Characterization of a nanocrystalline Mg–Ni alloy processed by high-pressure torsion during hydrogenation and dehydrogenation

•Mg2Ni powders were subjected to high pressure torsion.•Partial hydrogenation and dehydrogenation states were obtained.•Microstructure was monitored during hydrogen cycling.•Nanostructure is preserved during the entire hydrogenation–dehydrogenation process.

Ball-milled Mg-Ni powder has been cold-compacted and subsequently processed by severe shear deformation under high-pressure torsion. The effect of high pressure torsion on morphology and microstructure of the disk-shape samples has been characterized by scanning electron microscopy and X-ray diffraction, respectively. In order to achieve partially hydrogenated and dehydrogenated states of deformed samples, the hydrogen uptake or release was interrupted at 25%, 50% and 75% hydrogen contents in a Sieverts' type apparatus. In this paper we present the characterization of the microstructure during a full absorption-desorption cycle of the nanocrystalline Mg–Ni alloy.