Temperature Dependence of Grain Boundary Migration in 3

Temperature Dependence of Grain Boundary Migration in 3 -D Hao Zhang David J. Srolovitz Princeton University Princeton Materials Institute (PMI) Acknowledgements Moneesh Upmanyu Lasar Shvindlerman Gunther Gottstein S. Srinivasan ORNL Russian Academy of Sciences/RWTH Aachen LANL

Outline • Atomic Simulation Model • Modeling Approach • Driving Force Dependence of Migration • Recent 3 -D Results (Temperature Dependence) • Reduced Mobility • Grain Boundary Energy • Mobility • Activation Energy • Conclusions

Grain Boundary Migration Grain boundary migration • Absolute reaction rate theory (Turnbull, 1951) • Grain growth (capillarity-induced migration)

Modeling Approach • U-shaped half loop geometry • FCC Aluminium <111> Tilt Grain Boundary • EAM – Al • Periodic along X, Y and Z v(y) • Local velocity • Steady-state velocity • Boundary energy

Grain Boundary Energy (J/m 2) Migration rate v (ro/t) Reduced Mobility Mgbggb (ao/t) Driving Force Dependence of Migration Driving Force k=p/w (nm-1) For sufficiently low driving forces : • Reduced mobility is independent of driving force (2 -D) • Migration rate is proportional to driving force (2 -D) • Grain Boundary Energy is large (3 -D)

Grain Boundary Migration S 7 Grain Boundary at T=427 K

M* vs. Misorientation S 7 (m 4/Js) S 13 (deg)

Mobility and γ vs. Misorientation S 13 S 7 (m 4/Js) (J/m 2) S 13 (deg)

Mobility vs. Misorientation S 7 (m 4/Js) S 13 (deg)

Temperature Dependence of Mobility Simulation Experiments

Activation Energy vs. Misorientation S 7 experiment Q (e. V) S 13 Simulation (deg) Misorientation q (deg)

Conclusions • Reduced mobility shows local maxima at low S 7 • Mobility shows maxima at low S misorientations • Boundary energy exhibits minima at low S misorientations • Magnitude of activation energy in simulation << than in experiment • Possible reasons: simulations do not represent the true physics impurities