Magnesium (Mg) alloys are the lightest metallic structural materials, holding significant potential for automotive, aerospace, electronic, and biomedical applications. However, their broader adoption is impeded by inherent drawbacks, including low strength, limited ductility, and poor corrosion resistance. High-pressure torsion (HPT) has proven effective in generating ultrafine-grained (UFG) Mg alloys, resulting in substantial property enhancements. This review critically assesses the microstructure evolution of HPT-processed Mg alloys covering not only grain refinement but also solute segregation, texture evolution, dissolution and precipitation of second phases, allotropic transformation, crystal-to-amorphous transition and nanocrystallization. In particular, it elucidates the impact of these microstructures’ evolutions on mechanical properties, including yield strength, hardness and superplasticity. Additionally, the review discusses the improvements in the addresses the functional augmentation of HPT-processed Mg alloys, specifically corrosion behavior, hydrogen storage capabilities, and biomedical performance.

This study investigates the influence of carbon alloying and severe plastic deformation (SPD) processing by means of high pressure torsion (HPT) on the microstructural evolution and tensile behavior of a C1.1-Cantor alloy. The HPT processing at 300 degrees C produces a heterostructured alloy, comprising recrystallized and severely deformed regions, that simultaneously increases strength (1426 MPa) and ductility (4.2%) compared to the room-temperature HPT condition with significantly limited ductility (1.5%). Advanced characterization reveals that enhanced performance originates from a variety of non-equilibrium atomic-scale features, including nanotwins, amorphization, and incommensurate modulation. Periodic concentration fluctuations, analyzed by atom probe tomography, correspond well with the incommensurately modulated structure. A high density of crystal defects and associated strain energy impose barriers to dislocation glide and significantly contribute to the strength of the C1.1-Cantor alloy. These findings provide a fundamental framework for designing heterostructured high-entropy alloys by adding interstitial atoms. The mechanical response can be manipulated by controlling the degree of recrystallization, defect density and deformation-induced chemical patterning.

Ceramics are typically brittle at ambient conditions due to their covalent or ionic bonding and limited dislocation activities. While plasticity, and occasionally superplasticity, can be achieved in ceramics at high temperatures through thermally activated phenomena, creep, and grain boundary sliding, their deformation at ambient temperature and pressure remains challenging. Processing under high pressure via the high-pressure torsion (HPT) method offers new pathways for severe plastic deformation (SPD) of ceramics. This article reviews recent advances in HPT processing of ceramics, focusing primarily on traditional ceramics (e.g., oxides, carbides, nitrides, oxynitrides) and to a lesser extent advanced ceramics (e.g., silicon, carbon, perovskites, clathrates). Key structural and microstructural features of SPD-processed ceramics are discussed, including phase transformations and the generation of nanograins and defects such as vacancies and dislocations. The properties and applications of these deformed ceramics are summarized, including powder consolidation, photoluminescence, bandgap narrowing, photovoltaics, photocatalysis (dye degradation, plastic waste degradation, antibiotic degradation, hydrogen production, CO2 conversion), electrocatalysis, thermoelectric performance, dielectric performance, and ion conductivity for Li-ion batteries. Additionally, the article highlights the role of HPT in synthesizing novel materials, such as high-entropy ceramics (particularly high-entropy oxides), black oxides, and high-pressure polymorphs, which hold promise for energy and environmental applications.

Commercially pure (CP) titanium is widely used for long-term biomedical implants due to its high biocompatibility and corrosion resistance. However, its relatively low strength limits its use in highly loaded applications. Ultrafine-grained (UFG) titanium obtained through severe plastic deformation offers enhanced mechanical performance while maintaining the stability of CP titanium. This study investigates how electrochemical surface modification by anodization affects the corrosion, biological performance, and technological behavior of UFG titanium. TiO2 layers with nanotubular and nanoporous morphologies were produced at anodization voltages between 20 and 60 V. Corrosion tests in physiological solution confirmed stable passive behavior with corrosion rates below 4 µm year−1, and surface wettability increased markedly with anodization. Osteoblast-like MG-63 cells exhibited good viability on all anodized surfaces, with improved adhesion and proliferation on samples anodized at 60 V. The porous TiO2 layers were successfully intercalated with dimethyl sulfoxide and ibuprofen, demonstrating potential for local drug delivery. Implantation simulations on real Nanoimplant® prototypes confirmed sufficient mechanical stability of the anodized layer. Overall, the optimized anodization of UFG titanium enhances its biological response while maintaining corrosion resistance, supporting its clinical use in long-term dental and orthopedic implants with integrated drug-release functionality.

To date, nanostructuring through plastic deformation has rarely been reported in biodegradable zinc (Zn) based alloys that have great potential in load-bearing conditions. Here, typical high-strength Zn–Li-based alloys were subjected to SPD processes, including equal channel angular pressing (ECAP) and high-pressure torsion (HPT), to achieve nanostructured microstructures. The effects of SPD on the microstructures, mechanical properties, and corrosion behaviors were generally investigated. The two SPD routes resulted in totally different microstructures. ECAPed samples processed at 150 ​°C exhibited a complicated multilevel structure (nm to μm) with mixed Zn equiaxed grains and lamellar-like eutectoid regions (Zn ​+ ​α-LiZn4), and HPTed ones (25 ​°C) possessed a fully dynamically recrystallized (DRXed) microstructure with an average grain size below 0.4 ​μm. The tensile strength of the SPD samples could reach 500 ​MPa. Meanwhile, HPTed samples exhibited extraordinary fracture elongations higher than 100 ​%, because of a different grain boundary sliding deformation mechanism. HPTed samples and ECAPed samples displayed different corrosion patterns, and the former exhibited a much higher corrosion rate in Hank's solution, possibly due to the accelerated corrosion at grain boundaries. In summary, SPD is an efficient way to refine the microstructure of biodegradable Zn-based alloys, possibly improving their performances and clinical applications.

FeCrAl alloys are promising candidates to replace Zr alloys as fuel cladding materials in nuclear light-water reactors. Grain refinement has been indicated to improve irradiation resistance. To enhance corrosion resistance as well, the effects of grain refinement on steam corrosion behavior were investigated in this work. Samples of Kanthal D alloy (Fe-21Cr-5Al) with two different grain sizes (coarse-grained and ultrafine-grained) were exposed to steam at 1200 °C for 2 hrs. Results indicate improved steam corrosion resistance in ultrafine-grained Kanthal D with formation of a thinner protective Al oxide layer and the presence of a thin underlying Cr oxide layer.

Multi-principal element alloys demonstrate high strength, thermal stability, and irradiation resistance, making them excellent candidate materials for applications in nuclear reactors and other harsh environments. Some studies have examined the use of high-pressure torsion to strengthen MPEAs through grain size reduction and strain hardening. However, no studies have investigated the effect of HPT on secondary phases (precipitates) within an MPEA. Two alloys, (Fe0.3Ni0.3Mn0.3Cr0.1)(94)Ti2Al4 containing Ni(Ti, Al) B2 phase, and CrFe sigma phase, and single-phase Fe0.3Ni0.3Mn0.3Cr0.1, were fabricated by casting and heat treatment. Both alloys were then processed with HPT to study microstructural evolution. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the alloys before and after HPT processing. HPT processing produced a nanocrystalline structure in both alloys, but (Fe0.3Ni0.3Mn0.3Cr0.1)(94)Ti2Al4 exhibited a significantly smaller grain size and higher dislocation density than Fe0.3Ni0.3Mn0.3Cr0.1, with corresponding higher hardness. Before HPT, the (Fe0.3Ni0.3Mn0.3Cr0.1)(94)Ti2Al4 alloy consisted of large grain (similar to 400 mu m) and precipitates, including B2 of similar to 38 mu m average size, B2 of similar to 0.7 mu m average size, and small amounts of sigma of similar to 1.5 mu m average size. After HPT, the larger B2 precipitates were decreased in size and volume fraction, while the smaller B2 precipitates were completely dissolved; the sigma precipitates appeared unaffected by HPT, likely due to their much higher hardness. Observation of the B2 precipitate distribution along radial distance indicates that the strain caused the precipitates to fracture at intermediate strain (gamma = 125) and dissolve at high strain (gamma = 280).

The influence of high-pressure torsion (HPT) at room and elevated temperatures on the structureof the high-entropy alloy CoCrFeMnNi has been investigated. Dynamic processes of phasetransformation, including solid solution decomposition and dispersion particle precipitation, havebeen identified. The microstructure of CoCrFeMnNi was studied using transmission electronmicroscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction analysis (XRD).The kinetics of phase transformations was investigated by differential scanning calorimetry (DSC).As a result of deformation twinning processes in the HPT process at room temperature, there is asignificant grain refinement of the structure of the studied HEA to nanocrystalline size of 50 nm. Inturn, during the HPT process at 300 °C, the dynamic recovery process with the decomposition of thesolid solution begins. As a result, it was found that the increasing temperature of HPT leads to theformation of UFG structure with a grain size of ~400 nm. At the same time, nano-scale precipitatesconsisting of the following phases are formed in individual grains: Cr-rich BCC phase and tetragonalσ-phase with variable phase composition. The size of the precipitates reaches up to 10 nm with avolume fraction of less than 3%.

The last two decades have witnessed significant progress in the development of severe plastic deformation techniques to produce ultrafine-grained materials with new and superior properties. This review examines works and achievements related to the low-temperature superplasticity of ultrafine-grained aluminum alloys. The examples are provided of the possibility to observe low-temperature superplasticity in aluminum alloys at temperatures less than 0.5 Tmelt and even at room temperature, and herein, we demonstrate the cases of achieving high ductility and high strength in aluminum alloys from processing utilizing severe plastic deformation. Special emphasis is placed on recent studies of the formation of segregations of alloying elements at grain boundaries in UFG Al alloys and their influence on the development of grain boundary sliding and manifestation of low-temperature superplasticity. In addition, the current status and innovative potential of low-temperature superplasticity in aluminum alloys are observed.

FeCrAl alloys are considered as a candidate material for fuel cladding in commercial light water reactors (LWRs) replacing Zircaloy owing to their high temperature strength and corrosion resistance in steam environments (around 1000oC) [1]. However, FeCrAl alloys also suffer from embrittlement after aging at 475 oC and lower (the operating temperature of LWRs falls into this range), due to α’ Cr precipitation that results in an increase in the DBTT [2, 3]. This phenomenon is detrimental to the structural performance and also to the corrosion resistance of KD. Therefore, it is important to deeply study and understand α’ Cr precipitation in high Cr ferritic alloys. There exists no systematic study that looks into the influence of grain size on α’ Cr precipitation during isothermal aging. This study will be the first to systematically study the precipitation of nanoscale α’ Cr (5-10 nm) as a function of grain size [coarse-grained (CG, grain diameter >1 μm; ultrafine grained (UFG, 100 nm < grain diameter < 1 μm); nanocrystalline (NC, grain diameter < 100 nm)] during isothermal aging at or below 475 oC. Kanthal-D was manufactured and samples using two forms of severe plastic deformation (SPD), equal channel angular pressing (ECAP) and high-pressure torsion (HPT), respectively. had a non-homogenous microstructure with multi-modal grain size distribution revealed using electron-back scatter diffraction. Average

(Ti54Ni34Cu12)90Nb10 alloy with initial two-phase structure of B19 martensite and β-Nb phase was subjected to high-pressure torsion (HPT) process at room temperature. HPT leads to the formation of nanocrystalline bands of β-Nb phase alternating with amorphous matrix. Nanocrystalline debris of B2 phase was found to be embedded into the amorphous matrix. Refinement of β-Nb phase upon HPT is much greater compared to that for pure Nb alloy.

Grain refinement and precipitation hardening play critical important role for stabilization and improving functional properties of shape memory alloys. However, the relationship between precipitation and nanocrystalline grain growth behavior in NiTiHf alloys is still unclear. This work aims to investigate the role of precipitation in the nanocrystalline grain growth behavior of HPT-processed Ni50Ti30Hf20 high-temperature shape memory alloy. An abnormally low grain growth rate (n = 0.08) was observed after post-deformation annealing (PDA) at 550 °C for 1 h. It was proposed that grain growth suppression may be caused by the presence of relatively large H-phase precipitates, which act as barriers to grain boundary movement. A detailed analysis of the grain growth kinetics during PDA suggests that the coarsening process is controlled by Ni diffusion. Additionally, the dependence of strength and transformation temperatures on grain size in NiTiHf alloy is found to follow the Hall-Petch relation with some exceptions due to H-phase precipitation. The results of this research may be useful for the development of methods and strategies to stabilize the nanocrystalline structure in metallic materials.

Grain refinement and precipitation hardening play critical important role for stabilization and improving functional properties of shape memory alloys. However, the relationship between precipitation and nanocrystalline grain growth behavior in NiTiHf alloys is still unclear. This work aims to investigate the role of precipitation in the nanocrystalline grain growth behavior of HPT-processed Ni50Ti30Hf20 high-temperature shape memory alloy. An abnormally low grain growth rate (n = 0.08) was observed after post-deformation annealing (PDA) at 550 degrees C for 1 h. It was proposed that grain growth suppression may be caused by the presence of relatively large H-phase precipitates, which act as barriers to grain boundary movement. A detailed analysis of the grain growth kinetics during PDA suggests that the coarsening process is controlled by Ni diffusion. Additionally, the dependence of strength and transformation temperatures on grain size in NiTiHf alloy is found to follow the Hall-Petch relation with some exceptions due to H-phase precipitation. The results of this research may be useful for the development of methods and strategies to stabilize the nanocrystalline structure in metallic materials.

Ultrafine-grained (UFG) materials are innovative and quite promising for wide application. The important advantage associated with the use and commercialization of UFG materials includes first of all their advanced properties, also production efficiency is important due to the development of new SPD technique. This chapter discusses the innovative potential and practical applications of UFG materials. Titanium implants made of nanoTi are promising for dentistry and orthopedics. UFG copper alloys can be used for making electrodes for welding. UFG composites based on copper matrix and WС are attractive for manufacturing current carrying cores, electric motors, contact wires. Nanocrystalline alloy Cu–10 at.% Ta is an exciting example illustrating the possibility of increasing thermal stability at elevated temperatures by creating clusters of the alloying element on the grain boundaries, preventing their migration. Another example of successful production of aluminum alloy 6101 wires with improved mechanical properties and high electrical conductivity by SPD processing has been demonstrated. The prospects of using UFG metallic alloys as promising materials for hydrogen storage and transportation have been analyzed. Manifestations of the shape memory effect are of great interest for the use of UFG alloys in medicine, as a material for joining pipes and other practical applications. Nanostructured magnetic materials are promising for the creation of new high-speed electric machines with high strength and less energy dissipation. The small grain size not only provides increased strength but also preserves the homogeneous microstructure and isotropic properties while miniaturizing products.

The main challenge in using magnesium alloys, applied in medicine as biodegradable materials, is their difficult deformability, which in turn leads to frequent failure of samples during severe plastic deformation. This paper shows that the temperature mode of equal channel angular pressing (ECAP) of a Mg–Zn–Ca system magnesium alloy, which ensures deformation of samples without failure, can be determined based on the results of finite-element computer simulation of the stress-strain state of the billet, calculation of alloy damage using the Cockcroft–Latham model, and prediction of the sample failure area. Modelling showed that the surface area of the billet adjacent to the matrix inner corner during ECAP, is the area of possible failure of the magnesium alloy. The value of alloy damage during ECAP in this area at T=350 °C is less than 1, which corresponds to non-failure of the metal. To verify the computer simulation results, ECAP physical simulation was performed; billets without signs of failure were produced. A study of the mechanical properties of the Mg–1%Zn–0.06%Ca magnesium alloy was conducted before and after ECAP processing according to the selected mode: the ultimate strength limit increased by 45 %, the hardness increased by 16 %, while the plasticity increased by 5 %.

An experimental study is presented on the wear and failure of initial coarse-grained and modified ultrafine-grained Ti-6Al-4V alloy with a TiN protective coating, subjected to high-speed dynamic erosion by solid corundum particles with an average size of 109 μm in an air flow at a speed of 150 m/s and an erosion time of 30, 60, 180, 300 and 600 s. The experimental results are used to determine the erosive wear rate and the shear area percentage, as well as to measure the worn layer depth and erosion-induced changes in microhardness and structure of the alloy near the coated and uncoated surface. It is shown that all alloy samples are prone to wear and failure under the given high-speed erosion conditions, but their behavior is closely related to the erosion time and the structure of the substrate. The protective coating deposited onto the surface of ultrafine-grained Ti-6Al-4V titanium alloy significantly reduces the erosive wear rate compared to a similar coating on as-received coarse-grained alloy.

Multi-principal element alloys demonstrate high strength, thermal stability, and irradiation resistance, making them excellent candidate materials for applications in nuclear reactors and other harsh environments. Some studies have examined the use of high-pressure torsion to strengthen MPEAs through grain size reduction and strain hardening. However, no studies have investigated the effect of HPT on secondary phases (precipitates) within an MPEA. Two alloys, (Fe0.3Ni0.3Mn0.3Cr0.1)94Ti2Al4 containing Ni(Ti, Al) B2 phase, and CrFe σ phase, and single-phase Fe0.3Ni0.3Mn0.3Cr0.1, were fabricated by casting and heat treatment. Both alloys were then processed with HPT to study microstructural evolution. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the alloys before and after HPT processing. HPT processing produced a nanocrystalline structure in both alloys, but (Fe0.3Ni0.3Mn0.3Cr0.1)94Ti2Al4 exhibited a significantly smaller grain size and higher dislocation density than Fe0.3Ni0.3Mn0.3Cr0.1, with corresponding higher hardness. Before HPT, the (Fe0.3Ni0.3Mn0.3Cr0.1)94Ti2Al4 alloy consisted of large grain ( 400 μm) and precipitates, including B2 of 38 μm average size, B2 of 0.7 μm average size, and small amounts of σ of 1.5 µm average size. After HPT, the larger B2 precipitates were decreased in size and volume fraction, while the smaller B2 precipitates were completely dissolved; the σ precipitates appeared unaffected by HPT, likely due to their much higher hardness. Observation of the B2 precipitate distribution along radial distance indicates that the strain caused the precipitates to fracture at intermediate strain (γ = 125) and dissolve at high strain (γ = 280).

The paper reports on finite element simulation of extrusion of a complex-shaped billet from the ultrafine-grained Ti-6Al-4V alloy and vacuum-arc deposition of a protective coating based on the TiVZrCrAl high-entropy alloy. Temperature fields formed in the billet during extrusion are studied. Deformation heating and the necessary forming force are determined for the initial temperature-rate conditions. The strain rate distribution in the billet during extrusion is also analyzed. According to the obtained data, the chosen temperature-rate conditions allow using the ultrafine-grained titanium alloy as the initial billet without deteriorating its mechanical characteristics. Computer simulation of the coating deposition on the complex-shaped billet provides values of the temperature, chemical composition, and thickness of the high-entropy coating. Thus, the coating thickness varies within 6.5–7.5 μm, and the surface is heated during deposition to 368–597°C, which allows maintaining the ultrafine-grained structure in the alloy.

Ultrafine-grained (UFG) materials are a new class of metals and alloys characterized by a microstructure with grain sizes less than 1 μm and nanostructural features that provide advanced multifunctional properties. This chapter considers the underlying principles for the formation of UFG materials using severe plastic deformation (SPD) and outlines the conditions for achieving the UFG structures with predominantly high angle grain boundaries, including low temperatures, high degrees of straining, high applied pressures, turbulent, non-monotonic nature of the material flow, achieving higher dislocation density and smaller grain size by using alloys with an ordered structure and materials with low stacking fault energy. The most popular techniques of SPD processing are analyzed, such as high-pressure torsion (HPT) and equal-channel angular pressing (ECAP). The schemes and mechanisms of grain refinement and formation of UFG structures are considered. At the same time, special attention is paid to the analysis of the evolution of microstructures and phase transformation during SPD processing following the results of computer simulation and numerous modern experimental methods of research. Grain boundaries, nanotwins, nanoscale particles, and segregations of alloying elements in nanostructured materials obtained by SPD techniques are described and used for developing a concept of nanostructural design for increasing material properties.

UFG metals and alloys attract the materials science community owing to their superior mechanical properties. This chapter considers achieving enhanced mechanical properties in the UFG materials processed by SPD techniques. Special emphasis is laid on the examples and origins of the phenomenon of superstrength as well as the description of the hardening mechanisms in the materials. The chapter views the manifestation of the SPD paradox caused by the formation of equiaxial UFG structure and control of grain boundary type and segregations. The SPD paradox is evident in the simultaneous growth of strength and ductility. Mechanisms for enhancing the ductility of UFG materials are considered. The chapter also focuses on the importance of grain refinement in increasing fatigue strength and endurance, creep resistance of materials, the manifestation of the superplasticity effect at lower temperatures, and higher strain rates and its use in superplastic forming of complex shape parts. Advanced mechanical properties of UFG materials provide excellent opportunities for manufacturing new promising products for practical applications.