The microstructure and tensile properties of ferritic/martensitic steels T91, Eurofer-97 and F82H irradiated up to 20 dpa in STIP-III

Ferritic/martensitic (FM) steels, T91, Eurofer-97 and F82H, were irradiated up to a maximum displacement dose of 20 dpa (displacement per atom) at temperatures ranging from ∼120 to ∼600 °C in the 3rd experiment of the SINQ Target Irradiation Program (STIP-III). Tensile tests were performed at 25,400 and 450 °C. Microstructural observations show that irradiation-induced defect clusters formed in all investigated specimens, although the densities were low in specimens irradiated at temperatures >400 °C. High-density small He bubbles were observed in specimens irradiated to doses ≳ 9 dpa. Small bubble size in specimens of high doses of 17–20 dpa at temperatures >400 °C could be attributed low temperatures in the beginning phase of irradiation. The tensile test results demonstrate that not only the specimens irradiated at <350 °C but also those irradiated at >400 °C show significant hardening effect. The three FM steels present a great similarity in tensile properties under similar irradiation and testing conditions.