AN ATOM PROBE TOMOGRAPHY STUDY OF PROTON-IRRADIATED AUSTENITIC STAINLESS STEELS

摘要

Due to the recent development of highly efficient atom probes, the application of atom probe tomography (APT) in studying the mechanisms of irradiation-assisted stress corrosion cracking (IASCC) becomes feasible. Three austenitic alloys, HP-304, HP-304+Si and CP-304 with different IASCC susceptibility in simulated light water environment, were irradiated to 5 dpa using 2 MeV protons at 360°C. APT samples containing grain boundaries were fabricated from the irradiated alloys using the focused ion beam system. The APT samples were analyzed using a local electrode atom probe. Ni-and Si-rich clusters were observed in irradiated HP-304+Si and CP-304. The segregation of major elements, such as Fe, Ni and Cr was comparable to that measured by STEM/EDS method. No precipitation was observed on the grain boundaries. However, islands with high Ni and Si content were observed at the grain boundaries in irradiated HP-304+Si and CP-304. Boron was observed to enrich at grain boundaries in all three irradiated alloys. The enrichment of phosphorus at grain boundaries was also observed in irradiated CP-304.