Atomic-resolution studies on reactions of slip dislocations with {10(1)over-bar1} twin boundaries and local plastic relaxation in a Mg alloy

Reactions of {10 (1) over bar1} twin boundaries (TBs) with slip dislocations and evolution of associated steps at TBs in a Mg alloy were investigated and modeled, based on atomic-resolution observations and theory of interfacial defects. It was found that reactions between {10 (1) over bar1} TBs and low-angle grain boundaries composed of basal mixed 1/3(11 (2) over bar0) dislocations (referred to as < a(60)>) could produce asymmetric tilt grain boundaries. Each < a(60)>-TB reaction created a step with a b(+/- 3/+/- 2)-type residual dislocation and a two-layer twinning dislocation (TD) gliding away. A one-layer step with a b(+/- 1/+/- 1)-type residual dislocation could be generated either by the reaction of an < a(60)> or a < c + a(s)> dislocation from one side of a {10 (1) over bar1} TB with another < a(60)> dislocation from the other side, or through direct reaction with the {10 (1) over bar1} TB, emitting another < a(60)> dislocation into the other side. Local atomic structures of steps at {10 (1) over bar1} TBs could be modified by either emission of or reaction with TDs, < a(60)>, < c + a(60)> or 1/6(20 (2) over bar3) Frank partial dislocations, reducing local lattice strains at steps. Our experimental results may provide insights for understanding the plastic relaxation mechanisms at {10 (1) over bar1} TBs. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

In this study, reactions of {10 (1) over bar1} twin boundaries (TBs) with slip dislocations in a Mg alloy were investigated and modeled based on atomic-resolution observations and interfacial defect theory. The reactions were found to produce asymmetric tilt grain boundaries and various types of residual dislocations, leading to modifications in local atomic structures of steps at {10 (1) over bar1} TBs. These experimental results provide insights for understanding the plastic relaxation mechanisms at {10 (1) over bar1} TBs.