Solute softening and vacancy generation by diffusion-less climb in magnesium alloys

TL;DR

This study reveals diffusion-less dislocation climb in magnesium alloys at room temperature, showing how solutes facilitate vacancy generation and soften dislocation motion, potentially enhancing ductility.

Contribution

It demonstrates the mechanism of diffusion-less climb in Mg alloys and its effects on dislocation mobility and vacancy formation, a novel insight into alloy strengthening.

Findings

Dislocations climb via out-of-plane motion to bypass solute obstacles.

Flow stress increases linearly with solute concentration.

High vacancy concentrations are generated during climb.

Abstract

Active room temperature diffusion-less climb of the <a> edge dislocations in model Mg-Al alloys was observed using molecular dynamics simulations. Dislocations on prismatic and pyramidal I planes climb through the basal plane to overcome solute obstacles. This out-of-plane dislocation motion softens the high resistance pyramidal I glide and significantly reduces the anisotropy of dislocation mobility, and could help improve the ductility of Mg. The flow stress scales linearly with solute concentration, cAl. Dislocations climb predominantly in the negative direction, with climb angle on the order of 0.01cAl, producing very high vacancy concentration on the order of 10-4.