The Experts below are selected from a list of 2232 Experts worldwide ranked by ideXlab platform
Roohollah Jamaati - One of the best experts on this subject based on the ideXlab platform.
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Annealing Texture of Nanostructured Steel-Based Nanocomposite
Journal of Materials Engineering and Performance, 2015Co-Authors: Roohollah JamaatiAbstract:In this research, the evolution of annealing texture in Nanostructured Steel-based nanocomposite fabricated via accumulative roll bonding (ARB) process was investigated. Textural evolution after post-annealing of ARB-processed samples was evaluated using x-ray diffraction. Average grain size of the sample before and after the post-annealing was 55 nm and 1.5 µm, and the microstructures were uniform. All the samples indicated a strong α-fiber and γ-fiber and a relatively weak ζ-fiber. Also, there were texture transitions in the α-fiber, ε-fiber, γ-fiber, η-fiber, and θ-fiber. In addition, for all the samples, the intensities of the rolling textures were higher than those of the shear textures. Moreover, there was a progressive increase in the fraction of high-angle grain boundaries with the increasing strain. Finally, with increasing number of ARB cycles, the intensities of rolling and shear textures changed, and no stable texture was formed.
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Microstructural evolution of Nanostructured Steel-based composite fabricated by accumulative roll bonding
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015Co-Authors: Roohollah Jamaati, Sajjad Amirkhanlou, Mohammad Reza Toroghinejad, Hossein EdrisAbstract:Abstract In the present study, the effect of four-layer accumulative roll bonding (ARB) process at room temperature on the microstructure and mechanical properties of Steel-based composite was investigated. Microstructural observations were done by scanning transmission electron microscopy (STEM). Also, textural evolution during the ARB process was evaluated using X-ray diffraction. It was found that occurrence of discontinuously dynamic recrystallization (DDRX) in the interstitial free (IF) Steel during cold plastic deformation is possible. The four-layer ARB process at room temperature in the presence of SiC microparticles provided the stored energy required for DDRX in the IF Steel with high stacking fault energy (SFE). On the other hand, hindrance of initial grain boundaries to dislocation movement resulted in DDRX grains along initial grain boundaries in the IF Steel matrix. Average grain size of the final sample was 73 nm but the microstructure was relatively inhomogeneous. The results also indicated that particle stimulated nucleation (PSN) promoted texture randomization in the Steel-based composite. Dislocation density of the samples was determined from hardness measurement. The dislocation density increased continually until the dislocation density of the Steel-based composite after fourth cycle was about 5.3 times (10.73×10 9 cm −2 ) higher than that of the initial sample (2.02×10 9 cm −2 ). Also, significant increase in dislocation density occurred after first cycle and in the final cycles the dislocation density value was saturated. After first cycle, a remarkable improvement was observed in the yield strength value, from 84 MPa to 682 MPa which is almost 8.1 times greater than that of the initial sample. After final cycle, the yield strength value increased to 1061 MPa. Finally, the contribution of individual mechanisms such as the grain refinement, dislocation, second phase, and precipitation in strengthening of the IF Steel was evaluated. The contribution of grain refinement and precipitation to the improvement in yield strength was maximum (~67%) and minimum (~3.2%), respectively.
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Annealing texture of Nanostructured Steel-based composite
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015Co-Authors: Roohollah Jamaati, Ali Sonboli, Mohammad Reza Toroghinejad, Jerzy A. SzpunarAbstract:Abstract In this study, the evolution of annealing texture in Nanostructured Steel-based composite processed by accumulative roll bonding (ARB) was investigated. Textural evolution after post-annealing of ARB-processed samples was evaluated using X-ray diffraction. There was a texture transition in the e-fiber during ARB process and post-annealing treatment. Average grain size of the sample before and after the post-annealing was 73 nm and 1.8 µm, respectively, and the microstructures were relatively uniform. It was found that with increasing the number of cycles, the volume fraction of the low angle grain boundary (LAGB) decreased and that of the high angle grain boundary (HAGB) increased. Also, the shear texture was dominant after the second and third ARB cycles, while for other samples, the rolling texture was dominant. The two-cycle and three-cycle samples obviously indicated a weak α-fiber and γ-fiber and a relatively strong ζ-fiber. It was proposed that the recrystallization led to a decrease in the α-fiber and γ-fiber and rolling texture components such as {111}〈110〉 and {111}〈112〉. On the other hand, the grain growth after recrystallization resulted in an increase in the α-fiber and γ-fiber and rolling texture orientations.
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Annealing Texture of Nanostructured Steel-Based Nanocomposite
Journal of Materials Engineering and Performance, 2015Co-Authors: Roohollah JamaatiAbstract:In this research, the evolution of annealing texture in Nanostructured Steel-based nanocomposite fabricated via accumulative roll bonding (ARB) process was investigated. Textural evolution after post-annealing of ARB-processed samples was evaluated using x-ray diffraction. Average grain size of the sample before and after the post-annealing was 55 nm and 1.5 µm, and the microstructures were uniform. All the samples indicated a strong α-fiber and γ-fiber and a relatively weak ζ-fiber. Also, there were texture transitions in the α-fiber, e-fiber, γ-fiber, η-fiber, and θ-fiber. In addition, for all the samples, the intensities of the rolling textures were higher than those of the shear textures. Moreover, there was a progressive increase in the fraction of high-angle grain boundaries with the increasing strain. Finally, with increasing number of ARB cycles, the intensities of rolling and shear textures changed, and no stable texture was formed.
Harshad Kumar Dharamshi Hansraj Bhadeshia - One of the best experts on this subject based on the ideXlab platform.
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Strength and toughness of clean Nanostructured bainite
Materials Science and Technology, 2017Co-Authors: M. J. Peet, L. C. D. Fielding, A. A. Hamedany, Martin Rawson, P. Hill, Harshad Kumar Dharamshi Hansraj BhadeshiaAbstract:ABSTRACTA Nanostructured Steel has been produced using a clean Steel-making technique. The mechanical properties have been comprehensively characterised. The maximum strength of the material recorded was 2.2 GPa at yield, with an ultimate tensile strength of 2.5 GPa, accompanied by a Charpy impact energy of 5 J, achieved by heat treatment to refine the prior austenite grain size from 145 to 20 µm. This increased the strength by 40% and the Charpy V-notch energy more than doubled. In terms of resistance of the hardness to tempering, the behaviour observed was similar to previous alloys. Despite reducing the hardness and strength, tempering was observed to reduce the plane-strain fracture toughness.
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Hydrogen diffusion and the percolation of austenite in Nanostructured bainitic Steel
Proceedings of The Royal Society A: Mathematical Physical and Engineering Sciences, 2014Co-Authors: L. C. D. Fielding, Eun Ju Song, Harshad Kumar Dharamshi Hansraj BhadeshiaAbstract:The diffusion of hydrogen in austenite is slower than in ferrite. Experiments have been conducted to study the behaviour of hydrogen in a Nanostructured Steel sample consisting of a mixture of thin...
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Hydrogen diffusion and the percolation of austenite in Nanostructured Steel
2014Co-Authors: L. C. D. Fielding, Eun Ju Song, Harshad Kumar Dharamshi Hansraj BhadeshiaAbstract:The authors are grateful to the Worshipful Company of Ironmongers, Tata Steel UK, the EPSRC, to theWorld Class University Programme of the National Research Foundation of Korea, Ministry of Education, Science and Technology, project number R32–2008–000–10147–0, and the POSCO Steel Innovation Programme for supporting this work.
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Nanostructured bainite
Proceedings of the Royal Society A: Mathematical Physical and Engineering Sciences, 2009Co-Authors: Harshad Kumar Dharamshi Hansraj BhadeshiaAbstract:An alloy system based on iron is described in which it has been possible to create a high density of interfaces by heat treatment alone. The resulting structure consists of a mixture of slender platelets of bainitic ferrite, just 20–40 nm in thickness, embedded in a matrix of carbon-enriched austenite. The rate at which this structure evolves is slow by conventional standards, but this permits components to be made which are large in all three dimensions, with uniform properties throughout. The fundamental mechanisms behind this novel Nanostructured Steel are reviewed, along with the factors determining its strength, ductility and fracture toughness. It is argued that, although reasonable toughness can be achieved in the context of strength levels exceeding 2000 MPa, the impact toughness remains poor and that it may not be possible to improve this particular parameter.
Mona Naderi - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of nitrogen diffusion in thermo-mechanically Nanostructured and plasma nitrided stainless Steel
Surface & Coatings Technology, 2016Co-Authors: M. Golzar Shahri, S. R. Hosseini, Mansour Salehi, Mona NaderiAbstract:Abstract The effect of grain size on diffusion depth of nitrogen in AISI 321 stainless Steel during plasma nitriding was investigated. The repetitive cold rolling and subsequent annealing were conducted to achieve nano/ultrafine grains in AISI 321 stainless Steel. The grain size range of 130 nm up to 45 μm was obtained under these conditions. Plasma nitriding was performed at temperatures of 400, 450 and 500 °C for duration of 5 h. Microstructural evolutions were conducted by OM, SEM and TEM. The microstructure and composition of the nitrided layer were characterized by SEM and GDOES. Mechanical properties of the S phase were evaluated by micro-hardness testing. Results indicated that nitrided layer of the Nanostructured Steel have uniform appearance with no CrN precipitates, while CrN precipitations were formed in nitrided layer of the micro-grain one. The corrosion resistance of the nitride layer was improved in Nanostructured condition because of uniform appearance of the nitride layer. Furthermore, the hardness of the S phase improved by decreasing substrate grain size. Increasing austenite grain size from 130 nm up to 45 μm, caused to increase surface nitrogen concentration in nitride layer. Decreasing austenite grain size led to decreases the S phase thickness, while the nitrogen diffusion mechanism is the same.
Ruslan Z. Valiev - One of the best experts on this subject based on the ideXlab platform.
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Superior Strength and Multiple Strengthening Mechanisms in Nanocrystalline TWIP Steel.
Scientific Reports, 2018Co-Authors: N.a. Enikeev, M.m. Abramova, Marina V. Karavaeva, Jae-bok Seol, Ruslan Z. Valiev, Chan-gyung ParkAbstract:The strengthening mechanism of the metallic material is related to the hindrance of the dislocation motion, and it is possible to achieve superior strength by maximizing these obstacles. In this study, the multiple strengthening mechanism-based Nanostructured Steel with high density of defects was fabricated using high-pressure torsion at room and elevated temperatures. By combining multiple strengthening mechanisms, we enhanced the strength of Fe-15 Mn-0.6C-1.5 Al Steel to 2.6 GPa. We have found that solute segregation at grain boundaries achieves nanograined and nanotwinned structures with higher strength than the segregation-free counterparts. The importance of the use of multiple deformation mechanism suggests the development of a wide range of strong nanotwinned and Nanostructured materials via severe plastic deformation process.
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Structural strength and corrosion resistance of Nanostructured Steel 10
Steel in Translation, 2014Co-Authors: Ruslan Z. Valiev, G. V. Klevtsov, N. A. Klevtsova, V. M. Kushnarenko, A. V. GaneevAbstract:The ultrafine-grain Steel 10 obtained by equal-channel angular pressing at 200°C is investigated. The structural strength of the Steel samples is analyzed, with tensile tests and assessment of the impact strength and crack resistance. The strength of Steel increases by a factor of 2.5 after equal-channel angular pressing. In the specified conditions, such treatment does not change the cold-brittleness threshold of Steel 10. However, the interval of ductile-brittle transition becomes narrower. Calculations show that the crack resistance K 1C of Steel 10 with an ultrafine grain structure is somewhat greater than that of the regular Steel. The corrosion rate of uncoated Steel 10 samples after equal-channel angular pressing is somewhat greater than in the initial state. However, the corrosion rate of coated Steel 10 samples after equal-channel angular pressing is half that in the initial state. The significance of these findings is discussed.
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Microstructure, properties, and failure characteristics of medium-carbon Steel subjected to severe plastic deformation
IOP Conference Series: Materials Science and Engineering, 2014Co-Authors: Marina V. Karavaeva, M.m. Abramova, A. V. Ganeev, Svetlana K Kiseleva, Ruslan Z. ValievAbstract:The paper deals with two-stage processing of medium-carbon Steel 45 (0.45 % C; 0.27 % Si; 0.65 % Mn) via quenching and high pressure torsion. Such processing combination allowed producing a nanocomposite microstructure with a ferrite matrix and high-dispersed carbides. The ultimate tensile strength of the Nanostructured Steel is over 2500 MPa. The processing effect on the structure, mechanical properties and failure mechanisms of Steel 45 samples is studied. The peculiarities of static fractures in the samples after HPT are demonstrated in comparison with those after quenching.
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A New Deformation Mechanism in Nanoscale Fe-C Composite as a Result of a Stress-Induced α→γ Transformation
Materials Science Forum, 2006Co-Authors: Julia Ivanisenko, Ian Maclaren, Ruslan Z. Valiev, Hans-jörg FechtAbstract:Recent studies of nanocrystalline materials have often found that the deformation mechanisms are radically different to those in coarse-grained materials, resulting in quite different mechanical properties for such materials. The use of pearlitic Steels for the study of the deformation mechanisms in bcc materials with ultrafine grain sizes is quite convenient, because it is relatively straightforward to obtain a homogenous nanocrystalline structure with a mean grain size as small as 10 nm using various modes of severe plastic deformation (SPD). In this paper we show that highpressure torsion of an initially pearlitic Steel results in a Nanostructured Steel in which austenite has been formed at or close to room temperature. The orientation relationship between neighboring ferrite and austenite grains is the well-known Kurdjumov-Sachs orientation relationship, i.e. the same observed in temperature-induced martensitic transformation of iron and Steels. It is shown that this must have resulted from a reverse martensitic transformation promoted by the high shear strains experienced by the material during severe plastic deformation of the nanocrystalline structure. This transformation represents an alternative deformation mechanism that can be activated when conventional deformation mechanisms such as slip of lattice dislocations become exhausted.
K Lu - One of the best experts on this subject based on the ideXlab platform.
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Annealing-induced Hardening in a Nanostructured Low-carbon Steel Prepared by Using Dynamic Plastic Deformation
Journal of Materials Science & Technology, 2014Co-Authors: Matthias Kuntz, J.q. Yu, K LuAbstract:Lamellar nanostructures were induced in a plain martensitic low-carbon Steel by using dynamic plastic deformation at room temperature. The Nanostructured Steel was hardened after annealing at 673 K for 20 min, with a tensile strength increased from 1.2 GPa to 1.6 GPa. Both the remained nanostructures and annealing-induced precipitates in nano-scale play key roles in the hardening.
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Annealing-induced Grain Refinement in a Nanostructured Ferritic Steel
Journal of Materials Science & Technology, 2012Co-Authors: L. M. Wang, Z B Wang, K LuAbstract:A Nanostructured surface layer with a mean ferrite grain size of similar to 8 nm was produced on a Fe-9Cr Steel by means of surface mechanical attrition treatment. Upon annealing, ferrite grains coarsen with increasing temperature and their sizes increase to similar to 40 nm at 973 K. Further increasing annealing temperature leads to an obvious reduction of ferrite grain sizes, to similar to 44 nm at 1173 K. The annealing-induced grain refinement is analyzed in terms of phase transformations in the Nanostructured Steel.
