Irradiation behavior of nanostructured 316 austenitic stainless steel

In order to get information about radiation resistance of ultrafine grained austenitic stainless steels, a 316 steel was deformed by high pressure torsion. The mean diameter of the grain after deformation was 40 nm. This material was annealed at 350 C for 24 h or irradiated with 160 keV iron ions at 350 C. Changes in the microstructure during annealing or irradiation were characterised by transmission electron microscopy (grain size) and laser assisted tomographic atom probe (solute distribution). Results indicate that this annealing has no influence on the grain size whereas the grain diameter increases under irradiation. Concerning the solute distribution, atom probe investigations show evidence of radiation-induced segregation at grain boundaries. Indeed, after irradiation, grain boundaries are enriched in nickel and silicon and depleted in chromium. On the contrary, no intragranular extended defects or precipitation are observed after irradiation.