Influence of annealing treatment on the microstructure and hydrogen storage performance of Ti1.02Cr1.1Mn0.3Fe0.6 alloy for hybrid hydrogen storage application

•Annealing reduces the hydrogen absorption pressure and the desorption enthalpy.•Prolonging annealing time flattens the hydrogen desorption plateau of the alloy.•Prolonging annealing time enhances the hydrogen desorption plateau pressure.•Ti1.02Cr1.1Mn0.3Fe0.6 annealed at 1123 K for 5 h shows the best overall performance.

The as-cast Ti1.02Cr1.1Mn0.3Fe0.6 alloy for hybrid hydrogen storage vessel application was annealed at different temperatures (873 K, 973 K, 1123 K, 1173 K) for 2 h, and annealed at 1123 K for different time (2, 5, 8 h) respectively, and their microstructure and hydrogen storage properties were investigated systematically. The results show that the as-cast alloy has a single C14 Laves phase, and all annealed alloys consist of a C14 Laves main phase and a secondary phase. After annealing at different temperatures for 2 h, the hydrogen absorption pressure at 298 K decreases, however, the maximum hydrogen storage capacity and desorption pressures at 318 K decrease slightly too. As the annealing time extends, the hydrogen absorption plateau pressure at 298 K and hydrogen desorption plateau pressure at 318 K increase, and the hydrogen desorption capacity increases first and then decreases, which reaches the highest desorption capacity of 1.721 wt.% at the annealing time of 5 h. Among the studied alloys, the alloy annealed at 1123 K for 5 h has the best overall properties for hybrid hydrogen storage application, its hydrogen absorption plateau at 298 K is 29.09 MPa, its hydrogen desorption plateau pressure at 318 K is 45.12 MPa, its hydrogen storage capacity is 1.721 wt.% and its dissociation enthalpy (ΔHd) is 17.78 kJ/mol H2.

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