Response of magnesium single crystals to shock-wave loading at room and elevated temperatures

Abstract

A series of magnesium single crystals, from 0.2 to 3 mm thick, were shock loaded along specific axes, a and c, of the hexagonal closed packed (hcp) structure. Other experiments involved loading at 45 degrees to these principal axes. Shock compression along the c-axis causes inelastic deformation by means of pyramidal slip and twinning and is associated with the largest Hugoniot elastic limit (HEL) for this material. The low-energy basal slip was activated by shock loading along the inclined direction and has he smallest HEL. In all cases, we observe the decay of the elastic precursor wave and growth of the HEL with increasing temperature. For the c-orientation this change is caused by a decrease of elastic constants, not an increase of shear stress along the pyramidal slip planes. For the other orientations the shear stress on the slip planes increased with temperature. For the inclined shock compression, after the HEL, two plastic waves were found: the stress level of the first plastic wave depends on the ultimate shock stress. Finally, the largest spall strength was along the a-axis and the smallest in the off-axis direction.