Grain boundary plasticity in Mg binary alloys by segregation of p-block element

Abstract

The effect of p-block elements (Ga, Ge and In) addition on grain boundary structures and room temperature mechanical responses was investigated on extruded Mg binary alloys with fine-grained structures. Grain boundary segregation was confirmed in the Mg–Ga and Mg–In alloys, whereas the Mg–Ge alloy did not show such microstructures associated with solubility. Grain boundary segregation affected the plastic deformation of the Mg–Ga and Mg–In alloys. In particular, the Mg–In alloy had a large strain rate dependency and exhibited good deformability at low strain rate regimens. First-principles calculations indicated that p-block elements produce a bond-weakening effect at grain boundaries, and atomistic distances at grain boundaries varies according to the element. Solute atom which brings about both bond-weakening and bond-expansion effects to Mg atoms is effective in enhancing the contribution of grain boundary sliding in deformation.