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 W-Re alloys were investigated. Neutron irradiation of pure Wand W-Re alloys (Re concentration 3-26%) was carried out in the experimental fast reactor JOYO. The irradiation conditions were 0.44 displacement per atom (dpa) at 531 degrees C and 0.47 dpa at 583 degrees C for pure W and W-Re 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 Wand W-Re alloys after irradiation. The number density of voids in pure W was higher than that in W-3% Re, W-5% Re and W-10% Re. Only in the case of W-26% Re irradiated to 0.47 dpa at 583 degrees 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 W-Re 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 W-Re alloys. Irradiation hardening of W was also suppressed in hot-rolled W compared with arc-melted as-cast W.