LAUSR

To gain insights into the relative contributions of different plastic deformation mechanisms, particularly basal slip, for shocked hexagonal close-packed (hcp) metals, magnesium (Mg) single crystals were subjected to shock compression and release along a low-symmetry (LS) orientation to 1.9 and 4.8 GPa elastic impact stresses. LS-axis is a “nonspecific” direction resulting in propagation of quasilongitudinal and quasishear waves. Wave profiles, measured using laser interferometry, show a small elastic wave followed by two plastic waves in compression; release wave profiles exhibited a structured response for the higher stress and a smooth response for the lower stress. The LS-axis wave profiles are significantly different than profiles published previously for c- and a-axes, demonstrating that Mg single crystals exhibit strong anisotropy under shock compression/release. Numerical simulations, using a time-dependent anisotropic modeling framework, show that shock wave loading along the LS-axis involves the simultaneous operation of multiple deformation mechanisms. Shock compression along LS-axis is dominated by basal slip while prismatic slip and pyramidal I { 10 1 ¯ 1 } ⟨ 11 2 ¯ 3 ⟩ slip play a smaller role; coupling between longitudinal and shear deformations was observed. The unloading response is dominated by basal slip with some contribution from prismatic slip; pyramidal I slip is not activated. The present results, unlike results obtained for c- and a-axes, show that the deformation mechanism observed under quasistatic loading conditions along LS-axis is not sufficient to determine the shock response along this orientation. Although requiring numerical simulations for wave analysis, shock propagation along a LS-orientation provides new insights into the plastic deformation response of hcp metal single crystals.To gain insights into the relative contributions of different plastic deformation mechanisms, particularly basal slip, for shocked hexagonal close-packed (hcp) metals, magnesium (Mg) single crystals were subjected to shock compression and release along a low-symmetry (LS) orientation to 1.9 and 4.8 GPa elastic impact stresses. LS-axis is a “nonspecific” direction resulting in propagation of quasilongitudinal and quasishear waves. Wave profiles, measured using laser interferometry, show a small elastic wave followed by two plastic waves in compression; release wave profiles exhibited a structured response for the higher stress and a smooth response for the lower stress. The LS-axis wave profiles are significantly different than profiles published previously for c- and a-axes, demonstrating that Mg single crystals exhibit strong anisotropy under shock compression/release. Numerical simulations, using a time-dependent anisotropic modeling framework, show that shock wave loading along the LS-axis involves the...