Effects of Re Content and Fabrication Process on Microstructural Changes and Hardening in Neutron Irradiated Tungsten

The effects of the material fabrication process and rhenium (Re) content on the irradiation-induced changes in the microstructure and hardness of pure tungsten (W) and WRe alloys were investigated.Neutron irradiation of pure W and WRe alloys (Re concentration 326%) was carried out in the experimental fast reactor JOYO.The irradiation conditions were 0.44 displacement per atom (dpa) at 531°C and 0.47 dpa at 583°C for pure W and WRe alloys, respectively.After irradiation, microstructural observations using a transmission electron microscope (TEM) and Vickers microhardness tests were performed.Voids and dislocation loops were observed in both pure W and WRe alloys after irradiation.The number density of voids in pure W was higher than that in W3%Re, W5%Re and W10%Re.Only in the case of W26%Re irradiated to 0.47 dpa at 583°C were there no voids observed, but irradiation-induced fine precipitates and a few dislocation loops were observed.The irradiation hardening of pure W was greater than that of the WRe alloys.It was considered that irradiation hardening of pure W was caused mainly by the higher number density of voids.The addition of Re suppressed void formation and irradiation hardening of the WRe alloys.Irradiation hardening of W was also suppressed in hot-rolled W compared with arc-melted as-cast W. [