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 V 35 Ti 30 Cr 25 Fe 10 , V 35 Ti 30 Cr 25 Mn 10 , V 30 Ti 30 Cr 25 Fe 10 Nb 5 and V 35 Ti 30 Cr 25 Fe 5 Mn 5 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 V 35 Ti 30 Cr 25 Mn 10 alloy shows the highest hydrogen absorption capacity while the V 35 Ti 30 Cr 26 Fe 5 Mn 5 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 V 35 Ti 30 Cr 25 Fe 5 Mn 5 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. [Display omitted] • A series of high entropy alloys (HEAs) with BCC phase structure are prepared. • High Δ S promotes the formation of BCC phase while δ has the opposite effect. • HEAs with high BCC phase ratio show high H 2 absorption and desorption capacity. • The cause of the loss of hydrogen desorption capacity is revealed. [ABSTRACT FROM AUTHOR]