PHASE-STABILITY AND MICROSTRUCTURAL EVOLUTION IN CONCENTRATED ALLOYS UNDER IRRADIATION

Concentrated alloys under irradiation can be modelled as a collection of atoms which exchange lattice sites according to two mechanisms occu rring in parallel: thermally activated jumps of point defects and forc ed jumps imposed by the replacement collisions or cascade core mixing. Several techniques are presented for handling such a model: in partic ular, stochastic potentials which play a role similar to the free ener gy can be computed in simple cases; dynamical-equilibrium phase diagra ms can be constructed, and the evolution of the precipitate morphology for varying irradiation conditions can be modelled. The basic techniq ues are briefly introduced and some successful applications of the mod el are exemplified: they deal with the inversion of phase stability in Ni4Mo, the existence of capillarity-like effects, the various dissolu tion modes of ordered precipitates and the effects of cascade size and density on two-phase equilibria under irradiation.