Formation of a solid solution during quasi-spontaneous internal dispersion of tin in the presence of liquid gallium

Abstract

The driving force behind quasi-spontaneous dispersion is provided partly by the reduction in the free energy of the system during formation of a solid solution; this reduction compensates for the energy losses associated with the formation of new interfaces. It is evident that this factor alone cannot cause grain refinement; for instance, it cannot transform a single crystal into a finely-crystalline polycrystal. What is required in addition are specific kinetic conditions, which will ensure a higher rate of formation of a solid sotution (by reprecipitation of the initial solid phase from the dispersing medium, accompanied by a reduction in grain size) than that attained when the dispersing medium diffuses into the solid in the normal way [3]. Such, obviously, must be the physical character of the previously described examples of a particular type of spontaneous internal dispersion, i.e., the transformation of single tin crystals coated with thin liquid gallium films into polycrystals having a grain-size of the order of 10-3cm, and a similar transformation observed under some conditions in gallium-coated zinc single crystals [2]. The results of X-ray diffraction measurements of the lattice parameters ofgallinmbearing tin cited in the present article support the view that a solid solution is, in fact, formed in this case. *