Microstructures and properties of nanocrystalline W-based alloys produced by resistance sintering under ultrahigh pressure

W-2.5 wt% Y (WY) alloy with an average grain size of 9 nm and W-2 wt% TaC-2.5 wt% Y (WTY) alloy with an average grain size of 13 nm, were successfully prepared by resistance sintering under ultrahigh pressure (RSUHP) at low temperature, and the relative density of WY and WTY is 95.0% and 94.7%, respectively. The micro-structure characterization and theoretical calculation results show that the inhibition of W grain growth can be mainly ascribed to the thermodynamic aspect. The Vickers hardness of nanocrystalline WY and WTY alloys is 1770 +/- 62 kgf/mm2 and 1626 +/- 36 kgf/mm2, respectively, and their Vickers hardness is much higher than that of coarse-grained W-based alloys, and the mechanisms of their ultrahigh hardness were revealed. The deviation of the Hall-Petch relationship in WY and WTY alloys was found as the dislocation pileup model is not applicable. Deuterium (D) plasma irradiation experiments on nanocrystalline WY at the irradiation dose of 1.2 x 1024 D/m2, 2.4 x 1024 D/m2, and 3.6 x 1024 D/m2 were conducted, respectively. Blisters can be found at three irradiation doses in nanocrystalline WY alloy, the blister areal density and blister size increase with the increase of irra-diation dose, and the roles of grain boundaries (GBs) on the irradiation behaviors were illustrated. This article broke through the contradiction between the high melting point and low recrystallization temperature of W, and provided an experimental basis and theoretical guidance for the design and development of high-performance novel nanocrystalline W-based alloys.

Automated summary

W-2.5 wt% Y (WY) and W-2 wt% TaC-2.5 wt% Y (WTY) alloys with nanoscale grain sizes were successfully prepared by resistance sintering under ultrahigh pressure. The high Vickers hardness of these alloys was attributed to the inhibition of grain growth and the mechanisms of their ultrahigh hardness were revealed. Deuterium plasma irradiation experiments on nanocrystalline WY illustrated the effects of grain boundaries on the irradiation behaviors. This study provides experimental basis and theoretical guidance for the design and development of high-performance nanocrystalline W-based alloys.