the 

processes described. Therefore, fragmentation will be nothing but helpful no matter what went 

on before [A-5]. 

Neither induction slag or even the more scaleable induction skull process, which is based on the 

former, is currently scaleable to production size heats [A-5]. 

4.7.7 UTILIZATION OF ELECTRON BEAM MELTING IN THE PRODUCTION OF 

DEFECT FREE TI-6AL-4V INGOTS [A-3] 

Purpose: The purpose of this experiment was to produce a defect-free, “in-spec EB/VAR” 

titanium alloy ingot. 

A-14
Experiment/Conclusions: Prior to producing a “in-spec EB/VAR” ingot three experiments were 

conducted to evaluate the removal of dense particles during EB melting, removal of Type I 

defects during EB melting, and composition control of EB cast product. 

During the first experiment, dense particles (tungsten and tungsten carbide tool bits) were 

successfully removed (excluding nitrides) from the ingot through entrapment in the hearth. The 

second experiment involved contaminating the input materials with infoliated billet-end crops, 

which have extensive oxyacetylene flame cut residual metallic drool, characteristic of surface 

titanium nitrides. Sonic inspection of the EB cast product to a #3 FBH defect confirmed sonic 

indications in only one of the three ingots that were cast. It was believed that continued efforts 

were required on furnace design and melt control software to provide adequate residence time 

and/or temperatures to guarantee Type I defect dissolution. In the third experiment, 

compositional control of the EB cast product, was accomplished by controlling the mixing and 

blending practice through the use of computer models. 

A production quantity “in-spec” first stage EBCHM electrode was completed in 1985. No Type 

I or HDI defects were detected through sonic testing to a #2 FBH defect. The input material 

consisted of a large portion of scrap. The compositional variations for aluminum, vanadium and 

oxygen were within the range expected for a single melt process. Oxygen variability, however, 

was higher and attributed to a greater tendency for freezing segregation due to the sampling 

technique and appreciable variability in oxygen analytical techniques. 

4.7.8 STANDARDIZING DEFECTS FOR TITANIUM SEEDING EXPERIMENTS [A-12] 

Purpose: The purpose of this paper is to discuss a process which was developed to generate 

sponge particles with predictable nitrogen levels between zero and 15% and to establish a 

seeding procedure. 

Experiment/results: Sponge particles were nitrided at various temperatures (1400°F-2300°F) for 

five minutes in a 95Ar-5N2 atmosphere. The particles were subsequently crushed which allowed 

the weight and nitrogen content of both the brittle surface material and the more ductile core to 

be determined. The higher the temperature, the greater the nitrogen content of the particle. It 

was found that the bulk nitrogen content of the ductile core decreased to zero as the upper 

nitriding temperature (2300°F) was reached. 

Many experiments have used seeding densities varying from one defect in 20 pounds to one 

defect in 5 pounds. Recent trials have used the higher density to affect a more stringent test. To 

avoid agglomeration possibilities, the following HID seed mix was recommended: 

Particle Size Amount 

0.25 inch diameter Ti-15N seeds one per five pounds 

0.25 inch diameter Ti-2N seeds one per five pounds 

0.25 inch diameter Ti-8N seeds one per five pounds 

0.12 - 0.25 inch diameter production, burned 

sponge particles, 

one particle per fifty pounds 

A-15
2 inch by down torch cut sheet stock (Ti-6-2-4-2 

or Ti 6-2-4-6) representing flame cut cobbles or 

Feed stock A 

one particle per 250 pounds 

The following HDI seed mix was also recommended in the interest of establishing a common 

standard for all seeding efforts: 

Particle Size Amount 

3/8′′ /+ 1/4′′ mesh 37% 

1/4′′ /+ 8′′ mesh 25% 

8′′ /+ 14′′ mesh 15% 

14′′ /+ 20′′ mesh 10% 

20′′ /+ 40′′ mesh 8% 

40′′ /+ 60′′ mesh 5% 

one whole WC tool bit at midpoint of melt, 

0.04′′ diameter Mo wire, 1/4′′ to 1/2′′ long 

one particle per 125 pounds 

one piece of angular Mo 1/4′′ diameter one particle per 250 pounds 

one piece of angular Ta 1/4′′ diameter one particle per 250 pounds 

one piece of 0.03′′ diameter W wire, (1/4′′ to 

1/2′′ long) 

one particle per 250 pounds 

one piece of angular W 1/4′′ diameter one particle per 250 pounds 

4.7.9 TEST MELTING OF TIN AND WC SEEDED Ti-6-4 AND RESULTING INGOT 

STRUCTURES - A PROGRESS REPORT [A-13] 

Purpose: The purpose of this experiment is to evaluate the advantages of EBCHR for improved 

cleanliness of Ti-6-4 in comparison with conventionally processed VAR materials and to 

examine the capability of EBCHR for the production of in-specification chemistry of the Ti-6-4 

alloy. 

Experiment/Conclusions: Test melts of TiN and WC seeded and un-seeded Ti-6-4 were 

produced by EBCHR, by double VAR, and by the combination of EBCHR and VAR. The 

EBCHR test melts produced two unseeded and one seeded ingot, in which the seeded and one 

unseeded ingot were further VAR processed to produce two EBCHR-VAR ingots. One seeded 

ingot was produced by double VAR. The unseeded EBCHR, un-seeded EBCHR-VAR, seeded 

EBCHR-VAR, and seeded double VAR ingots were forged into bar. Defects were detected by 

x-ray in only the double VAR bars. Microscopic skull analysis of the seeded ingot melted by 

EBCHR showed both WC and TiN particles in the liquid-solid interface. 

A-16
4.7.10 THE ROLE OF MELT RELATED DEFECTS IN FATIGUE FAILURES OF Ti-6Al-4V 

[A-14] 

Purpose: The purpose of the study was to quantify the reduction of fatigue life caused by high 

interstitial defects (HID) and high density inclusions in titanium nitride and tungsten carbide 

seeded double vacuum-arc remelted titanium alloy Ti 6Al-4V. 

Experiment: Two lots of material, one triple VAR and one seeded double VAR, were tested. 

The seeded melt electrode contained compacts of master alloy, elemental aluminum, aluminumvanadium master alloy, 5% recycled Ti 6-4 scrap, 1.8% nitrided titanium sponge (about 40 each 

3 to 6 mm sized seeds/kg), and 0.079% tungsten carbide tool bit inserts (about 0.02 seeds/kg). 

The 16-inch diameter seeded ingot was beta forged to 8-inch diameter, and the top 1/8th of the 

ingot was alpha/beta forged to 3-inch diameter according to conventional practices. The 3-inch 

unseeded triple vacuum melted material was solution heat treated and overaged. 

Conclusions: Fatigue testing of the seeded and unseeded materials showed that both high 

interstitial defects and high density inclusions defects can reduce fatigue life by an order of 

magnitude. 

5. REFERENCES 

A-1. Henry, J.L., Hill, S.D., Schaller, J.L., and Campbell, T.T., “Nitride Inclusions in Titanium 

Ingots: A Study of Possible Sources in the Production of Magnesium-Reduced Sponge,” 

in Metallurgical Science and Heat Treatment, 1973, Vol. 4, No. 8, pp. 1859-1864. 

A-2. Entrekin, C.H., “The Removal of High Density Inclusions by Hearth Refining Process,” 

in edited Electron Beam Melting and Refining State of the Art 1985, by R.A. Bakish,

Bakish Materials Corporation, Englewood, NJ, 1985, pp. 40-47. 

A-3. Ostheimer, M., and Seagle, S.R., “Utilization of Electron Beam Melting in the Production 

of Defect Free Ti-6Al-4V Ingots,” Proceedings of the Sixth World Conference on 

Titanium, Cannes, June 6-9, 1988, pp. 579-582.

A-4. Herman, W.E. and Forsberg, V.K., “Electron Beam Melted “In-Spec” Titanium Remelt 

Electrodes,” Proceedings of Titanium 1986 Conference, October, 1986, Vol. II, pp. 904-

917. 

A-5. Bellot, J.P., Edie, C., and Mitchell, A., “The Formation and Removal of “Hard-Alpha” 

Material During the Melting of Titanium Alloys,” Eighth World Conference on Titanium

in Birmingham, England, Institute of Materials Abstract, pp. 22-16, October 1995. 

A-6. Grala, E.M., “Characterization of Alpha Segregation in Ti-6Al-4V Alloy,” TRW 

Equipment Laboratories, September 1968, Report ER-7224-2, NERAC Number USG 

7702 AD-845 805/1 D7. 

A-7. Private communication, Jim Hall, Honeywell Engine Systems. 

A-17
A-8. Tiller, W.A., et al., Vol. 1, Acta Met, p. 439, 1953. 

A-9. Bomberg, H.B., “Alpha Segregation in Titanium Alloys,” Proceedings of Titanium 80, 

Science and Technology, May 19-22, 1980, Vol. 3, pp. 2197-2202. 

A-10. Poulsen, E.R. and Parris, W.M., “Development of Seeds for Reproducible LDI’s in 

Titanium Melting Tests,” Electron Beam Melting and Refining State of the Art 1986, 

Bakish, R.A., 1986, pp. 347-353. 

A-11. Paige, J.I., and Redden, T.K., “Melting of Nitride Seeded Ti-6A1-4V Alloy Ingots,” 

Journal of Metals, March 1988, Vol. 40, No. 3, pp. 26-28. 

A-12. Paige, J.I. and Redden, T.K., “Melting of Nitrate Seeded Ti-gAl-4V Alloy Ingots,” 

Journal of Metals, March 1988, Vol. 40, No. 3, pp. 26-28. 

A-13. Malley, D. and Belchak, M., “Standardizing Defects for Titanium Seeding Experiments,” 

Electron Beam Melting and Refining State of the Art 1990, Bakish, R.A., 1990, pp. 224-

231. 

A-14. Clark, K.R., Dillar, A.B., Hendrix, J.K., Tien, J.K., and Denda, T., “The Role of Melt 

Related Defects in Fatigue Failures of Ti-6A1-4V,” edited by Fores, F. H. and Caplan, I. 

L., eds., in Proceedings of the Seventh World Conference on Titanium, 1992, pp. 2867-

2871. 

A-18
APPENDIX B—DEFECT CHARACTERIZATION PROTOCOL 

CBS ULTRASONIC AND METALLOGRAPHY PROCEDURE 

Scope: 

This procedure is intended to describe the ultrasonic process used to locate indications within the 

2- to 3-inch cubes sectioned from billets. The locations will be defined on three planes to 

provide a detailed geometric representation of the indication. Waveform and C-scan data will 

also be collected from these evaluations. This data will be analyzed for ultrasonic content and 

used to further reduce the sample block so that approximately 0.5′′ of material will surround the 

defect. The sectioned sample block will again be ultrasonically inspected using higherresolution transducers so that the location of the indication is accurately defined prior to the 

metallography. C-scan data will be recorded for later comparison to model calculations. A 

three-dimensional (3D) metallographic analysis will be done on these indications. This process 

involves gathering digital micrographs from the serial slices then stacking those images through 

a software program to create a 3D representation of the indication. 

Billet Sectioning: 

1. The indication will be sectioned from the billet so that approximately a 1′′ envelope of 

material surrounds the indication. Due to the depth of some of the indications, a 1′′

envelope may not be possible from the inspection surface side and this will be noted. 

The sample removal and metallographic section approach is depicted in the following 

drawing. 

Plane 1

5 mils 

between 

sectioning 

planes

Sample block will be 

polished in the 

orientation shown. 

Plane 1 to start at 

diffusion zone and 

continue through “n” 

planes until diffusion 

zone no longer 

evident in 

micrograph

Sample block with 1” 

envelope around 

defect as indicated by 

c-scan image in billet 

scan

Plane 1

5 mils 

between 

sectioning 

planes

5 mils 

between 

sectioning 

planes

Sample block will be 

polished in the 

orientation shown. 

Plane 1 to start at 

diffusion zone and 

continue through “n” 

planes until diffusion 

zone no longer 

evident in 

micrograph

Sample block with 1” 

envelope around 

defect as indicated by 

c-scan image in billet 

scan

B-1
2. During the sectioning, the orientation of the indication with respect to the original billet 

axis will be controlled by placing a large chamfer on the left corner of the curved surface 

tangent to the axial face containing the serial number of the billet. 

3. The six machined surfaces of each cube shall be finished so that the roughness is no 

greater than 16 microinches. 

4. An etching operation will be done on the cube at this stage to determine if the diffusion 

zone is present. If the diffusion zone is detected, the two remaining sections of the billet 

should be analyzed to determine the size of the diffusion zone. 

Note: Etchant will be ammonium bifluoride 10% with water. 

Ultrasonic Evaluation: 

Initial ultrasonic evaluations on the sectioned block will be performed on the Sonix system at 

GEQTC. The various transducers that will be used are listed below. The particular instrument 

parameters will be noted as they are developed during the evaluation. However, the beam 

diameter sensitivity will be (0.5)(3db) for all of these evaluations. 

1. RF waveforms will be collected at ISU from six sides of the 2- to 3-inch cubes using a 

5-MHz, F8, 6.0′′ focal length transducer. This data will be compared against the 

conventional 5-MHz billet data and the 3D model. 

2. The data from the scans described in the preceding step will be reviewed to determine in 

which plane the specimen will be serial sectioned. Note: the sectioning plane will be 

perpendicular to the direction of sound. 

3. After the serial section plane has been determined, the material envelope surrounding the 

indication will be reduced to 0.450′′. Again, the machine surfaces will have a surface 

roughness of 16 microinches. 

4. The orientation will be maintained by use of an EDM to machine two holes of different 

diameters through the side that will be serial sectioned. The holes shall be placed so that 

they are close to the axial face that contained the billet serial number. The larger of the 

two holes will be on the side where the 2- to 3-inch cube was chamfered. 

5. These pieces will be returned to ultrasonic where they will be evaluated using a 25-MHz, 

F10. RF waveforms will be collected from the original radial surface (billet curved 

surface) to compare flat surface data to the curved. Also, the depth of the indication, from 

the sectioning surface, will again be verified prior to metallography. C-scans will be 

done from all six sides using the 25-MHz, F10 transducer. 

6. All ultrasonic parameters will be recorded in inspection log book. 

B-2
X-ray CT: 

1. One specimen will be evaluated with this method. If the data collected form this 

evaluation provides good information, a decision will be made as to whether this process 

will be used on subsequent specimens. 

Metallography Process Preparation and Serial Sectioning for 3-D Modeling: 

Initial preparation and documentation: Before and after any cutting or grinding is performed on 

the sample provided for review, it is imperative that dimensions be clearly documented. 

Photodocumentation of the sample with cut locations outlined will aid greatly at report time, and 

is crucial for tracking material removal before the final working sample is defined. Important 

data that needs to be recorded includes length, width, height, and orientation of the sample from 

a larger piece, if applicable. The indication being documented will eventually have to be traced 

back to the original billet or forging. All subsequent sections cutoff of the sample in the course 

of getting closer to the indication, as well as the material loss due to cutoff blade thickness, must 

be measured and recorded. Below is a typical example. 

Fiducial marks: Information on the actual location of the indication of interest can come from xray or UT techniques. Once you are confident that you have cut down the sample as close to the 

indication as reasonably possible (approx. 50 mils away to allow for human error), fiducial or 

reference marks can be cut into the sample. The fiducial marks are required to be able to 

accurately orient the flaw with respect to the disk or billet surfaces. Also, without the fiducial 

marks for reference, a solid model of the flaw cannot be reconstructed since orientation from 

slice to slice is critical. Two fiducial marks should be made on opposite ends of the sample, 

perpendicular to the face to be polished and parallel to each other. To ensure parallelism and 

perpendicularity, these marks should be made in a machine shop. Below is an example of 

fiducial mark locations cut into a sample. The reference cube diagram is added to keep 

orientation clear to the reader. Making the marks as close to the indication as possible (this will 

be an estimation) will minimize the number of images taken later. 

B-3
Polish face 2

Indication

Face 

5

2

3 5 1

6

4

Polish face 2

Indication

Face 

5

2

3 5 1

6

4

Sample mounting: Once the reference marks are cut, the sample is ready to be mounted in 

Bakelite for serial polishing. Again, remember to track the face that is being polished and the 

orientation of the sample in relation to the original piece. Once the sample is mounted, lightly 

polish the sample with 600-grit paper to remove any mounting flash or burrs. Measure the 

thickness of the mount in the completed state. This number will be the starting measurement to 

which all future material removal measurements will be related. 

Serial polishing: All polishes in this procedure are done with an automated polishing system 

holding the samples in a rigid fixture or “rack”. The preferred rack is one that holds the sample 

with a pinching action rather than a setscrew. This system is necessary to maintain 

reproducibility from polish to polish. Before starting the polish procedure, you must decide on 

how much material will be removed on each polishing step. The first few polishes performed in 

the safe zone will define the steps to use to produce the same material removal rate with each 

polish. An example of typical polishing steps follows: 

Abrasive Time Pressure Lubricant Speed 

120-grit SiC 20 sec. 200 Newtons Water 300 rpm 

240-grit SiC 20 sec. 200 Newtons Water 300 rpm 

240-grit SiC 20 sec. 200 Newtons Water 300 rpm 

320-grit SiC 20 sec. 200 Newtons Water 300 rpm 

320-grit SiC 20 sec. 200 Newtons Water 300 rpm 

400-grit SiC 20 sec. 200 Newtons Water 150 rpm 

400-grit SiC 20 sec. 200 Newtons Water 150 rpm 

600-grit SiC 20 sec. 200 Newtons Water 150 rpm 

2400-grit SiC 20 sec. 200 Newtons Water 150 rpm 

The logical progression of papers in this procedure is common to all sample preparation in 

metallography. This combination was defined by trial and error to produce a 0.005-inch removal 

rate when performed with fresh SiC paper and the same “dummy” samples. A dummy is a 

sample of like material and size as the sample of interest, used to balance a rack when 

autopolishing. The final polish and etching of the sample is dependent on material properties. 

Material removal in the final polishing step is immeasurable and therefore neglected when 

searching for the right combination of papers and times. 

B-4
Documentation of indication: Once the sample has been prepared for review, documentation of 

the indication can be performed. Do not measure the material removal until after documentation 

as the micrometer or caliper used will scratch the polished/etched surface of the sample. Since 

image documentation of the entire indication from fiducial mark to fiducial mark will require a 

number of images to be linked together, the microscope must have enough travel to view both 

fiducial marks without moving the sample on the microscope stage. Align the sample so that it 

can be traversed from mark to mark in the x direction without moving the y-direction control. 

This will greatly help the operator who will be creating the photomontage from the individual 

images. 

Once it’s verified that all images can be taken without moving the sample, the imaging process 

can start. The first image is taken at an extreme edge of the area to be documented. Subsequent 

images must be taken with a small percent of overlap (approximately 5%) from one image to the 

next. The diagram below shows typical overlapping images in a montage. 

Fiducial

Mark

Both 

Sides

This pictorial representation purposely shows that the overlap in images does not have to be 

precisely the same from location to location, but it must include both fiducial marks (squared 

notch on left and elliptical notch on right) and all areas of interest. Note the asymmetric shape of 

the fiducial mark on the left, which distinguishes the orientation of the image uniquely to 

facilitate later reconstruction. Image capturing was performed on an inverted Reichert 

Metallograph using a digital camera and image capturing software. The images were taken at 

480 by 640 resolution at a magnification suitable to capture the details of the indication. The 

magnification and resolution that is determined, as appropriate for the job, must be documented 

and used through the entire sample analysis and for any other samples that could be compared 

with each other. 

After imaging is complete, measure and record the thickness of the micro. Subtracting the new 

thickness measurement from the previous measurement. At each slice (step), evaluate for 

detection of diffusion zone. Continue with this process until diffusion zone is detected. At this 

position, normally 0.040′′ to 0.050′′ from the indication, begin finer steps. The size of the finer 

steps will be determined based on the size of the indication and the direction of the polishing in 

reference to the indication. 

B-5
After each polishing step, etch and photograph. During the step polishing, it may be necessary to 

verify the location of the indication periodically to avoid the possibility of polishing through it. 

Etchant will be ammonium bifluoride 10% with water. Gray levels must be kept consistent at 

each step for the normal structure and the defect in all photos. Digitize each image (image 

analysis) along with photo. Digitized images will be compiled into a 3D representation of the 

indication. The EDM holes will provide the mark to maintain the registration of the digitized 

images. 

Microprobe and microstructure characterization: 

1. All microprobe work will be done at Pratt & Whitney. 

Microprobe will be done at 4 stages: 

a. In the diffusion zone 

b. Beginning of the indication 

c. Middle of the indication 

d. End of the indication 

Note: Microprobe data collection was reduced to one slice for most samples. 

2. Rayleigh wave and grain orientation images will be performed on the same slice that the 

microprobe data was collected for selected samples. 

B-6
APPENDIX C—INSPECTION RESULTS FOR CONTAMINATED BILLET 

The 12 Contaminated Billet Study billets were inspected for the initial customer in November 

1994, and the results were provided to the Engine Titanium Consortium as part of the purchase. 

In the initial inspection, precautions were not taken to prevent saturation of the ultrasonic signal. 

To enable capture of digital data using approved multizone and conventional inspection methods, 

and to ensure that saturation of the signals did not occur, the complete heat was reinspected in 

September 1995. The results were summarized for each of the billets. The billet ID is provided 

in the upper left corner of each sheet. Indications were identified alphabetically with the left 

most indication beginning with A, as shown in the first column. The second column lists the 

distance from the end of the billet. Indication depths are provided in the next six columns for 

each of the inspection times (September 1995 and November 1994) and inspection methods 

(conventional normal, conventional longitudinal, and multizone). Graphical representations, 

referred to as billet maps, provide the amplitude response and signal-to-noise ratio for each of the 

indications. Not all billets were tested with all methods in the 1994 inspection, as noted on 

specific billet maps. Other notes are also included on individual maps. 

C-1
B1AW1

September 1995 Inspection November 1994 Inspection

Multizone Conv. Normal Conv. Angle Multizone Conv. Normal Conv. Angle

Stamped I.D.Inches from top Depth Depth Depth Depth Depth Depth

A 3.3 0.2 0.3

B 25.9 0.6 0.6 0.6 0.5 0.5

C 66.4 1.6 1.8 1.6 1.6

D 92.7 1.7 1.8

E 95.2 0.6 0.6 0.7 0.5 0.5

Conventional Normal Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "C" 42%

1.91snr

Conventional Angle Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "B" 42%

2.62snr "C" 28%

1.85snr

 "E" 55%

4.44snr

Conventional Normal Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"B" 45% "E" 70%

Multizone Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "A" >100%

6.5snr "B">100%

4.8 snr "C" 95%

4.06snr "D" 62%

3.4snr

 "E" 89%

4.2snr

Conventional Angle Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"B" 70% "E" >100%

Additional indication reported on Nov 1994

Multizone, 12" from top, 0.94" deep,

amplitude 53%, 2.11 SNR (not rejectable)

Multizone Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"A" 190%

12.24snr "B" 201%

4.36 snr "C" 83%

5.47 snr "D" 73%

4.65 snr

"E" 127%

4.47 snr

Original billet 

length: 112.5"

C-2
B1AW2

September 1995 Inspection November 1994 Inspection

Multizone Conv. Normal Conv. Angle Multizone Conv. Normal Conv. Angle

Stamped I.D.Inches from top Depth Depth Depth Depth Depth Depth

A 42.5 0.3

B 72.0 0.2

C 89.0 0.8 0.8 0.8 1.5 1.5

D 98.0 0.7 0.7

E 104.0 1.3 1.3 1.3 1.5 1.5

F 114.4 1.1 1.0 1.1 1.5 1.5

(x) 98.7 0.5

Multizone Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"F" 268%

12.8 snr

 "A" 134%

13.59 snr

"B" 225%

21.7 snr

"C" 213%

16.29 snr "D" 134%

5.46 snr "E" 160%

4.29 snr

"X" 94%

5.05 snr

Conventional Normal Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "E">100%

3.2snr

"F" 94%

5.15 snr

"C" 65%

2.49snr "D"50%

2.61 snr

Conventional Angle Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"C" >100%

3.2 snr "E" >100%

2.92 snr

"F" 86%

4.52 snr

Conventional Normal Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"C" 80% "E" 90% "F" 80%

Conventional Angle Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"C" 80% "E" 90% "F" 80%

NOT

TESTED

original length: 

117"

C-3
B1AW3

September 1995 Inspection November 1994 Inspection

Multizone Conv. Normal Conv. Angle Multizone Conv. Normal Conv. Angle

Stamped I.D.Inches from top Depth Depth Depth Depth Depth Depth

A 60.0 0.7 0.8 0.8 0.8 2.0 2.0

B 63.0 0.9 1.2

C 79.0 1.5 1.5 1.5 1.5 2.0 2.0

D 94.8 1.1 1.1 1.5

E 106.0 1.6

(y) 77 1.3

(z) 81 1.3

Multizone Sept 1995

0.0 0.5 1.0 1.5 2.0 2.5 3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"A" 142%

5.02 snr

"B" 69%

2.05 snr "C" 253%

11.79 snr

"D" 101%

4.49 snr

"E" 47%

2.52 snr

"Y" 99%

5.05 snr

"Z" 77%

3.48 snr

Conventional Normal Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"A" 50%

2.92 snr "C" 62%

2.69 snr

Conventional Angle Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "A" 60%

2.48snr "C" >100%

5.7 snr

Conventional Normal Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "A" >100% "C" >100% "D" 70%

Multizone Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"A">100%

2.7 snr "B" 57%

 2.6snr "C" >100%

5.8snr

"D" 91%

 5.5snr

Conventional Angle Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "A" 90% "C" 80%

original length: 

111"

C-4
B1BW1

September 1995 Inspection November 1994 Inspection

Multizone Conv. Normal Conv. Angle Multizone Conv. Normal Conv. Angle

Stamped I.D.Inches from top Depth Depth Depth Depth Depth Depth

A 21.8 2.2 2.5

B 28.5 1.7 2.0 2.0

C 44.8 0.6 0.75 0.8 0.5 0.5

D 49.0 1.0

E 61.3 0.9 0.8 0.8

F 67.8 1.1 1.1 1.3 1.5 1.5

G 81.0 1.5 1.4 1.8 2.0 2.0

H 99.5 0.4

Multizone Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"A" 63%

2.96 snr

 "B" 113%

5.67snr

 "C" 142%

8.09snr "E" 69%

3.05snr

 "F" 450%

26.6snr

"G" 213%

8.28 snr

"H" 127%

6.56 snr

 "D" 56%

2.79snr

Conventional Normal Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"C" 70%

2.96 snr

 "F" 179%

4.6 snr

 "G" 100%

2.85snr

Conventional Angle Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"A" 68%

4.12 snr

"C">100%

5.36 snr "F" >100%

5.6snr

 "G" 80%

3.39snr

Conventional Normal Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "B" 70%

 "C" 70% "E" 30% "F" >100% "G" >100%

Conventional Angle Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"B" 30%

"C" >100% "E" >100%

"F" 70% "G" 90%

not

tested

original length: 104"

C-5
B1BW2B

September 1995 Inspection November 1994 Inspection

Multizone Conv. Normal Conv. Angle Multizone Conv. Normal Conv. Angle

Stamped I.D.Inches from top Depth Depth Depth Depth Depth Depth

A 1.1 1.2 1.0

B 17.4 0.3 0.3

C 43.2 0.3

D 51.2 1.6 1.5 1.5 1.5 1.5

E 65.0 1.5 1.5 1.5 1.5 1.5

Multizone Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "A"179%

13.27snr

 "B"160%

15.74snr

 "C" 113% 

7.55snr

 "D" 160%

11.38snr

 "E" 142%

8.38snr

Conventional Normal Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"A" 118%

5.54 snr

"B"108%

6.00snr "D" 46%

2.31 snr

"E"108%

2.57snr

Conventional Angle Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "D" 116%

4.14snr

"E"101%

5.42 snr

Conventional Normal Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"D" 90% "E" 90%

Conventional Angle Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"D" 90% "E" 90%

NOT

TESTED

0 TO 14.5" SECTION REMOVED 

BETWEEN INSPECTIONS

original length: 87"

C-6
B1BW3

September 1995 Inspection November 1994 Inspection

Multizone Conv. Normal Conv. Angle Multizone Conv. Normal Conv. Angle

Stamped I.D.Inches from top Depth Depth Depth Depth Depth Depth

A 22.0 1.3 1.3

B 43.5 1.1 1.0

C 66.0 0.5 0.4

D 86.0 1.5 1.5

Multizone Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "A" 113%

3.92 snr

"B"160%

7.56 snr

 "C" 127%

6.67 snr "D" 74%

5.06 snr

Conventional Normal Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

Conventional Angle Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

Conventional Normal Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

Multizone Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"C" >100%

3.52snr "B" >100%

5.78snr "A" 97%

3.99snr

"D" 70%

3.85 snr

Conventional Angle Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

2 indications

19% & 30%, long & 

shear 

not marked to cut.

No other conv. ind.

See RMI11/9/94 report

k

Addtional Multizone 31% 

amplitude, 1.85 snr reported

in Nov '95 test.

original length: 

107.5"

C-7
B2W1

September 1995 Inspection November 1994 Inspection

Multizone Conv. Normal Conv. Angle Multizone Conv. Normal Conv. Angle

Stamped I.D.Inches from top Depth Depth Depth Depth Depth Depth

A 10.7 0.5 0.8 0.8 0.6 0.6

B 24.5 1.3 1.5 1.8 1.5 1.5

C 65.0 0.9 1.0 1.0 1.0

D 69.5 0.5

original length: 133"

Multizone Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "A"142%

11.35 snr "B" 151%

11.05 snr

 "C"127%

6.67snr

"D" 87%

6.46 snr

Conventional Normal Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"A" 60%

3.46 snr "B" 85%

3.59 snr

Conventional Angle Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "A" 90%

4.59snr "B" 60%

2.76snr

 "C" 60%

2.35snr

Conventional Normal Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"A" 80%

"B" 100% "C" 80%

Conventional Angle Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"A" 80%

"B" 90%

"C" 80%

NOT

TESTED

C-8
B2W2

September 1995 Inspection November 1994 Inspection

Multizone Conv. Normal Conv. Angle Multizone Conv. Normal Conv. Angle

Stamped I.D.Inches from top Depth Depth Depth Depth Depth Depth

A

B 14.0 0.6

C 22.4 0.2

D 55.0 0.6 1.0 1.0

(X) 57 0.55

Multizone Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"B" 107%

6.55 snr

"C" 74%

4.09 snr

 "D"113%

4.46 snr

 "X" 61%

4.97 snr

Conventional Normal Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

Conventional Angle Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

Conventional Normal Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 10 20 30 40 50 60 70 80 90 100 110 120 130

Inches from Top

Depth (in)

"D" 65%

Conventional Angle Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 10 20 30 40 50 60 70 80 90 100 110 120 130

Inches from Top

Depth (in)

"D" 80%

Visible end burst - indications marked "A"

Not

tested

original 

length: 

123"

C-9
B2W3

September 1995 Inspection November 1994 Inspection

Multizone Conv. Normal Conv. Angle Multizone Conv. Normal Conv. Angle

Stamped I.D.Inches from top Depth Depth Depth Depth Depth Depth

A 20.1 0.2 0.3

B 27.8 2.3 2.3 2.3

C 31.0 2.0 2.0 0.3 0.3

Note: indication B mis-reported as C Nov 94, C not reported.

Billet map shows corrections determined from raw data

original length: 131"

Multizone Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "A"107%

6.81 snr

 "B" 72%

3.54 snr

 "C" 50%

2.59 snr

Conventional Normal Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

Conventional Angle Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "B"72%

3.78snr

Conventional Normal Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"C" 40%

Note: reported depth

may be wrong

Multizone Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "A" >100%

6.54snr

 "B" 49%

2.9snr

 "C" 36%

1.8snr

Conventional Angle Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"C" 60%

Note: reported depth

may be wrong

C-10
B3W1B

September 1995 Inspection November 1994 Inspection

Multizone Conv. Normal Conv. Angle Multizone Conv. Normal Conv. Angle

Stamped I.D.Inches from top Depth Depth Depth Depth Depth Depth

A 68.8 2.0 2.0 2.0 2.0 2.0

B 84.8 2.2

C 102.5 2.3 2.5 2.3 3.0

D 104.3 1.9 2.8 2.0 3.0

Multizone Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0

Inches from Top

Depth (in)

 "A" 84%

4 80 snr "B" 73%

2.45 snr

"C"99%

3.52 snr

 "D"134%

9.52 snr

0 - 11.5" section removed between tests

Conventional Normal Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0

Inches from Top

Depth (in)

"A" 35%

1.36 snr "C" 40%

1.95 snr

 "D" 50%

2.65snr

Conventional Angle Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0

Inches from Top

Depth (in)

"A" 55%

3.96 snr "C" 35%

1.91snr

"D" 7

4.91s

Conventional Normal Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0

Inches from Top

Depth (in)

"A" 70% "C,D" >100%

Conventional Angle Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0

Inches from Top

Depth (in)

"A" 40%

Test not 

run

C,D reported 

as same ind.

conv./norm

original length: 

106.5"

C-11
B3W2

September 1995 Inspection November 1994 Inspection

Multizone Conv. Normal Conv. Angle Multizone Conv. Normal Conv. Angle

Stamped I.D.Inches from top Depth Depth Depth Depth Depth Depth

A 1.9 0.7 2.0 2.0

B 3.3 0.3 2.0

C 8.7 2.1

D 16.9 1.5 1.0 1.0 0.7 1.0 1.0

E 40.0 1.3 1.0 1.1 1.0 1.0

F 85.5 0.2 0.2

G 113.0 1.3 1.3 1.5 1.5

Multizone Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"A" 357%, 12.25 snr "B"113%, 8.39snr

"C"201%

8.32 snr

 "D" 127%

5.06snr "E" 213%

12.53snr

 "F"160%

6.83snr "G" 142%

5.88 snr

Conventional Normal Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"D" 60%

3.0snr "E" 74%

4.47snr

Conventional Angle Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"B">100%

5.11 snr

"D" 54%

3.05 snr "H" 84%

5.74 snr

Conventional Normal Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"D" 80% "E" 80% "B" 100% "G" 80%

Multizone Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "D" >100%

4.23snr "E" >100%

6.7 snr "G" >100%

???snr

 "F" >100%

3.1snr

Conventional Angle Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"D" 80%

"E" 80%

"A" >100% "G" 80%

"A","B","C" are in region 

0 - 5.5" marked "no test, 

visible hole" on 12/5/94 

RMI report. "C" appears 

at 3.5" from end on Cscan inconsistent with 

RMI report). Additional 

MZ indication at 5", 

56%, SNR 2.3 (not 

rejectable) on RMI 

original 

length: 

119.5")

C-12
B3W3

September 1995 Inspection November 1994 Inspection

Multizone Conv. Normal Conv. Angle Multizone Conv. Normal Conv. Angle

Stamped I.D.Inches from top Depth Depth Depth Depth Depth Depth

A 12.3 0.6 0.6 0.8 0.5 0.5

B 51.0 0.8 1.0 1.0 0.8 0.5 0.5

C 67.6 2.9 2.5 2.5 2.9 3.0

D 109.6 0.9 0.9 1.0 1.0

Multizone Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"A" 113%

7.65 snr "B"120%

5.74snr "C"127%

8.99snr

 "D"142%

8.93snr

Conventional Normal Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

 "B"50%

2.39 snr "C">100%

3.08snr

Conventional Angle Sept 1995

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"A" 80%

3.96 snr "B" 60%

4.37snr "C" 85%

3.67snr

Conventional Normal Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"A" 50% "B" 50%

 "C" >100%

"D" >100%

Multizone Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"A" >100%

4.27 snr "B" >100%

4.83snr "C" >100%

6.35snr

 "D" >100%

4.53 snr

Conventional Angle Nov 1994

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0

Inches from Top

Depth (in)

"A" 90% "B" 40% "D" 60%

original length:

124.5"

C-13/C-14
APPENDIX D—ULTRASONIC C-SCAN RESULTS FOR INDICATIONS SELECTED FOR 

USE IN PROBABILITY OF DETECTION STUDIES 

Ten indications were selected for detailed characterization, including ultrasonic measurements, 

metallographic cutup, microprobe analysis, and three-dimensional reconstruction. Selection of 

the ten indications was based on review of the inspection data generated at the billet supplier in 

September 1995. Consideration was given to the location within the billet, inspection methods 

which resulted in a detection, and character of the C-scan image. The C-scan images and 

detection information for the ten indications are provided below. The billet ID and indication ID 

are listed (e.g., B3W3-B) along with the zone in which the indication was found. Inches from 

top indicates axial location of the defect within the billet. The amplitude, signal-to-noise ratio, 

and depth are tabulated from the billet maps (see appendix C of this report). Axial and radial 

lengths were estimated using the pixel size from the indication size C-scan images. 

D-1
Billet ID: B3W3 - B 

Zone: 1 

Inches from top: 51 

 Amplitude 

(%) 

S/N depth (in) axial 

length (in) 

radial 

length (in) 

Multizone 120 5.74 0.8 0.7152 0.2160 

Conv. 

Longitudinal 

50 2.39 1.0 

Conv. Angle 60% 4.37 1.0 

Billet Length: 124.5 

D-2
Billet ID: B1BW3 - C 

Zone: 1 

Inches from top: 66 

 Amplitude 

(%) 

S/N depth (in) axial 

length (in) 

radial 

length (in) 

Multizone 127% 6.67 0.5 1.4474 0.2301 

Conv. 

Longitudinal 

% 

Conv. Angle % 

Billet Length: 107.5 

D-3
Billet ID: B1BW3 - D 

Zone: 2 

Inches from top: 86.0 

 Amplitude 

(%) 

S/N depth (in) axial 

length (in) 

radial 

length (in) 

Multizone 74% 5.06 1.5 0.3268 0.2577 

Conv. 

Longitudinal 

% 

Conv. Angle % 

Billet Length: 107.5 

D-4
Billet ID: B1AW3-E 

Zone: 2 

Inches from top: 105 

 Amplitude 

(%) 

S/N depth (in) axial 

length (in) 

radial 

length (in) 

Multizone 47 2.52 1.6 .1860 .4123 

Conv. 

Longitudinal 

 

Conv. Angle 

Billet length: 111 

D-5
Billet ID: B1AW3-D 

Zone: 2 

Inches from top: 94.4 

 Amplitude 

(%) 

S/N depth (in) axial 

length (in) 

radial 

length (in) 

Multizone 101 4.49 1.1 0.2326 0.2215 

Conv. 

Longitudinal 

 

Conv. Angle 

Billet length: 111 

D-6
Billet ID: B1AW3-A 

Zone: 2 

Inches from top: 60.0 

 Amplitude 

(%) 

S/N depth (in) axial 

length (in) 

radial 

length (in) 

Multizone 142% 5.02 0.7 0.4186 0.3387 

Conv. 

Longitudinal 

50% 2.92 0.8 

Conv. Angle 60% 2.48 0.8 

Billet length: 111 

D-7
Billet ID: B2W2 - C 

Zone: 1 

Inches from top: 22.4 

 Amplitude 

(%) 

S/N depth (in) axial 

length (in) 

radial 

length (in) 

Multizone 74% 4.09 0.2 0.3273 0.1031 

Conv. 

Longitudinal 

% 

Conv. Angle % 

Billet Length: 123 

D-8
Billet ID: B1AW2 - D 

Zone: 2 

Inches from top: 98.0 

 Amplitude 

(%) 

S/N depth (in) axial 

length (in) 

radial 

length (in) 

Multizone 134% 5.46 0.7 0.4217 0.2681 

Conv. 

Longitudinal 

50% 2.61 

Conv. Angle % 

Billet Length: 117 

D-9
Billet ID: B1AW2 - B 

Zone: 1 

Inches from top: 

 Amplitude 

(%) 

S/N depth (in) axial 

length (in) 

radial 

length (in) 

Multizone 225% 21.7 0.2 0.2300 0.4188 

Conv. 

Longitudinal 

% 

Conv. Angle % 

Billet Length: 117 

D-10
APPENDIX E—DEFECT CHARACTERIZATION DATA 

Ten defects were selected for detailed characterization to provide improved understanding of 

hard alpha defects and to support probability of detection studies. Substantive amounts of data 

were generated for each of the defects and are provided in appendix E. The following categories 

of data are provided: 

• Defect location: Location of the mult as removed from the original billet. 

• Billet inspection: Inspection results from billet supplier including C-scan image. 

Tabulation of inspection results from repeat inspection performed at General Electric 

(GE). 

• Cube inspection: Tabulation of 25-MHz inspection results including C-scan image 

performed at GE. Comparison of 5-MHz experimental results to model predictions 

performed by Iowa State University. 

• Solid model results: Generation of solid models of the voiding was necessary for use in 

model prediction. A summary of geometric models parameters is provided along with 

connectivity trees for each of the sections used to reconstruct the defect. Full details of 

the process are provided in appendix F. Several views of the final solid model used in the 

model calculations are provided, including final dimensions for the void. 

• Microprobe analysis: Electron microprobe measurements were made to provide nitrogen 

profiles for each of the defects. Concentration was determined for the base alloy 

elements (titanium (Ti), aluminum (Al), and vanadium (V)) as well as the contaminants 

(carbon (C) and nitrogen (N)). Micrographs showing the location of the scans are 

provided along with a tabulation of the concentrations. A graph is provided of the 

nitrogen profiles. 

E-1
Indication: B3W3 – B

Original billet length: 130”

130 inches

Serial Number

56.5 inches

34.5 inches

Mult

removed

Mult inspection parameters: 

Transducer - Zone 1, 6” diameter, 5MHz

Index - 0.010 

Data Acquisition Rate - 0.010

Inspection Sensitivity - #2 FBH at 80-90% in Titanium

Inspection Range - 0.2” to 0.8”

Sampling Rate - 100 MHz

Depth Axial Length Amplitude Signal-to-Noise Ratio

0.8 0.8” 127% 5.7

 Amplitude 

(%) 

S/N depth 

(in) 

axial 

length (in) 

radial 

length (in) 

Multizone 120% 5.74 0.8 0.7573 0.2434 

Conv. 

Longitudinal 

50 2.39 1.0 

Conv. Angle 60% 4.37 1.0 

Billet inspection:

Zone 1

Side 5 Side 6

Indication: B3W3 – B

Original billet length: 130”

130 inches

Serial Number

56.5 inches

34.5 inches

Mult

removed

130 inches

Serial Number

56.5 inches

34.5 inches

Mult

removed

Mult inspection parameters: 

Transducer - Zone 1, 6” diameter, 5MHz

Index - 0.010 

Data Acquisition Rate - 0.010

Inspection Sensitivity - #2 FBH at 80-90% in Titanium

Inspection Range - 0.2” to 0.8”

Sampling Rate - 100 MHz

Depth Axial Length Amplitude Signal-to-Noise Ratio

0.8 0.8” 127% 5.7

 Amplitude 

(%) 

S/N depth 

(in) 

axial 

length (in) 

radial 

length (in) 

Multizone 120% 5.74 0.8 0.7573 0.2434 

Conv. 

Longitudinal 

50 2.39 1.0 

Conv. Angle 60% 4.37 1.0 

Billet inspection:

Zone 1

 Amplitude 

(%) 

S/N depth 

(in) 

axial 

length (in) 

radial 

length (in) 

Multizone 120% 5.74 0.8 0.7573 0.2434 

Conv. 

Longitudinal 

50 2.39 1.0 

Conv. Angle 60% 4.37 1.0 

Billet inspection:

 Amplitude 

(%) 

S/N depth 

(in) 

axial 

length (in) 

radial 

length (in) 

Multizone 120% 5.74 0.8 0.7573 0.2434 

Conv. 

Longitudinal 

50 2.39 1.0 

Conv. Angle 60% 4.37 1.0 

Billet inspection:

Zone 1

Side 5 Side 6

25 MHz inspection parameters:

Transducer - 25 MHz, F10 - focal point positioned at indication depth

Index - 0.010

Data Acquisition Rate - 0.010

Inspection sensitivity - #2FBH at 84% at 48dB

Inspection range - C-scan , Between Front and Back / B-scan entire volume 

Sampling Rate - 200 MHz

Side Depth Axial Length Amplitude % Sensitivity, dB

1 0.444” 0.8” 66 60

2 0.496” 0.8” 93 60

3 0.453 0.8 76 60

4 0.399” 0.8” 96 60

5 0.460” 0.8” 73 74

6 0.435” 0.8” 79 72 View is from Side 1(side which was 

polished). Sides 5 and 6 represent the 

axial ends as shown above. Sides 2 

and 4 represent the hoop direction 

(circumferential plane.)

Side 6

Side 5

Side 4

Side 2

UT characterization of cube:

UT measurements completed using multiple frequencies

5MHz 10MHz 20MHz

25 MHz inspection parameters:

Transducer - 25 MHz, F10 - focal point positioned at indication depth

Index - 0.010

Data Acquisition Rate - 0.010

Inspection sensitivity - #2FBH at 84% at 48dB

Inspection range - C-scan , Between Front and Back / B-scan entire volume 

Sampling Rate - 200 MHz

Side Depth Axial Length Amplitude % Sensitivity, dB

1 0.444” 0.8” 66 60

2 0.496” 0.8” 93 60

3 0.453 0.8 76 60

4 0.399” 0.8” 96 60

5 0.460” 0.8” 73 74

6 0.435” 0.8” 79 72 View is from Side 1(side which was 

polished). Sides 5 and 6 represent the 

axial ends as shown above. Sides 2 

and 4 represent the hoop direction 

(circumferential plane.)

Side 6

Side 5

Side 4

Side 2

UT characterization of cube:

UT measurements completed using multiple frequencies

5MHz 10MHz 20MHz

E-2
B3W3-B 5 MHz C-scan image comparisons:

Side 1

Model Experiment

Side 2 Model Experiment

Side 3

Model Experiment

Side 4

Model Experiment

Attenuation=10dB

peak amplitude =411 mv

deviation=-39% or -4.25 dB 

Attenuation= 10 dB

peak amplitude= 670mv

Attenuation=8dB

peak amplitude=614 mv

Deviation=11% or 0.92 dB 

Attenuation=8dB

peak amplitude= 552mv

Attenuation=8dB

peak amplitude=1845 mv

deviation=179% or 8.90 dB 

Attenuation=10dB

peak amplitude= 1012mv

deviation=56% or 3.89 dB 

Attenuation=10dB

peak amplitude= 647mv

Attenuation=8dB

peak amplitude= 662mv

Multizone Color Code

0 128 255

Experiment 255 = 1000mv

Experiment image: 171(H) x 51(V) @10 mils

Model image: 101(H) x 41(V) @10 mils

 

B3W3-B

940 mils

1

2

3

4

B3W3-B

940 mils

1

2

3

4

E-3
9

10

11

5

6

7

940 mils

8

E-4
12

13

14

940 mils

Orientation of Sub-Micrographs (B3W3-B) 

Y

Z

X

stack-up sequence

(polish in from side 4 of the cube)

1

2

14

E-5
119 mils (Y)

741 mils (X)

Dimensions of B3W3-B 

Unit: mils

min. max. size

X

Y

Z

298.78 1040.05 741.27

154.24 273.50 119.25

3.18 83.79 80.60

E-6
Scan 1

Scan 2

Scan 3

Microprobe analysis:

B3W3 – B - Section 5 – 20 mils

Microprobe analysis:

B3W3 – B - Section 5 – 20 mils

B3W3 - INDICATION B - TRANSVERSE PROFILE No. 1 

ELECTRON MICROPROBE COMPOSITION MEASUREMENTS 

Scanned perpendicular to long axis of defect with "zero" located at defect core. 

 Weight % 

Distance (mils) Ti Al V C O N 

50 91 7.2 1.7 < 0.2 < 0.2 0.7 

45 90 6.7 2.2 < 0.2 0.7* < 0.5 

40 85 7.3 1.6 < 0.2 < 0.2 < 0.5 

35 85 7.2 1.7 < 0.2 < 0.2 1.0 

30 89 6.9 2 0.6 0.4* 0.7 

25 88 6.9 2 0.3 < 0.2 0.7 

20 88 6.3 2.6 0.8 < 0.2 1.1 

18 89 6.3 1.9 0.6 < 0.2 1.1 

16 87 5.1 6.1 1.1 0.7* 1.4 

12 89 5.6 2.2 0.9 < 0.2 1.2 

10 88 5.5 2.1 1.1 < 0.2 1.5 

9 90 5.4 2.3 0.9 < 0.2 1.7 

8 89 5.4 2.1 1.1 < 0.2 1.7 

7 90 5.5 2 1.3 < 0.2 1.5 

6 90 4.9 1.7 1.0 < 0.2 1.5 

5 91 4.5 1.7 1.2 < 0.2 2.3 

4 91 3.6 1.9 1.9 < 0.2 2.2 

3 91 2.4 1.7 1.8 < 0.2 3.3 

2 91 0.5 1.7 1.4 < 0.2 3.9 

1 92 0.2 2 1.7 < 0.2 3.9 

0 91 0.3 1.9 1.3 < 0.2 3.5 

-1 93 0.3 1.9 1.8 < 0.2 3.8 

-2 94 0.3 1.9 1.6 < 0.2 3.4 

-3 93 0.4 2.2 1.3 < 0.2 3.2 

-4 92 2.9 1.8 2.1 0.8* 1.9 

-5 88 4.2 1.8 1.6 < 0.2 1.7 

-6 90 5.2 1.9 0.9 < 0.2 1.2 

-7 89 5.4 2.5 0.9 < 0.2 1.1 

-9 89 5 1.9 1.2 < 0.2 1.5 

-10 90 5.7 2 1.0 < 0.2 1.2 

-12 92 5.5 1.8 1.0 < 0.2 0.9 

-16 91 6.5 1.9 0.8 < 0.2 0.7 

-18 90 6.6 2 0.7 < 0.2 1.0 

-20 90 6.6 1.9 0.8 < 0.2 0.5 

-25 90 7 1.8 0.6 < 0.2 0.8 

-30 90 7 1.9 0.4 < 0.2 0.5 

-35 90 5.7 2 < 0.2 0.3 0.6 

-40 91 7.2 1.9 < 0.2 < 0.2 1.0 

-45 91 6.6 1.9 < 0.2 < 0.2 0.6 

-50 91 6.8 1.6 < 0.2 < 0.2 < 0.5 

* Occasional points of elevated oxygen concentration likely from contamination on 

specimen surface, and do not represent actual variations in composition. 

B3W3 - INDICATION B - TRANSVERSE PROFILE No. 2 

ELECTRON MICROPROBE COMPOSITION MEASUREMENTS 

Scanned perpendicular to long axis of defect with "zero" located at defect core. 

 Weight % 

Distance (mils) Ti Al V C O N 

50 90 7.0 1.7 < 0.2 < 0.2 < 0.5 

45 89 7.0 1.8 < 0.2 < 0.2 < 0.5 

40 90 6.8 2.0 0.2 < 0.2 < 0.5 

35 91 6.9 2.0 < 0.2 < 0.2 0.6 

30 89 6.5 2.1 < 0.2 < 0.2 < 0.5 

25 89 6.3 2.0 0.2 < 0.2 < 0.5 

20 88 6.0 2.1 0.2 < 0.2 0.6 

16 90 5.6 2.2 0.3 < 0.2 0.7 

14 89 5.6 2.1 0.4 < 0.2 0.6 

12 88 5.5 2.5 0.5 < 0.2 0.8 

10 84 0.7 2.1 1.7 2.4* 5.6 

9 83 0.1 0.9 1.0 < 0.2 3.5 

7 84 0.1 1.5 0.5 < 0.2 6.8 

5 85 0.2 1.9 0.9 < 0.2 6.8 

4 86 0.1 2.0 0.7 < 0.2 8.0 

3 83 0.4 1.6 0.8 < 0.2 8.6 

2 87 0.1 1.9 0.7 < 0.2 8.5 

1 86 0.1 1.9 0.8 < 0.2 8.5 

0 84 0.2 4.1 0.7 < 0.2 8.7 

-1 86 0.1 1.9 0.9 < 0.2 8.9 

-2 86 0.1 1.5 1.0 < 0.2 8.8 

-3 85 0.1 1.4 1.3 < 0.2 7.8 

-4 86 0.1 1.7 1.7 < 0.2 8.0 

-5 86 0.1 2.0 2.0 < 0.2 7.3 

-6 84 0.2 2.0 3.5 < 0.2 7.0 

-7 78 1.6 5.6 8.1 3.7* 4.9 

-13 91 5.4 2.1 0.9 < 0.2 1.0 

-14 91 5.4 2.3 0.7 < 0.2 0.5 

-16 93 5.4 2.2 0.4 < 0.2 0.6 

-18 92 5.8 2.2 0.4 < 0.2 < 0.5 

-20 93 6.1 1.9 0.2 < 0.2 < 0.5 

-25 92 6.6 1.9 < 0.2 < 0.2 < 0.5 

-30 94 6.9 1.7 < 0.2 < 0.2 < 0.5 

-35 94 6.8 1.4 < 0.2 < 0.2 < 0.5 

-40 90 7.1 1.8 < 0.2 < 0.2 < 0.5 

-45 91 7.2 1.7 < 0.2 < 0.2 < 0.5 

-50 92 7.1 1.6 < 0.2 < 0.2 < 0.5 

Note: Shaded points were located in the visible core of the defect. 

* Occasional points of elevated oxygen concentration likely from contamination on 

specimen surface, and do not represent actual variations in composition. 

B3W3 - INDICATION B - TRANSVERSE PROFILE No. 1 

ELECTRON MICROPROBE COMPOSITION MEASUREMENTS 

Scanned perpendicular to long axis of defect with "zero" located at defect core. 

 Weight % 

Distance (mils) Ti Al V C O N 

50 91 7.2 1.7 < 0.2 < 0.2 0.7 

45 90 6.7 2.2 < 0.2 0.7* < 0.5 

40 85 7.3 1.6 < 0.2 < 0.2 < 0.5 

35 85 7.2 1.7 < 0.2 < 0.2 1.0 

30 89 6.9 2 0.6 0.4* 0.7 

25 88 6.9 2 0.3 < 0.2 0.7 

20 88 6.3 2.6 0.8 < 0.2 1.1 

18 89 6.3 1.9 0.6 < 0.2 1.1 

16 87 5.1 6.1 1.1 0.7* 1.4 

12 89 5.6 2.2 0.9 < 0.2 1.2 

10 88 5.5 2.1 1.1 < 0.2 1.5 

9 90 5.4 2.3 0.9 < 0.2 1.7 

8 89 5.4 2.1 1.1 < 0.2 1.7 

7 90 5.5 2 1.3 < 0.2 1.5 

6 90 4.9 1.7 1.0 < 0.2 1.5 

5 91 4.5 1.7 1.2 < 0.2 2.3 

4 91 3.6 1.9 1.9 < 0.2 2.2 

3 91 2.4 1.7 1.8 < 0.2 3.3 

2 91 0.5 1.7 1.4 < 0.2 3.9 

1 92 0.2 2 1.7 < 0.2 3.9 

0 91 0.3 1.9 1.3 < 0.2 3.5 

-1 93 0.3 1.9 1.8 < 0.2 3.8 

-2 94 0.3 1.9 1.6 < 0.2 3.4 

-3 93 0.4 2.2 1.3 < 0.2 3.2 

-4 92 2.9 1.8 2.1 0.8* 1.9 

-5 88 4.2 1.8 1.6 < 0.2 1.7 

-6 90 5.2 1.9 0.9 < 0.2 1.2 

-7 89 5.4 2.5 0.9 < 0.2 1.1 

-9 89 5 1.9 1.2 < 0.2 1.5 

-10 90 5.7 2 1.0 < 0.2 1.2 

-12 92 5.5 1.8 1.0 < 0.2 0.9 

-16 91 6.5 1.9 0.8 < 0.2 0.7 

-18 90 6.6 2 0.7 < 0.2 1.0 

-20 90 6.6 1.9 0.8 < 0.2 0.5 

-25 90 7 1.8 0.6 < 0.2 0.8 

-30 90 7 1.9 0.4 < 0.2 0.5 

-35 90 5.7 2 < 0.2 0.3 0.6 

-40 91 7.2 1.9 < 0.2 < 0.2 1.0 

-45 91 6.6 1.9 < 0.2 < 0.2 0.6 

-50 91 6.8 1.6 < 0.2 < 0.2 < 0.5 

* Occasional points of elevated oxygen concentration likely from contamination on 

specimen surface, and do not represent actual variations in composition. 

B3W3 - INDICATION B - TRANSVERSE PROFILE No. 2 

ELECTRON MICROPROBE COMPOSITION MEASUREMENTS 

Scanned perpendicular to long axis of defect with "zero" located at defect core. 

 Weight % 

Distance (mils) Ti Al V C O N 

50 90 7.0 1.7 < 0.2 < 0.2 < 0.5 

45 89 7.0 1.8 < 0.2 < 0.2 < 0.5 

40 90 6.8 2.0 0.2 < 0.2 < 0.5 

35 91 6.9 2.0 < 0.2 < 0.2 0.6 

30 89 6.5 2.1 < 0.2 < 0.2 < 0.5 

25 89 6.3 2.0 0.2 < 0.2 < 0.5 

20 88 6.0 2.1 0.2 < 0.2 0.6 

16 90 5.6 2.2 0.3 < 0.2 0.7 

14 89 5.6 2.1 0.4 < 0.2 0.6 

12 88 5.5 2.5 0.5 < 0.2 0.8 

10 84 0.7 2.1 1.7 2.4* 5.6 

9 83 0.1 0.9 1.0 < 0.2 3.5 

7 84 0.1 1.5 0.5 < 0.2 6.8 

5 85 0.2 1.9 0.9 < 0.2 6.8 

4 86 0.1 2.0 0.7 < 0.2 8.0 

3 83 0.4 1.6 0.8 < 0.2 8.6 

2 87 0.1 1.9 0.7 < 0.2 8.5 

1 86 0.1 1.9 0.8 < 0.2 8.5 

0 84 0.2 4.1 0.7 < 0.2 8.7 

-1 86 0.1 1.9 0.9 < 0.2 8.9 

-2 86 0.1 1.5 1.0 < 0.2 8.8 

-3 85 0.1 1.4 1.3 < 0.2 7.8 

-4 86 0.1 1.7 1.7 < 0.2 8.0 

-5 86 0.1 2.0 2.0 < 0.2 7.3 

-6 84 0.2 2.0 3.5 < 0.2 7.0 

-7 78 1.6 5.6 8.1 3.7* 4.9 

-13 91 5.4 2.1 0.9 < 0.2 1.0 

-14 91 5.4 2.3 0.7 < 0.2 0.5 

-16 93 5.4 2.2 0.4 < 0.2 0.6 

-18 92 5.8 2.2 0.4 < 0.2 < 0.5 

-20 93 6.1 1.9 0.2 < 0.2 < 0.5 

-25 92 6.6 1.9 < 0.2 < 0.2 < 0.5 

-30 94 6.9 1.7 < 0.2 < 0.2 < 0.5 

-35 94 6.8 1.4 < 0.2 < 0.2 < 0.5 

-40 90 7.1 1.8 < 0.2 < 0.2 < 0.5 

-45 91 7.2 1.7 < 0.2 < 0.2 < 0.5 

-50 92 7.1 1.6 < 0.2 < 0.2 < 0.5 

Note: Shaded points were located in the visible core of the defect. 

* Occasional points of elevated oxygen concentration likely from contamination on 

specimen surface, and do not represent actual variations in composition. 

E-7
B3W3 - B

0

2

4

6

8

10

-50 -40 -30 -20 -10 0 10 20 30 40 50

Distance (mils)

Wt% Nitrogen

Scan 1

Scan 2

Scan 3

B3W3 - INDICATION B - LONGITUDINAL PROFILE 

ELECTRON MICROPROBE COMPOSITION MEASUREMENTS 

Scanned parallel to long axis of defect with "zero" located at one end of defect core. 

 Weight % 

Distance (mils) Ti Al V C O N 

0 89 5.6 1.9 1.1 < 0.2 1.0 

1 89 5.3 2.1 1.2 0.3 0.6 

2 88 5.5 2.2 0.9 < 0.2 0.6 

3 90 5.1 2.1 0.6 < 0.2 0.6 

4 90 5.3 2.2 0.7 0.3 0.6 

5 90 5.5 2.2 0.4 < 0.2 0.6 

6 90 5.4 2.1 0.4 < 0.2 0.5 

7 89 5.4 2.1 0.3 < 0.2 0.9 

8 90 5.6 2.0 0.6 0.6* < 0.5 

9 90 5.5 2.0 0.4 < 0.2 0.8 

10 90 5.5 2.1 0.4 < 0.2 0.6 

12 91 5.2 2.1 0.4 < 0.2 0.5 

14 91 5.2 2.1 0.3 < 0.2 0.6 

16 90 5.6 2.2 < 0.2 < 0.2 0.6 

20 90 5.5 2.3 < 0.2 < 0.2 0.5 

25 89 5.5 2.2 < 0.2 < 0.2 0.6 

30 91 5.9 2.1 < 0.2 < 0.2 0.8 

35 91 6.0 2.0 < 0.2 < 0.2 < 0.5 

40 90 6.1 2.2 < 0.2 < 0.2 0.5 

45 90 6.1 2.1 < 0.2 < 0.2 0.7 

50 90 6.2 2.2 < 0.2 < 0.2 < 0.5 

60 90 6.1 2.2 < 0.2 < 0.2 < 0.5 

70 90 6.4 2.1 < 0.2 0.3 < 0.5 

80 90 6.2 1.9 < 0.2 < 0.2 < 0.5 

100 91 6.4 2.0 < 0.2 0.4* 0.6 

125 91 6.9 2.0 < 0.2 < 0.2 < 0.5 

150 90 6.9 2.1 < 0.2 < 0.2 < 0.5 

175 90 7.1 1.8 < 0.2 < 0.2 < 0.5 

200 91 7.0 2.2 < 0.2 < 0.2 < 0.5 

225 91 7.2 2.0 < 0.2 < 0.2 < 0.5 

250 91 7.1 1.9 < 0.2 < 0.2 < 0.5 

275 90 7.1 1.8 < 0.2 < 0.2 < 0.5 

300 91 7.1 1.8 < 0.2 < 0.2 < 0.5 

350 91 7.2 1.8 < 0.2 < 0.2 < 0.5 

400 91 7.1 1.7 < 0.2 < 0.2 < 0.5 

* Occasional points of elevated oxygen concentration likely from contamination on 

specimen surface, and do not represent actual variations in composition.

E-8
Microprobe analysis:

B3W3 – B - Section 11 – 45 mils

Scan 1

Scan 2 Scan 3

DEFECT B3W3-B - METALLOGRAPHIC SECTION No. 11 - 

TRANSVERSE PROFILE No. 1 

ELECTRON MICROPROBE COMPOSITION MEASUREMENTS 

Scanned perpendicular to long axis of defect with "zero" located at defect core. 

 Weight % 

Distance (mils) Ti Al V C N 

50 87 7.4 1.9 0.2 < 0.5 

45 88 7.3 1.8 < 0.2 < 0.5 

40 88 7.1 1.8 0.2 < 0.5 

35 90 7.2 1.9 0.2 < 0.5 

30 93 7.0 1.8 0.2 < 0.5 

25 92 6.9 2.2 0.2 < 0.5 

20 92 6.8 1.8 0.2 < 0.5 

16 93 6.5 2.0 0.2 < 0.5 

12 91 6.5 2.2 0.2 < 0.5 

10 93 5.8 1.8 0.2 0.5 

8 93 6.1 2.1 0.2 < 0.5 

6 93 6.1 2.4 0.2 0.9 

5 92 5.8 2.3 0.2 0.7 

4 93 4.8 1.7 0.2 1.2 

3 93 1.9 1.9 0.8 2.3 

2 94 0.2 2.1 0.5 3.8 

1 93 0.2 2.1 0.8 3.8 

0 94 0.3 2.0 1.3 4.1 

-1 95 1.0 1.9 0.6 3.3 

-2 93 3.6 1.8 1.1 1.9 

-3 93 5.5 2.2 0.3 0.9 

-4 92 6.2 2.6 0.2 0.8 

-5 92 6.3 2.5 0.2 0.6 

-6 92 6.2 2.2 0.2 0.9 

-8 91 6.1 2.2 0.2 < 0.5 

-10 90 5.8 1.8 0.3 0.6 

-12 91 5.8 2.0 0.4 0.6 

-16 93 6.7 2.2 0.3 < 0.5 

-20 94 6.6 2.2 0.3 < 0.5 

-25 93 6.9 2.2 0.3 < 0.5 

-30 94 7.0 2.0 0.5 < 0.5 

-35 92 6.8 1.9 0.6 < 0.5 

-40 92 6.8 1.9 0.3 < 0.5 

-45 95 7.3 1.9 0.3 < 0.5 

-50 95 7.3 1.8 0.2 < 0.5 

DEFECT B3W3-B - METALLOGRAPHIC SECTION No. 11 - 

TRANSVERSE PROFILE No. 2 

ELECTRON MICROPROBE COMPOSITION MEASUREMENTS 

Scanned perpendicular to long axis of defect with "zero" located at defect core. 

 Weight % 

Distance (mils) Ti Al V C N 

50 86 7.1 1.7 0.2 0.6 

45 93 7.2 1.9 0.2 < 0.5 

40 91 6.9 2.0 0.3 < 0.5 

35 93 7.0 1.9 0.4 < 0.5 

30 91 6.8 2.1 0.5 < 0.5 

25 92 6.8 1.9 0.4 < 0.5 

20 88 6.3 2.0 0.5 0.6 

16 92 6.0 2.2 0.4 0.5 

12 90 5.8 2.1 0.6 0.5 

10 92 5.9 2.2 0.4 0.5 

8 92 6.1 2.3 0.5 0.5 

6 93 6.0 2.2 0.4 0.6 

5 92 5.8 2.6 0.4 1.2 

4 90 0.1 1.8 0.5 8.8 

3 87 0.1 2.0 1.2 7.8 

2 89 < 0.1 0.8 1.6 7.8 

1 90 0.1 2.0 0.6 8.5 

0 91 < 0.1 0.8 0.8 8.6 

-1 91 < 0.1 1.0 0.4 8.5 

-2 90 0.1 1.9 0.2 8.8 

-3 91 0.2 2.5 0.4 6.4 

-4 88 0.1 1.6 1.4 7.9 

-5 93 0.5 2.2 0.4 5.1 

-6 93 0.5 2.2 0.4 4.9 

-8 93 3.1 1.7 0.9 2.7 

-10 92 6.1 2.3 0.3 0.9 

-12 92 6.1 2.4 0.2 0.6 

-16 90 6.1 2.4 0.4 0.7 

-20 90 5.8 2.0 0.3 0.6 

-25 92 6.5 2.1 0.2 < 0.5 

-30 91 6.9 2.0 0.3 < 0.5 

-35 92 7.1 2.0 0.4 < 0.5 

-40 91 7.2 1.9 0.2 < 0.5 

-45 92 7.3 2.0 0.2 < 0.5 

-50 93 7.3 1.8 0.2 < 0.5 

Note: Shaded points were located in the visible core of the defect.

E-9
B3W3 - B

0

2

4

6

8

10

12

-50 -40 -30 -20 -10 0 10 20 30 40 50

Distance (mils)

Wt% Nitrogen

Scan 1

Scan 2

Scan 3

DEFECT B3W3-B - METALLOGRAPHIC SECTION No. 11 - 

TRANSVERSE PROFILE No. 3 

ELECTRON MICROPROBE COMPOSITION MEASUREMENTS 

Scanned perpendicular to long axis of defect with "zero" located at defect core. 

 Weight % 

Distance (mils) Ti Al V C N 

50 90 7.1 2.0 0.3 < 0.5 

40 93 6.8 2.1 0.3 < 0.5 

30 93 6.5 2.0 0.4 < 0.5 

20 92 6.1 2.1 0.4 < 0.5 

15 93 3.2 2.0 1.1 1.9 

10 93 5.5 2.1 0.5 0.7 

8 93 4.0 1.9 0.9 2.3 

6 86 1.0 2.3 0.7 4.5 

5 88 0.6 5.4 1.2 5.0 

4 91 0.1 1.6 0.6 8.4 

3 89 0.1 1.9 0.4 8.9 

2 88 0.1 1.9 0.6 9.0 

1 88 0.1 2.2 0.6 8.6 

0 90 0.1 2.1 0.5 9.3 

-1 89 0.1 2.0 0.4 9.7 

-2 88 0.1 2.3 0.5 9.5 

-3 87 0.2 3.2 0.4 8.4 

-4 88 0.1 1.6 0.5 8.8 

-5 92 0.2 1.9 0.8 7.3 

-6 94 0.2 2.1 0.4 4.6 

-8 96 0.7 2.0 0.5 3.2 

-10 94 5.3 2.1 0.4 1.0 

-15 90 6.3 2.2 0.2 < 0.5 

-20 93 6.9 1.8 0.2 < 0.5 

-30 92 7.2 1.6 0.2 < 0.5 

-40 88 7.2 1.7 0.2 < 0.5 

-50 92 7.4 1.7 0.2 < 0.5 

Note: Shaded points were located in the visible core of the defect.

E-10
Indication: B1BW3 – C

Original billet length: 107.5”

Mult inspection parameters: 

Transducer - Zone 1, 6” diameter, 5MHz

Index - 0.010 

Data Acquisition Rate - 0.010

Inspection Sensitivity - #2 FBH at 80-90% in Titanium

Inspection Range - 0.2” to 0.8”

Sampling Rate - 100 MHz

Depth Axial Length Amplitude Signal-to-Noise Ratio

0.5” 1.5” 127% 6.7

Billet inspection:

Zone 1

Mult

Side 5 removed Side 6

107.5 inches

Serial Number

48 inches 70 inches

 Amplitude 

(%) 

S/N depth 

(in) 

axial 

length (in) 

radial 

length (in) 

Multizone 127% 6.67 0.5 1.4474 0.2301 

Conv. 

Longitudinal 

% 

Conv. Angle % 

Indication: B1BW3 – C

Original billet length: 107.5”

Mult inspection parameters: 

Transducer - Zone 1, 6” diameter, 5MHz

Index - 0.010 

Data Acquisition Rate - 0.010

Inspection Sensitivity - #2 FBH at 80-90% in Titanium

Inspection Range - 0.2” to 0.8”

Sampling Rate - 100 MHz

Depth Axial Length Amplitude Signal-to-Noise Ratio

0.5” 1.5” 127% 6.7

Billet inspection:

Zone 1

Mult

Side 5 removed Side 6

107.5 inches

Serial Number

48 inches 70 inches

Mult

Side 5 removed Side 6

107.5 inches

Serial Number

48 inches 70 inches

 Amplitude 

(%) 

S/N depth 

(in) 

axial 

length (in) 

radial 

length (in) 

Multizone 127% 6.67 0.5 1.4474 0.2301 

Conv. 

Longitudinal 

% 

Conv. Angle % 

25 MHz inspection parameters

Transducer - 25 MHz, F10 - focal point positioned at indication depth

Index - 0.010

Data Acquisition Rate - 0.010

Inspection sensitivity - #1 FBH at 83% - 56 dB #2FBH at 84% at 48dB

Inspection range - C-scan , Between Front and Back / B-scan entire volume 

Sampling Rate - 200 MHz

Side Depth Axial Length Amplitude % Sensitivity, dB

1 0.304” 1.5” 70 65

2 0.465” 1.5” 89 65

3 0.447” 1.5” 81 65 

4 0.448” 1.5” 56 56

5 0.595” 1.5” 51 69

6 0.493” 1.5” 90 67

Side 6

Side 5

Side 4

Side 2

View is from Side 1(side which was 

polished). Sides 5 and 6 represent the 

axial ends as shown above. Sides 2 

and 4 represent the hoop direction 

(circumferential plane.)

Orientation of sample block and c-scan images: 

X

Z

Side 3 (top)

Side 5 

(right)

Y

Side 1 (bottom)

Side 6 

(left)

Side 2 

(back)

Side 4 (front) Side 2 Side 6

Side 5

Side 3

Side 1

Side 1

Side 6Side 5

Side 2

Side 4

Side 4

Side 6

Side 5

Side 1

Side 3

Side 3

Side 6Side 5

Side 4

Side 2

X

Z

Side 3 (top)

Side 5 

(right)

Y

Side 1 (bottom)

Side 6 

(left)

Side 2 

(back)

Side 4 (front)

X

Z

Side 3 (top)

Side 5 

(right)

Y

Side 1 (bottom)

Side 6 

(left)

Side 2 

(back)

Side 4 (front) Side 2 Side 6

Side 5

Side 3

Side 1

Side 1

Side 6Side 5

Side 2

Side 4

Side 4

Side 6

Side 5

Side 1

Side 3

Side 3

Side 6Side 5

Side 4

Side 2

E-11
B1BW3-C 5 MHz C-scan image comparisons:

Side 1

Model Experiment

Side 2

Model Experiment

Side 3

Model Experiment

Side 4

Model Experiment

Attenuation=6dB

peak amplitude =1316 mv

deviation=100% or 6.01 dB 

Attenuation= 6 dB

peak amplitude= 659mv

Attenuation=8dB

peak amplitude=902 mv

Deviation=45% or 3.26 dB 

Attenuation=8dB

peak amplitude= 620mv

Attenuation=12dB

peak amplitude=1901 mv

deviation=187% or 9.15 dB 

Attenuation=14dB

peak amplitude= 2675mv

deviation=329% or 12.64 dB 

Attenuation=14dB

peak amplitude= 624mv

Attenuation=12dB

peak amplitude= 663mv

Multizone Color Code

0 128 255

Experiment 255 = 1000mv

Experiment image: 201(H) x 61(V) @10 mils

Model image: 201(H) x 61(V) @10 mils

B1BW3-C 5 MHz C-scan image comparisons:

Side 1

Model Experiment

Side 2

Model Experiment

Side 3

Model Experiment

Side 4

Model Experiment

Attenuation=6dB

peak amplitude =1316 mv

deviation=100% or 6.01 dB 

Attenuation= 6 dB

peak amplitude= 659mv

Attenuation=8dB

peak amplitude=902 mv

Deviation=45% or 3.26 dB 

Attenuation=8dB

peak amplitude= 620mv

Attenuation=12dB

peak amplitude=1901 mv

deviation=187% or 9.15 dB 

Attenuation=14dB

peak amplitude= 2675mv

deviation=329% or 12.64 dB 

Attenuation=14dB

peak amplitude= 624mv

Attenuation=12dB

peak amplitude= 663mv

Multizone Color Code

0 128 255

Experiment 255 = 1000mv

Experiment image: 201(H) x 61(V) @10 mils

Model image: 201(H) x 61(V) @10 mils

Sub-Micrograph 

size - 12300(H) by 1700(V) pixels

color - 256 gray-scale of size

scale – 82.6 pixels =10 mils

Geometric Model

13 void flaw part (with branches)

42 geometric model parts

23 micrograph planes (including 8 patches)

168 void cross-section boundary traces (model part 7, 8 and 9 use 7; 

14, 29 and 39 use 6; 

6, 10, 15, 18, 19, 34, 38 use 5; 

16, 17, 23, 24, 25, 31, 32 use 4; 

the rest use 3 each)

B1BW3-C 3D Solid Model Parameters:

E-12
4

6

3

5

B1BW3-C

7

8

1490 mils

10

9

14

13

12

11

E-13
Orientation of Sub-Micrographs (B1BW3-C): 

Y

Z

X

stack-up sequence

(polish in from side 4 of the cube)

3

4

14

Orientation of Sub-Micrographs (B1BW3-C): 

Y

Z

X

stack-up sequence

(polish in from side 4 of the cube)

3

4

14

E-14
X

Y Z

Angle views of void model for B1BW3-C:

View 1

View 2

X

Y Z

Angle views of void model for B1BW3-C:

View 1

View 2

171 mils (Y)

1404 mils (X)

min. max. size

X 55 1459 1404

Y 19 190 171

Z 9 68 59

Unit: mils

Dimensions of B1BW3-C: 

E-15
Microprobe analysis:

B1BW3 – C - Section 6 – 20 mils

Scan 1

W %

Distance (mils) Ti Al V C N

40 90 6.2 2.1 < 0.2 0.6

30 92 6.3 2.2 < 0.2 0.8

25 91 6.2 2.1 0.2 0.8

20 92 5.9 2.1 < 0.2 0.5

16 89 5.9 2.2 < 0.2 1.3

14 93 4.8 2 < 0.2 0.9

12 92 5.3 2.2 < 0.2 1.2

10 90 5.2 2 0.3 1.6

8 92 2.6 1.8 < 0.2 1.5

6 91 0.2 2.2 0.4 5.2

5 91 0.2 2.4 0.3 5.4

4 89 0.6 2.2 0.3 5.0

3 89 0.4 2.4 0.4 7.7

2 89 0.1 1.6 0.4 8.7

1 89 < 0.1 1.2 0.6 9.7

0 90 < 0.1 1 < 0.2 8.4

-1 86 0.2 1.5 1.1 8.4

-2 87 0.4 3.2 0.9 8.6

-3 88 0.1 1.2 0.4 8.6

-4 88 0.2 2.3 0.3 7.4

-5 88 0.4 2.4 0.3 5.4

-6 89 0.3 2.1 1.8 6.8

-8 79 1.9 1.3 0.9 2.9

-10 88 5.2 2.2 < 0.2 1.7

-12 90 5.6 2.3 < 0.2 1.5

-14 90 5.5 2.1 < 0.2 1.0

-16 93 5.7 1.8 < 0.2 0.6

-20 92 6.3 2.1 < 0.2 0.5

-25 92 6.3 1.9 < 0.2 < 0.5

-30 92 6.8 2 < 0.2 1.0

-40 91 7 2 < 0.2 0.5

Scan 2

W %

Distance (mils) Ti Al V C N

40 91 7 2.1 < 0.2 < 0.5

30 90 6.8 1.9 < 0.2 0.5

25 90 6.6 2.3 < 0.2 0.7

20 91 6.3 2.1 < 0.2 < 0.5

16 92 6.4 2.3 < 0.2 0.9

12 92 6.1 2.3 < 0.2 < 0.5

10 90 5.2 2 < 0.2 1.1

8 92 5.3 2 0.3 1.6

6 91 5.6 2.1 < 0.2 1.5

5 91 5.6 2.2 0.2 1.0

4 91 4.6 1.9 0.2 1.9

3 92 2.7 1.8 < 0.2 2.8

2 93 1.4 1.8 0.3 3.7

1 92 0.8 2.1 0.6 3.3

0 94 0.2 1.9 0.5 3.4

-1 93 0.2 2 0.4 2.8

-2 92 0.3 1.7 0.2 2.9

-3 90 5.9 2.7 0.3 1.4

-4 90 5.7 2.6 0.2 1.5

-5 91 6 2.4 < 0.2 < 0.5

-6 90 6 2.1 < 0.2 0.6

-8 92 6.1 1.3 < 0.2 < 0.5

-10 90 6.1 2.2 < 0.2 1.1

-12 92 6.3 2.3 < 0.2 0.5

-16 89 6.1 1.8 < 0.2 1.0

-20 91 6 2.1 < 0.2 1.1

-25 90 6 1.9 < 0.2 1.0

-30 92 5.8 2 < 0.2 0.6

-40 90 7.1 2 < 0.2 < 0.5

Microprobe analysis:

B1BW3 – C - Section 6 – 20 mils

E-16
Scan 3

B1BW3 - C

0

2

4

6

8

10

-50 -40 -30 -20 -10 0 10 20 30 40 50

Distance (mils)

Wt% Nitrogen

Scan 1

Scan 2

Scan 3

W %

Distance (mils) Ti Al V C N

40 92 5.7 2.3 < 0.2 0.5

30 92 6.1 2.3 0.2 0.8

25 92 6.3 2.1 0.2 0.7

20 89 6.3 2.1 0.2 0.6

16 88 6.4 2.2 0.2 0.8

14 86 6.1 2.4 0.3 1.1

12 88 4.8 1.9 0.4 2.4

10 91 1.3 1.5 0.3 2.8

8 9332.1 0.3 2.

6 89 6.3 3 0.3 1.3

5 9252.2 0.4 1.

4 89 3.8 2.1 0.5 1.9

3 92 3.4 2.2 0.3 2.2

2 88 2.7 2.1 0.4 2.5

1 88 1.2 2.1 0.8 2.6

0 93 0.2 2.4 0.7 3.8

-1 93 0.2 2.2 0.5 4.5

-2 91 0.3 3.1 0.9 5.0

-3 93 0.5 1.5 0.8 1.4

-4 92 2.1 1.7 0.7 1.1

-5 93 5.8 2.2 0.3 1.3

-6 88 6.3 2.3 0.2 1.0

-8 91 6.7 2.4 0.3 0.8

-10 90 6.6 2.1 0.3 0.6

-12 91 6.7 2.2 < 0.2 0.7

-16 91 6.8 2.2 < 0.2 < 0.5

-20 91 7 2.3 < 0.2 < 0.5

-25 89 7.1 2.1 < 0.2 < 0.5

-30 91 7.2 2.2 < 0.2 < 0.5

-40 88 7.5 2.1 < 0.2 < 0.5

6

4

Microprobe analysis:

B1BW3 – C - Section 6 – 20 mils

E-17
 Amplitude 

(%) 

S/N depth 

(in) 

axial length 

(in) 

radial 

length (in) 

Multizone 47 2.52 1.6 .1860 .4123 

Conv. 

Longitudinal 

 

Conv. Angle 

Indication: B1AW3 – E

Original billet length: 109”

Mult inspection parameters: 

Transducer - Zone 3, 6” diameter, 5MHz

Index - 0.010 

Data Acquisition Rate - 0.010

Inspection Sensitivity - #2 FBH at 80-90% in Titanium

Inspection Range - 1.7” - 2.6”

Sampling Rate - 100 MHz

Depth Axial Length Amplitude Signal-to-Noise Ratio

1.725” 0.283” 47% 2.52

Billet inspection:

Side 5 Side 6

109 inches

Serial Number

103 inches

Zone 3

25 MHz inspection parameters

Transducer - 25 MHz, F10 - focal point positioned at indication depth

Index - 0.010

Data Acquisition Rate - 0.010

Inspection sensitivity - #1 FBH at 83% - 56 dB #2FBH at 84% at 48dB

Inspection range - C-scan , Between Front and Back / B-scan entire volume 

Sampling Rate - 200 MHz

Side Depth Axial Length Amplitude % Sensitivity, dB

1 406.6” 0.283 80 75

2 520.3” 0.283 25 79

3 386.0” 0.283 86 67

4 525.1” 0.283 19 79

5 519.1” 0.283 83 68

6 500.4” 0.283 82 66

View is from Side 1(side which was 

polished). Sides 5 and 6 represent the 

axial ends as shown above. Sides 2 

and 4 represent the hoop direction 

Orientation of sample block and c-scan images: (circumferential plane.)

Side 6

Side 5

Side 4

Side 2

X

Z

Side 2 (front)

Side 1 (top)

Side 5 

(right)

Y

Side 3 (bottom)

Side 6 

(left)

Side 4 (back)

X

Z

Side 2 (front)

Side 1 (top)

Side 5 

(right)

Y

Side 3 (bottom)

Side 6 

(left)

Side 4 (back)

E-18
Side 1 Model Experiment Side 2 Model Experiment

Model Side 3 Experiment Side 4 Model Experiment

41(H) x 31(V) @10 mils, 14dB

peak amplitude @14dB=94 mv

deviation=-15% or -1.4 dB 

150(H) x 120(V) @10 mils, 14dB

peak amplitude @14dB=110 mv

41(H) x 31(V) @10 mils, 14dB

peak amplitude @14dB=89 mv

deviation=-14% or -1.4 dB 

150(H) x 120(V) @10 mils, 14dB

peak amplitude @14dB=104 mv

41(H) x 31(V) @10 mils, 16dB

peak amplitude @16dB=77 mv

deviation=-31% or -3.2 dB 

41(H) x 31(V) @10 mils, 16dB

peak amplitude @16dB=83 mv

deviation=-27% or -2.7 dB 

150(H) x 120(V) @10 mils, 16dB

peak amplitude @16dB=113 mv

150(H) x 120(V) @10 mils, 16dB

peak amplitude @0dB=112 mv

B1AW3-E 5 MHz C-scan image comparisons:

120(H) x 100(V) @10 mils, 2dB

peak amplitude@2dB = 97 mv

41(H) x 31(V) @10 mils, 2dB

peak amplitude@2dB = 36 mv

deviation=-63% or -8.6 dB

Side 5 Model Experiment

Multizone Color Code

0 128 255

Experiment 255 = 125mv

100(H) x 30(V) @10 mils, 0dB

peak amplitude@0dB = 92 mv

41(H) x 31(V) @10 mils, 0dB

peak amplitude@0dB = 45 mv

deviation=-51% or -6.1 dB

Side 6 Model Experiment

B1AW3-E 3D Solid Model Parameters:

Geometric Model 

2 void part 

(with branches)

8 geometric model parts

13 micrograph planes 

(including 8 patches)

35 void cross-section boundary traces

(model part 1 uses 8 traces, 

2, 3 &8 use 5,

and the rest use 3 each)

E-19
B1AW3-E

5

7

6

8

9

E-20
5

Y

Z

Polish 8

X

stack-up sequence

(polish in from side 2 of the cube)

Z offset

6

9

5

Y

Z

Polish 8

X

stack-up sequence

(polish in from side 2 of the cube)

Z offset

6

9

Orientation of Sub-Micrographs (B1AW3-E): 

E-21
X

Z

X

Y

Z

Angle views of void model for B1AW3-E:

View 1

View 2

Y

20.6 mils (Z)

94.1 mils (X)

min. max. size

X 5.49 99.57 94.08

Y 2.47 18.23 15.76

Z 16.70 37.30 20.60

Unit: mils

20.6 mils (Z)

94.1 mils (X)

min. max. size

X 5.49 99.57 94.08

Y 2.47 18.23 15.76

Z 16.70 37.30 20.60

Unit: mils

Dimensions of B1AW3-E: 

E-22
Microprobe analysis:

B1AW3 – E - Section 5 – 20 mils

Scan 2 Scan 1

W %

Distance (mils) Ti Al V C N

40 91 7.5 1.6 < 0.2 < 0.5

30 89 7.5 1.8 < 0.2 < 0.5

25 90 7.5 2.2 < 0.2 < 0.5

20 90 7.2 1.8 < 0.2 < 0.5

15 90 7.2 2 < 0.2 < 0.5

10 92 6.7 1.8 < 0.2 < 0.5

8 92 6.3 2.1 < 0.2 < 0.5

6 92 6.3 2.4 < 0.2 0.7

5 91 5.9 2.3 < 0.2 0.6

4 92 5.3 1.7 < 0.2 < 0.5

3 93 5.6 1.9 < 0.2 0.6

2 92 5 2.1 < 0.2 0.8

1 95 4.3 2.1 0.2 1.0

0 94 3.4 1.5 0.2 1.2

-1 94 2.3 1.9 0.3 1.4

-2 96 1.7 1.8 0.7 1.5

-3 95 2.2 2.2 0.3 1.5

-4 94 4.8 2.6 < 0.2 < 0.5

-5 92 5.6 2.5 < 0.2 0.7

-6 93 5.9 2.2 < 0.2 < 0.5

-8 91 6.6 2.2 < 0.2 < 0.5

-10 93 6.8 1.8 < 0.2 < 0.5

-15 92 6.8 2 < 0.2 < 0.5

-20 92 7.1 2.2 < 0.2 < 0.5

-25 93 7.1 2.2 < 0.2 < 0.5

-30 93 7 2 < 0.2 < 0.5

-40 92 7.3 1.9 < 0.2 < 0.5

Profile #1 - Section 5

W %

Distance (mils) Ti Al V C N

40 86 7.1 1.7 < 0.2 < 0.5

30 93 7.2 1.9 < 0.2 < 0.5

20 91 6.9 2 < 0.2 < 0.5

15 93 7 1.9 < 0.2 < 0.5

10 91 6.8 2.1 < 0.2 < 0.5

8 92 6.8 1.9 < 0.2 0.6

6 88 6.3 2 < 0.2 < 0.5

5 92 6 2.2 < 0.2 0.5

4 90 5.8 2.1 < 0.2 < 0.5

3 92 5.9 2.2 0.2 0.6

2 92 6.1 2.3 0.3 0.5

1 9362.2 0.3 < 0

0 92 5.8 2.6 0.3 0.6

-1 90 0.1 1.8 < 0.2 1.0

-2 87 0.1 2 < 0.2 < 0.5

-3 89 < 0.1 0.8 < 0.2 < 0.5

-4 90 0.1 2 < 0.2 < 0.5

-5 91 < 0.1 0.8 < 0.2 < 0.5

-6 91 < 0.1 1 < 0.2 < 0.5

-8 90 0.1 1.9 < 0.2 < 0.5

-10 91 0.2 2.5 < 0.2 < 0.5

-15 88 0.1 1.6 < 0.2 < 0.5

-20 93 0.5 2.2 < 0.2 < 0.5

-30 93 0.5 2.2 < 0.2 < 0.5

-40 93 3.1 1.7 < 0.2 < 0.5

Profile #2 - Section 5

.5

B1AW3 - E

1st Polish

0.0

1.0

2.0

3.0

4.0

-60 -40 -20 0 20 40 60

Distance (mils)

%Nitrogen

Profile 1

Profile 2

E-23
Microprobe analysis:

B1AW3 – E - Section 10 – 31 mils

Scan 1

Scan 2

B1AW3 - E

2nd Polish

0.0

1.0

2.0

3.0

4.0

-60 -40 -20 0 20 40 60

Distance (mils)

%Nitrogen

Profile 1

Profile 2

W %

Distance (mils) Ti Al V C N

40 91 7.2 2 < 0.2 < 0.5

30 89 7.2 1.7 < 0.2 < 0.5

20 91 7.2 1.6 < 0.2 < 0.5

16 89 7 1.8 < 0.2 < 0.5

12 90 7.1 1.7 < 0.2 < 0.5

10 90 7 1.7 < 0.2 < 0.5

8 90 6.8 1.7 < 0.2 0.5

6 89 6.7 1.8 < 0.2 < 0.5

5 89 6.3 2 0.2 < 0.5

4 8961.9 0.3 0.8

3 89 5.7 2 0.4 1.3

2 89 4.8 2.1 0.5 1.3

1 91 3.5 1.8 0.6 2.4

0 91 3.2 1.8 0.7 1.7

-1 92 3.6 1.5 0.8 1.5

-2 92 4.4 1.8 0.5 1.2

-3 91 4.2 1.6 0.4 1.4

-4 89 5.4 1.9 0.2 1.3

-5 91 6 1.9 < 0.2 0.6

-6 88 6.2 1.9 < 0.2 < 0.5

-8 92 6.3 1.6 0.2 < 0.5

-10 89 6.4 1.9 < 0.2 0.7

-12 92 6.7 1.9 < 0.2 < 0.5

-16 89 6.8 1.8 < 0.2 0.8

-20 91 6.8 1.8 < 0.2 0.5

-25 89 7 1.9 < 0.2 0.6

-30 88 7.1 1.8 < 0.2 < 0.5

-40 88 7.1 1.8 < 0.2 < 0.5

Profile #1 - Section 10

W %

Distance (mils) Ti Al V C N

0 90 3.3 1.7 1.0 2.2

1 89 4.4 1.9 1.0 1.4

2 88 5.3 1.9 0.5 0.8

3 90 6 2.1 0.3 < 0.5

4 87 5.2 4.7 0.4 < 0.5

5 89 6.2 1.9 0.3 0.6

6 89 6.3 1.9 < 0.2 0.6

8 90 6.3 1.9 < 0.2 < 0.5

10 87 6.3 1.8 0.4 0.5

12 90 6.2 1.8 0.4 < 0.5

16 88 6.4 1.9 < 0.2 0.7

20 90 6.4 2 < 0.2 0.6

25 90 6.5 2 < 0.2 0.5

30 91 6.6 2 < 0.2 0.5

40 90 6.5 1.8 < 0.2 < 0.5

50 87 6.6 1.9 < 0.2 < 0.5

Profile #2 - Section 10

W %

Distance (mils) Ti Al V C N

0 89 2.6 1.6 0.9 1.3

1 91 2.6 1.6 0.3 1.6

2 89 3.9 1.9 0.3 1.6

3 89 5.4 1.8 0.4 1.1

4 88 5.2 1.7 0.3 1.6

5 90 5.7 2.3 0.2 1.2

6 88 5.8 1.9 0.2 1.4

8 90 5.8 1.9 0.2 0.6

10 87 6 1.8 0.2 0.7

12 91 6.1 1.9 < 0.2 < 0.5

16 91 6.3 1.9 < 0.2 0.7

20 90 6.4 1.9 < 0.2 0.9

25 90 6.5 2 < 0.2 0.7

30 91 6.2 1.9 < 0.2 < 0.5

40 91 6.4 1.9 < 0.2 < 0.5

50 91 6.2 1.9 < 0.2 0.6

Profile #2 - Section 10

E-24
Indication: B1BW3 – D

Original billet length: 107.5”

Mult inspection parameters: 

Transducer - Zone 2, 6” diameter, 5MHz

Index - 0.010 

Data Acquisition Rate - 0.010

Inspection Sensitivity - #2 FBH at 80-90% in Titanium

Inspection Range - 0.8” to 1.7”

Sampling Rate - 100 MHz

Depth Axial Length Amplitude Signal-to-Noise Ratio

1.5” 0.365” 74% 5.06

Billet inspection:

Side 5

107.5 inches

Serial Number

83 inches 93 inches

Side 6

 Amplitude 

(%) 

S/N depth 

(in) 

axial length 

(in) 

radial 

length (in) 

Multizone 74% 5.06 1.5 0.3268 0.2577 

Conv. 

Longitudinal 

% 

Conv. Angle % 

Zone 2

25 MHz inspection parameters:

Transducer - 25 MHz, F10 - focal point positioned at indication depth

Index - 0.010

Data Acquisition Rate - 0.010

Inspection sensitivity - #1 FBH at 83% - 56 dB #2FBH at 84% at 48dB

Inspection range - C-scan , Between Front and Back / B-scan entire volume 

Sampling Rate - 200 MHz

Side Depth Axial Length Amplitude % Sensitivity, dB

1 0.484” 0.365” 85 53

2 0.530” 0.365” 80 49

3 0.508” 0.365” 70 54

4 0.508” 0.365” 84 55

5 0.530” 0.365” 78 68

6 0.530” 0.365” 76 73 View is from Side 1(side which was 

polished). Sides 5 and 6 represent the 

axial ends as shown above. Sides 2 

and 4 represent the hoop direction 

(circumferential plane.)

Orientation of sample block and c-scan images: 

X

Z

Side 3 (top)

Side 5 

(right)

Y

Side 1 (bottom)

Side 6 

(left)

Side 2 

(back)

Side 4 (front) Side 2 Side 6

Side 5

Side 3

Side 1

Side 1

Side 6Side 5

Side 2

Side 4

Side 4

Side 6

Side 5

Side 1

Side 3

Side 3

Side 6Side 5

Side 4

Side 2

X

Z

Side 3 (top)

Side 5 

(right)

Y

Side 1 (bottom)

Side 6 

(left)

Side 2 

(back)

Side 4 (front)

X

Z

Side 3 (top)

Side 5 

(right)

Y

Side 1 (bottom)

Side 6 

(left)

Side 2 

(back)

Side 4 (front) Side 2 Side 6

Side 5

Side 3

Side 1

Side 1

Side 6Side 5

Side 2

Side 4

Side 4

Side 6

Side 5

Side 1

Side 3

Side 3

Side 6Side 5

Side 4

Side 2

Side 6

Side 5

Side 4

Side 2

E-25
B1BW3-D 5 MHz C-scan image comparisons:

Side 2 Model Experiment Side 4 Model Experiment

Side 1 Model Experiment Side 3 Model Experiment

51(H) x 31(V) @10 mils, 14dB

peak amplitude @14dB=280 mv

deviation=-11.4% or -1.1 dB 

60(H) x 30(V) @10 mils, 14dB

peak amplitude @14dB=316 mv

51(H) x 31(V) @10 mils, 22dB

peak amplitude @12dB=1263 mv

deviation=244.1% or 10.7 dB 

60(H) x 30(V) @10 mils, 12dB

peak amplitude @12dB=367 mv

51(H) x 31(V) @10 mils, 18dB

peak amplitude @12dB=793 mv

deviation=160% or 8.3 dB 

51(H) x 31(V) @10 mils, 16dB

peak amplitude @10dB=646 mv

deviation=105.7% or 6.3 dB 

60(H) x 30(V) @10 mils, 10dB

peak amplitude @10dB=314 mv

60(H) x 30(V) @10 mils, 12dB

peak amplitude @12dB=305 mv

Multizone Color Code

0 128 255

Experiment 255 = 500mv

B1BW3-D 3D Solid Model Parameters:

Summary:

Sub-Micrograph 

size - 2400(H) by 1000(V) pixels

color - 256 gray-scale

scale - 4340 pixels =690 mils

Geometric Model

1 void part 

(with branches)

8 geometric model parts

21 micrograph planes 

(including 8 patches)

33 void cross-section boundary traces

(model parts 5 and 8 uses 7 traces, 3 uses 4,

and the rest use 3 each)

E-26
B1BW3-D

1

4

3

2

5

6

7

8

9

10

11

12

13

382 mils

Orientation of Sub-Micrographs (B1BW3-D): 

Y

Z

Polish 8

X stack-up sequence

(polish in from side

1 of the cube)

1

2

13

E-27
X

Y

Z

Angle views of void model for B1BW3-D:

View 1

X

Z Y

View 2

E-28
106 mils (Y)

295 mils (X)

min. max. size

X 38.24 332.76 294.52

Y 23.37 129.26 105.88

Z -0.60 62.60 63.20

Unit: mils

Dimensions of B1BW3-D: 

E-29
.

.

21 22

24 23 25

26 27

28

29

30

.

. . . .

.

.

.

.

.

21 22

24 23 25

26 27

28

29

30

.

. . . .

.

.

.

Microprobe analysis:

B1BW3-D – 1st polish

. .

.

. . . . . . . . . .

. .

.

. .

. . 1

2

3 4 5

6

7

8

9 10

11

12

13 

14

15

16

17

18

19

20 

40 mils

. .

.

. . . . . . . . . .

. .

.

. .

. . 1

2

3 4 5

6

7

8

9 10

11

12

13 

14

15

16

17

18

19

20 

40 mils

B1BW3 - D

Pt # Ti Al V N

1 86.4 3.4 1.7 4.9

2 90.2 5.7 2.5 1.5

3 89.9 7.5 2.9 0.9

4 92.2 2.9 1.1 5.8

5 88.6 2.7 1.4 4.7

6 85.4 5.6 2.0 0.5

7 90.6 6.5 2.8 0.8

8 88.3 4.5 1.9 2.9

9 88.1 5.8 3.2 1.4

10 89.5 2.2 1.4 4.8

11 85.5 3.2 1.3 2.1

12 90.2 1.2 1.6 6.4

13 95.0 4.0 1.5 0.8

14 87.7 2.2 1.7 4.6

15 88.5 4.9 2.3 0.5

16 88.3 1.5 1.6 2.6

17 90.6 5.7 2.2 < 0.5

18 90.6 4.7 1.7 1.0

19 90.4 2.5 1.4 2.5

20 91.1 3.4 2.0 3.9

21 83.6 0.4 0.6 9.4

22 89.0 6.0 2.0 0.5

23 89.0 4.7 1.6 0.9

24 89.8 1.6 0.9 2.5

25 88.9 4.2 1.1 1.3

26 89.3 4.5 1.6 < 0.5

27 88.7 1.4 1.1 3.7

28 85.0 0.9 1.1 8.3

29 90.6 4.9 1.7 0.6

30 87.7 1.7 1.5 5.5

W %

B1BW3 - D

1st Polish

0.0

1.0

2.0

3.0

4.0

0 5 10 15 20 25

Distance (mils)

%Nitrogen

Profile 1

E-30
Original mag = 48x

1

2

3

4 5

6

7

8

9

10 .

.

.

.

.

.

.

.

.

.

Original mag = 48x

1

2

3

4 5

6

7

8

9

10 .

.

.

.

.

.

.

.

.

.

Data for areas around the defect.

B1BW3-D(2)

Pt # Ti Al V N

1 91.0 6.7 1.9 < 0.5

2 93.6 6.6 1.9 < 0.5

3 92.7 6.0 1.8 0.5

4 92.1 6.6 1.6 0.6

5 92.2 6.5 2.1 < 0.5

6 92.4 6.8 2.3 < 0.5

7 91.8 6.7 2.3 < 0.5

8 91.1 6.5 2.1 < 0.5

9 92.8 6.6 2.0 < 0.5

10 91.1 6.6 2.2 0.5

W %

Microprobe analysis:

B1BW3-D – 2nd polish

40 mils B1BW3 - D

0.0

1.0

2.0

3.0

4.0

-50 -40 -30 -20 -10 0 10 20 30 40 50

Distance (mils)

Wt% Nitrogen

Scan 1

E-31
 Amplitude 

(%) 

S/N depth 

(in) 

axial 

length (in) 

radial 

length (in) 

Multizone 134% 5.46 0.7 0.4217 0.2681 

Conv. 

Longitudinal 

50% 2.61 

Conv. Angle % 

Indication: B1AW2 – D

Original billet length: 117”

Mult inspection parameters: 

Transducer - Zone 1, 6” diameter, 5MHz

Index - 0.010 

Data Acquisition Rate - 0.010

Inspection Sensitivity - #2 FBH at 80-90% in Titanium

Inspection Range - 0.2” to 0.8”

Sampling Rate - 100 MHz

Depth Axial Length Amplitude Signal-to-Noise Ratio

0.780” 0.400” 134% 5.5

Billet inspection:

Side 5

Side 6

Zone 1

117 inches

Serial Number

95 inches 103 inches

25 MHz inspection parameters

Transducer - 25 MHz, F10 - focal point positioned at indication depth

Index - 0.010

Data Acquisition Rate - 0.010

Inspection sensitivity - #1 FBH at 83% - 56 dB #2FBH at 84% at 48dB

Inspection range - C-scan , Between Front and Back / B-scan entire volume 

Sampling Rate - 200 MHz

Side Depth Axial Length Amplitude % Sensitivity, dB

1 0.652” 0.400” 68 58

2 0.502” 0.400” 75 69

3 1.1011” 0.400” 58 79

4 0.472” 0.400” 65 65

5 0.508” 0.400” 75.6 75

6 0.520” 0.400” 78 79 View is from Side 1(side which was 

polished). Sides 5 and 6 represent the 

axial ends as shown above. Sides 2 

and 4 represent the hoop direction 

(circumferential plane.)

Orientation of sample block and c-scan images: 

Side 6

Side 5

Side 4

Side 2

X

Z

Side 3 (top)

Side 6 

(right)

Y

Side 1 (bottom)

Side 5 

(left)

Side 4 

(back)

Side 2 (front)

X

Z

Side 3 (top)

Side 6 

(right)

Y

Side 1 (bottom)

Side 5 

(left)

Side 4 

(back)

Side 2 (front) Side 2 Side 5

Side 6

Side 1

Side 3

Side 1

Side 5Side 6

Side 4

Side 2

Side 4

Side 5

Side 6

Side 3

Side 1

Side 3

Side 5Side 6

Side 2

Side 4

E-32
B1AW2 – D 5 MHz C-scan image comparisons:

Side 1

Model Experiment

Side 2

Model Experiment

Side 3

Model Experiment

Side 4

Model Experiment

Attenuation=10dB

peak amplitude = 557 mv

deviation=64% or 4.31 dB 

Attenuation=10dB

peak amplitude=339 mv

Attenuation=12dB

peak amplitude=473 mv

deviation=46% or 3.29 dB 

Attenuation=12dB

peak amplitude=324 mv

Attenuation=4dB

peak amplitude=1393 mv

deviation=312% or 12.30 dB 

Attenuation=2dB

peak amplitude=1052 mv

deviation=258% or 11.07 dB 

Attenuation=2dB

peak amplitude=294 mv

Attenuation=4dB

peak amplitude=338 mv

Multizone Color Code

0 128 255

Experiment 255 = 500mv

Experiment image: 60(H) x 30(V) @10 mils

Model image: 61(H) x 31(V) @10 mils

Side 1

Model Experiment

Side 2

Model Experiment

Side 3

Model Experiment

Side 4

Model Experiment

Attenuation=10dB

peak amplitude = 557 mv

deviation=64% or 4.31 dB 

Attenuation=10dB

peak amplitude=339 mv

Attenuation=12dB

peak amplitude=473 mv

deviation=46% or 3.29 dB 

Attenuation=12dB

peak amplitude=324 mv

Attenuation=4dB

peak amplitude=1393 mv

deviation=312% or 12.30 dB 

Attenuation=2dB

peak amplitude=1052 mv

deviation=258% or 11.07 dB 

Attenuation=2dB

peak amplitude=294 mv

Attenuation=4dB

peak amplitude=338 mv

Multizone Color Code

0 128 255

Experiment 255 = 500mv

Experiment image: 60(H) x 30(V) @10 mils

Model image: 61(H) x 31(V) @10 mils

B1AW2 – D 3D Solid Model Parameters:

Sub-Micrograph 

size - 4800(H) by 1300(V) pixels

color - 256 gray-scale of size

scale - 132 pixels =10 mils

Geometric Model 

1 void flaw part (with branches)

17 geometric model parts

23 micrograph planes (including 9 

patches)

72 void cross-section boundary traces (model part 5 uses 11; 

13 uses 8; 15,6 uses 6; 

3 uses 5; the rest use 3 each)

E-33
17

16

15

14

13

B1AW2 – D

364 mils

20

19

18

E-34
26

25

24

23

22

21

B1AW2 – D

364 mils

Orientation of Sub-Micrographs (B1AW2 – D): 

Y

Z

Polish 8

X stack-up sequence

(polish in from side 2 of the cube)

13

14

26

Y

Z

Polish 8

X stack-up sequence

(polish in from side 2 of the cube)

13

14

26

E-35
Angle views of void model for B1AW2 – D:

View 1

View 2

Dimensions of B1AW2 – D: 

51 mils (Y)

275 mils (X)

min. max. size

X 19 294 275

Y 30 81 51

Z 97 154 57

Unit: mils

E-36
Microprobe analysis:

B1AW2 – D – section 15

1

2

B1AW2 - D

1st Polish

0.0

2.0

4.0

6.0

8.0

10.0

0 5 10 15 20 25 30

Distance (mils)

%Nitrogen

Profile 1

Profile 2

. . . . . .

.

. . . .

. . . . .

.

. . 1 .

2 3

4

5

6

7

8

9

10

11 12

13 

14

15

16

17

18

19

20 

21 22

23

24 25

.

.

.

. .

. . . . . . .

.

. . . .

. . . . .

.

. . 1 .

2 3

4

5

6

7

8

9

10

11 12

13 

14

15

16

17

18

19

20 

21 22

23

24 25

.

.

.

. .

.

B1AW2-D B1AW2-D

Pt # Ti Al V N Pt # Ti Al V N

1 91.6 0.3 2.2 4.0 14 94.4 1.5 1.6 2.1

2 86.9 0.1 2.2 9.9 15 90.7 0.1 1.3 9.5

3 88.6 0.1 1.8 9.3 16 91.6 0.2 2.3 5.4

4 88.5 0.3 2.0 6.6 17 91.0 4.6 2.0 1.5

5 90.4 6.0 2.4 < 0.5 18 92.5 6.0 1.8 < 0.5

6 90.6 4.1 1.9 1.7 19 93.5 4.3 1.8 1.2

7 89.9 0.1 1.4 7.7 20 94.0 5.2 1.8 0.6

8 89.4 4.8 1.8 1.0 21 93.5 0.3 3.1 2.7

9 91.7 3.8 1.7 1.1 22 95.9 0.3 1.8 2.5

10 91.7 6.1 1.8 0.9 23 95.3 4.7 1.6 < 0.5

11 92.1 0.4 1.6 7.0 24 94.5 5.8 1.7 < 0.5

12 90.5 0.2 2.0 4.9 25 93.5 0.2 2.0 4.4

13 93.5 2.5 1.4 2.7

W % W %

E-37
. . . . . . . . .

. .

. . . . . . 1

2 3

4

5

6

7

8

9

10 11

12 13 

14

15

16 17

18

Profile 

1

2

.

Profile 2

Profile 3

. . . . . . . . .

. .

. . . . . . 1

2 3

4

5

6

7

8

9

10 11

12 13 

14

15

16 17

18

Profile 

1

2

.

Profile 2

Profile 3

Microprobe analysis:

B1AW2 – D – section 18

B1AW2-D (2)

Pt # Ti Al V N

1 94.6 0.3 2.2 4.2

2 91.1 3.9 1.7 2.5

3 90.9 0.2 2.4 6.6

4 89.3 4.6 1.6 1.7

5 93.5 6.2 2.1 < 0.5

6 90.7 0.3 1.8 6.7

7 92.8 3.7 1.5 1.6

8 89.2 0.1 1.6 8.8

9 90.5 5.6 2.0 1.0

10 84.8 0.4 6.2 8.0

11 94.0 5.0 2.0 1.1

12 87.9 0.3 2.0 6.8

13 89.9 0.0 1.1 9.2

14 92.5 0.2 2.4 5

15 92.0 4.3 1.5 2.1

16 93.6 1.2 1.5 3.3

17 93.8 0.3 2.1 4.2

18 95.6 0.3 1.7 3.7

W % B1AW2 - D

2nd Polish

0.0

2.0

4.0

6.0

8.0

10.0

0 5 10 15 20 25 30

Distance (mils)

%Nitrogen

Profile 1

Profile 2

Profile 3

40 mils

E-38
Indication: B1AW3 – A

Original billet length: 107.5”

Mult inspection parameters: 

Transducer - Zone 2, 6” diameter, 5MHz

Index - 0.010 

Data Acquisition Rate - 0.010

Inspection Sensitivity - #2 FBH at 80-90% in Titanium

Inspection Range - 0.8” to 1.7”

Sampling Rate - 100 MHz

Depth Axial Length Amplitude Signal-to-Noise Ratio

0.812” 0.400” 142% 5.1

Billet inspection:

Side 5 Side 6

Zone 2

109 inches

Serial Number

51 inches 69 inches

Mult

removed

 Amplitude 

(%) 

S/N depth 

(in) 

axial 

length (in) 

radial 

length (in) 

Multizone 142% 5.02 0.7 0.4186 0.3387 

Conv. 

Longitudinal 

50% 2.92 0.8 

Conv. Angle 60% 2.48 0.8 

25 MHz inspection parameters

Transducer - 25 MHz, F10 - focal point positioned at indication depth

Index - 0.010

Data Acquisition Rate - 0.010

Inspection sensitivity - #1 FBH at 83% - 56 dB #2FBH at 84% at 48dB

Inspection range - C-scan , Between Front and Back / B-scan entire volume 

Sampling Rate - 200 MHz

Side Depth Axial Length Amplitude % Sensitivity, dB

1 0.484” 0.365” 85 53

2 0.530” 0.365” 80 49

3 0.508” 0.365” 70 54

4 0.508” 0.365” 84 55

5 0.530” 0.365” 78 68

6 0.530” 0.365” 76 73

View is from Side 1(side which was 

polished). Sides 5 and 6 represent the 

axial ends as shown above. Sides 2 

and 4 represent the hoop direction 

Orientation of sample block and c-scan images: (circumferential plane.)

Side 6

Side 5

Side 4

Side 2

X

Z

Side 1 (top)

Side 5 

(right)

Y

Side 3 (bottom)

Side 6 

(left)

Side 4 

(back)

Side 2 (front)

X

Z

Side 1 (top)

Side 5 

(right)

Y

Side 3 (bottom)

Side 6 

(left)

Side 4 

(back)

Side 2 (front) Side 2 Side 6

Side 5

Side 3

Side 1

Side 1

Side 6Side 5

Side 2

Side 4

Side 4

Side 6

Side 5

Side 1

Side 3

Side 3

Side 6Side 5

Side 4

Side 2

E-39
B1AW3 – A 5 MHz C-scan image comparisons:

Side 1

Model Experiment

Side 2

Model Experiment

Side 3

Model Experiment

Side 4

Model Experiment

Attenuation=18dB

peak amplitude = 231 mv

deviation=-34% or -3.56 dB 

Attenuation=18dB

peak amplitude=348 mv

Attenuation=12dB

peak amplitude=564 mv

deviation=29% or 2.20 dB 

Attenuation=12dB

peak amplitude=438 mv

Attenuation=12dB

peak amplitude=511 mv

deviation=24% or 1.87 dB 

Attenuation=12dB

peak amplitude=578 mv

deviation=27% or 2.08 dB 

Attenuation=12dB

peak amplitude=455 mv

Attenuation=12dB

peak amplitude=412 mv

Multizone Color Code

0 128 255

Experiment 255 = 500mv

Experiment image: 70(H) x 30(V) @10 mils

Model image: 71(H) x 31(V) @10 mils

Side 1

Model Experiment

Side 2

Model Experiment

Side 3

Model Experiment

Side 4

Model Experiment

Attenuation=18dB

peak amplitude = 231 mv

deviation=-34% or -3.56 dB 

Attenuation=18dB

peak amplitude=348 mv

Attenuation=12dB

peak amplitude=564 mv

deviation=29% or 2.20 dB 

Attenuation=12dB

peak amplitude=438 mv

Attenuation=12dB

peak amplitude=511 mv

deviation=24% or 1.87 dB 

Attenuation=12dB

peak amplitude=578 mv

deviation=27% or 2.08 dB 

Attenuation=12dB

peak amplitude=455 mv

Attenuation=12dB

peak amplitude=412 mv

Multizone Color Code

0 128 255

Experiment 255 = 500mv

Experiment image: 70(H) x 30(V) @10 mils

Model image: 71(H) x 31(V) @10 mils

B1AW3 – A 3D Solid Model Parameters:

Sub-Micrograph 

size - 6000(H) by 1000(V) pixels

color - 256 gray-scale of size

scale - 132 pixels =10 mils

Geometric Model 

18 void flaw parts 

(with branches)

48 geometric model parts

17 micrograph planes 

(including 6 patches)

154 void cross-section boundary 

traces

(model part 18 uses 5, parts 2, 14, 

15, 16, 26, 34, 35, 

41 use 4 and the rest 

use 3 each)

E-40
B1AW3 – A

7

8

9

12

11

10

13

455 mils

E-41
Orientation of Sub-Micrographs (B1AW3 – A): 

Y

Z

Polish 8

X

stack-up sequence

(polish in from side 2 of the cube)

7

8

13

Y

Z

Polish 8

X

stack-up sequence

(polish in from side 2 of the cube)

7

8

13

X

Y

Z

X

Y

Z

Angle views of void model for B1AW3 – A:

View 1

View 2

E-42
Dimensions of B1AW3 – A: 

60 mils (Y)

370 mils (X)

min. max. size

X 39 409 370

Y 4 64 60

Z -13 19 32

Unit: mils

E-43
Microprobe analysis:

B1AW3 – A - section 8

.

. .

. .

.

. .. .

. .

. .

.

.

1

2 3 4

5

6 7

8

9 10

11

12

13 

14

15

16

17

18

19

20 

21

.

.

.

. .

.

1

2

Original mag = 54x

.

. .

. .

.

. .. .

. .

. .

.

.

1

2 3 4

5

6 7

8

9 10

11

12

13 

14

15

16

17

18

19

20 

21

.

.

.

. .

.

1

2

Original mag = 54x

40 mils

40 mils

23

24 25 22 . . . 21 . . 26

. 23

24 25 22 . . . 21 . . 26

.

B1AW3-A (1)

Pt # Ti Al V N

1 98.0 2.3 0.8 2.8

2 86.3 2.2 1.2 3.7

3 86.7 3.4 1.4 3.1

4 83.1 1.9 1.2 4.6

5 84.4 5.3 1.1 1.7

6 90.0 2.8 1.5 3.9

7 91.1 2.9 1.7 3.0

8 89.8 4.7 1.4 2.8

9 88.8 2.9 1.2 2.5

10 89.4 5.0 1.7 1.8

11 90.7 4.1 1.4 1.9

12 89.1 5.9 2.0 0.8

13 89.2 2.1 1.1 2.2

14 87.6 2.6 1.5 2.8

15 88.3 6.1 2.0 0.8

16 88.9 2.5 1.4 3.4

17 89.9 2.4 1.1 3.6

18 87.3 5.6 1.9 1.7

19 89.1 5.5 2.0 1.5

20 87.3 5.9 2.4 1.1

21 93.3 2.5 1.6 3.3

22 92.1 2.8 1.5 3.2

23 90.1 2.7 1.6 3.5

24 92.0 2.7 1.3 2.5

25 93.1 3.7 1.4 1.5

26 89.8 5.9 1.8 0.8

W %

B1AW3 - A

0.0

1.0

2.0

3.0

4.0

5.0

0 5 10 15 20 25

Distance (mils

%Nitrogen

Profile 1

Profile 2

40 mils

E-44
Microprobe analysis:

B1AW3 – A - section 11

. . .

. . .

.

. . . . .

.

1

2

3 4

5 6

7

8

9

10

11

12

13 

14

15

20

1

9

17 18 16

. .

.

. . .

Profile 1

Profile 2

. . . .

. . .

.

. . . . .

.

1

2

3 4

5 6

7

8

9

10

11

12

13 

14

15

20

1

9

17 18 16

. .

.

. . .

Profile 1

Profile 2

.

Data for areas around the defect.

B1AW3-A(2)

Pt # Ti Al V N

1 92.9 4.0 1.3 1.5

2 93.9 2.5 1.1 1.4

3 92.6 4.4 1.4 1.2

4 92.2 3.3 1.5 2.8

5 93.9 3.0 1.3 2.9

6 92.4 3.1 1.4 3.2

7 90.2 6.0 2.1 1.7

8 88.9 6.1 2.2 1.7

9 90.8 5.1 1.5 2.7

10 89.3 6.9 1.7 < 0.5

11 90.9 4.7 1.4 1.7

12 90.9 3.4 1.2 4.0

13 90.3 4.5 1.6 2.8

14 92.3 3.6 1.4 2.2

15 90.5 5.3 1.7 1.6

16 90.5 3.9 1.3 2.9

17 92.0 5.3 1.7 2.6

18 94.2 3.7 1.3 2.7

19 94.3 4.2 1.3 1.6

20 93.9 2.8 1.1 2.8

W %

40 mils

B1AW3 - A

0.0

1.0

2.0

3.0

4.0

5.0

0 10 20 30 40 50 60

Distance (mils)

%Nitrogen

Profile 1

Profile 2

E-45
 Amplitude 

(%) 

S/N depth 

(in) 

axial 

length (in) 

radial 

length (in) 

Multizone 101% 4.49 1.1 0.2326 0.2215 

Conv. 

Longitudinal 

 

Conv. Angle 

Indication: B1AW3 – D

Original billet length: 109”

Mult inspection parameters: 

Transducer - Zone 2, 6” diameter, 5MHz

Index - 0.010 

Data Acquisition Rate - 0.010

Inspection Sensitivity - #2 FBH at 80-90% in Titanium

Inspection Range - 0.8” to 1.7”

Sampling Rate - 100 MHz

Depth Axial Length Amplitude Signal-to-Noise Ratio

1.1400” 0.250” 101% 4.5

Billet inspection:

Side 5

109 inches

Serial Number

103 inches 89 inches

Side 6

Zone 2

25 MHz inspection parameters

Transducer - 25 MHz, F10 - focal point positioned at indication depth

Index - 0.010

Data Acquisition Rate - 0.010

Inspection sensitivity - #1 FBH at 83% - 56 dB #2FBH at 84% at 48dB

Inspection range - C-scan , Between Front and Back / B-scan entire volume 

Sampling Rate - 200 MHz

Side Depth Axial Length Amplitude % Sensitivity, dB

1 0.560” 0.250” 85 58

2 0.701” 0.250” 80 72

3 0.544” 0.250” 75 49

4 0.399” 0.250” 70 65

5 0.425” 0.250” 83 65

6 0.435” 0.250” 85 65

View is from Side 1(side which was 

polished). Sides 5 and 6 represent the 

axial ends as shown above. Sides 2 

and 4 represent the hoop direction 

(circumferential plane.)

Orientation of sample block and c-scan images: 

Side 6

Side 5

Side 4

Side 2

X

Z

Side 1 (top)

Side 6 

(right)

NOTE: Data were taken only from sides 1 and 3

Y Side 3 (bottom)

Side 5 

(left)

Side 4 (back)

Side 2 (front)

E-46
B1AW3-D 5 MHz C-scan image comparisons:

Multizone Color Code

0 128 255

Experiment 255 = 500mv

60(H) x 30(V) @10 mils, 10dB

peak amplitude@10dB = 402 mv

61(H) x 31(V) @10 mils, 10dB

peak amplitude@10dB = 444 mv

deviation=10% or 0.9 dB

Side 3 Model Experiment

Side 1 Model Experiment

61(H) x 31(V) @10 mils, 10dB

peak amplitude @10dB=437 mv

deviation=22% or 1.8 dB 

60(H) x 30(V) @10 mils, 10dB

peak amplitude @10dB=357 mv

E-47
B1AW3-D

IMAGE SIZE: 2000(H) by 500(V) pixels

SCALE: 134 pixels = 10 mils

7

8

9

10

11

12

13

150 mils

Orientation of Sub-Micrographs (B1AW3-D): 

Y

Z

Polish 8

X

stack-up sequence

(polish in from side 2 of the cube)

Polish 7

Polish 8

Polish 13

E-48
View 2

X

Y

Z

X

Y

Z

Angle views of void model for B1AW3-D:

View 1

32 mils (Z)

109 mils (X)

min. max. size

X 20 128 109

Y 11 26 15 

Z 0 32 32

Unit: mils

Dimensions of B1AW3-D: 

E-49
Microprobe analysis:

B1AW3-D – section 9

. . . . . . .

.

. . . . . . . .

. .

1 2 3 4

5 6

7

8 9

10

11

12

13 

14

15

16

17

18

Profile 1

Profile 2

. . . . . . .

.

. . . . . . . .

. .

1 2 3 4

5 6

7

8 9

10

11

12

13 

14

15

16

17

18

Profile 1

Profile 2

B1AW3-D(1)

Pt # Ti Al V N

1 92.8 4.7 2.0 0.8

2 94.4 0.7 2.3 3.6

3 96.4 1.9 1.9 0.9

4 93.1 5.4 2.2 5.8

5 95.1 1.5 2.1 2.6

6 94.4 1.2 2.1 2.7

7 92.4 6.3 2.0 < 0.5

8 88.8 0.4 8.5 2.2

9 94.3 0.5 2.2 3.5

10 89.4 3.3 2.5 2.2

11 93.5 0.5 2.6 3.5

12 89.5 3.9 2.3 1.8

13 93.0 0.5 2.6 3.6

14 90.4 5.7 2.4 < 0.5

15 91.7 5.4 2.0 1.5

16 91.1 0.5 2.4 4.6

17 92.0 5.1 2.0 0.7

18 93.7 0.4 2.1 3.6

W %

B1AW3 - D

0.0

1.0

2.0

3.0

4.0

5.0

0 5 10 15 20 25

Distance (mils

%Nitrogen

Profile 1

Profile 2

. . .

. . . . . . . . . . . 1

2

3

4

5

6 7

8 9

1011

12

13 1415

Profile 1

Profile 2

.

Microprobe analysis:

B1AW3-D – section 11

B1AW3-D(2)

Pt # Ti Al V N

1 94.6 1.6 1.1 2.0

2 90.2 0.5 1.9 5.0

3 91.3 0.1 2.5 4.7

4 88.7 3.7 1.6 2.1

5 91.1 0.2 1.8 5.9

6 89.0 0.2 2.1 5.5

7 90.0 5.8 1.8 0.7

8 89.9 0.2 2.0 2.7

9 89.3 6.2 1.8 < 0.5

10 89.3 0.3 1.8 5.3

11 90.1 1.2 2.6 4.3

12 87.5 6.4 1.7 1.3

13 88.6 0.3 3.0 4.0

14 92.4 0.3 1.7 3.9

15 92.8 1.5 1.7 2.4

B1AW3 - D W %

2nd Polish

0.0

2.0

4.0

6.0

8.0

10.0

0 5 10 15 20 25 30

Distance (mils)

%Nitrogen

Profile 1

Profile 2

40 mils

E-50
 Amplitude 

(%) 

S/N depth 

(in) 

axial 

length (in) 

radial 

length (in) 

Multizone 74% 4.09 0.2 0.3273 0.1031 

Conv. 

Longitudinal 

% 

Conv. Angle % 

Indication: B2W2 – C

Original billet length: 123”

Mult inspection parameters: 

Transducer - Zone 1, 6” diameter, 5MHz

Index - 0.010 

Data Acquisition Rate - 0.010

Inspection Sensitivity - #2 FBH at 80-90% in Titanium

Inspection Range - 0.2” to 0.8”

Sampling Rate - 100 MHz

Depth Axial Length Amplitude Signal-to-Noise Ratio

0.195 0.350” 74% 4.09

Billet inspection:

Side 6

Zone 1

123 inches

Serial Number

18 inches 36 inches

Side 5

25 MHz inspection parameters

Transducer - 25 MHz, F10 - focal point positioned at indication depth

Index - 0.010

Data Acquisition Rate - 0.010

Inspection sensitivity - #1 FBH at 83% - 56 dB #2FBH at 84% at 48dB

Inspection range - C-scan , Between Front and Back / B-scan entire volume 

Sampling Rate - 200 MHz

Side Depth Axial Length Amplitude % Sensitivity, dB

1

2 0.689” 0.350” 71 55

3 1.052” 0.350” 38 71

4 0.768” 0.350” 80 54

5 0.605” 0.350 63 74

6 0.629” 0.350” 80 74 Sides 5 and 6 represent the axial ends 

as shown above. Sides 2 and 4 

represent the hoop direction 

(circumferential plane.)

Orientation of sample block and c-scan images: 

Side 6

Side 5

Side 4

Side 2

NOTE: No data were taken from side 3 (bottom) due to large surface curvature

X

Z

Side 1 (top)

Side 5 

(right)

Y

Side 3 (bottom)

Side 6 

(left)

Side 4 

(back)

Side 2 (front)

X

Z

Side 1 (top)

Side 5 

(right)

Y

Side 3 (bottom)

Side 6 

(left)

Side 4 

(back)

Side 2 (front)

Side 2

Side 6Side 5

Side 3

Side 1

Side 1

Side 6Side 5

Side 2

Side 4

Side 6

Side 2Side 4

Side 1

Side 3

Side 5

Side 4Side 2

Side 1

Side 3

Side 4

Side 6Side 5

Side 1

Side 3

E-51
B2W2 – C 5 MHz C-scan image comparisons:

80(H) x 30(V) @10 mils, 6dB

peak amplitude@6dB = 373 mv

61(H) x 31(V) @10 mils, 10dB

peak amplitude@6dB = 654 mv

deviation=75% or 4.9 dB

Side 1 Model Experiment

Side 2 Model Experiment Side 4 Model Experiment

Side 5 Model Experiment Side 6 Model Experiment

61(H) x 31(V) @10 mils, 21.5dB

peak amplitude @12dB=1316 mv

deviation=219% or 10.1 dB 

60(H) x 30(V) @10 mils, 12dB

peak amplitude @12dB=412 mv

61(H) x 31(V) @10 mils, 0dB

peak amplitude @0dB=208 mv

deviation=-52% or -6.4 dB 

60(H) x 30(V) @10 mils, 0dB

peak amplitude @0dB=437 mv

61(H) x 31(V) @10 mils, 0dB

peak amplitude @0dB=394 mv

deviation=26% or 2.0 dB 

61(H) x 31(V) @10 mils, 25.5dB

peak amplitude @16dB=1167 mv

deviation=205% or 9.7 dB 

60(H) x 30(V) @10 mils, 16dB

peak amplitude @16dB=382 mv

60(H) x 30(V) @10 mils, 0dB

peak amplitude @0dB=313 mv

Multizone Color Code

0 128 255

Experiment 255 = 500mv

80(H) x 30(V) @10 mils, 6dB

peak amplitude@6dB = 373 mv

61(H) x 31(V) @10 mils, 10dB

peak amplitude@6dB = 654 mv

deviation=75% or 4.9 dB

Side 1 Model Experiment

Side 2 Model Experiment Side 4 Model Experiment

Side 5 Model Experiment Side 6 Model Experiment

61(H) x 31(V) @10 mils, 21.5dB

peak amplitude @12dB=1316 mv

deviation=219% or 10.1 dB 

60(H) x 30(V) @10 mils, 12dB

peak amplitude @12dB=412 mv

61(H) x 31(V) @10 mils, 0dB

peak amplitude @0dB=208 mv

deviation=-52% or -6.4 dB 

60(H) x 30(V) @10 mils, 0dB

peak amplitude @0dB=437 mv

61(H) x 31(V) @10 mils, 0dB

peak amplitude @0dB=394 mv

deviation=26% or 2.0 dB 

61(H) x 31(V) @10 mils, 25.5dB

peak amplitude @16dB=1167 mv

deviation=205% or 9.7 dB 

60(H) x 30(V) @10 mils, 16dB

peak amplitude @16dB=382 mv

60(H) x 30(V) @10 mils, 0dB

peak amplitude @0dB=313 mv

Multizone Color Code

0 128 255

Experiment 255 = 500mv

B2W2 – C 3D Solid Model Parameters:

Sub-Micrograph 

size - 2400(H) by 800(V) pixels

color - 256 gray-scale

scale - 132 pixels =20 mils

Geometric Model 

1 void part 

(with branches)

37 geometric model parts

14 micrograph planes 

(including 7 patches)

117 void cross-section boundary traces (model part 24 uses 6 traces, 

34 uses 5,

35 uses 4 and the rest use 3 each)

E-52
B2W2 – C

7

9

8

10

12

11

364 mils

Orientation of Sub-Micrographs (B2W2 – C): 

Y

Z

Polish 8

X

stack-up sequence

(polish in from side 2 of the cube)

7

8

12

Y

Z

Polish 8

X

stack-up sequence

(polish in from side 2 of the cube)

7

8

12

E-53
Angle views of void model for B2W2 – C:

View 1

View 2

27 mils (Z)

313 mils (X)

min. max. size

X 19 332 313

Y 28 86 58

Z 1 28 27

Unit: mils

27 mils (Z)

313 mils (X)

min. max. size

X 19 332 313

Y 28 86 58

Z 1 28 27

Unit: mils

Dimensions of B2W2 – C: 

E-54
Microprobe analysis:

B2W2 – C – 8 section

.

.

.

.

.

. .

. . . . . 1

2 3

4

5

6

7 8 9

10 11

12

13 

14

15

12 16

. .

.

.

.

1

2

.

.

.

.

.

. .

. . . . . 1

2 3

4

5

6

7 8 9

10 11

12

13 

14

15

12 16

. .

.

.

.

1

2

B2W2-C (1)

Pt # Ti Al V N

1 92.5 2.3 1.5 4.2

2 89.0 5.5 2.5 0.7

3 90.7 1.7 2.1 6.8

4 89.5 2.9 2.4 5.2

5 92.8 4.3 1.5 1.7

6 90.5 0.4 0.9 9.6

7 91.6 2.9 2.6 5.2

8 89.9 1.6 2.2 5.8

9 91.6 5.5 2.2 0.5

10 93.7 2.5 1.3 2.4

11 88.6 5.7 2.4 1.5

12 91.3 2.6 1.4 3.3

13 90.2 4.7 1.8 1.6

14 90.8 5.7 1.9 0.6

15 91.7 6.5 2.2 0.6

16 89.3 0.3 1.0 10.0

W %

40 mils

40 mils

B2W2 - C

1st Polish

0.0

2.0

4.0

6.0

8.0

10.0

0 5 10 15 20 25 30

Distance (mils)

%Nitrogen

Profile 1

Profile 2

E-55
.

. .

.

. . .

. . .

. .

1 2

3

4

5

6

7 8 9

10

11 12

13 14

15

1617 .

. . .

.

Profile 1

Profile 2

1819

20

.

.

. . 21

.

. .

.

. . .

. . .

. .

1 2

3

4

5

6

7 8 9

10

11 12

13 14

15

1617 .

. . .

.

Profile 1

Profile 2

1819

20

.

.

. . 21

Microprobe analysis:

B2W2 – C – section 11

B2W2-C (2)

Pt # Ti Al V N

1 93.7 4.2 1.4 1.4

2 95.1 3.1 1.7 2.9

3 94.3 2.5 1.3 2.8

4 92.5 4.5 2.1 2.3

5 90.8 4.6 1.7 2.0

6 92.3 6.2 1.6 0.6

7 94.3 3.1 1.6 2.9

8 93.4 5.5 1.9 1.0

9 93.7 5.8 1.8 2.4

10 94.0 2.9 1.5 1.5

11 93.3 5.8 2.2 1.5

12 93.0 2.2 1.6 6.3

13 90.9 4.6 1.8 2.4

14 94.1 1.7 1.4 4.8

15 88.9 0.6 0.9 8.7

16 95.6 1.2 1.6 4.9

17 94.4 5.2 2.0 1.2

18 91.6 2.8 1.4 2.2

19 92.3 1.3 1.2 4.4

20 93.0 4.9 1.5 < 0.5

21 93.3 3.4 1.5 1.9

W %

40 mils

40 mils

B2W2 - C

2nd Polish

0.0

2.0

4.0

6.0

8.0

10.0

0 5 10 15 20 25 30

Distance (mils)

%Nitrogen

Profile 1

Profile 2

E-56
Indication: B1AW2 – B

Original billet length: 117”

Mult inspection parameters: 

Transducer - Zone 1, 6” diameter, 5MHz

Index - 0.010 

Data Acquisition Rate - 0.010

Inspection Sensitivity - #2 FBH at 80-90% in Titanium

Inspection Range - 0.2” to 0.8”

Sampling Rate - 100 MHz

Depth Axial Length Amplitude Signal-to-Noise Ratio

0.200” 0.180” 225% 21.7

Billet inspection:

Side 5 Side 6

Zone 1

117 inches

Serial Number

51 inches 81 inches

 Amplitude 

(%) 

S/N depth 

(in) 

axial 

length (in) 

radial 

length (in) 

Multizone 69% 2.09 0.9 0.2300 0.4188 

Conv. 

Longitudinal 

% 

Conv. Angle % 

25 MHz inspection parameters

Transducer - 25 MHz, F10 - focal point positioned at indication depth

Index - 0.010

Data Acquisition Rate - 0.010

Inspection sensitivity - #1 FBH at 83% - 56 dB #2FBH at 84% at 48dB

Inspection range - C-scan , Between Front and Back / B-scan entire volume 

Sampling Rate - 200 MHz

Side Depth Axial Length Amplitude % Sensitivity, dB

1 Data Not Available

2 Cannot Detect Due to Curved Surface

3 1.065” 0.180” 80 71

4 0.750” 0.180” 75 71

5 0.460” 0.180” 70 71

6 0.675” 0.180” 60 78 View is from Side 4, which is opposite 

side 2. Sides 5 and 6 represent the 

axial ends with Side 5 having the serial 

number. Sides 2 and 4 represent the 

hoop direction (the circumferential 

plane) NOTE: Data from sides 1 and 

2 is unavailable.

Orientation of sample block and c-scan images: 

Side 6

Side 5

Side 4

Side 2

NOTE: No data were taken from sides 1 and 3 due 

to billet surface curvature on side 1

X

Z

Side 3 (top)

Side 5 

(right)

Y

Side 1 (bottom)

Side 6 

(left)

Side 4 

(back)

Side 2 (front)

X

Z

Side 3 (top)

Side 5 

(right)

Y

Side 1 (bottom)

Side 6 

(left)

Side 4 

(back)

Side 2 (front) Side 2 Side 5

Side 6

Side 3

Side 1

Side 5

Side 2Side 4

Side 1

Side 3

Side 4

Side 5

Side 6

Side 1

Side 3

Side 6

Side 2Side 4

Side 3

Side 1

E-57
B1AW2 – B 5 MHz C-scan image comparisons:

Side 2 Model Experiment Side 4 Model Experiment

Side 5 Model Experiment Side 6 Model Experiment

31(H) x 31(V) @10 mils, 2dB

peak amplitude @2dB=573 mv

deviation=155% or 8.1 dB 

60(H) x 30(V) @10 mils, 2dB

peak amplitude @2dB=225 mv

31(H) x 31(V) @10 mils, 2dB

peak amplitude @2dB=111 mv

deviation=-49% or -5.8 dB 

60(H) x 30(V) @10 mils, 2dB

peak amplitude @2dB=217 mv

31(H) x 31(V) @10 mils, 0dB

peak amplitude @0dB=192 mv

deviation=-51% or -6.1 dB 

51(H) x 31(V) @10 mils, 0dB

peak amplitude @0dB=901 mv

deviation=474% or 15.2 dB 

60(H) x 30(V) @10 mils, 0dB

peak amplitude @0dB=157 mv

60(H) x 30(V) @10 mils, 0dB

peak amplitude @0dB=384 mv

Multizone Color Code

0 128 255

Experiment 255 = 500mv for sides 2, 5 and 6

= 250mv for side 4

B1AW2 – B 3D Solid Model Parameters:

Sub-Micrograph 

size - 1100(H) by 300(V) pixels

color - 256 gray-scale

scale - 5110 pixels =810 mils

Geometric Model

1 void part 

(with branches)

6 geometric model parts

17 micrograph planes 

(including 4 patches)

30 void cross-section boundary traces

E-58
B1AW2 – B

17

14

16

15

18

19

20

21

22

23

24

25

174 mils

E-59
Orientation of Sub-Micrographs (B1AW2 – B): 

Y

Z

X

stack-up sequence

(polish in from side 2 of the cube)

14

15

25

X

Z Y

Angle views of void model for B1AW2 – B:

View 1

E-60
X

Z

Y

Angle views of void model for B1AW2 – B:

View 2

Dimensions of B1AW2 – B: 

31 mils (Y)

135 mils (X)

min. max. size

X 21 156 135

Y 7 38 31

Z -43 21 64

Unit: mils

E-61
Microprobe analysis:

B1AW2 – B – polish 1

1

2 3

4

5

6 7

8

9

10 .

. . . . .

.

. . .

11 12 13

14

15

.

.

. . . 1

2 3

4

5

6 7

8

9

10 .

. . . . .

.

. . .

11 12 13

14

15

.

.

. . .

Data for areas around the defect.

B1AW2-B

Pt # Ti Al V N

1 97.1 0.3 1.3 2.6

2 96.3 0.3 1.6 3.1

3 92.9 0.4 1.8 5.5

4 97.1 0.5 1.4 3.9

5 92.9 0.5 1.5 6.4

6 96.2 0.3 1.7 3.3

7 91.6 1.6 1.9 4.2

8 94.1 5.9 1.8 0.5

9 92.1 0.8 1.9 5.6

10 93.3 0.3 0.9 7.3

11 92.6 0.5 1.6 6.4

12 90.9 0.6 1.7 6.5

13 95.6 0.4 1.8 3.6

14 97.3 0.8 1.3 2.1

15 93.5 5.7 2.1 < 0.5

W % B1AW2 - B

0.0

2.0

4.0

6.0

8.0

10.0

-50 -40 -30 -20 -10 0 10 20 30 40 50

Distance (mils)

Wt% Nitrogen

Linescan 1

E-62
Indication: B1AW2 – X

Original billet length: 117”

Mult inspection parameters: 

Transducer - Zone 3, 6” diameter, 5MHz

Index - 0.010 

Data Acquisition Rate - 0.010

Inspection Sensitivity - #2 FBH at 80-90% in Titanium

Inspection Range - 0.8” to 1.7”

Sampling Rate - 100 MHz

Depth Axial Length Amplitude Signal-to-Noise Ratio

0.618” 0.160” Not detected in mult

Billet inspection:

Not detected by inspectors during production billet inspection

Side 5

Side 6

117 inches

Serial Number

95 inches 103 inches

25 MHz inspection parameters

Transducer - 25 MHz, F10 - focal point positioned at indication depth

Index - 0.010

Data Acquisition Rate - 0.010

Inspection sensitivity - #1 FBH at 83% - 56 dB #2FBH at 84% at 48dB

Inspection range - C-scan , Between Front and Back / B-scan entire volume 

Sampling Rate - 200 MHz

Side Depth Axial Length Amplitude % Sensitivity, dB

1 0.415” 0.160” Data Unavailable 64

2 0.529 0.160” 80 67

3 1.247” 0.160” 37 79

4 0.485” 0.160” 80 74

5 0.487” 0.160” 76 79

6 0.498” 0.160” 78 76 View is from Side 2, the side that was 

polished. Sides 5 and 6 represent the 

axial ends with Side 5 having the serial 

number. Sides 2 and 4 represent the 

hoop direction (the circumferential 

plane)

Orientation of sample block and c-scan images: 

Side 6

Side 5

Side 4

Side 2

X

Z

Side 2 (front)

Side 1 (top)

Side 5 

(right)

Y

Side 3 (bottom)

Side 6 

(left)

Side 4 (back)

X

Z

Side 2 (front)

Side 1 (top)

Side 5 

(right)

Y

Side 3 (bottom)

Side 6 

(left)

Side 4 (back)

E-63
B1AW2 - X 5 MHz C-scan image comparisons:

Multizone Color Code

0 128 255

Experiment 255 = 500mv

Side 1 Model Experiment

Model Side 3 Experiment

31(H) x 31(V) @10 mils, 6dB

peak amplitude @6dB=398 mv

deviation=-11% or -1.0 dB 

100(H) x 30(V) @10 mils, 6dB

peak amplitude @6dB=448 mv

31(H) x 31(V) @10 mils, 6dB

peak amplitude @6dB=461 mv

deviation=-7.2% or -0.6 dB 

100(H) x 30(V) @10 mils, 6dB

peak amplitude @6dB=430 mv

Side 1 Model Experiment

Model Side 3 Experiment

31(H) x 31(V) @10 mils, 6dB

peak amplitude @6dB=398 mv

deviation=-11% or -1.0 dB 

100(H) x 30(V) @10 mils, 6dB

peak amplitude @6dB=448 mv

31(H) x 31(V) @10 mils, 6dB

peak amplitude @6dB=461 mv

deviation=-7.2% or -0.6 dB 

100(H) x 30(V) @10 mils, 6dB

peak amplitude @6dB=430 mv

Side 2 Model Experiment

Side 4 Model Experiment

31(H) x 31(V) @10 mils, 0dB

peak amplitude @0dB=175 mv

deviation=-29% or -2.9 dB 

31(H) x 31(V) @10 mils, 0dB

peak amplitude @0dB=498 mv

deviation=94% or 5.7 dB 

100(H) x 30(V) @10 mils, 0dB

peak amplitude @0dB=257 mv

100(H) x 30(V) @10 mils, 0dB

peak amplitude @0dB=244 mv

Side 2 Model Experiment

Side 4 Model Experiment

31(H) x 31(V) @10 mils, 0dB

peak amplitude @0dB=175 mv

deviation=-29% or -2.9 dB 

31(H) x 31(V) @10 mils, 0dB

peak amplitude @0dB=498 mv

deviation=94% or 5.7 dB 

100(H) x 30(V) @10 mils, 0dB

peak amplitude @0dB=257 mv

100(H) x 30(V) @10 mils, 0dB

peak amplitude @0dB=244 mv

100(H) x 30(V) @10 mils, 0dB

peak amplitude@0dB = 374 mv

31(H) x 31(V) @10 mils, 0dB

peak amplitude@0dB = 309 mv

deviation=-17% or -1.7 dB

Side 5 Model Experiment

100(H) x 30(V) @10 mils, 0dB

peak amplitude@0dB = 374 mv

31(H) x 31(V) @10 mils, 0dB

peak amplitude@0dB = 309 mv

deviation=-17% or -1.7 dB

Side 5 Model Experiment

100(H) x 30(V) @10 mils, 0dB

peak amplitude@0dB = 450 mv

31(H) x 31(V) @10 mils, 0dB

peak amplitude@0dB = 403 mv

deviation=-10% or -1.0 dB

Side 6 Model Experiment

100(H) x 30(V) @10 mils, 0dB

peak amplitude@0dB = 450 mv

31(H) x 31(V) @10 mils, 0dB

peak amplitude@0dB = 403 mv

deviation=-10% or -1.0 dB

Side 6 Model Experiment

E-64
B1AW2 - X

Polish 8 R

L

Polish 11

S1 R S2 L

Polish 9

R

R

L

L

Polish 12 R L

Polish 13 L

Polish 10

L R

S2

75 mils

E-65
Orientation of Sub-Micrographs (B1AW2 - X): 

Y

Z

Polish 8

X

Polish 8

Polish 9

Polish 13

stack-up sequence

(polish in from side 2 of the cube)

Y

Z

Polish 8

X

Polish 8

Polish 9

Polish 13

stack-up sequence

(polish in from side 2 of the cube)

E-66
Y X

Z

Angle views of void model for B1AW2 - X:

View 1

View 2

34 mils (Z)

52 mils (X)

min. max. size

X 15 67 52

Y 9 27 18

Z -5 29 34

Unit: mils

34 mils (Z)

52 mils (X)

min. max. size

X 15 67 52

Y 9 27 18

Z -5 29 34

Unit: mils

Dimensions of B1AW2 - X: 

E-67
Microprobe analysis:

B1AW2 - X – section 10

. . . .

.

.

.

. .

.

. . .

. .

.

.

.

.

. 1 2

3

4

5

6

7

8 9 1011

12

13 

14

15

16

17

18

19

20 

21

22

23

24

26

27

28

25

.

.

.

.

.

. .

.

Profile 1

Profile 2

B1AW2-X

1st Polish

0.0

2.0

4.0

6.0

8.0

10.0

12.0

0 5 10 15 20 25 30

Distance (mils)

%Nitrogen

Profile 1

Profile 2

B1AW2-X

Pt # Ti Al V N

1 90.1 5.2 2.1 0.5

2 90.9 4.4 1.7 1.0

3 89.5 2.7 1.6 2.7

4 89.1 0.4 1.6 3.0

5 91.9 0.3 2.2 4.4

6 85.5 0.3 1.8 11.2

7 88.1 0.2 1.7 9.1

8 91.0 0.3 2.4 4.1

9 92.9 4.4 1.9 1.0

10 93.5 0.2 2.0 2.9

11 92.1 0.3 2.5 4.8

12 84.9 0.3 2.1 12.3

13 84.9 0.1 2.5 9.3

14 94.0 0.6 1.8 2.6

15 89.6 6.8 2.0 0.5

16 93.0 5.2 2.1 0.6

17 95.1 2.1 1.8 2.0

18 90.1 3.2 1.9 0.5

19 94.0 2.1 1.6 1.9

20 91.5 0.8 2.2 4.4

21 86.5 0.2 1.5 9.0

22 88.0 0.2 1.6 8.4

23 92.5 2.0 1.6 1.6

24 91.5 4.1 1.7 1.3

25 91.6 4.9 2.0 0.5

26 92.6 0.4 1.8 3.6

27 89.2 6.9 1.8 < 0.5

28 90.6 6.6 2.0 < 0.5

W %

E-68
Microprobe analysis:

B1AW2 - X – section 14

. .

.

.

. .

. .

.

. .

1

2

3

4

5

6

7

8

9

10

11

12

.

Profile 1

Profile 2

B1AW2-X

Pt # Ti Al V N

1 90.3 4.7 1.8 1.1

2 92.3 5.8 1.9 0.5

3 90.7 5.1 1.9 0.5

4 91.1 6.9 2.0 < 0.5

5 91.5 6.6 1.8 < 0.5

6 93.9 4.1 1.9 < 0.5

7 94.6 0.6 1.8 1.8

8 93.6 4.3 1.7 0.7

9 91.1 6.9 2.1 < 0.5

10 92.8 5.8 2.1 0.7

11 93.0 4.5 2.0 0.8

12 93.7 5.6 1.9 < 0.5

W % B1AW2 - X

2nd Polish

0.0

0.5

1.0

1.5

2.0

2.5

0 5 10 15 20 25

Distance (mils)

%Nitrogen

Profile 1

Profile 2

E-69/E-70
APPENDIX F—RECONSTRUCTION OF HARD ALPHA DEFECTS USING 

METALLOGRAPHIC SECTIONING DATA 

In this appendix, the techniques used in geometric reconstructions of the hard alpha defects are 

described more extensively. These were developed to build a uniform solid model of hard alpha 

defects using actual metallographic data. The objective of the earlier work was to develop the 

techniques to construct geometric models and enable testing of the ultrasonic model using output 

from these solid geometric models. Later efforts focused on determining the flaw boundary and 

using the nonuniform rational b-splines (NURBS). The appendix includes three sections: 

• Description of the flaw region extraction method using primary regional growth method 

or the manual tracing method. 

• Explanation of the scheme to determine the flaw boundary. 

• Description of the theory of NURBS, which is the backbone of the geometric model 

reconstruction work, are both used in the early solid model and later surface model. 

The geometrical models were derived from metallographic cross-section images taken from 

destructive sectioning of the defect regions. The reconstruction of a defect begins with the 

boundary determination of the respective defect regions on each of the metallographs by using 

some image-processing algorithms [F-1]. The three-dimensional geometrical model then 

follows by using the state-of-the-art NURBS techniques [F-2]. Once the geometrical models are 

constructed, the complete acoustical and material properties can be interpolated within the 

volume or on the surface of the defects. 

F.1 EARLY WORK: FLAW REGION EXTRACTION. 

Before the geometrical models of the flaws can be constructed, the flaw regions and their 

boundaries on the metallographic images need to be identified and extracted. In this work, 

several image-processing techniques were used for these tasks. In particular, a recursive regional 

growth routine was found effective in extracting the flaw regions and a boundary detection 

algorithm was useful for determining the flaw boundaries. 

Region growing is a procedure that groups pixels or subregions into larger regions. The simplest 

of these approaches is pixel aggregation, which starts with a set of seed (starting) points. From 

these, regions are grown by adding neighboring pixels to the region if they have similar 

characteristics. The characteristic that was used to include a pixel in a region is that the absolute 

difference between the gray-scale levels of the seed be less than a prescribed threshold. Any 

pixel that satisfies this property will be assigned to the region. Implementation of the regional 

growth routine for the cracks and voids in the metallographic images were easily acceptable 

because the region was very distinct in nature. 

Although the concept for which the regional growth routine works is easy to implement, 

problems arise in the actual practice. It was difficult to set a consistent threshold for a series of 

images with different intensity levels that would satisfy all the criteria for the boundary edge 

linking algorithm. A specific threshold had to be set manually for the individual image. Given 

F-1
this difficulty, an alternative brute-force approach was adapted. This method works by tracking 

the positions of the screen locator as it passes over the metallographic images on the computer 

display. In this way, a rough outline of the flaw boundaries can be manually drawn to reflect the 

users’ observation of intensity change around the flaw boundaries. 

F.2 EARLY WORK: BOUNDARY DETERMINATION. 

After applying the region growth technique, or the manual drawing to a metallographic image as 

described above, a new binary image was formed for each of the flaw regions on that image. 

The binary image is fully described by a set of pixels set to zero (black) and ones (white). A 

boundary determination algorithm was then used to detect the path around a binary image as 

accurately as possible. The algorithm is a recursive looped routine that uses a set of rules to 

detect a path around any arbitrary, binary region provided as input. The binary region of interest 

is indicated by a 0 or 1. The conditional statements that are used to obtain a boundary around a 

region are limited in number and reduce the computation by an order of magnitude over other 

algorithms that work on edge detection and edge linking [F-3]. 

The boundary determination algorithm used in this work was setup to find the least resistant path 

around any arbitrary binary image. The algorithm needs only three input parameters, which are 

the binary image, a starting point on the boundary of the region of interest, and the binary region 

itself. A clockwise direction and a closed boundary are assumed. The algorithm works by 

comparing two byte arrays as it traverses the boundary around the binary image. The first byte 

array stores the original binary image. The second byte array is initialized to the opposite value 

of the region of interest. During the traversing of the boundary around the region of interest, if 

any one of the conditional statements set up in the clockwise direction starting with the first test 

pixel are true, then the position of the satisfying pixel is added to the boundary and immediately 

becomes the next test position. In the occurrence of a test position being added to the boundary, 

the second byte array is turned to the opposite value at that location. The traversing of the 

boundary stops when none of the conditional statements are satisfied and the last point on the 

boundary is a pixel away from the starting pixel location. An example of these image-processing 

routines working together is shown in figure F-1. 

F-2
FIGURE F-1. RESULTS OF REGION GROWING AND BOUNDARY 

DETECTION ROUTINES 

F.3 THEORY OF NURBS. 

This section briefly discusses the theory of NURBS. For more details, the reader is referred to 

reference F-4 and the cited literature therein. The geometrical modeling of the hard alpha 

defects begins with the normalization of the extracted contour data from the image-processing 

routines. The normalization was carried out by subdividing each of the contours into n line 

segments of equal length. NURBS and their Bezier subsets are then used to interpolate the sets 

of contour data with n points into an m by n surface mesh where m is the number of contours 

being interpolated through. 

A generic NURBS surface can be expressed as [F-2] 

 (F-1) r r

Suv N uN v P i p jq i j

j

m

i

n

(,) = , , () ()

==

∑∑

00

,

F-3
where the surface is r

S , ’s are the control points, and r

Pi j , Nip jq , , ( ) ( ) u N v are the basis functions 

as given by 

N u if u u u

otherwise i

i i

,0( )

1 1

0 = ⎧ ≤ ≤ ⎨

⎩

⎫

⎬

⎭

+

N u

u u

u u

N u

u u

u uN i p

i

ip i

i p

i p

ip i i p

, ,

,

( ) = ( ) −

− + −

+ − −

+ +

++ + + −

1

1

1 11 1

 (F-2)

The p and q are the degree of interpolations in the u and v directions, respectively. For the 

calculation of Nj q, ( ) v , just substitute j for I, q for p, and v for u. v and u are knots in the knot 

vector given by equation F-3. Knot vectors are comprised of a set of nondecreasing real 

numbers called knots. 

 i rU uu u = { , ,..., ) 0 1 m − 1 = 0,..... m − 1 (F-3) 

Global surface interpolation is accomplished by using equation F-4 on a given set of points (n+1) 

x (m+1) data points{ }, k=0,...,n and l=0,...,m. p and q are the degrees of interpolation in 

the u and v directions, respectively. 

Qk l ,

r r r Q Su v N u N v P kl k l ip k jq l i j

j

m

i

n

, , = = ( ,) ( ) ()

==

∑∑

00

, , (F-4) 

An example of the flaw reconstruction procedure is illustrated in figure F-2. First, the position 

trace was manually drawn to define a region of interest in a metallographic image. A linear pixel 

interpolation followed to enclose the distance between the points and to have a one-to-one pixel 

boundary mapping on the image to ensure that the boundary was a closed loop defining a region 

of interest. Once the linear pixel interpolation was completed, the boundaries were normalized 

to a set of n points in a clockwise manner starting at the position having the coordinates of 

centroid of area in the horizontal direction and the lowest reading in the vertical direction. After 

the same procedure was applied to all of the metallographic images, a three-dimensional solid 

model was constructed, as shown in figure F-3. The model was created using a bilinear 

interpolation between each successive slice of data. This model also allowed for the solid to be 

sliced apart and the interior of the solid could be analyzed at any orientation, as shown in figures 

F-4 and F-5. Figure F-6 shows an improved surface model using the same manual boundary 

traces with Bezier interpolation routines. Finally, a global surface interpolation implementing 

the advanced NURBS on another set of metallographic images is depicted in figure F-7, in which 

the exact boundaries around void regions were extracted. 

NURBS were chosen for the interpolation of the model because of the control a user would have 

in modifying the shape of a surface once a model was initially created. A user could change the 

shape of a constructed model by modifying weights or control points. B-spline basis functions 

have been chosen over the Bezier and linear surface interpolation for the geometrical design of 

F-4
the model because of the high degree requirement by the Bezier curve function. To fit a curve 

containing n points, a Bezier curve has to complete an n-1 degree calculation. 

FIGURE F-2. BOUNDARY TRACE OF THE DIFFUSION ZONE OF A 

METALLOGRAPHIC CROSS SECTION OF A REAL HARD ALPHA DEFECT 

FIGURE F-3. SOLID MODEL RECONSTRUCTION AROUND A REGION OF INTEREST 

WITH LINEAR DYNAMIC, POSITION LOCATOR TRACES, AND PIXEL 

INTERPOLATION 

F-5
FIGURE F-4. A STACKUP OF BOUNDED SLICES 

FIGURE F-5. ANALYZE INTERIOR PROFILE FOR ARBITRARY ORIENTATION 

F-6
FIGURE F-6. BEZIER SURFACE MODEL OF THE TRACED BOUNDARIES 

FIGURE F-7. NONUNIFORM RATIONAL B-SPLINE INTERPOLATED SURFACE 

MODEL OF EXACT BOUNDARY EXTRACTION OF VOIDS IN A SET 

METALLOGRAPHIC IMAGES 

F-7
F.4 REFERENCES. 

F-1. Rafael C. Gonzalez and Richard E. Woods, Digital Image Processing, Addison-Wesley 

Publishing Company, 1992. 

F-2. Les Piegl and Wayne Tiller, The NURBS Book, Springer-Verlag Publishing Company, 

1995. 

F-3. C.-P. Chiou, F.J. Margetan, R.B. Thompson, and Brian Boyd, “Development of 

Ultrasonic Model for Hard Alpha Inclusions in Titanium Alloys,” Review of Progress in 

Quantitative Nondestructive Evaluation, D.O. Thompson and D.E. Chimenti, eds., Vol. 

16B, p. 1529, 1997. 

F-4. B. Boyd, “Development and Application of Geometrical Models of Defects for 

Ultrasonic Nondestructive Evaluation in Aircraft Engine Alloys,” Master thesis, Iowa 

State University, 1998. 

F-8
APPENDIX G—ULTRASONIC MODELING OF HARD ALPHA DEFECTS

This appendix discusses the details of the ultrasonic modeling effort with emphasis on a Born 

model for inclusion of complex morphology, a multilayered exact model for spherical inclusions, 

and a multifacet Kirchhoff model (MKIR) for voids of arbitrary shape. The basic framework has 

been described thoroughly in appendix A1 of the Engine Titanium Consortium Phase I report on 

probability of detection (PoD) [G-1]. To make this report self-contained, a portion of that 

appendix is cited below. 

G.1 MEASUREMENT MODEL FRAMEWORK. 

“The ultrasonic flaw response modeling approach in this work is derived within 

the context of Auld’s electromechanical reciprocity relation [G-2] as has been 

demonstrated previously in the derivation of the Thompson-Gray measurement 

model [G-3]. Auld’s reciprocity relation provides a general and rigorous way to 

relate ultrasonic scattering theory to the absolute level of signals observed at the 

electrical ports of a transducer. The key in this process is the specification of the 

wavefields in the vicinity of the flaw, in terms of scattering theory. Within this 

framework, the Thompson-Gray measurement model describes an immersion 

inspection process in which the flaw is small with respect to the ultrasonic beam 

width. In this small flaw limit, the prediction of the overall signal is made in 

terms of the product of a number of factors, which may be thought of as 

theoretical modules which describe the flaw scattering response, beam 

propagation, medium attenuation, and interface transmission effects. In order to 

make absolute predictions of flaw response, inference of the system response 

obtained from a separate reference experiment is required. The measurement 

model is formulated in the frequency domain. For a given inspection geometry 

and flaw particulars, the absolute values of various radio-frequency (rf) flaw 

waveforms can be predicted to great accuracy through the use of inverse Fourier 

transform techniques. 

Symbolically, the frequency domain components predicting the results of the 

inspection process, as predicted by the Thompson-Gray measurement model, can 

be summarized in the following expression: 

(G-1) ⎥

⎦

⎤ ⎢

⎣

⎡

⎥

⎦

⎤ ⎢

⎣

⎡

⎥

⎥

⎥

⎦

⎤

⎢

⎢

⎢

⎣

⎡

⎥

⎦

⎤ ⎢

⎣

⎡

⎥

⎥

⎥

⎦

⎤

⎢

⎢

⎢

⎣

⎡

∝

⎥

⎥

⎥

⎦

⎤

⎢

⎢

⎢

⎣

⎡

signature

flaw 

nattenuatio

& phase 

effectsother and 

focusing, 

 n,diffractio 

transmission

interface 

factor 

efficiency

 probe 

signalflaw of

component 

Spectral 

Here the “diffraction, focusing, and other effects” sub-module describing the 

effects of beam propagation, as influenced by the part geometry, is calculated 

based on the Gauss-Hermite beam model [G-4]. The “probe efficiency factor” 

sub-module, used to account for the system efficiency, is deduced from a 

measured rf reference signal for which backsurface echoes obtained from a fused 

quartz plate are normally used. This reference signal together with other 

geometry and material parameters, such as “interface transmission”, “phase & 

attenuation”, and “flaw signature”, are the necessary inputs to predict the signal 

G-1
response. After the “spectral component of flaw signal” is evaluated at all 

frequency components within the transducer bandwidth, the time domain rf signal 

can then be synthesized via fast Fourier transform techniques. The main 

advantage of taking this approach is the reduction of computational effort, while 

maintaining necessary modeling complexity, through the introduction of 

appropriate approximations in the various modules. The use of the GaussHermite beam model, for example, enables the wave fields to be rapidly 

calculated in the regions of interest; thereby enabling the evaluation of the 

“diffraction, focusing and other effects” sub-module. In contrast with other 

numerical methods such as finite element and boundary element, this beam model 

consumes much less computation time.” 

The key component of all these submodules is the flaw signature, which depends on the actual 

flaw morphology as well the illuminating ultrasonic beam pattern. The specific flaw signature 

for each of the three models mentioned above are discussed in the following paragraphs. 

G.2 BORN MODEL FOR INCLUSIONS. 

The basic Born inclusion model is the same as described in Appendix A.1 of the Phase I PoD 

report. For the sake of completeness, here again the related portions are cited. 

“In modeling weak scatterers such as the hard alpha inclusions, one good choice 

is the Born approximation, which has been extensively studied in the literature.” 

See, for example, references G-5 and G-6. 

“This approximation greatly simplifies the modeling effort by replacing the 

otherwise unknown scattered field quantities that appear within the kernel of 

various integral representations by their incident counterparts on the surface or 

within the volume of the flaw. In our new formulation, the Auld’s surface 

reciprocity relationship was first converted into a volumetric form via Gauss’ 

theorem. The paraxial and Born approximations were then utilized to reduce the 

new form to a three-dimensional volumetric integral involving the square of 

incident displacement field and the inclusion properties.” In the ordinary context 

of the Born approximation, both the density and wave speed are assumed to be 

very close to those of the host materials, i.e., the flaw is assumed to possess a 

weak (small) impedance mismatch. Intuitively, this weak impedance assumption 

is consistent with the Born approximation that replaces the wavefield quantities 

within the inclusion by the incident field counterparts. However, from a 

comparative study with the high-frequency Kirchhoff approximation [G-7], both 

approximations (Born & Kirchhoff) have been shown to be equivalent in 

modeling the leading specular (front surface) responses. As such, it has become 

unnecessary to impose this weak impedance assumption.” 

As was shown in the previous study [G-8], the normal Born model without the weak impedance 

assumption actually offers better accuracy in comparison with the experimental data for 

inclusions of higher impedance. 

G-2
In order to accommodate the complex geometry and composition of the Contaminated Billet 

Study hard alpha defect, a new implementation was adapted using a simple linear approximation. 

This was done by approximating the three-dimensional volumetric integral of the Born model as 

the linear sum of a series of two-dimensional planar surface integrals. The stackup sequence of 

the metallographic images (figure F-4 in appendix F of this report) provides a natural way of 

implementing such linear sum. For an inhomogeneous inclusion embedded in an otherwise 

isotropic, homogeneous media, the symbolic form of the flaw signature (equation G-1) for this 

implementation can be expressed as 

[ ] (G-2) i

M

i A

dLdA

acoustic property

material and 

f displacement field

 incident

flaw signature

i

 

1

2

∑ ∫∫ = ⎥

⎥

⎦

⎤

⎢

⎢

⎣

⎡

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ ≈

in which the double area integral is done on the flaw area Ai on each of the cross-section 

metallograph. The integrand consists of the square of displacement field of the incident 

ultrasonic beam as predicted by the beam model, and an expression as function of the material 

and acoustic properties that fully describe the inhomogeneity everywhere within the inclusion. 

dLi denotes the spacing distance in between the adjacent metallographic cross sections. The flaw 

signature at a specific frequency is then the linear summation of the product of the double 

integration and the spacing dLi over all metallographs. 

To demonstrate the capability of this model, a calculation was performed using the geometrical 

model constructed in figure F-6 in appendix F of this report as input. In figure G-1, the A-scan 

model predictions are compared between the test defect model and a cylindrical model of 

equivalent size. In both cases, the acoustic properties of pure titanium with 5.9% nitrogen 

contamination were assumed. The inspection scenario simulated was for both flaws orientated at 

their side-on positions at a depth of 1.5 inches scanned by a 5-MHz transducer at normal 

incidence. As was expected, due to its irregularities in shape, the front and back surface echoes 

of the test defect cannot be resolved as those of the same-size flaw of cylindrical shape. In 

addition, the peak amplitude of test defect is significantly lower than the cylindrical flaw 

counterpart. 

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

1 21 41 61 81 101 121 141 161 181 201 221 241 261 281 301 321 341 361 381

Time in 0.02 microsecond

Peak-Peak Amplitude in Volts

Test Hard-Alpha 

Inclusion

Cylindrical 

Inclusion of 

Equivalent Size 

FIGURE G-1. A-SCAN COMPARISON BETWEEN THE TEST HARD ALPHA INCLUSION 

AND A CYLINDRICAL INCLUSION OF EQUIVALENT SIZE (Both are 0.175′′ diameter by 

0.11′′ length at 1.5′′ depth, scanned by a 5-MHz transducer at central side-on position.) 

G-3
G.3 MULTILAYERED EXACT MODEL FOR SPHERICAL INCLUSIONS/VOIDS. 

As described previously, the material properties of the hard alpha defects and their surrounding 

regions were obtained by a material model using the metallographic images from destructive 

sectioning of the defects. These material property data are then input to the ultrasonic model to 

calculate the flaw signal predictions. In order to quantify the accuracy of the approximate Born 

models used in the inhomogeneous hard alpha defect calculations (discussed above and in 

references G-8 and G-9), other theoretical solutions are sought for independent verifications. 

However, to the authors’ best knowledge, an exact model suitable for real hard alpha defects of 

complicated morphology is not yet available today. At the first attempt to develop such a model, 

a classic exact series solution has been extended for spherical inclusion/void, which was first 

derived by Ying and Truell [G-10] and later integrated with void result by Pao and Mow [G-11], 

both using the separation-of-variable method. 

To accommodate the inhomogeneous structure of the hard alpha defects (in the spherical shape), 

a hard alpha defect was approximated by a number of concentrically homogeneous layers and 

applied the Pao and Mow building block solution to each layer. At each frequency, an overall 

matrix equation is assembled and solved for the coefficients of which the outer-most layer 

represents the out-going wave solution of interest. Following the basic framework as stated 

above, this layered spherical inclusion/void model is also cast into the Thompson-Gray 

measurement model framework in conjunction with the Auld’s reciprocity formulation. The 

symbolic form for flaw signature (equation G-1) in the far field can be expressed as 

[ ] (G-3) i

N

i

flaw signa ≈ ∑Cture iΦ =1

where Ci’s are the out-going wave coefficients from the matrix solutions and the Φi’s are 

combinations of spherical wave phase terms, Legendre functions and their derivatives. The 

series are truncated at N terms when convergence is reached. 

This new layered inclusion/void model has been tested against the Born model in cases of 

spherical inclusion and void cores, both surrounded by the hard alpha layers profiled by the 

material model, as shown in figure 34 of this report. Overall good agreement between the 

layered exact model and Born model is clearly shown in figure G-2. It is also observed that the 

30 mils thickness of the hard alpha layer seems to be insufficient to make a significant change on 

the overall ultrasonic response of the hard alpha defects. As was stated previously, this 

observation justifies the use of the Kirchhoff model (see section G.4), which was employed to 

calculate the ultrasonic response from void portions of the hard alpha defects. 

G-4
0.00E+00

5.00E-05

1.00E-04

1.50E-04

2.00E-04

2.50E-04

0 1 2 3 4 5 6 7 8 9 10 11

Inclusion Diameter in FBH Number (#1=1/64 in.)

Peak-Peak Amplitude

wl h-a shell (layer model)

wlout h-a shell (layer model)

wl h-a shell (Born model)

FIGURE G-2. PEAK AMPLITUDE COMPARISON BETWEEN MULTILAYERED EXACT 

MODEL AND BORN MODEL 

G.4 MULTIFACET KIRCHHOFF MODEL FOR VOIDS. 

As described previously, the morphology of hard alpha defects is complicated. Exact models 

capable of predicting the ultrasonic responses of real defects with such complexity, to the 

authors’ best knowledge, are not available. Even if such exact models were available, current 

technology does not provide sufficient and accurate morphological data. Thus, modeling efforts 

were focused on the use of approximations to reduce the complexity. An approximate ultrasonic 

model using the high-frequency Kirchhoff approximation has proven to be successful for 

modeling various volumetric voids or cracks. The Kirchhoff model is particularly suitable for 

making use of the multifaceted data of the defect surfaces provided by the geometric model. It 

should be noted that the modeling emphasis was placed on the void portions of these hard alpha 

defects because of their dominance in determining the ultrasonic responses. This choice of 

emphasis was justified by studies that have been conducted on the ultrasonic response from 

spherical inclusions/voids using exact series solutions, as discussed in appendix F. In these 

studies, the hard alpha layer was estimated to contribute at most 10% of the overall ultrasonic 

response of a typical hard alpha defect. 

In the frequency domain, the symbolic form of flaw signature for the general Kirchhoff model 

can be expressed as 

[ ] dA (G-4) wave field

incident flaw signa ture

elit surfac

2

∫∫ ⎥⎦

⎤ ⎢⎣⎡ ≈

where the incident wave field amplitudes and phases are calculated by a Gauss-Hermite beam 

model. 

G-5
Under the high-frequency Kirchhoff assumption, only the portions being illuminated by the 

ultrasonic beam contribute to the flaw response. This is indicated by the lit surface in the double 

surface integral of equation G-4. When plane-wave illumination and simple flaw geometry such 

as an elliptical crack or an ellipsoidal void are considered, analytic solutions to the surface 

integral are available. In dealing with finite-beam effect and complex flaw geometry, however, 

the integration has to be accomplished numerically. For the latter case, involving the intricate 

void components of the natural hard alpha defects, detailed geometrical information of the 

reflecting surface are required. By way of geometrical modeling, complete parameterization of 

the void surface has been established. In the current implementation, the geometrical 

information is given in terms of triangular element (facet) connections and the corresponding 

nodal coordinates. Using the geometrical information, one can proceed to compute the local 

contributions to the integral in each facet. The total surface integration is then the sum of 

contributions from all facets. Here, a simple scheme is adopted that numerically resembles the 

mean-value theorem, with the centroid points of the facets used to approximate the mean-value 

locations. This integration procedure is summarized below. 

[ ] (G-5) 

2

1

2

area of facet i at centroi id of facet

incident wave field dA wave fieldincident total lit facets

elit surfac i

∑ ⎥⎦

⎤ ⎢⎣⎡ ∫∫ ≅ ⎥⎦⎤ ⎢⎣⎡

=

Numerical experience has shown that equation G-5 gives a stable result when the proper ratio 

between wavelength and facet size is maintained. 

For each scan position, a ray-tracing algorithm was employed to determine the portions of the 

defect surface that were illuminated by the incoming ultrasonic beam and the strength of 

illumination on each of the triangular surface facets. Equation G-5 was then used to calculate the 

overall ultrasonic response of the defect as the sum of contributions from each of the illuminated 

facets. Finally, the time domain radio frequency (RF) waveform can be obtained via numerical 

inversion of the Fourier transform. From the RF waveform output, C- or B-scan can then be 

predicted for a specified scan plan. 

This new multifacet void model has been validated in the case of spherical void under planewave illumination for which, as was noted previously, an analytic solution known as plane-wave 

Kirchhoff model is available. Figure G-3 shows the comparison of the on-axis peak amplitude 

profile between the two models for a 5-mm-diameter spherical void located at various depths and 

illuminated by a 10-MHz immersion planar transducer with a fixed water path. Overall good 

agreement has been obtained. It is also observed that the agreement improves as the void depth 

increases toward the far-field region because the accuracy of the plane-wave Kirchhoff model 

increases as well. 

The performance of the multifacet Kirchhoff model is also quite encouraging when put to a real 

test on the naturally occurring hard alpha defects. At each scan position, the illuminated facets 

on the flaw surface model were indexed and their geometrical coordinates were used as the input 

to drive the multifacet Kirchhoff model calculations. An example of the results was 

demonstrated in section 3.4 for hard alpha defect B1AW2-X. As was shown in figure 43 of this 

report, it is evident that the shape and orientation of the experimental C-scan images of B1AW2-

X are in good agreement with the geometrical model. The overall performance summary and 

G-6
error analyses have also been provided in earlier sections. For a comparison of the individual 

defects of the ten selected hard alpha defects, the reader is referred to appendix E. 

2000

3000

4000

5000

6000

7000

4 6 8 10 12 14 16 18 20 22

Void Depth in cm

Peak-Peak Amplitude in m

v

multi-facet

Kirchhoff

plane-wave

Kirchhoff

FIGURE G-3. MODEL COMPARISON BETWEEN MULTIFACET KIRCHHOFF MODEL 

AND PLANE-WAVE KIRCHHOFF MODEL FOR THE ON-AXIS PEAK AMPLITUDES OF 

A SPHERICAL VOID AT DIFFERENT DEPTHS UNDER PLANE-WAVE ILLUMINATION 

G.5 REFERENCES. 

G-1. “A Methodology for the Assessment of the Capability of Inspection Systems for 

Detection of Subsurface Flaws in Engine Components,” FAA Report DOT/FAA/AR01/96, September 2002. 

G-2. B.A. Auld, “General Electromechanical Reciprocity Relations Applied to the Calculation 

of Elastic Wave Scattering Coefficients,” Wave Motion, 1, 1979, pp. 3-10. 

G-3. R.B. Thompson and T.A. Gray, “A Model Relating Ultrasonic Scattering Measurements 

Through Liquid-Solid Interfaces to Unbounded Medium Scattering Amplitudes,” Journal 

of Acoustical Society of America, 74 (4), 1983, pp. 1279-1290. 

G-4. B.P. Newberry, R.B. Thompson, and E.F. Lopez, “Development and Comparison of 

Beam Models for Two-Media Ultrasonic Inspection,” Review of Progress in Quantitative 

NDE, Vol. 6A, D.O. Thompson and D.E. Chimenti, eds., 1987, pp. 639-647. 

G-5. J.E. Gubernatis, E. Domany, J.A. Krumhansl, and M. Huberman, “The Born 

Approximation in the Theory of the Scattering of Elastic Waves by Flaws,” Journal of 

Applied Physics, 48 (7), 1977, pp. 2812-2819. 

G-6. J.H. Rose and J.M. Richardson, “Time Domain Born Approximation,” Journal of 

Nondestr. Eval., 3 (1), 1982, pp. 45-53. 

G-7
G-7. L.W. Schmerr, Jr., Fundamentals of Ultrasonic Nondestructive Evaluation – A Modeling 

Approach, Kluwer Academic Publishers, June 1998. 

G-8. C.-P. Chiou, F.J. Margetan, R.B. Thompson, and Brian Boyd, “Development of 

Ultrasonic Model for Hard Alpha Inclusions in Titanium Alloys,” Review of Progress in 

Quantitative Nondestructive Evaluation, D.O. Thompson and D.E. Chimenti, eds., 

Vol. 16B, 1997, p. 1529. 

G-9. C.-P. Chiou, F.J. Margetan, and R.B. Thompson, “Modeling of Ultrasonic Signals From 

Weak Inclusions,” Review of Progress in Quantitative Nondestructive Evaluation, D.O. 

Thompson and D.E. Chimenti, eds., Vol. 15A, 1996, pp. 49-55. 

G-10. C.F. Ying and R. Truell, “Scattering of a Plane Longitudinal Wave by a Spherical 

Obstacle in an Isotropically Elastic Solid,” Journal of Applied Physics, Vol. 27, No. 9, 

1956, pp. 1086-1097. 

G-11. Y-H. Pao and C.C. Mow, “Scattering of Plane Compressional Waves by a Spherical 

Obstacle,” Journal of Applied Physics, Vol. 34, No. 3, 1963, pp. 493-499. 

G-8