2007年, 第17卷, 第03期　刊出日期：2007-03-25

  

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  Numerical simulation of mold-temperature-control solidification

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  中国有色金属学报（英文版）. 2007, 17(03): 443-443.

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  A finite element method(FEM) for the numerical simulation of the columnar part of the mould-temperature-control solidification(MTCS) process was presented. The latent heat was taken into account and 3D transient heat transfer analysis was carried out by using the developed FEM software. The relative errors between the numerical and experimental data are less than 6%. Three MTCS cases were computed with this method. The first case only opens the cooling channels in the bottom of the mold. The second case individually controls the separate 7 groups of cooling channels by giving 7 control points. When the temperature of a control point reaches the preset value of 400℃, the corresponding channel will be opened. The third case opens all the cooling channels at the same time. The results indicate that in the second case, the solid-liquid interface keeps near-planar. The growth velocity of the solid-liquid interface is 0.3−0.4 mm/s, which is greater than 0.1−0.3 mm/s of the first case, performing better than the others. Thus the forming quality and efficiency part interior can be improved by mold-temperature-control and the numerical model is validated. The numerical simulation of MTCS can provide an available tool for the advanced investigation on the defect improvement and the crystal’s quality.
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  Numerical simulation of upsetting-extruding process of dispersion
  strengthened copper welding electrode

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  中国有色金属学报（英文版）. 2007, 17(03): 449-449.

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  The simulation of the upsetting-extruding process of dispersion strengthened copper welding electrode was carried out using Deform-2D finite element analysis software, and the characteristics of metal flow and the effect of different friction factors were analysed. The results show that the whole forming process consists of a forward extrusion and a backward extrusion. When the friction factor of the female die is 0.4, it is advantageous to the forward extrusion forming of the electrode work nose part, while the friction factor of the male die is only 0.1, it would be benefit to the backward extrusion forming of the electrode fit-up hole part. Addition of a scoop channel with 1.5 mm in depth and 4 mm in diameter at the bottom of the female die can avoid folds at the work nose. The rise in temperature is about 60 ℃ during the forming process.
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  Finite element analysis for delamination of laminated vibration damping
  steel sheet

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  中国有色金属学报（英文版）. 2007, 17(03): 455-455.

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  The material structure of laminated vibration damping steel sheet(LVDSS) was introduced in detail. An interface cohesive model between the skin sheets was developed by using a contact/interface approach, and the model was applied to simulate “T”-peel and lap-shear processes of LVDSS. The interface contact stress distribution during the “T”-peel and lap-shear processes is obtained, and the finite element analysis(FEA) results agree satisfactorily with the corresponding experimental results. As a result, the model is suitable to simulate the cohesive of LVDSS.
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  Kinetic Monte Carlo simulation of microalloying effect in Al-Ag alloys

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  中国有色金属学报（英文版）. 2007, 17(03): 461-461.

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  The kinetic Monte Carlo method, which based on the Multi-States Ising Model, was applied to simulate the effect of microelements on the microstructural evolution of Al-Ag alloys during initial aging stage. The simulation results suggest that the microelements In, Sn and Be have a dramatic depression effect on the Ag clustering because of their strong tendency to co-existed with vacancies. There are no significant effects on the process of Ag clustering in Al-Ag alloys containing Li or Cd, because of little interaction between Li/Cd and Ag/vacancies. Microelements can influence the aging by interacting with vacancies and the atoms of precipitated composition, in which the former seems more important. In this model, “vacancy-locking” and “vacancy clusters” are two important mechanisms in the aging process.
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  Processing and mechanical properties of porous 316L stainless steel for biomedical applications

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  中国有色金属学报（英文版）. 2007, 17(03): 468-468.

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   Highly porous 316L stainless steel parts were produced by using a powder metallurgy process, which includes the selective laser sintering(SLS) and traditional sintering. Porous 316L stainless steel suitable for medical applications was successfully fabricated in the porosity range of 40%−50% (volume fraction) by controlling the SLS parameters and sintering behaviour. The porosity of the sintered compacts was investigated as a function of the SLS parameters and the furnace cycle. Compressive stress and elastic modulus of the 316L stainless steel material were determined. The compressive strength was found to be ranging from 21 to 32 MPa and corresponding elastic modulus ranging from 26 to 43 GPa. The present parts are promising for biomedical applications since the optimal porosity of implant materials for ingrowths of new-bone tissues is in the range of 20%−59% (volume fraction) and mechanical properties are matching with human bone.
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  Hydrogen diffusion in Zr35Ni55V10 amorphous alloy

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  中国有色金属学报（英文版）. 2007, 17(03): 474-474.

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  Hydrogen diffusion in Zr₃₅Ni₅₅V₁₀ amorphous alloy was measured by chronopotentiometry. The results show that at lower molar ratio of hydrogen (x＜0.06, x=n(H)/n(M)), the diffusivity of hydrogen increases rapidly with increasing the molar ratio of hydrogen. However, when x(H)＞0.1, the diffusivity of hydrogen decreases slightly with increasing the molar ratio of hydrogen, which is similar to the change in crystalline alloy. It is proposed that hydrogen atoms mainly occupy the sites corresponding to tetrahedra with 4 Zr atoms at lower molar ratio of hydrogen. When the molar ratio of hydrogen is higher, the additional hydrogen atoms are in sites with higher energy and these sites in amorphous state are similar to these in crystalline states.
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  Deformed texture of copper processed by equal channel angular pressing via different angle routes

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  中国有色金属学报（英文版）. 2007, 17(03): 479-479.

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  The commercially pure copper with dimension of 80 mm×20 mm×4 mm was used for equal channel angular pressing (ECAP), of which their outward appearance coordinate is corresponded with that of rolling deformation modes. Cold-deformed texture was investigated. The results show that the texture character in pure copper processed by ECAP is related with intersection angle (F) of the die channel. When F is 90˚ and the sample is extruded for one pass, its texture consists of α and b orientation lines including mainly C, B, S and Goss components, moreover a little rotated cube is found. When F is 135˚, as extrusion pass increases, the weak texture forms on the scope of deviation from rotated cube (y=0˚, θ=0˚, j=45˚±15˚) and develops to the y=45˚ fiber mainly including rotated cube. When F is 120˚, the texture is y=45˚ fiber mainly including rotated cube that is maintained constant as extrusion pass increases.
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  Effect of activating flux on arc shape and arc voltage in tungsten inert gas welding

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  中国有色金属学报（英文版）. 2007, 17(03): 486-486.

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  The effects of activating fluxes on welding arc were investigated. A special set of water-cooling system and stainless steel were used as parent material. During welding process, high-speed camera system and oscillograph were used for capturing instantaneous arc shape and arc voltage respectively. The experimental results indicate that the SiO₂ flux can increase the arc voltage, while TiO₂ has no this effect on arc voltage. Compared with conventional tungsten inert gas welding (C-TIG), it is found that the arc shape of A-TIG welding used with the SiO₂ flux has changed obviously.
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  Influence of heat treatment on fracture and magnetic properties of radially oriented Sm2Co17 permanent magnets

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  中国有色金属学报（英文版）. 2007, 17(03): 491-491.

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   The quenching, fracture and aging treatment of radially oriented Sm₂Co₁₇ ring magnets were investigated. The results indicate that the ring magnets have obvious anisotropy of thermal expansion, which easily leads to the splits of the magnets during quenching. The fracture is brittle cleavage fracture. The difference (Δa) of the expansion coefficient reaches the maximum value at 800−850 ℃. So, various quenching processes at different steps are adopted in order to reduce the splits. When the magnets are aged, 1׃5 phase precipitates from the 2׃17 matrix phase and forms a cellular microstructure with 2׃17 phase. BH_max and _JH_c reach the maximum value 226 kJ/m³ and 2 170 kA/m after being aged at 850 ℃ for 4 h and 8 h, respectively. The aging treatment at 850 ℃ has little influence on remanence(B_r), which can always keep a high value (≥1.0 T). Through appropriate heat treatment, the ring magnets have uniform cellular microstructure and excellent magnetic properties: B_r≥1.0T, _JH_c≥2 100 kA/m, BH_max≥220 kJ/m³.
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  Effect of pressure on microstructures and mechanical properties of Al-Cu-based alloy prepared by squeeze casting

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  中国有色金属学报（英文版）. 2007, 17(03): 496-496.

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  A new high-strength aluminum alloy with better fluidity than that of ZL205A was developed. The effect of applied pressure during squeeze casting on microstructures and properties of the alloy was studied. The results show that the fluidity of the alloy is 16% and 21% higher than that of ZL205A at the pouring temperature of 993 K and 1 013 K, respectively. Compared with permanent-mold casting, mechanical properties of the alloy prepared by squeeze casting are much higher. The tensile strength and elongation of the alloy are 520 MPa and 7.9% in squeeze casting under an applied pressure of 75 MPa, followed by solution treatment at 763 K for 1 h and at 773 K for 8 h, quenching in water at normal temperature and aging at 463 K for 5 h. The improvement of mechanical properties is attributed to the remarkable decreasing of the secondary dendrite arm spacing(SDAS) and eliminating of micro-porosity in the alloy caused by applied pressure.
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  Corrosion properties of AZ31magnesium alloy and protective effects of chemical conversion layers and anodized coatings

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  中国有色金属学报（英文版）. 2007, 17(03): 502-502.

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  The corrosion properties of AZ31 magnesium alloys were studied by potentiodynamic polarization curves and electrochemical impedance spectroscopy(EIS) techniques, meanwhile, the protective properties of two environmentally protective types of chemical conversion layers and anodized coatings of AZ31 magnesium alloys were also discussed. The component of chemical conversion bath is NaH₂PO₄·12H₂O 20 g/L, H₃PO₄ 7.4 mL/L, NaNO₂ 3 g/L, Zn(NO₃)₂·6H₂O 5 g/L and NaF 1g/L, and components of the anodization bath is Na₂SiO₃ 60 g/L, C₆H₅Na₃O₇·2H₂O 50 g/L, KOH 100 g/L and Na₂B₄O₇·2H₂O 20 g/L. The results show that the corrosion resistance of AZ31magnesium increases with the increase of pH value of the corrosive medium. For the chemical conversion layer acquired at 80 ℃, 10 min is the best processing time and the charge transfer resistance of the chemical conversion layer is enhanced nearly by 10 times. The optimum processing time for the anodization of AZ31 is 60 min, the charge transfer resistance value of the anodized sample at the early immersion stage is nearly 26 times of that of the blank sample and the corrosion type of the anodized samples is pitting.
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  Effect of microstructures on superplasticity of Al-11%Si alloy

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  中国有色金属学报（英文版）. 2007, 17(03): 509-509.

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  Three kinds of Al-11%Si (mass fraction) alloy samples with different processes were produced to investigate the effect of microstructures on its superplasticity. Among them, the as-ECAP sample pressed 16 passes has ultrafine grains (300 nm) and the finest secondary particles. The ECAP-T6 sample, with ECAP 16 passes followed by T6 treatment, has fine secondary particles (3 μm) but the largest grains (8 μm). Contrarily, the T6-ECAP sample, with T6 treatment followed by ECAP 16 passes, has ultrafine grains and the large secondary particles (7 μm). The tensile testing results show that the as-ECAP sample exhibits superplasticity at high strain rate of 5.75×10^-1 s^-1 due to its fine secondary particles and ultrafine grains. The ECAP-T6 sample, however, does not exhibit superplasticity at the same high strain rate of 5.75×10^-1 s^-1 because it has relatively large secondary particles and large grains. Remarkably, the T6-ECAP sample does not have superplasticity even at the lower strain rate of 1.15×10^-1 s^-1, attributing to its comparatively large secondary particles. When most secondary particles are larger than 7 μm, the high strain rate superplasticity could not be obtained even if this sample has ultrafine grains.
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  Magnetocrystalline anisotropy and spin reorientation transition of DyMn6Sn6 compound

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  中国有色金属学报（英文版）. 2007, 17(03): 514-514.

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  The spin-reorientation transition of intermetallic compound DyMn₆Sn₆ was investigated by applying the molecular field theory. The temperature dependence of easy magnetization direction of compound and the magnetic moment directions of Dy and Mn ions were theoretically calculated and they have good agreement with the experimental data. In the framework of single ion model, the temperature dependence of magnetocrystalline anisotropic constants K_1R and K_2R of Dy ion were also calculated. The results show that the fourth-order crystal field parameter, B₄⁰ , and the corresponding second-order magnetocrystalline anisotropic constant, K_2R, of Dy ion must be taken into account in order to explain the spin-reorientation transition satisfactorily. The competition between K_2R and K_1R plays a key role in the spin-reorientation transition of DyMn₆Sn₆.
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  Densification mechanism of chemical vapor infiltration technology for carbon/carbon composites

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  中国有色金属学报（英文版）. 2007, 17(03): 519-519.

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  Carbon/carbon composites were fabricated using pressure-gradient chemical vapor infiltration(CVI) technology with propane (C₃H₆) as the carbon precursor gas and nitrogen (N₂) as the carrier gas. The chemical process of deposition of pyrolytic carbon was deduced by analyzing the component of molecules in gas phase and observing the microstructure of deposition carbon. The results show that the process of deposition starts from the breakdown of C—C single bond of propene (C₃H₆), and forms two kinds of active groups in the heterogeneous gas phase reaction. Afterwards, these active groups form many stable bigger molecules and deposit on carbon fiber surface. At the same time, hydrogen atoms of the bigger molecules absorbed on carbon fiber surface are eliminated and the solid pyrolytic carbon matrix is formed in the heterogeneous reaction process.
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  Evolution of {001}〈 110〉orientation and related lattice rotation of Al alloy 6111 during rolling

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  中国有色金属学报（英文版）. 2007, 17(03): 523-523.

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  The texture evolution and lattice rotation in Al alloy 6111 with an initial {001}〈  110〉 component during symmetrical and asymmetrical rolling were investigated by means of orientation distribution function(ODF). The results show that the as-rolled initial {001}〈  110〉 orientation evolves into not only the copper orientation but also all the other orientations along the β fiber, including the brass orientation, by lattice rotation around special directions. Compared with the symmetrical rolling, the {001}〈  110〉 component in the surface layer on the slower roller side evolves more quickly into the orientations along the β fiber during asymmetrical rolling, while that in the surface layer on the faster roller side evolves more slowly.
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  Influence of preparation process on sintering behavior and mechanical properties of ultrafine grained Ti(C, N)-based cermets

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  中国有色金属学报（英文版）. 2007, 17(03): 531-531.

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   The influences of forming and sintering processes on distortion, cracking as well as mechanical properties of sintered bodies of ultrafine grained Ti(C, N)-based cermets were investigated. The results show that lubricant is indispensable to fabrication of ultrafine Ti(C, N)-based cermets, however, with low binder content in powder mixture, the lubrication action of paraffin is attenuated. A appropriate level of 2% (mass fraction) paraffin is determined for a cermet with binder content of 36% (mass fraction). It is also found that the influence of compaction pressure on distortion and cracking of sintered bodies presents a complex relationship. A relatively lower or higher compaction pressure, less than 100 MPa and more than 400 MPa respectively, favors uniform density distribution in green compact. The heating rate of sintering should be strictly controlled. Too fast heating rate results in enclosed pores to burst and forms large size pores in sintering body. A heating rate of 3 ℃/min is recommended.
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  Difference in particle characteristics and coating properties between spraying metallic and ceramic powder cored wires

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  中国有色金属学报（英文版）. 2007, 17(03): 537-537.

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  The sprayed particles of metallic and cermet wires were collected to analyze the atomization state of the particles in arc spraying forming, the microstructure and properties of metallic and ceramic coatings were investigated and compared. Particle size analyzer was used for quantifying particle size. The XRD, SEM and optical microscope(OM) were used to analyze the phase composition and microstructure of the particles and coatings. From the experimental results, some difference of particle characteristics was established between the spraying metallic and ceramic cored wires, and the microstructure and properties of coatings depend strongly on the particles behaviors. The result shows that Fe-TiB₂/Al₂O₃ composite coating has a high potential for abrasive wear applications.
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  Selective laser sintering mechanism of polymer-coated molybdenum powder

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  中国有色金属学报（英文版）. 2007, 17(03): 543-543.

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  A type of polymer-coated molybdenum powder used in selective laser sintering technology was prepared by coating polymer on molybdenum particles and frozen grinding techniques, with the maximum particle diameter of 71 μm. The laser sintering experiments of polymer-coated molybdenum powder were conducted by using the self-developed selective laser sintering machine (HLRP-350I). The method of microscopic analysis was used to investigate the dynamic laser sintering process of polymer-coated molybdenum powder. Based on the study, the laser sintering mechanisms of polymer-coated molybdenum powder were presented. It is found that the mechanism is viscous flow when the laser sintering temperature is between 100 ℃ and 160 ℃, which can be described by a two-sphere model; and the mechanism is melting /solidification when the temperature is above 160 ℃.
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  Single-aging characteristics of 7055 aluminum alloy

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  中国有色金属学报（英文版）. 2007, 17(03): 548-548.

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  The microstructures and properties of 7055 aluminum alloy were studied at different single-aging for up to 48 h using hardness test, tensile test, electrical conductivity measurement, XRD and TEM microstructure analysis. The results show that at the early stage of aging, the hardness and strength of the alloy increase rapidly, the peak hardness and strength are approached after 120 ℃ aging for 4 h, then maintained at a high level for a long time. The suitable single-aging treatment of 7055 alloy is 480 ℃, 1 h solution treatment and water quenching, then aging at 120 ℃ for 24 h. Under those condition, the tensile strength, yield strength, elongation and electrical conductivity of the studied alloy are 513 MPa, 462 MPa, 9.5% and 29%(IACS), respectively. During aging, the solid solution decomposes and precipitation occurs. At the early aging stage of 120 ℃, GP zones form and then grow up gradually with increasing ageing time. η′ phase forms after ageing for 4 h and η phase starts to occur after 24 h aging.
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  In vitro biocompatibility of titanium-nickel alloy with titanium oxide film by H2O2 oxidation

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  中国有色金属学报（英文版）. 2007, 17(03): 553-553.

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  Titanium oxide film with a graded interface to NiTi matrix was synthesized in situ on NiTi shape memory alloy(SMA) by oxidation in H₂O₂ solution. In vitro studies including contact angle measurement, hemolysis, MTT cytotoxicity and cell morphology tests were employed to investigate the biocompatibility of the H₂O₂-oxidized NiTi SMAs with this titanium oxide film. The results reveal that wettability, blood compatibility and fibroblasts compatibility of NiTi SMA are improved by the coating of titanium oxide film through H₂O₂ oxidation treatment.
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  Effect of transformation pH on performance of nano-scale β-Ni(OH)2

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  中国有色金属学报（英文版）. 2007, 17(03): 558-558.

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   The influence of transformation pH value on the performance of nano-scale Ni(OH)₂ was analyzed. The measurement results of XRD and TEM indicate that the samples are composed of β-Ni(OH)₂ with crystal size of 20−50 nm, and the crystal lattice parameters of nano-scale Ni(OH)₂ prepared at different transformation pH values are different. With the increase of transformation pH value, the agglomeration of nano-scale Ni(OH)₂ becomes obvious. Cyclic voltammograms(CV) and electrochemical impedance spectroscopy(EIS) measurement results show that transformation pH value affects the proton diffusion coefficient(D) and charge-transfer resistance(R_ct) of the material. The specific capacity is up to 327.8 mA∙h/g, and the discharge performance of electrodes depends on both D and R_ct, so the kinetic characteristics that electrodes reaction is controlled by both mass-transfer step and charge-transfer step was put forward.
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  Dissolution mechanism of solid nickel in liquid zinc saturated with Fe

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  中国有色金属学报（英文版）. 2007, 17(03): 564-564.

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  The dissolution behavior of solid nickel in static liquid zinc saturated with Fe at 723 K was studied. The results show that when immersing solid Ni in liquid Zn saturated with Fe, the intermetallic compound layers consisted of γ and δ phases are formed on nickel substrate, which is the same as that in liquid pure zinc. However, some Γ₂ particles are formed in the liquid near the solid/liquid interface. These Γ₂ particles can easily heterogeneously nucleate on ζ particles and grow fast. The dissolution process is governed by diffusion of nickel atom across a concentration boundary layer in liquid Zn saturated with Fe, and is different from a mixed control mechanism of nickel in liquid pure zinc. The participation of Γ₂ particles makes the dissolution of solid Ni in the liquid accelerated.
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  Influence of load on sliding tribology of C/C composite with 40Cr steel couple coated by Cr

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  中国有色金属学报（英文版）. 2007, 17(03): 570-570.

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   With the 40Cr steel couple coated by Cr, the sliding tribology behavior of two kinds of C/C composites with different matrix was tested using a M2000 wear tester. The results show that with the increasing of load, the friction coefficients of the composite with resin carbon matrix(RC) decrease quickly from 0.156 under 60 N to 0.123 under 150 N, while those of the composite with rough lamination/smooth lamination /resin carbon (RL/SL/RC) change only between 0.122 and 0.101. The wear volume loss of the two composites increases except for under 100 N. The SEM morphology shows that with the increasing of load, the worn surface of the composite with RC becomes more and more integrated while the size of the debris becomes less and less. The Raman spectrum shows that the graphitization on the worn surface of the fibers draws down after 100 N, the graphitization of the boundary between the fiber and the matrix carbon rises up to 150 N, but the graphitization of the matrix carbon draws down all the while. With the increasing of load, the graphitization on the worn surface of all the worn areas becomes closer and closer, which indicates the worn surface of the different component has the similar friction ability. The composites with RL/SL/RC have better tribological characteristic than the composite with RC.
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  Calculation of free energy of Al-Cu-Li alloy under electric field

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  中国有色金属学报（英文版）. 2007, 17(03): 575-575.

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  Based on Thomas-Fermi model, the interior potential boundary condition with the effect of electric field was defined, the calculation method of free energy for atom cluster under electric field was established. The change of free energy of Al-Cu-Li alloy under the effect of electric field was calculated quantitatively. It is shown that: near the zero electric field and the side of positive electric field, the free energy of Cu₄LiAl₇ compound at aging temperature 460 K is higher than that of free energy at solid solution temperature 725 K, but once the negative electric field increases to certain degree there will be opposite result. Under the effect of electric field, at 725 K the free energy of Cu₄LiAl₇ is higher than that of Al-1.0%Li-4.0%Cu, and at 460 K the free energy of compound is lower than that of solid solution. When the copper content in the Al-Li-Cu solid solution is below 5%, under the effect of electric field the free energy of solid solution increases gradually with the increasing of copper content, but the increasing amplitude reduces with the increasing of copper content. The free energy of binary solid solution increases with the addition of lithium, and with the increasing of electric field intensity the free energy margin of two kinds of solid solution becomes bigger.
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  Numerical analysis of dimension precision of U-shaped aluminium profile rotary stretch bending

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  中国有色金属学报（英文版）. 2007, 17(03): 581-581.

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   In order to enhance the dimension precision of bent part, advanced bending technologies is requested recently. Rotary stretch bending(RSB) is a suitable technology to realize high precision of bent part. The effect of processing parameters, namely the side pressure and the stretching force, on the dimension precision of aluminium profile RSB part was studied by finite element method. The numerical simulation of the U-shaped aluminium profile RSB was carried out, and the validity of the simulation was checked. Parametric analysis shows that the section distortion of the U-shaped profile LY12M bent part decreases with the increasing of the side pressure, whereas the springback of curvature increases, and that both of the section distortion and the springback of curvature decrease with the increasing of the stretching force, moreover, the uniformity of curvature of the bent part is clearly enhanced with the increasing of the stretching force. The results above prove that RSB technology can better improve the dimension precision of aluminium profile bent part.

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  Solidification of Mg-28%Zn-2%Y alloy involving icosahedral quasicrystal phase

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  中国有色金属学报（英文版）. 2007, 17(03): 586-586.

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  Applying XRD, DTA, SEM and TEM techniques, an investigation on the solidification microstructure and solidification sequence of Mg-rich Mg-28%Zn-2%Y (mole fraction) alloy was carried out. It is found that, α-Mg dendrites, Mg₇Zn₃ phase and icosahedral quasicrystal phase coexist in the as-solidified alloy, where the icosahedral quasicrystal, whose structure is indentified to be a face-centered type, originates from a peritectic reaction occurring at 416 ℃. The primary phase of this peritectic reaction has the composition of Mg₂₀Zn₆₆Y₁₄, which is coincident with the H phase reported by TSAI as (Zn, Mg)₅Y. Furthermore, the single I-phase grain morphology was observed and its growth evolution was also discussed.
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  Formation of composites fabricated by exothermic dispersion reaction in Al-TiO2-B2O3 system

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  中国有色金属学报（英文版）. 2007, 17(03): 590-590.

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  The formation of aluminum matrix composites fabricated by exothermic dispersion reaction in Al-TiO₂-B₂O₃ system was investigated. The thermal analysis results show that the reactions are spontaneous and exothermic. The Gibbs free energy of α-Al₂O₃ is the lowest among all the combustion products, followed by TiB₂ and Al₃Ti. It is noted that when the B₂O₃/TiO₂ mole ratio is below 1, the reaction products are composed of particle-like α-Al₂O₃, TiB₂ and rod-like Al₃Ti. The α-Al₂O₃ crystallites, resulting from the reaction between Al and TiO₂ or B₂O₃, are segregated at the grain boundaries due to a lower wettability with the matrix. SEM micrographs show that rod-like Al₃Ti phase distributes uniformly in the matrix. When the B₂O₃/TiO₂ mole ratio is around 1, the Al₃Ti phase almost disappears in the composites, and the distribution of α-Al₂O₃ particulates is improved evidently.
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  Transient oxidation behavior of nanocrystalline CoCrAlY coating at 1 050 ℃

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  中国有色金属学报（英文版）. 2007, 17(03): 595-595.

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  Nanocrystalline CoCrAlY overlay coating was prepared on M38G superalloy by magnetron sputtering deposition. To investigate the oxidation behavior and phase transformation of alumina during oxidation, the oxidation experiments were conducted at 1 050 ℃ for various time in the range of 5−180 min. The phase compositions of the oxide scales were investigated by using glancing angle X-ray diffraction(XRD). The microstructure analysis of oxide scales was carried out by means of scanning electron microscopy(SEM). The growth process of metastable alumina at the grain boundaries and transformation to stable alumina were discussed. The results show that at the initial oxidation stage the mixture of δ-Al₂O₃, g-Al₂O₃ and α-Al₂O₃ is formed on the sample surface rapidly. Especially, δ-Al₂O₃ and g-Al₂O₃ prefer growing at the grain boundaries of CoCrAlY coating. With increasing oxidation time, δ-Al₂O₃ and g-Al₂O₃ transform to θ-Al₂O₃, afterwards θ-Al₂O₃ transforms to α-Al₂O₃ gradually. After 180 min oxidation, θ-Al₂O₃ transforms into α-Al₂O₃ completely.
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  Analysis of rolls deflection of Sendzimir mill by 3D FEM

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  中国有色金属学报（英文版）. 2007, 17(03): 600-600.

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   The deflection of rolls of Sendzimir mill with double AS-U-Roll was simulated by finite element method(FEM). The influences of rolling pressure, strip width and rolls-assignment on rolls deflection were analyzed. The results show that the work roll deflection increases with the increase of rolling pressure and the reduction of work roll radius, but the rigid displacement of work roll slightly changes; the work roll end might appear negative displacement for the narrow strip width and high rolling pressure that might cause the contact of work rolls. The research results are significant for guiding production and theoretical analysis of the rolls system of Sendzimir mill.
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  Effect of ultrasonic power on wedge bonding strength and interface microstructure

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  中国有色金属学报（英文版）. 2007, 17(03): 606-606.

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  During the aluminum wire wedge bonding, the ultrasonic power and bonding strength were obtained. Based on those data, the relationship between ultrasonic power and bonding strength was studied. The results show that: 1) ultrasonic power is affected by ultrasonic power ratio and other uncontrolled factors such as asymmetric substrate quality, unstable restriction on the interface between wedge tool and aluminum wire; 2) when ultrasonic power is less than 1.0 W, increasing ultrasonic power leads to increasing bonding strength and decreasing failure bonding; on the contrary, when ultrasonic power is greater than 1.6 W, increasing power leads to decreasing bonding strength and increasing failure bonding; 3) only when ultrasonic power is between 1.0 W and 1.6 W, can stable and high yield bonding be reached. Finally, the microstructure of bonding interface was observed, and a ring-shaped bond pattern is founded in the center and friction scrape besides the ring area.
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  Inhibition mechanism of aspartic acid on crystal growth of hydroxyapatite

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  中国有色金属学报（英文版）. 2007, 17(03): 612-612.

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  The effects of aspartic acid on the crystal growth, morphology of hydroxyapatite(HAP) crystal were investigated, and the inhibition mechanism of aspartic acid on the crystal growth of hydroxyapatite was studied. The results show that the crystal growth rate of HAP decreases with the increase of the aspartic acid concentration, and the HAP crystal is thinner significantly compared with that without amino acid, which is mainly due to the (10-10)  surface of HAP crystal being inhibited by the aspartic acids. The calculation analysis indicates that the crystal growth mechanism of HAP, following surface diffusion controlled mechanism, is not changed due to the presence of aspartic acid. AFM result shows that the front of terrace on vicinal growth hillocks is pinned, which suggests that the aspartic acid is adsorbed onto the (10-10)surface of HAP and interacts with the Ca²⁺ ions of HAP surface, so as to block the growth active sites and result in retarding of the growth of HAP crystal.
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  Pulsed electrodeposition of hydroxyapatite on titanium substrate in solution containing hydrogen peroxide

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  中国有色金属学报（英文版）. 2007, 17(03): 617-617.

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  Hydroxyapatite(HAP) coatings were prepared on the titanium substrate in the electrolyte containing H₂O₂ by the pulse electrodeposition. The introduction of H₂O₂ restrains the evolution of H₂ and improves the adhesive strength between coatings and substrate. The results of pulse electrodeposition show that the relaxation time of the pulse is beneficial to growth of HAP because it makes ions diffuse from bulk to the surface of electrode and reduces concentration polarization in the next pulse time. It is beneficial to the increase of the duty circle of the pulse for deposition of HAP, but the result is not good if it is increased excessively. With increasing potential, it is good for the growth of HAP coatings. If the potential is too high, it is easy for HAP coatings to drop off during the process of electrodeposition under too intensive polarization, such as −1.0 V (vs SCE), and there is not many coatings on the substrate. The combination of pulse electrodeposition and addition of hydrogen peroxide can assuredly improve the physico-chemical properties of hydroxyapatite coatings.
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  Thermodynamic analysis on sodium carbonate decomposition of calcium molybdenum

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  中国有色金属学报（英文版）. 2007, 17(03): 622-622.

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  According to the principle of mass balances and thermodynamic data, lg [Me]—pH diagrams (Me=Ca, Mo) for Ca-Mo-CO₃-H₂O system at 25 ℃ were presented with total dissolved carbon-containing ions concentrations of 0.01 mol/L and 1 mol/L, and lg [Me]—pH diagram for Ca-Mo-H₂O system at 25 ℃ was also depicted. The effects of system pH value and total dissolved carbon-containing ions concentrations on the concentrations of the species in Ca-Mo-CO₃-H₂O system were studied. The results show that the stability region of CaMoO₄ reduces significantly in the presence of sodium carbonate. In order to achieve effective leaching of molybdenum from CaMoO₄, a certain concentration of sodium carbonate is necessary. High total dissolved carbon-containing ions concentrations and high pH values facilitate to the leaching of CaMoO₄ and dissolved sodium carbonate is an efficient leaching agent for decomposing CaMoO₄.
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  Preparation of highly dispersed antimony-doped tin oxide nanopowders by azeotropic drying with isoamyl acetate

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  中国有色金属学报（英文版）. 2007, 17(03): 626-626.

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  Antimony-doped tin hydroxide colloid precipitates were prepared by hydrolysis of SnCl₄∙5H₂O and SbCl₃ ethanol solutions. Isoamyl acetate was selected as azeotropic drying solvent and was compared with the most commonly used n-butanol solvent on treating precipitate for low hard agglomeration precursor powders. The FT-IR, BET, XRD, and TEM results of the precursor powders and calcinated antimony-doped tin oxide powders were recorded. The results demonstrate that isoamyl acetate is an excellent azeotropic drying solvent that can effectively prevent the agglomeration of particles and greatly improve the fluffiness of the obtained dried powders. After these precursor powders are calcined, antimony-doped tin oxide nanopowders with tetragonal rutile structure and high dispersivity can be obtained.
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  Preparation and formation mechanism of Al2O3 nanoparticles by reverse microemulsion

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  中国有色金属学报（英文版）. 2007, 17(03): 633-633.

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  Al₂O₃ nanoparticles were prepared by polyethylene glycol octylphenyl ether(Triton X-100)/n-butyl alcohol/cyclohexane/ water W/O reverse microemulsion. The proper calcination temperature was determined at 1 150 ℃ by thermal analysis of the precursor products. The structures and morphologies of Al₂O₃ nanoparticles were characterized by X-ray diffraction, transmission electron microscopy and UV-Vis spectra. The influences of mole ratio of water to surfactant on the morphologies and the sizes of the Al₂O₃ nanoparticles were studied. With the increase of surfactant content, the particles size becomes larger. The agglomeration of nanoparticles was solved successfully. And the formation mechanisms of Al₂O₃ nanoparticles in the reverse microemulsion were also discussed.
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  Syntheses and cofluorescence of complexes of Eu(Ⅲ)/Y(Ⅲ) with terephthalic acid, 2-thenoyltrifluoroacetone and trioctylphosphine oxide

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  中国有色金属学报（英文版）. 2007, 17(03): 638-638.

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  A series of Eu(Ⅲ)/Y(Ⅲ) complexes of terephthalic acid(TPA) with 2-thenoyltrifluoroacetone(HTTA) and trioctylphosphine oxide(TPPO) were synthesized. Compositions of these complexes are revealed to be Eu_2(1−x)Y_2x(TPA)(TTA)₄- (TPPO)₄ or Eu_1−xY_x(TPA)(TTA)(TPPO)₂. Their IR spectra, fluorescent spectra and the thermal and optical stability were studied. The fluorescent excitation spectra of these complexes show more broad excitation bands than those of Eu₂(TPA)₃(TPPO)₄ and Eu(TTA)₃(TPPO)₂ corresponding to their formations. In addition, both the binuclear complex EuY(TPA)(TTA)₄(TPPO)₄ and the chain complex Eu_0.4Y_0.6(TPA)(TTA)(TPPO)₂ present higher thermal stability and better optical stability than the mononuclear complex Eu(TTA)₃(TPPO)₂ does. And their thermal and optical stabilities are preferably interpreted from the binuclear structure together with the chain polynuclear structure of the complexes. The fluorescence enhancement of cofluorescence Y³⁺ ions to the Eu(Ⅲ) complexes is clear. The optimum content of Y³⁺ is 0.6 (molar fraction) for the chain complexes Eu_1−xY_x(TPA)(TTA)- (TPPO)₂ and 0.5 for the binuclear complexes Eu_2(1−x)Y_2x(TPA)(TTA)₄(TPPO)₄. The formation of polynuclear structure of the complex Eu_1−xY_x(TPA)(TTA)(TPPO)₂ appears to be responsible for the good cofluorescence effect of Y³⁺ ions.
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  Preparation of Y2O3׃Eu3+ phosphor by molten salt assisted method

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  中国有色金属学报（英文版）. 2007, 17(03): 644-644.

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  A kind of fine and quasi-spherical Y₂O₃׃Eu³⁺ phosphor was prepared by firing a preparative precursor at 1 200 ℃ for 2 h with the molten salts of Na₂CO₃, S and NaCl. The precursor was obtained by homogeneous precipitation of yttrium and europium with oxalic acid when using EDTA, citric acid or starch as complexant. The structure and morphology of the phosphors were characterized by XRD and SEM, respectively. The influence of complexing environment, firing temperature and molten salts on formation of the phosphor Y₂O₃׃Eu³⁺ was discussed. The result show that the prepared Y₂O₃׃Eu³⁺ phosphor is of quasi-spherical structure with size of 2−3 μm. Its luminescent intensity is 30% higher than that of the same phosphor prepared by the same procedure but without molten salts, and is 5% higher than that of commercial Y₂O₃׃Eu³⁺ red phosphor.
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  Charge-discharge process of MnO2 supercapacitor

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  中国有色金属学报（英文版）. 2007, 17(03): 649-649.

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   Mechanochemical synthesis of α-MnO₂ was carried out with KMnO₄ and Mn(CH₃COO)₂ in 1׃1 mole ratio. The electrochemical performance of MnO₂ electrode was investigated by cyclic voltammograms and alternating current impedance. The charge-discharge process of MnO₂ supercapacitor in 6 mol/L KOH was studied within 1.2 V at 200 mA/g, suggesting that it displays double-layer capacibility in low potential scope and pseudo-capacitance properties in high potential scope. It is found that Mn₃O₄, an electrochemical inert, mainly forms in the initial 40 charge-discharge cycles. During cycling, the pseudo-capacitance properties disappear and the discharge curves are close to ideal ones, indicating double-layer capability. The maximum capacitance of MnO₂ electrode is as high as 416 F/g, and retains 240 F/g after 200 cycles. The equivalent series resistance increases from 17 to 41 Ω.

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  Electrochemical performance of multiphase nickel hydroxide

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  中国有色金属学报（英文版）. 2007, 17(03): 654-654.

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  The high density nano-crystalline multiphase nickel hydroxide containing at least three doping elements was synthesized and its electrochemical characteristics were studied. The electrochemical behavior of the high density spherical multiphases α-Ni(OH)₂ were also investigated. The results show that the structure of the material is a mixed phase of α-Ni(OH)₂ and b-Ni(OH)₂, which has a the same stabilized structure as α-Ni(OH)₂ during long-term charge/discharge process. High density spherical multiphases α-Ni(OH)₂ have a much better redox reversibility, a much lower oxidation potential of Ni(Ⅱ) than the corresponding oxidation state in the case of b-Ni(OH)₂, and a much higher reduction potential. They exchange one electron during electrochemical reaction and have a higher proton diffusion coefficient. The mechanism of the electrode reaction is proton diffusion, and the proton diffusion coefficient is 5.67´10⁻¹⁰ cm²/s. Moreover, they reveal a higher discharge capacity than b-Ni(OH)₂/b-NiOOH because they exchange one electron per nickel atom during charge/discharge process.
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  Structure and electrochemical properties of LiMn2O4

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  中国有色金属学报（英文版）. 2007, 17(03): 659-659.

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  LiMn₂O₄, a cathode material of lithium ion battery, was prepared by the citric acid complexing method using lithium acetate and manganese acetate as raw materials. The type of atom location confused degree, the confused degree and judgement method in LiMn₂O₄ were analyzed. The effect of sintering temperature on structure and electrochemical properties of LiMn₂O₄ was also investigated. The results show that the atom location confused degree increases with the decrease of the X-ray diffraction peak intensity ratio of LiMn₂O₄, I₁₁₁/I₃₁₁. The type of atom location confused degree depends on the variation tendency of I₁₁₁/I₃₁₁ and I₃₁₁/I₄₀₀ value. If the variation tendency is the same, it belongs to the 16c type location confusion, however, if the variation tendency is contrary, it belongs to the anti-spinel type location confusion. When the sintering temperature is low, it is apt to produce the anti-spinel location confusion in LiMn₂O₄. With the increase of sintering temperature, the confused degree with the anti-spinel type gradually reduces, however, the confused degree with 16c type increases to some extent. When the atom location confusion with the anti-spinel type appears in LiMn₂O₄, both the initial discharging capacity and cycling properties of LiMn₂O₄ reduce. However, the atom location confusion with 16c type does not affect the charge and discharge properties of LiMn₂O₄.
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  Fabrication and structure characterization of ITO transparent conducting film by sol-gel technique

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  中国有色金属学报（英文版）. 2007, 17(03): 665-665.

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  Using In(NO₃)₃∙5H₂O and acetylacetone as raw materials and anhydrous SnCl₄ as dopant, the transparent conducting indium tin oxide(ITO) films were prepared by sol-gel and dip-coating technique. The phase transformation, structure properties and physical properties (sheet resistance and transmittance) of the films were investigated by DTA-TG, XRD, SEM, four-probe method and UV-Vis spectrometry. The results indicate that it is feasible to fabricate ITO films on the quartz substrates by sol-gel technique, and the ITO films are formed by accumulating of particles with the size of several decades of nanometers. The prepared ITO film has cubic bixbyite structure, and (111) is its preferred plane. After five-times dip-coating, the ITO film has a thickness less than  150 nm, a sheet resistance of 110 Ω/□, a resistivity of 1.65×10⁻³ Ω∙cm and a transparency of 90%.