Inelastic deformation in shocked sapphire single crystals

摘要

To gain insight into orientation-dependent inelastic deformation of shocked sapphire (α-Al_2O_3) single crystals, resolved shear stresses, applicable for various dislocation slip and twinning systems, were determined for shock compression along different crystal orientations. Results from our anisotropic wave propagation analysis provide an explanation for why the measured elastic limit of shocked γ-cut sapphire is lower, compared to c-cut and α-cut sapphire: Shock wave compression of α-cut sapphire favors activation of basal slip and basal twinning. In contrast, shock wave compression of c-cut and α-cut sapphire favors rhombohedral twinning and prismatic slip, respectively. Also, basal slip and/or basal twinning may be important for understanding why γ-cut sapphire shocked beyond the elastic limit loses optical transparency gradually, when compared to c-cut and α-cut sapphire.