ISSN 0412-1961
CN 21-1139/TG
Started in 1956

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    , Volume 40 Issue 10 Previous Issue    Next Issue
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    Research Articles
    Recrystallization in Multi Phase Materials Containing Particles with A Two—Class Size Distribution
    SONG Xiaoyan; R. Markus; ZHANG Jiuxing
    Acta Metall Sin, 2004, 40 (10): 1009-1017 . 
    Abstract   PDF (14388KB) ( 1001 )
    Recrystallization in multi-phase materials containing particles with a two-class size distribution was studied with modeling and experiments. A 3D Monte-Carlo model combined with deterministic criteria was developed to describe nucleation stimulated by coarse particles and pinning effect of fine particles. The influences of various particle parameters on nucleation and growth of recrystallizing grains were quantitatively studied by simulations. The results show that the efficiency of particle stimulated nucleation depends on the stored energy in the particle-affected region and the local distribution of fine particles. The competition between the local stored energy, as the driving force for recrystallization, and the dragging force from fine particles, determines the final state of complete recrystallization, partial recrystallization or fully inhibited recrystallization in the whole material. Good agreements of morphologies and recrystallization kinetics are found in comparison between experiments and simulations for a series of Al-(0.3-1.1)%Zr (mass fraction) alloys under the same deformation and particle parameters.
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    Recognition of Metal Fracture Surface Morphologies Based on the Fuzzy Texture Spectrum
    ZHANG Xiaoqing; SUN Yongqing; ZHANG Zheng
    Acta Metall Sin, 2004, 40 (10): 1018-1022 . 
    Abstract   PDF (10576KB) ( 1209 )
    Fuzzy uncertainty texture spectrum (FUTS) is applied for the pattern recognition of fracture surface morphologies. Linear minor distance classifier is used to classify five typical fracture surface morphologies, including equiaxed dimple, elongated dimple, cleavage failure, fatigue and intergranular cracking. With testing results, the method of FUTS is highly efficient in fracture morphologies classification.
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    X--Ray Diffraction Analysis for the Recrystallization Behavior Of SiCw/Al Composite at High Temperature
    JIANG Chuanhai; WU Jiansheng; WANG Dezun
    Acta Metall Sin, 2004, 40 (10): 1023-1026 . 
    Abstract   PDF (3658KB) ( 1243 )
    By using in situ X-ray diffraction and profile analysis, the variations of subgrain size and microstrain in the cold-rolled SiCAl composite at high temperature were measured, and the recrystallization behavior of composite was investigated. Test results show that both of the activation energies of recrystallized grain growth and matrix recovery at higher temperature are close to the activation energy for self-diffusion of pure Al, which verifies that the recovery phenomenon was accompanied with the grain growth, and the whiskers can not affect the grain growth and recovery of matrix in composite at higher temperature.
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    Nucleation Model in Solidification Processes of the Alloys
    CHEN Zhongwei; JIE Wanqi
    Acta Metall Sin, 2004, 40 (10): 1027-1031 . 
    Abstract   PDF (63214KB) ( 1165 )
    An experiential nucleation model in solidification processes of the industrial alloys was established by introducing the experimental parameters. This model not only described nucleation rate of the alloys quantitatively, but also linked the nucleation rates with the final grain sizes. The surface area of effective catalysts per unit volume melt and the contact angle of effective catalysts in the melt in solidification processes were calculated with the model and the nucleation characteristic of the casting was analyzed. The model was also used to estimate the nucleation parameters of Al-7Si alloy and Al-7Si-0.55Mg alloy in the definite melting condition.
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    Effect of Grain Size and Holding Load on Nanoindentation Creep of Cu Film
    WANG Fei; XU Kewei
    Acta Metall Sin, 2004, 40 (10): 1032-1036 . 
    Abstract   PDF (69040KB) ( 859 )
    The effects of grain size and holding load on creep properties of polycrystalline Cu thin films were investigated using nanoindentation instrument. The results show that when grain size of polycrystalline Cu thin films is between 200 nm to 1500 nm, the stress exponent is insensitive to grain size. However, when the grain size is reduced below 200 nm, the stress exponents increases with decreasing grain size, implying that there is a critical grain size for stress exponents in nanoindentation tests. The stress exponent also increases with the increase of holding load. The above phenomena result from more grains to be involved and the creep rate decrease due to dislocation strengthening the plastic zone under the indenter tip.
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    Impact of Residual Oxygen on Hardness of Nano Structured TiN+Si3N4 Film
    MA Dayan; MA Shengli; XU Kewei; S.Veprek
    Acta Metall Sin, 2004, 40 (10): 1037-1040 . 
    Abstract   PDF (46017KB) ( 946 )
    Using direct current plasma enhanced chemical vapor deposition (PCVD) techniques, the nanocomposite films of nc-TiN + a-Si3N4 were synthesized. The detrimental effects of residual oxygen on the films hardness were explored. A minor content of residual oxygen can strongly decrease the hardness of the superhard film. Oxygen impurity of 1%-1.5% (atomic fraction) can make the hardness of film decrease to about 30 GPa as compared to 45-55 GPa for the film with below 0.2% oxygen, which is related to the formation of SiOx at interface of crystalline.
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    Size and Shape Dependent Melting--Thermodynamic Properties of Metallic Nanoparticles
    XIE Dan; QI Weihong; WANG Mingpu
    Acta Metall Sin, 2004, 40 (10): 1041-. 
    Abstract   PDF (39014KB) ( 1391 )
    A melting--thermodynamic model is developed, which can describe the effect of size and shape of metallic nanoparticle on its melting--thermodynamic properties. It is predicted that there exist a minimum critical size and a lowest melting temperature for metallic nanoparticle. The present theoretical results on the melting point, the melting entrapy and the melting enthalpy of nanoparticles Au, In, Al and Sn are consistent with the corresponding experimental values.
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    Study of Texture and Grain Boundary Character Distributions of IFSteels
    CAO Shengquan; ZHANG Jinxu; WU Jiansheng; CHEN Jiaguang
    Acta Metall Sin, 2004, 40 (10): 1045-1050 . 
    Abstract   PDF (69136KB) ( 1081 )
    The batch annealing and continuous annealing of IF steel sheets have been simulated. Texture, grain boundary character distributions (GBCD) and their relations with secondary working embrittlement (SWE) were investigated by electron back-scatter diffraction (EBSD).The results show that the two kinds of IF sheets are great difference in texture and grain boundary character distributions: (1) Continuous annealing IF sheets have a strong 111 recrystallization texture composed , while the batch annealing IF sheets is composed of weak texture ; (2) Large numberCSL boundaries produced in continuous annealing IF sheets, while in batch annealing IF sheets CSL boundaries obviously occurred; (3) Low energy boundaries distributed uniformly in continuous annealing IF sheets, while in batch annealing IF sheets low energy boundaries are accumulative, and random boundaries distribute around the low energy boundaries to form a thick network, which leads to the SWE.
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    Intelligent Expert System Used in Gear Material Selection and its Heat Treatment
    LI Xincheng; CHEN Guang; ZHU Weixing; WANG Yun; ZHANG KAihua; WANG Jianmin
    Acta Metall Sin, 2004, 40 (10): 1051-1054 . 
    Abstract   PDF (39545KB) ( 1023 )
    The characters and weakness of expert system (ES) and artificial neural networks (ANN) have been analyzed. The ANN were led into gear materials selection and heat treatment ES, and 2-grades back propagation (BP) ANN model which has conquered the weakness of traditional ES has been established. This system contains large quantity of knowledge of gear materials and heat treatment process.
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    Transformation Kinetics of Undercooled Austenite During Deformation of Low Carbon Mn Steels with Different Carbon and Manganese Contents
    ZHOU Rongfeng; YANG Wangyue; SUN Zuqing
    Acta Metall Sin, 2004, 40 (10): 1055-1063 . 
    Abstract   PDF (97400KB) ( 1024 )
    The effects of carbon and manganese on the kinetics and the ferrite nucleation of deformation enhanced ferrite transformation DEFT in low carbon Mn steels were investigated. It was found that the addition of carbon prolongs the transformation incubation period dramatically, which retards the ransformation kinetics. However, the ransformationincubation period is somewhat prolonged, and the kinetics becomes much more sluggish as the manganese content increased. The more pronounced refinement is achieved as the carbon or manganese content increased because of the higher nucleation rate, especially in the steels with high carbon content. The process of DEFT in the tested steels can be divided into three stages according to the characteristics of the DEFT kinetics, the first stage obeys Cahn site saturation mechanism, but the other two stages not.
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    Analysis and Calculation of Forces on Macroparticles in Plasma Sheath
    GUO Huimei; LIN Guoqiang; SHENG Mingyu; WANG Dezhen; DONG Chuang; WEN Lishi
    Acta Metall Sin, 2004, 40 (10): 1064-. 
    Abstract   PDF (57891KB) ( 834 )
    Applying the plasma sheath models given by Edlberg and Aydil, the charging effect and forces acting on macroparticles are analyzed and calculated in pulsed-bias arc ion plating, which gives an evidence to the experimental phenomenon and physical model in which macroparticles would be repulsed from electric force and hence are significantly reduced.
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    Calculation on Deposited Temperature During Pulsed Bias Arc Ion Plating
    BAI Xiao; LIN Guoqiang; DONG Chuang; WEN Lishi
    Acta Metall Sin, 2004, 40 (10): 1069-1073 . 
    Abstract   PDF (49810KB) ( 873 )
    The influencing factors and their weights on deposited temperature have been studied in detail during pulsed bias arc ion plating (PBAIP). Based on the model of deposited temperature calculation in arc ion plating (AIP), and under the condition of the rectangle substrate voltage waveforms, the input power intensity of ion bombardment in PBAIP can be equal to the product of the input power in AIP and duty cycle in PBAIP. On the basis of energy conversation principle, a substrate temperature calculation model for PBAIP is established when the bias voltage varies from -1000 V to 0. Experiments are also used to verify the calculated results and a good agreement is obtained.
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    Phase Transformations During Composite Hromization of Steel 20
    WU Cuilan; LUO Chengping; ZOU Ganfeng
    Acta Metall Sin, 2004, 40 (10): 1074-1078 . 
    Abstract   PDF (67057KB) ( 1317 )
    The morphology and formation mechanism of the microstructure of the composite ion-nitrided plus chromized layers obtained at various chromization temperatures in a plain low-carbon steel (steel 20) were investigated using metallography, X-ray diffraction and microanalysis. It was found that the surface zone of the composite--chromized layers obtained at various temperatures was composed of the phases in which the fractiondecreased with increasing the chromization temperature. During chromization of the nitrided layer, the diffusion-controlled reaction transformation occurred within the white (compound) layer of the former nitrided layer, forming a white composite-chromized layer. Meanwhile, the precipitation/eutectoid reaction took place in the transition (diffusion) zone of the nitrided layer during air cooling from a chromization temperature at or above 580℃, resulting in the formation of nitride precipitate zone and/or an eutectoid zone similar to the pearlitic structure.
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    Microstructure Evolution During Eformation--Enhanced Transformation in
    CHEN Guoan; YANG Wangyue; GUO Shouzhen; SUN Zuqing
    Acta Metall Sin, 2004, 40 (10): 1079-1084 . 
    Abstract   PDF (12106KB) ( 998 )
    The microstructure evolution during deformation enhanced transformation of supercooled austenite in Nb-microalloyed steel has been investigated by means of hot compression simulation experiment. The effect of Nb on the strain enhanced ferrite transformation has been studied and the transformation kinetics and orientation of Nb--microalloyed steel has also been analysed. The experimental results showed that the deformation-enhanced transformation is a dominated factor at the deformation temperature between A3 and Ar3. The transformation incubation period of Nb-microalloyed steel was prolonged and therefore the higher strain was needed to accomplish the transformation. The transformation kinetics curves moved to high strain parallelly, and can be divided into two stages: at the first stage the solute Nb dragged the ferrite transformation and led to a long incubation period; at the second stage the fine Nb(C, N) particles not only produced many favorable nucleation sites for ferrite transformation, but also inhibited the grain growth of ferrite. The microstructure evolution is a nucleation dominated process, in which the interchange between 001 and 111 texture appeared.
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    Modeling of the Effects of Oxygen Content on Flow Patterns in A-Tig Welding
    ZHAO Yuzhen; LEI Yongping; SHI Yaowu
    Acta Metall Sin, 2004, 40 (10): 1085-1092 . 
    Abstract   PDF (6123KB) ( 1226 )
    A 3D mathematical model was developed to calculate the temperature and velocity distributions in a moving A-TIG weld pool with different oxygen concentrations. It is shown that the oxygen element, which changes the temperature dependence of surface tension coefficient from a negative value to a positive value, can cause significant changes in the weld penetration and depth/width ratio (D/W) of the weld pool. When the oxygen content increases, the weld bead penetration and $ D/W increases sharply while the weld metal width decreases. When oxygen content exceeds 150 10-6, the surface temperature decreases and then remains a constant. When the oxygen content increased beyond 200 10-6, the increase in oxygen content did not effect the weld pool size and shape. As the oxygen content is less than 300 10-6, negative and positive exist at the same time in the weld pool. The increase of oxygen content and the decrease of surface temperature can extend the region of positive surface tension coefficient and increase the depth of the pool. As the oxygen content exceed 300 10-6 the temperature at the maximum surface tension increases beyond the simulated maximum surface temperature, andis positive. Depending upon the oxygen concentrations, three, one, or two vortexes with different positions, strengths, and directions may be found in the weld pool. The contrary vortexes can efficiently transfer the thermal energy from the arc, creating a deep weld pool.
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    Self Excite Reflowing and Interfacial Reaction of SnPb Eutectic Solder on BGA Pad Under Alternate Electromagnetic Radiation
    LI Mingyu; AN Rong; WANG Chunqing
    Acta Metall Sin, 2004, 40 (10): 1093-1098 . 
    Abstract   PDF (11316KB) ( 1018 )
    SnPb eutectic solder reflow on BGA pad metallized with Au/Ni to form solder bump with induction self excite heat under alternate electromagnetic radiation is performed, and impacts of induction self excite heat and solid state aging on interfacial reaction between SnPb eutectic solder and Au/Ni metallization are investigated. Experimental results show that Au layer disappeared completely from metallization layer under first reflow by alternate electromagnetic radiation and formed needle shape AuSn4 scattered in SnPb eutectic solder, it is the same as that re-flowed by infrared heat. Under second reflow by alternate electromagnetic radiation the AuSn4 is concentrated at interface between the solder and the pad due to effect of solid metal granule conglomeration in liquid metal under electromagnetic field. The needle shape AuSn4 is evolved into layer shape during solid state aging, it restrains growth at the interface.
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    Composition Optimization of the Zr-Al-Co Bulk Metallic Glasses
    ZHANG Xinfang; WANG Yingmin; PENG Min; WANG Qing; LI Dejun; DONG Chuang
    Acta Metall Sin, 2004, 40 (10): 1103-1103 . 
    Abstract   PDF (5950KB) ( 1312 )
    Composition optimization for locating the composition zone with the largest glass forming ability (GFA) in the Zr-Al-Co system is attempted. The criteria that we have developed are respectively related to the conduction electron concentration, termed the e/a-constant criterion, and to the special cluster structure, termed the e/a-variant criterion. For this system, the two criteria are incarnated into the e/a-constant line with constant e/a=1.5 and the (Zr9Co4-Al and (Zr78.5Co21.5)-Al e/a--variant lines. Bulk metallic glasses (BMGs) are obtained by suction casting for alloys on the (Al50Co50-Ale/a$--constant line and Zr9Co4-Al e/a--variant line. On the (Zr9Co4-Al e/a-variant line, the thermal stability and glass forming ability of BMGs are increased with increasing e/a ratio. The Zr53Al23.5Co23.5 BMG with the largest thermal stability and GFA locates in the intersecting point of the two lines, its characteristic thermodynamic indices are Tg=783 K, Tx=849K, Tg/Tm=0.637, Tg}/Tl=0.590.
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    Interface Fracture Mechanics of Failure For Oxide Scale on Superalloy
    LEI Mingkai; XU Zhongcheng; YANG Fujun; GAO Feng
    Acta Metall Sin, 2004, 40 (10): 1104-1108 . 
    Abstract   PDF (3678KB) ( 1255 )
    The stress state of the oxide scale on superalloy was analyzed using a bimaterial mode. The relationship between the maximum buckling deflection of oxide scale and the compressive stress of oxide scale was determined. Based on interface fracture mechanics, the buckling map for spalling was established. The spalling characteristics of the oxide scale described by the buckling map is consistent with the experimental data for the Al2O3 scale on the Ni-based superalloy under the conditions that the parameter relating to the roughness of the oxide alloy interface is between 0.3 and 0.4, a critical buckling index is 1 and a critical adhesion index is 1.15. The buckling and spalling course of the oxide scale on the superalloy was successfully explained with the buckling map.
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    Hot Deformation Behavior of 35CrMo Steel
    ZHANG Bin; ZHANG Hongbing
    Acta Metall Sin, 2004, 40 (10): 1109-1114 . 
    Abstract   PDF (5038KB) ( 1255 )
    The recrystallization behavior of the steel 35CrMo during hot deformation was investigated using physical simulation experiments, and the condition of dynamic recrystallizaiton (DRX) was obtained to be: T>1000℃, A modified DRX kinetic equation is submitted , from which the DRX fraction calculated is good agreement with the experiments. An equation describing dynamic recrystallization grain size can be written . Through the 2-stroke compression and 1-stroke compression followed by holding temperature experiment, the activation energy and kinetics equation of static recrystallization (SRX) of the steel 35CrMo are also obtained.
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    Effect of La2O3 on Hardness Distributions of Laser Clad Ferrite--Based
    ZHAO Gaomin; WANG Kunlin; LIU Jiajun
    Acta Metall Sin, 2004, 40 (10): 1115-1120 . 
    Abstract   PDF (8841KB) ( 1038 )
    The morphologies of laser clad ferrite--based alloy coatings with different contents of rare earth (RE) were observed by SEM. The nanohardness and the elastic modulus of the near the surface and overlapping area were tested by nanoindentation. The hardness distribution in the coating was measured by microhardness tester. The experimental results show that the microstructure of the coatings with RE was refined, the spacing of second dendrites was reduced, and spacing the nanohardness and elastic modulus were increased. The average hardness (HV) of the coating with RE is about 500, which is 50 higher than that without RE. The mechanism of the RE effect was discussed.
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