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Grain Boundary Premelting in Binary Alloys Using the Phase-Field Crystal Method. Elizabeth Rowan. Supervisor: Nikolas Provatas. Outline. Interfacial Thermodynamics What is Premelting ? Premelting at Grain Boundaries (GB) Disjoining Potential Phase-field Crystal Method (PFC) - PowerPoint PPT Presentation
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Grain Boundary Premelting in Binary AlloysUsing the Phase-Field Crystal Method
Elizabeth Rowan
Supervisor: Nikolas Provatas
2
Outline Interfacial Thermodynamics
What is Premelting? Premelting at Grain Boundaries (GB) Disjoining Potential
Phase-field Crystal Method (PFC) Comparison to other models Origin of Properties
My Research Binary Alloys Future Work
3
Premelting: The Basics
ϒSA>ϒLA+ϒLS
If true, liquid film is thermodynamically stable below Tm
Courtesy of M. Gallerneault (2012)
Liquid
Solid
Air
h
ϒLA
ϒLS
4
Premelting: Grain Boundaries
A.M. Alsayed et al. Science 19 August 2005
S.J. Fensin et al. PRE 81 (2010)
Liquid
Solid
Solid
h
Applications: Hot Tearing
Mellenthin et al. PRB 78 (2008)
5
Disjoining Potential, V(h)
Gexc(h,T)=ΔG(T)h + 2γSL+V(h)
equilibrium width
Courtesy of T. Power
Increasing temperature
6
Disjoining Potential – Function of Misorientation
h
Repulsive Boundary
Attractive Boundary “dry”
as T goes to Tm,h goes to ∞
Attractive-Repulsive
S.J. Fensin et al. PRE 81 (2010)
7
Phase-Field Crystal
8Emmerich et al. Advances in Physics 61 (2012)
9
(nm)
LiquidCrystal
0A0A
Position
Number Density
Position
Discrete Atoms
Vibrating on it’s lattice site
Courtesy of M. Greenwood
10
Phase-Field Crystal Model
Courtesy of M. Greenwood
Greenwood et al. PRL 105 (2010)
11 Number density =ρA-ρB /(ρA+ρB)
Temperature(rescaled)
α1+α2
α+L
α2α1
L
α
LiquidusSolidus
Adapted from Elder et al. PRE 81 (2010)
12
My Work: Comparison of Misorientations
Low Angle Grain Boundary: 6°
High Angle Grain Boundary: 32.2°Low γGB
High γGB
My Goal: Premelting in binary alloys
13
Low Angle Premelting
Concentration -0.18
Concentration -0.155
Concentration -0.15
Concentration -0.1475
Concentration -0.1425
Concentration -0.1425
Concentration -0.115
Overheating
14
High Angle Premelting: 27.8°
Concentration -0.1475
Concentration -0.1425Concentration -0.1525
Concentration -0.17
15
Next Steps Investigate the role of
solute in premelting: Plot disjoining potential
curves for several misorientations for alloys
Compare disjoining potential for alloys to that of the pure material
Acta Materialia 57 (2009)
Mishin et al. Acta Materialia 57 (2009)
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Acknowledgements A tremendous thank you
to Dr. Nik Provatas and Dr. Jeff Hoyt
Jonathan Stolle and all the people who
were so very supportive!
17