The hydrogen-induced ductility loss and strengthening of V-base alloys

Several V-base alloys were exposed to hydrogen gas at 700–800 °C for hydrogen charging. Tensile tests were performed after the exposure to evaluate the hydrogen embrittlement behavior. The results showed that neither the uniform nor the total elongation was significantly affected by the hydrogen before a critical hydrogen concentration (CCH) was reached when the alloys were tested at high strain rate of 1.1 × 10−3/s. However the total elongation of the V–4Cr–4Ti alloy (NIFS-Heat 2) decreased notably with increasing hydrogen concentration at the strain rate of 4.4 × 10−4/s. Hydrogen-induced hardening occurred for all of the alloys, which was thought to be a solid solution hardening. The hardening rate was found to decrease significantly with the addition of Ti/Al to the alloy and the increase of the strain rate. And also, the alloys with Ti or Al were shown to have better properties against the hydrogen embrittlement.