Segregation of impurities in platinum and platinum-based alloys

Abstract

This work presents the research results of formation the equilibrium and non-equilibrium segregations of impurities both in pure platinum and platinum alloys. It is shown that segregations strengthen in the case when impurities, absorbed on the surface of crystals, have the same sign or similar values of range deviations regarding to the pure platinum. Equilibrium of segregations occurs as the diffusion result of impurities to the grain boundaries with creation of concentration gradient. Non-equilibrium segregation of impurities occupies the area size of ten micrometers and is generated in the process of metal crystallization or in solid solution as the result of interaction the impurities with vacancies with formation a pair of vacancy-interstitial atom. Segregation of impurities in the platinum alloys is conditioned by the nature of impurities, their concentration, distribution in the volume of metal, interaction with the basic and alloying components as well as the temperature - time factor. The groups of impurities were observed in the form of foreign inclusions along with the equilibrium and non-equilibrium segregation of impurities in the platinum alloys.