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Phase selection and microstructure evolution within eutectic Ti-Si alloy solidified at containerless state

Science China(Technological Sciences) 2022年第7期65卷 1587-1598页

作者： LUO ZhiCong chang jian WANG HaiPeng School of Physical Science and Technology Northwestern Polytechnical UniversityXi'an 710072China

Phase selection and microstructure evolution of the undercooled eutectic Ti-Si alloy were systematically investigated by the electromagnetic levitation method, and the maximum undercooling achieved was 318 K(0.2 TE). The migration of the liquidsolid interface was in-situ detected by a high-speed camera system. When the undercooling is smaller than 140 K, the liquid-solid interface is smooth. Once the undercooling arrives at 230 K, the liquid-solid interface is irregular, which reflects the growth transition from the solute control to the combined controls of solute and thermal. The eutectic growth velocity increases as an exponential function of undercooling. The electromagnetic stirring effect makes it difficult to increase undercooling, but plays an important role in accelerating the eutectic reaction velocity at low and moderate undercoolings. Primary dendritic β-Ti phase appears in the solidified alloy from 63 to 176 K undercoolings, and the microstructure is completely composed of eutectic once the undercoolings increase up to 230 K. When the undercoolings exceed 273 K, the microstructure consists of uniformly distributed irregular eutectic. For the drop tube experiments, the microstructures composed of a large amount of dendritic α-Ti phase and eutectic phase are found in a wide range of diameters from 69 to 725 μm. As the decrease of diameter, the solubility of Si in the dendritic α-Ti phase dramatically increases from 6.80% to 10.73%, and the ratio of the area occupied by the dendritic α-Ti on a cross-section of solidified alloy obviously increases from 23.52% to 41.02%, which result from the combined effects of high undercooling and large cooling rate.

关键词： phase selection microstructure evolution high undercooling containerless large cooling rate

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Effects of tantalum on austenitic transformation kinetics of RAFM steel

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Journal of Iron and Steel Research International 2017年第7期24卷 705-710页

作者： jian-guo Chen Yong-chang Liu Chen-xi Liu Bi-yu Yan Hui-jun Li State Key Laboratory of Hydraulic Engineering Simulation and Safety School of Materials Science & EngineeringTianjin University

The RAFM（reduced activation ferritic/martensitic）steels containing different tantalum contents（0wt.%,0.027wt.%,0.073wt.%）were designed and *** scanning calorimetry and optical microscopy were employed to explore the influence of tantalum content on the austenitic transformation of RAFM *** austenitic transformation kinetics was described by aphase-transformation *** model,involving site saturation nucleation,diffusion-controlled growth and impingement correction,was established based on the classical Johnson-Mehl-Avrami-Kolmogorov *** phase-transformation kinetics parameters,including D_0（pre-exponential factor for diffusion）and Q_d（activation energy for diffusion）,were calculated by fitting the experimental data and the kinetic *** results indicated that the average grain size is decreased with the increase of *** values of A_（c1） and A_（c3）（onset and finish temperature of austenitic transformation,respectively）are increased by increasing the tantalum *** increase of tantalum caused the decrease of D_***,Q_d is increased with the increase of *** addition,as a carbides forming element,tantalum would reduce the carbon diffusion coefficient and slow down the austenitic transformation rate.

关键词： RAFM steel Tantalum content Grain growth Austenitic transformation kinetics Activation energy

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Comparison of microstructure and property of high chromium bearing steel with and without nitrogen addition

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Journal of Iron and Steel Research International 2017年第2期24卷 206-213页

作者： Hai-feng Xu Feng yu chang Wang Wan-li Zhang jian Li Wen-quan Cao Center for Fuel Cell Innovation State Key Laboratory of Material Processing and Die & Mould TechnologySchool of Materials Science and EngineeringHuazhong University of Science and Technology Special Steel Institute Central Iron and Steel Research Institute

Microstructure and property of bearing steel with and without nitrogen addition were investigated by microstructural observation and hardness measurement after different heat treatment processing. Based on the microstructural observation of both 9Cr18 steel and X90N steel, it was found that nitrogen addition could effectively reduce the amount and size of coarse carbides and also refine the original austenite grain size. Due to addition of nitrogen, more austenite phase was found in X90N steel than in 9Cr18 steel. The retained austenite of X90N steel after quenching at 1050℃ could be reduced from about 60% to about 7 9% by cold treatment at -73℃ and subsequent tempering, and thus finally increased the hardness up to 60 HRC after low temperature tempering and to 63 HRC after high temperature tempering. Furthermore, both the wear and corrosion resistance of X90N steel were found much more superior than those of 9Cr18 steel, which was attributed to the addition of nitrogen. It was proposed at last that nitrogen alloying into the high chromium bearing steel was a promising way not only to refine the size of both carbides and austenite, but also to achieve high hardness, high wear property and improved corrosion resistance of the stainless bearing steel.

关键词： Nitrogen addition High temperature tempering High hardness Austenite grain size Carbide Wear resistance High chromium bearing steel

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Complete study on polarization of γ(nS) hadroproduction at QCD next-to-leading order

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Chinese Physics C 2021年第1期45卷 187-195页

作者： yu Feng Bin Gong Chao-Hsi chang jian-Xiong Wang Department of Physics College of Basic Medical SciencesArmy Medical UniversityChongqing 400038China CAS Key Laboratory of Theoretical Physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China Institute of High Energy Physics Chinese Academy of SciencesP.O.Box 918(4)Beijing 100049China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100190China

By applying the nonrelativistic quantum chromodynamics factorization formalism toγ(1S.2S,3S)hadroproduction,a complete analysis of the polarization parametersλθ,λθФ、andλФfor the production is presented at QCD next-to-leading *** the long-distance matrix elements extracted from experimental data for the production rate and polarization parameterλθofγhadroproduction,our results provide a good description of the measured parametersλθФandλФin both the helicity and Collins-Soper *** our calculations,the frame invariant parameterλ^-is consistent in the two ***,we mention that there are discrepancies between the available experimental data and corresponding theoretical predictions forλ^-.

关键词： heavy quarkonium polarization NRQCD

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SOLVABILITY OF VECTOR KY FAN INEQUALITIES WITH APPLICATIONS

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Journal of Systems Science & Complexity 2013年第6期26卷 978-990页

作者： yu jian PENG Dingtao College of Science Guizhou University School of Science Beijing Jiaotong University

This paper aims to study the solvability of vector Ky Fan inequalities and the compactness of its solution *** vector-valued functions with the cone semicontinuity and the cone quasiconvexity in infinite dimensional spaces,the authors prove some existence results of the solutions and the compactness of the solution ***,some results for the vector Ky Fan inequalities on noncompact sets are built and the compactness of its solution sets are also *** applications,some existence theorems of the solutions of vector variational inequalities are obtained.

关键词： Compactness noncompact set solvability vector Ky Fan inequalities vector variationalinequality.

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Role of late transition metals on pitting resistance of Zr-Ti-(Cu, Ni,Co)-Al bulk metallic glasses in 0.6 M NaCl aqueous solution

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Journal of Materials Science & Technology 2017年第11期33卷 1278-1288页

作者： yu Li jian Xu Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Graduate School University of Chinese Academy of Sciences

Four quanternary Zr-based bulk metallic glasses（BMGs）were selected,including the Zr_（46）Ti_2Cu_（45）Al_7,Zr_（61）Ti_2Cu_（25）Al_（12）,Zr_（55）Ti_4Ni_（22）Al_（19）and Zr_（55）Ti_2Co_（28）Al_（15）,due to their robust glass-forming ability and containing a single species of late transition metal（LTM）in *** pitting resistances in 0.6 M Na Cl aqueous solution were investigated to examine the role of LTM elements in the alloys,with electrochemical measurements,surface morphology observation and x-ray photoelectron spectrometry *** is shown that in comparision with two Cu-bearing BMGs,Zr_（55）Ti_4Ni_（22）Al_（19）and Zr_（55）Ti_2Co_（28）Al_（15）BMGs exhibited significantly superior resistance to ***_（61）Ti_2Cu_（25）Al_（12）,Zr_（55）Ti_4Ni_（22）Al_（19）and Zr_（55）Ti_2Co_（28）Al_（15）BMGs manifested distinct passivation behaviour,because of the formation of surface passive film mainly comprising of Zr O_2,Ti O_2and Al_2O_***,no significant differences in the electrochemical resistive properties and thicknesses of passive films were found between Zr_（61）Ti_2Cu_（25）Al_（12）and Zr_（55）Ti_4Ni_（22）Al_（19）***,at the passive film/metal interface,copper enrichment took place in Zr_（61）Ti_2Cu_（25）Al_（12）,whereas the nickel was slightly deficient at the interface in Zr_（55）Ti_4Ni_（22）Al_（19）.During pitting propagation,selective dissolution of the zirconium,titanium and aluminum over the copper took place in Zr_（61）Ti_2Cu_（25）Al_（12）,but it was not the case in Zr_（55）Ti_4Ni_（22）Al_（19）.For the two Cu-bearing BMGs,reduction of passive base metal elements in composition resulted in local selective dissolution,even absence of the passivation.

关键词： Bulk metallic glass Pitting corrosion Electrochemical behavior Passive film

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Characterization of Essential Stability in Lower Pseudocontinuous Optimization Problems

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Journal of Systems Science & Complexity 2015年第3期28卷 638-644页

作者： ZHOU Yonghui yu jian School of Mathematics and Computer Sciences Guizhou Normal University Department of Mathematics Guizhou University

Characterization of essential stability of minimum solutions for a class of optimization problems with boundedness and lower pseudocontinuity on a compact metric space is given. It shows that any optimization problem considered here has one essential component(resp. one essential minimum solution) if and only if its minimum solution set is connected(resp. singleton) and that those optimization problems which have a unique minimum solution form a residual set(however, which need not to be dense).

关键词： Essential component essential minimum solution pseudocontinuity unique solution.

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Spheroidization and Ostwald Growth of Carbide in Isothermal Process of Hot-Deformed High Carbon Chromium Cast Steel

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Journal of Iron and Steel Research International 2003年第1期10卷 36-39页

作者： chang Li-min LIU jian-hua WANG Hai-yan yu Sheng-xue Siping Normal College Yanshan University

In isothermal spheroidizing process,the spheroidization and growth of the carbide formed in hot-deformed high-carbon chromium cast steel at high temperature were *** results showed that the spheroidizing growth of carbide proceeds in such a way that the bigger carbide particles swallow the smaller ones,and the short rhabdoid carbides dissolve and are spheroidized by *** the samples were held at 720℃ for more than 3 h,the spheroidization is not *** feature of the process is the size increment and the amount decrement of carbide *** empirical equation for growth rate of carbides was *** volume fraction of carbides keeps *** growth process agrees well with Ostwald Ripening Law.

关键词： hot-deformed high-carbon chromium cast steel carbide isothermal spheroidizing Ostwald Ripening Law

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Modeling and Analysis of A Rotary Direct Drive Servovalve

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Chinese Journal of Mechanical Engineering 2014年第5期27卷 1064-1074页

作者： yu Jue ZHUANG jian yu Dehong School of Mechanical Engineering Xi'an Jiaotong University

Direct drive servovalves are mostly restricted to low flow rate and low bandwidth applications due to the considerable flow *** studies mainly focus on enhancing the driving force,which in turn is limited to the development of the magnetic *** at reducing the flow forces,a novel rotary direct drive servovalve（RDDV）is introduced in this *** RDDV servovalve is designed in a rotating structure and its axially symmetric spool rotates within a certain angle range in the valve *** servovalve orifices are formed by the matching between the square wave shaped land on the spool and the rectangular ports on the *** order to study the RDDV servovalve performance,flow rate model and mechanical model are established,wherein flow rates and flow induced torques at different spool rotation angles or spool radiuses are *** model analysis shows that the driving torque can be alleviated due to the proposed valve *** fluid dynamics（CFD）analysis using ANSYS/FLUENT is applied to evaluate and validate the theoretical *** addition,experiments on the flow rate and the mechanical characteristic of the RDDV servovalve are carried *** simulation and experimental results conform to the results of the theoretical model analysis,which proves that this novel and innovative structure for direct drive servovalves can reduce the flow force on the spool and improve valve frequency response *** research proposes a novel rotary direct drive servovalve,which can reduce the flow forces effectively.

关键词： direct drive servovalve computational fluid dynamics(CFD) flow rate flow induced torque

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An analytical model for Network-on-Chip with finite input buffer

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Frontiers of Computer Science 2011年第1期5卷 126-134页

作者： jian Wang (1) wangjian3630@*** yu-bai Li (1) chang Wu (1) Univ Elect Sci & Technol China Didital Signal Proc Lab Sch Commun & Informat Engn Chengdu 610054 Peoples R China

An analytical model is proposed for input buffer router architecture Network-on-Chip （NoC） with finite size buffers. The model is developed based on M/G/ 1/K queuing theory and takes into consideration the restriction of buffer sizes in NoC. It analyzes the packet＇s sojourn time in each buffer and calculates the packets average latency in NoC The validity of the model is verified through simulation. By comparing our analytical outcomes to the simulation results, we show that the proposed model successfully captures the performance characteristics of NoC, which provides an efficient performance analysis tool for NoC design.

关键词： analytical model finite buffer Network-on-Chip (NoC) queue system

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