Hydrogen storage behavior and microstructural feature of a TiFe–ZrCr₂ alloy

The microstructural feature as well as the hydrogen storage properties of as-cast and annealed TiFe-6 wt% ZrCr₂ alloy samples has been investigated. Three phases, TiFe with the BCC structure, TiFe₂ with the C14 Laves hexagonal structure and Ti₂Fe with a cubic structure, are observed in both alloy samples, although the amount of TiFe₂ as a second phase is significantly reduced with a fragmented shape in the annealed sample. Both samples are hydrogenated under 31 bar of hydrogen at room temperature without a harsh activation process, although the annealed sample is hydrogenated after an incubation period of approximately 40 h. The pressure-composition-temperature curves of both samples are not much different from each other, exhibiting a maximum capacity of 1.7 wt% H₂. No significant degradation of hydrogen capacity is observed during 50 cycles of hydrogen sorption for the as-cast sample. The second phase TiFe₂ regions seem to assist the first hydrogenation of the alloy by acting as gateways for supplying hydrogen to the inside of the alloy.