Low-temperature softening of β-tin single crystals on doping with substitutional impurities

Abstract

The yield stresses of single crystals of solid solutions of β-tin with substitutional impurities of indium, cadmium, and zinc are measured over a wide interval of low temperatures (1.6–150 K). The low-temperature impurity softening effect is observed, which is manifested in a decrease in the yield stresses of the alloys in comparison with that of pure tin. The temperature and concentration boundaries of the existence region of this effect are established, and the dependence on the combined size and modulus misfit parameter between the atoms of tin and the impurities, which characterizes the strength of the impurity barriers for the motion of dislocations in the alloy, is determined. Analysis of the data obtained indicates a qualitative agreement of the observed regularities of the impurity softening effect and the behavior that follows from the model of Sato and Meshii, which takes into account the role of impurity atoms both as centers of nucleation of kinks on screw dislocations and as centers of opposition to the lateral dispersal of the kinks along the dislocation line.