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

Abstract

Active room temperature solute induced 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. This climb behavior was rationalized using an energy analysis by comparing the in-plane and out-of-plane motions between different Mg slip planes. The ease of climb depends on the strength of the solute-dislocation interaction and the compactness of the dislocation core.