Solid Solution Softening and Solid Solution Hardening in Concentrated KCl–KBr Model Crystals

Abstract

The dislocation motion at 0 K overcoming the concentrated solute atoms is calculated by a relaxation method using the string model. The concentration dependence of yield stress τy with Peierls barrier agrees with experimental data, and softening is revealed in c=0.04, where c is the concentration of KBr in KCl. The softening is due to the enhancement of double kink nucleations by solute atoms. Both Cl- and Br- ions are assumed to reveal the size effect against hypothetical anions with the average ionic radius to obtain the interaction force between dislocation and solute atom. For NaCl type lattice without Peierls barrier the equation, τy/µ≃Ks[c(1-c)]j[(1+ν)vε/2π(1-ν)b3]1+i(µb2/\\varGamma)i, where µ is the shear modulus, ν Poisson's ratio, vε the volume difference between solute and solvent atoms, b the Burgers vector, \\varGamma the line tension, Ks≃0.87, i≃0.25 and j≃0.64, is derived.