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Dynamic covalent gels assembled from small molecules：from discrete gelators to dynamic covalent polymers

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Chinese Chemical Letters 2017年第2期28卷 168-183页

作者： jian-yong zhang Li-Hua Zeng Juan Feng Sun Yat-Sen University Lehn Institute of Functional Materials MOE Key Laboratory of Polymeric Composite and Functional MaterialsGuangzhou 510275 China

Dynamic covalent chemistry has emerged recently to be a powerful tool to construct functional *** article reviews the progress in the research and development of dynamic covalent chemistry in gels assembled from small *** dynamic covalent reactions used in gels are reviewed to understand the dynamic covalent *** the catalogues of dynamic covalent gels are reviewed according to the nature of gelators and the interactions between *** covalent bonding can be involved to form low molecular weight *** molecular weight molecules with multiple functional groups react to form dynamic covalent cross-linked polymers and act as *** catalogues of gels show different properties arising from their different *** review aims to illustrate the structure-property relationships of these dynamic covalent gels.

关键词： Gels Dynamic covalent chemistry Supramolecular gels Molecular gels Porous materials

Hydrogen-induced delayed fracture of Cu-containing high-strength bolt steel

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Journal of Iron and Steel Research International 2023年第2期30卷 375-383页

作者： Xiao-li Zhao Cheng-xiang zhang yong-jian zhang Wei-jun Hui Xiu-ming Zhao Materials Science and Engineering Research Center School of MechanicalElectronic and Control EngineeringBeijing Jiaotong UniversityBeijing100044China School of Materials Science and Engineering Nanjing Institute of TechnologyNanjing211167JiangsuChina

The hydrogen-induced delayed fracture(HIDF)behavior of a 1300-MPa-grade high-strength bolt steel 42CrMoV containing 0.42 wt.%Cu was investigated by constant load tensile test in a pH 3.5 Walpole *** is shown that the addition of Cu is beneficial to enhance the HIDF resistance by~13%.The observation of the fracture surface revealed that the area fraction of brittle crack initiation zone decreased remarkably for the Cu-added *** the corrosion pit depth and the corrosion rate of the Cu-added steel in the Walpole solution are notably decreased,which is primarily because of the formation of a Cu-rich protective compact rust layer and slightly higher corrosion *** a result,the absorbed hydrogen content in that solution was also decreased by~21%.It is concluded that the improvement in the HIDF resistance of the tested steel is primarily due to the increase in corrosion resistance and resultant decrease in the absorbed diffusible hydrogen content in the acidic condition.

关键词： Hydrogen-induced delayed fracture Hydrogen embrittlement High-strength bolt steel Copper Corrosion

Microstructure and mechanical properties of hot-rolled V-microalloyed Al-containing medium-Mn steel

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Journal of Iron and Steel Research International 2020年第5期27卷 537-548页

作者： Ming Lei Wei-jun Hui Jiao-jiao Wang yong-jian zhang Xiao-li Zhao School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China

The microstructure and mechanical properties of a V-microalloyed Al-containing medium-Mn steel after hot rolling and intercritical annealing(IA)are *** tested steel exhibits a fne multiphase microstructure consisting of bimodal sizes of ferrite and retained austenite plus considerable amount of fne VC and/or M3C ***-chemical phase analysis shows that about 71.0%of the total V is in VC phase and more than 93%of VC particles is less than 5 *** calculated precipitation strengthening values of VC are^347 and^234 MPa for the specimens intercritically annealed at 625 and 750℃,*** excellent combination of strength and ductility as high as^50 GPa%and yield strength(YS)of 890 MPa was obtained at intercritical temperature(TIA)of 725℃,although it does not correspond to the maximum precipitation strengthening of VC ***,it is suggested that an optimization of TIA corresponding to both excellent combination of strength and ductility and high YS should be further explored through chemical composition and IA process optimization.

关键词： Medium-Mn steel Vanadium Intercritical annealing Microstructure Mechanical property

Influence of Vanadium on Fracture Splitting Property of Medium Carbon Steel

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Journal of Iron and Steel Research International 2016年第5期23卷 475-483页

作者： Wei-jun HUI Cheng-wei SHAO yong-jian zhang Si-lian CHEN Han DONG School of Mechanical Electronic and Control Engineering Beijing Jiaotong University Beijing 100044 China Central Iron and Steel Research Institute Beijing 100081 China

The fracture splitting property of medium carbon steel 37MnSiS microalloyed with V up to 0. 45% was investigated by using simulated fracture splitting test,for the development of new crackable medium carbon steel to manufacture high performance connecting rod. Conventional high carbon steel C70S6 was used for comparison. The results show that the volume fraction of both ferrite and V-rich M（ C,N） particles increases,and the pearlite interlamellar spacing decreases with increasing V content,which in turn results in gradual increase of strength and decrease of ductility and impact energy. The fracture splitting property of the tested steel could be improved significantly due to the increase of V content mainly through the precipitation hardening mechanism of fine M（ C,N） precipitates. The fraction of brittle cleavage fracture in the crack initiation area increases noticeably with increasing V content and full brittle cleavage fracture surface could be obtained when V content was increased to 0. 45%. It is concluded that medium carbon steel with V content higher than about 0. 28% possesses not only comparable or even higher mechanical properties with those of conventional steel C70S6,but also excellent fracture splitting property,and therefore,is more suitable to fabricate high performance fracture splitting connecting rod.

关键词： microalloyed medium carbon steel fracture splitting vanadium precipitation hardening microstructure

Effect of vanadium on dynamic continuous cooling transformation behavior of medium-carbon forging steels

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Journal of Iron and Steel Research International 2017年第6期24卷 641-648页

作者： Wei-jun Hui Na Xiao Xiao-li Zhao yong-jian zhang Yu-feng Wu School of Mechanical Electronic and Control Engineering Beijing Jiaotong University Beijing 100044 China Faculty of Materials Science and Engineering Kunming University of Science and Technology Kunming 650093 Yunnan China

Dynamic continuous cooling transformation （CCT） behavior of medium-carbon forging steels microalloyed with different V contents up to 0.29% was investigated by means of dilatometric measurement, microstructural observation and hardness measurement. The re- sults showed that the dynamic CCT diagrams were similar and the main difference was that the fields of the transformation products were shifted to the right side of the diagrams with the increase of V content, and this effect was more noticeable with an addition of 0. 290/00 V. The At1 and At3 temperatures showed increasing trends with increasing V content, while the critical cooling rates decreased with increasing V content. The increase of V content re- sulted in significant increase of hardness and this tendency was enhanced with increasing cooling rate until the formation of acicular ferrite （AF）. A promising approach of remark- ably improving the toughness of ferritic-pearlitic medium-carbon forging steels with suit- able V addition and the introduction of AF without notable penalty on its strength level was suggested.

关键词： Dynamic CCT diagramVanadiumMicroalloyed steelMierostruetureHardness

Thermal stability of retained austenite and mechanical properties of medium-Mn steel during tempering treatment

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Journal of Iron and Steel Research International 2017年第8期24卷 830-837页

作者： Xiao-li Zhao yong-jian zhang Cheng-wei Shao Wei-jun Hui Han Dong School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China Central Iron and Steel Research Institute Beijing 100081China

The thermal stability of retained austenite（RA）and the mechanical properties of the quenched and intercritical annealed 0.1C-5Mn steel with the starting ultrafine lamellar duplex structure of ferrite and retained austenite during tempering within the range from 200 to 500°C were studied by X-ray diffraction（XRD）,transmission electron microscopy（TEM）and tensile *** results showed that there was a slight decrease in the RA volume fraction with increasing tempering temperature up to 400°*** caused a slight increase in the ultimate tensile strength（UTS）and a slight decrease in the total elongation（TE）;thus,the product of UTS to TE（UTS×TE）as high as 31GPa·% was obtained and remained nearly ***,aportion of the RA began to decompose when tempered at 500°C and thus caused a^35% decrease of the RA fraction and a^16%decrease of the value of UTS×*** is concluded that the ultrafine lamellar duplex structure is rather stable and the excellent combination of strength and ductility could be retained with tempering temperature up to 400°***,thermal processes such as galvanization are feasible for the tested steel provided that their temperatures are not higher than 400°C.

关键词： Medium-manganese transformation-induced plasticity steel Tempering Microstructure Mechanical property Retained austenite

NUMERICAL SIMULATION OF UPLIFT FORCES ON SLAB IN PLUNGE POOL

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Journal of Hydrodynamics 2002年第3期14卷 91-96页

作者： Li, Yan-Ling Yang, yong-Quan zhang, jian-Min Hydraulics Lab. of High Speed Flows Sichuan Univ. Chengdu 610065 China

The mechanism of the fluid-solid coupled vibration is analyzed as the fluctuating pressure acts on the inlet and the outlet slits of a slab. The parameter multinomial method was exploited to calculate the pressure field within the joints of the slabs by solving the basic equations of the oscillation flow. The calculated result shows that the time-averaged uplift increases with the increase of the length of the slab and is large in the middle and is small in both sides. The time-averaged uplift reduces with the increase of water depth, and the fluctuating uplift reduces rapidly with the increase of the thickness of the slit. The calculated result is in agreement with the experimental results.

关键词： Energy dissipators Flow of fluids Numerical analysis Uplift pressure Vibrations (mechanical)

Hydrogen embrittlement of a microalloyed bainitic forging steel

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Journal of Iron and Steel Research International 2019年第9期26卷 1011-1021页

作者： Wei-jun Hui Zhan-hua Wang Zhi-bao Xu yong-jian zhang Xiao-li Zhao Materials Science and Engineering Research Center School of MechanicalElectronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China Yantai Branch of China North Industries Group Corporation No. 52 Institute Co. Ltd.Yantai 264003ShandongChina

The hydrogen embrittlement (HE) of a novel microalloyed bainitic forging steel with a strength level of 1100 MPa was evaluated using electrochemical charging and slow strain rate tensile test method with notched round bar specimens. The results show that the susceptibility to HE of the as-forged bainitic forging steel is notably higher than that of the quenched and tempered (Q&T) steel at same strength level, which is ascribed primarily to the presence of a relatively high amount of large blocky martensite/austenite (M/A) constituents of the former. It was found that low-temperature tempering treatment at 200 C could significantly alleviate the susceptibility to HE by a relative decrease of * 35% of the as-forged bainitic forging steel at no expense of strength and ductility, though its resistance to HE is still a little lower than that of the Q&T steel. Thus, it is suggested that efforts concerning refining of the large blocky M/A through optimizing chemical composition and processing route could help to further alleviate the susceptibility to HE of the tested bainitic forging steel.

关键词： Hydrogen embrittlement Bainitic forging steel Microstructure Granular bainite M/A constituent

Hot Deformation Behavior of Vanadium-microalloyed Medium-carbon Steel for Fracture Splitting Connecting Rod

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Journal of Iron and Steel Research International 2015年第7期22卷 615-621页

作者： Wei-jun HUI Si-lian CHEN Cheng-wei SHAO yong-jian zhang Han DONG School of Mechanical Electronic and Control EngineeringBeijing Jiaotong University Central Iron and Steel Research Institute

Single compression tests were carried out with a Gleeble-3800 thermal simulator to investigate hot deform- ation behavior of two vanadium-microalloyed medium-carbon steels for fracture splitting connecting rod. The tests were performed to a total true strain of 0.92 at true strain rates ranging from 10-2 to 10 s-1 and deformation temper- ature of 900--1 150 ℃, The results show that hot deformation behavior of the tested steels is similar to that of con- ventional medium-carbon microalloyed steels and dynamic recrystallization is easier to occur at higher deformation temperature and lower strain rate. The austenite deformation resistance and activation energy of deformation increase with increasing vanadium content from 0.15% to 0. 28% and thus the starting time of dynamic recrystallization was delayed. Finer recrystallized austenite grain could he obtained at higher strain rate, lower deformation temperature and higher vanadium content. TEM observation of the specimens quenched just before and after deformation reveals that vanadium is mainly in dissolved solute condition in austenite and thus affects the dynamic recrystallization behavior of the tested steels mainly through solute-drag effect.

关键词： vanadium microalloyed medium-carbon steel hot deformation dynamic recrystallization fracture splitting connected rod