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Commercial purity titanium (cp-Ti) is considered for replacing Ti64 as an implant material in various applications, due to the potential toxicity associated with the release of Al and V ions. However, the mechanical properties of cp-Ti, particularly fatigue resistance, are inadequate for this purpose. In this study, cp-Ti grade 4 rods were processed using a combination of equal channel angular pressing and rotary swaging (ECAP/RS). Tensile and fatigue tests were conducted, along with detailed microscopy and evaluation of corrosion resistance and biocompatibility. An average yield strength of 1383 MPa was obtained while maintaining moderate ductility of 10 %. This represents the highest strength ever recorded for cp-Ti, even exceeding that of Ti64. Additionally, fatigue endurance limit increased by 43 % up to 600 MPa, almost obtaining that of Ti64. Strengthening mechanisms were attributed to the ultrafine-grained (UFG) microstructure generated by ECAP/RS, along with strong crystallographic texture and formation of sub-grain structure. Furthermore, the corrosion resistance and biocompatibility of cp-Ti were largely unaffected, potentially easing regulatory transition in future medical devices. Thus, these results demonstrate high potential of combined ECAP/RS processing to manufacture UFG cpTi grade 4 materials that prospectively allow for the substitution of questionable alloys and downsizing of medical implants.

5xxx series aluminum alloys are widely used due to their corrosion resistance and weldability. These alloys exhibit interesting behavior when subjected to severe plastic deformation (SPD). Different SPD techniques allow the processing of materials in sheet forms, such as Repetitive Corrugating and Straightening (RCS) and Cumulative Roll Bonding (ARB). In this work, sheets of the aluminum 5083 alloy were processed by RCS up to 2 passes. The objective was to study the microstructural evolution of the AA5083 under heat treatment and plastic deformation processes, with the aim of finding a good balance between the yield strength and ductility. The microstructure changes and the mechanical effects of the process were studied by X-ray diffraction, Inverse Pole Figures, EBSD, and tensile test. The results showed the obtention of characteristic recrystallization and deformation textures (cube and brass component); in particular, the brass component decreased to ~10 % due to the RCS process. The first RCS pass obtained the best balance between yield strength-ductility (sy = 170 MPa and maximum elongation ~ 8%). With the results obtained, it was concluded that the microstructure and the mechanical properties of the processes alloy were determined by the accumulative dislocations density, which stopped the cube texture progression, microstructure stabilizing the microstructure, regardless of the work hardening., Peer Reviewed, Objectius de Desenvolupament Sostenible::12 - Producció i Consum Responsables, Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura, Postprint (published version)

Extensive research on severe plastic deformation (SPD) of metallic materials has been performed so far in order to improve mechanical properties, both at low and high temperatures. As a result of the extensive grain refinement obtained, increased superplastic behaviour has been attained at higher strains rates and lower temperatures than usual. This is due to finer grain sizes and higher average misorientations obtained, which enhance grain boundary sliding (GBS). However, the misorientation effect on superplasticity, and the prediction of misorientation evolution during SPD has remained so far, qualitative. In this research, especial attention has been given to the quantitative misorientation evolution with increasing equal channel angular pressing (ECAP) deformation, in order to propose an expression useful to describe and predict the influence of the different processing parameters on the misorientation evolution with strain. This is exemplified for ECAPed Al-Zn-Mg-Cu and other aluminium alloys, and it could serve as a basis for predicting the misorientation evolution, and its influence on superplasticity, of other SPD processes and metallic alloys.

Machinery components used in demanding applications are required to transmit or carry mechanical loads under severe loading conditions. They are subjected to cyclic loading and repeated sliding contact that in many cases result in a premature failure of components. Cyclic loading cause mechanical fatigue failure, while repeated sliding contact cause wear damage at the surface of components that can initiate crack nucleation and propagation under cyclic load. Wear and fatigue are the most common failure modes occurring in machinery components, and a synergetic effect of these two mechanisms accelerates component failure and reduces its service life. Understanding failure mechanisms and understanding the synergetic effect of wear and fatigue in relation to the components are therefore of high importance. In the present study, a detailed failure analysis was conducted on rock drilling components used under severe working conditions. Rock drill thread joints failed in the field application and cold-work punches working against advanced high-strength steels were investigated. Repeated laboratory sliding wear tests under high contact stresses have been performed on a number of high-strength metal alloys frequently used in demanding applications. A slider on flat surface SOFS tribo-tester and a three-point bending fatigue tester were used to simulate the wear and fatigue found in demanding applications. In particular, the influence of wear on the fatigue life of a high-strength steel was investigated. Surface analysis techniques were employed using instruments as 3D profile optical interferometer, scanning electron microscope, scanning transmission electron microscope, light optical microscope and X-ray diffractometer, to investigate the wear damage on the worn specimens, and to study fracture mechanisms of the failed specimens. The study describes the dominant failure modes of the present components when subjected to severe loading conditions. Further, the results explain, Machinery components used in demanding applications where severe contact conditions results in premature component failure. Wear and fatigue are considered as the most common failure mechanisms for such components. In general, the service life of a component is estimated based on its fatigue strength. However, wear might also have a significant effect on the component’s life too. Sliding wear results in surface damages that can be critical for metal alloys when subjected to cyclic stresses. Therefore, knowledge about sliding wear of metal alloys is a key factor in component designing. In addition, understanding the influence of sliding wear on fatigue life of metals will help to predict the component’s service life. The present study was focused on wear mechanisms of high-strength steels and ductile cast irons occurred under repeated sliding contact. Further, this study investigated the influence of wear on fatigue performance of a high-strength steel when subjected to cyclic bending.

The microstructure of Mo was significantly refined by high pressure torsion to verify its irradiation tolerance in comparison with its micrograined counterpart. After deformation microhardness increased from 231 Hv0.2 for a microgarined sample to 542 and 558 Hv0.2, respectively after one and five rotations. Concurrently, the grain refinement was observed, as the grain size decreased with the increase of the deformation degree down to 480 and 110 nm, respectively for one and five rotations. Subsequently, deformed Mo and a micrograined one were irradiated by He ions to the dose of 8 x 1016/cm 2 to verify their potential application as fusion mirrors. Irra-diations were followed by reflectivity measurements in the 300-2400 nm range with a dual beam spectrometer. The measurements revealed that the applied dose causes a decrease in total reflectivity of the micrograined sample, whereas the total reflectivity of deformed samples decreases by additional 2.5%. Nanohardness mea-surements, detailed microscopy observations using focused ion beam and scanning transmission electron mi-croscope as well as positron annihilation spectroscopy investigations were performed to elucidate changes in the microstructure and understand the different mechanisms of bubble creation after irradiation in micrograined and high pressure torsion processed samples., QC 20221122

Commercially pure copper rod was successfully subjected to severe plastic deformation by applying the continuous equal channel angular pressing (ECAP-Conform) method at room temperature. Microstructural characterizations of copper rod samples at various stages of plastic deformation were carried out by optical microscopy and electron backscatter diffraction methods. X-ray diffractometry and Kernal average misorientation were used for dislocation density estimations. Microstructural evaluations revealed grain size change of 30 mm for the initial annealed copper rod to less than 5 mm and even 100 nm for severely deformed samples. Mechanical behaviors of samples after different deformation stages were characterized using tensile and hardness tests. The ultimate tensile strength of the severely deformed copper rod was increased threefold by ECAP-Conform while elongation halved in comparison to the initial annealed copper. Low-temperature annealing of severely plastic deformed samples led to bi-modal grain size distribution and lowering of strength accompanied by the increase of elongation. Tensile properties of severely deformed and then annealed copper samples showed around a 40% increase in both ultimate tensile strength and elongation in comparison to the initial annealed copper rod.

In this work, the precipitation and the morphology of secondary phases after severe plastic deformation (SPD) processing followed by an isothermal treatment was investigated. High-pressure torsion (HPT) was the SPD process carried out on superduplex 2507 (UNS S32750) stainless steel material under P = 6 GPa at room temperature. At this high strain levels (e up to 170) samples have shown grain size decrease and strained microstructure with high dislocation density and nanostructure features. After a short isothermal treatment at 830 °C, the sigma phase and chromium nitrides were revealed as the main secondary phases identified by scanning and transmission electron microscopy and element analysis by energy dispersive spectroscopy. Scanning precession electron diffraction and automated crystal orientation mapping have been carried out in order to confirm the precipitation of the secondary phases. In fact, the results provide evidence that the precipitation of chromium nitrides seems to be the preferred nucleation site for sigma phase at higher deformation strain, in addition to the intergranular precipitation of sigma. Both the sigma phases nucleated integranularly and besides chromium nitrides are randomly orientated., Peer Reviewed, Postprint (author's final draft)

The transportation industry is constantly seeking methods to save weight in their products and thereby improve fuel efficiency. The high specific strength and stiffness of magnesium alloys make them an attractive option; however, their poor overall strength and formability hinder the adoption of magnesium on a larger scale. One solution to improving strength is grain refinement, which has allowed magnesium strengths to reach levels not previously seen, however, maintaining the fine grain sizes and resulting strength is difficult as magnesium exhibits poor thermal stability against grain growth at low homologous temperatures. Other mechanisms of strengthening include inclusion of nano-spaced planar defects, the introduction of fine precipitates or particulates, and texture control among others. All of these efforts to strengthen magnesium are typically accompanied by a drop in low-temperature uniform plasticity, which in most magnesium alloys is limited to begin with. This dissertation examines three different Mg alloy systems whose processing-structure-property combinations seek to minimize the aforementioned trade-offs. vi Some remaining knowledge on the ability to strengthen Mg alloys via nano-spaced planar defects was unraveled, and the contribution of texturing was ruled out. This research has also successfully strengthened Mg alloys via various processing approaches and resulting strengthening mechanisms while considering emerging understandings on the role of grain size in the micrometer and sub-micrometer regimes, and contributions of particulates to enhanced stability against grain grow and elevated temperature conditions. These finding may contribute to the design of high-strength Mg alloys and processing methods that increase the design space for their use in transportation and other applications.

Scientific innovation is often driven by novel processing capabilities, which enable the production of materials with new and exciting properties. A number of techniques referred to as severe plastic deformation (SPD) have recently been established, which utilize unprecedented extreme strain conditions to create advanced materials. Such processing has the potential to provide materials solutions to current technological issues humanity faces in areas such as energy, transportation, sustainability, and public health. Additionally, these processes enable exploration of complex microstructures to better understand fundamental relationships between processing, structure, properties, and performance.The SPD literature consists of many studies reporting the structures and properties garnered from a wide variety of techniques, material systems, and processing conditions. In some cases, reports may be at odds with each other or with expected material behavior, as has been the case for wear resistance and electrical conductivity. For both properties, specific strain-based characterization can improve comparison across the literature to better understand trends and highlight outlier reports in the established literature. For some processes, strain-based investigations may not even be reported, so novel characterization or analysis methods are necessary to enable such comparison across the SPD literature. In this dissertation, results from experiments on copper subjected to high-pressure processing has been compared to reports from the literature to identify trends in wear resistance and electrical conductivity across SPD techniques. To accomplish this, novel strain-based analysis and measurement methods have been put forth for the process of high-pressure torsion. These frameworks of strain-based analysis enabled trends to be drawn from comparison with the SPD literature. Identifying such trends for wear and conductivity across the SPD literature has helped to distinguish out

Metal additive manufacturing stands poised to disrupt multiple industries with high material use efficiency and complex part production capabilities, however many technologies deposit material with sub-optimal properties, limiting their use. This decrease in performance largely stems from porosity laden parts, and asymmetric solidification-based microstructures. Solid-state additive manufacturing techniques bypass these flaws, using deformation and diffusion phenomena to bond material together layer by layer. Among these techniques, Additive Friction Stir Deposition (AFSD), stands out as unique for its freeform nature, and thermomechanical conditions during material processing. Leveraging its solid-state behavior, optimized microstructures produced by AFSD can reach performance levels near, at, or even above traditionally prepared metals. A strong understanding of the material conditions during AFSD and the phenomena responsible for microstructure evolution. Here we discuss two works aimed at improving the state of knowledge surrounding AFSD, promoting future microstructure optimization. First, a parametric study is performed, finding a wide array of producible microstructures across two material systems. In the second work, a stop-action type experiment is employed to observe the dynamic microstructure evolution across the AFSD material flow pathway, finding specific thermomechanical regimes that occur within. Finally, multiple conventional alloy systems are discussed as their microstructure evolution pertains to AFSD, as well as some more unique systems previously limited to small lab scale techniques, but now producible in bulk due to the additive nature of AFSD.

The micro-injection upsetting (MIU) experiments of commercially pure aluminium have been conducted on two groups of specimens with different grain structures. One group is of coarse grain (CG, undeformed) and the other group is of fine grain (FG) achieved via the 4th pass equal channel angular pressing in micro-meso/scale. The two groups were further processed by micro/meso-scale extrusion before conducting MIU for fabricating tiny pins. Micro-upsetting test of the tiny pins showed that the material has a good isotropic flow forming and is free of undesirable defects comparing with the CG counterparts, which can be ascribed to the decreasing of grain boundary strengthening effect in the case of FG structure.

Serious issues including solidification porosity, columnar grains, and large grain sizes are common during fusion-based metal additive manufacturing due to the inherent melting and solidification that occurs during printing. In recent years, a high-temperature, rapid plastic deformation technique called additive friction stir deposition (AFSD) has shown great promise in overcoming these issues. Because the deposited material stays in the solid state during printing, there are no melting and solidification events and the process can result in as-printed material that is fully-dense with equiaxed, fine grains. As AFSD is an emerging process, developing an understanding of the synergy between material deformation and the resultant microstructure evolution, especially the strain magnitude, its influence on dynamic microstructure evolution, and material flow details, is imperative for the full implementation of AFSD. Therefore, the purpose of this work is to investigate the severe plastic deformation in AFSD through complementary studies on the concurrent evolution of shape and microstructure during the deposition of dissimilar aluminum alloys. In this work, we systematically study (1) the entire deposition via dissimilar cladding along with (2) specific volumes within the deposited layer via embedded tracers printed at varied processing parameters. X-ray computed tomography and electron backscatter diffraction are employed to visualize the complex shape of the deposits and understand the microstructure progression. Investigation of dissimilar cladding of homogeneous AA2024 feed-rods onto an AA6061 substrate establishes a working understanding of the mechanisms related to material flow and microstructure evolution across the whole deposit (macroscopic shape evolution) as well as at the interface between the deposit and the substrate. Variations in tooling and rotation rate affect the interfacial features, average grain size, and depth of microstructural influence. The no

Nanostructured metals with grain sizes smaller than 100 nm usually exhibit strengths which can be more than twice higher than their coarse-grained counterparts. The “smaller is stronger” effect is generally understood in terms of the Hall-Petch effect of grain size strengthening, or the capability of grain boundaries to obstruct the motion of dislocations as carriers of plastic deformation. Nanostructured steels take benefit of reductions in the grain size to show improved tensile strength, hardness and in-service properties. The steel nanostructures are usually multi-phase and hierarchical, maintaining or even improving the stress-ductility trade-off. The increasing demands for stronger, tougher, wear resistant and heat-tolerant materials have led to the development of new families of steels where the length scale that controls such properties is in the nanometer range. This chapter provides an overview of the current status of the most technologically relevant bulk nanostructured steels, describing the approaches to metallurgical design, processing routes, mechanical properties, in-use behavior and industrial applications.

In this work, a bioresorbable Mg-ZKQX6000 (Mg–6Zn–0.6Zr–0.4Ag–0.2Ca (wt%)) alloy was severely plastically deformed via equal channel angular pressing (ECAP) according to three unique hybrid routes at low temperatures (200 °C to 125 °C). The roles of ECAP processing on microstructure, and ensuing mechanical properties and corrosion rates, are assessed. Microstructurally, ECAP induces a complex plethora of features, especially variations in grain sizes and precipitates' sizes, distributions, and morphologies for individual cases. Mechanically, ECAP generally refined grain size, resulting in ultra-high strength levels of about 400 MPa in ultimate tensile strength for several cases; however, deformation via ECAP of precipitates induced embrittlement and low elongation to failure levels. Corrosion testing, conducted in simulated bodily fluid at bodily pH levels to mimic conditions in the human body, revealed consistent corrosion rates across several techniques (mass loss, hydrogen evolution, and electrochemical impedance spectroscopy (EIS)), showing that severe plastic deformation deteriorates corrosion resistance for this material. In-situ corrosion monitoring explained that corrosion accelerated after ECAP due to the creation of heterogeneous, anodic shear zones, which exhibited dense regions of refined grains and fine precipitates. Suggestions for future design and thermomechanical processing of Mg alloys for bioresorbable orthopedic implants are provided.

Nanostructuring of metals and alloys by methods of intensive plastic deformation (IPD) can significantly increase the mechanical and functional properties of materials. It is shown that the use of different modes and routes of IPD processing during the formation of nanostructured metals and alloys significantly affects their mechanical properties, especially brittleness and ductility, fatigue and superplasticity., Наноструктурирование металлов и сплавов методами интенсивной пластической деформации (ИПД) может значительного повышать механические и функциональные свойства материалов. Показано, что использование разных режимов и маршрутов ИПД обработки при формировании наноструктурных металлов и сплавов значительно влияет на их механические свойства, особенно, хрупкость и пластичность, усталость и сверхпластичность.

This paper proposes an approach to optimizing the temperature.velocity regime of severe plastic deformation induced by slyding indenter based on determining the optimal value of the Zener.Hollomon parameter based on the criterion of the maximum volume fraction of nanocrystallites in the surface layer., В работе предложен подход к оптимизации температурно.скоростного режима интенсивной пластической деформации, развиваемой скользящим индентором, на основе определения оптимального значения параметра Зинера–Холломона по критерию максимальной объемной фракции нанокристаллитов в поверхностном слое.

This work presents the recent results of mechanical tests of VT6 and VT8M.1 titanium alloy samples in coarse and ultrafine grained states with a V + (Ti + V)N vacuum.plasma coating sprayed onto their surface. The effect of the applied coating on the mechanical behavior of cylindrical samples on tensile strength at room and elevated temperatures is shown., В настоящей работе представлены недавние результаты механических испытаний образцов титановых сплавов ВТ6 и ВТ8М.1 в крупнозернистом и ультрамелкозернистом состояниях с напыленным на их поверхность вакуумно.плазменным покрытием V+ (Ti + V)N. Показано положительное влияние нанесенного покрытия на механическое поведение цилиндрических образцов на растяжение при комнатной и повышенных температурах.

A Master of Science thesis in Mechanical Engineering by Obadah Mosbah Al-Jarrah entitled, “Investigation of Friction Stir Back Extrusion”, submitted in January 2020. Thesis advisor is Dr. Mohammad Nazzal and thesis co-advisor is Dr. Bassil Darras. Soft copy is available (Thesis, Approval Signatures, Completion Certificate, and AUS Archives Consent Form)., College of Engineering, Department of Mechanical Engineering

A method of estimation of volume fraction of dispersed particles precipitated during equal channel angular pressing in Cu–Cr–Zr alloys was elaborated. The method involves the Matthiessen relationship for determination of electron scattering on solutes. The particles volume fraction calculated by the proposed approach correlated well (R 2 = 0,92) with the particles volume fraction measured by transmission electron microscopy., Предложен способ определения объемной доли дисперсных частиц, выделяющихся в процессе равноканального углового прессования (РКУП) Cu–Cr–Zr сплавов. Метод основан на применение зависимости Маттисона для оценки рассеяния электронов на атомах замещения. Результаты расчета объемной доли частиц с помощью предложенного подхода хорошо коррелируют (R 2 = 0,92) с объемной долей частиц, измеренной методом просвечивающей электронной микроскопии (ПЭМ).

This research is devoted to the study of the adhesive properties of a vacuum-plasma coating (Ti+V)N deposited on the surface of VT8M-1 titanium alloy with a coarse-grained (CG) and ultrafine-grained (UFG) structure. The influence of the UFG-structure on the increase of strength and adhesion properties of the coating was demonstrated., Работа посвящена изучению адгезионных свойств вакуумно-плазменного покрытия (Ti+V)N, нанесенного на поверхность титанового сплава ВТ8 М-1 с крупнозернистой (КЗ) и ультрамелкозернистой (УМЗ) структурой. Показано влияние УМЗ-структуры на повышение прочностных и адгезионных свойств покрытия.

Объект исследования – деформированные в результате интенсивной пластической деформации кручением под высоким давлением образцы на основе платины и алюминия. Цель работы – разработка технологии получения интерметаллида PtAl2 с последующим изучением микроструктуры и механических свойств полученных образцов. Методы исследования – проведение механосинтеза, изучение микроструктуры, измерение микротвердости. Результаты работы – методом кручения под высоким давлением из исходных металлических порошков получены образцы в виде пластин, содержащие интерметаллическую фазу. Образцы были исследованы в сканирующем электронном микроскопе и в рентгеновском дифрактометре. Произведены испытания микротвердости образцов. Рентгенофазовый анализ, показал наличие интерметаллида в продеформированных образцах. Новизна исследования состоит в способе получения интерметаллида PtAl2 путем механосинтеза при комнатной температуре (методом кручения под высоким давлением). Область применения – полученные результаты могут быть использованы при создании покрытий на основе интерметаллидов PtAl2 для авиастроения и машиностроения., Subject of the research are samples based on platinum and aluminum and deformed by using high pressure torsion. The purpose of the work is to develop a technique to produce PtAl2 intermetallic compounds with subsequent study of the microstructure and mechanical properties of the obtained samples. Research methods: carrying out mechanical alloying, studying the microstructure, conducting mechanical hardness tests of samples. As a result of the research samples in the form of plates containing an intermetallic phase were obtained by high pressure torsion the starting metal powders. Samples were examined using a scanning electron microscope and an X-ray diffractometer. The microhardness of the samples was tested. X-ray phase analysis showed the presence of intermetallic in deformed samples. The novelty of the study is to obtain intermetallic using high pressure torsion. Application field: the obtained results can be used to create PtAl22 intermetallic compounds for aircraft and machine building.

Объектом исследования являются медь и малолегированные бронзы, подвергнутые интенсивной пластической деформации. Целью работы было определение текущего состояния научных исследований по использованию меди и малолегированных бронз. А также предложить состав и исследовать структуру и свойства бронзы выбранного состава после интенсивной пластической деформации методом динамического канально-углового прессования. В процессе работы проводился анализ литературных источников. В результате исследования было установлено текущее состояние по проблематике работы и определен вектор исследований. Методами оптической металлографии, дюрометрического анализа, просвечивающей электронной микроскопии и сканирующей электронной микроскопии с применением дисперсионно-энергетического анализа и анализа на основе обратного рассеяния электронов было проведено исследование сплава Cu-0,8 вес.% Hf. При различных обработках методом динамического канально-углового прессования. Эксперимент включал различное состояние бронзы перед деформированием. Также было проведено исследование термической стабильности полученных методом динамического канально-углового прессования образцов. Было установлено, что гафниевая бронза после прессования обладает высокими механическими характеристиками и ультрамелкодисперсной структурой. При этом полученная структура стабильна при комнатной температуре и при последующем отжиге вплоть до 400 °С. Что позволяет рекомендовать данный материал как основу для широкого спектра электротехнических изделий., The object of research is copper and low-alloy bronzes after severe plastic deformation. The purpose of this work was to review scientific research on the use of copper and low-alloy bronzes. As well as the development of the composition and study of the structure and properties of bronze after severe plastic deformation by the method of dynamic channel-angular pressing had been carried out. Literature analysis was carried out. Methods of optical metallography, durometric analysis, transmission electron microscopy and scanning electron microscopy using energy dispersion analysis and analysis based on electron backscattering had been used to study the Cu-0.8 wt.% Hf alloy. Various processings had been carried out by the method of dynamic canal-angular pressing. The state of the bronze before deformation was variouse. We also studied the thermal stability of samples obtained by the method of dynamic channel-angular pressing. It was found that hafnium bronze after pressing has high mechanical characteristics and an ultrafine structure. In this case, the resulting structure is stable at room temperature and upon subsequent annealing up to 400 °C. That allows us to recommend this material as a basis for a wide range of electrical products.

Superplastic forming is a cost-effective process for manufacturing complex-shaped titanium parts. TIMETAL ® 54M (Ti54M) is a titanium alloy that has been commercially available since 2003, however studies on modelling its superplastic behaviour are scarce in the literature. Finite element modelling can be used to enable the manufacturing of complex-shaped parts economically as the number of experimental trials can be reduced. This paper illustrates the implementation of a microstructural-based model to predict the superplastic behaviour of Ti54M alloy during forming at elevated temperature. The parameters of the material model are derived in this work for the Ti54M alloy. A Matlab script has been developed for the calculation and calibration of the material model parameters based on material experimental data. The material model was implemented into the finite element commercial software Abaqus by means of a user-defined subroutine. The finite element calculations take into account also grain size evolution. Finally, a pressure profile was numerically calculated for forming a non-commercial part via superplastic forming targeting optimal conditions for the material., Acceptance in SAN (note of date from author). ST 29/07/20 Only MM/YYYY available for publication date, used last date in month ET 14/8/20 Journal doesn't permit OA in repositories (see: https://www.scientific.net/PolicyAndEthics/PublishingPolicies). Set AAM to closed with note to the author for info. ET 17/8/20 Author confirmed version is AAM by email. ET 15/9/20 If article proposed for REF - check for exception. ET 15/9/20 ; Article

Cu/Mg-composites, the copper matrix of which contains 1, 7 and 2730 magnesium filaments, were obtained by hyrdoextrusion at room temperature. The structure, mechanical and electrical properties of the deformed composite rods and thin wires were investigated. The yield strength and electrical resistivity were theoretically calculated and these estimations were compared with the experimental results. The XRD-method allowed discovering a change of the lattice constant of the Cu-matrix under deformation of the composites. It has been concluded that, under severe plastic deformation, a supersaturated Cu-based solid solution forms on the Cu/Mg-interface. As a result, the strength of the deformed Cu/Mg-composite with minimal volume fraction but maximal surface area of magnesium is abnormally high. A thick Cu-sleeve provides low electrical resistivity of this Cu/Mg-composite. The obtained results can be used for the development of high-strength Cu-based conductors. © 2019 The Authors

Martensitic creep-resistant P92 steel was deformed by different methods of severe plastic deformation such as rotation swaging, high-pressure sliding, and high-pressure torsion at room temperature. These methods imposed significantly different equivalent plastic strains of about 1–30. It was found that rotation swaging led to formation of heterogeneous microstructures with elongated grains where low-angle grain boundaries predominated. Other methods led to formation of ultrafine-grained (UFG) microstructures with high frequency of high-angle grain boundaries. Constant load tensile creep tests at 873 K and initial stresses in the range of 50 to 300 MPa revealed that the specimens processed by rotation swaging exhibited one order of magnitude lower minimum creep rate compared to standard P92 steel. By contrast, UFG P92 steel is significantly softer than standard P92 steel, but differences in their strengths decrease with increasing stress. Microstructural results suggest that creep behavior of P92 steel processed by severe plastic deformation is influenced by the frequency of high-angle grain boundaries and grain coarsening during creep.

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.

This article exposes what is known as nanostructured metallic material, explaining briefly the advantages of nanostructured materials regarding microstructural changes such as grain size refinement and texture modification and their effect in mechanical properties such as strength, ductility and formability. The most popular Severe Plastic Deformation (SPD) processes are succinctly defined and the SPD processes more recently developed for light alloys, especially aluminum and magnesium alloys, are commented.

The pitting corrosion of an aluminum alloy AA1050 after being processed by continuous closed die forging (CCDF) was evaluated by cyclic potentiodynamic polarization (CPP). Microstructure evolution, mechanical and corrosion behaviors were studied as a function of the total strain imposed. The CCDF process was carried out at 0, 16 and 24 passes with loading times of 10 and 15¿s. The electron backscatter diffraction (EBSD) analysis revealed a grain refinement of 0.78¿µm after 24 passes, which promoted an increment in the yield strength (YS), ultimate tensile strength (UTS) and vickers hardness (HV) by a factor of 9, 3 and 2 respectively; but the uniform strain and strain to rupture decreased by 93% and 72% respectively. Resistance to corrosion after 16 and 24 passes was compared with the reference material (0 passes), using CPP in a Na2S04 0.1¿mol/l +100¿mg/l of NaCl electrolyte. Results showed that the specimens with 24 passes decreased its corrosion rate one order of magnitude. In addition, specimens with very fine grain sizes have shown nobler pitting potential and lower pitting volume fraction than coarse grain specimens., Peer Reviewed, Postprint (author's final draft)

A four-component equimolar high-entropy alloy (HEA) with the composition of HfNbTiZr and body-centered cubic (bcc) structure was processed by HPT at RT. The evolution of the dislocation density, the grain size and the hardness was monitored along the HPT-processed disk radius for different numbers of turns between ¼ and 20. It was found that most of the increase of the dislocation density and the refinement of the grain structure occurred up to the shear strain of ∼40. Between the strains of ∼40 and ∼700, only a slight grain size reduction was observed. The saturated dislocation density and grain size were ∼2.1 × 10 16 m −2 and ∼30 nm, respectively. The saturation in hardness was obtained at ∼4450 MPa. These values were similar to the parameters determined in the literature for five-component HEAs processed by HPT. The analysis confirmed that the main component in the strength was given by the friction stress in the HPT-processed bcc HfNbTiZr HEA. It was also revealed that the contribution of the high dislocation density to the strength was significantly higher than the effect of the small grain size., QC 20190401

Aluminium rods with different copper sheath thicknesses were processed by severe plastic deformation at room temperature and then annealed, to join the constituent metals and produce a nanocrystalline microstructure. A study of the effects of the deformation parameters, copper cladding thickness and annealing temperature on the electrical conductivity and hardness of the conductors is reported. It is shown that an interface forms between constituents because of intermixing in the course of severe shear deformation under high hydrostatic pressure and diffusion during the subsequent annealing. The effective conductivity of the aluminium copper-clad conductor dropped after deformation, but was recovered during annealing, especially during short annealing at 200 °C, to a level exceeding the theoretically predicted one. In addition, the annealing resulted in increased hardness at the interface and copper sheath.

Previous research has demonstrated the potential of equal channel angular pressing (ECAP) for producing wood particle based biocomposites. By disturbing wood particle structure and reducing cellulose crystallinity, wood particles were consolidated by the severe shear deformation during ECAP with intermolecular interactions and crosslinking reactions. However, the cracking in the ECAP processed materials significantly weakened their mechanical properties. Wheat gluten was then used as binder, resulting in enhanced mechanical properties, while the low decomposition temperature of wheat gluten limited the processing temperature and lowered the thermal stability of the biocomposites. Therefore, this study aims at further improving the mechanical properties and thermal stability of the wood particle based biocomposites by adjusting raw material composition and ECAP processing conditions, as well as having a comprehensive understanding of the deformation and binding mechanisms. The processing conditions (pressing speed and temperature) were investigated for ECAP of wood particles into bulk materials without any additives. Crack formation and wood cell deformation were illustrated in conjunction with examination of the thermal stability and crystallinity of the biocomposites. Periodic cracks formed during ECAP under low friction, suggesting an inhomogeneous deformation with localised severe shear causing brittle fractures. It was found that in comparison to hot pressing (HP), ECAP caused decrease of crystallinity with severe deformation on wood cells. Higher temperature at 210 °C or lower speed at 10 mm/min may improve the thermal softening, which allows a more homogeneous deformation and reduces crack formation. Biocomposites were produced by ECAP of wood particles with the addition of polyethylenimine (PEI) to improve processability and binding performance. The highest flexural strength of ~50 MPa achieved in a fully densified bulk material is significantly greater than

Ti15Mo metastable beta Ti alloy was solution treated and subsequently deformed by high-pressure torsion (HPT). HPT-deformed and benchmark non-deformed solution-treated materials were annealed at 400 °C and 500 °C in order to investigate the effect of UFG microstructure on the a-phase precipitation. Phase evolution was examined using laboratory X-ray diffraction (XRD) and by high-energy synchrotron X-ray diffraction (HEXRD), which provided more accurate measurements. Microstructure was observed by scanning electron microscopy (SEM) and microhardness was measured for all conditions. HPT deformation was found to significantly enhance the a phase precipitation due the introduction of lattice defects such as dislocations or grain boundaries, which act as preferential nucleation sites. Moreover, in HPT-deformed material, a precipitates are small and equiaxed, contrary to the a lamellae in the non-deformed material. ¿ phase formation is suppressed due to massive a precipitation and consequent element partitioning. Despite that, HPT-deformed material after ageing exhibits the high microhardness exceeding 450 HV., Peer Reviewed, Postprint (published version)

The repair of high strength, high performance 7075 aluminum alloy is essential for a broad range of aerospace and defense applications. However, it is challenging to implement it using traditional fusion welding-based approaches, owing to hot cracking and void formation during solidification. Here, the use of an emerging solid-state additive manufacturing technology, additive friction stir deposition, is explored for the repair of volume damages such as through -holes and grooves in 7075 aluminum alloy. Three repair experiments have been conducted: double through-hole filling, single through-hole filling, and long, wide-groove filling. In all experiments, additive friction stir deposition proves to be effective at filling the entire volume. Additionally, sufficient mixing between the deposited material and the side wall of the feature is always observed in the upper portions of the repair. Poor mixing and inadequate repair quality have been observed in deeper portions of the filling in some scenarios. Based on these observations, the advantages and disadvantages of using additive friction stir deposition for repairing volume damages are discussed. High quality and highly flexible repairs are expected with systematic optimization work on process control and repair strategy development in the future.

The effect of severe plastic deformation (SPD) and subsequent thermal treatment on the microstructure and functional properties of 110Cr18Mo bearing steel was investigated. An increase in the number of cycles of the SPD before the standard heat treatment leads to a reduction in the coefficient of friction while maintaining the hardness at the same level as after heat treatment., В работе исследовано влияние интенсивной пластической деформации (ИПД) и последующей термической обработки на микроструктуру и функциональные свойства подшипниковой стали 110Х18М. Увеличение числа циклов ИПД перед стандартной термической обработкой приводит к снижению коэффициента трения при сохранении твердости на том же уровне, что и после термической обработки.

The 7075 (Al-Zn-Mg-Cu) aluminium alloy is the reference alloy for aerospace applications due to its specific mechanical properties at room temperature, showing excellent tensile strength and sufficient ductility. Formability at high temperature can be improved by obtaining superplasticity as a result of fine, equiaxed and highly misoriented grains prone to deform by grain boundary sliding (GBS). Different severe plastic deformation (SPD) processing routes such as ECAP, ARB, HPT and FSP have been considered and their effect on mechanical properties, especially at intermediate to high temperatures, are studied. Refined grains as fine as 100 nm and average misorientations as high as 39º allow attainment of high strain rate superplasticity (HSRSP) at lower than usual temperatures (250-300ºC). It is shown that increasing misorientations are obtained with increasing applied strain, and increasing grain refinement is obtained with increasing processing stress. Thus, increasing superplastic strains at higher strain rates, lower stresses and lower temperatures are obtained with increasing processing strain and, specially, processing stress.

We have investigated the physical origin of anomalous in-plane thermal expansion (TE) anisotropy leading to invar-like behavior and negative TE in nanostructured NiTi sheets manufactured via severe cold-rolling. The roles of grain size (GS), crystallographic texture, thermally-induced phase transformation, and intrinsic (lattice level) TE of austenite (B2) and martensite (B19') phases on the macroscopic TE behavior are addressed. It is shown that by controlling the cold-rolling thickness reduction and heat-treatment temperature the coefficient of thermal expansion (CTE) can be controlled in a wide range from positive (α ∼ 2.1 × 10−5 K−1) to negative (α ∼ −1.1 × 10−5 K−1) via in-plane anisotropy of TE. A very small CTE of α ∼ −5.3 × 10−7 K−1 (invar-like behavior) in a wide temperature window of 230 K (353–123 K) is obtained at an angle of 33.5° to the rolling direction (RD) of the severely cold-rolled sheet. TEM and XRD studies show that the microstructure underlying such anomalous TE behavior consists of a mixture of B2 nano-grains and retained/residual deformation-induced martensite and that the observed anomalous TE anisotropy is due to the intrinsic anisotropic TE of residual martensite. The invar-like behavior is the result of the cancellation of the positive TE of austenite phase with the negative TE of residual martensite along 33.5° to the RD. A simple rule of mixture model incorporating the intrinsic TE of B2 and B19' lattices and the texture coefficients of the sample is proposed which successfully captures the anomalous in-plane TE anisotropy. The discovery of high dimensional stability over a wide temperature window along with temperature insensitive non-hysteretic linear superelasticity of the severely-deformed NiTi opens up a new route for designing stable SMAs for applications in ragged environments. © 2016 Acta Materialia Inc.

На атомно-силовом микроскопе было проведено исследование микроструктуры быстрозакаленного аморфного сплава Ti50Ni25Cu25, подвергнутого воздействию интенсивной пластической деформации кручением (ИПДК). На фольгах для исследования из исходного аморфного сплава Ti50Ni25Cu25 развитого рельефа в АСМ не наблюдается. Можно предположить, что в результате ИПДК в аморфном сплаве Ti50Ni25Cu25 формируется структура наноразмерных аморфных кластеров, разделенных аморфными же границами, которая выявляется при ионном травлении при подготовке фольг, что наблюдается в АСМ., On an atomic force microscope, a study was conducted microstructure of the rapidly quenched amorphous Ti50Ni25Cu25 alloy after HPT. On initial amorphous Ti50Ni25Cu25 alloy method AFM developed relief is not observed. Maybe after HPT in amorphous Ti50Ni25Cu25 forming clusters of amorphous nanoscale structure after ion etching.

Проведены комплексные исследования влияния многократных мартенситных превращений В2-В19' на структуру и свойства ультрамелкозернистых и нанокристаллических сплавов TiNi. Показано, что, как и в крупнозернистых (КЗ) сплавах, в ультрамелкозернистых (УМЗ) и нанокристаллических (НК) сплавах TiNi происходят последовательные изменения структуры и свойств, вызванные фазовым наклепом, при увеличении количества термоциклов вплоть до n = 100 с быстрым нагревом и быстрым охлаждением до –196 °С., Comprehensive studies on the impact of multiple martensitic transformations В2-В19' on the structure and properties of ultrafine-grained and nanocrystalline titanium-nickel (TiNi) alloys are implemented. It is shown that in coarse-grained, ultrafine-grained and nanocrystalline TiNi alloys consecutive changes in the structure and properties take place, which are induced by phase hardening, when the number of thermocycles increases up to n = 100 with quick heating and quick cooling to –196 °С.

В работе исследована возможность деформирования закаленного состояния высокоуглеродистой подшипниковой стали после отпуска при различных температурах. Деформацию осуществляли методом равноканального углового прессования. Показано, что в результате повышения температуры предварительного отпуска наблюдается снижение прочностных характеристик: предела прочности и предела текучести, твердости стали., The possibility of deformation of the quenched state of high-carbon bearing steel after tempering at different temperatures has been investigated. The deformation was carried out by equal-channel angular pressing. It is shown the increasing of the temperature of the preliminary tempering results in a decrease in the strength characteristics: the tensile strength and yield strength, and the hardness of the steel.

High Pressure Torsion (HTP) is a popular physical simulator to produce ultra-fine grained materials. Existingsolutions of HPT predict a zero deformation and grain refinement near its sample’s longitudinal axis. However,experimental observations confirm that this is not typically the case. For a more realistic study of material’s flowduring the test, a detailed model was presented here in which the sample was represented as a “CylindricalSegment (CS)” with a small run-out. A HPT-CS model was developed which included a parametricrepresentation of the 3D problem and a kinematically admissible velocity field. The model was solved andthe effective strain rate and strain for the problem were formulated. To verify the HPT-CS solution, a specialcase with zero run-out and two general case solutions (non-zero run-out) were compared with the existingsolution of HPT as the reference. The sample comparisons confirmed the accuracy of the proposed solution.Distributions of effective strain rate and strain along the sample’s longitudinal axis were presented for thegeneral case solutions. These increased linearly from zero at the sample’s mid-plane to their maximum at itstop-plane. The maximum values for the second case were 0.138 s−1 and 0.290, respectively. An explanation forthe grain refinement near the sample’s centre was suggested based on the presented HPT-CS’ solution.

The excellent performance of dduplex and super duplex stainless steels due to their high corrosion resistance and high mechanical strength is directly related to their austeno-ferritic microstructure. However, these steels may suffer the formation of secondary brittle phases when they reach temperatures 600-950°C, with catastrophic service failure of components. In order to understand the influence of the mechanical history of the steel, the equal channel angular pressing (ECAP) was applied on UNS S32750 bar samples, processed by using a hydraulic press (DE-80). Microstructural characterisation was carried out on the severe plastic deformed samples by means of OM, SEM and EBSD. Ultimate tensile strength has improved with a low decreasing of elongation after the first pass. The hardness evolution of the same samples was also evaluated., Peer Reviewed, Postprint (author's final draft)

Изучено влияние интенсивной пластической деформации и последующего отжига на эволюцию микроструктуры аустенитной нержавеющей стали 03Х17Н12М2. Интенсивная пластическая деформация приводит к развитию деформационного двойникования и мартенситного превращения, которому способствуют полосы сдвига. Доля мартенсита деформации составила около ~ 0,25 при достижении истинной степени деформации ε = 3. Поперечный размер зерен при этом составил 70–80 нм. Последующий отжиг сопровождался обратным фазовым превращением мартенсита в аустенит и развитием непрерывной статической рекристаллизации. Полностью аустенитная структура восстанавливается при температуре выше 700 °C., The effects of severe plastic deformation and subsequent annealing on the microstructural evolution of an austenitic stainless steel were investigated. The cold rolling was accompanied by the development of deformation twinning and martensitic transformation. The martensite fraction approached 0,25 at a total strain of ε = 3. Subsequent annealing was accompanied by the development of reverse phase transformation of martensite to austenite and an increase in the grain size due to continuous static recrystallization. Fully austenitic structure was obtained at a temperature above 700 °C.

С помощью методов просвечивающей электронной микроскопии изучено влияние химического состава сплавов системы Al-Cu-Li на образование в них нанокристаллической структуры после мегапластической деформации кручением под высоким давлением и последующего отжига. Выявлено, что размерная стабильность зеренной структуры наноструктурированных сплавов обусловлена барьерным эффектом выделяющейся гетерогенно стабильной мелкодисперсной фазы T2., The effect of chemical composition on formation of nanocrystalline structure in Al-Cu-Li alloys subjected to severe plastic deformation by high-pressure torsion and subsequent annealing is investigated by methods of transmission electron microscopy. It has been shown that size stability of nanocrystalline structure is caused by the barrier effect of the finely heterogeneously dispersed stable T2-phases.

В данной работе предпринимается попытка повышения механических свойств листов из сплава 1545К за счет интенсивной пластической деформации. Рассмотрено влияние добавок переходных металлов на сплавы системы Al–Mg–Sc, в частности, марганца, циркония и хрома в упрочнении сплава и улучшении пластичности., In this paper we attempt to improve the mechanical properties of the alloy sheets 1545K by severe plastic deformation. The effect of additives on the transition metal system Al–Mg–Sc alloys, in particular, manganese, zirconium and chromium in the alloy hardening and improving ductility.

The effect of cryogenic temperature on the formation of solid solutions by mechanical alloying (MA) was studied using synchrotron diffraction and some additional methods. Two systems with different positive enthalpy of mixing (Cu-Ag Ee Cyrillic sign Au-Co) were involved. MA by severe plastic deformation at 293 K and 80 K leads to the formation of fcc substitutional solid solutions, with the excess of the equilibrium concentration for both systems. The effect of cryogenic deformation consists in smaller dissolution of the original basic element of the charge (Cu) for Cu-Ag solid solution and in increasing of solute (Co) for Au-Co one. Diffraction experiments were performed at the SR beamline #4 of the VEPP-3 storage ring. © 2016 The Authors.