EFFECTS OF NEUTRON-IRRADIATION ON MECHANICAL-PROPERTIES AND MICROSTRUCTURES OF DISPERSION AND PRECIPITATION-HARDENED COPPER-ALLOYS

Tensile specimens of Cu-Al2O3, CuCrZr and CuNiBe alloys were irradiate d with fission neutrons to fluences of 5 x 10(22), 5 x 10(23) and 1 x 10(24) n/m(2) (E > 1 MeV) at 47 degrees C. Tensile properties and Vick ers hardness were determined at 22 degrees C. Microstructures of irrad iated as well as unirradiated specimens were examined using a transmis sion electron microscope and the fractured surfaces were investigated in a scanning electron microscope, The most significant effect of irra diation is a drastic decrease in the ductility of copper alloys at a d ose level as low as 0.2 dpa. The loss of ductility appears to be relat ed to the intrinsic hardness of the grain interior and not to the grai n boundary embrittlement. It is suggested that the irradiation-induced hardening and the lack of uniform elongation may be understood in ter ms of difficulty in dislocation generation due to pinning of grown-in dislocation by defect clusters (loops) and/or impurity atoms.