Superfunctional Materials by Ultra-Severe Plastic Deformation

Abstract

Superfunctional materials are defined as materials with specific properties being superior to the functions of engineering materials. Numerous studies introduced severe plastic deformation (SPD) as an effective process to improve the functional and mechanical properties of various metallic and non-metallic materials. Moreover, the concept of ultra-SPD—introducing shear strains over 1000 to reduce the thickness of sheared phases to levels comparable to atomic distances—was recently utilized to synthesize novel superfunctional materials. In this article, the application of ultra-SPD for controlling atomic diffusion and phase transformation and synthesizing new materials with superfunctional properties is discussed. The main properties achieved by ultra-SPD include: (i) high-temperature thermal stability in new immiscible age-hardenable aluminum alloys; (ii) room-temperature superplasticity for the first time in magnesium and aluminum alloys; (iii) high strength and high plasticity in nanograined intermetallics; (iv) low elastic modulus and high hardness in biocompatible binary and high-entropy alloys; (v) superconductivity and high strength in the Nb-Ti alloys; (vi) room-temperature hydrogen storage for the first time in magnesium alloys; and (vii) superior photocatalytic hydrogen production, oxygen production, and carbon dioxide conversion on high-entropy oxides and oxynitrides as a new family of photocatalysts.

A Molecular Dynamics Simulation to Shed Light on the Mechanical Alloying of an Al-Zr Alloy Induced by Severe Plastic Deformation

“…During solidification and equilibrium, a tetragonal DO 23 Al-3at.%Zr phase is formed with a wide range of cooling rates [13]. Interestingly, SPDs with huge strain or ultrasevere plastic deformation [14] made it possible to overcome these physical limitations and form unusual metastable super-saturated solid solutions, even in immiscible systems [15]. Application of huge shear straining to an Al-5at.%Zr alloy demonstrated that up to 1 at.% of Zr can be dissolved in an Al matrix at room temperature [16].…”

Some Unresolved Problems of High-Pressure Torsion

“…An interesting observation that deserves mentioning is that after a certain threshold in strain perfect plasticity may break down leaving the stage to renewed strain hardening of the deforming material. 16,17) Again, it is not quite clear whether this resumption of strain hardening after a period of perfect plasticity without a change of the deformation path is universal or not.…”

“…In addition, HPT clearly has the potential to become part of manufacturing processes. 17,126129) However, despite burgeoning research activity in nanostructured and ultrafine-grained materials produced by SPD, it is fair to say that so far, the practical outcomes of research have not met the expectations of industry. The prevailing sentiment is that without upscaling of the SPD processes, commercialisation of laboratory-proven technologies would not be accepted by industry and enjoy commercialisation successes.…”

“…12) Besides, review articles focusing on various aspects of HPT were published. The areas covered include texture evolution, 13) solid state reactions, 14) phase transformations, 15) material behaviour at ultra-high strains (in excess of 1,000), 16,17) finite element modelling, 18) etc.…”

Severe Plastic Deformation of Light Metals (Magnesium, Aluminum and Titanium) and Alloys by High-Pressure Torsion: Review of Fundamentals and Mechanical/Functional Properties

“…13,14) Such materials are sometimes referred to as superfunctional materials due to their superior properties. 15,16) For the most recent progress in the field of SPD, the readers are referred to a 2023 special issue of Materials Transactions, 17) which covered various aspects like processing methods, [18][19][20][21][22][23][24][25][26] structural/microstructural features, [27][28][29][30][31][32][33] mechanical/functional properties, nanostructured metallic and non-metallic materials [56][57][58][59][60][61][62][63][64][65][66][67][68] and heterostructured materials. [69][70][71][72] Among various SPD methods, ECAP and ARB have the potential for commercialization.…”