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

ML-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 Mg(12)Mm inter-metallic precipitated preferentially at the boundary of magnesium grains in the microcrystalline microstructure, thus providing possible pathways for the enhanced hydrogen diffusion into the Mg. (C) 2006 Elsevier B.V. All rights reserved.