1. Grain Boundary Premelting in Binary Alloys Using the Phase-Field Crystal Method Elizabeth Rowan Supervisor: Nikolas Provatas

2. Outline 1  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  ϒ SA > ϒ LA + ϒ LS  If true, liquid film is thermodynamically stable below T m Courtesy of M. Gallerneault (2012) Liquid Solid Air h ϒ LA ϒ LS 2

4. Premelting: Grain Boundaries A.M. Alsayed et al. Science 19 August 2005 S.J. Fensin et al. PRE 81 (2010) Liquid Solid h Applications: Hot Tearing 3 Mellenthin et al. PRB 78 (2008)

5. Disjoining Potential, V(h) G exc (h,T)=ΔG(T)h + 2γ SL +V(h) equilibrium width 4 Courtesy of T. Power Increasing temperature

6. Disjoining Potential – Function of Misorientation 5 h Repulsive Boundary Attractive Boundary “dry” as T goes to T m,h goes to ∞ Attractive-Repulsive S.J. Fensin et al. PRE 81 (2010)

7. Phase-Field Crystal 6

8. 7 Emmerich et al. Advances in Physics 61 (2012)

9. (nm) Liquid Crystal Position Number Density Position Discrete Atoms Vibrating on it’s lattice site 8 Courtesy of M. Greenwood

10. 9 Phase-Field Crystal Model Courtesy of M. Greenwood Greenwood et al. PRL 105 (2010)

11. Number density =ρ A -ρ B /(ρ A +ρ B ) Temperature(resc aled) α 1 +α 2 α+L α2α2 α1α1 L α Liquidus Solidus 10 Adapted from Elder et al. PRE 81 (2010)

12. My Work: Comparison of Misorientations 11 Low Angle Grain Boundary: 6° High Angle Grain Boundary: 32.2° Low γ GB High γ GB My Goal: Premelting in binary alloys

13. 12 Low Angle Premelting Concentration -0.18 Concentration -0.155 Concentration -0.15 Concentration -0.1475 Concentration -0.1425 Concentration -0.115 Overheating

14. High Angle Premelting: 27.8° 13 Concentration -0.1475 Concentration -0.1425 Concentration -0.1525 Concentration -0.17

15. Next Steps 14  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)

16. Acknowledgements 15  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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