Tensile properties of 2.5 dpa 300oC neutron irradiated RA FM plate, powder HIP and EB and TIG weld. F82H-mod, JLF-1, JLF-1B, ORNL-3791. Final report EBP 95-98 programme, subtask SM1.2.2

Reduced Activation Ferritic/Martensitic (RAFM) alloys are being developed for application in future thermonuclear fusion reactors by various partners in the fusion community. One of the major issues of these alloys is the low temperature irradiation hardening. The irradiation behaviour of the RAFM steel F82H-mod (2 IEA heats) and its EB and TIG welded joints, together with small amounts of related alloys, such as JLF-1 and JLF-1B, were investigated by irradiation experiments in the High Flux Reactor (HFR) in Petten. Tensile properties of various RAFM steels and their EB- and TIG-welds were measured after irradiation up to approx. 2.5 dpa 300C and (for a few data points) up to approx. 2 dpa at 80C. This work is part of an experimental programme to characterise the low temperature irradiation hardening and embrittlement of recently developed RAFM alloys. In all cases the results show significant irradiation hardening and loss of ductility. For one irradiation it is observed that the amount of irradiation hardening deviates significantly from the other, identically targeted irradiation experiments. Irradiation temperature reduction in the order of 30C is the most likely cause. For the various irradiated RAFM plate materials in this study the amount of irradiation hardening measured at irradiation temperature varies between 140 and 200 MPa for the ILAS-4 and ILAS-8 irradiations. TIG welded joints of F82H show similar yield and ultimate strength before irradiation when compared to F82H plate material. 2.5 dpa 300C irradiation gives them a higher hardening and a lower ductility when compared to plate material. EB welded joints of F82H show higher yield and ultimate strength before irradiation when compared to F82H plate material. 2.5 dpa 300C irradiation gives the same hardening when compared to plate material. Powder HIPed F82H material shows tensile properties that are well comparable with plate material. 8 refs