Master equation approach to configurational kinetics of non-equilibrium alloys and its applications to studies of phase transformations

摘要

We review a series of works where the fundamental master equation is used to develop a consistent description of the evolution of non-equilibrium atomic distributions in an alloy. We derive exact equations for the temporal evolution of local concentrations and correlators of their fluctuations, as well as for the free energy of a non-equilibrium alloy. We discuss various approximate methods for treatments of these equations, such as the kinetic mean-field method and the develop a kinetic cluster field method which combines a high accuracy in the description of thermodynamics with a great simplification of calculations. We also present a microscopical model for deformational interactions in concentrated alloys to treat phase transitions with a lattice symmetry change, such as the tetragonal distortion under L1_0 ordering. We describe some recent applications of the developed methods to studies of alloy orderings with more than two types of ordered domains, such as the D0_3, L1_2 and L1_0 orderings. These studies reveal a number of new and interesting microstructural effects, many of them agreeing well with experimental observations.