Diffusion kinetics and spinodal decomposition in quasi-equilibrium solid solutions

A phenomenological theory of the transformation of multicomponent solid solutions with the hierarchy of atomic mobilities of the components has been developed within the local-equilibrium approximation. At the hydrodynamic stage, the evolution of these solutions is treated as a sequence of quasi-equilibrium states, for which only a part of conditions for the complete equilibrium are fulfilled. The equations describing the evolution of the distributions of “fast” components in the quasi-equilibrium solid solutions at arbitrary stages of the transformation are derived within the generalized lattice model accounting for the specific volumes of components by using the separation of “fast” and “slow” components of diffusion and the method of contracted descriptions. The conditions of the stability of quasi-equilibrium solutions against the spinodal decomposition are determined, and the equations for the metastability boundaries in these systems are obtained.