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Acta Metallurgica Sinica(English Letters) 2006年第4期19卷 251-257页

作者： H.Z. Huang x.q. wei L. Zhou x.D. Liu G.L. Guo School of Materials Science and Engineering Nanchang University Nanchang 330047 China East China Institute of Technology Fuzhou 344000 China

The potential of using a hypoeutectic, instead of eutectic, Sn-Zn alloy as a lead-free solder has been discussed. The nonequilibrium melting behaviors of a series of Sn-Zn alloys were examined by differential thermal analysis. It was found that at a heating rate of 5℃/min, *** exhibited no melting range. Dipping and spreading tests were carried out to characterize the wettability of Sn-Zn alloys on Cu. Both tests exhibited that Sn-6.5Zn has significantly better wettability on Cu than Sn-9Zn. The reaction layers formed during the spreading tests were examined. When the Zn concentration fell between 2.5wt%-9wt%, two reaction layers were formed at the interface, a thick and flat Cu5Zn8 adjacent to Cu and a thin and irregular Cu-Zn-Sn layer adjacent to the alloy. Only a Cu0Sn5 layer was formed when the Zn concentration decreased to 0.5wt%. The total thickness of the reaction layer（s） between the alloy and Cu was found to increase linearly with the Zn concentration.

关键词： lead-free solder Sn-Zn alloy wettability interface intermetallic compound

DISTRIBUTIONS OF MICROSTRUCTURES IN qUENCHED STEELS AS REVEALED BY COMPUTER SIMULATION

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Acta Metallurgica Sinica(English Letters) 2000年第2期13卷 788-793页

作者： L. Zhou and x.q. wei School of Chemistry and Materials Science and School of Mechanical/Electrical Engineering, Nanchang University, Nanchang 330047, China

A cellular automaton model of heat transfer and structural development in quenching steels has been developed and programmed for a three-dimensional computer simulation. A previous study has validated the simulation method by agreements of simulated cooling curves and hardenability with reported experimental data. In present work, a series of simulated quenching experiments for steel 1080 and 4140 steel have been carried out. With five adjustable parameters, a large variety of cooling conditions has been created and applied to the simulated quenching. Effect of delayed quenching and the associated phenomenon of inverse hardening have been addressed with emphasis.

关键词： microstructure steel computer simulation

A CELLULAR AUTOMATON-APPROACH TO SIMULATION OFGRAIN STRUCTURE DEVELOPMENT INELECTROSLAG CASTING

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Acta Metallurgica Sinica(English Letters) 2000年第2期13卷 794-799页

作者： x.q. wei and L. Zhou School of Mechanical Electrical Engineering and School of Chemistry and Materials Science, Nanchang University, Nanchang 330029, China Manuscript received 30 July 1999

A 3-D cellular automaton model of thermal transfer and solidification has been developed, aiming at a simulational study of the grain structure development in electroslag casting. The program we developed for simulation of the model allows the effects of both metallurgical factors, including solidification point, supercooling required for nucleation and its scattering, and liquid/solid interface energy, and thermophysical factors, including heat conduction coeffcients, heat transfer coefficients and latent heat, to be investigated. The effect of process control can be indirectly inspected with the simulation by varying the melting rate. A box counting algorithm was employed to estimate the local curvature of liquid/solid interface. A series of simulated experiments of electroslag casting processes have been carried out. The simulation started from the beginning of the electroslag casting and proceeds by iteration of certain rules, during which a uniform constant slag temperature and a constant melting rate were assumed. It has been observed that a pool of molten metal forms and deepens gradually under constant melting rate. The deepening of the pool slows down with the simulated electroslag casting process, and the depth and shape of the pool tends to be steady after certain height of cast is formed. A finger-like grain structure with the fingers approximately normal to the bottom of the molten metal pool was generally observed. Higher latent heat was found to enhance dendritic growth. The results agree well with general observation of the grain structures in electroslag castings and demonstrate the applicability of cellular automaton modeling to structural development in casting.

关键词： electroslay casting grain structure simulation

A SIMULATION STUDY OF DEPOSITION UNDER TWO TYPES OF IMPINGING TRAJECTORIES

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Acta Metallurgica Sinica(English Letters) 2004年第6期17卷 876-880页

作者： x.q.wei L.Zhou SchoolofMaterialsScience＆Engineering NanchangUniversityNanchang330047China

A model coupling particle aggregation and randomwalk surface diffusion has been developed for 2D simulation of depositional growth, in which impinging particles follow either a straight-line trajectory of cosine distribution, representing typically sputter deposition, or a scattered trajectory, representing typically electrochemical deposition. Simulations of the growth under various impinging conditions and effective surface diffusivity have been carried out. Pattern and defect development in deposition on flat, trenched and ridged substrates have been investigated. We found that on flat and ridged substrates, both types of trajectories yield similar features, including formation of cone-like defects on surface ridges. While on trenched substrate, the straight-line impingement yielded more uniform step coverage than the scattered impingement.

关键词： deposition simulation pattern formation ballistic model

Basic features of the multiscale interaction between tearing modes and slab ion-temperature-gradient modes

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Chinese Physics B 2019年第12期28卷 237-247页

作者： L wei Z x Wang J q Li Z q Hu Y Kishimoto Key Laboratory of Materials Modification by Laser Ionand Electron Beams(Ministry of Education)School of PhysicsDalian University of TechnologyDalian 116024China Southwestern Institute of Physics Chengdu 610041China Graduate School of Energy Science Kyoto UniversityGokashoUjiKyoto 1-0011Japan

Nonlinear interaction between tearing modes(TM) and slab ion-temperature-gradient(ITG) modes is numerically investigated by using a Landau fluid model. It is observed that the energy spectra with respect to wavenumbers become broader during the transition phase from the ITG-dominated stage to TM-dominated stage. Accompanied with the fast growth of the magnetic island, the frequency of TM/ITG with long/short wavelength fluctuations in the electron/ion diamagnetic direction decreases/increases respectively. The decrease of TM frequency is identified to result from the effect of the profile flattening in the vicinity of the magnetic island, while the increase of the frequencies of ITG fluctuations is due to the eigenmode transition of ITG induced by the large scale zonal flow and zonal current related to TM. Roles of zonal current induced by the ITG fluctuations in the instability of TM are also analyzed. Finally, the electromagnetic transport features in the vicinity of the magnetic island are discussed.

关键词： magnetic reconnection tearing modes magnetohydrodynamics drift waves nonlinear phenomena

PARTICLE SIZE AND MICROSTRUCTURE OF Ni NANOPOWDERS PREPARED BY ANODIC ARC PLASMA

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Acta Metallurgica Sinica(English Letters) 2005年第3期18卷 209-216页

作者： Z.q.wei H.x.q.ao J.F.Dai W.J.Feng q.Wang P.x.Yan SchoolofSciences LanzhouUniversityofTechnologyLanzhou730050China CollegeofCivilEngineering LanzhouUniversityofTechnologyLanzhou730050China SchoolofPhysicalScienceandTechnology LanzhouUniversityLanzhou730000China

Pure Ni nanopowders were successfully prepared by the method of anodic arc disch arged plasma with homemade experimental apparatus. The particle size, mircostruc ture and morphology of the particles by this process were characterized via x-ra y powder diffraction (xRD), transmission electron microscopy (TEM) and the corre sponding selected area electron diffraction (SAED); The specific surface area an d pore parameters were investigated by multi-point full analysis of nitrogen ads orption-desorption isotherms at 77K by Brunauer- Emmett-Teller (BET) surface are a analyzer; The chemical composition were determined by x-ray energy dispersive spectrometry (xEDS) equipped in SEM and element analyze instrument. The experime nt results indicate that the samples by this method with high purity,the crystal structure of the particles is as same as the bulk material, is fcc structure, w ith average particle sizes about 47nm, ranging from 20 to 70nm, and distributed uniformly in spherical chain shapes, the specific surface areavis 14.23m2/g, po re volume of pore is 0.09cm3/g and average pore diameter is 23nm.

关键词： anodic arc plasma Ni nanopowder particle size structure composition.

Dynamic Impact of High-Density Aluminum Foam

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Acta Mechanica Solida Sinica 2022年第2期35卷 198-214页

作者： q.Peng J.xie H.S.Ma x.Ling x.Liu Y.G.wei LNM Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China School of Engineering and Technology China University of GeosciencesBeijing 100083China College of Engineering Peking UniversityBeijing 100871China

High-density aluminum foam can provide higher stiffness and absorb more energy during the impact Obtaining the constitutive law of such foam requires tri-axial tests with very high pressure,where difficulty may arise because the hydrostatic pressure can reach more than 30 *** this paper,instead of using tri-axial tests,we proposed three easier tests-tension,compression and shear to obtain the parameters of constitutive model(the Deshpande-Fleck model).To verify the constitutive model both statically and dynamically,we carried out addi-tional triaxial tests and direct impact tests,*** on the derived model,we performed finite element simulation to study the impact response of the present *** dimensional analysis,we proposed an empirical equation for a non-dimensional impact time the impact time divided by the time required for plastic wave travelling from the impact surface to the bottom surface,to det ermine the deformation charac teristic of the aluminum foam after *** the case with t_(d)≤1,the deformation tends to exhibit a shock-type characteristic,while for the case with t_(d)>5,the deformation tends to exhibit an upsetting-type characteristic.

关键词： High density aluminum Foam Deshpande-Fleck model Finite element method Impact analysis Plastic wave

PARAMETRIC STUDY FOR THE PREPARATION OF ALIGNED SINGLE-WALLED CARBON NANOTUBES BY ANODE-ARC DISCHARGE METHOD

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Acta Metallurgica Sinica(English Letters) 2005年第3期18卷 261-268页

作者： J.F.Dai q.Wang W.x.Li Z.q.wei G.J.xu StateKeyLaboratoryofNewNonferrousMetalMaterials DepartmentofPhysicsLanzhouUniversityofTechnologyLanzhou730050China StateKeyLaboratoryofNewNonferrousMetalMaterials InstituteofMaterialsLanzhouUniversityofTechnologyLanzhou730050China

Well aligned quasi-straight single-walled carbon nanotubes (SWCNTs) and straight SWCNTs bundle have been prepared in large scale by anode-arc vaporization of gr aphite with metallic catalysts. Various parameters such as the catalyst preparat ion, the kinds and pressure of the buffer gases, the quantity of anode-arc curre nt intensity, and the method of purification have been examined. The influence o f these parameters on the deposited carbon yield is reported, together with obse rvations of the produced material. Improvement in synthetic techniques has resul ted in the optimal conditions for the production of large quantities of high qua lity SWCNTs in our semi-continuous synthesis method. The formation of carbon nan otubes (CNTs) was studied briefly in this paper. Owing to the magnetic pinching effect of arc current, the CNTs arrange in parallel lines along the arc current direction.

关键词： carbon nanotubes anode-arc preparation catalyst

NANOSIZE EFFECT IN GRAIN BOUNDARY MIGRATION OF COPPER

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Acta Metallurgica Sinica(English Letters) 2004年第1期17卷 11-15页

作者： L.Zhou x.q.wei N.G.Zhou D.G.Li School of Materials Science and Engineering Nanchang UniversityNanchang 330047ChinaSchool of Materials Science and EngineeringNanchang UniversityNanchang 330047ChinaSchool of Materials Science and EngineeringNanchang UniversityNanchang 330047ChinaCentral Iron and Steel Research InstituteBeijing 100083China

Molecular dynamics simulations of high temperature annealing of copper bicrystals have been carried out. The bicrystals have planar grain boundaries, and the gain size varies in nano range. An EAM (embedded atom method) potential of FS type is used for calculating the interatomic forces. The results show that in nanocrystalline copper, GB migration driven by inter-GB reaction can take place. A critical grain size is identified, below which the inter-GB reaction becomes strong enough to trigger GB motion, which accelerates rapidly and leads to annihilation of the grain boundaries. The critical size is found to be 16 atomic radii. A "through intermediate grain mechanism" is identified for the nano-grain boundary motion observed, which is never reported for GB migrations of conventional polycrystalline metals.

关键词： grain boundary migration nanocrystal copper

INVESTIGATION OF WO3-DOPED TiO2 FILM COMPOSITE PHOTOCATALYST

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Acta Metallurgica Sinica(English Letters) 2004年第3期17卷 263-268页

作者： q.F. Meng K.R. Liu L. Jiang q. Han J.S. Chen x.J. wei School of Materials & Metallurgy Northeastern University Shenyang 110004 ChinaSchool of Materials & MetallurgyNortheastern University Shenyang 110004 ChinaSchool of Materials & MetallurgyNortheastern University Shenyang 110004 ChinaSchool of Materials & MetallurgyNortheastern University Shenyang 110004 ChinaSchool of Materials & MetallurgyNortheastern University Shenyang 110004 ChinaSchool of Materials & MetallurgyNortheastern University Shenyang 110004 China

The nano--crystal composite WO_3-TiO_2 photocatalyst was prepared by ultrasonic as-sisted sol--gel process. The effects of various factors, such as the crystal form, thesubstrates, the pH, the dissolved oxygen and the ultrasonic on the photocatalytic ac-tivity were investigated in view of the photodegradation of Rhodamine B. The resultsshow that the crystal form of WO_3-TiO_2 film with highest photocatalytic activity isrutile. The introduction of ultrasonic to the course of preparation can accelerate thedeposit time of the sol and increase the photocatalytic activity significantly in view ofthe highest photodegradation of Rhodamine B being 72.7% in 5 hours. The poroustitanium plate is the most suitable substrate in four kinds of investigated materials.Meanwhile the smaller the pH and the higher the concentration of the dissolved oxygenin the solution is, the higher the photodegradation is.

关键词： ultrasonic sol-gel process photocatalytic photodegradation