Temperature dependence of grain boundary excess free volume

Grain boundary energy and mobility are strongly correlated with the grain boundary excess free volume, whose dependence on temperature has yet to be investigated. Using molecular dynamics simulations on face-centered-cubic and body-centered-cubic metals, we found that the boundary free volume decreases with temperature, diminishing the interatomic bond distortion and the grain boundary energy per atom. Interestingly, the free volume shrinks much faster above a critical temperature; meanwhile, the activation energy for grain boundary migration jumps due to collective atomic motion. These insights on the temperature dependence of grain boundary free volume can be instrumental in stabilizing the microstructure of nanocrystals. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.