Decomposition of solid solutions having a tendency toward ordering or separation

Thermodynamic, kinetic and morphological aspects of the decomposition process of binary substitutional solid solutions having either positive or negative signs of ordering energy are considered. Using the model of the free energy relaxation for the separation case or ordering one, a method of computer simulation of those transformations in 3D binary substitutional solid solutions with vacancies is developed. The temporal behavior of a solid solution is described by a system of nonlinear equations obtained from a microscopic kinetic model including the induced elastic strain effects. The simulation results confirmed by the microstructural ones show that periodic microstructures are formed usually as a result of a separation process. The particles of the second phase aligned along 〈1 0 0〉 matrix directions are formed as a result of ordering of nonstoichiometric solid solutions.