Role of micro-alloying element in dynamic deformation of Mg-Y alloys

Abstract

The microscopic mechanism of the effect of alloying element on the shock behavior for alloy materials is still limited. In this work, based on our developed Finnis–Sinclair (F–S) interatomic potential of Mg-Y alloy, using nonequilibrium molecular dynamics (NEMD) simulations, we gave new insights into the role of alloying element Y in dynamic deformation of Mg-xat.%Y (x = 1, 3, 6, 8 and 10) alloys, and further revealed the deformation mechanisms of these solid solution alloys, which is dependent on the compositions of Y and the crystallographic orientations. The results confirm that the lattice instability caused by Y atoms results in the reduced yield stress. Under shock along the [0001] direction, the improved plasticity is mainly attributed to the increasing amorphous activity and decreasing amorphous annihilation rate with Y additions, but the other mechanisms, e.g., the dislocation nucleation and phase transition, are suppressed. Furthermore, for the [101¯0] direction, the energy barriers of stacking faults and disordering can be overcome at high Y content, so these two deformation modes are activated accompanying with the lattice reorientation to release the large internal stress, and the enhanced plastic activity is mainly related to the inhibited phase transition. This work can broaden the knowledge of the dynamic response of Mg-Y alloys at atomic-scale, which is significant for the shock experiments and material design.