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 Mg 96 Y 2 Zn 2 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 Mg 3 Y 2 Zn 3 particles leads to the aggregation of Y and Zn atoms. Hot-extrusion can enhance the pulverization resistance of Mg 96 Y 2 Zn 2 alloy by increasing the lattice parameter ratio of c to a. The reduced hydrogen capacity of hot-extruded Mg 96 Y 2 Zn 2 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 YH 2 nanoscale particles that embed in the α-Mg matrix, which contributes to faster de/hydrogenation kinetics. [Display omitted] • High proportion of widely dispersed LPSO phase is obtained by 14H precipitation. • Hot-extrusion motivates dynamic precipitation resulting in aggregation of Y and Zn. • Faster kinetics is obtained by more uniformly distributed YH 2 nanophase. [ABSTRACT FROM AUTHOR]