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      20 December 2018, Volume 46 Issue 12 Previous Issue    Next Issue
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    REVIEW
    Research Progress in Oxide/Oxide Ceramic Matrix Composites and Processing Technologies
    Rui YANG, Zhe QI, Jin-hua YANG, Jian JIAO
    2018, 46 (12): 1-9.   DOI: 10.11868/j.issn.1001-4381.2018.000306
    Abstract ( 1363 ( PDF (30808KB)( 823 Citation

    Oxide/oxide ceramic matrix composites (CMCs) are ideal candidate materials in high-temperature and oxidative environment, due to their low density, high temperature resistance, oxidation resistance, etc, with tremendous potential applications in hot section components of aero engines, such as combustor liners, shrouds, vanes, blades, exhaust nozzle, etc. The research progress of oxide/oxide CMCs was reviewed, including the development of oxide fibers, ceramic matrix, composite material design and processing technologies, with an emphasis on the design of oxide/oxide CMCs, including the selection of interphase and the design of porous matrix, and the processing technologies of CMC materials, especially the prepreg method were introduced in details. Last, the evaluation of oxide/oxide CMCs abroad was summarized, and their future application in hot section components of aero engines was pointed out.

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    Progress in Additive Manufacturing Technique Based on Pulsed TIG
    Long-long GUO, Yu-tian HE, Lu-yan JU, Ze-bing WU, Yong ZHANG, Lan-tao LYU, Wen-juan WANG
    2018, 46 (12): 10-17.   DOI: 10.11868/j.issn.1001-4381.2018.000267
    Abstract ( 907 ( PDF (30180KB)( 378 Citation

    Additive manufacturing based on PTIG (pulsed tungsten inert gas, PTIG) is a branch of arc additive manufacturing technique. Its notable advantages are low cost, high deposition rate, high material utilization ratio, and suitable for manufacturing parts of large size. In this paper, the research results on the control of formation quality, microstructure and properties of the parts deposited by PTIG additive manufacturing were emphasized in view of experimental research and numerical simulation. Meanwhile, the shortcomings of current investigations were also summarized. Based on accurate prediction and accurate control on the formation quality, microstructure and properties, the research directions for further study on PTIG additive manufacturing technique in the future were put forward, including the influence mechanism of process factors on the formation quality, defects forming mechanism and the suppression measures, numerical simulation on microstructure evolution in molten pool, formation and regulation mechanisms on internal stress and deformation, and the establishment on quantitative relationship model between the microstructure and mechanical properties.

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    Research Progress on Synthesis and Application of Graphene Reinforced Metal Matrix Composites
    Jian-qiao WANG, Wei-ning LEI, Zi-ming XUE, Hai-feng QIAN, Wei-qiao LIU
    2018, 46 (12): 18-27.   DOI: 10.11868/j.issn.1001-4381.2017.001534
    Abstract ( 1791 ( PDF (69078KB)( 838 Citation

    Graphene, a two-dimensional carbon material made up of a single atomic layer structure, shows unique physical and chemical properties.Graphene reinforced metal matrix composites have attracted more and more attention due to excellent properties.In this paper, the synthesis methods of graphene reinforced metal matrix composites were reviewed.The research progress of graphene reinforced metal matrix composites in strength, thermal conduction, conductivity and corrosion resistance was comprehensively analyzed.Finally, on the basis of pointing out the importance of the study on interfacial bonding mechanism, the development trend of graphene reinforced metal matrix composites in improving the performance and extending the scope of application was prospected.

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    Research Status on Strengthening Mechanism of Particle-reinforced Metal Matrix Composites
    Xiang-ping YE, Ying-lei LI, Ji-dong WENG, Ling-cang CAI, Cang-li LIU
    2018, 46 (12): 28-37.   DOI: 10.11868/j.issn.1001-4381.2016.001214
    Abstract ( 2210 ( PDF (40898KB)( 2046 Citation

    The research status on theoretic models and the coupling relationships of Orowan strengthening, dislocation strengthening, load-bearing effect of the reinforcement strengthening and others strengthening are successfully described in this study for particle-reinforced metal matrix composites(MMCs) with a volume fraction lower than 14%. Some conclusions can be obtained:Orowan strengthening and dislocation strengthening stress can be enhanced by increasing volume fraction, decreasing size of reinforcement and improving homogeneous distribution of reinforcement, load-bearing strengthening stress can also be enhanced by increasing volume fraction; yield strength and ductibility of MMCs can be enhanced much more by increasing load-bearing strengthening stress and plastic deformation region and adopting the material design method of metal matrix surrounded by particles with microstructural inhomogenous distribution; grain boundary strengthening and Peierls-Nabarro stress can also affect the yield strength of MMCs as a part of matrix strengthening, solid solution strengthening can be ignored usually; there are three coupling relationships for the sum strengthening contributions:linear summation, multiplicative combination and the root of the sum of the squares. The linear summation and multiplicative combination can be applied to nanoparticle-reinforced MMCs, the linear summation is generally applicable in the case when there are few factors influencing the strength, the multiplicative combination is the most commonly used method. The root of the sum of the squares is applied to micronparticle-reinforced MMCs.

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    Development and Application of Adhesive Materials for Advanced Composite Bonding
    Hai-tao QIAO, Bin LIANG, Jun-ying ZHANG, Qing-fang LIU, Song LU, Sheng-long ZHAO, Rui-xiu ZHANG
    2018, 46 (12): 38-47.   DOI: 10.11868/j.issn.1001-4381.2018.000297
    Abstract ( 870 ( PDF (779KB)( 674 Citation

    To meet the needs of large composite bonding for aircraft, development, comprehensive experimental and application of adhesive materials have been carried out. Development process, adhesive bonding performance, operability and batch production of parts of adhesives are presented in brief. Traditional metal structural adhesives are widely applied to composite bonding for military use and civil use. We have made some progresses in development of toughened cyanate film adhesive and toughened BMI film adhesive. Development of high temperature resistant adhesives such as polyimide adhesive will be an important investigation area. All kinds of adhesives with different heat-resistant and chemical compositions need to be developed to meet adhesive selections for various composite bonding.

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    RESEARCH ARTICLE
    Modification of Bismaleimide Resin and Its Composites by Using Functionalized Graphene Oxide
    Chuang LI, Wei LI, Ming-yu WANG, Bai-chen WANG, Bo-wen FENG, Bo-han LI, Qiang LI
    2018, 46 (12): 48-53.   DOI: 10.11868/j.issn.1001-4381.2017.000494
    Abstract ( 649 ( PDF (23075KB)( 338 Citation

    Maleic anhydride was used to functionalize the graphene oxide (GO). The prepared functionalized GO was used to modify the bismaleimide (BMI) resin and the carbon fiber/BMI composites. The structure and properties of the composites were characterized. The results indicate that the maleic anhydride molecules are successfully grafted onto the GO surfaces. Due to the introduction of functionalized GO, the tensile strength, elastic modulus, blending strength, impact strength and glass transition temperature of the BMI resin were substantially improved. The impact fracture morphologies show that brittle fracture is transformed into ductile fracture after modification; moreover, the interfacial adhesions of carbon fiber/BMI composites were also enhanced obviously. The ILSS of composites increased from 84.0MPa to 104.6MPa after modification.

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    Synthesis of Silicon Carbide Fiber Containing Beryllium from Polyberylliumocarbosilane Using Electron Beam Irradiation
    Wen-hua ZHU, Jian-ling YUE, Xiao-zhong HUANG, Chun-qi WANG, Si-min HU, Chang WANG
    2018, 46 (12): 54-60.   DOI: 10.11868/j.issn.1001-4381.2017.000982
    Abstract ( 595 ( PDF (34493KB)( 187 Citation

    Polyberylliumocarbosilane(PBeCS) precursor fibers were irradiated using electron beam in an atmosphere with N2:O2 rate of 200:1, They were then pyrolyzed at high temperature under nitrogen to give silicon carbide fiber containing beryllium(SiC(Be)).The effect of irradiation dose on the chemical structure, gel content, oxygen content, and tensile strength was studied.The results show that Si-H bonds in the molecular structure of PBeCS react with oxygen in the electron beam irradiation under low oxygen partial pressure bombarding to get Si-OH groups, and then Si-OH groups undergo dehydration condensation reactions to produce Si-O-Si linkage, Si-H and Si-CH3 decompose and polymerize to produce Si-CH2-Si linkage, resulting in cross-linking.SiC(Be) fibers prepared at 1250℃ have smooth and dense surface.XRD curve reveals that β-SiC microcrystals are formed in the fibers.The atom fraction of oxygen of the fiber is less than 5%, and the molar ratio of C to Si is close to 1:1, and the average tensile strength and tensile modulus are 1.8 GPa and 179 GPa, respectively.

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    Moisture Behavior of Aeronautic Carbon Fiber Reinforced Resin Composite Stiffened Panel
    Xiang-fei TAN, Peng-da TAN, Yu-ting HE, Yu FENG, Tao AN, Tian-yu ZHANG, Kai LIU
    2018, 46 (12): 61-69.   DOI: 10.118681/j.issn.1001-4381.2017.000728
    Abstract ( 644 ( PDF (128458KB)( 227 Citation

    In order to investigate the moisture property of carbon fiber reinforced resin composite stiffened panel in hygrothermal environment, moisture experiments were conducted in condition of 70℃/85%RH. Stage moisture model was proposed and moisture behaviors were analyzed by finite element method. The results show that the moisture curve of experimental result agrees with Fick's diffusion law perfectly in initial moisture stage. However, stage moisture behavior exists in later moisture period. The moisture curve of stage moisture model agrees with finite element result, with an error less than 5% compared with the experimental result. The composite stiffened panel moisture mechanism is revealed by moisture concentration distribution. Additionally, the saturated moisture rate in different thickness zones is not synchronous, which is main reason resulting in stage moisture.

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    Synthesis and Properties of Aliphatic Polyester Block Copolymers Filled with Nano Layered Clay Prepared by In-situ Graft Polymerization
    Long MAO, Yue-jun LIU, Jin YAO, Hui-qing WU, Yong-kang BAI
    2018, 46 (12): 70-77.   DOI: 10.11868/j.issn.1001-4381.2017.001427
    Abstract ( 559 ( PDF (69242KB)( 241 Citation

    Aliphatic polyester block copolymers poly(ε-caprolactone) -poly(butylene succinate) -poly(ε-caprolactone) (PCL-PBS-PCL) were synthesized by the ring-opening polymerization of ε-CL in the presence of the pre-polymerized PBS as the macro-initiator. LDHs-g-PCL were prepared by in-situ ring-opening polymerization of ε-CL. Then LDHs-g-PCL/PCL-PBS-PCL nanocomposites were prepared by blending PCL-PBS-PCL and LDHs-g-PCL via solution casting method. The chemical structures of PCL-PBS-PCL and LDHs-g-PCL were investigated. And crystallization behavior, mechanical properties and barrier properties of nanocomposites were also deeply studied. The results of thermal analysis confirm that the crystallization of PBS blocks is restrained markedly with the addition of LDHs-g-PCL. On the contrary, the crystallization of PCL chains is gradually increasing. The changes of crystallization for nanocomposites lead to the decrease in the high temperature melting peaks and the increase in the low temperature melting peaks. Even though a slight decrease (6%) in tensile strength, elongation at break of nanocomposites reaches to the maximum value of 772% (increased by 35%) in the presence of LDHs-g-PCL containing 20% (mass fraction). Compared with pure PCL-PBS-PCL, the O2 permeability of nanocomposites decreased by nearly 52% as LDHs-g-PCL content increase up to 50% (mass fraction). The key parameters to improve the barrier properties of nanocomposites are not only the barrier effect of the LDHs (a decrease in diffusion is expected because of a more tortuous path for diffusing molecules) but also the bulk effect that they develop in the polymer matrix.

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    Effect of Cr3C2 Addition on Properties of ZrB2-SiC Ceramic
    Qi LI, Biao YU, Feng-wei GUO, La-mei CAO, Xiao-su YI
    2018, 46 (12): 78-84.   DOI: 10.11868/j.issn.1001-4381.2017.000402
    Abstract ( 531 ( PDF (101553KB)( 202 Citation

    ZrB2-SiC ceramics with different Cr3C2 contents (0%, 5%, 10%, 20%, volume fraction) were successfully prepared by spark plasma sintering(SPS) process at 1700℃. The effect of Cr3C2 content on mechanical properties and the oxidation behavior of ZrB2-SiC ceramics at 1500℃ was investigated. The results show that the internal defects of ceramics reduce due to the reaction between Cr3C2 and the substrate phases during SPS sintering. With the increase of Cr3C2 content (from 0% to 20%), the hardness increases from 12.6GPa to 15.8GPa and the fracture toughness increases from 4.9MPa·m1/2 to 6.7MPa·m1/2. By adding 10%Cr3C2, the bending strength at room temperature can be improved to 708MPa, and the mass gain of ceramic after being oxidized for 10h at 1500℃ in air is less than 10mg/cm2, the thickness of the oxidation layer reaches a minimum value of 160μm, which indicates that the oxidation resistance significantly enhances.

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    Effects of Spray Drying Conditions on Morphology and Performance of Nano/Micro Structure LiFePO4/C
    Yi-ju LYU, Jia-xu TAN, Shi-quan JIANG, Yan-xuan WEN, Shu-fen ZHANG
    2018, 46 (12): 85-94.   DOI: 10.11868/j.issn.1001-4381.2017.001530
    Abstract ( 603 ( PDF (104948KB)( 219 Citation

    The nano/micro LiFePO4/C composite was prepared by a wet milling-spray drying-carbothermal reduction process. The structure and morphology were characterized by X-ray diffraction (XRD) and electron scanning microscope(SEM), electrochemical properties were characterized by cyclic voltammetry, AC impedance testing with galvanostatic charge-discharge method to investigate the influence under different spray drying conditions. The results show that the morpholoyy and electrochemical performance are significantly influenced by slurry concentration, inlet temperature and feed rate, while are mildly influenced by nozzle diameter. The morphology of the obtained sample is transformed from bowl-like mesoporous structure to spheres with the decrease of the slurry concentration. With a slurry concentration of 200g/L, an inlet temperature of 200℃, a feed rate of 1.3L/h and a spray nozzle diameter of 0.5mm, the obtained sample has the best electrochemical properties. Under that condition, the discharge capacities at 0.5C and 10C under room-temperature are 160mAh·g-1 and 123mAh·g-1, respectively, and no obvious capacity fading is observed after 100 cycles.

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    Ag Incorporation in Cu2ZnSnS4 Thin Film Solar Cell Absorbed Layer
    Tong LI, Lin-rui ZHANG, Yan-han YANG, Yong-zhe ZHANG, Xue-mei SONG, Hao WANG, Hui YAN
    2018, 46 (12): 95-100.   DOI: 10.11868/j.issn.1001-4381.2017.001238
    Abstract ( 664 ( PDF (65506KB)( 223 Citation

    The (Ag1-xCux)2ZnSnS4 (ACZTS) absorption layers with different Ag atomic ratio were fabricated by using co-electrodeposition and magnetron sputtering. The composition, structure, morphology and performance of the film were investigated by X-ray diffraction (XRD), raman spectra, scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and electrochemical measurements. The results show that the ACZTS film is Cu poor and Zn rich. The incorporation of Ag has a great influence on the morphology of the film. The growth of grain size can be obviously improved with the increase of the Ag atomic ratio, and the surface of film becomes denser; after the incorporation of Ag, the surface of the film has n-type and p-type semiconductor features; when the Ag atomic ratio is 22%, the absorption of the incident light is significantly enhanced, and the transient current density is the largest, when the Ag atomic ratio is 28%, the enhancement of steady current density is the most obvious.

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    Weight Analysis of Atmospheric Aging of Polycarbonate Impact Factors Based on MIV Method
    Bin YANG, Jing-yang LI, Lei WEN
    2018, 46 (12): 101-109.   DOI: 10.11868/j.issn.1001-4381.2018.000317
    Abstract ( 741 ( PDF (171006KB)( 205 Citation

    The mean impact value (MIV) method which is an effective factor weight analysis method was used to quantitatively analyze the effect weight of 15 impact factors on the aging properties of polycarbonate (chromatic aberration, tensile strength, elongation at break, and bending strength) and the corresponding exposure time, climatic factors and environmental factors. The impact factors were exposure time, mean temperature, humidity, sunshine hours, precipitation, wind speed, sea salt ion, SO2, HCl, NO2, H2S, sulfation rate, NH3, water soluble dust fall, and non-water soluble dust fall. The results show that with the regulation rate increasing from 15% to 25% gradually, for the certain aging property, the effect weight of certain impact factor change little, while the sensitivities of aging properties to various impact factors are different; the climatic factors and exposure time are the greatest factors influencing the aging properties of polycarbonate, among environmental factors, the influence of dust fall quantity on the aging properties is the largest; exposure time is the main impact factor influencing chromatic aberration and elongation at break, mean relative humidity has the greatest impact on tensile strength and bending strength.

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    Sealing Effects of Silica Sol Modified Waterborne Acrylic Resin on Chromium Trivalent Passivation Film of Galvanized Steel
    Wei SUN, Li-qun ZHU, Wei-ping LI, Hui-cong LIU
    2018, 46 (12): 110-116.   DOI: 10.11868/j.issn.1001-4381.2016.001247
    Abstract ( 752 ( PDF (35837KB)( 248 Citation

    In order to improve the corrosion resistance of the trivalent chromium passivation film on galvanized steel, the effects of silica sol modified waterborne acrylic resin on the passivation film were studied. The corrosion resistance and the thermal stability of the passivation film were measured by Tafel polarization curve, electrochemical impedance spectroscopy (EIS), salt water immersion test and neutral salt spray test (NSS), and the morphology and properties of the film were characterized by SEM, FT-IR and TGA. The results show that compared with the unmodified and unsealed passivation film on galvanized steel, silica sol modified sealant can significantly improve the resistance of the passivation film, effectively slow down the corrosion rate of the passivation film in 3.5%NaCl solution, and extend the enduring time under salt spray test; and the heat resistance of the passivation film can be improved remarkably by the introduction of silica sol.

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    Rapid Cooling and Solidification Microstructure of Argon Atomized Ti-48Al Alloy Droplets
    Ying BAO, Lin LUO, Ze-min YU, Dong-ye YANG, Na LIU, Guo-qing ZHANG, Jian-fei SUN
    2018, 46 (12): 117-123.   DOI: 10.11868/j.issn.1001-4381.2016.000570
    Abstract ( 592 ( PDF (51461KB)( 428 Citation

    An analytical approach was developed to investigate nucleation and growth of Ti-48Al (atom fraction/%) alloy droplets during their flight in an argon atomization process. Evolution of microstructure of the solidified powders was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron back-scatter diffraction (EBSD). Newton cooling model based on the initial number of nuclei, liquid/solid interface velocity, cooling rate and size of droplets was established. The results show that statistical nucleation events increase exponentially with the increase of powders size, and the growth of nuclei is transformed from a twinned spherical segment into a concentric liquid/solid interface geometry. Temperature of atomized droplets decreases rapidly with the cooling rate of 105-106K·s-1.Then temperature increases sharply to near the liquidus temperature during recalescence. When the recalescence is completed, the droplet solidifies at a relatively slower rate. Afterwards the cooling rate of the fully solid phase decreases to about 105K·s-1.

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    Effects of Matrix Components on Microstructure and Properties of SiCP/Al-Fe-V-Si Composites
    Yi-qiang HE, Hu-lin XU, Chen-chen QIAN, Yun-fei DING, Wen FENG, Jing-song CHEN, Hua-qiang LI, Li-chao FENG
    2018, 46 (12): 124-130.   DOI: 10.11868/j.issn.1001-4381.2016.001293
    Abstract ( 503 ( PDF (18390KB)( 217 Citation

    Spray deposited SiCP/Al-Fe-V-Si composites were densified by twice hot pressing and subsequently multi-pass hot rolling. Scanning electron microscope, transmission electron microscope and tensile test were used, and the effect of matrix alloy components and Fe/V ratio on microstructure, mechanical properties and heat resistance of the composites were analyzed.The results show that the as-rolled composites have high volume fraction Al12(Fe, V)3Si dispersoids, and volume fraction of the dispersoids increases with Fe content increasing. Volume fraction of Al12(Fe, V)3Si dispersoids is up to 40% when Fe content of the matrix alloy is 11.5%(mass fraction). Al12(Fe, V)3Si dispersoids with the diameter of 50-80nm are distributed along the grain boundaries, and exhibit excellent thermal stability up to 500℃. However, above 500℃ the Fe atoms diffuse in the form of bulk diffusion, and accordingly the dispersoids both along the grain boundaries and in the grains become coarsened at a relative high velocity. Coarsening velocity of Al12(Fe, V)3Si dispersoids falls with the increase of Fe/V ratio. Strength of the composite increases with volume fraction of Al12(Fe, V)3Si dispersoid increasing, and decreases with the tensile temperature rising; the elongation of the composite decreases both with rise of volume fraction of Al12(Fe, V)3Si dispersoid and tensile temperature.

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    Influence of Retrogression Time on Mechanical Properties and Microstructure of 7150 Aluminum Alloy
    Yan ZHANG, Yun-lai DENG, Shi-tong FAN, Tao LONG
    2018, 46 (12): 131-136.   DOI: 10.11868/j.issn.1001-4381.2016.001032
    Abstract ( 587 ( PDF (28968KB)( 212 Citation

    The influence of the retrogression time on properties and microstructure of 7150-T77 aluminum alloy was studied by hardness testing, tensile property testing, exfoliation corrosion test and TEM. Results indicate that the matrix precipitated η' phase re-dissolves first, and then η phase re-precipitates and becomes coarsened with the extending of retrogression time. The ultimate mechanical properties increase first then decrease as retrogression time increases. The critical time of the η' phase re-dissolution and the η phase precipitation is 30min, At this point, alloys have the highest ultimate mechanical properties, and the grain boundary precipitated η phase becomes coarsened and discontinuous, leading to lower mechanical properties and better corrosion resistance, peak hardness exists at re-aging stage. With the retrogression time extending, the time for the alloy to reach the peak hardness becomes shorter. Optimal T77 aging treatment is 105℃/17h+190℃/30min+120℃/23h. With this treatment, the ultimate tensile strength (σb), yield strength (σ0.2) and elongation (δ) are 608, 544MPa and 10.4%, respectively, the exfoliation corrosion test gets EA level, the σb and δ loss in constant loading tensile testing is 4.9% and 5.0%, respectively.

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    Effect of Plug Materials on Microstructure and Tensile Fracture Behavior of Aluminum Alloy Friction Plug Welds
    Bo DU, Xin-qi YANG, Zhuan-ping SUN, Dong-po WANG
    2018, 46 (12): 137-143.   DOI: 10.11868/j.issn.1001-4381.2017.001582
    Abstract ( 634 ( PDF (124094KB)( 238 Citation

    Friction plug welding (FPW) experiments were performed on 6mm 2219-T87 aluminium alloy using 2219-T87 and 2A14-T6 plugs. Digital image correlation method was used to determine the deformation and fracture behaviour of FPW joints in tensile process, meanwhile the microstructure, microhardness, and tensile fracture surface of the two FPW joints were observed and tested respectively. The results show that the two joints present similar microstructure, while 2A14-T6 joint exhibits wider partial recrystallized zone in plug thermo-mechanically affected zone than 2219-T87 joint. The plug material has slight effect on ultimate tensile strength, but has a significant effect on the elongation. The tensile strength and elongation of 2219-T87 joint can reach 346.2MPa and 5.76%, for 2A14-T6 joint, they are 351.2MPa, 3.54%. The deformation mainly concentrates in softening plug thermo-mechanically affected zone and plug metal for 2219-T87 joint, while the deformation concentrates in softening thermo-mechanically affected zone and heat affected zone for 2A14-T6 joint. Recrystallized zone and the softening zone are the weakening zones across the whole joint, and the tensile fracture morphologies are characterized by dimples.

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    Microstructure and Mechanical Properties of Laser Deposition Repaired TA15 Titanium Alloy
    Ru-fei XING, Xing-yuan XU, Shuang-jun HUANG, Lei WANG, Song ZHOU, Liang XU
    2018, 46 (12): 144-150.   DOI: 10.11868/j.issn.1001-4381.2016.000406
    Abstract ( 693 ( PDF (50663KB)( 249 Citation

    The technology of laser deposition repair was used to repair two kinds of mis-machining defects in TA15 titanium alloy forgings. The effect of solution-aging treatment on microstructure and tensile properties of TA15 titanium alloy at room temperature was investigated. The results show that the entire heat affected zone of annealing state presents a continuous microstructural transition from bimodal structure to basket weave characterized by coarse columnar β with fine α/β lamellar structure. After solution-aging treatment, martensitic transformation occurs in β phase, the primary α phase and hexagonal martensite α' are obtained, a part of continuous prior α boundary is broken, becomes spheroidized and illegible, and α laths grow up to bunch on some broken boundary. The strength of annealing sample is higher than that of forging, but the plasticity is lower. The tensile properties of groove repair sample and body repair sample after solution-aging are obviously improved compared with the annealing.

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    Influence of Thermal Exposure at Different Temperatures on Room Temperature Tensile Ductility of Cast TiAl Alloy
    Hong-wei WANG, Chun-lei ZHU, Ji ZHANG, Rui CAO
    2018, 46 (12): 151-156.   DOI: 10.11868/j.issn.1001-4381.2016.001556
    Abstract ( 546 ( PDF (56111KB)( 181 Citation

    The effect of thermal exposure at 600-750℃ for 300h in atmosphere on room temperature tensile ductility of cast Ti-47.5Al-2.5V-1.0Cr-0.2Zr(atom fraction/%) was investigated.The results indicate that no surface layer on the specimen surface is observed after exposure at 600℃, but tensile ductility at room temperature decreases from 2.81% to 2.54%, the reduction is only 9.6%;after exposure at 650℃, a Al depleted layer is formed on the surface of substrate, tensile ductility is further reduced to 1.54%, the reduction reaches 45%. When exposure temperature increases to 700℃, tensile ductility does not continuously decrease due to no significant increase in the thickness of the Al depleted layer; when the exposure temperature increases to 750℃, tensile ductility is further reduced to 1.12% due to remarkable increase in the thickness of Al depleted layer with the reduction of 60%.Tensile ductility at room temperature decreases in different degrees as the exposure temperature increases, which is attributed to emerging and step-increase of the Al depleted layer adjacent to the substrate, and is not related to the formation of outside oxide layer and the changes in thickness.

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    Effect of Laser Remelting Treatment on Microstructure and Properties of Aluminum Alloy Micro-arc Oxidation Coatings
    Shi-guang TANG, Quan-zhi CHEN, Zhi-qiu JIANG, Qing TONG, Wan-bing DONG, Wei-zhou LI
    2018, 46 (12): 157-164.   DOI: 10.11868/j.issn.1001-4381.2016.001517
    Abstract ( 654 ( PDF (36701KB)( 217 Citation

    The coating was treated by laser with different power. Microstructures of two kinds of coatings were examined by scanning electron microscopy(SEM). The phase of two kinds of coatings was detected by X-ray diffraction(XRD). The micro hardness of the coatings was tested by micro hardness tester. Corrosion resistance of the coatings was evaluated by electrochemical workstation. Wear resistance of the coatings was detected by friction and wear test. The results show that micro-arc oxidation coating is remelted by laser treatment, the coating is more dense after being remelted and cooling.The coating after laser treatment is still composed of γ-Al2O3 phase. Part of γ-Al2O3 in the coating is transformed to α-Al2O3. With the increase of laser power, micro hardness of the coating firstly increases and then decreases. When the laser power is 150W, the micro hardness is the maximum, which is 625HV. The electrochemical measurements show that corrosion potential of the coating is shifted to -0.577V and corrosion current density reduces significantly to 3.903×10-6A/cm2 after 150W laser treatment. The friction and wear experiments show that the surface of the coating appears spalling phenomenon. Friction and wear loss is about 1/323 of the substrate.

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