TEMPERATURE AND DOSE DEPENDENCIES OF MICROSTRUCTURE AND HARDNESS OF NEUTRON-IRRADIATED OFHC COPPER

Tensile specimens of pure oxygen free high conductivity (OFHC) copper were irradiated with fission neutrons between 320 and 723 K to fluences in the range 5 x 10(21) to 1.5 x 10(24)n/m(2) (E > 1 MeV) with a flux of 2.5 x 10(17) n/m(2) s. Irradiated specimens were investigated by transmission electron microscopy (TEM) and quantitative determinations were made of defect clusters and cavities. The dose dependence of tensile properties of specimens irradiated at 320 K was determined at 295 K. Hardness measurements were made at 295 K on specimens irradiated at different temperatures and doses. Microstructures of tensile tested specimens were also investigated by TEM. Results show that the increase in cluster density and hardening nearly saturate at a dose of similar to 0.3 dpa. Irradiations at 320 K cause a drastic decrease in the uniform elongation already at similar or equal to 0.1 dpa. It is suggested that the irradiation-induced increase in the initial yield stress and a drastic decrease in the ability of copper to deform plastically in a homogeneous fashion are caused by a substantial reduction in the ability of grown-in dislocations to act as efficient dislocation sources.