MONTE-CARLO SIMULATIONS OF LONG-RANGE ORDER KINETICS IN B2 PHASES

The thermodynamic parameters that drive the atomic migration in B2 all oys are studied using Monte-Carlo simulations. The model is based on a vacancy jump mechanism between nearest neighbor sites, with a constan t vacancy concentration. The ordering energy is described through an I sing Hamiltonian with interaction potentials between first and second nearest neighbors, Different migration barriers are introduced for A a nd B atoms. The results of the simulations compare very well with thos e of experiments. The ordering kinetics are well described by exponent ial-like behaviors with two relaxation times whose temperature depende nces are Arrhenius laws yielding effective migration energies. The ord ering energy contributes significantly to the total migration energy.