Stability of the structure and properties of an ultrafine-grained Cr-Ni steel irradiated with neutrons in nuclear reactor core conditions

An ultrafine-grained (UFG) austenite Cr-Ni stainless steel was produced by equal-channel angular pressing. The UFG samples were irradiated in a research nuclear reactor up to damaging doses of 12 and 15 dpa at 350 degrees C and 450 degrees C, respectively. The post-irradiation examination featured in this work covers microstructural and mechanical property changes at test temperatures of 20-650 degrees C. Microstructural studies showed that the concentration of Frank loops was considerably lower in the UFG steel compared to in the coarse-grained material. It was also found that irradiation resulted in precipitation of a-phase in triple junctions of the UFG steel. The post irradiation examination of mechanical properties testified that the UFG steel exhibited lower irradiation hardening and higher strength compared to the coarse-grained material in the entire testing temperatures range, and improved ductility when tested at 500-650 degrees C. In summary, we testified that microstructure refinement of an austenite stainless steel down to UFG scale led to enhancement of its resistance to neutron irradiation at elevated temperatures.