Kinetics of structural phase transitions in the Fe$_{80.5}$Ga$_{19.5}$ alloy

This work is devoted to the Monte Carlo simulation of the kinetics of phase transitions of the order-disorder type in the Fe$_{80.5}$Ga$_{19.5}$ alloy using the Blume–Emery–Griffiths Hamiltonian. The study of phase transformations was carried out in two stages: (1) different cooling rates (different number of Monte Carlo steps at a constant value of the binding energy); (2) isothermal annealing (the binding energy depends on the number of Monte Carlo steps at a fixed temperature). In the first case, a high cooling rate leads to one phase transition A2$\to$D03+A2 at 700$^\circ$С, while slow cooling leads to a transition A2$\to$D03+A2 at 700$^\circ$С through a mixture of phases A2, D0$_3$, B2 and L1$_{2}$ in the temperature range from 850 to 700$^\circ$С. In the second case, an increase in the volume fraction of the L1$_{2}$ phase is shown with an increase in the duration of annealing at 750$^\circ$С. Based on the data obtained, a thermokinetic diagram of phase transformations was constructed.