Cyclic properties of hydrogen absorption and desorption in V–Ti–Cr–Fe(Al,Si) alloy

The cyclic properties of hydrogen absorption and desorption in V55Ti20.5Cr18.1Fe6.4 and V54.8Ti20.4Cr18Fe6.4Si0.1Al0.3 were studied. With increasing cycle number, the hydrogen absorption and desorption capacity decreases, but the decay rate of hydrogen desorption content slow down, while the plateau region becomes narrowed and the desorption pressure increases. The hydrogen absorption rate increases before the first 55-cycles and then decreases, where the impurities and pulverization have influence upon the alloys’ kinetic properties. The deterioration of the reversibility of structure transformation is the main mechanism that leads to the decrease of the alloys’ hydrogen capacity with the increase of cycle number. Al and Si elements promote the phase transformation from FCC(γ) to BCC(β) during hydrogen desorption process and enhance the pulverization resistance of V55Ti20.5Cr18.1Fe6.4 during cycles.