Modelisation de composes ordonnes sous irradiation: disgrammes d'equilibre dynamique et evolutions microstructurales

To model the behaviour under irradiation of a B.C.C. alloy presenting the B2-A2 order-disorder transition, we propose a mean-field approximation of a kinetic model with two atomic exchange mechanisms acting in parallel: thermally activated and forced jumps. By integration of deterministic evolution equations, we show that irradiation can induce the stabilization of two-phase alloy, while the classical equilibrium phase diagram only displays single phase fields (the B2-A2 transition is second order). Steady-state diagram are computed: in the two-phase region, antiphase boundaries are found to be unstable with respect to the disordered solid solution and smaller precipitates shrink to the benefit of the larger ones. The different dissolution paths of B2 precipitates are studied.