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Recent advancements in additive manufacturing (AM) fuel efforts for expanding the design envelopes for components obtained via this technology through continuous improvement in mechanical behavior. Damping properties can also be altered depending on the microstructure evolved during AM. Therefore, achieving enhanced monotonic mechanical response with better damping properties is highly sought-after. In this respect, thermo-mechanical processing via severe plastic deformation (SPD) and artificial aging is imparted on the additive-manufactured samples with the target of grain refinement and densification to further improve mechanical and damping properties. Employing microstructural characterizations and mechanical experiments, a multi-scale exploration is carried out to develop a relation between the evolved microstructure and the resulting behavior. It is concluded that introducing a refined microstructure decorated with well-distributed (Mg,Si)-rich phase and favorable dislocation substructure in AlSi10Mg positively affects the resulting mechanical behavior. Moreover, it is shown that artificial aging can be employed to improve the damping characteristics of severely deformed additive-manufactured AlSi10Mg alloy. [ABSTRACT FROM AUTHOR]

High strength-ductility synergy is difficult to achieve in Nb alloys. Although high strength has been achieved through severe plastic deformation (SPD) technology, led to low ductility in alloys. In this work, FSP technology was applied to treat Nb–5W–2Mo–1Zr-0.1C (Nb521) alloys in preparation of fine-grained (FG)/ultrafine-grained (UFG) Nb521 with excellent strength and ductility. The microstructure evolution and mechanical property improvement mechanism were systematically studied for Nb521 alloy through various characterization pathways. The research results indicated that UFG Nb521 alloy with a grain size of 0.63 ± 0.41 μm can be prepared using low shoulder plunge depth FSP (LPD-FSP), which is the first report of UFG Nb521 alloy. The main reason for the formation of onion rings structure in SZ is the periodic wear of the stirring tool, and the onion rings structure does not cause mechanical damage. The texture formed by Nb521 alloy under different processing parameters is off-axis shear texture, which matches the ideal shear texture of D2 (112‾)[111] after rotation. In addition, this study also elaborated on the refinement mechanism of the second phase particles (Nb, Zr) C in Nb521 alloy during FSP. This study also indicated that the increase in yield strength of FSP samples at room temperature is mainly determined by grain refinement. These findings provided new ideas for the development of high-performance niobium alloys.

Light metals and alloys based on magnesium, aluminum, and titanium are of significance in daily life and industrial applications due to their low density and superior mechanical and functional properties. The formation of nanostructures and ultrafine grains can further improve the properties of these materials. High-pressure torsion (HPT), as a severe plastic deformation (SPD) method, is one of the most effective processes for nanostructuring these materials. Various modifications of HPT such as conventional HPT with discs, HPT with rings, and continuous HPT with strips and wires are currently applied to light metals and their alloys, composites, intermetallics, and metallic glasses. The HPT processing of these materials is effective for grain refinement, hardening through the Hall-Petch mechanism, lattice defect generation, phase transformations, and solid-state reactions through fast diffusion with reasonable time/thermal stability. This article after discussing these fundamental issues, reviews some mechanical and functional properties of nanostructured lightweight materials such as tensile, compression, and bending properties, superplasticity including room-temperature superplasticity, wear resistance, electrical conductivity, superconductivity, biocompatibility, hydrogen production, and hydrogen storage. [ABSTRACT FROM AUTHOR]

Among the procedures developed for structure grain refinement, equal channel angular extrusion techniques experience a great popularity, owing to its proficiency to produce significant grain refinement in fully dense bulk-scale materials. It is essential to compromise between the design of die and processing parameters to estimate a homogeneous deformation, optimize the strain distribution, and load requirement. In this regard, numerical modelling has been done to comprehend the impact of temperature and friction on the newly developed plastic deformation technique known as "nonequal channel multi-angular extrusion" (NECMAE), which experienced a cross-sectional area reduction on the subsequent channel. Three friction coefficients were examined combined with heat generation analysis to evaluate the plastic strain homogeneity. The preliminary results obtained show that 30% reduction case with µ=0.1 has the most uniform strain distribution across the workpiece and improves strain homogeneity significantly by 6 times greater than the frictionless case. In general, the optimum strain distribution could be achieved by using the right combination of area reduction and frictional conditions. The analysis implies that plastic strain, temperature, and required load are significantly affected by localized plastic deformation zone and the incrementation of heat generated. Current study opens the opportunity to satisfy the workpiece hardening level due to different localizations of plastic deformation of the proposed die design.

Microstructural evolution and changes in hardness and electrical conductivities of a cast hypoeutectic Cu-2.7 at%Zr alloy processed by high-pressure torsion (HPT) were investigated. The cast alloy had a net-like microstructure composed of a primary Cu phase and a eutectic consisting of layered Cu and Cu5Zr phases. The Cu and Cu5Zr phases in the eutectic had a cube-on-cube orientation relationship. The cast alloy with the hardness of 137HV exhibited a value of electrical conductivity of 32%IACS. With increasing the number of HPT-revolutions, the eutectic was severely sheared and elongated along the rotational direction. In addition, mechanical dissolution of the Cu5Zr phase into the Cu phase by the HPT was confirmed after 5 HPT-revolutions through XRD measurements and TEM observations. After 20 HPT-revolutions, the Cu phase was significantly refined and formed the lamellar structure having an average grain size of 15 nm. The electrical conductivity decreased and saturated at a value of 8%IACS after 50 HPT-revolutions. The significant decrease in the electrical conductivity was primarily attributable to the mechanical dissolution of the Cu5Zr phase into the Cu phase by the HPT, followed by the formation of a nanocrystalline Cu-Zr supersaturated solid-solution alloy with the hardness of 430HV. [ABSTRACT FROM AUTHOR]

Several copper alloys with the addition of Zn and Sn are taken for the study. In order to determine the effect of severe plastic deformation (SPD) on microstructure formation, these alloys are subjected to severe plastic deformation on a Gleeble-3800 thermomechanical simulator. The study uses a special case of 3D forging—2D forging, using a MaxStrain multi-axis deformation module. Two modes are developed for processing: 10 deformation cycles (20 impacts) at room temperature with a total degree of deformation greater than 7; 20 deformation cycles (40 impacts) at room temperature with a total degree of deformation greater than 17. The results of the analysis of the microstructure of copper alloys after physical modeling are presented in the study. [ABSTRACT FROM AUTHOR]

Six cycles of ARB at three elevated temperatures (400, 450, and 500 °C) were applied on Al/Mg laminated metallic composites. Samples were studied by microscopy, spectroscopy, and x-ray diffraction to investigate the effect of temperature on microstructures, second phases, and preferred crystallographic orientations. Stoichiometry analysis indicated the formation of non-equilibrium intermetallic phases at the Al/Mg interface. The thickness of the intermetallic layer increased in consecutive passes and by increasing process temperature. Annealing moved the composition toward predicted thermodynamically stable phases by absorbing Al and rejecting excess Mg. EDS examination showed the formation of Al2Mg and Al30Mg23 phases in addition to the previously reported Al12Mg17 and Al3Mg2. XRD results indicated that the preferred crystallographic orientation of the Al layer deviates from the expected plain-strain rolling texture. At the same time, for the Mg layer, the hexagonal c-axis remained parallel to the applied rolling force direction. The most uniform crack-free structure has been formed at 450 °C. [ABSTRACT FROM AUTHOR]

Aluminium (Al) alloys are known for their high strength and good ductility, making them materials of choice in many aerospace and transport industries. However, they tend to yield to failure in practice as a result of localized corrosion including stress corrosion cracking, exfoliation corrosion, intergranular corrosion, and pitting corrosion. The formation of gradient-structured layers through several severe plastic deformation methods and heat treatments/coatings are the leading possible means of addressing their present shortcomings. The present work reviews the practical ways by which the aforementioned localized corrosion in Al alloys can be reduced to the minimum if not totally eradicated. The corrosion properties of severely plastic-deformed Al alloys obtained via different routes including ultrasonic shot peening, equal-channel angular processing, constrained groove pressing, among others, were extensively reviewed and summarized. The corrosion mechanisms as well as the factors responsible for the improvement or deterioration in corrosion resistance of Al alloys after surface modification were discussed, and the prospects and research trends for future developments are summarized. [ABSTRACT FROM AUTHOR]

Pure titanium is limited to be used in biomedical applications due to its lower mechanical strength compared to its alloy counterpart. To enhance its properties and improve medical implants feasibility, advancements in titanium processing technologies are necessary. One such technique is equal-channel angular pressing (ECAP) for its severe plastic deformation (SPD). This study aims to surface modify commercially pure titanium using micro-arc oxidation (MAO) or plasma electrolytic oxidation (PEO) technologies, and mineral solutions containing Ca and P. The composition, metallography, and shape of the changed surface were characterized using X-ray diffraction (XRD), digital optical microscopy (OM), and scanning electron microscope (SEM), respectively. A microhardness test is conducted to assess each sample's mechanical strength. The weight % of Ca and P in the coating was determined using energy dispersive spectroscopy (EDS), and the corrosion resistance was evaluated through potentiodynamic measurement. The behavior of human dental pulp cell and periodontal cell behavior was also studied through a biomedical experiment over a period of 1-, 3-, and 7-days using culture medium, and the cell death and viability can be inferred with the help of enzyme-linked immunosorbent assay (ELISA) since it can detect proteins or biomarkers secreted by cells undergoing apoptosis or necrosis. This study shows that the mechanical grain refinement method and surface modification might improve the mechanical and biomechanical properties of commercially pure (CP) titanium. According to the results of the corrosion loss measurements, 2PassMAO had the lowest corrosion rate, which is determined to be 0.495 mmpy. The electrode potentials for the 1-pass and 2-pass coated samples are 1.44 V and 1.47 V, respectively. This suggests that the coating is highly effective in reducing the corrosion rate of the metallic CP Ti sample. Changes in the grain size and the presence of a high number of grain boundaries have a significant impact on the corrosion resistance of CP Ti. For ECAPED and surface-modified titanium samples in a 3.6% NaCl electrolyte solution, electrochemical impedance spectroscopy (EIS) properties are similar to Nyquist and Bode plot fitting. In light of ISO 10993-5 guidelines for assessing in vitro cytotoxicity, this study contributes valuable insights into pulp and periodontal cell behavior, focusing specifically on material cytotoxicity, a critical factor determined by a 30% decrease in cell viability. [ABSTRACT FROM AUTHOR]

Ultra-fine grained and even nanostructured magnesium alloys obtained by processing with methods of severe plastic deformation (SPD) are promising biomaterials for absorbable orthopaedic implants due to their enhanced mechanical properties, adequate corrosion resistance and biocompatibility. This paper presents an overview of the impact of the most important SPD methods equal-channel angular pressing (ECAP) and high-pressure torsion (HPT) on microstructure refinement and improvement of the mechanical properties of magnesium alloys intended for medical implants. Several selected groups of magnesium alloys which have the potential for use as bioabsorbable implants are discussed. The presented results of many years of research indicate the beneficial effect of SPD methods on obtaining ultra-fine and even nanostructures of magnesium alloys with improved mechanical and better functional properties, which are necessary for bioabsorbable implants. [ABSTRACT FROM AUTHOR]

This overview article discusses the Equal Channel Angular Pressing (ECAP) processing of different metallic materials. Particular emphasis is given to the microstructural evolution from the coarse grain (CG) to the ultrafine-grained (UFG) states throughout the electron backscattering diffraction (EBSD) technique. Iron-based alloys, such as duplex and 1020 low-carbon steels reached higher hardening with a lower deformation and lower non-ultrafine average grain sizes than the ultrafine pure iron condition due to fast grain fragmentation, i.e., more geometrically necessary dislocation (GND) grouping. Moreover, due to the magnesium adhesion, copper alloys reached superior mechanical properties compared to pure copper even when the initial grain size for as-cast alloys was over 1000 µm. On the other hand, low melting temperature (TMP) materials processed at 250°C, like the ZK60 magnesium and AA6082 aluminum alloys (i.e., homologous temperatures (TH) of 0.38TMP and 0.37TMP, respectively), showed grain refinement without reaching the ultrafine regime and mechanical softening due to the static and dynamic recrystallization phenomena. CP titanium also displayed heterogeneous grain sizes with average values of above 1 µm after four ECAP passes for temperatures ranging between 150°C and 400°C (TH between 0.09TMP = 0.24TMP). The evolution of the GNDs suggested that the initial deformation stages of severe plastic deformation (SPD) by ECAP produced the most notorious density increments from 1012m-2 to 1014m-2, which level up at high deformations (more than four ECAP passes) around 10141015m-2, explaining the fast and slow grain size reduction rates, respectively. The ECAP processing on different metallic material systems showed a larger grain fragmentation capacity in high melting points and alloyed materials, giving rise to steep yield strength increases and low ductility. The low ductility and grain size saturation correspond to a low capacity to create new grain boundaries manifested by the GNDs saturation in the UFG range. [ABSTRACT FROM AUTHOR]

In the last years, nanostructured metals prepared by severe plastic deformation (SPD) techniques have emerged as a promising class of advanced biomaterials for load-bearing applications such as orthopedic implants. This is mainly because of the simultaneous improvements in mechanical and biocompatibility properties during the creation of nanostructures. This article provides a brief overview of the effects of SPD techniques in producing nano/ultrafine-grained structures in advanced biomaterials for implant applications. The role of microstructure refinement achieved by SPD and its effect on mechanical properties and biocompatibility, together with processing challenges are reviewed. As advanced biomaterials, pure titanium, and Ti-based alloys which possess a broad range of applications in the biomedical industry are initially discussed. Further, the recent results on high-entropy alloys and metal-protein composites obtained by means of SPD for biomedical purposes are reviewed. The results discussed here clearly demonstrate the beneficial effects of SPD techniques in designing and producing nanostructured advanced biomaterials with exceptional mechanical and functional properties desired for implants. [ABSTRACT FROM AUTHOR]

This paper presents an overview of the recent development of incremental feeding high-pressure sliding (IF-HPS) process for grain refinement of metallic sheets with enlarged areas. The IF-HPS process is a method of severe plastic deformation (SPD) under high pressure without increasing the machine capacity. The IF-HPS process combines an incremental feeding technique with the high-pressure sliding (HPS) process so that a severely deformed area can be extended. Development of the IF-HPS process includes the use of flat-type anvils instead of groove-type anvils, which makes it easier to enlarge the SPD-processed areas. The development is also described in terms of the sliding mode and the feeding pattem, where the former is determined by the sliding distance and the numbers of the reciprocation of the sliding and the latter by the feeding distance and the feeding direction. The application of the IF-HPS process is made to metallic materials such as a Ni-based superalloy (Inconel 718), a Ti-6Al-7Nb alloy (F1295) and commercially available Al alloys (A1050, A3105, A5052 and A5182). It is shown that the grain refinement is successfully achieved so that superplastic elongation more than 400% is attained in the Ni- and Ti-based alloys, and the room-temperature tensile strength is well enhanced in the Al alloys. It is then demonstrated that the IF-HPS process is promising to extend the SPD-processed area without increasing the machine capacity. Furthermore, a new approach is suggested for material design, such as the hybrid materials composed of conventional and fine-grained materials and functionally graded materials. [ABSTRACT FROM AUTHOR]

Severe plastic deformation drives bulk materials far away from equilibrium and thus opens up a new opportunity to explore hitherto uncharted regions of structure-property correlations with respect to grain size, strain and defect density under extreme conditions. This allows addressing long-standing issues in materials research, such as the validity of "effective temperature" concept and provides a set-screw for exploring the possible levels of defect design and property tuning by deformation processing. As a pre-requisite, basic issues concerning the interaction of defects of different dimensionality during deformation and their interrelation with fluxes of solutes or with segregation fields, resulting in chemo-mechanical coupling effects need to be analyzed quantitatively. In the following review, we address issues related to internal interfaces in severely deformed metals and alloys by highlighting recent observations. [ABSTRACT FROM AUTHOR]

Due to their unique properties, titanium (Ti) and Ti-alloys are particularly suitable for biomedical devices. Ti has a high specific strength and low Young's modulus (reducing stress shielding), high corrosion resistance, and superior biocompatibility. However, Ti's moderately low Young's modulus (100-110GPa) is still considerably higher than to bones (5-30GPa). The)8-Ti phase, whose elastic modulus is closer to the bone, can be kept by increasing the contents of non-toxic ß stabilizing elements. Besides stress shielding and corrosion resistance, adjusted bioactivity (bone-bonding ability) is another primary prerequisite for implants that can be improved by ultrafine-grained (UFG) microstructures and surface modification (anodization and acid+alkaline treatment). UFG by HPT also enhances wear resistance and mechanical properties. Representative alloys (Ti-6Al-7Nb (TAN), Ti-13-Nb-13Zr (TNZ), and Ti-35Nb-7Zr-5Ta (TNZT)) and cp-Ti, were presented in this overview. Samples started with different phases and morphologies. Deformation by HPT induced phase transformation in the alloys, which depended on the amounts of a or ß stabilizers, the strain rate, applied loads, and starting phases and a morphologies. Grain sizes were reduced to about 120 nm. Mechanical properties depended mainly on the number of grain boundaries and their nature and different phases, sizes, and strengths. Young's modulus diminished when the ß was increased. Polished surfaces and cp-Ti presented similar corrosion resistance, improved by surface treatments, which reached maximum protection in anodized samples processed by HPT. After bioactivity tests, different growth rates for various processing conditions and alloys were observed, the highest for the TNZ alloy, and improved after HPT processing. [ABSTRACT FROM AUTHOR]

In this paper, the impact of the number of passes of equal channel angular pressing (ECAP) on mechanical properties and corrosion behavior of Al5085 alloys in an HNO3 solution is investigated. After a single pass of ECAP, the ultimate tensile strength (UTS) was increased noticeably from 275 MPa to 342 MPa. Also, the yield strength (YS) and microhardness were improved from 82 MPa to 118.5 MPa and 94 HV to 136 HV, respectively. After the second pass all UTS, YS, and microhardness increased by 13.5%, 17.8%, and 11.7% compared to the first pass. Meanwhile, the elongation to failure was reduced by 15% and 7.5% after one and two passes of the ECAP, respectively. According to scanning electron microscope (SEM) micrographs, unlike the unprocessed sample in which there is no evidence of pitting corrosion occurrence, after one pass ECAP, the pitting corrosion occurred through all the surfaces of the sample. Also, there is no evidence of pitting corrosion after two passes of ECAP. [ABSTRACT FROM AUTHOR]

The presence of dislocations significantly modifies the mechanical properties of crystalline solids. Severe plastic deformation (SPD) and the most used SPD process – the Equal Channel Angular Pressing (ECAP), affect the multiplication and localized accumulation of dislocations. This research is related to the observation of dislocation pile-up and significant reduction of the crystalline grain size caused by severe deformations in the ECAP process of the widely used aluminium material (Al 99.5%). Because of its lightweight, the application of Al 99.5 % can pose a challenge for the aviation and space industry, especially since its mechanical properties limit its application. Improving these mechanical properties can extend its applicability in cases of demanding constructions as well as influence the final product cost. As a confirmation of SPD in-fluence on mechanical properties, material hardness has been examined and described. Dislocation monitoring is enabled using the light and electron microscopy and AFM (Atomic Force Microscope) device. A numerical simulation of the Equal Channel Angular Pressing process using the ABAQUS software package determined the representative area of the most severe deformation. [ABSTRACT FROM AUTHOR]

The presence of dislocations significantly modifies the mechanical properties of crystalline solids. Severe plastic deformation (SPD) and the most used SPD process – the Equal Channel Angular Pressing (ECAP), affect the multiplication and localized accumulation of dislocations. This research is related to the observation of dislocation pile-up and significant reduction of the crystalline grain size caused by severe deformations in the ECAP process of the widely used aluminium material (Al 99.5%). Because of its lightweight, the application of Al 99.5 % can pose a challenge for the aviation and space industry, especially since its mechanical properties limit its application. Improving these mechanical properties can extend its applicability in cases of demanding constructions as well as influence the final product cost. As a confirmation of SPD in-fluence on mechanical properties, material hardness has been examined and described. Dislocation monitoring is enabled using the light and electron microscopy and AFM (Atomic Force Microscope) device. A numerical simulation of the Equal Channel Angular Pressing process using the ABAQUS software package determined the representative area of the most severe deformation.

Strengthening by grain refinement via the Hall–Petch mechanism and softening by nanograin formation via the inverse Hall–Petch mechanism have been the subject of argument for decades, particularly for ultrafine-grained materials. In this study, the Hall–Petch relationship is examined for ultrafine-grained magnesium, aluminum, copper, and iron produced by severe plastic deformation in the literature. Magnesium, aluminum, copper, and their alloys follow the Hall–Petch relationship with a low slope, but an up-break appears when the grain sizes are reduced below 500–1000 nm. This extra strengthening, which is mainly due to the enhanced contribution of dislocations, is followed by a down-break for grain sizes smaller than 70–150 nm due to the diminution of the dislocation contribution and an enhancement of thermally-activated phenomena. For pure iron with a lower dislocation mobility, the Hall–Petch breaks are not evident, but the strength at the nanometer grain size range is lower than the expected Hall–Petch trend in the submicrometer range. The strength of nanograined iron can be increased to the expected trend by stabilizing grain boundaries via impurity atoms. Detailed analyses of the data confirm that grain refinement to the nanometer level is not necessarily a solution to achieve extra strengthening, but other strategies such as microstructural stabilization by segregation or precipitation are required. [ABSTRACT FROM AUTHOR]

Recently, researchers have shown interest in developing integrated severe plastic deformation (SPD) processes to produce ultra-fine grained (UFG) metal in a single pass. This article proposes a new integrated severe plastic technique named Multi-angular twist channel extrusion (MATE). The method was devised to impose a large strain in a single pass with better strain homogeneity and lower punch load. The effects of MATE die geometries on the effective strain, strain inhomogeneity, and punch load were analyzed by performing finite element analysis (FEA) to understand the mechanism of the process. The developed artificial neural network (ANN) model was used to optimize the die geometries by genetic algorithm (GA) to attain the desired output characteristics. The twist slope angle (β) = 43°, channel angle (Ø) = 108°, and outer corner angle (ψ) = 50° were determined as the optimum die geometries. With the optimized MATE die, an average effective strain of 2.703 was achieved with good strain homogeneity. Based on the simulation results MATE die was fabricated with the optimum die geometries and experiments were conducted using pure copper. The experimental studies reveal that the ultimate tensile strength and hardness of pure copper was increased by 65.6% and 102%, respectively. The electron back scatter diffraction (EBSD) analysis reveals that the average grain size was 3.1 µm in the extruded copper. The simulated and experimental results corroborate the EBSD findings. [ABSTRACT FROM AUTHOR]

Severe plastic deformation (SPD) is effective in producing bulk ultrafine-grained and nanostructured materials with large densities of lattice defects. This field, also known as NanoSPD, experienced a significant progress within the past two decades. Beside classic SPD methods such as high-pressure torsion, equal-channel angular pressing, accumulative roll-bonding, twist extrusion, and multi-directional forging, various continuous techniques were introduced to produce upscaled samples. Moreover, numerous alloys, glasses, semiconductors, ceramics, polymers, and their composites were processed. The SPD methods were used to synthesize new materials or to stabilize metastable phases with advanced mechanical and functional properties. High strength combined with high ductility, low/room-temperature superplasticity, creep resistance, hydrogen storage, photocatalytic hydrogen production, photocatalytic CO2 conversion, superconductivity, thermoelectric performance, radiation resistance, corrosion resistance, and biocompatibility are some highlighted properties of SPD-processed materials. This article reviews recent advances in the NanoSPD field and provides a brief history regarding its progress from the ancient times to modernity. Abbreviations: ARB: Accumulative Roll-Bonding; BCC: Body-Centered Cubic; DAC: Diamond Anvil Cell; EBSD: Electron Backscatter Diffraction; ECAP: Equal-Channel Angular Pressing (Extrusion); FCC: Face-Centered Cubic; FEM: Finite Element Method; FSP: Friction Stir Processing; HCP: Hexagonal Close-Packed; HPT: High-Pressure Torsion; HPTT: High-Pressure Tube Twisting; MDF: Multi-Directional (-Axial) Forging; NanoSPD: Nanomaterials by Severe Plastic Deformation; SDAC: Shear (Rotational) Diamond Anvil Cell; SEM: Scanning Electron Microscopy; SMAT: Surface Mechanical Attrition Treatment; SPD: Severe Plastic Deformation; TE: Twist Extrusion; TEM: Transmission Electron Microscopy; UFG: Ultrafine Grained

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, CO 2 conversion, corrosion resistance and biocompatibility. It is shown that achieving such properties is not limited to pure metals and conventional metallic alloys, and a wide range of materials are currently 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 mechanisms of geological and astronomical phenomena and the origin of life. [ABSTRACT FROM AUTHOR]

The indentation of bearing raceways frequently contributes to bearing failures, as in gearboxes. The dents act as surface stress raisers through the Rolling Contact Fatigue (RCF) cycles, leading to crack initiation and spalling. The microstructural evolution mechanism occurring is not completely understood. Hence, to enhance bearing lifetime, it is crucial to identify microstructural parameters that influence crack initiation and propagation. Therefore, this study presents a multi-scale characterization of martensitic 100Cr6 bearings before and after RCF. It includes SEM, SEM/FIB, EBSD, TKD and ACOM-ASTAR observations. It showed that, before RCF, the bearing raceway features a 0.5 µm thick surface layer consisting in refined martensite and spread primary carbides, resulting from finishing operations. After RCF, no further grain refinement was observed along the raceway, except beneath the dent shoulder where a material plastic flow, nano-grains and ultra-fine grains of martensite, and sheared and spread primary carbides were detected up to 1.4 µm deep. Below and up to 3 µm deep, a fine grain layer is observed. The martensite morphology, size and disorientation suggest that it undergoes refinement through continuous Dynamic Recrystallisation and twinning. Crack initiation was preferentially observed in the nano-grains layer, at primary carbides/matrix interfaces. Above the crack, another refined region is observed resulting from high deformation and stresses through crack propagation. Finally, even in severely deformed areas, nanosized retained austenite islands were detected, indicating that it is not completely transformed. [Display omitted] [ABSTRACT FROM AUTHOR]

This study examines the corrosion resistance of ultrafine-grained Al 0.1 CoCrFeNi high-entropy alloy processed by high-pressure torsion (HPT), focusing on stored energy, diffusion, and the high-entropy effect. Microstructural analysis revealed a single-phase FCC structure with numerous defects and reduced crystallite size following the HPT process. Samples with higher HPT turns formed high - angle grain boundaries, equiaxed nanograins, and numerous nanotwins, contributing to a notable increase in Vickers microhardness from 159 Hv for the initial sample to 550 Hv after 5 turns of HPT. Corrosion behavior is found to be influenced by stored energy and chromium diffusion. Low HPT turns increased the corrosion rate due to sluggish diffusion of chromium and high stored energy in the form of dislocations. Conversely, corrosion resistance improved with increased HPT turns due to fast diffusion through non-equilibrium grain boundaries and the formation of nanotwins with lower stored energy. These findings suggest that a relatively low entropy plays a critical role in the chromium segregation from the solid solution for forming a passive film and enhancing corrosion resistance. • Corrosion resistance of Al 0.1 CoCrFeNi-HEA after HPT was examined. • Hardness increased from 159 to 550 Hv and corrosion resistance improves after 5 turns. • Low stored energy initially reduces corrosion rate due to limited chromium diffusion. • Corrosion resistance increases with the formation of films containing chromium. • Grain boundaries and low high-entropy effect lead to the enrichment of chromium. [ABSTRACT FROM AUTHOR]

A Mg-based composite material has been produced by the consolidation at room temperature of a Mg-5wt.% Ni-2wt.% Nb2O5 powder mixture subjected to high-pressure torsion (HPT), one of the processing methods to induce severe plastic deformations. The microstructure, density, and microhardness of the consolidated disks were characterized after the application of up to 30 revolutions in torsion under compression stresses of 3 and 5 GPa. According to the density measurements, the composite was consolidated in full after the application of five revolutions, although disks subjected to only one revolution exhibited densities close to the maximum measured value. On the other hand, grain size and microhardness measurements showed that differences existed at locations near the center and the periphery of the HPT-processed disks. Under the stress of 5 GPa, the grain size in the central regions stabilized at about 0.35 μm after five revolutions, while at the peripherical regions it gradually decreased with an increasing number of revolutions down to about 0.15 μm after 30 revolutions. In turn, the microhardness measured along a diametral cross section steadily increased with the number of revolutions between 1 and 10 revolutions, maintaining a gradient from the center to the periphery in all cases. With the application of 20 and 30 revolutions, only the peripheral regions increased considerably in hardness. It was discovered that the magnesium particles in the initial powder mixture had formed an oxide—hydroxide surface layer, which changed the expected final density of the consolidated material by about 2 to 4.5%. This superficial contamination of the Mg powders did not prevent the material from achieving full consolidation. [ABSTRACT FROM AUTHOR]

Pure titanium is limited to be used in biomedical applications due to its lower mechanical strength compared to its alloy counterpart. To enhance its properties and improve medical implants feasibility, advancements in titanium processing technologies are necessary. One such technique is equal-channel angular pressing (ECAP) for its severe plastic deformation (SPD). This study aims to surface modify commercially pure titanium using micro-arc oxidation (MAO) or plasma electrolytic oxidation (PEO) technologies, and mineral solutions containing Ca and P. The composition, metallography, and shape of the changed surface were characterized using X-ray diffraction (XRD), digital optical microscopy (OM), and scanning electron microscope (SEM), respectively. A microhardness test is conducted to assess each sample’s mechanical strength. The weight % of Ca and P in the coating was determined using energy dispersive spectroscopy (EDS), and the corrosion resistance was evaluated through potentiodynamic measurement. The behavior of human dental pulp cell and periodontal cell behavior was also studied through a biomedical experiment over a period of 1-, 3-, and 7-days using culture medium, and the cell death and viability can be inferred with the help of enzyme-linked immunosorbent assay (ELISA) since it can detect proteins or biomarkers secreted by cells undergoing apoptosis or necrosis. This study shows that the mechanical grain refinement method and surface modification might improve the mechanical and biomechanical properties of commercially pure (CP) titanium. According to the results of the corrosion loss measurements, 2PassMAO had the lowest corrosion rate, which is determined to be 0.495 mmpy. The electrode potentials for the 1-pass and 2-pass coated samples are 1.44 V and 1.47 V, respectively. This suggests that the coating is highly effective in reducing the corrosion rate of the metallic CP Ti sample. Changes in the grain size and the presence of a high number of grain boundaries have a significant impact on the corrosion resistance of CP Ti. For ECAPED and surface-modified titanium samples in a 3.6% NaCl electrolyte solution, electrochemical impedance spectroscopy (EIS) properties are similar to Nyquist and Bode plot fitting. In light of ISO 10993-5 guidelines for assessing in vitro cytotoxicity, this study contributes valuable insights into pulp and periodontal cell behavior, focusing specifically on material cytotoxicity, a critical factor determined by a 30% decrease in cell viability.

This paper presents a study on the perspectives of structure refinement of aluminum and its alloys by reciprocating extrusion (cyclic extrusion compression—CEC). The study included Al99.5 and Al99.992 aluminum and AlMg5 and AlCu4Zr alloy. Aluminum and alloys were deformed by reciprocating extrusion (CEC) in the strain range ϕ = 0.42 (1 CEC cycle) to ϕ = 59.8 (67 CEC cycles). After deformation, the structure of the specimens was investigated by optical microscopy (OM) and transmission electron microscopy (TEM), which revealed that the primary mechanism of hardening, over the range of applied strains, was the result of the propagation of shear bands throughout the specimens. The intersection of shear bands was found to divide the volume of the specimens into nano and microvolumes with dimensions limited by the width of the microbands. Due to structure renewal processes such as polygonization and dynamic geometric recrystallization, the formed micro and nano volumes were transformed into nano and micrograins with large misorientation angles. In terms of the occurrence of grain microstructure, a sustained uniform level of hardening was found, which was defined as steady-state flow. The research has shown that the steady state of flow is a result of the competitive interaction between the processes of hardening and structure renewal. The higher the metal purity, the higher the intensity of the structure renewal processes was. The formation of new grains and their growth under dynamic and post-dynamic recrystallization was observed in Al99.992 aluminum, in which high purity of the metal and high strain accumulation caused the growth of new grains at room temperature. [ABSTRACT FROM AUTHOR]

The production of metal matrix composites (MMCs) through recycled materials is a cost-saving process. However, the improvement of the mechanical and physical properties is another challenge to be concerned. In this study, recycled aluminium 6061 (AA6061) chips reinforced with different volumetric fractions of boron carbide (B4C) were produced through hot equal channel angular processing (ECAP). Response surface methodology (RSM) was carried out to investigate the dependent response (compressive strength) with independent parameters such as different volumetric fractions (5-15%) of added contents of B4C and preheating temperature (450 – 550°C). Also, the number of passes were examined to check the effect on the mechanical and physical properties of the developed recycled AA6061/B4C composite. The results show that maximum compressive strength and hardness of recycled AA6061/B4C were 59.2 MPa and 69 HV respectively at 5% of B4C contents. Likewise, the density and number of pores increased, which were confirmed through scanning electron microscope (SEM) and atomic force microscopes (AFM) analysis. However, the number of passes enhanced the mechanical and physical properties of the recycled AA6061/B4C composite. Therefore, the maximum compressive strength and hardness achieved were 158 MPa and 74.95 HV for the 4th pass. Moreover, the physical properties of recycled AA6061/B4C composite become denser of 2.62 g/cm3 at the 1st pass and 2.67 g/cm3 for the 4th pass. Thus, it can be concluded that the B4C volumetric fraction and number of passes have a significant effect on recycled AA6061 chips.

Photoreforming is a sustainable photocatalytic process that degrades plastic waste while simultaneously producing hydrogen (H 2) from water. However, this process has received limited attention due to the scarcity of effective catalysts capable of both plastic degradation and H 2 production, such as titanium dioxide (TiO 2). In this study, an active catalyst is developed by stabilizing the high-pressure orthorhombic phase of TiO 2 , known as columbite, using a high-pressure torsion (HPT) method. This material effectively degrades polyethylene terephthalate (PET) plastic under light, converting it into valuable organic compounds such as formic acid, terephthalate, glycolic acid, and acetic acid. Additionally, it produces a significant amount of H 2. The findings show that the high-pressure orthorhombic phase, especially in the presence of oxygen vacancies, enhances catalytic H 2 production and microplastic degradation by increasing light absorption, reducing electron-hole recombination, and generating hydroxyl radicals. These results highlight the substantial potential of modified high-pressure TiO 2 photocatalysts in simultaneously addressing the plastic waste crisis and the demand for H 2 fuel. • The high-pressure orthorhombic TiO2 phase rich in oxygen vacancies is stabilized. • The phase is used for the photoreforming of polyethylene terephthalate (PET) plastic. • PET is converted into formic acid, terephthalate, glycolic acid and acetic acid. • Significant hydrogen and hydroxyl amounts are also produced during photoreforming. • The activity of the vacancy-rich high-pressure phase is higher than anatase. [ABSTRACT FROM AUTHOR]

Cyclic extrusion compression (CEC) is an effective fabrication process for producing fine, ultrafine grains with superior physical and mechanical properties.In the present work, CEC process was applied on Al alloy 6061 and its silicon carbide (SiCp) composite containing 5 and 10 wt. % SiCp. . The specimens were pressed at room temperature up to 6 cycles for Al alloy 6061, 5 cycles for Al 6061 5 wt. % and 4 cycles for Al 6061 10 wt. % SiC corresponding to plastic strains of 3.72, 3.1 and 2.48 respectively. The evolution of microstructure, hardness and dry sliding wear tests were conducted. The samples were investigated before and after the CEC process by optical microscope, and the worn surfaces were investigated by Scanning Electron Microscope (SEM) and (EDX) analysis. The CEC cycles reduced the grain size, porosity % and SiC particle size. These microstructural parameters were reflected on the increase in hardness and reduction in wear rate and a slight reduction in coefficient of friction. In general, this improvement in properties is associated with the following parameters; grain refining, reinforcement volume fraction, size and distribution of SiCp as well as the number of CEC cycles. Regarding the composite samples, a significant improvement in wear resistance was obtained and the Al 6061 10 wt. % SiC, showed the best performance. The wear mechanism was also affected by the CEC process.

In this study, a preparation route of Co–Cu alloys with soft magnetic properties by high-pressure torsion deformation is introduced. Nanocrystalline, supersaturated single-phase microstructures are obtained after deformation of Co–Cu alloys, which are prepared from an initial powder mixture with Co-contents above 70 wt.%. Isochronal annealing treatments up to 400 °C further reveal a remarkable microstructural stability. Only at 600 °C, the supersaturated phase decomposes into two fcc-phases. The coercivity, measured by SQUID as a function of annealing temperature, remains significantly below the value for bulk-Co in all states investigated. In order to understand the measured magnetic properties in detail, a quantitative analysis of the magnetic microstructure is carried out by magnetic force microscopy and correlated to the observed changes in coercivity. Our results show that the rising coercivity can be explained by a magnetic hardening effect occurring in context with spinodal decomposition.

Severe plastic deformation (SPD) is effective in producing bulk ultrafine-grained and nanostructured materials with large densities of lattice defects. This field, also known as NanoSPD, experienced a significant progress within the past two decades. Beside classic SPD methods such as high-pressure torsion, equal-channel angular pressing, accumulative roll-bonding, twist extrusion, and multi-directional forging, various continuous techniques were introduced to produce upscaled samples. Moreover, numerous alloys, glasses, semiconductors, ceramics, polymers, and their composites were processed. The SPD methods were used to synthesize new materials or to stabilize metastable phases with advanced mechanical and functional properties. High strength combined with high ductility, low/room-temperature superplasticity, creep resistance, hydrogen storage, photocatalytic hydrogen production, photocatalytic CO2 conversion, superconductivity, thermoelectric performance, radiation resistance, corrosion resistance, and biocompatibility are some highlighted properties of SPD-processed materials. This article reviews recent advances in the NanoSPD field and provides a brief history regarding its progress from the ancient times to modernity. Abbreviations: ARB: Accumulative Roll-Bonding; BCC: Body-Centered Cubic; DAC: Diamond Anvil Cell; EBSD: Electron Backscatter Diffraction; ECAP: Equal-Channel Angular Pressing (Extrusion); FCC: Face-Centered Cubic; FEM: Finite Element Method; FSP: Friction Stir Processing; HCP: Hexagonal Close-Packed; HPT: High-Pressure Torsion; HPTT: High-Pressure Tube Twisting; MDF: Multi-Directional (-Axial) Forging; NanoSPD: Nanomaterials by Severe Plastic Deformation; SDAC: Shear (Rotational) Diamond Anvil Cell; SEM: Scanning Electron Microscopy; SMAT: Surface Mechanical Attrition Treatment; SPD: Severe Plastic Deformation; TE: Twist Extrusion; TEM: Transmission Electron Microscopy; UFG: Ultrafine Grained This article comprehensively reviews recent advances on development of ultrafine-grained and nanostructured materials by severe plastic deformation and provides a brief history regarding the progress of this field. [ABSTRACT FROM AUTHOR]

In this study, evolution of intermetallic layer of the cold roll bonded bilayer of Aluminum-Steel sheets, during severe plastic deformation (SPD) followed by annealing has been investigated. The effect of such evolution on mechanical properties has been discussed. For this purpose, Constrained Groove Pressing (CGP) was used as a SPD process. Field emission scanning electron microscope equipped with energy dispersive spectroscopy and optical microscopy were used for examination of intermetallic compounds morphology and composition. Meanwhile, tensile properties of the bilayer sheets were evaluated. According to microstructural observations, continuous intermetallic layer was formed during rolling and annealing processes. This intermetallic layer was completely cracked into very fine particles after the first pass of CGP. Some of these intermetallic compounds were pushed into the base layers by the shear stress and some of them remained at the interface. Moreover, it was observed that during the CGP process, at the interface and between remaining intermetallic compounds and fresh surfaces of both Al and steel, new bonds were formed. After formation of such new bonds and during the second step of the CGP process, flattening process, mechanical interlocks were created. However, after the second CGP pass, no intermetallic compound was observed at the interface yet delamination was seen. Due to formation of intermetallic compounds at the bonding area and the vicinity of it, reinforced area, mechanical interlocks and higher dislocation density in that region, the ultimate tensile strength (UTS) increased after the first pass of CGP, but due to delamination, it decreased in second pass. The effect of evolution of bond structure on the tensile strength was measured by using bonding portion (BP) criterion defined as the difference in the UTS of the bonded versus non-bonded samples undergone similar deformation and annealing treatment. The BP values show similar trend to the UTS data, increased at the first pass and decreased at the second pass. In the following study, the CGPed samples have been annealed in order to recover the intermetallic layer. The CGPed samples were annealed at 350 °C, 400 °C and 450 °C for 30, 60 and 90 min. The optimum thickness of 2.6 μm was observed at the 450 °C in 30 min annealing treatment. The UTS, BP and elongation to break increased 7%, 32% and 60%, respectively, in comparison to those of the as-CGPed sample.

Strengthening by grain refinement via the Hall–Petch mechanism and softening by nanograin formation via the inverse Hall–Petch mechanism have been the subject of argument for decades, particularly for ultrafine-grained materials. In this study, the Hall–Petch relationship is examined for ultrafine-grained magnesium, aluminum, copper, and iron produced by severe plastic deformation in the literature. Magnesium, aluminum, copper, and their alloys follow the Hall–Petch relationship with a low slope, but an up-break appears when the grain sizes are reduced below 500–1000 nm. This extra strengthening, which is mainly due to the enhanced contribution of dislocations, is followed by a down-break for grain sizes smaller than 70–150 nm due to the diminution of the dislocation contribution and an enhancement of thermally-activated phenomena. For pure iron with a lower dislocation mobility, the Hall–Petch breaks are not evident, but the strength at the nanometer grain size range is lower than the expected Hall–Petch trend in the submicrometer range. The strength of nanograined iron can be increased to the expected trend by stabilizing grain boundaries via impurity atoms. Detailed analyses of the data confirm that grain refinement to the nanometer level is not necessarily a solution to achieve extra strengthening, but other strategies such as microstructural stabilization by segregation or precipitation are required.

A Mg-based composite material has been produced by the consolidation at room temperature of a Mg-5wt.% Ni-2wt.% Nb2O5 powder mixture subjected to high-pressure torsion (HPT), one of the processing methods to induce severe plastic deformations. The microstructure, density, and microhardness of the consolidated disks were characterized after the application of up to 30 revolutions in torsion under compression stresses of 3 and 5 GPa. According to the density measurements, the composite was consolidated in full after the application of five revolutions, although disks subjected to only one revolution exhibited densities close to the maximum measured value. On the other hand, grain size and microhardness measurements showed that differences existed at locations near the center and the periphery of the HPT-processed disks. Under the stress of 5 GPa, the grain size in the central regions stabilized at about 0.35 μm after five revolutions, while at the peripherical regions it gradually decreased with an increasing number of revolutions down to about 0.15 μm after 30 revolutions. In turn, the microhardness measured along a diametral cross section steadily increased with the number of revolutions between 1 and 10 revolutions, maintaining a gradient from the center to the periphery in all cases. With the application of 20 and 30 revolutions, only the peripheral regions increased considerably in hardness. It was discovered that the magnesium particles in the initial powder mixture had formed an oxide—hydroxide surface layer, which changed the expected final density of the consolidated material by about 2 to 4.5%. This superficial contamination of the Mg powders did not prevent the material from achieving full consolidation.

The production of metal matrix composites (MMCs) through recycled materials is a cost-saving process. However, the improvement of the mechanical and physical properties is another challenge to be concerned. In this study, recycled aluminium 6061 (AA6061) chips reinforced with different volumetric fractions of boron carbide (B4C) were produced through hot equal channel angular processing (ECAP). Response surface methodology (RSM) was carried out to investigate the dependent response (compressive strength) with independent parameters such as different volumetric fractions (5-15%) of added contents of B4C and preheating temperature (450 – 550°C). Also, the number of passes were examined to check the effect on the mechanical and physical properties of the developed recycled AA6061/B4C composite. The results show that maximum compressive strength and hardness of recycled AA6061/B4C were 59.2 MPa and 69 HV respectively at 5% of B4C contents. Likewise, the density and number of pores increased, which were confirmed through scanning electron microscope (SEM) and atomic force microscopes (AFM) analysis. However, the number of passes enhanced the mechanical and physical properties of the recycled AA6061/B4C composite. Therefore, the maximum compressive strength and hardness achieved were 158 MPa and 74.95 HV for the 4th pass. Moreover, the physical properties of recycled AA6061/B4C composite become denser of 2.62 g/cm3 at the 1st pass and 2.67 g/cm3 for the 4th pass. Thus, it can be concluded that the B4C volumetric fraction and number of passes have a significant effect on recycled AA6061 chips. [ABSTRACT FROM AUTHOR]

Electrocatalysis using renewable energy sources provides a clean technology to produce hydrogen from water. Titanium oxide is considered as a potential electrocatalyst not only for hydrogen production but also for CO2 conversion. In this study, to enhance the cathodic electrocatalytic activity of TiO2, the phase composition on TiO2 surface is modified by inclusion of high-pressure TiO2-II phase using high-pressure torsion (HPT) straining. Detailed spectroscopic studies revealed that the energy band gap is reduced and the valence band energy increased with increasing the TiO2-II fraction. The highest electrocatalytic activity for hydrogen production was achieved on an anatase-rich nanocomposite containing TiO2-II nanograins.

High-pressure torsion (HPT) is widely used as a severe plastic deformation technique to create ultrafine-grained structures with promising mechanical and functional properties. Since 2007, the method has been employed to enhance the hydrogenation kinetics in different Mg-based hydrogen storage materials. Recent studies showed that the method is effective not only for increasing the hydrogenation kinetics but also for improving the hydrogenation activity, for enhancing the air resistivity and more importantly for synthesizing new nanostructured hydrogen storage materials with high densities of lattice defects. This manuscript reviews some major findings on the impact of HPT process on the hydrogen storage performance of different titanium-based and magnesium-based materials.

Severe plastic deformation (SPD) techniques are prospective ones having ability for desirable high mechanical properties to be achieved without any chemical change in metals. Equal-channel angular pressing (ECAP), one of SPD techniques, was used to obtain ultra-high mechanical compressive response of stainless steel pyramidal lattice core. For this purpose, the stainless steel 304 L samples were processed by ECAP at 500 °C. Then, it was sliced into struts and built lattice core after bending processes. At the compression tests, the ECAP lattice core has huge mechanical properties, at nearly two times collapse load and energy absorption values. [ABSTRACT FROM AUTHOR]

Tensile deformation behavior of high-strength nanostructured CuSi solid-solution alloys processed by high-pressure torsion (HPT) with 5 rotations was investigated at room and low temperatures. With increasing Si concentration, tensile strength of the nanostructured CuSi solid-solution alloys was significantly increased. The maximal tensile strengths were 980 MPa at room temperature, and 1350MPa at 77K in a Cu2.04 wt.%Si alloy. This significant strengthening was achieved by grain refinement and increased dislocation density through severe plastic deformation (SPD) with the effect of Si addition on the decreasing stacking fault energy of the CuSi alloy. With increasing Si concentration, strain-rate sensitivity m of the nanostructured CuSi solid-solution alloys was decreased due to the increased dislocation density, resulting in accelerating plastic instability of tensile specimens, caused by the diminishing strain-rate hardening capacity after necking. [ABSTRACT FROM AUTHOR]