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

1. 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 stablebelowTm ϒLA Air h ϒLS Liquid Solid Courtesy of M. Gallerneault (2012)

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

5. Disjoining Potential, V(h) Gexc(h,T)=ΔG(T)h + 2γSL+V(h) Increasing temperature equilibrium width Courtesy of T. Power

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

7. Phase-Field Crystal

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

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

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

11. Adapted from Elder et al. PRE 81 (2010) L α+L α Solidus Liquidus Temperature(rescaled) α1 α2 α1+α2 Number density =ρA-ρB /(ρA+ρB)

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

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

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

15. Next Steps • Investigate the role of solute inpremelting: • Plot disjoining potential curves for several misorientations for alloys • Compare disjoining potential for alloys to that of the pure material • ActaMaterialia 57 (2009) Mishin et al. ActaMaterialia 57 (2009)

16. Acknowledgements • A tremendous thank you to Dr. NikProvatas and Dr. Jeff Hoyt • Jonathan Stolle • and all the people who were so very supportive!