Hydrogen-induced phase transition of MgZrTiFe0.5Co0.5Ni0.5 high entropy alloy

In this study, the MgZrTiFe0.5Co0.5Ni0.5 high entropy alloy was processed by high-energy ball milling under both argon and hydrogen atmospheres. The hydrogen storage behavior of the samples was evaluated by combination of thermal analyses and in-situ synchrotron powder X-ray diffraction. It is shown that this alloy forms a body-centered cubic (BCC) structure when milled under argon pressure. The BCC phase is capable to absorb up to 1.2%wt. of hydrogen and during absorption it undergoes a phase transition forming a face-centered cubic (FCC) high entropy hydride. This FCC hydride can be directly synthesized by high-energy ball milling under hydrogen pressure.