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Effect of Cooling Rates in Coiling Process on Microstructures and Mechanical Properties in Al-Bearing Hot-Rolled TRIP Steel

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Acta Metallurgica Sinica(English Letters) 2019年第10期32卷 1207-1218页

作者： Xiao-Hui wang Jian Kang Yun-Jie Li guo Yuan R. D. K. Misra guo-dong wang State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110819 China Laboratory for Excellence in Advanced Steel Research Department of Metallurgical Material and Biomedical Engineering University of Texas at El Paso El Paso TX 79968 USA

In this study, the effect of cooling rates on microstructures and mechanical properties in a Al-bearing hot-rolled transformation- induced plasticity steel was investigated. The experiments were carried out using hot simulation machine and hot rolling mill, where the samples were cooled at different cooling rates. The results showed that with the increase in cooling rates, film-like retained austenite gradually disappeared and only blocky retained austenite was retained at higher cooling rates. The volume fraction of retained austenite was 9-11% at cooling rates of 0.05-1 ℃/s and 4-6% at cooling rates of 5-10 ℃/s. In addition, martensite/austenite island was observed because of the heterogeneous carbon distribution. The samples cooled at 0.05℃/s and 0.5 ℃/s exhibited excellent mechanical properties, with tensile strengths of 712 MPa and 726 MPa, total elongations of 42% and 36% and strength and ductility balances of 29.91 GPa% and 26.15 GPa%, respectively. During plastic deformation, the instantaneous work hardening exponent of the sample cooled at 0.05 ℃/s increased continuously until it reached the maximum value, while the instantaneous work hardening exponent of the sample cooled at 0.5℃/s remained stable.

关键词： Hot-rolled TRIP steels Cooling rate Microstructures Mechanical properties Work hardening behavior

Carbide Precipitation in Ferrite in Nb–V-Bearing Low-Carbon Steel During Isothermal Quenching Process

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Acta Metallurgica Sinica(English Letters) 2017年第11期30卷 1067-1079页

作者： Xiao-Lin Li Cheng-Shuai Lei Xiang-Tao Deng Yan-Mei Li Yong Tian Zhao-dong wang guo-dong wang State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110819 China

The precipitation behavior of nanometer-sized carbides in ferrite in Nb-V-bearing low-carbon steel was studied by electron microscopy and nanoindentation hardness measurements. The results indicated that interphase precipitation and random precipitation could occur simultaneously for the specimen isothermally treated at 700 ℃ for 60 min, while in other specimens, only random precipitation was observed. This phenomenon might be explained by mass balance criterion during the diffusional phase transformation. Nanohardness result indicated that the average hardness of the specimens isothermally held at 600 ℃ for 20 min was 3.87 GPa. For the specimen isothermally holding at 650 ℃ for 20 min, the average hardness was 4.10 GPa and the distribution of the nanohardness was in a narrower range compared with that of the specimen isothermal holding at 600 ℃ for 20 min. These implied that the carbides in the specimens isothermal treated at 650℃ were more uniformly dispersed, and the number density of the carbides was greater than that treated at 600 ℃. Using Ashby-Orowan model, the contribution of precipitation strengthening to yield strength was estimated to be 110 MPa for the specimen isothermally treated at the temperature of 650 ℃ for 20 min.

关键词： High-strength low-alloy(HSLA) Interphase precipitation Carbides Nanoindentation hardness High-resolution transmission electronic microscopy(HRTEM)

Effects of Processing Variables on Microstructure and Yield Ratio of High Strength Constructional Steels

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Journal of Iron and Steel Research International 2016年第8期23卷 815-821页

作者： Jian KANG Cheng-ning LI Xiao-lei LI Jin-hua ZHAO guo YUAN guo-dong wang State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110819 Liaoning China Shougang Qian'an Iron and Steel Co. Ltd. Qian'an 064404 Hebei China

The process of“controlled rolling＋relaxation＋ultra fast cooling（UFC）”for high strength constructional steel with low yield ratio was *** and corresponding relationship with low yield ratio were *** results showed that the constructional steels with multiphase microstructure of bainitic ferrite,martensite-austenite（M-A）and lath bainite were obtained through the creative *** grain size decreased with the decrease in finish rolling temperature,which enhanced the strength by the grain refinement *** proper relaxation treatment promoted the bainitic ferrite lath width and the formation of blocky M-A *** addition,both the tensile and yield strength increased with the decrease in finish rolling temperature and UFC final temperature,but the yield strength increased more significantly than tensile strength,which caused the increase in yield *** using the process of“controlled rolling＋relaxation＋ultra fast cooling”,the excellent comprehensive mechanical properties of 780 MPa grade constructional steels of 12-40 mm in thickness were achieved.

关键词： relaxation tensile martensite rolling steels refinement ferrite austenite creative finish

Fast compression and reconstruction of astronomical images based on compressed sensing

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Research in Astronomy and Astrophysics 2014年第9期14卷 1207-1214页

作者： wang-Ping Zhou Yang Li Qing-Shan Liu guo-dong wang Yuan Liu School of Information and Control Nanjing University of Information Science & Technology

With the fast increase in the resolution of astronomical images, the question of how to process and transfer such large images has become a key issue in astronomy. We propose a new real-time compression and fast reconstruction algorithm for astronomical images based on compressive sensing techniques. We first reconstruct tile Original signal with fewer measurements, according to its compressibility. Then, based on the characteristics of astronomical images, we apply Daubechies orthogonal wavelets to obtain a sparse representation. A matrix representing a random Fourier ensembleis used to obtain a sparse representation in a lower dimensional space. For reconstructing the image, we propose a novel minimum total variation with block addptive sensing to balance the accuracy and eomputation time. Our experimental results show that the proposed algorithm can efficiently reconstruct colorful astronomicai images with high resolution and improve the applicability of compressed sensing.

关键词： methods: data analysis -- methods: numerical -- techniques: image processing

Effect of Sulfur Content and Sulfide Shape on Fracture Ductility in Case Hardening Steel

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Journal of Iron and Steel Research International 2011年第8期18卷 58-64页

作者： XIAO guo-hua dong Han wang Mao-qiu HUI Wei-jun National Engineering Research Center of Advanced Steel Technology Central Iron andSteel Research Institute Beijing 100081 China

The effects of sulfur content and calcium addition on smooth axisymmetric tensile fracture ductility of case hardening steel DIN 18CrNiMo7-6 have been investigated. The quantitative metallographic analysis of sulfide inclusions and the correlations between sulfide inclusions and fracture ductility were examined. Sulfide inclusions were found to have deleterious effect on fracture ductility, whereas the effect can be offset to some extent by calcium-treat- ment due to less easily deforming of sulfides during hot-working. The product （AA·λAW） of sulfide inclusion area fraction （An） and its area-weighted aspect ratio （λAW） can be used as a parameter to describe the effect of sulfide inclusions on fracture true strain.

关键词： case hardening steel calcium treatment sulfide fracture ductility

Modeling flow stress and grain size of GCr15 bearing steel at hightemperature deformation near end of solidification

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Journal of Iron and Steel Research International 2023年第1期30卷 88-101页

作者： Rui-hao Li Hai-jun Li Ning Xiang guo-dong wang Li-juan Bai The State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819LiaoningChina HBIS Group Technology Research Institute Shijiazhuang 050000HebeiChina

Hot-core heavy reduction rolling is an innovative technology for continuous casting billet at the end of *** deformation characteristics of GCr15 bearing billet were investigated over the temperature range of 1000-1300℃ with the strain rate of 0.001-10 s^(-1) by the Gleeble 3800 thermo-mechanical ***,the true stress-strain data are calibrated by the friction correction method to acquire accurate parameters near the ***,the Laasraoui-type constitutive model and dynamic austenite grain size model are established by the thermal compression results and corrosion experimental results,and the predicted values of the experimental interval are obtained by using the ***,the accuracy of models is verified by comparing the predicted curves with the experimental *** but not the least,the dynamic parameters between solidus and liquidus are predicted by the two models,and the difficulty of experimental collecting near the melting point is solved.

关键词： Hot-core heavy reduction rolling High-temperature deformation GCr15 bearing billet Dynamic recrystallization Dynamic grain model

Dynamical changing patterns of histological structure and ultrastructure of liver graft undergoing warm ischemia injury from non-heart-beating donor in rats

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World Journal of Gastroenterology 2006年第30期12卷 4902-4905页

作者： Yi Ma guo-dong wang Lin-Wei Wu Rui-De Hu Organ Transplantation Center the First Affiliated Hospital Sun Yat-Sen UniversityGuangzhou 510080 Guangdong Province China Department of Pathology Sun Yat-Sen UniversityGuangzhou 510080 Guangdong Province China

AIM： To investigate the histological and ultra-structural characteristics of liver graft during different of warm ischemia time （WIT） in rats and to predict the maximum limitation of liver graft to warm ischemia. METHODS： The rats were randomized into 7 groups undergoing warm ischemia injury for 0, 10, 15, 20, 30, 45 and 60 min, respectively. All specimens having undergone warm ischemia injury were investigated dynamically by light and electron microscopy, and histochemistry staining. After orthotopic liver transplantation （OLT）, the recovery of morphology of liver grafts after 6, 24 and 48 h was observed. RESULTS： The donor liver from non-heart-beating donors （NHBD） underwent ischemia injury both in the warm ischemia period and in the reperfusion period. Morphological changes were positively related to warm ischemia injury in a time-dependent manner during the reperfusion period. The results demonstrated that different degrees of histocyte degeneration were observed when WIT was within 30 min, and became more severe with the prolongation of WIT, no obvious hepatocyte necrosis was noted in any specimen. In the group undergoing warm ischemia injury for 45 min, small focal necrosis occurred in the central area of hepatic Iobule first. In the group undergoing warm ischemia injury for 60 rain, patchy or diffused necrosis was observed and the area was gradually extended, while hepatic sinusoid endothelial cells were obviously swollen. Hepatic sinusoid was obstructed and microcirculation was in disorder.CONCLUSION： The rat liver graft undergoing warm ischemia injury is in the reversible stage when the WIT is within 30 min. The 45 min WIT may be a critical point of rat liver graft to endure warm ischemia injury. When the WIT is over 60 min, the damage is irreversible.

关键词： Liver transplantation Warm ischemia injury Morphological observation

Hydrogen Embrittlement of Advanced High-Strength Steel for Automobile Application:A Review

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Acta Metallurgica Sinica(English Letters) 2023年第7期36卷 1144-1158页

作者： Ming-Tu Ma Ke-Jian Li Yu Si Peng-Jun Cao Hong-Zhou Lu Ai-Min guo guo-dong wang State Key Laboratory of Vehicle NVH and Safety Technology Chongqing 401122China China Automotive Engineering Research Institute Co. Ltd.Chongqing 401122China School of Metallurgy and Materials Engineering Chongqing University of Science&TechnologyChongqing 401331China CITIC Metal Co.Ltd Beijing 100004China RAL of dongbei University Shenyang 110819China

The hydrogen embrittlement(HE)fracture of advanced high-strength steels used in lightweight automobiles has received increasing public *** source,transmission,and movement of hydrogen,characterization parameters,and test methods of HE,as well as the characteristics and path of HE fractures,are *** mechanisms and modes of crack propagation of HE and hydrogen-induced delayed fracture are *** recent progress surrounding micro and macro typical fracture characteristics and the influencing factors of HE are ***,methods for improving HE resistance can be summarized as follows:(1)reducing crystalline grain and inclusion sizes(oxides,sulfides,and titanium nitride),(2)controlling nano-precipitates(niobium carbide,titanium carbide,and composite precipitation),and(3)increasing residual austenite content under the reasonable tension strength of steel.

关键词： Hydrogen embrittlement High-strength steel Hydrogen-induced delayed cracking Hydrogen trapping Residual austenite

Growth and Electronic Properties of Ag Nanoparticles on Reduced CeO2-x（111） Films

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Chinese Journal of Chemical Physics 2012年第6期25卷 713-718,I0004页

作者： Dan-dan Kong Yong-he Pan guo-dong wang Hai-bin Pan Jun-fa Zhu National Synchrotron Radiation Laboratory University of Science and Technology of China Hefei230029 China

Ag nanoparticles grown on reduced CeO2-x thin films have been studied by X-ray plhotoelec- tron spectroscopy and resonant photoelectron spectroscopy of the valence band to understand the effect of oxygen vacancies in the CeO2-x thin films on the growth and interracial elec- tronic properties of Ag. Ag grows as three-dimensional particles on the CeO2-x （111） surface at 300 K. Compared to the fully oxidized ceria substrate surface, Ag favors the growth of smaller particles with a larger particle density on the reduced ceria substrate surface, which can be attributed to the nucleation of Ag on oxygen vacancies. The binding energy of Ag3d increases when the Ag particle size decreases, which is mainly attributed to the final-state screening. The interracial interaction between Ag and CeO2_x（lll） is weak. The resonant enhancement of the 4f level of Ce3＋ species in RPES indicates a partial Ce4＋--＋Ce3＋ reduction after Ag deposited on reduced ceria surface. The sintering temperature of Ag on CeO 1.85 （111） surface during annealing is a little higher than that of Ag on CeO2 （111） surface, indicating that Ag nanoparticles are more stable on the reduced ceria surface.

关键词： Silver Ceria Growth Electronic structure X-ray photoelectron spectroscopy Resonant photoelectron spectroscopy