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      20 December 2013, Volume 0 Issue 12 Previous Issue    Next Issue
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    Recent Progress of Electrically Conductive Adhesives with Nano-fillers
    HE Peng, WANG Jun, GU Xiao-long, LIN Tie-song
    2013, 0 (12): 1-7.   DOI: 10.3969/j.issn.1001-4381.2013.12.001
    Abstract ( 800 ( PDF (1155KB)( 1164 Citation
    The effects of nano-fillers on electrically conductive adhesives (ECAs) applied to electronic packaging were theoretically analyzed. Research progress in influencing factors of properties of nano-filler ECAs,such as content, size, shape,surface state of nano-fillers, curing temperature and curing time etc, was reviewed. The methods for improving properties such as in-situ synthesis of nano-fillers and sintering of nano-fillers were emphatically introduced. Main challenges of nano-filler ECAs research were proposed, as the improvement of ECAs properties,such as the electrically and thermally conductive performance, bonding strength and reliability, conductive flexible adhesives, ink-jet adhesives and cost reduction.
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    Tensile Property of Single Countersunk Bolt Composite Laminate Joints
    HUANG Wen-jun, SUN Yong-bo, CHENG Xiao-quan, NIE Hong
    2013, 0 (12): 8-12.   DOI: 10.3969/j.issn.1001-4381.2013.12.002
    Abstract ( 806 ( PDF (2168KB)( 312 Citation
    A 3D finite element progressive damage model was established with ABAQUS software.The offset bearing failure load of the single countersunk bolt composite laminate joint was calculated, and the damage mechanism and failure course were analyzed. Laminate damage criteria and stiffness attenuation rules for this type of structure were applied and verified. The numerical results indicate good agreement with the test results, which prove validity of this model.The influence of the contact surface friction, bolt stiffness and stiffness of the connecting metal plate on the joint tensile property is studied. The results show that the contact surface friction factor and bolt stiffness have a great effect on the joint tensile performance, but the effect of the metal plate stiffness can be ignored almost.
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    Microstructure and Crystallographic Feature of Semi-continuous Cast Slab Under Magnetic Field
    LI Lei, ZHU Qing-feng, ZUO Yu-bo, ZHAO Zhi-hao, CUI Jian-zhong
    2013, 0 (12): 13-18,26.   DOI: 10.3969/j.issn.1001-4381.2013.12.003
    Abstract ( 599 ( PDF (4420KB)( 226 Citation
    Static magnetic fields were imposed during the semi-continuous casting of hypoeutectic Al-Fe alloys, and the effects of the magnetic fields on the microstructures and crystallographic features were investigated with EBSD technology. The results show that the static magnetic fields transfer the columnar grains to twinned lamellas, accompanying by a change of preferred growth directions of crystals from <100> to <110>.
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    Research on Hot Compressive Behavior of Ti-5Mo-5V-1Cr-3Al Alloy
    CUI Xue-fei, MI Xu-jun, LIN Chen-guang, HUI Song-xiao, WEI Yan-guang, TAO Hai-ming
    2013, 0 (12): 19-26.   DOI: 10.3969/j.issn.1001-4381.2013.12.004
    Abstract ( 587 ( PDF (3129KB)( 307 Citation
    Isothermal compression test was carried out for Ti-5Mo-5V-1Cr-3Al (abbreviated as 1Cr) alloy in the temperature range of 700-900℃ and in the strain rate range of 0.001-1s-1. The results show that the flow stress is sensitive to the deformation temperature and the strain rate. Dynamic recrystallization occurs in the temperature range of 700-800℃. In the temperature range of 800-900℃, multi-peaks stress dynamic recrystallization exhibits in the low strain rate of 0.001s-1 and dynamic recovery exhibits in the strain rate range of 0.01-1s-1. The flow stress behaviors of Ti-5Mo-5V-1Cr-3Al alloy during the isothermal compression could be expressed by the Arrhenius constitutive equation including Zener-Holomon parameters. The hot deformation activation energy is 456kJ/mol. The metallographic results indicate that the dynamic behavior of the material in hot compression process is affected by not only the rate and the temperature of the deformation, but also the microstructure and phase structure of the material. During hot compression deformation under a low strain rate of 0.001s-1, the alloy presents the dynamic recrystallization behavior even near the phase transition point or the higher temperature (800-900℃), which is closely related to the martensitic transformation induced by the strain. The precipitation of the martensite promotes dynamic recrystallization behavior during the hot deformation.
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    Effect of Repair Process on Flexural Behavior of Honeycomb Sandwich Structures with Closed Edgewise
    GUO Xia, GUAN Zhi-dong, LIU Sui, YAN Dong-xiu, LIU Wei-ping, SUN Kai
    2013, 0 (12): 27-31.   DOI: 10.3969/j.issn.1001-4381.2013.12.005
    Abstract ( 640 ( PDF (2953KB)( 198 Citation
    The flexural behavior of the repaired honeycomb sandwich structures with closed edgewise, was investigated by four-point bending test. The influence of damage type, damage size and repair equipment on bending performance of the repaired plate was analyzed. The results show that the strength recovery of all the repaired plate is more than 90%. The effect of autoclave is a little better than the effect of hot honder. The bending strength recovery with different damage sizes is almost the same with each other when the quality of bonding is good.But the large damage size need better bonding quality. The bending strength recovery of repaired honeycomb structures on the flatwise is larger than that on the closed edgewise.
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    Research on Abrasive Wear Properties of Bionic Non-smooth Coating by Laser Cladding
    LIU Jing, GAO Xiao-li, XU Yang, CHEN Xiao-min, LING Gang
    2013, 0 (12): 32-36.   DOI: 10.3969/j.issn.1001-4381.2013.12.006
    Abstract ( 830 ( PDF (2124KB)( 140 Citation
    On the basis of the morphology of organism's surface,bionic non-smooth coatings of wave and plane-type on 45 steel were prepared by laser cladding. The abrasive wear test was carried out with abrasion tester, and the wear scar was observed.The wear mechanism was analyzed. The results show that the wear resistance of plane type coating is remarkably better than that of the wave type. The criterion for designing and preparing a good wear-resistant coating is:geometric hardening rate(GHR) was no less than 50%. The wear mechanism of wave-type coating is that the hardening belt's non-smooth surface and the impact of the grinding head function together. The wear mechanism of flat-type coating is the combination of the wear mechanisms of the hardening belt's non-smooth surface and its non-smooth geometric surface morphology.
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    Optimization of Mo-(NiCr-Cr3C2) Composite Coating for Piston Ring Application
    LI Hui, SUN Ri-chao, YANG Hai-xin, GU Jia-bin, LI Zhuo-xin
    2013, 0 (12): 37-43.   DOI: 10.3969/j.issn.1001-4381.2013.12.007
    Abstract ( 833 ( PDF (4531KB)( 347 Citation
    The composite powder of Mo-(NiCr-Cr3C2) was mechanically blended and deposited using atmospheric plasma spraying. The mechanical property and tribological performance of the prepared coating were tested. The results show that the porosity and the microhardness of the composite coating are inversely proportional to the Mo content. The coating with the Mo addition of 20%(mass fraction) presents better performance in the frictional test. All the composite coatings mainly endures adhesive wear and abrasive wear. The coating containing large portion of NiCr-Cr3C2 is prone to flake during the wear. The wear resistance of the coating shows a good accordance with the index of H/E of the coating.
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    Interfacial Product of ZrB2-SiC Brazing Joint and Growth Kinetics of Reaction Layer
    LI Zhuo-ran, XU Xiao-long, WANG Zheng-zheng
    2013, 0 (12): 44-48.   DOI: 10.3969/j.issn.1001-4381.2013.12.008
    Abstract ( 785 ( PDF (1179KB)( 379 Citation
    The ZrB2-SiC (ZS) ceramic composite was brazed in vacuum using TiZrNiCu amorphous active filler. Combined with the brazing process in each stage, the interfacial reaction product and the forming mechanism were analyzed by SEM, EDS and XRD. Ti atom is the most active element in the filler metal. Its reaction product distributes along the joint, which having significant effect on microstructure and mechanical property of the joint. Based on diffusion theory and the diffusion of Ti atom in the solid solution layer, the growth behavior of the Zr(s,s) solid solution layer is discribed and the dynamic equations for growth behavior of zirconia solid solution layer are obtained.
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    Effects of Cr on Microstructure and Properties of Al-Mg-Si-Cu Aluminum Alloy
    ZHANG Xin-ming, ZHOU Zhi-le, TANG Jian-guo, KE Bin, HU Ji-long, OUYANG Hui
    2013, 0 (12): 49-53,58.   DOI: 10.3969/j.issn.1001-4381.2013.12.009
    Abstract ( 1065 ( PDF (2883KB)( 479 Citation
    The effects of Cr on the microstructures and properties of Al-Mg-Si-Cu aluminum alloy were studied by hardness test, tensile test, TEM, SEM and energy spectrum analysis. The results show that Cr addition promotes the phase transition from β-AlFeSi to α-AlFeSi. The formation of Al7Cr dispersion phase inhibits the generation and growth of recrystallization.However, Cr and Fe, Si element prior form the combination of AlFeCrSi phase, make the main limitation precipitated phase (Mg2Si) reduce, weaken the strengthening effect. With the increasing of Cr content, the strength and plasticity of the alloy increase, when the Cr content is more than 0.20%(mass fraction), the strength and the plasticity of the alloy reduce in a certain degree. It is mainly due to the combination of Cr, Fe and Si elements and formation large number of AlFeCrSi phase,which reduces the precipitation of Mg2Si phase in the alloy and weakens the ageing treatment effects.
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    Effect of Sintering Additives on Microstructures and Properties of In-situ Transformed Carbon Fiber/Alumina Composites
    CAO Jing-jing, CHEN Hua-hui, DU Fei, CHEN Gong-zhe
    2013, 0 (12): 54-58.   DOI: 10.3969/j.issn.1001-4381.2013.12.010
    Abstract ( 736 ( PDF (1254KB)( 214 Citation
    In-situ transformed carbon fibers toughened alumina composites were prepared by hot-pressing sintering in vacuum, using pre-oxidized polyacrylonitrile fibers as the precursor and alumina as the main raw material, and by adding SiO2-MgO-CaO sintering additives. Effect of sintering additives on phase structure, microstructures, density,hardness and fracture toughness of the composites was studied. The results show that the composites can be densified at a relatively low temperature of 1650℃ via the liquid phases sintering mechanism and the density and mechanical properties of the composites increase with adding sintering additives. The sintering additives react with alumina to generate spinel phase as pinning in the grain boundary and inhibit alumina grain growth. Furthermore,the sintering additives eliminate porosity and promote the densification of the composite. The spinel phase in the composites improves the interfacial bonding strength between the carbon fiber and the matrix, increases the fracture toughness.
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    Effect of Shot Peening Processing on Bending Deformation of High Strength 7150 Aluminum Alloy
    WANG Qiang, ZHANG Wei, QIAO Ming-jie
    2013, 0 (12): 59-62.   DOI: 10.3969/j.issn.1001-4381.2013.12.011
    Abstract ( 597 ( PDF (1430KB)( 168 Citation
    The effect of compressive residual stress and plastic strain induced by shot peening processing on bending deformation (BD) of 7150 aluminum alloy was studied using the XRD residual stress testing and the FWHM value. The results indicate that BD rate is higher when the shot time is less than 60s,and the BD rate reaches 10.3μm/s when shot pressure is 0.05MPa, due to the compressive residual stress and plastic strain induced by shot peening processing. When the shot time is more than 60s, the compressive residual stress field reaches saturated,and the BD rate reduces to 1.3μm/s which only depends on the surface plastic defomation induced by shot peening processing. The BD rate and total amount of BD increase with the increasing of shot pressure.
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    Cathodic Electrogenerated Chemiluminescence of Ru(bpy)32+ Catalyzed by MWCNTs
    GUO Wei-ling, LI En-zhong, WANG Hai-dou, YANG Da-xiang
    2013, 0 (12): 63-67,73.   DOI: 10.3969/j.issn.1001-4381.2013.12.012
    Abstract ( 725 ( PDF (3410KB)( 346 Citation
    The modified glassy carbon(GC)electrode with multi-walled carbon nanotubes (MWCNTs/GC) was used to detect electrogenerated chemiluminescence (ECL) of Ru(bpy)32+ aqueous solution. The results show that,when the applying potential on the MWCNTs/GC electrode is at positive potential of +0.3V (vs Ag/AgCl), a strong cathodic ECL of Ru(bpy)32+ is observed. Limit of detection of dopamine (DA) in solution tested by means of this catalytic property of MWCNTs/GC is 1.2×10-11M. The intermediate generated from electrochemical reduction of MWCNTs could increase the cathodic ECL of Ru(bpy)32+.
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    Stability of Retained Austenite of Low Si Containing Al TRIP Steel During Deformation
    DING Wei, GONG Zhi-hua, TANG Di, JIANG Hai-tao, WANG Bao-feng
    2013, 0 (12): 68-73.   DOI: 10.3969/j.issn.1001-4381.2013.12.013
    Abstract ( 706 ( PDF (1714KB)( 254 Citation
    Retained austenite(RA) evolution during deformation of low Si TRIP steel was studied by pre-tension test, and relationship of stability of retained austenite during deformation with work hardening exponent n was established. Different heat treatment processes were designed in order to acquire TRIP steel with different incipient retained austenite or different microstructures, and then stability of retained austenite of the TRIP steel was analyzed. The results show that, as the progressing deformation the stability of retained austenite increases, the work hardening performance gets better and the stability of retaining austenite during deformation also increases with the increasing of initial carbon content. The stability of retaining austenite is influenced by the carbon content and distribution of retained austenite as well as surrounding phases.
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    Influence of Silver Content on Fatigue Life and Failure Mechanism of Lead-free Solder Joints Under Drop Conditions
    YANG Jin-li, LEI Yong-ping, LIN Jian, XIAO Hui
    2013, 0 (12): 74-79.   DOI: 10.3969/j.issn.1001-4381.2013.12.014
    Abstract ( 764 ( PDF (2531KB)( 173 Citation
    Drop tests were carried out with three kinds of materials (Sn-3.0Ag-0.5Cu,Sn-1.0Ag-0.5Cu and Sn-0.3Ag-0.7Cu),respectively. Half-sine acceleration loads was applied in the experiment, the peak value of half sine acceleration and pulse duration were 3200g and 1ms. The failure position of solder joint was identified and analyzed using electrical test, optical microscope, scanning electron microscope. The results show that most of the failures joints for the three kinds of materials locate at the printed circuit board (PCB) side. The solder joints at four outermost corners fail at first. And the failure modes of Sn-3.0Ag-0.5Cu and Sn-1.0Ag-0.5Cu were all brittle fractures, while the Sn-0.3Ag-0.7Cu is brittle-ductile fracture. The thickness of intermetallic compound(IMC) gradually decreases and the life of solder joint enhances with the reduction of Ag content.
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    Equivalent Elastic Modulus of Zero Poisson’s Ratio Honeycomb Core
    LU Chao, LI Yong-xin, DONG Er-bao, YANG Jie
    2013, 0 (12): 80-84.   DOI: 10.3969/j.issn.1001-4381.2013.12.015
    Abstract ( 1114 ( PDF (2135KB)( 281 Citation
    A flexible cantilever beam model and Euler beam model were used to analyze zero Poisson's ratio honeycomb core compression deformation under the conditions of large deformation oblique wall bending deformation and horizontal siding small deformation respectively.The plane elastic modulus calculation formula of the zero Poisson's ratio honeycomb core were derived. Moreover, the results of theoretical calculations, finite element simulation and mechanical model experiments were also compared and analyzed. The results show that: theoretical formula are correct and effective; elastic modulus of zero Poisson's ratio honeycomb core in the direction of large deformation presents obvious nonlinear characteristics; equivalent elastic modulus calculations are based both on the size of the strain and the direction of the force; the angle θ of the walls has strong influence on the calculation of equivalent elastic modulus. Therefore zero Poisson's ratio honeycomb structure parameters can be designed appropriately.
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    Research Progress in Preparation of Graphene by Mechanical Exfoliation
    DUAN Miao, LI Si-zhong, CHEN Guo-hua
    2013, 0 (12): 85-91.   DOI: 10.3969/j.issn.1001-4381.2013.12.016
    Abstract ( 1457 ( PDF (1027KB)( 496 Citation
    The preparation methods of graphene as a "star" material were mainly tended to chemical ways in recent years. However, many intrinsic physical properties of graphene were discovered from the graphene that was prepared by micro-mechanical peeling method. In this review, the recent advances in all kinds of mechanical exfoliation methods which contained "scotch tape" method,"nanopencil" method, ultrathin sections method, ultrasonic method, planetary ball milling method, stirred ball milling method, low energy pure shear milling method and three-roll milling method were highlighted, and the advantages and disadvantages of these methods were analyzed. The development trend of mechanical exfoliation was prospected.
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    Research Status of Hexaaluminate Thermal Barrier Coatings with Magnetoplumbite Structure
    HUANG Liang-liang, MENG Hui-min, CHEN Long
    2013, 0 (12): 92-99.   DOI: 10.3969/j.issn.1001-4381.2013.12.017
    Abstract ( 928 ( PDF (1779KB)( 410 Citation
    Hexaaluminate materials have excellent high-temperature phase stability and thermophysical properties for its special magnetoplumbite structure. It has the potential to substitute the state-of-the-art yttria partially stabilized zirconia (YSZ) thermal barrier coatings and will be applied at the temperature above 1200℃.The structure characteristics, synthesis methods, physical properties and thermal shock resistance of hexaaluminate, and summarized its research status on failure mechanism and coating performance improvements were mainly reviewed in this article. The direction of development on the hexaaluminate thermal barrier coating system was proposed.
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