Monte-Carlo simulation of order–disorder kinetics in 2D and fcc binary alloys

The thermodynamic parameters that drive the atomic migration in 2D and 3D binary alloys are studied using Monte-Carlo simulations. The model is based on a vacancy–atom jump mechanism between nearest neighbour sites, with a constant vacancy concentration, so that only the migration counterpart (EM) of the total activation energy (EA=EM+EF, where EF is the vacancy formation energy) is determined. The ordering kinetics are well described by exponential like behaviours with one (respectively two) relaxation time in the 2D (respectively 3D) cases. The temperature dependence of the long relaxation time is an Arrhenius law yielding effective migration energies. Slowing down of the relaxation is observed at the Order–Disorder transitions. In both cases, we observe a linear variation of the effective migration energy with the Order–Disorder critical temperature.