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

The yield stresses of single crystals of solid solutions of beta-tin with s ubstitutional impurities of indium, cadmium, and zinc are measured over a w ide interval of low temperatures (1.6-150 K). The low-temperature impurity softening effect is observed, which is manifested in a decrease in the yiel d stresses of the alloys in comparison with that of pure tin. The temperatu re and concentration boundaries of the existence region of this effect are established, and the dependence on the combined size and modulus misfit par ameter between the atoms of tin and the impurities, which characterizes the strength of the impurity barriers for the motion of dislocations in the al loy, is determined. Analysis of the data obtained indicates a qualitative a greement of the observed regularities of the impurity softening effect and the behavior that follows from the model of Sato and Meshii, which takes in to account the role of impurity atoms both as centers of nucleation of kink s on screw dislocations and as centers of opposition to the lateral dispers al of the kinks along the dislocation line. (C) 2000 American Institute of Physics. [S1063-777X(00)01302-5].