Commerce

NISTIR 6797

National Institute of

Standards and Technology

Te

U.S.

chnology Administration

Department of MSEL

September 2001

FY 2001 PROGRAMS 

AND ACCOMPLISHMENTS

METALLURGY

DIVISION
On the Cover:

Cross-section of a nanoscale trench (dimensions of 90 

nm wide and 500 nm high), fabricated with an initial seed 

layer of copper, later filled with electrodeposited nickel. 

Transmission electron microscopy and compositional

mapping reveal salient features on the nanometer 

scale: electron energy loss spectroscopy was used to 

generate a compositional map (left), where the red color 

indicates copper and blue denotes the nickel region. The 

cross-sectional TEM image (right) reveals microstructural 

features (note the planar twins in the copper seed 

layer). Such information supports the development of 

new electrodeposition metrology techniques for micro- and 

nano-electromechanical devices (MEMS/NEMS).
National Institute of

Standards and Technology

Karen H. Brown, 

Acting Director

Technology

Administration

U.S. Department of

Commerce

Donald L. Evans, 

Secretary

MATERIALS

SCIENCE AND 

ENGINEERING

LABORATORY

FY 2001 PROGRAMS 

AND

ACCOMPLISHMENTS

METALLURGY

DIVISION

Carol A. Handwerker, Chief

Frank W. Gayle, Deputy

Jacob E. Ricker

NISTIR 6797

September 2001

ME

UNITED STATES OF AMERICA

DEPARTMENT OF COM RCE
1

Executive Summary

The mission of the NIST Metallurgy Division is to provide

critical leadership in the development of measurement methods,

standards, and fundamental understanding of materials behavior

needed by U.S. materials producers and users to become or

remain competitive in the changing global marketplace. As a

fundamental part of this mission we are responsible not only for

developing new measurement methods with broad applicability

across materials classes and industries, but also for working with

individual industry groups to develop and integrate measurements, standards, software tools, and evaluated data for specific,

technologically important applications.

With our mission in mind we establish our research priorities

through extensive consultation and collaboration with our

customers in U.S. industry and with our counterparts in the

international metrology community, using the following criteria:

ï Magnitude and immediacy of industrial need

ï Match to our mission

ï Whether the NIST contribution is critical for success

ï Anticipated impact relative to our investment

ï Our ability to respond in a timely fashion with high-quality

output

ï Opportunity to advance mission science

Using these criteria, our priorities are established by the

Divisionístechnical leadersthrough formal and informal means,

including industrial roadmapping activities, workshops, technical

meetings, standards committee participation, and individual

consultation with our customers. Within the context of industrial

relevance and potential impact of our research, technology trends

strongly influence the technical directions addressed in Metallurgy Division programs. We prefer to work in rapidly evolving

technologies, where advancesin measurementscience are needed

to understand the limitations on system behavior, and, thereby,

address issues where our contributions are likely to have an

impact on the course of technology.

The Division is composed of 39 scientists, supported by 6

technicians, 6 administrative staff members, and more than 30

guest scientists, organized into five groups that represent the

Divisionís core expertise in Metallurgical Processing, Electrochemical Processing, Magnetic Materials, Materials Structure

and Characterization, and Materials Performance. However, by

virtue of the interdisciplinary nature of materials problems in the

industrial and metrology sectors that we serve, Program teams

are assembled across group, division and laboratory boundaries

to best meet our project goals. We are committed to assembling

the expertise and resources to fulfill our technical goals with the

speed and quality necessary to have the desired impact.

Our current research portfolio focuses on fulfilling specific

measurement needs of the magnetic data storage, microelectronics packaging, automotive, aerospace, and optoelectronics

industries and on establishing national traceable hardness

standards needed for international trade. Our output consists of

a variety of forms, from scientific publications elucidating

fundamental materials behavior to measurement techniques,

standard reference materials, evaluated data, software tools, and

sensors for on-line process control.

Magnetic Data Storage:In the program on Materials for

Magnetic Data Storage, we are examining issues of magnetization

control in thin films through the development of microstructureprocessing-property relationships for giant magnetoresistance

(GMR) spin valves, ferromagnetic measurements and modeling

for magnetization control in thin films, a suite of SRMs for

magnetic calibration, an international working group creating

standard problems to test micromagnetics software used to

design magnetic structures, and measurements of magnetic

properties of dispersed nanomaterials. In the past year we have

started two new major projects in this program. As part of the

National Nanotechnology Initiative, a major collaboration

between MSEL and the Electronics and Electrical Engineering

Laboratory (EEEL) is developing new measurement methods and

models for magnetic damping, needed by the magnetic data

storage industry in the next 3-5 years to increase switching

speed. Our long-term project on GMR thin films is being

refocused into Spintronics, the use of spin-polarized electrons

for new devices and magnetic imaging. Through an extensive

network of university and industrial collaborators, we are using

the process measurement and control capabilities of the MSEL

Magnetic Engineering Research Facility to develop an understanding of the materials structure and processing issues in the

creation and transfer of spin-polarized electrons.

Microelectronics Packaging: In the MSEL Program on

Materials for Microelectronics, we are providing tools for

producing improved metal interconnects, from copper on-chip

interconnects at the nanometer scale to wire bonding to solder

joints on printed wiring boards. Our project on measurements

and modeling of electrodeposited copper for nanometer scale

chip interconnection technology has produced significant value

to the microelectronics community. In the two years since

beginning the project, we have developed a measurement

technique, a theory for control of interface dynamics, and

modeling software for predicting quantitatively the ability of

complex electrolytes to fill vias and trenches, and have transferred all of these to the appropriate industrial customers.

During the last six months we have demonstrated the generality

of the theory to electrodeposited metals other than copper, and

are examining itsrelevance to nanoelectromechanicalsystems

(NEMS). Our expertise in soldering alloys and processes has led

us to work with U.S. industry to develop alternative technologies mandated by international environmental legislation: US

manufacturers feel an urgency to have the ability to assembly

circuit boards with lead-free solders due to impending restrictions in Japan and Europe. We have been working with an

NCMS Consortium since 1997 and with a NEMI Task Force

since 1999 to evaluate the manufacturing and reliability of leadfree solders.

Automotive: Within the expanding program on the Forming of

Lightweight Materials, we are developing standard test methods

for sheet metal forming, measurements of surface roughness, and

physically based constitutive laws and measurement tools
needed to reveal them.This year we completed the development

of process models and data to improve the manufacturing of

metal matrix composites for drivetrain components and will

continue to work with our industrial partners to apply these

models to production. Our new projects are also done in close

collaboration with the automotive industry through formal

partnerships, such as the United States Council for Automotive

Research (USCAR) and the Partnership for a New Generation of

Vehicles(PNGV), and will help accelerate the design of forming

operations for lightweight materials such as aluminum, that will

ultimately improve fuel economy.

Aerospace and Power Generation: Within the Metals

Processing Program, we continue to help U.S. aerospace and

power generation industries improve responsiveness and

competitiveness by accelerating the design of manufacturing

processes for turbine engines. In the past year we have completed the thermodynamic database for use by casting foundries

in commercialsoftware for modeling solidification of eleven

component systems. Our reaction path analysis of multicomponent alloys, also developed this year, is being evaluated by our

industrial partners for use in alloy and process design.

Optoelectronics: As a result of a growing collaboration between

EEEL and MSEL, a Program on Wide-Band Gap Semiconductors

was established at the end of FY2001. Building on the existing

projects on metal interconnects for GaN (Metallurgy Division)

and on interface and bulk defects in GaN (Ceramics Division),

the EEEL-MSEL program will develop a comprehensive suite of

measurement methodsfor characterizing interface and bulk

defects limiting the application of GaN and related materials.

National Hardness Standards: In addition to industry-specific

goals, national and international standardization activities are a

continuing responsibility. As part of our core NIST mission, we

provide national and international leadership in the standardization of Rockwell hardness, the primary test measurement used

to determine and specify the mechanical properties of metal

products. Our responsibility requires us not only to develop the

US national standards with traceability from NIST through

NVLAP to secondary standards labs and US metals producers

and users, but also to provide leadership to ASTM Standards

Committees, the US delegation to ISO, BIPM, and OIML.

In addition to starting or expanding program areas in FY2001, we

have completed projects in Thermal Spray Processing,HighTemperature Fatigue Resistant Solders, Magnetization Control

in Thin Films, and Mechanical Properties of Multilayered and

Nanomaterials. In FY2002 the staff members and resources from

these projects (≈ 18% of the Division financial resources) will

shift to the areas described above. One possible new program for

FY2002 is being evaluatedin response to 2001 industrial

roadmapping and consortium building for powder processing,

particularly for automotive applications.

In addition to these programs there are three themes that cut

across these topical areas. Combinatorial/high-throughput

methods, computational materials science, and internet delivery

of NIST output will have a profound effect on the way we do

business in the next five years.Combinatorial methods are

designed to rapidly generate knowledge of materials properties

by the fabrication and measurement of extensive arrays of

extremely small sample elements, followed by data collection

and analysis. In the corporate R&D environment, the aim of

combinatorial research is the identification of new materials with

product-specific characteristics. Combinatorial methods are in

their infancy.Through the development of the NIST Combinatorial Methods Research Center, NIST has the opportunity to

contribute to the measurement infrastructure needed to exploit

this concept. Likewise, computational materials science will help

reveal increasingly complex relationships among materials

composition, nano and microstructure, and properties. The

MSEL Center for Theoretical and Computational Materials

Science plays a leading role in the development of software tools

needed in our programs and is directed by Metallurgy Division

staff.Software tools will continue to be a major part of our

strategy for delivering materials models, and the internet will be

the most important mechanism for transferring not only

software, but also, data, measurement methods, and fundamental

information on materials behavior.

In FY2001, Metallurgy Division staff members were recognized

for their outstanding contributions to measurement science and

technology transfer in the areas of solidification and magnetism.

For his pioneering work in crystal growth and solidification, Sam

Coriell was made a Fellow of the American Physical Society in

March 2001 and was awarded the triennial F. C. Frank Award

(co-shared with Don Hurle) by the International Organization

for Crystal Growth in Kyoto, Japan (July, 2001).William

Boettinger received the 2001 TMS Bruce Chalmers Award, in

New Orleans (February 2001), ìfor showing how fundamental

thermodynamic and kinetic models, with modern computational

power, lead directly to quantitative predictions of the microstructure generated by solidification.î Dr. Boettinger was also

named the Van Horn Lecturer at Case Western Reserve University, April 2001 and the Robert B. Pond, Sr. Distinguished

Lecturer at The Johns Hopkins University, May 2001. Robert

McMichael was awarded the NIST Samuel Wesley Stratton

Award for his internationally acclaimed research on measurements and modeling needed for magnetization control in thin

film; thisis NISTís highest award forscientific excellence.

In this report we have tried to provide insight into how our

research programs meet the needs of our customers, how the

capabilities of the Metallurgy Division are being used to solve

problems important to the national economy and the materials

metrology infrastructure, and how we interact with our

customers to establish new priorities and programs. We welcome

feedback and suggestions from our customers on how we can

betterserve their needs and encourage increasing collaboration

with them to this end.

Carol A. Handwerker

Chief, Metallurgy Division
3

Technical Highlights

The following Technical Highlightssection includes expanded

descriptions of research projects that have broad applicability

and impact.These projects generally continue for several years.

The results are the product of the efforts of several individuals.

The Technical Highlightsinclude:

ï Electrodeposited Copper for On-chip Interconnects: Tools for

the Microelectronics Industry

ï High Temperature Lead Free Solders: Tools for the Microelectronics Industry

ï Process Modeling of Low Cost Powder Metallurgy Technology for Particle Reinforced Aluminum

ï Standard Problems for Computational Micromagnetics

ï Particle Temperature Measurement Issues for Thermal Spray

Processing

ï NIST Research for Springback Predictability and Sheet Metal

Forming in the Auto Industry

ï Thermodynamic and Kinetic Modeling of Multicomponent

Alloys
Technical Highlights

4

Electrodeposited Copper for On-chip Interconnects:

The introduction of copper metallization and low dielectric constant materialsinto chip manufacture isthe most difficult interconnect

challenge of modern microelectronics.Current state-of-the-art chips have interconnects, or on-chip ìwiring,î as narrow as 150 nm to

180 nm with height to width ratios as great as 2:1. The filling of such trenches with copper can currently be accomplished by electrodeposition, but roadmaps for the semiconductor industry state needs for trenches as narrow as 50 nm with a 10:1 aspect ratio.

Researchers at NIST are providing the fundamental understanding required to achieve these goals.Models of the mechanism behind

superfilling during copper electrodeposition, and associated computational and measurement tools developed at NIST are addressing

the needs of the microelectronics community and are already in use by industry to streamline the development of electrodeposition

baths.

Tools for the Microelectronics Industry

The semiconductor industry has recently shifted from the use of

aluminum for interconnects, or on-chip ìwiring,î in integrated

circuits to copper because of its lower resistivity and higher

electromigration resistance. Electrodeposition has been found to

be the best means to deposit copper into the narrow, deep

trenches used for circuitry, since ìsuperconformalî deposition is

possible which fills very narrow trenches without porosity.

An electrolytic copper linewidth of 180 nm is now commonly

found in IC fabrication. Extension to the narrower and deeper

lines needed in the next generation of IC requires industrial

development of new electrolytes and deposition schemes.

Development of plating baths able to deposit in trenches with

aspect ratios (height/width) as high as 10:1 is limited by the

necessity of time-consuming, resource-intensive evaluations with

actual nano-scale patterned substrates. Such experiments require

microstructural characterization by focused ion beam (FIB),

scanning electron microscopy (SEM) and transmission electron

microscopy (TEM) on an individual basis.

NIST efforts address metrology needed for superconformal

deposition that minimizes this time-consuming experimental

work. The mechanism responsible for superconformal electrodeposition of copper in high aspect ratio features has been

determined. Simulations from a model based on this mechanism

have been shown to predict results of electrodeposition filling

experiments in trenches as small as ≈90 nm wide and≈450 nm

deep. No fitting parameters are required to model this behavior.

This work has built upon two recent Metallurgy Division

discoveries. First, an electrolyte was developed that yields

superconformal electrodeposition of copper. Second, voltage

cycling-induced hysteresis of copper deposition rate on flat

copper specimens was shown to be indicative of the ability of an

electrolyte to yield superconformal deposition. Superconformal

deposition was shown to occur only when both an inhibiting

additive and an accelerating additive are present in the electrolyte.

Kinetic parameters for particular electrolytes are obtained from

the cyclic voltammetry described above. These kinetic parameters

describe the rate at which the accelerating additive accumulates on

the copper surface, displacing the inhibiting additive that retards

local copper deposition.They also quantify the impact this

accumulation has on the local copper deposition rate.

The NIST Curvature Enhanced Accelerator Coverage (CEAC)

model of superconformal electrodeposition uses these parameters

to predict filling of features. Most importantly, this model

recognizes changes of local coverage of accelerator on the interface

both by accumulation from the electrolyte and by changes of the

local area upon which the accelerator has adsorbed. Accumulation

of accelerator at the bottom of superfilling trenches is dominated

by this geometrical effect.Accelerator coverage on the bottoms of

Figure 1. (top) Experimental current-voltage curves for

copper deposition on a flat copper substrate in electrolytes

containing a deposition inhibiting additive plus varying

amounts of an accelerating additive. Note the hysteresis

and the saturation at high concentrations.(bottom) Fit of

accelerator accumulation used to extract kinetic parameters for the Curvature Enhanced Accelerator Coverage

(CEAC) model of superfill.

fine features thus increases as the surface area decreases during

copper deposition.This, in turn, accelerates copper deposition.

The positive feedback cycle results in filling of the trench from

the bottom upward, i.e., superconformal deposition. The finer

the feature, the more important area change can be - it requires an

appropriately designed electrolyte composition and appropriate

deposition conditions to take full advantage of this effect.

This research, largely conducted in the past two years, has

already resulted in accomplishments and impacts of consequence

to the microelectronics industry.These include:

ï Explained the significance for superconformal deposition of

hysteresis in deposition on flat copper substrates.

ï Showed how the hysteretic behavior can be modeled to extract

kinetic parameters describing the rate and impact of

additive accumulation on the copper/electrolyte interface.

(Figure 1.)
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On This Topic:

5

Figure 2 (Left side) Superfill results for accelerator

concentrations of (0, 0.5, 5 and 40) μmol/L (top to bottom). A

window for superfill exists around 5 μmol/L concentration.

(Right side) Predictions of the newest computer code for the

three finest features at (0.5 and 5) μmol/L (top and bottom).

Inclusion of diffusional effects results in voids indicating

failure to fill. Simplifications in the first NIST model of

superfill resulted in seams in features that failed to fill.

ï Developed the Curvature Enhanced Accelerator Coverage

(CEAC) model that explains how accumulation of

accelerator is impacted by changing area at the bottoms of

fine features and how this effect causes superconformal

deposition.

ï Developed computer codes to predict superfilling of fine

features using only the results of cyclic voltammetry

studies with flat copper substrates. The most recent of

these codes describes diffusion of the cupric ion and

accelerator through the electrolyte, interface kinetics

affecting transfer onto the copper/electrolyte interface,

motion of the interface, and the impact of interfacial area

change on accelerator concentration and local copper

deposition rate.

This information has been conveyed to U.S. industry, academia

and other national laboratories through eight presentations given

in professional society meetings attended by industry representatives from electrolyte suppliers, analytical tool, plating tool

and chip manufacturing industries.

In FY 2001 this work has also been disseminated through

ï Refereed journal publications (3) showing the predictive power

of the CEAC model by comparison of experimental filling

results with model predictions. These publications are

already being cited in the literature by industry and

academia.

ï Invited talks (2) at leading electrolyte and tool manufacturers.

ï Industry-initiated collaboration with a major chip manufacturer.

ï Mailing of publications to industrial and academic researchers

in the field of copper electrodeposition (≈50).

In the coming year we will address several short and long term

objectives:

ï Examine the aspect ratio and dimensional fill limitations of the

model electrolyte.

ï Study additives for inhibiting and accelerating deposition of

metals other than copper.

ï Probe the generality of the CEAC model by studying

superconformal deposition of metals other than copper.

ï Disseminate modeling codes on the web page of NISTís Center

for Theoretical and Computational Materials Science.

Through this work, researchers at NIST are providing the

electrodeposition community with a better understanding of the

mechanism by which organic addition agents lead to

superconformal deposition of sub-micron features. It is

anticipated that this will lead to the development of on-line

monitoring tools that will allow industry to determine additive

efficacy and consumption in commercial copper plating baths.

ì We are very excited about the capabilities of this tool, and we

want to put it to use ASAP!!! Yet another example of NIST

innovation helping industrial competitiveness!!! ì

ó Dennis Buss, Vice President, Silicon Technology Development, Texas Instruments

ìThis is exactly the kind of project where NIST can add to the

fundamental understanding of our technology and help us all

move forward.î

ó Tom Ritzdorf, Director of ECD Technology, Semitool, Inc.

D. Josell, D. Wheeler, W. H. Huber, and T. P. Moffat, ìSuperconformal Electrodeposition

in Submicron Features,î Phys. Rev. Lett. 87, 016102 (2001).

T. P. Moffat, D. Wheeler, W. H. Huber, and D. Josell, ìSuperconformal Electrodeposition

of Copper,î Electrochem. and Solid-State Lett. 4, (4) C26 (2001).

T. P. Moffat, D. Josell, and Daniel Wheeler
Technical Highlights

6

Microelectronics assembly has, from its infancy, been based on

tin-lead eutectic solder, a mixture of tin and lead that melts at

183C. In recent years there has been an increasing need within

the avionics, telecommunications, oil exploration, and automotive industries for solders which perform reliably at ever-higher

temperatures, temperatures which approach the melting point of

tin-lead eutectic. Such harsh environment applications require

solders with melting points higher than that of tin-lead eutectic

in order to achieve the required reliability. In addition, recent

legislative and marketing pressures in Europe and Japan have

pushed U.S. manufacturers to pursue lead-free solders for all

microelectronics applications, leading to the double challenge of

developing high temperature, Pb-free solders.

In 1996, the National Center for Manufacturing Sciences

(NCMS) initiated the High Temperature Fatigue Resistant Solder

Project to address the need for high temperature, high reliability

solders in response to a need identified and defined by a number

of companies in the microelectronics, automotive, avionics and

telecommunicationsindustries.

The resulting consortium, consisting of eight industrial corporations, academia and NIST, has completed its four-year program.

Consortium membersincludeAllied Signal,Amkor Technologies,

Delphi Delco Electronics Systems, Ford Motor Company,

Heraeus Corporation, Indium Corporation, Johnson Manufacturing, Rockwell International Corporation, Iowa State University, and NIST.The goal of the project was to determine

whether highly reliable, nontoxic, cost-effective substitutes could

be found for high lead and Sn-Ag eutectic solders in harsh

environments.This goal required gaining extensive knowledge of

the properties and manufacturability of alternative solder alloys.

The project members initially identified about 200 candidate

solder compositions.Experimental measurements on 52 of the

alloys were made to characterize melting and wetting behavior

and reactions with substrates during prolonged exposure at high

temperature. A thermal-fatigue screening test was run on 12 of

the most promising Pb-free alloys. From these candidates, 7

alloys were chosen for full scale manufacturing and reliability

trials, utilizing a variety of surface mount components cycled up

to 160C.

The project was divided into two major task groups ñ the Alloy

Selection and Characterization Group and the Testing Group. In

addition to chairing the Alloy Task Group throughout the

project, NIST performed various other critical roles. As part of

the initial assessment, NIST surveyed 12,000 binary and ternary

metallic phase diagrams to identify eutectic compositions and

congruently melting compounds with potential as candidate

solder alloys. NIST had a leadership role in formulating the

down selection criteria,and conducted the metallurgical analysis

and metallography for the project. NIST also coordinated the

High Temperature Lead-Free Solders:

Tools for the Microelectronics Industry

Increasing global concern about the environment is bringing regulatory and consumer pressure on the electronics industry in

Europe and Japan to reduce or completely eliminate the use of lead in most products. Worldwide, the microelectronics industry has

made great progress toward application of lead-free solders in the relatively benign conditions of consumer electronics. In 2001, the

National Center for Manufacturing Sciences (NCMS) completed the High Temperature Fatigue Resistant Solder Project to address

the industrial need for lead-free solders in harsh environments, such as encountered in automotive under-the-hood applications.

NIST played a leadership role in this research project, chairing the alloy task group and providing definitive, timely materials data

and critical analyses needed for evaluating candidate solders, leading to the development of new lead-free solders with excellent

performance, outperforming industry-standard compositions.

Figure 1. Plastic leaded chip carriers on ceramic (top) and

polymeric (bottom) substrates assembled with Pb-free

solders and surface finishes.

final analysis of the data, the determination of conclusions and

recommendations, and the writing of the NCMS final report.

The High Temperature Fatigue Resistant Solder Project was

summarized in an invited article in Advanced Materials and

Processes, April 2001, written by NIST staff. In addition, a

technical paper presented by NIST was selected as one of the 5

best papers out of 58 presented at the TMS 2001 Annual

Meeting Symposium on ìRecent Progress in Pb-Free Solders

and Soldering Technologies.î This distinction included electronic
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7

publication on the web through e-JOM as well as publication in

the June issue of JOM journal (Journal of Metals). Major

conclusions of the High Temperature Fatigue Solder Project are:

ï Six lead-free alloycompositions were identifiedthatexhibit

fatigueperformance during ñ55C to +160C cycling of

a wide range of components which is superior to the

industry standard eutectic Sn-Ag alloy.

ï The seven lead-free alloys cycled with ball grid array (BGA)

packages through 0C to +100C and ñ40C to +125C

cycling all outperformed Sn-Pb eutectic solder.

ï Manufacturing of these alloys and generation of solder pastes

does not present any special problems.

ï Present manufacturing equipment can be used to build

assemblies in many cases.

ï Alloy costs will not be a major factor .

Figure 2.Reliability Test Vehicle used to test

manufacturability and thermal fatigue resistance of a

variety of surface mount components on printed circuit

boards.

Figure 3Microstructure of an experimental alloy.

ìNIST personnel brought unique skills and expertise to both

NCMS projects [the Lead-Free Solder Project, and the High

Temperature Fatigue Resistant Solders Project].Without the

support from NIST, both these projects would have extended

over a longer period of time and would have been more costly to

the projectís industrial partners.î

ó Duane Napp, NCMS Program Manager

NCMS High Temperature Fatigue Resistant Solder Project Final Report, NCMS, Ann

Arbor, MI, 2001. Frank W. Gayle, ìFatigue-Resistant, High Temperature Solder,î Advanced Materials & Processes 159 (4), April 2001, p. 43-44;Frank W. Gayle, et al., ìHigh

Temperature Lead-free Solder for Microelectronics,î JOM, June 2001, p. 17-21.
Technical Highlights

8

Reducing the mass of certain engine components, such as

connecting rods andtransmission fluid gerotor pumps, can have

a large effect on engine efficiency and responsiveness far beyond

the simple weight reduction. For this reason, these components

were targeted by the U.S. Automotive Materials Partnership

(USAMP) as candidates for their program on Low Cost Powder

Metallurgy Technology for Particle Reinforced Aluminum.

Currently, these components are produced from steel powder.

NIST provided models of many of the various processes that

had to be modified to switch to aluminum and these contributions are summarized here. Dr. John Allison of Ford and former

Chairman of the USAMP Advanced Metals Division wrote of

the NIST contributions, ìThe modeling effort Ö is an integral

and very critical aspect of this program,î andì[NISTís] impact

could eventually extend well beyond this particular project.î

In collaboration with the Micromechanics Centre at Cambridge

University, a physically based constitutive law for consolidation

of reinforced powder was developed. Its validity was tested at

NIST on powders relevant to the USAMP program and found to

accurately describe the consolidation behavior of reinforced

powders. This model was implemented in a finite element model

to predict the behavior of parts having complex shapes.

USAMP funded a small business to develop the model for the

specific shapes of interest to the program. The computermodeling package is now available in a user-friendly, commercially supported form.

Figure 2. Finite Element Model of Gerotor Die filled with

powder that is modeled using the constitutive equation and

data developed in this project.

Process Modeling of Low Cost Powder Metallurgy

Technology for Particle Reinforced Aluminum

Major research efforts within the U.S. auto industry are driven by the need to reduce the weight of future vehicles to meet U.S. Council

for Automotive Research (USCAR) and Partnership for a New Generation of Vehicles (PNGV) goals. This can most readily be

accomplished by the substitution of lightweight materials for the heavy materials currently used.With the completion of this project,

NIST has assisted industry in developing a low cost powder processing technology for aluminum alloy and particle-reinforced

aluminum parts that may be substituted for iron-based powder metallurgy products. Efforts to mass produce acceptable parts using

press-and-sinter and direct powder forging are underway. The NIST part of this effort focused on modeling each step in these consolidation processes from powder to fully dense part.Modeling provided a basis for rapidly designing successful processes.

As part of the validation process, NIST developed databases for

the materials of interest.These databases included the consolidation behavior ofthe various ductile phases as a function of

temperature and the effect of various concentrations of

reinforcement on this behavior.Additional modeling was carried

out at NIST to provide guidance to the efforts. For example, one

direction undertaken was to develop materials based on blends

of soft, unalloyed aluminum powder with hard, alloyed

powders.A natural question arose as to what minimum amount

of unalloyed aluminum was needed to achieve a given level of

density during cold pressing. The modeling approach was

modifiedtoprovide some guidance and the nomograph in

Figure 3 was the result. This particular figure predicts the

Figure 1. Parts targeted by the USAMP project on Low Cost

PM Technology for Particle Reinforced Aluminum.

amount of aluminum needed to reach a relative density of 0.90 as

a function of the size of the soft aluminum powder particles

relative to the hard powder particles under a pressure of620

MPa(45 tsi).The figure can be easily changed to address

particular industrial requirements. It emphasizes the importance

of particle size on the resulting behavior.

Another area in which process modeling helped was in sintering.

In contrast tosome other systems,sintering in powder

metallurgy is carried out mainly to develop strength. No change

in density is normally desired since this results in distortion or

cracking.The modeling approach adopted for this project

attempted to simply predict the time and temperature required

to homogenize the elemental blends into the intended alloy.

Again, a strong dependence on particle size was found. This

provided guidance to the powder suppliers as to what sieve

sizes were desireable to blend to achieve homogenization on an

industrial timeframe. NIST provided assistance to this project

when an unexpected issue ñ powder flowability ñ stood in the

Figure 3. Effective of pure aluminum on compressability of

prealloyed powder.
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Figure 4. Fluidized feedshoe and associated equipment for

improving the flowability of fine or irregularly shaped

powders into die cavities.

Figure 5. Weight distribution for gears made with and

without the fluidized feedshoe technology.

way of industrial implementation. Mechanical properties studies

showed that these materials would only be successful if a

relatively fine SiC powder were used as the reinforcement. NIST

research showed that fine aluminum powders were required to be

blended with such fine SiC powders. However, the resulting

mixture would not flow down commercial feed tubes or through

feed shoes into the dies for pressing. Using the Small Business

Innovative Research (SBIR) program at NIST, modeling of

powder flowability was carried out in conjunction with a small

business. One outcome of this work was a means of using a gas

to lubricate the powder particles and make flow possible.This

technology was incorporated into the fluidized feedshoe shown

in Figure 4. It has been used to make many sorts of powders

flow from cosmetic and medicinal powders to ultrafine carbide

powders for tools. The fluidized feedshoe is now commercially

available from a powder press manufacturer as an accessory to

their presses. It is being used by a number of U.S. companies to

make parts usingfine powders or better parts using existing

powders. One unexpected outcome of the technology is shown

in Figure 5 ñ improved part uniformity. This figure shows the

improved mass uniformity using the fluidized feedshoe. This

mass uniformity translates into improved dimensional tolerances

for PM parts.It also permits more rapid feeding and increases

productivity.

R. J. Field, T. Zahrah, and Y. Shim
Technical Highlights

10

Micromagnetic modeling is used to compute magnetic domain

structure and dynamics in magnetic materials starting from

sample morphology, materials properties, and applied fields.

This type of modeling is a very important part of device design,

particularly for read heads in hard drives and magnetic random

access memory (MRAM) cells. Micromagnetic modeling has

also contributed a large amount to our understanding of recording

processes and noise in magnetic recording media.

Our involvement in standard problems was designed to fill a

need in industrial and academic labs for a method to check the

accuracy of micromagnetic modeling software, usually developed

independently in each lab, and tested by parts, energy term by

energy term. Beyond finding ìbugsî in software, the standard

problems also provide benchmarks for modeling practice which

can help to avoid errors introduced by overly coarse

discretization, or loose convergence criteria.

The standard problems were one of two action items recommended in the initial workshop of the micromagnetic modeling

activity group (μMAG) that drew approximately 100 attendees.

This workshop was held as an evening session at the 1995

INTERMAG conference, and was sponsored by MSELís Center

for Theoretical and Computational Materials Science.

The standard problems were designed with the following criteria

in mind:

ï Geometries and materials properties should be similar to ìrealworldî applications.

ï Specifications should be loose enough to allow different

computational methods to be used, but tight enough to

ensure that results can be meaningfully compared.

ï The scope of the problem should be small enough that it would

not be too expensive in manpower or computational time

to compute a solution.

ï The problems should be significant enough to allow solutions

to be published in the usual scientific journals.

The specifications for the standard problems presented below

were all written by NIST, based on suggestions received from

members of the micromagnetic modeling community.Solutions

to these problems were calculated by NIST and by contributors

from across the globe. Detailed specifications and results are

available on the μMAG website:

Standard Problem #1 is a 1 mm x 2 mm x 20 nm rectangle of

material with properties to mimic Permalloy, and the requested

results are hysteresis loops and magnetization patterns obtained

at zero applied field.When the first few submitted results were

Computational micromagnetic modeling is the dominant method used to calculate magnetization patterns and dynamics in materials

and devices on length scales from nanometers to several micrometers. The demand for accurate micromagnetic modeling is accelerating as the industry wide trend of over 60% per year increase in bit density for hard disks creates increasing demands on our ability to

predict and control the magnetization in materials and devices. Development of new magnetic devices including magnetic random

access memory (MRAM) increasingly depends on the behavior of magnetization on nanometer length scales. Our activity in computational micromagnetics,started in 1995, is designed to facilitate testing of micromagnetic computer codes by specifying and publicizing a

number of standard problems and then computing, collecting, comparing and publishing solutions to these problems.

Standard Problems for Computational

Micromagnetics

http://www.ctcms.nist.gov/~rdm/mumag.html

found to have wide disagreement, we quickly decided to protect

the contributors by collecting results anonymously. Nine

solutions were collected and posted on the mMAG website with

widely varying results. While Standard Problem #1 may be

regarded as a failure regarding its use in checking micromagnetic

software, it remains important as the first attempt at a public

standard problem in micromagnetics, and as a computational

challenge.

Standard Problems #2 and #3 were developed from discussions

at a second μMAG workshop held as an evening session of the

1998 Joint MMM-INTERMAG conference.

Standard Problem #2 is a variable-sized bar of material with

aspect ratios of 5:1:0.1. All lengths are expressed in units of the

magnetostatic exchange length, which is a function of the material

exchange stiffness constant and the magnetization. The results

collected for comparison are the coercive field and the remanant

magnetization as a function of the width of the rectangle.

Four solutions for Problem #2 have been collected and posted on

the μMAG website. Three of these results were first presented

at the MMMí99 conference in a special evening session on

micromagnetic standard problems. The attendees, numbering

more than 100, were delighted to see good agreement between

results calculated independently and by different methods. The

fourth Problem #2 result is our revision of our earlier result and

an analytical result for the coercivity in the limit of a small

particle.

Standard Problem #3 is specifically designed for 3-D calculations. The object is to calculate the minimum energymagnetization configuration for a cube of material with some uniaxial

anisotropy. For small cubes, the minimum energy configuration

is a ìflowerî state, and for larger cubes, the expected minimum

energy state is a ìvortexî state. The result collected for

comparison is the critical length of the cube edge for which the

energies of the two states are equal.One of the submitted

results revealed a surprise ìtwisted flower stateî which has

lower energy than either the flower state or the vortex state.

A comparison of coercivity values calculated for Standard

Problem #2.
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Standard Problem #4 is designed to test dynamic calculations

based on Landau-Lifshitz-Gilbert equations of motion. The

details of magnetization dynamics are becoming more important

for magnetic recording as data rates increase, and for MRAM

development, the details of switching behavior are critical.In

Problem #4, switching is calculated for a 500 nm x 125 nm x

3†nm rectangle of Permalloy starting from an equilibrium state in

zero applied field. One of two specifiedapplied fields are

turned on to induce switching, and the magnetization dynamics

are traced as a function of time. For one applied field, the

magnetization rotates in the same direction everywhere in the

sample, but for the other, the switching is more complicated,

with rotation starting in one direction near the ends of the bar

and in the other direction in the middle.

Diagrams of the flower state and vortex state from the

specification for Standard Problem #3.

Standard Problem specifications and results are published on the μMAG web page:

http://www.ctcms.nist.gov/~rdm/mumag.html

R. McMichael, (NIST/MSEL) and M. Donahue and D. Porter (NIST/ITL)

(a)

(b)

Snapshot of the magnetization during reversal (a) and (b)

magnetization dynamics from Standard Problem #4.

These micromagnetic standard problems provide computational

physicists and engineers in industry and academia with

benchmarksfor micromagnetic software development and

micromagnetic modeling practice. By assuming a leadership role

in the field, by providing standard problem specifications and by

providing electronic access to submitted solutions including our

own solutions, we have raised the quality of micromagnetic

modeling, and we have provided a means to assess the reliability

of micromagnetic modeling resultsfor modelers and for their

customers. NIST could not have made these standard problems

without the contributions of colleagues across the globe,

especially in Europe, who computed and provided solutions to

the standard problems.
Technical Highlights

12

Particle Temperature Measurement Issues for

Temperature and velocity measurements of particles and droplets provide important process parameter data for modeling and control

of the Thermal Spray (TS) coating process. Accurate measurement of particle temperature using non-contact temperature sensors

depends on the use of appropriate sensor calibration procedures. In this project completed this year, we demonstrated several

methods for calibrating two-color optical pyrometers including a high temperature blackbody and a tungsten ribbon standard lamp as

calibration sources. Comparing the different methods shows that the absolute temperature and wavelength-dependent emissivity of any

non-blackbody calibration source must be well known to obtain an accurate sensor calibration. Further, emissivity data on individual

heated particles were shown to improve the accuracy of particle temperature measurement by two-color pyrometry.

Thermal Spray Processing

In the air plasma thermal spray (TS) process for producing

coatings, solid particles are injected into and heated by a plasma

jet. From the beginning of the injection process through

interactions with the plasma jet, the particles will have wide

ranges of temperatures, velocities and trajectories that then

translate into a microstructure as the impinging particles solidify

to form the coating layer. Particle diagnostics within the TS

plume are favored as a means of improving process reproducibility because they yield information on both the physics of the

coating process itself and the process variability. TS particle

sensors fill two roles. They are used in quality control operations to ìtuneî thermal spray torches to ensure consistent

coating deposition. They are also widely used in thermal spray

research, including developing parameter sets for new spray

materials, evaluating improved spray torches, and studying

relationships between processing conditions and coating

properties. Such diagnostics make rational process improvement

possible, a difficult endeavor when only process settings, such

as torch power or gas pressures, or a final coating property can

be measured.

These important particle data are provided by non-contact

optical temperature and velocity measurements from sensors and

software that process light intensity readings from particles

within the TS plume. Two-wavelength ratio pyrometry is

usually employed for measuring particle temperatures because it

is insensitive to particle size, absolute emissivity and particle

position within the sensor field of view. It requires only that the

particle emissivity not vary over the operating wavelengths of

the sensor, known as the graybody assumption. Several

approaches are now available: 1) Single particle, non-imaging

sensors that collect data one particle at a time and average the

results from several particles at the same location or, by moving

the sensor position, within a defined area; 2) Particle ensemble,

non-imaging techniquesthat acquire data related to some average

temperature and velocity of the particle stream; and 3) Imaging

pyrometry that measures multiple individual particles simultaneously by focused imaging of a large volume of the spray

plume. Temperature measurement using these optical techniques

requires a calibration procedure to provide the appropriate

coefficients for conversion of the measured light intensities to

temperature values.

In the last few years NIST has been working to assess industry

needs and address several of these non-contact temperature

measurement issues. Industry needs have been determined by

reviewing published papers and reports, discussions with

colleagues, and through workshops (several sponsored by NIST)

focused on issues related to the TS coating industry. At the

Workshop on Non-Contact Thermometry held at NIST in

October, 2000, the importance of absolute temperature

measurement and traceability for industrial applications was

discussed. At the recent workshop on Thermal Spray Process

Reliability held at NIST in January, 2001, the consensus was

that the reproducibility and reliability of TS coatings need to be

improved in order to realize the full benefits of this technology.

As a possible solution, representatives of industry and academe

expressed interest in combining process measurements with

coating property data into an integrated database that would

provide guidance in the use of thermal spray technology to

coating developers and potential users alike. Their hope is that

improved process measurements, coupled with increased

awareness of thermal spray as a well-understood means for

enhancing surface properties and synthesizing novel materials

will expand its broad-based benefit. A report is available that

includes the workshop presentations and discussions (NISTIR

6776.)

During the Thermal Spray Process Reliability workshop,

specific questions were raised concerning the calibration of

particle temperature sensors, and how the properties of the

particles being measured (e.g., composition, oxidation, etc.)

affect the accuracy with which temperature is determined. In

response, the Metallurgy Division has taken steps to outline

recommended calibration procedures for thermal spray particle

temperature sensors and to provide particle emissivity data for

improving temperature measurement accuracy.

Current work on calibration procedures has involved evaluating

the use of tungsten standard ribbon lamps as calibration sources

for two-color pyrometers. Tungsten lamps are used because

they are readily available, but because of their deviation from

graybody behavior they are not as suitable as an ideal blackbody

calibration source. Errors caused by the deviation from graybody

behavior are shown in Figure 1. They can be corrected using

tungsten emissivity data available in the literature, or by direct

measurement of the emissivity of the lamp by spectroscopy.

An additional calibration issue involves the fact that tungsten

lamps are typically calibrated to serve as radiance temperature

standards. These lamps are appropriate for calibrating singlecolor but not two-color pyrometers. The reason is that the

radiance temperature scale, which is defined for a perfectly

radiating surface (e.g., blackbody, ε = 1), is meaningful only at

the calibrated wavelength of the lamp, and therefore it cannot be

transferred to a pyrometer that operates at two wavelengths.

Absolute temperature of the filament must be determined and

used instead. Radiance temperature can be converted to absolute

temperature using the normal spectral emissivity of tungsten at

the lamp wavelength. Though easily addressed, this error is often

overlooked, resulting in serious systematic errors in particle

temperature measurements. Figure 2 shows the errors incurred

using radiance temperature rather than absolute temperature in

the calibration of a generic two-color pyrometer. The accuracy of
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13

Figure 1. This figure shows the effect of the deviation from

graybody behavior of the calibration source for a two-color

imaging pyrometer.

Figure 2. This graph shows the error associated with the

use of radiance temperature rather than true temperature

in the calibration of a generic two-wavelength pyrometer

operating at λ1 = 700†nm and λ2 = 900†nm. The calibration

source has a normal spectral emissivity of ε = 0.43.

these corrections using literature data is evaluated by comparing

the resulting calibration to calibrations obtained using a blackbody.

With the transfer of these results throught the technical

literature, our project on Thermal Spray Processing has now

been successfully completed.

S. D. Ridder, Thermal Spray Process Reliability: Sensors and Diagnostics, NISTIR 6776,

August, 2001. S. D. Ridder, F. S. Biancaniello, S. P. Mates, and R. D. Jiggetts (NIST/

MSEL)
Technical Highlights

14

One area that has long been a concern to the auto industry, but

has become a major concern due to the increasing pressure to use

lighter materials and reduce die development time and costs, is

springback. When the material being formed is a low strength

material,springback from the die face following stamping will be

relatively small and can be accounted for by experience and

during die tryout. This sitation is no longer the case - new, higher

strength steels and aluminum alloys have greater springback

magnitudes; designs of increased complexity are often accompanied by unpredictable springback magnitudes and directions; and

demands continue for reduce time to market.These factors

point to the need for spingback to be addressed earlier in the die

design, development and tryout process.

The industry thus needs better predictive models based on a

sound fundamental understanding of springback phenomena and

appropriate measurements, standards, and data. In response to

this need, a consortium of aluminum and steel producers, a

software company, and the three automotive manufacturers and

their suppliers received support from NIST for 5 years to

develop finite element software that can predict springback. The

resulting ATP Springback Predictability Project (SPP) greatly

reduced the uncertainty in springback predictions by finite

element models and brought a higher level of understanding of

springback to the sheet metal forming industry.The ATP/SPP

concluded in October 2000.

Figure 1. Plaque given to NIST staff that presented

research results to SPP during the ATP funded phase.

NIST Research for Springback Predictability and

Sheet Metal Forming in the Auto Industry

Market and regulatory pressures are driving the automotive industry to develop and use new materials and manufacturing methods

while competitive pressures are forcing them to keep costs low and reduce the time required to bring a new vehicle from concept to

market. Current automotive production technology has evolved around stamping of relatively low strength steel to form automotive

body panels and components.While this approach was acceptable when designs and materials were not changing dramatically, this

process of die design and tryout may limit U.S. automakersí abilities to utilize new materials in their designs or to bring a new design

rapidly to market. NIST has been working with the automotive industry to improve the die design process and reduce die development

and tryout costs.

The Metallurgy Division was involved with this project from its

beginning, carrying on a set of parallel, non-proprietary research

projects complementing SPP activities.There were three

projects: fundamental dislocation studies, deformation-induced

surface roughening, and standard test methods.The most

significant contributions by these projects to a deeper understanding ofspringback and forming in general were:

ï A model based on percolation theory was derived to describe

and predict the movement of dislocations through a workhardened microstructure.

ï Analyses and experimental measurements demonstrated the

importance of anelastic effects in plastic deformation and

springback.

ï A new experimental technique, ultra small angle x-ray scattering

(USAXS) imaging, was shown to hold promise as a useful

tool for studying dislocation structures in situ.When a

USAXS scan is made, the data are in the form of a slitsmeared scan through a single-direction in reciprocal

space.Once a scan is made, interesting features can be

identified and the analyzer crystals can be set to a specific

location on the scattering curve.The sample can then be

imaged through the analyzer stage. What makes this

technique potentially useful is that USAXS imaging can

select weak scattering components (such as dislocations)

and form the image from just these components.

Figure 2. The inner panel of a car hood was one of the

components targeted by industry for in-depth investigation

of its springback behavior.
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ï The influence of microstructural and compositional differences

on the roughening rate during uniaxialstraining was

determined. A generic model for deformation-induced

surface roughening was developed.

ï A biaxial test facility was set up at NIST to generate well

defined multiaxial strain states to simulate forming

conditions and develop standard measurement methods.

ï A well attended conference on the fundamentals of dislocations

and plasticity was held at NIST to provide U.S. industry

with the most up-to-date science.

R. J. Fields, T. Foecke, L. E. Levine, and R. E. Ricker (NIST/MSEL)

Figure 3. Springback measured in 3-point bend showing

linear and non-lined components.

The Springback Predictability Project and joint venture

partnership was considered so successful that industry decided

to continue its activities with their own funds after ATP support

ended. A poll was taken of the industrial members to decide the

assignment of priorities to a list of17 activities.Continued

interaction with the NIST forming research effort was ranked

second highest in priority.

NIST has responded to this request from industry. The three

projects that arose from the initial industrial interaction form the

basis of the Forming of Lightweight Materials Program described

in this Annual Report of the Metallurgy Division.Some specific

actions to address the industrial needs are:

ï The conclusion that anelastic recovery may be able to account

for this remaining uncertainty was well received by the

SPP members. To enable obtaining a better understanding

of the role of anelastic deformation in springback and

dislocation dynamicsin surface roughening, a dynamic

mechanical analyzer was purchased. This system is

capable of testing mechanical testing at frequencies up to

200 Hz and temperatures from (ñ150 to 600)C with a

strain resolution of 1.0 nm. This system can be used for

dislocation damping (internal friction) measurements,

creep, stress relaxation measurements, and anelastic strain

recovery measurements. This system will enable NIST to

relate fundamental dislocation structures and dynamics to

the deformation behavior important to the forming

industry.

ï We will participate in two other industry-led consortia: Warm

Forming of Aluminum and Active, Flexible Binder

Program for Metal Stampings. Our involvement will be to

investigate the elevated temperature formability of sheet

metal by upgrading our biaxial testerto carry out tests on

heated metal.The role of roughening on friction will also

be pursued to improve predictability.

Figure 4. Inner panel of car hood.
Technical Highlights

16

During the last decade, researchers from the Metallurgy Division

have collaborated with scientists from universities and industry

on several projects with emphasis on modeling tools for the

design and manufacture of superalloys. Structural parts made

from superalloys not only must withstand extended periods of

service at high temperatures, but also must tolerate severe

environmental conditions, such as highly corrosive fumes from a

jet engine. In addition to the increased performance required for

aerospace applications, the performance demands for land-based

energy applications are also increasing. The traditional approach

for development of a new alloy relies on the knowledge and

experience of the engineer, which can be costly due to the

significant amount of testing required to obtain the correct

properties.

Two projects, the NIST-sponsored Consortium on Casting of

Aerospace Alloys and the DARPA-sponsored Investment

Casting Cooperative Arrangement, focused on the modeling of

casting processes. For these projects, the Metallurgy Division

developed phase equilibria subroutines, which used a modified

version of public domain software code, and constructed a

thermodynamic database for Ni-based alloys. On the basis of

these subroutines, programs were developed that perform

equilibrium (lever) and Scheilsolidification calculationsfor

multicomponent alloys. UES Software, Inc., implemented these

codes into ProCAST, a finite element method software

package for the simulation of casting processes. The original

NIST Ni-superalloy thermodynamic database includes 9

elements, Ni-Al-Co-Cr-Mo-Re-Ta-Ti-W, and is based on

critically evaluated literature work and NIST work on Co-Mo,

Co-Ti, Co-Re and Re-Ti systems. Figure 1 shows the results of

the assessment of the Co-Ti system. This database includes all

known phases in this 9-component system. Recently, the

description of the liquid, γ, and γí phases were expanded to

include Hf. Electronic versions of the NIST database have been

distributed to various industries, universities, and national

laboratories.

As a result of this work, the detailed solidification behavior for

Ni-base superalloys can be predicted. This has improved the

quality of solidification simulations for investment castings, by

providing more reliable predictions of casting defects, and thus

allows industry to eliminate the need for extensive testing of

many castings to reach an acceptable design.

In addition to a dependence on multicomponent thermodynamics, a wide variety of Ni-base superalloy applications are

made more complex by diffusion processes, including solidification, homogenization, γí precipitation, bonding and repairing

processes, and protective bond coats. Many of these industrial

problems can be addressed using a commercial finite-difference

diffusion simulation code that incorporates compositiondependent diffusivities combined with multicomponent

Thermodynamic and Kinetic Modeling of

Commercial alloys rarely consist of only two elements and some contain up to 10 elements.In addition, many important industrial

processes rely on diffusion to control the formation and dissolution of precipitate phases within a matrix or at an interface.The

development of thermodynamic and diffusion databases enables the extrapolation of these properties from binary and ternary systems

to needed higher order systems.NISTís development of such databases for Ni-base superalloys allows the modeling of various

processing applications. The approach has been shown to give reasonable predictions for complex alloys and provides a compact

storage method for vast quantities of data.

Multicomponent Alloys

Figure 1. The assessed Co-Ti phase diagram (lines)

compared to selected experimental data(symbols)

thermodynamics. The first step in modeling these multicomponent multiphase diffusion problems is the development of a

multicomponent diffusion mobility database. This database is

used in conjunction with the developed thermodynamic database

to calculate the composition-dependent diffusivities for a given

phase. As part of a General Electric-lead DARPA project for

Accelerated Insertion of Materials (AIM), NIST is developing a

diffusion mobility database for Ni-base superalloys. The NIST

mobility database can be used in conjunction with the NIST Nisuperalloy thermodynamic database, as well as other commercial

thermodynamic databases.

The diffusion data in various constituent binary systems have

been assessed to establish this multicomponent diffusion

mobility database. The initial diffusion mobility database is

focused on substitutional diffusion in the γ (fcc) phase for the

Ni-Al-Co-Cr-Hf-Mo-Nb-Re-Ta-Ti-W system. The mobilities

determined for the self-diffusion of the components in the

metastable fcc phase (where applicable) are consistent with the

well-known correlation of melting point and diffusivity. The

general agreement of calculated and measured diffusion coefficients in the Ni-Co-Cr-Mo and Ni-Al-Cr-Mo systems demonstrates the validity of the database for the extrapolation to higher

order systems.

The current diffusion mobility database has been distributed

electronically to various industrial partners who are evaluating

the database and providing additional experimental data for

further validation of the database. One such validation, which is

in progress, compares the simulation diffusion profile between

two commercial Ni-base superalloys in the single-phase γ (fcc)
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region with experimental results. Figure 2 shows the composition profiles predicted from a diffusion couple simulation using

the current mobility database.

ìDevelopment of a Diffusion Mobility Database for Ni-Base Superalloysî, C.

E.†Campbell, W. J. Boettinger and U.R. Kattner, Acta mater, in press

W. J. Boettinger, C. E. Campbell and U.R. Kattner (NIST/MSEL)

In addition to the prediction of diffusion profiles between

commercial superalloys, an approach that combines multicomponent thermodynamics and diffusion is being utilized to

determine the γí particle size and γí particle size distribution that

is obtained after solidification and heat treatment. Also, diffusion

simulations can be used to optimize the heat treatment schedules

for cast superalloys to avoid incipient melting while minimizing

cost. Further advancement of multicomponent multiphase

diffusion simulations includes modeling the diffusion in the

ordered γí phase and development of a more user-friendly

electronic diffusion database for public use.

NISTís work on multicomponent thermodynamics and diffusion

has been widely recognized by various forums including:

ï The 1998 Award for Excellence in Technology Transfer by the

Federal Laboratory Consortium for ìTransfer to the

Aerospace Industry of Technology Developed for use in

the Analysis of Advanced Casting Processesî (together

with other researchers from MSEL and CSTL) .

ï The 1999 Department of Commerce Gold Medal and the 2001

TMS Bruce Chalmers Award were both bestowed on W.

J. Boettinger, partly for his work in solidification

research.

ï The paper ìThermodynamic Assessment of the Co-Mo

Systemî was awarded the 2001 Alloy Phase Diagram

International Committee Award for outstanding evaluation

of phase equilibria data.

Figure 2. Composition profiles predicted for a diffusion

couple of RenÈ N4 and CMSX-6 superalloys in the singlephase γ (fcc) region at 1550 K for 10 h.

ìThe efforts of NIST researchers on the Cast Aerospace Alloys

consortium were instrumental in making solidification science

available to the foundry floor. Their efforts on developing a

thermodynamic database for Ni-base superalloys and coupling it

with solidification pathway analysis, thermophysical property

measurements, spurious grain formation studies, and solid/liquid

interface sensors have significantly increased our understanding

of solidification in the investment casing process.The success

of these activities is paving the way for additional collaborations

with important commercial benefit to Howmet.î

ó Boyd A. Mueller, Howmet Research Corporation
18

Forming of Lightweight Materials for

Automotive Applications

Contact Information: Richard J. Fields

Automobile manufacturing is a materials intensive industry that

involves about 10% of the US workforce. In spite of the use of

the most advanced, cost effective technologies, this globally

competitive industry still has productivity issues related to

measurement science and data. Chief among these is the

difficulty encountered in die manufacture for sheet metal

forming. In a recent ATP sponsored workshop (The Road

Ahead, June 20-22, 2000, at U. S. Council for Automotive

Research (USCAR) Headquarters), the main obstacle to reducing

the time between accepting a new design and actual production

of parts was identified as producing working die sets. This

problem exists even for traditional alloys with which the

industry is familiar. Figure 1 shows an example of where the cost

of tooling (dies) is the largest single cost in the production of

parts for small cars. (This does not include assembly costs.)

Figure 1. Part cost breakdown for small cars. (Kelkar et al.,

J. ofMetals, pp 28-32, Aug 2001.)

To benefit from the weight saving advantages of high strength

steel and aluminum alloys, a whole new level of formability

measurement methods and data is needed, together with a better

understanding of the physics behind metal deformation.This

project is meeting the industrial needs (see Table 2) by developing standard formability test methods, multiscale, physicallybased constitutive laws, and models for consolidation of

aluminum matrix composites.In the past year, we have

established a sheet metal formability laboratory.A state-of-theart formability testing machine equipped with an advanced

surface displacement analysis system permits us to investigate

industrially important measurement problems in formability and

pursue standard test methods for formability. The facility

provides test samples of biaxially deformed metal for other

aspects of this program.For example, deformation-induced

surface roughening of sheet metal is a poorly understood

phenomenon that is highly relevant to industry. We are currently

performing controlled experiments on biaxially strained sheets to

develop a surface roughening data base and a generic model

which industry has identified as a high priority need.

Table 1.Industries needs being met byNIST solutions.

On a more fundamental level, we are using MSELís advanced

characterization capabilities such as transmission electron

microscopy, synchrotron radiation, and neutron scattering at the

NIST National Center for Neutron Research to understand the

basic dislocation patterning responsible for the observed

behavior of metals. A predictive model based on percolation

theory has been developed from the measurements and observations. All aspects of the research at NIST will impact our

customers by improving the commercially available, finite

element computer codes that are heavily used by this industry.

A key element in the design of this program is that an insight or

advancement gained in one area can be immediately used in a

piecewise fashion in the design process, i.e., total success of the

program is not required to have an impact. Other means of

transferring this technology, such as through standardizing

organizations and by direct interaction with industrial counterparts, are being pursued. While targeting the auto industry, our

research will have extended applications to all other industries

that employ metal forming in their production lines.

Figure 1. Part cost breakdown for small cars. (Kelkar et al,.

J. of Metals, pp 28-32, Aug 2001.)
 Forming of Lightweight Materials 

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Collaborators:

19

In order for the U.S. auto companies to be able to transition to

new materials for formed sheet metal parts, they must be able to

mechanically characterize the starting materials under forming

conditions, and input this information into die design models.

The Metallurgy Division has initiated a project intended to

develop a sheet metal formability test, along with associated

metrology, that can be standardized and easily used by industry.

Our research has focused on a modified Marciniak geometry biaxial tension test.By modifying the geometry of the blank and

washer, we are able to produce strain states that vary continuously from balanced biaxial through plane strain to nearly

drawing conditions.Using this testing scheme, one can produce

an in-plane forming limit diagram (FLD) using a single tooling set

and machine.One eventual goal of this project is to develop the

methodology to measure an unambiguous multiaxial stress-strain

curve in sheet metal.An image correlation software package is

being tailored to measure the entire strain response, and several

techniques are being investigated to directly measure the stress in

the sample.If successful, these techniques combined will allow

the first clean measurement of a multiaxial stress-strain curve.

Current work is investigating the uniformity of biaxial strain

Standard Test Method

Development for Sheet

Metal Formability

In order to meet its goals for fuel efficiency, the U.S. automotive

industry is moving to lighter, high strength materials for auto

bodies.However, their lack of experience in forming these

materials translates into difficulty in making accurate dies for

producing body parts.Through a survey ofthe U.S. auto

industry, NIST identified a critical need to provide designers with

accurate material properties and with a way to incorporate them

into finite element models of sheet metal forming dies. This

project seeks to develop new standard tests and metrology to

accurately determine sheet metal mechanicalresponse under

forming conditions. Tim Foecke and Stephen W. Banovic

states for a given blank and washer geometry, the effect of

strain rate on uniformity and strain state, and the effect of burrs

and defects on premature localization.The plot shows the

results to date in attempting to duplicate the published forming

limit curve in 5052-H32 aluminum.Measured limit strains are

consistently below those reported previously, but follow an

identical trend.This is due to the fact that most published

FLDs have been produced using simulative experiments such as

the limiting dome height (LDH) test, in which the sample

experiences out of plane bending and unquantified frictions

during deformation.Our modified Marciniak test is intrinsic, in

that it is testing the real properties of the sheet and is not limited

by these experimental artifacts.Our results show lower limit

strains because we do not have friction-stabilized instabilities on

the surface and because we are testing a much larger area in a

given strain state, and sample a larger population of defects. We

have also modified the basic plane-strain configuration to

increase the uniformly strained area.The result is shown below,

along with a plot of the minor strains (avg. of 10 runs), acceptable values colored blue.The typical uniform area in the old

geometry is traced in black.Using this new geometry, we are

able to test a much larger area of material, and get a more accurate

intrinsic plane strain limit.

Figure 2. NIST plane-strain geometry and uniformity plot.

Samples produced by this project are used in other facets of the

formability program to study friction, surface roughening and

texture changes as a function of strain state and history in a

number of sheet metal material systems. These parameters are all

needed for accurate modeling ofsheet metal forming.

R. deWit and Y-W. Chung (NIST/MSEL), W. Tong (Yale University), and Y.Xu (Ford)

Figure 1. Forming Limit Curve comparing LDH and NIST

experimental values.
Forming of Lightweight Materials

Contributors

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Collaborators:

20

)

During FY2001, research was conducted in four different areas:

(i) uniaxial tension, (ii) forming friction, (iii) biaxial tension, and

(iv) springback.Uniaxial tension experiments are used to evaluate

specific hypotheses on the influence of metallurgical variables on

surface roughening during deformation.This year, experiments

into the influence of grain size on the roughening rate of a

commercial aluminum alloy (AA 5052), initiated in FY2000,

were completed. Although this work found that grain size

strongly influencesroughening rate, commercial Al alloyssuch as

5052 contain second phases at grain boundaries that influence

deformation and limit grain growth. Follow-up studies were

initiated to measure the influence of grain size on roughening of a

high purity Al-Mg binary alloy without these particles and of a

steel alloy where a wide range of grain sizes can be investigated.

The metallurgical factorsthat determine friction during forming

and the relative importance of surface roughness and deformation

character are unclear. Static friction experiments were performed

on AA 5052 with different amounts of strain induced roughness

to determine the influence of initial roughness on friction when

there is minimal contact induced deformation. These experiments

found that the coefficient of static friction initially increased and

then decreased for these conditions, as shown below. To enable

measurement of sliding friction over a range of contact induced

deformation volumes and sliding velocities, a system for the

measurement ofsliding friction was designed and fabricated for

mounting on a servo-hydraulic testing machine. Initial experiments indicate that this system will enable measurement of

frictional forces over a wide range of conditions relevant to the

forming industry for evaluation of die wear mechanisms.

Surface Roughening and

Homogeneity of Plastic

Deformation

Richard E. Ricker, Mark R. Stoudt, and

Stephen W. Banovic

The automotive industry has found that lightweight alumimum

alloys do not deform as homogeneously as currently used alloys.

In addition, an industry consortium determined that existing

measurement methods, data, and knowledge of surface roughening mechanisms, friction, and wear were insufficient to meet their

finite element modeling needs. To fulfill this need and enable

greater application of energy efficient lightweight alloys, this

project examinesthe metallurgical factorsthat influence the

distribution of slip, friction, and wear during forming and

quantifies these processes for use by the metals forming industry

in finite element codes.

Since most forming operationsinvolve complex loading

conditions, the NIST metal formability testing machine was used

to evaluate surface roughening ratesin biaxialstrain.Thisresearch

found that the orientation dependence of roughening rates

observed in uniaxial tension disappearsin biaxialstrain indicating

that this effect is related to orientation of the loading axis and not

the shape of the grains.

Also, slightly different roughening rates were observed in these

experiments for different lots of the same alloy, a common

industrial observation.Working with the NIST Center for

Neutron Research and the MSEL Ceramics Division, neutron

diffraction and X-ray diffraction measurements were used to

analyze changes in the crystallographic texture of samples

induced by biaxial strain as shown in the pole figures below.

From these measurements it was determined that the different

initial starting textures of the alloy lots were responsible for the

observed difference in roughening rates.

D. J. Pitchure, T. J. Foecke, D. Dayan, L. Ives, M. Vaudin, H. Prask, and T. GnaupelHerold (NIST/MSEL), and A. Rollet and G. Rohrer (Carnegie Mellon University)

To enable investigation deformation dynamics in springback, and

formability, a high frequency response thermal-mechanical

testing machine was acquired. This system will enable NIST to

relate fundamental dislocation structures and dynamics to the

behavior important to the forming industry.

Figure 1.Static friction for surface roughnesses generated

by plastic strain.

Figure 2.Influence of biaxial strain on (111) pole figure.
 Forming of Lightweight Materials 

Contributors

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21

Fundamental Studies of

Plastic Deformation

Plastic deformation of metals (as in cold rolling, stamping,

drawing, extrusion, or metal fatigue) is of great importance to

industries worldwide, and improvements in the basic technology

would have a significant effect on our economy. As one example,

stamped metal parts comprise about a third of the weight of an

automobile. If the currently used mild steel could be replaced by

aluminum alloys or high strength steels, weight could be reduced

considerably, thus greatly increasing fuel economy.

The design of new metal products is often accomplished by

computer simulation of the production process using empirically-derived constitutive equations. Unfortunately, existing

constitutive equations cannot accurately predict the material

behavior, and many tryout and redesign steps are required. For

stamped aluminum parts for automobiles, this trial and error

process is prohibitively expensive and more accurate constitutive laws are required. We are working on developing constitutive

laws that are based upon the underlying physical processes that

produce the observed mechanical behaviors.

The fundamental problems involved in this project are formidable. Researchers around the world have been working on this

topic for nearly 70 years and, until recently the prospects for

success have been poor. In recent years, however, tremendous

progress has been made in the areas of statistical physics and

experimental techniques. These advances are now being applied

to the problem of deformation and progress has been rapid.

NIST is deeply involved in this research activity and coordinates

a growing multi-institutional project that currently includes 16

researchers from 2 national labs (NIST and Pacific Northwest

National Laboratory) and 3 universities (Washington State

University, Massachusetts Institute of Technology and

University of Maryland Baltimore County). The project

includes work on theory, experiments and computer simulations.

Approximately half of this research is conducted at NIST.

The major activities currently underway at NIST include

finishing the mathematical development ofstrain percolation

theory, a statistical physics theory for how strain propagates

through a metal during deformation.Comparison with experimental results was necessary, so a new experimental effort to

obtain these data was implemented. This effort has just started

Lyle E. Levine

A substantial increase in the use of aluminum alloys and high

strength steelsin automobiles would greatly increase fuel

efficiency. A major reason why this has not yet been done is a

lack of accurate deformation models for use in designing the

stamping dies. An improved understanding of the fundamental

processes that are responsible for the mechanical properties

would allow the development of such a model. This project is

developing a physically based model of plastic deformation using

a combination of statistical physics approaches and advanced

measurement techniques.

using a combination of transmission electron microscopy (TEM)

and atomic force microscopy (AFM) to explore the relation

between the internal microstructure and the surface slip features.

Figure 1 shows an AFM image of the surface of an aluminum

single crystal, deformed in situ.

D. E. Kramer, D. J. Pitchure, M. F. Savage,R. Thomson , G. G. Long (NIST/MSEL),

Y. Shim (University of Georgia), H. Zbib (Washington State University), J. Gan and

J. Vetrano (Pacific Northwest National Laboratory)

Each of the large steps is a slip band. Higher resolution images

show that these bands are composed of many smaller steps

called slip lines. TEM studies of identical samples clarify the

underlying deformation microstructure.

Another topic that theorists at NIST are working on is why the

slip lines collect into distinct bands. This heterogeneous nature

of slip is important since it occurs at the ìboundaryî between

microscopic and macroscopic deformation. Any physicallybased model of macroscopic deformation must include this

effect.

Finally, NIST researchers are developing completely new

experimental techniques using high-intensity X-ray beams at

national synchrotron facilities.Rapid advances have taken place

in ultra-small angle x-ray scattering (USAXS) imaging, a

revolutionary imaging technique first demonstrated by NIST in

2000.Among these advances are a four-fold increase in spatial

resolution and the demonstration of stereo USAXS imaging in

which three-dimensional images are acquired.

Figure 1.Slip bands on the surface of an aluminum

sample.The sample was deformed to 15 %, polished

electro-chemically, and deformed in situ in an AFM.
Forming of Lightweight Materials

Contributors

and

Collaborators:

22

Major research efforts within the U.S. auto industry are driven

by the need to reduce the weight of future vehicles to meet the

U. S. Council for Automotive Research (USCAR) and Partnership for a New Generation of Vehicles (PNGV) goals. This can

mostreadily be accomplished by the substitution of lightweight

materials for the heavy materials currently used. This project

aids the commercial development of a low cost powder

processing technology for aluminum alloy and particle reinforced

aluminum (PRA) parts. The aim is to substitute aluminum alloy

and aluminum composite powder metallurgy (PM) materials for

iron-based PM products.This approach has been recognized

by the auto industry, and the technical barriers to success have

been identified: the cost of existing powder processing routes is

too high, and the production of acceptable parts using press-andsinter and direct powder forging is not yet achieved. NISTis

addressing these needs through a focus on modeling each step in

these consolidation processes from powder to fully dense part.

Modeling provides the basis for knowing what properties and

parameters of a powder or a process need to be measured in

order to more rapidly design successful processes and to monitor

consistency.Physical modeling of the process can be used with

a cost model to make decisions that optimize cost and properties. The modeling is complex and has been carried out with

significant academic and industrial collaboration. NISTís primary

role has been to coordinate the modeling efforts between

academia and industry, validate the models, and provide industry

with working models and a preliminary data base. In collaboration with MatSys Inc., the modeling is being made available to

industry in a user-friendly, commercially supported software

package.

The NIST powder consolidation modeling effort has established

a validated set of equations that describe the densification of

reinforced (or unreinforced) metal powder in terms of the

processing conditions. These equations are used in a commercial

software package that accurately models potential processes and

that saves U.S. industry time and money otherwise spent on

trial-and-error investigations.

NIST reports its results quarterly to an industrial consortium

consisting of the three U.S. auto producers, Valimet,Stackpole,

Saint Gobain, Hoeganaes, and Mascotech.This group was

organized by USCAR and tracked by PNGV.

Process Models for

Particle Reinforced

Composites

Richard J. Fields

The primary objective of this project isto facilitate the introduction of lightweight powder metallurgical materialsinto automobiles in support of the U.S. auto industryís goal to develop

automobiles with substantially higher energy efficiency and lower

emissions. This is being accomplished by providing models for

lightweight metal consolidation, measurements and data for

model validation, software that readily transfers the models, and

the data required for implementing the models to the auto

companies and their suppliers.

In past years, studies at NIST of the green strength of aluminum

powders showed that bonding was by an interlocking mechanism, rather than oxide rupture followed by metal bonding.

Strength measurements showed that small additions of SiC

resulted in increased green strength due to a particle shape that

was conducive to interlocking. However, at higher SiC concentrations the strengthening was compromised by increased SiC to

SiC contacts which have virtually no strength.The maximum

strengthening effect was found to depend on the ratio of

reinforcement particle size to aluminum particle size and

concentration of reinforcement.In FY2001, this effect has been

modeled successfully using a percolation theory approach (see

Figure 1).

J. Fink, D. E. Harne, L. E. Levine, and Y. Shim (NIST/MSEL), W. Jandeska (GM),

R. Chernakov (Ford), G. Lynn (Daimler Chrysler), G. Campbell (Valimet), N. Chawla

(University of Arizona), M. F. Ashby and N. Fleck (Cambridge University),

I. Anderson (Ames Laboratory), and P. J. Blau (ORNL)

Comparison of this model with experimental results was

presented at the U.S. Congress on Computational Mechanics in

August 2001.While we plan to refine the model of green

strength of composite powders, our responsibilities in the U.S.

Automotive Materials Partnership (USAMP) project have been

fulfilled.We will continue attending quarterly meetings and

working with USAMP project members on modeling and

materials issues through their final prototyping phase.

Figure 1. Percolation model of reinforcing particles (red) in

aluminum powder (yellow) matrix.
 Forming of Lightweight Materials 

Contributors

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23

Machining of metal parts, e.g. turning, milling, drilling, broaching,

etc., to required dimensional tolerances is an essential part of the

manufacturing process. Efficient processes can greatly reduce the

price of a part and enhance the competitive position of the

manufacturer. A recent survey by the Kennametal Corporation

found that industry chooses the correct tool for machining a part

less than 50% of the time. Advances in machines and tooling

stimulated by the NIST Advanced Technology Program (ATP)

has made obsolete the traditional, experience-based approaches

to finding the optimal process parameters such as feed rate,

cutting rate, tool material, tool shape, etc.Pressure from

international competitors is driving industry to seek more costeffective means of choosing process parameters through

modeling and simulation. Current models give impressive results,

but data to validate these results is nearly nonexistent. This

Metallurgy Division project is advancing the state-of-the-art in

two areas: (1) fundamental advanced machine metrology, and (2)

measurement of fundamental data on the behavior of materials at

the high strain and heating rates needed for input into the

models. This project within the MSEL Metallurgy Division is

part of a larger ATP intramural collaboration with MEL, ITL,

and PL.The research in Metallurgy is directed at obtaining the

materials data in item (2).This effort requires an extension of

our current capabilities in high-rate heating to include high rate

straining.

Materials Data and

Metrology for Machining

Simulation

Richard Fields

The U.S. spends $200 billion annually on machining of metal

parts. Industry studies have shown that considerable improvementsin the efficiency of these operations are possible. Also, the

rapid development of tooling and high-speed machines makes

traditional knowledge-based approachesto improved efficiency

ineffective.Predictive modeling has been promoted by industry

as a method to realize the improved efficiency.Through this

project NIST will provide measurement capabilities and

materials data needed to make accurate predictions with these

models.

Figure 1. Temperature distribution due to heat pulse.

Three significant activities have been completed this year.First,

a model of the modified Hopkinson bar compression test device

to include high-rate heating has been designed and modeled.This

model has permitted us to explore various approaches to

obtaining uniform heating of the sample during the test.

Figure 2. Temperature transients at points along bar during

and after pulse heating.

D. Basak, L. Levine, and R. deWit (NIST/MSEL), M. Davies, R. Rhorer, R. Polvani, K

Jurrens, B. Dutterer, and M. Kennedy (NIST/MEL), T. Burns (NIST/ITL), and H. Yoon

(NIST/PL)

Second, a Hopkinson bar compression tester has been constructed that will provide strain rates of the order of 105 per

second and heating rates of 103

C per second.Third, calibrations were completed that assure that the temperatures measured

during the high rates of heating are accurate. In the next year, the

facility will be used to develop databases on a variety of

materials of interest to the machining industry.These data will

be used in simulations of prototypical machining operations and

compared to the advanced machine metrological database.

Evaluation of various models and simulations will provide

direction to future research in this area.
24

Materials for Magnetic Data Storage

For the magnetic data storage industry, the market potential is

vast and growing, but global competition is intense, and the

technical challenges extreme. Leading commercial magnetic disk

drives today store about 25 gigabits of data per square inch. The

National Storage Industry Consortium (NSIC) plans to demonstrate a recording density of 1 terabit per square inchó40 times

todayís levelóby 2006.

New materials are needed that have smaller grain structures, can

be produced as thin films, and can be deposited uniformly and

economically. Recording heads must be designed to produce

higher output signals and lower noise. Component dimensions

must be made smaller, and the measurements more precise.New

lubricants are needed to prevent wear as spacing between the

disk and head becomes smaller than the mean free path of air

molecules. New methods are needed to standardize components

and increase yields.

The National Institute of Standards and Technology is working

to achieve these goals. For the past century, NIST has been

helping U.S. magnetic data storage industries invent and

manufacture product with superior reliability. NIST offers stateof-the-art technology, measurement tools, and standardsómany

of which cannot be found elsewhereóas well as a reputation for

technical excellence and neutrality. Staff expertise spans all fields

relevant to magnetic data storage, including materialsscience,

electrical engineering, physics, mathematics and modeling,

manufacturing engineering, chemistry, metrology, and computer

science. By addressing important measurement issues in

magnetism, by bringing together the industrial and scientific

communities through the organization of workshops and

conferences in the area, and by the development and preparation

of appropriate standards, NIST acts to accelerate the use of

advanced magnetic data storage materials by the industrial sector,

and to enable industry to take advantage of new discoveries and

innovations. In addition, close linkage with NSIC increases the

industrial relevance of our program and improves technology

transfer.Additional collaborations with Xerox, General Motors,

Hewlett Packard, IBM, Seagate, and Motorola Corporations, for

example, enable NIST to leverage its activities with the much

larger, but complementary, capabilities of other organizations.

In FY2001, the Program on Materials for Magnetic Data Storage

in the Materials Science and Engineering Laboratory focused on

the following projects that were continued from the previous

year:

ï Processing of magnetic multilayersfor optimal giant magnetoresistance effect (Metallurgy Division)

ï Magnetic domain imaging and micromagnetic modeling of

magnetic domainsfor understanding magnetization statics

and dynamicsin recording heads and magnetic media

(Metallurgy Division)

ï Understanding the nanotribology of magnetic hard disks

through the measurement of stiction, friction, and wear at

the nanometerscale (Ceramics Division)

ï Measuring nanoscale magnetic interactions and structure in

multilayers, nanocomposites, and low dimensional

systems, needed for understanding and applying materials

physics at small scales (Metallurgy Division, NIST

Center for Neutron Research)

ïMeasuring and understanding the origin of magnetic exchange

bias in conventional and advanced magnetic structures and

devices (Metallurgy Division, NIST Center for Neutron

Research)

ï Developing a measurement system for magnetic susceptibility

of small samples at high frequencies (Metallurgy

Division)

ï Preparing magnetic measurementstandard reference materials.

(Metallurgy Division)

Two new projects were initiated in FY2001:

ï Processing and measuring the properties of ìspintronicî

systems wherein spin-dependent magnetic devices are

integrated directly onto semiconductor chips (DARPAsponsored; Metallurgy Division)

ï Developing measurements of magnetic damping (NIST

Nanotechnology Initiative Funding with EEEL; Metallurgy and Materials Reliability Divisions.)

Contact Information: Robert D. Shull
 Materials for Magnetic Data Storage 

Contributors

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Collaborators:

25

Materials for Giant

Magnetoresistance and

Spintronics Applications

The objective of this program is to provide assistance to U.S.

companies manufacturing products based on the giant magnetoresistance (GMR) materials and developing products based on

creation and manipulation of spin-polarized electrons.Our

work in GMR provides U.S. companies with significant

competitive help by investigating the science underlying the

manufacturing process of these nanometer scale devices. In the

area of Spintronics, we are examining fundamental materials

issuesin the identification and fabrication of magnetic materials

whose electrons exhibit 100% spin polarization.

William F. Egelhoff, Jr.

Computer memory and hard-disk-drive products are a major

force in todayís economy, representing over $50B in annual

sales, worldwide. The current generation of hard-disk drives read

stored bits using ultrathin films which exhibit the giant magnetoresistance (GMR) effect. In order to maintain exponential

growth rates in storage density ever larger values of the GMR

effect are required. In addition to hard-disk applications,

emerging markets for GMR include nonvolatile memory chips,

magnetic field sensors, and ultrahigh speed isolators. For the last

five years, our research has focused on GMR materials,

particularly on surfactants that improve interface flatness during

growth and thereby increase specular scattering and on the effect

of layer thickness and pinholes on magnetic coupling. A growing

research area isin the identification and fabrication of magnetic

materials whose electrons exhibit 100% spin polarization for

imaging and spin electronics (Spintronics) applications.

GMR Thin Films. The idea of surfactant-assisted growth of

metal films was pioneered at NIST in the 1980ís and is now

widely used in industry. This year introducing one monolayer of

Ag as a surfactant early in the growth process was found to

increase GMR of Co/Cu/Co films through a smaller magnetic

coupling between Co layers, especially in spin valves with very

thin Cu layers. Transmission electron microscopy suggests that

Ag helps to suppress pinholes in the Cu. Although Ag is not as

successful in improving spin valve properties as oxygen, the

most successful surfactant we have found so far, these data

contribute to our understanding of the role of both surfactants

and pinholes in determining GMR.

Pinholes in ultrathin films are the largest impediment to

achievingincreased magnetoresistance values in GMR spin

valves and magnetic tunnel junctions.We have developed a

novel method of studying pinholes.We deposit a sandwich

structure, such as Co/Al2

O3/Co, in which the film to be

investigated for pinholes has a magnetic thin film above it and

one below it.One magnetic film is pinned magnetically in a fixed

direction, while the other is free to switch in an applied field.If

pinholes are present, the free film is partially pinned by the

contact with the pinned film.By studying the magnitude of this

ìtransfer of pinningî through pinholes, we can determine,

directly, the influence of pinholes.The novel aspect of this

work is that we separate the influence of pinholes from the

influence of magnetostatic ìorange peelî coupling by measuring

the ìtransfer of pinningî at cryogenic temperatures. The

influence of pinholes has a strong temperature dependence while

magnetostatic ìorange peelî coupling is temperature independent. We are using this novel approach to improve our understanding of the thin-film growth processes that lead to pinholes.

This understanding may lead to better methods for suppressing

pinholes.

Spin-Polarized Electrons. In collaboration with the Naval

Research Labs we have developed growth techniques to deposit

magnetic tunnel junctions on GaAs substrates. The structure of

the junctions is typically Fe/Al2

O3/GaAs. The electron tunneling

properties through an insulator like Al2

O3 are a sensitive

function of deposition and processing conditions. These

conditions were optimized, and the shape of the intensityvoltage curves indicate that our structures can be used to inject

electrons from Fe ballistically into GaAs. This property is

important since ohmic contacts do not inject spin-polarized

electrons into semiconductors.Ballistic injection appears to be

the best hope for achieving this key goal of Spintronics. Our next

step will be to deposit these structures on 2-D quantum-well

structures incorporated in GaAs to look for circularly polarized

photon emission, which is the definitive proof of spin injection.

This work is supported by DARPA.

For Spintronics and magnetic imaging, magnetic materials are

needed whose electrons exhibit 100% spin polarization. In a

DARPA-sponsored study we have demonstrated that CrO2 can

be grown on H-terminated Si(100), Al2

O3/H-terminated Si(100),

polycrystalline α-Fe2

O3, polycrystalline NiO, thermal oxide on

Si(100), Ta, Ti, and Al films oxidized by exposure to air, and on

STM probes of Al, PtIr, Co, Ti, Au, Cr, and W, as well as TiO2

and Al2O3 single crystal substrates. A collaboration with the

University of Maryland is investigating magnetic imaging with

these coated STM probes.

R. D. McMichael(NIST/MSEL),M. Stiles( NIST/PL), 6 U.S. Corporations,

2 Federal Laboratories, 7 U.S. Universities, 8 International Universities
Materials for Magnetic Data Storage

Contributors

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Collaborators:

26

This project is concerned with the thermal stability of ìspin

valveî multi-layer films, the micromagnetics of magnetization

control in thin films, and dynamic measurements of thin

magnetic films. In FY2001, we are wrapping up our work on

robust magnetization control methods, allowing us to shift our

attention to new efforts in magnetization dynamics and damping.

The magnetization in a thin magnetic film must be held fixed in a

certain direction or ìpinnedî for proper operation ofread heads

in disk drives. In earlier generations of read heads, pinning was

accomplished by coupling one of the Co layers to an antiferromagnetic ìexchange biasingî material.

More recently, however, the trend among head manufacturers

has been toward substituting a Co/Ru/Co synthetic antiferromagnet (SAF) trilayer for one of the Co films.The Ru layer creates a

strong coupling between the adjacent Co layers that tends to

align the magnetizations antiparallel. In this configuration, the

net interaction with an external field is much weaker than for a

single Co film, so the SAF trilayer is harder to switch.

While the SAF structure has a decreased interaction with an

applied field, it still requires stabilization because 1) the net

moment of the SAF is not exactly zero, and 2) the SAFis

unstable to a spin-flop transition in which the magnetizations in

the Co layers rotate nearly perpendicular to the applied field,

and slightly toward the applied field. The SAF is typically

stabilized using an antiferromagnetic exchange bias material.

Previously, we had found that a large anisotropy can be

produced in Co films by using an obliquely deposited underlayer

of Ta. The oblique deposition creates an anisotropically rough

surface which is filled in by the Co. Anisotropy fields in excess

of0.1 T(1 kOe) can be generated by as little as 5 nmof Ta

(see Figure 1). These results were published in 2000.

In FY 2001, we have found that the anisotropy arising from the

oblique Ta underlayer can be used to pin the SAF structure very

effectively. Switching fields in the SAF were as high as 0.15 T

(1.5 kOe) when the bottom Co layer of the SAF was made 0.5

nm to 0.7 nm thicker than the upper layer (see Figure 2).This

extra thickness was needed to balance the SAF structure by

compensating for the a magnetically ìdeadî layer at the Co/Ta

interface.

Magnetization Control in

Thin Magnetic Films

Robert D. McMichael

For many applications of magnetic thin films in devices, it is

important to be able to control the magnetization direction of a

thin film in a way that is insensitive to elevated temperatures.We

are providing measurement methods, computational methods,

and data on the thermal stability, magnetization control and

micromagnetics of thin magnetic films to the magnetic recording,

magnetic sensor, and other magneto-electronic industries.

This demonstration shows that obliquely sputtered Ta can

provide stable pinning of the SAF structure without using

thicker, thermally unstable, often corrosion prone antiferromagnetic materials, possibly resulting in more stable, reliable

magnetic sensors and disk drives.Preparation of a final

publication on these results is underway.

J. Bonevich,R. Fry, and D. Mathews (NIST/ MSEL); C.-G. Lee (Changwon National

University, Korea), and Y.-W. Tahk (KAIST, Taejon, Korea)

Figure 2.Magnetoresistance curves for two SAF-pinned

spin valves deposited on oblique Ta and normally sputtered

Ta underlayers.The obliquely deposited Ta underlayer

stabilizes the SAF structure.The spin flop transition is

visible as a bump in the normal Ta spin valve curve starting

at 0.06 T.

Figure 1.Schematic structure of a spin valve with an

oblique Ta underlayer to stabilize the Co/Ru/Co SAF

trilayer.
 Materials for Magnetic Data Storage 

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27

Nanomagnetodynamics

Robert D. McMichael

The objectives of this MSEL-EEEL collaborationt are to provide

industry with (1) an improved understanding of magnetic

damping mechanisms, (2) improved magnetic damping

measurements and standards, and (3) data on methods for

controlling magnetic damping in technically relevant materials.

The knowledge, measurement methods, standards and data

generated by this project will enable industries involved in

magnetic information storage to predict and control magnetization on shorter time scales and in smaller dimensions, enabling

faster and smaller magnetic data storage devices.

This new project funded under the National Nanotechnology

Inititative is focusing on magnetization damping mechanisms and

measurement of damping and damping control in thin magnetic

films.In FY2001 we constructed a new broadband ferromagnetic resonance spectrometer, performed calculations of defectinduced phonon generation and measured linewidth in films with

intentional defects.In collaboration with EEEL, our future plans

include studies of switching dynamics with controlled damping.

Damping time is important for high data rate reading and writing

in disk drives and in magnetic memory (MRAM) chips under

development.The magnetization-lattice coupling that governs

damping is also important for the stability of written bits in the

ultra high density disk drives of the near future. One of the best

ways to measure damping is by ferromagnetic resonance, where

the width of the peak in susceptibility at the precession

frequency includes the effects of damping.Unfortunately, the

D. J. Twisselmann, A. B. Kunz, J. E. Bonevich D. E. Mathews, W. F. Egelhoff, Jr., A. P. J.

Chen , D. C. Hurley (NIST/MSEL), and S. E. Russek , T. J. Silva, and J. M. Moreland

(NIST/EEEL)

Figure 1.Ferromagnetic resonance linewidth in a 64 nm

film of Ni80Fe20 as a function of magnetization direction

relative to parallel scratches in the substrate (top inset).M

is perpendicular to the scratches at 0.The scratches

contribute to linewidth only when perturbation wavevectors

coincide with wavevectors of degenerate spinwave modes

(bottom inset).

width of the susceptibility peak, or ìlinewidth,î also includes

the effects of inhomogeneities and defects in the material.A

straightforward (but incorrect) assessment of the effect of

inhomogeneity on the linewidth would equate the linewidth to

the dispersion in the local precession frequency in the material.

Our measurements show in a dramatic fashion that the ìtwomagnonî model gives a much more accurate description of

extrinsic linewidth.The two-magnon process scatters the

uniform precession into degenerate spinwaves, and is not a form

of true damping since the energy does not transfer to the lattice,

but stays in the magnetization. In addition to two magnon

broadening, defects can couple the magnetization to sound

waves.We calculated the magnetic damping rate due to

generation of sound waves and found that this effect was several

orders of magnitude too small to describe the measurements of

damping in thin films, meaning that the two-magnon process

does not mask a significant amount of true damping to the

lattice.

Figure 2.Ferromagnetic resonance signals from a 50 nm

thick film of Ni80Fe20 measured on a new broadband

spectrometer constructed this year.The instrument is

capable of measurements up to 20 GHz.The frequency

dependence of ferromagnetic resonance linewidth is

especially important for discriminating between different

damping mechanisms.
Materials for Magnetic Data Storage

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Since the recognition of nanomaterialsí potential in science and

technology, NIST has been a major advocate for a U.S. Government R&D focus on nanotechnology.Robert Shull and Michael

Cassasa served on the interagency committee that developed the

National Initiative on Nanotechnology. Robert Shull will

continue to work with NSF, ONR, AFOSR, NIH, DOE, and

NASA on establishing national priorities through FY2002. In

addition, Dr. Shull is a leader in the international nanoscience and

nanotechnology community.

The nanomaterials project in the Metallurgy Division has

focused on developing an understanding of the magnetic

behavior of nanoparticles as a function of size, composition, and

interparticle spacing. The current areas of research are in

dendrimers containing magnetic particles and nanoferrofluids.These two areas were chosen because they not only

are simple systems for which the particles sizes and spacings

can be controlled, but also have possible industrial applications.

Magnetic dendrimers. For the first time ever, NIST, in

collaboration with the University of Michigan, have created

magnetic dendrimer nanocomposites by forming Fe, Co, and Ni

nanoparticles (0.3 % mass fraction) in hydrophobic

polyamidoamine (PAMAM) dendrimer hosts and then

embedding them in a polystyrene matrix.This technique

facilitates the formation of ferromagnetic clusters of well-defined

size and spacing, and puts them in a solid form easily measured

at low temperatures and high magnetic fields. SQUID magnetometry on these nano-composites showed that after subtraction of diamagnetic polymer background, at 300 K all exhibited

paramagnetic behavior with magnetization (M) being linear with

Magnetic Properties of

Nanostructured Materials

Robert D. Shull and Richard A. Fry

In the past 10 to 15 years there has been a remarkable improvement in the technology for materials preparation resulting in

todayís capability of controlling morphology and features at the

nanometer level.In magnetism, such control allows the

fabrication of nm-thick (or separated) composite materials of

dissimilar magnetism, leading to materials with novel bulk

magnetic character and unusual property combinations.In

order for U.S. industry to take advantage of these new materials,

their behavior needs to be understood and their method of

proper measurement determined.We are providing materials

metrology to do that.

C. Silva (Federal University of Pernambuco), S. Taketomi (Matsumoto, Inc.),

A. Uhlman (NewYork Polytechnic Institute), L. Balogh (University of

Michigan), and B. Bauer, V. Provenzano, and J. Li (NIST/MSEL)

In contrast, 7 nm diameter colloidal Fe3O4 particles suspended in

alkylnaphthalene behaved differently. For these materials, their

superparamagnetic M vs. H behavior observed at 300 K for

different concentrations superimposed when appropriately

scaled by the dilution (i.e., interparticle separation), indicating

the lack of magnetic interactions. Since particle size and

separation are usually equivalent variables, differences in

magnetic behavior of the two ìnano-ferrofluidsî highlights the

need for improved characterization and modeling.

Nanocomposite refrigerants. In a project partially supported

by NASA, successful preparation of magnetic nanocomposite

refrigerantsfrom Fe-containing dysprosium-gallium garnets was

accomplished in FY2001. The powders show superparamagnetic

behavior and enhanced magnetocaloric effects of magnitudes

similar to those found earlier in Gd-Ga-Fe magnetic nanocomposite garnets.These results extend NISTís invention of

nanocomposite magnetic refrigerants with enhanced

magnetocaloric effects.

Figure 2. Magnetization behavior as a function of temperature for γ-Fe2

O3 suspensions in carboxylic acid, with

concentrations as labeled.

Figure 1.(1/M) vs T for Ni, Fe-, and Co-containing

dendrimers exhibiting straight line fits at high temperatures (Curie-Weiss behavior) with small deviations at low

temperatures, particularly in the case of Fe.

applied magnetic field (H). Curie-Weiss (1/M vs. T) graphs

supported this conclusion by displaying a linear high temperature behavior with only small deviations below 100 K.

Nano-ferrofluids. To probe particle interaction effects two

different suspensions of Fe-oxide were studied.Figure 2 shows

data measured for (40 to 80) nm diameter maghemite (γ− Fe2

O3)

suspensions in a carboxylic acid. Differences between field

cooling (FC) and zero field cooling (ZFC) were observed for all

materials, but the magnetic strength did not simply scale with

the dilution (i.e., particle size) as expected, indicating unusual

particle interaction effects. Despite the interactions, the nanometer size maghemite led to superparamagnetism in all samples.
 Materials for Magnetic Data Storage 

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29

The MOIF technique is a quantitative, simple, fast, illustrative,

and sensitive tool for nondestructively characterizing materialsí

magnetic microstructures at the micron scale and the real-time

visualization of the elemental events of the magnetization

process. A transparent YIG film with in-plane anisotropy is

placed on top of the sample. Polarized light passing through the

indicator film is reflected by a thin Al underlayer and the normal

component of the magnetic stray field from the sample (e.g., as

would exist at a domain wall or sample edge) is detected by its

effect in locally magnetizing the yttrium iron garnet (YIG) film

out of plane. Consequently, it is possible to determine the

location of domain walls and magnetization directions in the

vicinity of crystal edges and defects by contrasts in the

polarization rotation of reflected light from the indicator film due

to the double magneto-optic Faraday effect.

The quality of the magneto-optical imaging is greatly enhanced

by digital image processing: magnetic imperfections of the

indicator film and inhomogeneitiesin the illumination are

practically eliminated, image contrast is strongly increased, and

quantification of the magnetic information becomes possible.

We have recently applied the MOIF technique for studying the

magnetization reversal process in thin nanocomposite magnetic

multilayer systems, in which technologically important effects,

such as unidirectional anisotropy, and exchange hardening, which

enhances the maximum energy product, have been observed. One

such system we investigated this year was a synthetic antiferromagnet (SAF) proposed for use in the technologically important

sensors based on the giant magnetoresistance (GMR) effect.

Specifically, we investigated the magnetization reversal mechanism in the SAF structure Co/Ru(0.5 nm)/Co stabilized by a

large (0.1 T) magnitude, uniaxial anisotropy (in excess of 120

kA/m) induced by an obliquely sputtered Ta underlayer.

The obliquely deposited Ta layer and both Co layers varied in

thickness, and the main result of this study was a finding that

the reversal mechanism was accomplished by domain wall

nucleation and growth, rather than by rotation of the magnetic

moments (as was previously observed in the SAF deposited on

an antiferromagnet). A canted magnetization state is formed

between the two ferromagnetic (Co) layers which has often been

Magneto-Optical

Indicator Film (MOIF)

Technique

Alexander J. Shapiro, Robert D. Shull

Understanding of the magnetization reversal mechanism in a

material isfundamental to understanding the magnetic character

of that material. For coupled magnetic systems, in particular,

detailed knowledge of their magnetization reversal processes

holds the key to enabling their commercialization. Developed by

NIST and ISSP RAS, the advanced magneto-optical indicator film

(MOIF) imaging technique provides a unique method for

studying such processes. Our goals are (1) to develop MOIF into

a widely available and broadly useful technique for dynamic

imaging and (2) to use it to perform leading-edge research in

magnetic dynamics.

attributed to biquadratic coupling between ferromagnetic layers.

Here, we have found that a canted spin structure can also be

formed by competition between antiparallel coupling (across the

Ru layer) and ferromagnetic coupling (via pinholes through the

Ru).

R. D. McMichael and W. F. Egelhoff (NIST/MSEL), V. I. Nikitenko (Johns Hopkins

University), and V. S. Gornakov (ISSP, Russian Academy of Sciences)

Knowing the magnetization reversal mechanism is critical to the

understanding of that materialís behavior and its subsequent

application. Since very thin layers of any material willpossess

pinholes, the present discovery will certainly have an impact on

the future development of advanced thin film magnetic materials

(e.g., for permanent magnets, transformers, sensors). The MOIF

technique will also become an indispensible analytic tool.

Figure 1. MOIF Images of the SAF structures

Co/Ru(0.5 nm)/Co stabilized by uniaxial anisotropy.
Materials for Magnetic Data Storage

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30

Magnetic Properties and

Standard Reference

Materials

Robert D. Shull and Robert D. McMichael

Users of magnetic materials, including the recording industry,

the permanent magnet industry, and the manufacturers of electric

motors and transformers of all types, need standard reference

materials (SRMís) to calibrate instruments used to measure the

critical magnetic properties of their starting materials.The

Magnetic Materials group is developing such a suite of standards.Methods for improving the efficiency and accuracy of

measuring and characterizing magnetic materials of industrial

importance are also under investigation.

L. J. Swartzendruber, R. A. Fry, A. J. Shapiro, R.V. Drew, D. E. Mathews, G. E. Hicho,

L.C. Smith, and F. S. Biancaniello (NIST/MSEL), D. Pappas and F. DiSilva (NIST/EEEL),

Industrial and Academic Collaborators, and L. H. Bennett and E. Della Torre (George

Washington University)

Commercial instruments for the measurement of magnetic

properties are relative instruments that rely on known samples

for their calibration. To produce standard samples for such

instruments, an absolute magnetometer was developed and

assembled at NIST. A picture of this instrument is shown below.

Modifications to the absolute magnetometer to improve its

sensitivity have been made during the current reporting period.

These improvements have enabled the development of standards

with much smaller magnetic moments.

Prior to FY2001, two SRMís had been issued: a nickel sphere

(SRM 772a) and a nickel disc (SRM 762).As a result of the

improved sensitivity of the NIST magnetometer, two new SRMs

were under development this year. The first was a 1 mm

diameter yttrium iron garnet (YIG) sphere for use in calibrating

the more sensitive ranges of magnetometers. In addition, it will

be useful for calibrating very sensitive instruments such as

alternating gradient magnetometers and SQUID magnetometers.

Because of its high resistivity, the YIG sphere should also be

useful for calibrating the magnitude and phase in alternating

current magnetometers. The second SRM is a platinum cylinder

paramagnetic susceptibility standard. This will be useful in

calibrating the zero field point and linearity of magnetometers

because of its absolutely linear magnetization vs. magnetic field

relationship resulting from its paramagnetic nature.In addition,

it will also be useful for calibrating the field scale after the

Figure 1. NIST absolute magnetometer.

magnetization scale has been calibrated. Pd, Al, and MnF2

susceptibility SRMs are planned for the future.

In addition to the improved sensitivity, the automated measurement capability of the absolute magnetometer shown at left has

been improved, as has the temperature measurement system.

The temperature dependence of the Ni and YIG spheres and the

Ni disk were determined. This information will make these

SRMs, currently certified only near room temperature, more

useful in the many commercial magnetometers which measure

over extended temperature ranges. The Ni disc SRM has also

been selected this year as the sample material to be used by the

members of the International Disk Drive Equipment and

Materials Association (IDEMA) for the round robin measurement of magnetic strength.

A thin film magnetic moment standard is being assessed jointly

with the Magnetics Technology Division of the Electronics and

Electrical Engineering Laboratory. Thin Ni films(3mm x 4mm x

2nm) lithographically prepared inside a planar superconducting

coil have been examined metallurgically for homogeneity in

thickness, coverage, and adhesion, and measured magnetically to

determine their magnetic moment. Several films have been

observed, and a thin film SRM for calibrating B-H loopers

appears feasible for FY2002.

This past year, NIST helped organize the Third International

Symposium on Hysteresisand Micromagnetics Modeling in

Ashburn, Virginia which addressed recent theories, measurements, and other developments in hysteresis, with theprimary

focus on magnetics. Of the 65 attendees from 16 foreign

countries almost all the leading expertsin micromagnetic

computation were present. The attendees felt that the symposium provided an unusually productive occasion for them to

present and exchange ideas, methods and results. Included in that

discussion were several anecdotes on how the NIST Standard

Problems in Computational Micromagnetics had caused the

international community to re-evaluate and improve its

computational codes.The proceedings from the symposium will

be published in Physica B.
Contact Information:

31

Materials for Microelectronics

Frank W. Gayle

Todayís U.S. microelectronics and supporting infrastructure

industries are in fierce international competition to design and

produce new smaller, lighter, faster, more functional, and more

reliable electronics products more quickly and economically than

ever before.

Recognizing this trend, in 1994 the NIST Materials Science and

Engineering Laboratory (MSEL) began working very closely

with the U.S. semiconductor, component and packaging, and

assembly industries.These early efforts led to the development

of an interdivisional MSEL program committed to addressing

industryís most pressing materials measurement and standards

issues central to the development and utilization of advanced

materials and material processes within new product technologies, as outlined within leading industry roadmaps.The vision

that accompanies this program ñ to be the key resource within

the Federal Government for materials metrology development

for commercial microelectronics manufacturing ñ may be realized

through the following objectives:

ï Develop and deliver standard measurements and data;

ï Develop and apply in situ measurements on materials and

material assemblies having micrometer- and

submicrometer-scale dimensions;

ï Quantify and document the divergence of material properties

from their bulk values as dimensions are reduced and

interfaces contribute strongly to properties;

ï Develop models of small, complex structures to substitute for

or provide guidance for experimental measurement

techniques; and

ï Develop fundamental understanding of materials needed in

future microelectronics.

With these objectives in mind, the program presently consists of

twenty separate projects that examine and inform industry on

key materials-related issues, such as: electrical, thermal,

microstructural, and mechanical characteristics of polymer,

ceramic, and metal thin films; solders, solderability and solder

joint design; photoresists, interfaces, adhesion and structural

behavior; electrodeposition, electromigration and stress voiding;

and the characterization of next generation interlevel and gate

dielectrics.These projects are conducted in concert with

partners from industrial consortia, individual companies,

academia, and other government agencies.The program is

strongly coupled with other microelectronics programs within

government and industry, including the National Semiconductor

Metrology Program (NSMP) at NIST.

FY2001 Projects (and division leading project)

Lithography/Front End Processing

ïCharacterization of Ultrathin Dielectric Films (Ceramics)

ïLithographic Polymers (Polymers)

On-chip Interconnects

ïInterconnect Materials and Reliability Metrology (Materials

Reliability)

ïMeasurements and Modeling of Electrodeposited Inter-

connects (Metallurgy)

ïThin Film Metrology for Low K Dielectrics (Polymers)

Packaging and Assembly

ïPackaging Reliability (Materials Reliability)

ïSolder Interconnect Design (Metallurgy)

ïSolders and Solderability Measurements for Microelectronics

(Metallurgy)

ïTin Whisker Mechanisms (Metallurgy)

ïWafer Level Underfill Experiment and Modeling (Metallurgy)

ïWire Bonding to Cu/Low-K Semiconductor Devices (Metal

lurgy)

ïX-ray Studies of Electronic Matls. (Materials Reliability)

Crosscutting Measurements

ïDielectric Constant and Loss in Thin Films and Composites

(Polymers)

ïElectron Beam MoirÈ (Materials Reliability)

ïFerroelectric Domain Stability Measurements (Ceramics)

ïMeasurement of In-Plane Thermal Expansionand Modulus of

Polymer Thin Films (Polymers)

ïMechanical Properties of Thin Films (Ceramics)

ïPermittivity of Polymer Films in the Microwave Range

(Polymers)

ïPolymer Thin Films and Interfaces (Polymers)

ïTexture Measurements in Thin Film Electronic Materials

(Ceramics)

ïThermal Conductivity of Microelectronic Structures

(Materials Reliability)

Contact Information:
Materials for Microelectronics

Contributors

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32

f

The U.S. microelectronics industry has clearly articulated the

measurement needs for Pb-free solders and for solderability and

assembly. For example, the urgency for materials data for Pb-free

solders has been specified in the 1997 IPC, 1999 International

Technology Roadmap for Semiconductors, 2000 National

Electronics Manufacturing Initiative (NEMI), and 2000 IPC

Lead-Free Solder Roadmaps. The pressure from the Japanese

consumer product market and from the European Union to

produce lead-free microelectronics continues to increase.In

addition, the lack of understanding and control of current

standard solderability measurements has inhibited the development of improved measurements necessary for new solders and

for new packaging schemes. These industrial needs are addressed

under this NIST project.

NIST has taken a major role working with industry through a

NEMI Task Force to identify and move Pb-free solders into

practice. NIST co-chairs the NEMI Alloy Group which is

responsible for providing key measurements and data needed to

understand manufacturing and reliability issues. This year, NIST

held a workshop cosponsored by NEMI, the National Science

Foundation, and The Metallurgical Society on Modeling and

Data Needs for Lead-Free Solders. The report from this

workshop is serving as a roadmap for research on the reliability

of lead-free solders. In addition, NIST is currently evaluating the

metallurgy and thermal cycle performance of boards assembled

by NEMI to evaluate Pb-free solder performance with a variety

of components, with and without Pb contamination (see figure).

NIST was also active in the National Center for Manufacturing

Sciences (NCMS) High Temperature Fatigue Resistant Solder

Consortium, including 8 companiesin the microelectronics and

automotive industries, which completed a four-year project this

year to develop Pb-free solders for harsh environment applications, such as automotive and telecommunications. NIST lead

the alloy selection task group and took the lead in writing the

final report. NIST accomplishments and future directions are

described above in the Highlightssection.

In a third major activity, NIST has developed a database needed

to calculate multicomponent phase diagrams essential for Pb-free

alloy development. This phase diagram project is described

under ìThermodynamic Databases for Industrial Processes.î

Solder and Solderability

Measurements for

Microelectronics

Solders and solderability are increasingly tenuous links in the

assembly of microelectronics as a consequence of ever shrinking

chip and package dimensions and the movement toward

environmentally friendly lead-free solders. We are providing the

microelectronics industry with measurement tools and data to

address solder issues.A thermodynamic database has been

publicly distributed for modeling lead-free solder systems.We

also work closely with industry groups on measurement tools

needed for development of lead-free solders for use in harsh

environments, and provide guidance for adoption of these

solders into assembly processes through work with industrial

standards organizations.

Figure 1. Metallographic cross-section of a lead-free

SnAgCu solder selected under the NIST-led NEMI Pb-free

Alloy Task Group.The chip-scale package shown here has

been assembled with a SnPb component finish to determine

how Pb contamination affects reliability.

We are also working in collaboration with IPC Standards

Committees (most closely with members from Celestica, Lucent,

Raytheon, Rockwell, and Shipley-Ronel) to establish reproducible solderability test standards for board assembly. Activities

include providing benchmark experimentsfor the wetting balance

tests to predict on-line solderability for a wide range of surface

finishes, lead materials, and solder alloys.New NIST research

to develop electrochemical solderability tests and an understanding of whisker formation in Sn-based, Pb-free electroplated

surface finishes complements the solderability studies.

Highlightsfrom our work include:

ï Sources of uncertainty have been established for wetting

balance solderability tests, leading to increased repeatability and reproducibility of tests.

ï Recent flux studies performed at NIST have led to a change in

test procedures for the IPC/EIA J-STD ANSI solderability standards.

L. C. Smith (NIST/MSEL), K-W. Moon (University of Maryland), D. Napp (National

Center for Manufacturing Sciences, and associated consortium members), and R. Gedney

(NEMI Lead-Free Task Force, and associated consortium members)

Frank W. Gayle, William J. Boettinger,

Carol A. Handwerker, Ursula R. Kattner,

and Maureen E. Williams
 Materials for Microelectronics 

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Assembly of IC Chips

Utilizing Wafer-Level

Underfill

Assembly of advanced area array microelectronic chips and

componentsrequiresself-alignment of interconnects with

restoring forces supplied by molten solder joints. To provide the

necessary detailed understanding of the restoring forces

provided by misaligned solder joints, we are providing computer

simulations as well as experimental studies that verify the

accuracy of these simulations.As a result, we demonstrate that

the restoring force to be expected during assembly of flip chips

with an underfill/solder bump system applied at the wafer level

can be accurately predicted using such codes as the publicdomain Surface Evolver software.

Daniel Josell and Daniel Wheeler

This project involves experimental studies and computer

modeling of the geometries of solder joints subjected to a range

of loading conditions. The ability of capillary (surface energy)

based models to predict solder joint restoring forces has been

determined. The relationship between restoring force and solder

joint misalignment obtained in this work determines the restoring

forces responsible for flip-chip realignment during reflow

operations. Wafer-level underfill, which is deposited prior to

solder joint formation, retards self-alignment of the chip and

substrate promoted by the molten solder joints. Underfill

between a chip and substrate reduces solder joint fatigue; waferlevel underfill eliminatesthe need for time-consuming infiltration

after chip attachment. A model that incorporates the solder joint

restoring force relationship and the viscous drag associated with

the wafer-level underfill has been developed.

The capillary realignment forces for different pad dimensions

and solder volumes were experimentally measured. Solder joints

with volumes of eutectic lead-tin solder down to 0.0023 mm3

were studied with pad diameters down to 0.35 mm. The loading

conditions were systematically varied and the post-solidification

solder joint geometry measured in order to obtain the forcedisplacement relationships for the solder joints under both

aligned and misaligned conditions. The experimental results were

compared to predictions of our model which is based on the

commonly used Surface Evolver freeware computer code. This

model considers only capillary and gravitational forces to predict

solder joint geometries.

The predictions of the model were shown to be consistent with

the results of the experiments.As a result, this class of

computer codes has been shown to be an accurate means of

studying solder joint restoring forces for wafer-level underfill

applications.This model has been extended to combine the

restoring force information obtained in the first part of this

study with viscosity data for wafer-level underfill materials.A

range of realignment behaviors is predicted, with key parameters

being the mass of the flip-chip, the restoring force relationship

and number of solder joints, the equilibrium standoff-height and

the viscosity of the underfill material.

Figure 1. Measured lateral offset (misalignment) and

normal offset (standoff height) for ≈0.0023 mm3 Pb63Sn37

solder connecting 0.35 mm diameter pads as functions of

applied shear force.The curves are predictions of Surface

Evolver.

Realignment can occur through monotonic decrease of the

misalignment or through oscillation about the equilibrium

location, with all of the noted parameters affecting the particular

behavior.

An article to appear in the Journal of Electronic Packaging

presents the results of this study. In addition, the software

developed in this project has been made publicly available on the

Center for Theoretical and Computational Materials Science

CTCMS web site:

http://www.ctcms.nist.gov/~djl/solder/new.html

as part of the library of Evolver files modeling different

industrial solder joint geometries. The generality of the joint

geometries that can be studied using this code is a significant

benefit.

W. Wallace and C. Schultheisz (NIST/MSEL)
Materials for Microelectronics

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34

The introduction of copper and low dielectric constant(LoK)

polymersinto advanced ultra-large scale integration (ULSI)

copper-damascene chips have created new wire bonding

challenges. Three areas of particular interest are: 1) oxidation

inhibitors to ensure bondability to the top surface, 2) low

modulus, low dielectric constant materials positioned underneath

the pad, and 3) under-pad mechanical support structures. There

are also various polymer/metallurgical interactions(resulting in

long term device reliability problems) that can occur as the result

of the wire bonding process over low modulus, LoK, materials

with barriers. These include cracked diffusion barriers, copper

diffusion into the LoK polymers, spalling/crazing of the

polymers, and bond pad indentation (cupping).

In the past, bonds have been made to aluminum pads over silicon

or oxide. This presented an ideal metallurgy and a rigid platform

for thermosonic bonding. However, with the introduction of

LoK alternatives, copper pads may be positioned over low

modulus polymers that are themselves encased in brittle barriers.

This can lead to bond yield and/or reliability problems.

Although there are a number of areas that must be considered in

wire bonding to advanced Cu/LoK devices, this project focuses

on the top surface metal that is present to promote bondability.

Specifically, we are evaluating gold coatings placed directly on

copper as an oxidation inhibitor and determining the impact that

interdiffusion of copper and gold may have on long term

reliability for wire bonding. Gold- copper bond interfaces have

been shown by Lucent Technologies to be more reliable than AuAl interfaces which are currently used approximately 1012 times/

year in devices today.

Gold has traditionally been the top metal surface of choice on Cu

for wire bondability, usually with a Ni barrier between it and the

Cu. However, the Ni is an extra manufacturing step and can

diffuse through the gold (by grain boundary diffusion) and result

in unbondable nickel oxide on the surface. Fortunately, gold can

be directly plated onto Cu. When gold and copper interdiffuse,

they primarily form superlattice structures, which are ductile

and not considered a reliability hazard. Cu will diffuse through

Au and oxidize on the surface; however, it diffuses more slowly

than Ni through Au. The diffusion coefficient of the copper

Evaluation of Bond Pads

for Wire Bonding

Several problems that are encountered in wire bonding to

advanced damascene copper/low-K devices result from 1)

oxidation of the copper pads during handling, wafer sawing, and

high temperatures encountered during die attachment and

thermosonic bonding, and 2) diffusion of copper into the top

surface metal/inhibitor coating. NIST is evaluating the direct

deposition of gold onto damascene copper as a top coat oxidation

inhibitor while determining the diffusion coefficient of electrodeposited copperinto gold for bondability impact.

Christian E. Johnson and David R. Kelley

(damascene-process) into and through an autocatalytic Au film

has not been established. Solution additives, such as a few ppm

of Pb to slow down grain boundary diffusion, inhibit autocatalytic deposition. Thus, in order to avoid copper diffusing to the

Au surface during the various packaging thermal steps, the Au

thickness should be greater than 0.5 mm. Measurements are

currently being made of the diffusion coefficient on a first-timeof-arrival Auger hot-plate technique so that a more accurate

(minimum) thickness can be determined.

A constraint in using Au (or any other plated metal) on a chip is

that the Au must be plated by a non-electrolytic process, since

some of the semiconductor pads may have no ground-return

connection. To achieve this in our work, a two-step immersion/

autocatalytic deposition process had to be adopted, since the

available autocatalytic gold would not deposit directly onto Cu.

The copper surface was first primed with an immersion gold that

resulted in a 10 nm primer coating. This step was followed by a

pH-neutral autocatalytic gold build-up to the (0.5 to 1) mm

desired thickness. Ball bonding tests were conducted on these

films to establish adhesion and bondability. The films were then

deposited on silicon test chips having bond pads of approximately 0.5 mm of damascene-process copper. Bondability was

established with manual ball bonders using both 60 and 120 kHz

ultrasonic frequencies. The bonding stage was maintained at

150†C. Shear test results established that the bonds made at

both frequencies were approximately 80% welded. Although the

long term reliability of the Au/Cu interface (bonded or plated) is

known, data from damascene-Cu structures is still needed. This

will be the focus of future work.

G. G. Harman (NIST/EEEL), E. Steel (NIST/CSTL), C. Evans (NIST/MEL), D. Frear,

T-A. Tran, and L. Yong (Motorola), and R. Augur (International Sematech)
 Materials for Microelectronics 

Contributors

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35

The mechanism responsible for superconformal electrodeposition of copper in high aspect ratio features has been determined.

Simulations from a model based on this mechanism have been

shown to predict results of electrodeposition filling experiments

in trenches as small as 90 nm wide and 450 nm deep. No fitting

parameters are required to model this behavior.

These developments have built upon two recent Metallurgy

Division discoveries. First, a simple electrolyte was developed

that yields superconformal electrodeposition of copper in

trenches as small as 75 nm wide.Second, hysteresis in cyclic

current-voltage studies of copper deposition on flat copper

specimensin an electrolyte was found to be indicative of the

ability of that electrolyte to yield superconformal deposition in

fine features. Those results demonstrated that superconformal

deposition only occurs when both an inhibiting additive and an

accelerating additive are present in the electrolyte.

For the model, we obtain kinetic parameters for particular

electrolytes from cyclic voltammetry experiments described

above. These kinetic parameters describe both the rate at which

the dilute accelerating additive accumulates on the copper

surface, displacing the inhibiting additive that retards local

copper deposition, and the impact this accumulation has on the

local copper deposition rate.

The new model uses these parameters to predict filling of

features.The most important and novel aspect of this model is

its recognition of the fact that local coverage of accelerator

changes both by accumulation from the electrolyte and by

changes of the local area upon which it has accumulated.

Accumulation of accelerator at the bottom ofsuperfilling trenches

is dominated by the latter, geometrical effect. The decreasing area

of the copper surface growing up from the bottom of fine

features thus results in increasing accelerator coverage on this

surface.This, in turn, accelerates copper deposition there,

resulting in filling of the trench from the bottom upward, i.e.,

superconformal deposition. The finer the feature, the more

important area change can be ñ it requires an appropriately

designed electrolyte composition and appropriate deposition

conditions to take full advantage of this effect.

Measurements for

Electrodeposited On-Chip

Copper Interconnects

Copper hasrapidly been introduced into chip interconnection

technology as a replacement for aluminum. Electrodeposition is

the preferred depositionmethod due to its unique ability to

superconformally fill high aspectratio features when organic

inhibitors and accelerators are added to the plating bath. NIST

hasrecently developeda predictive capability forthe influence

of additives on superconformal deposition. This capability is

based on the development of an electrochemical signaturefor

superfill, a quantitative model forinterface motion and competitive adsorption, and the demonstration ofdeposition down to

75†nm trench widths. Daniel Josell and Thomas P. Moffat

Experimental fill results are compared with model predictions in

Figures 1 and 2, respectively.Note the agreement of fill versus

failure to fill.Also note the overfill bumps ñ the model shows

that this so-called ìmomentum platingî is due to the enhanced

accelerator coverage on the upward moving surface. These

results also explain the initial period of conformal plating

(uniform deposition on all surfaces) visible through the model as

the time required forsignificant accumulation of accelerator from

the electrolyte.

This model provides a means of rapidly assessing electrolytes

for superfilling submicron features on the basis of the rapid,

inexpensive cyclic voltammetry studies on flat copper.Only

those electrolytes that yield filling according to the model

predictions need be moved to full scale testing of fine feature

filling.We are now working with Texas Instruments to

intergrate NIST models and measurements in TI production.

D. Wheeler and J. E. Bonevich (NIST/MSEL)

Figure 1 (left) Superfill results for accelerator concentrations of (0, 0.5, 5 and 40) mMol/L (top to bottom).A window

for superfill exists around the 5 mMol/L concentration.

Figure 2 (right) Model predictions for the second largest and

smallest trenches for accelerator concentrations of (0.5, 5 and

40) mMol/L. Vertical seams indicate failure to fill.
Materials for Microelectronics

Contributors

and

Collaborators:

36

The National Electronics Manufacturing Initiative (NEMI) PbFree Task Force, of which NIST is a member, has identified a

serious concern of original equipment manufacturers (OEMs),

contract manufacturers, and component manufacturers with the

conversion from Sn-Pb to Pb-free surface finishes for circuit

boards and component leads. It is well known that the use of

pure Sn protective surface finishes can cause serious problems:

tin whiskers (1 mm diameter and several mm long) can grow

from the plated tin surface and cause electrical shorts and failure.

Historically Pb was added to Sn plate to prevent whisker

growth, and thus the ìwhisker problemî disappeared. With the

rapid move to environmentally-friendly Pb-free assemblies, the

microelectronics industry must remove Pb from the surface

finishes. For many applications an electroplated Sn-based

surface finish remains a preferred surface for ease of processing,

however the possible growth of whiskers is currently a perilous

drawback.

Based on these needs, this NIST project is focusing on: (1)

understanding the effect of alloying elements other than Pb on

the tendency for whisker formation; (2) developing techniques to

separate possible physical and microstructural factors affecting

whisker formation, and (3) assisting the NEMI Standardization

Technology Integration Group (TIG) with both test development and understanding the root causes of whisker formation.

The Sn-Cu system was chosen as the most versatile for

electroplating, since it is compatible with Sn-3.9Ag-0.6Cu and

Sn-0.7Cu, the Pb-free solders selected as the new national

standard alloys by NEMI for reflow soldering and for wave

soldering, respectively.

Whiskers are generally believed to grow to relieve residual stress

in electroplated Sn. However the origin of this stress has yet to

be determined definitively. In the process of studying the

mechanisms for whisker growth, we have developed methods to

control grain size, residual stress and alloy composition in order

to sort out underlying factors in whisker growth. The probability of whisker growth from as-deposited Sn electrodeposits has

been measured as a function of copper (Cu2+) additions to a

commercial bright water-based methanesulfonate electrolyte. To

provide reproducible plating conditions and to approximate flow

conditions in commercial strip plating, a rotating disk electrode

assembly was used.

Mechanism of Sn Whisker

Growth from Electrodeposits

Christian E. Johnson, Maureen E. Williams,

and Kil-Won Moon

The electrodeposition of metallic alloys has been central to the

growth of the electronics industry. This is largely due to the

exceptional properties exhibited by electrodeposited material as

well as the favorable economy of scale associated with electrodeposition processes. A technology important to electronics

manufacturing isthe electrodeposition of Sn-based coatings and

surface finishes to guarantee solderability. With the rapid move to

Pb-free solder surface finishes, new test methods are needed for

predicting the tendency of such coatings to form Sn whiskers that

can lead to catastrophic failures.

W.J. Boettingerand G. R. Stafford (NIST/MSEL)

A fixed plating current at 25C was used to produce deposits 3

μm and 10 μm thick. Two substrates were used: free standing

250 μm thick pyrophosphate Cu deposits and 40 nm thick fine

grain Cu evaporated onto a Si (100) wafer. Electrolyte Cu2+

concentrations from 0 to 25 x 10-3 mol/L produced deposits with

average Cu compositions between 0 % and 3.3 % mass fraction,

respectively.

As shown in Figure 1, both whiskers and eruptions appear as

defects. In the absence of Cu additions, no defects were observed

on either substrate after 60 days of room temperature aging.

With Cu additions, no whiskers were observed on the Cu-coated

Si substrates, but whiskers were observed within two days on

the free-standing Cu substrates increasing to a density of

102

/mm2 for the highest Cu contents as indicated in the Table.

The deposits on the free-standing Cu and Cu evaporated onto Si

(100) substrates had different preferred orientations, (103) and

(101), respectively, but the effect of Cu on the deposit microstructure was the same. The increase in Cu content reduced the

grain size of the Sn deposit from 0.65 μm to 0.2 μm, independent of substrate. Much of the Cu in the deposits occurred as

Cu-rich particles on the Sn grain boundaries. The primary

correlation observed was that Sn-Cu deposits with (103)

preferred orientation were most likely to form whiskers.

We continue to be active participants in the NEMI TIG where

test methods are being developed and where experimental results

are shared.Our goal is to provide an understanding of the

fundamentals of the whisker formation, which ensures that the

test developed by the NEMI group will have widespread

applicability.

Figure 1. Defects include both (a) whiskers and (b) eruptions.
Contact Information:

37

Metals Characterization

Engineering design depends on the specification of the properties

of the materials that are used. Equally important, manufacturers

and their suppliers need to agree on how these properties should

be measured. The MSEL Metals Characterization Program,

centered within the Metallurgy and the Materials Reliability

Divisions, spans the measurement spectrum from the innovative

use of state-of-the-art measurement systems, to leadership in the

development of standardized test procedures and traceability

protocols, to the development and certification of Standard

Reference Materials (SRMs).

The NIST effort in metals characterization has a strong emphasis

on electron microscopy, which is capable of revealing microstructures within modern nanoscale materials and atomic-resolution

imaging and compositional mapping of complex crystal phases

with novel electronic properties. The MSEL microscopy facility

consists of two high-resolution transmission electron microscopes (TEM) and a high-resolution field-emission scanning

electron microscope (FE-SEM) capable of resolving features

down to 1.5 nm. Novel experimental techniques using these

instruments have been developed to study the mechanical

properties of multilayered and nano-scaled materials.

The Metals Characterization Program is contributing to the

development of test method standards through committee

leadership roles in standards development organizations such as

ASTM and ISO. In many cases, industry also depends on

measurements that can be traced to NIST Standard Reference

Materials (SRMs). This program generates the following SRMs

for several quite different types of measurements.

Hardness of Metallic Materials (Metallurgy Division): Hardness

is the primary test measurement used to determine and specify

the mechanical properties of metal products. The hardness

standardization project is providing industry with primary

transfer standards for the Rockwell hardness and Vickers and

Knoop microhardness scales. These SRM test block standards

are used for the periodic calibration of hardness testing machines.

Magnetic Properties (Metallurgy Division): The need for reliable

magnetic measurementsis becoming increasingly acute because

of new technologiesinvolving magnetic phenomena in data

storage and microelectronics. Such measurementsrequire

calibration of magnetometers using certified magnetic standards

in several different shapes and magnetic strengths, and with a

wide range in magnetic character. These standards are now being

produced under this program.

Coating Thickness (Metallurgy Division): Coating thickness

standards are produced by electrodeposition and are widely used

for calibration of coating-thickness measuring instruments. SRM

coupons are produced with a wide range of thicknesses, and are

bar coded to allow analysis of degradation and life expectancy

when the standards are returned for verification.

Charpy Impact (Materials Reliability Division): The Charpy

impact machine verification project provides rapid, accurate

assessment of test data generated by our customers using SRM

Charpy standards, and, where merited, certifies the conformance

of Charpy impact test machines to ASTM Standard E 23.

Participation in ISO Committee TC 164, assures that specimens

and procedures are compatible with international standards.

In addition to the SRM activities above, NIST (Materials

Reliability Division) provides assistance to the Bureau of

Reclamation (BOR) on metallurgical issuesthat arise during

maintenance, inspection, and failure assessment of dams and

water conveyance infrastructure projects. NIST advice and data

provide BOR engineers with an independent check of other

input.

Samuel R. Low, III
Metals Characterization

Contributors

and

Collaborators:

38

Nanomaterials have been found to exhibit a number of extraordinary mechanical properties.Strengths and hardnesses that are

many times that of either constituent material have been

observed in nanograined (3D) and nanolayered (1D) structures.

In particular, multilayered materials with wavelengths in the

micron and submicron regime offer exciting opportunities,

because the ability to fabricate these materials using physical

vapor deposition (PVD) or electrodeposition makes these

economically viable to produce.Also, one can use pairings of

materials that are immisible, and not able to be conventionally

processed.

Recent in situ TEM observations of cracking in Cu/Ni

nanolaminates have revealed a possible explanation for the

extreme flaw sensitivity of this class of materials.As seen in the

Figure 1, cracking progresses behind an extremely localized

plastic zone.While there is negligible plasticity away from

Figure 1. TEM micrograph of crack in 30 nm Cu / 60 nm Ni

single crystal nanolaminate.Note extension of plasticity

upon deflection of crack path.

Mechanical Properties of

Multilayered and

Nanomaterials

Mechanical performance of layered structuresis critically

important to large sectors of industry:reliability of microelectronic devices, tribology of magnetic media, and integrity of

advanced aerospace thin film coatings.Predictive design of

mechanical properties relies heavily on knowledge about how

these materials deform and fracture at very fine scales.Research

in this project is aimed at determining what deformation

mechanisms operate in these classes of materials as a function of

layer thickness and constitutent materials using novel experimental techniques.This information will be useful in designing

devices and modeling layered systems. Tim Foecke, Donald Kramer, Dan Josell

the crack, within the crack zone, plastic strains in excess of 30 %

are seen.This correlates well with ex situ fracture observations

of thin foils, where no plasticity is measured but high ductility is

observed on the fracture surface.The structure studied appears

to lack a mechanism for work-hardening, leading to extremely

easy localization. The results from our mechanical property

measurements are being used by theory groups at Ohio State and

Los Alamos National Lab to modify their models of these

structures.These groups are now concentrating on the details

of how dislocations interact with interfaces, and how interfaces

act as barriers to dislocation motion.

Figure 2. Schematic of model detailing progression of

ìOrowanî dislocation bows through the structure in TEM

micrograph (from Peter Anderson, OSU).

Another facet of the project deals with the high-temperature

structural stability and mechanical behavior of Nb / Nb5

Si3

microlaminated materials.Work performed in conjunction with

researchers at Johns Hopkins University has determined how to

form these structures so that they are stable for hundreds of

hours at temperatures exceeding 1300C.

The Air Force is interested in this class of materials for use as a

strong, damage tolerant critical coating on jet engine turbine

blades, and isinvestigating whether microlaminated silicide /

refractory metal microlaminates may be used to form hollow

turbine blades in the absence of any superalloy substrate.

T. Moffat, D. Smith and G. White (NIST/MSEL), T. Weihs and D. van Heerden

(Johns Hopkins University),P. Anderson (Ohio State University), H. Kung,

J. Hirth, and R. Hoagland (LANL), and J. Embury (McMaster)
 Metals Characterization 

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39

Hardness is the primary test measurement used to determine and

specify the mechanical properties of metal products. The

Metallurgy Division is engaged in all levels of standards

activities to assist U.S. industry in making hardness measurements compatible with other countries around the world. These

activities include the standardization of the national hardness

scales, development of primary reference transfer standards,

leadership in national and international standards writing

organizations, and interactions and comparisons with U.S.

laboratories and the National Metrology Institutes of other

countries.

INTERNATIONALACTIVITIES: At the international level,

we are participating in the Working Group on Hardness (WGH)

under the International Committee for Weights and Measures

(CIPM). The primary goal is to standardize hardness worldwide.

As secretary of the WGH, we participated in an international

Key Comparison of Vickers hardness scales, and prepared the

U.S. Hardness Calibration and Measurement Capability data for

the international Mutual Recognition Arrangement (MRA). We

also head the U.S. delegation to the ISO committee on hardness

testing of metals, which oversees the ISO hardness test method

standards.

NATIONALACTIVITIES: Our primary task at the national

level is to standardize the U.S. national hardness scales and to

provide a means of transferring these scale values to industry.

Currently, we are producing test block Standard Reference

MaterialsÆ (SRMs) for the Rockwell, Vickers and Knoop

hardness scales, as well as developing new reference standards.

Eight different microhardness SRMs for Vickers and Knoop

hardness are currently available. Using electro-deposition

technology, the standards are produced with uniform properties

and microstructure. This year, a mechanical polishing procedure

for copper was developed, substantially improving the number

of standards that can be produced. We also completed the

development and began calibration of three new SRMs for the

Rockwell B scale (HRB) to complement the three SRM

Rockwell C scale blocks currently available. The HRB scale is

used for testing softer metals, such as aluminum, copper and

brass. These new HRB standards should be available for sale in

early 2002.

Hardness Standardization:

Rockwell, Vickers, and

Knoop

Sam R. Low, Christian E. Johnson, James L.

Fink, and David R. Kelley

U.S. industry needs to be able to make measurements that are

traceable to nationalstandards and compatible with the

measurements made in other countries. This need is being

emphasized by the requirements of quality standards such as ISO

17025. For the measurement of hardness, NIST is meeting this

need by standardizing U.S. national hardness scales, producing

hardness reference standards, and providing assistance and

guidance to U.S. industry through national and international

standards activities.

J. Song, C. Evans, and R. Clary (NIST/MSEL), W. Liggett, Jr. and N. Zhang (NIST/ITL)

C. Beauchamp, N. Trahey, D. Faison, and W. Stiefel (NIST/TS), and G. Hicho (NIST/

MSEL)

In addition to developing SRMs, our national standards activities

include chairing the ASTM hardness subcommittee E28.06. To

assist ASTM, the Metallurgy Division, with the assistance of

the NIST Information Technology Laboratory, drafted a new

procedure for determining the uncertainty of Rockwell hardness

measurements, currently being balloted for approval as a new

appendix to the Rockwell hardness test method standard ASTM

E18. This procedure was requested by manufacturing companies

and hardness calibration agenciesthat have recently begun

determining hardness measurement uncertainties as required by

accreditation programs.

Figure 1. SRM test blocks for Rockwell hardness and

Vickers and Knoop microhardness

In May, the Metallurgy Division

published a new NIST Recommend

Practice Guide: Rockwell Hardness

Measurement Of Metallic

Materials. The Guide helps to

explain the causes of variability in

Rockwell hardness test results and

supplements the information given

in test method standards with good

practice recommendations. Since it

has become available to the public,

over 3000 copies have been

requested, including some hardness

equipment manufacturers that will

be providing a copy of the Guide

with their products. The Guide is

also available for download at

http://www.metallurgy.nist.gov/

publications.html .
Metals Characterization

Contributors

and

Collaborators:

40

The Electrochemical Processing Group is responsible for

producing seventeen different thickness standards of nonmagnetic coatings over magnetic substrates, with thicknesses ranging

from 6.0†mm (≈†0.2†mils)to 2000†mm (≈†80†mils). Each standard

consists of a 1270†mm (≈†50†mils) thick magnetic steel substrate,

electroplated with fine-grain copper of varying thickness, and a

thin nonmagnetic layer of chromium for wear resistance. These

standards are packaged into preconfigured sets of four coupons.

Each set consists of different ranges, depending on the needs of

our customers. The standards are certified with a maximum

expanded uncertainty of 2 % of the mean at the 95 % level of

confidence and are used for the calibration of instruments based

on the magnetic pull-off technique or those based on magnetic

induction.

These standards are used by the organic and inorganic coating

industry for non-destructive measurements of non-magnetic

coatings over magnetic substrates. Some of the industries using

our standards are paint, electronics, aerospace, automotive, steel,

nuclear, railroad, welding, and tool and dye. Typical applications

where our SRMs provide a critical need include the evaluation of

wear in coatings and coating thickness measurement during the

surface finishing stages or the repair of worn parts.In addition,

these coating thickness standards are used to verify compliance

with minimum coating thickness requirements for corrosion

protection as well as thickness tolerances for the successful

assembly of coated parts.These standards are also used by

coatings industries where properties such as solderability and

electrical and thermal conductivity are optimized by the

thickness of the coating.

In FY2001, our goal was to deliver the 817 outstanding units for

FY2000 and to replenish the inventory of SRMs 1361b and

1364b with 77 additional units. At this time, all 3,576 outstanding coupons have been measured.From these coupons, 646 of

the combined 894 units owed have been assembled and the

remaining 248 units are in the finalstages of labeling and

packaging for delivery to NISTís Standard Reference Materials

Program.

In addition to our SRM fabrication/certification activities, we are

initiating two outreach efforts. The first is the publication of a

Electrodeposited Coating

Thickness Standards

Standard Reference Materials (SRMs) of nonmagnetic coatings

over magnetic substrates, with nominal thickness values ranging

from 6.0†mm (≈ 0.2 mils) to 2000†mm (≈ 80†mils), are produced

for use by the organic and inorganic coating industries for

nondestructive measurements of coating thickness. Traceability

to NIST coating thickness SRMs is specified for a wide range of

industrial and military products. Prototype zinc standards for

the electrogalvanizing industry are being developed that provide

standardization of composition and microstructure.

Carlos R. Beauchamp, Hilary B. Gates, and

David R. Kelley

NIST Recommended Practice Guide which we expect to be

available in FY2002. The Practice Guide will focus on the

magnetic induction measurement and the uncertainties associated

with its application to thin film analysis. In addition to the

Practice Guide, we are planning to host a gathering of instrument

manufacturers, standards producers, and end-users to discuss

their materials and metrology needs for the future.This meeting

is expected to take place in Winter 2002.Two new SRMs are

currently being developed for the electrogalvanizing industry.

The first is a 3 cm x 3 cm zinc-coated steel coupon intended for

the verification of gravimetric procedures used in the ìweighstrip-weighî method for zinc determination. A second standard,

used for on-line x-ray fluorescence measurements, is also being

developed. Although these coupons will be certified by mass,

the industry has requested that the crystallographic texture of

the zinc electrodeposit match that produced commercially.

Towards this end, we are determining the influence of deposition

potential on the crystallographic orientation of electrodeposited

zinc from sulfate-based electrolytes.

S. D.Leigh (NIST/ITL)

Figure 1. Coating Thickness Standard Reference Materials

available sets and their corresponding nominal thickness.
 Metals Characterization 

Contributors

and

Collaborators:

41

Atomic-scale structure and compositional characterization of

materials can lend crucial insights to the control of their properties. For instance, direct observation of local structures by

transmission electron microscopy provides an important

information feedback to the optimization of crystal growth and

processing techniques. Various characteristics may be observed

such as crystal structure and orientation, grain size and morphology, defects, stacking faults, twins and grain boundaries, and

second phase particles, with details of structure, composition, and

internal defects, compositional variations and the atomic structure

of surfaces and interfaces.

The MSEL Electron Microscopy Facility consists of two

transmission electron microscopes (TEM), three scanning electron

microscopes (SEM), a specimen preparation laboratory, and an

image analysis/computational laboratory. The state-of-the-art

JEOL3010 UHR-TEM has atomic scale resolution as well as

detectors for analytical characterization of thin foil specimens. An

X-ray detector (EDS) provides compositional analysis and an

energy selecting imaging filter (IF) allows compositional mapping

at atomic resolution.

Highlights from the EM Facility for FY2001 include:

ï A new field-emission SEM (FE-SEM) has been deployed

with spatial resolutions of 1.5 nm at 15 kV and 2.5 nm at 1

kV.The FE-SEM allows nano-scale imaging of uncoated

specimens, an important consideration for ceramic and

polymeric materials.

ï A new electron back-scattered diffraction (EBSD) system has

been deployed with interfaces to both a conventional SEM

and the new FE-SEM. This system allows for detailed,

automated texture measurement and, when coupled with

EDS, phase identification of unknown materials.

ï New linewidth standard reference materials for the semiconductor electronics industry have been characterized. The

reference features are based on {111} planes of Si on

bonded and etched-back silicon on insulator wafers. Atomic

resolution lattice counting provides an absolute measurement of width traceable to the meter (see Figure 1).

ï TEM characterization of sub-100 nm electrodeposited

copper lines complemented focused ion beam imaging of

patterned cross-sections (see Figure 2).

Nanoscale

Characterization: Electron

Microscopy

Electron microscopy is used to characterize the structure and

chemistry of materials at the nanometer scale to better

understand and improve their properties. New measurement

techniquesin electron microscopy are being developed and

applied to materials science research. The MSEL Electron

Microscopy Facility primarily serves the Metallurgy, Ceramics,

and Polymers Divisions but is made available to other NIST

staff as well as for outside collaborative research efforts.

John E. Bonevich

R. D. McMichael, D. Josell, and T. P. Moffat (NIST/MSEL),M.W. Cresswell and R.A.

Allen (NIST/EEEL),E. B. Steel andJ. H. Scott (NIST/CSTL), andA. Stanishevsky

(University of Maryland, Institute for Plasma Research)

Figure 2.TEM image of copper electrodeposited nanoscale

features in ìsuperfilledî trenches.The electrodeposited

copper contained microstructural defects such as voids,

dislocations and twins that could not be revealed in the

focused ion beam imaging.

Figure 1.Cross-sectional TEM view of silicon linewidth

feature.The absolute width of the feature can be directly

related to the meter.
42

Metals Processing

The Metals Processing Programapplies NIST expertise in a wide

range of disciplines, including thermodynamics, electrochemistry,

fluid mechanics, diffusion, x-ray, and thermal analysis, to

understand the processing steps which will lead to products

having the desired form and properties, at an acceptable cost.

Working with industries ranging as widely as automotive,

aerospace, coating, and microelectronics,several important

processing problems are being addressed including melting and

solidification of welds, castings of single crystals, powder

production and consolidation, and coating production by thermal

spray and electrodeposition.

The increasingly competitive manufacturing environment fuels

the search for new metal alloys as well as efficient processing

techniques to fully realize their potential. The processing cycle

can include many steps, including a formation process such as

casting or electrodeposition, a heat treatment process, a deformation process such as rolling or stamping, joining by welding, or

coating to enhance surface properties.In each of these processes,

the distribution of crystal phases, the grain structure, the alloy

compositional segregation, and the defect structure are altered,

with resulting changes in properties such as strength, ductility,

corrosion resistance, and conductivity which form the basic

rationale for the use of metals in industrial products. The

following projects in the Metals Processing Program focus on

measurements and predictive models needed by industry to

design improved processing methods, provide better process

control, develop improved alloy and coating properties, and

reduce costs.

ï Modeling of Solidification andMicrostructure Development:

(Metallurgy Division): Models of alloy solidification,

crystal growth processes and heat treatment are being

developed to aid industry in designing production systems

that increase product yield and performance.

ï Processing-Structure-Property Data For Thermal Spray

Coatings (Metallurgy Division): Coating reproducibility

and reliability are addressed by the development and

calibration of advanced sensors, applying these measurement tools to the control and characterization of TS

coatings, and working with the Thermal Spray (TS)

community to establish a coating processing-microstructure-property database.

ï Weld Process Sensing, Modeling and Control (Materials

Reliability Division): Advanced instrumentation and data

analysis techniques are used to develop a better understanding of the underlying physics governing the arc

weldingprocess.

ïHigh-energy X-ray Diffraction Studies (Materials Reliability

Division): Investigations are underway on the use of highenergy x-ray diffraction as an alternate, nondestructive

option to the conventional destructive methods for

measuring physical properties.

ï Tailored Metallic Powders(Metallurgy Division): Measurement techniques for the characterization of

microengineered powders are developed to advance our

understanding of the relationships among properties,

processing, and microstructure.

ï Electrodeposition of Aluminum Alloys (Metallurgy Division):

Guidelines for the electrodeposition of aluminum-based

alloys from low-temperature, low-vapor pressure nonaqueous electrolytes are being developed as an inexpensive

method for producing homogeneous and fine-grained

aluminum-based thin films for corrosion protection.

ï Electrochemical Processing of Nanostructural Materials

(Metallurgy Division): Electrochemical methods for the

synthesis and characterization of nanoscale

magnetoresistive device architectures are being examined

with an emphasis on the use of surfactants and segregation

phenomena in controlling homo- and hetero-epitaxial film

growth.

ï Reaction Path Analysis in Multicomponent Systems (Metallurgy Division): Costly experimental investigations of

bonding and reaction processes involving interdiffusion at

interfaces between metals, oxides, and vapors are supplanted by models, based on thermodynamic data, that

predict the formation of transient phases and rates of

reaction in complex multicomponent systems.

Metals Processing projects with an especially strong focus on

areas which are of special interest to MSEL have evolved to

become part of other program areas such as Materials for

Microelectronics and Forming of Lightweight Materials. Because

processing plays such a basic role in determining the properties

and performance of metals, we expect this program to continue

providing a foundation for advanced metalstechnologies.

Contact Information: Stephen D. Ridder
 Metals Processing 

Contributors

and

Collaborators:

43

Modeling of microstructures produced by solidification, electrodeposition and other processes involves mathematical solution of

equations for heat flow, fluid flow, current flow and/or solute

diffusion. Boundary conditions on external surfaces reflect the

macroscopic processing conditions. Boundary conditions at

internal interfaces correspond to the liquid-crystal (grain) or graingrain interfaces. These internal interfaces are moving boundaries

and require boundary conditions with thermodynamic and kinetic

character. For solid-solid transformations, stress and strain

replace fluid flow as a consideration.

In order to deal with the complex interfacial shapes which

develop during solidification, electroplating and grain growth, the

phase field method has become the technique of choice for

computational materials scientists. This approach often requires

numerical techniques to solve the model equations but readily

deals with complex interface shapes and topology changes. The

research, conducted in the Metallurgy Division, is also supported

by the NIST Center for Theoretical and Computational Materials

Science (CTCMS).

Dendritic and eutectic growth, generally present in castings,

involves extremely complex interface shapes. Several of the

accomplishments of this year deal with the application of

diffuse interface modeling to these types of growth:

ï The phase field approach has been used to describe the

growth and final impingement of differently oriented

dendritic alloy grains.A previously developed NIST

model has been simplified with no apparent sacrifice in

accuracy.The new model employs only one more order

parameter than standard phase field models of solidification.

ï A multiphase field model has also been explored to obtain

knowledge about the last stages of solidification. Such

information has practical applications in predicting

porosity and hot tearing of castings. The temperature

required for the bridging (coalescence) of dendritic

microstructures has been determined. For comparison, a

sharp interface model of this phenomenon has also been

developed.

Modeling Solidification,

Electrodeposition and

Microstructure Evolution

Many properties of structural and functional materials depend on

the distribution of composition, phases and grain orientations on

the scale of 1 to100 mm.The scale of such structures is a

natural result of the fabrication processes used in their production, a scale of interface motion which is modeled well by the socalled ìphase fieldî approach. The ultimate goal of this project

is to provide a set of phase field modeling tools to simulate the

development of complex structures.These models are already

providing information to aid industry in designing production

systems that increase product yield and performance.

James A. Warren, William J. Boettinger,

Jonathan E. Guyer, and Daniel J. Lewis

ï The effects of vacancieshave been included in a phase field

model of grain microstructure evolution in order to treat

sintering.

ï A phase field model of ternary eutectic alloys has been

developed and validated in the 2-D binary case by

comparing with the classical (Jackson-Hunt) model.

Future work will include the microstructure of ternary

alloy structures, which requires 3-D modeling.

ï Adaptive grid methods are being applied to phase field

problems.These numerical techniques allow researchers

to automatically numerically resolve the interfacial region

of a calculation, improving the speed and accuracy of a

calculation.These methods are particularly important for

calculations done in three dimensions or where fluid flow

is included. A variety of adaptive codes have been

collected and are being distributed onthe world wide

web, through the CTCMS.

ï Recent interest in Cu metallization by electrodeposition

into small features for integrated circuits has indicated the

need for a modeling approach that avoids the simplifications usually employed.Thus, the phase field technique

has been applied to electrochemistry. With a single set of

governing equations, current is carried by valence

electrons in the metal and by ionic diffusion and

electromigration in the electrolyte. This model naturally

produces the charged double layer at the metal-electrolyte

interface. Investigations are underway to determine the

phase field kinetic description necessary to recover

classical Butler-Volmer electrodeposition behavior.

G. B. McFadden and W. F. Mitchell (NIST/ITL) andR. Kobayashi (Hokkaido

University,Japan)

Figure 1. View of a

phase field simulation

of 4 alloy dendrites of

differing orientation.

The colorsrepresent

composition variations

in the system, while

orientation differences

are evident from the

axes of the dendrite

trunks.
Metals Processing

Contributors

and

Collaborators:

44

The focus of this project in FY2001 was on improving the

reproducibility and reliability of thermal spray (TS) coatings

through (1) evaluating the errors associated with improper use of

non-contact thermometry (described above in the Highlights

section), (2) characterizing the instabilities in the thermal spray

deposition system, and (3) developing with leaders in the

industry a coatings processing-microstructure-properties

database. Participants at the NIST Thermal Spray Process

Reliability workshop held in January, 2001 confirmed the

importance of each of these research areas for NIST. Participants

representedmost major thermal spray processing equipment

manufacturers, thermal spray users, national laboratories, and

universities.

Significant progress was made in measurement of instabilities in

the powder delivery and arc power systems in the thermal spray

deposition system. A Coriolis meter in the powder delivery line

was installed to measure powder mass flow-rate fluctuations has

revealed the dynamics of powder flow. The most common

technology for powder mass flow-rate control relies on the use

of an electronic mass balance. As a result of the time constants

inherent in the mass balance and in removing equipment

vibration either by mechanical damping or by using electronic or

software filters, the powder mass flow sampling rate is limited

to approximately 0.1 Hz with the corresponding resolution of

flow-rate fluctuations limited to <0.05 Hz. In contrast the

Coriolis meter has a sampling rate >20†Hz, and therefore, can

resolve flow-rate fluctuations>5†Hz.The improvement in

resolution can be seen in the figure comparing the two flow-rate

measurement techniques and the intensity from a photodiode,

corresponding to an integrated light intensity from the plume.

The impact of this fluctuation is that the time scale in the figure

is proportional to a distance tranversed by the spray gun. This

translates into a gradient in particle deposition rate and in

particle velocities and temperatures, and, therefore, in coating

thickness, microstructure, and properties.

A thermodynamic model of the plasma was developed that

calculates the heat and momentum transfer to particles using

thermodynamic and transport data for plasmas currently

available in the literature. This model can be used to maintain

particle velocities and temperatures in spite of changing gun

conditions, including electrode wear, a majorsource of

variability. The gun is typically controlled by specifying average

arc current. As the electrodes wear, the physics of the arc

changes and the power delivered to the plasma jet drops even

Processing-StructureProperty Data for

Thermal Spray Coatings

Stephen D. Ridder

Reproducibility and reliability of thermalspray (TS) coatings are

the major impediments to the realization of the full benefits of this

technology. In addition, the processing procedures and properties of TS coating systems are not well documented or available.

These needs have beenaddressed by the development and

calibration of advanced sensors, applying these measurement

tools to the control and characterization of TS coatings, and

working with the TS community to establish a coating processing-microstructure-property database.

0.5

0.0

1.0

30

25

20

15

0 1234 5 6 7 8 9 10

photo diode

powder flow

feeder pulses

electronic scale

Coriolis meter

Time (s)

Flow

Rate (g/min)

Relative Intensity

Figure 1. Data from powder flow-rate sensors and photo

diode showing improved temporal resolution and correlation of powder flow with powder feeder pulses .

with constant average arc current. This simple model is now

available through an article in the Journal of Thermal Spray

Technology.

The remaining activity is the development of a processingstructure-properties database for thermal spray coatings under

consideration by the Information Development and Delivery

Committee of the ASM Thermal Spray Society.This activity

was proposed to the Committee by Christopher Berndt of

SUNY, Richard Knight of Drexel University, and Steve Ridder of

NIST.The TS community will provide data to be critically

evaluated by a review group before inclusion in the database. It

is envisioned that this database would be disseminated through

equipment manufacturers as new thermal spray processing

equipment is sold, through ASM andNIST to current users, and

through the well-attended ASM short courses on ìThermal

Spray Technologyî taught by Berndt and Knight.NISTís role in

this activity would be primarily in organization and data

evaulation.

F. S. Biancaniello, R. D. Jiggetts, S. P. Mates, and T. H. Gn‰upel-Herold (NIST/MSEL)

C. Presser (NIST/CSTL), J. F. Widmann (NIST/BFRL), D. Basak (University of

Tennessee), and J. Geist (Sequoyah Technology LLC)
 Metals Processing 

Contributors

and

Collaborators:

45

The objective of this research is to develop measurement

techniques for the structural and chemical characterization of

microengineered powders ñ powders that are either intrinsically

nanoscale or combine nanoscale coatings/layers with conventional micropowders. The availability of such measurement

techniques will lead to improved understanding of critical

microengineered powder fabrication processessuch as chemical

vapor deposition, physical vapor deposition, multilayer

formation, powder agglomeration and sintering, interfacial

reactions, and grain growth.

This year we concentrated on the following tasks: (1) Continue

to improve the electron energy-loss spectroscopy (EELS) and

energy-dispersive x-ray spectrometry (EDS) spectrum imaging

methods, (2) Develop special TEM specimen preparation

methods to study an interface between a base and a coating layer

of nanoengineered powders, (3) Evaluate the capabilities and

limitations of a recently acquired double-tilt/rotate TEM holder

for manipulation of nanoparticles, and (4) Investigate new

approaches to attain improved electron backscatter diffraction

(EBSD) analysis of nanoscale particles.

In the first task, a new method for EELS spectrum-line imaging

was developed. The imaging energy filter (EELS spectrometer)

attached to a CM300FEG TEM was modified by insertion of a

slotted grid in the entrance aperture. The electron optics in the

filter are operated in a nonstandard mode to obtain a spectrumline image, a profile data set containing one spatial dimension and

one energy-loss spectrum simultaneously. Spectrum-line images

were collected from ultrathin dielectric gate oxide film samples,

demonstrating EELS profiling across nanometer-scale structures

of technological importance (Figure 1).

In the fourth task, to improve the EBSD pattern quality for

submicrometer particles, a sample holder was constructed that

enables particle mounting on a thin, electron transparent

substrate. The hypothesis was that the thin substrate would

dramatically reduce the noise contribution from electrons that

scatter into the substrate, and thus, improve pattern quality

from small particles.

Tailored Metallic Powders

John Henry J. Scott (NIST/CSTL) and

Leonid A. Bendersky

There is an intensive search for new ìtailoredî materials

properties through manipulation oftheir microstructural

components. The success of ìcreatingî such materials is

strongly dependent on how well we understand the relationships

among properties, processing and microstructure. The objective

of this research is to develop measurement techniques for the

structural and chemical characterization of micro-engineered

powders.

The hypothesis proved correct. The quality of the EBSD

pattern from a 150 nm Al2

O3 particle mounted on a 20 nm

carbon thin-film is clearly superior to the pattern from the

particle mounted on the bulk substrate.The pattern has a high

enough signal-to-noise ratio to conduct a phase identification

analysis of the particle and identify it as hexagonal Al2

O3.

S. Turner, J. H. J. Scott, and J. A. Small (NIST/CSTL)

Figure 1.(a) TEM image of 5 nm SiO2 gate dielectric film

(bottom arrow) on a Si substrate (top arrow).(b) Spectrum

line image of approximate area in yellow box in (a).

Horizontal axis is energy loss in eV; vertical axis is position

on sample in nm.White arrows indicate plasmon peaks.

(c) EELS profiles from the spectrum line image.
Metals Processing

Contributors

and

Collaborators:

46

Metal-on-metal homo-epitaxial growth and hetero-epitaxial

growth are topics of long standing scientific and technological

interest. Remarkable progress has occurred in the last thirty

years due to the application of ever more sophisticated

analytical tools. In particular, the advent of a range of in situ

methods has resulted in a renaissance in the study and application of electrochemical processing. Proximal probe methods are

playing a central role in this development.

At NIST we are using Scanning Tunneling Microscopy (STM)

and Atomic Force Microscopy (AFM) to examine the influence

of inorganic surfactants such as halides and Group IIIa-IVa

metals on the surface structure and electrodeposition of

transition metals. These nominally simple systems exhibit quite

complex behavior. For example, in the case of saturated halide

adsorption, ordered 2-D adlayer structures are observed at

potentials corresponding to the copper/cupric ion potential. In

the presence of a metal deposition flux the adlayer floats on the

surface and acts as a template which guides step motion. At

more negative potentials a series of adlayer phase transitions

occurs coincident with the decreasing coverage of halide. We are

examining the influence of these surface phases on the metal

deposition reaction as well as the possibility of using potential

modulation to perturb the adlayer structure and thereby

influence roughness evolution during metal deposition. Preliminary studies reveal a strong effect of potential modulation on

roughness evolution during copper deposition in the presence of

halide. This represents a first step towards understanding the

influence of potential perturbation on electrocrystallization; a

topic of some importance to the widely applied practice of pulse

plating. In a similar manner underpotential deposition (upd) of

metals is being explored for use as surfactants in homoepitaxial

deposition or alternatively, as a novel processing scheme for

producing alloys. Thus far, our work has centered on examining

Pb upd on Cu. Clear evidence of a coverage dependent twodimensional alloy-dealloying phase transition has been observed

by voltammetric and STM studies of Cu(111), Cu(110) and

Cu(100) and is a subject of ongoing study (Figure 1). Similarly,

surface segregation of Cu during Cu/Co multilayer deposition on

Cu(100) is also being examined.

Electrochemical

Processing of

Nanostructural Materials

The precise temporal control of supersaturation provided by

electrochemical methods holds promise for the synthesis and

characterization of materials and structures of very small

dimensions ñ nanomaterials.Surfactants and segregation

phenomena are investigated here for their role in controlling

homo- and hetero-epitaxial film growth at the nanometer level.

Measurements using proximal probes for directed synthesis are

also being explored. Electrodeposition is also being used to

produce materials of interest to the GMR and Spintronics

projects in the MSEL Program on Materials for Magnetic Data

Storage.

Thomas P. Moffat

J. E. Bonevich, R. D. McMichael, M. Vaudin, D. E.Kramer, and T. Foecke (NIST/MSEL),

A. Ford (NIST/SURF), W. Schwarzacher, (University of Bristol), and D. van Heerden

(Johns Hopkins University)

Metal-semiconductor contacts have been widely studied for

interconnect applications. More recently, the realization of spin

dependent transport effects has created a range of new opportunities from spin valves to metal-semiconductor spintronic

devices. In the latter case, ferromagnetic metals may be used as a

source of spin polarized electrons while semiconductors such as

GaAs allow coherent transport of polarized electrons over a long

range, up to 100 mm, suggesting all sorts of device possibilities.

The literature suggests that the most difficult challenge is to

transfer the polarized electrons from the ferromagnetic source

into the non-ferromagnetic semiconductor without substantially

degrading the polarization. Currently, the electrodeposition of

bcc-Co on GaAs(100) is being studied. The good lattice match

(<1 % misfit), is thought to stabilize a bcc-Co phase, which does

not exist as a bulk phase. TEM provides evidence of the

formation of 6 to 8 monolayers of this phase at the GaAs/Co

interface which is subsequently covered by textured hcp Co. The

possibility of stabilizing the bcc phase by adding Fe to the

system is being explored.

Figure 1. Cyclic voltammetry reveals a potential driven 2-D

phase transition between a halide and lead-covered Cu(111)

surface. The peak current decreases and an additional peak

appears with continued cycling of the potential. This

reflects Pb alloying which accompanies the adsorbate

driven step faceting.
 Metals Processing 

Contributors

and

Collaborators:

47

Multicomponent diffusion is important in many industrial

processes, especially in the processing and application of Nibased superalloys where diffusion determines the γ¥ precipitate

size and particle size distribution after solidification and heat

treatment.An a priori understanding of this diffusion-controlled

microstructure would allow the optimization of heat treatments

that avoid incipient melting and the prediction of freezing

temperatures and solidification paths for Ni-based superalloys.

All of these processes require the use of a diffusion mobility

database to describe the composition-dependent diffusion

coefficients.

Diffusion Mobility Database. Concentration-dependent

diffusion coefficients in a multicomponent system are defined as

the product of a thermodynamic factor and a mobility term. The

NIST composition-dependent mobility database is being

constructed using an approach which assumes that quaternary

and higher order interactions are negligible. Thus, binary and

ternary effects can be combined to extrapolate to higher order

systems. For the Ni-Al-Cr-Co-Mo-Hf-Mo-Nb-Re-Ta-Ti-W

system, a diffusion mobility database has been constructed for

the γ (disordered FCC) phase. The current database includes

only binary interactions. The database was validated using

comparisons of the correlation of the melting temperature of the

pure material with diffusivity, experimental quaternary diffusion

coefficients, and other diffusion assessments. Diffusion

calculations made with other thermodynamic databases have also

been compared.The development of this diffusion mobility

database has been submitted for publication and made available

to industry.

Future work will incorporate diffusion in the ordered γ¥ phase

and development of a user-friendly electronic interface for public

use. In addition, we are working with General Electric Corporate

Research and Development (GE-CRD) and Howmet Corporation who will perform supporting experimental work.The

experimental results will be analyzed by NIST and incorporated

into the diffusion mobility assessments.

γ¥ Precipitation. The precipitation of the ordered phase, γ¥, in

the disorderedγ (FCC) matrix is the dominant strengthening

mechanism in Ni-based superalloys.Thus, control of the

Reaction Path Analysis in

Multicomponent Systems

Carelyn E. Campbell and William J.

Boettinger

Many commercially important processes rely on multicomponent

diffusion to control the formation and dissolution of precipitate

phases with a matrix or at an interface.A multicomponent

diffusion database for Ni-based superalloys developed at NIST

provides a tool which enables modeling of various processes,

including non-isothermal γ¥precipitation, heat treatment

optimization,solidification, transient liquid phase bonding, and

thermal barrier applications.

particle size distribution ofγ¥ is critical to achieving needed

mechanical properties.As a part of a General Electric-led

DARPA project, the γ¥ precipitation process is being numerically modeled by Questek Innovations.This model requires

inputs of equilibrium chemical potentials inγ and γ¥, the

composition dependent diffusivity in the γ matrix, γ and γ¥

lattice parameters, and interfacial energy. NIST has provided

Questek with an electronic version of the diffusion database to

calculate the necessary diffusion coefficients.

Homogenization.NIST has initiated an effort to develop heat

treatment optimization techniques to address industryís need

for more efficient heat-treating practices of cast Ni-based

superalloys.The ideal heat treatment of a cast Ni-base

superalloy consists of a heating schedule that avoids incipient

melting while minimizing either the power expenditure or the

heating time to achieve a homogeneous single phase structure.

Initial simulations with linear heating rates have been completed

for a Ni-Al-Ta alloy that had a liquid to γ to γ+γ¥ solidification

path.This model case demonstrated the potential for optimization.Future work will include investigation into the effects

of non-linear heating rates and more rigorous optimization

methods.

G. B. McFadden (NIST/ITL), R. F. Sekerka (Carnegie Mellon University), R. Reed

(University of Cambridge), B. Muller (Howmet Corp.), J.-C. Zhao, (GE-CRD), and

C. Kuehmann and H. Jou (Questek Innovations)

Figure 1. Calculated incipient melting temperature as a

function of linear heating rates for Ni-0.045Ta-0.12Al mole

fraction alloy solidified assuming a Scheil solidification.

Local equilibrium distributions of γ¥ and Ni3

Ta are

assumed.
48

Combinatorial Methods

The Combinatorial Methods Program develops new measurement techniques and experimental strategies needed for rapid

acquisition and analysis of physical and chemical data of

materials by industrial and research communities. A multidisciplinary team from the NIST Laboratories participates to

address key mission-driven objectives in this new field, including

needed measurement infrastructure, expanded capability,

standards and evaluated data.

Measurement tools and techniques are developed to prepare and

characterize materials over a controlled range of physical and

chemical properties on a miniaturized scale with a high degree of

automation and parallelization.Combinatorial approaches are

used to validate measurement methods and predictive models

when applied to small sample sizes.All aspects of the combinatorial process, from sample ìlibraryî design and library preparation to high-throughput assay and analysis, are integrated

through the combinatorial informatics cycle for iterative

refinement of measurements. The applicability of combinatorial

methods to new materials and research problems is demonstrated

to provide scientific credibility for this new R&D paradigm. One

anticipated measure of the success of the program would be more

efficient output of traditional NIST products of standard

reference materials and evaluated data.

Through a set of cross-NIST collaborations in current research

areas, we are working to establish the infrastructure that will

Contact Information: Leonid A. Benderksy

serve as a basis for a broader effort in combinatorial research. A

Combinatorial Methods Working Group (CMWG) actively

discusses technical progress within NIST on combinatorial

methodsthrough regular meetings. The technical areas and

activities of the CMWG are available in a brochure ìCombinatorial Methods at NISTî (NISTIR 6730). Within MSEL, novel

methods for combinatorial library preparation of polymer

coatings have been designed to encompass variations of diverse

physical and chemical properties, such as composition, coating

thickness, processing temperature, surface texture and patterning. Vast amounts of data are generated in a few hours that

promote our understanding of how these variables affect material

properties, such as coatings wettability or phase miscibility.

Additional focus areasfor both organic and inorganic materials

include multiphase materials, electronic materials, magnetic

materials, biomaterials assay, and materials structure and

properties characterization. State of the art on-line data analysis

tools, process control methodology, and data archival methods

are being developed as part of the program.

In order to promote communication and technology transfer with

a wide range of industrial partners, an industry-national

laboratories-university combinatorial consortium, the NIST

Combinatorial Methods Center (NCMC), is being organized by

MSEL.The NCMC will facilitate direct interactions on

combinatorial measurement problems of broad industrial interest

and efficient transfer of the methods developed to U.S. industry.
 Combinatorial Methods 

Contributors

and

Collaborators:

49

Recently, the effectiveness of the combinatorial approach to the

development of thin film electronic materials has been demonstrated. In this approach, in order to rapidly survey a large

compositional landscape, combinatorial assays with up to

thousands of compositionally varying cells are synthesized,

processed, and screened in a single experiment. Dielectric and

magnetic properties of the cells or compositional spreads can

then be measured by using the recently developed scanning tip

microwave near-field microscope (MNFM) and micro-superconducting quantum interference device (microSQUID), respectively. The properties, however, depend strongly on the

microstructure of the thin films. In order to study the effect of

library fabrication method on the observed structure-property

relationships, combinatorial assays of thin films were prepared

by two methods using controlled pulsed laser deposition: (1)

deposition of cells using precursor layers, followed by postdeposition annealing, or (2) deposition of continuous compositional spreads using multiple targets controlled by synchronized

shutters. Because the first method is quite versatile and requires

relatively simple equipment, yet is unconventional as a

production technique, it is of great interest to investigate the

microstructural details of these films. It is also of great importance to understand and quantify the interdiffusion reaction in

order to apply this combinatorial methodology to other

materials.

In FY2001 we have continued our collaboration with the

University of Maryland (Prof. I. Takeuchi) to investigate, using

transmission electron microscopy (TEM), microstructural

evolution in a model system of BaTiO3 thin films fabricated

from amorphous precursor multilayers consisting of TiO2 and

BaF2

. We have shown by TEM that with carefully controlled

thermal treatments, the precursor TiO2

, BaF2/BaCO3, and SrF2/

SrCO3multilayers can be turned into predominantly single-phase

epitaxial (Ba,Sr)TiO3 films on lattice-matched substrates. We are

also investigating the microstructure of (Ba,Sr)TiO3 compositional spreads and have correlated the structural details (type

and distribution of dislocations, defects) with measured dielectric

properties.

Combinatorial Methods

for Thin Films

Leonid A. Bendersky

In the search for new functional materials for use in modern

communication technology, a variety of complex oxides with

different chemistry and structural states are under consideration.

With the ability to measure locally the relevant dielectric and

magnetic properties, combinatorial methods can have significant

impact. The method can be used to create the ìlibrariesî

designed to either search a composition with an optimal set of

physical properties or study fundamentals of the relationship

between crystallo-chemistry and physical properties, e.g.,

polarization or magnetic ordering in complex oxides.

Figure 1. A series of TEM micrographs showing the

evolution of mixing of the BaF2 and TiO2 precursor layers.

Microstructures at different stages of annealing of the

precursors, (a) 200C; (b) 400C; (c) 700C and (d) 900C,

are shown. From the investigation we concluded that

epitaxial BaTiO3 thin films of good quality can be formed

by a nucleation and growth process on a substrate.

C. J. Lu, R. Parke, and M. Turchinskaya (NIST/MSEL), I.Takeuchi (University of

Maryland), and X. D. Xiang (Lawrence Berkeley National Laboratory)
Combinatorial Methods

Contributors

and

Collaborators:

50

Much industrial research currently focuses on Ti/Al-based metal

contacts to n-GaN, aiming at the minimization of contact

resistivity as a function of: a) semiconductor doping levels, b)

metallization scheme (Ti/Al layer sequence and thickness, and

alloy composition); and c) annealing treatment. We have

employed thermodynamic and diffusion modeling of the Ti-AlGa-N system in combination with high-throughput (combinatorial) experiments to provide understanding for development of

these contacts.

The combinatorial experiments involve the physical vapor

deposition of Ti and Al on doped GaN in a patterned array of

elements with different compositions. Each element will be

subpatterned with a grid to enable the measurement of contact

resistance. After annealing, those elements showing promising

properties will be analyzed by cross-sectional scanning electron

microscopy (SEM) and transmission electron microscopy

(TEM). Properties will be correlated to reaction products. An

example of the subpattern grid for co-deposited Ti-Al metallization on GaN is shown in Figure 1.

To establish the thermodynamic basis for the combinatorial

study, we have examined phase relations in two subsystems of

the above quaternary system: Ti-Ga and Ti-Ga-N, where limited

and contradictory data exist in the literature. Ti/Ga and Ti/GaN

diffusion couples were characterized by x-ray diffraction and

SEM/ x-ray energy dispersive spectroscopy. Interfacial phases

were identified and compared with powder-sintered Ti-Ga and

Ti-Ga-N alloys. The Ti/Ga couple (Fig. 2) unambiguously

shows the following intermetallic phases in the Ti-Ga system:

Ti(Ga) solid solutions, Ti3

Ga, Ti2Ga, Ti5Ga4, TiGa, Ti2Ga3,

TiGa2

, and TiGa3. The homogeneity ranges of these compounds

were also accurately determined at 1173 K. In the Ti/GaN

diffusion couple, two new phases were identified: Ti3

GaN (this

phase was also found in the powder-sintered alloys) and a phase

with a estimated composition of Ti3

Ga2N2.

The next step in this study is to reconcile the Ti/GaN diffusion

path with the experimentally determined Ti-Ga-N phase

diagram, so that predictions of diffusion reactions in more

complex Ti-Al-Ga-N quaternary system can be estimated to

help design the Ti/Al combinatorial metallization experiments.

As a first step in thermodynamic modeling, we are re-evaluating

the Ga-N phase diagram including pressure influence on phase

equilibria. Figure 2. Concentration profiles in the Ti/Ga diffusion

couple after annealing at 800 o

C for 430 hrs.

Application of Phase

Diagrams to Combinatorial Research: Interconnects to GaN Semiconductors

Albert V. Davydov, William J. Boettinger,

and Ursula R. Kattner

Gallium nitride based semiconductorsfind increasing application

in photonic (blue LEDs, lasers) and microelectronic (high-power

transistors) devices. Effective use of these devices requires

improved electrical contact characteristics: lowerresistance and

higherthermalstability of metal contacts especially to p-GaN and

AlGaN alloys. This project examines the properties of metal/GaN

contacts and focuses on quantifying the relationship between the

resistance of metal contacts and fundamental compositional,

microstructural, and electronic properties of the metal/GaN

interface. An improved understanding of these relationships will

aid in designing optimal electrical contacts to GaN devices and

demonstrate the utility of combinatorial methodsin thin film

research.

D.Josell,A.J. Shapiro, S.W. Claggett, and L. H. Robins(NIST/ MSEL),

A.V. Davydov (University of Maryland), and V. Dmitriev (TDI)

Figure 1.Fragment of photolithographically patterned TiAl co-deposited metallization array (plane view): horizontal

metal pads (gray, 75 % Ti and dark gray, 90 % Ti) are

separated by gaps of various widths (white lines) for

measuring contact resistance by transmission line method

(TLM).

The results of this research were presented at the 30th International CALPHAD Conference (May 2001, York, UK) and 4th

International Conference on Nitrides (July 2001, Denver, Co).
Contact Information:

51

Data Evaluation and Delivery

Materials data are critical to the rapid and decentralized design

and manufacture of communication, transportation and other

devices, which characterize 21st century life. The goal of the Data

Evaluation and Delivery Program is to provide the producers and

users of materials with the means of fulfilling their data

requirements in the most efficient ways. This goal is accomplished by providing improved access to materials data,

developing methods for transferring materials data across the

World Wide Web, providing protocols for data evaluation, and

enhancing the functionality of existing collections of evaluated

data. Much of this research is based on information technology

and includes: the development of a materials mark-up language

(MatML), the linkage of digitized crystallographic information

with full structure analysis in cooperation with the International

Ursula R. Kattner

Center for Diffraction Data and Fachinformationszentrum (FIZ)

Germany, and the production of phase diagrams through the

NIST/American Ceramics Society Phase Equilibria Program.

Other informatics available to the community are contained in

the Ceramics WebBook at the Ceramics Division Website. The

Ceramics WebBook provides links to other sources of ceramic

data and manufacturerísinformation,selected evaluated data

sets, structural ceramics and high temperature superconductor

databases, glossaries, and tools for analysis of ceramic materials.

Databases for metals will be developed on web pages in the

form of phase diagrams, deformation mechanism maps, and

simple - but useful - interactive calculations of thermodynamic

and mechanical properties.Annotation and interpretation will

be conducted by the Metallurgy Division.
Data Evaluation and Delivery

Contributors

and

Collaborators:

52

Ursula R. Kattner

In order to deliver materials data efficiently to the end user it is

important to present technical data in a concise but useful form

and utilize the interactive medium that the worldwide web offers

for their retrieval. Downloaded databases and software for

thermodynamic calculations are efficient for regular, expert users

but are cumbersome for the occasional, less expert user.

Retrieval of data through direct interaction with software on the

server may be convenient for the occasional user, but may slow

server responses significantly.The challenge is to develop

interactive software for the potentially large set of non-expert

users with sufficient versatility to allow complicated technical

questions to be answered, sufficient speed to make the calculations efficient, and sufficient interpretation to allow the user to

properly use the information.

In this project we will initially develop phase equilibria data on

the web pages in the form of phase diagrams and simple, but

useful, interactive calculations of thermodynamic properties,

with sufficient annotation and interpretation to make them

useful for the non-expert.In addition, the data on which these

graphs are based will be available in the form of downloadable

databases which can be processed into customized output by

user software, or by specialized software developed by us and

downloadable from our web site.

The phase diagram web site will also provide links to the NIST

mechanical properties internet site allowing the user to examine

the mechanical properties data that are available for the material.

Thermodynamic

Databases for Industrial

Processes

Many industries that process and use metals, from microelectronics to aerospace, need data for complex alloys (three or more

components), including thermodynamic data describing behavior

of alloys.The number of images that would be needed for

graphical representation of these data is prohibitively large. Thus

the development of thermodynamic databases that permit

extrapolation of binary and ternary systems to higher order

systems is needed.Access to these databases through an internet

site with interactive software tools will allow the user to retrieve

the needed phase diagram information.

Figure 2. Path for equilibrium and Scheilsolidification

of Sn-3.5Ag-4.8Bi with and without a 6 % Pb

contamination.

The following information has been posted on the site

http://www.metallurgy.nist.gov/phase/

ïAn introductory page with links to information on phase

diagram activities within the division and external links.

ïA series of pages with ternary solder phase diagrams.Each

page contains a calculated liquidus projection for Sn-rich

systems and an enlargement of the Sn-rich corner and a

table of the invariant reactions in the systems. The ternary

systems currently available are: Ag-Bi-Cu, Ag-Bi-Pb, AgBi-Sn, Ag-Cu-Pb, Ag-Cu-Sn, Ag-Pb-Sn, Bi-Cu-Pb, Bi-CuSn and Cu-Pb-Sn.

ïA link to files with the thermodynamic database description

that was used to generate these phase diagrams.

ïA tutorial page that illustrates the usage of phase diagram

information for the case of Pb-contamination of Pb-free

solder alloys.This page will also serve as an introduction

to task-specific phase diagram software for the calculation

of liquidustemperature, lever rule equilibrium and Scheil

solidification.

Future work will include the development of easy-to-use

interfaces for the task-specific software that will be posted either

for interactive use or downloads on the on the web site. A Best

Practice Guide for interpretation of differential thermal analysis

(DTA) experiments will be integrated into the web site.

W. J. Boettinger, R. J. Fields, andJ. E. Bonevich (NIST/MSEL), andK.-W. Moon

(University of Maryland)

Figure 1. Phase diagram for a Sn-3.5Ag-4.8Bisolder

with contamination from a Sn-37 Pb solder.
Data Evaluation and Delivery 

Contributors

and

Collaborators:

53

Mechanical properties are used to predict the performance of

metallic components during and after fabrication. There is a great

abundance of mechanical properties data, but access to this data

by traditional literature searching is a laborious, time consuming,

and costly process. With the advent of the Internet, more and

more scientists and engineers representing the full range of U.S.

industry, academia, and government agenciessearch for data

electronically almost to the exclusion of print media. There are

already some sites that provide this information to a limited

extent. This project intends to provide a special site for NIST

generated or evaluated data, and a easily adaptable interactive

site that will address more precisely the userís needs.

In the past year, the following information has been posted on

the site http://www.metallurgy.nist.gov/materials_performance/

ï Mechanical and physical properties of copper-tin and

nickel- tin intermetallics

ï Tension and torsion properties of eutectic Pb-Sn solder

ï Fracture mechanism maps of copper, iron, and three steels

(Figure 1)

ï Deformation mechanism maps for LiF and NaCl

ï Transient deformation mechanism maps for mild steel

ï Crack growth mechanism maps (Figure 2)

Figure 1.Fracture Mechanism Map for Pure Iron

Mechanical Properties

of Metals and Alloys

on the Internet

Figure 2. A crack growth mechanism map for aluminum

alloy 2219

Richard J. Fields

U. R. Kattner and J. Bonevich (NIST/MSEL) and H. J. Frost (Dartmouth College)

A useful feature of the NIST mechanical properties internet site

is the ability to link to NIST phase diagram or thermochemistry

data online by transferring to the phase information site for that

material, and vice versa.

An effort was also begun in collaboration with Professor H. J.

Frost of Dartmouth to have an online capability to access the

high information density of deformation mechanism maps.

These maps not only include most available data for a given

material, but also provide constitutive equations that permit

prediction of behavior in regions of stress and temperature of

interest to the user, but where no data exists.This combination

of deformation maps and constitutive equations will be a

powerful tool for scientists and engineers to model and quantify

the effects of microstructure, fabrication processes and use

conditions on mechanical performance.

Mechanical properties are widely needed by U.S. industry for

both estimates of materials performance and for use in finite

elementsoftware.Critically evaluated data for many metal

systems either do not exist or are hard to obtain by traditional

literature search methods.This projectís goals are to (1) develop

a web site where users can easily find data generated or

evaluated by NIST and (2) develop an interactive site where

users can access the precise information they need from fracture

and deformation mechanism maps.
54

Publications

Combinatorial Methods

Combinatorial Methods for Thin Films:

Hewes, J. and Bendersky, L. A., ìHigh Throughput Method for

Materials R&D: A Growing Effort at NIST,î Proceeding of

the Japan-U.S. Workshop on Combinatorial Materials

Science and Technology, (2000).

Application of Phase Diagrams to Combinatorial Research:

Interconnectsto GaN Semiconductors:

Davydov, A. V., Boettinger, W. J., Kattner, U. R., and Anderson,

T. J., ìThermodynamic Assessments of the Gallium-Nitrogen

System,î Phys. Status Solidi (a), in press.

Tsvetkov, D., Melnik, Y., Davydov, A., Shapiro, A.,

Kovalenkov, O., Lam, J. B., Song, J. J., and Dmitriev, V.,

ìGrowth of Submicron AlGaN/GaN/AlGaN

Heterostructures by Hybrid Vapor Phase Epitaxy (HVPE)î

Phys. Status Solidi (a), in press.

Data Evaluation and Delivery

Thermodynamic DatabasesforIndustrial Processes

Agren, J., Hayes, F. H., Hoglund, L., Kattner, U. R., Legendre,

B., and Schmid-Fetzer, R., ìApplications of Computational

Thermodynamics,î Z. Metallkd., in press.

Boettinger, W. J., ìThermodynamics and Phase Diagrams,î

Encyclopedia of Materials Science & Technology, K. H. J.

Buschow, Elsevier Science Ltd., Oxford, UK, (2001).

Davydov, A. V., Boettinger, W. J., Kattner, U. R., and Anderson,

T. J., ìThermodynamic Assessments of the Gallium-Nitrogen

System,î Phys. Status Solidi (a) in press.

Kattner, U. R., and Handwerker, C. A., ìCalculation of Phase

Equilibria in Candidate Solder Alloys,î Z. Metallkd., 92 (7)

(2001).

Moon, K. W., Boettinger, W. J., Kattner, U. R., Biancaniello, F.

S., and Handwerker, C. A., ìExperimental and Thermodynamic Assessment of Sn-Ag-Cu Solder Alloys,î J. Electron.

Mater., 29 (10) 1122-1136 (2000).

Moon, K. W., Boettinger, W. J., Kattner, U. R., Biancaniello, F.

S., and Handwerker, C. A., ìThe Ternary Eutectic of Sn-AgCu Solder Alloys,î Proceedings of 2000 SMTA Conference,

Edina, MN, Surface Mount Technology Assoc, 941-944

(2000).

Moon, K. W., Boettinger, W. J., Kattner, U. R., Handwerker, C.

A., and Lee, D. J., ìThe Effect of Pb Contamination on the

Solidification behavior of Sn-Bi Solders,î J. Electron. Mater.,

30 45-52 (2001).

Moon, K. W., Williams, M. E., Johnson, C. E., Stafford, G. R.,

Handwerker, C. A., and Boettinger, W. J., ìThe Formation of

Whiskers on Electroplated Tin Containing Copper,î

Proceedings of The 4th Pacific Rim Conf. on Adv. Materials

and Processing, Honolulu, HA (2001) in press.

Forming of Lightweight Materials

Standard Test Method Development:

Foecke, T., Banovic, S. W., and Fields, R. J., ìSheet Metal

Forming Studies at NIST,î JOM, 53 (2) 27-30, (2001).

Surface Roughening and Homogeneity of Plastic Deformation:

Stoudt, M. R., and Ricker, R. E., ìThe Influence of Grain Size

on the Roughening Behavior of Al-Mg Alloys,î Innovations

in Processing and Manufacturing of Sheet Materials, M.

Demeri, TMS, Warrendale, PA, 237-244, (2001).

Fundamental Studies of Plastic Deformation

Kramer, D. E., Yoder, K. B., and Gerberich, W. W., ìSurface

Constrained Plasticity: Oxide Rupture and the Yield Point

Process,î Philos. Mag. A, in press.

Levine, L., Kubin, L., and Becker, R., Edt., Dislocations 2000,

An Internationl Conference on the Fundamentals of Plastic

Deformation, Mater. Sci. Eng.A, A309-210, Elsevier Science,

NY, (2001).

Levine, L. E., Kubin, L., and Becker, R., ìPreface to Dislocations

2000 Proceedings,î Mater. Sci. Eng. A, A309-310 (2001).

Savage, M. F., Neeraj, T., and Mills, M. J., ìObservations of

Room Temperature Creep Recovery in Titanium Alloys,î

Metall. Mater. Trans A, in press.

Savage, M. F., Tatalovich, J., Zupan, M., Hemker, K. J., and

Mills, M. J., ìDeformation Mechanisms and Microtensile

Behavior of Single Colony Ti-6Al-2Sn-4Zr-2Mo-Si,î Mater.

Sci. Eng. A, in press.

Slutsker, J. and Roytburd, A., ìModeling of Superelastic

Adaptive Composites,î Proceedings of IUTAM Symposium

on Mechanics of Martensitic Transformations in Solids, in

press.

Materials for Magnetic Data Storage

Materials for Giant Magnetoresistance and Spintronics

Applications:

Bae, S., Egelhoff, Jr., W. F., Chen, P. J., and Judy, J. H., ìEffects

of Deposition Process Parameters on Exchange Coupling of
 Publications 

55

a-Fe2O3/NiFe Bi-layers and GMR in a-Fe2O3/NiFe/Cu/NiFe

Spin Valves,î IEEE Transaction on Magnetics, 36 2892

(2000).

Bae, S., Egelhoff, Jr., W. F., Chen, P. J., and Judy, J. H., ìThe

Structural and Microscopic Analyses of a-Fe2

O3/Co(NiFe)/

Cu/Co(NiFe) Bottom GMR Spin Valves,î Proceedings of

IEEE Trans. Mag. 36, 2617 (2000).

Bae, S., Judy, J. H., Chen, P. J., Egelhoff, Jr., W. F., Shayne, Z.,

Sheppard, L., and Torok, E. J., ìApplication of a-Fe2

O3

Bottom GMR Spin-Valves for Magnetoresistive Random

Access Memory (MRAM)î Proceedings of International

Conference on Ferrites, Kyoto, Japan, in press, (2000).

Bae, S., Judy, J. H., Chen, P. J., Egelhoff, Jr., W. F., and Zurn, S.,

ìHigh Thermal Stability of Exchange-Biased Bilayers and

Bottom Giant Magnetoresistive Spin Valve Using a-Fe2

O3

Antiferromagnetic Layer,î Appl. Phys. Lett., 78 (26) 4163-

4165, (2001).

Bae, S., Zurn, S., Egelhoff, Jr., W. F., Chen, P. J., Sheppard, L.,

Torok, E. J., and Judy, J. H., ìFabrication and ThermalChemical Stability of Magnetoresistive Random Access

Memory (MRAM) Cells Using a-Fe2

O3 Bottom GMR SpinValves,î IEEE Trans. Magn., in press.

Bae, S., Zurn, S., Egelhoff, Jr., W. F., Chen, P. J., Sheppard, L.,

Torok, E. J., and Judy, J. H., ìMagnetoelectronic Devices

using a-Fe2

O3 Bottom GMR Spin Valves,î IEEE Transaction

on Magnetics, in press.

Chopra, H. D., Pepetski, E. J., Brown, H. J., Chen, P. J.,

Swartzendruber, L. J., and Egelhoff, Jr., W. F., ìMagnetic

Behavior of Atomically Engineered NiO-Co-Cu-based Giant

Magnetoresistance Spin Valves Using Pb as a Surface

Modifier,î Acta Mater., 48 3501 (2000).

Egelhoff, Jr., W. F., Chen, P. J., McMichael, R. D., Powell, C. J.,

Deslattes, R. D., Serpa, F. G., and Gomez, R. D., ìSurface

Oxidation as a Diffusion Barrier for Al Deposited on

Ferromagnetic Metals,î J. Appl. Phys., 89 (9) 5209-5214

(2001).

Egelhoff, Jr., W. F., Chen, P. J., Powell, C. J., and McMichael, R.

D., ìSurface and Interface Effects in the Growth of Giant

Magnetoresistance Spin Valves for Ultrahigh-Density DataStorage Applications,î Proceedings of the 20th International

Seminar on Surface Physics, Progressin Surface Science,

(2000).

Egelhoff, Jr., W. F., Gan, L., Chen, P. J., Powell, C. J.,

McMichael, R. D., Fry, R. A., Beach, G., Martien, D., and

Berkowitz, A. E., ìDetection of Pinholes in Ultrathin Films

by Magnetic Coupling,î MRS Symposium Proc., (2001).

Lu, R. P., Morgan, B. A., Kavanagh, K. L., Powell, C. J., Chen,

P. J., Serpa, F. G., and Egelhoff, Jr., W. F., ìInterfacial

Scattering of Hot Electrons in Ultrathin Au/Co Films,î J. Vac.

Sci. Technol. B, 18 2047 (2000).

Mangan, M. A., Spanos, G., McMichael, R. D., Chen, P. J., and

Egelhoff, Jr., W. F., ìEffects of Annealing on the GMR of

Co-Cu-based Spin Valves,î Metall. Mater. Trans. A, 32A 577

(2001).

Munoz, M., Qian, G. G., Karar, N., Cheng, H., Saveliev, I. G.,

GarcÌa, N., Moffat, T. P., Chen, P. J., Gan, L., and Egelhoff,

Jr., W. F., ìBallistic Magnetoresistance in a Nanocontact

between a Ni Cluster and a Magnetic Thin Film,î Appl.

Phys. Lett., in press.

Parks, D. C., Chen, P. J., Egelhoff, Jr., W. F., and Gomez, R. D.,

ìInterfacial Roughness Effects on Interlayer Coupling in Spin

Valves Grown on Different Seed Layers,î J. Appl. Phys., 87

3023 (2000).

Rezende, S. M., Lucena, M. A., Azevedo, A., Oliveira, A. B., de

Aguiar, F. M., and Egelhoff, Jr., W. F., ìExchange Anisotropy

in NiFe Films on (100) NiO Single-Crystal Substrate,î

Proceedings of the International Conference on Magnetics,

(2000).

Wang, D. X., Shashishekar, B., Chopra, H. D., Chen, P. J., and

Egelhoff,Jr., W. F., ìAtomic Engineering of Spin Valves

Using Ag as a Surfactant,î Appl. Phys. Lett., 89 7121

(2001).

Magnetization Control in Thin Films:

Boisvert, R. F., Donahue, M. J., Lozier, D. W., McMichael, R.,

and Rust, B. W., ìMathematics and Measurement,î J. Res.

Natl. Inst. Stand. Technol., 106 293 (2001).

Bonevich, J. E., McMichael, R. D., Lee, C. G., Chen, P. J.,

Miller, W., and Egelhoff, Jr., W. F., ìLarge Magnetic

Anisotropy Induced Via Oblique Sputtering of Ta

Underlayers,î Magnetic Materials, Structures and Processing

for Information Storage, B. J. Daniels, et al., MRS,

Warrendale, PA, (2000).

Fry, R. A., McMichael, R. D., Bonevich, J. E., Chen, P. J.,

Egelhoff, Jr., W. F., and Lee, C.-G., ìThermal Stability of Tapinned Spin Valves,î J. Appl. Phys., 89 (11) 6825-6827

(2001).

McMichael, R. D., Bonevich, J. E., Chen, P. J., Egelhoff, Jr., W.

F., and Lee, C. G., ìStructural Origin of Large Uniaxial

Pinning Fields Induced by Obliquely Sputtered Underlayers,î

J. Appl. Phys., in press.

McMichael, R. D., Donahue, M. J., Porter, D. G., and Eicke, J.,

ìSwitching Dynamics and Critical Behavior of Standard

Problem No. 4,î J. Appl. Phys., 89 7603 (2001).

McMichael, R. D., Lee, G. C., Bonevich, J. E., Chen, P. J.,

Miller, W., and Egelhoff, Jr., W. F., ìStrong Anisotropy in

Thin Magnetic Films Deposited on Obliquely Sputtered Ta

Underlayers,î J. Appl. Phys., 88 (6) 3561-3564 (2000).

Moreland, J., Kabos, P., Jander, A., Lohndorf, M., McMichael,

R. D., and Lee, C. G., ìMicromechanical Detectors for

Ferromagnetic Resonance Spectroscopy,î Proceedings of

SPIE Symposium on Micromachining and Microfabrication,

in press, (2000).
Publications

56

Moreland, J., Lohndorf, M., Kabos, P., and McMichael, R. D.,

ìFerromagnetic Resonance Spectroscopy with a

Micromechanical Calorimeter Sensor,î Rev. Sci. Instrum., 71

(8) 3099-3103 (2000).

Shima, M., Salamanca-Riba, L. G., Moffat, T. P., and

McMichael, R. D., ìCorrelations between Structural

Imperfection and Giant Magnetoresistance Efffect in

Electrodeposited Co/Cu Multilayers,î J. Electrochem. Soc.,

in press.

Stiles, M. D. and McMichael, R. D., ìCoercivity in Exchange

Bias Bilayers,î Phys. Rev. B, 6305 (6) 4405 (2001).

Magnetic Properties of Nanostructured Materials:

Della Torre, E., Fry, R. A., Alejos, O., and Cardelli, E., ìIdentification of Parameters in Multilayer Media,î IEEE Trans.

Magn., 36 (4) 1272-75 (2000).

Della Torre, E. and Reimers, A., ìEnergy Considerations in

Vector Magnetization Models,î J. Appl. Phys., 89 (11)

7269-7241 (2001).

Fry, R. A., Shull, R. D., Uppuluri, S., and Balogh, L., ìMagnetic

Properties of Transition Metal-Dendrimer Nanocomposites,î

Proceedings of MRS Sym., Materials Research Society, 674,

(2001).

Garg, S., Della Torre, E., and Cardelli, E., ìAutomatic Parameter

Identification for the Multilayer Media Preisach Model,î J.

Appl. Phys., 89 (11) 7242-44 (2001).

Zheng, L. A., Lairson, B. M., Barrera, E. V., and Shull, R. D.,

ìFormation of Nanomagnetic Thin Films by Dispersed

Fullerenes,î Appl. Phys. Lett., 77 (20) 3242 (2000).

Magneto-Optical Indicator Film (MOIF) Technique:

Shapiro, A. J., Gornakov, V. S., Nikitenko, V. I., McMichael, R.

D., Egelhoff, Jr., W. F., Tahk, Y. W., Shull, R. D., and Gan, L.,

ìFeatures of Domain Nucleation and Growth in Co/Ru/Co

Synthetic Antiferromagnets Deposited on Obliquely

Sputtered Ta Underlayers,î Journal of Magnetism and

Magnetic Materials, in press.

Shull, R. D., Shapiro, A. J., Gornakov, V. S., Nikitenko, V. I.,

Jiang, J. S., Kaper, H., Leaf, G., and Bader, S. D., ìSpin

Spring Behavior in Exchange Coupled Soft and HighCoercivity Hard Ferromagnets,î IEEE Trans. Magn., in

press.

Materials for Microelectronics

Solders and Solderability Measurements

Gayle, F. W., ìFatigue-Resistant, High Temperature Solder, î

Adv. Mater. Process., 159 (4) 43-44 (2001).

Gayle, F. W., Becka, G., Syed, A., Badgett, J., Whitten, G., Pan,

T.-Y., Grusd, A., Bauer, B., Lathrop, R., Slattery, J.,

Anderson, I., Foley, J., Gickler, A., Napp, D., Mather, J.,

and Olson, C., ìHigh Temperature Lead-free Solder for

Microelectronics,î Proceedings of The 4th Pacific Rim Conf.

on Adv. Materials and Processing, Honolulu, HA (2001) in

press.

Gayle, F. W., Becka, G., Syed, A., Badgett, J., Whitten, G., Pan,

T.-Y., Grusd, A., Bauer, B., Lathrop, R., Slattery, J.,

Anderson, I., Foley, J., Gickler, A., Napp, D., Mather, J.,

and Olson, C., ìHigh Temperature Lead-free Solder for

Microelectronics,î JOM, 53 (6) 17-21 (2001).

Kattner, U. R. and Handwerker, C. A., ìCalculation of Phase

Equilibria in Candidate Solder Alloys,î Z. Metallkd., 92 (7)

(2001).

Moon, K. W., Boettinger, W. J., Kattner, U. R., Biancaniello, F.

S., and Handwerker, C. A., ìExperimental and Thermodynamic Assessment of Sn-Ag-Cu Solder Alloys,î J. Electron.

Mater., 29 (10) 1122-1136 (2000).

Moon, K. W., Boettinger, W. J., Kattner, U. R., Biancaniello, F.

S., and Handwerker, C. A., ìThe Ternary Eutectic of Sn-AgCu Solder Alloys,î Proceedings of 2000 SMTA Conference,

Edina, MN, Surface Mount Technology Assoc, 941-944

(2000).

Moon, K. W., Williams, M. E., Johnson, C. E., Stafford, G. R.,

Handwerker, C. A., and Boettinger, W. J., ìThe Formation of

Whiskers on Electroplated Tin Containing Copper,î

Proceedings of The 4th Pacific Rim Conf. on Adv. Materials

and Processing, Honolulu, HA (2001) in press.

Assembly of IC Chips Utilizing Wafer-Level Underfill:

Josell, D., Wallace, W. E., Warren, J. A., and Wheeler, D.,

ìMisaligned flip-chip solder joints: prediction and experimental determination of force-displacement curves,î J.

Electron. Packaging, in press.

Wheeler, D., Josell, D., Warren, J. A., and Wallace, W. E.,

ìPrediction of Lateral and Normal Force-Displacement

Curves for Flip-Chip Solder Joints,î Proceedings of Fall

Extraction and Process Metallurgy Meeting-Computational

Modeling of Materials, Minerals, and Metals, TMS, in press.

Measurementsfor Electrodeposited On-chip CopperInterconnects:

Josell, D., Wheeler, D., Huber, W. H., and Moffat, T. P.,

ìSuperconformal Electrodeposition in Submicron Features,î

Phys. Rev. Lett., 87 016102 (2001).

Moffat, T. P., Bonevich, J. E., Huber, W. H., Stanishevsky, A.,

Kelly, D. R., Stafford, G. R., and Josell, D., ìSuperconformal

Electrodeposition of Copper in 500-90 nm Features,î J.

Electrochem. Soc., 147 (12) 4524-4535 (2000).

Moffat, T. P., Wheeler, D., Huber, W. H., and Josell, D.,

ìSuperconformal Electrodeposition of Copper,î Electrochem.

Solid State Letters, 4 (4) C26 (2001).

Stafford, G., Moffat, T., Jovic, V., Kelley, D., Bonevich, J.,

Josell, D., Vaudin, M., Armstrong, N., Huber, W., and

Stanishevsky, A., ìCu Electrodeposition for On-Chip

Interconnections,î Characterization and Metrology for ULSI
 Publications 

57

Technology, D. G. Seiler, et al., AIP, New York, 439-443,

(2001).

Metals Characterization

Mechanical Properties of Multilayered and Nanomaterials:

Kramer, D. E. and Foecke, T., ìCorrelations of Microstructure

and TEM Observations of Plasticity in Metallic

Nanolaminates,î Proceedings of MRS Sym., Materials

Research Society, 634, (2001).

Stoudt, M. R., Ricker, R. E., and Cammarata, R. C., ìThe

Influence of a Multilayered Metallic Coating on Fatigue

Crack Nucleation,î Int. J. Fatigue, in press.

van Heerden, D., Gavens, A. J., Subramanian, P. R., Foecke, T.,

and Weihs, T. P., ìThe Stability of Nb/Nb5

Si3 Microlaminates

at High Temperatures,î Metall. Mater. Trans A, in press.

Hardness Standardization:

Low, S. R., ìRockwell Hardness Measurement of Metallic

Materials,î National Institute of Standards and Technology,

NIST Recommended Practice Guide, SP 960-5, Gaithersburg,

(2001).

Ma, L., Zhou, J., Low, S., and Song, J., ìFEA Modeling and

Hardness Performance Prediction of Rockwell Diamond

Indenters,î Proceedings of the NCSL International 2001

Workshop and Symposium, eDoc Publish Inc., (2001).

Nanoscale Characterization:

Bendersky, L. A., ìElectron Diffraction via Transmission

Electron Microscopy,î Am. Crystallogr. Assoc. Newsletter,

(4) 28-29 (2000).

Bendersky, L. A., Chen, R., Fawcett, I. D., and Greenblatt, M.,

ìTEM Study of the Electron-Doped Layered La2-

2xCa1+2xMn2

O7: Orthorhombic Phase in 0.8=X=0.9 Composition Range,î Journal Solid State Chem, 157 309-323 (2001).

Bendersky, L. A., Krajewski, J. J., and Cava, R. J., ìDielectric

Properties and Microstructure of Ca5

Nb2TiO12 and

Ca5

Ta2TiO12 Compounds,î Proceedings of the International

Conference on Microwave Materials and Their Applications,

Slovenia, (2000).

Bendersky, L. A., Levin, I., Roth, R. S., and Shapiro, A. J.,

ìCa4

Nb2O9-CaTiO3: Phase Equilibria and Microstructures,î

Journal Solid State Chemistry, 160 257-271 (2001).

Bonevich, J. E., McMichael, R. D., Lee, C. G., Chen, P. J.,

Miller, W., and Egelhoff, Jr., W. F., ìLarge Magnetic

Anisotropy Induced Via Oblique Sputtering of Ta

Underlayers,î Magnetic Materials, Structures and Processing

for Information Storage, B. J. Daniels, et al., MRS,

Warrendale, PA, (2000).

Cresswell, M. W., Bonevich, J. E., Allen, R. A., Guillaume, N.

M. P., Giannuzzi, L. A., Everist, S. C., Murabito, C. E., Shea,

P. J., and Linholm, L. W., ìElectrical Linewidth Test

Structures Patterned in (100) Silicon-on-Insulator for Use as

CD Standards,î in press.

Fry, R. A., McMichael, R. D., Bonevich, J. E., Chen, P. J.,

Egelhoff, Jr., W. F., and Lee, C.-G., ìThermal Stability of Tapinned Spin Valves,î J. Appl. Phys., 89 (11) 6825-27 (2001).

Grey, I. E., Roth, R. S., Mumme, W. G., Planes, J., Bendersky,

L., Li, C., and Chenavas, J., ìCharacterization of New 5M

and 7M Polytypes of Niobia-Doped Ca2

Ta2O7,î J. Solid

State Chem., in press.

Maier, R., Cohn, J. L., Neumeier, J. J., and Bendersky, L. A.,

ìFerroelectricity and Ferrimagnetism in Iron-Doped

BaTiO3

,î Appl. Phys. Lett., 78 (2001).

Magness, L., Kesckes, L., Chung, M., Kapour, D., Biancaniello,

F., and Ridder, S. D., ìBehavior and Performance of

Amorphous and Nanocrystalline Metals in Ballistic

Impacts,î Proceedings of International Ballistics Symposium

(IBS) Switzerland, (2001).

Roytburd, L., Alpay, S. P., Bendersky, L. A., Nagarajan, V., and

Ramesh, R., ìThree-domain Architecture of Stress-Free

Epitaxial Ferroelectric Films,î J. Appl. Phys., 89 553 (2001).

Metals Processing

Modeling of Solidification, Electrodeposition, and Microstructure:

Beckermann, C., Gu, J. P., and Boettinger, W. J., ìDevelopment

of a Freckle Predictor via Rayleigh Number Method for

Single-Crystal Nickel-Base Superalloy Castings,î Metall.

Mater. Trans A, 31A 2545-2557 (2000).

Boettinger, W. J. and Warren, J. A., ìAn Introduction To The

Phase-Field Method: Simulation Of Alloy Solidification,î

Proceedings of the Merton C. Flemings Symposium on

Solidification and Materials Processing, R. Abbaschian, et al.,

TMS, Warrendale, PA, 101-112, (2001).

Glotzer, S. C. and Warren, J. A., ìComputational Materials

Science and Industrial R&D: Accelerating Progress,î

Computing in Science & Engineering, 3 (1) 67-71 (2001).

Kobayashi, R., Warren, J. A., and Carter, W. C., ìA Continuum

Model of Grain Boundaries,î Physica D, 140 (1-2) 141-150

(2000).

Lewis, A. C., Mann, A. B., van Heerden, D., Josell, D., and

Weihs, T. P., ìBiaxial Zero Creep measurements of Interface

Energies in Ni/Ag Multilayers,î Influences of Interface and

Dislocation Behavior on Microstructure Evolution, M.

Aindow et al., Materials Research Society, Warrendale, PA,

(2001).

Lobkovsky, A. and Warren, J., ìPhase-field Model of Crystal

Grains,î Journal of Crystal Growth, 225 282-288 (2001).

Lobkovsky, A. E. and Warren, J., ìSharp Interface Limit of a

Phase-Field Model of Crystal Grains,î Phys. Rev. E, 6305

(5) 1605 (2001).
Publications

58

Lobkovsky, A. E. and Warren, J. A., ìA Phase Field Model of

the Premelting of Grain Boundaries,î MRS Proceedings,

MRS, (2000).

Roytburd, A. and Slusker, J., ìSuperelastic Deformation of

Adaptive Nano-Composites,î MRS Proc., 1-6, (2001).

Roytburd, A. and Slutsker, J., ìDeformation of adaptive

materials. Part III: Deformation of Crystals with Polytwin

Product Phases,î J. Mech. Phys. Sol., 49 1795-1822 (2001).

Sims, J. S., Hagedorn, J. G., Ketcham, P. M., Satterfeld, S. G.,

Griffin, T. J., George, W. L., Fowler, H. A., am Ende, B. A.,

Hung, H. K., Bohn, R. B., Koontz, J. E., Martys, N. S.,

Bouldin, C. E., Warren, J. A., Feder, D. L., Clark, C. W., Filla,

B. J., and Devaney, J. E., ìAccelerating Scientific Discovery

Through Computation and Visualization,î J. Res. Natl. Inst.

Stand. Technol., 105 (6) 875-894 (2001).

Warren, J. A., Kobayashi, R., and Carter, W. C., ìModeling

Grain Boundaries Using a Phase Field Technique,î Journal of

Crystal Growth, 211 (18) (2000).

Warren, J. A., Kobayashi, R., and Carter, W. C., ìPhase Field

Modeling of Grain Boundaries Formed by Impingement

during Melt Growth,î Proceedings of Modeling of Casting

Welding andAdvanced Solidification Processes-IX, S. H.

Conley, (2000).

Processing-Structure-Property Data for Thermal Spray

Coatings:

Ridder, S. D., ìThermal Spray Process Reliability: Sensors and

Diagnostics,î National Institute of Standards and Technology,

NISTIR, 6776, Gaithersburg, MD, (2001).

Electrochemical Processing of Nanomaterials:

Moffat, T. P., ìElectrochemical STM,î Encyclopedia of

Electrochemistry, P. Unwin, et al., Wiley-VCH, Weinheim,

Germany, (2001).

Reaction Path Analysis in Multicomponent Systems:

Boettinger, W. J., Coriell, S. R., Kattner, U. R., and Williams, M.

E., ìAlpha Case Thickness Modeling in Investment

Castings,î Metall. Mater. Trans. B, 31B (6) 1419-1427

(2000).

Campbell, C. A., Boettinger, W. J., and Kattner, U. R., ìDevelopment of a Diffusion Mobility Database for Ni-Base

Superalloys,î Acta Mater., in press.

Campbell, C. E. and Boettinger, W. J., ìTransient Liquid Phase

Bonding in the Ni-Al-B System,î Metall. Materials. Trans.

A, 31A 2835-2847 (2000).

Josell, D., Basak, D., McClure, J. L., Kattner, U. R., Williams,

M. E., Rappaz, M., and Boettinger, W. J., ìMoving the

Pulsed Heating Technique Beyond Monolithic Specimens:

Experiments with Coated Wires,î J. Mater. Res., 16 2421

(2001).

Publications in Other Areas

Nabarro, F. R. and Cahn, J. W., ìThermal Activation Under

Shear,î Philos. Mag. A, 81 (5) 1409-1426 (2001).

Shepherd, D., Hagwood, C., and Fields, R., ìEvaluation of the

Elevated Temperature Creep Strength of Three Lead-Free

Solder Alloys in Soldered Joints,î J. Test. Eval., 29 (7) 380-

386 (2001).

Stafford, G. R. and Hussey, C. L., ìElectrodeposition of

Transition Metal-Aluminum Alloys from Chloroaluminate

Molten Salts,î Advancesin Electrochemical Science and

Engineering, R.Alkire and D. Kolb, Wiley-VCH, Weinheim,

Germany, 275, (2001).

Zhu, Q., Hussey, C. L., and Stafford, G. R., ìElectrodeposition

of Silver-Aluminum Alloys from a Room-Temperature

Chloroaluminate Molten Salt,î J. Electrochem. Soc., 148

C88-C94 (2001).
59

Metallurgy Division

Chief

Carol A. Handwerker

Phone: 301-975-6158

E-mail: carol.handwerker@nist.gov

Deputy Chief

Frank W. Gayle

Phone: 301-975-6161

E-mail: frank.gayle@nist.gov

NIST Fellow

John W. Cahn

Phone: 301-975-5664

E-mail: john.cahn@nist.gov

Group Leaders

Electrochemical Processing Group

Gery R. Stafford

Phone: 301-975-6412

E-mail: gery.stafford@nist.gov

Magnetic Materials Group

Robert D. Shull

Phone: 301-975-6035

E-mail: robert.shull@nist.gov

Materials Performance Group

Richard J. Fields

Phone: 301-975-5712

E-mail: richard.fields@nist.gov

Materials Structure and Characterization Group

Frank W. Gayle

Phone: 301-975-6161

E-mail: frank.gayle@nist.gov

Metallurgical Processing Group

Stephen D. Ridder

Phone: 301-975-6175

E-mail:stephen.ridder@nist.gov
Research Staff

60

Research Staff

Banovic, Stephen W.

E-mail:stephen.banovic@nist.gov

Metal forming

Mechanical properties

Texture analysis

Beauchamp, Carlos R.

E-mail: carlos.beauchamp@nist.gov

Compositionally modulated alloys

Standard reference materials

Baker, Brett C.

E-mail: brett.baker@nist.gov

Deposition of metals/alloys

Bendersky, Leonid A.

E-mail: leonid.bendersky@nist.gov

Functional ceramics

Analytical and high-resolution TEM

High-temperature intermetallics

Combinatorial methods

Biancaniello, Frank S.

E-mail:frank.biancaniello@nist.gov

Spray deposition measurements and

diagnostics

Inert gas atomization: metal powder

measurements and consolidation

Nitrogenated steels, standard reference materials

Special alloys, heat treating melt-spinning

Boettinger, William J.

E-mail: william.boettinger@nist.gov

Relation of alloy microstructures toprocessing

conditions; solidification

Thermal analysis

Solder

Bonevich, John E.

E-mail: john.bonevich@nist.gov

Electron holography

Interfacial structure and chemistry

High resolution/analytical electron microscopy

Magnetic materials

Boyer, Paul A.

E-mail: paul.boyer@nist.gov

Powder analysis

Data management

Vacuum technology

Plasma spray

Campbell, Carelyn E.

E-mail: carelyn.campbell@nist.gov

Transient liquid phase bonding

Multicomponent diffusion simulations

Alloy design methodology

Claggett, SandraW.

E-mail:sandra.claggett@nist.gov

Specimen preparation for electron microscopy

Digital imaging

Specimen preparation for scanning electron

microscopy

Drew, Rosetta V.

E-mail: rosetta.drew@nist.gov

Magnetometry

Database maintenance

Egelhoff,Jr., William F.

E-mail: william.egelhoff@nist.gov

Giant magnetoresistance

Molecular beam epitaxy

Surface physics

Ultrahigh density data storage

Fields, Richard J.

E-mail: richard.fields@nist.gov

Mechanical properties

Mechanical testing

Powder consolidation

Metal forming

Fink, James L.

E-mail: james.fink@nist.gov

Hardness standards

Hardness testing

Mechanical properties measurement

Metal powder consolidation

Environmental corrosion

Metallography

Foecke, Timothy J.

E-mail: timothy.foecke@nist.gov

Metal forming standards

Nanostructured materials

Experimental fracture physics

SEM, TEM, SPM

Micro- and nano-mechanics of materials

Dislocation-based deformation mechanisms

Historical metallurgy and failure analysis
 Research Staff 

61

Fry, Richard A.

E-mail: richard.fry@nist.gov

SQUID magnetometry

Ferromagnetic resonance

Magnetic dendrimer nanocomposites

Giant magnetoresistance

Gates, Hilary G.

E-mail: hilary.gates@nist.gov

Standard reference materials

Gayle, Frank W.

E-mail: frank.gayle@nist.gov

Structure/property relationships

Transmission electron microscopy

Aluminum metallurgy

Solderscience

Guyer, Jonathan E.

E-mail: jonathan.guyer@nist.gov

III-V semiconductors

Molecular beam epitaxy

Alloy film deposition

Stress-induced mass transport

Handwerker, Carol A.

E-mail: carol.handwerker@nist.gov

Interface thermodynamics and kinetics

Solderscience

Microstructure evolution

Jiggetts, Rodney D.

E-mail: rodney.jiggetts@nist.gov

Substrate analysis

Grit blasting

Roughness measurements

Metallography of coatings

Image analysis

Microanalysis/characterization

Hot isostatic processing

Johnson, Christian E.

E-mail: christian.johnson@nist.gov

Ultra-black coatings

Electroless deposition processes

Metallic glass alloy deposition

Microhardness SRM research

Chromium deposition

Pulse alloy deposition

Lead-free solder

Josell, Daniel

E-mail: daniel.josell@nist.gov

Mechanical and thermal properties of multilayer

materials

Measurement and modeling of solder joint

geometries

Filling of sub-0.1μm features by electrodeposition

Kattner, Ursula R.

E-mail: ursula.kattner@nist.gov

Computational thermodynamics

Alloy phase equilibria evaluations

Solder alloy systems

Superalloy systems

Kelley, David R.

E-mail: david.kelley@nist.gov

Microhardness SRM development

Dye penetrant SRM development

Precious metal electrodeposition

Plating on aluminum

Electroplating

Kramer, Donald E.

E-mail: donald.kramer@nist.gov

Nanoindentation

Atomic force microscopy

Thin film mechanical behavior

Transmission electron microscopy

Nanostructured material

Kunz, Andrew W.

E-mail: akunz@nist.gov

Micromagnetic calculations

Levine, Lyle E.

E-mail: lyle.levine@nist.gov

Diffraction theory

Dislocation-based deformation

Synchrotron x-ray techniques

Percolation theory

TEM, SEM, SPM

Lewis, Daniel J.

E-mail: daniel.lewis@nist.gov

Modeling of eutectic solidification

Electric packaging

Lobkovsky,Alexander E.

E-mail: alexander.lobkovsky@nist.gov

Formation and evolution of microstructure

Plasticity

Dynamics of crystalline defects

Thermodynamics of fluid membranes

Low III, Samuel R.

E-mail:samuel.low@nist.gov

Hardness standards

Hardness testing

Mechanical properties of materials

Mechanical testing of materials

Mates, Steven P.

E-mail:steven.mates@nist.gov

Compressible fluid flow

Metal sprays

Fluid flow visualization
Research Staff

62

McMichael, Robert D.

E-mail: robert mcmichael@nist.gov

Giant magnetoresistance

Micromagnetic modeling

Ferromagnetic resonance

Nanocomposites

Moffat, Thomas P.

E-mail: thomas.moffat@nist.gov

Electrochemistry

Scanning probe microscopy

Nanostructures

Pierce Jr., Thomas A.

E-mail: tpierce@nist.gov

Hardness measurements

Metallography

Pitchure, David J.

E-mail: david.pitchure@nist.gov

Mechanical testing

Computer-aided design

Mechanical engineering

Ricker, Richard E.

E-mail:richard.ricker@nist.gov

Corrosion

Deformation mechanisms

Fracture mechanisms (SCC, CF HE)

TEM, SEM

Ridder, Stephen D.

E-mail:stephen.ridder@nist.gov

Spray dynamics and deposition

Thermal spray processes

Process modeling and control

Savage, Michael F.

E-mail: michael.savage@nist.gov

Mechanical behavior

Dislocation deformation mechanisms

Transmisssion electron microscopy

Titanium alloys and intermetallics

Schaefer, Robert J. (Retired)

E-mail: robert.schaefer@nist.gov

Solidification of metals

Defects in castings

Consolidation of metal powders

Shapiro,AlexanderJ.

E-mail: alexander.shapiro@nist.gov

MOIF method microscopy

Mˆssbauer effect

Scanning electron microscopy (SEM) and

X-ray microanalysis

Image analysis

Shepherd, Dominique,A.

E-mail: dominique.shepherd@nist.gov

Titanium alloys

Mechanical testing

Mechanical properties

SEM, TEM

Shull, Robert D.

E-mail: robert.shull@nist.gov

Nanocomposites

Magnetic susceptibility

Mˆssbauer effect

X-ray and neutron diffraction

Magneto-caloric and magneto-optical effects

Magnetic domain imaging

Siu,I-Liang

E-mail: iliang.siu@nist.gov

Thin film processing

Giant magnetoresistance

Magnetization dynamics

Slutsker,Julia

E-mail: julia.slutsker@nist.gov

Smart composites

Shape memory alloy

Massive transformations

Superelastic material

Stafford, Gery R.

E-mail: gery.stafford@nist.gov

Electrochemical transients

Electrodeposition

Molten salt electrochemistry

Stoudt, Mark R.

E-mail: mark.stoudt@nist.gov

Metal fatigue

Thin films

Mechanical properties

Environmentally assisted cracking

Twisselmann, Douglas J.

E-mail: douglas.twisselmann@nist.gov

Ferromagnetic resonance

Magnetometry

Warren,JamesA.

E-mail: james.warren@nist.gov

Computer simulations of solidification

Dendrite pattern formation

Modeling of solder/substrate wetting processes

Modeling grain boundaries

Williams, Maureen E.

E-mail: maureen.williams@nist.gov

Differential thermal analysis

Powder x-ray diffraction

Solder wettability

SEM
63

Organizational Charts