Hardening and microstructure of neutron- and ion-irradiated Fe-Cr alloys

Understanding the irradiation behaviour of binary Fe-Cr alloys is basic for the optimization of ferritic/martensitic chromium steels for future applications under conditions of high neutron exposures. In this work self-ion irradiation with the ion beam scanned over the sample was used in order to simulate neutron damage in Fe-12.5at%Cr. The material irradiated at 300°C up to a damage level of 1 dpa was exposed to isochronal annealing treatments in the range from 300 to 550°C and the indentation hardness was measured as a function of annealing temperature. We have found the presence of two recovery steps. The first one takes place at 300°C, i.e. at irradiation temperature, and gives rise to a 45% recovery of the irradiation-induced hardness increase. The second step occurs in the range from 400 to 550°C and gives rise to full recovery. The findings are discussed in terms of the dissolution of hardening features, such as dislocation loops and ’-phase particles. In addition, rate theoretical considerations were used to investigate possible flux effects caused by the pulsed irradiation experienced by the material due to the scanning ion beam. It was found, that no significant additional flux effects arise from the pulsing.