Atomistic Simulation of Grain Boundary Sliding in Mg during High Temperature Deformation

A series of molecular dynamics simulations were performed to study grain boundary sliding of three types of [10-10] tilt grain boundaries in a magnesium bicrystal. In particular, a near Sigma 11 twin boundary, an asymmetric near Sigma 11 twin boundary and a theta=40.3 degrees general [10-10] tilt grain boundary were investigated. Simulations showed that grain boundary. sliding (a rigid motion of two grains relative to each other along boundary plane) did not occur over the stress range applied; instead, coupled shear motion (grain boundary sliding induced boundary migration) was dominant. While the measured coupling coefficient, the ratio of boundary tangential displacement to boundary normal displacement, was in good agreement with theoretical prediction, the detailed shear behavior was different, depending on types of grain boundary, magnitude of applied shear stress and temperature. It was also noted that grain boundary twining was the predominant mechanism that allowed the coupled shear motion to occur in HCP magnesium.