Phase evolution process and hydrogen storage performances of V72Ti18Cr10 alloy prepared by Co-precipitation-reduction method

The V72Ti18Cr10 alloy was prepared by a co-precipitation-reduction method in order to consume less energy during whole-life alloy manufacturing, and the phase evolution process in hydrogenation/dehydrogenation process was investigated. The structure refinement analysis of the alloy contented with 1 ​wt% hydrogen after hydrogenation shows that BCC phase, BCC-hydride phase and FCC phase coexisted, but little BCT phase was found. It indicates that the phase evolution process during hydrogenation was BCC→ BCC-hydride→ FCC, nevertheless the formation of BCT phase was restrained. The limited particle sizes of the alloy in the range of 0.1–5 ​μm and fewer defects than the normal alloy ingot contributed to the suppression of BCT formation. The annealed alloy, which had similar particle sizes with the unannealed alloy, has less unevenness of the compositions than the unannealed alloy, and the annealed alloy showed flatter plateau in the hydrogenation PCT (pressure-composition-temperature) curves. However, the BCT phase in the annealed alloy appeared in its dehydrogenation process owing to the produced defects during the following dehydrogenation and the hydrogenation process. The alloy with the limited particle sizes even in the range from 0.1 ​μm to 5 ​μm could not prevent the generation of BCT phase in the dehydrogenation process.