Monte Carlo Simulation of Simultaneous Ordering and Precipitation in BCC Lattice

Abstract
Fe-Al system quenched into its two-phase field undergoes a phase separation leading to the coexistence of A2 and B2 phases. Using transmission electron microscopy, three different decomposition behaviours have been reported with increasing aluminium concentration : nucleation-growth of B2 inside a disordered matrix, decomposition of interconnected ordered phases which was attributed to spinodal decomposition, and nucleation-growth of A2 inside B2 domains. This work presents the first Monte Carlo simulations of simultaneous phase separation and ordering in a two-phase A2/B2 domain. Calculations were performed using an Atomistic Kinetic Model ; one vacancy allows atomic diffusion and a residence time algorithm is used. The three experimentally observed morphologies of evolution are reproduced. Moreover decomposition kinetics is compatible with the classical Lifshits-Slyosov-Wagner coarsening theory.