Comparative study of solid-solution treatment and hot-extrusion on hydrogen storage performance for Mg₉₆Y₂Zn₂ alloy: The nonnegligible role of elements distribution

The utilization of Mg alloys for solid-state hydrogen storage has attracted considerable attention, and the Mg-based alloys with long period stacking ordered (LPSO) structure show optimized hydrogen storage properties. In this study, solid-solution treatment and hot-extrusion are utilized to modify the hydrogen storage properties of Mg₉₆Y₂Zn₂ alloy. The results indicate 14H-type LPSO structure is precipitated after solid-solution treatment. Dynamic recrystallization occurs during deformation process with the refined grain size of 2 μm approximately and the dynamic precipitation of Mg₃Y₂Zn₃ particles leads to the aggregation of Y and Zn atoms. Hot-extrusion can enhance the pulverization resistance of Mg₉₆Y₂Zn₂ alloy by increasing the lattice parameter ratio of c to a. The reduced hydrogen capacity of hot-extruded Mg₉₆Y₂Zn₂ alloy is attributed to the increased pulverization resistance and decreased lattice parameters. The apparent activation energies for hydrogenation and dehydrogenation of solid-solution treated alloy are 6.86 and 13.65 kJ·mol⁻¹ less than those of hot-extruded alloy, respectively. The dehydrogenation temperature of solid-solution treated alloy hydride is 18 °C lower than that of hot-extruded alloy. More abundant and uniform distribution of Y atoms can generate accordingly more abundant and uniform YH₂ nanoscale particles that embed in the α-Mg matrix, which contributes to faster de/hydrogenation kinetics.