Transmutation of Basal Dislocations by {1012} twinning in magnesium

Abstract

Basal dislocations in hexagonal close-packed materials remarkably can enhance the mobility of {1012} twin boundaries which absorb them. This behavior has been extensively studied and leads to complex faceting, disclination content, and mobile disconnections. However, we recently uncovered that under loading which suppresses {1012} twin mobility, certain basal dislocations can punch through the boundary, generating 〈c+a〉 dislocations inside the twin. The transmutation requires two mixed basal dislocations to move into the boundary and produces a mixed 〈c+a〉 dislocation on the prismatic plane of the twin along with a mobile twinning disconnection. This reaction is nearly identical to one predicted decades ago by Price. The reaction is both stress and temperature sensitive and depends heavily on complex faceting reactions at the boundary. By studying the dependence of transmutation versus absorption upon stress and faceting, we have uncovered general new insights showing how interfaces react with dislocations.