MONTE-CARLO SIMULATION OF SIMULTANEOUS ORDERING AND PRECIPITATION IN BCC LATTICE

Fe-Al system quenched into its two-phase field undergoes a phase separ ation leading to the coexistence of A2 and B2 phases. Using transmissi on electron microscopy, three different decomposition behaviours have been reported with increasing aluminium concentration: nucleation-grow th of B2 inside a disordered matrix, decomposition of interconnected o rdered phases which was attributed to spinodal decomposition, and nucl eation-growth of A2 inside B2 domains. This work presents the first Mo nte Carlo simulations of simultaneous phase seperation and ordering in a two-phase A2/B2 domain. Calculations were performed using an Atomis tic Kinetic Model; one vacancy allows atomic diffusion and a residence time algorithm is used. The three experimentally observed morphologie s of evolution are reproduced. Moreover decomposition kinetics is comp atible with the classical Lifshits-Slyosov-Wagner coarsening theory.