First-principles study on the mechanical, thermal properties and hydrogen behavior of ternary V-Ni-M alloys

Abstract Studying hydrogen behavior in alloys and the mechanical properties of alloys are essential to various practical uses, such as separation membranes, as well as hydrogen embrittlement protection. In order to further develop the non-Pd-alloy membranes used in hydrogen separation, the mechanical, thermal properties of V14NiM (M= Al, Fe, Si, Ti, Zn) and hydrogen solubility and diffusion behaviors of V-based ternary alloys were studied by first principles calculation. The results indicated that the hydrogen solution energies of V-Ni-M are greater than pure vanadium. And the mono-vacancy in pure vanadium can capture 6 H atoms while the V-Ni-M alloys can only capture 5 H atoms. Therefore, the V-Ni-M alloys exhibit lower solubility of hydrogen and higher brittleness resistance to embrittlement compared with pure vanadium. And the diffusion coefficients of V-Ni-M alloys are smaller than that of pure vanadium thanks to smaller hydrogen solubility. The hydrogen solubility and hydrogen permeability can maintain relatively balanced. The study of mechanical properties suggests that the V-Ni-Ti has the best resistance to deformation and pure vanadium has the best ductility. Moreover, V-Ni-Si alloy has the smallest thermal expansion coefficient in the temperature range of 473-723 K, which is the temperature of hydrogen separation, indicating that V-Ni-Si is the best for hydrogen separation according to thermal properties.