The effect of solidification rate on microstructural evolution of a melt-spun Mg–20Ni–8Mm hydrogen storage alloy

Mg-based Mg–20Ni–8Mm (wt%) (Mm = Ce, La-rich Mischmetal) hydrogen storage alloy with microcrystalline, nanocrystalline, and amorphous microstructures was obtained by controlling the solidification rate of the melt-spun ribbon. The microstructure was remarkably refined by rapid solidification compared with that of a conventionally prepared polycrystalline alloy. The optimal microstructure with a considerable amount of nanocrystalline Mg and Mg2Ni in an amorphous matrix was expected to have the highest hydrogen storage capacity. Mischmetal-containing Mg12Mm intermetallic precipitated preferentially at the boundary of magnesium grains in the microcrystalline microstructure, thus providing possible pathways for the enhanced hydrogen diffusion into the Mg.