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      20 November 2014, Volume 0 Issue 11 Previous Issue    Next Issue
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    Broadening and Optimizing Microwave Absorbing Bandwidth by Metamaterial Unit Contour Method
    HUANG Da-qing, KANG Fei-yu, ZHOU Zhuo-hui, LIU Xiang, DING He-yan
    2014, 0 (11): 1-6.   DOI: 10.11868/j.issn.1001-4381.2014.11.001
    Abstract ( 727 ( PDF (5533KB)( 635 Citation
    A metamaterial absorber was designed which is constituted of metal resonance unit, FR4 substrate and metal backing. The S parameters and reflectivity characteristics were calculated by means of the numerical simulation method in 2-8GHz.The model was outlined and calculated again, the results show that the contour treatment, on the whole, has no effect on the resonance frequency. Based on this, dual band microwave attenuation absorption is achieved by virtue of combining other resonant metamaterial unit into the former unit contour, which provides an excellent technological approach to further study the broadband microwave absorbing materials. The samples of all the simulation model are verified by laser etching technology and the calculation results match very good with the experimental results, which verifies the technological thinking of metamaterials contour broadening the wave absorbing materials and paves a good path to broaden the bandwidth of microwave absorbing.
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    Preform Permeability Prediction and Influence of Shear Deformation
    YANG Bo, JIN Tian-guo, BI Feng-yang, LI Jian-guang
    2014, 0 (11): 7-14.   DOI: 10.11868/j.issn.1001-4381.2014.11.002
    Abstract ( 694 ( PDF (5741KB)( 172 Citation
    The accurate prediction of preform permeability has important implications for mould-filling simulation of liquid composite molding. The shear deformation of textile during draping process has a great influence on the local permeability of preform. Considering the permeability of yarn, the unified mathematical model for the resin flow in unit-cell was established, and the geometry model close to the real orthogonal unit-cell structure was built. Based on the Adams-Bashforth difference scheme and Chorin projection method, a numerical method with high resolution TVD schemes for solving the governing equations of resin flow was developed, and then the permeability was predicted using Darcy's law. The prediction results agreed well with experimental results, the validity of the algorithm was proved. On the basis of the permeability prediction of orthogonal unit-cell, the body-fitted coordinates system was employed and the governing equations were converted from physical domain to computational domain to simulate the resin flow in the sheared unit-cell and predict its permeability, then the relationship between the ratio of principal permeability and shear angle was studied. The results indicate that the method provided by this paper is convenient and effective.
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    Numerical Simulation on Directional Solidification Process of DD6 Single Crystal Superalloy Thin-walled Specimen
    YANG Liang, LI Jia-rong, JIN Hai-peng, XIE Hong-ji, HAN Mei, LIU Shi-zhong
    2014, 0 (11): 15-22.   DOI: 10.11868/j.issn.1001-4381.2014.11.003
    Abstract ( 991 ( PDF (5668KB)( 294 Citation
    For the difficulty in preparation of thin-walled specimen of DD6 single crystal superalloy, the finite element model of thin-walled slab specimen was established to simulate the directional solidification process of investment casting thin-walled slab specimen using a numerical simulation software ProCAST. The effects of specimen shape and solidification parameters on temperature field, temperature gradient field and mushy zone were investigated. The results show that temperature gradient at the working end of the thin-walled slab specimen's centre location ranges from 60℃/cm to 65℃/cm. The solidus isotherm of mushy zone is relatively flat, but liquidus isotherm closed to furnace wall is slightly lower than that far away from furnace wall. Geometrical shape has great effect on the directional solidification process of single crystal superalloy specimen. Increasing the pouring temperature or decreasing the withdrawal rate helps to increase the temperature gradient in solid/liquid interface front and reduce the mushy zone width. The numerical simulation results of the directional solidification are consistent with that of the actual casting results. The solidification simulation can provide the technical support for the preparation of thin-walled specimen.
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    Preparation and Microstructure of In-situ Al2O3/Al-Cu Composite
    LIU Hui-min, WANG Nan, SU Juan
    2014, 0 (11): 23-27.   DOI: 10.11868/j.issn.1001-4381.2014.11.004
    Abstract ( 902 ( PDF (2062KB)( 289 Citation
    In-situ reactive near-liquidus cast 3.6%(mass fraction) Al2O3 /Al-6.8Cu composite was re-heated isothermally at 580, 590,600℃and 610℃,which is in the two-phase (liquid and solid) zone of Al-6.8Cu alloy, for 10-60min, then quenched in water to stabilize the semi-solid structure. The microstructures of in-situ reactive near-liquidus cast 3.6% Al2O3 /Al-6.8Cu composite were observed using OM and TEM, to study the effect of in -situ Al2O3 particles on structure. The results show that the in-situ Al2O3 particles can not make near-liquidus cast Al-6.8Cu alloy with equiaxed grains but can make it with fine grains. In-situ Al2O3 particles control evidently grains growth by pinning effect during reheating. The average grain sizes of 3.6% Al2O3 /Al-6.8Cu alloys decrease 20-40μm compare to matrix Al-6.8Cu alloy at the same condition of reheating.
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    Effect of Layer Thickness Ratio on Microstructure and Properties of Magnetron Sputtered Cr/CrN Multilayer Coatings
    TAN Shu-yong, WU Xiang-jun, ZHANG Xu-hai, ZHANG Yan, JIANG Jian-qing, ZHU Xue-feng, JIANG Xian-biao
    2014, 0 (11): 28-33.   DOI: 10.11868/j.issn.1001-4381.2014.11.005
    Abstract ( 807 ( PDF (2619KB)( 195 Citation
    A series of Cr/CrN multilayer coatings with different layer thickness ratio under the same modulation cycle were prepared by ultrahigh vacuum magnetron sputtering. The phase composition, microstructure, hardness, adhesion, and tribological performance of the coatings were analyzed by XRD, SEM, microhardness tester, scratch tester, and abrasion tester, respectively. The results show that under the modulation cycle of 400 nm, when layer thickness ratio is decreased from 2.0 to 0.2,Cr/CrN multilayer coatings are always composed of two phases Cr and CrN, and the preferred orientation remains at CrN(200), and also the coatings become more and more dense, the coating hardness is increased from 1550 HV to 2300 HV, and wear rate is decreased from 2.4×10-8mm3·N-1·m-1to 0.6×10-8mm3·N-1·m-1, Cr/CrN multilayer coatings have good adhesion properties.
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    Influence of Deforming Amount on Mechanical Properties of TC18 Alloy
    SHA Ai-xue, LI Xing-wu, WANG Qing-ru
    2014, 0 (11): 34-37.   DOI: 10.11868/j.issn.1001-4381.2014.11.006
    Abstract ( 836 ( PDF (2014KB)( 488 Citation
    The influence of β zone deforming amount (changing from 10% to 65%) on microstructure and key mechanical properties of TC18(Ti-5Al-5Mo-5V-1Cr-1Fe) alloy has been studied by using a patent technology, specially for the quantitative study of titanium alloy forging process parameters. The results show that when β zone deforms, the deforming amount has little effect on the tensile strength, and σb is at around 1150MPa; but has obvious influence on the elongation rate, ductility and fracture toughness. When forging in beta field, the deforming amount is increased every 10%, the elongation rate is increased about 0.7%, fracture shrinkage is increased about 4%, fracture toughness is reduced about 3MPa·m1/2. In order to achieve the optimum match for TC 18 titanium alloy strength, plasticity and toughness, β zone deforming amount should be controlled around 35%.
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    Effect of ZrB2 and POSS on Ablation Properties of Carbon Fabric/Phenolic Composite
    WEI Hua-zhen, LI Ying, AN Zhen-he
    2014, 0 (11): 38-42.   DOI: 10.11868/j.issn.1001-4381.2014.11.007
    Abstract ( 847 ( PDF (1337KB)( 428 Citation
    Using ZrB2 as modifier, and adopting hot pressing process, a kind of carbon fabric reinforced phenolic(C/PF) composite was made. The ablation property of the C/PF composite was studied by oxygen/ethyne ablation test. The composite ablation appearance and the composition were analyzed by scanning electron microscope and energy spectrometer respectively after the ablation test. The results show that one ceramic layer is formed on the composite surface after ablated by the oxygen/ethyne flame. The mass ablation rate is 0.04585g/s and the line ablation rate of the composite is -0.013g/s. After second ablation, the mass ablation rate is 0.0096g/s. However, the mass ablation rate can reach 0.025g/s when the composite is modified by ZrB2 and POSS, the second time mass ablation rate can reach 0.0089g/s.
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    Analysis on V(C,N) Precipitated Behaviors in Ferrite of V-N Microalloyed Anti-seismic Rebars
    LYU Yu-kun, SHENG Guang-min, YIN Li-jing
    2014, 0 (11): 43-49.   DOI: 10.11868/j.issn.1001-4381.2014.11.008
    Abstract ( 885 ( PDF (3570KB)( 312 Citation
    Tempering hardness method for two different V, N content of anti-seismic reinforcing steel bars were studied on microstructure of tempering isothermal process and variation regulars of microhardness. V (C, N) precipitation theoretical thermo-kinetic in ferrite was quantitatively determined according to the J-M-A(Johnson-Mehl-Avrami)theory, and compared with the experimental PTT curve. V (C, N) precipitation rule was observed by transmission electron microscopy. The results show that due to the effects of abundant and dispersed second phase particles, the tempering microstructure of V-N microalloyed rebar (0.04V-0.0135N) is more uniform and fine than V microalloyed rebar (0.076V-0.0055N). The PTT curve which is attained from variety microhardness of two materials are consistent with the calculation result. V microalloyed rebar presents a "C" shape and its precipitation kinetics is accelerated in the nosal temperature zone about 670℃, V-N microalloyed rebar is monotonous curve, which is mainly affected by N content. Also in this experiment fibrous carbides, interphase precipitation of V(C,N) in supersaturated ferrite, and precipitations on dislocation after phase transformation are observed, their formation mechanism is discussed.
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    Preparation and Catalytic Performance of La0.3Sr0.7Fe0.7Cu0.2Mo0.1O3-δ Ultrafine Perovskite Powder
    MENG Bo, HAO Gui-zeng, QIN Jing-can, TAN Xiao-yao
    2014, 0 (11): 50-54.   DOI: 10.11868/j.issn.1001-4381.2014.11.009
    Abstract ( 709 ( PDF (1678KB)( 249 Citation
    La0.3Sr0.7Fe0.7Cu0.2Mo0.1O3-δ(LSFCM) ultrafine perovskite powder with homogeneous composition was synthesized via sol-gel low temperature combustion process. The phase, morphology, particle size and electrical conductivity of samples were characterized by XRD,SEM and TA measurements. The effect of LSFCM powder on the catalytic activity and stability in the partial oxidation of methane (POM) into syngas was investigated. The results indicate that LSFCM ceramic powders with cubic perovskite structure and the mean particle size of less than 35 nm can be obtained by calcinations of sol-gel combustion ash at 800℃ for 4 h. The conductivity of the LSFCM oxide measured on a sintered body having the relative density of 96.7% reaches up to 26.27 S·cm-1 at 600 ℃ in air atmosphere. The LSFCM powders exhibit excellent catalytic activity and good stability to the partial oxidation of methane into syngas. The methane conversion and CO and H2 selectivities reach above 90% in the CH4/O2 feed ratio of 1.5-2.0 at 950 ℃. XRD and TA analysis reveal that the LSFCM powders still maintain the perovskite structure with a slight coke deposition after 43 h of reaction.
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    Mechanical Properties and Fracture Feature of CNTs/Al-5%Mg Composite Prepared by High-energy Ball Milling
    CHEN Ya-guang, CAI Xiao-lan, WANG Kai-jun, HU Cui, SUN Hong-peng, LE Gang
    2014, 0 (11): 55-61.   DOI: 10.11868/j.issn.1001-4381.2014.11.010
    Abstract ( 859 ( PDF (2718KB)( 334 Citation
    The composite powders of carbon nanotubes(CNTs) and Al-5%Mg(mass fraction) were fabricated by high-energy ball milling and hot-pressing sintering were used to consolidate the ball-milled composite powders with different CNTs contents. The results show that a certain mass of CNTs can be homogeneously dispersed in the matrix through the high-energy ball milling, the most of CNTs are embedded in the Al matrix and the CNTs have a close bonding with the Al matrix. In addition, the CNTs can play the role of grain refining. When the CNTs content is increased to 3 %, the average grain size of the composite powder reaches the minimum value 63.6nm and then the CNTs content is further increased, the average grain size of the composite powder grows big. When the CNTs content reaches 2%, tensile strength and hardness of the composites reaches the maximum value, up to 42.39% in tensile strength and 36.5% in hardness, compared to the matrix. Fine grain strengthening and load transfer are proved to be the strengthening mechanism of the CNTs/Al composite.
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    Microstructure and Mechanical Properties of Ultra-fine Grained Al Alloy Processed by Combined SPD Technology
    LIU Zhao-hua, WANG Xiao-qi, CHEN Liang-wei, QI Hua-rong, SHI Qing-nan
    2014, 0 (11): 62-66.   DOI: 10.11868/j.issn.1001-4381.2014.11.011
    Abstract ( 737 ( PDF (1694KB)( 301 Citation
    The annealed 6061Al alloy was subjected to four pass combined extrusion deformation at room temperature using the procedure of cyclic channel die compression and equal channel angular pressing, equixed ultra-fine grained(UFG) 6061 Al alloy was successfully obtained. The evolution of the microstructure during deformation was investigated by means of transmission electron microscopy analysis. The grain refinement was discussed during combined extrusion deformation. The hardness and tensile tests were conducted, respectively. The average hardness value doubled on the three orthogonal planes. The tensile strength increases from 165 MPa to 402.7 MPa after four pass, meanwhile the elongation reduces from 26.8% to 9.7%. These results demonstrate the influence of the combined extrusion deformation on the mechanical properties of the samples is more severe in comparison to equal channel angular pressing.
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    Electrodeposition and Properties of Mn-doped NiO Thin Films
    CHEN Na, SU Ge, LIU Wei, CAO Li-xin, MA De-wen, QI Xin-ying
    2014, 0 (11): 67-72.   DOI: 10.11868/j.issn.1001-4381.2014.11.012
    Abstract ( 983 ( PDF (2150KB)( 287 Citation
    Undoped and Mn-doped NiO electrochromic thin films were synthesized by electrochemical deposition on FTO conducting glasses in organic system. The effect of Mn doping on the morphology, composition, optical and electrochemical properties of the NiO films were investigated by means of scanning electronic microscope (SEM), energy disperse spectroscopy (EDS), ultraviolet-visible (UV-vis) spectrophotometer and electrochemical workstation. The results show that the Mn-doped NiO films are formed by some elaborative agglomerated particles, which grow into worm-like particles when the dosage is bigger. The optical and electrical properties of NiO film are improved by Mn doping. The transmittance variation of the NiO film at 550 nm doped with a moderate amount of Mn reaches 93%, while the undoped NiO film is only 68%. The coloration efficiency increases up to 30.9mC·cm-2, the reversibility improves, and the response (decoloration/coloration) time decreases.
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    Effect of Aging Temperature on Microstructure and Mechanical Properties of Steel 0Cr17Ni4Cu4Nb
    HU Chun-yan, LIU Xin-ling, TAO Chun-hu
    2014, 0 (11): 73-78.   DOI: 10.11868/j.issn.1001-4381.2014.11.013
    Abstract ( 1060 ( PDF (4336KB)( 391 Citation
    Based on 0Cr17Ni4Cu4Nb martensite precipitation hardening stainless steel, the effect of aging temperature on the microstructure and mechanical properties was analyzed and the fracture feature of sample was observed. The experimental results indicate that as the aging temperature goes up(480-550℃), the tensile strength σb and the yield strength σ show the tendency of gradually decreasing, while the fracture shrinkage Ψ and elongation rate δ5 exhibit the tendency of gradually increasing; the impact toughness a is affected obviously by the aging temperature, is gradually increasing, among which, at 550℃, areaches 213.4(J·cm-2). While, the analysis results from fracture observation show that when the aging temperature is at 550℃, the radiation zone of tensile fracture is the minimum, the plasticity is the best; impact fracture plastic deformation is most obvious, the shear lip zone and fibrous zone occupy the largest proportion. For 0Cr17Ni4Cu4Nb stainless steel, as the aging temperature rises, quenching martensite matrix begins to restore, recrystallize, reverse austensite starts to form and grow, resulting in the increase of content of residual austenite, while the existing of residual austenite is conducive to maintain excellent plastic property and the toughness.ku kup0.2
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    Vacuum Dehydrogenate Carbonization and Pore Structure Changes of Pillared Montmorillonite
    ZHANG Zeng-zhi, DU Hong-mei, YANG Chun-wei
    2014, 0 (11): 79-84.   DOI: 10.11868/j.issn.1001-4381.2014.11.014
    Abstract ( 625 ( PDF (3012KB)( 267 Citation
    A kind of carbonized pillared montmorillonite was prepared. Na-montorillonite was organically modified by cetyl trimethyl ammonium bromide and then carbonized at different carbonization temperature under vacuum condition. Thermogravimetry-differential thermal analyzer (TG-DTA) was used to analyze its thermal stability, X-ray diffraction (XRD) was used to determine its interlayer distance changes, scanning electron microscope (SEM) was used to observe its micro morphology, and low-temperature nitrogen adsorption analysis was used to characterize the pore structure and the specific surface area of the carbonized pillared montmorillonite. The results show that the carbonized montmorillonite is mainly based on mesopores. Vacuum carbonization makes its lamellar structure more obvious and its thermal property more stable. As the carbonization temperature rises, the interlayer distance and the average pore diameter of the carbonized montmorillonite increase first and then decrease, while the BET specific surface area increases all the time. Adsorption property of the carbonized pillared montmorillonite has been greatly improved due to its well-developed pore structure.
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    Effect of Alternating Current Frequency on Corrosion Behavior of X65 Steel in CO32-/HCO3- Solution
    ZHU Min, DU Cui-wei, LI Xiao-gang, LIU Zhi-yong, ZHAO Tian-liang, LI Jian-kuan, HU Jie-zhen
    2014, 0 (11): 85-89.   DOI: 10.11868/j.issn.1001-4381.2014.11.015
    Abstract ( 755 ( PDF (5612KB)( 463 Citation
    Effect of alternating current(AC) frequency (30-1000Hz) on corrosion behavior of X65 steel in concentrated carbonate/bicarbonate solution was studied by potentiodynamic polarization curve measurements, immersion tests and surface characterization technique. The results show that in the range of 30-1000Hz, except 200Hz, at low AC frequency (≤300Hz), as AC frequency decreases, the passivation region become obviously narrow, the broken potential of pitting corrosion shifts negatively, the passive current density increases and the critical passivation current density increases; at high AC frequency(>300Hz), frequency has a slight effect on the passivity of X65 steel. The corrosion rates of X65 steel decrease with the AC frequency increase, at low AC frequency, the corrosion rates of X65 steel decrease rapidly as AC frequency increases, while at high AC frequency, the corrosion rates decrease slightly as AC frequency increases.
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    Synthesis and Properties of CIP@PANI Composite Powders for Anticorrosion and Microwave-absorbing Application
    WANG Xiao-qin, XU Jin-xin, HUANG Da-qing, XIONG Shan-xin, DENG Yu-qiang, GONG Ming, ZHANG Yong, GUO Fei
    2014, 0 (11): 90-96.   DOI: 10.11868/j.issn.1001-4381.2014.11.016
    Abstract ( 911 ( PDF (2499KB)( 665 Citation
    Core-shell structured CIP@PANI composite powders were synthesized by in-situ polymerization through triggering aniline, which is adsorbing on the surface of DBSA modified CIP. The results show that DBSA can protect CIP from oxidization. The coating exhibits the excellent anticorrosion performance because the metal under or in the coating had lower oxidation corrosion rate due to higher corrosion potential and gentler changes of anodic polarization current, after CIP was encapsulated by PANI. Due to the chemical bonds and the hydrogen bonds produced between —NH— on the polyaniline chains and epoxy groups on epoxy resin chains, the coating filled with CIP@PANI has higher strength and toughness than the coating filled with CIP. Additionally, the coating filled with CIP@PANI has stronger microwave absorption, wider effective bandwidth and higher frequency of maximum-absorption microwave than the coating filled with CIP.
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    Numerical Simulation for Three-point Bending Failure of Aluminum Foam Sandwich Panels with Cohesive Interface
    QIANG Bin, LIU Yu-jie, KAN Qian-hua
    2014, 0 (11): 97-101.   DOI: 10.11868/j.issn.1001-4381.2014.11.017
    Abstract ( 957 ( PDF (1770KB)( 354 Citation
    The deformation characteristics on three-point bending of aluminum foam sandwich panels were investigated by the experimental observation and numerical simulation. The 3-D finite element(FE) model for aluminum foam sandwich panels was developed by FE software ABAQUS. The bonding layer was descried by the cohesive zone model. The interfacial debonding between the face sheet and the core of aluminum foam,a typical failure mode of bonding aluminum foam sandwich panels under three-point bending, was simulated reasonably. The numerical results show a good agreement between the load-displacement responses and the failure mode observed in experiments. Furthermore, the influence of the thickness of face sheet and the core of aluminium foam on bearing force and energy absorption capacity was analyzed. The results show that an increased core thickness of aluminum foam can provide higher bearing force and energy absorption capacity of aluminum foam sandwich panels.
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    Metal Magnetic Memory Signal Feature of Fatigue Cracking Propagation
    JIN Bao, DI Xin-jie, ZHANG Jian-jun, LI Wei
    2014, 0 (11): 102-106.   DOI: 10.11868/j.issn.1001-4381.2014.11.018
    Abstract ( 818 ( PDF (2591KB)( 237 Citation
    Tension-tension fatigue tests on notched specimens made of Q235B steel were conducted by square wave load and on-line magnetic memory signals on the surface of specimens were measured under different fatigue cycles using magnetic memory detector. The results show that magnetic memory signals along the notch of untreated samples distribute randomly in the initial stage of fatigue. After 5000 cycles, magnetic memory signal curve transforms into waveform curve with one peak-to-trough. Magnetic memory signal curves tend to be stable before the cracks initiated, but diverge after macroscopic crack appeared. In the last stage, magnetic memory signal densities increase with increasing cycles. Based on magneto-mechanical effect, the variation of magnetic memory signals in the initial stage of fatigue can be well explained.
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    Progress in Research on Interface Layer of Continuous Fiber Reinforced Ceramic Matrix Composites
    LU Guo-feng, QIAO Sheng-ru, XU Yan
    2014, 0 (11): 107-112.   DOI: 10.11868/j.issn.1001-4381.2014.11.019
    Abstract ( 909 ( PDF (874KB)( 509 Citation
    The interface layer is a key component of the ceramic matrix composite (CMCs), and has an important influence on the properties of the CMCs, and become one of the key points of the research on CMCs. Based on the description of the function of interface layer, the research status on the interface layer of the structural CMCs and oxidation resistant CMCs is discussed; the problems in the research work are analyzed, the direction and focus of future research are pointed out.
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