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Grain boundary segregation in UFG alloys processed by severe plastic deformation  [PDF]
Xavier Sauvage,Artur Ganeev,Yulia Ivanisenko,Nariman Enikeev,Maxim Murashkin,R. Z. Valiev
Physics , 2012, DOI: 10.1002/adem.201200060
Abstract: Grain boundary segregations were investigated by Atom Probe Tomography in an Al-Mg alloy, a carbon steel and Armco\trademark Fe processed by severe plastic deformation (SPD). In the non-deformed state, the GBs of the aluminium alloy are Mg depleted, but after SPD some local enrichment up to 20 at.% was detected. In the Fe-based alloys, large carbon concentrations were also exhibited along GBs after SPD. These experimental observations are attributed to the specific structure of GBs often described as "non-equilibrum" in ultra fine grained materials processed by SPD. The grain boundary segregation mechanisms are discussed and compared in the case of substitutional (Mg in fcc Al) and interstitial (C in bcc Fe) solute atoms.
Formation of nanocrystalline surface layers in various metallic materials by near surface severe plastic deformation
Masahide Sato, Nobuhiro Tsuji, Yoritoshi Minamino and Yuichiro Koizumi
Science and Technology of Advanced Materials , 2004,
Abstract: The surface of the various kinds of metallic materials sheets were severely deformed by wire-brushing at ambient temperature to achieve nanocrystalline surface layer. The surface layers of the metallic materials developed by the near surface severe plastic deformation (NS-SPD) were characterized by means of TEM. Nearly equiaxed nanocrystals with grain sizes ranging from 30 to 200 nm were observed in the near surface regions of all the severely scratched metallic materials, which are Ti-added ultra-low carbon interstitial free steel, austenitic stainless steel (SUS304), 99.99 wt.%Al, commercial purity aluminum (A1050 and A1100), Al–Mg alloy (A5083), Al-4 wt.%Cu alloy, OFHC-Cu (C1020), Cu–Zn alloy (C2600) and Pb-1.5%Sn alloy. In case of the 1050-H24 aluminum, the depth of the surface nanocrystalline layer was about 15 μm. It was clarified that wire-brushing is an effective way of NS-SPD, and surface nanocrystallization can be easily achieved in most of metallic materials.
The Cyclic Deformation Behavior of Severe Plastic Deformation (SPD) Metals and the Influential Factors  [PDF]
Charles C. F. Kwan,Zhirui Wang
Metals , 2012, DOI: 10.3390/met2010041
Abstract: A deeper understanding of the mechanical behavior of ultra-fine (UF) and nanocrystalline (NC) grained metals is necessary with the growing interest in using UF and NC grained metals for structural applications. The cyclic deformation response and behavior of UF and NC grained metals is one aspect that has been gaining momentum as a major research topic for the past ten years. Severe Plastic Deformation (SPD) materials are often in the spotlight for cyclic deformation studies as they are usually in the form of bulk work pieces and have UF and NC grains. Some well known techniques in the category of SPD processing are High Pressure Torsion (HPT), Equal Channel Angular Pressing (ECAP), and Accumulative Roll-Bonding (ARB). In this report, the literature on the cyclic deformation response and behavior of SPDed metals will be reviewed. The cyclic response of such materials is found to range from cyclic hardening to cyclic softening depending on various factors. Specifically, for SPDed UF grained metals, their behavior has often been associated with the observation of grain coarsening during cycling. Consequently, the many factors that affect the cyclic deformation response of SPDed metals can be summarized into three major aspects: (1) the microstructure stability; (2) the limitation of the cyclic lifespan; and lastly (3) the imposed plastic strain amplitude.
Microstructure refinement of selected copper alloys strips processed by SPD method  [PDF]
W. G?uchowski,J.P. Stobrawa,Z.M. Rdzawski
Archives of Materials Science and Engineering , 2011,
Abstract: Purpose: A growing trend to use the new copper-based functional materials is observed recently world-wide. Ultrafine grained copper, solid solution hardened and age-hardened copper alloys are applied where combination of high electrical conductivity with high strength is required.Design/methodology/approach: This study was aimed to investigate microstructure in strips of copper alloys with different stacking fault energy value. The investigated materials have been processed by one of the severe plastic deformation method, using different variants of continuous repetitive corrugation and straightening (CRCS). Deformation was executed by parallel and perpendicular corrugation and straightening of strip sample.Findings: Continuous repetitive corrugation and straightening is a promising method for refining of microstructure of metallic strips.Practical implications: A growing trend to use new copper-based functional materials is observed recently world-wide. Within this group of materials particular attention is drawn to those with ultra fine or nanometric grain size.Originality/value: The paper contributes to the microstructure evolution of solid solution hardened and age-hardened copper alloys strips produced by original RCS method.
Processing of metals by severe plastic deformation (SPD) – structure and mechanical properties respond  [PDF]
J. Zrnik,S. V. Dobatkin,I. Mamuzi?
Metalurgija , 2008,
Abstract: SPD methods are used to convert coarse grain metals and alloys into ultrafine grained (UFG) materials. Obtained UFG materials then possess improved mechanical and physical properties which destine them for a wide commercial use. This paper, in one direction, looks into historical development of SPD processes and their effect at obtaining fine crystalline structure, and on the other side also partially focuses on development of UFG structure and its stability in commercial pure aluminium as a function of strain and post-deformation annealing applied.
Microstructure evolution of a recycled Al–Fe–Si–Cu alloy processed by tube channel pressing  [PDF]
M. H. Farshidi,M. Rifai,H. Miyamoto
- , 2018, DOI: https://doi.org/10.1007/s12613-018-1668-6
Abstract: Although excellent recyclability is one of the advantages of Al alloys, a recycling process can reduce different properties of these alloys by adding coarse AlFeSi particles into the alloys’ microstructures. One of the well-known methods for modifying the microstructure of metallic materials is the imposition of severe plastic deformation (SPD). Nevertheless, the microstructure evolutions of recycled Al alloys containing extraordinary fractions of AlFeSi particles during SPD processing have seldom been considered. The aim of the present work is to study the microstructure evolution of a recycled Al–Fe–Si–Cu alloy during SPD processing. For this purpose, tubular specimens of the mentioned alloy were subjected to different numbers of passes of a recently developed SPD process called tube channel pressing (TCP); their microstructures were then studied using different techniques. The results show that coarse AlFeSi particles are fragmented into finer particles after processing by TCP. However, decomposition and dissolution of AlFeSi particles through TCP processing are negligible. In addition, TCP processing results in an increase in hardness of the alloy, which is attributed to the refinement of grains, to an increase of the dislocation density, and to the fragmentation of AlFeSi particles.
Combined volumetric, energetic and microstructural defect analysis of ECAP-processed nickel  [PDF]
Gerrit Reglitz,Bernd Oberdorfer,Nina Fleischmann,Jaromir Anatol Kotzurek,Sergiy V. Divinski,Wolfgang Sprengel,Gerhard Wilde,Roland Würschum
Physics , 2015,
Abstract: Difference dilatometry and differential scanning calorimetry (DSC) are used to investigate defect annealing in ultrafine grained nickel processed by equal channel angular pressing (ECAP) at various temperatures. Different defect types and processes such as vacancies, dislocations, grain boundaries and grain-boundary relaxation can be detected. They can be distinguished due to their distinct kinetics as revealed by the release of excess volume and excess heat during linear heating. The data are quantified in combination with a detailed characterization of the microstructure. Values for the absolute vacancy concentration, the dislocation density, the grain boundary expansion and the excess of grain boundary expansion in ECAP-processed nickel are derived.
Grain boundaries in ultrafine grained materials processed by severe plastic deformation and related phenomena  [PDF]
Xavier Sauvage,Gerhard Wilde,Sergiy Divinski,Zenji Horita,Ruslan Valiev
Physics , 2012, DOI: 10.1016/j.msea.2012.01.080
Abstract: Grain boundaries in ultrafine grained (UFG) materials processed by severe plastic deformation (SPD) are often called "non-equilibrium" grain boundaries. Such boundaries are characterized by excess grain boundary energy, presence of long range elastic stresses and enhanced free volumes. These features and related phenomena (diffusion, segregation, etc.) have been the object of intense studies and the obtained results provide convincing evidence of the importance of a non-equilibrium state of high angle grain boundaries for UFG materials with unusual properties. The aims of the present paper are first to give a short overview of this research field and then to consider tangled, yet unclear issues and outline the ways of oncoming studies. A special emphasis is given on the specific structure of grain boundaries in ultrafine grained materials processed by SPD, on grain boundary segregation, on interfacial mixing linked to heterophase boundaries and on grain boundary diffusion. The connection between these unique features and the mechanical properties or the thermal stability of the ultrafine grained alloys is also discussed.
Development of SPD continuous processes for strip and rod production  [PDF]
S. Dobatkin,J. Zrnik,Ilija Mamuzi?
Metalurgija , 2010,
Abstract: Grain refinement upon the severe plastic deformation (SPD) at low temperatures (below the recrystallization temperature) and an unusual improvement the properties of such materials are shown reliably. However, the industrial application is limited due to the absence of effective continuous SPD processes. The potential of development of continuous SPD processes based on the equal channel angular pressing (ECAP) process from one side and continuous extrusion or drawing processes from another side is considered. Existing various continuous SPD processes for strip, rod and wire production are analyzed.
The role of carbon segregation on nanocrystallisation of pearlitic steels processed by severe plastic deformation  [PDF]
Xavier Sauvage,Yulia Ivanisenko
Physics , 2008, DOI: 10.1007/s10853-006-0750-z
Abstract: The nanostructure and the carbon distribution in a pearlitic steel processed by torsion under high pressure was investigated by three-dimensional atom probe. In the early stage of deformation (shear strain of 62), off-stoichiometry cementite was analysed close to interphase boundaries and a strong segregation of carbon atoms along dislocation cell boundaries was observed in the ferrite. At a shear strain of 300, only few nanoscaled off-stoichiometry cementite particles remain and a nanoscaled equiaxed grain structure with a grain size of about 20 nm was revealed. 3D-AP data clearly point out a strong segregation of carbon atoms along grain boundaries. The influence of this carbon atom segregation on the nanostructure formation is discussed and a scenario accounting for the nanocrystallisation during severe plastic deformation is proposed.
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