2007年, 第17卷, 第01期　刊出日期：2007-01-25

  

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  Effects of surfactant on properties of MIM feedstock

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  中国有色金属学报（英文版）. 2007, 17(01): 1-1.

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  Effects of the surfactant for improving the properties of MIM feedstock were investigated. Feedstocks were prepared by 17-4PH stainless steel(SS) powder and paraffin wax-based binder containing different contents of stearic acid(SA) as the surfactant. The viscosity of the feedstock decreases significantly when the SA is added. Besides, the wetting angle of the binder against the 17-4PH SS powder decreases greatly and the critical solid loading increases with the adding of the SA. Fourier transformation infrared spectroscopy(FTIR) analysis was used to prove the interaction between the SA and the 17-4PH SS powder. Chemical bonding is found on the surface of 17-4PH SS powder after mixing and it helps a lot to enhance the interacting force between the binder and the powder. Then an adsorbing model was adopted to estimate the least content of the surfactant that formed a monolayer adsorption on the mono-sized spherical powder (with smooth surface). The least content of the surfactant is calculated to be 0.19%. Whereas, the experiments indicate that about 5% is the optimal value to improve the properties of the feedstock. The reason may come from two aspects: firstly, the powders used in current experiment are not all mono-sized spheres and the coarse surface of the powder has a great effect on the adsorptive capacity of the powder; secondly, multilayer adsorption is likely to occur on the powder surface, which will also increase the adsorptive capacity.
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  Electrodeposition of Ni-SiC nanocomposite film

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  中国有色金属学报（英文版）. 2007, 17(01): 9-9.

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   The point of zero charge(PZC) of SiC nanoparticles was determined by means of standard potentiometric titration method, while the influences of the main technological parameters on the microstructure of electrodeposited Ni-SiC composite film were studied and optimized. The results show that high bath pH value favors SiC nanoparticles negatively charged and high bath temperature promotes them positively charged. Under the experimental conditions, sodium dodecyl-glycol is proven to be an effective surface modification anionic surfactant for SiC nanoparticles. The results also show that the optimized Ni-SiC composite film is composed of the nanoparticles with the average grain size in the nanometer range (100 nm), and SiC nanoparticles disperse into the nickel matrix uniformly.
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  Formation and mechanical properties of bulk Cu-Ti-Zr-Ni
  metallic glasses with high glass forming ability

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  中国有色金属学报（英文版）. 2007, 17(01): 16-16.

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   Bulk amorphous Cu_52.5Ti₃₀Zr_11.5Ni₆ and Cu_53.1Ti_31.4Zr_9.5Ni₆ alloys with a high glass forming ability can be quenched into single amorphous rods with a diameter of 5 mm, and exhibit a high fracture strength of 2 212 MPa and 2 184 MPa under compressive condition, respectively. The stress—strain curves show nearly 2% elastic strain limit, yet display no appreciable macroscopic plastic deformation prior to the catastrophic fracture due to highly localized shear bands. The present work shows clearly evidence of molten droplets besides well-developed vein patterns typical of bulk metallic glasses on the fracture surface, suggesting that localized melting induced by adiabatic heating may occur during the final failure event.
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  Mechanical wet-milling and subsequent consolidation
  of ultra-fine Al2O3-(ZrO2+3%Y2O3) bioceramics by using
  high-frequency induction heat sintering

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  中国有色金属学报（英文版）. 2007, 17(01): 21-21.

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  Alumina/zirconia composites were synthesized by wet-milling technique and rapid consolidation with high frequency induction heat sintering(HFIHS).  The starting materials were a mixture of alumina micro-powder (80%, volume fraction) and 3YSZ nano-powders (20%). The mixtures were optimized for good sintering behaviors and mechanical properties. Nano-crystalline grains are obtained after 24 h milling. The nano-structured powder compacts are then processed to full density at different temperatures by HFIHS. Effects of temperature on the mechanical and microstructure properties were studied. Al₂O₃-3YSZ composites with higher mechanical properties and small grain size are successfully developed at relatively low temperatures through this technique.
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  Reaction diffusion in continuous SiC fiber reinforced Ti matrix composite

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  中国有色金属学报（英文版）. 2007, 17(01): 27-27.

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   SiC continuous fiber-reinforced pure Ti(TA1) matrix composites were fabricated by a vacuum hot pressing(VHP) method and then heat-treated in vacuum under different conditions. The interfacial reaction and the formation of interfacial phases were studied by using SEM, EDS and XRD. The results show that there exists reaction diffusion at the interface of SiC fibers and Ti matrix, and the concentration fluctuation of reaction elements such as C, Ti and Si appears in interfacial reaction layer. The interfacial reaction products are identified as Ti₃SiC₂, TiC_x and Ti₅Si₃C_x. At the beginning of interfacial reaction, the interfacial reaction products are TiC_x and Ti₅Si₃C_x. Along with the interfacial reaction diffusion, Ti₃SiC₂ and Ti₅Si₃C_x single-phase zones come forth in turn adjacent to SiC fibers, and the TiC+Ti₅Si₃C_x double-phase zone appears adjacent to Ti matrix, which forms discontinuous concentric rings by turns around the fibers. The formed interfacial phases are to be Ti₃SiC₂, Ti₅Si₃C_x and TiC_x+Ti₅Si₃C_x from SiC fiber to Ti matrix. The interfacial reaction layer growth is controlled by diffusion and follows a role of parabolic rate, and the activation energy (Q^k) and (k₀) of SiC/TA1 are 252.163 kJ/mol and 7.34×10⁻³ m/s^1/2, respectively
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  Plasma cladding of Stellite 6 powder on Ni76Cr19AlTi exhausting valve

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  中国有色金属学报（英文版）. 2007, 17(01): 35-35.

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   Heavy duty engine valve head was prepared by Ni76Cr19AlTi alloy. It was coated by cobalt-base alloy on the surface to promote its wear-resistance. Hardness tester, metallograph, scanning microscopy, energy spectrum and X-ray diffraction were used to analyze the mechanical properties, the microstructure of the welds and the coated layer of cobalt-base alloy. The results show that the grains are obviously coasened in the side of Ni76Cr19AlTi alloy in the welds and it contains a typical dentritic structure in the side cobalt-base alloy. It is found that micro-strain in weld is stronger than that in heat-effected-zone. Micro-strain in nickel-base alloy is stronger than that cobalt-base alloy. There are not obvious imperfects in the weld. Hardness in cobalt-base alloy is more than 390HV and the major carbides in cobalt-base alloy are Cr₇C₃ and W₂C.
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  Effect of temperature on mechanical behavior of AZ31 magnesium alloy

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  中国有色金属学报（英文版）. 2007, 17(01): 41-41.

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   Strain rate sensitivity and tension/compression asymmetry of AZ31 magnesium alloy at different temperatures and strain rates were investigated. Both of mechanical behaviors are temperature dependent. Strain rate sensitivity increases with increasing temperature. Thermally activated slip is the source of strain rate sensitivity. At the temperature below or near 373 K, strain rate sensitivity is very little. Tension/compression asymmetry in yielding decreases with increasing temperature. Twinning is the reason of tension/compression asymmetry. At the temperature above or near 573 K, the material shows little tension/compression asymmetry of the flow stress.
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  Preparation of semi-solid billet of magnesium alloy and its thixoforming

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  中国有色金属学报（英文版）. 2007, 17(01): 46-46.

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  Preparation of semi-solid billet of magnesium alloy and thixoforming was investigated by applying equal channel angular extrusion to magnesium alloy. The results show that mechanical properties of AZ91D alloy at room temperature, such as yield strength(YS), ultimate tensile strength(UTS) and elongation, are enhanced greatly by four-pass equal channel angular extrusion(ECAE) at 573 K and microstructure of AZ91D alloy is refined to the average grain size of 20 μm. Through using ECAE as strain induced step in SIMA and completing melt activated step by semi-solid isothermal treatment, semi-solid billet with fine spheroidal grains of 25 μm can be prepared successfully. Compared with common SIMA, thixoformed satellite angle frame components using semi-solid billet prepared by new SIMA have higher mechanical properties at room temperature and high temperature of 373 K.
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  Deformation behavior of SiC particle reinforced Al
  matrix composites based on EMA model

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  中国有色金属学报（英文版）. 2007, 17(01): 51-51.

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   Effects of the matrix properties, particle size distribution and interfacial matrix failure on the elastoplastic deformation behavior in Al matrix composites reinforced by SiC particles with an average size of 5 μm and volume fraction of 12% were quantitatively calculated by using the expanded effective assumption(EMA) model. The particle size distribution naturally brings about the variation of matrix properties and the interfacial matrix failure due to the presence of SiC particles. The theoretical results coincide well with those of the experiment. The current research indicates that the load transfer between matrix and reinforcements, grain refinement in matrix, and enhanced dislocation density originated from the thermal mismatch between SiC particles and Al matrix increase the flow stress of the composites, but the interfacial matrix failure is opposite. It also proves that the load transfer, grain refinement and dislocation strengthening are the main strengthening mechanisms, and the interfacial matrix failure and ductile fracture of matrix are the dominating fracture modes in the composites. The mechanical properties of the composites strongly depend on the metal matrix.
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  Effects of minor yttrium addition on hot deformability
  of lamellar Ti-45Al-5Nb alloy

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  中国有色金属学报（英文版）. 2007, 17(01): 58-58.

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   The effects of 0.3%(molar fraction, the same below) yttrium addition on hot deformability of lamellar Ti-45Al-5Nb alloy were investigated by simulated isothermal forging tests. The ingots with the nominal compositions of Ti-45Al-5Nb and Ti-45Al-5Nb-0.3Y were prepared by induction skull melting. Simulated isothermal forging tests were conducted on Gleeble 1500D thermo-simulation machine using a 6 mm in diameter and 10 mm in length compressive specimen at the deformation temperatures of    1 100, 1 150, 1 200 ℃ and strain rates of 1.0, 0.1, 0.01 s⁻¹. The results show that yttrium addition remarkably improves hot deformability of Ti-45Al-5Nb alloy. An appropriate hot deformation processing parameter of Ti-45Al-5Nb-0.3Y alloy is determined as 1 200 ℃, 0.01 s⁻¹. The flow stresses are decreased by yttrium addition under the same compressive conditions. The activation energies of deformation Q are calculated as 448.6 and 399.5 kJ/mol for Y-free and Y-containing alloys, respectively. The deformed microstructure observation under 1 200 ℃, 0.01 s⁻¹ condition indicates that Ti-45Al-5Nb-0.3Y alloy shows more dynamic recrystallization. The improvement of hot deformability of Ti-45Al-5Nb-0.3Y alloy induced by yttrium addition should be attributed to that the smaller the original lamellar colonies, the lower the deformation resistance and activation energy of deformation are, and the more the dynamic recrystallization is.
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  Microscopic phase-field simulation coupled with elastic
  strain energy for precipitation process of Ni-Cr-Al
  alloys with low Al content

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  中国有色金属学报（英文版）. 2007, 17(01): 64-64.

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   The precipitation process of Ni-Cr-Al alloy with low Al content was studied at atomic scale based on the microscopic phase-field kinetic model coupled with elastic strain energy. The aim is to investigate the effect of elastic strain energy on precipitation mechanism and morphological evolution of the alloy. The simulation results show that in the early stage of precipitation, D0₂₂ phase and L1₂ phase present irregular shape, and they randomly distribute in the matrix. With the progress of aging, L1₂ phase and D0₂₂ phase change into the quadrate shape and their orientations become more obvious. In the later stage, L1₂ phase and D0₂₂ phase present quadrate shape with round corner and align along the [100] and [010] directions, and highly preferential selected microstructure is formed. The mechanism of early precipitation of L1₂ phase in Ni-17%Cr-7.5%Al (mole fraction) alloy is the mixed style of non-classical nucleation growth and spinodal decomposition and the D0₂₂ phase is the spinodal decomposition. The mechanisms of early precipitation of L1₂ phase and D0₂₂ phase in Ni-12.5%Cr-7.5% Al alloy are both the non-classical nucleation and growth. The coarsening process follows the rule of preferential selected coarsening.
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  Effects of Ti addition on microstructures of melt-spun CuCr ribbons

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  中国有色金属学报（英文版）. 2007, 17(01): 72-72.

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  The microstructure and resistivity of melt-spun CuCrTi ribbon were studied. The results reveal that the maximal size of the primary Cr particles in the microstructures is below 100 nm by 0.65%−3.8%Ti (mole fraction) addition and the resistivity of annealed ribbons of 0.65%−1.3%Ti addition can meet the need of the contact materials used by the medium-voltage vacuum interrupters. By contrasting the melt-spun microstructures to the annealed microstructures, the primary Cr particles do not grow up quickly in the annealing process. The X-ray diffraction studies reveal that alloying increases the amount of the solute in Cu and Cr phases and results in the increase of resistivity. By the thermodynamic analysis, adding Ti to CuCr₂₉ alloys increases the critical supercooling of the liquid/solid transformation, which makes the critical radius of nucleation decrease and the rate of nucleation increase. As a result, the microstructure of CuCr ribbon can be further refined.
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  Thermodynamic optimization of Mg-Nd system

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  中国有色金属学报（英文版）. 2007, 17(01): 77-77.

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  Based on the reported experimental data, the phase diagram of Mg-Nd binary system was optimized using the CALPHAD approach. Gibbs energies of the disordered BCC_A2 and ordered BCC_B2 phases were modeled with a single expression based on a 2-sublattice model. Liquid and terminal solutions, such as dHCP and HCP, were modeled as substitutional solutions. Intermediate phases Mg₂Nd, Mg₃Nd and Mg₄₁Nd₅ were treated as stoichiometric compounds. The optimization was carried out in the Thermo-Calc package. A set of thermodynamic parameters is obtained. Calculated phase diagram, enthalpies of formation and Gibbs energies of formation are in reasonable agreement with the experimental data.
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  Alumina nanostructures prepared by two-step anodization process

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  中国有色金属学报（英文版）. 2007, 17(01): 82-82.

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   Alumina nanostructures were obtained by two-step anodization process. The porous anodic aluminum oxide(AAO) membranes were anodized in oxalic acid, which was subsequently treated with chemical etching process with 1.0 mol/L sodium hydroxide solution, or mixed solution of phosphoric acid (6.0%) and chromic acid (1.8%), respectively. Field emission scanning electron microscopy(FE-SEM) and transmission electron microscopy(TEM) were employed to character the morphology and structure of the obtained alumina nanostructure. It is found that alumina nanowires are generated in the acidic chemical etching solution, while nanotube structures are formed in the alkaline solution. The influence of acid and alkaline solution on alumina morphologies in the chemical etching process was discussed.
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  Effect of high density electropulsing treatment on formability
  of TC4 titanium alloy sheet

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  中国有色金属学报（英文版）. 2007, 17(01): 87-87.

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  An annealed TC4 titanium alloy sheet was treated by high density electropulsing (J_max=(5.09−5.26)×10³A/mm², t_p=110 μs) under ambient conditions. The effect of electropulsing treatment(EPT) on the plastic deformation behavior of TC4 titanium alloy sheet was studied using uniaxial tension tests. The experimental results indicate that electropulsing treatment significantly changes the mechanical properties of sheet metal: the uniform elongation is increased by 35%, the yield stress is decreased by 19.8% and the yield to tensile ratio is decreased by 17.6%. It is of significant meaning to improve the formability of TC4 titanium alloy sheet. The optical microscope and scanning electron microscope(SEM) were used to examine the changes of the microstructure and the fracture morphology before and after the electropulsing treatment. It is found that recrystallization occurs in the sheet metal and dimples in fracture surface are large and deep after the electropulsing treatment. The research results show that the electropulsing treatment is an effective method to improve the formability of titanium alloy sheets.
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  Sound insulation property of Al-Si closed-cell aluminum
  foam bare board material

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  中国有色金属学报（英文版）. 2007, 17(01): 93-93.

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  Al-Si closed-cell aluminum foam bare boards of 1 240 mm×1 100 mm with different densities and thicknesses were prepared by molten body transitional foaming process. The sound reduction index(R) of Al-Si closed-cell aluminum foam bare boards was investigated experimentally under different frequencies (100−4 000 Hz). It is found that sound reduction index(R) is small under low frequencies, large under high frequencies and is controlled by different mechanisms. The sound insulation property basically conforms with the monolayer board sound insulation theory. The sound reduction index(R) increases with the even growth of thickness and density, but its rising trend is tempered. The single number sound reduction indexes(R_W) of specimen with thickness of 20 cm and density of 0.51 g/cm³ are 30.8 dB and 33 dB respectively, which demonstrates good sound insulation property for lightmass materials.
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  Worn surface characteristics of Cu-based powder
  metallurgy bake materials for aircraft

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  中国有色金属学报（英文版）. 2007, 17(01): 99-99.

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  Cu-based powder metallurgy brake materials are used for aircraft widely and successfully. The characteristics of worn surface of Cu-based powder metallurgy brake materials for aircraft after working under service condition were studied, and two main wear mechanisms were discussed. The results show that the main components of worn surface are graphite, SiO₂, Fe, Cu and oxide of Fe (Fe₃O₄ and FeO); the worn surface can be divided into three zones: severe wear zone, mild wear zone, and low wear zone; fatigue wear and grain wear are the main wear mechanisms of Cu-based materials. Some debris kept between brake discs reduce the wear rate to a certain extent by taking part in the regeneration of friction film.
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  Deformation mechanism at impact test of
  Al-11% Si alloy processed by equal-channel
  angular pressing with rotary die

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  中国有色金属学报（英文版）. 2007, 17(01): 104-104.

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  Al-11%Si (mass fraction) alloy was transformed into a ductile material by equal-channel angular pressing (ECAP) with a rotary die. Two mechanisms at impact test, slip deformation by dislocation motion and grain boundary sliding, were discussed. The ultrafine grains with modified grain boundaries and the high content of fine particles (＜1 µm) were necessary for attaining high absorbed energy. The results contradict the condition of slip deformation by dislocation motion and coincide with that of grain boundary sliding. Many fine zigzag lines like a mosaic were observed on the side surface of the tested specimens. These observed lines may show grain boundaries appeared by the sliding of grains
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  Influence of Y3+ doping on structure and electrochemical
  performance of layered Li1.05V3O8

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  中国有色金属学报（英文版）. 2007, 17(01): 110-110.

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   LiOH∙H₂O, V₂O₅ and Y(NO₃)₃ were used as raw materials to synthesize the precursors containing Li, V and Y by liquid-state reaction, then the cathode materials Li_1.05Y_xV_3−xO₈ (x=0, 0.002 5, 0.005, 0.01, 0.02, 0.1, 0.2) for lithium-ion battery were obtained by calcining the precursors. The influence of Y³⁺ doping on structure, conductivity and electrochemical performance of Li_1.05V₃O₈ were investigated by using XRD, cyclic voltammograms, AC impedance, etc. The results show that Li_1.05Y_xV_3−xO₈ with different doping amounts have well-developed crystal structure of layered Li_1.05V₃O₈ and lengthened interlayer distance of (100) crystal plane. Y³⁺ can insert into crystal lattice completely when the doping amount is small and the impurity phase of YVO₄ is found when x≥0.1. There is no change in the process of Li⁺ insertion-deinsertion with Y³⁺ doping. The conductivity is clearly improved due to small amount of Y³⁺ doping and it tends to increase first and then decrease with increasing doping amount. The initial discharge capacity and plateau potential are both enhanced with proper amount of Y³⁺ doping. When x is 0.005, the first specific discharge capacity reaches 288.9 mA∙h/g, 4.60 % larger than that of undoped sample (276.2 mA∙h/g). When x≤0.1, the average discharge plateau potentials are enhanced by about 0.15 V, which makes for higher energy density.
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  Effect of different incidence angles on bonding
  performance in cold spraying

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  中国有色金属学报（英文版）. 2007, 17(01): 116-116.

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   The deformation behaviour of spray particles impacting upon a substrate under the oblique impact condition in cold spraying was investigated using finite element analysis(FEA) method. The effect of incidence angle of particle on the deformation of particle and substrate was examined. It is found that the contact area between the deformed particle and substrate decreases and the crater depth in the substrate reduces with increasing the tilting angle at the same impact velocity. The normal component of impact velocity takes an important role in the impacting process and formation of bonding.
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  Effects of different tempers on precipitation
  hardening of 6000 series aluminium alloys

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  中国有色金属学报（英文版）. 2007, 17(01): 122-122.

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   By means of Vickers hardness, mechanical property and formability tests, the effects of different tempers on precipitation hardening of 6000 series aluminium alloys for automotive body sheets were investigated. The results indicate that the short-time pre-aging at 170 ℃ makes for subsequent artificial aging precipitation hardening. With the increase of pre-aging time, the artificial aging hardenability increases. The aging hardening rate reaches the maximum when pre-aging time is up to 10 min, and then it decreases. The short-time pre-aging at 170 ℃ benefits sheets to obtain lower strength under delivery condition and consequently to improve stamping formability of automotive body sheets. The effects of different tempers on precipitation hardening are much more obvious than those of the alloying elements. It is a good treatment schedule to perform pre-aging for 5 min at 170 ℃ right after solution treatment.
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  Processing parameters for Cu nanopowders prepared by anodic arc plasma

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  中国有色金属学报（英文版）. 2007, 17(01): 128-128.

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  Copper nanopowders were successfully prepared by anodic arc discharging plasma method with home-made experimental apparatus. The effects of various processing parameters on the particle size of Cu nanopowders were investigated in the process, and the optimum processing parameters were obtained. In addition, the morphology, crystal structure, particle size distribution of the nanopowders were characterized via X-ray diffraction(XRD), transmission electron microscopy(TEM) and the corresponding selected area electron diffraction(SAED). The experimental results show that the crystal structure of the samples is the same fcc structure as that of the bulk materials. The processing parameters play a major role in controlling the particle size. The particle size increases with the increase of the arc current or gas pressure.
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  Microdistortion behavior of Al alloy reinforced
  by SiCp

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  中国有色金属学报（英文版）. 2007, 17(01): 133-133.

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  Al alloy reinforced with SiC_p was fabricated by the method of pressureless infiltration. The effects of factors such as SiC_p size, volume fraction, matrix material and heat treatment process on microdistortion behavior of Al alloy were investigated. The results show that microdistortion decreases along with lessening of SiC_p size and increasing of SiC_p volume fraction. Matrix material has influence on the microdistortion behavior, and solution-aging can improve the microdistortion behavior. Stress and residual strain related to microdistortion behavior were simulated by FEM. It is found that the distribution of strain and stress is not symmetrical; residual strain and stress at interface are higher than those at the other places; at the sharp-angled area of a particle, matrix has the highest strain and stress where plastic distortion is caused at first; the microdistortion and stress far from the interface are smaller.
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  Effects of milling and crystallization conditions on
  microstructure of Nd2Fe14B/α-Fe powder

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  中国有色金属学报（英文版）. 2007, 17(01): 138-138.

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  Effects of milling and crystallization conditions on microstructure, such as amorphous phase and nanocrystalline phase, were investigated by X-ray diffractometry(XRD), differential scanning calorimetry(DSC), and transmission electron microscopy (TEM), respectively. The results show that nanocomposite Nd₂Fe₁₄B/α-Fe powder can be prepared by mechanical milling in argon atmosphere and a subsequent vacuum annealing treatment. The grain sizes of both Nd₂Fe₁₄B and α-Fe phase decrease drastically with increasing milling time. After milling for 5 h, the as-milled material consists of α-Fe nanocomposite phases with the grain size of 10 nm, and some amorphous phases, which can be turned into Nd₂Fe₁₄B/α-Fe nanocomposite phases by the subsequent annealing treatment. Milling energy of mechanical milling after 5 h by theoretical calculation is 6 154.25 kJ/g.
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  Effects of electric field on recrystallization
  texture evolution in cold-rolled high-purity
  aluminum sheet during annealing

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  中国有色金属学报（英文版）. 2007, 17(01): 143-143.

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   The effects of an external DC (direct current) electric field on recrystallization texture evolution in the cold-rolled aluminum sheets with 99.99% purity were investigated by means of X-ray diffraction techniques. The cold-rolled high-purity aluminum sheets were annealed for 60 min at 200, 300 and 400 ℃, respectively with and without an external DC electric field of 800 V/mm. The results show that with DC electric field, the recrystallization cube texture is strengthened at the stage of grain growth. Possible reason for the strengthening of the recrystallization cube texture with the applied electric field may be attributed to both selected nucleation and selected growth of cube oriented crystal nuclei.

   

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  Fabrication of transparent YAG ceramics by traditional
  solid-state-reaction method

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  中国有色金属学报（英文版）. 2007, 17(01): 148-148.

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  Transparent polycrystalline YAG ceramics were fabricated by solid-state reaction method using commercial ultrafine yttria and α-Al₂O₃ powders. The starting materials were milled and calcined at 1 400 ℃, and sintered into transparent YAG ceramics at   1 750 ℃ in the vacuum for 4 h. Neither the starting materials as-milled or those calcined into YAG phase at 1 500 ℃ can be sintered into transparent ceramics. Wide grain boundaries emerge in the YAG ceramics sintered at 1 850 ℃ for 4 h, at the edge of which YAG phases decompose into perovskite YAlO₃(YAP) and α-Al₂O₃.
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  Electrodeposition of dixanthogen(TETD) on pyrite surface

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  中国有色金属学报（英文版）. 2007, 17(01): 154-154.

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   The electrochemical reaction of xanthate on the surface of pyrite was studied using cyclic voltammogrametry, chronopotentiometry and rotating-disc electrode measurements. Experimental results demonstrate that the first step in the reaction is electrochemical adsorption of xanthate ion, and then the adsorbed ion associates with a xanthate ion from the solution and forms a dixanthogen on the pyrite electrode surface. The diffusion coefficient of butyl xanthate on pyrite electrode surface can be determined to be about 1.09×10⁻⁶ cm²/s. Using the galvanostatic technique, the kinetic parameters of oxidation of the butyl xanthate ion on the pyrite surface are calculated as J_a=200 μA/cm², β= 0.203 and J₀=27.1 μA/cm².
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  Wetting agent investigation for controlling dust of lead-zinc ores

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  中国有色金属学报（英文版）. 2007, 17(01): 159-159.

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  The purpose of this project is to control the pollution of dust, which occurred in a typical lead-zinc mine. Two kinds of surfactants and water glass were chosen as the wetting agents to study the behaviours of suppressing the dust. The performances of the wetting agents of various sizes and water content of dust and their compositions among different weting agents were investigated. Firstly, the chemical compounds, dispersity, water content, bulk density and other relevant physico-chemical properties of the choiced dust of lead-zinc ore were mensurated. A great number of down-ward penetrating tests were conducted to different partical sizes of dust and to analyze the dust wetting behaviour respectively. The optimal compositions of wetting agents were obtained in accordance with different water contents and partical sizes of the dust after analyzing and statisting the achieved experimental data. The data show that the efficiency of chemical dust suppression of weting agents is much better than that of water. The results of the research work prove that the partical size and the water content of the dust are very important factors to the dust suppression. The results are also proved validly by the dropping experiment, which takes the penetrating diameter and penetrating time as the major factors. The superfine dust is much more difficult to be wetted. Since increasing the water content of dust is the best approach to control it, the choice of wetting agents for improving dispensation is significant.
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  A new strain Acidithiobacillus albertensis BY-05
  for bioleaching of metal sulfides ores

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  中国有色金属学报（英文版）. 2007, 17(01): 168-168.

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  An acidophilic, rod-shaped Gram-negative sulfur oxidizing strain BY-05 was isolated from an acid mine drainage of copper ore in Baiyin area, Gansu Province, China. Ultrastructural studies show that the isolate has a tuft of polar flagella and possesses sulfur granules with clear membrane adhering to the cell innermembrane. Physiological study shows that this isolate grows autotrophically and aerobically by oxidizing S⁰ and reduced inorganic sulfur compounds ( S₂O^2-₃, S₂O^2-_4,  S²⁻ and ZnS) with the optimum growth at pH 3.5−4.0 and at the temperature range of 25−30 ℃. The 16S rRNA gene sequence (DQ 423683) of strain BY-05 has 100% sequence similarity to that of Acidithiobacillus albertensis (DSM 14366). So it is identified and named as A. albertensis BY-05. Bioleaching experiments with this new strain show that it can play an important role in recovery of metals from chalcopyrite and sphalerite.

   

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  Effect of surfactants on preparation of nanometer TiO2 by pyrohydrolysis

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  中国有色金属学报（英文版）. 2007, 17(01): 176-176.

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  The nanometer TiO₂ was prepared by pyrohydrolysis with titanic solution. The effects of species and content of the surfactants on the particle size, morphology and phase of TiO₂ were studied by using LPA, XRD and TEM respectively. The results show that it is beneficial to reducing the aggregation of TiO₂ particles with adding surfactants to the solution. Nanometer TiO₂ powders with the size of 40−55 nm are obtained by adding the anion surfactants in the optimal content of 1.5% (mass fraction). The effect of cationic surfactant for reducing particle aggregation is not as good as that of anion. The crystal phase constitutent of TiO₂ is dependent on the temperature of thermal treatment and complete anatase can be achieved after calcining in the temperature range of 350−750 ℃.
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  Electrical conductivity of Na3AlF6-AlF3-Al2O3-CaF2-LiF(NaCl)
  system electrolyte

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  中国有色金属学报（英文版）. 2007, 17(01): 181-181.

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  A PGSTAT 30 and a BOOSTER 20A were used to measure cell impedance. Electrical conductivity was gained by the Continuously Varying Cell Constant Technique. Electrical conductivity of KCl was measured for comparison. The results prove that the method is reliable and accurate. The electrical conductivity of Na₃AlF₆-AlF₃-Al₂O₃-CaF₂-LiF(NaCl) system was studied by this method. Activation energy of conductance was obtained based on the experiment results. The experiments show that electrical conductivity is increased greatly with NaCl and LiF added. Increasing 1%LiF(mass fraction) results in corresponding increase of 0.0276 S/cm for superheat condition of 15 ℃. For NaCl, it is 0.024 S/cm. Electrical conductivity is increased by 0.003 S/cm with   1℃ temperature increase. The electrical conductivity is lower than that predicted by the WANG Model and higher than that predicted by the Choudhary Model.
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  Kinetic study on pressure leaching of high iron sphalerite concentrate

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  中国有色金属学报（英文版）. 2007, 17(01): 187-187.

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  The kinetics of pressure leaching high iron sphalerite concentrate was studied. The effects of agitation rate, temperature, oxygen partial pressure, initial acid concentration, particle size, iron content in the concentrate and concentration of Fe²⁺ added into the solution on the leaching rate of zinc were examined. The experiment results indicate that if the agitation rate is greater than 600 r/min, its influence on Zn leaching rate is not substantial. A suitable rise in temperature can facilitate the leaching reaction, and the temperature should be controlled at 140−150 ℃. The increase trend of Zn leaching rate becomes slow when pressure is greater than 1.2 MPa, so the pressure is controlled at 1.2−1.4 MPa. Under the conditions of this study, Zn leaching rate decreases with a rise in the initial sulfuric acid concentration; and Zn leaching rate increases with a rise of iron content in the concentrate and Fe²⁺ concentration in the solution. Moreover, the experiment demonstrates that the leaching process follows the surface chemical reaction control kinetic law of “shrinking of unreacted core”. The activation energy for pressure leaching high iron sphalerite concentrate is calculated, and a mathematical model for this pressure leaching is obtained. The model is promising to guide the practical operation of pressure leaching high iron sphalerite concentrate.
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  Characteristics of graphite felt electrode electrochemically
  oxidized for vanadium redox battery
  application

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  中国有色金属学报（英文版）. 2007, 17(01): 195-195.

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   The graphite felt was oxidized at a positive electrode potential in sulfuric acid solution. The electrochemical performance of the treated graphite felt served as electrode for vanadium redox battery was investigated with FT-IR, SEM, XPS, BET, cyclic voltammetry and testing VRB system, respectively. The results show that the molar ratio of O to C increases from 0.085 to 0.15 due to the increase of —COOH functional groups during electrochemical oxidation treatment, and the GF surface is eroded by electrochemical oxidation, resulting in the surface area increase from 0.33 m²/g to 0.49 m²/g. The VRB with modified GF electrode exhibits excellent performance under a current density of 30 mA/cm². The average current efficiency reaches 94% and average voltage efficiency reaches 85%. The improvement of electrochemical activity for the electrode is ascribed to the increase of the number of —COOH group and the special surface of GF.
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  Effect of surface modification of metal hydride electrode
  on performance of MH/Ni batteries

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  中国有色金属学报（英文版）. 2007, 17(01): 200-200.

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   A novel method was applied to the surface modification of the metal hydride(MH) electrode of MH/Ni batteries. Both sides of the electrode were plated with a thin silver film about 0.1μm thick using vacuum evaporation plating technology, and the effect of the electrode on the performance of MH/Ni batteries was examined. It is found that the surface modification can enhance the electrode conductivity and decrease the battery ohimic resistance. After surface modification, the discharge capacity at 5C (7.5A) is increased by 212 mA∙h and the discharge voltage is increased by 0.11 V, the resistance of the batteries is also decreased by 32%. The batteries with modified electrode exhibit satisfactory durability. The remaining capacity of the modified batteries is 89% of the initial capacity even after 500 cycles. The inner pressure of the batteries during overcharging is lowered and the charging efficiency of the batteries is improved.
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  Mechanism of mechanical activation for sulfide ores

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  中国有色金属学报（英文版）. 2007, 17(01): 205-205.

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   Structural changes for mechanically activated pyrite, sphalerite, galena and molybdenite with or without the exposure to ambient air, were systematically investigated using X-ray diffraction analysis(XRD), particle size analysis, gravimetrical method, X-ray photo-electron spectroscopy(XPS) and scanning electron microscopy(SEM), respectively. Based on the above structural changes for mechanically activated sulfide ores and related reports by other researchers, several qualitative rules of the mechanisms and the effects of mechanical activation for sulfide ores are obtained. For brittle sulfide ores with thermal instability, and incomplete cleavage plane or extremely incomplete cleavage plane, the mechanism of mechanical activation is that a great amount of surface reactive sites are formed during their mechanical activation. The effects of mechanical activation are apparent. For brittle sulfide ores with thermal instability, and complete cleavage plane, the mechanism of mechanical activation is that a great amount of surface reactive sites are formed, and lattice deformation happens during their mechanical activation. The effects of mechanical activation are apparent. For brittle sulfide ores with excellent thermal stability, and complete cleavage plane, the mechanism of mechanical activation is that lattice deformation happens during their mechanical activation. The effects of mechanical activation are apparent. For sulfide ores with high toughness, good thermal stability and very excellent complete cleavage plane, the mechanism of mechanical activation is that lattice deformation happens during their mechanical activation, but the lattice deformation ratio is very small. The effects of mechanical activation are worst.
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  Electrocatalytic oxidation of methanol
  on carbon-nanotubes/graphite electrode modified with platinum
  and molybdenum oxide nanoparticles

  匿名

  中国有色金属学报（英文版）. 2007, 17(01): 214-214.

  摘要 ( )   可视化   收藏

  Electrochemical codeposition and electrocatalytic properties of platinum and molybdenum oxide nanoparticles (Pt-MoO_x) on carbon-nanotubes/graphite electrode for methanol oxidation were investigated. The micrograph and elemental composition of the resulting Pt-MoO_x/CNTs/graphite electrode were characterized by scanning electron microscopy(SEM) and energy dispersive X-ray spectroscopy(EDS). The results show that the Pt-MoO_x particles with the average size of about 50 nm are highly dispersed on the CNTs surface. The Pt-MoO_x/CNTs/graphite electrode delivers excellent electrocatalytic properties for methanol oxidation. The highest mass activity(A_m) reaches 264.8 A/g at the loading mass of 159.3 mg/cm². This may be attributed to the small particle size and high dispersion of Pt-MoO_x catalysts deposited on the CNTs surface. The kinetic analysis from electrochemical impedance spectroscopy(EIS) reveals that the existed MoO_x phase can improve the chemisorptive and catalytic properties for methanol oxidation.