Fundamental radiation effects parameters in metals and ceramics

Several fundamental aspects of defect cluster accumulation in irradiated ce ramics and face centered cubic metals are reviewed, with particular emphasi s on radiation hardening and the microstructural evolution in Cu observed b y transmission electron microscopy (TEM). At temperatures where interstitia ls are mobile (> 50 K in Cu), the defect cluster density in pure Cu is init ially proportional to the dose and exhibits a square root dose dependence a bove similar to 10(-4) displacements per atom. This fluence dependence (det ermined from electrical resistivity and TEM studies) helps to resolve a lon g-standing controversy on the fluence dependence of radiation hardening. Th e fraction of freely migrating interstitials in copper irradiated with 14 M eV neutrons at room temperature is similar to 11%. The activation energy fo r annealing stage V (stacking fault tetrahedra evaporation) in neutron-irra diated copper has been measured to be 0.84 eV. Some features of the point d efect accumulation behavior in ceramics are found to be very similar to the trends observed in pure Cu, despite the obvious differences in the physica l properties of these two types of materials. Finally, microstructural evid ence for some processes unique to nonmetals are summarized, particularly io nization induced diffusion.