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Mohammad Moallemi - One of the best experts on this subject based on the ideXlab platform.
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Deformation behavior of a high-Plasticity nano/ultrafine-grained N-bearing duplex stainless steel: Twin/twin-like induced Plasticity Effect
2019Co-Authors: Mohammad Moallemi, Abbas Zarei-hanzaki, Kim, Sung Joon, Changwan Hong, Pooriya Dastranjy NezhadfarAbstract:The present study deals with the grain refinement of a high nitrogen duplex stainless steel through cold rolling up to 80% and subsequent reversion annealing in the range of 750 degrees C to 1100 degrees C at various duration times. The microstructural observations showed that the nano/ultrafine-grained (NG/UFG) austenite with the grain size of 400 nm was obtained by annealing at 900 degrees C for 30 s due to alpha-martensite to austenite complete reverse transformation. The NG/UFG duplex steel indicated a superior mechanical properties consist of 1 GPa yield strength (YS) and 40% elongation to fracture. The transmission electron microscopy study of the tensile deformed NG/UFG material indicated that the nature of extraordinary Plasticity in NG/UFG material is because of the dense planar defects, specifically, the twin/twin-like induced Plasticity Effect in austenite, accompanied with strain accommodation of coarse grain ferrite phase.The present study deals with the grain refinement of a high nitrogen duplex stainless steel through cold rolling up to 80% and subsequent reversion annealing in the range of 750 degrees C to 1100 degrees C at various duration times. The microstructural observations showed that the nano/ultrafine-grained (NG/UFG) austenite with the grain size of 400 nm was obtained by annealing at 900 degrees C for 30 s due to alpha-martensite to austenite complete reverse transformation. The NG/UFG duplex steel indicated a superior mechanical properties consist of 1 GPa yield strength (YS) and 40% elongation to fracture. The transmission electron microscopy study of the tensile deformed NG/UFG material indicated that the nature of extraordinary Plasticity in NG/UFG material is because of the dense planar defects, specifically, the twin/twin-like induced Plasticity Effect in austenite, accompanied with strain accommodation of coarse grain ferrite phase.1
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deformation behavior of a high Plasticity nano ultrafine grained n bearing duplex stainless steel twin twin like induced Plasticity Effect
2017Co-Authors: A Zareihanzaki, Mohammad Moallemi, Changwan Hong, Pooriya Dastranjy NezhadfarAbstract:Abstract The present study deals with the grain refinement of a high nitrogen duplex stainless steel through cold rolling up to 80% and subsequent reversion annealing in the range of 750 °C to 1100 °C at various duration times. The microstructural observations showed that the nano/ultrafine-grained (NG/UFG) austenite with the grain size of 400 nm was obtained by annealing at 900 °C for 30 s due to ά-martensite to austenite complete reverse transformation. The NG/UFG duplex steel indicated a superior mechanical properties consist of 1 GPa yield strength (YS) and 40% elongation to fracture. The transmission electron microscopy study of the tensile deformed NG/UFG material indicated that the nature of extraordinary Plasticity in NG/UFG material is because of the dense planar defects, specifically, the twin/twin-like induced Plasticity Effect in austenite, accompanied with strain accommodation of coarse grain ferrite phase.
Dierk Raabe - One of the best experts on this subject based on the ideXlab platform.
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unexpected cyclic stress strain response of dual phase high entropy alloys induced by partial reversibility of deformation
2018Co-Authors: Thomas Niendorf, Zhiming Li, Thomas Wegener, Dierk RaabeAbstract:Abstract The recently developed dual-phase high-entropy alloys are characterized by pronounced strain hardening and high ductility under monotonic loading owing to the associated transformation induced Plasticity Effect. Fatigue properties of high-entropy alloys have not been studied in depth so far. The current study focuses on the low-cycle fatigue regime. Cyclic tests were conducted and the microstructure evolution was studied post-mortem. Despite deformation-induced martensitic transformation during cycling at given plastic strain amplitudes, intense strain hardening in the cyclic stress-strain response is not observed. This behavior is attributed to the planar nature of slip and partial reversibility of deformation.
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nanolaminate transformation induced Plasticity twinning induced Plasticity steel with dynamic strain partitioning and enhanced damage resistance
2015Co-Authors: Meimei Wang, Cemal Cem Tasan, Dirk Ponge, Ann Christin Dippel, Dierk RaabeAbstract:Abstract Conventional martensitic steels have limited ductility due to insufficient microstructural strain-hardening and damage resistance mechanisms. It was recently demonstrated that the ductility and toughness of martensitic steels can be improved without sacrificing the strength, via partial reversion of the martensite back to austenite. These improvements were attributed to the presence of the transformation-induced Plasticity (TRIP) Effect of the austenite phase, and the precipitation hardening (maraging) Effect in the martensitic matrix. However, a full micromechanical understanding of this ductilizing Effect requires a systematic investigation of the interplay between the two phases, with regards to the underlying deformation and damage micromechanisms. For this purpose, in this work, a Fe–9Mn–3Ni–1.4Al–0.01C (mass%) medium-Mn TRIP maraging steel is produced and heat-treated under different reversion conditions to introduce well-controlled variations in the austenite–martensite nanolaminate microstructure. Uniaxial tension and impact tests are carried out and the microstructure is characterized using scanning and transmission electron microscopy based techniques and post mortem synchrotron X-ray diffraction analysis. The results reveal that (i) the strain partitioning between austenite and martensite is governed by a highly dynamical interplay of dislocation slip, deformation-induced phase transformation (i.e. causing the TRIP Effect) and mechanical twinning (i.e. causing the twinning-induced Plasticity Effect); and (ii) the nanolaminate microstructure morphology leads to enhanced damage resistance. The presence of both Effects results in enhanced strain-hardening capacity and damage resistance, and hence the enhanced ductility.
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multistage strain hardening through dislocation substructure and twinning in a high strength and ductile weight reduced fe mn al c steel
2012Co-Authors: I Gutierrezurrutia, Dierk RaabeAbstract:Abstract We investigate the kinetics of the deformation structure evolution and its contribution to the strain hardening of a Fe–30.5Mn–2.1Al–1.2C (wt.%) steel during tensile deformation by means of transmission electron microscopy and electron channeling contrast imaging combined with electron backscatter diffraction. The alloy exhibits a superior combination of strength and ductility (ultimate tensile strength of 1.6 GPa and elongation to failure of 55%) due to the multiple-stage strain hardening. We explain this behavior in terms of dislocation substructure refinement and subsequent activation of deformation twinning. The early hardening stage is fully determined by the size of the dislocation substructure, namely, Taylor lattices, cell blocks and dislocation cells. The high carbon content in solid solution has a pronounced Effect on the evolving dislocation substructure. We attribute this Effect to the reduction of the dislocation cross-slip frequency by solute carbon. With increasing applied stress, the cross-slip frequency increases. This results in a gradual transition from planar (Taylor lattices) to wavy (cells, cell blocks) dislocation configurations. The size of such dislocation substructures scales inversely with the applied resolved stress. We do not observe the so-called microband-induced Plasticity Effect. In the present case, due to texture Effects, microbanding is not favored during tensile deformation and, hence, has no Effect on strain hardening.
Pooriya Dastranjy Nezhadfar - One of the best experts on this subject based on the ideXlab platform.
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Deformation behavior of a high-Plasticity nano/ultrafine-grained N-bearing duplex stainless steel: Twin/twin-like induced Plasticity Effect
2019Co-Authors: Mohammad Moallemi, Abbas Zarei-hanzaki, Kim, Sung Joon, Changwan Hong, Pooriya Dastranjy NezhadfarAbstract:The present study deals with the grain refinement of a high nitrogen duplex stainless steel through cold rolling up to 80% and subsequent reversion annealing in the range of 750 degrees C to 1100 degrees C at various duration times. The microstructural observations showed that the nano/ultrafine-grained (NG/UFG) austenite with the grain size of 400 nm was obtained by annealing at 900 degrees C for 30 s due to alpha-martensite to austenite complete reverse transformation. The NG/UFG duplex steel indicated a superior mechanical properties consist of 1 GPa yield strength (YS) and 40% elongation to fracture. The transmission electron microscopy study of the tensile deformed NG/UFG material indicated that the nature of extraordinary Plasticity in NG/UFG material is because of the dense planar defects, specifically, the twin/twin-like induced Plasticity Effect in austenite, accompanied with strain accommodation of coarse grain ferrite phase.The present study deals with the grain refinement of a high nitrogen duplex stainless steel through cold rolling up to 80% and subsequent reversion annealing in the range of 750 degrees C to 1100 degrees C at various duration times. The microstructural observations showed that the nano/ultrafine-grained (NG/UFG) austenite with the grain size of 400 nm was obtained by annealing at 900 degrees C for 30 s due to alpha-martensite to austenite complete reverse transformation. The NG/UFG duplex steel indicated a superior mechanical properties consist of 1 GPa yield strength (YS) and 40% elongation to fracture. The transmission electron microscopy study of the tensile deformed NG/UFG material indicated that the nature of extraordinary Plasticity in NG/UFG material is because of the dense planar defects, specifically, the twin/twin-like induced Plasticity Effect in austenite, accompanied with strain accommodation of coarse grain ferrite phase.1
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deformation behavior of a high Plasticity nano ultrafine grained n bearing duplex stainless steel twin twin like induced Plasticity Effect
2017Co-Authors: A Zareihanzaki, Mohammad Moallemi, Changwan Hong, Pooriya Dastranjy NezhadfarAbstract:Abstract The present study deals with the grain refinement of a high nitrogen duplex stainless steel through cold rolling up to 80% and subsequent reversion annealing in the range of 750 °C to 1100 °C at various duration times. The microstructural observations showed that the nano/ultrafine-grained (NG/UFG) austenite with the grain size of 400 nm was obtained by annealing at 900 °C for 30 s due to ά-martensite to austenite complete reverse transformation. The NG/UFG duplex steel indicated a superior mechanical properties consist of 1 GPa yield strength (YS) and 40% elongation to fracture. The transmission electron microscopy study of the tensile deformed NG/UFG material indicated that the nature of extraordinary Plasticity in NG/UFG material is because of the dense planar defects, specifically, the twin/twin-like induced Plasticity Effect in austenite, accompanied with strain accommodation of coarse grain ferrite phase.
A Zareihanzaki - One of the best experts on this subject based on the ideXlab platform.
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the sequential twinning transformation induced Plasticity Effects in a thermomechanically processed high mn austenitic steel
2018Co-Authors: Eskandari H Sabzi, A Zareihanzaki, H R Abedi, A Mateo, J J RoaAbstract:Abstract Different initial microstructures with various bimodal grain size distributions (BGSD) were produced in a high Mn austenitic steel through applying a predetermined set of thermomechanical processing cycles. The corresponding room temperature mechanical properties and the related strain hardening behaviors were assessed using tensile testing method. The results indicated that in the microstructure with high grain size bimodality, the length and amplitude of rapid hardening region was well higher than the others. This was attributed to its higher capability to α'-martensite formation. In addition, the threshold strain to initiate martensitic transformation was shifted to the lower one in the microstructure with higher bimodal grain size distribution. The latter was related to the lower arisen back stresses in the interior regions of the coarser grains. Furthermore, different transformation paths were identified as the BGSD changed. The austenite could directly transform to α'-martensite (γ → α') in the microstructure with lower BGSD; in this case the α'-martensite mainly appeared at the intersections of deformation twins. In contrast, in microstructures with higher BGSD, the nucleation occurred at the intersections of e-martensite platelets. The co-existence of these transformation paths provided an extended transformation induced Plasticity Effect ending to a higher elongation to fracture in the course of deformation. In order to summarize the contribution of various strain hardening mechanisms, a deformation map was also constructed. Accordingly, the enhanced ductility/strength properties were attributed to the sequential operation of extended transformation induced Plasticity and twinning induced Plasticity Effects.
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deformation behavior of a high Plasticity nano ultrafine grained n bearing duplex stainless steel twin twin like induced Plasticity Effect
2017Co-Authors: A Zareihanzaki, Mohammad Moallemi, Changwan Hong, Pooriya Dastranjy NezhadfarAbstract:Abstract The present study deals with the grain refinement of a high nitrogen duplex stainless steel through cold rolling up to 80% and subsequent reversion annealing in the range of 750 °C to 1100 °C at various duration times. The microstructural observations showed that the nano/ultrafine-grained (NG/UFG) austenite with the grain size of 400 nm was obtained by annealing at 900 °C for 30 s due to ά-martensite to austenite complete reverse transformation. The NG/UFG duplex steel indicated a superior mechanical properties consist of 1 GPa yield strength (YS) and 40% elongation to fracture. The transmission electron microscopy study of the tensile deformed NG/UFG material indicated that the nature of extraordinary Plasticity in NG/UFG material is because of the dense planar defects, specifically, the twin/twin-like induced Plasticity Effect in austenite, accompanied with strain accommodation of coarse grain ferrite phase.
Hongwu Song - One of the best experts on this subject based on the ideXlab platform.
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in situ x ray diffraction study of martensitic transformation in austenitic stainless steel during cyclic tensile loading and unloading
2012Co-Authors: Shihong Zhang, Ming Cheng, Hongwu SongAbstract:In situ X-ray diffraction was carried out to identify and evaluate strain-induced martensitic transformation in 304 austenitic stainless steel under cyclic tensile loading and unloading. Experimental results indicated that the fraction of strain-induced martensite increases due to the alteration of the internal structure involving the internal stress and dislocation configuration when unloading occurs. It is found that the enhanced transformation-induced Plasticity Effect can prolong the time to neck formation to a significant extent. (c) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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the enhancement of transformation induced Plasticity Effect on austenitic stainless steels by cyclic tensile loading and unloading
2011Co-Authors: Shihong Zhang, Hongwu Song, Ming Cheng, Haiqu ZhangAbstract:Abstract The Effect of loading modes of tensile deformation on the mechanical properties of a metastable austenite stainless steel has been investigated. The stress–strain curves, microstructures and fraction of the martensite are measured and analyzed separately. The results of tensile test indicate that a special loading mode referred as cyclic tensile loading and unloading can improve the strength and the formability of the specimens Effectively. It is noted that the elongation and the ultimate strength are increased by 24.3% and 9.2% respectively at room temperature. Such enhancement of the transformation induced Plasticity Effect is mainly related to remarkable increase of the fraction of strain-induced martensite by the cyclic tensile loading and unloading.