Two-step temperature dependence of the yield stress in crystals

Abstract

The temperature dependence of the critical resolved shear stress (CRSS) of single crystals often exhibits a two-step change. On the basis of the Peierls mechanism of the dislocation glide, a two-step change can theoretically be expected for (1) a depressed-top or a flat-top Peierls potential, (2) the Peierls mechanism of a narrowly dissociated dislocation and (3) two stable core configurations with different Peierls stresses and different kink energies. In this paper, after discussing the CRSS versus T relations for bcc metals and tetrahedrally coordinated crystals, detailed discussion has been made on the two-step CRSS versus T curves reported for (1 0 0)[0 1 0] and (1 0 0)[0 0 1] slips in tetragonal β-Sn reported by Kirichenko [Phys. Met. Metallogr. 63 (1) (1987) 144] and on that reported for single crystals of NiAl with the hard orientation.