Emergence of directionally-anisotropic mobility in a faceted $Σ$11 <110> tilt grain boundary in Cu

Abstract: Faceted grain boundaries, where grain boundary area is increased in the name of producing low-energy segments, can exhibit new and unexpected migration trends. For example, several faceted $\Sigma$3 boundaries have demonstrated anti-thermal and thermally damped mobility. $\Sigma$11 <110> tilt boundaries represent another promising but relatively unexplored set of interfaces, with a (113) low-energy plane that can lead to faceting. In this study, molecular dynamics simulations are used to study grain boundary migration of an asymmetric $\Sigma$11 <110> grain boundary in two face centered cubic metals. Mobility of this boundary in Cu is strongly dependent on the direction of the applied driving force. The mobility anisotropy generally becomes smaller, but does not disappear completely, as temperature is increased. In contrast, the same boundary in Al demonstrates similar mobilities in either direction, illustrating that the anisotropic mobility phenomenon is material-dependent. Finally, relationships between stacking fault energy, facet junction defect content, and boundary crystallography are uncovered that may inform future studies of faceted grain boundaries.