Severe Plastic Deformation Technology Research Articles

A mini-review of surface severe plastic deformation methods and their effects on steel and stainless steel

Surface severe plastic deformation is an important technology for the preparation of bulk ultrafine grain or even nanocrystalline materials. Based on the technical achievements made in the field of surface severe plastic deformation at home and abroad, this article presents the basic principles of various kinds of surface severe plastic deformation techniques in detail. In addition, the effects of surface severe plastic deformation on the microstructure and mechanical properties of steel and stainless steel are reported. The current status of research on the effects of surface severe plastic deformation on fatigue properties and the tribological and biological properties of steel and stainless steel are summarized. The problems of the current surface severe plastic deformation technology for steel and stainless steel are pointed out, and the future development trend is foreseen.

Severe Plastic Deformation for Advanced Electrocatalysts for Electrocatalytic Hydrogen Production

Developing electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) of water splitting is very important for electrocatalytic hydrogen production. Very recently, emerging study have demonstrated that materials show some superior HER and OER performances of water splitting after processed by severe plastic deformation (SPD). In this work, recent advances on electrochemical hydrogen production performances of materials by SPD are summarized. Some basic principles of electrocatalytic water splitting are briefly described, and then the development of SPD technology and recent advances on SPDed materials with enhanced hydrogen production properties are comprehensively reviewed. Moreover, future direction on SPDed materials for hydrogen production is also prospected.

Evolution of the grain structure of metals and alloys under intense plastic deformation: multilevel models

It is well known that the performance properties of products made of metals and alloys are determined mainly by the meso- and microstructure of the latter. The structure of materials is formed and undergoes significant changes in the processes of manufacturing parts and structures using thermomechanical processing methods. A very important parameter that determines the physical and mechanical characteristics of materials is the grain structure (size, shape, relative positions of grains and inclusions of various phases). In recent decades, in this regard, special attention has been paid to the processes of severe plastic deformation (SPD), which make it possible to obtain a submicro- and nanocrystalline grain structure, which provides a significant increase in the performance properties of products made of metals and alloys. The development of SPD technologies in modern conditions is unthinkable without mathematical modeling of the processes under consideration; the most important component in the development of such a "toolkit" are constitutive relations (or, more broadly, constitutive models). In connection with the foregoing, the latter should be able to describe the evolutionary structure at various scale levels. Until now, the practice of developers of materials processing technologies has been dominated by the use of macrophenomenological models based on classical continuum theories of plasticity, viscoplasticity, and creep. From the second half of the 20th century to the present, various improvements to the constitutive models of the above class have been proposed, in which additional parameters and kinetic equations are introduced for them, describing certain characteristics of the structure of materials. As a rule, such models make it possible to obtain an adequate picture of the changing structure, however, for specific materials and methods of thermomechanical treatment. At the same time, such models, unfortunately, do not have the necessary universality; when changing the material or processing method, they have to be significantly “customized” to specific conditions, up to a complete change in the relationships included in the model. A brief review of works devoted to the creation and application of models of this class is given in the previous article by the authors. The most promising and possessing a significant degree of universality, according to the authors, are currently multilevel constitutive models based on the introduction of internal variables and physical theories of plasticity (elastoviscoplasticity). A review of works that consider various aspects of the formulation, modification, numerical implementation and application of such models is proposed in this article. The main attention is paid to models focused on the description of changes in the structure of materials due to dislocation-disclination mechanisms; a brief note is given on models that take into account thermally activated diffusion mechanisms, due to which the processes of recovery and recrystallization are realized.

Microstructure evolution and mechanical properties of severely deformed TA15 alloy by multi‐directional forging and annealing

AbstractMulti‐directional forging technology, as a representative severe plastic deformation technology, is urgent to be developed because it has strong microstructure refinement and performance improvement effects. In this paper, multi‐directional forging experiments of TA15 titanium alloy with different passes were carried out at 700 °C using unrestricted multi‐directional forging die structure. Then the samples of TA15 titanium alloy after multi‐directional forging deformation were subjected to a high‐temperature vacuum annealing treatment. The test results reveal TA15 alloy was effectively refined through multi‐directional forging without any cracking with the increasing of deformation passes. The mechanism of grain refinement during multi‐directional forging included dynamic recrystallization, grain crushing and adiabatic shear deformation bands refinement. The amount and grain size of recrystallization grains increased when the annealing time increased from 1 hour to 4 hours. Supplemented by annealing, the adiabatic shear deformation bands microstructure with the mixed microstructure of coarse αp and fine αs were obtained and the hardness after multi‐directional forging and annealing was investigated. The yield strength and ultimate tensile strength increased by 26.1 % and 25.5 % respectively when the deformation pass increased to 3 passes compared with the initial specimen. The present work revealed that multi‐directional forging deformation combined with appropriate annealing could represent an efficient route to improve the microstructure and mechanical property of TA15 alloy.

The Deformation Characteristics and Effect of Processing Parameters on the Microstructure of 7075 Al Shell Part Manufactured by Rotating Backward Extrusion

Rotating backward extrusion (RBE) is known as a new severe plastic deformation technology that effectively combines the features of conventional backward extrusion (CBE) and torsion deformation. In this study, 7075 Al alloy shell parts were successfully prepared by CBE and RBE with a different number of revolutions (N = 5, 10, 15, 25, 50) at 410 °C. The effects of the RBE process on the grain refinement, precipitates and properties of extruded parts were revealed, and the deformation characteristics were compared with CBE. The results showed that the RBE process could greatly eliminate the dead deformation zone at the bottom of the CBE section and significantly improved the comprehensive strain level of the material due to the addition of severe torsional deformation via an open punch. The grain refinement feature of RBE parts showed a gradient distribution that continuously weakened from the inner wall to the outer wall with decreasing compressive and torsional stress. Increasing the number of revolutions significantly promoted the level of grain refinement, the grain refinement range, and effectively broke down and refined the coarse insoluble Fe-rich phases of the extruded parts. It was revealed that the finest grain size of approximately 1.3 μm could be obtained in the inner wall region when N was increased to 25, which was linked to the comprehensive effects of continuous dynamic recrystallization and geometric dynamic recrystallization. RBE greatly promoted an improvement in properties of the extruded parts. After T6 treatment, the microhardness of the fine-grained region of the RBE (25 N) part increased to ~192–197 HV, compared with ~180 HV in the initial T6-extruded state.

Deformation temperature impact on microstructure and mechanical properties uniformity of GWZ932K alloy under reciprocating upsetting-extrusion

At present, there are great technical difficulties in achieving microstructure and mechanical properties uniformity in large-size billets prepared by severe plastic deformation technology. How to improve the process route to realize the microstructure and mechanical properties uniformity of the billets has become an urgent problem to be solved at present. In this paper, GWZ932K alloy is used for two reciprocating upsetting-extrusion (RUE) deformation methods with a cumulative strain of 5.38. The influence of isothermal temperature reciprocating upsetting-extrusion (IT-RUE) and decreasing temperature reciprocating upsetting-extrusion (DT-RUE) on the microstructure and mechanical properties uniformity of GWZ932K alloy is discussed in detail. The results show both IT-RUE and DT-RUE deformation methods can effectively refine grains. IT-RUE can prepare Mg alloy billet with uniform microstructure and mechanical properties from center region (CR) to edge region (ER). The microstructure and mechanical properties of the billet prepared by DT-RUE show obvious gradient characteristics from CR to ER. After 4 passes IT-RUE deformation, double-peak textures appear on the (0001) basal texture of the ER, middle region (1/2R) and CR, which is mainly attributed to the occurrence of dynamic recrystallization (DRX) behavior. It should be noted that changes in the deformation temperature will not cause changes in the DRX mechanism. The deformation mechanisms of continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) jointly promote grain refinement.

A review paper on magnesium alloy fabricated by severe plastic deformation technology and its effects over microstructural and mechanical properties

Abstract This review paper mainly focused on microstructural and mechanical properties ofultrafine grained nanocrystalline (Nc) Magnesium alloy fabricated by Severe Plastic Deformation(SPD) process. The influence of SPD over mechanical, microstructural, physical, optical, and corrosion properties of Nanocrystalline magnesium alloy are detailed and discussed. It has been observed that nanocrystalline (Nc) magnesium materials has shown superior properties over the bonding of grains while during the Extrusion, Annealing, quenching, Normalizing, Spark Plasma Sintering (SPS) processes. The outcome based by many researchers showed that nanocrystalline Magnesium alloy processed by Severe Plastic Deformation (SPD) showed an improved properties over the Hardness, Dislocation density, Compressive, Tensile and texture, and it’s found to be increased up to certain limit beyond that decrease of microstructural stability, micro hardness and dislocation density were seen to be observed. The Microstructural and Mechanical properties are well improved by Spark Plasma Sintering (SPS), Extrusion, Annealing, Equal channel angular pressing (ECAP), Accumulative Roll Bonding (ARB) and High-Pressure Torsion (HPT) processes. Grain growth Mechanism, Energies Activation during grain growth, Thermal stability, Relative density and stress corrosion rate were observed by previous Researchers during Fractography analysis over several nanocrystalline (Nc) Magnesium alloy specimens.

Toward the development of Mg alloys with simultaneously improved strength and ductility by refining grain size via the deformation process

Magnesium (Mg) alloys, as the lightest metal engineering materials, have broad application prospects. However, the strength and ductility of traditional Mg alloys are still relativity low and difficult to improve simultaneously. Refining grain size via the deformation process based on the grain boundary strengthening and the transition of deformation mechanisms is one of the feasible strategies to prepare Mg alloys with high strength and high ductility. In this review, the effects of grain size on the strength and ductility of Mg alloys are summarized, and fine-grained Mg alloys with high strength and high ductility developed by various severe plastic deformation technologies and improved traditional deformation technologies are introduced. Although some achievements have been made, the effects of grain size on various Mg alloys are rarely discussed systematically and some key mechanisms are unclear or lack direct microscopic evidence. This review can be used as a reference for further development of high-performance fine-grained Mg alloys.

The dynamic recrystallization and mechanical property responses during hot screw rolling on pre-aged ZM61 magnesium alloys

In order to investigate the microstructure and texture evolution induced by precipitation during severe plastic deformation (SPD), pre-aging was conducted on ZM61 alloys, followed by screw rolling (at 300 °C), a special type of SPD technology. The mechanical properties were measured by uniaxial tensile testing at room temperature. The results showed that a gradient structure was obtained, and the grain size was more refined in the outer region along the radial direction. All samples expressed a basal texture, and the intensity gradually weakened when the pre-aging time increased, with the strength and ductility improving concurrently. The fracture elongation improved from 15.2% on as-received samples to 27.8% after pre-aging for 12 h, an 82.9% increase. This is mainly related to dynamic recrystallization mechanisms, including continuous dynamic recrystallization (CDRX), discontinuous dynamic recrystallization (DDRX), and particle simulated nucleation (PSN).

Contribution of ultrasonic surface rolling process to the fatigue properties of TB8 alloy with body-centered cubic structure

The effect of ultrasonic surface rolling process (USRP) as a severe plastic deformation technology was investigated on the evolution of microstructure, residual stress and surface morphology of TB8 alloys with body-centered cubic structure. Stress-controlled rotating-bending fatigue tests indicated increased fatigue strength in USRP samples prepared using different number of passes compared to the base material, which was attributed to the presence of gradient structure surface layers. Five subsequent USRP passes resulted in the highest fatigue strength, due to the optimal surface properties including higher extent of grain refinement, larger compressive residual stresses, “smoother” surface morphology and increased micro-hardness. However, the effect of USRP technology on improving fatigue strength of TB8 alloy was not significant in comparison with that of other titanium alloys (for example, Ti6Al4V), which was attributed to the notable surface residual stresses relaxation revealed from measurements on post-fatigued USRP samples. Electron backscatter diffraction analysis confirmed that fatigue crack initiation occurred in the larger grains on the surface with high Schmid factor. Small cracks were found to propagate into the core material in a mixed transgranular and intergranular mode. Further analysis indicated that grain growth existed in post-fatigued USRP-treated TB8 samples and that the average geometrically necessary dislocations value reduced after fatigue loading.

Optimization of the Mechanical Performance of Titanium for Biomedical Applications by Advanced, High-Gain SPD Technology

This recent study deals with the optimization of the mechanical performance of Grade 2 and Grade 4 titanium with Conform severe plastic deformation (SPD) processing and subsequent rotary swaging. A comprehensive study of the materials behaviour and characterisation during and after processing is given by (finite element method - FEM) numerical simulation, microscopy methods and mechanical testing. The mechanical and fatigue properties are discussed in terms of texture and microstructure evolution. It is shown that the combination of Conform SPD and rotary swaging is a promising technique for economically reliable, high-gain production of titanium alloys fulfilling requirements for biomedical applications. Such a processing can improve the mechanical properties of the unalloyed titanium to the level of the commonly used Ti-6Al-4V.

Investigation of mechanical properties on composite materials by several of severe plastic deformation (SPD) methods

The technology of severe plastic deformation (SPD) is the process on forming metals of large plastic strain that is used for mass production in order to make ultrafine-grained (UFG). Through research on the characterization of aluminium-based composite materials with several SPD methods, the ideal variable will be obtained in producing high-strength materials. The development of a new SPD method driven by requirements simplifies the process, so that it can be applied for mass production, some of the development of SPD technology is able to produce high plastic strain. The market for nanostructured materials produced by SPD technology is in sectors where superior traits such as specific strength is needed. This research is focused on a comparison of several SPD methods; APB, MAF, ECAP-PC and RPRF, in the scope of mechanical characterization on aluminium based composites. Result of mechanical properties obtained, the RPRF method is the best that is able to produce higher mechanical characteristics than other methods. That produces 75.9 VH10 hardness on RPRF, while APB 45.82 VH10, ECAP-PC 66.12 and MAF of 42.9 VH10

A grain level model for deformation and failure of ultrafine-grained tungsten

Ultrafine-grained tungsten (UFG W) produced by severe plastic deformation technology has many potential applications due to its high strength and ductility. To reveal the mechanism for the high ductility of UFG W, the deformation and failure behaviors of coarse-grained tungsten (CG W) and UFG W have been compared based on a three-dimensional crystal plastic finite element method (CPFEM) simulation. Cohesive element method has been utilized to model the behavior of grain boundaries (GBs). Both plastic deformation in grain interiors and grain boundary opening have been observed in different periods of deformation in UFG W. It is concluded that the high GB density and elongated microstructure in the UFG W suppress crack propagation, decrease the stress concentration and impurity concentration on GBs, therefore enhance the ductility of the material.

Accumulative Roll Bonding for Improvement mechanical properties of Aluminum based Composite

The Aluminum has special properties such as light weight, ductile and a lower melting point. It has very suitable for applied as composite material, with ceramic as reinforcement. Accumulative roll bonding (ARB) is part of technology of Severe Plastic Deformation (SPD) that has been developed of manufacturing process for metals, alloys and composites as well. It has a potential becoming an industrial process to produce composite and ultrafine-grained (UFG) metal sheets. In this research, the development of aluminum-based composites is made by SPD technology using the ARB method on aluminum plate sheets with boron carbide (B4C) as reinforcement, is expected to improve its mechanical properties along with the rules of microstructure analysis. To get of the UFG metallic materials where the mean grain size must be smaller than 1μm are expected can be exhibit excellent mechanical properties. The ARB process consists of multiple cycles of rolling, cutting, stacking and solid-state deformation bonding. Two plates were prepare for the ARB sample process, cleaning uses acetone liquid to prevent attachment of dust and dirt on the surface to be made in contact with other samples. Acetone and grinding to produce a rough surface to facilitate the surface binding process between samples, B4C powder is sprinkled between the centers of aluminum plate surface and stacked going together.

Constrained bending and straightening-a proposed method for severe plastic deformation of metals

The use of severe plastic deformation (SPD) technology to process ultra-fine/nano grains metals with enhanced desired properties for structural and biomedical applications have shown good results. However, SPD technology is still limited to discrete processes, small size samples with inhomogeneous strain. This paper proposes a new method for severe plastic deformation of metals known as constrained bending and straightening (CBS). The method is aimed to provide continuous production of ultra-fine/nano grains metals with improved strain homogeneity. The CBS process analytical model and its working principle are presented, a constitutive relation of feed length, bend roller diameter, effective strain and tensile strength is established. Results show that the magnitude and homogeneity of induced effective strain and tensile strength increase with the decrease of both feed length and bending roller diameter. Effective strain increased by 200% from 6mm to 2mm feed lengths. At 2mm feed length, tensile stress increased from 1223.8 MPa at 1 pass to 1302.5 MPa at 4 pass. Results from this study promise that CBS technique is potential to be adapted for continuous SPD of bulky length metal sheets with enhanced homogeneous properties.

Crack‐induced intergranular corrosion behavior of aerial aluminum alloy subjected to severe plastic deformation

The influence of crack‐induced on the intergranular corrosion (IGC) behavior of aerial aluminum alloy subjected to severe plastic deformation (SPD) is investigated in this work. Addressing this problem, a particular SPD technology, namely elliptical cross‐sectioned spiral equal channel extrusion (ECSEE), is employed to prefabricate cracks. The microstructure, induced‐crack observation and IGC behavior of the ECSEE‐ed alloy are observed. ECSEE can significantly refine the grains, while lots of small and deep dimples as well as broken second‐phase particles appear on fracture surface. The formation mechanism of the fracture surface is revealed based on the observation of fracture morphology. A typical stress corrosion cracking characteristic is observed in IGC tested ECSEE‐ed alloy, and the corroded fracture consisted of higher volume fraction of brittle intergranular fractures that are made up of rockcandy‐like brittle and intergranular fracture. The mechanism of intergranular corrosion of dehiscence and cracking is determined considering the factors such as grain refinement, grain boundary precipitations, preexisted crack, and residual stress.

Strain hardening and nanocrystallization behaviors in Hadfield steel subjected to surface severe plastic deformation

A gradient nanocrystalline layer with a thickness in a range of millimeter magnitude was successfully produced on the surface of Hadfield steel by a novel severe plastic deformation technology, high speed pounding. The surface hardness was measured, and the microstructure evolution during nanocrystallization process was characterized by X-ray diffraction and transmission electron microscopy. Results showed that the hardness increment and nanocrystallization in Hadfield steel were obtained at different stages under high speed pounding. The first stage was strain hardening, where surface hardness of Hadfield steel increased gradually during high speed pounding until a steady-state value was obtained. The hardening degree and rate of Hadfield steel were determined by deformation stress and strain rate, respectively. The second stage was microstructure nanocrystallization, at which twin boundaries interacted with dislocations to form general high angle grain boundaries. In this stage, the surface hardness of Hadfield steel remained basically the same. Moreover, a physical model was established to explain the strain hardening and surface nanocrystallization behaviors in accordance with the microstructure evolution at different stages in Hadfield steel.

Aluminum based Composites by Severe Plastic Deformation Process as New Methods of Manufacturing Technology

Composites a material was developed to replace metal and alloys, because of the properties such as light weight and unique mechanical properties. Processing of aluminum-based composites has been developing by new manufacturing technology, namely severe plastic deformation (SPD), to produce unique of mechanical properties. Some of the methods used are; equal channel angular pressing (ECAP), accumulative roll bonding (ARB) and multi-axial forging (MAF). The results of some of these methods were compared with the latest method of new SPD, namely: repetitive press roll forming (RPRF). Based on grain morphology and mechanical properties, the result of RPRF has superior to another method. The properties produced by SPD technology was varies, the highest of hardness produced by RPRF process was 88 HV10, ECAP produced 65 HV10, MAF was 46 HV10 and ARB reached 50 HV10. While the highest of tensile strength produced by MAF was 237 MPa while the RPRF process just only around 147 MPa, but the ultrafine grains just only produced by RPRF method which is 0.9 μm, compared to other methods: MAF 1.2 μm, ECAP 5.7 μm and ARB is not so far with MAF that is equal to 1.4 μm. The RPRF process can be recommended for the interest of the aluminum-based composite materials processing industry. Because currently some component product by industries have been substituted from metal alloy materials to metal-based composites.

Technical-economic evaluation of severe plastic deformation processing technologies—methodology and use case of lever-arm-shaped aircraft lightweight components

This paper presents an innovative methodology for integrated technical-economic evaluations of extrusion technologies and aims to show potentials of severe plastic deformation (SPD) technologies. Extrusion technologies and processes such as SPD have a strong influence on properties of aluminium-based lightweight materials. Hence, research and development regarding such processes may contribute to gain competitive advantages for companies as they can differentiate from competitors by offering or processing materials with distinctive properties (e.g. light weight and high yield strength) causing customer’s benefit. Consequently, it is of great importance for companies of the aluminium extrusion industry to select technologies that are promising from both a technical and an economic point of view. Using the integrated methodology, selected SPD technologies are analysed. The application to the use case of lever-arm-shaped aircraft components shows that these technologies bear technical as well as considerable economic potentials: extrusion at room temperature can increase yield strength by 25% compared to commercial extrusion at a similar level of manufacturing costs and the monetary appraisal of the benefits of lower weight for the users of aircraft components indicates a significant economic potential of extrusion at room temperature.

The influences of extrusion-shear process on microstructures evolution and mechanical properties of AZ31 magnesium alloy

Severe plastic deformation (SPD) technologies are difficult to be promoted to be industrialized, and the processes are complicated, and the costs are high. To promote industrial application of the SPD technology for magnesium alloy, a new successive SPD method has been explored which includes direct extrusion and two steps equal channel angular extrusion (ECAE) continuously. The processing technology is called extrusion-shear (ES) in this paper. The components of ES dies have been designed, manufactured and installed on extruder to manufacture the AZ31 magnesium alloy rods. Microstructures of AZ31 magnesium alloy processed by ES process have been observed and investigated. The texture evolution during ES process has also been studied. The results show that fine and uniform microstructures can be obtained by ES process. Basal texture (0002) has been weakened owing to shear deformation of ES process. Research results show that relationship between grain sizes and hardnesses is consistent with hall-petch law at 420 °C. ES process with low billet temperature could improve hardness obviously and enhance compression performance, and raise strengths. And there exits strong tension-compression asymmetry of AZ31 magnesium alloy fabricated by ES process. The results indicate that ES process can produce large plastic deformation and introduce ultra-fined grains in the AZ31 magnesium alloy.