Atomic-resolution investigations on formation and evolution of symmetric tilt grain boundaries near the {10(1)over-bar2} twin orientation in a Mg alloy

Formation and evolution of symmetric tilt grain-boundaries (STGBs) near the {10 (1) over bar2} twin orientation in a Mg alloy were studied with atomic-resolution. The STGBs could be formed by reactions of {10 (1) over bar2} twin boundaries with 60 degrees basal dislocations (referred to as < a(60)>) coming respectively from the twin and matrix, with each pair of < a(60)> forming a grain-boundary dislocation (GBD). Incident < a(60)> dislocations reacted with GBDs, consequently activating emission of twinning dislocations which resulted in migration of the STGBs. Interestingly, STGBs could be transformed into {10 (1) over bar2} twin boundaries by either grainboundary sliding or reacting with an array of basal < a(60)> dislocations. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.