The effect of crystallographic parameters of interphase boundaries on their surface tension and parameters of the boundary diffusion

Abstract

Aiming to study the effect of cristallographic parameters of interphase boundaries on their properties the method has been developed of growing bicrystalline specimens with single interphase boundaries, whose misorientation parameters are given by the single-crystal seeds. The system of the 〈001〉 tin-germanium twist interphase boundaries has been chosen for the study, being similar geometrically to the 〈100〉 twist grain boundaries, the orientation dependences of the surface tension of these boundaries has been obtained, as well as those of the parameters of the boundary diffusion of indium at various temperatures and pressures. The minima of surface tension and maxima of activation parameters of the boundary diffusion (energy and entropy of activation, activation volume) correspond to the positions of special boundaries within the frameworks of coincidence sites theory. It has been also shown, that special interfaces may correspond to both minimum and maximum diffusion coefficient at a maximum values of activation parameters. The real situation is determined by the position of the so called compensation temperature with respect to the temperature interval studied. The numeric values of preexponential factor and activation volume of the boundary diffusion obtained make it possible to assume, that diffusion mechanism along special interphase boundaries differs from that of noncorrelated random walks of diffusing atoms. This is, to our opinion, connected with the ordered structure of special interphase boundaries.