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 0.47dpa 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 0.47dpa 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. [doi:10.2320/matertrans.MBW201110]

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