Investigation of radiation-induced segregation at fully characterized coherent twin boundaries in proton-irradiated 316L stainless steel

The effect of grain boundary character on radiation-induced segregation (RIS) is investigated in a 316L austenitic stainless steel irradiated with 2 MeV protons at 360 °C. Orientation imaging microscopy is employed to select specific grain boundaries (GBs), including Σ3{111} coherent twin boundaries, fully characterized by a five-degree of freedom analysis, as well as high angle GBs. Chemical maps along these GBs below the irradiated surface, at depths corresponding to damage levels ranging from 2.3 dpa to 4.2 dpa, are acquired using energy-dispersive spectrometry in a scanning transmission electron microscope (STEM-EDS). RIS levels are defined as elemental GB excess quantities and are used to compare RIS at twin boundaries and high-angle GBs. These measurements are complemented by the analysis of void distributions near GBs and by characterizing the structure of coherent twin GBs prior to and after irradiation using high-resolution STEM imaging. In light of the results obtained in this work, the evolution of the efficiency for point defect elimination of coherent twin GBs with the irradiation dose is discussed.