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 September 2003, Volume 19 Issue 05 Previous Issue    Next Issue
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    Research Articles
    Microstructural Evolution of Localized Shear Bands Induced during Explosion in Ti-6Al-4V Alloy
    Yongbo XU, M.A.Meyers
    J. Mater. Sci. Technol., 2003, 19 (05): 385-387. 
    Abstract   HTML   PDF (1332KB)
    Microstructures of the localized shear bands generated during explosion with a thick-walled cylinder specimen in Ti-6Al-4V alloy, were characterized by TEM and SEM. The results show that the twinning is a major mode of deformation, and the distortion-free grains in the bands with the size of 10 µm in diameter were proposed to be the re-crystallization during dynamic explosion. The further observations show that the α→α2 phase transformation may occur in the bands, and this kind of transformation could be confirmed by its dark field image and electron diffraction analysis. Analysis shows that there is specified orientation between the α→α2 Phases.
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    Measurement and Analyses of Molten Ni-Co-Al Alloy Density
    Feng XIAO, Liang FANG
    J. Mater. Sci. Technol., 2003, 19 (05): 388-390. 
    Abstract   HTML   PDF (448KB)
    The density of molten Ni-Co-Al alloy was measured using a modified pycnometric method. It has been found that the density of the molten Ni-Co-Al alloy decreases with increasing temperature, Co concentration and the ratio of Co concentration to Ni concentration in the alloy. The coefficient of volume expansion of the molten Ni-Co-Al alloy decreases with increasing Co concentration and the ratio of Co concentration to Ni concentration. The temperature coefficient of density increases with increasing the Co concentration or the ratio of Co concentration to Ni concentration in the alloy. The density of the molten Ni-Co-Al alloy as functions of both temperature and Co concentration was expressed.
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    3D Stochastic Modeling of Grain Structure for Aluminum Alloy Casting
    Qingyan XU, Weiming FENG, Baicheng LIU
    J. Mater. Sci. Technol., 2003, 19 (05): 391-394. 
    Abstract   HTML   PDF (883KB)
    A 3D stochastic modeling was carried out to simulate the dendritic grains during solidification of aluminum alloys, including time-dependent calculations for temperature field, solute redistribution in liquid, curvature of the dendritic tip, and growth anisotropy. The nucleation process was treated by continuous nucleation. A 3D simplified grain shape model was established to represent the equiaxed dendritic grain. Based on the Cellular Automaton method, a grain growth model was proposed to capture the neighbor cells of the nucleated cell. During growing, each grain continues to capture the nearest neighbor cells to form the final shape. When a neighbor cell was captured by other grains, the grain growth along this direction would be stopped. Three-dimensional calculations were performed to simulate the evolution of dendritic grain. In order to verify the modeling results, the predictions were compared with the observation on samples cast in the sand mold and the metal mold.
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    Modeling of Mold Filling and Solidification in Lost Foam Casting
    Fengjun LI, Houfa SHEN, Baicheng LIU
    J. Mater. Sci. Technol., 2003, 19 (05): 395-397. 
    Abstract   HTML   PDF (636KB)
    Based on the characteristics of the lost foam casting (LFC) and the artificial neural network technique, a mathematical model for the simulation of the melt-pattern interface movement during the mold filling of LFC has been proposed and experimentally verified. The simulation results are consistent with the experiments in both the shapes of melt front and filling sequences. According to the calculated interface locations, the fluid flow and the temperature distributions during the mold filling and solidification processes were calculated, and the shrinkage defect of a lost foam ductile iron casting was predicted by considering the mold wall movement in LFC. The simulation method was applied to optimize the casting design of lost foam ductile iron castings. It is shown that the model can be used for the defects prediction and for casting design optimization in the practical LFC production.
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    Modeling and Simulation of the Microstructure Evolution of the Gas-atomized Alloy Droplets during Spray Forming
    Jiuzhou ZHAO, Dongming LIU, Hengqiang YE
    J. Mater. Sci. Technol., 2003, 19 (05): 398-402. 
    Abstract   HTML   PDF (986KB)
    In order to understand the solidification process of an atomized droplet and predict the fraction solidification of droplets with flight distance during spray forming, a numerical model based on the population dynamics approach is developed to describe the microstructure evolution under the common action of the nucleation and growth of grains. The model is coupled with droplets heat transfer controlling equations and solved for Al-4.5~wt~pct Cu alloy. It is demonstrated that the numerical results describe the solidification process well.
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    Laser Shock Processing of an Austenitic Stainless Steel and a Nickel-base Superalloy
    Huaming WANG, Xijun SUN, Xiaoxuan LI
    J. Mater. Sci. Technol., 2003, 19 (05): 402-404. 
    Abstract   HTML   PDF (1621KB)
    An austenitic stainless steel 1Cr18Ni9Ti and a solid solution-strengthened Ni-base superalloy GH30 were shock processed using a Q-switched pulsed Nd-glass laser. Microstructure, hardness and residual stress of the laser shock processed surface were investigated as functions of laser processing parameters. Results show that high density of dislocations and fine deformation twins are produced in the laser shock processed surface layers in both the austenitic stainless steel and the nickel-base superalloy. Extensive strain-induced martensite was also observed in the laser shock processed zone of the austenitic steel. The hardness of the laser shock processed surface was significantly enhanced and compressive stress as high as 400 MPa was produced in the laser shock processed surface.
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    Double Glow Plasma Surface Alloying Process Modeling Using Artificial Neural Networks
    Jiang XU, Xishan XIE, Zhong XU
    J. Mater. Sci. Technol., 2003, 19 (05): 404-406. 
    Abstract   HTML   PDF (1030KB)
    A model is developed for predicting the correlation between processing parameters and the technical target of double glow by applying artificial neural network (ANN). The input parameters of the neural network (NN) are source voltage, workpiece voltage, working pressure and distance between source electrode and workpiece. The output of the NN model is three important technical targets, namely the gross element content, the thickness of surface alloying layer and the absorption rate (the ratio of the mass loss of source materials to the increasing mass of workpiece) in the processing of double glow plasma surface alloying. The processing parameters and technical target are then used as a training set for an artificial neural network. The model is based on multiplayer feedforward neural network. A very good performance of the neural network is achieved and the calculated results are in good agreement with the experimental ones.
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    Kinetics and Mechanism of Interfacial Reaction in a SiCf/Ti Composite
    Guoxing ZHANG, Qiang KANG, Nanlin SHI, Geping LI, Dong LI
    J. Mater. Sci. Technol., 2003, 19 (05): 407-410. 
    Abstract   HTML   PDF (1254KB)
    In order to evaluate the interfacial reaction, a SiCf/Ti (TA1) composite was fabricated by a vacuum hot pressing method and then heat-treated in vacuum at 800℃ for up to 100 h. The elemental distributions of C, Si and Ti at the interfacial reaction zone were investigated. It was found that the reaction zone occurs during the fabrication process and continuously grows at high temperature because the Si and C atoms diffuse from SiC fibers to the matrix and Ti atoms diffuse in the opposite direction. The growth of the reaction zone is diffusion controlled and the mechanism of the reaction can be described by a reactive diffusion model of solid-state growth of an AmBn layer between two elementary substances A and B.
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    Quasistatic and Dynamic Tensile Behavior of Zr52.5Al10Ni10Cu15Be12.5 Bulk Metallic Glass
    Xueshan XIAO, Weihuo LI, Lei XIA, Shoushi FANG, Qin HUA, Yu, a DONG
    J. Mater. Sci. Technol., 2003, 19 (05): 410-412. 
    Abstract   HTML   PDF (1455KB)
    Quasistatic and dynamic tensile behavior of Zr52.5Al10Ni10Cu15Be12.5 bulk amorphous alloy was investigated at the strain rates of 10-4~103 s-1 by using a Shimadzu AG-100KNA autograph and a pneumatic tensile impact tester. It was shown that the tensile fracture strength and the fracture morphology were sensitive to the strain rate. With the increase of the strain rate, the tensile fracture strength decreased and the fracture morphology changed from cleavage into quasi-cleavage, and then into a mixture of microvoid-coalescence dimples and quasi-cleavage veins.
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    Microsegregation and Improved Methods of Squeeze Casting 2024 Aluminium Alloy
    Yong ZHONG, Guoyue SU, Ke YANG
    J. Mater. Sci. Technol., 2003, 19 (05): 413-416. 
    Abstract   HTML   PDF (1256KB)
    The squeeze casting of a 2024 Al alloy was carried out to investigate the effect on microsegregation in the alloy of the application of pressure followed by diffusion annealing. The experimental results indicate that an optimum applied pressure followed by an optimum diffusion annealing process can markedly reduce the degree of microsegregation and improve the mechanical properties to a degree that can approach the level of forged 2024 Al alloy.
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    Martensitic Transformation of TiNi Shape Memory Alloy Fiber Reinforced Ni Matrix Composites
    Lishan CUI, Yan LI, Yanjun ZHENG, Huibin XU
    J. Mater. Sci. Technol., 2003, 19 (05): 416-418. 
    Abstract   HTML   PDF (1254KB)
    In this paper, a TiNi shape memory alloy fiber Ni matrix composite was fabricated by an electroplating method using TiNi alloy as the cathode and Ni as the anode. The constrained martensitic transformation behaviors of the TiNi alloy were studied by differential scanning calorimeter (DSC), and the results showed that two endothermic peaks appear on the DSC heating curves and the reverse transformation temperatures increase with increasing prestrain levels. Moreover, comparing to the free transformation, the temperature window of the constrained reverse transformation is widely expanded due to the influence of recovery stress.
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    Equilibrium Phase Constituents and Discontinuous Precipitation Behavior of Al-Zn-Cu Alloy with Symmetrical Composition
    Shiming HAO, Yuping REN, Hua DING, Dapeng WANG, Gang ZHAO, Hongxiao LI
    J. Mater. Sci. Technol., 2003, 19 (05): 419-421. 
    Abstract   HTML   PDF (1345KB)
    Through microstructure observation and X-ray diffraction analysis, the equilibrium phase constituents of Al-Zn alloy that contains 2 at.pct Cu at room temperature have been determined as Al-based solid solution (α), Zn-based solid solution and Al4Cu3Zn phase (T'-phase), which are different from α phase, Zn phase and CuZn4 phase originally believed. It is determined that the products of discontinuous precipitation transformation below 277℃ are not the equilibrium phase constituents, but the metastable phases made up of α phase, Zn phase and CuZn4 phase. The phase constituents after discontinuous precipitation of AlZn-2Cu alloy would transform to the ones in equilibrium status: Al-based solid solution (α) in fcc structure, Zn-based solid solution in hcp structure and A4Cu3Zn phase (T'-phase) ultimately through plastic deformation at room temperature and re-heating treatment below 277℃
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    Characterization and Magnetic Properties of Cobalt Nano-Particles Prepared by Metal Vapor Synthesis Technique
    Shihua WU, Shoumin ZHANG, Weiping HUANG, Juan SHI, Baoqing LI, Yongqi SUN
    J. Mater. Sci. Technol., 2003, 19 (05): 422-424. 
    Abstract   HTML   PDF (580KB)
    The metal vapor synthesis technique was employed to prepare Co anoparticles. The characteristics and properties of the particles were studied by ransmission electron microscopy, X-ray diffraction, emperature-programmed desorption, chemisorption and magnetic easurements. The experimental results showed that the particle size of Co powders depended on the initial Co concentration in the toluene matrix, reaching average crystallite diameter of 1.5nm for the highest concentration (6.4 at. pct) investigated. The particles with size of 10nm exist, due to the agglomerates of microcrystallites. The Co particles were surrounded by a thin carbonaceous layer formed due to toluene decomposition on cocondate melt-down and subsequent warming to room temperature. The carbonaceous layer was composed primarily of C1 fragments. The Co powders demonstrated ferromagnetic behavior.
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    Study on Fine Structure of Gas Atomized LaNi5-based Alloys
    Hai JING, Hong GUO, Shuguang ZHANG, Zili MA, Shaoming ZHANG
    J. Mater. Sci. Technol., 2003, 19 (05): 425-427. 
    Abstract   HTML   PDF (1341KB)
    The fine structure of hydrogen storage alloy powders MlNi4.3-xCoxMn0.4Al0.3(x=0.75, 0.45, 0.10; Ml: La-rich misch metal) prepared by rapidly solidifying gas atomization was investigated using a Rietveld analysis method. Two sets of CaCu5-type crystal constants were observed in the studied alloys and one set was larger than the other. With decreasing powder radius the solidification rate of powder increased, and so did the percentage of a particle part with larger crystal constants. The reason why there were two sets of crystal constants might be the difference of solidification rate between the outside and inside of a particle.
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    Crystal Nucleation and Growth of Al-based Alloys Produced by Electrolysis
    Zhiyong LIU, Mingxing WANG, Yonggang WENG, Tianfu SONG, Yuping HUO, Jingpei XIE
    J. Mater. Sci. Technol., 2003, 19 (05): 427-430. 
    Abstract   HTML   PDF (2075KB)
    The nucleation and growth of grains in a series of Al-based alloys produced by electrolysis are observed under SEM. The atomic Ti/Al ratios of the nuclei and the distribution of Ti at certain points are analyzed by point EDS. The particles in different atomic Ti/Al ratios might act as the nuclei of α-Al. At the early stage of growth, the spherical Ti-enriched regions might form around these particles within very limited temperature ranges in which the reactions such as the peritectic reactions etc occur. At the latter stage of growth, the dendrites freely develop in the radial orientations, and the concentration of Ti decreases linearly along the dendrite arm and becomes negligible in the region near the periphery of the dendrite. It is believed that the nucleation is closely related with the number and dispersion of primary spherical areas in the melts, and the segregation of Ti leads to the free growth of dendrite, which is necessary for the formation of equiaxial grains.
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    Effects of Composition and Thermal Cycle on Transformation Behaviors, Thermal Stability and Mechanical Properties of CuAlAg Alloy
    Yunqing MA, Chengbao JIANG, Lifen DENG, Huibin XU
    J. Mater. Sci. Technol., 2003, 19 (05): 431-434. 
    Abstract   HTML   PDF (2097KB)
    The phase transformation behavior, mechanical properties, and the thermal stability of CuAlAg alloy were studied and minor rare earth (0.1 wt pct La+Ce) was added to improve the mechanical property of the studied alloy. It was found that Ag addition in the CuAl binary alloy can improve the stability of martensitic transformation and high Al content leads to the disappearing of martensitic transformation. The tensile strength and strain of the Cu-10.6Al-5.8Ag (wt pct) alloy were measured to be 383.5~MPa and 0.86%, respectively. With rare earth addition, the tensile strain increased from 0.86% to 1.47%. The CuAlAg alloy did not exhibit martensitic transformation on the second heating process. Its poor thermal stability still needs to be improved.
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    Precipitation Study in Inconel 625 Alloy by Positron Annihilation Spectroscopy
    M.Ahmad, W.Ahmad, M.A.Shaikh, Mahmud Ahmad, M.U.Rajput
    J. Mater. Sci. Technol., 2003, 19 (05): 434-436. 
    Abstract   HTML   PDF (1867KB)
    Precipitation in Inconel 625 alloy has been studied by positron annihilation spectroscopy and electron microscopy. The observed dependence of annihilation characteristics on aging time is attributed to the change of the positron state due to the increase and decrease of the density and size of the γ″ precipitates. Hardness measurements and lifetime measurements are in good agreementr
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    Microstructural Features of Spray-Deposited Immiscible Bearing Alloys Al-43Sn and Al-7Sn-1.3Cu-1.3Ni
    O.P.P, ey
    J. Mater. Sci. Technol., 2003, 19 (05): 437-443. 
    Abstract   HTML   PDF (3047KB)
    Two commercial grade aluminum based immiscible bearing alloys were spray-deposited using convergent-divergent type of nozzle. The processing parameters for spray-deposition were adjusted in such a way that most of the droplets arrived on the deposition substrate in either liquid or semi-liquid state. The microstructural features of spray-formed and as-cast alloys are compared. In spray-formed alloys equiaxed grains were observed. The cell boundaries and intercellular regions were observed to be decorated with sub-micron sized particles whereas in normal casting the second phase was observed to be segregated along grain boundaries. The morphology and distribution of second phase were observed to have similarity with those in over-spread and atomized powders produced under similar processing conditions. The microstructural features observed with variation in spray conditions are discussed in detail.
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    Relations between the Lattice Parameter and the Stability of Austenite against ε Martensite for the Fe-Mn Based Alloys
    Xing LU, Zuoxiang QIN, Xing TIAN, Yansheng ZHANG, Bingzhe DING, Zhuangqi HU
    J. Mater. Sci. Technol., 2003, 19 (05): 443-446. 
    Abstract   HTML   PDF (3676KB)
    The influences of lattice parameter of austenite, the electron concentration, the yield strength of parent phase on γ→ε martensite start temperature MS in the Fe-Mn alloys containing C, Al, Ge and Si have been experimentally investigated. The results show that the lattice parameter of austenite is more important than the electron concentration and the yield strength of parent phase in governing the γ→ε martensitic transformation in Fe-Mn based alloys. A relation between the MS and lattice parameter of austenite in Fe-Mn based alloys is suggested. The elements Mn, C, Al, Ge, which increase the lattice parameter of austenite lower the MS while the element Si, which decreases the lattice parameter increases the MS. The depressing effect of antiferromagnetic transition on the γ→ε martensitic transformation may be related to the increase of lattice parameter due to the positive magnetostriction during the antiferromagnetic transition.
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    Microstructures and Mechanical Properties of TiCP/Al-4.5Cu-0.8Mg Composites by Direct Reaction Synthesis
    Mingzhen MA, Dayong CAI, Tianhua WEI
    J. Mater. Sci. Technol., 2003, 19 (05): 447-449. 
    Abstract   HTML   PDF (1771KB)
    Direct reaction synthesis (DRS), based on the principle of self-propagating high-temperature synthesis (SHS), is a new method for preparing particulate metal matrix composites. TiCP/Al-4.5Cu-0.8Mg composites were fabricated by DRS. Particulate composites were fabricated with Ti carbide (TiC) particles, generally less than 1.0µm. The reacted, thermal extruded samples exhibit a homogeneous distribution of fine TiC particles in Al-4.5Cu-0.8Mg matrix. Mechanical property evaluation of the composites has revealed a very high tensile strength relative to the matrix alloy. Fractographic analysis indicates ductile failure.
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    Relationship between CO2 Sensor Voltage Response and Phase Equilibrium of Solid Electrolyte Na, K-β/β''-Al2O3
    J.H.YANG, H.Nä, fe, F.Aldinger, D.S.YAN
    J. Mater. Sci. Technol., 2003, 19 (05): 450-452. 
    Abstract   HTML   PDF (554KB)
    A type of CO2 sensor based on oxygen concentration cell was designed as following: Cell I: Pt | Au, O2, CO2| Na2CO3(Au)|NKBA(Au)|YSZ|O2, CO2|Pt or Cell II: Pt | Au, O2, CO2|K2$CO3(Au)|NKBA(Au)|YSZ|O2, CO2|Pt. (Na, K-β/β''-Al2O3 is named by NKBA). The sensor signal is consistent with the Nernstian slope within the region of phase equilibrium for Na, K-β/β''-Al2O3 material. The relationship between CO2 sensor voltage response and phase equilibrium of solid electrolyte Na, K-β/β''-Al2O3 is discussed in this paper.
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    Atmospheric Corrosion of Steel A3 Deposited with Ammonium Sulfate and in the Presence of Sulfur Dioxide
    Ye WAN, Chuanwei YAN, Chunan CAO, Jun TAN
    J. Mater. Sci. Technol., 2003, 19 (05): 453-455. 
    Abstract   HTML   PDF (693KB)
    A laboratory study of the atmospheric corrosion of carbon steel deposited with (NH4)2SO4 in the presence of SO2 is reported. The different levels of (NH4)2SO4 (0, 15, 30, 45, 60μg·cm2 were added on the surface of the samples before the exposure. The corrosion was investigated by a combination of gravimetry, Fourier transform infrared spectroscope and scanning electron microscopy. A detailed knowledge about the corrosion products was acquired, both quantitatively and qualitatively. The results show that the metal loss increased and the increasing tendency of corrosion rates slowed down with the increasing exposure time. The phase constituents of the corrosion products are mainly α-FeO(OH), γ-FeO(OH), and δ-FeO(OH).
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    Accelerated Corrosion of Pure Fe Induced by Gaseous ZnCl2 at High Temperatures
    Haitao MA, Lai WANG, Yuanshi LI
    J. Mater. Sci. Technol., 2003, 19 (05): 456-458. 
    Abstract   HTML   PDF (1135KB)
    ZnCl2 is one of the dominant aggressive species in waste incinerators or other advanced combustion power generation systems. In this study, the influence of minor amount of gaseous ZnCl2 on the corrosion behavior of pure iron was examined at 600~800 °C in a pure oxygen environment. The corrosion rate usually increased markedly with increasing temperatures at a fixed ZnCl2 content or with increased ZnCl2 contents at a constant temperature. The corrosion products were composed of a thin outer layer of ZnFe2O4 spinel and an inner zone with a much thicker layer of Fe2O3, which exhibited a serious separation from the matrix. Moreover, a molten FeCl2 layer was observed at the scale substrate interface. The accelerated corrosion of pure iron was attributed to the existence of FeCl2 with low melting point on the metal surface, which destroyed the cohesion and adhesion of the oxide scale. The results are discussed in relation to the thermodynamic factors and the presence of volatile compounds in the reaction system.
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    Preparation and Corrosion Resistance of Magnesium Coatings by Magnetron Sputtering Deposition
    Hongwei HUO, Ying LI, Fuhui WANG
    J. Mater. Sci. Technol., 2003, 19 (05): 459-462. 
    Abstract   HTML   PDF (2041KB)
    Magnesium coatings were fabricated on stainless steel substrates (1Cr11Ni2W2MoV) by a plane magnetron sputtering technique. The argon pressure and the substrate condition (including temperature and the substrate was rotated or fixed) were varied in order to evaluate the influence of the parameters on the crystal orientation and morphology of the coating. The corrosion behavior of the coatings in 1 wt pct NaCl solution was studied by electrochemical methods. The results showed that all coatings exhibited preferred orientation (002) as the argon pressure increased from 0.2 to 0.4 Pa. The morphologies of the coatings varied with the argon pressure and with whether the substrate was rotated or fixed. The open circuit potential of the coatings was more positive than that of cast AZ91D magnesium alloy. However, the immersion test in 1 wt pct NaCl solution showed that the corrosion rates of the coatings were higher than that of cast AZ91D magnesium alloy.
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    Study on the Phase Transformation Behavior of Nanosized Amorphous TiO2
    Huaqing XIE, Tonggeng XI, Qinghong ZHANG, Qingren WU
    J. Mater. Sci. Technol., 2003, 19 (05): 463-466. 
    Abstract   HTML   PDF (712KB)
    Nanosized amorphous TiO2 powders with a specific surface area of 501 m2•g-1 were prepared by hydrolysis. After calcined at 400 °C for 2 h, the prepared amorphous TiO2 powders were fully transformed into anatase crystallites with a specific surface area of 141 m2•g-1. Differential scanning calorimetric (DSC) experiments were performed on the samples of nanosized amorphous TiO2 mixed with microsized anatase, nanosized anatase, or nanosized α-Al2O3 respectively. Effects of sample packing, anatase addition, or α-Al2O3 addition on the crystallization behavior of nanosized amorphous TiO2 were analyzed.
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    Mold Filling Analysis in Vacuum Infusion Molding Process Based on a High-Permeable Medium
    Yingdan ZHU, Hua TAN, Jihui WANG
    J. Mater. Sci. Technol., 2003, 19 (05): 467-471. 
    Abstract   HTML   PDF (1291KB)
    The objective of this paper is to understand the flow mechanism through visualization experiments and discuss the influence of process parameters on mold filling process. A 2D leakage flow model is developed to simulate the molding process, and the simulation results show good agreement with experiments.
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    Microstructure and Eutectic Carbide Morphology of the High Speed Steel Strips Produced by Twin Roll Strip Casting Process
    Hongshuang DI, Xiaoming ZHANG, Guodong WANG, Xianghua LIU
    J. Mater. Sci. Technol., 2003, 19 (05): 472-474. 
    Abstract   HTML   PDF (1212KB)
    The M2 high-speed steel strip was produced by using the laboratory scale twin roll strip caster. The microstructure and eutectic carbide morphology of thus produced products were observed and analyzed, and the comparison of those with conventional products was carried out. The effects of the processing parameters such as the melting temperature, the pouring temperature, rolling speed and separating force on the microstructure and eutectic carbide morphology and their distribution were analyzed. The spheroidizing process of the strips in the annealing process was investigated. The relations between the growth and spheroidizing of the eutectic carbide and the annealing technology were obtained, and the mechanism of the twin roll strip casting process improving the eutectic carbide spheroidizing was discussed. The theoretical instruction for determining the subsequent treatment process was provided.
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    Laser Welding of TC-1 Titanium Alloy
    Hanbin DU, Lunji HU, Xiyuan HU, Jianhua LIU
    J. Mater. Sci. Technol., 2003, 19 (05): 475-478. 
    Abstract   HTML   PDF (1356KB)
    The technology of CO2 laser welding and joint properties of titanium alloy were investigated. The problem of molten pool protection was resolved by designing a shielding trailer and a special clamp. Joints with silvery appearance were obtained, which have no pore and crack. In addition, the welding speed could reach 3 m/min for the plate of 1.5 mm thickness being penetrated. The reason of the porosity formation in partial penetration joints is that the keyholes can be easily cut apart in the radial direction, which makes the gas enclosed in the molten pool. The surface oxide of specimens can not affect the porosity formation in welds directly.
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    Metallurgical and Mechanical Properties of Underwater Laser Welds of Stainless Steel
    Xudong ZHANG, Wuzhu CHEN, Eiji ASHIDA, Fukuhisa MATSUDA
    J. Mater. Sci. Technol., 2003, 19 (05): 479-483. 
    Abstract   HTML   PDF (3131KB)
    In this paper, the microstructures and mechanical properties of underwater laser welds of Type 304 stainless steel were investigated. JISY308L type filler wire was used as filler wire during welding. A gas-shielding nozzle was used to form a local dry cavity surrounding the welding zone. The main results are summarized as follows: (1) The shielding condition of the local dry cavity severely affects the oxygen content of the weld, the worst shielding condition leading to the oxygen content of 800×10-6, which largely increases the oxide inclusions and somewhat reduces the ferrite content. (2) The increase of oxygen content reduces the elongation rate and reduction of area in tensile test, but has no influence on the tensile strength. (3) In appropriate shielding condition, the mechanical properties of the underwater laser welds can be as same as that in the air.
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    Effect of Post-weld Heat Treatment on Microstructure and Fracture Toughness of 30CrMnSiNi2A Steel Welded Joints
    Lixing HUO, Furong CHEN, Yufeng ZHANG, Li ZHANG, Fangjun LIU, Gang CHEN
    J. Mater. Sci. Technol., 2003, 19 (05): 483-486. 
    Abstract   HTML   PDF (3131KB)
    The electron beam local post-weld heat treatment (EBLPWHT) is a rather new method that provides the advantages of high precision, flexibility and efficiency, energy saving and higher productivity. This paper studies the effect of two post-weld heat treatment processes on the microstructure, mechanical properties and fracture toughness of an electron beam welded joints in 30CrMnSiNi2A steel. EBLPWHT, in a vacuum chamber, immediately after welding and a traditional furnace whole post-weld heat treatment (FWPWHT) were compared. The experimental results show that, after EBLPWHT treatment, the main microstructure of weld was changed from coarse acicular martensite into lath martensite, HAZ was changed from lath martensite, bainite into lower bainite, and base metal was changed from ferrite and pearlite into upper bainite and residual austenite. The microstructures of different zones of joints in FWPWHT condition were tempered sorbite. The properties of welded joints can be improved by the EBLPWHT in some extent, and especially largely for the fracture toughness of welded joints. However the value of fracture toughness of base metal is comparatively low, so appropriate heat treatment parameters should be explored in the future.
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    Repetitious-Hot-Pressing Technique in Hot-Pressing Process
    Shixue SONG, Xing AI, Wei GAO, Jun ZHAO
    J. Mater. Sci. Technol., 2003, 19 (05): 486-488. 
    Abstract   HTML   PDF (3131KB)
    A new pressing method was proposed for hot-pressing process. Experimental results indicated that the porosity in Al2O3/TiC/ Ni/Mo (hereafter called Al2O3/TiC composite) composite compacts decreases by 6% after adopting this new technique, compared to traditional hot-pressing technique under the same sintering temperature. The flexural strength and Vicker hardness increase from 883~MPa to 980~MPa and from 16 GPa to 21.1 GPa, respectively. A theoretical model was given to analyze the densification mechanism of the composite in the process of repetitious-hot-pressing.
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    Preparation of Manganese Oxide Nanobelts
    Jisen WANG, Jinquan SUN, Ying BAO, Xiufang BIAN
    J. Mater. Sci. Technol., 2003, 19 (05): 489-491. 
    Abstract   HTML   PDF (1555KB)
    Oriented nanobelts of manganese oxide have been firstly and successfully prepared by a microemulsion technique under controlled circumstances. The samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM). Influences of sodium chloride and annealed temperature on the synthesis of Mn3O4 nanobelts were investigated. It was found that NaCl is the key factor to synthesize oriented Mn3O4 nanobelts and 827 K is optimum temperature to produce fine nanobelts. Oriented growth mechanism of Mn3O4 nanobelts was discussed.
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    Reduction of Coercivity of Fe-N Soft Magnetic Film by Heat Treatment
    Dan LI, Yousong GU, Xiangrong CHANG, Fushen LI, Lijie QIAO, Zhongzhuo TIAN
    J. Mater. Sci. Technol., 2003, 19 (05): 491-494. 
    Abstract   HTML   PDF (1555KB)
    200 nm thick Fe-N magnetic thin films were deposited on glass substrates by RF sputtering. The as-deposited films have high saturation magnetization but their coercivity is also higher than what is needed Therefore it is very important to reduce coercivity. The samples were vacuum annealed at 250 °C under 12000 A/m magnetic field. When the N content was in the range of 5~7 at.pct, the thin films consisted of α'+α'' after heat treatment and had excellent soft magnetic properties of 4πM2=2.4 T, Hc<80 A/m. However, the thickness of a recording head was 2 μm, and Hc increased as thickness increased. In order to reduce the Hc, the sputtering power was raised from 200 W to 1000 W to reduce the grain size. 2 μm Fe-N thin films were vacuum annealed under the same condition, when the N content was in the range of 5.9~8.5 at.pct, the thin films kept its excellent magnetic properties of 4πM2=2.2 T, Hc<80 A/m. The properties of the films meet the need of a recording head material used in the dual-element GMR/inductive heads.
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    Sol-gel Preparation and Preliminary in vitro Evaluationof Fluorapatite/Hydroxyapatite Solid Solution Films
    Chenlu SONG, Wenjian WENG, Kui CHENG, Haibo QU, Piyi DU, Ge SHEN, Gaorong HAN, Juan YANG, Jose M.F.Ferreira
    J. Mater. Sci. Technol., 2003, 19 (05): 495-499. 
    Abstract   HTML   PDF (1288KB)
    Fluorapatite/hydroxyapatite solid solution has better biological properties than other apatites, especially used as films or coatings. In this work, sol-gel preparation and in vitro behavior of fluorapatite/hydroxyapatite solid solution films on titanium alloy were investigated. Ca(NO3)2·4H22O and PO(OH)x(OEt)3-x were selected as precursors, and hexafluorophosphoric acid (HPF6) was used as a fluorine containing reagent. The Ca and P precursors were mixed with HPF6 to keep the Ca/P molar ratio 1.67. The mixtures refluxed for 12 h were used as dipping sols for the preparation of the films. The phase of the films obtained at 600°C was apatite. The F contents in the films increased with the concentrations of HPF6 in the dipping sols. The solid solution films were shown to have better stability than hydroxyapatite films, and a reasonably good bioactivity in the in vitro evaluation.
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    Reliability of Measured Fractal Dimension and Roughness Exponent as Materials Dimensionless Parameters for Fracture Surfaces
    Shenggang WANG, Hanlong LI, Chiwei LUNG
    J. Mater. Sci. Technol., 2003, 19 (05): 499-502. 
    Abstract   HTML   PDF (1356KB)
    The effects of accuracy of measured fractal dimension D and roughness exponent H are investigated in this paper with a view to examine the reliability of D and H as materials dimensionless parameters of fracture surfaces. D and H are different from general physical quantity, because they are dimensionless quantities and often appear as exponents in a theoretical function or formula. In many cases, the error of the physical quantity related to D or H may far exceed 10%, if D or H has error around 10%. The required accuracy of fractal dimension and roughness exponent should be higher, but it depends on the specific material, the associated physical quantity and the scale of measurement.
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    Off-line Simulation of PFC for Hot Rolling Strip
    Xiangwei KONG, Hezhou YE, Jianzhong XU, Guodong WANG, Liying BA, Xiaoming HE
    J. Mater. Sci. Technol., 2003, 19 (05): 502-504. 
    Abstract   HTML   PDF (1143KB)
    In order to improve the quality of the strip for the hot continuous rolling, the high accuracy set-up control must be applied to production. In the paper, we analyze the PFC (profile and flatness control) system and simulate the set-up process. Calculation results are in agreement to the actual measurements. It is the basis on the developing model.
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    A New Ceramic Substrate Glaze with High Resistance to Molten Aluminum
    Ming ZHOU, Ke LI, Da SHU, Jiao ZHANG, Baode SUN, Jun WANG
    J. Mater. Sci. Technol., 2003, 19 (05): 505-506. 
    Abstract   HTML   PDF (1585KB)
    Corrosion resistance of ceramic substrate glazes to molten aluminum was studied in this paper. The glazes can spread slightly in aluminum alloy according to SEM examination of solidified interface between the glazes and aluminum alloy. The components of B2O3-P2O5 glazes were not detected with electron probe at the side of aluminum alloy near the interface, but the components of boron-free glaze were detected. It is shown that borophosphate glazes can resist the corrosion of molten aluminum.
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    Deformation Processed Cu-15 wt pct Cr Composite Synthesized by Hot Hydrostatic Extrusion of Mechanical Milled Powders
    Jinglei LIU, Zuyan LIU, Erde WANG
    J. Mater. Sci. Technol., 2003, 19 (05): 507-508. 
    Abstract   HTML   PDF (580KB)
    A novel technique was developed for the preparation of Cu-15 wt pct Cr composite with high strength and conductivity. The composite powders with refined microstructure and curly lamellae strengthening phase was first prepared by mechanical milling in favorite milling time and then were hot hydrostatic extruded after pre-densification with sintering or hot pressing. It was shown that the extrusion densified the composite powders well and at the same time the chaos curled strengthening phase was aligned into lines and further deformed as strengthening ribbons. The deformation processed Cu-15 wt pct Cr composite prepared by this technique is of superior conductivity, strength and thermal stability.
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    Effects of Al2O3 Particulates on the Thickness of Reaction Layer of Al2O3 Joints Brazed with Al2O3-Particulate-Contained Composite Filler Materials
    Jianguo YANG, Jingwei WU, Hongyuan FANG
    J. Mater. Sci. Technol., 2003, 19 (05): 509-510. 
    Abstract   HTML   PDF (404KB)
    In order to understand the rate-controlling process for the interfacial layer growth of brazing joints brazed with active composite filler materials, the thickness of brazing joints brazed with conventional active filler metal and active composite filler materials with different volume fraction of A2O3 particulate was studied. The experimental results indicate although there are A2O3 particulates added into active filler metals, the time dependence of interfacial layer growth is t2 as described by Fickian law for the joints brazed with conventional active filler metal. It also shows that the key factor affecting the interfacial layer growth is the volume fraction of alumina in the composite filler material compared with the titanium weight fraction in the filler material.
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    Synthesis and Sintering of ZrNiSn-based Half-Heusler Compounds
    Qiang SHEN, Lianmeng ZHANG, Lidong CHEN, Takashi GOTO, Toshio HIRAI
    J. Mater. Sci. Technol., 2003, 19 (05): 511-512. 
    Abstract   HTML   PDF (0KB)
    In contrary to the commonly used arc melting method, samples in the present paper were prepared by the solid state reaction from elemental powders at 1173 K under a flowing Ar atmosphere for 96~168 h. The constituent phases and the elemental compositions were determined and shown that the samples were of single phase and stoichiometry. Then the spark plasma sintering technique was used to consolidate them. It is found that, dense ZrNiSn-based compounds with fine grain size and homogeneous microstructure were achieved under the condition of 1123 K/40 MPa/25 min.
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ISSN: 1005-0302
CN: 21-1315/TG
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