Microstructure analysis of Xe20+ irradiation and postirradiation corrosion of Zr-4 and Zr–1Nb alloys

The microstructure evolution of 5 MeV Xe20+ irradiation and the corrosion behavior of postirradiation in Zr-4 and Zr–1Nb alloys have been investigated. Positron results showed that vacancy defects, such as vacancies and vacancy clusters, are produced in Zr-4 and Zr–1Nb alloys after Xe20+ irradiation, and less vacancy defects are formed at 360 °C irradiation than at room temperature irradiation, resulting in lower S parameters due to recombination of defects. The nanoindentation results found that vacancy defects produced by irradiation lead to the hardening of both Zr-4 and Zr–1Nb alloys. Corrosion weight gain tests showed that the damaged layer induced by irradiation accelerates the oxidation rate during the corrosion process. Compared to the Zr-4 alloy, the damaged layer of Zr–1Nb alloy contains more vacancy defects after room temperature irradiation, which correspond to higher hardness increase and faster corrosion weight gain, resulting in the formation of cracks in oxide films as is observed by SEM. At the early stage of the corrosion, the postirradiation corrosion resistance of Zr-4 alloy may be better than that of Zr–1Nb alloy.