Chromium hardening and Peierls mechanism for basal slip in sapphire (α-Al2O3) at temperatures between 900 and 1500 °C

The plastic deformation of Cr3+-doped α-Al2O3 (ruby) with four distinct Cr concentrations has been studied at temperatures between 900 and 1500 °C. The mechanical tests indicate that the processes of dislocation multiplication and the adjustments of the slip velocity of these dislocations to the imposed strain rate in undoped α-Al2O3 are not significantly affected by the Cr concentration. The yield stress increment is approximately constant with temperature and the hardening increases with the Cr concentration. The critical resolved shear stress (CRSS) is fitted to a model based on dislocation glide controlled by the nucleation and propagation of kink pairs, modified to include the hardening due to Cr. Satisfactory fits are achieved with adjustable parameters close to those employed for undoped α-Al2O3.