Effects of the dose and depth on the microstructural characteristics of proton-irradiated austenitic 316 stainless steel

Type 316 austenitic stainless steel was irradiated at 360 °C with 2 MeV protons to doses up to 6.0 displacements per atom at a depth of approximately 10 μm and the various effects of proton irradiation on the irradiation defects and microstructural changes were characterized using transmission electron microscopy. The irradiation defects produced by protons consisted of Frank loops, network dislocations, voids and nanotwins. The size and the density of the irradiation defects increased depending on the increase of the dose. Frank loops, dislocations and nanotwins were found mainly in regions irradiated at a low dose, whereas voids were dominant in regions near the damage peaks. The evolution of typical irradiation defects changed according to the irradiation depth, in agreement with the characteristics of the dose variation depending on the depth. This behavior during the production of distinct irradiation defects according to the irradiation depth appears to be an intrinsic characteristic of any type of ion irradiation. A simple and effective method of preparing TEM specimens to remove chemically the surface damage layers induced by a high-energy focused ion beam and/or low-energy ion milling treatments is suggested.