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      20 May 2011, Volume 0 Issue 5 Previous Issue    Next Issue
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    Texture Evolution of Al-Zn-Mg-Cu Aluminum Alloy Plate During Cold Rolling
    CHEN Jun-zhou, HUANG Min, DAI Sheng-long
    2011, 0 (5): 1-6.  
    Abstract ( 306 ( PDF (1923KB)( 322 Citation
    The evolution of through-thickness texture in Al-Zn-Mg-Cu aluminum alloy plate during cold rolling was investigated by using electron backscattered diffraction(EBSD) technique.The results show that shear type texture {001}<110> near the surface of the plate tends to rotate towards a typical rolling texture consisted of Bs,S and Cu components with the reduction,while,at the quarter and the center of thickness,typical rolling texture rotates towards the {001}<110> orientation.Shear strain is the prime reason resulted in the transition from rolling texture to shear type texture.With the shear strain,Cu and Bs orientation rotates towards {001}<110> along Ф1=90° and Ф1=35°,respectively.
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    Pseudopotential Plane-wave Investigation on Influences of Mg Atom Vacancy Defect on Dehydrogenation Properties of MgH2
    ZHANG Jian, HUANG Ya-ni, LONG Chun-guang, SHAO Yi-min, PENG Ping, ZHOU Dian-wu
    2011, 0 (5): 7-12.  
    Abstract ( 316 ( PDF (1296KB)( 459 Citation
    Using the first-principles pseudopotential plane-wave method based on density functional theory,the influences and micro-mechanisms of Mg atom vacancy defect on the dehydrogenation properties of MgH2 system were investigated.The results show that the appearance of Mg atom vacancy results in the shrinkage of crystal cell and distortion of MgH2 lattice,which significantly decreases the structural stability and remarkably improves the dehydrogenation kinetics of this system.Further analysis on electronic structures shows that the mico-mechanisms for Mg atom vacancy improving the dehydrogenation properties of MgH2 attribute to the decreasing bonding electrons number below Fermi energy level and the narrowing energy gap near Fermi energy level of MgH2 system with Mg atom vacancy.
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    Three-point Bending Test of 2A50 Forging Aluminum and Analysis by High-resolution Computed Tomography
    AO Bo, DENG Cui-zhen, WU Guan-hua
    2011, 0 (5): 13-16.  
    Abstract ( 340 ( PDF (1270KB)( 200 Citation
    Three-point bending test of notched specimens of 2A50 forging aluminum was carried out by high frequency fatigue tester,specimens of computed tomography(CT) which contain fatigue crack were obtained.Fatigue specimen was reconstructed by high-resolution CT,CT images of crack were analysed;a reference plane was introduced,crack was projected on the reference plane in all CT images,and a damage risk factor was proposed.Results show that the damage of fatigue is uneven in different regions,the three-dimensional(3D) morphology of crack is visualized;the value of damage risk factor is 0.34,the defect area is 2.1 times the size of the most serious damage cross section,the damage risk factor is synchronized varying according to the fatigue cycles,it can be used to characterize damage of fatigue.
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    Effects of Material Plasticity of Nickel Base Alloy on Stress-strain Field at Tip of Stress Corrosion Cracking
    XUE He, ZHAO Dan, PENG Qun-jia, TANG Wei, FANG Xiu-rong, GONG Xiao-yan
    2011, 0 (5): 17-20,25.  
    Abstract ( 468 ( PDF (1158KB)( 325 Citation
    To understand the effect of material plasticity on stress corrosion cracking(SCC) growth in structural materials at high temperature water environments of nuclear power plants,the stress-strain field at the tip of a SCC constituted by base metal and oxide film in nickel base alloy was analyzed by elastic plastic finite element method(EPFEM) in a commercial FEM code.The effects of yield stress on the stress-strain field at the tip of the SCC were obtained.The results show that the stress in the base metal zone increases as the material yield stress increases and the plastic strain in base metal zone decreases as the material yield stress increases at the crack tip,and show that both the stress and the plastic strain in the oxide film decreases as the material yield stress increases at the crack tip.
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    Effects of Grain Refinement on Tensile Properties of Mg-3Al Alloy Modified by Carbon and Alkaline-earth Elements
    HAN Dong, DU Jun, LI Wen-fang
    2011, 0 (5): 21-25.  
    Abstract ( 360 ( PDF (1542KB)( 160 Citation
    The Mg-3Al alloy was modified by 0.2%C(mass fraction) and/or alkaline-earth elements of 0.2%Ca or 0.2%Sr to refine its grain size.The effect of grain refinement on the tensile properties of the Mg-3Al alloy was investigated.The results show that higher grain refining efficiency can be obtained for the Mg-3Al alloy modified by the combination of carbon and alkaline-earth elements.Compared to the Mg-3Al alloy without any treatment,the tensile properties of the Mg-3Al alloy are remarkably improved after being modified by the combination of carbon and a little addition of alkaline-earth elements.The ultimate tensile strength and elongation to failure are improved by about 20% and 40%,respectively.After being refined either by carbon or by the combination of carbon and a little addition of alkaline-earth elements,the main fracture mechanism is changed from cleavage mode with large cleavage planes for the unrefined Mg-3Al alloy to mixed mode of cleavage and quasi-cleavage fracture.The fracture surfaces are almost composed of small cleavage planes with thin river patterns and quasi-cleavage planes with severe plastic deformation.
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    Monitoring Fatigue Damage Using Magnetic Memory Technique
    LENG Jian-cheng, XU Min-qiang, WANG Kun, LI Jian-wei
    2011, 0 (5): 26-29.  
    Abstract ( 325 ( PDF (756KB)( 257 Citation
    Tension-tension fatigue experiments of demagnetized notched specimens made of middle-carbon 45 steel were conducted,and off-line magnetic signal characteristics in the stress concentration zone under different numbers of cycles were investigated using magnetic memory testing instrument simultaneously.The results show that an abnormal wave occurs in the notch position due to the leakage magnetic field caused by discontinuous geometric shape before loading,and may reverse after loading.The magnetic signal curves hardly change after the specimen is loaded in some specific number of cycles,and the wave heights in the notch increase with increasing cycle in the last stage until there is a sharp increase when the specimen fractured.Maximum magnetic field gradients of magnetic signals induced only by stress concentration were extracted by eliminating the disturbance of two clamps made of steel,and the fatigue procedure can be divided into four stages,which reflect different damage degree in the stress concentration zone.The experimentally measured damage values expressed by characteristic quantity of magnetic signal coincide with theoretically calculated fatigue damage evolution law,early predicting the residual fatigue lifetime.
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    Preparation and Characterization of Carbon-encapsulated Ni Core-shell Structure Nanoparticles
    WEI Zhi-qiang, LIU Li-gang, FENG Wang-jun, YANG Hua, ZHANG Cai-rong, YAN Peng-xun
    2011, 0 (5): 30-33.  
    Abstract ( 336 ( PDF (612KB)( 509 Citation
    Carbon encapsulated Ni core-shell structure nanoparticles were successfully prepared by anodic arc discharging plasma method and subsequently purified with acid treatment and magnetic separation.The composition,morphology,microstructure and particle size of the products by this process were investigated via the high-resolution transmission electron microscopy(HRTEM),X-ray diffraction(XRD),transmission electron microscopy(TEM) and X-ray energy dispersive spectrometry(XEDS).The results show that the carbon encapsulated Ni nanoparticles possess clear core-shell structure,the core of the particles is face centered cubic structure Ni,and the shell of the particles is disorder carbons.The particles are scattered homogeneously in spherical or ellipsoidal shapes.The particle size of the nanocapsules ranges from 15nm to 40nm,with an averaged value about 30nm,and the thickness of the shells is about 6-8nm.
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    Tension-tension Fatigue Behavior of 3D-Cf/SiC Composite at 1500℃
    DU Shuang-ming, QIAO Sheng-ru
    2011, 0 (5): 34-37,47.  
    Abstract ( 362 ( PDF (836KB)( 205 Citation
    The tension-tension fatigue tests were conducted at 1500℃ under 10-4 Pa vacuum with a sinusoidal loading-frequency of 20,60Hz and stress ratio R of 0.1 and 0.5 for 3D-braided carbon fiber reinforced silicon carbide ceramic matrix composites(3D-Cf/SiC) fabricated by chemical vapor infiltration(CVI) process.Morphology of fatigue fracture and microstructure of pyrocarbon interphase of 3D-Cf/SiC composites were observed by SEM and HRTEM respectively.The results show that while stress ratio is 0.1,the fatigue limit(based on 106 cycles) at 20Hz and 60Hz is 230MPa and 240MPa respectively.While stress ratio is 0.5,the fatigue limit is 230MPa at 60Hz.Fracture morphology is more rough in low fatigue stress-ratio,high loading-frequency and more fatigue cycles,and the pull-out lengths of fiber and fibers bundles on the fracture surface is longer.Nanoscale pyrocarbon flake of interphase curls up evidently.
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    Analysis on Melt Spinning Mastercurves of Polyethylene
    ZHONG Lei, LIANG Ji-zhao
    2011, 0 (5): 38-40,52.  
    Abstract ( 416 ( PDF (982KB)( 181 Citation
    Based on the results of low density polyethylene(LDPE) and linear low density polyethylene(LLDPE) melts at various temperatures,mastercurves of melt spinning technique were plotted.Scaling factor b shows the combination effects on the unwrapping and orientation of molecular chains.A linear relationship between b and temperature is found.By using the values of b and reference curves,extension viscosity curves of setting temperature are calculated,the results show good agreement with the experimental values.Mastercurve analysis can expand the measurement range of melt spinning technique.
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    Three Organic Corrosion Inhibitors on LY12CZ Aluminum Alloy in Acid Solution
    LIU Jian-hua, SHENG Hua, LI Ming, LI Song-mei, YU Mei
    2011, 0 (5): 41-47.  
    Abstract ( 517 ( PDF (2005KB)( 377 Citation
    The inhibiting effect of three organic compounds on the corrosion of LY12CZ aluminum alloy in 0.5M H2SO4 solution was investigated.The organic compounds are 2-mercaptobenzoxazole(MBIH),benzotriazole(BTA) and 8-hydroxy-quinoline(8Q).The inhibiting effect to the corrosion dynamics of LY12CZ aluminum alloy in 0.5M H2SO4 solution was evaluated by using mass loss method and the corrosion morphology was observed by using optical microscopy(OM),scanning electron microscopy coupled with energy dispersive spectroscopy(SEM/EDS).Electrochemical impedance spectroscopy(EIS) and potentiodynamic polarization were used to study the inhibiting mechanism.The results show that MBIH,BTA and 8Q all provide anti-corrosion protection for LY12CZ aluminum alloy by forming a thin organic layer of insoluble complexes on the surface of the alloy.Their inhibitive properties are given by the following order: MBIH>BTA>8Q.MBIH and BTA provide anti-corrosion protection by absorbing selectively on the corrosion active intermetallic zones and suppressing the cathode processes of corrosion reaction.The whole surface of the alloy was absorbed by 8Q to form chelate 8Q complexes,but the absorbed layer was destroyed as the anode dissolution.
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    Effects of Additives on Formation Interaction Mechanism of Rare Earth Conversion Coating of Zinc Plating
    ZHANG Jiang-hong, ZHANG Ying-jie
    2011, 0 (5): 48-52.  
    Abstract ( 358 ( PDF (1240KB)( 180 Citation
    It was of great significance to the efficient formation of rare earth conversion coating with high corrosion resistance by using chemical immersion method through the addition of oxidant and promoter of coating-formation for the preparation of rare earth conversion coating on the surface of zinc plating.The results show that through the electrochemistry test,morphology analysis and dynamics data calculation,reductive reaction at micro-cathode is speeded up by the addition of oxidant H2O2 into the treatment solution,and promoting the increase of pH within the micro-cathode region,which is favorable to the formation of conversion coating with high content of Ce.The addition of coating-formation promoter can improve the shape quality of the coating,whose essence is to lower effectively the apparent activation energy for coating-formation reaction with three stages,giving rise to the realization of promotion for conversion coating's growing.
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    Effects of Heat Treatment Temperature on Structure and Corrosion Behavior of Original Oxide Scale on 510L Hot Rolled Strip
    YE Zhi-guo, ZHU Min, ZHOU Xian-liang, HUA Xiao-zhen, CUI Xia
    2011, 0 (5): 53-57,61.  
    Abstract ( 364 ( PDF (1177KB)( 361 Citation
    The structure of surface original scale of 510L hot rolled strip was processed by heat treatment at different temperatures.Corrosion behavior of hot rolled strips with different oxide scales structure was investigated in sodium bisulfite solution by SEM,XRD,EDS,polarization curves and electrochemical impedance spectroscopy(EIS).The results show that when temperature is below 570℃,the microstructure of oxide scale evolved into coniferous shape from granular with burr,the oxide scales become more dense and the relative content of Fe2O3 increases with temperature increasing.White diffusion-like phases on the oxide scales reduce with temperature adding,while the thickness of oxide scales increases.The order of corrosion resistance of the scales prepared at different temperatures from good to poor is as follows: 550,500,450,400,350℃.When 570℃>T> 450℃,the corrosion resistance of original scale can be improved by heat treatment.
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    Effects of Molding Temperature on Properties of Porous SiC Ceramics
    YANG Yang, ZHAO Hong-sheng, LIU Zhong-guo, ZHANG Kai-hong, LI Zi-qiang
    2011, 0 (5): 58-61.  
    Abstract ( 361 ( PDF (1272KB)( 433 Citation
    The core-shell structure precursor powders were synthesized through coat mix process,and a small amount of Al2O3,SiO2 and Y2O3 composite additives was added.A series of porous silicon carbide ceramics were produced after molding,carbonization and sintering.The porosity,density,thermal expansion coefficient,bending strength and thermal shock resistance of porous silicon carbide ceramics were analyzed.The results show that the porous silicon carbide ceramic with molding temperature 80℃ possesses best general performance.When the molding temperature is very low,the barium phenolic resin coated over the core-shell structure precursor powders can not flow adequately,leading a loose structure and lower strength for the final porous silicon carbide ceramic.While the phenolic resin flows too much with excessive high molding temperature,some of composite additives are coated by phenolic resin and can not touch each other adequately,thereby the effect of composite additive is weaken.
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    Hot Deformation Behavior of Extruded γ-TiAl Alloy
    FU Ming-jie, JING Yong-juan, ZHANG Ji
    2011, 0 (5): 62-65.  
    Abstract ( 356 ( PDF (1527KB)( 191 Citation
    The hot compressive deformation behavior of extruded γ-TiAl alloy with a reduction of the cross section of 12:1 was investigated at 900-1100℃ and at strain rate 0.01-1.0s-1 and with 70% height reduction on Gleeble-1500 hot simulator.The effects of thermomechanical parameters on flow stress and dynamic recrystallization were analyzed.A constitutive relationship based on the Zener-Hollomn parameter and Arrhenius equation was proposed for γ-TiAl alloy.The result shows that the calculation results of the proposed model agree well with the experimental data.Therefore,the proposed model can lay foundation of quality control and process design for the secondary processing of γ-TiAl alloy.
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    Protection of AZ91D Melt Under Protective Atmosphere Containing SO2 in a Sealed Furnace
    WANG Xian-fei, XIONG Shou-mei
    2011, 0 (5): 66-69,75.  
    Abstract ( 286 ( PDF (834KB)( 175 Citation
    The effects of the SO2 concentration,the melting temperature and the addition of CO2 on the protection of molten AZ91D alloy were investigated in a sealed furnace filled once with an atmosphere containing SO2.The morphology and composition of the surface film were also studied.Results show that cauliflower-like oxides are formed on almost all the surface of AZ91D alloy,the protective area increases with the increase of SO2 concentration.Increasing the melting temperature reduces the protective effect on AZ91D alloy,and the alloy is completely not protected when the temperature reaches 700℃.Results also indicate that the cauliflower-like oxides are only composed of MgO,and the protected surface film contains Mg,O,Al and S elements.When CO2 is added into the atmosphere,the protective effect on AZ91D alloy is improved and C element is formed in the surface film.
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    Effects of Hydrogen on Hot Deformation Behavior of TC21 Alloys
    JIANG Bo, WANG Yao-qi, HOU Hong-liang, NIU Yong, LI Miao-quan
    2011, 0 (5): 70-75.  
    Abstract ( 347 ( PDF (1199KB)( 248 Citation
    The effects of hydrogen on the transformation temperature and hot deformation behavior of TC21 alloys were investigated through microscopic analysis and isothermal compression tests respectively.The results indicate that the transformation temperature of TC21 alloys decreases significantly after hydrogenating,so that the transformation temperature of TC21 alloys containing 0.7%(mass fraction)H is 810℃,which decreases by 145℃ compared with natural hydrogen.Meanwhile,the flow stress of TC21 alloys decreases effectively too after hydrogenating and the effects of hydrogen on flow stress become obvious with deformation temperature decreasing and strain rate increasing.The steady state stress of TC21 alloys containing 0.28%H reaches 202MPa,which decreases by 28% compared with natural hydrogen.Under the same stress level,deformation temperature decreases by 40℃ and strain rate increases one order of magnitude after hydrogenating.
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    Effects of Sensitizing Treatment on Microstructure and Mechanical Properties of 2205 Duplex Stainless Steel
    LUO She-ji, ZHENG Xin-xia
    2011, 0 (5): 76-80.  
    Abstract ( 351 ( PDF (2229KB)( 285 Citation
    The effect of sensitizing treatment on the microstructure and the mechanical properties of 2205 duplex stainless steel was studied by means of optical microscopy(OM),scanning electron microscopy(SEM),transmission electron microscopy(TEM) and mechanical property testing.The results show that the σ phase and the χ phase are precipitated at the boundaries ferrite/austenite and ferrite/ferrite under sensitizing treatment at 850℃,and the precipitated phase content increases with increasing of sensitizing treatment time.Sensitizing treatment leads the increase of the strength and dramatic decrease of the plasticity.The tensile fracture surfaces are characteristic of cleavage and facet,and the second cracking exists on the main fracture surface as the sensitizing treatment time increases.When sensitizing treatment time is 2h,the impact toughness of the samples at room temperature decreases from 290J to 10J.The impact fracture surfaces are changed from dimple to cleavage.The decrease of the impact toughness can be attributed to appearance of the precipitated phase.
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    Research of Asymmetrical Cold Rolling and Recrystallization Annealing Experiment of Flange Plate Steel
    TANG Di, DAI Hui, SUN Ji-quan
    2011, 0 (5): 81-87,92.  
    Abstract ( 304 ( PDF (1835KB)( 180 Citation
    Asymmetrical cold rolling technology was adopted for flange plate steel.Microstructure of rolled pieces was observed under the accumulated reduction of 78%.The results show that as the ratio of working rollers' speed is greater,the ratio of length to width of gain is higher.The idea is put forward that the ratio of length to width of gain can reflect the additional shear deformation size of rolled pieces under the condition of asymmetrical rolling.The tensile tests and annealing tests at different annealing temperatures were made for cold rolled pieces and the microstructure was observed by the transmission electron microscopy.The results show that as the ratio of working rollers' speed is greater,proof strength increases,average grain diameter decreases after cold rolled pieces annealed.With increase of the ratio of working rollers' speed,high density dislocations and the small size subgrains are observed.It indicates that asymmetrical rolling can present more additional shear strain than that of symmetrical rolling,more dislocations and subgrains can be generated in the course of asymmetrical rolling,and the strength of the flange plate steel is enhanced and the straining accumulation energy increases under the condition of asymmetrical rolling.It proves that annealing temperature of recrystallization is reduced.
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    Microstructure and Mechanical Behavior of New Type Multi-layer Metallic Composite Material in Hot Forming
    MA Ning, ZHANG Zong-hua, HU Ping, GUO Wei, LIU Shu-tian, SHEN Guo-zhe
    2011, 0 (5): 88-92.  
    Abstract ( 309 ( PDF (974KB)( 253 Citation
    The hot forming(quenching and forming at the same time) oxidizes and decarburizes the steel surface.The automotive components and parts formed in this technique show soft surface and hard inside.The material properties present gradient distributions in the thickness direction.The exterior hardness and strength are low,while the interior hardness and strength are high.Then the new type multi-layer metallic composite material is formed.To investigate the crashworthiness of the new metallic composite materials,the hot forming stamping pieces are experimentally and numerically studied.Taking the door reinforced beam for the samples,the three-point bending was carried out by experiment and finite element analysis(FEA).By comparing the crash force and energy absorption between the metallic composite materials and its every single phase material,it is found that the metallic composite materials have the comprehensive performance of every single phase material.So the new metallic composite material is a good alternative material in application of absorbing energy.
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    Progress in Fabrication and Application of Superhydrophobic Surfaces on Metal Substrates
    XU Wen-ji, SONG Jin-long, SUN Jing, DOU Qing-le
    2011, 0 (5): 93-98.  
    Abstract ( 470 ( PDF (1627KB)( 762 Citation
    On the basis of the fundamental theories,the fabrication and application of superhydrophobic surfaces on metal substrates were reviewed.It emphasized to discuss preparation methods of anodization,electrochemical deposition,chemical etching,chemical deposition,one step solution immersion,thermal oxidation,template,composite,etc.Superhydrophobic surfaces on metal substrates were also summarized in the application of response switch,self-cleaning,drag reduction,corrosion resistance,anti-icing,water and oil mixture separation,miniature transporter over water.Meanwhile,characteristics of different kinds of techniques were discussed.Finally,the problems about fabrication of superhydrophobic surfaces on metal substrates were brought forward.
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