Investigation on hydrogen storage properties of as-cast, extruded and swaged Mg–Y–Zn alloys.

In this work, three different states of Mg-9.1Y-1.8Zn alloys including as-cast, extruded and swaged were prepared by semi-continuous casting, extrusion and swaging processes, respectively. Their compositions, microstructures and hydrogen storage properties were investigated. The results show that Mg-9.1Y-1.8Zn alloys in three different states are all composed of Mg and long-period stacking ordered (LPSO) phases. The LPSO phases occurs to break and decompose after hydrogenation and in-situ forms the YH χ(χ = 2,3) nano-hydrides. The nano-hydrides can be used as in-situ catalysts to improve the hydrogen storage properties of alloys. Meanwhile, many nanocrystalline grains appear in the core of alloy after swaging, and the average grain size ranges from 80 to 200 nm. The presence of nanocrystals may increase the specific surface area of alloy, facilitating the diffusion and absorption of hydrogen. Comparatively, the swaged alloy exhibits the largest hydrogen storage capacity and excellent hydrogen sorption kinetics relative to other states of alloys. • The as-cast, extruded, and swaged Mg-9.1Y-1.8Zn alloys were prepared. • The LPSO phases decomposes and in-situ forms YH χ(χ = 2,3) hydrides upon hydrogenation. • The YH χ(χ = 2,3) hydrides present in-situ catalytic and pinning effects on Mg matrix. • The swaged alloy exhibits the highest hydrogen storage capacity. [ABSTRACT FROM AUTHOR]