The origin of activation of non-basal slip in Mg-Ce dilute alloy - An atomistic simulation study

Abstract

Mg-Ce alloys have been attracting attention because a small amount of Ce addition improves the ductility of Mg at room temperature. When Ce is added, non-basal slip related to improved ductility has been observed. However, the mechanism for activating non-basal slip by Ce has not been understood. In this study, the effect of Ce on slip behavior in Mg is investigated using a molecular dynamics simulation and interatomic potentials for pure Ce and Mg-Ce binary systems have been developed based on the second nearest-neighbor modified embedded-atom method formalism for molecular dynamics simulations. It is found that a small amount of Ce addition has little effect on the critical resolved shear stress (CRSS) of the pyramidal II slip, but significantly increases the CRSS of the basal and prismatic slip. Consequently, it reduces the CRSS anisotropy among slip systems and activates the non-basal slip. This study suggests that reduced CRSS anisotropy due to the difference in the solute-dislocation binding tendency among slip systems can be the reason for the non-basal slip activation, providing a guideline for Mg alloy design to improve the alloy’s ductility.