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      20 November 2012, Volume 0 Issue 11 Previous Issue    Next Issue
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    Microstructure and Wear Behaviors of In-situ Al2O3P/7075 Composites
    LIU Hui-min, YANG Shu-qing, XU Ping, LI Jin-fu
    2012, 0 (11): 1-5.  
    Abstract ( 631 ( PDF (2983KB)( 374 Citation
    The Al2O3P/7075 Al composites were synthesized by in-situ reaction near-liquidus casting. The microstructure and dry sliding wear behavior of the prepared composites were analyzed using OM, SEM and TEM as well as wear friction testing. The results reveal that in-situ Al2O3 particle with average size of approximately <1μm is uniformly distributed in the matrix, which exhibits desirable refining effects on microstructure of 7075 Al alloy. The wear behavior of the composites is greatly superior to that of the matrix, which is attributed to the grain refining and formation of a compact interface of Al2O3P/7075 Al composites. In addition, in-situ Al2O3 particles exhibit coupling effects of inhibiting metal flow and bearing some load in process of friction. The wear mechanism of the matrix 7075Al alloy is adhesive wear, while the wear surface of Al2O3P/7075 Al composites is superior to that of the matrix 7075 Al alloy. The wear mechanism of Al2O3P/7075 Al composites is abrasive wear, and wear resistance of Al2O3P/7075 Al is improved.
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    Microstructure and Mechanical Properties of Inconel 625 Components Deposited by Pulsed Plasma Arc Rapid Prototyping
    XU Fu-jia, LU Yao-hui, LIU Yu-xin, HE Peng, SHU Feng-yuan, XU Bin-shi
    2012, 0 (11): 6-11.  
    Abstract ( 730 ( PDF (2393KB)( 486 Citation
    The microstructure and mechanical properties of Inconel 625 component deposited by pulsed plasma arc rapid prototyping were investigated. The precipitation principle and distribution characteristics of phases in deposits were analyzed. The results indicated that the as-deposited samples exhibited homogenous cellular dendrite structure in nature, which grew epitaxially along the deposition direction. The microstructure of the interface regions between deposited layers exhibited refined structure. The composition distribution in the whole sample was pretty uniform and no significant segregation occurred. Some intermetallic phases such as Laves phase, some minor MC (NbC, TiC) and needle-like δ (Ni3Nb) were observed in γ-Ni matrix. Disperse MC particles precipitates in interdendritic and grain boundary. Micro-hardness measured at various location (including transverse plane and longitudinal plane) revealed hardness in the range of 260-285HV0.2. Due to highly refined structure,micro-hardness at the interface region is slightly higher than the other regions. Ultimate tensile strength of Inconel 625 sample deposited as short raster pattern was found to be 750MPa, and the percentage elongation was found to be 50%.
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    Effects of Mn Addition on Corrosion Resistance of Mg-5Al Magnesium Alloy
    ZHOU Gui-bin, LIU Zi-li, LIU Xi-qin, ZHU Xiao-chun, LI Jian
    2012, 0 (11): 12-17,22.  
    Abstract ( 725 ( PDF (2993KB)( 373 Citation
    The effects of Mn content on microstructure and corrosion behavior in NaCl solution of as-cast Mg-5Al alloy have been studied. The results show that with the addition of Mn, Al8Mn5 phase forms preferentially and the grain is refined obviously, meanwhile, the continuous or semi-continuous net-like β-Mg17Al12 phase is converted into discontinuous or dispersed one and the amount of β-Mg17Al12 phase reduce. With increase addition of Mn, the corrosion rate and corrosion current of the alloys are reduced whereas the film and charge resistance are improved, indicating that the corrosion resistance of the alloys is improved remarkably. The alloy with 0.5% Mn has the best corrosion resistance, and the corrosion rate is only 1.08mg·cm-2·d-1, which is decreased 72% compared with the alloy without Mn addition.
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    Behavior of Al Basic Sacrificial Anodes Containing Ga Element Under Wet and Dry Condition
    SONG Gao-wei, HUANG Yan-bin, DING Hua-dong, BA Guo-zhao, YAN Yong-gui
    2012, 0 (11): 18-22.  
    Abstract ( 658 ( PDF (1801KB)( 278 Citation
    The activation mechanism of anodes under condition of wet and dry cycle and effect of Ga content on anodes performance of Al-Zn-In-Mg-Ga-Mn was investigated. The results show that the anodes performance of Al-Zn-In-Mg-Ga-Mn under condition of wet and dry cycle is best when the Ga content is 0.02%(mass fraction). With the increase of Ga content, Ga is enriched at the grain boundary where was dissolution firstly because activation of Ga, which resulted grain flaked away and its current efficiency decreased. In the process of anodes dissolution, Ga and In both redeposited on the surface of anodes and oxide film was destroyed which promoted anodes to dissolve efficiency.
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    Failure Analysis on an Auto Hub Axle
    HU Chun-yan, LIU Xin-ling
    2012, 0 (11): 23-26.  
    Abstract ( 844 ( PDF (1816KB)( 346 Citation
    An auto hub axle was fractured after the service of 17km, the material of the auto hub axle is 65Mn spring steel. The failure feature and cause of the auto hub axle were analyzed by appearance observation, micro and macro observation on fracture surfaces, metallographic examination, hardness testing and chemical analysis. The results show that the fracture mode of the auto hub axle is fatigue fracture. The main cause of the forging cracks was massive defect in the end of raw material of auto hub axle which due to short of cutting output.
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    Randomness Characterization of Microstructure of WC-Co Cemented Carbides
    WANG Dong, ZHAO Jun, LI An-hai
    2012, 0 (11): 27-30,76.  
    Abstract ( 925 ( PDF (1942KB)( 305 Citation
    In order to characterize the randomness of microstructure of WC-Co cemented carbides, Matlab and VC++ were hybrid programmed to analyze the scanning electron microscopy (SEM) images of the microstructure, and the outline of the microstructure was extracted. Then the microstructural topology parameters were calculated, and the distribution regularity of the microstructural parameters was statistically investigated. The results show that, the average grain diameter, major axes and minor axes, centroid, orientation angle, and Co volume fraction of WC-Co cemented carbides can be accurately measured by using the image processing software. Moreover, the randomness characterization of the microstructure of WC-Co cemented carbides can be well accomplished by using probability density function.
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    Study of Environmental Aging of T700/5288 CFRP in Hainan
    ZHANG Dai-jun, TANG Bang-ming, BAO Jian-wen, LIU Gang
    2012, 0 (11): 31-33,56.  
    Abstract ( 720 ( PDF (1747KB)( 318 Citation
    The experiment of natural aging durability of T700/5288 carbon fiber reinforced plastic in the Wanning (Hainan Province) under the South China Sea environmental condition was carried out. The specimens were placed in natural environment for three years. Microscopic morphology, mechanical properties and thermal properties were researched. The result showed that the presence of thermo-oxidative aging and photo-oxidative aging caused the composite surface epoxy chemical degradation, surface fibers exposed, the specimen longitudinal compressive strength decreased by 19%, transverse compressive strength decreased by 14%. The other mechanical properties remained basically unchanged. The glass transition temperature was reduced by 27℃.
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    Preparation and Properties of Polydimethysiloxane/Polycaprolactone/Epoxy Resin Composites
    HE Li-hua, LIU Ping-gui, DING He-yan
    2012, 0 (11): 34-37,71.  
    Abstract ( 742 ( PDF (1755KB)( 443 Citation
    A series of resin composites were prepared by blending epoxy and Silyl-terminated polyprolactone/polydimethysiloxane (PCL-TESi/PDMS-TESi). The morphology and the surface element of composites system were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy. Mechanical properties, water-resistance properties and thermal properties of the composites were also studied. The results showed that the morphologies, mechanical properties, water resistance properties and thermal properties of the composites were quite dependent on the content of PCL-TESi/PDMS-TESi. The Si element migrated toward surface to some extent. When mass ratio of PCL-TESi/PDMS-TESi and epoxy was 5∶5, the mass change of composite is below 1% after soaked in distilled water at 50℃ for 7 days, the elongation rate at break increased from 0% to 27% while tensile strength remain 23MPa, and in thermogravimetry analysis (TGA), the characteristic decomposition temperature at 5% mass loss was evidently increased from 155.8℃ of pure epoxy to 310.2℃.
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    Fatigue Behavior of 30Cr1Mo1V Rotor Steel at Elevated Temperature After Long-term Service
    YAN Yi-min, HU Zheng-fei, LIN Fu-sheng, ZHAO Shuang-qun
    2012, 0 (11): 38-41,96.  
    Abstract ( 1091 ( PDF (1527KB)( 318 Citation
    The low cycle fatigue and fatigue crack growth rate tests are described in the detail for a steam turbine rotor steel 30Cr1Mo1V which had been in service for 16 years. Three typical sections of the examined rotor, i.e. high-temperature, high-stress and medium-stress, were experimented at 538℃. The test results shows that the property of the high temperature section is degraded most severely and the high stress section takes the second place. The corresponding microstructure observations show that the original sorbite structure decomposed almost completely in high temperature and high stress sections. Carbides were coarsened or spheroidized strikingly, with a continuous chain of large size carbides present in the grain boundary. A few microvoids were found at grain boundary in the high temperature section. These phenomena in microstructure might be the reasons for properties degradation.
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    Rapid Synthesis and Photocatalytic Performance of Milky and Rod-like Nanometer Zinc Oxide by Combustion Method
    ZHAO Rong-xiang, LI Xiu-ping
    2012, 0 (11): 42-46,51.  
    Abstract ( 618 ( PDF (1781KB)( 315 Citation
    Zinc nitrate as the oxidant, ascorbic acid as reducing agent and combustion agent, milky and rod-like zinc oxide rapid synthesized by combustion method. The sample was characterized by XRD, IR, UV, SEM. The Rhodamine B acted as target of degradation, the experiment inspected various sample, illumination time, dosage of zinc oxide, dosage of H2O2, pH value and rotation speed of centrifuge impact on photocatalytic degradation of Rhodamine B. The optimal experiment conditions: zinc nitrate: ascorbic acid is 1∶3, ZnO of 0.4g/50mL,H2O2 of 0.2mL/50mL, pH value 8, rotating at 2500r/min, Rhodamine B faded to colorless in 150min.
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    Study on the Interrupted Aging Treatment of Al-Cu-Mg-Ag Heat-resistant Alloy
    PAN Qing-lin, LIU Xiao-yan, CAO Su-fang, LU Zhi-lun, HE Yun-bin
    2012, 0 (11): 47-51.  
    Abstract ( 624 ( PDF (1892KB)( 320 Citation
    The effects of the interrupted aging treatment on the microstructure and the properties of the Al-Cu-Mg-Ag alloy were studied by means of HV hardness tests, tensile testing and transmission electron microscopy (TEM), respectively. The results show that the lower secondary aging temperature for interrupted aging process accelerated the precipitations of θ' but restrained the precipitations of Ω. And correspondingly, it decreased the strength of the alloy and increased the elongation of the alloy. Whereas the higher secondary aging temperature accelerated the precipitations of Ω and refined its size, but restrained the precipitations of θ', and it could also modify the distribution of the particles on the grain boundaries which led to the enhanced strength and elongation of the alloy. The suitable interrupted aging process for Al-Cu-Mg-Ag alloy was 185℃/2h+150℃/6h.
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    Synthesis and Study of Functional Polymer Viscosity Reduction Materials for Crude Oil
    LU Xiao-bo, WEI Yun-he, YU Ping, MU Chun-ling, ZHANG Chang-qiao
    2012, 0 (11): 52-56.  
    Abstract ( 748 ( PDF (1743KB)( 421 Citation
    A new functional polymer which derived from mixed ester, styrene, and 4-vinyl pyridine monomers was synthesized by solution polymerization and simulated by Materials Studio. When obtained, the polymer was characterized by Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), gel permeation chromatography(GPC), and differential scanning calorimetry (DSC). Later, it was added to ShengLi crude oils, and evaluated by scanning electron microscopy (SEM) and RS rheogoniometer, then the viscosity reduction mechanism was discussed. Results indicate that the polymer shows a good performance for the oil, and it is observed that the visbreaking rate is up to 79% at temperature 30℃ when the amount of the copolymer is 463×10-6.
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    Investigation on the Cellular Structure and Mechanical Properties of SGF/PP Foam Composites Modified with PP-g-MAH
    YANG Ji-nian, LI Zi-quan
    2012, 0 (11): 57-60,65.  
    Abstract ( 786 ( PDF (2310KB)( 404 Citation
    The short glass fiber (SGF)/polypropylene (PP) foam composites modified with maleic anhydride grafted PP (PP-g-MAH) were prepared via post-foaming process in designed dies. The influence of PP-g-MAH content on the cellular morphologies, microstructures and mechanical properties of composites were investigated. The results show that the outstanding improvement in foaming effect is realized by the addition of PP-g-MAH with a 35% reduction for average cell size and nearly four-fold increase in cell density. The compatibilities between SGF and PP are improved and their interfacial adhesion is enhanced significantly by the surface pretreatment of coupling agent as well as PP-g-MAH. The flexural strength of SGF/PP foam composites is increased first and then decreased. However, the impact strength exhibits the trend of rapid increasing and then moderating with the increase of PP-g-MAH.
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    Early Fatigue Damage Evaluation of 321 Stainless Steel by Eddy Current Method
    LIU Kun-peng, ZHAO Zi-hua, ZHANG Zheng
    2012, 0 (11): 61-65.  
    Abstract ( 740 ( PDF (2115KB)( 284 Citation
    The early fatigue damage of AISI 321 stainless steel was conducted evaluation by eddy current array. In the fatigue test, the change of eddy current amplitude could be divided into three stages: rapid growth, stability and accelerated growth. The relationship between the eddy current amplitude and the logarithmic fatigue life was nearly linear at the first stage. The area of fatigue damage was not changed in the fatigue crack initiation life. Microstructure with different fatigue cycles indicated that the dislocation proliferation and interaction were the main reasons for the increasing of eddy current amplitude at the beginning of fatigue.
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    Study on the Orientation of Pre-oxidized PAN Fiber in Steady-state High Magnetic Field
    REN Xiao-meng, WANG Yuan-sheng, MEI Yong-jia, XIA Zheng-cai, HE Te
    2012, 0 (11): 66-71.  
    Abstract ( 656 ( PDF (1803KB)( 244 Citation
    The orientation of pre-oxidized PAN fiber (POF) was one of the critical factors which could determine the performance of subsequent carbon fibers. The POFs treated at 240, 260, 280, 300℃ were processed in a steady-state high magnetic field for 10min, 30min, 50min respectively. And the magnetic field was generated by PPMS. The effect of magnetic field on overall orientation and crystalline orientation was investigated and the reason for orientation was analyzed. The results showed that here were two kinds of magnetic units which were cyano and carbon-nitrogen heterocycle in POF. The orientation of POFs was modified due to the movements of magnetic units. The overall orientation increased as the magnetic field intensity enhanced and the processing time extended. However, the crystalline orientation increased in the initial stage and decreased later. Furthermore, the magnetic field facilitated the conversion from amorphous to crystal region and improved the crystal size and crystallization.
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    Research on Rotomoulding Mould Based on Incremental Forming
    XU Zhen-ying, ZHANG Kai, WANG Yun, WU Jun-feng, QIAN Zheng
    2012, 0 (11): 72-76.  
    Abstract ( 601 ( PDF (1644KB)( 435 Citation
    Sheet metal incremental forming (SMIF) has been applied to the rotomoulding formation of single-person slider. After introducing the forming principle of the single-person slider mould of rotomoulding, the experimental forming results of the mould of single-person slide with three forming parameters were compared. The failures and defects emerged from forming process were analyzed based on the structural characteristics of the product. The influencing law of the forming parameters on the forming of product was studied. It was found that all of the foresaid factors affected the shape quality. To obtain high quality products, the process variables need to be optimized. It shows that it is feasible to use SMIF to form mould of rotomoulding, and specific parameters, such as manufacturability, amount of feed, tool parameters and processing parameters, should be considered to ensure the high-quality forming.
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    Reasearch on Phytic Acid Passivation Technology of Stainless Steel and Corrosion Resistance
    WANG Hai-ren, SHI Ri-hua, QU Jun-e, LIU Shao-bo, CHEN Geng, GUO Xing-peng
    2012, 0 (11): 77-81.  
    Abstract ( 1128 ( PDF (1396KB)( 334 Citation
    The effect of process parameters of phytic acid passivation on the corrosion resistance performance of the stainless steel passivation film was studied by polarization curves, AFM and infrared spectrum testing. And the optimal process parameters were determined to obtain passivation film with excellent performance. For the phytic acid passivation method, the raw materials is easy to be obtained with low prices,and the operation is convenient.Moreover,passivation process does not produce poisonous and harmful substances,so it is a kind of high-efficiency environmental friendly passivation treatment method.
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    Effect of Pre-strain on Hot Ductility of Nb-microalloyed 09MnNiDR Cryogenic Steel
    LI Jian-hua, WU Kai-ming, QIU Jin-ao
    2012, 0 (11): 82-85,91.  
    Abstract ( 660 ( PDF (2133KB)( 340 Citation
    The effect of tensile pre-strain on the hot ductility of the Nb-microalloyed 09MnNiDR cryogenic steel was investigated by examining microstructures of the tensile fracture using optical microscopy and electron microscopy, and by measuring the reduction of area. When 5% tensile pre-strain was applied at 800℃, the microstructure was composed of ferrite grains and lots of grain boundary ferrite allotriomorphs along grain boundaries, the reduction of area being 63%. When it was applied at 900℃, the microstructure was composed of bainite, acicular ferrite and lots of massive grain boundary carbonitrides, the reduction of area falling to 35%. When it was applied at 1000℃ the microstructure mainly consisted of lath-like martensite, the reduction of area climbing up to 95%. Comparing with the specimens without applying pre-strain, the reduction of area of the specimens applied with pre-strain between 800℃ and 920℃ dropped remarkably. Results indicate that pre-strain severely deteriorated the hot ductility of the Nb-microalloyed 09MnNiDR cryogenic steel, which was mainly attributed to precipitation of grain boundary niobium carbonitride (10-100nm).
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    Review on the Structure/Damping Cocured Composite Materials and Their Applications
    ZHAO Yun-feng, YOU Shao-xiong
    2012, 0 (11): 86-91.  
    Abstract ( 1106 ( PDF (797KB)( 325 Citation
    The structure/damping cocured composites is a new technique developed about 20 years ago. This paper gives a comprehensive review on this new kind of materials and its applications. By applying the structure/damping cocured composites, the mode damping factor of the structure is obviously increased, and the magnitude and respond of vibration of the structure is decreased, and its mass is reduced about 40%. The practical examples showed that the composites are not only with a high rigidity and strength, but also have a higher damping factor. These would provide a better environment for the instrument installed on the structures. Therefore, it is a good vibration-reduction treatment method with a prospective application in the field of aerospace.
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    Progress of Actively Cooled Ceramic Matrix Composites Applied in Advanced Propulsion Systems
    LI Wei, CHEN Zhao-hui, WANG Song
    2012, 0 (11): 92-96.  
    Abstract ( 967 ( PDF (620KB)( 330 Citation
    Actively cooled ceramic matrix composite technology is a novel thermal management concept for advanced propulsion systems e.g. scramjet engine, cryogenic rocket engine and gas turbine engine etc.. Combining both advantages of refractory materials and cooling structures, the concept is able to meet high performance goals at improving operating temperature margin, lower weight, increasing payloads and range, which is identified as a key technology for enabling reliable and low-cost space access. Through the collaborative efforts between US and Europe, this technology development is undergoing the transition from theoretical research and sub-scale investigation to full scale components fabrication for ground tests. In this concept,the integrated design that all CMC structure with built-in regenerative cooling channels or effusion holes by innovative preforming techniques are more efficient and feasible, thus is regarded as the most promising one for future propulsion system applications.
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