| About this Abstract |
| Meeting |
2022 TMS Annual Meeting & Exhibition
|
| Symposium
|
Grain Boundaries and Interfaces: Metastability, Disorder, and Non-Equilibrium Behavior
|
| Presentation Title |
Migration Free Energy of Twin Boundaries and Other Crystalline Defects |
| Author(s) |
David Rodney, Yuji Sato, Arnaud Allera, Thomas D Swinburne |
| On-Site Speaker (Planned) |
David Rodney |
| Abstract Scope |
The thermally-activated migration of crystalline defects, such as twin boundaries or dislocations, can be modeled using the transition state theory. Computing activation free energies remains however computationally challenging. Approximations are classically used but often without justification. In particular, a harmonic approximation is often used with the entropic term incorporated as a constant in the attempt frequency. Here we take advantage of a recent linear scaling method, the projected average force integrator (PAFI) method, that fully accounts for anharmonic thermal vibrations, to compute in three-dimensional cells, the activation free energy for {1012} twin boundary migration under stress. We find a strongly stress-dependent entropic contribution and show that the harmonic approximation overestimates the twin migration velocity above 100K, the discrepancy reaching several orders of magnitude at high temperatures. We extend these calculations to screw dislocations in BCC metals, where entropy is also found to play a crucial, yet so far unrecognized, role. |
| Proceedings Inclusion? |
Planned: |
| Keywords |
Mechanical Properties, Modeling and Simulation, Magnesium |