Magnesium and hafnium, two hydride-forming and biocompatible metals with hexagonal close-packed crystal structures, are thermodynamically immiscible even in the liquid form. In this study, these two elements were mechanically mixed by high-pressure torsion straining, and a new FCC (face-centered cubic) phase was formed although these two elements do not form the FCC phase even under high pressure or at high temperature. Microstructural examination by scanning-transmission electron microscopy combined with an ASTAR automatic crystal orientation and phase mapping technique confirmed that the FCC phase was stabilized mainly in the Hf-rich nanograins with localized supersaturation. Attempts to control the phase transformations under a hydrogen atmosphere to produce ternary magnesium–hafnium hydrides for hydrogen storage applications were unsuccessful; however, the material exhibited enhanced hardness to an acceptable level for some biomedical applications.

TiFe as a room-temperature hydrogen storage material is usually synthesized by ingot casting in the coarse-grained form, but the ingot needs a thermal activation treatment for hydrogen absorption. Herein, nanograined TiFe is synthesized from the titanium and iron powders by severe plastic deformation (SPD) via the high-pressure torsion (HPT). The phase transformation to the TiFe intermetallic is confirmed by X-ray diffraction, hardness measurement, scanning/transmission electron microscopy, and automatic crystal orientation and phase mappings (ASTAR device). It is shown that the HPT-synthesized TiFe can store hydrogen at room temperature with a reasonable kinetics, but it still needs an activation treatment. A comparison between the current results and those achieved on high activity of HPT-processed TiFe ingot suggests that a combination of ingot casting and SPD processing is more effective than synthesis by SPD to overcome the activation problem of TiFe.