Solution Hardening and Softening in KCl–KBr Single Crystals at Low Temperatures

Abstract

The temperature and concentration dependence of the critical resolved shear stress (CRSS) for KCl and KCl–KBr solid solutions was measured from 4.2 K to 293 K. At lower temperatures the solid solutions with the concentration below 10 mol% KBr and above 90 mol% KBr showed solution softening. The other concentrations of solid solutions were hardened at all temperatures tested. The concentration dependence of the CRSS was given by a c(1-c) relation except for the case of lower concentrations at lower temperatures. The activation free energy of deformation varied linearly with temperature and independently of the concentration. It was concluded from the analysis of the activation volume that the dislocation motion in the higher concentration region was impeded only by the solute ions, and that in the lower concentration region by the Peierls barriers in addition to the solute ions.