Effect of hypo-stoichiometry on microstructure and hydrogenation behaviors of multiphase ZrTi0.1V2-x alloys

Abstract

ZrTi0.1V2-x (x = 0, 0.2, 0.4) alloys are designed to investigate the effect of hypo-stoichiometry on hydrogenation properties of Laves phase dominated multiphase alloys. The samples are synthetized by arc melting and homogenizing annealing treatment. Phase abundances and lattice parameters are studied by XRD and Rietveld refinement. The morphology of each phase is confirmed by SEM and EDS, hydrogenation kinetics, pressure-composition-temperature characteristics and hydrides have been studied. Annealing increases the content of Laves phase and Zr3V3O, while decreases that of V-BCC and α-Zr. The decrease in atomic ratio B/A, i.e. V/(Zr + Ti), results in the increase of Zr3V3O, the decrease of Laves and V-BCC, and the lattice expansion for each phase. Alloys show easy activation and fast hydrogenation kinetics, which is controlled by a different process. Hydrogen absorption capacity and formation enthalpy increase while equilibrium pressure decreases with the decrease in B/A ratio, which could be related to the decrease of V-BCC phase and lattice expansion for each phase. Zr8V16H36.29 is the dominated hydride after saturated hydrogenation, the proportion of hydrides and their hydrogen mass fraction accord with the hydrogen absorption behavior. Among the samples, ZrTi0.1V1.6 shows the best overall properties for rapid and massive hydrogen absorption at low pressure.