Laboratory of Hybrid Nanostructured Materials

Moscow, Russia

Laboratory of Hybrid Nanostructured Materials

Moscow, Russia
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Lee D.J.,Pohang University of Science and Technology | Yoon E.Y.,Korea Institute of Materials Science | Ahn D.-H.,Pohang University of Science and Technology | Park B.H.,Pohang University of Science and Technology | And 5 more authors.
Acta Materialia | Year: 2014

The paper is concerned with large strain deformation behavior of metallic materials as exemplified by copper under high-pressure torsion (HPT). To that end, the evolution of microstructure was considered in terms of a dislocation density-based constitutive model embedded in a finite element code. The variation of the specimen geometry, the hydrostatic pressure state, the equivalent strain and the dislocation density were examined by numerical simulations. The concurrent variation of the average dislocation cell size, which was identified with the emerging new grain size of the material, was also traced. The simulated results for the dislocation density and the grain size were shown to be in good agreement with the experimental data for commercial purity copper. It was concluded that the dislocation density-based constitutive model is well placed as a tool for describing and predicting the evolution of microstructure during severe plastic deformation, particularly HPT, using the finite element method. © 2014 Elsevier Ltd. All rights reserved.

Orlov D.,Ritsumeikan University | Orlov D.,University of Nova Gorica | Pelliccia D.,Monash University | Fang X.,Monash University | And 6 more authors.
Acta Materialia | Year: 2014

The evolution of intermetallic precipitate particles in Mg-Zn-Zr alloy ZK60 during thermomechanical processing by integrated extrusion and equal channel angular pressing was investigated in detail. Electron microscopy was employed to analyse individual particles and their orientation within the Mg matrix, while small-angle X-ray scattering (SAXS) was used for an assessment of global particle behaviour and statistical significance of their volume in the microstructure. A significant redistribution of prismatic rod-type and basal platelet-type precipitates, as well as their resolutioning followed by the formation of prismatic platelets, was found. The platelet-type precipitates lying on prismatic {21̄1̄0}α planes were hitherto unknown for the Mg-Zn-Zr system. These precipitates were present in a statistically significant amount detectable by SAXS. Such precipitates should favour an increase of critical resolved shear stress for basal slip in the Mg matrix, thus contributing to an improved performance of the Mg-Zn-Zr alloy. The possibility of formation of prismatic platelet-type precipitates in Mg alloys proven in this paper opens up a new avenue for the design of relatively inexpensive high-performance magnesium alloys. © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Dobatkin S.V.,RAS Institute of Metallurgy | Rybal'chenko O.V.,RAS Institute of Metallurgy | Kliauga A.,University of San Carlos | Tokar' A.A.,Laboratory of Hybrid Nanostructured Materials
Metal Science and Heat Treatment | Year: 2015

The structure and properties of metastable austenitic steel 08Kh18N10T and stable austenitic steel ASTM F138 under shear deformation implemented by torsion under hydrostatic pressure (THP) at T = 300 and 450°C and by equichannel angular pressing (ECAP) at T = 400°C are studied. The THP yields an ultrafine-grain structure in a fully austenitic matrix with grain size 45 – 70 nm in steel ASTM F138 and 87 – 123 nm in steel 08Kh1810T. The ECAP at 400°C yields a grain-subgrain structure with structural elements 100 – 300 nm in size in steel 08Kh18N10T and 200 – 400 nm in size in steel ASTM F138. © 2015, Springer Science+Business Media New York.

Li Y.,Seoul National University | Pang Ng H.,Monash University | Jung H.-D.,Seoul National University | Kim H.-E.,Seoul National University | And 2 more authors.
Materials Letters | Year: 2014

Commercial purity titanium (Grade 4) was processed by encapsulation-aided equal-channel angular pressing. Encapsulation in a copper cartridge made it possible to carry out the process repeatedly, up to 8 passes, at a relatively low temperature of 300 C. Extremely high values of yield strength and tensile strength close to record literature values for this titanium grade and matching, or even surpassing, the levels for conventional Ti-6Al-4V alloy were obtained. A bi-modal grain structure observed may be responsible for a favorable combination of strength and ductility the processed material exhibits. © 2013 Elsevier B.V.

Vinogradov A.,Norwegian University of Science and Technology | Yasnikov I.S.,Togliatti State University | Matsuyama H.,Osaka City University | Uchida M.,Osaka City University | And 3 more authors.
Acta Materialia | Year: 2016

A phenomenological dislocation-based approach is proposed to account for the necking phenomenon during tensile deformation of metals and alloys. The critical strain corresponding to the onset of tensile instability is predicted in a simple explicit form based on the Kocks-Mecking dislocation kinetics approach. The model strongly suggests that uniform elongation is controlled primarily by the rate of dislocation recovery. The role of the stain rate sensitivity in stabilizing uniform plastic flow is also elucidated. Model predictions are found to be in excellent agreement with experimental data obtained for ultrafine grained 316L steel produced by severe plastic deformation. The approach presented provides general ques for designing materials with enhanced ductility, including ultrafine grained and bulk nanostructured metals and alloys. The proposed recipe is based on microstructural control of the rate of dynamic recovery of dislocation. © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Yasnikov I.S.,Togliatti State University | Vinogradov A.,Togliatti State University | Estrin Y.,Monash University | Estrin Y.,Laboratory of Hybrid Nanostructured Materials
Scripta Materialia | Year: 2014

We demonstrate that the Considère condition for plastic instability, which is traditionally obtained from solid mechanics considerations, also follows from the intrinsic evolution laws for dislocation density. Taking strain-rate effects into account, a modified instability condition emerges in a form that resembles Hart's criterion, but is not identical to it. The Considère strain predicted from the dislocation-based model shows good agreement with experimental data, highlighting the primary role played by dynamic recovery in the mechanical response. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Vinogradov A.,Kazan Federal University | Yasnikov I.S.,Kazan Federal University | Estrin Y.,Monash University | Estrin Y.,Laboratory of Hybrid Nanostructured Materials
Materials Science and Technology (United Kingdom) | Year: 2015

In this paper, we describe a simple methodology that offers a familiar constitutive description of plasticity in terms of the dislocation density evolution as an outcome of the approach based on the thermodynamics of irreversible processes. We further demonstrate that the dislocation density evolution approach can organically predict the critical strain corresponding to the Considère instability point. Finally, we show that the fractal dimension (FD) of the dislocation population of a deforming material can be integrated in the proposed modelling framework and, consequently, the FD behaviour can be traced, providing insights in the evolution of the dislocation structure in the course of deformation. © 2015 Institute of Materials, Minerals and Mining.

Qi Y.,Monash University | Lapovok R.,Deakin University | Estrin Y.,Monash University | Estrin Y.,Laboratory of Hybrid Nanostructured Materials
Journal of Materials Science | Year: 2016

Equal-channel angular pressing (ECAP) was used to fabricate Al/steel bimetallic rod for potential application in overhead transmission conductors. Bimetallic rods consisted of an austenitic stainless steel 316L core and an Al alloy 6201 cladding layer. By means of ECAP processing at 175°C, increase of mechanical strength without loss of electrical conductivity was achieved for one particular rod geometry out of three geometries tested. X-ray diffraction and transmission electron microscopy were employed to analyse how the microstructure was influenced by the number of processing passes and the bimetallic rod geometry. The co-deformation mechanism of the bimetallic rod under ECAP and accelerated dynamic ageing of Al alloy 6201 were discussed based on the microstructure characterisation results. © 2016, Springer Science+Business Media New York.

Chen C.,CNRS Study of Microstructures, Mechanics and Material Sciences lab | Beygelzimer Y.,University of Lorraine | Beygelzimer Y.,Ukrainian Academy of Sciences | Toth L.S.,CNRS Study of Microstructures, Mechanics and Material Sciences lab | And 3 more authors.
Journal of Engineering Materials and Technology, Transactions of the ASME | Year: 2016

Modern techniques of severe plastic deformation (SPD) used as a means for grain refinement in metallic materials rely on simple shear as the main deformation mode. Prediction of the mechanical properties of the processed materials under tensile loading is a formidable task as commonly no universal, strain path independent constitutive laws are available. In this paper, we derive an analytical relation that makes it possible to predict the mechanical response to uniaxial tensile loading for a material that has been preprocessed by simple shear and, as a result, has developed a linear strain gradient. A facile recipe for mechanical tests on solid bars required for this prediction to be made is proposed. As a trial, it has been exercised for the case of commercial purity copper rods. The method proposed is recommended for design with metallic materials that underwent preprocessing by simple shear. © 2016 by ASME.

Beygelzimer Y.,Ukrainian Academy of Sciences | Beygelzimer Y.,University of Lorraine | Estrin Y.,Monash University | Estrin Y.,Laboratory of Hybrid Nanostructured Materials | Kulagin R.,Karlsruhe Institute of Technology
Advanced Engineering Materials | Year: 2015

An emerging direction of research into severe plastic deformation (SPD), which we refer to as SPD-induced synthesis of hybrid materials, is presented. At its core is the creation of inner structure made from various materials within the bulk of a solid. As distinct from the traditional metal forming, SPD-induced synthesis produces an engineered inner architecture of the solid without changing its exterior geometry. The possibilities of the SPD techniques with regard to materials synthesis are demonstrated. Research in this nascent area will open up new avenues for fabrication of advanced hybrid materials, while also posing a number of challenging scientific problems. A particular application discussed concerns the development of hybrid ultrafine-grained materials with enhanced structural ductility. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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