The role of crystallography and the mechanisms associated with migration of incoherent twin grain boundaries

With twin grain boundaries playing an important role in numerous materials, it is important to understand their behavior across the full range of possible boundary plane orientations. This work examines the migration of 41 computed Sigma 3 nickel grain boundaries over a range of temperatures. The boundary plane orientation appears to play the determining role in the nature of the migration observed, which is evident when the data are plotted in the fundamental zone of possible boundary plane orientations. GBs whose boundary plane lie between (1 1 1) and (2 (1) over bar (1) over bar) exhibit thermally activated migration and the atoms do not move in a coordinated fashion. The remaining GBs, including the (1 0 (1) over bar) GB, exhibit some form of thermally damped migration. The thermally damped migration is characterized by inverse temperature dependence where the GBs migrate faster at lower temperatures and move in a coordinated fashion involving Shockley partial dislocations. The inverse temperature dependence, which is confirmed by random walk simulations, appears to be consistent with dislocation drag, which could be related to the Shockley partial dislocations. At least one GB exhibits mixed mobility trends due to the presence of both thermally activated and thermally damped migration characteristics. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.