Microstructure and hydrogen storage properties of Ti–V–Cr based BCC-type high entropy alloys

In this work, the crystal structure and hydrogen storage properties of V35Ti30Cr25Fe10, V35Ti30Cr25Mn10, V30Ti30Cr25Fe10Nb5 and V35Ti30Cr25Fe5Mn5 BCC-type high entropy alloys have been investigated. It was found that high entropy promotes the formation of BCC phase while large atomic difference (δ) has the opposite effect. Among the four alloys, the V35Ti30Cr25Mn10 alloy shows the highest hydrogen absorption capacity while the V35Ti30Cr26Fe5Mn5 alloy exhibits the highest reversible capacity. The cause of the loss of desorption capacity is mainly due to the high stability of the hydrides. The higher room-temperature desorption capacity of the V35Ti30Cr25Fe5Mn5 alloy is due to higher hydrogen desorption pressure. After pumping at 400 °C, the hydrides can return to the original BCC structure with only a small expansion in the cell volume.