Fabrication using a levitation melting method of V–4Cr–4Ti–Si–Al–Y alloys and their mechanical properties

Reduction of interstitial impurities such as O and N is a potential method to improve various properties of vanadium alloys. It was shown that addition of Si, Al and Y was useful to reduce the oxygen concentration and to improve post-irradiation ductility at relatively low temperatures for V–Cr–Ti alloys. Several 2.5 kg alloys of V–4Cr–4Ti–Si–Al–Y type were fabricated by using a levitation melting method. Charpy impact test by an instrumented testing machine has been conducted using miniaturized specimens. Tensile tests have been carried out before and after neutron irradiation. The miniaturized specimens were irradiated up to 8×1022 n/m2 (E>1 MeV) at 290 °C in Japan Materials Testing Reactor. By adopting a levitation melting method, high-purity kg-scale ingots of V–4Cr–4Ti–Si–Al–Y alloys with ∼80 ppm C, <170 ppm O and ∼110 ppm N were obtained. The V–4Cr–4Ti–0.1Si–0.1Al–0.1Y alloy fabricated in this study showed good impact properties compared with a previous laboratory-scale alloy. This alloy showed good tensile properties even after neutron irradiation at 290 °C. Levitation melting can be adopted to produce large ingots of V–Cr–Ti–Si–Al–Y type alloys by controlling the amount of yttrium addition. In this study, the technology for fabrication of high-purity kg-scale ingots of V–4Cr–4Ti–Si–Al–Y alloy has been demonstrated, and has made it possible to investigate systematically various properties of the alloy.