Deformation of magnesium during c-axis compression at low temperatures

Abstract

In this study, large scale atomistically informed three-dimensional (3D) discrete dislocation dynamics (DDD) simulations were conducted to investigate the mechanical response of single crystal magnesium (Mg) during c-axis compression at low temperatures. In these simulations the plastic anisotropy of slip on pyramidal planes were accounted for to quantify the effects of misorientation, dislocation climb, and pyramidal 〈c+a〉 dislocation mobility. The simulation results show that a simple mobility rule based on the properties of edge and screw dislocations will lead to drastically different predictions of the response of Mg during c-axis compression as compared to a more rigorous dislocation orientation dependent mobility rule suggested by atomistic simulations. In addition, the current simulations suggest that plasticity is predominantly mediated by 〈c+a〉 slip on pyramidal I planes with less contribution from slip on pyramidal II planes. Furthermore, dislocation climb is observed to have an important effect even at low temperatures. A misorientation of the loading axis within a few degrees is shown to have a negligible effect on the results. The predicted dislocation microstructure are also shown to be in qualitative agreement with experimental results. Finally, the current simulations indicate that 〈c+a〉 pyramidal I slip cannot be neglected in crystal plasticity simulations.