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Dislocation Densites of Deformed Steel Sheets Based on Positron Annihilation

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International Journal of Minerals,Metallurgy and materials 1998年第1期12卷 47-50页

作者： Yonglin Kang Xianjin Wang (materials science and {2. school, University of science and technology beijing, beijing 100083, china) materials science and {2. school University of Science and Technology Beijing Beijing 100083 China

The variation regularity of dislocation densites of some deformed steel sheets under three kinds of strainpaths as uniaxial tension, plane strain and equal biaxial stretching was investigated by means of positron lifetimespectrum and Doppler-broadening techniques. The results show that the increasing rate of dislocation densites isrelated to the plastic strain path. A relationship between the increasing rate of micro-defects, macro-instability andforming limits during the process of steel sheet forming was got based on analyzing the mechanism of dislocationdensity increasing under different stress-strain condihons.

关键词： positron annihilation dislocation steel sheet strain path

Sol-gel Preparation and Infrared Radiation Property of Boron-substituted Cordierite Glass-ceramics

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Journal of materials science & {2. 2010年第5期26卷 445-448页

作者： Shuming Wang and Fenghua Kuang school of materials {2. and engineering,University of {2. & technology beijing,beijing 100083,china school of materials {2. and engineering University of Science & Technology Beijing Beijing 100083 China

Boron for aluminum substitution in the cordierite structure has been examined by sol-gel preparation of different samples along the compositional junction Mg2.l4-xBxSi5O18 with x=0,0.5,1,*** increasing the x value from 0 to 1.5 the crystallization behavior changed *** amount B2.3 doping can promote the sintering of amorphous cordierite gel,effectively restrain the precipitation of μ-cordierite and enhance the crystallization of α-*** substitution of B3＋ for Al3＋ in cordierite crystal structure can effectively improve the near-infrared spectral emissivity of this cordierite based glass-ceramics.

关键词： Sol-gel Glass-ceramics Infrared radiation B3+ substitution Solid solution

Microstructural Features During Strain Induced Ferrite Transformation in 08 and 2.Mn Steels

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Journal of University of science and technology {2. 2001年第2期8卷 105-110页

作者： Ping Yang, Feng-e Cui, Fuming Wang (materials science and {2. school, University of science and technology beijing, beijing 100083, china) (Metallurgy school, University of science and technology beijing, beijing 100083, china) materials Sci. and Eng. school University of Science and Technology Beijing 100083 China

The microstructure evolution during strain induced ferrite transformation was followed in thermal-simulation tests of clean 08 and 2.Mn steels. The influences of carbon equivalence and initial austenite grain size on ferrite grain refinement and the volume fraction of ferrite during straining were inspected. The results revealed that the accelerating effect of ferrite transformation by strain was increased as the carbon equivalence decreased. However, finer ferrite grains were obtained at higher carbon content. At strain of similar to1.5 ferrite grains less than 3 mum and 2.mum can be obtained in 08 and 2.Mn steels respectively. Whereas the ferrite grain refinement in 08 steel was due to both effects of strain induced transformation and ferrite dynamic recrystallization, that in 2.Mn was mainly due to strain induced transformation. Heavy strain can produce fine ferrite grains in coarse austenite grained 08 steel, but it would lead to band microstructure in coarse austenite grained 2.Mn.

关键词： clean carbon steel strain induced transformation grain refinement ferrite dynamic recrystallization

Effects of silver powder particle size on the microstructure and properties of Ag-Yb_2._3 electrical contact materials prepared by spark plasma sintering

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Rare Metals 2010年第4期29卷 366-370页

作者： CHEN Xiaohua,JIA Chengchang,and LIU Xiangbing school of materials {2. and engineering,University of {2. and technology beijing,beijing 100083,china school of materials {2. and engineering University of Science and Technology Beijing Beijing China

mg-Yb2.3 electrical contact materials were fabricated by spark plasma sintefing （SPS）. The effects of silver powder particle size on the microstructure and properties of the samples were investigated. The surface morphologies of the sintered samples were examined by optical microscope （OM）, and the fracture morphologies were observed by scanning electron microscopy （SEM）. The physical and mechanical properties such as density, electrical resistivity, microhardness, and tensile strength were also tested. The results show that the silver powder particle size has evident effects on the sintered materials. Comparing with coarse silver powder （5 ktm）, homogeneous and fme microstmcture was obtained by fine silver powder （_〈0.5-1am）. At the same time, the electrical conductivity, microhardness, and tensile strength of the sin- tered samples with fine silver powder were higher than those of the samples with coarse silver powder. However, silver powder particle size has little influence on the relative densities, which of all samples （both by free and coarse silver powders） is more than 95%. The fracture characteristics are ductile.

关键词： composites electrical contact materials spark plasma sintering particle size microstructure physical properties mechanical properties

Application of the annexation principle to the study of thermodynamic properties of ternary metallic melts In-Pb-Ag and In-Bi-Sb

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Rare Metals 2002年第2期21卷 142-151页

作者： ZHANG JianMetallurgical engineering school.University of {2. and technology beijing, beijing 100083, china Metallurgical engineering school University of Science and Technology Beijing 北京 100083

Based on the phase diagrams, measured activities an the annexationprinciple, the calculating models of mass action concentrations forin-Pb-Ag and In-Bi-Sb ternary metallic melts have been *** results of calculation both agree with practice, and obey the lawof mass action, showing that the models formulated can reflect thestructural reality of the corresponding melts and the annexationprinciple is applicable to the them.

关键词： activity mass action concnetration th annexation principle In-PB-Ag

Effect of powder mixing process on the microstructure and thermal conductivity of Al/diamond composites fabricated by spark plasma sintering

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Rare Metals 2010年第1期29卷 86-91页

作者： CHU Ke, JIA Chengchang, LIANG Xuebing, and CHEN Hui school of materials {2. and engineering, University of {2. and technology beijing, beijing 100083, china school of materials {2. and engineering University of Science and Technology Beijing Beijing China

Two powder mixing processes, mechanical mixing （MM） and mechanical alloying （MA）, were used to prepare mixed Al/diamond powders, which were subsequently consolidated using spark plasma sintering （SPS） to produce bulk Al/diamond composites. The effects of the powder mixing process on the morphologies of the mixed powders, the microstructure and the thermal conductivity of the composites were investigated. The results show that the powder mixing process can significantly affect the microstructure and the thermal conductivity of the composites. Agglomerations of the particles occurred in mixed powders using MM for 30 min, which led to high pore content and weak interfacial bonding in the composites and resulted in low relative density and low thermal conductivity for the composites. Mixed powders of homogeneous distribution of diamond particles could be obtained using MA for 10 min and MM for 2.h. The composite prepared through MA indicated a high relative density but low thermal conductivity due to its defects, such as damaged particles, Fe impurity, and local interfacial debonding, which were mainly introduced in the MA process. In contrast, the composite made by MM for 2.h demonstrated high relative density and an excellent thermal conductivity of 32. W.m^-1.K^-1, owing to its having few defects and strong inter-facial bonding.

关键词： metal matrix composites thermal properties sintering powder mixing

Predicting Equation for Adjusting Glass Temperature of Binder Used for P/M Warm Compaction Processing

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International Journal of Minerals,Metallurgy and materials 1998年第1期12卷 39-40页

作者： Shiju Guo Tao Lin Mingyi Li (materials science and {2. school, University of science and technology beijing, beijing 100083, china) materials science and {2. school University of Science and Technology Beijing Beijing 100083 China

Based on considering both negative effect of compacting pressure on glass temperature (Tg) and positiveeffect of plasticizer added into organic binder, a mathematical equation for adjusting Tg of binder used for warmcompaction processing is given. The equation shows that mass fraction of plasticizer need for lowering Tg is function of compacting plessure. The rationality of the equation for warm compaction processing is also discussed.

关键词： warm compaction binder glass temperature

Fabrication of pure copper rods containing continuous columnar crystals by continuous unidirectional solidification technology

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Journal of University of science and technology {2. 2004年第3期11卷 240-244页

作者： Hong zhang Jianxin Xie Zidong Wang materials science and {2. school, University of science and technology beijing, beijing 100083, china Mat. Sci. and Eng. Sch. Univ. of Sci. and Technol. Beijing Beijing 100083 China

Pure copper rods containing continuous columnar crystals were fabricatedusing the downward CUS (Continuous Unidirectional Solidification) equipment. When the technologicalparameters were set as the ranges of mould temperature 1100-1300℃, cooling distance (the distancefrom the exit of the cast mould to the start point of cooling) 10-2. mm, casting speed 0.2.2.5 mm/s,cooling water (2.-2.℃) volume 1000-132. L/h, and when these parameters matched reasonably, the CUSprocess was performed stably, and pure copper rods containing continuous columnar crystals withbright and smooth surface were produced. The dendritic arm spacing of the crystals in copper rodsdecreased with increasing the casting speed. The results of the texture by X-ray diffractionanalysis showed that the rods has strong fiber texture.

关键词： copper continuous unidirectional solidification mould temperature castingspeed microstructure texture

Effects of Na/K ratio on the phase structure and electrical properties of Na_xK_(1-x)NbO_3 lead-free piezoelectric ceramics

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Rare Metals 2010年第2期29卷 220-225页

作者： ZHANG Qian, ZHANG Boping, Li Haitao, and SHANG Pengpeng school of materials {2. and engineering, University of {2. and technology beijing, beijing 100083, china school of materials {2. and engineering University of Science and Technology Beijing Beijing China

Lead-free piezoelectric NaxK1-xNbO3（x = 0.3-0.8）（NKN） ceramics were fabricated by normal sintering at 1060°C for 2.*** and electrical properties of the ceramics were investigated with a special emphasis on the influence of Na *** grain size of the produced dense ceramic was decreased by increasing Na content.A discontinuous change in the space distance was found at the composition close to Na0.7K0.3NbO3 ceramic, which indicates the presence of a transitional composition between two different orthorhombic phases, which is similar to the behavior of morphotropic phase boundary（MPB） in NaxK1-xNbO3 *** MPB-like behavior contributes to the enhanced piezoelectric coefficient d33 of 12. pC/N, planar-mode electromechanical coupling coefficient kP of 2..6%, and dielectric constant εr of 703, respectively for the Na0.7K0.3NbO3 *** temperature TC and the transitional temperature TO-T from orthorhombic to tetragonal phase are observed at around 42.°C and 2.0°C, respectively.

关键词： lead-free piezoelectric ceramics NKN sintering morphotropic phase boundary(MPB)