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Microstructure Study on Semi-solid 60Si2Mn during Compressing

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Journal of University of science and Technology Beijing 2001年第2期8卷 115-118页

作者： Yonglin Kang, Xiongfei Yang, Renbo Song, Weimin Mao, Maosheng Yang (material science & engineering School, University of science and Technology Beijing, Beijing 100083, china) material Sci. and Eng. School University of Science and Technology Beijing 100083 China

The microstructure behavior and deformation mechanism of semi-solid 60Si2Mn fabricated by electromagnetic stirring under different deformation conditions during thixoforming are studied by means of Gleeble-1500 thermal-strain-stress simulator. The micro- structure of deformed 60Si2Mn and that of the non-deformed are compared. The results show that the grain size within deformation zone decreases as the amount of deformation increases or deformation temperature decreases, but deformation fate has small effect on grain size when the rate is very low. Besides, there is a critical amount of deformation to reduce grain size. These results offer theoretical and experimental basis for further producing semi-solid material with high melting temperature and direct forming of semi-solid slurry.

关键词： semi-solid microstructure grain size segregation, reduction

Optimization of control parameters of CdZnTe ACRT-Bridgman single crystal growth

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science china(Technological sciences) 2004年第6期47卷 725-740页

作者： LIU Juncheng School of material science and engineering, Shandong University of Technology, Zibo 255091, china 1. School of material science and engineering Shandong University of Technology 255091 Zibo China

The CdZnTe vertical Bridgman single crystal process with accelerated crucible rotation technique (ACRT) has been simulated. Effects have been investigated of the ACRT wave parameters on the solid-liquid interface concavity and the solute segregation of the crystal. The results show that ACRT can result in the increase of both the solid-liquid interface concavity and the temperature gradient of the melt in the front of the solid-liquid interface, of which the magnitude varies from small to many times when the ACRT wave parameters change. Of the ACRT wave parameters, the increase of the crucible maximum rotation rate can hardly improve the radial solute segregation of the crystal, but the variation of the crucible acceleration time, the keep time at the maximum rotation rate, and the crucible deceleration time can affect the solute segregation of the single crystal extraordinarily. With suitable wave parameters, ACRT greatly decreases the radial solute segregation of the crystal, and even makes it disappear completely. However, it increases both the axial solute segregation and the radial one notably with bad wave parameters. An excellent single crystal could be gotten, of which a majority part is with no segregation, with ACRT-Bridgman method by adjusting both the ACRT wave parameters and the crystal growth control parameters, such as the initial temperature of the melt, the temperature gradient, and the crucible withdrawal rate, etc.

关键词： crystal growth solute segregation numerical simulation CdZnTe ACRT

Stability of Ultra-fine Microstructures during Tempering

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Journal of University of science and Technology Beijing 2001年第2期8卷 119-122页

作者： Shanwu Yang, Chengjia Shang,Xinlai He, Xuemin Wang, Yi Yuan (material science and engineering School, University of science and Technology Beijing, Beijing 100083, china) Univ Sci & Technol Beijing Mat Sci & Engn Sch Beijing 100083 Peoples R China

The stability of ultra-fine microstructure during tempering at 650 degreesC was investigated on a Nb-containing steel. The steel had undergone 5 passes controlled rolling, then was relaxed lair cooled) to 730 degreesC: and cooled in water. The evolution of microstructure was that, in early stage of tempering, no obvious change was detected by means of optical microscopy while dislocation cells were formed inside bainitic laths. With further tempering, bainitic laths started to coalesce in some regions. Finally, polygonal ferrite was formed while hardness decreased dramatically. Some samples taken from the same primary plate were reheated at 930 degreesC for 0.5 h followed by quenching into water before tempering. Despite their lower original hardness, the reheated samples softened Faster during tempering. Ferrite was quickly formed in the reheated samples. These results indicate that the evolution of microstructures towards equilibrium during tempering of the steel is mainly determined by whether dislocations are pinned rather than the dislocation density.

关键词： microalloyed steel bainite tempering

New Developed Welding Electrode for Improving the Fatigue Strength of Welded Joints

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Journal of materials science & Technology 2002年第6期18卷 527-531页

作者： Wenxian WANG, Lixing HUO, Yufeng ZHANG, Dongpo WANG and Hongyang JINGCollege of material science and engineering, Tianjin University, Tianjin 300072, china Coll. of Mat. Sci. and Eng. Tianjin Univ. Tianjin 300072 China

A new welding electrode, low transformation temperature electrode (LTTE), was introduced in this paper. It was described in design principle, mechanics, chemical compositions of their deposited metal and manufacturing methods. It was proved that the best transformation starting temperature from austenite to martensite of the deposited metal of LTTE was at about 191℃ and it was obtained by adding alloying elements such as Cr, Ni, Mn and Mo. The microstructure of the weld metal of the LTTE was low carbon martensite and residual austenite. The compressive residual stress was induced around the weld of the LTTE and the -145 MPa in compression could be obtained in middle of weld metal. The fatigue tests showed that the fatigue strength of the longitudinal welded joints welded with the LTTE at 2×106 cycles was improved by 59% compared with that of the same type of welded joints welded with conventional E5015 and the fatigue life was increased by 47 times at 162 MPa. It is a very valuable method to improve the fatigue performance of welded joints.

关键词： Low transformation temperature electrode Compressive residual stress Fatigue strength Welded joints

Synthesis and Luminescence Properties of Red Phosphor CaO:Eu^(3+)

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Journal of Wuhan University of Technology(materials science) 2009年第1期24卷 20-24页

作者：康明 School of material science and engineering Southwest University of Science and Technology College of materials science and engineering Sichuan University

Ca（NO3）2·4H2O, Eu（NO3）3 and H2C2O4·2H2O were adopted to synthesize CaO： Eu3＋ with the chemical co-precipitation method, and the effects of the calcination temperature and Eu3＋ doping concentration on the phosphor structure and its luminescent properties were investigated by TG-SDTA, XRD, and PL-PLE. The results confirm that the Eu3＋ ions as luminescent centers substi-tutes Ca2＋ sites without changing the crystal structure of cubic CaO. The optimum calcination tem-perature and the optimum concentration of Eu3＋ are 1 100 ℃ and 1 mol%, respectively, under which the best crystallinity and highest PL intensity appeared. The maximum emission wavelength is 592 nm （5D0→7F1） which is excited by xenon lamp with the wavelength of 200-280 nm, indicating that the Eu3＋ ion mainly locates in the symmetric position （Oh） in the crystal lattice of CaO.

关键词： red phosphor CaO Eu^3+ co-precipitation method rare earths

TECHNIQUES ABOUT DIRECT OPTIMIZING CONTROL OF GREEN SAND QUALITY

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Chinese Journal of Mechanical engineering 2002年第1期15卷 83-86,93页

作者： Li Dayong Xu Xiongfei Ma Xuliang Zhang Yutong School of material science and engineering，Harbin University of science and Technology， Harbin 150080，china School of material science and engineering Harbin University of Science and Technology Harbin 150080

Green sand casting is still a main method in the world at present and it isvery significant to develop the technology of controlling green sand quality. A new concept, fromcontents test to contents control, is advanced. In order to realize the new idea, a new method toon-line test active clay and moisture of green sand - double powers energizing alternately (DPEA)method is put forwards. The principle of the new method is to energize standard sand sample with ACand DC powers and to test the electric parameters, and then, to calculate active clay and moistureof green sand by using artificial neural network (ANN). Based on this new method, a directoptimizing system for controlling green sand quality is developed. Techniques about testing andcontrolling methods, hardware and software are discussed.

关键词： New technology Green sand quality Optimizing control

A new composite:spray-deposited M2 high speed steel reinforced by WC particles

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International Journal of Minerals,Metallurgy and materials 1997年第3期11卷 14-17页

作者： ZHANG Liying TIAN Haige HUANG Thuo WU Chengyi (material science and engineering School, University of science and Technology Beijing, Beijing 100083, china) Univ of science and Technology Beijing Beijing China

The fabrication of the high speed steel matrix composites reinforced by WC particles utilizing the ultrasonicgas atomization and spray-deposition was studied. The change of microstware and mechanical Properties of thecomposites added WC Particles were investigated and analyzed as well. As some results, the WC particles exhibit tWomorphologies (spherical and angular) with different content of WC particles; and with the increase of content of WCparticles, the hardness of the composites increases, yet the bending strength appears a trend of decreasing.

关键词： spray-deposition high speed steel composite

Reaction Sintering of Fe-Al Powder Mechanically Activated

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International Journal of Minerals,Metallurgy and materials 1998年第4期12卷 233-236页

作者： Chengchang jia Xiaosen Lu Jun Zhao Zizhang Xie(material science and engineering School, University of science and Technology Beijing, Beijing 100083, china) (Beijing Hard Metal Factory, Beijing 100055, china) material science and engineering School University of Science and Technology Beijing Beijing 100083 China Beijing Hard Metal Factory Beijing 100055 China

The mixture of Fe and Al powder was mechanically activated and sintered to study a non-melting methodof producing the intermetallics Fe3Al. High-energy ball milling was used as an activation method, X-ray diffractionand SEM were chosen to analyze the materials variation before and after activation and sintering, and hot press ofFe-Al powder was inveshgated to compare mechanical activation with sintering. The results show that combiningmechanical activation with reaction sintering can complete the transformation from pure Fe and Al powder to intermetallics. It is difficult to do the transformation by either mechanical activation or hot press.

关键词： intermetallic compound sintering metal powder mechanical activation

SOLIDIFICATION MICROSTRUCTURE OF Ni-BASE SUPERALLOY POWDER

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Acta Metallurgica Sinica(English Letters) 1991年第2期4卷 97-102页

作者： HU Benfu LI Huiying WU Chengjian ZHANG Shouhua University of science and Technology Beijing,Beijing,china Associate Professor,dept.of material science and engineering,University of science and technology Beijing,Beijing 100083,china.

The solidification microstructure and phase composition of Ni-base superalloy FGH95 pow- der with different mesh size have been *** structure transition was found from dendrite in major into cellular structure as the powder size reduces and the cooling rate in- *** predominant phase was identified as MC-type carbide,with different morphologies,which may be related to their composition and the condition of *** phases,such as boride,Laves and primary γ' are also present as ac- companiments of the carbide.

关键词： powder metallurgy superalloy microstructure solidification