With a drive towards utilization of lightweight structural materials, fundamental understanding of plastic deformation in magnesium as a function of strain rate has assumed significant importance. The anisotropy in plastic flow behavior is complicated by the asymmetric crystal structure of the hexagonal close packed lattice on one hand and the initial texture on the other. This results from complex deformation modes, with twinning begin a dominant mode of deformation under some orientations of loading. We study the rate dependence of plastic flow an AZ31B magnesium alloy processed by Equal Channel Angular Extrusion (ECAE) using dynamic compression experiments and post-mortem microscopy.
Uniaxial compression experiments were performed along three principal directions of the extruded block using conventional and desktop kolsky bars in the strain rate range of 〖10〗^3-〖10〗^4 s^(-1) and compared with quasi-static data from Krywopusk et al in the range 〖10〗^(-4)-〖10〗^0 s^(-1). The rate sensitivity of flow stress was found to be significant only for one loading orientation at small strains. Work hardening response, however, was found to be higher at higher rates of loading for two of the loading orientations. In-situ imaging at 5 million frames per second indicated significant shear localization at multiple length scales along these two orientations. To understand the mechanisms active, recovery experiments were performed followed by post-mortem microscopy. Results indicate texture evolution during compression along both orientations with twinning being dominant in one. Further analysis is being performed to understand the effect of strain rate on the active mechanisms during deformation.