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

Plastic deformation of alpha-Al2O3 single crystals of several orientations has been performed at intermediate temperatures (400-700degreesC) under 1.5 GPa hydrostatic con. ning pressure to activate basal slip and basal and rhombohedral deformation twinning. The Schmid law for basal slip is maintained between 600 and 1500degreesC. 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 1/3 (10(1) over bar 0) 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.