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Dynamic recrystallization during hot torsion of Al-4Mg alloy

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Journal of university of science and technology beijing 2003年第2期10卷 45-48页

作者： Junpin Lin, Yanli Wang, Zhi Lin, and Guoliang ChenState Key Laboratory of advanced Metal Materials, university of science and technology beijing,{2., China Lab. of Adv. Metal Mat. Univ. of Sci. and Technol. Beijing Beijing 100083 China

Binary Al-4Mg alloy have been deformed by hot torsion at 300-500 deg C andstrain rates of 0.006-1.587 s^(-1) to a true strain of 5.5. The specimens were annealed in vacuumfor 1.5 h at 500 deg C and then water quenched. The study indicates that the dynamicrecrystallization occurs during hot torsion of Al-4Mg alloy in a certain range of Z parameter(Zener-Hollmon Parameter), i.e. 19.3 2..8. Increasing the strain rate at higher deformationtemperature or reducing the strain rate at lower deformation temperature accelerates the occurrenceof dynamic recrystallization in the alloy.

关键词： Al-4Mg alloy dynamic recrystallization hot torsion

The steady-state solution of dendritic growth from the undercooled binary alloy melt with the far field flow

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science China(Technological sciences) 2009年第8期52卷 2280-2287页

作者： CHEN MingWen1,2. WANG ZiDong2.& XU JianJun2.3,4 1 School of Applied sciences, university of science and technology beijing,{2., China 2.School of Materials science and Engineering, university of science and technology beijing,{2., China 3 School of Mathematical sciences, Nankai university, Tianjin 300071, China 4 Department of Mathematics and Statistics, McGill university, Montreal H3A 2.6, Canada School of Applied sciences University of Science and Technology Beijing Beijing 100083 China School of Materials science and Engineering University of Science and Technology Beijing Beijing 100083 China School of Mathematical sciences Nankai University Tianjin 300071 China Department of Mathematics and Statistics McGill University Montreal H3A 2K6 Canada

The steady-state dendritic growth from the undercooled binary alloy melt with the far field flow is considered. By neglecting the interface energy, interface kinetics and buoyancy effects in the system, we obtaine the steady-state solution for the case of the large Schmidt number, in terms of the multiple variable expansion method. The changes of the temperature and concentration fields, the morphology of the interface, the normalization parameter and the Peclet number of the system induced by uniform external flow are derived. The results show that, compared with the system of dendritic growth from undercooled pure melt, the convective flow in the system of growth from undercooled binary alloy has stronger effects on the morphology of the interface. Nevertheless, the shape of the interface still remains nearly a paraboloid.

关键词： binary alloy melt convection dendritic growth interfaces steady-state solution multiple variable expansion method

ESKD-A new Structure of Expert System Based on Knowledge Discovery

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International Journal of Minerals,Metallurgy and Materials 2000年第1期14卷 63-71页

作者： Bingru Yang Fasheng liu Jiangtao Shen Information Engineering School, university of science and technology beijing, beijing,{2., China Information Engineering School University of Science and Technology Beijing Beijing 100083 China

A new structure of ESKD (expert system based on knowledge discovery system KD (D&K)) is first presented on the basis of KD (D&K)-a synthesized knowledge discovery system based on double-base (database and knowledge base) cooperating mechanism. With all new features, ESKD may form a new research direction and provide a great probability for solving the wealth of knowledge in the knowledge base. The general structural frame of ESKD and some sub-systems among ESKD have been described, and the dynamic knowledge base based on double-base cooperating mechanism has been emphased on. According to the result of demonstrative experi- ment, the structure of ESKD is effective and feasible.

关键词： knowledge discovery expert system dynamic knowledge base, double-base cooperating mechanism

Fractal structure reconstruction for alumina-silicate refractory fiber and simulation of the thermal conductivity

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Journal of Thermal science 2010年第1期19卷 80-86页

作者： XIA Dehong,GUO Shanshan,and Ren Ling Department of Thermal Engineering,university of science and{2. beijing,beijing 100083,China Department of Thermal Engineering University of Science and Technology Beijing Beijing China

In this paper, it is proved that the intemal porous structure of alumina-silicate refractory fiber has fractal characteristics, which is reconstructed by the computer and the reconstructed structure further proved to have fractal characteristics. Based on the reconstructed structure, the network-thermal-resistance model is established to calculate the thermal conductivity of the fiber. It is shown that the calculated results agree well with the previous experimental ones, proving the correctness of the method.

关键词： fractal refractory fiber thermal conductivity

Influence of sample surface condition on nano indentation experiment

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Rare Metals 2002年第2期21卷 131-132页

作者： WANG Yanli, LIN Zhi, LIN Junpin, PENG Jihua, and CHEN GuoliangState Key laboratory for advanced Metals and Materials, university of science and technology beijing,{2., China university of science and{2. beijing State Key Laboratory for Advanced Metals and Materials 北京 100083

The microhardness and elastic modules of the materials weremeasured using the Nano Indenter II, which is a new measuring systemfor the mechanical properties of materials on nano-scale. It candetermine themicrohardness, elastic modules and other mechanicalproperties of materials through measuring applied load and depthunder indenter tip. The results indicated that surface condition ofsample such as the surface roughness affects the experimental preci-sion.

关键词： microhardness elastic modules Nano Indenter

Effect of coherent-light phase on tunneling process

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Journal of university of science and technology beijing 2003年第4期10卷 61-64页

作者： Peng FengApplied science School, university of science and technology beijing,{2., China Univ Sci & Technol beijing Appl Sci Sch Beijing 100083 Peoples R China

The coherent-light-driven tunneling in double quantum wells has been *** electrons are coupled to a system of phonons and subjected to the two beams of coherentlyoptical waves. By adopting a gauge to both the external field and the phonon field, the phonon fieldoperators in the Schrodinger equations are eliminated. In this way, an expression of the tunnelingcurrent is conveniently derived considering the relaxation effect. It is shown that under theintense laser field, the tunneling current oscillates rapidly with time at low temperature. Theduration of the oscillations is related to the temperature. By adjusting the phase difference of thetwo light-beams, the oscillation frequency can be modulated.

关键词： tunneling current quantum wells gauge transformation

Mass transfer coefficients in metallurgical reactors

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Journal of university of science and technology beijing 2003年第2期10卷 1-9页

作者： Ying QuMetallurgical Engineering School, university of science and technology beijing, beijing 100083, China Univ Sci & Technol beijing Met Engn Sch Beijing 100083 Peoples R China

An overview on the application and achievements of physico-mathematicalmodeling of metallurgical processes in China is briefly declared. The important role of coefficientsin model formulation is shown from our experience. The mass transfer coefficients of the slag-metalreactions and the gas-metal reactions are discussed referring to the flow conditions near theinterface. The influence of the surface-active species on the mass transfer and the interfacialreaction is also discussed briefly.

关键词： mass transfer modeling pyrometallurgy reaction engineering interfacial flow stirring power

Microstructure Evolution of Semi-solid Processed Hyper-eutectic Al-30%Si Alloy

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International Journal of Minerals,Metallurgy and Materials 1999年第4期13卷 259-261页

作者： Yanjun Li Weimin Mao Xueyou Zhong(Material science and Engineering School, university of science and technology beijing,{2., China) Material science and Engineering School University of Science and Technology Beijing Beijing 100083 China

An investigation was made on the influences of mechanical stirring on microstructure of hyper-eutectic Al-30%Si alloy (inmass fraction) during solidification. The primary Si crystals formed in the alloy melt were gradually changed from elongated platelets tonear-spherical shapes by mechanical stirring. The spheroidization of primary St crystals occurs by the mechanism of bending and fractureof Si platelets, wear and collision between Si crystals, and coalescence of small Si particles. The influence of under-cooling and coolingrate of the alloy melt on primary Si crystals of semi-solid processed alloys is investigated as well. The increase of under-cooling andcooling rate decreases the size of primary Si crystals.

关键词： semi-solid state process solidification structure mechanical stirring hyper-eutectic Al-Si alloy

Microstructural Characteristics of CuCr50 Alloy by Laser Refining

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International Journal of Minerals,Metallurgy and Materials 1998年第3期12卷 156-159页

作者： Baihe Miao Jianping He Donglang Shao(Material science and Engineering School, university of science and technology beijing,{2., China)(State Key Laboratory for advanced Metals and Materials, university of science and technology beijing, Beij Material science and Engineering School University of Science and Technology Beijing Beijing 100083 China State Key Laboratory for advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China

An investigation conceming the thecrostructural characterization of CuCr50 alloy layer by laser surface refining on the powder metallurgy substrate was carried out Significant refined procutectic chromium crystals distributed in an Cr-rich eutectic and high mutual solubility of Cu and Cr elements in the CuCr50 alloy were exam ined by Backscattered Eectron Imaging (BEI) and Energy Dispersive X-ray Spectrum (EDS) techniques. The results show that surface refining and alloying by high-power laser have a great potential to develop new and high performance alloys in the immiscible and limited solubility systems like Cu-Cr and other similar alloy systems.

关键词： laser refining Cu-Cr alloy mutual solubility microstructure