Superior irradiation resistance via nanocrystalline grains of 316L austenitic stainless steel

Abstract

The microstructural changes in nanocrystalline (NC) 316L and cold worked (CW) 316L austenitic stainless steels were investigated under irradiation. The nanocrystalline grain structure remained stable under all irradiation conditions of 0.3, 1.14, and 157 dpa and temperatures up to 300 °C due to the significantly higher grain boundary density compared to coarse grains. This character enables the superior radiation resistance of the material. The grain boundary structures act effectively as defect sinks, resulting in fewer dislocation loops and smaller/fewer bubbles, with a better performance against irradiation swelling and radiation induced segregation. Meanwhile, bubble depleted zones were observed around the GBs, due to the sink effect. Their width was found to decrease with the increase of the angle of the grain boundaries in the NC sample under He irradiation, which is closely related to the stress-strain and the dislocation density at the grain boundaries.