Atomic-resolution studies on reactions of slip dislocations with {101¯1} twin boundaries and local plastic relaxation in a Mg alloy

Abstract Reactions of { 10 1 ¯ 1 } 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 ¯ 1 } TBs and low-angle grain boundaries composed of basal mixed 1 / 3 〈 11 2 ¯ 0 〉 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 ¯ 1 } TB with another 〈 a 60 〉 dislocation from the other side, or through direct reaction with the { 10 1 ¯ 1 } TB, emitting another 〈 a 60 〉 dislocation into the other side. Local atomic structures of steps at { 10 1 ¯ 1 } TBs could be modified by either emission of or reaction with TDs, 〈 a 60 〉 , 〈 c + a 60 〉 or 1 / 6 〈 20 2 ¯ 3 〉 Frank partial dislocations, reducing local lattice strains at steps. Our experimental results may provide insights for understanding the plastic relaxation mechanisms at { 10 1 ¯ 1 } TBs.