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An amount of 100 dpa Si2+ irradiation was used to study the effect of transmutation rhenium content on irradiated microscopic defects and hardening in W-xRe (x = 0, 1, 3, 5 and 10 wt.%) alloys at 550 °C. The increase in Re content could significantly refine the grain in the W-xRe alloys, and no obvious surface topography change could be found after high-dose irradiation via the scanning electron microscope (SEM). The micro defects induced by high-dose irradiation in W and W-3Re alloys were observed using a transmission electron microscope (TEM). Dislocation loops with a size larger than 10 nm could be found in both W and W-3Re alloy, but the distribution of them was different. The distribution of the dislocation loops was more uniform in pure W, while they seemed to be clustered around some locations in W-3Re alloy. Voids (~2.4 nm) were observed in W-3Re alloy, while no void was investigated in W. High-dose irradiation induced obvious hardening with the hardening rate between 75% and 155% in all W-xRe alloys, but W-3Re alloy had the lowest hardening rate (75%). The main reasons might be related to the smallest grain size in W-3Re alloy, which suppressed the formation of defect clusters and induced smaller hardening than that in other samples. [ABSTRACT FROM AUTHOR]

Microstructure and irradiation hardening of V-4Cr-4Ti alloys with different yttrium (Y) contents were studied by self-ion irradiation at 550 °C via TEM and nano-indentation test technology. The peak damage of the V-4Cr-4Ti-xY alloy (x = 0, 0.1, 0.5, and 1, wt.%) irradiated by 2.5 MeV self-ion (V2+) is 8 dpa. Dense dislocation loops were observed in all vanadium alloy samples after irradiation. With the increase of Y content, both average size and number density of dislocation loops using g = <110> near the pole [001] decreased, while the irradiation hardness increment first decreased and then increased. In order to better reduce the irradiation hardening, it is considered that the addition of 0.1 wt.% Y in V-4Cr-4Ti alloy is reasonable. [ABSTRACT FROM AUTHOR]

• Compared with pure W, the mean size of dislocation loop was smaller in W-3Re alloy when irradiated to 33.8 dpa for both temperatures. • The addition of 3 wt.% re element could indeed decrease the irradiation hardening rate of W, since the irradiation hardening rate of W was larger than that of W-3Re alloy under the same irradiation conditions. • The hardening rate might be saturated after ∼53.8 dpa irradiation at 550 °C for W-3Re alloy, which might be related to the saturated loop densities. Si2+ irradiation with the dose of 33.8–100 dpa was used to study the dislocation loops and hardening in W and W-3Re alloy at 400 °C and 550 °C using transmission electron microscope (TEM) and nano-indentation tests. When irradiated at 550 °C, larger dislocation loops and numerous dislocation network formed with the dose increased from 33.8 dpa to 100 dpa for both materials. The density of dislocation loops might be saturated between 33.8–100 dpa for W and saturated at ∼53.8 dpa for W-3Re alloy. Compared with pure W, the mean size of dislocation loop was smaller in W-3Re alloy when irradiated to 33.8 dpa for both temperatures. Meanwhile, it was found that the irradiation hardening rate of W was larger than that of W-3Re alloy under the same irradiation conditions, indicating that the addition of 3 wt.% Re element could indeed decrease the irradiation hardening rate of W. The hardening rate might be saturated after ∼53.8 dpa irradiation for W-3Re alloy, which might be related to the saturated loop densities. [ABSTRACT FROM AUTHOR]

• The addition of the 1 wt% Y element can refine the grain size to be about one-seventh of V-4Cr-4Ti alloy, compelely inhibit the formation of large size Ti-rich precipitates. • The addition of the Y element can inhibit the formation of voids and reduce the size of the dislocation loops. • Irradiation hardening can be reduced by adding the Y element. V-4Cr-4Ti-xY alloys with different yttrium (Y) contents (x = 0, 0.1, 1 wt. %) were prepared and irradiated with Fe2+ at 550 ℃ to the peak damage dose of 35 dpa (displacement per atom). The microstructure and hardness of the alloys before and after irradiation were obtained with transmission electron microscopy (TEM), scanning electron microscopy (SEM) and nano-indentation test. With the increase of Y contents, the grain size decreased monotonously, and the formation of needle-like Ti-rich precipitates was suppressed. After irradiation, voids were not observed in Y added alloys but in the V-4Cr-4Ti alloy, showing that the addition of Y could inhibit the formation of voids and irradiation-induced swelling. Dislocation loops and obvious irradiation hardening were observed in all V-4Cr-4Ti-xY alloys, and the size of the dislocation loops and the irradiation hardness increment decreased with the increase of the Y content. The irradiation-induced growth of Ti-rich precipitates was observed, which may be an important factor contributing to the irradiation hardening besides the dislocation loops and voids. The possible mechanism of the effect of the Y element on the irradiation behavior was discussed. Among the three Y contents, V-4Cr-4Ti-1Y alloy exhibits the best performance in the suppression of the formation of Ti-rich precipitates and irradiation hardening. [ABSTRACT FROM AUTHOR]