Grain Boundary Premelting in Binary Alloys Using the Phase-Field Crystal Method

Grain Boundary Premelting in Binary AlloysUsing the Phase-Field Crystal Method

Elizabeth Rowan

Supervisor: Nikolas Provatas

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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

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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

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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)

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Disjoining Potential, V(h)

Gexc(h,T)=ΔG(T)h + 2γSL+V(h)

equilibrium width

Courtesy of T. Power

Increasing temperature

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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)

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Phase-Field Crystal

8Emmerich et al. Advances in Physics 61 (2012)

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(nm)

LiquidCrystal

0A0A

Position

Number Density

Position

Discrete Atoms

Vibrating on it’s lattice site

Courtesy of M. Greenwood

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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)

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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

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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

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High Angle Premelting: 27.8°

Concentration -0.1475

Concentration -0.1425Concentration -0.1525

Concentration -0.17

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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!

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