DEFECT ORDERING IN METALS UNDER IRRADIATION

A review is given of the experimental observations of ordered defect s tructures formed in metals under irradiation with energetic particles, such as neutrons, ions, and electrons. These phenomena of self-organi zation in solids far from thermodynamic equilibrium comprise periodic walls of point defect clusters, void and bubble lattices, and periodic compositional patterns in alloys. An intriguing result is that all of these structures are partially or completely isomorphic with the host lattice. Conditions for the formation of these structures and their s tability regimes in the corresponding parameter space are discussed. D etailed modelling has been developed for periodic defect walls and for void lattices in irradiated metals. These approaches are based on the coupling of point defects with the defect structure by non-linear dif fusion-controlled reactions. An evaluation of existing data indicates that the isomorphy of the ordered defect structures is due to elastic interactions in the case of defect walls, and due to low-dimensional d efect transport in the case of bubble and void lattices.