Started in 1985 Semimonthly
ISSN 1005-0302
CN 21-1315/TG
Impact factor:6.155

The journal has been awarded the excellent periodical in China, and its articles are covered by SCI, EI, CA, SA, JST, RJ, CSA, MA, EMA, AIA etc., PASCAL web. ISI web of Science,SCOPUS.

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      28 January 2004, Volume 20 Issue 01 Previous Issue    Next Issue
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    Research Articles
    Modification of Analytical Expression of Electron Dynamical Diffraction
    Canying CAI, Qibin YANG, Hongrong LIU
    J. Mater. Sci. Technol., 2004, 20 (01): 1-2. 
    Abstract   HTML   PDF (143KB)
    Assuming that the wave function , the Schrodinger equation can be written as . Neglecting the last two terms, an analytical expression of electron dynamical diffraction was derived by Qibin YANG et al. In this paper, the analytical expression is modified by further considering the second-order differential term . When the accelerating voltage is not very high, or the sample is not very thin, the reciprocal vector ɡ is large, the modification of the second-order differential is necessary; otherwise it can be neglected.
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    Analysis of in situ Reaction and Pressureless Infiltration Process in Fabricating TiC/Mg Composites
    Qun DONG, Liqing CHEN, Mingjiu ZHAO, Jing BI
    J. Mater. Sci. Technol., 2004, 20 (01): 3-7. 
    Abstract   HTML   PDF (496KB)
    An innovative processing route, in situ reaction combined with pressureless infiltration, was adopted to fabricate magnesium matrix composites, where the reinforcement TiC formed in situ from elemental Ti and C powders and molten Mg spontaneously infiltrated the preform of Ti and C. The influences of primarily elemental particle sizes, synthesizing temperature, holding time etc on in situ reactive infiltration for Mg-Ti-C system were systematically investigated in order to explore the mechanism of this process. In fabricating TiC/Mg composites, Mg can not only spontaneously infiltrate the preform of reinforcement and thus densify the as fabricated composites as matrix metal, but also it can accelerate the in situ reaction process and lower the synthesizing temperature of Ti and C as well. In situ reaction of Ti and C and Mg infiltration processes are essentially overlapping and interacting during fabrication of TiC/Mg composites. The mechanism proposed in this paper can be used to explain the formation and morphologies of the reinforcement phase TiC.
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    Synthesis and Characterizations of Nanocrystalline WC-Co Composite Powders by a Unique Ball Milling Process
    Jun SHEN, Jianfei SUN, Faming ZHANG
    J. Mater. Sci. Technol., 2004, 20 (01): 7-10. 
    Abstract   HTML   PDF (526KB)
    In order to explore the high efficiency of fabricating nanocrystalline WC-Co composite powders, this paper presented a unique high energy ball milling process with variable rotation rate and repeatious circulation, by which nanocrystalline WC-10Co-0.8VC-0.2Cr3C2 (wt pct) composite powders with mean grain size of 25 nm were prepared in 32 min, and the quantity of the powders for a batch was as much as 800 grams. The as-prepared powders were analyzed and characterized by chemical analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential thermal analysis (DTA). The results show that high energy ball milling with variable rotation rates and repeatious circulation could be used to produce nanocrystalline WC-Co powder composites with high efficiency. The compositions of the powders meet its specifications with low impurity content. The mean grain size decreases, lattice distortion and system energy increase with increasing the milling time. The morphology of nanocrystalline WC-Co particles displays dominantly sphere shape and their particle sizes are all lower than 80 nm. The eutectic temperature of the nanocrystalline WC-10Co-0.8VC-0.2Cr3C2 composites is about 1280℃.
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    Preparation and Photoluminescence of Ordered ZnO Nanowire Arrays
    Mingzai WU, Lianzeng YAO, Weili CAI, Guowei JIANG, Xiaoguang LI, Zhen YAO
    J. Mater. Sci. Technol., 2004, 20 (01): 11-13. 
    Abstract   HTML   PDF (515KB)
    Ordered ZnO nanowire arrays embedded in anodic aluminum oxide (AAO) membranes were fabricated by electrochemical deposition of Zn(NO3)2+H3BO3 solution in a boiling bath. Scanning electron microscope (SEM) and transmission electron microscope (TEM) observation results show that the polycrystalline ZnO nanowires with diameters around 100 nm were uniformly assembled into the ordered nanochannels of the AAO. The results of the investigation into photoluminescence (PL) and electronic paramagnetic resonance (EPR) measurements reveal that the interfaces between the ZnO nanowires and the pore walls of the AAO create a lot of oxygen vacancies, which are responsible for the green light emission (peaking around 512 nm) and the huge enhancement of the PL emission.
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    Visible Light Induced Photocatalysis of Cerium Ion Modified Titania Sol and Nanocrystallites
    Yibing XIE, Chunwei YUAN
    J. Mater. Sci. Technol., 2004, 20 (01): 14-18. 
    Abstract   HTML   PDF (630KB)
    The cerium ion (Ce4+) doped titania sol and nanocrystallites were prepared by chemical coprecipitation-peptization and hydrothermal synthesis methods, respectively. The X-ray diffraction pattern shows that Ce4+-TiO2 xerogel powder has semicrystalline structure and thermal sintering sample has crystalline structure. Ce4+-TiO2 nanocrystallites are composed of the major anatase phase titania (88.82 wt pct) and a small amount of crystalline cerium titanate. AFM micrograph shows that primary particle size of well-dispersed ultrafine sol particles is below 15 nm in diameter. The particle sizes are 30 nm for xerogel sample and 70 nm for nanocrystallites sample, which is different from the estimated values (2.41 nm and 4.53 nm) by XRD Scherrer's formula. The difference is mainly due to aggregation of nanocrystallites. The experimental results exhibit that photocatalysts of Ce4+-TiO2 sol and nanocrystallites have the ability to photodegrade reactive brilliant red dye (X-3B ) under visible light irradiation with the ion-TiO2/VIS/dye system. Moreover, Ce4+ doped titania sol has shown higher efficiency than the nanocrystallites sample in respect of potocatalytic activity. Meanwhile, dye photodegradation mechanisms are proposed to different photocatalytic reaction systems, which are dye photosensitization, ion-dye photosensitization and interband photocatalysis & dye photosensitization with respect to TiO2 nanocrystallites, Ce4+-TiO2 sol and Ce4+-TiO2 nanocrystallites system.
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    Numerical Simulation of Morphology and Microsegregation Evolution during Solidification of Al-Si Alloy
    Dayong GUO, Yuansheng YANG, Wenhui TONG, Zhuangqi HU
    J. Mater. Sci. Technol., 2004, 20 (01): 19-23. 
    Abstract   HTML   PDF (679KB)
    A stochastic model coupled with transient calculations for the distributions of temperature, solute and velocity during the solidification of binary alloy is presented. The model can directly describe the evolution of both morphology and segregation during dendritic crystal growth. The model takes into account the curvature and growth anisotropy of dendritic crystals. Finite difference method is used to explicitly track the sharp solid liquid (S/L) interface on a fixed Cartesian grid. Two-dimensional mesoscopic calculations are performed to simulate the evolution of columnar and equiaxed dendritic morphologies of an Al-7 wt pct Si alloy. The effects of heat transfer coefficient on the evolution of both the dendrite morphology and segregation patterns during the solidification of binary alloys are analyzed. This model is applied to the solidification of small casting. Columnar-to-equiaxed transition is analyzed in detail. The effects of heat transfer coefficient on final casting structures are also studied. Final casting structures changing from wholly columnar dendrites to wholly equiaxed dendrites are described. The effect of melt flow on the morphological development during Al-7 wt pct Si alloy soilidification is also described.
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    Numerical Simulation of Microporosity Evolution of Aluminum Alloy Castings
    Shuyong DONG, Shoumei XIONG, Baicheng LIU
    J. Mater. Sci. Technol., 2004, 20 (01): 23-26. 
    Abstract   HTML   PDF (521KB)
    A mathematical model to calculate the size and distribution of microporosities was studied and coupled with a stochastic microstructure evolution model. The model incorporates various solidification phenomena such as grain structure evolution, solidification shrinkage, interdendritic fluid flow and formation and growth of pores during solidification processes. The nucleation and growth of grains were modeled with a cellular automaton method that utilizes the results from a macro scale modeling of the solidification process. Experiments were made to validate the proposed models. The calculated results of aluminum alloy castings agreed with the experimental measurements.
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    Physical Simulation of Mold-Filling Processing of Thin-Walled Castings under Traveling Magnetic Field
    Yanqing SU, Tiejun ZHANG, Jingjie GUO, Hongsheng DING, Weisheng BI, Jun JIA, Hengzhi FU
    J. Mater. Sci. Technol., 2004, 20 (01): 27-30. 
    Abstract   HTML   PDF (1022KB)
    Mold-filling process of thin-walled castings under the condition of traveling magnetic field has been studied by physical simulation method using gallium melt and fast speed photography. Flow morphology and its formation mechanism were obtained and discussed for thin-walled casting. The influences of magnetic field density on the filling ability, filling velocity and mold filling time have been studied. The differences in filling capability between gravity casting and casting under the traveling magnetic field have been compared. The results indicate that the mold filling ability of the gallium melt increases greatly under the condition of traveling magnetic field; the filling time is shortened from 18 s under gravity field to 3 s under the traveling magnetic field and average flow rate of the melt increases from 1.6 to 8.68 cm3/s; the change law of the cross-section morphology of the gallium melt during the mold filling is that at first, the cross-section area does not change, then it decreases gradually. When the front of the melt reaches the end of the mold cavity, the front melt will backfill the mold; the wider the width of mold cavity, the better the mold filling ability. The mold filling ability of gallium melt in mold with upper magnetic conductor is better than that without upper magnetic conductor.
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    Photocatalytic Property of TiO2 Films Deposited by Pulsed DC Magnetron Sputtering
    Wenjie ZHANG, Shenglong ZHU, Ying LI, Fuhui WANG
    J. Mater. Sci. Technol., 2004, 20 (01): 31-34. 
    Abstract   HTML   PDF (427KB)
    TiO2 thin films were prepared by DC magnetron sputtering with the oxygen flow rate higher than the threshold. The film deposited for 5 h was of anatase phase with a preferred orientation along the <220> direction, but the films deposited for 2 and 3 h were amorphous. The transmittance and photocatalytic activity of the TiO2 films increased constantly with increasing film thickness. When the annealing temperature was lower than 700℃, only anatase grew in the TiO2 film. TiO2 phase changed from anatase to rutile when the annealing temperature was above 800℃. The photocatalytic activity decreased with increasing annealing temperature.
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    Photocatalytic Property of TiO2 Films Deposited by Pulsed DC Magnetron Sputtering
    Wenjie ZHANG, Shenglong ZHU, Ying LI, Fuhui WANG
    J. Mater. Sci. Technol., 2004, 20 (01): 31-34. 
    Abstract   HTML   PDF (427KB)
    TiO2 thin films were prepared by DC magnetron sputtering with the oxygen flow rate higher than the threshold. The film deposited for 5 h was of anatase phase with a preferred orientation along the <220> direction, but the films deposited for 2 and 3 h were amorphous. The transmittance and photocatalytic activity of the TiO2 films increased constantly with increasing film thickness. When the annealing temperature was lower than 700℃, only anatase grew in the TiO2 film. TiO2 phase changed from anatase to rutile when the annealing temperature was above 800℃. The photocatalytic activity decreased with increasing annealing temperature.
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    Magnetic Properties of Nanometer-Scale NiZnCu Ferrite Thin Films Fabricated by Spray-Spin-Heating-Coating Method
    Yulan JING, Huaiwu ZHANG, lijun JIA, Yu SHI, Yingli LIU
    J. Mater. Sci. Technol., 2004, 20 (01): 35-37. 
    Abstract   HTML   PDF (439KB)
    A new nanometer-scale ferrite thin film with excellent high-frequency characteristics has been developed by the spray-spin-heating-coating method. The effects of the ion synthesis mechanism, chemical stoichiometry, fabrication method, and doping content on the magnetic properties and microstructure of the thin films have been analyzed. The films formed between 75℃ and 90℃ by spray-spin-heating-coating methods was discovered with fine grain size of about 21 nm, high saturation magnetization (4 Ms) of about 6.5 kGs, coercivity of about 9.8 Oe, as well as initial permeability of about 14.0. These films can be widely used in radio-frequency integrated circuit devices.
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    Influence of Water Vapor on the Isothermal Oxidation Behavior of Thermal Barrier Coatings
    Chungen ZHOU, Jingsheng YU, Shengkai GONG, Huibin XU
    J. Mater. Sci. Technol., 2004, 20 (01): 38-40. 
    Abstract   HTML   PDF (390KB)
    The oxidation of specimens with thermal barrier coating (TBC) consisted of nickel-base superalloy, low-pressure plasma sprayed Ni-28Cr-6Al-0.4Y (wt pct) bond coating and electron beam physical vapor deposited 7.5 wt pct yttria stabilized zirconia (YSZ) top coating was studied at 1050℃ respectively in flows of O2, and mixture of O2 and 5%H2O under atmospheric pressure. The thermal barrier coating has relatively low oxidation rate at 1050℃ in pure O2. Oxidation rate of thermal barrier coating in the atmosphere of O2 and 5%H2O is increased The oxidation kinetics obeys almost linear law after long exposure time in the presence of 5% water vapor. Oxide formed along the interface between bond coat and top coat after oxidation at 1050℃ in pure O2 consisted of Al2O3, whereas interfacial scales formed after oxidation at 1050℃ in a mixture of O2 and 5%H2O were mainly composed of Ni(Al,Cr)2O4,NiO and Al2O3. It is suggested that the effect of water vapor on the oxidation of the NiCrAlY coating may be attributed to the increase in Ni and Cr ions transport in the oxides.
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    Development of Magnesium-Insertion Positive Electrode for Rechargeable Magnesium Batteries
    Huatang YUAN, Lifang JIAO, Jiansheng CAO, Xiusheng LIU, Ming ZHAO, Yongmei WANG
    J. Mater. Sci. Technol., 2004, 20 (01): 41-45. 
    Abstract   HTML   PDF (473KB)
    Magnesium-based rechargeable batteries might be an interesting future alternative to lithium-based batteries. It is so far well known that Mg2+ ion insertion into ion-transfer hosts proceeds slowly compared with Li+, so it is necessary to realize fast Mg2+ transport in the host in addition to other requirements as practical cathode materials for magnesium batteries. Positive electrode materials based on inorganic transition-metal oxides, sulfides, and borides are the only ones used up to now to insert magnesium ions. In this paper, the available results of research on materials suitable as possible, for secondary magnesium batteries, are reviewed.
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    Synthesis and Structure Transformation of Orthorhombic LiMnO2 Cathode Materials by Sol-gel Method
    Shixi ZHAO, Hanxing LIU, Qiang LI, Shixi OUYANG
    J. Mater. Sci. Technol., 2004, 20 (01): 46-48. 
    Abstract   HTML   PDF (371KB)
    Orthorhombic LiMnO2 cathode materials were synthesized successfully at lower temperature by sol-gel method. When LiMnO2 precursor prepared by sol-gel method was fired in air, the product was a mixture of spinel structure LiMn2O4 and rock-salt structure Li2MnO3, whereas in argon single-phase orthorhombic LiMnO2 could obtain at the range of 750℃ to 920℃. The substitution of Mn by Zn2+ or Co3+ in LiMnO2 led to the structure of LiMnO2 transiting to α-LiFeO2. The results of electrochemical cycles indicated that the discharged capacity of orthorhombic-LiMnO2 was smaller at the initial stages, then gradually increased with the increasing of cycle number, finally the capacity stabilized to certain value after about 10th cycles. This phenomenon reveals that there is an activation process for orthorhombic LiMnO2 cathode materials during electrochemical cycles, which is a phase transition process from orthorhombic LiMnO2 to tetragonal spinel Li2Mn2O4. The capacity of orthorhombic LiMnO2 synthesized at lower temperature is larger than that synthesized at high temperature.
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    Influence of Metal Oxides on the Arc Erosion Behaviour of Silver Metal Oxides Electrical Contact Materials
    P.Verma, O.P.P, ey, A.Verma
    J. Mater. Sci. Technol., 2004, 20 (01): 49-52. 
    Abstract   HTML   PDF (524KB)
    In the present work investigations have been made to see the role of metal oxides on the performance of the silver metal oxides electrical contact materials. Silver metal oxide materials of three different compositions Ag-10CdO, Ag-7.6SnO2-2.3In2O3 and Ag-10ZnO were prepared by internal oxidation process under identical processing conditions. These materials were tested for electrical conductivity, hardness, and erosion loss. Performing an accelerated test on the actual contactor assessed the electrical performance, involving erosion loss and temperature rise of the processed materials. The arc-eroded surface was characterized under scanning electron microscope. The study of the eroded surfaces of contacts indicates that the thermal stability of metal oxides depends on nature of silver-metal oxide interface and their mode of erosion. An attempt is made to correlate the surface features of the eroded contacts with the thermal stability of metal oxides.
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    Ionic Conduction in Cubic Zirconias at Low Temperatures
    Ying LI, Yunfa CHEN, Jianghong GONG
    J. Mater. Sci. Technol., 2004, 20 (01): 52-54. 
    Abstract   HTML   PDF (337KB)
    The ac conductivities of Y2O3 or CaO-stabilized cubic zirconias were obtained from complex impedance measurements in the temperature range from 373 to 473 K. By analyzing the temperature-dependence of the resultant dc conductivities, it was shown that the activation energies for conduction are lower than those reported previously for the same materials at high temperatures. Comparing the activation energy data with the theoretically estimated values revealed that there may exist a certain, although very small, amount of free oxygen vacancies in the test samples at low temperatures and the conduction in the test samples is a result of the migration of these free oxygen vacancies.
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    Effect of Sequence of Impregnation on the Structure and Catalytic Properties of Cu-Co-Al-Oxide System
    Suzan A.Ali
    J. Mater. Sci. Technol., 2004, 20 (01): 55-58. 
    Abstract   HTML   PDF (600KB)
    Twelve samples of Co-Cu/Al2O3 were prepared by impregnating Al2O3 with cobalt salt followed by copper salt or vice versa. The composition of the prepared samples varied in the molar ratios 1:1, 1:2 and 1:3 with respect to CuO:CoO or CoO:CuO, while Al2O3 content was kept at about 13-15 mol. The prepared solids were calcined at different temperatures and the products were characterized by means of XRD-analysis. The catalytic activity of the calcined solids was tested in H2O2 decomposition. The XRD-analysis revealed that the sequence of impregnation affects much the structure of the samples. The loading of alumina with cobalt followed by copper salts produced sample with structure differs from that for sample firstly treated with copper followed by cobalt salts. XRD- analysis showed the formation of crystalline spinel Co1-x Cux Al2O4 with nearly the same crystal structure as CoAl2O4 even with high copper content. The examination of catalytic activity of these samples showed that catalysts with Co-loaded over Cu were more active than catalysts with Cu loaded over Co. In all cases the double oxides loaded over Al2O3 were more active than the single oxide over Al2O3.
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    Ultrastructural Analysis on the Osteogenesis and Transformation of Calcium Phosphate Ceramics in Vivo
    Honglian DAI, Shipu LI, Yuhua YAN, Xianying CAO, Xuehui LU, Yang LENG
    J. Mater. Sci. Technol., 2004, 20 (01): 59-62. 
    Abstract   HTML   PDF (354KB)
    To study the osteogenesis and transformation process of calcium phosphate bioceramic in vivo, biodegradable porous beta-tricalcium phosphate ceramics (β-TCP, 5×8 mm) were implanted in the tibia of rabbits. β-TCP ceramics with surrounding bone tissue were retrieved and observed by SEM, TEM and EPMA every month after implantation. The results showed that osteogenesis was active and β-TCP ceramics bonded to bones directly. The new bones were forming and maturing as materials were continuously degrading, and materials were finally replaced by new bone. Parts of the materials were degraded, absorbed and recrystallized, while the rest were dispersed to the spongy bone and the Haversian lamella in an irregular arrangement, becoming incorporated into bone formation directly by remodeling the structure. Some β-TCP crystals cleaved along its (001) rhombohedral plane and formed lath-like crystals in vivo.
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    Temperature Characteristics of Surface Acoustic Waves Propagating on La3Ga5SiO4 Substrates
    Guowei ZHANG, Wenkang SHI, Xiaojun JI, Tao HAN, Feng DU, Lianger LI
    J. Mater. Sci. Technol., 2004, 20 (01): 63-66. 
    Abstract   HTML   PDF (634KB)
    Langasite (LGS) is a novel piezoelectric crystal. The authors numerically analyses the temperature stability of surface acoustic waves (SAW) and the relation of SAW propagation with temperature on certain optimal cuts on LGS in this paper. The results show that LGS has better temperature stability than traditional piezo crystals. The results also demonstrate that the velocity of SAW decrease with temperature, the electro-mechanical coupling constant (k2) and temperature coefficient of frequency increases parabolically and the power flow angle increases linearly on certain optimal cuts of LGS. The calculation result compared with the experimental and show good agreement.
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    Characterization of Bi-substituted Dysprosium Iron Garnet Films Prepared by Sol-gel Process
    Yuepin ZHANG, Xianying WANG, Haiping XIA, Defang SHEN, Fuxi GAN, Songyou WANG, Liangyao CHEN
    J. Mater. Sci. Technol., 2004, 20 (01): 66-68. 
    Abstract   HTML   PDF (426KB)
    Bi-substituted dysprosium iron garnet films were prepared by sol-gel process, and were annealed for crystallization. The crystallographic structures of garnet films annealed at different temperatures were analyzed by XRD, the film annealed at 650℃ was polycrystalline garnet with no preferred orientation and no impurity crystalline phase. Magnetic and magneto-optical properties were investigated, the film had magnetic anisotropy perpendicular to the film plane, and exhibited strong coercivity of 1100~1600 Oe and high squareness. These films had large figures of merit applicable to magneto-optic storage, with 2 deg. at λ=430 nm and 1.5 deg. at λ=520 nm respectively.
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    Preparation of DyFe2 and TbFe2 by Reduction-Diffusion Process
    Guangsi GUO, Guangtai WANG, Zhitong SUI
    J. Mater. Sci. Technol., 2004, 20 (01): 68-70. 
    Abstract   HTML   PDF (436KB)
    The pure intermetallic compounds (Tb1-xDyx)Fe2 are super-magnetostriction materials, which were produced from DyFe2 and TbFe2 in this paper. The thermodynamic possibility and kinetic feasible conditions for DyFe2 and TbFe2 preparation by reduction-diffusion in Ca-Dy2O3-Fe and Ca-Tb4O7-Fe systems were analyzed and the products of DyFe2 and TbFe2 were confirmed by XRD. The contracting core model was applied to describe the reduction-diffusion process in which the diffusion is a rate-controlled step. The apparent activation energies of DyFe2 and TbFe2 processes are 45 and 39 kJ/mol respectively.
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    Computer Aided Composition Design of Prehardened-Mould Steel for Plastic
    Yanlin HE, Lin LI, Xiaochun WU, Patrick WOLLANTS
    J. Mater. Sci. Technol., 2004, 20 (01): 71-74. 
    Abstract   HTML   PDF (499KB)
    The improvement of machining behavior of prehardened-mould steel for plastic is realized by using computer-aided composition design in this work. The results showed that the matrix composition of large sectional prehardened mould steel for plastic markedly influences the precipitation of non-metallic inclusion and the control of composition aided by Thermo-Calc software package minimizes the amount of detrimental oxide inclusion. In addition the modification of calcium is optimized in the light of composition design.
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    Thermodynamic Assessment and Microstructure of the ZrO2-CeO2-Al2O3 System
    Shuigen HUANG, Lin LI, J.Vleugels, O.V.D.Biest, Peiling WANG
    J. Mater. Sci. Technol., 2004, 20 (01): 75-78. 
    Abstract   HTML   PDF (451KB)
    The ZrO2-CeO2-Al2O3 system has been assessed with the CALPHAD (Calculation of Phase Diagrams) technique using the PARROT procedure. The experimental information on the ZrO2 -Al2O3, Al2O3-CeO2 systems as well as the isothermal sections of the ternary system at 1673 K and 1873 K is well reproduced. According to the assessed isothermal section at 1723 K, no alumina dissolves into the tetragonal zirconia phase. Specimens with different alumina content are fabricated from commercial 12 mol pct CeO2-stabilized ZrO2 powder (12Ce-ZrO2). The thermodynamic properties are consistent with the observed microstructure, which present a combination of tetragonal phase and alumina grains.
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    Effect of Precipitating Phases on Tensile Strength and Microstructural Stability of a Spray-Deposited Al-Si-Fe-Mn-Cu-Mg Alloy
    Feng WANG, Yuansheng JIN, Dunyuan HU, Jishan ZHANG
    J. Mater. Sci. Technol., 2004, 20 (01): 78-80. 
    Abstract   HTML   PDF (451KB)
    Spray deposition is a novel process which is used to manufacture rapidly solidified bulk and near-net-shape preforms. In this study, Al-20Si-5Fe-3Mn-3Cu-1Mg alloy was synthesized by spray deposition technique. The aging process of the alloy was investigated by differential scanning calorimetry (DSC) analysis and transmission electron microscopy (TEM). The results show that two kinds of phases, i.e. S(Al2CuMg) and sigma(Al5Cu6Mg2), precipitate from matrix and improve the tensile strength of the alloy efficiently at both the ambient and elevated temperatures (300℃). In addition, the sigma-Al5Cu6Mg2 is a relatively stable phase which improves microstructural stability of the alloy.
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    Determination of Neutron Irradiation-Induced Phosphorus Segregation on Grain Boundaries in a P-doped 2.25Cr1Mo Steel
    Shenhua SONG, R.G.Faulkner, P.E.J. Flewitt, Dongdong SHEN, Jing LIU, Zexi YUAN
    J. Mater. Sci. Technol., 2004, 20 (01): 81-85. 
    Abstract   HTML   PDF (663KB)
    Irradiation-induced impurity segregation to grain boundaries is one of the important radiation effects on materials. For this reason, phosphorus segregation to prior austenite grain boundaries in a P-doped 2.25Cr1Mo steel subjected to neutron irradiation is examined using field emission gun scanning transmission electron microscopy (FEGSTEM) with energy dispersive X-ray microanalysis (EDX). The steel samples are irradiated around 270 and 400℃, respectively. The irradiation dose rate and dose are ~1.05×10-8 dpa/s and ~0.042 dpa respectively for 270℃ irradiation, and 1.7×10-8 dpa/s and 0.13 dpa respectively for 400℃ irradiation. The FEGSTEM results indicate that there is no apparent phosphorus segregation during 270℃ irradiation but there is some during 400℃ irradiation
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    Effect of Delay Time on Microstructural Evolution during Warm Rolling of Ti-Nb-IF Steel
    A.Najafi-zadeh, R.Ebrahimi
    J. Mater. Sci. Technol., 2004, 20 (01): 86-88. 
    Abstract   HTML   PDF (596KB)
    The effect of delay time with constant first finishing pass temperature (800℃) has been investigated by means of multi-pass torsion tests on Ti-Nb-IF steel. All the tests have been carried out at a strain rate of 2 s-1 with 11 passes and 0.3 strain each pass. During the final pass, dynamic recrystallization occurs to a degree that depends on the delay time. In short interpass time (1 s) and at these temperatures (T≤800℃) there is not enough time to start static recrystallization, therefore, accumulation of strain occurs and after some passes, strain reaches a critical strain for starting dynamic recrystallization. In this study, the changes of mean flow stress during each pass and also the microstructural observation confirms that dynamic recrystallization occurs after some passes in ferrite phase of this steel. The stress-strain curves with constant temperature obtained by using a kinetic model and compensation of the increasing mean flow stress with decreasing temperature. Thus, this result also confirms that dynamic recrystallization occurs in warm rolling of this IF steel.
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    Effect of Hot Deformation on Pearlite Transformation of 86CrMoV7 Steel
    Ming GAO, Hongxing GU, Furen XIAO, Bo LIAO, Guiying QIAO, Ke YANG, Yiyin SHAN
    J. Mater. Sci. Technol., 2004, 20 (01): 89-91. 
    Abstract   HTML   PDF (525KB)
    The continuous cooling transformation (CCT) diagrams of 86CrMoV7 steel samples including hot deformed and not hot deformed were constructed by dilatometry, metallography and transmission electron microscopy (TEM). The results showed that hot deformation accelerated pearlite transformation and fine pearlite microstructure. Moreover, the undissolved carbides became the nucleating sites of pearlite, accelerated pearlite formation and fine pearlite if the steel had been deformed at high temperature. In contrast, undissolved carbides did not make any influence on pearlite transformation if the steel had not been deformed at high temperature.
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    Investigation of SUS304 Stainless Steel with Warm Hydro-mechanical Deep Drawing
    Yongchao XU, Dachang KANG, Shihong ZHANG
    J. Mater. Sci. Technol., 2004, 20 (01): 92-93. 
    Abstract   HTML   PDF (369KB)
    Basing on warm mechanical property of SUS304 stainless steel and hydro-mechanical deep drawing process, warm hydro-mechanical deep drawing process is proposed and discussed with experiments in this paper. The experiments are performed at four different temperatures. The results show that the formability of stainless steel is improved under the condition of warm temperature. Warm hydro-mechanical deep drawing raises limiting drawing ratio of SUS304 effectively, and limiting drawing ratio 3.3 is obtained, which is beyond 2.0 with conventional deep drawing. The temperature of 90℃ is beneficial to the forming of SUS304 stainless steel, the strain-induced martensite is controlled effectively, and the thickness distribution is more uniform.
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    Influential Factors on Electromagnetic Properties of Selected 3D Reticulated Ceramics
    Qing GONG, Xiaoming CAO, Jinsong ZHANG, Zheng FANG
    J. Mater. Sci. Technol., 2004, 20 (01): 94-96. 
    Abstract   HTML   PDF (418KB)
    3D reticulated ceramics (3DRCs) with the composition containing SrFe12O19-SiC-TiO2 were prepared by a replication process with polyurethane sponges as the template in ceramic slurry. The electrical conductivity, dielectric and magnetic parameters of 3D reticulated ceramics (3DRCs) were measured with changes in cell size of the sponges, contents in the slurry and sintering temperature in this paper. Discussions about the influential factors of those parameters were focused on their electrical conductivity. The experimental results indicated that the electrical conductivity of 3DRCs raised with the increase of cell size, SiC/SrO·6Fe2O3 with weight ratio and sintering temperature. X-ray diffractions and SEM were used to investigate the relationship between electrical conductivity and sintering temperature. Deoxidizing reactions of SrO·6Fe2O3 caused the increasing electrical conductivity. The real part of permittivity (ε') and imaginary part of permeability (μ'') raised with the increase of electrical conductivity (σ). The imaginary part of permittivity (ε'') has a maximum at 100S/cm with the increase of sigma, and the real part of permeability (μ') changes slightly with the increase ofσ. When sigma is at the range of 10-4 S/cm to 100 S/cm (a semi conductive state), both the imagine part of permittivity and permeability raises with increasing sigma, therefore, the 3DRCs present their high electromagnetic loss properties.
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    Microstructure, Compression Property and Shape Memory Effect of Equiatomic TaRu High Temperature Shape Memory Alloy
    Xin GAO, Yufeng ZHENG, Wei CAI, Su ZHANG, Liancheng ZHAO
    J. Mater. Sci. Technol., 2004, 20 (01): 97-99. 
    Abstract   HTML   PDF (1086KB)
    The microstructure, phase transformation, compression property and strain recovery characteristics of equiatomic TaRu super high temperature shape memory alloy have been studied by optical microscope, XRD, DTA, compression tests and TEM observations. When cooling the alloy specimen from high temperature to the room temperature, (parent phase)→ (interphase)→ (martensite) two-step phase transformations occur. The microstructure at room temperature show regularly arranged band morphology, with the monoclinic crystal structure. The twinning relationship between the martensite bands is determined to be (101) of Type I. Reorientation and coalescence of the martensite bands inside the variant happened during compression at room temperature. The → reversible transformation contributes mainly the shape memory effect, with the maximum completely recovery strain of 2%.
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    Microstructural Changes of Cu-Ni-Si Alloy during Aging
    Qiming DONG, Dongmei ZHAO, Ping LIU, Buxi KANG, Jinliang HUANG
    J. Mater. Sci. Technol., 2004, 20 (01): 99-102. 
    Abstract   HTML   PDF (1086KB)
    Age hardening in Cu-3.2Ni-0.75Si(wt pct) and Cu-1.0Ni-0.25Si (wt pct) alloys from 723 to 823 K is studied. After an incubation period strengthening appears which is due to precipitates in the Cu-1.0Ni-0.25Si (wt pct) alloy. On other hand an immediate increase of the yield strength characterizes the aging of the alloy. This is followed by the regions of constant yield strength and further by a peak. The microstructure of the alloy was studied by, means of transmission electron microscope (TEM) and X-ray diffraction (XRD). Spinodal decomposition takes place followed by nucleation of the ordering coherent (Cu,Ni)3Si particles, further precipitation annealing coherent δ-Ni2Si nucleated within the (Cu,Ni)3Si particle. Any change of the yield strength can be described by an adequate change of the structure in the sample. The nature of the aging curves with a "plateau" is discussed. The formulas of Ashby and Labusch can be used to explain the precipitation.
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    Tensile Fracture Location Characterizations of Friction Stir Welded Joints of Different Aluminum Alloys
    Huijie LIU, Hidetoshi FUJII, Masakatsu MAEDA, Kiyoshi NOGI
    J. Mater. Sci. Technol., 2004, 20 (01): 103-105. 
    Abstract   HTML   PDF (629KB)
    The tensile fracture location characterizations of the friction stir welded joints of the AA1050-H24 and AA6061-T6 Al alloys were evaluated in this study. The experimental results show that the fracture locations of the joints are different for the different Al alloys, and they are affected by the FSW parameters. When the joints are free of welding defects, the AA1050-H24 joints are fractured in the HAZ and TMAZ on the AS and the fracture parts undergo a large amount of plastic deformation, while the AA6061-T6 joints are fractured in the HAZ on the RS and the fracture surfaces are inclined a certain degree to the bottom surfaces of the joints. When some welding defects exist in the joints, the AA1050-H24 joints are fractured on the RS or AS, the AA6061-T6 joints are fractured on the RS, and all the fracture locations are near to the weld center. The fracture locations of the joints are dependent on the internal structures of the joints and can be explained by the microhardness profiles and defect morphologies of the joints.
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    Effects of Pressure on the Solidification Microstructure of Mg65Cu25Y10 Alloy
    Jia ZHANG, Keqiang QIU, Aimin WANG, Haifeng ZHANG, Mingxiu QUAN, Zhuangqi HU
    J. Mater. Sci. Technol., 2004, 20 (01): 106-108. 
    Abstract   HTML   PDF (373KB)
    The Mg65Cu25Y10 melts were quenched at a temperature of 973 K under various pressures in the range of 2~5 GPa and ambient pressure. The microstructure of the solidified specimens has been investigated by X-ray diffraction, transmission electron microscope and electron probe microanalysis. Experimental results show that the pressure has a great influence on the solidification microstructure of the Mg65Cu25Y10. At ambient pressure, the solidification products are Mg2(Cu,Y) and a very small amount of Y2O3 inclusion. As the pressure is above 2 GPa, a new Cu2(Y,Mg) phase appears, while Y2O3 is not observed at the pressure of 3, 4 and 5 GPa. When the pressure increases from 2 GPa to 5 GPa, the grain sizes of Mg2(Cu,Y) and Cu2(Y,Mg) decrease from 125, 96 nm to 80, 7 nm, respectively. The mechanisms for the effects of the pressure on the phase evolution and microstructure during solidification process of Mg65Cu25Y10 alloy have been discussed.
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    A New Model of Interfacial Physical Contact in Diffusion Bonding
    Peng HE, Jicai FENG, Yiyu QIAN
    J. Mater. Sci. Technol., 2004, 20 (01): 109-112. 
    Abstract   HTML   PDF (405KB)
    Through eliminating voids not affecting the primary bonding process, and incorporating interlayer and flexible base material, the interface geometry character and brief mathematics process were put forth. Through analyzing contact process of diffusion bonding, contact area model was settled. It can interpret the phenomenon of different interface areas taking on different strengths. In the course of physical contact, shear stresses serve an important function for the plastic deformation and the cohesion of interface voids.
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    Evaluation on Fracture Toughness at Dynamic Loading for Welded Joint Based on the Local Approach
    Hongyang JING, Lianyong XU, Lixing HUO, Yufeng ZHANG
    J. Mater. Sci. Technol., 2004, 20 (01): 113-117. 
    Abstract   HTML   PDF (947KB)
    The changes in mechanical properties and fracture toughness by dynamic loading were investigated with experiments. The parameter R, which can reflect the effect of the loading rate and the temperature rising during the high loading rate, could be employed to describe the constituent relation for the typical structure steel and its weld metal. The dynamic loading effect on the stress/strain fields and the temperature variation in the vicinity of the crack tip was analyzed by the finite element method, the dynamic fracture behavior was evaluated based on the local approach. It has been found that the Weibull stress is an effective fracture parameter, independent of the temperature and the loading rate.
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    3D Finite Element Numerical Simulation of Residual Stresses on Electron Beam Welded BT20 Plates
    Lixing HUO, Furong CHEN, Yufeng ZHANG, Li ZHANG, Fangjun LIU, Gang CHEN
    J. Mater. Sci. Technol., 2004, 20 (01): 117-120. 
    Abstract   HTML   PDF (472KB)
    A three-dimensional finite-element model (FEM) used for calculating electron beam (EB) welding temperature and stresses fields of thin plates of BT20 titanium has been developed in which the nonlinear thermophysical and thermo-mechanical properties of the material has been considered. The welding temperature field, the distributions of residual stresses in as-welded (AW) and electron beam local post-weld heat treatment (EBLPWHT) conditions have been successfully simulated. The results show that: (1) In the weld center, the maximum magnitude of residual tensile stresses of BT20 thin plates of Ti alloy is equal to 60%~70% of its yield strength δs. (2) The residual tensile stresses in weld center can be even decreased after EBLPWHT and the longitudinal tensile stresses are decreased about 50% compared to joints in AW conditions. (3) The numerical calculating results of residual stresses by using FEM are basically in agreement with the experimental results. Combined with numerical calculating results, the effects of electron beam welding and EBLPWHT on the distribution of welding residual stresses in thin plates of BT20 have been analyzed in detail.
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    Corrosion Behaviour of Nickel in Chloroacetic Acids and its Inhibition
    S.M.Rashwan, A.Emam, S.M.Abd El-Wahab, M.M.Mohamed
    J. Mater. Sci. Technol., 2004, 20 (01): 121-125. 
    Abstract   HTML   PDF (661KB)
    Anodic dissolution behaviour of Ni in mono-, di- and trichloroacetic acids has been investigated by measuring current densities of Ni electrode (versus SCE) at different potentials. Effects of acid concentration, pH, scan rate and additive inhibitor on the potential were studied and they revealed that there is a considerable shift of potential. Potentiodynamic polarization measurements show that the corrosion rate of Ni in chloroacetic acid solutions increases by increasing the previous factors. However, by adding inhibitor, it decreases.
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    Magnetic Field Design by Using Image Effect from Iron Shield
    Quanling PENG, S.M.McMurry, J.M.D.Coey
    J. Mater. Sci. Technol., 2004, 20 (01): 125-128. 
    Abstract   HTML   PDF (535KB)
    Permanent magnet rings are presented, which exploit the image effect in the surrounding circular iron shields. The theory is given for a general permanent ring when the magnetization orientation φ at each coordinate angle ψ changes by φ=(n+1)ψ, where n is a positive or negative integer. For the uniformly magnetized case n=-1, the permanent ring produces no field in its bore, and the field is that of a dipole outside. When the ring is surrounded by a soft iron shield, its field becomes uniform in the bore, and zero outside the ring. The field can be varied continuously by moving the iron shield along the magnet axis. A small variable field device was constructed by using NdFeB permanent rings, which produced a field flux density of 0~0.5 T in the central region.
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