Started in 1988 Monthly
ISSN: 1006-7191
CN: 21-1361/TG
Impact factor: 2.090

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China Association for Science and Technology
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The Chinese Society For Metals
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Institute of Metal Research, Chinese Academy of Science

  Current Issue
      25 April 2009, Volume 22 Issue 2 Previous Issue    Next Issue
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    Research paper
    Temperature field analysis and its application in hot continuous rolling of Inconel 718 superalloy
    Fengli SUI,Liqing CHEN,Xianghua LIU,Lintao WANG,Wei LI
    Acta Metallurgica Sinica (English Letters), 2009, 22 (2): 81-90.  DOI: 10.1016/S1006-7191(08)60074-5
    Abstract   PDF (13999KB) ( 2106 )

    A coupled thermo-mechanical model containing metal flow and temperature field for calculating temperature variation has been developed on fourteen-pass hot continuous rolling of round rod for Inconel 718 alloy using 3D elastic-plastic finite element method (FEM). The temperature of characteristic analysis points in the intermediate cross-section of the workpiece has been simulated at initial temperature ranging from 960 to 1000 ℃ and initial velocity in range of 0.15-0.55 m.s-1. Based on finite element analysis and microstructural observation in cylindrical hot compression experiments, the appropriate hot continuous rolling technologies have been designed for rod products with different diameters. For a real rolling practice, the simulated surface temperature was examined and is in good agreement with the measured one.

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    A mathematical model for electrochemical chloride removal from marine cast iron artifacts
    Weizhen OUYANG,Xia CAO2,Ning WANG
    Acta Metallurgica Sinica (English Letters), 2009, 22 (2): 91-99. 
    Abstract   PDF (1074KB) ( 1251 )

    The aim of this article was to theoretically study diffusion and migration of chloride ions during electrochemical chloride removal. The proposed model would enable optimization of its application by predicting the optimal treatment time and current combination. A mathematical model for simulating the transport behavior of chloride ions was developed by consideration of diffusion and migration of chloride ions when a constant DC current density was applied through the marine cast iron artifacts. The corresponding tests were conducted to validate the mathematical model. This model predicted the data of the extraction ratio of the chloride ion that correlated satisfactorily with the experimental values. An important issue in electrochemical chloride removal was to understand how chloride ions moved, taking account of diffusion and migration of chloride ions and the release of binding chloride ions. The effects of the treatment time, externally applied current density, chloride diffusion coefficient, and rate constant of release of binding chloride ion on chloride removal are studied. The specific quantitative details applied to one-dimensional model were discussed here. This article has proposed a mathematical model for the first time, which was showed to be a useful tool that can reveal the ionic transport mechanism and optimize the application during electrochemical chloride removal.

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    Effect of silicon and prior deformation of austenite on isothermal transformation in low carbon steels
    Minghui CAI,Hua DING,Jiansu ZHANG,Long LI
    Acta Metallurgica Sinica (English Letters), 2009, 22 (2): 100-109.  DOI: 10.1016/S1006-7191(08)60076-9
    Abstract   PDF (27707KB) ( 1428 )

    Isothermal transformation (TTT) behavior of the low carbon steels with two Si contents (0.50 wt pct and 1.3 wt pct) was investigated with and without the prior deformation. The results show that Si and the prior deformation of the austenite have significant effects on the transformation of the ferrite and bainite. The addition of Si refines the ferrite grains, accelerates the polygonal ferrite transformation and the formation of M/A constituents, leading to the improvement of the strength. The ferrite grains formed under the prior deformation of the austenite become more homogeneous and refined. However, the influence of deformation on the tensile strength of both steels is dependent on the isothermal temperatures. Thermodynamic calculation indicates that Si and prior deformation reduce the incubation time of both ferrite and bainite transformation, but the effect is weakened by the decrease of the isothermal temperatures.

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    Study on the hot deformation behavior of Al-Zn-Mg-Cu-Cr aluminum alloy during multi-stage hot compression
    Gaoyong LIN,Xiaoyan ZHENG,Wei YANG,Di FENG,Dashu PENG
    Acta Metallurgica Sinica (English Letters), 2009, 22 (2): 110-116.  DOI: 10.1016/S1006-7191(08)60077-0
    Abstract   PDF (19962KB) ( 906 )

    The mechanical behavior and microstructures of an Al-Zn-Mg-Cu-Cr aluminum alloy during multi-stage hot deformation were investigated by thermal stimulation test, optical microscopy, and transmission electron microscopy. The true stress vs true strain curves and the microstructure evolution of two hot deformation procedures were gained. The flow stress of the alloy studied decreases with increasing the deforming passes and declining the temperature, and the larger the temperature decline between adjacent stages, the larger the peak stress fall is. The stress-strain behavior mainly result from the dynamic recovery during deformation, the static recovery and re-crystallization in the delay time, and the second phases precipitated from the matrix at high temperature.

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    First principle study on the possibilities of magnetism in onedimensional In and Tl atomic wires with the full-potential linearized augmented plane wave method
    Zhili ZHU,Jinhua GU,Yu JIA,Xing HU
    Acta Metallurgica Sinica (English Letters), 2009, 22 (2): 117-122.  DOI: 10.1016/S1006-7191(08)60078-2
    Abstract   PDF (5042KB) ( 1126 )

    Using ab initio total energy calculations with the full-potential linearized augmented plane wave method, the possibilities of magnetism in one-dimensional In and Tl wires were explored and their properties as the function of geometric structures were studied. The results suggest that the linear In and Tl wires show magnetization at the equilibrium bond distance with magnetic moments of 0.71 and 0.67μB/atom, respectively. Allowing ions to relax, the wires were deformed as zigzag structures, but no dimerization occurs. The zigzag wires also exhibit spontaneous magnetization, although the magnetic moments are  lower than those of straight wires.

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    Yield criterions of metal plasticity in different stress states
    Fengping YANG,Qin SUN,Wei HU
    Acta Metallurgica Sinica (English Letters), 2009, 22 (2): 123-130.  DOI: 10.1016/S1006-7191(08)60079-4
    Abstract   PDF (11824KB) ( 2946 )

    Five types of tensile tests were conducted to study the yield behavior of 2A12-T4 aluminum alloy. Parallel finite element models were built for each test and solved with ABAQUS with different yield criterions. The result shows that any of the four criterions: von Mises yield criterion, Tresca criterion, Twin-Shear criterion and von Mises criterion with hydrostatic pressure correction, overestimates the yield strengths of the specimens. Rather than hydrostatic pressure, Lode stress parameter is the key factor that affects the differences between experimental and simulation results. Based on this concept, a new yield model with Lode dependence modified from von Mises criterion is postulated. Although one more parameter needs to be confirmed, the simulation results of this yield model are better than those of other criterions.

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    Effects of temperature, slip amplitude, contact pressure on fretting fatigue behavior of Ti811 alloys at elevated temperatures
    Xiaohua ZHANG,Daoxin LIU
    Acta Metallurgica Sinica (English Letters), 2009, 22 (2): 131-137.  DOI: 10.1016/S1006-7191(08)60080-0
    Abstract   PDF (14266KB) ( 1589 )

    Effects of the temperature, slip amplitude, and contact pressure on fretting fatigue (FF) behavior of the Ti811  titanium alloy were investigated using a high frequency fatigue machine and a home-made high temperature apparatus. The fretting  fatigue failure mechanism was studied by observing the fretting surface morphology features. The results show that the sensitivity to fretting fatigue is high at both 350 and 500℃. The higher the temperature, the more sensitive to the fretting fatigue  failure is. Creep is an important factor that influences the fretting fatigue failure process at elevated temperatures. The  fretting fatigue life of the Ti811 alloy does not change in a monotonic way as the slip amplitude and contact pressure increase.  This is owing to the fact that the slip amplitude affects the action of fatigue and wear in the fretting process, and the nominal contact  pressure affects the distribution and concentration of the stress and the amplitude of fretting slip at the contact surface, and thus  further influences the crack initiation probability and the driving force for propagation.

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    Role of silicon in steels on galvanized coatings
    Chunshan CHE,Jintang LU,Gang KONG,Qiaoyu XU
    Acta Metallurgica Sinica (English Letters), 2009, 22 (2): 138-145.  DOI: 10.1016/S1006-7191(08)60
    Abstract   PDF (13453KB) ( 1362 )

    In this article, five kinds of silicon-containing steel sheets have been electrodeposited, and then immersed in a pure molten zinc bath at 450℃ for various periods of time. The results by scanning electron microscopy (SEM) show that the coating of the sample (0.09 wt pct Si) with iron-electrodeposited pretreatment eliminates the reactive zones which are found in the coating without iron-electrodeposited pretreatment. The galvanized sample (0.28 wt pct Si) with iron-electrodeposited pretreatment exhibits a compact and coherent coating. The coating of the sample (0.37 wt pct Si) with the iron-electrodeposited pretreatment experiences a transition from a compact and coherent coating to a reactive one. The energy dispersive spectrum (EDS) results reveal that for the galvanized samples with iron-electrodeposited pretreatment, excessive silicon accumulates on the surface of the substrate due to the low solubility of silicon in the τ, after the iron layer is depleted by the increasing growth of the Fe-Zn intermetallics. With the movement of the substrate/τ interface toward the substrate, silicon-enriched α-Fe peels off from the substrate and breaks into the particles. The particles move toward the δ layer through the τ layer because silicon-enriched α-Fe cannot be absorbed in the τ layer. When the particles reach the δ/τ interface, they are dissolved in the δ layer, making the  τlayer thin or even vanish.

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    Theoretical study of the elastic properties of titanium nitride
    Dong CHEN,Jingdong CHEN,Yinglu ZHAO,Benhai YU,Chunlei WANG,Deheng SHI
    Acta Metallurgica Sinica (English Letters), 2009, 22 (2): 146-152.  DOI: 10.1016/S1006-7191(08)60082-4
    Abstract   PDF (986KB) ( 2291 )

    The equilibrium lattice parameter, relative volume V/V0, elastic constants Cij, and bulk modulus of titanium nitride are successfully obtained using the ab~initio plane-wave pseudopotential (PW-PP) method within the framework of density functional theory. The quasi-harmonic Debye model, using a set of total energy vs molar volume obtained with the PW-PP method, is applied to the study of the elastic properties and vibrational effects. We analyze the relationship between the bulk modulus and temperature up to 2000 K and obtain the relationship between bulk modulus B and pressure at different temperatures. It is found that the bulk modulus B increases monotonously with increasing pressure and decreases with increasing temperature. Moreover, the Debye temperature is determined from the non-equilibrium Gibbs functions.

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    Current spin polarization and spin injection efficiency in ZnO-based ferromagnetic semiconductor junctions
    Gang JI,Ze ZHANG1,Yanxue CHEN,Shishen YAN,Yihua LIU,Liangmo MEI
    Acta Metallurgica Sinica (English Letters), 2009, 22 (2): 153-160.  DOI: 10.1016/S1006-7191(08)60083-6
    Abstract   PDF (2688KB) ( 1308 )

    [FeNi(3~nm)/Zn1- xCoxO(3~nm)]2/ZnO(d nm)/[Zn1-xCoxO(3 nm)/Co(3 nm)]2 (d=3 and 10) semiconductor junctions were prepared by magnetron sputtering system and photolithography. The spin valve effect was observed in these junctions because the utility of the ferromagnetic composite layers acted as soft and hard magnetic layers. The electrical detection was performed by measuring the magnetoresistance of these junctions to investigate the current spin polarization αsc in the ZnO layer and the spin injection efficiency η of spin-polarized electrons. αsc was reduced from 11.7% (and 10.5%) at 90 K to 7.31 % (and 5.93 %) at room temperature for d=3 (and d=10). And η was reduced from 39.5 % (and 35.5 %) at 90 K to 24.7 % (and
    20.0 %) at room temperature for d=3 (and d=10).

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CN: 21-1315/TG
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