Evidence for irradiation-induced metallic precipitates in neutron-irradiated model alloys and pressure vessel weld steel, using Doppler-broadening positron spectroscopy

Positron Doppler-broadening spectoscopy was used to examine a series of neutron-irradiated model alloys and 73W-weld steel. The composition of the model alloys was systematically varied in the amounts of copper, nickel and phosphorus. The 73W-weld steel contains 0.31 % copper and 0.60 % nickel. The samples were examined in the non-irradiated and neutron-irradiated states, as well as after successive isochronal anneals at temperatures ranging from 200 °C to 600 °C.
By comparing the Doppler-broadening spectroscopy W-parameters measured in pure metals with those measured in the materials in this study, we were able to draw inferences as to the nature of the irradiation-induced defects that cause hardening and embrittlement. The results indicate that the damage is a combination of irradiation-induced metallic precipitates and vacancy-type defect clusters.