Atomic Simulations of Interactions between Edge Dislocations and a Twist Grain Boundary in Mg

Abstract

The roles of mechanical size and chemical bonding effect of segregated elements in grain boundaries (GBs) on the interactions between the GBs and dislocations are still not well understood. Because a twist GB tends to have a higher GB energy than a tilt GB owing to its random structure, the mechanical and chemical effects of solute elements on the dislocation-GB interactions in a twist GB are generally different from those in a tilt GB. In addition, dislocation emission from a GB in hcp metals is more complex than that in fcc metals because of the intense plastic anisotropy in hcp metals. In this study, interactions between basal 〈a〉 edge dislocations and a twist GB were studied in non-segregated and Al- and Fe-segregated twist Mg GBs by molecular dynamics simulations. The simulations showed that a prismatic dislocation was emitted from the GB after two basal dislocations were adsorbed into the GB. Dislocation adsorption into the GB was enhanced by Al and Fe segregation, but dislocation emission from the GB was suppressed by the segregation. Analyses of the GB width and potential energy suggested that the dislocation adsorption was mainly determined by mechanical effects, while dislocation emission strongly depended on chemical effects.