Radiation-Induced Precipitates in a Self-ion Irradiated Cold-Worked 316 Austenitic Stainless Steel Used for PWR Baffle-Bolts

摘要

5 meV Ni~(++) and Fe~(++) ion irradiations were performed to investigate radiation-induced precipitates evolution in a cold-worked 316 austenitic stainless steel at high doses and temperatures. The irradiation conditions were 23 dpa at 380 °C, 130 dpa at 380 °C, 23 dpa at 500 °C, and 15 dpa at 600 °C. TEM selected electron diffraction (SAED), TEM dark-field imaging and energy dispersive spectroscopy (EDS) mapping were used as complementary techniques to determine crystallography, morphology and chemical composition of radiation-induced pre-cipitates. The precipitates were predominantly in form of the Ni-Si rich γ' phase at all irradiation conditions. The EDS analysis further determined Ni-Si-Mo-P and Ni-Si-Mn rich precipitates after irradiation at 380 and 600 °C, respectively. The precipitates were found close to saturated state between 23 and 130 dpa at 380 °C irradiation conditions. A different effect of higher irradiation temperatures was found between 500 and 600 °C. In case of the irradiation to 23 dpa at 500 °C, the average size of precipitates was similar to irradiations at 380 °C, but the density was lower. However, the precipitates revealed large size and very low density following the irradiation to 15 dpa at 600 °C. The original dislocation network introduced by cold-working was found as dominant sink for intra-granular solute radiation-induced segregation (RIS) and possibly took place as primary nucleation site of radiation-induced precipitates at irradiation temperatures 380 and 500 °C. At the temperature 600 °C, the RIS at dislocation network almost vanished and the main nucleation sites became twin boundaries as more energetically favorable intra-granular sinks.