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      20 September 2014, Volume 0 Issue 9 Previous Issue    Next Issue
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    Precipitation and Models at Ferrite Phase Zone for Niobium Bearing Steel Under Ultra Fast Cooling Conditions
    ZHOU Xiao-guang, WANG Meng, LIU Zhen-yu, YANG Hao, WU Di, WANG Guo-dong
    2014, 0 (9): 1-7.   DOI: 10.11868/j.issn.1001-4381.2014.09.001
    Abstract ( 881 ( PDF (3083KB)( 302 Citation
    Precipitation behaviors at ferrite phase zone for Nb bearing steel under ultra fast cooling conditions were investigated by using Gleeble-3800 thermomechanical simulator. Corresponding models were also obtained by considering solid solubility of Nb(C, N) and diffusion coefficient at ferrite phase zone. The results indicate that entering ultra fast cooling immediately and cooling to 650℃(ferrite phase zone) after rolling can restrain precipitation of Nb at austenite phase zone and realize precipitation at ferrite phase zone. Compared with precipitation behavior at austenite phase zone, the number of precipitates increases and sizes of precipitates are refined obviously at ferrite phase zone. The density of precipitates increases from 79 number·μm-2 to 373 number·μm2 and sizes of precipitates are refined from 12.9nm to 8.1nm. This can embody the effect of precipitation strengthening. The temperature of the maximum nucleation rate and the fastest precipitation are about 620℃ and 700℃ for the Nb bearing steel, respectively. The calculated and experimental volume fractions of precipitation are in good agreement. It proves that these models can simulate precipitation behavior of Nb at ferrite phase zone under ultra fast cooling conditions.
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    Preparation and Abradability Evaluation of Aluminum Bronze Polyester Abradable Sealing Coating
    YANG Jie, AN Yu-long, ZHAO Xiao-qin, CHEN Jie, ZHOU Hui-di, CHEN Jian-min
    2014, 0 (9): 8-13.   DOI: 10.11868/j.issn.1001-4381.2014.09.002
    Abstract ( 1014 ( PDF (3253KB)( 204 Citation
    CuAl-polyester composite powders were prepared by mechanical mixing fine polyester powders and CuAl alloy powders with irregular shape. This mixed powder and a commercial CuAl-polyester Metco 605NS were used for depositing abradable sealing coatings by atmosphere plasma spraying. Sliding wear tests against Ti6Al4V alloy at different temperatures were conducted on the two kinds of sealing coatings to compare their abradability. The results show that at room temperature and 200℃, the coatings obtained from the mixed powder have friction coefficients about 0.4 and smooth wear scars, as well as better abradability than the coatings deposited by the commercial powder. While at 400℃, adhesive spalling and abrasive wear are observed in Ti6Al4V, and the friction coefficients of both coatings increase and are unstable which should be attributed to the burn of polyester and the densification of the coatings, as well as the point contact mode of the wear tests which is apt to generate higher Hertzian stress.
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    Microstructures and Properties of AZ31/7005 Dissimilar Joints by GTAW with Filler Wire
    DU Hong-yan, LI Ya-jiang
    2014, 0 (9): 14-19.   DOI: 10.11868/j.issn.1001-4381.2014.09.003
    Abstract ( 900 ( PDF (3296KB)( 244 Citation
    AZ31/7005 dissimilar materials were welded successfully by using gas tungsten arc welding (GTAW) with ER4043 and ER4047 welding wire of Al-Si system. Microstructure of the joints was observed and microhardness of the joints was analyzed. The results indicate that joints with good surface and free defects are achieved by GTAW.The fusion zone near magnesium side is the weak zone for mechanical performance of the joints. Contents of Mg and Al keep stable in the fusion zone near magnesium. The fusion zone is mainly composed of Mg17Al12+Mg eutectic microstructure. There is no obvious high hardness brittle phase in the fusion zone near magnesium side. The hardness of joints is slightly higher than that of Mg base metal, but far less than that of Al base metal.
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    Numerical Simulation of Contact Stress on Y-TZP/LZAS Glass-ceramic Gradient Coatings on Q235 Steel Substrate
    GONG Wei, ZHOU Li-ming, WANG En-ze, BAI Chao-zhong
    2014, 0 (9): 20-25.   DOI: 10.11868/j.issn.1001-4381.2014.09.004
    Abstract ( 935 ( PDF (2146KB)( 322 Citation
    The contact stress of the Y-TZP/ LZAS glass-ceramic gradient coatings on Q235 steel substrate under Hertz contact conditions was investigated by using finite element software. The effects of coating thickness, the number of graded layers and graded modes of physics properties (the volume difference of 3Y-TZP in various gradient layers) on the distributions of contact stress were discussed. The results show that the maximum radial contact stress and Mises stress of the coating occur at the contact center, and the maximum shear stress lies beneath the outer layers of coating, and near the contact center. The number of layer, the coating thickness, and the volume difference of 3Y-TZP in various gradient layers have an important influence on the surface radial stress, Mises stress and the shear stress.
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    Microstructure and Property of High-frequency Induction Brazed Joints of Titanium Alloy TC4 and Cemented Carbide YG8
    SHAO Chang-bin, XIONG Jiang-tao, SUN-Fu, ZHANG Fu-sheng, LI Jing-long
    2014, 0 (9): 26-31.   DOI: 10.11868/j.issn.1001-4381.2014.09.005
    Abstract ( 945 ( PDF (3294KB)( 374 Citation
    High-frequency induction brazing in vacuum was carried out between titanium alloy TC4 and cemented carbide YG8 by using copper based brazing filler metal B-Cu64MnNi at 920-970℃ for holding time of 20s. The microstructure, elements distribution and the phases of the joint were analyzed by SEM, EDS and XRD. The tensile strength of the joints was tested. The fracture surface morphologies and elements distribution were analyzed. The results indicate that the interface structure of the joints is composed of TC4/β-Ti/TiCu+Ti3Cu4+TiMn+Cu(Mn, Ni)/YG8, which shows an embedded structure when the temperature changes from 920℃ to 940℃. As the brazing temperature increases, the embedded structure is thus destroyed due to the overgrown brittle TiMn intermetallics, which also leads to the degradation of the mechanical properties. The maximum tensile strength of 206MPa is achieved at 930℃.
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    Effect of Annealing Temperature on Structure and Optical Properties of Ge/SiO2 Multilayer Films
    PENG Jie, LI Zi-quan, LIU Jing-song, JIANG Ming, XU Qi
    2014, 0 (9): 32-38.   DOI: 10.11868/j.issn.1001-4381.2014.09.006
    Abstract ( 760 ( PDF (3356KB)( 304 Citation
    Multilayered (Ge/SiO2)15 film was deposited on quartz by radio frequency (RF) magnetron sputtering technique, and then annealed at different temperatures. XRD and Raman results indicate that the as-deposited film is amorphous. When the film is annealed at 500℃, obvious crystal diffraction peaks occur, and then the crystallinity of the film increases. When the annealing temperature goes beyond 600℃, the crystallinity of the film remains stable. The results of the FESEM and small angle X-ray diffraction(SAXRD) show that the distinct interface between the layers is observed in the as-deposited film, exhibiting periodic structure. As the annealing temperature increases, the film still keeps periodic structure and its crystal size increases. The UV-VIS spectra suggest that increasing annealing temperature leads to the red shift of absorption edge, and optical band gap of as-deposited sample reduces from 1.86eV(as-deposited) to 1.59eV (600℃).
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    Influence of Nano-alumina Particles on Glass Transition Temperature of High-performance Epoxy Resin
    ZHANG Zong-hua, LIU Gang, ZHANG Hui, ZHANG Zhong, WANG Xiao-qun
    2014, 0 (9): 39-44.   DOI: 10.11868/j.issn.1001-4381.2014.09.007
    Abstract ( 968 ( PDF (2401KB)( 517 Citation
    Alumina/epoxy composites were prepared by mechanical mixing technique. The effect of filler content and surface modification of the nano-alumina on the glass transition temperature (Tg) of epoxy composites was investigated. The result shows that the addition of micron-sized alumina particles does not change the Tg of epoxy polymer, but the unmodified nano-alumina affects the Tg of epoxy composites. There is a significant drop in Tg of the epoxy samples when the filler content is above 10% (mass fraction). At the filler content of 18%, the Tg of the nanocomposite sample declines by as much as 25℃ in comparison with that of the neat epoxy sample. Comparatively, the surface-modified nanoparticles have better compatibility with epoxy resin than the un-modified ones, and thus showing minor thickening effect.
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    Optimization and Tribological Performance of Engineering Ceramics via Representative Metals Pairs
    TIAN Xin-li, WANG Long, WANG Peng-xiao, WU Zhi-yuan, ZHANG Bao-guo, WANG Jian-quan
    2014, 0 (9): 45-50.   DOI: 10.11868/j.issn.1001-4381.2014.09.008
    Abstract ( 841 ( PDF (1891KB)( 297 Citation
    The friction and wear orthogonal tests for three types of engineering ceramics such as Si3N4, SiC, ZrO2 and representative metals such as 45 steel, GCr15 bearing steel, tin bronze QSn4-3, tin-based babbit ZChSnSb8-4 under oil-less lubrication were carried out. The results show that ceramics-metals pairs possess good tribological performance on the whole. The friction coefficients are between 0.1-0.25. The wear rates of ceramics and metals are 10-7mm3/(N·m) in magnitude. The friction coefficient of Si3N4-babbit is the lowest, and so is the wear rate of SiC-babbit. Due to the self-lubricating property of Si3N4, Si3N4-metals have better tribological performance prominently as a result of oxide film formed on the surface. As the material of the pair sample, tin-based babbit is able to form film of metals oxide, which shows that it possesses better tribological performance than the other tested metals. The Si3N4-babbit pair has the optimum tribological performance.
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    Microstructural Evolution and Deformation Mechanism of 5A90 Al-Li Alloy During Superplastic Deformation
    ZHANG Pan, YE Ling-ying, GU Gang, JIANG Hai-chun, ZHANG Xin-ming
    2014, 0 (9): 51-56.   DOI: 10.11868/j.issn.1001-4381.2014.09.009
    Abstract ( 987 ( PDF (2700KB)( 272 Citation
    The microstructural evolution and deformation mechanism of 5A90 Al-Li alloy sheets during superplastic deformation were studied by optical microscopy, scanning electron, electron back scattering diffraction and high temperature tensile test. The results show that the elongation of the specimen, which is recrystallized at 450℃ for 30min before the tensile test, could increase from 480% to 880% at an appropriate superplastic condition of 475℃/8×10-4s-1. The superplastic mechanisms of 5A90 Al-Li alloy sheets are explored by investigating the microstructural evolution. The misorientation increases and dislocation activity plays a key role at the initial stage (ε≤0.59). Dynamic recrystallization begins to occur when the true strain reaches 0.59. With recrystallization, the misorientation between grains becomes larger and grain boundary sliding (GBS) starts at this stage (0.59<ε<1.55). With larger true strains (ε≥1.55), grain continues to grow with a stable microstructure, and superplastic mechanism is dominated by GBS.
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    Microstructures and Wear Resistance of Fe-Cr-B-C Hardfacing Alloys
    WANG Zhi-hui, WAN Guo-li, HE Ding-yong, JIANG Jian-min, CUI Li
    2014, 0 (9): 57-62.   DOI: 10.11868/j.issn.1001-4381.2014.09.010
    Abstract ( 903 ( PDF (3945KB)( 382 Citation
    Fe-Cr-B-C hardfacing alloys were deposited by flux-cored wire using metal active gas arc welding (MAG). The effect of boron contents on the microstructures and boride morphologies of the hardfacing alloys was analyzed by optical microscopy(OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicate that the microstructures of Fe-12Cr-xB-0.1C alloys consist of ferrite, austenite, (Fe, Cr)2B, and (Fe, Cr)23(B, C)6. The morphology of borides transforms from the discontinuous network to continuous network gradually with boron content increasing to 3% (mass fraction). As the boron content is higher than 3%, the amount of massive primary (Fe, Cr)2B increases with the increasing of boron contents. Meanwhile, the size and distributing of (Fe, Cr)2B become more homogeneous. The morphology of primary boride has many kinds of distribution shape, including massive, strip, fish-bone-like, honeycomb and chrysanthemum. The shape of the primary (Fe, Cr)2B is quadrangular column which tends to grow perpendicular to the overlayer surfaces. Increasing boron content can significantly improve the hardness and abrasive wear resistance of Fe-Cr-B-C hardfacing alloys when the boron content is lower than 4%.
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    Superplastic Deformation and Constitutive Equations of TC4-DT Alloy
    ZHENG Man-qing, WANG Gao-chao, XU Xue-feng, YU Miao-zhen
    2014, 0 (9): 63-67.   DOI: 10.11868/j.issn.1001-4381.2014.09.011
    Abstract ( 958 ( PDF (1731KB)( 345 Citation
    Superplastic deformation tests of TC4-DT alloy were performed with a superplastic tensile testing machine CMT4104. The constant strain rate method and the strain rate circulation method were used. In the constant strain rate test, the strain rate was fixed at 3.3×10-4 s-1 and the temperature was fixed at 870℃; in the strain rate circulation test, the strain rates were tuned from 3.3×10-5s-1 to 3.3×10-3s-1 and the temperature was from 850℃ to 890℃ respectively. The results show that dynamic recovery and dynamic recrystallization occur during the superplastic deformation and the dynamic recrystallization kinetics behavior can be described by Avrami equation. The experimental results of the strain rate circulation method were used to establish the constitutive relationship of the TC4-DT alloy. Regression analysis was carried out with the 1stopt software and a precise constitutive equation for superplastic deformation of the TC4-DT alloy is obtained.
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    Metal Flowing Behavior During Welding Process of Porthole Extrusion for Complicate Al-alloy Profile
    HUANG Dong-nan, YU Yang, LI You-lai, ZUO Zhuang-zhuang
    2014, 0 (9): 68-75.   DOI: 10.11868/j.issn.1001-4381.2014.09.012
    Abstract ( 995 ( PDF (3971KB)( 687 Citation
    Using FEM combined with mesh reconstruction technology in welding zone, the metal flowing behaviors during welding process of porthole extrusion for a complicate profile were obtained. The die construction, including adjusting the porthole area, position, the expanding angle, was optimized. After optimizing, the number of metal planes welding simultaneously increases from 1 to 5. The homogeneity of the metal flowing velocities near the center and the left side of the profile is improved, and the warp at the bottom of the profile is avoided. The maximal hydrostatic stress in welding chamber is 484MPa which is enough to meet the requirement of welding. The distribution of the hydrostatic stress around the mandrel is uniform which is beneficial to avoid thickness deviation of the profile.
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    Effects of Raw Materials Size on Properties of Graphite Oxide and Graphene
    ZHAO Tian-yu, YANG Cheng, SONG Hong-song
    2014, 0 (9): 76-82.   DOI: 10.11868/j.issn.1001-4381.2014.09.013
    Abstract ( 889 ( PDF (4219KB)( 733 Citation
    The graphite oxide (GO) was prepared from natural graphite of different size with the modified Hummers method, and then the graphene was prepared by using hydrazine hydrate to reduce the exfoliated graphite oxide. The chemical structure, spectroscopy and the crystallinity of graphite, graphite oxide and graphene were characterized by using FTIR, Raman and XRD, respectively. The results show that the natural graphite is fully oxidized to graphite oxide, the graphite oxide is reduced to the perfect graphene. The smaller the size of natural graphite is, the greater the degree of oxidation, and the greater the interlayer spacing of graphite oxide are. The ratio of graphene D to G band intensities is proportional to size of graphite; compared with graphite oxide at similar size, the ratio of graphene D to G band intensities is higher than that of graphite oxide, suggesting that the average size of sp2-hybridized carbon layer surface of graphene is smaller than that of graphite oxide, and the new generation graphitization region is separated to smaller sp2-hybridized regions by some defects.
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    Surface Characteristics of Domestic T800-grade Carbon Fibers and Microscopic Interphase Properties of Composites
    LUO Yun-feng, LI Yang, ZHAO Yan, XIE Fu-yuan
    2014, 0 (9): 83-88.   DOI: 10.11868/j.issn.1001-4381.2014.09.014
    Abstract ( 1021 ( PDF (3828KB)( 463 Citation
    The surface properties of two domestic T800-grade sized and desized carbon fibers were characterized by scanning electron microscope(SEM), atomic force microscope(AFM) and X-ray photoelectron spectroscopy(XPS). The micro-interface shear strength(IFSS) of single fiber composites was also analysed by single fiber fragmentation test(SFFT). The influences of surface properties on micro-interphase strength of single carbon fiber composites and hygrothermal properties were investigated. The results show that the amount of surface active functional groups decreases and surface roughness increases, but the interfacial adhesion between fiber and matrix enhances after desizing. In addition, the hygrothermal environments dramatically decrease the micro-interphase strength, especially degrade the chemical bond force on the interphase, but interphase properties can partially recover after humidity desorption.
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    Characterization of Atom Segregation at Phase Interfaces in RPV Model Steel by APT
    ZHANG Zhi-quan, ZHOU Bang-xin, CAI Lin-ling, WANG Jun-an, LIU Wen-qing
    2014, 0 (9): 89-93.   DOI: 10.11868/j.issn.1001-4381.2014.09.015
    Abstract ( 714 ( PDF (2781KB)( 260 Citation
    The specimens of nuclear reactor pressure vessel (RPV) model steel with higher Cu content were firstly austenitized at 880℃ for 0.5h, water quenched, then tempered at 660℃ for 10h, and finally aged at 400℃ for 1000h. The state-of-the-art atom probe tomography (APT) was employed to investigate the segregation of solute or impurity atoms at the interfaces of carbide/α-Fe matrix, Cu-rich phase/α-Fe matrix and Cu-rich phase/carbide, respectively. The results indicate significant segregation of phosphorous at the interface of carbide/α-Fe matrix. Obvious segregation of nickel and weak segregation of manganese can be found at the interface of Cu-rich phase/α-Fe matrix. No solute or impurity atoms segregation is observed at the interface of Cu-rich phase/carbide. Atom segregation at different interfaces depends not only on the microstructure of the interfaces themselves, but also on the chemical environment in the vicinity of the interfaces.
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    Photocatalytic Degradation of Reactive Brilliant Red X-3B on TiO2 Supported on HZSM-5 Pretreated with Phosphoric Acid
    YANG Li-li, DU Ling, YU Yang, ZHANG Wen-jie
    2014, 0 (9): 94-99.   DOI: 10.11868/j.issn.1001-4381.2014.09.016
    Abstract ( 657 ( PDF (1683KB)( 294 Citation
    A phosphoric acid treated HZSM-5 zeolite was used as support and a sol-gel method was used to prepare TiO2/HZSM-5 photocatalyst. The composite photocatalysts were characterized by XRD, SEM, BET, FT-IR and XPS measurements. The results show that the TiO2 disperses well on the surface of HZSM-5 without aggregation of TiO2 particles. The supported TiO2 maintaines anatase phase and TiO2 crystallite size decreases after loading on HZSM-5. Specific surface area of TiO2/0.5HZSM-5 and reactive brilliant red (RBR) X-3B adsorption amount increase with the increase of HZSM-5 content. The supported TiO2 has higher photocatalytic activity than pure TiO2. The 50%(mass fraction)TiO2/0.5HZSM-5 has the maximal photocatalytic activity, on which 93.4% of RBR X-3B is degraded after 2h of irradiation, while only 61.0% of the dye is degraded on pure TiO2.
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    Influence of Mo on Microstructure and Electrochemical Properties of A2B7-type La-Mg-Ni Hydrogen Storage Electrode Alloy
    JIANG Ming, LI Zi-quan, LIU Jing-song, PENG Jie, XIE Li-ming
    2014, 0 (9): 100-105.   DOI: 10.11868/j.issn.1001-4381.2014.09.017
    Abstract ( 751 ( PDF (2110KB)( 397 Citation
    The influence of a small amount substitution of Mo for Ni on microstructure and conventional electrochemical performance of La0.75Mg0.25Ni3.5-xMox(x=0-0.5, atom fraction/%) hydride storage electrode alloy was investigated by the means of X-ray diffraction(XRD), battery stored program control tester and electrochemical workstation. The results show that the alloys have multiphase-structure which mainly consists of La2Ni7(Ce2Ni7-type) and LaNi5(CaCu5-type) and good activation performance which achieve the complete activation state after four charging-discharging process. With the increase of Mo content, MoNi4 gradually appears in the alloys and the lattice parameters of the La2Ni7 and LaNi5 then linearly increase. The high rate discharge(HRD) performance significantly is improved. HRDI=900mA/g increases from 82.58%(x=0) to 86.72%(x=0.5). The cycle stability performance(S100) also is improved, increasing firstly and then reduces and achieves the best S100 with 76.61%(x=0.3). However, the maximum discharge capacity(Cmax) gradually slightly decreases.
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    Progress in Research on Microwave Absorbing Coatings Prepared by Thermal Spraying Technology
    LIU Yi, WEI Shi-cheng, TONG Hui, TIAN Hao-liang, XU Bin-shi
    2014, 0 (9): 106-112.   DOI: 10.11868/j.issn.1001-4381.2014.09.018
    Abstract ( 907 ( PDF (934KB)( 758 Citation
    The recent research of microwave absorbing coatings prepared by thermal spraying technology is introduced. The SiC, C and ferrite coatings are discussed respectively. The advantage, disadvantage and adaptability of such materials system are analyzed and compared, which provides suggestion for the material selection of subsequent research work. The problems of this technology are also put forward. The enlargement of spray materials system, the balance among the coating thickness, bond strength and microwave absorbing efficiency, so as to prepare high quality and effective microwave absorbing coatings are the future development trend.
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