Severe Plastic Deformation Method Research Articles

Correlation of structure development and electric characteristics within high pressure torsion processed copper

AbstractCopper of a high purity features excellent electric conductivity, but generally very low mechanical properties. Nevertheless, optimized deformation/thermomechanical treatment can introduce favorable combinations of both. The presented study characterizes the correlation of microstructure development and electric properties within copper processed by the severe plastic deformation method of high pressure torsion, the primary advantage of which is that it enables to achieve grains with the sizes in the ultra‐fine, or even nano scales. The study investigates structure development during progressive deformation. In other words, samples processed by single and double high pressure torsion revolutions were evaluated from the viewpoints of grain sizes and grain boundaries, and the results were correlated with the experimentally measured electric conductivity. The single high pressure torsion revolution contributed to grain size decrease, while the structure after double revolution exhibited very fine grains, especially at the sample periphery featuring the highest imposed strain. Both the samples also exhibited increases in microhardness (especially after double revolution), and electric conductivity higher than 100 % IACS. The results confirmed that copper conductors featuring enhanced mechanical properties and favorable electric conductivity can be manufactured by severe plastic deformation.

The deformation behavior of aluminum alloy in a novel severe plastic deformation process known as combined SSE-FE process

In this study, a novel method for severe plastic deformation (SPD) was introduced, entitled as Combined SSE-FE (CSSE-FE). The process was investigated experimentally and numerically on AA1050 alloy. After this process, due to the unique design of the die channel, the sample significantly fills the die outlet channel. Also, the CSSE-FE process can produce large strains without repeating the cycle. Therefore, this parameter was increased by around 53.16 % in comparison to simple shear extrusion (SSE) process after the first pass. Also, microhardness was increased by about 87.93 % in comparison to annealed sample.

Long term hydrogen storage properties of ZK60 Mg-alloy as processed by different methods of SPD

Hydrogen storage characteristics is studied in the Mg-alloy ZK60 after processing by different SPD (Severe Plastic Deformation) methods such as High Pressure Torsion (HPT) and Friction Stir Processing (FSP), applying various deformation extents and rates. The capacity and kinetics of hydrogen storage was investigated and analysed, up to 100 storage cycles. While the degree of SPD deformation is less important for the storage capacity, the SPD processing method itself matters, yielding about ~ 30% more capacity in FSP than in HPT. As shown by DSC and XRD analyses, it is the density of SPD-induced vacancy agglomerates which is significantly higher in FSP than in HPT (~ 10–3 instead of ~ 10–4) because of the enhanced dislocation slip activity. Thanks to their stabilization through Mg(Zn,Zr) precipitates, the vacancy agglomerates survive numerous cycles of hydrogen storage in spite of the high storage temperature of 350 °C, and can act as thermally stable heterogeneous nuclei for the hydrogenation. This latter mechanism was found in all SPD methods applied irrespective of the deformation extent, on the basis of Johnson–Mehl–Avrami-Kolmogorov analysis providing the Avrami exponent n = 1, already from the second up to the highest hydrogen storage cycles.

Enhancing mechanical properties in Mg microtubes using tubular channel angular pressing-extrusion (TCAPE): A promising severe plastic deformation method

In this study, a novel method, Tubular Channel Angular Pressing-Extrusion (TCAPE), is introduced for manufacturing ultrafine microtubes. This method, integrating Tubular Channel Angular Pressing (TCAP) and microtube extrusion (MTE) processes, reduces the number of stages in the fabrication of ultrafine microtubes while achieving favorable mechanical properties. In the TCAPE process, the tube undergoes Severe Plastic Deformation (SPD) in the shaping region and is subsequently shaped into the desired geometric dimensions through the extrusion process at the end. To investigate the effect of the number of SPD passes on the microstructure and mechanical properties of the produced microtubes, one-pass and two-pass SPD were applied. Metallography, XRD testing, tensile testing, and hardness measurement were employed for analysis. For a one-pass SPD, the sample was processed only through the TCAPE process (TCAP + MTE), while for a two-pass SPD, the sample underwent the TCAP process first and then underwent TCAPE for the second processing step (2TCAP + MTE). Tensile test results indicate an increase in Ultimate Tensile Strength (UTS) from the initial value of 73 MPa–103.1 MPa and 148 MPa, and elongation altered from the initial value of 10 to 7.1 and 17.5 after two-pass SPD. Metallography results show a reduction in grain size from the initial value of 160 μm to 15 μm and 3 μm after two-pass SPD. The TCAPE process, due to applying higher strain (1.955) compared to the TCAP process (1.64), exhibits better performance in refining the microstructure and improving mechanical properties. The hardness and ultimate strength of the TCAPE-processed sample are 13.33% and 13.5% higher than those of the TCAP-processed sample, respectively.

Rational Methods of Plastic Deformation Providing Formation of Ultrafine-Grained Structure in Large-Sized Products

Based on the peculiarities of plastic deformation mechanics and physical mesomechanics, the processes are considered and technological schemes for their realization are proposed to ensure the formation of ultrafine-grained structure in axisymmetric products of large sizes. Deformation of coarse-grained materials in temperature-velocity conditions of superplastic deformation and methods of severe plastic deformation are taken as methods of preparation of such a structure. All of these deformations include large strain, and they are carried out at low hydraulic press speeds, but at different temperatures: in the mode of superplasticity at hot temperatures, and in the mode of severe plastic deformation at warm or cold temperature deformation. The first mode allows grains to be refined to microcrystalline sizes of 1–10 microns, and such a material acquires the ability to deform in a state of superplasticity, i.e., in tension with low resistance to deformation and high elongation. The second mode (severe plastic deformation) refines grains to submicro- (1÷0.1 µm) and nanosizes (less than 0.1 µm), thus giving metal materials record structural strength, as well as the possibility to use processing in extended temperature-velocity conditions of superplastic deformation in comparison with microcrystalline structure.

Magnetic Shape Memory Nanocomposites Assembled with High Speed High Pressure Torsion.

When a severe plastic deformation (SPD) process is performed at high temperatures, it becomes more versatile. Designed originally for the bulk nanoconstruction of hard-to-deform alloys, high-speed high-pressure torsion (HSHPT) is an SPD method used in this research for assembling multiple layers of shape memory nanocomposites. Three hard-to-deform magnetic alloys in the cast state were used. Soft magnetic shape memory alloys, NiFeGa and FePdMn, and a potentially hard magnetic alloy, CoZr, were assembled in various composites. Both grain refinement and strong layer bonding were achieved in ZrCo/FePdMn and ZrCo/NiFeGa composites in seconds. The very short SPD time is specific to HSHPT because of the intense friction that occurs under high pressures, which generates huge amounts of heat. After SPD, the temperature rises in bulk material like a pulse, being dissipated mostly through heat conduction. The SPD parameters were carefully controlled with an advanced automation system using a programmable logic controller. Nevertheless, the major drawbacks of high-pressure torsion were overcome, and large SPD discs were obtained. Various investigation techniques (optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and atomic force microscopy) show well-defined interfaces as well as a fine and ultrafine structure.

Structural Phenomena Introduced by Rotary Swaging: A Review.

Rotary swaging is an industrially applicable intensive plastic deformation method. Due to its versatility, it is popular, especially in the automotive industry. Similar to the well-known methods of severe plastic deformation (SPD), rotary swaging imparts high shear strain into the swaged materials and thus introduces grain refinement down to a very fine, even ultra-fine, level. However, contrary to SPD methods, one of the primary characteristics of which is that they retain the shapes and dimensions of the processed sample, rotary swaging enables the imparting of required shapes and dimensions of workpieces (besides introducing structure refinement and the consequent enhancement of properties and performance). Therefore, under optimized conditions, swaging can be used to process workpieces of virtually any metallic material with theoretically any required dimensions. The main aim of this review is to present the principle of the rotary swaging method and its undeniable advantages. The focus is primarily on assessing its pros and cons by evaluating the imparted microstructures.

High-Pressure Torsion for Highly-Strained and High-Entropy Photocatalysts

Nowadays, the environmental crisis caused by using fossil fuels and CO2 emissions has become a universal concern in people’s life. Photocatalysis is a promising clean technology to produce hydrogen fuel, convert harmful components such as CO2, and degrade pollutants like dyes in water. There are various strategies to improve the efficiency of photocatalysis so that it can be used instead of conventional methods; however, the low efficiency of the process has remained a big drawback. In recent years, high-pressure torsion (HPT), as a severe plastic deformation (SPD) method, has shown extremely high potential as an effective strategy to improve the activity of conventional photocatalysts and synthesize new and highly efficient photocatalysts. This method can successfully improve the activity by increasing the light absorbance, narrowing the bandgap, aligning the band structure, decreasing the electron-hole recombination, and accelerating the electron-hole separation by introducing large lattice strain, oxygen vacancies, nitrogen vacancies, high-pressure phases, heterojunctions, and high-entropy ceramics. This study reviews the recent findings on the improvement of the efficiency of photocatalysts by HPT processing and discusses the parameters that lead to these improvements.

Fabrication of Functionally Graded Materials through Severe Plastic Deformation of Powders: Process, Significance, and Future Development

Functionally graded materials (FGMs) are a remarkable invention in materials science and engineering, that offers unique properties useful in various applications. Having the ability to gradually change properties, like composition, microstructure, or mechanical properties of materials, gives FGMs unparalleled adaptability, making them suited for a wide range of high-strength applications. One of the novel methods of creating FGMs is to use severe plastic deformation (SPD) techniques on powdered materials. The SPD of powders involves a few critical steps; The process begins with selecting materials with varied compositions and phases then mixing the powders, cold compaction, SPD methods, and, if necessary, heat treatment. The process is completed with characterization and testing, to evaluate the microstructure and characteristics of the final FGM formed. FGMs will continue transforming materials engineering and pushing the boundaries of their applications in many engineering fields and industries since they exhibit attractive capabilities like improved efficiency, durability, and performance. Therefore, this article explores the process of fabricating FGMs by SPD and emphasizes its significance and future trends in FGM production.

Design, Finite Element Analysis and Optimization of Helical Angular Pressing (HAP) Method as a Novel SPD Technique

Severe Plastic Deformation (SPD) processes improve the mechanical properties of materials by obtaining Ultra Fine Grained (UFG) materials, orienting the grains and reforming the grains. Helical Angular Pressing (HAP) is a newly proposed Severe Plastic Deformation (SPD) method. In order to improve the efficiency of the HAP method, its die geometry should be optimized first. In this context, four parameters (helical diameter, helical pitch, helical height and channel radius) were determined for the die channel geometry, each with four levels according to the literature. Then, thanks to Taguchi L16 combinations, 16 Finite Element Analyses (FEA) were carried out using Deform 3D software instead of 256 simulations, and effective strain values and maximum pressing load values were obtained. Later on, using the SPSS 16 software, Taguchi optimization was carried out to obtain the optimum HAP die channel geometries by minimizing the press load and maximizing the effective strain values. Next, the Finite Element Analysis (FEA) was repeated with these determined optimum die channel parameters. Finally, the efficiency of this novel HAP method was compared with conventional Equal Channel Angular Pressing (ECAP) and Twist Extrusion (TE) methods. As a result, HAP method provides effective strain values equivalent to 10 number of passes after processing with ECAP. And it is approximately 4 times higher than that achieved by TE processing. As a result of the Taguchi optimization, it is concluded that the values in the combination of diameter (d)=60 mm, height (h)=50 mm, radius (r)=4 and pitch (p)=1.25 are the optimum die geometry. In conclusion, these results indicate that the proposed novel HAP method is an efficient and applicable SPD technique.

Simultaneous improvement of mechanical strength and corrosion resistance in aluminum alloy 5083 via severe plastic deformation

In this study, the Repeated Upsetting (RU) process as a severe plastic deformation method was performed on the aluminum alloy 5083 (AA5083) to refine the microstructure. The microstructure, mechanical properties, and corrosion behavior of AA5083 before and after applying 1, 3, and 5-pass through the RU process were investigated. Based on the EBSD analysis, the average grain size of AA5083 decreased from 21.9 μm for the base metal (BM) to less than 5 μm for RUed samples. The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) results have shown that the corrosion resistance of the AA5083 increased after applying the RU process due to the grain refinement and homogenous distribution of the second phase. By increasing the RU passes from 1 to 5, the corrosion rate of AA5083 was enhanced because of rising localized plastic deformation. Scanning electron microscopy and optical microscopy images confirmed the electrochemical results, in which the BM showed a severe corrosion surface compared with the RUed samples. On the other hand, tensile tests confirmed that the maximum improvement in mechanical properties occurred after the first pass. Accordingly, the 1-pass RU product can be an ideal candidate for application under severe corrosive environments and high-loading conditions.

Influence of ultrafine-grained structure parameters on the annealing-induced hardening and deformation-induced softening effects in pure Al

This work investigates the influence of parameters of initial ultrafine-grained (UFG) structure in commercially pure (CP) Al on annealing-induced hardening (AIH) and deformation-induced softening (DIS) effects. UFG structures were formed via processing CP Al by various methods of severe plastic deformation (high pressure torsion (HPT), equal channel angular pressing (ECAP) and combination of ECAP and cold rolling (CR)). AIH and DIS effects are observed in all the studied UFG structures. However, HPT Al demonstrates large increase of strength due to annealing and drastic gain of ductility after subsequent additional deformation whereas in ECAP Al and ECAP + CR Al both effects are much less pronounced. Microstructure characterization by X-ray diffraction (XRD) analysis, electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) was performed for HPT Al and ECAP + CR Al in the three studied states: before and after annealing and after annealing and subsequent additional deformation. Analysis of microstructure evolution during annealing and subsequent additional deformation shows that the key microstructure parameter which is responsible for AIH and DIS effect is the change of dislocation density in grain interior in ECAP + CR Al, whereas in HPT Al the effects are related to the change of dislocation density at/near grain boundaries. In addition, outstanding combination of high strength (∼210 MPa), high electrical conductivity (∼62 %IACS) with sufficiently good ductility (7–10 %) and thermal stability (up to 150°С, at least) was achieved for ECAP + CR Al after annealing at 150 °C, 1h.

Deformation behaviour, microstructure evolution and dynamic recrystallization mechanism of AZ31 magnesium alloy under co-extruded by Mg-Al composite billet

Conventional methods for hot extrusion of magnesium (Mg) alloy sheets have limitations for microstructure improvement and mechanical property enhancement. Co-extrusion of Mg alloy with an Al alloy core provides an opportunity for refining the grain size and improving basal texture. This study introduces a novel severe plastic deformation (SPD) method, Direct Extrusion-Continuous Shear (DE-CS), utilizing 6063 Al alloy as the core to fabricate innovative Mg/Al clad composite sheets. Monolithic Mg sheets (non-co-extruded condition) are extruded under identical conditions for comparison. By evaluating the microstructure and mechanical properties of AZ31 Mg alloy under co-extrusion and non-co-extrusion conditions, the positive effect of Mg-Al composite billet co-extrusion on AZ31 Mg alloy is established. The grain refinement effect in co-extruded samples is superior, enhancing plasticity without significant reduction in tensile strength. The microstructure evolution and dynamic recrystallization (DRX) behaviour of AZ31 Mg alloy during co-extrusion were analyzed comprehensively. The results indicate that, in the initial stages of deformation, various variants of {10−12} extension twins (ETs) play a crucial role in refining the original grains, forming initial [10−10]//ED fiber texture components alongside other non-basal components. Upon entering the shear deformation (SD) zone, deformed twins disappear, and small dynamically recrystallized (DRXed) grains emerge along boundaries of coarse deformation grains and within the grains. Strong shear deformations and compressive stress from transverse direction (TD) induce intensified prismatic <a> and pyramidal <c+a> slip, promoting continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX). CDRX predominantly affects elongated deformed grains, forming an [10−10]//ED fiber texture through high-energy grain boundary segmentation. Subsequently, compatible stress increases due to the activity of non-basal slip dislocation and the reduction in grain boundary (GB) size. DDRX emerges as the dominant mechanism, generating randomized [10−10]//ED fiber and non-fiber textures within parent grains and at boundaries.

Surface Energy in the Processes of Disintegration of Solids

Objective. The purpose of the study is to experimentally measure the surface energy of solids during their grinding.Method. The study is based on the use of methods for determining the surface tension of solids. At least 20-25% of all electricity produced in the world is spent on grinding materials in industry. When the resulting particles are reduced to tens of nanometers, the contribution of surface energy (st) to the grinding work becomes so large that it is difficult not to take it into account. Measuring the surface tension of liquids has long been proven. But measuring (st) of solids causes great difficulties. Currently, more than twenty methods for determining (st) are known.Result. Based on the phenomenon of spontaneous bending of thin thread-like structures, a method for determining (st) has been developed. Examples are given in which (st) at the phase interface plays an important role in obtaining samples with a microstructure using the method of severe plastic deformation (SPD). To obtain fine metal powders, one of the variants of the SPD method has been proposed. A method has been found for the physical activation of aluminum granules, which increases the reaction rate of the metal in an aqueous environment by about a thousand times. This is necessary for the development of an anaerobic power plant capable of operating at great depths.Conclusion. The new technology makes it possible to obtain high-purity, non-oxidized metal powders without toxic waste and emissions and with energy costs lower than in all known methods.

Novel severe plastic deformation method for extrusion compression composite processing

The capability of a novel severe plastic deformation method for extrusion compression composite processing was investigated. Deform-3D software was used to study the effect of back pressure on the strain distribution of a workpiece by simulating the forming process with and without back pressure. The Mg-12.5Gd-4Y-2Zn-0.5Zr alloy was used to analyze the effect of strain on microstructure and mechanical properties. Results showed that back pressure led to the uniform strain distribution of the deformed workpiece and the decrease in the effective strain standard deviation from 0.73 to 0.68. With increasing strain, the grain size tended to decrease and then increase, contrary to the recrystallization rate trend. The tensile strength gradually increased with increasing strain, but the elongation change trend was changed due to the influence of the bimodal structure.

A new wavy cross-sectional torsion extrusion method with an application to improve the mechanical properties of an aluminum matrix composite

Torsion extrusion (TE) as a severe plastic deformation (SPD) method has shown promise in effectively improving the mechanical properties of metal matrix composites (MMCs) by means of extreme shear strain. However, the circumferential sliding between the rotating die and the material seriously degrades the shear effects during TE processing. In order to address this challenge, a modified torsion extrusion method, namely wavy cross-sectional TE (W-TE), was proposed to enhance the shear effect. The method applied a rotating die consisting of a deformation cavity followed by a bearing segment with a wavy cross-section. The material is extruded through the rotating die, and the wavy cross-section holds the deformed billet to rotate with the rotating die, so that the relative sliding is prevented. The method was applied to an in-situ TiB2 particle reinforced 2026 Al composite for dispersing the reinforcing particles and refining the microstructures. Numerical simulations indicated that the W-TE processed material undertook larger torsion deformation than the ones processed by the conventional TE, so the shear effect was enhanced. Experiments showed that, compared with the conventional TE, W-TE can efficiently disperse the reinforced particles and refine the microstructure of the extruded materials. Mechanical tests demonstrated that the samples processed by W-TE exhibits a simultaneously increase in the strength and ductility. Furthermore, with the aid of the enhanced shear effect, the extrusion force of W-TE was reduced greatly compared with conventional extrusion or other TEs, thus making the proposed W-TE an efficient way for improving mechanical properties of metal matrix composites.

Cyclic contraction-expansion extrusion (CCEE): An innovate severe plastic deformation method for tailoring the microstructure and mechanical properties of magnesium AZ91 alloy

In this study, the Cyclic Contraction-Expansion Extrusion (CCEE) process, a novel severe plastic deformation (SPD) technique, is applied to the AZ91 magnesium alloy to enhance its mechanical properties through microstructural refinement. The CCEE method combines cyclic expansion extrusion (CEE) and cyclic extrusion compression (CEC), integrating their advantages while overcoming drawbacks. The CCEE process is capable of inducing substantial plastic strain (3.38) within a single processing cycle, eliminating the need for secondary punches or a synchronized backpressure system. The process is conducted at a temperature of 300 °C, resulting in a bimodal microstructure through the dynamic recrystallization (DRX) mechanism. This microstructure consists of refined equiaxed α-Mg grains with an average size of 2.8 μm, surrounded by a network of newly nucleated α-Mg grains and Mg17Al12 particles with an average size of 500 nm in the two-pass processed sample. Results obtained from the tensile test technique indicate a significant enhancement in the ultimate tensile strength (UTS) of the AZ91 alloy, increasing from 139 MPa to 276 MPa and 290 MPa, and a notable improvement in elongation, increasing from 4% to 8% and 12% after two passes of the CCEE process. Macro-texture X-Ray diffraction (XRD) measurements reveal the formation of a pyramidal deformation texture in the one-pass sample, contributing to the UTS improvement. This texture weakens during the second pass, leading to an increase in elongation. Furthermore, microhardness measurements show an increase from HV 62 to HV 85 after the first pass of the CCEE and HV 73 after the second pass.

Fabrication of ultrafine-grained Cu-Mn alloy with uniform microstructure and high mechanical properties

Homogenization, random orientation, and high strength are the research goals of target materials. In this study, the bulk ultrafine-grained (UFG) Cu-5Mn alloy target materials were prepared by two typical severe plastic deformation methods, equal channel angular pressing (ECAP) and auxiliary-cooling multi-pass friction stir processing (MPFSP), and their structure-property relationships were comparatively investigated. Compared to the ECAP sample with extremely heterogeneous microstructure, the MPFSP sample exhibited finer and more uniform equiaxed microstructure with weaker texture and higher tensile strength of 614 MPa, which was consistent with the requirements of an ideal target material. This study provides a new perspective on the optimization of target materials.

Grain refinement effect on fatigue life of two grades of commercially pure titanium

The fatigue life and fatigue limit of commercially pure Ti grade 2 and 4 in coarse-grained and ultrafine-grained states were experimentally determined. Ultrafine structures were prepared by Conform severe plastic deformation method and by conventional Equal channel angular pressing, respectively. The differences in the improvement of fatigue life and the influence of both procedures on the fatigue limit based on 107 cycles to fracture are discussed in terms of grain refinement, microstructure, differences in fatigue damage mechanism and influence of surface roughness on the initiation of fatigue cracks. Improvement in fatigue life was observed for both materials, however, the improvement of the fatigue limit was found only for Ti grade 2.

Magnesium Alloys Processed by Severe Plastic Deformation (SPD) for Biomedical Applications: An Overview

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.