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 fluence s in the range 5 x 10(21) to 1.5 x 10(24)n/m(2) (E > 1 MeV) with a flu x 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 ten sile properties of specimens irradiated at 320 K was determined at 295 K. Hardness measurements were made at 295 K on specimens irradiated a t different temperatures and doses. Microstructures of tensile tested specimens were also investigated by TEM. Results show that the increas e in cluster density and hardening nearly saturate at a dose of simila r to 0.3 dpa. Irradiations at 320 K cause a drastic decrease in the un iform elongation already at similar or equal to 0.1 dpa. It is suggest ed that the irradiation-induced increase in the initial yield stress a nd a drastic decrease in the ability of copper to deform plastically i n a homogeneous fashion are caused by a substantial reduction in the a bility of grown-in dislocations to act as efficient dislocation source s.