Synergy between BCC and C14 phases on the hydrogenation properties of the two phases high-entropy alloy Ti16Zr4V35Cr15Ni10Mn20

In this paper, we show a comparative analysis of the first hydrogenation properties in a two phases High Entropy Alloy (HEA). When the Ti 16 Zr 4 V 35 Cr 15 Ni 10 Mn 20 alloy is cast, two phases BCC and C14, with respective compositions of Ti 8.6 V 51.1 Cr 20.9 Ni 2.5 Mn 16.9 and Ti 24.1 Zr 7.9 V 18.8 Cr 8.2 Ni 18.6 Mn 22.4 are produced. This alloy absorbs hydrogen at room temperature, reaching a capacity of 1.9 wt% within 3 h. When the two phases are synthesized separately, neither absorbs hydrogen. However, when they are mixed via ball milling, the composite absorbs hydrogen at room temperature, achieving a capacity of 1.8 wt% after 10 h. This is a proof that there is some synergy between the phases and it depends on the nature of the contact between the phases. • Despite thermodynamic predictions of a single phase, the Ti 16 Zr 4 V 35 Cr 15 Ni 10 Mn 20 alloy exhibits both BCC and C14 phases. • The alloy showed rapid hydrogen absorption at room temperature under hydrogen pressure of 2000 kPa due to BCC/C14 synergy. • None of the single synthesized phases could absorb hydrogen under the same conditions as the original alloy. • Mechanical milling of BCC and C14 phases enabled hydrogen absorption but with slower kinetics than the cast alloy.