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This paper introduced a novel single-pass severe plastic deformation method, W-shaped channel extrusion (WCE), for the direct manufacturing of magnesium alloy shells. Based on a strategically installed mandrel and die with a sloping asymmetric step structure, the WCE constructed a narrow severe plastic deformation gap specially reinforced by a backpressure-shear structure and an asymmetric shear-extrusion section. Therefore, slender bar with large height-to-diameter ratio (i.e. small diameter, large height) could easily be extruded into larger diameter shell in narrow gap through only one pass, and an impressive average plastic strain of over 4.1 was concurrently achieved, evidenced by upper bound theory calculation. The WCE process was further experimentally conducted on AZ80 alloy at 340 °C, demonstrating remarkable improvements in yield strength, ultimate tensile strength, and elongation of the extruded part by factors of 2.4, 2.2, and 4.3 over the as-cast condition. The consecutive multi-stage shear and high hydrostatic pressure catalyzed extreme grain refinement, favored high matrix dislocations and concurrently facilitated the early dynamic conception of granular β-Mg17Al12 particles in subgrains stage, all of which served the superior performance. Moreover, no prominent anisotropy detected in the extruded part due to the development of a special bimodal basal texture under shear stress, where its synergistic effect with grain refinement evidently promoted the balance of strength and plasticity. Finally, the mechanism of bimodal texture formation associated with specific slip activations during WCE and anisotropic weakening was revealed in detail.

Abstract In recent years, extensive studies have been conducted on severe plastic deformation based on suitable processes for sheets and solid materials. Considering the limitations in some properties and crucial applications of titanium metal, these methods are considered intriguing avenues for enhancing the efficiency of this practical metal. Therefore, efforts have been made to investigate and develop effective severe plastic deformation processes for producing titanium samples. Severe plastic deformation is widely recognized as the primary method for producing ultrafine and nanostructured materials with high strength and hardness. This study focuses on exploring the most recent methods in this family suitable for producing nanostructured titanium samples with ultrafine grains. Furthermore, the study assesses the impact of several key severe plastic deformation methods on titanium properties, comparing them based on the advantages and disadvantages of these methods from both processing and property perspectives. Findings: In this regard, in recent years, severe plastic deformation methods have been introduced and extensively studied. In this research, by examining and reviewing the latest studies related to the advantages and disadvantages of three methods: simple shear extrusion, accumulative roll bonding, and equal channel angular pressing, the following results have been obtained : All past research indicates that these three methods have a significant and positive impact on the mechanical properties of titanium metal. These positive effects show an increasing acceleration up to a certain number of passes and then reach a saturation point. Temperature, speed, and appropriate processing are three fundamental and important factors concerning severe plastic deformation of titanium metal. Some studies suggest that pure titanium metal can also be processed at room temperature using methods of severe plastic deformation. The frequency of using these methods in relation to titanium metal and its alloys includes methods such as ECAP, accumulative roll bonding, and simple shear extrusion, respectively. A noticeable weakness in most studies conducted on processed titanium using severe plastic deformation methods is the lack of investigation into the biocompatibility properties of titanium concurrently with its mechanical properties after the process. 6. It can be almost stated that in none of the studies conducted on severe plastic deformation methods, a specific industrial output has been introduced, and it remains at the level of research work.

Magnesium alloys are of considerable current interest for use as degradable implants due to their unique properties including biodegradability, biocompatibility, low density and adequate mechanical properties. Nevertheless, there is a need to further improve these properties either by alloying or through the use of appropriate processing. Among the different biodegradable Mg alloys now in use, the Mg‒Zn series are of special interest and have been the subject of many research investigations. This is primarily because Zn is an essential element for the human body in addition to its positive effects in improving the mechanical strength and lowering the degradation rate of the implant. The properties of Mg‒Zn alloys may be further improved both through the addition of third and fourth alloying elements such as Ca, Ag, Sn or Sr and/or by thermo-mechanical processing where the latter is more environmentally and economically favorable. In practice, procedures based on the application of severe plastic deformation (SPD) are especially suited to produce fine-grained microstructures with improved mechanical, degradation and cell behavior. Equal-channel angular pressing (ECAP) is a popular SPD technique that has the capability of producing bulk materials that are sufficiently large for use as typical implants. Accordingly, this review is designed to provide a comprehensive summary of the research that has been undertaken on ECAP-processed biodegradable Mg‒Zn alloys.

The use of low-carbon unalloyed steel with minimal silicon content is widespread in structural steel and automotive applications due to its ease of manipulation. The mechanical properties of this steel can be significantly enhanced through severe plastic deformation (SPD) techniques. Our study focuses on the practical benefits of the dual rolling equal channel extrusion (DRECE) method, which strengthens the steel and has implications for material hardness and the thickness of subsequently applied hot-dip zinc galvanizing. Furthermore, the steel’s corrosion potential and current are investigated as a function of material hardness and thickness. The findings show a 20% increase in hardness HV 30 after the first run through the forming machine, with an additional 10% increase after the second run. Subsequent galvanizing leads to a further 1–12% increase in HV 30 value. Notably, the DRECE hardening demonstrates no statistically significant effect on the corrosion potential and current; however, the impact of galvanizing is as anticipated.

The strain-induced martensitic transformation (α′-martensite) and residual stress (RS) introduction in the gradient nanostructured (GNS) austenitic stainless steel have been extensively reported in the last three decades, however, their correlation is still unclear. Here, the XRD, EBSD, ECCI and TEM were used to study the RS distribution and martensite behaviors in a GNS SS304 fabricated by ultrasonic surface nanocrystallization modification. We found the non-linear relationship between the magnitude of RS and the fraction of α′-martensite due to the role of α′-martensite in the development of type II intergranular RS. The maximum compressive RS of about 1,244 MPa was obtained as the γ-austenite and α′-martensite phases were each at approximately 50 %. Otherwise, the RS would decrease with the second phase fraction. The developed maximum compressive RS arises from the α′-martensite that formed directly from the γ-austenite. By contrast, the RS from other deformation structures, i.e., α′-martensite produced by γ → ε → α′, ε-martensite, nanotwin and dislocations, is relatively low. The current study classified the correlation of RS and the role of martensite for the first time, which may inspire new approaches for improving the fatigue properties of materials by controlling the phase fraction.

This study describes the evolution of the microstructure and mechanical properties of bimetallic aluminum-copper rods during straining by Equal channel angular pressing-drawing (ECAP-drawing). The study was conducted by means of a transmission electron microscope, EBSD analysis, tensile tests and determination of microhardness. The paper shows that an ultrafine-grained copper-aluminum composite with a gradient structure is formed during straining by ECAP-drawing. Microhardness of copper shell during 4 cycles of straining by ECAP-drawing increased from 57 to 165, and hardness of aluminum rod increased from 25 to 75 HV. This is associated with grain refinement and hardening of their boundaries by increasing the density of dislocations. Tensile test diagrams analysis has shown that straining leads to an increase in strength properties of bimetallic wire by 2 times, and as a result the plastic properties are also reduced by almost 2 times, but remain at a level applicable for further use. Application of such bimetallic rods in construction will allow reducing specific quantity of metal per structures without reduction of strength properties.

The paper studies the evolution of microstructure and mechanical properties of copper wire during a new combined straining process. The main point of the technological process is to strain the wire in a rotating equal-channel step die and subsequent drawing. The die rotates around the wire axis and thereby creates tension due to equal-channel angular pulling and twisting in the die. Transmission electron microscopy and EBSD analysis, as well as tensile testing and microhardness determination investigated the strained copper wire. Ultra-fine grain gradient microstructure with a high component of high-angle grain boundaries was obtained as a result of straining. The tensile strength of the strained copper wire compared to the unstrained one increases more than twice from 302 to 635 MPa, and the yield strength increases from 196 to 406 MPa. The use of such hardened copper wire in construction will reduce the weight of the structure due to the reduction of diameter.

The evolution of the microstructure and mechanical properties of a vacuum arc melted non-equiatomic Al0.4Co0.5V0.2FeNi high-entropy alloy (HEA) subjected to severe plastic deformation was investigated experimentally and by simulations. The present work explored duplex HEAs, comprising a face-centered cubic (FCC) matrix and a body-centered cubic (BCC) phase, towards outstanding their mechanical responses. The Al0.4Co0.5V0.2FeNi alloys had a duplex structure, i.e., with dispersed B2-phase islands (with sizes of dozens of microns) in several hundred micron-, even millimeter-sized FCC grains. The mechanical properties of this HEA were strongly deformation dependent, i.e., when deformation increased from 30 % up to 60 %, the yield strength and ultimate strength tensile increased from ∼0.9 GPa and 1.0 GPa to ∼1.2 GPa and 1.3 GPa, respectively. During tensile deformation, initial fractures occurred in the FCC phase located close to the interface between the FCC and BCC phases. With an increase of deformation, the fracture degree in the FCC phase got larger, and fractures also appeared in the BCC phase. Combined with the geometric dislocation density calculation results from an electron backscatter diffraction (EBSD) analysis, it can be seen that the dislocation density near the phase interface of FCC was higher, making it more likely to produce defects.

Significant deformation of the metal structure can be achieved without breaking or cracking the metal. There are several methods for deformation of metal plastics. The most important of these methods are angular channel pressing process, high-pressure torsion, multidirectional forging process, extrusion-cyclic compression process, cumulative climbing connection process, consecutive concreting and smoothing method, high-pressure pipe torsion. The nanocomposite is a multiphase material which the size of one of its phases is less than 100 nm in at least one dimension. Due to some unique properties, metal-based nanocomposites are widely used in engineering applications such as the automotive and aerospace industries. Polymer-based nanocomposites are two-phase systems with polymer-based and reinforcing phases (usually ceramic). These materials have a simpler synthesis process than metal-based nanocomposites and are used in a variety of applications such as the aerospace industry, gas pipelines, and sensors. Severe plastic deformation (SPD) is known to be the best method for producing bulk ultrafine grained and nanostructured materials with excellent properties. Different Severe plastic deformation methods were developed that are suitable for sheet and bulk solid materials. During the past decade, efforts have been made to create effective Severe plastic deformation processes suitable for producing cylindrical tubes. In this paper, we review Severe plastic deformation processes intended to nanostructured tubes, and their effects on material properties and severe plastic deformation is briefly introduced and its common methods for bulk materials, sheets, and pipes, as well as metal background nanocomposites, are concisely introduced and their microstructural and mechanical properties are discussed. The paper will focus on introduction of the tube Severe plastic deformation processes, and then comparison of them based on their advantages and disadvantages from the viewpoints of processing and properties.

Recent observations indicate that very high deformation temperatures (673 K corresponding to 0.7 of Mg's melting point) by high pressure torsion (HPT) are mandatory to successfully synthesize bulk Mg-Fe nanocomposites with homogenous microstructure and exceptionally high strength (2.2 GPa Hardness). This spurs the development of new fabrication strategies to further strengthen the material while maintaining microstructural homogeneity for lower processing temperatures (T

The evolution of the stress-strain state and the relative density distribution throughout a porous workpiece in the two-stage hot forging process was studied. The primary stage involved hot deformation of a cylindrical preform with the application of force to its lateral surface to form an intermediate semi-finished product with a cross-section shaped as a truncated cone. Further deformation in the secondary stage involved hot forging of the conical workpiece into a prism. These process stages were simulated using the finite-element method with the DEFORM 2D/3D software package. The starting preform was a cylinder with uniformly distributed porosity throughout the volume. The simulation results revealed significant uneven strains εi across the workpiece following the primary process stage, leading to an area with increased strains εi concentrated near the upper punch. Conversely, the secondary process stage noticeably evened out the strain values across the forged workpiece. This occurred because the severe deformation area in the secondary process stage matched the stagnant area in the primary stage. The proposed two-stage deformation pattern achieved sufficiently high strains (1.3–1.7), allowing the production of forged materials with excellent mechanical properties. [ABSTRACT FROM AUTHOR]

Using transmission electron microscopy, the features of the grain and defect structure of the V–4Ti–4Cr alloy after 16 acts of biaxial and triaxial pressing at room temperature are studied. The microstructure of the alloy after these treatments is a structural composite with the elements of fine-crystalline and submicrocrystalline states. The defect structure is characterized by a crystal lattice curvature from 10 to 30°/μm. It is established that biaxial pressing contributes to a more intensive grinding of the crystallites and a formation of an anisotropic microstructure. The dislocation-disclination mechanism and localization in the direction of maximum shear stresses are thought to be the main mechanisms of structural transformation under conditions of high-strength state, formed as a consequence of dispersion strengthening by the second phase particles. The role of local internal stresses and their gradients in the processes of crystal lattice fragmentation under conditions of severe plastic deformations is discussed. [ABSTRACT FROM AUTHOR]

In this study, the effect of bonding surface conditions on the strength evolution of Cu/Cu joints during ultrasonic welding was investigated. Lap shear tests and microstructure characterisation revealed that contact area formation could be affected by bonding surface conditions and clamping force. That is, the fraction of contact area quickly evolved with smoother bonding surfaces, leading to a rapid strength increase to base metal fracture (1100 N of lap shear load after 1.0 s of welding). Comparatively, rough surface combinations exhibited a slow strength evolution owing to a lower fraction of contact areas. To overcome this situation, a higher clamping force was employed to facilitate contact area formation (1100 N of lap shear load after 0.5 s of welding). [ABSTRACT FROM AUTHOR]

An approach that allows a qualitative and quantitative analysis of the grain structure of ultrafine grained nickel by electrochemical etching surface is proposed. The data on the etching relief of ultra-fine-grained nickel obtained by scanning tunneling microscopy are analyzed. The bimodality of the structure is revealed, which is confirmed by statistical analysis. [ABSTRACT FROM AUTHOR]

Magnesium-based alloys hold potential for medical applications, but face challenges like rapid bioresorption and limited mechanical strength during early bone healing. In our study, we present a novel Mg–Zn–Zr–Ce alloy with low cerium content (up to 0.1 wt.% Ce) processed using two severe plastic deformation (SPD) techniques. Through an innovative combination of multiaxial forging and multipass rolling, we have achieved a fine-grained structure with an average grain size of the primary α-Mg phase of 1.0 μm. This refined microstructure exhibits improved mechanical properties, including a substantial increase in yield strength (σYS) from 130 to 240 MPa, while preserving ductility. The alloy's composition includes α-Mg grains, cerium and zinc hydrides, and intermetallic phases with cerium and zinc elements. Tensile testing of the fine-grained alloy demonstrates an enhancement in yield strength (σYS) to 250 MPa, marking a 2.8-fold improvement over the conventional state (σYS = 90 MPa), with a modest 2-fold reduction in ductility. Crucially, electrochemical tests conducted in physiological solutions highlight substantial advancements in corrosion resistance. The corrosion current was reduced from 14 to 2 μA/cm2, while polarization resistance decreased from 3.1 to 8.1 kΩ∙cm2, underlining the alloy's enhanced resistance to biodegradation. Our results show that the novel Mg–Zn–Zr–Ce alloy, after combined SPD, demonstrates mitigated bioresorption and enhanced mechanical properties. Our findings highlight the fact that the introduction of this innovative alloy and the application of SPD represent significant steps towards addressing the limitations of magnesium-based alloys for medical implants, offering potential improvements in safety and effectiveness. [ABSTRACT FROM AUTHOR]

The effect of quasi-continuous (QC) equal-channel angular pressing (ECAP) in various pre-aged states on the structure formation and mechanical and functional properties of a hyper-equiatomic titanium nickelide (TiNi) shape memory alloy is studied. QC ECAP with a channel intersection angle of 110° is carried out at a temperature of 450 °C after aging for 1 and 5 h for three passes. To investigate the obtained structure and properties, the following research methods are applied: transmission electron microscopy, XRD analysis, calorimetric study, tension and hardness tests, and a special technique for the determination of functional properties. QC ECAP allows for the considerable refinement of structural elements and results in obtaining a mixed fine-grade structure, with structural elements of average sizes of 92 nm after pre-aging for 1 h and 115 nm after pre-aging for 5 h. Pre-aging for 5 h before QC ECAP, in combination with QC ECAP and post-deformation aging at 430 °C for 1 h, provides the best combination of mechanical and functional properties: a dislocation yield stress of 1410 MPa, ultimate tensile strength of 1562 MPa, and total recoverable strain of 11.6%. These values are comparable with the best results obtained for titanium nickelide and expand opportunities for the application of smart shape memory devices. [ABSTRACT FROM AUTHOR]

Modern materials often have multicomponent alloys, whose properties are determined by their phase and structural composition formed as a result of previous thermomechanical processing. Therefore, the problem of managing the structural state occupies an important place in the overall strategy of developing new materials. Particular attention is drawn to phase transformations in ultrafine systems, in particular, in alloys subjected to severe plastic deformation. In this case, the sample size becomes an important parameter determining the physical properties of the substance and, in particular, its structural and phase compositions. Despite the considerable interest of researchers, until recently, it was not possible to achieve significant theoretical results in this area. Therefore, the development of modern models for describing structural transformations in heterogeneous systems and their application to ultrafine-grained materials seem promising and relevant. [ABSTRACT FROM AUTHOR]

To satisfy the requirements for the precise formation of large-scale high-performance lightweight components with inner ring reinforcement, a new multidirectional loading rotary extrusion forming technology is developed to match the linear motion with the rotary motion and actively increases the strong shear force. Its principle is that the radial force and rotating torque increase when the blank is axially extruded and loaded. Through the synergistic action of axial, radial, and rotating motions, the orderly flow of metal is controlled, and the cumulative severe plastic deformation (SPD) of an "uplift-trowel" micro-area is generated. Consequently, materials are uniformly strengthened and toughened. Simultaneously, through the continuous deformation of a punch "ellipse-circle," a high reinforcement component is grown on the cylinder wall to achieve the high-quality formation of cylindrical parts or the inner-ring-reinforcement components. Additionally, the effective strain increases with rotation speed, and the maximum intensity on the basal plane decreases as the number of revolutions increase. The punch structure also affects the axial extrusion loading and equivalent plastic strain. Thus, the proposed technology enriches the plastic forming theory and widens the application field of plastic forming. Furthermore, the formed large-scale high-performance inner-ring-stiffened magnesium components have been successfully verified in aerospace equipment, thereby solving the problems of integral forming and severe deformation strengthening and toughening. The developed technology has good prospects for mass production and application. [ABSTRACT FROM AUTHOR]

Accurate temperature measurement is critical to understanding the thermomechanical conditions and microstructural evolution that materials experience during severe plastic deformation (SPD). Others have previously measured the interface between a non-deforming tool and metal workpiece using thermocouples, infrared measurement, and the thermoelectric principle. Measuring temperature within the deforming material itself, especially at a high-shear deforming interface, has proven to be extremely difficult, thus limiting the application of these measurements to fundamental SPD research. In this study, the thermoelectric principle is used to directly measure temperature at the interface between copper and nickel billets undergoing SPD. This is done by utilizing the deforming materials themselves as two halves of a thermocouple junction. The spatial resolution of this measurement is shown via microscopy to be less than 1 micron. Temperature changes are sensed almost instantly, with time delays on the order of the data logger frequency (0.01 seconds). Process variations that are both very brief (<0.05 seconds) and minute (<3°C) are able to be detected by this method. [ABSTRACT FROM AUTHOR]

This paper discusses the formation of ultrafine-grained (UFG) structure and nanosized second-phase precipitates in commercially pure Grade 4 titanium subjected to severe plastic deformation by high pressure torsion at room temperature with subsequent heat treatment. It was found that the combined processing of Grade 4 titanium provides very high tensile strength (σB ≈ 1500 MPa), which significantly exceeds the previous results for this material. Analysis of the strengthening mechanisms showed that the superstrength of commercially pure titanium is due to several factors: UFG structure formation, dispersion strengthening from second-phase nanoparticles, high dislocation density, and grain boundary segregation. The contribution of these strengthening mechanisms is evaluated and compared with experimental data. [ABSTRACT FROM AUTHOR]

The influence of the semi-die angle (α = 45°, 30° and 22.5°employed in the present experiments) of the cyclic expansion extrusion (CEE) process on grain refinement in Al-alloy AA 6063 processed at 100°C at a pressing velocity of 0.5 mm.s− 1 and subjected to different number of passes is examined. The strain imparted on the specimen strongly depends on the die geometry. Grain refinement as well as increase in the ultimate tensile strength and micro-hardness after 10 CEE passes is the highest when the semi-die angle (α) is 22.5°. TEM images reveal the formation of fine grains after 10 CEE passes. Dislocation generation and cell formation directly depend on the strain imparted and the interactions between the dislocations and the Mg2Si precipitates. The tensile strength and hardness of the CEE processed specimens were compared as a function of the semi-die angle (α) and the results were compared with those of the unprocessed alloy also. [ABSTRACT FROM AUTHOR]

Using lightweight systems and friction reduction approaches are two main contributors towards modern and efficient powertrains in the automotive industry. New materials and processes are required to achieve the demanding and ever-increasing performance requirement of automotive systems. Nanostructure induced by severe plastic deformation methods involves bimodal microstructures and hence, shows exceptional mechanical characteristics which can be exploited for automotive application. Through this study, samples were prepared using pure copper, aluminum alloy (series 7000) and were processed to attain bulk nanostructured samples using a Single Step High Pressure Torsion technique with appropriate dimensions applicable as the rolling elements of automotive bearings. The induced nanostructures resulted micro hardness and frictional characteristics of the bulk samples were assessed using transmission electron (TEM) and atomic force (AFM) microscopies as well as microhardness evaluations. The results revealed that a fully refined nanostructured samples were achieved with 90% increase in the hardness at the outer diameter of the sample. The AFM measurements indicated that the friction coefficient of nanostructured copper and aluminum samples were ~ 25 and ~ 45% less than that of both the unprocessed samples, respectively. Characteristics of treated samples suggest that these processes can be potentially used in demanding conditions of rolling element bearings with reduced weight and frictional losses. [ABSTRACT FROM AUTHOR]

In this study, a severe plastic deformation method of hydrostatic cyclic extrusion compression (HCEC) was used to produce ultrafine-grained copper rods. The process was applied up to two cycles on annealed copper rods and microstructural and mechanical properties of the produced specimens were investigated. The optical and transmission electron microscopy results revealed a notable decrease in the grain size of the sample after the HCEC process. The average grain size of the copper sample after the second cycle of the process reached ~ 292 nm compared to the initial size of ~ 32 μm. Mechanical investigations revealed a considerable increase in the strength and hardness of the samples. The ultimate tensile strength of the copper rods increased to 441.7 MPa after the second pass of the process. Also, the microhardness value increased ∼ 73.4% compared to the initial sample. Generally, HCEC is a notable technique to produce ultrafine-grained copper rods with high lengths and superior characteristics, which can fulfill the requirements of different industries. [ABSTRACT FROM AUTHOR]

Heterostructured materials (HSMs) constitute heterogeneously distributed soft and hard zones with a mismatch in mechanical or physical properties of at least 100% between them. A synergistic effect resulting from the interactive coupling between the heterogeneous zones surpasses the properties predicted by the rule of mixtures. Therefore, the mechanical or physical properties of HSMs are not achievable by their homogeneous counterparts. HSM production commonly requires plastic deformation to refine the microstructure and subsequent partial recrystallization heat-treatments to obtain heterogeneous distributions of grain size, texture, or defect density. Other routes are by applying surface plastic deformation or by stacking layers with a high property mismatch between them. All of those routes can be achieved by severe plastic deformation (SPD) techniques. This overview focuses on describing the fundamentals of HSMs produced by SPD. A critical description of the physics of SPD and HSMs, as well as the factors influencing their microstructural evolution, perspectives, and outstanding issues, are included. A critical comparison of the strength--ductility relationship in HSMs produced by different SPD techniques is also included to guide upcoming research. This overview is intended to serve as a basis for understanding and designing future HSMs produced by SPD. [ABSTRACT FROM AUTHOR]

In the present study, formability of the ultrafine grained (UFG) Cu–Zn tubes were investigated during hydroforming process. The coarse-grained brass tubes were processed by the parallel tubular channel angular pressing (PTCAP) resulting in significant grain refinement. Then, coarse grained and UFG tubes were processed in a square-sectional hydroforming die. The results showed that the UFG tubes due to the lower formability and higher strength had a larger corner radius which was 6.35 mm while it was 1.9 mm for the annealed tube which is in good agreement with the tensile test data. Thickness distribution of the tubes were also examined through FEM simulation, and it was compared with the experimental data. SEM micrography was applied to evaluate fracture surface of the tubes after bursting. [ABSTRACT FROM AUTHOR]

In this work, a new process for severe plastic deformation (SPD) with active friction forces - CCDB Conform R3D2, a variation of the so-called "active bending", which is a continuous two-stage bending in calibers with small relative bending radius, is analyzed. A mechanical scheme of a device for realization of the process with a bending roller is proposed, based on a developed 3D virtual tool for its realization. Using CAD/CAE software 3D simulation, two virtual solutions of the process were compared, differing in terms of the location of the bending roller relative to the axes of the feeding and output rolls. The distribution and magnitude of the effective strains in the volume of the deformed long workpiece in the two bending stages at small relative bending radiuses were analyzed. An analytical expression is developed to determine the effective strains achieved in the SPD operation by constrained continuous bending in calibers with grooved rolls. The strain calculation methodology is based on the results obtained by simulation modelling of the CCB Conform R3D2 process in trapezoidal calibers with a bending roller located above and below the rolls line. [ABSTRACT FROM AUTHOR]

In the present study, the welding of coarse- (CG) and ultrafine-grained (UFG) Al-Mg-Si alloy using friction stir welding (FSW) was attempted. The purpose of welding the UFG material was to check the possibility of applying FSW to materials with a thermally unstable microstructure, which is achieved by severe plastic deformation. This group of materials has significant potential due to the enhanced mechanical properties as a result of the elevated number of structural defects. The CG sample was also examined in order to assess whether there is an influence of the base material microstructure on the weld microstructure and properties. To refine the microstructure, incremental equal channel angular pressing was used. Plastic deformation resulted in grain refinement from 23 µm to 1.5 µm. It caused an increase in the microhardness from 105 HV0.1 to 125 HV0.1 and the tensile strength from 320 MPa to 394 MPa. Similar welds obtained using an FSW method exhibited good quality and grain size in a stir zone of 5 µm. For both welds, a decrease in the microhardness occurred in the stir zone. However, for the weld of UFG Al-Mg-Si, the microhardness distribution was homogeneous, while for the weld of the CG, it was inhomogeneous, which was caused by different characteristics of the second-phase precipitates. The tensile strength of the welds was lowered and equaled 269 MPa and 220 MPa for the CG and UFG welds, respectively. [ABSTRACT FROM AUTHOR]

Using repeated bundle extrusion of a Cu/NbTi composite, we have obtained a high-strength heterophase alloy having superconducting properties. X-ray diffraction characterization has shown that the material we obtained has an unstressed, relaxed structure in the form of self-consistent, locally diffusion-alloyed atomic groups ranging widely in size, which can be divided into three groups: (1) microcrystalline long-range-ordered particles about 450 Å in size, showing up as Debye peaks with sharp tops; (2) mesoscopic clusters with a nanoscale atomic order, responsible for broad diffuse lines; and (3) small low-dimensional atomic groups with short-range order (10–50 Å), responsible for incoherent diffuse X-ray scattering (very broad diffuse halos). [ABSTRACT FROM AUTHOR]

This study investigated the simultaneous effect of adding lithium and severe plastic deformation on Al–Cu–Mg alloy's microstructure, mechanical property, and corrosion resistance. The results showed that under the influence of the dynamic recrystallization executed in the thermo-mechanical process, the initial coarse dendritic structure was replaced by the fine and equiaxed structure. Moreover, adding lithium in amounts less than 0.5 wt% did not have a noticeable effect on the grain size of the extruded alloy. In both series of cast and extruded samples, adding lithium caused a slight change in texture parameters. In the extruded samples, the intensity of the {110} texture was slightly reduced, and the {100} and {111} textures were strengthened compared to the cast sample. Increasing the lithium content in the aluminum intensified the relative amount of lithium in the S-Al2Cu (Li, Mg) precipitate. The formation of fine GPB zones and {100} texture enhancement resulted in high strength and elongation. By increasing lithium up to 0.5 wt% on Al–Cu–Mg alloy, the corrosion potential and current density decreased 67 and 51%, respectively. [ABSTRACT FROM AUTHOR]

Increased industrial production stimulates the development of procurement industries. Technological processes for the production and processing of materials and products are being improved to reduce the material consumption for production, increase economic efficiency, reduce the environmental burden, and increase reliability and durability of machines. The tasks in modern mechanical engineering determine the material and component requirements of machines and mechanisms. New methods for processing known available materials to improve the complex of their properties to use them in new areas, including under conditions of complex loading and undesirable external influence. Our paper discusses a new method for the intensive plastic deformation of metal billets in the form of a hemispherical layer made of high-purity aluminum. Hardening of materials by severe plastic deformation is a widely used method for improving the mechanical characteristics of materials and products, including those not hardened by thermal processing. However, the possibility of this improvement method is limited by the strength of the materials processed. This article presents the results of experimental and theoretical studies on the hardening process of hemispherical billets, including a mathematical model of the process based on the deformation theory of plasticity. [ABSTRACT FROM AUTHOR]

The paper presents the results of computer simulation of a new technology for forming and strengthening screw fittings, carried out using the planned experiment. The purpose of the simulation was to determine the parameters at which the deformation process is stable. The friction coefficient in the rolls, the distance of the matrix from the forming rolls and the initial diameter of the workpiece were selected as variable factors. The workpiece speed was considered as the main parameter and the model was considered unsuccessful if the front end of the workpiece had a zero value of speed (the workpiece was stuck). It was found that all three parameters have a significant impact on the process stability. The best parameters are an increase in the friction coefficient in the rolls and the initial diameter of the workpiece (or absolute compression in the rolls) and a decrease in the distance of the matrix from the forming rolls. Also, a rational factor that has a beneficial effect on the process is the reduction of backpressure from the matrix, which can be realized by reducing its length. [ABSTRACT FROM AUTHOR]

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This research reveals the critical role of basal slip in the substructure development during friction stir processing of a magnesium alloy. In this respect, the intragranular lattice rotation axes are considered to identify the activity of different slip systems. The applied shear strain during the procedure is stored in the matrix through slip‐induced rotations at the grain level. The rotations around distinct Taylor axes produce "slip domains" separated by necessary boundaries from the parent grains, significantly contributing in grain refinement. The basal slip is easily activated in grains holding different stored energy; however, the nonbasal slip has a higher dependency on the amount of local applied strain. Determining the contribution of different slip systems in strain accommodation reveals that the basal slip imposes the highest fraction of low‐angle boundaries into the microstructure leading to the development of the ultimate grain boundary structure. [ABSTRACT FROM AUTHOR]

In a recent experimental work, as a result of severe plastic deformation, a non-equilibrium solid solution was obtained despite the very limited solubility of zirconium (Zr) in aluminum (Al). This opens up a new path in the development of heat-treatable alloys with improved electrical and mechanical properties, where mechanically dissolved elements can form intermetallic particles that contribute to precipitation strengthening. In the present study, molecular dynamics simulations were performed to better understand the process of mechanical dissolution of Zr within an Al model, with Zr atoms segregated along its grain boundaries. Stress–strain curves, radial distribution functions, and mechanisms of plastic deformation and dissolution of Zr in Al were analyzed. It is revealed that orientation of the grain boundary with segregation normal to the shear direction promotes more efficient mixing of alloy components compared to its parallel arrangement. This happens because in the second case, grain boundary sliding is the main deformation mechanism, and Zr tends to remain within the interfaces. In contrast, the involvement of dislocations in the case of normal orientation of grain boundaries with Zr segregation significantly contributes to deformation and facilitates better dissolution of Zr in the Al matrix. The findings obtained can provide new insights considering the role of texture during mechanical alloying of strongly dissimilar metals. [ABSTRACT FROM AUTHOR]

In this study, the effect of severe plastic deformation during friction stir back extrusion of Al-Cu-Mg alloy with different amounts of Li microalloying on microstructure, mechanical properties, and corrosion resistance was investigated. The Cu:Mg ratio in the Al-Cu-Mg alloy was 3.8. The results show that regardless of the amount of lithium microalloying added in the Al-Cu-Mg alloy, a significant change in the size of the dendrites, as well as the amount of secondary phase particles, and the eutectic structure formed in the inter-dendritic space, is not visible. Although with the increase of lithium percentage up to 0.5 wt.%, a slight decrease in grain size is observed in the central area and surface areas of the extruded wires, the difference in the average grain size in the three samples is not large. As the amount of lithium increases, the amount of lithium in the structure of S-Al2CuMg precipitates increases, and finer precipices are formed. By adding 0.5 wt.% of lithium, the evidence shows that the corrosion resistance has increased by 35 %. It is also observed that the corrosion potential decreases by 7 % with the increase of lithium percentage up to 0.5 wt.%. [ABSTRACT FROM AUTHOR]

The strength evolution during the processing/cycling of the metal matrix composite through accumulative roll bonding (ARB) as a severe plastic deformation method is studied by performing a twofold model. It is shown that the strength evolution during cycling consists of two parts: monolithic-like behavior and composite-like behavior. The contribution of each behavior is obtained. The particle effectiveness is at the lowest value at the beginning of the cycling and reaches its highest during the final cycles. It is shown that there is a critical strain at which monolithic-like behavior initiates to decline. The process also shows a minimum strain at which composite-like behavior dominates.

In this study, a new modified tube cyclic expansion extrusion process named M-TCEE was utilized for producing tubes with ultrafine grained (UFG) microstructure and improved properties. In M-TCEE process, the utilization of a moving mandrel inside the hollow tube during the process provides the possibility of using bulk rod-shaped punch, instead of hollow tubular punch which has been used in conventional TCEE process. This leads to that a higher pressing load can be applied to the material without the risk of punch buckling. So, the production of longer and larger tubes, which needs a higher required pressing load, can be performed easier in M-TCEE process. In current study, the capabilities of M-TCEE process in improving microstructure, mechanical properties and corrosion resistance of the Mg–9Al–1Zn-0.2Mn magnesium alloy tubes were investigated. The results showed that after two passes of M-TCEE process, the yield strength increased from 36 MPa to 137 MPa (3.8 time greater), the ultimate tensile strength increased from 73 MPa to 265 MPa (3.6 time greater) and the ductility was enhanced from 11.2% to 20.2% (1.8 time greater). Three passes of M-TCEE led to improving hardness from 54 HV to 99 HV (1.83 time greater). Also, corrosion results revealed the capability of the M-TCEE process in improving the corrosion resistance of AZ91 tubes. It seems that the M-TCEE process can produce ultrafine-grained AZ91 magnesium alloy tubes with significant mechanical properties and improved corrosion resistance.

Two severe plastic deformation (SPD) techniques of simple shear extrusion (SSE) and equal channel angular pressing (ECAP) were employed to process an extruded Mg−6Gd−3Y−1.5Ag (wt%) alloy at 553 K for 1, 2, 4 and 6 passes. The microstructural evolutions were studied by electron back scattered diffraction (EBSD) analysis and transmission electron microscopy (TEM). The initial grain size of 7.5 µm in the extruded alloy was reduced to about 1.3 µm after 6 SPD passes. Discontinuous dynamic recrystallization was suggested to be operative in both SSE and ECAP, with also a potential contribution of continuous dynamic recrystallization at the early stages of deformation. The difference in the shear strain paths of the two SPD techniques caused different progression rate of dynamic recrystallization (DRX), so that the alloys processed by ECAP exhibited higher fractions of recrystallization and high angle grain boundaries (HAGBs). It was revealed that crystallographic texture was also significantly influenced by the difference in the strain paths of the two SPD methods, where dissimilar basal plane texture components were obtained. The compression tests, performed along extrusion direction (ED), indicated that the compressive yield stress (CYS) and ultimate compressive strength (UCS) of the alloys after both SEE and ECAP augmented continuously by increasing the number of passes. ECAP-processed alloys had lower values of CYS and UCS compared to their counterparts processed by SSE. This difference in the mechanical responses was attributed to the different configurations of basal planes with respect to the loading direction (ED) of each SPD technique.

This work dealt with the damping performance and its underlying mechanism in SiC nanoparticles reinforced AZ91D composite (SiCnp/AZ91D) processed by cyclic extrusion and compression (CEC). It was found that the CEC process significantly affects the damping performance of the composite due to alterations in the density of dislocations and grain boundaries in the matrix alloy. Although there would be dynamic precipitation of the Mg17Al12 phase during processing which increases the phase interface and limits the mobility of dislocations and grain boundaries. The results also showed that the damping capacity of 1%SiCnp/AZ91D composite continuously decreases with adding CEC pass number and it consistently increases with rising the applied temperature. Considering the first derivative of the tanδ–T curve, the dominant damping mechanism based on test temperature can be divided into three regions. These three regions are as follows (i) dislocation vibration of the weak pinning points (≤Tcr), (ii) dislocation vibration of the strong pinning points (Tcr∼TV), and (iii) grain boundary/interface sliding (≥TV).

Relevance. Titanium and its alloys are the most durable and corrosion-resistant metal materials that makes them widely used in mechanical engineering, aircraft and machinery, chemical apparatus construction, medicine. The use of such construction materials with increased resistance in aggressive environments makes it possible to increase the efficiency of technologies for processing natural raw materials (high-pressure reactors, centrifuges, separators, high-speed pumps, heat exchangers, communications), the production of chlorine and alkalis (evaporators, electrolysis equipment), organic synthesis (equipment for the production of halogen derivatives), the production of nitric acid, ammonia and nitrogen fertilizers. The combination of mechanical and thermal treatment of alloys, including the use of severe plastic deformation, allows modifying their structure and obtaining materials with improved physical and mechanical characteristics. Purpose: to determine the effect of various modes of the deformation and heat treatment of titanium alloys VT6 and VT22 on their corrosion resistance in aqueous solutions of acids, alkalis and salts. Objects: samples of VT6 and VT22 alloys with different structures, aqueous solutions of acids, alkalis and salts. Methods: DC voltammetry, gravimetry under conditions of free corrosion, optical microscopy, scanning electron microscopy, X-ray diffractometry, atomic emission spectroscopy. Results. Under conditions of severe plastic deformation, samples of titanium alloys VT6 (triaxial pressing in the temperature range from 550 to 800 °C) and VT22 (radial shear rolling in the temperature range from 750 to 850 °C, additional cold rolling of hot-rolled samples, aging at 550 °C for 3...6 hours) with ultrafine-grained structure have been produced. It was found that VT6 alloy with ultrafine-grained structure has less corrosion resistance under conditions of free corrosion in solutions of sulfuric acid of a high concentration (5 M), as well as in 3,5 % NaCl solution at anodic polarization compared to the initial alloy with coarse-grained structure. The main types of corrosion damage to the surface of the ultrafine-grained samples were ulcers and pitting, whereas for samples with a coarse-grained structure, continuous corrosion was characteristic. The increase in the rate of corrosion and morphological features of the destruction of the surface are explained by structural-phase heterogeneity and segregation of alloying elements as a result of the deformation and thermal effects. The corrosion resistance of VT22 samples with an ultrafine-grained structure correlates with the content of the b-phase and with the features of the interphase distribution of alloying elements resulting from the polymorphic transformation of a-TiDb-Ti under conditions of the deformation and heat treatment. It is shown that VT22 samples after hot rolling are the most stable in acid solutions (0,1 M HCl, H2SO4) and the least stable in alkali solution (0,1 M NaOH) compared to samples treated under other regimes. In a 3,5 % NaCl solution, the ultrafine-grained sample VT22 showed the least resistance after additional cold rolling due to a large concentration of structural defects that contribute to increased corrosion cracking of the material. The interpretation of the experimental results was carried out using theoretical calculations of the equilibrium composition of corrosion products formed in the multicomponent systems under study.

Crack nucleation mechanisms, its growth, and the determination of critical failure parameters are of industrial importance. Therefore, it is inevitable to study the mechanical behavior of cracked materials under applied load during severe plastic deformation. The present study studied the mode I fracture behavior, mechanical properties, and microstructure characterization of the 6061 aluminum alloy fabricated by friction stir processing (FSP). For this purpose, a milling machine made a perfect stirring zone to perform the FSP method with the specific non-consumable tool. According to the tensile test results, the yield and ultimate tensile strength of the FSP-processed sample have increased by 39% and 37%, respectively. Based on the three-point bending test, the fracture toughness of the processed aluminum was calculated as 10.86 MPa√m, which shows a 14.3% improvement compared to the as-received annealed state. Eventually, the average grain size of the annealed and processed samples was measured as 35 and 15, respectively, which indicated a 57% reduction in the aluminum grain size after FSP. Note that this grain refinement is associated with improved strength and toughness.

The forming limit of AZ31 alloy, a representative Mg-Al-Zn-based wrought alloy, and the effect of severe plastic deformation (SPD) by examining the microstructure change caused by dynamic recrystallization led by high temperature and high dislocation density at 300℃ using a biaxial alternate forging (BAF) were investigated in this study. As a result of BAF test for AZ31 Mg alloy, significant cracks on the ends of workpieces occurred after 7 passes. The microstructure of as-extruded specimen showed the non-uniform distribution of the relatively coarse grains and the fine grains considered to be sub-grains. However, as the number of passes increases, the area of coarse grains gradually disappeared and the fine grains became more dominant in the microstructures. The result of tensile test for workpieces with each forging pass showed an increase in strength depending on pass number was shown with a slight increase of elongation. The Electron Backscatter Diffraction (EBSD) results exhibited that, the microstructure showed the presence of coarse grains and twins after only 1 pass, while the grains appeared to be significantly refined and uniformly distributed after 3 pass, at which the strength and elongation began to increase, simultaneously.

Linear friction welding (LFW) was performed on face-centered cubic materials, that is, Al alloys (AA1050 and AA5052) with different stacking fault energies (SFEs). The pressure was controlled during the LFW to clarify the effects of temperature, strain, and strain rate on microstructural evolution and dynamic recrystallization (DRX) mechanism. The microstructural evolution during DRX was mainly dependent on the temperature. The grain structures and textural evolution at high temperatures were governed by a continuous DRX, whereas those at low temperatures were primarily controlled by a discontinuous DRX. Various parameters determined the grain structure and textural evolution in different regimes. The evolution of grain structures and texture was dominated by strains and strain rates at temperatures above 0.5Tm (Tm: melting temperature) and by the SFE at temperatures below 0.5Tm. The Zener–Hollomon parameters of the Al alloy joints were investigated. It was found that the slope in AA5052 is larger than that in AA1050 during LFW. At a lower Z value, the grain diameter of the AA5052 joints was larger than that of the AA1050 joints, presumably because of the lower strain rate. Contrastingly, at a higher Z value, the grain diameter of the AA5052 joints was smaller than that of the AA1050 joints, even though the strain rates of the AA5052 joints were considerably lower than those of the AA1050 joints. These results were mainly attributed to the lower SFE of AA5052, which promoted DRX and grain refinement during the LFW. This report reveals the effects of SFE, temperature, strain, and strain rate on the DRX-induced microstructural evolutions during severe plastic deformation.

This paper reports a controllable gradient microstructure sheet fabricated at room temperature conditions by a severe plastic deformation method, called plastic flow machining (PFM). The forming mechanism, microstructure evolution, and mechanical properties of the gradient-structured sheet for different machining parameters were investigated in detail. Results show that the prepared sheet by the PFM process is stratified into three structured surface layers, deformed grains layer (DGL), transition layer (TI), and ultrafine grains layer (UGL) from top to bottom, whereas microstructures present layer-by-layer refinement. The gradient structure can be controlled by adjusting the constraint tool angle and extrusion thickness in PFM. The gradient-structured sheet exhibits the concurrent combination of strength and ductility by comparison with homogeneous counterparts. It confirms that the extraordinary strength-ductility balance comes from the gradient structural effect. The insights in this study show that the continuous sheet production by PFM has superior performance and application perspectives in the structural materials, which can offer an effective and practicable one-step approach for low-cost fabricating the gradient-structured material.

The effect of high pressure torsion processing on mechanical properties and corrosion behavior of pure magnesium and Mg-Zn, Mg-Zn-Ca, Mg-Li-Y and Mg-Y-RE alloys is investigated. Micro-tomography and SEM characterization are used to estimate corrosion rate and evaluate non-uniform corrosion features. The results show that severe plastic deformation processing improves the strength of all magnesium alloys, but deformation localization can take place in the Mg-Zn-Ca and Mg-Y-RE alloys. The occurrence of deformation localization is associated with low strain rate sensitivity in these alloys and with severe corrosion localization. Pure magnesium and Mg-Zn and Mg-Li-Y alloys display good corrosion resistance with a low corrosion rate and maintain integrity after 28 days of immersion in Hank's solution.

The study deals with the influence of various variants of severe plastic deformation in the Equal Channel Angular Pressing (ECAP) process on the microstructure, microhardness, and conductivity of CuCoNi alloy. The microstructure evolution was studied by microscopic observations and electron back-scattered diffraction (EBSD) in a scanning electron microscope (SEM). The Vickers method was used to test the microhardness of the samples after various variants of the ECAP process. The conductivity was measured with an eddy current electrical conductivity meter based on the complex impedance of the probe. The results indicated the possibility of deformation of CuCoNi alloys in the process of pressing through the ECAP angular channel and developing their microstructure and properties. The method is an effective tool for strengthening the tested copper alloy by refining its microstructure. After the first pass, the grain size was reduced by 80%. Increasing the plastic deformation temperature did not significantly affect the obtained level of microstructure fragmentation - the average grain size is approx. 1.4-1.5 μm. The fragmentation of the microstructure had a negligible effect on the conductivity of the CuCoNi alloy, which oscillated at the value of 13 MS/m after the ECAP process.