The microstructure and associated tensile properties of irradiated fcc andbcc metals

The differences and similarities of behaviour between fee and bcc metals af ter irradiation have been investigated. For this purpose, fee Cu, Pd and 30 4 stainless steel and bcc Fe, Mo and Mo-5% Re were irradiated with either n eutrons or 590 MeV protons at temperatures below recovery stage V. It is sh own that a dense population of defect clusters (up to 10(22)-10(24) m(-3)) develops, the type of cluster formed depending apparently on the stacking f ault energy. In the case of stacking fault tetrahedra formed in Cu, their s ize is independent of dose, while interstitial loops in stainless steel gro w at neutron doses higher than 1 dpa. The defect microstructure is found to be independent of the recoil energy spectra in this temperature region, bu t shows a very strong dependence on the type of crystalline structure. The results of tensile testing indicate the presence of radiation hardening, st arting at very low doses as an upper yield point develops followed by a (se rrated) yield region. The main deformation mode observed is dislocation cha nneling. The hardening is modelled in terms of the initial dislocation lock ing by the irradiation-induced defects followed by the dispersed hardening induced by the global distribution of clusters in the matrix. (C) 2000 Publ ished by Elsevier Science B.V. All rights reserved.