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      20 December 2014, Volume 0 Issue 12 Previous Issue    Next Issue
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    Effects of Yttrium(Y) and Cerium(Ce) on Microstructure and Stretch Formability of Hot Rolled Mg-1.5Zn Magnesium Sheet at Room Temperature
    LIU Peng, JIANG Hai-tao, DUAN Xiao-ge, KANG Qiang
    2014, 0 (12): 1-10.   DOI: 10.11868/j.issn.1001-4381.2014.12.001
    Abstract ( 845 ( PDF (6681KB)( 365 Citation
    Mg-1.5Zn-xY and Mg-1.5Zn-xCe (x= 0,0.2,0.5,1.0) alloys were designed to investigate the effect of Y and Ce on microstructure and formability of hot rolled Mg-1.5Zn sheet at room temperature via optical microscope(OM), scanning electron microscopy(SEM) and X-ray diffraction(XRD) etc. The results show that Y and Ce elements can effectively weaken and modify the basal texture where the position of basal plane is tilted from normal direction(ND) toward transverse direction(TD). The formation of second phase particles Mg2Y5,Mg3Zn3Y and MgZnCe due to the addition of Y and Ce element plays a fine grain size strengthening role in the alloys. Besides, it is conducive to the recrystallization, leading to the great improvement of ductility (the maximum of elongation is 27%), strength (the maximum of tensile strength is 252MPa) and stretch formability (the maximum of Erichsen value is 5.46) of alloys. However, excessive addition of Y and Ce elements is harmful to further improvement of alloys' performance.
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    Thermo-mechanical Coupled Finite Element Model for Whole Process of Friction Stir Welding
    CUI Jun-hua, KE Li-ming, LIU Wen-long, GUO Zheng-hua, ZHAO Gang-yao, FANG Ping
    2014, 0 (12): 11-17.   DOI: 10.11868/j.issn.1001-4381.2014.12.002
    Abstract ( 846 ( PDF (4768KB)( 404 Citation
    With ALE(Arbitrary Lagrangian-Eulerian) mesh adaptive technique and proper management of corresponding boundary conditions, thermo-mechanical coupled finite element model of whole process of friction stir welding (including under pressure stage and stable welding stages) was established. The model was tested by a 6061 aluminum alloy weldment. The results show that the highest temperature of the whole process temperature field is about 463℃, under its melting point. At 6s of stable welding stage, the plastic deformation field distribution on the cross section behind the tool looks like a V shape, the degree of deformation and the deformation region at the advancing side is more intensely and larger than that at the retreating side.
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    Synthesis and Characterization of Polypyrrole/Ni0.5Zn0.5Fe2O4 Composites
    ZHAO Hai-tao, LIU Rui-ping, LI Cheng-wu, MA Rui-ting
    2014, 0 (12): 18-22.   DOI: 10.11868/j.issn.1001-4381.2014.12.003
    Abstract ( 797 ( PDF (2461KB)( 210 Citation
    The polypyrrole/Ni0.5Zn0.5Fe2O4(PPy/NZFO) composites were prepared by in-situ polymerization method under the ultrasonic field. The structural characteristics, morphology, electric properties and wave absorbing properties of composites were analyzed by X-ray diffractometer(XRD), scanning electron microscope(SEM), four-probe instrument and network analyzer, respectively. The results indicate that little united and uniform polypyrrole particles can be made when APS/Py mole ratio is 0.75. The particle size of polypyrrole increases with increasing of ultrasonic reacting time and electrical conductivity is directly proportional to the PPy content. The wave absorbing properties of the Ni0.5Zn0.5Fe2O4/polypyrrole composites are higher than that of pure PPy. The reflection loss of the PPy/NZFO composite with NZFO content of 40%(mass fraction) is above -12dB within 5-20GHz, with a minimum reflection loss of -16.76dB at 18.15GHz and a bandwidth of -15dB over the extended frequency range of 1.65GHz.
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    Study on Microstructure and Properties of W-Ti-N Composite Films with Different Titanium Content
    ZHAO Shu-fang, YU Li-hua, MA Bing-yang, XU Jun-hua
    2014, 0 (12): 23-27.   DOI: 10.11868/j.issn.1001-4381.2014.12.004
    Abstract ( 778 ( PDF (2053KB)( 223 Citation
    W-Ti-N composite films with different titanium content were fabricated by reactive magnetron sputtering technique. The microstructure and mechanical properties of films were characterized by XRD,SEM and CSM. Tribological performance of the films was tested on UMT-2 multifunctional tribometer in the condition of room temperature,atmosphere environment and without lubrication. At the same time, the mechanisms of hardness enhancement and friction were also discussed. The results show that, at titanium content (atom fraction) of 5%-23.48%, the hardness of the film is in the peak area,and the maximums hardness is up to 39GPa,friction coefficient is about 0.4. When the Ti content is higher than 23.48%, the hardness decreases with increasing of the titanium content. In addition, the friction coefficient increases.
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    Pores in TIG Welding of Die Casting AZ91D Magnesium Alloy
    YOU Guo-qiang, DU Juan, CHEN Lei, WANG Xiang-jie
    2014, 0 (12): 28-33.   DOI: 10.11868/j.issn.1001-4381.2014.12.005
    Abstract ( 793 ( PDF (6668KB)( 153 Citation
    The plates of die casting AZ91D magnesium alloy were autogenously welded by tungsten inert gas welding(TIG) processing. The effect of welding currents on porosity was investigated. The characteristic and formation mechanism of pores in different zones in the weld were also analyzed. The results indicate that pores are mainly present in the subsurface and near the fusion line in the weld. The area of convexity, melting and porosity all increase with the increasing welding currents. Pores in the subsurface are induced by hydrogen, which results mainly from the base metal. And pores in the center of weld, influenced by the fluid force and buoyancy, are not a serious problem. However, pores in the partially melted zone have few chances to float out of the molten pool,because of the effect of fluid force and the high viscosity of molten metal, which results in a great number of large pores in the partially melted zone.
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    Corrosion Resistance Behavior of TiO2 Thin Films Prepared by Sputtering
    WANG Jun, LIU Ying, DING Hong-yan
    2014, 0 (12): 34-38.   DOI: 10.11868/j.issn.1001-4381.2014.12.006
    Abstract ( 757 ( PDF (2853KB)( 290 Citation
    TiO2 thin films were prepared by sputtering on 316L stainless steel and fused quartzes. The microstructure and surface morphology of the films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atom force microscopy (AFM). The results indicate that the as-deposited TiO2 thin film has uniform and crack-free surface with anatase structure. The rutile phase is formed in the film annealed at 600℃. The calculated optical band-gap of the films is around 3.2eV based on transmission spectra. The potentiodynamic polarization is tested in PBS simulated body solution. It shows that the corrosion resistance of 316L stainless steel is improved with TiO2 thin films. The corrosion potential shifts positively +94mV for the annealed TiO2 thin film. While, it has the lowest corrosion current density(4.828μA·cm-2).
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    Effect of PEG4000 Amount on Porous Strontium Titanate Photocatalyst by Sol-gel Method
    WANG Hong, DU Ling, SUN Xin, ZHANG Wen-jie
    2014, 0 (12): 39-43.   DOI: 10.11868/j.issn.1001-4381.2014.12.007
    Abstract ( 903 ( PDF (3466KB)( 174 Citation
    PEG4000 was used as the template to prepare porous strontium titanate by sol-gel method. The effect of PEG4000 amount on composition and properties of the photocatalysts was investigated. The results show that, specific surface area of the porous samples increases apparently and strontium titanate phase changes from Sr2TiO4 to SrTiO3 after the addition of the template. Particle size of the samples and crystallite size of SrTiO3 decrease constantly with increasing template amount. The porous sample prepared using 1.5g PEG4000 is composed of SrTiO3 and SrCO3 phase, presenting both the strongest diffraction peak of SrTiO3 and the maximum photocatalytic activity.Degradation rate of methyl orange is 97.9%, which is obviously higher than that on the sample without PEG4000, after 120min of irradiation on the porous sample.
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    RDP and APP/MC/PPO Compound Intumescent Flame Retardant of Polyethylene
    ZANG Chong-guang, CHEN Hua-hua, HU Yang-cheng
    2014, 0 (12): 44-49.   DOI: 10.11868/j.issn.1001-4381.2014.12.008
    Abstract ( 873 ( PDF (3508KB)( 373 Citation
    Poly ammonium polyphosphate (APP), melamine cyanurate (MC) and polyphenylene oxide (PPO) were combined to prepare intumescent flame retardant (IFR) for polyethylene (PE) by adding the synergistic agent resorcinol bis-(diphenyl phosphate) (RDP). The limiting oxygen index (LOI) and vertical burning test were used to study the synergistic effects between IFR and RDP,the effect of add amount of RDP to the combustion performance, and mechanical property of the composite flame retardant IFR. The thermal analysis methods of TG and DTG were used to test and verify the synergistic effect. The results show that there are synergistic effect between RDP and IFR, and the effective synergistic effect of RDP mainly in the first stage of thermal decomposition. The RDP catalyzes the decomposition of APP earlier and decreases the heat release, promotes the formation of carbon layer, and improves the carbon residue significantly during the process of thermal decomposition. When the amount of RDP is 5%(mass fraction), the LOI reaches the maximum value of 31, and passes the criterion UL94 V-0. Obviously,the combination of RDP and APP/MC/PPO can significantly improve the inflaming retarding properties of PE.
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    Preparation and Characterization of BiFeO3 Powders by Sol-gel Method
    WANG Da-wei, WANG Mei-li, LI Zhong-xiang, ZHAO Quan-liang, CUI Yan
    2014, 0 (12): 50-54.   DOI: 10.11868/j.issn.1001-4381.2014.12.009
    Abstract ( 822 ( PDF (4433KB)( 345 Citation
    Using ferric nitrate and bismuth nitrate as reactants, acetic acid and 2-methoxyethanol as dissolvent, BiFeO3 powder was prepared. The phase, morphology and structure of products were characterized by XRD, SEM, EDS, TG-DSC and FT-IR methods. The effects of calcination temperature and holding time on the BiFeO3 powders were studied. The results show that the optimum annealing condition of BiFeO3 is 550-600℃ and 0.5-1.5h. In addition, excess Bi is added in the process of BiFeO3 preparation.When 3%-6% excess of Bi is added, the fewest impurity phase could be found in the BiFeO3 products.
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    Hot Deformation Behaviors and Microstructure Evolution of GH4049 Alloy
    LI Qing, GUO Hong-zhen, WANG Yan-wei, ZHAO Zhang-long, YAO Ze-kun
    2014, 0 (12): 55-59.   DOI: 10.11868/j.issn.1001-4381.2014.12.010
    Abstract ( 781 ( PDF (3227KB)( 201 Citation
    The GH4049 alloy's true stress-strain curves were constructed by data from the hot compression test carried out by thermal mechanical simulator of Gleeble-1500 in the temperature of 1090-1180℃ at strain rates of 0.1-50s-1. The material constants of the alloy in different deformation conditions were obtained by the linear regression of peak stress, and constitutive equation of GH4049 alloy was established through non-linear regression. The results show that, as deformation temperature increases, microstructure had a more full dynamic recrystallization and grains size increases; as the strain rate increases, the grains are more uniform and grains size first decreases and then increases.
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    Diffusion Bonding of TiC Cermet/304SS with Ti/Nb/Cu Relief Interlayers
    LI Jia, SHENG Guang-min
    2014, 0 (12): 60-65.   DOI: 10.11868/j.issn.1001-4381.2014.12.011
    Abstract ( 739 ( PDF (2250KB)( 294 Citation
    The vacuum diffusion bonding of TiC cermet and 304 stainless steel (304SS) was conducted with Ti/Nb/Cu multi-interlayer at 925℃ for 20min with a pressure of 8MPa. The microstructures,fracture morphology elemental distribution of reaction interface and phase composition of fracture surface were investigated with optical microscopy(OM),scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The results show that an obvious transition zone is formed between TiC cermet and 304SS, and the interface products are[Ti,Nb] solid solution+Ti+NbTi4,Nb, remnant Cu+[Cu,Fe] solid solution+Cr. The shear strength of joints is up to 84.6MPa. The failure mostly occurs in diffusion reaction layer between TiC and Ti within TiC cermet.Nb interlayer plays a major role in the relief of the residual stress, and the interface strength is higher than that of TiC cermet weakened due to the effect of residual stress.
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    Research on Microstructures and Mechanical Properties of Hot Rolled Ti-microalloyed TRIP Steel
    YI Hai-long, XU Wei, LONG Lei-zhou, LIU Zhen-yu, WANG Guo-dong
    2014, 0 (12): 66-71.   DOI: 10.11868/j.issn.1001-4381.2014.12.012
    Abstract ( 689 ( PDF (5255KB)( 333 Citation
    A Ti-microalloyed TRIP steel was selected, and the continuous cooling transformation curve was measured.The microstructures and mechanical properties of steels were investigated at different rolling and cooling processes. The results show that the austenite/ferrite and austenite/martensite transformation temperature are at about 500-650℃ and 450℃,respectively. The microstructure of steel is composed of ferrite/bainite and a small amount of retained austenite. The yield strength and tensile strength of steel decrease with the increasing of finish rolling temperature. The yield strength of steel decreases with the decreasing of air cooling end temperature. When the finish rolling and air cooling end temperature are 796℃ and 722℃, respectively, and the yield strength, tensile strength and the product of strength and elongation of the steel are 661, 888MPa and 25042MPa·%,respectively. The microstructure is consisted of fine ferrite and lath bainite,and a large number of fine precipitates presents on the ferrite matrix.
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    Globularizing and Dynamic Recrystallization of ZnAl10Cu2 Alloy During Hot Deformation
    WU Xiao-ping, LI De-fu, GUO Sheng-li, XU Xiao-qing, HU Jie, HE Jin-yu
    2014, 0 (12): 72-78.   DOI: 10.11868/j.issn.1001-4381.2014.12.013
    Abstract ( 767 ( PDF (6054KB)( 218 Citation
    The microstructural evolution of ZnAl10Cu2 alloy during hot deformation was investigated using the Gleeble-1500D thermomechanical simulator at the temperature of 180-330℃, strain rate of 0.01-30s-1 and true strain value of 0.3-1.2. The results show that the sheet α2 phase of eutectic structure has different degrees of globularizing and bending under different hot deformation conditions, the globulous degree increases with the decreasing strain rate and the increasing deformation temperature and true strain. Meanwhile, the dynamic recrystallization occurrs in β-matrix, the degree increases with the increasing deformation temperature when temperature is below 270℃; the dynamic recrystallization grain appears locally grown when the temperature higher. The size of dynamic recrystallization grain decreases with the increasing strain rate which is below 1s-1. The size of dynamic recrystallization is small and uniform when strain rate is 1s-1, but when strain rate is above 1s-1,the dynamic recrystallization grain becomes uneven phenomenon.
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    Microstructure and Toughness of TiB2 Based Coatings with Cu, Ag and Ni Doped
    WANG Huai-yong, LI Sheng-zhi, GUO Jun, WANG Bo, ZHU Ping, HUANG Feng
    2014, 0 (12): 79-85.   DOI: 10.11868/j.issn.1001-4381.2014.12.014
    Abstract ( 648 ( PDF (5198KB)( 329 Citation
    Magnetron co-sputtering method was used to prepare TiB2 based coatings with about 10%(atom fraction) metal (Cu, Ag, Ni) doped.The microstructure of coatings was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Three methods including plastic parameter δH, scratching and indentation test were used for the toughness characterization. The results show that: three metals exhibite different effects on TiB2 grain size and growth structure due to their different forms of existence in the coatings. In detail, Ag exists as crystals, while Cu and Ni are amorphous; TiB2 grains exist in all coatings, Ni and Ag inhibit grain growth, while Cu promotes; TiB2-Cu and TiB2-Ni coatings present a columnar structure with grains embedded in the surface, and TiB2-Ag coating tends to be column-free without grains. Moreover, these differences on the structure have obviously influence on the mechanical properties. All the coatings remain a high hardness (>35GPa). As compared with pure TiB2 coating,the toughness of three coatings improves with metals doped, the coating with Ni doped is more effective on the improvement of toughness than that with Cu and Ag.
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    Influence of Shot Peening on Fatigue Life of 2XXX Aluminum Alloy
    ZHOU Song, XIE Li-yang, HUI Li, ZHANG Xiao-chen, XU Liang
    2014, 0 (12): 86-91.   DOI: 10.11868/j.issn.1001-4381.2014.12.015
    Abstract ( 751 ( PDF (2273KB)( 207 Citation
    The influence of shot peening on the tension-tension fatigue properties of 2XXX aluminum alloy was studied. The microstructure, microhardness, residual stress and tension-tension fatigue performance of the specimens were analyzed,before and after shot peening.The results show that the structure and microstructure of the specimens have no obvious change,but the roughness,residual compressive stress and microhardness increase obviously, which are 6.25, 3.85, 1.12 times respectively of samples without shot peening. The tension-tension fatigue properties improve greatly,average life of the shot peening specimens is 1.67 times of that specimens without shot peening. Under 99.9% survival rate, the safety life of specimens after shot peening is 1.45 times of that specimens without shot peening. After shot peening, the fatigue crack source on the surface changes to one source from multi sources.
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    A Novel Thermal Cycling Test Method for Thermal Barrier Coatings Under CMAS Coupled Condition
    HE Qing, WU Peng, QU Yi, WANG Rui-jun, WANG Wei-ping
    2014, 0 (12): 92-98.   DOI: 10.11868/j.issn.1001-4381.2014.12.016
    Abstract ( 753 ( PDF (6415KB)( 194 Citation
    A thermal cycling test method of thermal barrier coatings(TBCs) under high temperature gradient,gas heating and CMAS(CaO-MgO-Al2O3-SiO2) deposition condition were proposed.The reasons for the early failure of the plasma-sprayed coating with CMAS deposits at 1200℃ were discussed. The results show that, thermal cycling life of TBCs without CMAS deposition is 573 cycles, and thermal cycling life of TBCs with CMAS deposition reduces to 70 cycles. CMAS infiltrates into the surface layer of ceramic coating, forms a dense layer,and transverse cracks increase. The failure of TBCs occurs mainly by peeling of the ceramic layer under CMAS coupled condition.
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    Multiaxial Fatigue Life and Damage Characteristics of 50CrVA Spring Steel Under Tension-bending-torsion Proportional Loading
    ZHAO Kai, HE Yu-huai, LIU Xin-ling, TAO Chun-hu
    2014, 0 (12): 99-103.   DOI: 10.11868/j.issn.1001-4381.2014.12.017
    Abstract ( 833 ( PDF (3277KB)( 150 Citation
    The multiaxial fatigue life of 50CrVA spring steel standard specimens and eccentric specimens under proportional loading was studied with MTS 809 tension-torsion electro-hydraulic servo tester, and the morphology of fatigue fracture were analyzed by scanning electron microscopy(SEM). The results show that, when the bending stress amplitude is not more than 11% of the equivalent stress, additional bending moment can hardly have an effect on fatigue life of the specimens. At the fracture areas of all the specimens forming in the early stage of fatigue crack propagation, tire patterns can be found; fatigue cracks grow in two directions: circumferential and radial. Fatigue characteristics at the fracture are caused by combined stresses, fatigue striations distributing in the radial direction form because of the effect of axial stress, and fatigue striations distributing in the circumferential direction form owing to the effect of torsional shear stress.
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    Research Progress on Microstructure and Heat Treatment of 6000 Series Aluminum Alloys Sheet for Automotive Body
    JIA Zhi-hong, DING Li-peng, WU Sai-nan, WANG Xue-li, LIU Qing, CHEN Chang-yun
    2014, 0 (12): 104-113.   DOI: 10.11868/j.issn.1001-4381.2014.12.018
    Abstract ( 1093 ( PDF (675KB)( 432 Citation
    The properties and application status of 6000 series aluminum alloys in automotive body panel were introduced. Besides, the precipitation behavior, strengthening mechanism, texture evolution and the influence of alloying element to properties were also discussed in detail. Additionally, the conventional heat treatment and the effect of pre-aging or pre-straining to bake hardening were described. Then some current problems and research directions about 6000 series aluminum alloys for automotive body were discussed.
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