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Evolution of carbides and carbon content in matrix of an ultra-high carbon sintered steel during heat treatment process

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International Journal of Minerals,Metallurgy and Materials 2009年第3期16卷 299-303页

作者： yuan-zhi zhu Zhe zhu zhi-min Yin zhi-dong Xiang Key Laboratory of the Ministry of Education of China for Ferrous Metallurgy and Resources Utilization Wuhan University of Science and Technology Wuhan 430081 China School of Materials and Metallurgy Wuhan University of Science and Technology Wuhan 430081 China School of Material Science ＆ Engineering Central South University Changsha 410083 China

DTA, thermal expansion, XRD, and SEM were used to evaluate the effect of quenching temperature on the mechanical properties and microstructure of a novel sintered steel Fe-6Co-1Ni-5Cr-5Mo-1C. Lattice parameters and the mass fraction of carbon dissolved in the matrix of the steel quenched were investigated. It is discovered that the hardness of the steel increases with quenching temperature in the range of 840-900℃ and remains constant in the range of 900 to 1100℃. It decreases rapidly when the temperature is higher than 1100℃. The mass fraction of carbon dissolved in the matrix of the steel quenched at 840℃ is 0.38, but when the quenching temperature is increased to 1150℃, it increases to 0.98. The carbides formed during sintering are still present at grain boundaries and in the matrix of the steel quenched at low quenching temperatures, such as 840℃. When the quenching temperature is increased to 1150℃, most of the carbides at grain boundaries are dissolved with just a small amount of spherical M23C6 existing in the matrix of the quenched steel.

关键词： ultra-high carbon sintered steel heat treatment mechanical properties microstructure

A method to study interface diffusion of arsenic into a Nb-Ti microalloyed low carbon steel

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International Journal of Minerals,Metallurgy and Materials 2012年第9期19卷 821-826页

作者： yuan-zhi zhu Jian-ping XU The Key Laboratory of the Ministry of Education of China for Ferrous Metallurgy and Resources Utilization Wuhan University of Science and Technology Wuhan 430081 China School of Materials and Metallurgy Wuhan University of Science and Technology Wuhan 430081 China

A novel diffusion couple method was used to investigate the interface diffusion of arsenic into a Nb-Ti microalloyed low carbon steel and its effects on phase transformation at the interface. It is discovered that the content of arsenic has great effect on grain growth and phase transformation at high temperature. When the arsenic content is no more than lwt%, there is no obvious grain growth and no obvious ferrite transitional region formed at the diffusion interface. However, when the arsenic content is no less than 5wt%, the grain grows very rapidly. In addition, the arsenic-enriched ferrite transitional layer forms at the diffusion interface in the hot-rolling process, which results from a slower diffusion rate of arsenic atoms than that of carbon in ferrite.

关键词： low carbon steel alloy steel arsenic diffusion bonding phase transformation grain growth

Grain boundary segregation of minor arsenic and nitrogen at elevated temperatures in a microalloyed steel

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International Journal of Minerals,Metallurgy and Materials 2012年第5期19卷 399-403页

作者： yuan-zhi zhu Zhe zhu Jian-ping Xu The Key Laboratory of the Ministry of Education of China for Ferrous Metallurgy and Resources Utilization Wulaan University of Science and Technology Wuhan430081 China School of Materials and Metallurgy Wuhan University of Science and Technology Wuhan 430081 China

Auger electron spectroscopy （AES） was used to investigate the grain boundary segregation of arsenic and nitrogen in a kind of microalloyed steel produced by a compact strip production （CSP） technology at 950 to 1100℃, which are similar to the hot working temperature of the steel on a CSP production line. It was discovered that arsenic segregated on grain boundaries when the steel was annealed at 950℃ for 2 h. When the annealing temperature increased to 1100℃, arsenic was also found to have segregated on grain boundaries in the early annealing stage, for instance, within the first 5 min annealing time. However, if the holding time of the steel at this temperature increased to 2 h, arsenic diffused away from grain boundaries into the matrix again. Nitrogen was not found to have segregated on grain boundaries when the steel was annealed at a relatively low temperature, such as 950℃. But when the annealing temperature increased to 1100℃, nitrogen was detected to have segregated at grain boundaries in the steel.

关键词： alloy steel arsenic nitrogen segregation grain boundaries

Effects of the microstructure of twin roll cast and hot rolled plates on the surface quality of presensitized plates

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International Journal of Minerals,Metallurgy and Materials 2014年第9期21卷 919-924页

作者： yuan-zhi zhu Ya-Feng Zhang Chao-Qi Zhao Feng Zhou College of Mechanical and Electrical Engineering North China University of Technology Key Laboratory for Ferrous Metallurgy and Resources Utilization of the Ministry of Education Wuhan University of Science and Technology

The effect of the microstructure of plates fabricated both in the traditional process, involving casting, hot rolling and cold rolling （HR）, and in the novel twin roll casting ＋ cold rolling （TRC） process on the surface quality of presensitized （PS） plates was analyzed by optical microscopy （OM）, scanning electron microscopy （SEM）, and energy-dispersive X-ray spectroscopy （EDXS）. The formation of pores on the surface of the electrolyzed HR plate could be attributed to the presence of approximately 1-μm-sized large Al-Fe precipitates in the HR plate compared to the smaller precipitates in the TRC plate. Moreover, residual graphite lubricants used during the TRC process were entrapped on the surface of the TRC plate during the subsequent rolling process. The entrapped pollutants tended to further deteriorate the formation of pores on the surface of the TRC plate, and no residual carbon was detected on the surface of the HR plate. Furthermore, the surface quality of the TRC plate can be improved by surface cleaning before the cold rolling process, which could dramatically lower the residual graphite on the surface.

关键词： aluminum plates microstructure presensitizing surface quality

Adaptive Fuzzy Dynamic Surface Control for Uncertain Nonlinear Systems

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International Journal of Automation and computing 2009年第4期6卷 385-390页

作者： Xiao-yuan Luo zhi-Hao zhu Xin-Ping Guan Institute of Electrical Engineering Yanshan University Qinhuangdao 066004 PRC

In this paper, a robust adaptive fuzzy dynamic surface control for a class of uncertain nonlinear systems is proposed. A novel adaptive fuzzy dynamic surface model is built to approximate the uncertain nonlinear functions by only one fuzzy logic system. The approximation capability of this model is proved and the model is implemented to solve the problem that too many approximators are used in the controller design of uncertain nonlinear systems. The shortage of ＂explosion of complexity＂ in backstepping design procedure is overcome by using the proposed dynamic surface control method. It is proved by constructing appropriate Lyapunov candidates that all signals of closed-loop systems are semi-globally uniformly ultimate bounded. Also, this novel controller stabilizes the states of uncertain nonlinear systems faster than the adaptive sliding mode controller （SMC）. Two simulation examples are provided to illustrate the effectiveness of the control approach proposed in this paper.

关键词： Uncertain nonlinear systems fuzzy logic system dynamic surface control backstepping design

Commwarrior worm propagation model for smart phone networks

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The Journal of China Universities of Posts and Telecommunications 2008年第2期15卷 60-66页

作者： XIA Wei LI Zhao-hui CHEN Zeng-qiang yuan zhu-zhi College of Information Technical Science Nankai UniversityTianjin 300071 China

Commwarrior worm is capable of spreading through both Bluetooth and multimedia messaging service （MMS） in smart phone networks. According to the propagation characteristics of Bluetooth and MMS, we built the susceptibleexposed-infected-recovered-dormancy （SEIRD） model for the Bluetooth and MMS hybrid spread mode and performed the stability analysis. The simulation results show good correlation with our theoretical analysis and demonstrate the effectiveness of this dynamic propagation model. On the basis of the SEIRD model, we further discuss at length the influence of the propagation parameters such as user gather density in groups, moving velocity of smart phone, the time for worm to replicate itself, and other interrelated parameters on the propagation of the virus. On the basis of these analytical and simulation results, some feasible control strategies will be proposed to restrain the spread of mobile worm such as commwarrior on smart phone network.

关键词： smart phone virus spreading model Bluetooth,MMS

Isothermal oxidation behavior and mechanism of a nickel-based superalloy at 1000°C

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International Journal of Minerals,Metallurgy and Materials 2017年第7期24卷 776-783页

作者： zhi-yuan zhu yuan-fei Cai You-jun Gong Guo-ping Shen Yu-guo Tu Guo-fu Zhang School of Material Science and Engineering Jiangsu University of Science and Technology Technology Center Jiangsu Shenyuan Special Steel Co.Ltd

The oxidation behavior of a nickel-based superalloy at 1000°C in air was investigated through X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy analysis. A series of oxides, including external oxide scales（Cr_2O_3,（TiO_2 ＋ Mn Cr_2O_4）） and internal oxides（Al_2O_3,Ti N）, were formed on the surface or sub-surface of the substrate at 1000°C in experimental still air. The oxidation resistance of the alloy was dependent on the stability of the surface oxide layer. The continuity and density of the protective Cr_2O_3 scale were affected by minor alloying elements such as Ti and Mn. The outermost oxide scale was composed of TiO_2 rutile and Mn Cr_2O_4 spinel, and the growth of TiO_2 particles was controlled by the outer diffusion of Ti ions through the pre-existing oxide layer. Severe internal oxidation occurred beneath the external oxide scale, consuming Al and Ti of the strength phase γ′（Ni_3（Al,Ti）） and thereby severely deteriorating the surface mechanical properties. The depth of the internal oxidation region was approximately 35 μm after exposure to experimental air at 1000°C for 80 h.

关键词： nickel-based superalloy isothermal oxidation oxide scale internal oxidation

Spreading behavior of SIS model with non-uniform transmission on scale-free networks

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The Journal of China Universities of Posts and Telecommunications 2009年第1期16卷 27-31页

作者： XIA Cheng-yi LIU Zhong-xin CHEN Zeng-qiang yuan zhu-zhi Department of Automation Nankai University Tianjin 300071 China Tianjin Key Laboratory of Intelligence Computing and Novel Software Technology Tianjin University of Teclmology Tianjin 300191 China

The non-uniform transmission and network topological structure are combined to investigate the spreading behavior of susceptible-infected-susceptible （SIS） epidemic model. Based on the mean-field theory, the analytical and numerical results indicate that the epidemic threshold is correlated with the topology of underlying networks, as well as the disease transmission mechanism. These discoveries can greatly help us to further understand the virus propagation on communication networks.

关键词： spreading behavior SIS non-uniform transmission scale-free networks virus propagation

Heteroatom-Doped Black Phosphorus and Its Application:A Review

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Chinese Journal of Chemistry 2021年第3期39卷 690-700页

作者： Lu-dong He Pei-chao Lian yuan-zhi zhu Jun-ping Zhao Yi Mei Faculty of Chemical Engineering Kunming University of Science and TechnologyYunnan Provincial Key Laboratory of Energy Saving in Phosphorus Chemical Engineering and New Phosphorus-based MaterialsKunmingYunnan 650500China

Few-layer black phosphorus(BP)is a promising semiconductor with excellent optoelectronic ***,the poor stabilization and strong asymmetry between electron and hole transports hinder the application of *** of heteroatoms is an effective strategy to regulate the electronic structure and stability of BP without sacrificing its unique 2D structure,which is a promising way to tune the physico-chemical properties of BP for various *** this review,the recent advances in doping engineer-ing of BP are summarized,involving the theoretical prediction of new characteristic for doped BP and the corresponding experimental synthesis *** effects of dopant atoms on the structure and perfor-mance of BP and its related applications,such as the field-effect transistors,optoelectronic devices,in-verter devices,and catalysis,are also summarized.

关键词： Black phosphorus Phosphorus Doping methods Physicochemical properties I Sensors