Atomic-resolution studies on reactions between basal dislocations and [formula omitted] coherent twin boundaries in a Mg alloy

Abstract

Reactions between basal a60 dislocations and 101¯2 coherent twin boundaries (CTBs) in a Mg alloy were studied with atomic resolution. Individual dislocation-CTB reactions produced steps with residual dislocations and multiple twinning dislocations (TDs) gliding away, consequently resulting in TB migration. Reactions between 101¯2 CTBs and low-angle grain boundaries composed of basal a60 dislocations created either basal-prismatic/prismatic-basal interfaces or asymmetric tilt grain boundaries, depending on whether TDs gliding away or not. Not only the emission of TDs by dislocation-TB reactions may drive TB migration, but also the resultant steps or facets along TBs can act as TD sources to facilitate TB migration. Our results indicate that roughness or severe loss of local coherency induced by dislocation-TB reactions does not intrinsically impede TB migration in Mg alloys. Dislocation-TB reactions may provide another feasible strategy to improve the ductility of Mg alloys, in addition to other techniques like grain refinement and texture modification.