Deformation of sapphire (α-Al2O3) by basal slip and basal twinning below 700°C

Abstract

Plastic deformation of α-Al₂O₃ single crystals of several orientations has been performed at intermediate temperatures (400–700°C) under 1.5 GPa hydrostatic confining pressure to activate basal slip and basal and rhombohedral deformation twinning. The Schmid law for basal slip is maintained between 600 and 1500°C. The stress for basal twinning has been determined; its temperature dependence is similar to that of the critical resolved shear stress for basal slip. This suggests that glide of dislocations through the Peierls potential controls both basal slip and basal twinning and further supports the double-cross-slip model for basal twinning in sapphire proposed by Pirouz et al. and He et al.