STOCHASTIC STATISTICAL THEORY OF NUCLEATION ANDEVOLUTION OF NANO-SIZED PRECIPITATES IN ALLOYS WITHAN APPLICATION TO PRECIPITATION OF COPPER IN IRON

摘要

A consistent and computationally efficient stochastic statistical approach (SSA) is developed to study the ki-netics of nucleation and evolution of nano-sized precipitates in alloys. To increase the accuracy of the method, many refinements of the previous simplified versions of this approach have been made. We consider a realistic vacancy-mediated exchange kinetics rather than the simplified direct-atomic-exchange model; use quantitative, cluster statistical methods rather than simple mean-field-type approximations; allow strong concentration and temperature dependences of generalized mobilities in the resulting kinetic equations; consider realistic alloy models based on first-principle calculations, and so on. We also introduce the "maximum thermodynamic gain" principle to determine the key kinetic parameter of the SSA, the characteristic length of local equilibrium in the course of the nucleation process. For several realistic models of iron–copper alloys studied, the results of the SSA-based simulations of precipitation kinetics made in this work agree well with the kinetic Monte Carlo simulation results for all main characteristics of the microstructure. The approach developed is also used to study the kinetics of nucleation and changes in microstructural evolution under variations of temperature or concentration.