Microstructure Development in Neutron Irradiated Tungsten Alloys

Abstract

The aim of this work is to investigate the influence of neutron irradiation condition, especially temperature, on irradiation hardening and microstructure development in irradiated tungsten-rhenium (W-Re) alloys. Neutron irradiations were carried out in JOYO at the range of 400 to 750 C, up to 1.54 dpa. Micro Vickers hardness tests and micro structural observations using a TEM were performed. Irradiation hardening of WRe alloys irradiated at 538 C were clearly larger than those irradiated at other temperatures. Fine voids and fine needle-or plate-like precipitates were observed in pure W and W-Re alloys irradiated at 538 C, respectively, with high number density. The fine complex microstructure seems to be the cause of the characteristic irradiation hardening.

Evaluation of Ion-Irradiation Hardening of Tungsten Single Crystals by Nanoindentation Technique Considering Material Pile-Up Effect

“…Figure 6 summarizes the ion-irradiation hardening results, based on the eq. (10) of this work in comparison with the previously obtained ion-irradiation results by our group 5) as well as with the neutron-irradiation hardening results by Vickers hardness tests of other researchers 34,35) . The damage levels that are referred to in this gure are averaged damage levels over the projected ion range up to 2000 nm and represent the dpa at a depth of about 600 nm.…”

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

“…Because the amount of precipitate was minimal, the precipitate could not be identified by using a diffraction pattern. However, the shape and direction of the precipitates were the same as those observed in our previous studies, 9,11,13) and it is therefore considered that the precipitates in W26%Re (HR) are chi-phase precipitates. Precipitates were not observed when the Re content was below 10 mass%.…”

“…Irradiation hardening of WRe alloys (526% Re) irradiated to 0.96 dpa at 538°C was mainly caused by precipitates. 13) From the comparison of the irradiation hardening of pure W irradiated to the same damage level, the effect of the fabrication process on irradiation hardening behavior of pure W was not clear. As mentioned above, the microstructures of both pure W (HR) and pure W (AC) were in a recrystallized state, and the effect of the fabrication process was not observed.…”

“…5) Although the solute Re improves the mechanical properties of W, 1416) the irradiation-induced precipitates cause severe irradiation hardening and embrittlement. 9,10,13) The mechanical properties of W also change depending on the fabrication process, including the subsequent heat treatment. Different fabrication processes and heat treatments change the grain structure, such as grain size and shape, as well as other aspects of the microstructure, such as dislocation and defect density.…”

Microstructural modifications in tungsten induced by high flux plasma exposure: TEM examination

“…To our best knowledge, this is the first observation of the edge interstitial dislocation loops at conditions corresponding to low-energy plasma exposure. Previously both a 0 /2〈111〉 and a 0 〈100〉 interstitial and vacancy loops were observed in W under high energy ion [24] and fast neutron irradiation [25], but as a result of collapse of the cascade region or by agglomeration of selfinterstitial defects.…”