EVOLUTION DYNAMICS OF 3D PERIODIC MICROSTRUCTURES IN IRRADIATED MATERIALS

The formation and evolution of defect microstructures in irradiated ma terials is analysed in the framework of a dynamical model for the evol ution of the two fundamental defects of irradiated microstructures, na mely vacancy and interstitial clusters. The effects of irradiation on materials is described by dynamical equations for two mobile atomic si ze species (vacancies and interstitial atoms), and two basic immobile elements of the microstructure (vacancy and interstitial clusters). It is shown that uniform vacancy and interstitial loop distributions may become unstable during irradiation and that they will form large-scal e spatially organized distributions, in a specific range of irradiatio n and material conditions. The selection and stability of the resultin g microstructures are studied in the quasi-static approximation and in the weakly non-linear regime around the bifurcation point. It is show n that, after transients corresponding to three-dimensional BCC patter ns, the final pattern should correspond to planar wall structures in a greement with experimental observations.