Single crystals with the zincblende structure were deformed in compression, at a strain rate of 2 x 10-4/s, between room and liquid-N temperatures. It was found that they exhibited 2 well-defined regions in the critical resolved shear stress versus temperature relationship. At 78 to 150K, the slope of the straight line fitted to the data points, plotted in log-linear coordinates, was found to be 2.9 times greater than that at between 150 and 300K. A similar behavior was observed in the case of the temperature dependence of the activation volume which was associated with the critical resolved shear stress. Data analysis, in terms of the kink-pair nucleation model of plastic flow, showed that stress-assisted thermally-activated escape of screw dislocations, trapped in Peierls troughs, introduced slip at below 150K. At temperatures above 150K, the critical resolved shear stress was governed by the un-pinning of edge-dislocation segments from groups of randomly dispersed point defects such as residual gaseous and metallic impurities or deformation-induced defects which had formed during the pre-yield stage.

Kinetics of Plastic Deformation in CuBr Single Crystals at Low Temperatures. M.Z.Butt, J.Y.Qazi: Czechoslovak Journal of Physics, 2001, 51[8], 819-28