Analysis of a kink pair model applied to a peierls mechanism in basal and prism plane slips in sapphire deformed between 200C and 1800C

Abstract

A model based on dislocation glide controlled by the nucleation and propagation of kink pairs in a high Peierls stress crystal is revisited and modified to account for changes in dislocation densities and segment lengths with temperature and stress. It is applied to the critical resolved shear stress (CRSS) for basal and prism plane slip in sapphire (alpha-Al2O3). According to agreed-upon knowledge on dislocations in sapphire, basal slip and prism plane slip are modelled with undissociated and dissociated dislocations, respectively. In the latter case, partial dislocations move independently. Amongst a number of sets of fitting parameters, good fits between experimental and modelled CRSS9s are obtained in the long segment limit over the whole range of temperatures by making use of physically sound parameters, including a stress dependence of the dislocation density.