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MgH2 is a promising material for solid‐state hydrogen storage due to its high gravimetric and volumetric storage capacity and its relatively low cost. Severe plastic deformation (SPD) processing techniques are being explored as an alternative to high‐energy ball‐milling (HEBM) in order to obtain more air resistant materials and reduce processing times. In this work, Mg, MgH2, and MgH2–Fe mixtures were severely mechanically processed by different techniques such as high‐pressure torsion (HPT), extensive cold forging, and cold rolling. A very significant grain refinement was achieved when using MgH2 instead of Mg as raw material. The mean crystallite sizes observed ranged from 10 to 30 nm, depending on the processing conditions. Enhanced H‐sorption properties were observed for the MgH2‐based nanocomposites processed by HPT when compared with MgH2 mixtures. Additionally, cold forging and cold rolling also proved effective in nanostructuring MgH2. These results suggest a high potential for innovative application with the use of low cost mechanical processing routes to produce Mg‐based nanomaterials with attractive hydrogen storage properties.

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Mg-based nanocomposites are promising candidates for hydrogen storage applications exhibiting fast H-sorption kinetics at reasonably low temperatures when processed by high-energy ball milling techniques. However, since compaction of the highly reactive nanometric powder is desirable before application, the search for other effective processing routes for the preparation of Mg-based nanocomposites is relevant. In this work, we have used a combination of equal channel angular pressing, cold rolling and high-energy ball milling in the processing of the commercial AZ31 extruded alloy to evaluate its use as a hydrogen storage material. Severe plastic deformation carried out at different temperatures, combined with further mechanical processing resulted in a controlled texture and signifiant grain refinement, which are desirable microstructural characteristics for hydrogen storage applications.

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