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NBS SPECIAL PUBLICATION 260-76

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U.S. DEPARTMENT OF COMMERCE/National Bureau of Standards

Standard Reference Materials:

A Standard Reference Material

Containing Nominally

Five Percent Austenite

(SRM 485a)

:DO

57

d. 260-76

382
I NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards' was established by an act of Congress on March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology

and facilitate their effective application for public benefit. To this end, the Bureau conducts

research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau's technical work is per- formed by the National Measurement Laboratory, the National Engineering Laboratory, and

the Institute for Computer Sciences and Technology.

THE NATIONAL MEASUREMENT LABORATORY provides the national system of

physical and chemical and materials measurement; coordinates the system with measurement

systems of other nations and furnishes essential services leading to accurate and uniform

physical and chemical measurement throughout the Nation's scientific community, industry,

and commerce; conducts materials research leading to improved methods of measurement,

standards, and data on the properties of materials needed by industry, commerce, educational

institutions, and Government; provides advisory and research services to other Government

agencies; develops, produces, and distributes Standard Reference Materials; and provides

calibration services. The Laboratory consists of the following centers:

Absolute Physical Quantities2 — Radiation Research — Chemical Physics —

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research and provides scientific and technical services to aid Federal agencies in the selection, acquisition, application, and use of computer technology to improve effectiveness and

economy in Government operations in accordance with Public Law 89-306 (40 U.S.C. 759), relevant Executive Orders, and other directives; carries out this mission by managing the Federal Information Processing Standards Program, developing Federal ADP standards

guidelines, and managing Federal participation in ADP voluntary standardization activities; provides scientific and technological advisory services and assistance to Federal agencies; and

provides the technical foundation for computer-related policies of the Federal Government.

The Institute consists of the following centers:

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' Headquarters and Laboratories at Gaithersburg, M D, unless otherwise noted; mailing address Washington, DC 20234. 'Some divisions within the center are located at Boulder, CO 80303.
Standard Reference Materials:

A Standard Reference Material Containing

Nominally Five Percent Austenite (SRM 485a)

N hb %f^' «X ^jMOuvH m_ National Bure3U of st3ndards G. E. Hicho and E. E. Eaton ^"'Jo

^

BWb' OCT 2 5 1982

tno-i ace - O

Fracture and Deformation Division

Center for Materials Science

1

National Measurement Laboratory

National Bureau of Standards

Washington, DC 20234

o 9

o

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

Issued August 1982
Library of Congress Catalog Card Number: 82-600574

National Bureau of Standards Special Publication 260-76

Natl. Bur. Stand. (U.S.), Spec. Publ. 260-76, 25 pages (Aug. 1982)

CODEN: XNBSAV

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1982

For Sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402.

Price $3.50

(Add 25 percent for other than U.S. mailing.)
PREFAC E

Standard Reference Materials (SRM's) as defined by the

National Bureau of Standards are we 1 1- ch ar a c t e r i z e d materials

produced in quantity and certified for one or more physical

or chemical properties. They are used to assure the accuracy

and compatibility of measurements throughout the Nation.

SRM's are widely used as primary standards in many diverse

fields in science, industry, and technology, both within the

United States and throughout the world. They are also used

extensively in the fields of environmental and clinical analysis. In many applications, traceability of quality control

and measurement processes to the national measurement system

are carried out through the mechanism and use of SRM's. For

many of the Nation's scientists and technologists it is

therefore of more than passing interest to know the details

of the measurements made at NBS in arriving at the certified

values of the SRM's produced. An NBS series of papers, of

which this publication is a member, called the NBS Special

Publication - 260 Series , is reserved for this purpose.

This 260 Series is dedicated to the dissemination of

information on different phases of the preparation, measurement, certification and use of NBS-SRM's. In general, much

more detail will be found in these papers than is generally

allowed, or desirable, in scientific journal articles. This

enables the user to assess the validity and accuracy of the

measurement processes employed, to judge the statistical

analysis, and to learn details of techniques and methods

utilized for work entailing the greatest care and accuracy.

These papers also should provide sufficient additional information not found on the certificate so that new applications

in diverse fields not foreseen at the time the SRM was originally issued will be sought and found.

Inquiries concerning the technical content of this paper

should be directed to the authors. Other questions concerned

with the availability, delivery, price, and so forth will

receive prompt attention from:

Office of Standard Reference Materials

National Bureau of Standards

Washington, D.C. 20234

George A. Uriano, Chief

Office of Standard Reference Materials

iii
OTHER NBS PUBLICATIONS IN THIS SERIES

Catalog of NBS Standard Reference Materials

(1981-83 edition), R. W. Seward, ed., NBS

Spec. Publ. 260 (November 1981).

Michaelis, R. E., and Wyman, L. L. Standard

Reference Materials: Preparation of White Cast

Iron Spectrochemical Standards. NBS Misc.

Publ. 260-1 (June 1964). COM 74- 1 1 06 1 * * Michaelis, R. E., Wyman, L. L., and Flitsch, R.. Standard Reference Materials: Preparation of

NBS Copper-Base Spectrochemical Standards.

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1 1063**

Michaelis, R. E., Yakowitz, H., and Moore, G. A., Standard Reference Materials: Metallographic

Characterization of an NBS Spectrometric LowAlloy Steel Standard. NBS Misc. Publ. 260-3

(October 1964). COM74-I 1060**

Hague, J. L. Mears, T. W., and Michaelis, R. E., Standard Reference Materials: Sources of

Information, NBS Misc. Publ. 260-4 (February

1965). COM74-I1059

Alvarez, R., and Flitsch R., Standard Reference

Materials: Accuracy of Solution X-Ray Spectrometric Analysis of Copper-Base Alloys. NBS

Misc. Publ. 260-5 (March 1965). PB168068**

Shultz, J. L, Standard Reference Materials:

Methods for the Chemical Analysis of White

Cast Iron Standards, NBS Misc. Publ. 260-6

(July 1975). COM74-1 1068**

Bell, R. K., Standard Reference Materials:

Methods for the Chemical Analysis of NBS

Copper-Base Spectrochemical Standards. NBS

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Richmond. M.S., Standard Reference Materials:

Analysis of Uranium Concentrates at the

National Bureau of Standards. NBS Misc. Publ. 260-8 (December 1965). COM74- 1 1066**

Anspach, S. C, Cavallo, L. M. Garfinkel, S. B. Hutchinson, J. M. R., and Smith, C. N., Standard Reference Materials: Half Lives of Materials

Used in the Preparation of Standard Reference

Materials of Nineteen Radioactive Nuclides

Issued by the National Bureau of Standards

NBS Misc. Publ. 260-9 (November 1965).

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Yakowitz, H., Vieth, D. L., Heinrich, K. F. J., and

Michaelis, R. E., Standard Reference Materials:

Homogeneity Characterization on NBS Spectrometric Standards II: Cartridge Brass and LowAlloy Steel, NBS Misc. Publ. 260-10 (December

1965). COM74-1 1064**

Napolitano, A., and Hawkins, E. G., Standard

Reference Materials: Viscosity of Standard

Lead-Silica Glass, NBS Misc. Publ. 260-11

(November 1966). NBS Misc. Publ. 260-11**

Yakowitz, H., Vieth, D. L., and Michaelis, R. E., Standard Reference Materials: Homogeneity

Characterization of NBS Spectrometric Standards III: White Cast Iron and Stainless Steel Powder Compact, NBS Misc. Publ. 260-12

(September 1966). NBS Misc. Publ. 260-12**

Spijkerman, J. L., Snediker, D. K., Ruegg, F. C,

and DeVoe, J. R., Standard Reference Materials: Mossbauer Spectroscopy Standard for the Chemical Shift of Iron Compounds, NBS Misc.

Publ. 260-13 (July 1967). NBS Misc. Publ.

260-13**

Menis, O., and Sterling, J. T., Standard Reference

Materials: Determination of Oxygen in Ferrous

Materials - SRM 1090, 1091, and 1092, NBS

Misc. Publ. 260-14 (September 1966). NBS Misc.

Publ. 260-14**

Passaglia, E., and Shouse, P. J. Standard Refer- ence Materials: Recommended Method of Use

of Standard Light-Sensitive Paper for Calibrating Carbon Arcs Used in Testing Textiles for Colorfastness to Light, NBS Misc. Publ. 260-15

(June 1967). (Replaced by NBS Spec. Publ.

260-41.)

Yakowitz, H., Michaelis, R. E., and Vieth, D. L., Standard Reference Materials: Homogeneity

Characterization of NBS Spectrometric Standards IV: Preparation and Microprobe Characterization of W-20% MO Alloy Fabricated by

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Publ. 260-16 (January 1969). COM74- 1 1062**

Catanzaro, E. J., Champion, C. E.. Garner, E. L., Marinenko, G., Sappenfield, K. M., and Shields,

W. R. Standard Reference Materials: Boric

Acid; lsotopic and Assay Standard Reference

Materials, NBS Spec. Publ. 260-17 (February

1970). Out of Print

iv
t

Geller, S. B., Mantek, P.A., and Cleveland, N.

G., Standard Reference Materials: Calibration of NBS Secondary Standard Magnetic Tape

(Computer Amplitude Reference) Using the

Reference Tape Amplitude Measurement

"Process A, "NBS Spec. Publ. 260-18 (November

1969). (See NBS Spec. Publ. 260-29.)

Paule, R. C, and Mandel, J., Standard Reference

Materials: Analysis of Interlaboratory Measurements on the Vapor Pressure of Gold (Certifica- tion of Standard Reference Material 745). NBS

Spec. Publ. 260-19 (January 1970). PBI90071**

Paule, R. C, and Mandel, J., Standard Reference

Materials: Analysis of Interlaboratory Measurements on the Vapor Pressures of Cadmium and

Silver, NBS Spec. Publ. 260-21 (January 1971).

COM74-1 1359**

Yakowitz, H., Fiori, C. E., and Michaelis, R. E., Standard Reference Materials: Homogeneity

Characterization of Fe-3 Si Alloy, NBS Spec.

Publ. 260-22 (February 1971). COM74- 1 1357**

Napolitano, A., and Hawkins, E. G., Standard

Reference Materials: Viscosity of a Standard

Borosilicate Glass, NBS Spec. Publ. 260-23

(December 1970). COM71-00157**

Sappenfield. K. M., Marineko, G., and Hague, J. L., Standard Reference Materials: Comparison

of Redox Standards, NBS Spec. Publ. 260-24

(January 1972). COM72-50058**

Hicho, G. E., Yakowitz, H., Rasberry, S. D., and

Michaelis, R. E., Standard Reference Materials:

A Standard Reference Material Containing

Nominally Four Percent Austenite, NBS Spec.

Publ. 260-25 (February 1971). COM74-1 1356**

Martin, J. F., Standard Reference Materials:

National Bureau of Standards-US Steel Corportion Joint Program for Determining Oxygen and

Nitrogen in Steel, NBS Spec. Publ. 260-26

(February 1971). 85 cents* PB 81 176620

Garner, E. L., Machlan, L. A., and Shields, W. R., Standard Reference Materials: Uranium

lsotopic Standard Reference Materials, NBS

Spec. Publ. 260-27 (April 1971). COM74-

1 1358**

Heinrich, K. F. J., Myklebust, R. L., Rasberry, S. D., and Michaelis, R. E., Standard Reference

Materials: Preparation and Evaluation of

SRM's 481 and 482 Gold-Silver and GoldCopper Alloys for Microanalysis, NBS Spec.

Publ. 260-28 (August 1971). COM71-50365**

Geller, S. B., Standard Reference Materials: Cali- bration of NBS Secondary Standard Magnetic

Tape (Computer Amplitude Reference) Using

the Reference Tape Amplitude Measurement

"Process A-Model 2," NBS Spec. Publ. 260-29

(June 1971). COM71-50282

Gorozhanina, R. S., Freedman, A. Y., and

Shaievitch, A. B. (translated by M. C. Selby),

Standard Reference Materials: Standard

Samples Issued in the USSR (A Translation

from the Russian). NBS Spec. Publ. 260-30 (June

1971). COM71-50283**

Hust, J. G., and Sparks, L. L., Standard Reference

Materials: Thermal Conductivity of Electrolytic Iron SRM 734 from 4 to 300 K, NBS Spec. Publ.

260-31 (November 1971). COM71-50563**

Mavrodineanu, R., and Lazar, J. W., Standard

Reference Materials: Standard Quartz Cuvettes,

for High Accuracy Spectrophotometry, NBS

Spec. Publ. 260-32 (December 1973). 55 cents* SN003-003-01213-1

Wagner, H. L., Standard Reference Materials:

Comparison of Original and Supplemental

SRM 705, Narrow Molecular Weight Distri- bution Polystyrene, NBS Spec. Publ. 260-33

(May 1972). COM72-50526**

Sparks, L. L., and Hust, J. G., Standard Reference

Materials: Thermoelectric Voltage, NBS Spec.

Publ. 260-34, (April 1972). COM72-50371**

Sparks, L. L., and Hust, J. G., Standard Refer- ence Materials: Thermal Conductivity of

Austenitic Stainless Steel, SRM 735 from 5 to 280 K, NBS Spec. Publ. 260-35 (April 1972.)

35 cents* COM72-50368**

Cali, J. P., Mandel, J., Moore, L. J., and Young, D.

S., Standard Reference Materials: A Referee

Method for the Determination of Calcium in Serum, NBS SRM 915, NBS Spec. Publ. 260-36

(May 1972). COM72-50527**

Shultz, J. 1. Bell., R. K. Rains, T. C, and Menis,

O., Standard Reference Materials: Methods of

Analysis of NBS Clay Standards, NBS Spec.

Publ. 260-37 (June 1972). COM72-50692**

Richmond, J. C, and Hsia, J. J., Standard Refer- ence Materials: Preparation and Calibration of

Standards of Spectral Specular Reflectance,

NBS Spec. Publ. 260-38 (May 1972). COM72-

50528**

Clark, A. F., Denson, V.A., Hust, J. G., and

Powell, R. L., Standard Reference Materials

The Eddy Current Decay Method for Resistivity

Characterization of High-Purity Metals, NBS

Spec. Publ. 260-39 (May 1972). COM72-50529**
t

McAdic, H. G.. Gain, P.D.,and Menis, O., Standard Reference Materials: Selection of Thermal

Analysis Temperature Standards Through a Cooperative Study (SRM 758, 759, 760), NBS

Spec. Publ. 260-40 (August 1972.) COM72-

50776**

Wood, L. A., and S ho use. I'. J., Standard

Reference Materials: Use of Standard LightSensitive Paper for Calibrating Carbon Arcs Used in Testing Textiles lor Colorfastness to Light, NBS Spec. Publ. 260-41 (August 1972)

COM72-50775**

Wagner. H. L. and Vcrdier, P. H., eds.. Standard

Reference Materials: The Characterization ol Linear Polyethylene, SRM 1475, NBS Spec.

Publ. 260-42 (September 1972). COM72-

50944**

Yakowitz, H.. Ruff, A. W.. and Michaelis, R. E., Standard Reference Materials: Preparation and

Homogeneity Characterization ot an Austenitic

Iron-Chromium-Nickel Alloy, NBS Spec. Publ. 260-43 (November 1972). COM 73-50760**

Schooley, J. F., Soulen, R. J., Jr., and Evans, G. A.,

Jr., Standard Reference Materials: Preparation

and Use o I Superconductive Fixed Point

Devices, SRM 767, NBS Spec. Publ. 260-44

(December 1972). COM 73-50037**

Greifer, B., Maienthal, E. J. Rains, T. C, and

Rasberry, S. D.. Standard Reference Materials:

Powdered Lead-Based Paint, SRM 1579, NBS

Spec. Publ. 260-45 (March 1973). COM73-

50226**

Hust, J. G., and Giarratano, P. J., Standard Refer- ence Materials: Thermal Conductivity and

Electrical Resistivity Standard Reference Materials: Austenitic Stainless Steel, SRM's 735 and

798, from 4 to 1200 k, NBS Spec. Publ. 260-46

(March 1975). SN003-003-0 1 278-5

Hust, J. G., Standard Rel erence Materials: Electrical Resistivity of Electrolytic Iron, SRM 797,

and Austenitic Stainless Steel, SRM 798, from 5

to 280 K, NBS Spec. Publ. 260-47 (February

1974). COM 74-50 1 76**

Mangum, B. W., and Wise, J. A., Standard Refer- ence Materials: Description and Use of Precision

Thermometers lor the Clinical Laboratory,

SRM 933 and SRM 934, NBS Spec. Publ. 260-48

(May 1974). 60 cents* SN003-003-0 1 278-5

Carpenter, B. S., and Reimer, G. M., Standard

Reference Materials Calibrated Glass Standards for Fission Track Use, NBS Spec. Publ. 260-49 (November 1974). COM74-51I85

vi

Hust, J. G., and Giarratano, P. J., Standard Refer- ence Materials: Thermal Conductivity and Electrical Resistivity Standard Reference Materials:

Electrolytic Iron, SRM's 734 and 797 from 4 to 1000 K, NBS Spec. Publ. 260-50 (June 1975).

$1.00* SN003-003-OI425-7

Mavrodineanu, R., and Baldwin, J. R., Standard

Reference Materials: Glass Filters As a Standard

Reference Material for Spectrophotometry;

Selection; Preparation; Certification; Use-SRM

930. NBS Spec. Publ. 260-51 (November 1975).

$1.90* SN003-003-0I48I-8

Hust, J. G., and Giarratano, P. J., Standard Refer- ence Materials: Thermal Conductivity and Electrical Resistivity Standard Reference Materials

730 and 799, from 4 to 3000 K, NBS Spec. Publ. 260-52 (September 1975). $1.05* SN003-003-

01464-8

Durst, R. A., Standard Reference Materials:

Standardization of pH Measurements, NBS

Spec. Publ. 260-53 (December 1975, Revised).

$1.05 SN003-003-0I551-2

Burke, R. W., and Mavrodineanu, R. Standard

Reference Materials: Certification and Use of Acidic Potassium Dichromate Solutions as an

Ultraviolet Absorbance Standard, NBS Spec.

Publ. 260-54 (August 1977). $3.00* SN003-003-

01828-7

Ditmars, D. A., Cezairliyan, A., lshihara, S., and

Douglas, T. B., Standard Reference Materials:

Enthalpy and Heat Capacity; Molybdenum

SRM 781, from 273 to 2800 K, NBS Spec. Publ. 260-55 (September 1977). $2.20* SN003-003-

01836-8

Powell, R. L., Sparks, L. L., and Hust, J. G., Standard Reference Materials: Standard

Thermocouple Materials, Pt.67: SRM 1967, NBS

Spec. Publ. 260-56 (February 1978). $2.20*

SN003-003-0 18864

Cali, J. P. and Plebanski, T., Guide to United

States Reference Materials, NBS Spec. Publ. 260-57 (February 1978). $2.20* PB 277173

Barnes, J. D., and Martin, G. M., Standard Refer- ence Materials: Polyester Film for Oxygen Gas

Transmission Measurements SRM 1470, NBS

Spec. Publ. 260-58 (June 1979) $2.00* SN003-

003-02077

Chang, T., and Kahn, A. H. Standard Reference

Materials: Electron Paramagnetic Resonance

Intensity Standard; SRM 2601, NBS Spec.

Publ. 260-59 (August 1978) $2.30* SN003-

003-01975-5
Velapoldi, R. A., Paule, R. C, Schaffer, R.,

Mandel, J., and Moody, J. R., Standard Refer- ence Materials: A Reference Method for the Determination of Sodium in Serum, NBS Spec.

Publ. 260-60 (August 1978). $3.00* SN003-003

01978-0

Verdier, P. H., and Wagner. H. L., Standard Refer- ence Materials: The Characterization of Linear

Polyethylene (SRM 1482, 1483, 1484), NBS

Spec. Publ. 260-61 (December 1978). $1.70*

SN003-003-02006-

1

Soulen, R. J., and Dove, R. B., Standard Reference

Materials: Temperature Reference Standard

for Use Below 0.5 K (SRM 768). NBS Spec.

Publ. 260-62 (April 1979). $2.30* SN003-003-

02047-8

Velapoldi, R. A., Paule, R. C, Schaffer, R. Mandel, J., Machlan, L. A., and Gramlich, J. W.,

Standard Reference Materials: A Reference

Method for the Determination of Potassium in Serum. NBS Spec. Publ. 260-63 (May 1979).

$3.75* SN003-003-02068

Velapoldi, R. A., and Mielenz, K. D., Standard

Reference Materials: A Fluorescence Standard

Reference Material Quinine Sulfate Dihydrate

(SRM 936), NBS Spec. Publ. 260-64 (January

1980). $4.25* SN003-003-02 148-2 Marinenko, R. B., Heinrich, K. F. J., and Ruegg,

F. C, Standard Reference Materials: MicroHomogeneity Studies of NBS Standard Reference

Materials, NBS Research Materials, and Other

Related Samples. NBS Spec. Publ. 260-65

(September 1979). $3.50* SN003-003-021 14-1 Venable, W. H., Jr., and Eckerle, K. L., Standard

Reference Materials: Didymium Glass Filters for Calibrating the Wavelength Scale of Spectrophotometers (SRM 2009, 2010, 2013). NBS Spec.

Publ. 260-66 (October 1979). $3.50* SN003-003-

02127-0

Velapoldi, R. A., Paule, R. C, Schaffer, R., Mandel,

J., Murphy, T. J., and Gramlich, J. W., Standard

Reference Materials: A Reference Method for the Determination of Chloride in Serum, NBS Spec.

Publ. 260-67 (November 1979). $3.75* SN003-

003-02136-9

Mavrodineanu, R. and Baldwin, J.R., Standard

Reference Materials: Metal-On-Quartz Filters as a Standard Reference Material for Spectrophotometry-SRM 2031, NBS Spec. Publ. 260-68

(April 1980). $4.25* SN003-003-02I67-9

Velapoldi, R. A., Paule, R. C, Schaffer, R.,

Mandel, J., Machlan, L. A., Garner, E. L., and

Rains, T. C, Standard Reference Materials: A

Reference Method for the Determination of

Lithium in Serum, NBS Spec. Publ. 260-69 (July)

1980). $4.25* SN003-003-02214-4

Marinenko, R. B., Biancaniello, F., Boyer, P. A., Ruff, A. W., DeRobertis, L., Standard Reference

Materials: Preparation and Characterization of an Iron-Chromium-Nickel Alloy for Microanalysis, NBS Spec. Publ. 260-70 (May 1981).

$2.50* SN003-003-02328-1

Seward, R. W., and Mavrodineanu, R., Standard

Reference Materials: Summary of the Clinical

Laboratory Standards Issued by the National

Bureau of Standards, NBS Spec. Publ. 260-71

(November 1981). $6.50* SN003-003-0238 1-7 Reeder, D.J., Coxon, B., Enagonio, D., Christensen,

R. G., Schaffer, R., Howell, B. F., Paule, R. C,

Mandel, J., Standard Reference Materials: SRM

900, Antiepilepsy Drug Level Assay Standard,

NBS Spec. Publ. 260-72 (June 1981). $4.25*

SN003-003-02329-9

lnterrante, C. G., and Hicho, G. E., Standard Refer- ence Materials: A Standard Reference Material

Containing Nominally Fifteen Percent Austenite

(SRM 486), NBS Spec. Publ. 260-73 (January

1982). $2.75* SN003-003-02386-8

Marinenko, R. B., Standard Reference Materials:

Preparation and Characterization of K-411 and

K-414 Mineral Glasses for Microanalysis: SRM

470. NBS Spec. Publ. 260-74 (in press).

Weidner, V. R., Hsia, J. J., Standard Reference

Materials: Preparation and Calibration of First Surface Aluminum Mirror Specular Reflectance

Standards (SRM 2003a), NBS Spec. Publ. 260-75

(in press).

Hicho, G. E. and Eaton, E. E., Standard Reference

Materials: A Standard Reference Material

Containing Nominally Five Percent Austenite

(SRM 485a). NBS Spec. Publ. 260-76 (in press).

* Send order with remittance to Superintendent

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Washington, DC 20402. Remittance from

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one-fourth of the purchase price for postage.

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v i i
TABLE OF CONTENTS

PAGE

Abstract. 1 Introduction 2 General Description of the SRM 3 Preparation of the Compacts 4

Characterization of SRM 485a 8

Conclusions 14

Acknowledgements 14

References 16

LIST OF TABLES

1. Chemical Analysis of Stainless Steel Powder 4

LIST OF FIGURES

1. Scanning electron micrographs of the powders used

to produce SRM 485a 5 2. Fabrication procedure for SRM 485a 6

3. General microstructure of a compact 7 4. Characterization steps for SRM 485a 11

5. Calibration curve showing the volume percent

austenite as a function of weight percent nickel.... 13

6. Histogram showing frequency of occurrence versus

the volume percent austenite 15

viii
A Standard Reference Material Containing

Nominally Five Percent Austenite (SRM 485a)

G. E. Hicho and E. E. Eaton

^

Fracture and Deformation Division

Center for Materials Science

National Measurement Laboratory

National Bureau of Standards

Washington, D.C. 20234

Abstract

This Standard Reference Material, SRM 485a, is a renewal of

SRM 485 , and is intended for the calibration of x-ray diffraction

equipment used in determining the amount of retained austenite in

hardened steels. The SRM was produced using powder metallurgical

techniques and involved blending 5 percent by weight AISI type 310

stainless steel powder (austenitic) with AISI type 430 stainless

steel powder (ferritic) . From this blend, 216 compacts were

produced and subsequently examined for nickel content by x-ray

fluorescence spectrometry. A calibration curve was established

using 13 compacts randomly selected from the population of 216. The curve relates the weight percent nickel from x-ray fluorescence

measurements to the volume percentage austenite as determined by

quantitative microscopy measurements of area percent. The curve was

then used to assign the certified values to the remaining compacts.

This SRM may be used as an x-ray diffraction standard for retained

austenite or in very special cases as an x-ray fluorescence standard

for nickel content.

Key words: austenite in ferrite; powder metallurgy; quantitative

microscopy; retained austenite standard; Standard Reference

Material; x-ray fluorescence.

(1) Student currently enrolled in the Mechanical Engineering

Department at the University of Maryland.
Introduction

This Standard Reference Material was produced in order to

calibrate x-ray diffraction (XRD) equipment used to determine the

amount of retained austenite in hardened steels.

In various heat treating processes, steel is heated to a temperature where a f ace-centered-cubi c solid phase called austenite

is formed. After a sufficient stabilization time, the steel is

quenched into a medium where the austenite may be entirely

transformed to a metastable, body-centered-tetragonal solid phase

called martensite. However, sometimes the austenite is not

completely transformed to martensite. The untransformed (retained)

austenite is sometimes detrimental to the properties of the finished

product. Often there are requirements as to the maximum amount of

retained austenite permitted in hardened steels. Therefore, it is

necessary to quantitatively determine the amount of the retained

austenite in the finished product.

The amount of retained austenite in steel is usually determined

by XRD procedures using a direct comparison of the integrated

intensities of a series of both austenite and ferrite diffraction

lines. It is highly recommended that the user of SRM 485a read

National Bureau of Standards (NBS) Technical Note 709, [1]

,

describing the x-ray method used at the National Bureau of Standards

(NBS) to determine the amount of austenite in an austenite-ferrite

mixture, prior to using this SRM.

An XRD reference material for retained austenite, should be

reasonably free of certain metallurgical confoundments which

severely affect the intensities of both the austenite and ferrite

lines - preferred granular orientation, large grain size, and

residual stress. The previous SRM [2] , was found to be reasonably

free of these confoundments . Therefore, the present SRM (485a)

,

since it was prepared in a similar manner, should be free of these

confoundments , and be very useful in determining the amount of

retained austenite in hardened steels.

The National Bureau of Standards is in the process of producing

a series of SP.M's containing various percentages of austenite in

ferrite. The first of these was issued in 1970 and contained

nominally four percent austenite [3]. This SRM, 485a, is a renewal

of that (1970) SRM. Standard Reference Materials containing 15% and

30% austenite in ferrite have also been prepared.

Following the preparation and production of SRM 485, an automated XRF unit, used to determine the nickel content of each

2
compact, was purchased. Therefore the characterization procedures

used for SRM 485a will not be the same as that used for 485.

A separate characterization of the austenite content for each

compact is required because a homogenous blend of austenite ir

ferrite can not be guaranteed to the degree required. Therefore,

each unit of the SRM is individually certified.

The purpose of this paper is to present a detailed description

of the preparation and characterization of the 216 compacts, and

their subsequent certification as SRM 485a.

General Description of the SRM

This SRM is composed of two constituents whose structures are netallurgically different. The components are ATSI type 310

stainless steel (austentic) and AISI type 430 stainless steel

(ferritic) powders. The 3.10 is a highly stabie austenitic stainless

steel (24.99 weight percent Cr and 20.41 weight percent Ni)

requiring a substantial change in composition to produce s transformation to a structure other than austenite. The 430

contains 16.03 weight percent Cr, and effectively no nickel - .09

weight percent.

Following the blending of the powders, the powders were pressed

into compacts and subsequently sintered, repressed, and vacuum

annealed. The finished compacts were approximately 21 mm (.83 in)

in diameter and 2.4 mm (.094 in) thick. Only one surface of the SRM was polished, and it is that surface which is certified as to the

austenite content. No surface preparation of the SFM is necessary,

in fact damage to the surface renders the certification void.

The main concept of the SRM lies in the fact that the nickel

content for each compact is related directly to the austenite

content

Because of the significant differences between the nicke]

content of the austenitic component (20.41 weight percent) and that

of the ferritic component (.09 weight percent), it was possible to use XRF analysis to obtain a very precise measurement of total

nickel counts on the surface of the compact. The total nickel

counts were then corrected to weight percent nickel.

Using a calibration curve (described later) and the values

obtained by XRF analyses, it was then possible to assign a volume

percent austenite to each compact.

3
Preparation of the Compacts

The austenitic and ferritic powders used to make this SRM were produced by water atomization techniques. The preliminary sizing of

the powders was done by the manufacturer, however, final sizing was

done at the National Bureau of Standards.

The austenitic stainless steel powder, passed the 250 mesh

screen, but was retained on a 325 mesh screen. This sieving yielded

the 310 stainless steel powder in the particle size range of 53 to

44 micrometers. The ferritic stainless steel powder passed a 325

mesh screen, but was retained on a 400 mesh screen. This yielded

430 stainless steel particles in the size range of 44 to 37

micrometers. Micrographs of the powders are shown in figure 1. Each

powder was then sampled and chemically analyzed. The results of the

chemical analyses are shown in Table 1.

Table 1. Chemical Analysis of Stainless Steel Powder.

(Content in Weight Percent)

Elements 310 Stainless Steel 430 Stainless Steel

Chromium 24.99 16.03

Nickel 20.41 0.09

Iron bal bal

Carbon 0.05 0.05

Manganese 0.20 0.10

Phosphorus 0.01 0.011

Sulfur 0.007 0.01

Silicon 0.75 0.40

The steps in the preparation of SRM 485a are shown in figure 2.

Since this SRM was a renewal of a previously prepared SRM, 485, the

powder for SRM 485a was taken from jars of already blended material

[3]. A total of 216 units were produced.

After three cycles of pressing and heat treatment (843°C, 30

minutes) in a vacuum, each compact was hand ground on silicon

carbide papers, and then polished on felt cloths using 6ym, and lura,

diamond paste with mineral spirits as the lubriciant. The

temperature of 843°C was chosen as the sintering temperature since

it was found [2] that at this temperature diffusion of the nickel

into the ferrite material was minimal. A micrograph of a compact,

at low and high magnifications, is shown in figure 3.

4
a

b

Figure 1. Scanning electron micrographs of the powders

used to produce SRM 485a. Mag. X160

a. as sized 310 stainless steel powder

b. as sized 430 stainless steel powder

5
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Figure 3. General microstructure of a compact.

a. Optical micrograph showing the white

austenite particles in the ferrite matrix.

Magnification x40.

b. Optical micrograph on an enlarged austenite

particle. Magnification x800.

7
As the final step in the procedure, each compact was polished

on microcloth using 3-alumina as the abrasive and distilled water as the lubricant. Upon completion of this step, the weight percent

nickel of each compact's surface was determined using x-ray

fluorescence spectrometry.

Characterization of SPM 485a

Certain basic XRF concepts were used in the determination of

the weight percent nickel in SRM 485a. These concepts will now be

discussed

.

Each compact consists primarily of high purity Fe , Ni , and Cr

powders and in the XRF analysis were treated as ternary unknowns.

Because of this, it was possible to analyse for all three elements

in each compact using the combined procedure of Rasberry-Heinrich

[4] and the Naval Research Laboratory [5] programs for the

correction of intere]ement effects.

An AXS, automated wavelength x-ray spectometer, employing a Cr

target with an Al filter, operating at 50 kv and 10 ma was used. To

reduce the effect of surface inhomogeneity of the austenite, each

compact was rotated with its axis tilted approximately 60° to the

beam, and examined for approximately 30 seconds.

For check purposes during XRF examination, three specimens,

each containing a different weight percent nickel, were prepared.

Specimen A, containing 1.439 weight percent nickel, was prepared in

the same manner as described previously; i.e., press, sinter, press,

etc. An extensive number of measurements using a quantitative

microscope (QM) were performed upon this compact and its area percent austenite value was known with high accuracy. Specimens B

and C (corresponding to the 5 and 30 area percent austenite

compacts) were made from pure chromium, nickel, and iron powders.

But unlike A they were vacuum melted into buttons and subsequently

machined to fit a holder. Filings from these compacts were

individually examined for nickel content using atomic absorption

spectrometry. The mean for six determinations of weight percent

nickel in B, was 1.511 with a standard deviation of 0.009.

Likewise, the mean for four determinations of nickel in C, was 6.478

with a standard deviation of 0.015 weight percent nickel.

Specimens A, B, and C were then measured for nickel content by

XRF along with each set of compacts whose weight percent nickel was

to be determined. These same samples were then used to monitor the

8
output of the unknown samples and were checks on the x-ray

spectrometer in that any deviation from the predetermined values of

A, B, and C indicated an abnormality in the analyses of the

unknowns

.

A summary of the XRF precision data on samples A, B, and C is as follows. The mean weight percent nickel for 20 XRF

determinations of specimen A was 1.439 with a standard deviation of

0.012 and relative standard deviation of 0.8 percent. The mean

weight percent nickel for 14 XRF determinations of specimen B was

1.518 with a standard deviation of 0.014 and relative standard

deviation of 0.92 percent. The mean for 14 determinations of

specimen C was 6.481 weight percent nickel with a standard deviation

of 0.028 and a relative standard deviation of 0.43 percent.

Following the XRF determination of the weight percent nickel

for each compact, the total population was ranked from lowest to

highest weight percent nickel in order to select compacts to be used

in the establishment of the calibration curve. The selection was

done in the following manner.

Arbitrarily, selection was started at the fourth lowest weight

percent nickel value. That compact and every 2 2nd compact was selected until the total population was exhausted. From the

population of 216 compacts, 13 compacts were chosen for the

calibration curve.

The calibration curve is a plot of the volume percent, which is

equivalent to the area percent [6] austenite value as determined

from QM procedures, along the ordinate and the weight percent nickel

value as determined by XRF along the abscissa. It is this

calibration curve which permits the assignment of a volume percent

austenite from a corresponding weight percent nickel (XRF) . The

development of the calibration curve follows.

In order to obtain a more accurate value of the area percent

austenite when using the QM method, it was necessary to examine each

calibration compact for surface porosity prior to the austenite

determination. In the QM determination for porosity, the surface was considered as being divided into individual quadrants, each

0.625 mm square. There are 34 of these quadrants in a row, and 34 rows. The area percent porosity for each quadrant was obtained and

entered into the computer's memory. An area equal to about 90% of

the sample's total area was subsequently used to establish a mathematical relationship which yielded a mean porosity, and a

9
standard deviation for each compact's surface. If a compact had

excessive porosity it was discarded. Once the porosity was determined for each compact, the compacts were stained.

In order to determine the area percent of austenite on the

compact's surface using QM methods, the austenite (the 310 stainless

steel component) had to "stand out" from the ferrite background. An

extensive amount of research was conducted in order to find a stain

that permitted this. One reagent, Murakami's satisfied our needs.

This reagent, 10 grams sodium hydroxide (NaOH) , 10 grams potassium

ferricyanide (K Fe (CN) ) , and 100 mL distilled water, who- heated

to about 100°C, stained the compact to the extent that under the

microscope the austenite (310) was unattacked and the ferrite was stained dark red. Hence it was now possible to use the QM to

determine the percentage of white particles (i.e. austenite) on the

components surface.

Following the same QM procedure described previously for the

porosity determination, each of the 13 calibration compacts were

stained with Murakami's reagent and the area percent austenite and

standard deviation determined.

In order to ascertain the extent of inhomogenei ty of the

austenite over the compacts surface, a normalization of the data

using the standard deviation was performed.

The equation used in the normalization procedure was (A-B)/S,

where A is the area percent austenite value for that quadrant, and B

and S were the mean and standard deviation obtained for the

compact's surface. The value obtained for each quadrant was subsequently plotted and a pattern was obtained which revealed the

extent of inhomogenei ty that existed on the compact's surface. If

the normalization revealed a surface with excesive inhomogeneity of

the austenite, the compact was discarded. None of the calibration

compacts showed any severe inhomogeneity to the extent that it would

be discarded.

Since a total of three hours was needed for each set of

observations only two orientations of the compact were used. The

characterization steps used for this SRM ore shown in figure 4.

The calibration curve was fitted using least-square regression

methods. The variance representing the fit of the calibration

curve ' s experimental data points was 0.04 area percent austenite.

10
X-RAY

FLUORESCENCE

ANALYSIS

216 COMPACTS

RANKED BY

WGT % NICKEL

SELECT 13

CALIBRATION

SPECIMENS

MEASURE

BY QM I POROSITYMETHODS

< STAIN: MURAKAMI'S

REAGENT

1 DETERMINE AREA

PERCENT AUSTENITE

BY QM METHODS

CORRECT AREA

% FOR POROSITY

ESTABLISH

CALIBRATION

CURVE

ASSIGN PERCENT

AUSTENITE TO

203 COMPACTS

195 COMPACTS

AS CERTIFIED

STANDARD

REFERENCE

MATERIALS

8 COMPACTS

RETAINED FOR

USE IN RESEARCH

AT NBS

Figure 4. Characterization steps for SRM 485a.

II
The correlation coefficient, a measure of the fit of the curve to

the data points was found to be 0.97. The equation for the curve using the 13 calibration points is as follows:

Volume percent austenite = 4.758W - 1.121

where W represents the weight percent nickel as determined by XRF

spectometry. The calibration curve, along with the data points used

to develop this curve, is shown in figure 5.

A question arose as to what uncertainity (i.e. standard

deviation) should be assigned to each SRM compact. It was noted

that two prime factors in this analysis were the QM determination

for area percent austenite itself and the associated porosity

correction.

A statistical analysis of the data revealed that the variance

of fit of the porosity correction contributed less than 2% of the

total variance of a single austenite determination. In addition, an analysis of the austenite values for replicate determination of the

calibration samples revealed that the variance associated with short

term replication errors was found to be less than 10% of the

variance of fit for the calibration curve. These results raised the

question whether the lack of fit of this calibration curve was due

to sample problems, long term errors (i.e., measurement

variability), or sample idiosyncrasies. Analysis of the data proved

the latter true, therefore a smaller uncertainty should be assigned

to the certified value since we are only dealing with the

imprecision of the calibration curve.

This conclusion was corroborated in an QM experiment performed

on a single sample over a period of 14 days. An analysis of the QM

measurements for a single 5% austenite sample showed a variance of

0.06 which is comparable to the variance of fit listed previously.

The equation to be used for the standard deviation (i.e.

uncertainty) of a single compact based on errors of the calibration

curve, is:

SD = (0.20) [1/13 + 3.0812 ( X-l . 2171)

2

] 1/2

[7]

Considering that this uncertainty encompasses the errors

associated with both the QM determinations of the porosity and the

austenite, and the errors associated with the XRF measurements, we believe the certified value assigned to each compact is within +_

12
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13
0.25 of the assigned volume percent austenite. The

of the percent austenite for the 195 compacts is shown

The values for the population ranged from 3.58 to

percent austenite.

Conclusions

SRM 485a is satisfactory for issuance as a standard for x-ray

determination of retained austenite in hardened steels. The range

for the 195 certified compacts was found to be 3.58 to 5.55 volume

percent austenite. The mean for this population was approximately

4.55 volume percent austenite. In using SRM 485a, care must be

taken not to alter the certified face. During x-ray diffraction

examination of the compact, it is highly recommended that the

compact be rotated in order to minimize the effect of possible

inhomogeneity of the certified surface. In addition, the user

should read NBS Technical Note 709 prior to using the SRM.

Acknowledgements

The authors thank J. Early and C. Interrante for their guidance

during the preparation of this SRM. In particular, Dr. Early's aid

in helping us solve our powder metallurgical problems was greatly

appreciated

.

We would also like to thank P. Pella of the X-Ray Fluorescence

Group for his effort in determining the nickel content of the

compacts. In addition, S. Low for his assistance during the

computer programming of the calibration curve and F. Biancaniello

who prepared the XRF check samples and heat treated all of the

compacts

.

Special thanks are due also to the statisticians who aided us

in the analysis of the data generated during all stages of the

preparations of this SRM. They are J. Filliben, H. Ku, and S.

Leigh. Thanks also are given to J. Mandel and R. Paule who helped

corroborate some of the results we obtained during the final stages

of our research on this SRM.

And finally to our secretaries P. Salpino and C. Gallupe, both

of whom worked so diligently on this manuscript.

distribution

in figure 6.

5.55 volume

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15
References

Bechtold, C. J. An X-Ray Diffraction Method for Determining

the amount of Austenite in an Austenite-Ferrite Mixture.

Natl. Bur. Stand. (U.S.) Tech. Note 709; 1972 February. 14p.

Interrante, C. G. and Hicho, G. E., A Standard Reference

Material Containing Nominally Fifteen Percent Austenite.

Natl. Bur. Stand. (U.S.) Spec. Publ. 260-73; 1982 January. 25p.

Hicho, G. E. et al., A Standard Reference Material Containing

Nominally Four Percent Austenite. Natl. Bur. Stand. (U.S.)

Spec. Publ. 260-25; 1971 February. 14p.

Rasberry, S. D., and Heinrich, K. F. J., Calibration of

Interelement Effects in X-Ray Fluorescence Analysis, Analytical

Chemistry, Vol. 46, Page 81, 1974 January.

Birks, L. S., Gilfrich, J. V., and Criss, J. W. , NRLXRF, A

Fortran Program for X-Ray Fluorescence Analysis, X-Ray Optics

Branch, Materials Science Division, NRL, Washington, D.C. 1977

(COSMIC) Suite 112, Barrow Harrow, Athens, GA. 30602. Project

Number DOD-00065 (July 1977 revision).

Delesse, A., "Pourdeterminer la composition des roches,"

Ann. des Mines B (1848), fourth series, pp. 378-388.

Walpole, R.E., Myers, R.H., Probability and Statistics for

Engineers and Scientists, 2nd editions, pp. 289-295.

fr U.S. GOVERNMENT PRINTING OFFICE : 1982 O—360-997 (2223)

16
U.S. DEPT. OF COMM.

niDI IAPDADUIP nATA BIBLIOGRAPHIC DAI A SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBS SP 260-76

2. Performing Organ. Report No. 3. Publ i cation D ate

August 1982

4. title and SUBTITLE standard Reference Materials:

A Standard Reference Material Containing Nominally

Five Percent Austenite (SRM 485a)

5. AUTHOR(S)

G. E. Hicho and E. E. Eaton

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8. Type of Report & Period Covered

Final

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City, State, ZIP)

Same as item 6.

10. SUPPLEMENTARY NOTES

Library of Congress Catalog Card Number: 82-600574

Document describes a computer program; SF-185, FlPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here)

This Standard Reference Material, SRM 485a, is a renewal of

SRM 485 , and is intended for the calibration of x-ray diffraction

equipment used in determining the amount of retained austenite in

hardened steels. The SRM was produced using powder metallurgical

techniques and involved blending 5 percent by weight AISI type 310

stainless steel powder (austenitic) with AISI type 430 stainless

steel powder (ferritic). From this blend, 216 compacts were

produced and subsequently examined for nickel content by x-ray

fluorescence spectrometry. A calibration curve was established

using 13 compacts randomly selected from the population of 216. The curve relates the weight percent nickel from x-ray fluorescence

measurements to the volume percentage austenite as determined by

quantitative microscopy measurements of area percent. The curve was

then used to assign the certified values to the remaining compacts.

This SRM may be used as an x-ray diffraction standard for retained

austenite or in very special cases as an x-ray fluorescence standard

for nickel content.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

austenite in ferrite; powder metallurgy; quantitative microscopy; retained

austenite standard; Standard Reference Material; x-ray fluorescence

13. AVAILABILITY

[x j Unl imited

[7~| For Official Distribution. Do Not Release to NTIS

[k ! Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402.

"

I Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

25

15. Price

$3.50

USCOMM-DC 6043-P80



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