Effect of annealing and Re-irradiation on the copper-enriched precipitates in a neutron-irradiated pressure vessel steel weld

摘要

An atom probe tomography study has been performed to estimate the matrix composition, and the size, composition and number density of the ultrafine copper-enriched precipitates that formed under neutron irradiation in a submerged arc weld (Weld 73W). This high copper (0.27 at. % Cu) weld was examined after a typical stress relief treatment of 40 h at 607°C, after neutron irradiation to a fluence of 1.8 × 10{sup}23 n m{sup}-2 (E .1 MeV) at a temperature of 288°C, after irradiation and thermal annealing for 168 h at 454°C, and after irradiation, thermal annealing and re-irradiation to an additional fluence of 0.8 × 10{sup}23 n m{sup}-2 (E > 1 MeV). A high number density of ultrafine copper-enriched precipitates were found to form on irradiation. These precipitates were found to coarsen and decrease in number density after the annealing treatment at 454°C. These precipitates were present after re-irradiation and some additional subnanometer diameter copper-enriched precipitates were also observed Segregation of nickel, manganese, silicon, copper and phosphorus atoms to dislocations was also observed.