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In the feudal structure of the Middle Ages, the nobles who lived in the country ... In feudal cities, where there was a small middle-class population, life was a little ...
U.S. Army Research, Development and Engineering Command

U.S. Army Research, Development and Engineering Command

The “Nanocrystalline Metals” Renaissance of the 21st Century: Tailoring “Bulk” Nanocrystalline Metals for Enhanced Thermal Stability and Mechanical Properties

Mark Tschopp, Heather Murdoch, Laszlo Kecskes, Kris Darling Lightweight & Specialty Metals Branch U.S. Army Research Laboratory

Approved for Public Release / Distribution Unlimited

U.S. Army Research, Development and Engineering Command

The “Nanocrystalline Metals” Renaissance of the 21st Century: Tailoring “Bulk” Nanocrystalline Metals for Enhanced Thermal Stability and Mechanical Properties

Mark Tschopp, Heather Murdoch, Laszlo Kecskes, Kris Darling Lightweight & Specialty Metals Branch U.S. Army Research Laboratory

Approved for Public Release / Distribution Unlimited

U.S. Army Research, Development and Engineering Command

The “Nanocrystalline Metals” Renaissance of the 21st Century: Tailoring “Bulk” Nanocrystalline Metals for Enhanced Thermal Stability and Mechanical Properties

Mark Tschopp, Heather Murdoch, Laszlo Kecskes, Kris Darling Lightweight & Specialty Metals Branch U.S. Army Research Laboratory Mark de’ Medici

Approved for Public Release / Distribution Unlimited

The “Renaissance” period

"Renaissance" (French for "rebirth“) perfectly describes the intellectual and economic changes that occurred in Europe from the 14th through the 16th centuries.

In the feudal structure of the Middle Ages, the nobles who lived in the country provided the king with protection in exchange for land. Peasants worked the land for the nobles, for which they received protection and their own small parcels of land. These rural peasants worked from sunup to sundown, but even the nobles had few creature comforts. In feudal cities, where there was a small middle-class population, life was a little easier and individuals had the freedom to pursue whatever trade or industry they liked. In the late Middle Ages, when the threat of invasion from barbarians had lessened, people left the country for towns and cities so they could engage in more profitable pursuits.

The “Renaissance” period

"Renaissance" (French for "rebirth“) perfectly describes the intellectual and economic changes that occurred in Europe from the 14th through the 16th centuries.

In the feudal structure of the Middle Ages, the nobles who lived in the country provided the king with protection in exchange for land. Peasants worked the land for the nobles, for which they received protection and their own small parcels of land. These rural peasants worked from sunup to sundown, but even the nobles had few creature comforts. In feudal cities, where there was a small middle-class population, life was a little easier and individuals had the freedom to pursue whatever trade or industry they liked. In the late Middle Ages, when the threat of invasion from barbarians had lessened, people left the country for towns and cities so they could engage in more profitable pursuits.

The “Renaissance” period

"Renaissance" (French for "rebirth“) perfectly describes the intellectual and economic changes that occurred in Europe from the 14th through the 16th centuries.

Life in the city was soon to change drastically. During the late Middle Ages and early Renaissance (1350-1450) the bubonic plague, also called the "Black Death," devastated one half of the population of Europe. The plague, which was almost always fatal, spread most rapidly in cities, where people were in close contact with each other. The only way to avoid the disease was to leave the city for the country. This solution was, unfortunately, available only to those wealthy enough to make the trip.

The “Renaissance” period

"Renaissance" (French for "rebirth“) perfectly describes the intellectual and economic changes that occurred in Europe from the 14th through the 16th centuries.

The population decrease caused by the plague led to an economic depression. As incidence of the plague decreased in the late fifteenth century, populations swelled, creating a new demand for goods and services. A new middle class began to emerge as bankers, merchants, and tradespeople once again had a market for their goods and services. As the fortunes of merchants, bankers, and tradespeople improved, they had more than enough money to meet their basic needs for food, clothing, and shelter. They began to desire larger, more luxurious homes, fine art for these residences, sumptuous clothing to show off their wealth in public, and exotic delicacies to eat. These desires of the middle class stimulated the economy.

Army Research Laboratory What does the Army Research Laboratory do?

Army Research Laboratory The primary mission of the U.S. Army Research Laboratory is to “Provide the underpinning science, technology, and analysis that enables full-spectrum operations.” Army of Today

Rapid Innovation

Fundamental Research That Accelerates Development for Future Needs of the Army Transformative Vision

Armed with Science

State of the Art, Art of the Possible!

Army of the Future

Army Research Laboratory The primary mission of the U.S. Army Research Laboratory is to “Provide the underpinning science, technology, and analysis that enables full-spectrum operations.”

WMRD (Weapons & Materials Research Directorate)

Jones, T., et al. ARL-TR-4664, ARL-TR-4664

Army Research Laboratory The primary mission of the U.S. Army Research Laboratory is to “Provide the underpinning science, technology, and analysis that enables full-spectrum operations.”

WMRD ARL-TR-4664

Capability

Old Paradigm

Weight

Materials research that focuses on reducing weight as well as increasing strength and/or functionality can help extend operating ranges of vehicles, increase available mission scope and add additional sensors or payloads.

Army Research Laboratory The primary mission of the U.S. Army Research Laboratory is to “Provide the underpinning science, technology, and analysis that enables full-spectrum operations.”

WMRD e.g., Heat Treatment, Severe Plastic Deformation

Capability

Capability

Old Paradigm

Weight

e.g., Alloy Change, Material Change

Weight

Materials research that focuses on reducing weight as well as increasing strength and/or functionality can help extend operating ranges of vehicles, increase available mission scope and add additional sensors or payloads.

Army Research Laboratory The primary mission of the U.S. Army Research Laboratory is to “Provide the underpinning science, technology, and analysis that enables full-spectrum operations.”

WMRD

New Paradigm

Capability

Capability

Old Paradigm

Weight

Weight

Materials research that focuses on reducing weight as well as increasing strength and/or functionality can help extend operating ranges of vehicles, increase available mission scope and add additional sensors or payloads.

Army Research Laboratory

What is the underlying fundamental science that contributes to performance in these applications? TODAY’S SEMINAR: Innovative Materials Science and Design of “Bulk” Nanocrystalline Metals

GBs in Nanocrystalline At Small Grain Sizes Macroscopic Deformation is Governed To a Large extent By GB-Mediated Processes

10 nm ~ 30 vol% Defects

10%

1%

As grain size decreases to the nanocrystalline regime (< 50 nm), the volume fractions of grain boundaries and triple junctions are increased, which leads to different properties.

Smaller is Better! Nano-Fe surpassing previous Steels!!!

Youssef, Scattergood, Murty, APL (2005)

Yield Strength (MPa)

1000% Increase in Mechanical Strength!!!

Nanocrystalline materials have a corresponding increase in mechanical properties and changes in the deformation mechanisms due to the increased fraction of grain boundaries and the peasants rejoiced…

Smaller is Better? T = 100 C Pure Cu

However, nanocrystalline materials have problems pertaining to thermal stability, which limits processing techniques as well as applications at moderate to high (and sometimes low) temperatures. S.Simoes, R.Calinas, P.J. Ferreira, M.T. Vieira, F. Viana and M.F. Vieira, Mat. Sci. For. Vols. 587, 2008, p 483-487. S.Simoes, R.Calinas, P.J. Ferreira, M.T. Vieira, F. Viana and M.F. Vieira,, Nanotech. 21 2010 pg 145701 .

aaaah…

Outline ARL Expertise in Nanocrystalline Materials Material Processing:

Microstructure Control:

Properties:

Mechanical Alloying

Thermodynamic Stability

Mechanical Properties

Material Processing:

Powder Consolidation (ECAE Processing)

Thermal Stability

Bulk Consolidation

PROCESSING

STRUCTURE

PROPERTY

PERFORMANCE

Outline ARL Expertise in Nanocrystalline Materials Material Processing:

Microstructure Control:

Properties:

Mechanical Alloying

Thermodynamic Stability

Mechanical Properties

Material Processing:

Powder Consolidation (ECAE Processing)

Thermal Stability

Bulk Consolidation

PROCESSING

STRUCTURE

PROPERTY

PERFORMANCE

A Processing Introduction: High Energy Mechanical Alloying

Motivation: While many nanocrystalline processes focus on electrodeposition and vapor deposition, we are interested in creating bulk parts and materials with dimensions greater than 1 mm.

Mechanical alloying is a scalable powder metallurgy process for generating bulk nanocrystalline parts!

Mechanical Alloying can be applied to: Nanocrystalline Alloys, Amorphous Metals, Nanostructured Composites, Energetic Materials, Intermetallics, High Entropy Alloys, Solid State Foaming, Thermoelectrics, etc.

A Processing Introduction: High Energy Mechanical Alloying

Milling Time

Grain Size Reduction

Al-Mn

Fe-Zr

With increasing milling time, the mixing within powders increases, solute can be forced into solution, particles can be dispersed, and the grain size is reduced! KA Darling, AJ Roberts, L Armstrong, D Kapoor, MA Tschopp, LJ Kecskes, SN Mathaudhu, MSEA 589, 2014, pg. 57-65 KA Darling, BK VanLeeuwen, JE Semones, CC Koch, RO Scattergood, LJ Kecskes, MSEA , 528, 2011, pg. 4365-4371

A Processing Introduction: High Energy Mechanical Alloying

Nanocrystalline Material Processing Elemental Powders

High energy Mechanical Alloying

Nanostructured Powder

Fast Kinetic Studies & Characterization

Consolidation & Mechanical Testing

Nanocrystalline Material Process Flow Path

Critical Step in Nanocrystalline Preparation: Powder consolidation (e.g., sintering) requires temperatures greater than 0.5Tm (melting temperature). Thermal stability of nanocrystalline grain size is important!

Surface Nanocrystallization: Surface Mechanical Attrition Treatment

High Energy Cryogenic Surface Mechanical Attrition Treatment

A

B

C

Surface Mechanical Attrition Treatment (SMAT) produces ultrafine or nanocrystalline grains at the surface. At ARL, we have used cryogenic SMAT to further refine the grain size (60% smaller) through a change in deformation mechanism at the surface (dislocation based to shear band based). KA Darling, MA Tschopp, AJ Roberts, J Ligda, L Kecskes, Scripta Mat. 69, 2013, pg. 461-464.

Solid State Foaming:

Exceeding the Theoretical Limit of Porosity

Additive Expansion by the Reduction of Oxides (AERO)

Developed a new solid state foaming processing route whereby intraparticle expansion enables porosity levels that exceed 70% porosity (previously identified as the theoretical limit for solid state foaming). Reconstructing a 3D microstructure shows pore widths and wall thicknesses on the order of 1 micron. Parts have been produced with ~70% porosity. MA Atwater, KA Darling, MA Tschopp, Adv. Engr. Mat. 2014 (selected for cover image).

Outline ARL Expertise in Nanocrystalline Materials Material Processing:

Microstructure Control:

Properties:

Mechanical Alloying

Thermodynamic Stability

Mechanical Properties

Material Processing:

Powder Consolidation (ECAE Processing)

Thermal Stability

Bulk Consolidation

PROCESSING

STRUCTURE

PROPERTY

PERFORMANCE

Achieving Stability:

Kinetic and Thermodynamic Approaches

Pure Cu

2 0  Qm  v  M  P  M 0 exp     r  RT 

v = velocity of grain boundary M = mobility of grain boundary P = pressure on grain boundary M0 = pre-exponential factor Qm = activation energy for GB mobility γ0 = interfacial energy per unit area r = mean grain radius

Two approaches for thermal stability: Kinetic (M) and Thermodynamic (γ) S.Simoes, R.Calinas, P.J. Ferreira, M.T. Vieira, F. Viana and M.F. Vieira, Mat. Sci. For. Vols. 587, 2008, p 483-487. S.Simoes, R.Calinas, P.J. Ferreira, M.T. Vieira, F. Viana and M.F. Vieira,, Nanotech. 21 2010 pg 145701.

Achieving Stability:

Kinetic Grain Size Stability

Kinetic (M)

 Qm  M  M 0 exp     RT  http://aluminium.matter.org.uk/

Pinned Grain Boundary

The kinetic approach for thermal stability relies on second phase particles, pores, and solute drag to pin grain boundaries and reduce their mobility. However, the grain boundary mobility follows an Arrhenius temperature dependence.

Achieving Stability:

Thermodynamic Grain Size Stability

Thermodynamic (γ)

Before segregation

After segregation

Solvent (B) Solute (A) Grain boundary

Reduction in Energy

The thermodynamic approach for thermal stability relies upon a reduction in grain boundary energy by solute segregation to the boundary, thereby reducing the driving force for grain growth (i.e., lowering the grain boundary energy).

Outline ARL Expertise in Nanocrystalline Materials Material Processing:

Microstructure Control:

Properties:

Mechanical Alloying

Thermodynamic Stability

Mechanical Properties

Material Processing:

Powder Consolidation (ECAE Processing)

Thermal Stability

Bulk Consolidation

PROCESSING

STRUCTURE

PROPERTY

PERFORMANCE

Thermodynamic Stability: Solute Segregation

Visual representation of thermodynamic stability changes as function of grain size, solute fraction, and temperature

Developed a methodology that utilizes thermodynamic principles and experimental data to predict solutes that would tend to stabilize the nanocrystalline grain structure. MA Atwater, KA Darling, ARL-TR-6007; MA Tschopp, KA Darling, MA Atwater, et al. ARL-TR-6743; KA Darling, MA Tschopp , BK Vanleeuwen, MA Atwater, ZK Liu, Comp. Mat. Sci. (2014)

Thermodynamic Stability: Solute Segregation

Thermodynamic Stability Map

Experimental Validation

(1294 binary systems)

The present thermodynamic stability model agrees with previously measured stabilized grain sizes as a function of temperature. Recently, it has been extended to map all solutes in our database as well as the stabilizing solute concentration. MA Tschopp, KA Darling, et al. ARL-TR-6743; KA Darling, MA Tschopp, BK Vanleeuwen, MA Atwater, ZK Liu, Comp. Mat. Sci. (2014)

Thermodynamic Stability: Solute Segregation

The present thermodynamic stability model agrees with previously measured stabilized grain sizes as a function of temperature. Recently, it has been extended to map all solutes in our database as well as the stabilizing solute concentration. Tschopp, M.A., Murdoch, H.A., Kecskes, L.J., Darling, K.A., JOM (2014); KA Darling, MA Tschopp , BK Vanleeuwen, MA Atwater, ZK Liu, Comp. Mat. Sci. (2014).

Achieving Stability:

Thermodynamic Grain Size Stability

Thermodynamic stability is a function of 1. Grain size 2. Solute fraction 3. Temperature

Thermodynamic Stability:

Thermokinetic Model for Grain Growth

Towards a predictive grain growth model

Sensitivity Analysis

QL

~25% increase (300 C)

Model extended to account for temperature dependence

T Model overly sensitive to temperature

> 300% increase (100 C)

High temperature XRD measurements

A thermokinetic model that incorporates the thermodynamics and kinetics of grain growth has been extended to include temperature dependence of grain growth in nanocrystalline materials using high temperature XRD measurements. MA Tschopp, KA Darling, MA Atwater, KN Solanki, ARL TRL, in press.

Grain Boundaries in nc Metals: Atomistic Simulations of Segregation

Atomistic simulations are used to quantify segregation behavior and long term dynamics of substitutional and interstitial species (solute, impurities, point defects) at the grain boundary and how grain boundary character (atomic structure) affects segregation. MA Tschopp et al. (2011) Scripta Materialia; MA Tschopp et al. (2012) PRB; NR Rhodes et al. (2013) MSMSE; KN Solanki et al. (2013) Met Trans; MA Tschopp et al. (2014) JAP.

Outline ARL Expertise in Nanocrystalline Materials Material Processing:

Microstructure Control:

Properties:

Mechanical Alloying

Thermodynamic Stability

Mechanical Properties

Material Processing: Thermal Stability

EXAMPLE: PowderCu-Ta Consolidation (ECAE Processing) Bulk Consolidation

PROCESSING

STRUCTURE

PROPERTY

PERFORMANCE

Microstructural Evolution: Cu Grain Size

Increasing Temperature

Cu-Ta TEM

Grain Growth Peak

nc CuTa

0

100

200

300

400

Temperature Increase 500

600

700

800

900

DSC Ave Cu GS 6 nm

to

20 nm

Ave Ta 25 nm

to

130 nm

DSC measurements combined with interrupted SEM/TEM can show the evolution of grain size and particle size with increasing temperature. First, the grain size increases (grain growth regime). KA Darling, AJ Roberts, Y Mishin, SN Mathaudhu, LJ Kecskes, J. Alloys. Comp. 573, 2013, pg. 142-150

Microstructural Evolution: Ta Particle Size

Increasing Temperature

Cu-Ta SEM

Grain Growth Peak

nc CuTa

0

100

200

300

400

Temperature Increase 500

600

700

800

900

DSC Ave Cu GS 6nm

to

20nm

Ave Ta 25nm

to

130 nm

DSC measurements combined with interrupted SEM/TEM can show the evolution of grain size and particle size with increasing temperature. Next, precipitation occurs and the Ta particle size increases. KA Darling, AJ Roberts, Y Mishin, SN Mathaudhu, LJ Kecskes, J. Alloys. Comp. 573, 2013, pg. 142-150

Thermal Stability:

Molecular Dynamics Modeling

Pure Cu Anneal at 750 K for 0.4 ns

Cu-6.5 at% Ta Anneal at 750 K for 24 ns

Cu-6.5 at% Ta Anneal at 1100 K for 24 ns

Molecular dynamics simulations of pure Cu and Cu-6.5%Ta show very different responses with respect to grain size stability. At 750 K, Ta stays at the grain boundaries. At 1100 K, Ta forms clusters! T Frolov, KA Darling, LJ Kecskes, Y Mishin, Acta Mat. 60, 2012, pg. 2158-2168

Thermal Stability:

TEM Evidence of Ta clusters

Atomic Clusters of Ta Dislocation

BCC TEM analysis shows the formation of large and small Ta clusters. Notice the string of small Ta clusters similar to the molecular dynamics simulations. KA Darling, AJ Roberts, Y Mishin, SN Mathaudhu, LJ Kecskes, J. Alloys. Comp. 573, 2013, pg. 142-150

Molecular Dynamics Modeling: Cluster and Grain Boundary Pinning

Grain stability in nc Cu (1200 K)

Initial

Final (18 ns)

Grain stability in nc Cu-5%Ta (1200 K)

Initial

Molecular dynamics simulations of pure Cu and Cu-5%Ta show very different responses with respect to grain size stability. This mechanism can be attributed to kinetic pinning. T Frolov, KA Darling, LJ Kecskes, Y Mishin, Acta Mat. 60, 2012, pg. 2158-2168

Final (18 ns)

Microstructural Evolution:

High Energy Mechanical Alloying of Cu-Ta

MD simulations

Atom probe results show a portion of the Ta forms clusters with the balance (4 at%) in a solid solution with Cu, similar to molecular dynamics simulations.

Stabilizing Grain Size Through:

Kinetic and Thermodynamic Mechanisms

Mean 166 nm Median 160 nm STDEV 50 nm

Nanocrystalline Cu-Ta isothermally annealed at 1040°C or 97%TM for 4 hrs.

Stabilizing Grain Size Through:

Kinetic and Thermodynamic Approaches

Vickers Hardness (GPa)

5.3

Cu 10at% Ta

4.8

Nanocrystalline Pure Cu

4.3

Melting Point of Cu

Avg Grain size 10 nm

3.8 3.3

Conventional Cu

Avg Grain size 60 nm

2.8

2.3 Avg Grain size 200 nm

1.8 Avg Grain size 5 mm

1.3 0.8 0.3 0

200

400

600

800

1000

Annealing Temperature (oC) Nanocrystalline Cu-10%Ta isothermally annealed at 1040°C or 97%TM for 4 hrs.

Outline ARL Expertise in Nanocrystalline Materials Material Processing:

Microstructure Control:

Properties:

Mechanical Alloying

Thermodynamic Stability

Mechanical Properties

Material Processing:

Powder Consolidation (ECAE Processing)

Thermal Stability

Bulk Consolidation

PROCESSING

STRUCTURE

PROPERTY

PERFORMANCE

Powder Consolidation: High Temperature ECAE

Route BC 90°

Three ECAE conditions: a) Cu- 1%Ta 700 °C b) Cu-10%Ta 900 °C c) Cu-10%Ta 700 °C

High temperature ECAE processing route 4Bc was utilized for bulk consolidation Tschopp, M.A., Murdoch, H.A., Kecskes, L.J., Darling, K.A., JOM (2014); Darling, K.A., Tschopp, M.A., et al., Acta Materialia (2014)

Post-ECAE Processing: Cu Grain Size Distributions

mean grain size

168 nm

213 nm

70 nm

Cu Darling, K.A., Tschopp, M.A., Kecskes, L.J., et al., Acta Materialia (2014).

Post-ECAE Processing:

Ta Particle Size Distributions

Grain Boundary vs Lattice Diffusion: Bimodal Particle size Distribution • Large Ta particles located on grain boundaries • Small particles located within the lattice

• Distribution a function of both temperature and Ta concentration • Both small and large particle fraction increase in size with temperature

Darling, K.A., Tschopp, M.A., Kecskes, L.J., et al., Acta Materialia (2014).

ARL Expertise in Nanocrystalline Materials Material Processing:

Microstructure Control:

Properties:

Mechanical Alloying

Thermodynamic Stability

Mechanical Properties

Material Processing:

Powder Consolidation (ECAE Processing)

Thermal Stability

Bulk Consolidation

PROCESSING

STRUCTURE

PROPERTY

PERFORMANCE

Mechanical Properties Capabilities

Indentation Creep Shear Punch Test

1 mm

A combination of mechanical testing is used to assess the properties and performance of nanocrystalline materials, even at high strain rates and high temperatures, including: shear punch test, indentation creep, miniature tension (FIB), split Hopkinson bar, micropillar compression, dynamic hardness, etc.

Mechanical Properties

Shear Punch Test

Shear punch testing probes the shear, relaxation (creep), and strain rate sensitivity response of nanocrystalline materials at small volumes (punch diameter currently down to 1 mm) in a multiaxial stress state.

Mechanical Properties:

Shear Punch Testing: Activation Volume

b

YS 650 MPa US 690 MPa

Initial shear punch relaxation tests show physical activation volumes for nanocrystalline Cu-Ta that are ~1 order of magnitude lower than conventional coarse-grained Cu samples (i.e., faster relaxation, but at much higher stresses).

Mechanical Properties:

Activation Volume vs Grain Size

Physical activation volume measured through stress relaxation agrees with values for pure Cu of similar grain size taken from literature. Ta precipitation does not appear to alter dislocation mechanisms governing plasticity. Darling, K.A., Tschopp, M.A., Kecskes, L.J., et al., Acta Materialia (2014).

J Chen, L, Lu and K. Lu Scripta Mat. 54 (2006) 1913

Mechanical Properties: Strain Rate Sensitivity

Strain Rate Sensitivity

3kT 3 3kT m  v vH

Hardness values are 2X higher than pure Cu of similar grain size

H = hardness Activation volumes measured via instrumented indentation strain rate sensitivity experiments agree reasonable well with shear punch measured values Materials

Cu-10Ta-700

Cu-10Ta-900

Cu-1Ta-700

V*(b3)

17

30

23

Darling, K.A., Tschopp, M.A., Kecskes, L.J., et al., Acta Materialia (2014).

RJ Asaro, S Suresh Acta Mat. 53 (2005) 3369

Mechanical Properties: Strain Rate Sensitivity

Strain Rate Sensitivity, m, falls in line with previous results as a function of grain size.

Darling, K.A., Tschopp, M.A., Kecskes, L.J., et al., Acta Materialia (2014); Tschopp, M.A., Murdoch, H.A., Kecskes, L.J., Darling, K.A., JOM (2014).

Mechanical Properties: Hall-Petch plot

Tschopp, M.A., Murdoch, H.A., Kecskes, L.J., Darling, K.A., JOM (2014); Darling, K.A., Tschopp, M.A., et al., Acta Materialia (2014).

Mechanical Properties:

Quasi Static Room and High Temperature Compression

Room Temperature Quasi-Static Compression

High Temperature Quasi-Static Compression

• Strength values 2X higher than pure nanocrystalline Cu of similar GS

• Dramatic decrease in YS with increasing temperature

Mechanical Properties:

Quasi Static Room and High Temperature Compression

High Temperature Yield Stress vs Post-test RT Yield Stress

At Temperature YS Room Temperature YS Measured by taking the Hv/3 Post Testing Softening due to Thermal Energy Softening due to Microstructure Evolution

Softening is due to thermal effects and not microstructure evolution! (Notice that the strength of nc Cu-Ta at 1000 deg C is same as RT nano Cu)

ARL Expertise in Nanocrystalline Materials Material Processing:

Microstructure Control:

Properties:

Mechanical Alloying

Thermodynamic Stability

Mechanical Properties

Material Processing:

Powder Consolidation (ECAE Processing)

Thermal Stability

Bulk Consolidation

PROCESSING

STRUCTURE

PROPERTY

PERFORMANCE

Large Scale Power Production: Zoz Milling

Large scale mechanical alloying equipment was utilized for powder processing of large bulk objects • Different types of technology available • Processing times are relatively short • System is hermetically sealed • Semi-continuous scale up is possible • Can be done cryogenically

Large Scale Processing: Near Net Shaping

Pilot Scale Manufacturing Field Assisted Sintering (FAST) • Drastically reduced sintering times • Near net shaping possible

Hot Isostatic Pressing • Can produce large billets • Initial starting microstructure can be retained in consolidated bulk parts

World Class ARL facility visited by university, national laboratory and industry partners: Specializing in Rapid Development of New Materials

Large Scale Processing: Cu-Ta Dome

Fully Dense with nc structure! No visible porosity via SEM

Schematic of the HIP canister with SS tooling

Dome after machining out of the HIP can

Compare to nc Tantulum

2-3 times stronger Cu-1Ta 700 (168 nm)

Cu-10Ta 900 (213 nm)

Cu-10Ta 700 (70 nm)

NC Pure Cu (70 – 250 nm)

NC Ta (44 – 250 nm)

HV

2.12

2.12

3.75

1.35-1.0

4.1-2.5

HV/3

0.7

0.7

1.23

0.45-0.35

1.36-0.83

HV/6

0.35

0.35

0.62

0.23-0.18

0.68-0.42

0.45-0.35

1.3-0.9

SPT

σYS

0.43

0.45

0.69

QS

σYS

0.7

0.66

1.1

σ0.1

0.8

0.8

1.3

σ0.1

1.0

1.0

1.5

DY

1.6-0.95 0.88-0.55

2.0-1.2

Who would have thought that you can get the strength of nc Ta by adding 90% Cu?

Cu-10Ta 700 (70 nm)

NC Pure Cu (70 – 250 nm)

NC Ta (44 – 250 nm)

HV

2.12

2.12

3.75

1.35-1.0

4.1-2.5

HV/3

0.7

0.7

1.23

0.45-0.35

1.36-0.83

HV/6

0.35

0.35

0.62

0.23-0.18

0.68-0.42

0.45-0.35

1.3-0.9

σYS

0.43

0.45

0.69

QS

σYS

0.7

0.66

1.1

σ0.1

0.8

0.8

1.3

σ0.1

1.0

1.0

1.5

DY

1.6-0.95 0.88-0.55

2.0-1.2

100% Cu

SPT

Cu-10% Ta

Cu-10Ta 900 (213 nm)

Strength

Cu-1Ta 700 (168 nm)

100% Ta

Summary

Assumes same nanocrystalline grain size

% Ta Addition to Cu

ARL is STRENGTHENING and STABILIZING nc metals, enabling BULK nanocrystalline specimens to be a reality

Other Research Interests HCP mechanical behavior

crashworthiness & vehicle design

Bridging the gap between materials science & solid mechanics

PROCESSING

STRUCTURE

PROPERTY

PERFORMANCE

Other Research Interests L W S M MMSD M R B D

PE Deformation

Future Work / Working on: • 3D Characterization • VPSC - HCP metals • Small Scale Testing • Material Informatics • Neural Networks • nc Grain Boundaries • Mg Atomistic Modeling • First Principles / Mesoscale Models

Polymer Potential Development

Nanocrystalline Design Maps

3D Materials Science – Metal Foam

Thermokinetic Grain Growth Model

MEDE Metals Modeling CTRG

Lightweight & Specialty Metals Branch (LSMB)

PROCESSING

STRUCTURE

PROPERTY

PERFORMANCE

Other Research Interests Deformation in HCP metals

Army Interest in HCP and Magnesium

Twinning in FCC

Challenges for Magnesium

Generalized Framework for Shear and Shuffles

Twinning in HCP

Flat and Corrugated K 1

Discussion, Experiments, Implications, Conclusions

Collaboration with Haitham El Kadiri, Kip Barrett (MSU)

PROCESSING

STRUCTURE

PROPERTY

PERFORMANCE

Other Research Interests High Temperature Materials, 3D Materials Science

AFOSR funded, w/ AFRL (A. Rosenberger, J. Miller), MSU (A. Oppedal), and ASU (K. Solanki)

PROCESSING

STRUCTURE

PROPERTY

PERFORMANCE

Other Research Interests Scale Bridging / Understanding Interatomic Potentials

Tools That Can Help

Potential Design and Design Optimization Understanding Potentials and their Parameterization

Collaboration with S. Nouranian (Ole Miss), K. Solanki (ASU), and M. Baskes (MSU/LANL/UCSD)

PROCESSING

STRUCTURE

PROPERTY

PERFORMANCE

Other Research Interests Integrated Computational Materials Engineering

How do we accelerate the materials discovery cycle and engineer transformational materials?

Statistical Sampling StructureProperty Database Data Reduction & Informatics

Metamodel Generation

PROCESSING

Design Optimization

Materials Design Sensitivity Analysis / Uncertainty Quantification

Optimal Alloy / Process

Virtual Experiments

STRUCTURE

PROPERTY

PERFORMANCE

Other Research Interests Grain Boundary (Segregation) Engineering

Atomistic and Mesoscale Modeling of Grain Boundaries: Exploiting Interfacial Structure-Property Relationships to Improve the Damage Tolerance of Boron Carbide and Boron Suboxide TASK 5

Expand time/length scales towards the mesoscale calculated

experiment TASK 4

Evaluate and develop interatomic potentials

TASK 3

Quantify, predict, and validate grain boundary properties

LEVERAGE INTERNAL PROGRAMS & MEDE B4C CMRG

Kleebe et al., 2008

V TASK 2

Characterize and validate grain boundary structures

B4C B6O

TASK 1

Develop and optimize grain boundary generation State of the Art, Art of the Possible!

Virtual Diffraction Techniques (LAMMPS)

PROCESSING

STRUCTURE

PROPERTY

PERFORMANCE

A L I D A T E W I T H

E X P E R I M E N T S

Any Questions?

Mark de’ Medici

Contact Info: Mark Tschopp, U.S. Army Research Lab [email protected]