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Prediction of mechanical behavior of ferrite-pearlite steel

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Journal of Iron and Steel Research International 2017年第3期24卷 321-327页

作者： Lei Wang di tang Yong Song Institute of Engineering Technology University of Science and Technology Beijing Beijing 100083 China

A new approach describing the flow stress of ferrite-pearlite steel has been proposed,which divided the deformation process into three stages based on whether ferrite or pearlite yielded. Iso-work increment assumption was applied to describe the transfer of load between the components. The physically based model to describe ferrite was approximated with Swift＇s equation in order to obtain the analytic *** tensile strength of ferrite-pearlite had a linear relation with pearlite volume fraction,square root reciprocal of ferrite grain size and reciprocal of pearlite interlamellar spacing. Moreover,a model to calculate the tensile strength of ferrite-pearlite steel was proposed. The predicted values of tensile strength were in good agreement with experimental results when the pearlite volume fraction was less than 20%.Considering the plastic relaxation mechanisms,the internal stress was modified with pearlite volume fraction,total strain,yield stress of ferrite and pearlite when the pearlite volume fraction was more than 20%.

关键词： Modeling Ferrite-pearlite steel Flow stress Tensile strength Internal stress

IR study on surface chemical properties of catalytic grown carbon nanotubes and nanofibers

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第5期9卷 720-726页

作者： Li-hua TENG Tian-di tang Institute of Biology and Environmental Science Zhejiang Wanli University Ningbo 315100 China College of Chemistry Northeast Normal University Changchun 130024 China）

In this study, the surface chemical properties of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) grown by catalytic decomposition of methane on nickel and cobalt based catalysts were studied by DRIFT (diffuse Reflectance Infrared Fourier Transform) and transmission Infrared (IR) spectroscopy. The results show that the surface exists not only carbon-hydrogen groups, but also carboxyl, ketene or quinone (carbonyl) oxygen-containing groups. These functional groups were formed in the process of the material growth, which result in large amount of chemical defect sites on the walls.

关键词： Carbon nanotubes (CNTs) Carbon nanofibers (CNFs) Functional surface groups Infrared (IR) spectroscopy

Microstructure evolution of Al-4Cu-Mg alloy during semi-solid treatment

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Journal of University of Science and Technology Beijing 2007年第2期14卷 151-156页

作者： Haitao Jiang Zhenli Mi di tang Miaoquan Li National Engineering Research Center for Advanced Rolling Technology University of Science and Technology Beijing Beijing 100083 China School of Materials Science and Engineering Northwestern Polytechnical University Xi＇an 710072 China

The microstructure of a cold-deformed Al-4Cu-Mg alloy during semi-solid treatment was investigated, which shows that grain detachment and grain spheroidization processes during the semi-solid treatment are very important to control the fabricated semi-solid microstructures. For the two different processes, the driving force comes from the external heat source and the reduction in total interfacial area, respectively. The evolution models of microstructure morphology in the two processes were presented based on microstructure observations. It can be found that these models are useful to provide a reasonable estimated critical time of the evolution of microstructure during the semi-solid treatment.

关键词： Al-4Cu-Mg alloy semi-solid microstructure morphology evolution model

Influence of isothermal bainitic processing on the mechanical properties and microstructure characterization of TRIP steel

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Journal of University of Science and Technology Beijing 2008年第5期15卷 574-579页

作者： Haitao Jiang Hubin Wu di tang Qiang Liu National Engineering Research Center for Advanced Rolling Technology University of Science and Technology Beijing Beijing 100083 China

The mechanical properties of transformation induced plasticity （TRIP） steel are strongly affected by the conditions of iso-thermal bainitic processing. The multiphase microstructure of TRIP steel under different conditions of isothermal bainitic processing was investigated using OM,SEM,XRD and TEM. The volume fraction of retained austenite and the carbon content in austenite were determined quantitatively using X-ray diffraction patterns. The relationship between mechanical properties and isothermal bainitic processing parameters was investigated. The stability of retained austenite was analyzed by the volume fraction of retained austenite and the carbon content in retained austenite. The experimental results show that the multiphase microstructure consists of ferrite,bainite and metastable retained *** obtain good mechanical properties,the optimal conditions of isothermal bainitic temperature and holding time are 410-430°C and 180-240 s,respectively. After isothermal bainitic processing under the optimal conditions,the corresponding volume fraction of retained austenite is 5vol%-15vol%,which can provide enough retained austenite and plastic stability for austenite with high carbon content.

关键词： transformation induced plasticity steel isothermal bainitic processing mechanical properties microstructure

Texture of AZ31B magnesium alloy sheets produced by differential speed rolling technologies

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Rare Metals 2012年第5期31卷 415-419页

作者： LIU Huaqiang tang di CAI Qingwu LI Zhen National Engineering Research Center of Advanced Rolling Technology University of Science & Technology Beijing Beijing 100083 China

The effects of differential speed rolling (DSR) on the texture of AZ31B magnesium alloy sheets were investigated, which were achieved by tailoring deformation temperature, reduction, and speed ratio. The results show that the intensity of basal texture weakens with DSR. With the increase of the rolling temperature, the intensity of basal texture decreased first and then increased, which had a relation with the change of the orientation of the new grains of dynamic recrystallization during rolling. The effect of the reduction on the basal texture was made with the changing degree of sharp point of texture. With increasing the deformation at the same rolling temperature, the intensity of basal texture decreased, and the extending of contour lines decreased in the transverse direction, which was close to the circular distribution. differential speed ratio has a greater impact on the intensity of the basal texture and has a less effect on the basal deflection. © The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg 2012.

关键词： Crystallization Deformation Dynamic recrystallization Magnesium alloys Speed

Research and development of 780 MPa cold rolling TRIP-aided steel

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International Journal of Minerals,Metallurgy and Materials 2009年第4期16卷 399-406页

作者： Qiang Liu di tang Hai-tao Jiang Ren-dong Liu Xiao-yong tang National Engineering Research Center for Advanced Rolling Technology University of Science and Technology Beijing Beijing 100083 China Researchand Development Center Anshan Iron and Steel （Group） Corp. Anshan 114001 Liaoning China

As an industry-university cooperative project, an experimental research was conducted to develop a new cold-rolled transformation-induced plasticity （TRIP） steel with a tensile strength of 780 MPa and an elongation of 25% under the conditions that some processing parameters were preestablished according to the actual conditions of factory production lines. The optimal heat treatment conditions for obtaining excellent strength-ductility balance, specifically in intercritical annealing temperature and isothermal treatment temperature, were investigated by means of thermal simulation tests. Ultimately the desirable mechanical properties were attained successfully, and the microstructure and retained austenite stability were studied by optical microscopy （OM） and electron back-scattered diffraction （EBSD）. It has been discovered that the sizes of retained austenite grains are generally proportional to the sizes of carbon-clear space （ferrite and bainite） around them, and there is marked selectivity in their transition sequences under stress-strain.

关键词： TRIP steel heat treatment retained austenite stability

High-Strength and High-Plasticity TWIP Steel for Modern Vehicle

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Journal of Materials Science & Technology 2005年第4期21卷 451-454页

作者： Zhenli MI di tang Ling YAN Jin GUO National Engineering Research Center for Advanced Rolling Technology University of Science and Technology Beijing Beijing100083 China

In this paper new high-strength and high-plasticity twinning induced plasticity （TWlP） steel for modern automobile body was investigated. Some basic experimental results were given. The results indicate the TWlP steel has excellent properties. It exhibits high ultimate tensile strength （600,--1100 MPa） and extremely large elongation of 60% to 90%.In the future it would be capable of satisfying the requirements of new generation of vehicle.

关键词： TWIP steel Strength Plasticity

Characterization of( Nb,Ti,Mo) C Precipitates in an Ultrahigh Strength Martensitic Steel

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Journal of Iron and Steel Research International 2016年第5期23卷 495-500页

作者： Biao JU Hui-bin WU di tang Ning DANG National Engineering Research Center for Advanced Rolling Technology University of Science and Technology Beijing

A study on ultrahigh strength steel plate subjected to novel thermo-mechanical control process was presented. The mechanical properties examination showed that the investigated steel exhibited excellent combination of ultra-high strength（ 2 200 MPa） and toughness（ 26 J）. The microstructure of the experimental steel was observed by scanning electron microscope and transmission electron microscope. Desired martensitic lath with width of about 180- 250 nm was obtained. Nanostructured carbide precipitates with sizes of 20-50 nm,which contained Nb,Ti and Mo,were observed in the lath martensitic microstructure,and confirmed to be MC-type carbides with B1 structure by means of selected area electron *** compositional characteristics revealed by energy dispersive X-ray spectrometer mapping implied that the carbide forming elements Nb,Ti and Mo distributed in the precipitates evenly. Three-dimensional atom probe tomography reconstruction further indicated that Mo incorporated into the precipitates without enrichment in the carbide-matrix interface and probably substituted for Nb and Ti to form the（ Nb,Ti,Mo） C carbides.

关键词： ultrahigh strength steel precipitate (Nb Ti Mo) C compositional characteristic structural characteristic

Effect of simulated thermomechanical processing on transformation behavior and microstructure of 82B steel

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Journal of Iron and Steel Research International 2019年第1期26卷 69-77页

作者： He Wei Yin-li Chen Lan Su di tang Collaborative Innovation Cemer of Steel Technology University of Science and Technology BeijingBeijing 100083China Beijing Laboratory of Metallic Materials and Processing for Modern Transportation Beijing 100083China

The effects of loop-laying temperature and austenite deformation on the phase(ransformation behavior during continuous cooling,microstructure,and pearlite interlaminar spaci ng in 82B steels were *** and dynamic conti nu ous cooling transformation(CCT)diagrams were measured with a Gleeble-3500 thermal simulator,and the mechanisms governing changes in the initial temperature,initial time,and duration of the phase transformation zone were also analyzed and *** results show that CCT diagram shifted to the bottom right,the initial temperature of the phase transition decreased,the initial time of the phase transition increased,the duration of the phase transition increased,and the lamellar spacing of pearlite was finer as the loop-layi ng temperature in *** initial phase transition time decreased,and the phase transition duration first reduced,then increased,and finally decreased in the static condition and in the dynamic condition at 850℃as the cooling rate ***,the phase transition duration continuously decreased in the dynamic condition at 900℃.At a given loop-laying temperature,the lamellar spacing in pearlite was finer due to austenite deformation compared with the undeformed *** with the results shown in the dynamic CCT diagram,the corresponding phase diagrams of the static CCT diagram slightly shifted to the bottom ***,there was a clear lin ear relationship between the reciprocal of the lamellar spaci ng in pearlite and the average undercooling degree in the phase transformation zone.

关键词： 82B steel Phase transformation Loop-laying temperature Austenite deformation Microstructure