  Magnesium and its alloys are the most investigated materials for solid-state
hydrogen storage in the form of metal hydrides, but there are still unresolved
problems with the kinetics and thermodynamics of hydrogenation and
dehydrogenation of this group of materials. Severe plastic deformation (SPD)
methods, such as equal-channel angular pressing (ECAP), high-pressure torsion
(HPT), intensive rolling and fast forging, have been widely used to enhance the
activation, air resistance, and hydrogenation/dehydrogenation kinetics of
Mg-based hydrogen storage materials by introducing ultrafine/nanoscale grains
and crystal lattice defects. These severely deformed materials, particularly in
the presence of alloying additives or second-phase nanoparticles, can show not
only fast hydrogen absorption/desorption kinetics but also good cycling
stability. It was shown that some materials that are apparently inert to
hydrogen can absorb hydrogen after SPD processing. Moreover, the SPD methods
were effectively used for hydrogen binding-energy engineering and synthesizing
new magnesium alloys with low thermodynamic stability for reversible
low/room-temperature hydrogen storage, such as nanoglasses, high-entropy
alloys, and metastable phases including the high-pressure {\gamma}-MgH2
polymorph. This article reviews recent advances in the development of Mg-based
hydrogen storage materials by SPD processing and discusses their potential in
future applications.

Materials Science;Chemical Physics