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Control of Strain Hardening Behavior in High-Mn Austenitic Steels

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Acta Metallurgica Sinica(English Letters) 2014年第3期27卷 546-556页

作者： Wenwen Song Tobias Ingendahl wolfgang bleck Steel Institute RWTH Aachen University Intzestr.1 52072 AachenGermany

Austenitic high-Mn steels with Mn contents between approximately 15 and 30 wt% gain much interest because of their excellent mechanical properties and the option for adjusting strain hardening behavior due to different deformation mechanisms. 2D and 3D composition-dependent stacking fault energy （SFE） maps indicate the effect of chemical composition and temperature on SFE and consequently on the deformation mechanisms. Three steels with different chemical compositions and the same or different SFE are characterized in quasi-static tensile tests. The control parameters of strain hardening behavior in the high-Mn austenitic steels are described, and consequences for future developments are discussed.

关键词： High-Mn austenitic steels Stacking fault energy Strain hardening

New Microalloyed Steels for Forgings

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Journal of Iron and Steel Research International 2011年第S1期18卷 104-111页

作者： Christoph Keul wolfgang bleck Department of Ferrous Metallurgy RWTH Aachen UniversityGermany

Microalloyed steels for forging applications have been newly developed in order to increase strength and toughness properties which thereby give the possibility for light weight *** properties of these steels are set up by a controlled cooling directly from the forging heat without an additional heat *** aim can be achieved on the one hand by a further development of precipitation hardening ferritic pearlitic steels (AFP-steel) due to an extended use of microalloying elements (AFP-M steel) and on the other hand by microalloyed steels which employ a bainitic microstructure (HDB steel).To adjust the targeted microstructure the temperature control has to be assured down to approx.500℃ for the AFP-M steels and down to approx.300℃ for the HDB steels.

关键词： forgings bainite microalloying controlled cooling

Hydrogen effect on the mechanical behaviour and microstructural features of a Fe-Mn-C twinning induced plasticity steel

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International Journal of Minerals,Metallurgy and Materials 2021年第5期28卷 835-846页

作者： Xiaofei Guo Stefan Zaefferer Fady Archie wolfgang bleck Steel Institute RWTH Aachen UniversityIntze-str.1Aachen 52072Germany Max-Planck-Institut für Eisenforschung GmbH Max-Planck-Straße 1Düsseldorf 40237Germany NLMK Europe Eutelis-Platz 2Ratingen 40878Germany

The influences of hydrogen on the mechanical properties and the fracture behaviour of Fe-22Mn-0.6C twinning induced plasticity steel have been investigated by slow strain rate tests and fractographic *** steel showed high susceptibility to hydrogen embrittlement,which led to 62.9%and 74.2%reduction in engineering strain with 3.1 and 14.4 ppm diffusive hydrogen,*** fracture surfaces revealed a transition from ductile to brittle dominated fracture modes with the rising hydrogen *** underlying deformation and fracture mechanisms were further exploited by examining the hydrogen effects on the dislocation substructure,stacking fault probability,and twinning behaviour in pre-strained slow strain rate test specimens and notched tensile specimens using coupled electron channelling contrast imaging and electron backscatter diffraction *** results reveal that the addition of hydrogen promotes planar dislocation structures,earlier nucleation of stacking faults,and deformation twinning within those grains which have tensile axis orientations close to//rolling direction and//rolling *** developed twin lamellae result in strain localization and micro-voids at grain boundaries and eventually lead to grain boundary decohesion.

关键词： twinning induced plasticity steel hydrogen mechanical behaviour dislocation twinning electron channelling contrast imaging

Semi-hot Stamping as an Improved Process of Hot Stamping

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Journal of Materials Science & Technology 2011年第4期27卷 369-376页

作者： Malek Naderi Mostafa Ketabchi Mahmoud Abbasi wolfgang bleck Department of Mining and Metallurgy Amirkabir University of Technology Department of Ferrous Metallurgy RWTH-Aachen University

Reducing the forming load, deletion of springback, increasing the formability of sheets as well as producing high strength parts are the main reasons to apply hot stamping process. Hot stamping process and 22MnB5 steels are the state of the art process and grades, respectively; however novel processes and steel grades are under considerations. In the current research, behavior of the steel grade MSW1200 blanks under semi and fully hot stamping processes was characterized. During semi-hot stamping process, the blank was firstly heated to a temperature of about 650℃ and then formed and quenched in the die assembly, simultaneously. Microstructure and mechanical properties of semi and fully hot stamped blanks were studied and the results were compared with those of normally water/air quenched blanks. The hot stamped blanks attained the strength values as high as water quenched blanks. The highest ductility and consequently, the best formability were achieved for the blank which had been semi-hot stamped. It was concluded that for the mentioned steel, semi-hot stamping process could be considered as an improved thermo-mechanical process which not only guaranteed a high formability, but also led to ultra high strength values.

关键词： Semi-hot stamping Hot stamping MSW1200 steel Mechanical properties

Improvement of center segregation in high-carbon steel billets using soft reduction

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Journal of University of Science and Technology Beijing 2006年第6期13卷 490-496页

作者： Wenjun Wang Xionggang Hu Linxin Ning Raimund Bülte wolfgang bleck Institute of Ferrous Metallurgy RWTH Aachen University Intzestrasse 1 52072 Aachen Germany Shougang Group Research Institute Beijing 100041 China

Center segregation is the main reason for cup fracture of high-carbon wire rod during drawing. Therefore, to continuously produce cast billets with very low center segregation is an important objective. The soft reduction technology is considered to be an effective method to minimize center segregation. To elucidate the effect of soft reduction on the internal quality of high-carbon steel billets, soft reduction was applied with different solid fractions in the core area of billets in a laboratory casting machine. A coupled temperature/displacement finite element model was developed to calculate the solid fraction using the commercial software ABAQUS. Center segregation, center porosity, homogeneity of elements, and equiaxed crystal zone were obviously improved by applying soft reduction, especially when the solid fraction was less than 1.0. The optimal results were obtained when the solid fraction was approximately 0.9.

关键词： steel 100Cr6 centre segregation soft reduction finite element model internal cracks

Multiphase-field simulation of austenite reversion in medium-Mn steels

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International Journal of Minerals,Metallurgy and Materials 2021年第5期28卷 847-853页

作者： Yan Ma Rui Zheng Ziyuan Gao Ulrich Krupp Hai-wen Luo Wenwen Song olfgang bleck Steel Institute(IEHK) RWTH Aachen UniversityIntzestraße 152072 AachenGermany Department of Ferrous Metallurgy University of Science and Technology BeijingBeijing 100083China Max-Planck-Institut für Eisenforschung GmbH(MPIE) Max-Planck-Straße 140237 DüsseldorfGermany

Medium-Mn steels have attracted immense attention for automotive applications owing to their outstanding combination of high strength and superior *** steel class is generally characterized by an ultrafine-grained duplex microstructure consisting of ferrite and a large amount of *** a unique microstructure is processed by intercritical annealing,where austenite reversion occurs in a fine martensitic *** the present study,austenite reversion in a medium-Mn alloy was simulated by the multiphase-field approach using the commercial software MICRESS®coupled with the thermodynamic database TCFE8 and the kinetic database *** particular,a faceted anisotropy model was incorporated to replicate the lamellar morphology of reversed *** simulated microstructural morphology and phase transformation kinetics(indicated by the amount of phase)concurred well with experimental observations by scanning electron microscopy and in situ synchrotron high-energy X-ray diffraction,respectively.

关键词： medium-Mn steels intercritical annealing austenite reversion phase-field simulation faceted anisotropy model

Knowledge Based Steel Design for Improved Performance

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Knowledge Based Steel Design for Improved Performance

Microalloyed Engineering Steels

第十届中国钢铁年会暨第六届宝钢学术年会

作者： bleck wolfgang IEHK Steel Institute RWTH Aachen University

Modern steel concepts aim at improved properties by tailoring the microstructure. Three trends are of major interest in nowadays materials development activities: the decrease of the structural length of microstructural constituents towards nanosized quantities, the increase of alloying level and by this the interaction of different elements in enriched zones, extensive use of numerical materials design over various length scales and through long process chains.

关键词： AHSS(advanced high strength steels) HMn S(high Mn steels) bainitic steels virtual microstructure damage tolerance

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Microalloyed Engineering Steels

Recent Developments of Modern Rail Steels

中国金属学会特殊钢分会理事会暨2013年汽车零部件用高品质特殊钢研讨会

作者： bleck wolfgang KONOVALOV Sergey PRAHL Ulrich Steel Institute RWTH Aachen University

Microalloying has been successfully applied for various steel made long products in order to improve component performance or to ease *** might contribute to cost savings due to optimized or substituted heat treatments,it can improve the balance of strength and toughness or improve the cyclic behavior due to improved *** approaches are to provide damage tolerant matrix behavior and by this to increase the service lifetime in high strength *** to the well-known application of microalloying for flat products,the use of Niobium,Titanium and Vanadium in steels with higher C content and during long process chains requests for specific materials and process design *** paper deals with the beneficial options for the control of austenite grain size and transformation kinetics as well as with the constraints for dissolution, precipitation coarsening and segregation effects.

关键词： Engineering Steels Microalloying Forging Steels Case hardening Damage tolerance C-solution

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Recent Developments of Modern Rail Steels