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      20 September 2012, Volume 0 Issue 9 Previous Issue    Next Issue
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    Factors Analysis and Preventive Measures of Pure Titanium Tube Blank Internal Copper Canning Cracking
    XIE Chong-bo, WANG Cheng-zhang, ZHU Mei-sheng, MA Jian-ming, CHEN Gui-zeng, CHAO Hong-tao
    2012, 0 (9): 1-6.  
    Abstract ( 873 ( PDF (2265KB)( 428 Citation
    The cracking of internal copper canning during pure titanium tube blank extruding was studied. The second phase on the cracked copper canning surface was analyzed by metallography, energy spectrum and XRD. The cause of second phase formation and its effect on the copper canning cracking was also analyzed. The results show that the compounds on the copper canning surface which contact to the internal surface of pure titanium extruded tube blank are Cu3Ti. The friction and distortion heat increase significantly when extrusion ratio increases, leading to the failure of oil-base lubricant, the titanium reacts with copper to yield Cu3Ti within 10s due to the elevated temperature(>850℃), leading to the cracking of internal copper canning. Following the test results, the preventive measures to avoiding the internal canning cracking and internal pits were put forward.
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    Surface Roughness of Si3N4 Based on Texture Analysis
    TIAN Xin-li, WANG Jian-quan, ZHANG Bao-guo, TANG Xiu-jian, LI Fu-qiang
    2012, 0 (9): 7-13,18.  
    Abstract ( 746 ( PDF (3365KB)( 414 Citation
    The inherent relationships about surface texture features and roughness of ground Si3N4 were investigated through the gray level co-occurrence matrix(GLCM), based on surface images captured by digital microscope. The sampling offset and total gray levels of GLCM were 4 and 64 respectively. And then 4 matrices concerning 0, 45, 90? and 135? were built up to acquire the average of each texture feature. Six features such as contrast and entropy were set as main texture parameters according to the correlation analysis, and the relations between texture features and roughness parameters were discussed later. Furthermore, the multiple nonlinear regression technique was applied to establish the forecasting models of texture features and roughness. The result shows that the deviation of predicted roughness and measured result is less than 0.25, which reveals a good predictive effect of these models.
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    Microstructures and Adhesion of Oxide Scale Formed on Ti3AlC2 After Cyclic Oxidation
    ZHOU Yuan, LI Yu-xiang, QIAN Xu-kun, WU Hua-xia
    2012, 0 (9): 14-18.  
    Abstract ( 769 ( PDF (2014KB)( 337 Citation
    The surface, section morphology and adhesive strength of anticyclic-oxidized Ti3AlC2 were analyzed by SEM and ultrasound scratch method at 650-950℃. The results show that after 40-cycle oxidation the abnormal oxidation occurs at 650℃. At 750-950℃ the oxidation kinetics follows a parabolic rate law and the flat, dense and microcrack-free oxide scales are formed which can effectively impedance the inner-diffusion of O and the outer-diffusion of Ti and Al,protect the substrate of Ti3AlC2, well adhesive to the substrate and demixing, the adhesive strength is greater than 50mN.
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    Relationship Between Mixed Potential and Coverage of Zinc-immersion on AZ31 Magnesium Alloy
    DENG Juan-li, ZHAO Xiao-li, ZHOU Chuan-zhe, LI De-yu, LI Ning
    2012, 0 (9): 19-22,27.  
    Abstract ( 709 ( PDF (2321KB)( 431 Citation
    E-t curves, Tafel curves and SEM were applied to study the formation of zinc on AZ31 magnesium alloy in the process of zinc-immersion and the relationship between mixed potential (Eg) and coverage(θ). The results show that the coverage reaches 0.983 at the instantaneous contact of AZ31 magnesium alloy and the zinc-immersion solutions, and up to above 1 after 400s immersion and the reaction reaches equilibrium. The relations between Eg and θ were derived, and the mechanism of zinc-immersion on AZ31 magnesium alloy was discussed.
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    Properties of Cr-n-Al2O3 Composite Coatings Grown on Grey Cast Iron Substrates
    ZHANG Shuo, HU Shu-bing, CHEN Wen-qi, ZHANG Liao
    2012, 0 (9): 23-27.  
    Abstract ( 885 ( PDF (3225KB)( 381 Citation
    Cr-n-Al2O3 composite coating was grown on grey cast iron substrates by brush plating. X-ray diffraction (XRD) and scanning electron microscope (SEM) were employed to investigate the grain size and morphology of the coatings. Energy dispersive spectrometer (EDS) was used to analyze the distribution of n-Al2O3 in the surface of the coatings. In addition, hardness, wear resistance and corrosion resistance of the coating were also tested on microhardness tester, wear tester and electrochemical workstation. Results indicate that the composite coating presents compact structure, and there are no obvious defects. The addition of n-Al2O3 leads smaller grain size. With the dispersion-strengthening and fine-grain strengthening effect,the Cr-n-Al2O3 composite coating exhibits enhanced hardness and improved wear resistance. The content of n-Al2O3 also affects the corrosion resistance of the composite coating.
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    Mechanical Properties of Stress Frame Casting Under Different Filling Conditions
    FAN Zhen-zhong, XIONG Yan-cai, HONG Run-zhou
    2012, 0 (9): 28-34,38.  
    Abstract ( 867 ( PDF (6323KB)( 435 Citation
    The influence of gravity filling and low-pressure filling on the cast structure of A357 aluminum alloy stress frame was investigated by test and numerical simulation methods. The mechanical properties and fracture morphology of two castings were also observed with the use of tensile test,SEM and EDS after T6 heat treatment. The results indicate that low-pressure filling can reduce the casting shrinkage and micro-cavity region. Crystal fracture is the principal split pattern of A357 aluminum alloy in casting state,cracks appear and fast grow until casting fracture from the defect area. Dimple rupture is the main fracture factor with some crystal fracture after T6 heat treatment. China cast CAE simulation study confirms that the low-pressure filling is superiority.
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    Synthesis of Fe2O3/Ag Core-shell Composite Nanoparticles by One Step In-situ Method
    GUO Wei, WU Hang, ZHENG Zhen-zhong, CHEN Qing-chang, ZHANG Ming
    2012, 0 (9): 35-38.  
    Abstract ( 752 ( PDF (1115KB)( 321 Citation
    α-Fe2O3 and Fe2O3/Ag core-shell nanocomposites were synthesized by one step in-situ method. The structure of α-Fe2O3 and Fe2O3/Ag core-shell composite nanoparticles was confirmed by XRD, TEM and UV spectra. The results show that α-Fe2O3 and Fe2O3/Ag core-shell nanocomposite can be synthesized by one step, the average size of the α-Fe2O3 nanocomposites is 20-30nm, with a thickness of 10-15nm of Ag layer, core-shell structure is formed. Conductivity of Fe2O3/Ag core-shell nanocomposites is 0.317S/cm. Saturation magnetization of α-Fe2O3 is 1.28A·m2·kg-1, coercive force is 8.2784kA·m-1. Saturation magnetization of Fe2O3/Ag is 0.92A·m2·kg-1, coercive force is equal with α-Fe2O3 particles.
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    Influence of Continuous Annealing and Water Quenching & Tempering Processes on Yield Characteristics of DP1000 Steel
    ZHAO Xian-meng, KANG Yong-lin, HAN Qi-hang
    2012, 0 (9): 39-43,47.  
    Abstract ( 955 ( PDF (3038KB)( 517 Citation
    The annealing of 1000MPa cold rolled dual phase (DP) steel based on continuous annealing and water quenching(WQ) & tempering processes was performed. The yield strength of the continuous annealing steels, which was very low, was 472MPa and 454MPa when overaging temperatures were 250℃ and 320℃, respectively. For the WQ & tempering steels, when the tempering temperatures were 250℃ and 320℃, the yield strength was 1083MPa and 887MPa, respectively, and was much higher than that of the continuous annealing steels. The final microstructure constituents for the continuous annealing steels were ferrite, martensite and tempered martensite. But for the WQ & tempering steels, ferrite and tempered martensite constituted the final microstructure. It’s found that martensitic transformation also appeared during the final cooling stage in the continuous annealing processes. The martensite didn’t undergo tempering and would result in higher dislocation density and internal stress in the DP steels. That is the main reason for the yield strength of the continuous annealing steels is lower than that of the WQ & tempering steels.
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    Preparation of C/SiC Composites at Low Temperature
    ZHOU Chang-cheng, ZHANG Chang-rui, HU Hai-feng, ZHANG Yu-di
    2012, 0 (9): 44-47.  
    Abstract ( 892 ( PDF (14179KB)( 374 Citation
    In order to introduce actively cooling technology into ceramic matrix composites, it is essential to decrease the preparation temperature of ceramic matrix composites. The conversion process of the polycarbosilane (PCS) into silicon carbide (SiC) was investigated by TG-DTA, infrared spectrum analysis (IR) and X-ray diffraction (XRD) etc, which indicated the feasibility of transition from PCS to SiC ceramic at low temperatures under 1000℃. The carbon fiber reinforced silicon carbide (C/SiC) composites were hereby prepared at low temperatures as 900℃ through precursor infiltration and pyrolysis (PIP), and polycarbosilane (PCS) acted as precursor, carbon fiber as enhanced fiber. The results show that the mechanical properties of C/SiC composites prepared at 900℃ are excellent, flexural strength of composites prepared at 900℃ reaching 657.8MPa,shear strength 61.02MPa, fracture toughness 22.53MPa·m1/2, and density being only 1.70g/cm3. Furthermore, the fracture surface was analyzed by SEM.
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    Acoustic Emission Wavelet Analysis of Coating During Contact Fatigue Damage Process
    ZHANG Zhi-qiang, LI Guo-lu, WANG Hai-dou, XU Bin-shi, PIAO Zhong-yu
    2012, 0 (9): 48-53.  
    Abstract ( 729 ( PDF (2985KB)( 321 Citation
    Acoustic emission (AE) signals during different contact fatigue damage phases of Fe-based alloy coating were collected. The signals were five-layer decomposed and reconstructed by dB10 wavelet. Characteristics of waveform and frequency of AE signals during fatigue damage were analysed. The results show that continuous type of untreated AE waveform is dominant during crack initiation phase, then mixed type is dominant during crack stable growth phase, and burst type is dominant during crack unstable growth phase. That separation fatigue damage signals from interference waves by wavelet transform was achieved, and fatigue damage signals of improved signal-to-noise ratio were obtained. Distribution of frequency is different during different fatigue damage phases, and the more severe of fatigue damage, the more extensive of frequency distribution and the larger of waveform amplitude in every layers.
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    Effect of Surface Properties on Interfacial Properties of Aramid Fiber Reinforced Bismaleimide Resin Matrix Composites
    JIANG Shi-cai, SHI Feng-hui
    2012, 0 (9): 54-57.  
    Abstract ( 465 ( PDF (1659KB)( 297 Citation
    The surface properties of aramid fibers were characterized by means of inverse gas chromatography (IGC)and SEM. The results show that the surface physical morphology of K1 and K2 aramid fibers is glossier, and the surface energies of the fibers are similar while different in the dispersive and specific surface energy. Interlaminar shear strength (ILSS) was used to measure the interfacial binding strength of composites based on aramid fiber reinforced bismaleimide resin composite. The ILSS of K2/5405 composite is higher than that of K1/5405 composite and the impact failure mode is interfacial debonding and matrix broken respectively. Good-Girifalco interaction parameter was proved as a key compatible parameter to analysis the effect of surface properties on interfacial properties of aramid fiber reinforced composite. The interfacial binding strength could be improved with the increase of interaction parameter between fiber and resin.
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    Tensile Strain of Composite Laminates Using Embedded Fiber Bragg Grating Sensors
    ZHOU Yu-jing, SONG Hao, LIU Gang, WANG Wen-juan, LI Xue-qin
    2012, 0 (9): 58-61,65.  
    Abstract ( 407 ( PDF (2447KB)( 285 Citation
    Fiber Bragg grating (FBG) sensors embedded in composite laminates were used to monitor the strain during tension process of the composite laminates and the strain derived from the FBG was compared with the strain gage. It was verified that the effectivity and reliability of the FBG sensors in the process of monitoring composite strain. FBG sensors were embedded in different plys of the laminates, and the tension properties of the composites were studied. The results show a good agreement with the strain gages. The FBG sensors could measure the strain of composites laminates effectively. While the embedded FBG has a little effect on the tensile strength of the composite laminates.
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    Ultrasonic Scanning Imaging for Austenitic Thick-wall Welds
    HAN Zan-dong, WANG Bing-fang, YUAN Ke-yi, ZHU Xin-jie
    2012, 0 (9): 62-65.  
    Abstract ( 418 ( PDF (2101KB)( 242 Citation
    Ultrasonic scanning imaging was carried out on a 99mm-thick austenitic weld block with self-developed ultrasonic transducers and acoustically transparent wedge. To eliminate the scattering noise from the wedge, testing signals were processed by deducting a signal that is only relative to the wedge. A signal processing method combining matching pursuit and wavelet analysis was proposed to remove the material noise caused by coarse grain. It is proved that the method could effectively enhance the signal-to-noise ratio. Ultrasonic scanning image of the weld block was generated with the preprocessed ultrasonic scanning signals, the resolution of ultrasonic imaging and defect positioning accuracy were analyzed. The results show that the method could find the 2mm-diameter artificial cross-drilled holes in the weld block and construct ultrasonic scanning imaging of the weld.
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    Preparation and Characterization of Acrylate/Nanosilica Composite Miniemulsion
    NI Shi-bao, WANG Zheng, NIE Wang-yan, ZHOU Yi-feng, SONG Lin-yong
    2012, 0 (9): 66-69.  
    Abstract ( 560 ( PDF (1528KB)( 309 Citation
    The acrylate/nano-SiO2 composite emulsion was prepared through miniemulsion polymerization of nanosilica powder with acrylate monomers. The structure, morphology, thermal and mechanical properties of composite emulsion and films were characterized by FT-IR,TEM, tensile testing machine and thermal analyzer. The influence of the amount of nanosilica on the properties of composite emulsion and films was studied. The results show that the composite emulsion particle shows core-shell structure. Thermal stability and mechanical property of films are greatly improved by adding nanosilica particles. The films have good transparency when nanosilica mass fraction is 5%.
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    Properties and Structure of Al-doped Conductive Zinc Oxide Powder
    XIONG Yu, ZHENG Ji, LI Yan, LIU Xue-jia, LIANG Lu
    2012, 0 (9): 70-73.  
    Abstract ( 551 ( PDF (1237KB)( 258 Citation
    Using zinc nitrate, aluminium nitrate and urea as raw materials, basic zinc carbonate powder was prepared by homogeneous precipitation, Al-doped ZnO powders were prepared by calcining the precursor. The property was characterized by SEM, TGA, XPS and XRD. The results show that the volume resistivity of the zinc oxide decreases to 1.05×105 Ω·cm when the Al3+ doping content is 1.5%(mole fraction),much lower than that of the conventional zinc oxide powders. Al-doped ZnO nanoparticles are wurtzite structure,and similar to ellipsoidal.The grain size distribution of doped ZnO nanopowders is narrow. Meanwhile,the conductivity of Al-doped ZnO powders was improved greatly.
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    Effect of Stress in Nonoriented Silicon Steel on Texture and Grain Boundary Development During Grain Growth
    ZHOU Shun-bing, FENG Da-jun
    2012, 0 (9): 74-78.  
    Abstract ( 940 ( PDF (1245KB)( 252 Citation
    The rules of texture and grain boundary transformation in the nonoriented silicon steel under applied stress or without applied stress during grain growth were investigated by EBSD. The results show that the {111}〈112〉 and {111}〈110〉 components in the nonoriented silicon steel without stress are strengthened during grain growth whereas {100}〈001〉 component is weakened, but the growth rate of {111}〈112〉 and {111}〈110〉 component decreases, while the area fraction of {100}〈001〉 component doesn’t change significantly in the sample under stress. For the {111}〈112〉,{111}〈110〉 and {100}〈001〉 components changing continuously during grain growth, the frequency of high angle misorientation grain boundary of {111}〈112〉 and {111}〈110〉 components decreases, and that of {100}〈001〉 component increases, and whereas the stress being applied in the sample, the frequency decreasing rate of {111}〈112〉 and {111}〈110〉 components rate becomes low and that increasing rate of {100}〈001〉 component becomes a little lower.The segregation behavior of alloying agent in grain boundary was studied.
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    Electrochemical Detection of Pyruvic Acid on Cobalt Oxyhydroxide and Copper Modified ITO Dual-electrode
    WANG Jing-yi, DIAO Peng, ZHANG Qi
    2012, 0 (9): 79-82,87.  
    Abstract ( 538 ( PDF (1352KB)( 233 Citation
    Cobalt oxyhydroxide and copper are electrodeposited on a dual-ITO substrate to obtain CoOx(OH)y/ITO and Cu/ITO, and cyclic voltammetry technique is applied for investigating the oxidation and reduction of pyruvic acid over CoOx(OH)y/ITO and Cu/ITO. The results reveal that pyruvic acid arises an oxidation current on CoOx(OH)y/ITO and a reduction current on Cu/ITO. Based on the results, potentials of 0.45V and -1.4V are respectively applied on CoOx(OH)y/ITO and Cu/ITO by using chronoamperometry technique via dual-current channel. As a result, CoOx(OH)y/ITO has a linear response to pyruvic acid at relative low concentrations while Cu/ITO has a linear response at relative high concentrations, therefore the pyruvic acid detection in a wide concentration range (1.67μmol·L-1-6.01mmol·L-1) can be accomplished by the dual-electrode of CoOx(OH)y/ITO and Cu/ITO.
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    Fatigue Performance of Scarfed Lap Joint
    YANG Shi-chao, WANG An-qiang, YAN Wu-zhu, YUAN Xin
    2012, 0 (9): 83-87.  
    Abstract ( 649 ( PDF (3103KB)( 244 Citation
    A series of fatigue tests were carried out on scarfed lap joints to explore the effect of lap angle on its fatigue performance. Finite element method (FEM) was employed to analyze the stress distribution around the circular holes under tensile load. On the basis of calculation results, fatigue life was predicted by nominal stress approach. The results show that the first row of fasteners undergoes the most severe stress concentration. The fatigue life increases with the increase of lap angle.The relationship between lap angle and fatigue life can be expressed as:lgN=6.047-1.020×0.6601α.
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    Quasi-static Indentation Damage Failure of Laminated Composites Ex-situ Toughened
    MA Hong-yi, AN Xue-feng, YI Xiao-su
    2012, 0 (9): 88-91,98.  
    Abstract ( 558 ( PDF (1536KB)( 278 Citation
    The bismaleimide composite laminates were toughened via "Ex-situ" toughened technique. Then the toughened and non-toughened composite laminates were tested by using the quasi-static indentation and compression after impact, and the damage of laminates was also investigated by ultrasonic C-scan and deply. The results indicate that the thermoplastic resin/thermoset resin bicontinuous structure forms in the interlayer of the toughened bismaleimide laminates. The special structure can inhibit the damage area of the toughened laminates and improve the damage resistance of laminates, resulting in a more apparent dent depth on the laminates surface. In addition, the damage tolerance of laminates is also improved.
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    Research Progress on Preparation of Mono-sized Spherical Micro Particles
    DONG Wei, LI Ying, FU Yi-fan, TAN Yi
    2012, 0 (9): 92-98.  
    Abstract ( 671 ( PDF (1541KB)( 457 Citation
    The present paper reviews preparation principles, features, applications, existing problems and development trends of several important preparation methods of spherical micro particles, such as cutting, punching-remelting method, atomization, uniform-droplet spray method (UDS) and pulsated orifice ejection method (POEM). In addition, solidification behavior of droplets is particularly pointed out. In summary, POEM is a promising practical method with characteristics of identical size, high sphericity, particle size controllable and the same cooling history, especially in preparing function particles and high melting point materials.
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