Single Phase Layer Formation in Nanostructured Multiphase Layered Structures

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Single Phase Layer Formation in Nanostructured
Multiphase Layered Structures
NIST Diffusion Workshop May 12-13, 2008,
Gaithersburg, MD
Ximiao Pan, John E. Morral, Yunzhi
Wang Department of Materials Science and
Engineering The Ohio State University Columbus,
Ohio
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OUTLINE

• Introduction
• Particle coarsening in equilibrium layers
• Single phase layer formation and horns
• Single phase layer growth
• Application of the KKS phase field model
• Conclusions

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INTRODUCTIONMultiphase Layer structure
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INTRODUCTIONRegular Solution Phase Diagram
W12 W23 20kJ/mole
W13 0
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PARTICLE COARSENING IN EQUILIBRIUM LAYERSPhase
field simulation of nanostructured A/A? layers
on a tie-line
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PARTICLE COARSENING IN EQUILIBRIUM LAYERSPhase
field simulation of nanostructured J/J? layers
on a tie-line
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PARTICLE COARSENING IN EQUILIBRIUM LAYERSPhase
field simulation of nanostructured J/J? layers
on a tie-line
 
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PARTICLE COARSENING IN EQUILIBRIUM LAYERSPhase
Field Simulation of nanostructured J/J? layers
on a tie-line
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SINGLE PHASE LAYER FORMATION AND HORNS1-D
simulations of diffusion paths across multiphase
layers
Constant Dij Atomic mobilities b1 b2 b3 Linear
zigzag path
Variable Dij Atomic mobilities b110, b2 5,
b31 Path with horns
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SINGLE PHASE LAYER FORMATION AND HORNS1-D
simulations of variable diffusivity paths with
and without single phase layers
Variable Dij Atomic mobilities b110, b2 5,
b31 Path with horns
Horns with a Single phase layer
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SINGLE PHASE LAYER FORMATION AND HORNS1-D
simulations of variable diffusivity paths with a
larger single phase layer
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SINGLE PHASE LAYER GROWTHInvestigated layer pair
compositions
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SINGLE PHASE LAYER GROWTHTime evolution and
diffusion path of layers E/E?
Diffusion path predicted by
1-D
phase field
phase field 1-D
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SINGLE PHASE LAYER GROWTHLayer growth in E/E? in
repeated simulations
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SINGLE PHASE LAYER GROWTHComparison of phase
field simulations after 3000

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APPLICATION OF THE KIM/KIM/SUZUKI PHASE FIELD
MODELEffect of surface tension and length scale
on the interdiffusion microstructure
(a) KKS s25 mJ/m2
(b) KKS s50 mJ/m2
(c) KKS s100 mJ/m2
(d )KKS s200 mJ/m2
(e) KKS s400 mJ/m2
(f) Classical model
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APPLICATION OF THE KIM/KIM/SUZUKI PHASE FIELD
MODELEffect of rescaling the length to make the
surface tensions equal and reducing the time to
make the microstructures equal
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CONCLUSIONS
In model nanostructured multiphase multilayers

• Interdiffusion, capillarity and the Kirkendall
  effectall play a role in the evolution of single
  phase layers.
• The starting distribution of random precipitates
  can lead to significant differences in single
  phase layer growth kinetics.
• While 1-D simulations predict that horns may or
  may not lead to single phase layer formation,
  non-equilibrium phase field simulations predict
  single phase layers even when the 1-D models
  dont.
• The KKS and classical phase field model results
  were comparable.
• The initial precipitate size needs to be taken
  into account when comparing KKS simulations
  performed at different length scales.

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Single Phase Layers formed by Horns
Diffusion Couple results
Predicted by DICTRA
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Theory of horns and an example using a finite
difference simulation
K. Wu, J.E. Morral, and Y. Wang, in press Acta
Mater, Oct. 2006