Analysis of observations on solid-solution hardening in KBr–KCl single crystals

Abstract

Available data on the temperature and concentration dependences of the critical resolved shear stress (CRSS) of KBr–KCl solid-solution crystals containing 8–41 mol% KCl in the temperature range 77–230 K have been analysed within the frame work of the kink-pair nucleation model of plastic flow in solid-solution crystals. It is found that CRSS τ decreases with the increase in temperature T in accord with the model relation ln τ = A−BT, where A and B are positive constants. The CRSS τ at a given temperature depends on solute concentration c as τ ∝ cp, where exponent p has a value between 0.5 and 1 depending on the temperature at which deformation is carried out. The model parameter Wo, i.e. binding energy between the edge-dislocation segment involved in the unit activation process and the solute atoms close to it (T→0 K), which is inversely proportional to B, increases with solute concentration c monotonically in accord with the model prediction Wo ∝ c1/4 upto a critical value cm = 35 mol% KCl. However, Wo decreases with increase in c beyond cm, which indicates somewhat ordered distribution of solute in the host lattice of concentrated solid-solutions with c > cm.