Microstructure of Cu-Ni alloys neutron irradiated at 210 deg. C and 420 deg. C to 14 dpa

Transmission electron microscope (TEM) disks of pure copper and copper containing 0.17-10% Ni were neutron irradiated at 210 deg. C and 420 deg. C in Hf-shielded capsules in the High Flux Isotopes Reactor to doses of 13.5 and 14.9 displacements per atom (dpa), respectively. Void swelling was not observed in any of the specimens irradiated at 210 deg. C. Instead, a high density of stacking fault tetrahedra (SFTs) and a moderate density of dislocation loops were observed. There was no evidence for defect cluster patterning (wall formation) in any of the specimens irradiated at 210 deg. C. The SFT density was independent of Ni content, whereas the loop density was highest in the alloy containing ∼2% Ni. Pronounced void swelling was observed in all of the specimens irradiated at 420 deg. C. A void denuded zone of ∼2 μm width was observed adjacent to grain boundaries. The void swelling in copper containing ∼2% Ni showed a pronounced maximum in a 10-μm wide band adjacent to the grain boundary denuded zones. Matrix voids aligned along <1 1 0> directions were observed in Cu-10%Ni irradiated at 420 deg. C. The occurrence of the peak swelling zone and the partial ordering of voids are both consistent with the predictions of the recent production bias model which includes 1-D diffusional transport of clusters of self-interstitial atoms