Severe Plastic Deformation by Fast Forging to Easy Produce Hydride from Bulk Mg-Based Alloys

The study of metal forging over long period of time has made it possible to establish the major basic principles up to the most recent, those of Severe Plastic Deformation (SPD). Thus the fundamental characteristics resulting from the stresses and deformations applied have led to the definition and modelling of microstructural variations in grain size and shape, density of dislocations, slip bands and twins, all factors to be considered during the transformation of the micro/nanostructure by SPD. For this purpose, SPD techniques such as ECAP, HPT, ARB have produced invaluable results namely in views of solid state hydrogen storage. So the present report focuses on magnesium-based materials with the aim of generating a deformed structure that will react quickly to allow massive and reversible hydrogen storage. However, all here above mentioned methods are rather difficult to scale up to mass production because they are either too time-consuming or too energy and labor intensive. Furthermore, it is revealed that at extreme, fast forging (FF) can introduce high densities of vacancies, voids and finally cracks in addition to grain refinement down to the ultrafine and nano-scale sizes. This leads in the FF worked material exhibiting excellent hydrogen reactivity as shown on a few examples

Severe plastic deformation for producing Superfunctional ultrafine-grained and heterostructured materials: An interdisciplinary review

Ultrafine-grained and heterostructured materials are currently of high interest due to their superior mechanical and functional properties. Severe plastic deformation (SPD) is one of the most effective methods to produce such materials with unique microstructure-property relationships. In this review paper, after summarizing the recent progress in developing various SPD methods for processing bulk, surface and powder of materials, the main structural and microstructural features of SPD-processed materials are explained including lattice defects, grain boundaries and phase transformations. The properties and potential applications of SPD-processed materials are then reviewed in detail including tensile properties, creep, superplasticity, hydrogen embrittlement resistance, electrical conductivity, magnetic properties, optical properties, solar energy harvesting, photocatalysis, electrocatalysis, hydrolysis, hydrogen storage, hydrogen production, CO2 conversion, corrosion resistance and biocompatibility. It is shown that achieving such properties is not currently limited to pure metals and conventional metallic alloys, and a wide range of materials are processed by SPD, including high-entropy alloys, glasses, semiconductors, ceramics and polymers. It is particularly emphasized that SPD has moved from a simple metal processing tool to a powerful means for the discovery and synthesis of new superfunctional metallic and nonmetallic materials. The article ends by declaring that the borders of SPD have been extended from materials science and it has become an interdisciplinary tool to address scientific questions such as the mechanism of geological and astronomical phenomena and the origin of life