Severe Plastic Deformation

Compared to common metals, with a grain size of tens or hundreds of μm, Ultrafine Grained (UFG) metals, also known as nanocrystalline metals or nonmetals, have their grain size reduced mechanically to about 0.1-1 μm. This structural change affects many mechanical and physical prop- erties of metals. The effect of severe plastic deformation (SPD) during equal-channel angular pressing (ECAP) on grain refinement and strain hardening are studied and was attempted at room temperature to refine grain size of pure Al, Al-5083, and Al-1050. Mechanical properties and the deformation behavior of the ECAP processed material were investigated by the hardness . We can summarize that the increase in velocity (ram speed) on pure Al, Al-5083, and Al-1050 leads to decrease in hardness and an increase in temperature during the ECAP and thus given the opportunity to re-crystallization (geometric dynamic re-crystallization (GDR)) occurs.

Tomographic images constructed from small-angle X-ray scattering (SAXS) intensities utilizing microbeams have been examined for a model multilayered aluminum alloy sample heat-treated to form spatially modulated composition and microstructures. Spatial distributions of composition and precipitation microstructure have been examined by one-dimensional scanning SAXS measurements and two-dimensional tomographic images of attenuation parameters and integrated intensity of SAXS intensity. Reconstructed images using the integrated intensity reflected the distribution of precipitates in terms of their volume fraction over the sample inside the sample, and agreed with more detailed analysis made in the one-dimensional case.

The microstructural characterizations and partitioning of carbon element in the weld heat affected zones of a commercial API 5L X60 line pipe steel were studied by applying a high speed heating and cooling dilatometry technique in the present research work. The hollow cylindrical specimens were quickly heated to 1000°C, soaked for only 5 s followed by continuous cooling to ambient temperature. Besides the construction of CCT diagram of this high strength low alloy steel using the dilatation data, the hardening response, microstructural features and carbon partitioning of weld simulated specimens were investigated. The obtained results showed that the hardening response of samples increased from 142 to 261HV10kg with increasing cooling rates. These hardening variations were attributed to the changes in microstructural features and carbon partitioning that occurred between the microconstituents present in the microstructures of weld simulated samples.

Severe plastic deformation (SPD) induced by conventional forming processes such as extrusion has a significant effect on texture evolution and strength of metals. Conventional twist extrusion (TE) process can be used to produce ultra-fine grained (UFG) structures without introducing any significant change in the overall dimensions of the sample. However, the commercialization for industrial usage has been limited because of production efficiency and nonuniform distribution of grain refinements. In order to overcome these difficulties a new process called nonlinear twist extrusion (NLTE) has been introduced recently where TE mold channel is modified to restrain strain reversal and rigid body rotation of the workpiece. Prediction of the texture evolution in these processes is crucial for mold design and process parameters. In this work, the texture evolution during NLTE and TE processes are investigated through crystal plasticity finite element method. Single copper crystal which has a billet form is fully extruded through the TE and NLTE mold models separately. In addition to spatial stress and strain evolution investigations, the orientation differences and texture evolution of extruded billets are examined for two different initial orientations of single copper crystal. Moreover, the deformation histories at different locations of the sample are analyzed with crystal plasticity finite element method (CPFEM) to compare the performance of both techniques.

The paper presents the results of studies of tribological properties of the contact of the tool steel composition Fe-18W-4Cr-1,2V with the magnesium alloy AZ91D strengthened by submicron powder filling out of SiC and severe plastic deformation (SPD), namely equalchannel angular pressing (ECAP). It is stated that introduction of SiC powder filling to the magnesium alloy the friction coefficient on the moving frictional contact increases, the wear rate reduces. These tribotecnical characteristics are influenced by the size and volume of the particles of powder filling, normal loading force and slip rate. SPD of the initial material results in reduction of the adhesion constituent of the friction coefficient.

Al-2.5%Mg alloy (A5052) sheets were processed by accumulative roll bonding (ARB) for 1 to 7 cycles (equivalent strains from 0.8 to 5.6) at room temperature. The sheets processed by ARB for 7 cycles were then annealed isochronally for 30 min at temperatures in the range from 100°C to 400°C. Interestingly, it was found that the specimen annealed at 200°C followed by 7 cycles of ARB had the same level of yield stress (about 320 MPa) but a larger uniform elongation than the specimen processed by 3 cycles of ARB. The improvement in uniform elongation by low-temperature annealing is discussed in terms of the mechanism that the evolution of dislocation substructures inside ultra-fine grains causes plastic instability at a very early stage of the tensile test. Hardening by annealing was also observed in the specimen annealed at 100°C followed by 7 cycles of ARB.

Heterostructured materials are an emerging class of materials with superior performances that are unattainable by their conventional homogeneous counterparts. They consist of heterogeneous zones with dramatic ( > 100%) variations in mechanical and/or physical properties. The interaction in these hetero-zones produces a synergistic effect where the integrated property exceeds the prediction by the rule-of-mixtures. The heterostructured materials field explores heterostructures to control defect distributions, long-range internal stresses, and nonlinear inter-zone interactions for unprecedented performances. This paper is aimed to provide perspectives on this novel field, describe the state-of-the-art of heterostructured materials, and identify and discuss key issues that deserve additional studies. This paper delineates heterostructured materials, which are emerging as a new class of materials with unprecedented properties, new materials science and economic industrial production.

In the present work, effects of loading scheme and strain reversal on structure and hardness evolution have been studied by using high pressure torsion (HPT) and twist extrusion (TE) techniques. High purity aluminium (99.99%) was processed at room temperature up to a maximum total equivalent strain of ¾ max μ 8 by TE, and HPT in monotonic and reversal deformation modes with strain increment ¦¾ max = 1. Minimum subgrain sizes reached in this study were 1.6 µm for TE and 1.1 µm for HPT. It was revealed that microstructural change with straining was a common consequence of severe plastic deformation (SPD) processing and was not affected significantly by the loading scheme. Among the SPD methods used in this study, HPT in monotonic regime produced the smallest grain size, while the most homogeneous microstructure was obtained by TE due to specific vortex-like flow field imposed by the tool geometry.

A commercial purity aluminum was heavily deformed up to an equivalent strain of 4 at various temperatures and strain rates by torsion deformation to produce specimens with various ultrafine grained (UFG) microstructures. The microstructures were characterized by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The microstructural observation revealed that the torsion deformed specimens had various mean grain sizes ranging from 0.38 to 8.6 µm. The grain size and dislocation density in the microstructures depended on the deformation conditions organized by ZenerHollomon parameter. The mechanical properties of the torsion deformed specimens were investigated by tensile test at room temperature. It was found that the ultrafine grained specimens showed high strength which reached a value almost three times higher than that of the starting material. The strength of the UFG aluminum was higher than the level expected from the Hall Petch relationship for conventionally coarse grained aluminum. The strengthening mechanisms in the UFG aluminum were discussed in terms of substructures introduced during torsion deformation.

Most of severe plastic deformation processes involve strain reversal. Till now quite big number of researches has been done on indirect study of its role, which discusses the effect of loading path in ultra-fine grained structure formation. This work is aimed to study directly the role of the strain reversal in grain refinement by severe plastic deformation. A 99.99% purity aluminum was processed by high pressure torsion up to 96 • rotation (maximal equivalent strain ε ≈ 8) with two deformation modes: monotonic and reversal deformations with a step of 12 • rotation (maximal equivalent strain ε ≈ 1). It was shown that strain reversal retarded the grain refinement in comparison with the monotonic deformation. This explains slower rate of the nanostructure formation of the SPD processes that involve strain reversal.

Twist extrusion (TE) is known as one of newly developed, but still moderately studied severe plastic deformation methods. This research was initiated to conduct a detailed study of structure-properties relationship evolution during TE processing. The evolution of macrostructure, Vickers hardness and tensile properties was studied in 99.99% purity aluminum during twist extrusion processing at room temperature up to 4 TE passes (total average equivalent strain of ∼4.8). The process resulted in almost homogeneously refined structure that cannot be resolved optically. Significant increase in Vickers hardness, yield strength and ultimate tensile strength with moderate degradation in ductility of Al was observed. Apart from some structural inhomogeneity, all the mechanical properties were almost homogeneous and isotropic after four TE passes.

Cu-30 Zn (wt%) alloy is widely used for cartridge case. As received hot rolled (HR) cartridge brass is rolled about 15%, 30%, 40%, and 50% by plane strain rolling at normal room temperature in laboratory. The quantitative microstructure details such as mean grain size and grain size distribution are characterized by optical microscope equipped with microstructure analysis software. The developments of deformation texture are measured by X-ray texture Goniometer and analysis of texture details is done by LaboTex-Edu texture analysis software. The mean grain size is increased with rolling in rolling direction. The grain size distribution shows higher frequency for larger grains with deformation by rolling. The initial stages of rolling produce bi-modal grain size distribution. Later it shifts to multi-modality. The deformation strengthens Bs, L, R, Goss, Taylor, Cu and S texture components. Though the Cu texture orientation shows an increasing trend, the strength of Cu orientation is much less than that of Bs and S components. The transition of texture for Cu, S and Bs texture components is not found in this study.

We analyzed X-Ray diffraction data on the White Etching Layer (WEL) excised from the surface of a railway track and WEL-like structures obtained by high pressure torsion of the same steel as the rail was made. Data analysis was performed by the whole-pattern fitting method. The railway WEL shows a clear asymmetry of the diffraction lines, which can be attributed to either tetragonal martensite structure or to the formation of a ferrite nanophase with a lattice parameters larger than that of the raw material. X-Ray patterns of the natural WEL were fitted with the two models. The quality of the fit clearly favors the model with two cubic phases over the model with a single tetragonal phase. Artificial WEL samples could be fitted with a single cubic phase model. Several alternative methods were simultaneously used to extract information on crystallite size and internal stress. The analysis of the natural WEL shows that the secondary cubic nanophase is formed of the crystallites of the average size of 8 nm essentially free of any strain. The lattice parameter 0.2881nm corresponds to the 0.26 wt.% concentration of the dissolved carbon. In the artificial WEL samples the crystallite size decreases down to 9 nm at the maximum shear stress of 430, while the internal strain gradually increases. There is however no change of the lattice parameter. This means that no carbon from cementite dissolves in the lattice of ferrite. It must therefore be located in the grain boundaries and dislocation cores. We conclude that the high pressure torsion produces a WEL with a different distribution of carbon than in the natural process of the WEL formation. It involves an immediate severe deformation the sample while natural process takes numerous subsequent cycles of modest deformation with simultaneous local heating of the deformation area. Such a process may lead to the gradual diffusion of the carbon atoms from the grain boundaries into the crystal lattice of ferrite.

One method of metal welding is a solid-state incorporation process, namely friction stir welding (FSW). This technique can be used on materials that are difficult to weld with fusion welding processes. Among the benefits of FSW are reducing distortion, eliminating solidification, saving energy and being environmentally friendly. This research investigates the effect of three different transverse speeds at 1.2, 2.4 and 3.6 (mm / s) on the hardness, tensile and micro structure properties of friction stir welds of AA6061-T651 plates. The research result find that the micro hardness and strength increase when the transverse speeds are increase. The micro structure showed that the grain size more smaller by increase the transverse speeds.

Copper is one of the most important materials used for electrical connectors with a high thermal and electricial conductivity, and there is an ongoing demand to improve its mechanical properties without sacrificing other beneficial properties. A possible approach to achieving this aim is to use the method of severe plastic deformation to obtain an ultrafine grained microstructure. Significant grain refinement obtained by equal channel angular pressing (ECAP) leads to an improvement of mechanical, microstructural and physical properties. This paper gives an overview of a range of the properties that can be achieved by ECAP processing of pure copper including microstructural features, thermal stability, thermal conductivity and corrosion resistance.

We report the results of measurements of the grain size distribution function and the thermal conductivity of ultrafine-grained copper produced by equal channel angular pressing (ECAP), with special attention to the evolution of these quantities with the number of pressing cycles. To explain the experimental findings, the equilibrium grain size distribution function (GSDF) evolving during ECAP has been calculated on the basis of a simplified theoretical model. The model involves a single unknown physical parameter -the most probable grain size. With this parameter fitted to the experimental data the calculated GSDF fairly closely reproduces the experimental data. A model for thermal conductivity of ECAP processed copper has been proposed, which relates thermal conductivity to the GSDF parameters to the coefficient of electron reflection at grain boundaries.

Multiple extrusion of Al-4Mg-1Zr (wt.%) is presented as a severe plastic deformation technique to develop an ultra-fine grained material, using rapidly solidified needles as a feedstock. After each extrusion pass the microstructure is refined, the primary Al 3 Zr precipitates are broken down and <50-nm-scale cubic Al 3 Zr are precipitated from solution. Recovery dominates the initial passes with recrystallisation becoming dominant during later passes, but the grains remain at the sub-m scale. Interestingly, the yield stress and the ultimate strength increased significantly after the first pass, and then decreasedany strength increment gained from the grain refinement was offset by coarsening of the metastable nano-scale Al 3 Zr dispersoids.

The microstructure evolution of Cu-n anostructured powders versus the ball milling conditions was investigated using X-ray diffraction an alysis. The characteristics of as-milled Cu powder microstructure in terms of crystallite size, dislocations and twin boundary densities were determined by fitting the simulated X-ray diffraction peak profiles to the experimental ones in order to establish a correlation between the powder microstructure and the ball milling parameters. It was shown that the simulated X-ray diffraction peak profiles agree satisfactorily with the experimental ones taking into account transmission electronic microscopy observations where twin boundaries and dislocations were observed.

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Equal channel angular drawing (ECAD) represents the most successful severe plastic deformation (SPD) technique for continuous industrial manufacturing of longer wires, with a constant cross section, characterized by smaller diameters and better mechanical properties (i.e. high strains and hardness) mainly attributed to the grain size refinement. In this paper an advanced innovative concept to impose SPD, on commercial 1370 pure aluminium wires (Al 99.7%), is proposed to improve the flexibility of the classic manufacturing method of ECAD by controlling and regulating process parameters in real time to obtain several combinations of mechanical properties and to increase manufacture productivity. This paper provides a preliminary analysis of mechanical and microstructural changes occurring during ECAD process and, preserving the principle of the ECAD method, describes an innovative concept of plastic deformation showing the potential improvements to practice. The proposed manufacturing...

Equal channel angular drawing (ECAD) represents the most successful severe plastic deformation (SPD) technique for continuous industrial manufacturing of longer wires, with a constant cross-section, characterized by smaller diameters and better mechanical properties (i.e. high strain and hardness) mainly due to the grain size refinement. In this paper an advanced innovative concept to impose SPD, on commercial 1370 pure aluminium wires (Al 99.7%), is proposed to improve the flexibility of the classic manufacturing method of ECAD by controlling and regulating process parameters in real time, obtaining several combinations of mechanical properties and increasing productivity. This paper provides an analysis of mechanical and microstructural changes occurring during ECAD process and, preserving the principles of the ECAD method, describes an innovative concept of plastic deformation showing the potential improvements to practice. The proposed manufacturing system has been validated in ...

Kinetics of ␤Љ precipitation in an Al-0.55 pct Mg-1.1 wt pct Si (AA6022) in both deformed and undeformed conditions were investigated by means of differential scanning calorimetry (DSC). Transmission electron microscopy (TEM) analysis on predeformed samples was also performed to study the effect of deformation on ␤Љ precipitates. It was found that the introduction of dislocations changes the precipitate type from ␤Љ to ␤Ј and QЈ. Also the measured activation energy for precipitate formation in the case of predeformed and undeformed samples was compared. The results show that dislocations facilitate precipitation by decreasing the activation energy.

This article presents a new method of obtaining bars from aluminum alloys D16 with ultrafine-grained (UFG) structure. The ultrafine-grained structure is obtained by implementing severe plastic deformation developed by a radialshear mill (RSM). This paper investigates the stress-strain state (SSS) of the workpiece during rolling in a radial-shear mill. The (FEM) and the MSC Super Forge program allowed us to obtain quantitative data and establish the main laws of the distribution of SSS and temperature while modeling the rolling in the RSM. The rational technology of rolling aluminum alloy D16 was developed and tested in laboratory conditions. Particular attention is paid to the analysis of the effect of rolling conditions in the RSM on the formation of UFG structures in the aluminum alloy D16.

Highlights • AlTiNbZrTa RHEAs were prepared via casting and thermomechanical treatments • The RHEAs showed the remarkable specific YS and ductility up to 873 K • Solid solution, second phases, dislocation, and grain refinement rise the strength • Solute segregation is observed within the RHEA after thermomechanical treatment

The photosynthetic light-harvesting complex II of plants, known as LHCII, possesses an excellent ability to harvest solar energy and transfer the excitation energy to the photosynthetic reaction centre with near-unity quantum efficiency. In addition to light-harvesting, LHCII plays a photoprotective role under high-light intensities. The nature of the energy transfer dynamics and the underlying photoprotective mechanisms in LHCII are subjects of intense research. Unfortunately, individual LHCII complexes suffer from low intrinsic fluorescence and poor stability at high illumination intensity, which limits the amount of information that can be retrieved. I will show that chemically synthesized gold nanorods can enhance the fluorescence brightness of individual LHCII complexes by two orders of magnitude and simultaneously decrease the fluorescence lifetime of the complexes by two orders of magnitude.

Ключови думи: напрежения, армировка, корозия, утилизационно използване РЕЗЮМЕ При възстановяване и усилване на сгради и съоръжения се налага използване на армировъчната стомана със силно изразена корозия от атмосферно влияние и/или импулсни натоварвания. Корозията намалява механичните свойства по два основни начина: намаляване на площта на сечението и увеличаване на дефектите по повърхността. В доклада е изследвано влиянието на 18-годишен корозионен процес върху армировъчна стомана Ø6,5 (A-I) при атмосферни условия от обект в София. Представени са експериментално получени данни и са анализирани възможностите за възстановяване и усилване на сгради и съоръжения.

An ultra-low carbon IF steel was heavily deformed up to an equivalent strain of 36 at various high temperatures of ferrite single-phase region and various strain rates. Effects of temperature and strain rate on the microstructures evolved in torsion deformation were clarified. On the other hand, it was found that homogeneous ultrafine grained structures were not obtained by the present torsion deformation though very high strain was applied. The coarser grain sizes than those obtained by conventional severe plastic deformation (like ARB) were due to the deformation at higher temperature and lower strain rate, but lower fraction of high-angle grain boundaries in the torsion specimen was suggested to be attributed to the characteristics of monotonic torsion (or simple shear) deformation including the way of strain evaluation.

Ͻ0)。ここで，a は定数，m は剛性率，b はバーガース・ベ 8 金属材料の超強加工に伴う超微細粒組織の形成 辻 伸泰 * Formation Mechanisms of Ultrafine Grained Structures in Severe Plastic Deformation of Metallic Materials Nobuhiro TSUJI Synopsis : Formation mechanisms of ultrafine grained structures in severe plastic deformation (SPD) of metallic materials are overviewed and discussed on the basis of experimental results. It is concluded that the formation of ultrafine grained structures in SPD can be understood in terms of grain subdivision. The ultrafine grained structures in the as-SPD materials are essentially deformation structures, although they can be simultaneously considered as grain structures from a viewpoint of large misorentation to each other. When the SPD processed materials are annealed, a continuous change in microstructures can happen, which might be called continuous recrystallization. The phenomenon is fundamentally discussed after determining the nucleation events in recrystallization.

The objective of the study is to evaluate the effects of severe plastic deformation (SPD) and annealing on creep behaviour of advanced tungsten modified creep-resistant 9 % Cr martensitic P92 steel. The as-received P92 steel was deformed by high-pressure torsion (HTP), high-pressure sliding (HPS) and rotary swaging (RS) at room temperature prior creep testing. These SPD methods imposed significantly different equivalent plastic strain in the range from 1 up to 20. Constant load creep tests in tension were performed in an argon atmosphere at 873 K and applied stress ranging from 50 to 200 MPa. The microstructure and phase composition of P92 steel were studied using a scanning electron microscope Tescan Lyra 3 and a transmission electron microscope Jeol 2100F. The results show that under the same creep loading conditions the HPT and HPS-processed P92 steel exhibited significantly faster minimum creep rates, creep fracture strain and the decrease in the value of the stress exponent of the creep rate in comparison with as-received P92 steel. However, it was revealed that the RS-processed specimens exhibited one order of magnitude lower minimum creep rate and lower ductility compared to commercial P92 steel. The creep curves for the HPT and HPS-processed states exhibited a pronounced minimum of strain rate. The pronounced minimum of strain rate disappeared when these states were annealed at 923K/500h before application of creep loading. The microstructure changes occurring during creep and different creep behaviour between as-received and deformed states are discussed.

The paper is dedicated to Professor Terence G. Langdon on his 80th Birthday Creep testing is conducted on an advanced martensitic-ferritic creep-resistant P92 steel (ASME Grade 92) to evaluate the effects of grain refinement and the predeformation impact after processing by severe plastic deformation (SPD), namely, by high-pressure torsion and high-pressure sliding. Constant-load tensile creep tests are carried out in an argon atmosphere at 600 C and under an applied stress ranging from 50 to 200 MPa. The results show that under the same creep loading conditions, the ultrafine-grained (UFG) microstructure states after SPD processing exhibit higher minimum creep rate εm and creep fracture plasticity ε f , but significantly shorter creep lives in comparison with the coarse-grained (as-received) state of the steel. These distinct differences between the coarsegrained and UFG states are explained by the different deformation mechanisms that operate; creep behavior in a coarse-grained state is controlled by the intragranular climb of dislocations, while creep in UFG states can be interpreted as the synergistic action of the dynamic recovery of free dislocations at high-angle grain boundaries and grain boundary-mediated deformation processes.

This study explores the effect of preheating before rolling on the microstructural and mechanical properties of an AA5052/Ti/AA5052 lamellar composite fabricated by roll bonding. The roll bonding was done in two ways: conventional rolling and preheating before rolling. Preheating was done before rolling for 7 min at 350 • C. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), microhardness, and tensile tests were used for microstructural and mechanical investigations. By performing preheating, the strength increased from 468 MPa to 511 MPa, elongation changes were insignificant, and hardness decreased in aluminum and titanium layers from 108 to 100 HV and 234 to 212 HV, respectively. By preheating, aluminum diffusion in titanium and metallurgical connection occurred. Therefore, SEM showed better bonding in preheated specimens.

Stainless steel 316L is widely used in medical applications. A ISI 316L has good mechanical properties, good corrosion resistance and easy fabrication. On the other hand, 316L should be upgraded its surface mechanical properties fo r implantable materials. One o f the treatment used is shot peening. shot peening can increase surface hardness in the presence o f micro structure changes. These changes are due to plastic deformation and residual stress. This study discusses the effect o f shooting time duration o f 2, 4, 10, 20, and 30 against the micro structure and surface hardness. The steel balls used are 0.6mm in diameter and 40-50 H RC hardness with 8 bar pressure during shooting. the results o f surface hardness on the duration o f 2

This paper presents a current research trend for micro-and nano-structure controls using severe plastic deformation (SPD). The survey is carried out based on the special issue published in July and August, 2019, in Materials Transactions (Vol. 60, Nos. 7 and 8). The SPD-related research is rapidly growing particularly after the year 2000. The research ranges over processing, modeling, simulation, synthesis, characterization and evaluation. Among the various topics, a brief introduction is given for innovative approaches which will further promote the development of the SPD-related research.

Anatase TiO 2 was severely deformed using high-pressure torsion and the effect of plastic strain and grain size on phase transformations was investigated. A high-pressure TiO 2 -II phase (columbite) with the orthorhombic structure was formed under pressures of 1 and 6 GPa. Fraction of TiO 2 -II increased with increasing the plastic strain and remained stable at ambient pressure. Microstructural analysis showed that TiO 2 -II was stabilized in grains with sizes less than ~15 nm because of high energy barrier for reverse phase transformation, while larger grains had the anatase structure. Large densities of oxygen vacancies and dislocations were also formed after severe plastic deformation.

Severe plastic deformation using high-pressure torsion (HPT) is successfully applied at room temperature to partially stabilized ZrO 2 . X-ray diffraction and Raman spectroscopy analyses reveal that appreciable strain is introduced in the sample and a phase transformation with a coherent interface occurs from the metastable tetragonal phase to the monoclinic phase during HPT. The fraction of the stress-induced monoclinic phase increases with straining, reaches a saturation level. Transmission electron microscopy shows that nanograins of high dislocation density but with no twins are formed during HPT.

The mechanical characteristics of polycrystalline metallic materials are influenced significantly by various microstructural parameters, one of which is the grain size. Specifically, the strength and the toughness of polycrystalline metals exhibit enhancement as the grain size is reduced. Applying severe plastic deformations (SPDs) has a noticeable result in obtaining metallic materials with ultrafine-grained (UFG) microstructure. SPD, executed through conventional shaping methods like extrusion, plays a pivotal role in the evolution of the texture, which is closely related to the plastic behavior and ductility. A number of SPD processes have been developed to generate ultrafine-grained materials, each having a different shear deformation mechanism. Among these methods, linear twist extrusion (LTE) presents a non-uniform and non-monotonic form of severe plastic deformation, leading to significant shifts in the microstructure. Prior research demonstrates the capability of the LTE process to yield consistent, weak textures in pre-textured copper. However, limitations in production efficiency and the uneven distribution of grain refinement have curbed the widespread use of LTE in industrial settings. This has facilitated the development of an improved novel method, that surpasses the traditional approach, known as the nonlinear twist extrusion procedure (NLTE). The NLTE method innovatively adjusts the channel design of the mold within the twist section to mitigate strain reversal and the rotational movement of the workpiece, both of which have been identified as shortcomings of twist extrusion. Accurate anticipation of texture changes in SPD processes is essential for mold design and process parameter optimization. The performance of the proposed extrusion technique should still be studied. In this context, here, a single crystal (SC) of copper in billet form, passing through both LTE and NLTE, is analyzed, employing a rate-dependent crystal plasticity finite element (CPFE) framework. CPFE simulations were performed for both LTE and NLTE of SC copper specimens having <100> or <111> directions parallel to the extrusion direction initially. The texture evolution as well as the cross-sectional distribution of the stress and strain is studied in detail, and the performance of both processes is compared.

The process of nanocrystalline structure formation during mechanical milling was studied in Cu powders. A detailed microstructural study of powder samples was carried out by X-ray diffraction experiments as a function of milling time. As a result, nanosized powders have been synthesized with microstructures showing a significant decrease of the coherent diffraction domains and the creation of a large number of linear defects, which induce microstrains. SEM results show that welding of very small particles to the surfaces of larger particles occurred and that the powder particles tended to form a matrix of randomly welded thin layers of highly deformed particles.

Magnesium is a promising material for solid state hydrogen storage, since it has low cost and its hydride can store reversibly up to 7.6 wt.% of hydrogen. Fast H-sorption kinetics at around 300 • C can be achieved after processing Mg-based mixtures by high energy ball milling (HEBM), which produces nanostructured composite powders. Severe plastic deformation (SPD) processing techniques are being explored as an alternative to HEBM in order to obtain more air-resistant materials and to reduce the time and energy required for processing. In this paper, MgH 2 and MgH 2 -Fe mixtures were severely mechanically processed by extensive cold forging (CF) and cold rolling (CR). A very significant grain refinement (up to 10 nm) was achieved, which is comparable to the values typically obtained after processing by HEBM. Enhanced H-sorption properties were observed for these mechanically processed MgH 2 -based nanocomposites in comparison with commercial magnesium hydride. The obtained compacts after CR and CF presents a much lower specific surface area than the ball-milled powders and therefore show higher air-resistance. These results are promising from the point of view of applications since it reveals the potential of the use of low cost mechanical processing routes to produce Mg-based nanomaterials for hydrogen storage.

Prediction of the deformation characteristics is an important step to understand the workability of alloys during imposing large strains. In this research, severe plastic deformation of Sn-5Sb solder alloy was carried out under different t deformation conditions, including the temperature range of 298, 330, 36, 400 K and die designs. The current study applies an experimentally validated finite element method (FEM) to establish a model for predicting workability in equal channel angular pressing (ECAP). To do this object, two ECAP dies were prepared with channel angle of 90 and the outer corner angle of 30O with and without choked angle in outlet channel. Angularly pressed Sn-5Sb solder alloy were utilized for validating the proposed FEM model. Different parameters such as die angles (angle between the channels and the outer corner angle), pressing temperature and the die outlet channel geometry were studied using FEM simulation. In conclusion, experimentally verified numerical data ...

Localized plastic deformation and hardening was studied in laser shock peened (LSP) Inconel 718 SPF (Super plastic forming), a fine grained Ni-Base superalloy, using electron backscatter diffraction (EBSD), nanoindentation, and micro pillar compression testing. 718SPF samples were LSP-treated with two different laser power densities. After LSP, the plastic deformation is manifested as increase in the fraction of low angle misorientations and the formation of sub-grain boundaries. EBSD was used to study plastic deformation as a function of distance from the peened surface for different laser intensities. Different approaches like image quality mapping and local misorientations analysis were used to study the in-depth distribution of the plastic strain. Results show that EBSD is effective in the qualitative characterization of localized plastic strain of the materials subjected to LSP.

Enhancing the strength of materials is of great concern in that the failures such as wear, corrosion and fatigue occur on the surface. A tantalum (Ta), which is a refractory metal, was subjected to severe plastic deformation induced by ultrasonic nanocrystalline surface modification (UNSM) technique at room-and high-temperatures of 200 0 C and 800 0 C. The mechanical properties and wear resistance of Ta before and after UNSM treatment were characterized by X-ray diffraction (XRD), hardness tester, and ball-on-disk tribometer, respectively. The UNSM treatment at 800 0 C led to the intensity reduction and broadening, and the diffraction peaks were shifted to lower angles, which means the presence of compressive residual stress and grain size refinement. The hardness of the UNSM-treated sample at room temperature was higher than that of the untreated one, and it was further increased with increasing the UNSM treatment temperature. In addition, the effect of UNSM treatment at hightemperature on wear resistance was significant than that of the UNSM treatment at roomtemperature. We demonstrate the possibility of further increasing the mechanical properties and wear resistance of Ta by UNSM treatment at high-temperatures in comparison with the untreated and UNSM-treatment at room temperature, which would be beneficial for applications of Ta.

Particles of commercially pure Al are successfully consolidated at 200 °C by a novel method named equal channel angular pressing-forward extrusion (ECAP-FE). Using this method, both ECAP and forward extrusion processes are carried out subsequently in a single tool. The extrusion process exerts a back pressure for ECAP process which prevents surface cracking and improves microstructure and mechanical properties of the produced material. The improvement is related to the shear deformation induced during ECAP and the increase in self-diffusion coefficient of Al due to the exerted back pressure.

Introduction and Objectives: Determining the constitutive equations which describe the material flow stress, microstructural investigation, and preparing a processing map are essential for designing and optimizing metals forming. The aim of this paper is to obtain a relationship between stress, strain, temperature, and strain rate for Al-7.5Mg alloy in order to use it in the forming process.
Materials and Methods: In this study, stress-strain diagrams at four temperatures and three strain rates and friction elimination using experimental and computational methods were used. The activation energy value of hot deformation was calculated in the Arrhenius model. A processing map at strain 0.6 was drawn to establish the relationship between stress, temperature, and strain rate, and the instability region at a specific temperature and strain rate was determined. The metallography examination was performed to study the microstructure of the alloy.
Results: In the Arrhenius model, the activation energy value of hot deformation increased with increasing strain. As the temperature decreased and the strain rate increased, the Zener-Hollomon parameter also increased. The instability region increased with increasing temperature and decreasing strain rate. The metallography test results showed that dynamic recrystallization occurred due to the high magnesium content in this alloy.
Conclusion: In this paper, the Arrhenius model (as a phenomenological model) was correctly extracted using a hot plane strain test on an extruded plate of Al-7.5Mg alloy, and a relationship between stress, temperature, strain, and strain rate was obtained using the constitutive equations and the Arrhenius model.

Simultaneous effect of pressure, temperature and plastic strain on structural evolution of titania ceramic nanopowder was investigated using the high-pressure torsion (HPT) method. Unlike static annealing, in which the anatase-to-rutile phase transformation occurred at 1173 K, the transformation was observed at low temperatures as 473-573 K by HPT processing. The formation of rutile phase accompanied with dynamic recrystallization and an unusual grain growth, indicating that severe plastic deformation at low homologous temperatures does not necessarily result in grain refinement of metastable nanoceramics. Besides the coarsened grains of rutile phase, a high-pressure TiO 2 -II columbite phase was also detected in small nanograins.