INTERPHASE AND ANTIPHASE BOUNDARY STABILITY IN BCC COMPOUNDS UNDER IRRADIATION

To model the behaviour under irradiation of a bcc alloy presenting the B2-A2 order-disorder transition, we propose a mean-field approximatio n of a kinetic model with two atomic exchange mechanisms acting in par allel: thermally activated and forced jumps. By integration of determi nistic evolution equations, we show that irradiation can induce the st abilization of a two-phase alloy, while the classical equilibrium phas e diagram only displays single-phase fields (the B2-A2 transition is s econd order). Steady-state diagrams are computed: in the two-phase reg ion, surface tension-like effects are identified, antiphase boundaries are found to be unstable with respect to the disordered solid solutio n and smaller precipitates shrink to the benefit of the larger ones. M onte Carlo simulations confirm that the transition can become of first kind under irradiation and allow to study cascade size effects.