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ARB (Accumulative Roll‐Bonding) and other new Techniques to Produce Bulk Ultrafine Grained Materials
Accumulative roll‐Bonding (ARB) is a severe plastic deformation (SPD) process invented by the authors in order to fabricate ultrafine grained metallic materials. ARB is the only SPD process applicable to continuous production of bulky materials. In the process, 50 % rolled material is cut into two, stacked to be the initial dimension and then rolled again. In order to obtain one‐body solid material, the rolling in ARB is not only a deformation process but also a bonding process (roll‐bonding). By repeating this procedure, SPD of bulky materials can be realized. In this review paper, various kinds of new SPD mechanical properties of the ARB processed materials are indicated. 相似文献
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Over the past decades severe plastic deformation (SPD) techniques advanced to one of the most potent ways of producing bulk ultrafine grained materials. The main advantage of SPD is the ultra‐high strength they can deliver. While the improvement of the strength there is a limit to what is achievable SPD when they are applied to individual materials especially for strain‐hardening and ductility. Therefore a new application of SPD processes in manufacturing of architecture hybrid materials with simultaneous nanostructuring is investigated experimentally and theoretically. 相似文献
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In this brief communication, we would like to review present data on fatigue performance of ultra‐fine grain materials fabricated by severe plastic deformation (SPD) and to discuss the possible mechanisms of their plastic deformation and degradation in light of currently available experimental data. The most prominent effect of SPD is often associated with significant grain refinement down to the nanoscopic scale. The other evident effect, which accompanies intensive plastic straining, is the dislocation accumulation up to limiting densities of 1016 m–2. Since namely these two factors, the grain size and the dislocation density, govern the strengthening of polycrystalline materials, we shall primarily confine ourselves to their role in cyclic deformation of severely pre‐deformed metals. 相似文献
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Processing by severe plastic deformation (SPD) leads to very significant grain refinement in metallic alloys. Furthermore, if these ultrafine grains are reasonably stable at elevated temperatures, there is a potential for achieving high tensile ductilities, and superplastic elongations, in alloys that are generally not superplastic. In addition, the production of ultrafine grains leads to the occurrence of superplastic flow at strain rates that are significantly faster than in conventional alloys so that processing by SPD introduces the possibility of using these alloys for the rapid fabrication of complex parts through superplastic forming operations. This paper examines the development of superplasticity in various aluminum alloys processed by equal‐channel angular pressing (ECAP). 相似文献
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综述了非连续增强金属基复合材料剧烈塑性变形(SPD)行为的研究进展,系统阐述了等径弯曲通道变形(ECAP)、高压扭转(HPT)、多向锻造(MF)、累积叠轧(ARB)和循环挤压压缩(CEC)5种SPD的加工原理和方法。集中介绍了这些方法在铝基、镁基、铜基和钛基等金属基复合材料方面应用的研究进展。重点介绍了金属基复合材料SPD的微观组织演化和变形力学行为,详细阐明了金属基复合材料SPD机制以及超细晶形成机理,指出了金属基复合材料在SPD中存在的深层次问题及发展趋势,展望了利用SPD方法制备超细晶非连续增强金属基复合材料的应用前景。 相似文献
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R. Lapovok A. Pougis V. Lemiale D. Orlov L. S. Toth Y. Estrin 《Journal of Materials Science》2010,45(17):4554-4560
Among the known severe plastic deformation (SPD) techniques, one particular group can be defined as SPD processing of thin
samples. Their distinctive feature is that one of the sample dimensions, namely the thickness, is much smaller than the other
two dimensions. Examples include High Pressure Torsion and two recently developed techniques: the Cone–Cone Method and the
High Pressure Tube Twisting. The mentioned group of SPD processes involve frictional forces acting on the large surfaces and
a high hydrostatic pressure within the deformation zone. These techniques are particularly suited for microforming of metals.
In this article, we outline the commonalities between these three techniques. The microstructure of copper samples deformed
by all the three processes is presented and compared with those obtained by equal-channel angular pressing as a reference
bulk forming SPD technique. 相似文献
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Review of principles and methods of severe plastic deformation for producing ultrafine-grained tubes
Severe plastic deformation (SPD) is known to be the best method for producing bulk ultrafine-grained and nanostructured materials with excellent properties. Different SPD methods were developed that are suitable for sheet and bulk solid materials. During the past decade, efforts have been made to create effective SPD processes suitable for producing cylindrical tubes. In this paper, we review SPD processes intended to produce ultrafine-grained and nanostructured tubes, and their effects on material properties. The paper will focus on introduction of the tube SPD processes, and then comparison of them based on their advantages and disadvantages from the viewpoints of processing and properties. 相似文献
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Severe plastic deformation (SPD) is an efficient approach for producing ultrafine or nanostructured bulk materials. Equal channel angular extrusion (ECAE) is the most effective SPD solution for material nanostructuring, as material billet undergoes severe and large deformation and the grains are efficiently broken up in the process. To improve material nanostructuring, the ECAE die design and process configuration are critical. The deformation behavior study through FE simulation in ECAE process provides basic and useful information for optimizing die design and process determination. In this research, the deformation behavior for three different die design scenarios is studied and the related deformation mechanisms and nanostructuring performance are investigated via FE simulation. Through multi-pass simulation, the optimal design scenario is then identified. The simulation results reveal deformation phenomena, and nanostructuring performance of the designs and the corresponding process can be recommended accordingly for improving die and process performance. 相似文献
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Severe plastic deformation (SPD) processes are widely recognised as efficient techniques to produce bulk ultrafine-grained
materials. As a complement to experiments, computational modelling is extensively used to understand the deformation mechanisms
of grain refinement induced by large strain loading conditions. Although considerable research has been undertaken in the
modelling of SPD processes, most of the studies have been accomplished using mesh-based methods, such as the finite element
method (FEM). Mesh-based methods have inherent difficulties in modelling high-deformation processes because of the distortions
in the mesh and the resultant inaccuracies and instabilities. As an alternative, a mesh-free method called smoothed particle
hydrodynamics (SPH) is used. The effectiveness of this technique is highlighted for modelling of one of the most popular SPD
techniques, equal channel angular pressing. A benchmark between SPH and FE calculation is performed. Furthermore, a number
of simulations under different processing conditions are compared to existing literature data. A satisfactory agreement is
found, which indicates that SPD processes can be approached by mesh-free methods, such as SPH. 相似文献
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Ultra-fine grained (UFG) metals fabricated by severe plastic deformation (SPD) sometimes exhibit peculiar mechanical properties. For example, the “hardening by annealing and softening by deformation” was reported in UFG aluminum, which was totally opposite to the behaviors of conventionally coarse-grained materials. In this study, the effect of SPD strain on the peculiar phenomena was investigated. The UFG aluminum was fabricated by various cycles of the accumulative roll-bonding (ARB) process with lubrication at ambient temperature. The specimen ARB-processed by ten cycles certainly showed the peculiar phenomena. On the other hand, the 6-cycle specimen did not show the phenomena but was softened by annealing and hardened by deformation normally. From the results of microstructural characterization, it was suggested that the difference in the change of the mechanical property during annealing and deformation between 6-cycle and 10-cycle specimens was caused by the difference in the grain size and/or the texture components, which depended on the SPD strain. 相似文献
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Severe plastic deformation(SPD)-induced gradient nanostructured(GNS)metallic materials exhibit supe-rior mechanical performance,especially the high strength and good ductility.In this study,a novel high-speed machining SPD technique,namely single point diamond turning(SPDT),was developed to produce effectively the GNS layer on the hexagonal close-packed(HCP)structural Mg alloy.The high-resolution transmission electron microscopy observations and atomistic molecular dynamics sim-ulations were mainly performed to atomic-scale dissect the grain refinement process and corresponding plastic deformation mechanisms of the GNS layer.It was found that the grain refinement process for the formation of the GNS Mg alloy layer consists of elongated coarse grains,lamellar fine grains with deformation-induced-tension twins and contraction twins,ultrafine grains,and nanograins with the grain size of~70 nm along the direction from the inner matrix to surface.Specifically,experiment results and atomistic simulations reveal that these deformation twins are formed by gliding twinning partial dis-locations that are dissociated from the lattice dislocations piled up at grain boundaries.The corresponding deformation mechanisms were evidenced to transit from the deformation twinning to dislocation slip when the grain size was below 2.45 μm.Moreover,the Hall-Petch relationship plot and the surface equivalent stress along the gradient direction estimated by finite element analysis for the SPDT process were incorporated to quantitatively elucidate the transition of deformation mechanisms during the grain refinement process.Our findings have implications for the development of the facile SPD technique to construct high strength-ductility heterogeneous GNS metals,especially for the HCP metals. 相似文献
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Stress-based model on work hardening and softening of materials at large strains: corrugation process of sheet 总被引:1,自引:0,他引:1
In this article, a stress-based model is proposed to investigate the strength evolution during severe plastic deformation
(SPD) or large strains. In this model, the work hardening mechanisms are described by Frank-Read sources, while the cross-slip
and climb processes are considered as the mechanisms for work softening phenomenon. Within all SPD processes, one of corrugation
processes such as constrained groove pressing is chosen to assess the validity of the model predictions. The model predictions
are in agreement with the earlier reports and the experimental results achieved in this study. 相似文献
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Influence of the Al2Cu‐phase on the superplasticity of AlCuMn alloy High‐temperature creep‐resistant AlCuMn wrought alloy has been investigated and optimised with respect to their superplastic deformability; a maximal elongation ε of 850 per cent was thus attained at a deformation temperature of 530°C. Prerequisites for superplastic deformation behaviour and for the associated high elongation values of these aluminium alloys are an especially fine‐grained structure as well as a decrease in the amount of Al2Cu phase and a uniform distribution of this phase in the structure. Superplastic deformation (SPD) results in a pronounced change in the shape of the large particles of the θ‐phase; the particles of this phase thereby form veins along the boundaries of adjacent grains. During deformation, the grains lose their equiaxial shape and elongate in the direction of tension as a result of pronounced intragranular sliding dislocation in the microstructure. Transmission electron micrographs of the deformed structure have revealed a pile‐up of dislocations in the grains of the aluminium alloy. The grain size of commercially available sheets of AlCuMn wrought alloys with a thickness of 1 mm is approximately 30 μm. After optimising, the grain size of the sheets produced by the new method was on 12 μm until 5 μm. The new technique differs only slightly from industrial manufacture. 相似文献
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In this present study, the isothermal forging of two different gears is carried out from material previously deformed by the severe plastic deformation (SPD) process known as Equal Channel Angular Pressing (ECAP). At present, there are only a few studies which use this material predeformed that exhibits improved mechanical properties as a result of the SPD process for use in subsequent processes or applications. The design and optimization of the die geometry required for the isothermal forging of gears are shown and both microhardness and microstructure are compared when these forged gears are obtained from annealed material (N0) and ECAP-processed material (N2). With this present research work, it is demonstrated that there is an improvement in forgeability and microhardness as well as a decrease in the grain size of the material predeformed by SPD. 相似文献