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      20 July 2014, Volume 0 Issue 7 Previous Issue    Next Issue
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    Effects of Temperature in the New Compound Extrusion on Microstructures and Properties of AZ61
    ZHANG Ding-fei, GENG Qing-mei, YANG Xu-sheng, YU Da-liang, PAN Fu-sheng
    2014, 0 (7): 1-4.   DOI: 10.11868/j.issn.1001-4381.2014.07.001
    Abstract ( 745 ( PDF (1963KB)( 289 Citation
    A new composite extrusion (shorten ES) combining extrusion and shear was presented, for the industrial preparation and process of magnesium alloy rods. Microstructures, hardness test, tensile test and SEM experiments were used to investigate the effects of temperature on microstructure and properties of AZ61 magnesium alloy deformed by ES. The results show that, when the temperature increases from 380℃ to 400℃,dynamic recrystallization becomes more fully and more recrystallized grains are generated. But when the temperature rises to 440℃, grains grow up. The fractography shows ductile fracture characteristics under these three temperatures. And at the temperature of 400℃, the bars have the best comprehensive mechanical properties with tensile strength of 296.7MPa, yield strength of 158.9MPa and elongation of 15.4%.
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    Effect of Austenitization Condition on the Martensitic Transformation in 675 Armor Steel
    QIAO Zhi-xia, LI Lian-jin, NING Bao-qun
    2014, 0 (7): 5-9.   DOI: 10.11868/j.issn.1001-4381.2014.07.002
    Abstract ( 970 ( PDF (1766KB)( 292 Citation
    The effect of austenitization temperature and holding time on the martensitic phase transformation in 675 armor steel was investigated using a combination of high-resolution dilatometric measurements and microstructural analysis, including prior austenite grains size, martensite morphology and martensitic transformation temperature (Ms). The results show that austenitization temperature has much more significant effect on prior austenite grains size than holding time at austenite region. Carbides of vanadium microalloying elements can completely dissolve into austenite when the austenitization temperature reaches about 1000℃, and thus ceases to be effective in pinning austenite grain boundaries. The length and width of martensite laths or needles increase with increasing austenite grain size, showing apparent characteristic of hereditary. The variation of Ms temperature is a synthetic effect of the austenite grain size and the dissolution extent of vanadium microalloying elements into austenite.
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    Electrochemical Behavior of PbO2 Electrode Modified by AEO for the Degradation of Methyl Orange
    FAN Ying-ying, CHEN Zhen, LI Jia-ying, FU Guo-bing, LIN Qiang
    2014, 0 (7): 10-15.   DOI: 10.11868/j.issn.1001-4381.2014.07.003
    Abstract ( 861 ( PDF (2795KB)( 299 Citation
    A set of PbO2 electrode modified by fatty alcohol ethoxylate (AEO) were prepared on stainless steel substrate by means of anodic oxidation. The surface morphology and phase compositions of the modified electrodes were measured by SEM and XRD respectively. Electrochemical properties of modified electrode were analyzed by steady state polarization method and cyclic voltammetry in simulated methyl orange wastewater, and the electrocatalytic degradation experiment was carried under simulated wastewater conditions with 10 mg·L-1 methyl orange. It is found that the modified electrode has smoother and denser surface compared with pure PbO2 electrode. And the modified electrode shows higher oxygen evolution potential and higher oxidation peak, which is conducive to the degradation of organic pollutants. The results of degradation experiments indicate that the modified electrode gets better electrocatalytic activity than the pure PbO2 electrodes and graphite electrodes.
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    Hot Deformation Behavior and Constitutive Relationship of Biomedical TC20 Alloy
    LIU Yan-hui, YAO Ze-kun, NING Yong-quan, GUO Hong-zhen
    2014, 0 (7): 16-21.   DOI: 10.11868/j.issn.1001-4381.2014.07.004
    Abstract ( 750 ( PDF (2488KB)( 187 Citation
    The hot compression behavior of TC20 alloy was investigated by Gleeble-1500 simulation at the deforming temperature range from 750℃ to 900℃ and the strain rate range from 0.001s-1 to 1.0s-1.The organizational structures and flow stress under the different temperature and strain rate were analyzed. The results show that the flow stress and the microstructure are influenced strikingly by both deforming temperature and strain rate;the flow stress decreases with increasing deforming temperature and decreasing strain rate. After work hardening of the rising stage, the flow stresses achieve hardening and softening equilibrium stability stage. The stress exponential n and deformation activation energy Q are obtained on the base of the hyperbolic sin constitutive equations, and they are 4.43 and 340.908kJ/mol, respectively. The constitutive equation of TC20 alloy is:ε=2.706×1016[sinh(0.0091σ)]5.72 exp[-340908/(RT)].
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    Electrochemical Corrosion Behavior of Copper in Marine Microbial Medium
    CHEN Hai-yan, LIN Zhen-long, CHEN Pi-mao, QIN Chuan-xin, TANG Zhen-zhao, YU Jing
    2014, 0 (7): 22-27.   DOI: 10.11868/j.issn.1001-4381.2014.07.005
    Abstract ( 987 ( PDF (2704KB)( 245 Citation
    The effects of salinity and microbe on the corrosion behavior of copper were investigated by using open-circuit potential of electrode, polarization curves and electrochemical impedance spectroscopy (EIS). Results show that in the sterile medium, the pure copper has more opportunity to corrode with the increase of salinity, because of the moving of the open-circuit potential towards negative direction. Scanning electron microscopy (SEM) reveals that the microbe adhesions on the copper mainly pole shape bacteria. The speed of corrosion in estuary water further increases with the microbe adhesions on the copper are higher in estuary water than in seawater.EIS results reveal that the transfer resistance and passive film resistance decrease with bacteria in estuary water and seawater. It indicate that the adhesion of marine microorganism accelerate the corrosion progress of pure copper.
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    Effect of Graphite on the Properties of Slag-free Self-shielded Flux Cored Wires
    LIU Da-shuang, LIU Ren-pei, WEI Yan-hong
    2014, 0 (7): 28-33.   DOI: 10.11868/j.issn.1001-4381.2014.07.006
    Abstract ( 765 ( PDF (2877KB)( 430 Citation
    A series of Fe-Cr-C slag-free self-shielded metal cored wires with different graphite contents were developed and their droplet transfer pattern, welding spatter characters, welding appearance, alloy microstructures and hardness were investigated. The results show that, as the graphite content increase from 0%-8%(mass fraction), the size of droplet is smaller, the transition frequency of droplet becomes faster. When the graphite content reaches 6%, the value of welding spatter is smallest; the welding appearance is excellent, which indicating that the wire possesses idea protection efficiency. Graphite promotes the formation of primary carbides but embarrasses the formation of eutectic carbides. Graphite is also in favor of the orientation of primary carbide vertical to the surface of specimen. With the graphite increasing, the hardness increases obviously, but it increases slowly and cracks appears when the graphite content exceeds 6%. The idea content of graphite added into the flux core is about 6%.
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    Effect of C/C Porous Preform on the Preparation and Properties of C/C-SiC Composites
    WANG Ling-ling, MA Wen-min, JI A-lin, CUI Hong, YAN Lian-sheng, HUANG Jian
    2014, 0 (7): 34-38.   DOI: 10.11868/j.issn.1001-4381.2014.07.007
    Abstract ( 817 ( PDF (1823KB)( 937 Citation
    Carbon fiber reinforced silicon carbide matrix (C/C-SiC) composites were prepared by precursor impregnation pyrolysis (PIP) process, using the four kinds of porous C/C composites with the same quasi-three dimensional needling preform but different pyrocarbon content filled by chemical vapor infiltration (CVI). The preparation and final performance of C/C-SiC composites have been investigated. The resullts show that the lower the density of C/C, the higher the open porosity and SiC matrix content of corresponding C/C-SiC. The existence of SiC matrix improves the bending strength of the C/C-SiC composite which was influenced significantly by the interfance of the fibers and matrix. The bending strength of the C/C-SiC composites produced of the C/C preform with the density of 1.35g/cm3 is the highest with the excellent fibers-matrix adhesion. It was also shown that with the increase of the SiC matrix content, the anti-ablative property improves observably.
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    Fast Preparation of Graphene Using High-energy Microwave Vacuum Radiation
    XUE Wei-jiang, YU Juan, DING Tao, ZHANG Shou-chun, WANG Ji-gang
    2014, 0 (7): 39-43.   DOI: 10.11868/j.issn.1001-4381.2014.07.008
    Abstract ( 929 ( PDF (1826KB)( 302 Citation
    Fast preparation of graphene via high-energy microwave irradiation was achieved. Rapid and complete exfoliation and in-situ reduction of graphite oxide film layer were realized in about 10 s under the strong unsteady state treatment composing of 6 kW-power microwave irradiation and low vacuum (≤35kPa) environment. Microstructure characterizations were carried out by using SEM, TEM, XRD, Raman and TG-DSC. Results show that the majority of the products are characterized with the stacking of 2-3 layers, and a very small amount of residual oxygen-containing functional groups remain in the sample. Meanwhile, due to the strong unsteady state treatment, the distribution of microwave energy or the exfoliation of carbon-rings can be founded in the resonant cavity, resulting in the existing of some graphene nanosheets characterized with the stacking of 10-20 layers. The result indicates that high-energy irradiation, combined with vacuum environment, benefits in the fast exfoliation and reduction of carbon-rings layers, and realizing the production of high quality graphene effectively.
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    Evolutions of Microstructure and Texture of Rolled Mg-1.5Zn-0.2Gd Alloy During Hot Rolled and Subsequently Annealed
    CAI Zheng-xu, TANG Di, JIANG Hai-tao, MA Zhao
    2014, 0 (7): 44-49.   DOI: 10.11868/j.issn.1001-4381.2014.07.009
    Abstract ( 785 ( PDF (3655KB)( 223 Citation
    Microstructure, texture and stretch formability of rolled Mg-1.5Zn-0.2Gd alloy during hot rolling and subsequently annealing were investigated. The results show that Mg-1.5Zn-0.2Gd alloy after hot rolling and annealing exhibits excellent elongation and high stretch formability, which is attributed to the reduction in basal texture intensity and the split of basal plane. After rolling at 450℃, the maximum texture intensity of the alloy is 3.4 and the elongation is 6.7% in RD direction. However, after annealing at 350℃ for 60min, the texture intensity of the alloy decreases and the maximum intensity is 2.3, and basal texture is tilted from TD, which result in the elongation increases to 26.7% in RD direction. EBSD analysis indicates that the addition of Gd hinders dynamic recrystallization (DRX) during hot rolling process. The nucleation and growth of non-basal orientation grains occur at the original high angle grain boundaries during the subsequent annealing, which plays an important role in the weakened basal texture intensity of the Mg-1.5Zn-0.2Gd alloy.
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    Research on Attenuation Correction in Nonlinear Ultrasonic Testing for Creep Status Evaluation of P91 Weldment
    YUAN Ke-yi, HAN Zan-dong, CHEN Yi-fang, ZHONG Yue-xian
    2014, 0 (7): 50-54.   DOI: 10.11868/j.issn.1001-4381.2014.07.010
    Abstract ( 879 ( PDF (1176KB)( 235 Citation
    The distortion of nonlinear ultrasonic measurement caused by attenuation was analyzed theoretically. According to practical testing condition, an attenuation correcting method was suggested, which used time domain energy as a correcting parameter. To verify this attenuation correcting method, P91 steels and welds with different creep status were selected as inspection objectives in a testing experiment. Attenuation corrected and non-corrected nonlinear ultrasonic measurement results of different creep status were compared respectively. And the results show that while creep is well developed or attenuation is large, the suggested method can effectively correct the distortion of nonlinear ultrasonic measuring results caused by attenuation. In other words, this method can evaluate creep status of P91 steels and welds more accurately.
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    Fatigue Crack Growth Behavior of Spray Formed GH738 Alloy
    YANG Dong-ye, CAO Fu-yang, XU Wen-yong, ZUO Xin, LI Zhou, ZHANG Guo-qing, SUN Jian-fei
    2014, 0 (7): 55-59.   DOI: 10.11868/j.issn.1001-4381.2014.07.011
    Abstract ( 715 ( PDF (1592KB)( 233 Citation
    The fatigue crack growth tests of spray formed GH738 superalloy with compact tension (CT) specimens were carried out at different temperatures, loading frequency and R-ratios. The effects of temperatures, loading frequency and R-ratios on fatigue crack growth behaviors were investigated .The results show that the crack propagation rate increases with the increase of temperature; Fatigue crack propagation increases with the decrease of loading frequency; Fatigue crack growth rate da/dN is also found to increase with the larger R-ratios. The crack initiates multi-sites, and the fatigue fracture individually exhibits a series of fatigue striations mode in the crack steady growth region.
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    Synergistic Accelerated Corrosion of Ultraviolet Irradiation on Epoxy Coating Aging Behavior
    LI Song-mei, LI Xiang-cheng, XIN Chang-sheng, LIU Jian-hua, YU Mei
    2014, 0 (7): 60-66.   DOI: 10.11868/j.issn.1001-4381.2014.07.012
    Abstract ( 813 ( PDF (2890KB)( 193 Citation
    The structure component, surface topography and electrochemical impedance spectroscopy features of the epoxy coating under two synergistic accelerated corrosions (moist heat-salt spray-fatigue and moist heat-ultraviolet-salt spray-fatigue) were investigated through FTIR, SEM and EIS. The surface topography of inter coating under synergistic accelerated corrosion without ultraviolet has no significant change. After 8 cycles, the edge of coating has fracture and corrosion on the base metal occurs under the coating. In the process of synergistic accelerated corrosion with ultraviolet, the surface roughness of the coating increase and produce powder and loss of light phenomenon after ultraviolet irradiation. Along with the accelerating period extension, coating surface has crackle and the quantity of coating surface crack increase. The results of FTIR indicate that the coating structure is unchanged under synergistic accelerated corrosion without irradiation. But the coating structure is changed obviously under synergistic accelerated corrosion with irradiation. The polymer chains rupture and keys O-H, C-H, C=C and benzene ring disappear. After 8 cycles, the electrochemical impedance value of synergistic accelerated corrosion with ultraviolet was only 1/2 of synergistic accelerated corrosion without ultraviolet.
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    High Temperature Thermal Fatigue Life Prediction of Plasma Sprayed Thermal Barrier Coatings Structure
    QI Hong-yu, MA Li-qiang, LI Shao-lin, YANG Xiao-guang, WANG Ya-mei, WEI Hong-liang
    2014, 0 (7): 67-72.   DOI: 10.11868/j.issn.1001-4381.2014.07.013
    Abstract ( 1123 ( PDF (1874KB)( 335 Citation
    According to the deformation characteristics of plasma sprayed ceramic thermal barrier coatings (TBC) structure and the summary of research for thermal fatigue life of TBC structure, high temperature oxidation test and thermal fatigue test of thermal barrier coating structures were designed and conducted. Based on the high temperature oxidation data and Fick's second law of diffusion, Al depletion model of bond coating was established. Then, Al concentration of bond coating was introduced to existing life prediction model. Combined with the thermal fatigue test data, life prediction model was established, which can characterize the coupling effect of oxidation damage and thermal fatigue damage. The life prediction results are reasonable and the method is feasible.
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    Synthetical Environmental Spectrum Aging of T300/5405 Advanced Composite Material
    CAO Dong, ZHANG Xiao-yun, LU Feng, LIU Jian-hua
    2014, 0 (7): 73-78.   DOI: 10.11868/j.issn.1001-4381.2014.07.014
    Abstract ( 889 ( PDF (3140KB)( 248 Citation
    Scanning electron microscope (SEM), dynamic mechanical analysis (DMA) and infrared spectra analysis (IR) were employed to investigate the absorption properties, flexural strength and shear strength of T300/5405 advanced composite material after synthetical environmental spectrum aging. The aging mechanism of composite T300/5405 was also discussed. The results show that the absorption properties exhibit no obvious change in different synthetical aging methods; the mechanical properties of the material are not relevant to synthetical aging method as well. SEM results show that discontinued ultraviolet radiation causes damage to the composite. Synthetical aging mode 4 exhibits greatest effect on the physical properties of composites and the glass transition temperature (Tg) decreases after aging.
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    Residual Stress and Deformation of Jointed 7022 Aluminum Alloy by FSJ
    WANG Hong-feng, ZUO Dun-wen, DAI Sheng, PAN Ling
    2014, 0 (7): 79-84.   DOI: 10.11868/j.issn.1001-4381.2014.07.015
    Abstract ( 991 ( PDF (2666KB)( 218 Citation
    FSJ process of 7022 aluminum alloy was simulated by the finite element method. The residual stress and deformation laws were obtained by the simulation. The simulation results were verified correctly by the experiments. The simulation shows that the residual stress is mainly concentrated in the jointing region. The maximum tensile stress is located in the middle of jointing region. The residual compressive stress is located in the ends and other parts of jointing region. The deformation in the advancing side in the direction of vertical the jointing region is greater than that in the retreating side. The tilting in the key eye side is higher than that in the staring side. The whole deformation is such as the saddle shape.
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    Censored Data Approximation Methods in Fatigue Reliability
    WANG Jing, ZHANG Yi-liang, LI Xiao-hui, HU Wei, LI Jin-wei
    2014, 0 (7): 85-91.   DOI: 10.11868/j.issn.1001-4381.2014.07.016
    Abstract ( 1032 ( PDF (1824KB)( 247 Citation
    For obtaining fatigue limit and dealing with censored data, the "pair-life-weighted" and "censored life approximation" methods were proposed. According to the fatigue testing of TA15 electron beam welded specimens, conventional methods and two methods in this article were used separately to calculate the fatigue limit and lognormal distribution parameters of the lives at different stress levels, and C-P-S-N curves were obtained and their corresponding mathematical expressions of 12 groups under 2 confidence and 6 reliability were expressed as a three-parameter model. The results show that the "pair-life-weighted method" is in good agreement with the traditional method, when the lives have a difference of 3 times at the same stress, the fatigue limit only have a difference of 0.5%, it is the further evidence of the practicability in engineering about the traditional method ;And the relative error of "censored life approximation" and conventional method is less than 1% in the life of N> 106 cycles; The confidence mainly affects the short-lived areas of fatigue curve, when N≥106 cycles, the stress error determined by 90% and 50% confidence level two curves is less than 4.5%.
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    Low-velocity Impact Response of 3D Braided Composites by Acoustic Emission
    YAN Shi, ZHAO Jin-yang, LU Xia-mei, ZENG Tao
    2014, 0 (7): 92-97.   DOI: 10.11868/j.issn.1001-4381.2014.07.017
    Abstract ( 686 ( PDF (2352KB)( 238 Citation
    The damage process of 3D six-directional carbon/epoxy braided composites with different braiding technological parameter under the low-velocity impact was investigated. The test procedure was monitored by the acoustic emission (AE) technique. The AE energy, amplitude and the peak frequency of a dominant frequency band after treated with the fast Fourier transform (FFT) were analyzed. And the waveforms of the type signals were discussed by spectral analysis. Results reveal that the behavior of AE parameters describes well the damage process on the low-velocity impact behavior.
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    Research Progress in Ferrite Based Core-shell Structured Composite Microwave Absorb Materials
    LIU Yuan, LIU Xiang-xuan, WANG Xuan-jun
    2014, 0 (7): 98-106.   DOI: 10.11868/j.issn.1001-4381.2014.07.018
    Abstract ( 1082 ( PDF (1695KB)( 1055 Citation
    The core-shell structured composite materials have become a research hotspot in recent years because of their unique physical,chemical properties and good microwave absorbing ability. The recent research on ferrite-based core-shell structured composite microwave absorb materials are reviewed. Firstly, the research progress of core-shell structured absorbing materials principle is introduced, and then grouped the ferrite-based core-shell structured composite absorbing materials into four major categories, metal the micropowder/ferrite, composite of different types ferrite composite, conductive polymer/ferrite composites and the other composite. Finally, it is pointed out that the future research problems to be solved and the development direction of ferrite-based core-shell structured composite absorber.
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    Optimum Mix Ratio of Hybrid Fiber Reinforced Polymer Composites and Their Researching Progress
    ZHANG Bo-ming, LI Jia, LI Xu
    2014, 0 (7): 107-112.   DOI: 10.11868/j.issn.1001-4381.2014.07.019
    Abstract ( 780 ( PDF (1071KB)( 639 Citation
    Hybrid composites had been developed rapidly and used widely due to their low cost and good performance. The proportion of fibers not only affects the properties, but also the costs. This article described the advantages of performance of the hybrid composites. The suitable proportion led to the best performance and the best proportion led to the suitable costs from reports were also been described. The latest application and the disadvantage of the hybrid composites were introduced. This paper presents a review of the future of hybrid composites.
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