Advanced Manufacturing Processes

8/10/2019 Advanced Manufacturing Processes

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Program Overview

The competitiveness of U.S. manufacturersdepends on their ability to create new product conceptsand to speed the translation from concept to marketwhile decreasing product cost. This is equally truefor well-established commodity industries, suchas automotive and aerospace, and rapidly growingor emerging industries, such as biotechnology andnanotechnology. For existing products, manufacturingis a critical step in reducing product cycle time. Rapid,low-cost development of manufacturing processes isneeded to incorporate new materials into complexproduct shapes with higher performance at equivalentor lower cost as the competing, established materialsand methods. For innovative product concepts, newmaterials with increasing functionality are needed totranslate these concepts to reality.

To realize such improvements in materials andmanufacturing, MSEL is developing robust measurementmethods, models, standards, and materials and processdata needed for design, monitoring, and control ofmanufacturing processes. A growing challenge is beingable to design, monitor, and control such materials andmanufacturing processes at size scales from nanometersto meters. The Advanced Manufacturing ProcessesProgram focuses on the following high-impact areas:

Combinatorial, high-throughput methods for materialsranging from thin films and nanocomposites tomicro- and macroscale material structures;

Industry-targeted R&D centered on uniquemeasurement facilities in forming of lightweightmetals for automotive applications, polymerprocessing, and high-speed machining;

Innovative testbeds for emerging materials,including carbon nanotubes and fuel cells;

National traceable standards having a major impacton trade, such as hardness standards for metalsand process standards for polymers; and

Innovative, physics-based process modeling tools.

Our research is often conducted in close

collaboration with industrial consortia and standardsorganizations. These collaborations not only ensurethe relevance of our research, but also promote rapidtransfer of our research to industry for implementation.Three projects focused on Advanced ManufacturingProcesses are highlighted below.

NIST Combinatorial Methods Center (NCMC)

The NCMC develops novel high-throughputmeasurement techniques and combinatorial experimentalstrategies specifically geared towards materials research.

Advanced Manufacturing Processes

These tools enable rapid acquisition and analysis ofphysical and chemical data, thereby accelerating thepace of materials discovery and knowledge generation.By providing measurement infrastructure, standards, andprotocols, and expanding existing capabilities relevantto combinatorial approaches, the NCMC lowers barriersto the widespread industrial implementation of this newR&D paradigm. MSEL uses a two-pronged strategy foraccelerating the development and implementation of theseapproaches: an active intramural R&D program thatdemonstrates the ability of combinatorial methods toproduce cutting-edge scientific research and an ambitiousoutreach activity; key to this effort is the validation ofthese approaches with respect to traditional one at a timeexperimental strategies.

Forming of Lightweight Metals

Automobile manufacturing is a materials intensiveindustry that involves about 10 % of the U.S. workforce.In spite of the use of the most advanced, cost-effectivetechnologies, this globally competitive industry has majorproductivity issues related to measurement science anddata. Chief among these is the difficulty of designingstamping dies for sheet metal forming. An ATP-sponsoredworkshop (The Road Ahead, June 2022, 2000) identifiedproduction of working die sets as the main obstacle toreducing the time between accepting a new design andactual production of parts. This is also the largest singlecost (besides labor) in car production. To benefit fromweight savings enabled by new high-strength steelsand aluminum alloys, a whole new level of formabilitymeasurement methods, models, and data is needed,together with a better understanding of the physicsbehind metal deformation. MSEL is working withU.S. automakers and their suppliers to fill this need.

Polymer Processing

Polymers have become ubiquitous in the moderneconomy because of their processability, high functionality,and low cost. However, these materials can exhibitcomplex and sometimes catastrophic responses to theforces imposed during manufacturing, thereby limiting

processing rates and the ability to predict ultimateproperties. The focus of our polymer research is onmicrofluidics and microscale processing, modeling ofprocessing instabilities, and on-line process monitoringof polymers. Our unique extrusion visualization facilitycombines in-line microscopy and light scattering for thestudy of polymer blends, extrusion instabilities, and theaction of additives. These measurements are carried outin close collaboration with interested industrial partners.


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Table of Contents

Table of Contents


Ceramics

Synchrotron X-ray Measurements in Support of

Solid Oxide Fuel Cell Development ...................................................................................1

Data, Reference Materials, and Measurement Methods .....................................................2

Metallurgy

Sheet Metal Forming for Automotive Applications:

Anelasticity and Springback Prediction ............................................................................. 6

Microstructural Origins of Surface Roughening

and Strain Localizations .................................................................................................... 7

Plasticity, Fabrication Processes, and Performance ........................................................... 8

Standard Tests and Data for Sheet Metal Formability ....................................................... 9

The NIST Center for Theoretical and Computational

Materials Science ...............................................................................................................10

Underlying Processes of Plastic Deformation in Metal Alloys .........................................11

High Speed Machining ......................................................................................................12

Mechanisms for Delivery of Thermodynamic and Kinetic Data .......................................13

Phase Field Modeling of Materials Systems:

Simulation of Polycrystalline Growth ...............................................................................14

Hardness Standardization: Rockwell, Vickers, Knoop ..........................................15

Polymers

NIST Combinatorial Methods Center (NCMC)

Pioneer and Partner in Accelerated Materials Research ................................................16

Polymer Formulations: Rapid Prototyping Technology

for Polymeric Materials Development ...............................................................................17

Carbon Nanotube Processing .............................................................................................18

Processing Flows and Instabilities .....................................................................................19

Quantitative Polymer Mass Spectrometry .........................................................................20

Polymer Standards .............................................................................................................21


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Control of solid oxide fuel cell microstructure andelectrochemistry close to the electrodeelectrolyte-interconnect interfaces is important for optimizingfuel cell performance and lifetime. Quantifyingthe associated gradients and degradation effectsduring service life is needed to exploit fully theunderlying phenomena governing the materialproperties. A combination of third-generationx-ray synchrotron measurements at the AdvancedPhoton Source seeks to address this need.

Andrew J. Allen

Solid oxide fuel cell (SOFC) systems are undergoingrapid development for large-scale power applications.We are addressing the long-term need to improve thecontrol and integrity of the gradient microstructures withinthe cathode and anode close to, and at, the interfaces withthe dense electrolyte layer. At the typical SOFC operatingtemperatures of 600 C to 800 C, this issue can influencethe in-service performance degradation and SOFC lifetimeduring successive thermal cycles. The operativeelectrochemistry at the electrolyteelectrode interfaces is,itself, ultimately affected by these changes. A combinationof third-generation x-ray synchrotron measurementsat the Advanced Photon Source seeks to quantify themicrostructure and electrochemistry, and establish

the relationships between them.

Synchrotron X-ray Measurements in Support of

Solid Oxide Fuel Cell Development

Figure 1: USAXS.

Figure 1 presents spatial variations in the absolutevoid volume fraction and surface area within a SOFC,with respect to the electrolyte membrane position.The data were obtained by ultrasmall-angle x-ray scattering(USAXS), as were complete void size distributions.A dense yttria-stabilized zirconia (YSZ) electrolyte layerclearly separates the porous cathode (lanthanum strontiummanganate or LSM) and anode (Ni/YSZ cermet) layers.An x-ray vertical beam dimension of less than 10 m

was achieved to provide the needed spatial resolution.Degradation or changes in the measured void variations,as a function of fabrication process or service cycling,would affect both the SOFC electrochemical performanceand structural integrity.

Figure 2: HE-WAXS.

Figure 2 shows high-energy wide angle x-ray scattering(HE-WAXS) measurements of the complete x-raydiffraction pattern at successive positions with respect tothe SOFC electrolyte layer. HE-WAXS and correspondinghigh-energy small-angle x-ray scattering (HE-SAXS)studies of the void surface area variation (calibrated bycross-reference to USAXS) have been made with a 5 mx-ray beam size. At the 80 keV x-ray energy, both WAXS

and SAXS data can be obtained with similar measurementgeometries and at identical sample positions. Thus, thespatial variations in void microstructure and phase can becross-referenced to infer the electrochemical behavior ofthe electrode microstructures close to the interface withthe YSZ electrolyte.

Recently, the electrochemical issues have beenexplored more directly through measurement of x-rayfluorescent yield (FY) spectra. We have used an in-situheating chamber to study SOFC cathode layers undercontrolled atmosphere conditions at temperaturesclose to those encountered in an operating SOFC.By combining the electrochemical data obtained for

specific interfaces with knowledge of the SOFCmicrostructure and phase information above,we seek to facilitate improved SOFC design.

Contributors and Collaborators

J. Woicik (Ceramics Division, NIST); J. Ilavsky,J. Almer (Argonne National Laboratory); A. Virkar(University of Utah); L. Wilson (NETL); P. Singh,J. Stevenson (PNNL); J. Ruud (GE Corporate Research);M. Seabaugh (NexTech Materials)


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NIST Standard Reference Database 31

NIST/ACerS Phase Equilibria Diagrams. Producedjointly by NIST and the American Ceramic Society;thirteen regular book volumes, four topical volumes,three annual volumes, and a computerized database onCD ROM; more than 53,000 units have been sold; thecurrent CD contains approximately 20,000 critically

evaluated diagrams and 15,000 expert commentaries.(Free demo CD available from NIST.) Available forpurchase at http://www.nist.gov/srd/nist31.htm .

Data, Reference Materials, and Measurement Methods


NIST/Sandia/ICDD Electron Diffraction Database.Chemical, physical, and crystallographic information formore than 81,500 materials, including minerals, metals,intermetallics, and general inorganic compounds; thedatabase and associated software enable highly selectiveidentification procedures for microscopic and

macroscopic crystalline materials. Available forpurchase at http://www.nist.gov/srd/nist15.htm .


NIST Structural Database. Crystallographic andatomic position information for metallic crystallinesubstances, including alloys, intermetallics andminerals; the database is distributed in an ASCIIformat, convenient for reading into a variety ofdatabase management systems or processing byindependent software routines. Available forpurchase at http://www.nist.gov/srd/nist83.htm .

NIST Standard Reference Database 84FIZ/NIST Inorganic Crystal Structure Database,Release 2004/1 (February 2004); producedcooperatively by the FachinformationszentrumKarlsruhe (FIZ) and NIST; a comprehensivecollection of full structural crystallography dataof inorganic compounds; contains more than70,000 entries. Available for purchase athttp://www.nist.gov/srd/nist84.htm.


Structural Ceramics Database. Physical,mechanical, and thermal properties; more than38,000 numeric values. Available online athttp://www.ceramics.nist.gov/srd/scd/scdquery.htm .


High Temperature Superconductors. Physical,mechanical, thermal, and superconducting properties;more than 30,000 numeric values. Available online athttp://www.ceramics.nist.gov/srd/hts/htsquery.htm.

The Ceramics Division has been a vigorousparticipant in support of NISTs core missionas a Measurement Standards Institute. The Divisionhas made significant contributions to all aspects ofstandard reference databases, standard referencematerials, and standard measurement methods andpractices. As may be observed here, the productsestablished by the Division provide a substantialresource spanning a considerable sector ofmaterials metrology.

DATABASES

Crystallography

NIST principal investigator:V.L. Karen

Phase EquilibriaDiagrams

NIST principal investigator:T.A. Vanderah

Materials Properties

NIST principal investigator:R.G. Munro


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NIST Property Data Summaries

Focused studies with comprehensive propertysets for specific materials and topical studies focusedon one property for a wide range of materials.Available as follows:

Alumina,http://www.ceramics.nist.gov/srd/

summary/scdaos.htm Silicon Carbide, http://www.ceramics.nist.gov/srd/summary/scdscs.htm

Titanium Diboride, http://www.ceramics.nist.gov/srd/summary/scdtib2.htm

Yttrium Barium Copper Oxide, http://www.ceramics.nist.gov/srd/summary/htsy123.htm

Elastic Moduli Data, http://www.ceramics.nist.gov/srd/summary/emodox00.htm

Fracture Toughness Data, http://www.ceramics.nist.gov/srd/summary/ftmain.htm

Fracture Data for Oxide Glasses, http://www.ceramics.nist.gov/srd/summary/glsmain.htm

Standard Reference Material 1018b

Glass Beads Particle Size Distribution, a particlesize standard for size range 220 m to 750 m.



Standard Reference Material 659

Particle Size Distribution for Sedigraph Calibration,a particle size standard for size range 0.2 m to 10 m.


Sand for Sieve Analysis.


Zirconia Thermal Spray Powder Particle SizeDistribution, a particle size standard for size range

10 m to 150 m.


Thermal Spray Powder Particle Size Distribution,Tungsten Carbide/Cobalt (Acicular), a particle sizestandard for size range 9 m to 30 m.


Thermal Spray Powder Particle Size Distribution,Tungsten Carbide/Cobalt (Spheroidal), a particle sizestandard for size range 18 m to 55 m.

Characterization of Fracture Origins

Provides an efficient and consistent methodologyto locate and characterize fracture origins inadvanced ceramics. May be used in conjunctionwith ASTM standard C-1322. Available online athttp://www.ceramics.nist.gov/webbook/fracture/fracture.htm.

STANDARD REFERENCE MATERIALS

SRMs produced by the Ceramics Division areavailable for purchase at http://ts.nist.gov/ts/htdocs/230/232/232.htm.




Standard Reference Material 1003cGlass Beads Particle Size Distribution, a particlesize standard for size range 20 m to 50 m.





Fractography

NIST principal investigator:G.D. Quinn

Particle SizeMetrology SRMs

NIST principalinvestigator:J. Kelly


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Knoop Hardness of Ceramics.


Vickers Hardness of Ceramics and Hardmetals.


Fracture Toughness of Ceramics.

Standard Reference Material 640c

Silicon Powder Line Position/Profile SRM, siliconpowder, used for calibration of line position andcharacterization of the instrument profile function,certified with respect to lattice parameter.

Standard Reference Material 660a

LaB6Powder Line Position/Profile SRM, LaB6powder, used to characterize the instrument profilefunction and calibrate line position, certified withrespect to lattice parameter.


Mica Powder Line Position (Low Angle) SRM,synthetic fluorophlogopite mica powder, used tocharacterize the instrument line position at lowtwo-theta angle, certified with respect to lattice parameter.

Standard Reference Material 1976aInstrument Response, a sintered alumina plate,certified with respect to lattice parameter anddiffraction intensity as a function of two-theta angle(texture), used for general calibration of diffractionequipment, with respect to line position and intensity,via conventional data analysis methods.


Alumina Powder for Quantitative Analysis, highpurity alumina powder for general quantitative analysesvia powder diffraction methods, certified with respectto lattice parameter.

Standard Reference Material 1878aQuantification of Alpha Quartz, respirable (5 m)powders, certified with respect to amorphous content,used primarily by the industrial hygiene community forquantification of quartz in airborne dust.

Standard Reference Material 1879a

Quantification of Cristobalite, respirable (5 m)powders, certified with respect to amorphous content,used primarily by the industrial hygiene community forquantification of cristobalite in airborne dust.


Quantitative Analyses, four powders, Cr2O3, CeO2,TiO2and ZnO, allows the user to match the linearattenuation of the standard to that of the unknown,certified for phase purity using neutron time-of-flightdiffraction. Supplemental information will include thereference intensity ratio (RIR) or I/Ic value and thelattice parameters as determined with conventionalx-ray diffraction.


Si3N4Powder for Quantitative Analysis, two samplesof high purity silicon nitride powder, one high in the

alpha phase while the other is high in the beta phase,for quantitative analyses via powder diffractionmethods, certified with respect to phase purityand the alpha to beta phase ratio.


Calcium Hydroxyapatite, calcium hydroxyapatitepowder for use in evaluating calcium apatites, primarilyin the field of biological research, certified with respectto lattice parameters and phase purity.


Crystallite Size/ Line Broadening, CeO2andZnO powder which exhibits diffraction line profilebroadening due to crystallite size effects, certified withrespect to particle size via XRD line profile analysis,applicable to a range of materials research and industrialinterests concerned with crystallite size determinationvia powder diffraction techniques.


MechanicalProperties SRMs

NIST principalinvestigator:G.D. Quinn

X-Ray MetrologySRMs

NIST principalinvestigator:J. Cline


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STANDARD TEST METHODS


ASTM C 1211 (2002)

Standard Test Method for Flexural Strength ofAdvanced Ceramics at Ambient Temperature.

ISO Standard 14704 (2000)Fine Ceramics (Advanced Ceramics, AdvancedTechnical Ceramics) Test Method for FlexuralStrength of Monolithic Ceramics at RoomTemperature.

ISO Standard 18756 (2003)

Fine Ceramics (Advanced Ceramics, AdvancedTechnical Ceramics) Determination of FractureToughness of Monolithic Ceramics at RoomTemperature by the Surface Crack in Flexure(SCF) Method.

ISO Standard 17565 (2004)

Fine Ceramics (Advanced Ceramics, AdvancedTechnical Ceramics) Test Method for FlexuralStrength of Monolithic Ceramics at ElevatedTemperature.

ASTM C 1161 (2002)

Standard Test Method for Flexural Strength ofAdvanced Ceramics at Ambient Temperature.

ASTM C 1322 (2002)

Standard Practice for Fractography and Characterizationof Fracture Origins in Advanced Ceramics.

ASTM C 1326 (2003)

Standard Practice for Knoop Hardness of AdvancedCeramics.

ASTM C 1327 (2003)

Standard Practice for Vickers Hardness of AdvancedCeramics.

ASTM F 2094 (2001)

Standard Specification for Silicon Nitride Bearing Balls.This standard addresses the basic quality, physicaland mechanical properties, and test requirements for

silicon nitride balls used for ball bearings and otherspecialty applications.

MechanicalProperty

Test Methods

NIST principalinvestigator:G.D. Quinn


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Increased computing power coupled with finiteelement modeling methods (FEM) has broughtspringback-compensated die design withinreach of the automotive industry. In developingthis technology, industry has determined thatbetter measurement methods and an improvedunderstanding of the influence of large plasticstrains on the properties and behavior of materialsduring springback is required. This project seeksto develop the understanding, measurements,and data to meet this need.

Richard E. Ricker

AU.S. Council for Automotive Research (USCAR)Consortium on Springback Prediction hasdeveloped finite element springback prediction modelsto reduce die design and tryout costs. However,these models consistently underpredict springback.Three alloy properties could vary with plastic strainand contribute to prediction errors: (1) elastic modulus,(2) anelastic modulus, and (3) strain-dependentanelastic behavior (reverse creep or plastic hysteresis).Currently, FEM modelers compensate for theseerrors with arbitrary constants estimated from trialsor prior experience. The objectives of this study are todetermine the origin of these errors, evaluate relevant

measurement methods, and provide materials datathat improves FEM springback prediction codes.

In FY 2003, we demonstrated that the large biaxialstrains typical of forming can significantly reduce theelastic modulus of Al alloys (18 %) and that texturechanges cannot explain this behavior. In FY 2004,finite element models were used to analyze the resultsof NIST 3-point bend springback measurements.Combining these results with modulus data obtained inFY 2003, it was determined that the strain and elasticmodulus variations are too small to measure in theseexperiments. During FY 2004 these results were

presented at industry workshops (USCAR Consortium,Deep Drawing Research Group) and at metallurgy and

physics conferences (ASM, TMS, APS).

Also in FY 2004, Mg and Mg alloys were studiedto determine how widespread this anomalous modulusbehavior is and to gain additional clues as to its origin.Mg is an extremely lightweight HCP metal that wouldbe a prime candidate for automotive applications ifnot for its poor formability and high chemical reactivity.Biaxial strain experiments did not produce a significantchange in the elastic modulus, but the limited ductilityprevented measurements at the high strains required tounambiguously reduce the modulus in Al alloys. Dynamicmodulus analysis (DMA) found that plastic strain produceda broad peak in the imaginary component of the complex

modulus. Previous researchers attributed this peak tograin boundary sliding, but plastic strain and twinning werefound to be responsible for this peak which analysisindicated contains 4 subpeaks (Figure 1).

Sheet Metal Forming for Automotive Applications:Anelasticity and Springback Prediction

In a separate study, niobium is a BCC metal thatDOEs Jefferson Laboratory (JL) uses to fabricatesuperconducting structures by stamping and formingoperations similar to those used by the automotiveindustry to form BCC steel. The Jefferson Laboratoryhas funded NIST to investigate the catastrophic effectof impurities on the forming behavior of high purity Nb.DMA experiments detected variations in the interstitialimpurity content of this high purity metal (Figure 2),which will now be correlated with forming behavior.


S.W. Banovic, R.J. Fields, L. Ma, D.J. Pitchure(Metallurgy Division, NIST); D. Dayan, A. Munitz(NRC-Negev); V. Luzin (NCNR); G. Myneni (JL);E. Chu (Alcoa); USCAR Springback Consortium(Alcoa, DaimlerChrysler, Ford, GM, LSTC, U.S. Steel)Figure 1: DMA peak in deformed Mg alloy AZ31.

Figure 2: DMA peaks from two lots of Nb compared to thecalculated locations for O, C, and N.


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Other topics explored during this fiscal year include:1) statistical analyses of surface roughness data aimed

at determining what roughness measures would be mostuseful for industry; 2) EBSD/SLCM studies of AlMgbinary alloys as a function of strain; and 3) exploratorywork on new methods for measuring friction underconditions designed to emulate actual forming operations.


J. Liu, T. Foecke, R.E. Ricker, L.E. Levine (MetallurgyDivision, NIST); M.D. Vaudin (Ceramics Division, NIST);T. GnupelHerold, (NIST Center for Neutron Research);J.B. Hubbard (CSTL, NIST); R. Reno, E. Moore (UMBC)


The existing data, measurement methods, andbasic understanding of metallurgical factors thatinfluence friction, tearing, and surface finishduring sheet metal fabrication are insufficient tomeet the predictive modeling requirements of theautomotive industry. This project addresses theseneeds by exploring the microstructural originsof the distribution of slip, surface roughening,and strain localization during plastic straining.The primary focus of these investigations isthe relationships between the initial materialcharacteristics and the deformation behaviorof Al and Fe base sheet materials.

Mark R. Stoudt and Stephen W. Banovic

Replacement of conventional steel sheet by aluminumalloys and high-strength low-alloy steels wouldsignificantly reduce automobile weight and increase fuelefficiency. However, wide spread application of thesematerials by the automotive industry is limited primarilydue to formability issues and deficiencies in materialdatabases/constitutive laws affecting finite elementmodeling. This project examines the underlying structureproperty relationships associated with formability in anattempt to improve the numerical simulations that predictdeformation behavior of materials.

Microstructural Origins of Surface Rougheningand Strain Localizations

In FY 2004, several experimental techniques wereused together to explore the relationships between strain,local crystallographic texture and surface roughening ofaluminum alloys. Figure 1a is an electron backscattereddiffraction (EBSD) map showing the variations in surfacegrain orientation on a 6xxx series aluminum sample afterapplying a uniaxial strain of 0.08. As reflected in the figureinset, the surfaces of grains 1, 2 and 3 have , and orientations, respectively. A 3D topographof the same region obtained with a scanning laser confocalmicroscope (SLCM) is shown directly below Figure 1ain Figure 1b. The labels indicate the same grains inboth figures. There are clear differences in the slip bandstructures of the grains. The roughness profiles shownin Figure 2 were acquired from the SLCM data along the

white lines in Figure 1b. The different crystallographicorientations in the three grains produced distinctly differentroughness characters for the same level of macroscopicuniaxial strain. New statistical analysis techniques arecurrently being developed to investigate correlationsin these data.

Figure 1: Surface Characterization of 6xxx series aluminumdeformed to 0.08 uniaxial strain. a) EBSD generated grainorientation map; b) SLCM surface topograph of same region.

Figure 2: Roughness profiles obtained from the three individualgrain orientations shown in Figure 1.


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Predicting the final shape of a part producedusing a complex fabrication process can beextremely challenging. This is particularly true

when microstructure and residual stresses playsignificant roles. Understanding the interplay ofthese factors in industrially important test cases isthe goal of this project. Work on this project wascompleted this fiscal year.

Lyle E. Levine and Hank Prask (856)

Diffraction provides a powerful means of veryaccurately measuring both microstructure andmechanical behavior in a way that provides insight

simultaneously into both, and offers particularopportunities for understanding plasticity. This projectcollaborated with the developers of the NIST ObjectOriented Finite Element (OOF) program to implementa plasticity model into OOF and devise criticalexperimental and computational benchmarks to validateOOF using the NCNR neutron diffractometer tomeasure residual stress, texture and elastic properties.Conventional X-ray sources were also used wherestress states measured at or near surfaces wereimportant for understanding the behavior of materialsor to compare with predictions. Synchrotron X-rayswere used to deal with subsurface residual stresses

in the thin, highly textured samples that result fromsimulated forming operations. Specifically, thefollowing tasks were part of this project:

Experimentally validate calculation of the importantrole played by residual stresses on high-precisionmachining and forming operations (includescollaborative contributions from MEL, ALCOA andBoeing Corporation);

Provide technical assistance and validation testingto CTCMS staff engaged in adding 3D plasticityto OOF;

Develop the ability to characterize near-surfaceresidual stresses; and

Further develop neutron and synchrotron radiationsources to provide high-resolution data needed torelate microstructure, residual stresses, and theireffect on springback.

Overall Project Accomplishments

Validation of Distortion Prediction Method: In2002, we validated residual stress measurement and

prediction methods used by industry. In 2003 and2004, we used the NCNR to measure residual stressdistributions within 7000 series aluminum bars andused high-speed machining to produce test parts.The shapes of the final parts were measured using acontact measuring machine and ALCOA will comparethese shapes to their model predictions.

Test of OOF: In FY 2003, textured polycrystallinesamples were tested for elastic modulus dependenceon texture. These results were compared withpredictions using Electron Backscatter Diffractionand OOF.

Measurement of residual stresses in standardspringback cups in FY 2002: Measurements wereprovided for the project on Standard Tests and Datafor Sheet Metal Formability. In addition, analyseswere done to understand the origin of these stresses.

Incorporation of plasticity: Project personnelworked with CTCMS staff to provide algorithmsand techniques for incorporating plasticity into OOF.

Although this project is ending this fiscal year,outgrowths of the work on residual stress

measurements of deformed sheet metal and plasticitymodeling for OOF continue in other projects.


R. Fields, R. deWit (Metallurgy Division, NIST);T. GnupelHerold, V. Luzin (NIST Center for NeutronResearch); R. Ivester, R. Polvani (ManufacturingMetrology Division, NIST); D. Bowden (Boeing);E. Chu (ALCOA); R. Reno (University of Maryland)

Figure 1: Aluminum parts machined to test shape changescaused by relaxation of residual stresses.

Plasticity, Fabrication Processes, and Performance


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To meet the PNGV goals for fuel efficiency, theU.S. automotive industry is moving to lighter,high-strength materials for auto bodies. NIST

has surveyed industry and found that providingdesigners with accurate material properties, andmethods to incorporate them into finite elementmodels of sheet metal forming dies, is a criticalneed for the US auto industry. This project seeksto develop new standard tests and metrology toaccurately determine sheet metal mechanicalresponse under forming conditions.

Tim Foecke and Mark Iadicola

For the U.S. automotive industry to transition tonew materials for formed sheet metal parts, theymust be able to mechanically characterize the startingmaterials under realistic forming conditions, and inputthis information into die design models. The MetallurgyDivision is conducting research to develop two sheetmetal formability tests, along with associated metrology,that can be standardized and used by industry.

Springback is the elastic shape change to a partassociated with the residual stresses that develop duringthe stamping process. This shape change complicatesassembly and accurate fit-up; thus, the automotive

industry has a strong desire to be able to either avoid it,or at least be able to predict its magnitude and designdies to account for it. The proposed test for springbackconsists of splitting open a ring cut from the sidewallof a deep drawn cup.

This year, the springback cup test was introducedto ASTM at its national meeting in Florida, leading toindustrys proposal to form a new ASTM committee

to explore standardization of this test. A crucial stepin this process has been taken by identifying severalindustrial partners that are willing to participate.Additional participants from both the producer andend-user sides of the sheet metal industry are nowbeing sought for this new committee. The initialrobustness data set generated at NIST last yearforms a solid basis for the design of a round-robintesting matrix to be implemented as part of thestandardization process.

Last year, an x-ray stress measuring system wasinstalled on the sheet metal formability station. Thisunique instrumentation allows for the direct, in situ

measurement of the stress in a given direction whilethe sample is under multiaxial load. This year we madesignificant progress in mapping the multiaxial stressstrainsurface for three aluminum sheet alloys of interest to theautomotive industry: 5182, 6111 and 6022. Typical datais shown in the Figure 1, where for the first time thebiaxial hardening exponent has been measured. In addition,both the flow stress and the hardening exponent, n, werefound to differ in the transverse and rolling directions ofthe sheet. These data will be used by industry to eliminateseveral assumptions in place that extrapolate estimatedbiaxial flow behavior based on a series of uniaxial tensiletests. This should lead to more accurate designs and

cost savings.

This year, NIST was asked to generate materialsproperty data for simulations of prototype parts as part ofthe NUMISHEET 2005 conference. In addition, takingadvantage of our unique capabilities to measure stress ina forming part, another layer of complexity of the prototypepart simulation will require reproducing the measuredstresses at points of the part under the forming load.

Plans for FY 2005 involve completing measurementof the multiaxial stressstrain surfaces for the threeabove-mentioned aluminum alloys, as well as for a

series of steel alloys. This new project, in collaborationwith modelers at GM, will involve studying how theflow surface evolves with different types and amountsof multiaxial prestrain.


T. GnupelHerold (NIST Center for NeutronResearch); M. Shi (USS); E. Chu (ALCOA); C. Xia(Ford); T. Stoughton, M. Wenner, C.T. Wang (GM);A. Andersson (Volvo); E. Schedin (Avestapolarit)

Standard Tests and Data for Sheet Metal Formability

Figure 1: Balanced biaxial flow stress for 5182 Al alloy intransverse (TD) and rolling (LD) directions.



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The NIST Center for Theoretical andComputational Materials Science was foundedin 1994 in order to fulfill its three-fold mission:to investigate important problems in materialstheory and modeling with novel computationalapproaches; to create opportunities forcollaboration where CTCMS can make a positivedifference by virtue of its structure, focus, andpeople; and to develop powerful new tools formaterials theory and modeling and acceleratetheir integration into industrial research. TheCTCMS supports numerous materials theory andmodeling projects both within and externally to theMaterials Science and Engineering Laboratory.

James A. Warren and Benjamin P. Burton

The NIST Center for Theoretical and ComputationalMaterials Science (CTCMS) is a research programaddressing industry needs for theory and modeling toolsfor materials design and processing. The CTCMS is acenter of expertise in computational materials researchthat develops tools and techniques and fosterscollaborations.

CTCMS integrates ongoing research at various

institutions by forming temporary multidisciplinary andmulti-institutional research teams as required to attackkey materials issues of national importance. TheCTCMS has three principal activities, all operatinginteractively: planning, research, and technologytransfer. Workshops are held as the first step indefining technical research areas with significanttechnological impact, identifying team members, andbuilding the infrastructure for collaborative research.The CTCMS provides infrastructure and support forits members, including an interactive World Wide Webserver (www.ctcms.nist.gov) and modern computingand workshop facilities.

Current research areas include theory and simulationof a wide range of materials behavior, including phasetransformation kinetics and morphology, micromagnetics,composite materials, foams, microstructure anddynamics of disordered and partially ordered materials,complex fluids, materials reliability, reactive wetting,pattern formation, crystal growth, sintering, phasetransitions in biological systems, and solidification.Current CTCMS working groups include the following:

High-Throughput Analysis of MulticomponentMultiphase Diffusion Data.

The NIST Center for Theoretical and ComputationalMaterials Science


Phase Field Modeling Tools: The phase fieldmethod has become one of the most flexible andpowerful methods for predicting the evolution ofmaterials microstructure. This effort focuseson the development of both new applications forthis method and tools enabling the solution of thecomplex equations which emerge from these models.

Effective Hamiltonian Methods:Use of fundamental,quantum-mechanical descriptions to derive theproperties of matter is the ultimate goal of materialsmodeling. This effort uses electronic structurecalculations to derive the phase stability of alloys.

WWW Tools for Scientific Collaboration: CTCMS

is working with information science specialists todevelop web-based tools for scientific collaboration.

Tools for Neutron Scattering Measurements:While neutron scattering has become a critical toolfor the probing of material structure and properties,interpretation of the results of experiments presentsa host of challenges for the scientist. This effortattempts to develop a better theoretical frameworkfor the interpretation of such experiments.

Object-oriented finite element modeling of compositematerials: This team of researchers is developing a

set of object-oriented finite element modeling tools toimprove the characterization and property predictionof composite materials. Public domain software toolsare available at www.ctcms.nist.gov.

The CTCMS also hosts web pages with resources andtools in the following areas: an interactive, electroniclibrary of Greens function and boundary element solution;accurate, standardized micromagnetics modeling tools;software tools to improve electronic packaging processes;and a tool to compute equilibrium crystal shapes.More detail can be found at www.ctcms.nist.gov.

Mechanisms for Collaboration with CTCMS

The CTCMS facilitates numerous interactions betweenindustry, academia, NIST, and other government andnational labs to apply materials theory and modeling tosolve U.S. industrial problems in materials design andprocessing. Researchers interested in joining existingefforts or starting new ones are encouraged to contactthe CTCMS. The CTCMS participates in the NationalResearch Council postdoctoral fellowship program andhosts short-term and long-term visitors.


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A substantial increase in the use of aluminumalloys and high-strength steels in automobileswould greatly increase fuel efficiency. The primary

reason why this has not yet occurred is a lack ofaccurate deformation models for use in designingthe stamping dies. This project is developing aphysically based model of plastic deformationusing a combination of statistical physicsapproaches, atomistic modeling and advancedmeasurement techniques.

Lyle E. Levine

P

lastic deformation of metals (as in cold rolling,

stamping, drawing, and metal fatigue) is of greatimportance to industries worldwide, and improvementsin the basic technology would have a significanteffect on the U.S. economy. Unfortunately, existingconstitutive equations cannot accurately predict thematerial behavior, and many tryout and redesign stepsare required. Another related difficulty is in the designof new alloys with improved formability characteristics.Currently, alloy design is done empirically with littleunderstanding of how the various constituents affectthe mechanical properties.

Addressing both of these issues, this project isfocused on developing constitutive laws based upon

the underlying physical processes that produce theobserved mechanical behaviors in metal alloys. Suchconstitutive laws are inherently multi-scale since theymust describe phenomena on length scales rangingfrom the atomistic all the way to the macroscopicstressstrain behavior of bulk material.

Since the underlying processes are extremely complex,most of our theory, modeling and experimental effortsover the past several years were concentrated on

single-crystal pure Al as a model system. This workculminated in the development of the segment lengthdistribution (SLD) model, that describes how macroscopicdeformation arises from the statistical behavior of largenumbers of dislocations. The model correctly predictsthe flow stress (Figure 1), the linear behavior of stage IIhardening, the non-linear hardening in stage III and thedevelopment of slip lines and slip bands. The statisticalvariables, and N0, represent the density of primarydislocations and pinning points, respectively, in the sample.Alloying the Al changes the mechanical properties byaffecting these statistical variables. Thus, this criticalsurface is a universalsurface for all Al alloys. The nextstep is to connect the evolution of the statistical variablesto the underlying physics for Al alloys using atomisticsimulations that accurately incorporate the effects ofalloy chemistry.

Quantum-mechanics based (ab initio) modeling isrequired to adequately describe the effects of chemistryin atomistic simulations. Unfortunately, such simulationsare extremely CPU intensive and thereby limited to afew hundred atoms. Atomistic modeling using classicalpotentials can handle much larger systems but failsfor large bond distortions and chemistry effects.A ground-breaking approach for directly coupling thetwo methods has been developed that allows the use of

large-scale atomistic simulations with simple classicalpotentials while limiting the more accurate ab initioapproaches to critical regions. Preliminary calculationsof vacancy energies near dislocations are now underway.

Washington State University (WSU) is conductingexperimental validation tests of the SLD model usingchemi- and photo-emission techniques to study thetime dependence of new surface production duringdeformation. NIST researchers designed the UHVtensile stage and single-crystal growth facilities, andWSU paid for the fabrication with funding from DOE.

Finally, NIST researchers are supporting the

development of supporting science by serving on theexecutive committee of the international conferenceDislocations 2004 and coorganizing symposia at theFall 2004 MRS meeting and at Plasticity 2005.


D. Pitchure, F. Tavazza (Metallurgy Division, NIST);A. Chaka (Physical & Chemical Properties Division,NIST); T. Dickinson, S. Langford, M. Cai (WSU)

Underlying Processes of Plastic Deformation in Metal Alloys

Figure 1: Universal flow surface (critical surface) for Al alloysat 15 % strain.



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U.S. industry annually spends $200 billion onthe machining of metal parts, and potentialcost savings are a driver towards high-speed

machining. Traditional knowledge-basedapproaches have not been effective in improvingthe efficiency of this rapidly developing field:One recent study showed that industry chosethe correct machining parameters less than halfof the time. Through this project, NIST willprovide measurement capabilities, materialsdata, and assessment of constitutive laws anddeformation models, which will provide users witha capability of producing a first part correct.

Carelyn E. Campbell

To improve the efficiency of high-speed machiningand tooling, industry has employed finite elementmodeling (FEM) to predict correct tooling andmachining parameters. However, FEM has had limitedsuccess as much of the needed material property datafor high speed machining processes, which involvelarge strains (>>1), high-strain rates (up to 106s1),and high-heating rates (greater than 105C/s), isinsufficient. This project emphasizes two complementaryareas: (1) the development of fundamental data ondynamic material behavior at high strain and heating

rates and the assessment of the constitutive lawsused to model this behavior; (2) the modeling andcharacterization of the microstructural changes thatoccur during the rapid deformation and rapid heatingin real machining operations. Residual stresses,responsible for part distortion after machining, are beingmeasured at the NIST Center for Neutron Research.

The first research effort is focused on obtainingthe materials data and assessing whether currentlyused constitutive laws are appropriate. A dynamicmaterial testing facility using a pulse-heated Kolskybar has been developed at NIST and is being used to

measure dynamic stressstrain data at high-strain rates(approximately 500 s1to 105s1) with heating ratesranging from 103Ks1to 1 Ks1. Measurementson 1045 steel showed significant differences in thestressstrain behavior depending on the heating andstrain rates (Figure 1). The two microstructuresshown in Figure 1 demonstrate the observedmicrostructural differences resulting from differentheating rates. Test 504 was rapidly heated andquenched, leaving no time for the pearlite to dissolveand reform. In contrast, test 509 was heated, held attemperature for 1.4 s, then quenched, leaving enough

time for the pearlite to dissolve and then re-crystallizeduring quenching, producing a finer grain size.

These results demonstrated that the non-time dependent

constitutive relationships used by industry to describethe stressstrain data for machining simulations are notcorrect. A time-dependence must be included in theconstitutive relationship to correctly model the materialbehavior during high-speed machining. Using the dynamicmaterial property data collected using the pulse-heatedKolsky bar, time-dependent constitutive laws will bedeveloped and then tested in machining simulations.

High Speed Machining

Figure 1: The effect of various heating and strain rates on boththe stressstrain behavior and the microstructure of 1045 steel.

The second area of research focuses oncharacterizing and modeling microstructural changes inthe deformation/hot zone of aluminum alloys duringmachining. Transmission electron microscopy (TEM)correlated with optical microscopy of the chip hasrevealed bands of re-crystallized grains. The worksurface is being characterized using microhardnessmeasurements, TEM, optical microscopy and residualstress measurements. A model based on thesemicrostructural characterizations and temperature vs.time data from thermal images will be used as input to amicrostructure model. The microstructure model,along with the time-dependent constitutive relationship,will be implemented into a finite element code for

machining simulation.


D. Basak, L. Levine, R. Fields, R. deWit, W. Boettinger,L. Bendersky, T. GnupelHerold, H. Prask (NIST/MSEL);R. Ivester, R. Rhorer, K. Jurrens, J. Soons, R. Polvani,E. Whitenton, M. Kennedy, B. Dutterer, G. Blessing(Manufacturing Engineering Laboratory, NIST); T. Burns(Information Technology Laboratory, NIST); H. Yoon(PL); M. Davies (U. North CarolinaCharlotte)



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The availability of reliable materials data is thekey to successful design of new materials andmanufacturing processes. Many commercial

processes are controlled by the thermodynamicand diffusion properties of the material.Thermodynamic and diffusion mobility databasesprovide an efficient method of storing the wealthof these data, and software tools allow the userto efficiently retrieve the needed information.

Ursula R. Kattner and Carelyn E. Campbell

The complexity of traditional thermodynamics anddiffusion kinetics prevented their direct applicationto the design of complex materials and processes inthe past. By the same token, graphical representationof multicomponent systems is too complex, and storageof every single datum is inefficient due to the enormousamount of data. However, mathematical functions thatrepresent thermodynamic and diffusion properties ofthe phases permit efficient storage. Since these functionsare based on physical models, they further provide thepower of extrapolation of binary and ternary systems tohigher order systems. Software then allows calculationof the desired quantities. This approach is called theCALPHAD methodology. Unfortunately, previoussoftware was tailored to be efficient for expert users andwas difficult for the occasional, less-experienced user.

The databases and software developed in thisproject are designed to provide users with simple toolsto retrieve and disseminate information needed forefficient materials and process design.

Mechanisms for Delivery of Thermodynamic and Kinetic Data

Figure 1: Graphical user interface for solidification calculations.

A modern, user-friendly front end for user input hasbeen developed for solidification calculations (Figure 1).The results of the calculation are delivered to the userin graphical as well as in tabular form. This programis bundled with the NIST superalloy and solderthermodynamic databases, but has the capability towork with user-supplied databases as well. Results canbe used with a Mathematica script for DTA analysissimulation. The software, databases and scripts areavailable on the Metallurgy Division website(www.metallurgy.nist.gov ).

Figure 2: Schematic of an optimization scheme to allow directinput of diffusion couple composition profiles.

Multicomponent, multiphase diffusion couples canbe simulated using NIST thermodynamic and diffusionmobility databases, and experimental and calculatedcomposition profiles can be compared. However,the complexity of such couples prevents experimental

diffusion coefficients from being easily extracted.Current work focuses on methods to allow experimentalcomposition profiles to be directly inputted into a dataassessment process, so the composition profiles canbe directly related to the diffusion mobility parametersstored in the database (Figure 2).

Interactions developed through the High ThroughputAnalysis of Multicomponent Multiphase Diffusionworkshop series have led to several software codes aimedto improve the analysis of multicomponent diffusioncouples based on combinatorial libraries. These codesand other resources are listed on the groups website(www.ctcms.nist.gov ).

Work continues to convert the NIST Diffusion DataCenter into an electronic searchable form. A preliminaryversion should be available by December 2004.


W.J. Boettinger (Metallurgy Division, NIST);A.R. Roosen (Center for Theoretical and ComputationalMaterials Science, NIST); J.-C. Zhao (GeneralElectric); L. Hglund (Thermo-Calc AB)



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Many properties of structural and functionalmaterials depend on the distribution of composition,phases, grain orientations, internal surface stresses,and microstructure. These structures span lengthscales from nanometers to meters. Predictivemodels are needed to reduce the enormous costsand development times involved in designing andinserting new materials into products. Phase fieldmodels of solidification, coupled to stress, grainorientation, and solute and vacancy dynamics arebeing developed to address these needs.

James A. Warren

Modeling of microstructures produced by solidifi-cation, grain evolution, and stress, as well as otherprocesses, involves mathematical solution of equationsfor heat flow, fluid flow, current flow and/or solutediffusion. Boundary conditions on external surfaces reflectthe macroscopic processing conditions, while boundaryconditions at internal interfaces correspond to the liquidcrystal (grain) or graingrain interfaces. These internalinterfaces are moving boundaries and require boundaryconditions with thermodynamic and kinetic character.

To deal with the complex interfacial shapes that develop

during solidification, grain growth, and the application ofexternal stress or pressures, the phase field method hasbecome the technique of choice for computational materialsscientists. This approach often requires numericaltechniques to solve the model equations but readily dealswith complex interface shapes and topological changes.The research, conducted in collaboration with the PolymersDivision, is also supported by the NIST Center forTheoretical and Computational Materials Science.

This year, significant advances were made in theunderstanding of the formation of multi-grained(polycrystalline) materials. Polycrystals often arise by

either the impingement and growth of grains nucleated ina liquid (equiaxed grains), or via the nucleation of columnargrains on a surface. In collaboration with researchersin Japan and Hungary, we developed a phase field modelto study such growth. In a surprising development, thissame model has now elucidated a third mechanism ofpolycrystalline growth: growth front nucleation. Thismode of growth is manifested when new orientationsnucleate on the front of a growing crystal, yielding adensely branched morphology in which the structuralsymmetries that arise due to effects of surface energyanisotropy are disrupted by the nucleation process, yielding

an isotropic pattern. This model demonstrated that thistype of growth can be initiated by either static or dynamic

heterogeneities in the solidifying system, solving a riddlethat has been of substantial interest to materials scientists.This work, published inNature Materials, has attractedextensive academic and industrial interest.

Phase Field Modeling of Materials Systems:Simulation of Polycrystalline Growth

Figure 1: Two simulations of seaweed-like growth of an alloy.The left column shows the solute profile while the right column

shows grain orientation. The upper row is a single crystal whilethe lower is polycrystalline. Using such techniques, the potential

for polycrystalline growth to disrupt the influence of surfaceenergy anisotropy (which gives dendritic growth) is demonstrated.

Although a remarkable amount of progress has beenmade, there are still physical phenomena that need to beproperly included in phase field models if engineeringimpact is desired. With this in mind, much effort hasbeen devoted to account for the effects of stress andvacancies on both solidification and interdiffusion. It is

also believed that our model for polycrystalline growthmay explain spherulitic growth as well as provide insightinto the observations of Bendersky and NIST coworkersof a stable glass phase in highly supercooled alloys.


W. Boettinger, J. Guyer, D. Wheeler (MetallurgyDivision, NIST); J. Douglas (Polymers Division,NIST); L. Granasy, T. Pusztai (RISSPO, Hungary)



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Hardness is the primary test measurementused to determine and specify the mechanicalproperties of metal products. The MetallurgyDivision is engaged in all levels of standardsactivities to assist U.S. industry in makinghardness measurements compatible with othercountries around the world. These activitiesinclude the standardization of the nationalhardness scales, development of primary referencetransfer standards, leadership in national andinternational standards writing organizations,and interactions and comparisons with U.S.laboratories and the National MetrologyInstitutes of other countries.

Carlos Beauchamp and Sam Low

At the international level, we are leading theWorking Group on Hardness (WGH) under theInternational Committee for Weights and Measures(CIPM). The primary goal is to standardize hardnessmeasurements worldwide. As secretary of the WGH,we have led an effort this year to better define theRockwell hardness test procedure used by NationalMetrology Institutes (NMIs). Other activities includechairing the ASTM-International committee onIndentation Hardness Testing and heading the U.S.delegation to the ISO committee on hardness testingof metals, which oversees the development of therespective hardness test method standards publishedby those organizations; and as the Secretariat forthe International Organization of Legal Metrology(OIML) committee on hardness, we have revisedthe international requirements for regulatingRockwell hardness machines.

The primary task at the national level is tostandardize the U.S. national hardness scales and toprovide a means of transferring these scale valuesto industry. Currently, we are producing test blockStandard Reference Materials(SRMs) for the

Rockwell, Vickers, and Knoop hardness scales, aswell as developing new reference standards. Twelvedifferent microhardness SRMs for Vickers and Knoophardness are now available. Fifteen units of a newsteel SRM are in the process of being certified at anominal hardness of 760 kgf/mm2for each of theVickers and Knoop hardness scales. These SRMsare being certified at loads of 2.943 N, 4.905 N, and9.81 N. In addition, renewal of low inventory of twoof the Knoop Scale SRMs is underway. Ten units ofeach of the copper and nickel SRMs are being certifiedwith nominal hardness levels of 125 kgf/mm2and

600 kgf/mm2, respectively, at loads of 0.245 N,0.490 N, and 0.981 N.

We also introduced two new SRMs for theRockwell B scale (HRB) to complement the threeSRM Rockwell C scale blocks currently available.The HRB scale is used for testing softer metals, such asaluminum, copper and brass. Work is also continuingto produce a new Rockwell hardness diamond indenterSRM, which has become feasible due to the successfulcompletion of a Small Business Innovative Research(SBIR) Phase-2 project with Gilmore Diamond Toolsto develop an improved method for manufacturinggeometrically correct Rockwell diamond indenters.

Other activities at the national level occurringthis year included: the assessment of commercialsecondary hardness calibration laboratories for theNIST National Voluntary Laboratory AccreditationProgram (NVLAP) providing direct linkage to the useof the NIST SRMs; the development of a NVLAPproficiency testing program for hardness calibrationlaboratories; and the development of indentation FiniteElement Analysis models that have been used to analyzethe effect of using different indenter materials forRockwell hardness tests in support of proposedrevisions to international test standards.


C. Johnson, J. Fink, D. Kelley, L. Ma, H. Gates(Metallurgy Division, NIST); J. Song (ManufacturingEngineering Laboratory, NIST); W. Liggett, Jr.,N. Zhang (Information Technology Laboratory, NIST);S. Doty, B. Belzer, D. Faison (National VoluntaryLaboratory Accreditation Program, NIST); W. Stiefel(Technology Services, NIST); M. Mihalec (GilmoreDiamond Tools, Providence, RI)

Hardness Standardization: Rockwell, Vickers, Knoop

Figure 1: Prototype of new steel microhardness SRM.



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NIST Combinatorial Methods Center (NCMC)Pioneer and Partner in Accelerated Materials Research

Combinatorial and high-throughput (C&HT)techniques hold great potential for makingmaterials research more productive, morethorough, and less wasteful. However, significantbarriers prevent the widespread adoption ofthese revolutionary methods. Through creative,cost-effective measurement solutions, and withan eye towards fruitful collaboration, the NISTCombinatorial Methods Center (NCMC) strivesto ease the acquisition of C&HT techniques bythe materials research community.

Cher H. Davis and Michael J. Fasolka

Now in its third year, the NIST Combinatorial MethodsCenter continues to be a sought after partner amongindustry, government laboratories, and academicsinterested in acquiring C&HT research capabilities formaterials research. Indeed, the NCMC consortiumcurrently includes 22 member institutions (see table)representing a broad cross-section of the materialsresearch sector.

The NCMC is successful because it serves thecombinatorial materials research community on severallevels. Our foundation is the extensive suite of NCMCtechnologies, which provide measurement solutions toparties interested in acquiring C&HT capabilities. Many

of these methods are described elsewhere in this report,as identified by the NCMC symbol (see top right corner).

Technology transfer efforts complement our methodsfoundation, as evidenced by the many institutions thathave adopted NCMC techniques. For example, AirProducts, Rhodia, National Starch (ICI), Dow, Procterand Gamble, and Eastman, plus many universities, havereplicated NCMC devices in their laboratories. In thisrespect, NCMCFocused Projects are a new paradigm forNIST/industry partnership, which are extremely effectivefor both methods development and technology transfer.

with Procter and Gamble and National Starch (ICI) toproduce HT microfluidic measurements of interfacial

tension. The second Focused Project, sponsored by Inteland National Starch (ICI), will produce C&HT methodsthat gauge the performance of epoxy adhesives for flipchip electronics applications. Several other FocusedProjects are in development.

New scientific endeavors (such as C&HT materialsresearch) gain momentum when stake-holding parties arebrought together. Accordingly, to advance the field, theNCMC invests itself in community formingactivities aimedat information transfer and goal consolidation amonginstitutions interested in C&HT research. Industryworkshops play a major role in this endeavor, and inFY04 we hosted the 4th and 5th additions to the NCMC

workshop series, focused on Polymer FormulationsandProcessing and Characterization, respectively.

Under a Focused Project, NIST scientists and 23 membercompanies collaborate to develop a particular C&HTmeasurement solution. While the research is co-fundedby industry members, we avoid the study of proprietarymaterials and all results are published; this allows theresearch to have the broadest impact. Currently, thereare two Focused Projects. In the first, NIST is working

The focused project approach is particularly effective since itallows active collaboration with industry, allowing real needsto be addressed, and resulting technology transferred. The

[NCMC] is at the leading edge of combi-based material sciencediscovery, and this reflects both the quality of the research programand of the people.

Dr. J. Carroll, ICI/National Starch,Strategic Technology Group

The NCMC provides a unique platform to exchange informa-

tion and ideas with other member companies who form a part ofthis consortium.

D. Bhattacharya, Global Coatings ApplicationDevelopment, Eastman Chemical Co.

Moreover, we have been very active in organizingsymposia at national conferences. In FY04 alone,NCMC staff developed and organized multi-daysymposia on C&HT methods for the Materials ResearchSociety, the American Chemical Society, the AdhesionSociety, and the Knowledge Foundation.

For more information on the NCMC, C&HTtechnologies, or post-doctoral research opportunities,see our website at http://www.nist.gov/combi.

I have heard nothing but praise from all who attended therecent NCMC conference. . .NIST did a superb job organizingthe symposia, selecting thought-provoking topics, and leading

good general discussions. Personal observation of J. Dias,

ExxonMobil; Chair ACS PMSE


K.L. Beers, C.M. Stafford, A. Karim, E.J. Amis,The Multivariant Measurement Methods Group(Polymers Division, NIST)

NCMC Members (*New in FY2004):

3M Honeywell International Accelrys* Hysitron International*Air Force Research Lab Intel*Air Products & Chemicals ICI /National Starch & Chemicals

Akzo Nobel MichelinAtof ina Chemicals* PPG Industr iesBP * Procter & GambleBA SF RhodiaBayer Polymers Sealed Air Corp*Dow Chemical Company Symy x*Eastman Chemical* Univ. of Southern MississippiExxonMobil Research Veeco/Digital Instruments*


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Industrial development of complex mixtures ofmaterials known as formulations has traditionallyrelied upon empirical data and technical intuition,resulting from years of trial and error studies.We accelerate product discovery and optimizationby providing new testing platforms that usehigh-throughput and combinatorial methods torationally explore formulations variable space.These techniques, which have proven powerfullyeffective in drug and catalyst discovery, are nowadapted to the myriad of materials measurementsto which complex mixtures are typically submitted.

Kathryn L. Beers and Joo T. Cabral

Commercially available combinatorial and high-throughput (C&HT) fluid handling and measurementcapabilities have enabled tremendous progress in industrialproduct development; however, the platforms are oftencostly and time-consuming to implement. The approachadopted by most manufacturers has been to build theseautomated platforms that mimic the development processfor a specific material in a narrow application. This greatlyincreases data acquisition rates, but it is challenging toadapt this system-specific infrastructure to changing R&Dneeds. In response, our research aims to develop new

methods for the manipulation and measurement ofcomplex polymeric fluids, thereby providing flexible andinexpensive alternatives to robotics-driven instrumentation.

To improve the versatility of high-throughputformulations testing, we employ microfluidic technologyto build a toolset of complementary library fabricationand test methods. The preparation of devices is fastand modular, allowing for rapid prototype development

Polymer Formulations: Rapid Prototyping Technologyfor Polymeric Materials Development

Figure 1: Profilometry image of a fluidics device masterprepared by patterning an optical resin. 3-D channel structure ispossible due to the frontal polymerization mechanism of the resin.

Figure 2: High-throughput cloud point curves (graph)determined from uniform temperature sweeps of an array ofblend compositions in a prototyped sample plate (top images).

Complex fluid capabilities developed this year tocomplement our library fabrication include a highthroughput microfluidic device for measuring interfacialtension (see related article in this report), a combinatorialmagneto-driven rheometer, and a small angle lightscattering (SALS) instrument for high throughputscreening of polymer blends and solutions. The SALS

instrument builds upon our work demonstrating highthroughput cloud point mapping of polymer blends usingsample libraries prepared in prototyped arrays (Figure 2).


J.T. Cabral, Z.T. Cygan, A.I. Norman, H.J. Walls,T. Wu, C. Xu, Y. Mei, S.D. Hudson, J.F. Douglas,M.J. Fasolka, A. Karim, E.J. Amis (Polymers Division,NIST); J.D. Batteas (Surface and MicroanalysisDivision, CSTL)

and increased flexibility. Our fabrication method is anadaptation of existing procedures that uses an optical

resin with good solvent resistance and obeys a frontalpolymerization mechanism, which enables us to preparequasi-three-dimensional channel structures (Figure 1).

This year, we have built and demonstrated severalmethods of preparing polymer libraries in microfluidicdevices (see Technical Highlights: Polymer LibraryFabrication Techniques Using Microfluidic Technology).The libraries produced are designed to feed directly intothe thin film gradient tools previously developed in theNCMC as well as the fluid measurement capabilitiescurrently being built in our lab.


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We are developing new metrologies for quantifyingthe dispersion and orientation of carbon nanotubesin polymer melts and solutions. This will open

the door to innovative processes and in-linecharacterization methods that will, in turn,empower novel approaches in materials scienceand engineering, creating a pathway toward therealization of a modern generation of materialsand applications for carbon nanotubes.

Erik K. Hobbie and Barry J. Bauer

Carbon nanotubes exhibit remarkable physicalproperties, and there is considerable interest in usingthem as nanoscale building blocks for a new generation

of novel materials. Despite this promise, fundamentalissues related to the dispersion, fractionation, andorientation of individual carbon nanotubes remainunresolved, and bulk processing schemes do not yetexist. In fact, techniques for measuring these parametersin nanotubes are primitive. In light of these issues, wehave established a program to enable proficient nanotubeprocessing by quantifying the response of carbon nanotubesuspensions and melts to changes in such parameters ascomposition, aspect ratio, shear stress, and dispersant.

The manufacture of nanotube-based devices andcomposites typically entails suspending them in anaqueous or molten polymeric media and subjecting them

to shearing stresses. We have completed a comprehensiveset of measurements detailing the response of nanotubesuspensions to imposed flows. These experimentshave been conducted over a wide range of shear rates,concentrations, and tube type (single or multi-wall).By combining optical methodologies with neutronscattering, the influence of flow on nanotube clustering,orientation, and dispersion has been elucidated.

Typical optical measurements are shown in Figure 1a,which shows scaled birefringence as a function of ascaled shear rate (Peclet number), where the left inset(red scale bar) is a SEM image of the multi-wall

nanotubes (MWNT), and the right inset (blue scale bar)is an AFM image of a single-wall nanotube (SWNT)bundle (scale bar = 50 nm). The measured orderparameter has been scaled onto the data, and the lineis a power-law fit. Figure 1b shows an analogous plotof the birefringence, where the left inset is an opticalmicrograph of a MWNT (scale bar = 5 m), and theright inset is a SANS pattern for a SWNT suspension(scale bar = 0.06 nm1). The scaling shown in Figure 1confirms theoretical predictions of the importance ofhydrodynamic interactions in the semi-dilute regime.One intriguing result is a segregation by tube length in

Carbon Nanotube Processing

the shear cell; this suggests a path towards the goalof the production of monodisperse nanotubes.

A grand challenge in nanotube research is to breakup the clusters and ropes that naturally form so thatisolated single-wall tubes are realized, which can beutilized in applications. Numerous recipes for dispersingthe nanotubes have been proposed, but there is littlequantification of the resulting suspensions and nopowerful method for comparing different techniques.

We are employing neutron scattering to establishbase-line standards for nanotube dispersion andorientation using a variety of functionalization anddispersion methods. These measurements will resolvea number of controversial and outstanding questionsregarding form and structure in single-walled carbonnanotube suspensions, including persistence lengthand phase behavior.


D. Fry (Polymers Division, NIST); H. Wang(Michigan Tech)

Figure 1: Scaled birefringence (n) and dichroism (n) asa function of Peclet number for a variety of carbon nanotube

suspensions. (is the volume fraction.)


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As polymer processing is carried out under highlynon-equilibrium conditions, it is difficult to assessthe state of the polymer without in-situ real-time

measurements. Our program develops and appliesin-situ measurement technology to problems chosenon the basis of input from our industrial partners.This years focus has been on the state of dispersionof nanoclay-polymer composites, as well as onadditives to control the extrusion process.

Anthony Bur and Kalman Migler

In the marketplace of commodity polymers, muchof the value added is due to processing operations.Indeed, the ability to precisely control product qualityoften determines the economic viability of a product.Due to the highly non-linear and non-equilibriumprocesses that occur during large-scale processingoperations, it is generally not feasible to obtain accuratedeterminations of the relevant process state that wouldallow precision control. Thus, most of the qualitycontrol is engineered into the manufacturing processduring the R&D stage.

Our program has built numerous collaborativerelationships with the upstream industries, such asmaterials producers, additive suppliers, and instrumentmanufacturers to further industrys ability to monitor

processing parameters. We have developed a varietyof on-line instruments which can characterize criticalparameters of the polymer during processing such asits temperature, velocity field, molecular orientationand morphology of dispersed components. This yearwe focused on two projects: the behavior of polymeradditives during processing; and techniques to assess thestate of dispersion of clay in polymer nanocomposites.

Additives are frequently mixed into polymericmaterials in minute quantities in order to make themprocessable into the typical products well known toconsumers, such as plastic sheets, pipes, and wireinsulation. However, the basis for the effectiveness

of these additives remained unknown because theexisting tools available to measure their behavior in themanufacturing process were rather crude. We utilizedthe optical phenomena of Frustrated Total InternalReflection (Frus-TIR) to directly visualize the behaviorof fluoropolymer additives in polyethylene melts.

From visualization of the additive coating process,we developed a semi-quantitative model which predictsthe coating efficiency as a function of additive dropletsize and shear rate. A collaboration between NIST,DuPont Dow Elastomers, The University of Minnesota,

Processing Flows and Instabilities

and The University of Maryland is now using thisFrus-TIR technique to test for the critical factorsthat influence the coating efficiency.

Figure 1: Use of dielectric spectroscopy to assess the state ofdispersion of a nanoclay composite. Nylon 11 compounded with

four different clays.

The second focus was to measure the dispersion

of nanoclay additives using an on-line dielectric cell.This cell is effectively a slit die with interdigitatedelectrodes glazed onto one wall. Past work has shownthat it can also be used to carry out rheological andoptical measurements. The program achieved its goalof finding the signature of exfoliation in the spectra ofthe dielectric measurements (see Figure 1). Further,the state of exfoliation was measured from twocomplementary methods: the changes in the opticalfluorescence when certain dyes were incorporatedinto the clay; and changes in the transparency of thematerial as a function of exfoliation. This last methodis particularly inexpensive and may be of use toend-users. These measurements correlated wellwith the traditional laborious off-line techniques(transmission electron microscopy and x-ray).


S. Kharchenko, Y.H. Lee, S. Roth (Polymers Division;NIST); M. McBrearty (Chemical Electrophysics);D. Bigio, M. Meillon, D. Morgan (U. Maryland); S. Oriani(DuPont Dow Elastomers); C. Macosko (U. Minnesota);J. Gilman (BFRL, NIST); P. Maupin (DOE)


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Traditional measures of molecular mass (andthe standards derived from them) provide eitherabsolute values for only one moment of the

distribution or relative values for the entiredistribution. As we discovered from our tworecent industry workshops, producers and usersof synthetic polymers, analytical laboratories,and standards developing organizations, needa method (and standards derived from it)for absolute molecular mass distributiondetermination. Mass spectrometry is beingdeveloped as such a method. Both Type A(random) and Type B (systematic)uncertainties must be included in determiningthe uncertainty budget for mass spectrometry.

William E. Wallace

In mass spectrometry, methods exist to calibratethe mass axis with high precision and accuracy.In contrast, the ion-intensity axis is extremely difficultto calibrate. This leads to large uncertainties inquantifying the content of mixtures. This is truewhether the mixture is composed of differentoligomeric species of the same polymer (i.e., themolecular mass distribution), of polymers with thesame repeat unit but having different end groups(e.g., pre-polymers), or polymers having different

repeat units (i.e., copolymers). The aim of this projectis to calibrate the ion intensity axis. This task hasbeen divided into three parts: sample preparation/ionproduction, instrument optimization, and data analysis.

Matrix-assisted laser desorption/ionization(MALDI) is used to create intact gaseousmacromolecular ions. We have begun to study theMALDI ion-creation process using two-dimensionalcombinatorial libraries where the analyte:matrix ratiois varied in one dimension and the analyte:salt ratiois varied in the other. We add a factorial designmethodology to optimize the instrument parameters

at each composition using the signal-to-noise ratio.Instrument parameters to be optimized includedlaser energy, several critical ion optics voltages,detector voltage, as well as analyte:matrix ratio andmatrix material. From this, it was discovered thatthe detector voltage was the single most importantfactor, followed by the laser energy. Additionally,we continue to develop the MassSpectator computercode to perform unbiased processing of the data.

To gain greater insight into the complex mechanismsof ion creation, the MALDI process was studied as a

Quantitative Polymer Mass Spectrometry

function of sample temperature. The common MALDImatrix 2,5-dihydroxybenzoic acid (2,5-DHB) was useddue to the extensive literature on its physical properties.

Due to the high vapor pressure of 2,5-DHB, singlecrystals were necessary to minimize the surface-to-volume ratio and thereby decrease the sublimation rate.


Figure 1: A 2,5 DHB single crystal on the sample stage.The bright yellow feature is the near UV laser spot. Notice thelight pipe effect as visible radiation escapes from the ends ofthe sample. The sample is approximately 3 mm long.

It was observed that a steep rise in ion productionoccurs at 90 C, achieved a maximum between 120 Cto 130 C, then decreased sharply to a minimum at 130 Cto 140 C, and returned to a second maximum value at150 C. Above 150 C, useful information could not beobtained because of rapid volatilization of the sampleinto the vacuum. The overall trend in ion production iswell described by a recent two-step theory of the laserdesorption/ionization process, which takes into accountthe temperature-dependent effects of plume expansion.It was observed that thermal dehydration, condensation,and decarboxylation reactions increase the volume ofgas released under laser ablation at high temperatures.The resultant higher local pressure at the crystal surfacewas found to have a profound effect on gas-phase ionformation with higher pressures leading to lower ionproduction.


M.A. Arnould, B.J. Bauer, W.R. Blair, H.C.M. Byrd,B.M. Fanconi, K.M. Flynn, C.M. Guttman, D.L. VanderHart,S.J. Wetzel (Polymers Division, NIST); A.J. Kearsley,P.M. Ketcham (Mathematical and Computational SciencesDivision, NIST); J.J. Filliben, J. Lu (Statistical EngineeringDivision, NIST); S.A. Audino, J.E. Girard, Z. Vakili(American University); R. Knochenmuss (Novartis);N. Sari (CARB); Y. Brun (DuPont)


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Polymer Standards

Producers, processors, and users of syntheticpolymers use polymer standards for calibration ofinstruments, assessment of laboratory proficiency,

test method development, and materials improvement.NIST assists in the standards process by providingstandard reference materials (SRM), referencematerials (RM), and reference data. Activitiesinclude recertifying SRMs and RMs as stock isdepleted, determining opportunities for productionof new SRMs and RMs, producing new SRMsand RMs and building databases of relevant datapertaining to SRMs and RMs.

Bruno Fanconi, Charles Guttman, and John Tesk

Recertification of SRM1476

SRM1476, a branched polyethylene, was originally

issued as a melt flow rate standard. It was discontinuedbecause insufficient material remained for recertificationas a melt flow rate standard. During its availability,SRM1476 was also used in studies of branching inpolyethylene, a desirable molecular characteristic forcertain types of products. Although chemists now havemethods to produce a variety of branch structures,measurement methods to quantify the critical aspectsof the branch architecture are lacking. Owing to theavailable molecular data on SRM1476, manufacturers

of chromatographs include small quantities of theoriginal SRM1476 with purchases of their instrumentsfor comparative measurements. NIST has receivedinquiries from manufacturers, researchers and resinproducers about making the remaining supply of SRM

1476 resin available, not as a melt flow rate standard,but as an aid in chromatographic measurements. Theremaining supply of SRM1476 resin was sufficientfor this purpose. Hence, recertification of SRM1476resin for chromatographic measurements was completedin FY 2004. Although the new SRM is not intended asa melt flow rate standard, it remains certified for thispurpose to assure continuity with the original material.

Reference Scaffolds for Tissue EngineeringAt the November 19, 2003 meeting of ASTM

International Committee F04.42 Tissue EngineeredBiomaterials, a task force was initiated for the developmentof reference scaffolds for tissue-engineered medicalproducts (TEMPs). Reference scaffolds had beenidentified at a NIST workshop as the most neededreference material for TEMPs. The task force will conductmeasurements to characterize test scaffolds that willbe supplied to its members; the results will be used todetermine the most useful characterizations to employ when

the reference scaffolds are produced. Scaffolds of knownporosity, interconnectivity, surface and bulk chemistry,physical and mechanical properties, and cellular reactivity

are needed. Initially, the focus will be on characterizingporosity (pore volume and pore size distribution),connectivity, and interconnectivity of pores and worktoward consistent, unambiguous understanding ofterminology. Scaffolds that consist of a regular array ofcubic pores, such as with 600 m pore-edge dimensionsand consistent interconnections, were identified forthe task forces initial study. Micro-x-ray ComputedTomography (-CT) was used for preliminary evaluationof scaffold designs manufactured by different processes,materials, dimensions, and pore size. On this basis, twodesigns were chosen for distribution to the 17 laboratoriesparticipating in the ASTM activity. Laboratory evaluationsof these designs will ensure that the characteristics needed

for the reference scaffolds will be well defined and thattheir measurements will produce consistent results whenthe reference scaffolds are produced. The referencescaffolds will be available for distribution to researchersand developers of scaffolds for tissue engineeringapplications. Initial measurements by NIST showed that-CT would be an important measurement method fordistinguishing scaffolds with acceptably consistent features.

Figure 1: Cubic scaffold with cubic pores (left) and -CTscaffold slice (right).

Figure 2: Porosity as a function of depth of -CT slice (layer).


J. Dunkers, F. Wang, M. Chiang, M. Cicero

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Advanced Manufacturing Processes