Irradiation-induced precipitates in a neutron irradiated 304 stainless steel studied by three-dimensional atom probe

Abstract Irradiation-induced precipitates in a 304 stainless steel, neutron-irradiated to a dose of 24 dpa at 300 °C in the fuel wrapper plates of a commercial pressurized water reactor, were investigated by laser-assisted three-dimensional atom probe. A high number density of 4 × 1023 m−3 of Ni–Si rich precipitates was observed, which is one order of magnitude higher than that of Frank loops. The average diameter was ∼10 nm and the average chemical composition was 40% Ni, 14% Si, 11% Cr and 32% Fe in atomic percent. Over a range of Si concentrations, the ratio of Ni to Si was ∼3, close to that of γ′ precipitate (Ni3Si). In some precipitates, Mn enrichment inside the precipitate and P segregation at the interface were observed. Post-irradiation annealing was performed to discuss the contribution of the precipitates to irradiation-hardening.