Formation and Stability of Metastable Phases in Mechanochemical Synthesis

Abstract

Some conditions of formation of solid solutions and intermetallic compounds in the course of mechanochemical synthesis are considered. The main factor among those determining the thermodynamic possibility of formation of metastable phase in mechanochemical synthesis is substantial increase in the internal energy of the initial material due to accumulation of stored strain energy and appearance of nanostructural (excited) state. Competition (choice) between phases possible in the given system is determined by kinetic factors. As a rule, the first to appear in metallic systems are regions of solid solution phase based on a relatively low-mobility component. Energy barriers in generation and growth of excess phase (especially for phases with low energy of formation) are an additional factor of stability of the metastable state of supersaturated solid solution in the process of mechanochemical synthesis due to scarceness of mobile vacancies.