Atomistic study of plastic deformation in Mg-Al alloys

An atomistic study has been carried out to understand plastic deformation in Mg-Al alloys. We investigate the possible plastic deformation mechanisms of intermetallic β-Mg17Al12 which is a key precipitate phase in Mg-Al alloys. Based on the analysis of the generalized stacking fault energy, we predict the preferential slip systems in this phase and speculate that partial dislocations and complex stacking faults are responsible for its plastic deformation. Using Rice's criterion on ductile-to-brittle transitions, we confirm the intrinsic brittleness of the intermetallic phase. We also simulate the interaction between the basal edge dislocation and dissolved Al particles. We have determined the binding energy between the dislocation and the particles and examined the energetic dependence on the particle size, particle concentration and dislocation-particle distance. The strengthening effect due to the Al solutes is characterized by two quantities - the Peierls stress and the solid solution strengthening factor. The former reflects the changes in dislocation core structure while the latter results primarily from the elastic dislocation-particle interaction. Both quantities are examined and their dependence on particle size and concentration is elucidated. The dislocation core structure and the long-range elastic interaction between the dislocation and the Al particles are also examined.