EFFECTS OF ELECTRON-IRRADIATION ON THE KINETICS OF ORDER-DISORDER TRANSFORMATIONS

The response of an ordered alloy to high energy electron irradiation has been theoretically investigated in terms of the magnitude and sign of the change in long-range order parameter, S, with time. A theoretical model is developed for the two competing processes of disordering by atomic displacements and ordering by vacancy migration. This predicts that radiation-induced disordering should be favored at low irradiation temperatures, but that it should be balanced by radiation-enhanced ordering at higher temperatures where the vacancies produced by irradiation are sufficiently mobile to restore some degree of order to the lattice. The response of an ordered material to irradiation also depends on the initial value of order parameter prior to irradiation, and on the displacement rate.