The hardening of copper by neutron irradiation

Copper wires of 0.060 in. diameter were irradiated at 50 deg C for 1 to 3 weeks. At a fixed neutron dose and testing temperature the yield stress of irradiated polycrystalline copper increases within accuracy limits of experimental measurements. Lattice friction hardening and source hardening proceed simultaneously. The increased yield strength of irradiated copper at -78 deg C compared with 20 deg C arises from a temperature dependence of the lattice friction component of hardening. (C.J.G.)