Monte Carlo simulations of the decomposition of metastable solid solutions: Transient and steady-state nucleation kinetics

We present a study on the kinetics of coherent precipitation in weakly supe r-saturated substitutional solid solutions by the Monte Carlo method. Our s imulations are based on a simple atomistic model of diffusion by vacancy ju mps. The whole precipitation process (from early stages to late stage coars ening) is followed for various supersaturations and temperatures, and typic al behaviors observed in the simulations are compared to those predicted by the classical theories. Special emphasis is placed on the first stages of the decomposition (incubation and nucleation) and on the effects of the vac ancy diffusion mechanism. Finally we consider the addition of a third (impu rity) element, which can be used to control the kinetic pathway: such effec ts are quantitatively explored with the Monte Carlo method.