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      20 April 2012, Volume 0 Issue 4 Previous Issue    Next Issue
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    Anisotropy of Stress Rupture Properties of DD6 Single Crystal Superalloy at 980℃/250MPa Near [001] Orientation
    YU Jian, LI Jia-rong, HAN Mei, SHI Zhen-xue, LIU Shi-zhong
    2012, 0 (4): 1-5.  
    Abstract ( 1458 ( PDF (2983KB)( 1623 Citation
    The DD6 single crystal superalloy with various orientations was tested at 980℃/250MPa. The influence of orientation on the stress rupture properties at 980℃ was investigated. The results showed that DD6 single crystal superalloy with orientation deviated from [001] direction within 15? exhibited almost the same stress rupture lives at 980℃/250MPa, and there was no anisotropic behavior. The reason of no anisotropic stress rupture properties at 980℃/250MPa was multiple 〈110〉{111} slip systems operated. The γ′ raft caused by the atom diffusion and the dislocation networks formed on γ/γ′ also reduced the anisotropy of stress rupture properties.
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    Anisotropy Study of Thin Metallic Sheets with Strain Measurement of Digital Speckle Correlation
    ZHANG Yang, ZANG Shun-lai, GUO Xiang, LIANG Jin, GUO Cheng
    2012, 0 (4): 6-11.  
    Abstract ( 774 ( PDF (1835KB)( 426 Citation
    Method of experiment and data processing using digital speckle correlation method to investigate sheet’s anisotropy was systematically introduced, then the anisotropy and its evolution of SPCC steel sheet and AA6061 aluminum sheet were researched. The results show that: the speckle strain measuring method is an effective tool to obtain the mechanical properties of sheets, whose greatest advantage is its capability to capture the whole strain field during deformation, and this is key to study mechanical properties of materials under complex loading conditions; for the SPCC steel sheet, the anisotropy of flow stress is not distinct, while the total and incremental Lankford coefficient (r values and r′ values) show obvious anisotropy, moreover its values decrease with the increasing of deformation, which is different with the constant Lankford coefficient by traditional strain measuring using extensometer; for the AA6061 aluminum sheet, the anisotropy of flow stress and r value are not obvious, however, the elongations of specimens in different directions to rolling show an distinct anisotropy, and the working hardening rate of flow stress and r′ value appear a sharp fluctuation when the true tensile strain is between 0.15 and 0.20; the anisotropy of the two sheet’s strain increases gradually with the increasing of deformation, especially for SPCC steel sheet.
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    Analysis of Tube Bursting at Superheater
    DOU Ying-ting, LI Jun, ZHANG Zheng
    2012, 0 (4): 12-16.  
    Abstract ( 688 ( PDF (2633KB)( 346 Citation
    The failure causes of tube bursting at superheater were analyzed by many tests and several research methods, such as macro inspection, dimensional measurement of tube perimeter change, microstructure examination, mechanical testing and stress check. The results show that the tube is severely oxidized and overheated, which intensifies the situation of overheating operation. Inflation of the tube, thinning of the tube wall and fully pearlite spheroidized microstructure can be observed, and the strength of the material deteriorates significantly. It is concluded that the tube failure mode is overloading. At the same time, some useful suggestions such as periodic measurement of tube perimeter and metallographic examination are proposed, which can be a reference for operation and maintenance.
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    Effect of Rolling Deformation on Properties of Roll Casting Lead Alloy Strips
    LI Jian-ping, JIANG Hong-feng, MAO Da-heng, ZENG Li-bang
    2012, 0 (4): 17-21.  
    Abstract ( 933 ( PDF (2557KB)( 483 Citation
    The effect of rolling reduction on the microstructure and properties of roll casting quaternary Pb-Ag-Ca-Sr alloys was investigated through anodic polarization stable potential, corrosion rate, surface morphology before and after polarization,conductivity, tensile properties and hardness. The results show that: During the process of anodic polarization there are no significant changes on the final stable potential of different lead alloys strips, but the corrosion resistance and mechanical properties of lead alloy strips are improved significantly. The conductivity of lead alloy strips decreases slightly during the rolling. Especially,on the condition of two pass roll with a reduction of 30%, the corrosion resistance is 1.48 times as that of the original lead alloy strips; the ultimate tensile strength σb and yield strength σp0.2 of the lead alloy strips increase by 28.5% and 79.4%, respectively; the hardness HBS also increases 2.8.
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    Preparation of Silica Aerogel via Ambient Pressure Drying
    LU Peng-peng, ZHAO Hai-lei, LIU Xin, LI Xing-wang
    2012, 0 (4): 22-26.  
    Abstract ( 1135 ( PDF (2404KB)( 447 Citation
    Hydrophobic silica aerogel was prepared from commercial water glass via ambient pressure drying. The effects of aging times, aging agents, drying solvent categories and surface modification on the microstructure and properties of silica aerogel were investigated. The results showed that the density, porosity and specific surface area of the prepared silica aerogel were 0.082g/cm3, 96.26% and 585.4m2/g, respectively. The structure and properties of hydrophobic silica aerogel were analyzed by scanning electron microscope(SEM),Fourier transform infrared spectra(FT-IR),thermogravimetric (TG) and differential thermal analysis(DTA).
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    Microstructural and Mechanical Characteristics of Friction Stir Welded 6005A-T6 Aluminium Alloy
    DONG Peng, SUN Da-qian, LI Hong-mei, GONG Wen-biao, LIU Jie
    2012, 0 (4): 27-31.  
    Abstract ( 1394 ( PDF (3092KB)( 374 Citation
    Microstructural and mechanical characteristics of friction stir welded 6005A aluminum alloy were investigated by means of optical microscope, scanning electron microscopy (SEM), transmission electron microscope (TEM), tensile test machine and Vickers hardness tester. The results show that the nugget zone (NZ), thermo-mechanically affected zone (TMAZ) and heat affected zone (HAZ) are characterized by a fine equiaxed, elongated and coarse grain structures, respectively. All the precipitates dissolved in the NZ, and the TMAZ contains high density dislocation, and the HAZ shows over-aged state. Compared with the base metal, the FSW joint has a reduction in strength and elongation, and there is a distinctly soften region where the minimum hardness value located in HAZ of advancing side. At the optimum welding parameters (rotation speed of 1200r/min and welding speed of 200mm/min), the tensile strength and elongation of the FSW joint are equivalent to 72% and 69% of those of the base metal, respectively.
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    Research on Microstructure and Mechanical Properties of Ti+Nb and Ti+V Ultra-low Carbon Bake Hardening Steels
    CHEN Ji-ping, QIAN Jian-qing, LI Sheng-zhi, KANG Yong-lin
    2012, 0 (4): 32-35.  
    Abstract ( 753 ( PDF (1538KB)( 420 Citation
    Deformation resistance and dynamic continuous cooling transformation of Ti+Nb and Ti+V bearing ultra-low carbon bake hardening steels were studied using Gleeble-1500 thermal simulator. The microstructures of two experimental steels under different cooling conditions were also analyzed. The results showed that the deformation resistance of Ti+Nb bearing ultra-low carbon bake hardening steel was 13MPa higher than that of Ti+V bearing ultra-low carbon bake hardening steel at 1100℃ with the strain rate of 1s-1. The morphology of the microstructures and the grain size have big difference for two experimental steels under the same deformation conditions. The room temperature microstructures of the two experimental steels are polygonal ferrites under various cooling conditions. The ferrites of Ti+Nb bearing ultra-low carbon bake hardening steel are finer and have irregular shape with the average grain size of 16μm, while for Ti+V bearing ultra-low carbon bake hardening steel, the ferrites are coarse and have regular shape with the average grain size of 26μm.
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    Microstructure and Mechanical Properties of As-cast Mg-4Al-4Si-0.75Sb Magnesium Alloy
    SONG Pei-wei
    2012, 0 (4): 36-41.  
    Abstract ( 736 ( PDF (2212KB)( 524 Citation
    Mg-4Al-4Si-0.75Sb (AS44-0.75Sb)(mass fraction/%) magnesium alloys were prepared by the gravity casting. Microstructure and mechanical properties at room temperature of the as-cast AS44-0.75Sb alloy were investigated. The results show that the as-cast microstructure consists of α-Mg matrix, β-Mg17Al12 phase, Mg2Si phase and Mg3Sb2 phase; the addition Sb of 0.75 results in the formation of Mg3Sb2 phase with high melting-point, the morphology of skeleton-like primary Mg2Si phase can be modified significantly and becomes refinement Chinese script Mg2Si. The hardness HV of alloy is 65.9, yield strength, ultimate tensile strength and extension percentage are about 1364MPa, 1723MPa and 3.3% respectively. The fracture forms of the alloy is quasi-cleavage brittle fracture.
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    Preparation and Tensile Properties of 14CrODS Ferritic Steel
    LIAO Lu, ZHOU Zhang-jian, LI Ming
    2012, 0 (4): 42-46.  
    Abstract ( 773 ( PDF (4052KB)( 389 Citation
    A ODS ferritic steel powder with the chemical composition (mass fraction/%)of Fe-14Cr-05Ti-0.35Y2O3 was prepared by mechanically alloying (MA), and the element distribution was homogenous. The MA powder was consolidated by hot isostatic pressing (HIP), followed by forging and annealing. Compared to 14CrNA steel without ODS particles, the tensile strength of 14CrODS steel was excellent,but not so good compared with MA957, thus need improvement. The ductility of 14CrODS was much better than MA957, and could be enhanced further by forging. However, residual stress existed during forging, making the 14CrODS steel brittle in room temperature tensile tests. Annealing could remove the residual stress and significantly improve the ductility of 14CrODS, which was more excellent than MA957.
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    Air-tight Reliability Analysis of Aero-port Seal Structure
    LIU Wei, LIU Zhi-qun, ZHAO Xiao-bo, XI Bao-an, YUE Zhu-feng
    2012, 0 (4): 47-51.  
    Abstract ( 918 ( PDF (1960KB)( 497 Citation
    The reliability method was applied to analyze the influence of the seal structure parameters on the air-tight performance of aero-port. The Ogden constitutive model was fitted based on compression experimental data of two types of aero-port sealing strip, which was applied to simulate the implicit response of secondary contact force between the door body and door frame by FEM. The seal structure’s parameters such as closing-stroke, assembly dimension, and baffle size etc were treated as random variables, the reliability of the two sealing strips types was compared by Monte Carlo method. The mean value sensitivity and variance sensitivity of above parameters were obtained. The results were helpful for the sealing strip selection and seal structure optimum design.
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    CCT Diagram and Hardenability of 65Mn Steel Produced by Compact Strip Production
    HUANG Gang, WU Kai-ming, ZHOU Feng, ZHOU Chun-quan, ZHOU Ming-wei, JIAO Guo-hua
    2012, 0 (4): 52-55.  
    Abstract ( 876 ( PDF (2678KB)( 445 Citation
    Using Formaster dilatometer and metallographic method, the CCT diagram of 65Mn steel produced by thin slab continuous casting and rolling process (Compact Strip Production,CSP) was measured. The critical points are AC1=719℃, AC3=747℃, Ms=267℃ and the critical cooling rate is 35℃/s. By hardness tester and scanning electron microscopy (SEM) analysis showed that quenched 65Mn steel produced by CSP has fine and uniform microstructure and high hardness, and its hardenability was superior to that of the steel produced by traditional process.
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    Ultrasonic-induced Morphology Control of Palladium Nanoparticles in CTAB/SDS Solution and Its Electrocatalytic Activity for Oxidation of Formaldehyde
    WANG Yan-li, ZHANG Ming-xu, WANG Xiao-yu
    2012, 0 (4): 56-61.  
    Abstract ( 878 ( PDF (1797KB)( 405 Citation
    Nano-Pd particles were prepared using ultrasonic irradiation in the palladium(Ⅱ) chloride H2O/EtOH(5/1,V/V) solution by the addition of a quantity of hexadecyl trimethyl ammonium bromide(CTAB) and sodium dodecyl sulfonate(SDS). The samples were characterized by XRD,TEM,selected area electron diffraction (SAED),HRTEM and low temperature nitrogen adsorption-desorption. The effects of the composition of CTAB and SDS on the growth morphology of palladium nanoparticles were investigated. The electrocatalytic properties of the nano-Pd modified glassy carbon electrode (Pd/GCE) for formaldehyde oxidation were also investigated by cyclic voltammetry. The results indicate that a promising possibility of a size and morphology for the nano-Pd particles are controled by adjusting the composition of CTAB and SDS. The polygonal nano-Pd particles with a distributed size of 10-20nm are obtained when the molar ratio of CTAB∶SDS is 1∶1 and the reaction time is 60min. The nanoparticles obtained by addition of two surfactants (CTAB and SDS) increase the BET surface area by 14m2?g-1 compared to that obtained without surfactant, which show the excellent electrocatalytic activity for the oxidation of formaldehyde.
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    Effect of Corrosion Product Films on Corrosion Behavior of X80 Pipeline Steel in Ku’erle Soil Simulated Solution
    LIANG Ping, ZHANG Yun-xia, HU Chuan-shun
    2012, 0 (4): 62-67.  
    Abstract ( 645 ( PDF (1916KB)( 420 Citation
    The corrosion product films were formed on the surface of X80 pipeline steel immersed in Ku’erle soil simulated solution for 1 month, and the micrographs,compositions were observed and tested using scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The effect of corrosion product films on the corrosion resistance of X80 steel in simulated solution was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements. The results showed that the corrosion product films accelerated the cathodic reduction processes, which were translated from activation control into diffusion control. The corrosion product is mainly composed of inner Fe3O4 layer and outer Fe2O3, Fe(OH)3 and FeO(OH) layer. The outer layer, which is loose and caducous, does not protect X80 from corrosion. There are some microcracks and microvoids in the inner corrosion product, which is compact, and these defects increase the effective area of cathodic reduction, reduce the transfer resistance of charge ions, promote the formation of corrosion microcell, thus, X80 steel with corrosion product films exhibits a higher corrosion rate than bare steel in Ku’erle soil simulated solution.
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    Microstructure and Precipitation Kinetics of β-Mg17Al12 Phase in AZ91 Alloy Compressed at Room Temperature
    YANG Lin, HUANG Ting, LIN Li, LIU Zheng
    2012, 0 (4): 68-71.  
    Abstract ( 880 ( PDF (2598KB)( 366 Citation
    Microstructure and precipitation kinetics of β-Mg17Al12 phase after aging treatment in AZ91 alloy, which was fabricated with raw magnesium by direct smelting and compressed at room temperature, were investigated. The results showed that lots of twinning would emerge as a result of compression at room temperature, serving as nucleation substrate for β-Mg17Al12 phase precipitation. The β-Mg17Al12 phase precipitated preferentially at grain and twinning boundaries. Phase precipitation and growth were frequently observed at the intersection between twinning and original grain, or among various twinning; certain orientation relationships were also discovered among the β-Mg17Al12 phase precipitated in twinning and the α-Mg matrix. The amount of β-Mg17Al12 phase increased with gradually aging time, whereas the required time for a definite amount of precipitates decreased with increasing temperature. The activation energy for β-Mg17Al12 phase precipitation in AZ91 alloy was calculated to be 238-37.9kJ/mol using the JMAK equation, in accordance with experimental data.
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    Experimental Research on Thermal Wave Imaging Inspection for Hidden Corrosion on Airframe
    ZHAO Zhi-chang, YAO Hong-yu, CAO Da-shu, SUN Yan-chun
    2012, 0 (4): 72-75.  
    Abstract ( 619 ( PDF (1441KB)( 386 Citation
    With acceleratedly corroded samples and real corroded airframe parts, application of thermal wave imaging technology to hidden corrosion inspection was experimentally studied. The results show that this technology is able to reveal hidden corrosion, especially good for exfoliation corrosion, regardless corrosion product remains or not as well as presence of paint on the surface. The image of corrosion has details and is easy to understand. This technology is able to reveal disbond as well as lack of sealant inside bonded joints.
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    Effects of Current Density on Electrodeposited Matt Tin in Methanesulfonate Electrolytes
    ZHANG Zhu, GUO Zhong-cheng, LONG Jin-ming, CAO Mei
    2012, 0 (4): 76-81.  
    Abstract ( 897 ( PDF (2001KB)( 387 Citation
    The effects of current density on cathode polarization, overpotential,deposition efficiency, deposition rate, throwing power, surface morphology and crystallization orientation in stannous methanesulfonate baths were studied using constant current polarization, scanning electron microscope and X-ray diffraction patterns. The results showed that, the cathode polarization and deposition rate increased, throwing power decreased, deposition efficiency initially increased and then decreased with the increasing of current density(0.5-4A?dm-2). Increase in current density made the tin electro-crystallization varied from outward to lateral growth modes and crystallization orientation varied from (321) and (431) to (112) and (332) crystal faces. The additives adsorb onto crystal faces, the surface energies and growth rate decreased, preferred orientations and growth modes could be modified.
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    Effect of Nano-palygorskite Additive in Base Oil on Anti-wear and Self-repairing Properties of 45# Steel Tribo-pair
    WU Xue-mei, ZHOU Yuan-kang, YANG Lu, WANG Chen-xiang, LI Yi, CHEN Jian-hai
    2012, 0 (4): 82-87.  
    Abstract ( 719 ( PDF (2429KB)( 386 Citation
    The 150N base oil containing 2% and 4% mass fraction of nano-palygorskites modified with KH550 as additive were prepared. The anti-wear,friction-reducing and self-repairing behaviors of nano-palygorskites as additive in base oil were observed on the MMU-10G abrasive-wear tester. The wear loss of the sample was studied by electronic balance (EB). The morphographies of the worn surfaces were analyzed by means of scanning electron microscopy (SEM) and optical microscope. Elemental analysis was performed using an energy-dispersive X-ray (EDX) microanalyzer. The results show that the lubricating base oil containing 2% mass fraction of nano-palygorskites as additive has very weak self-repairing performance to 45# steel tribo-pair, the wear loss decreases limited and the anti-wear only occurs in early running-in stage; Lubricating base oil containing 4% mass fraction of nano-palygorskites as additive exhibits better anti-wear and self-repairing performance. Total wear loss decreases observably as high as 26.5% compared to that of pure base oil. Self-repairing films made up of characteristic elements of palygorskite in patchy distribution are observed on the surface of the sample.
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    Study on Corrosion Behavior of 30CrMnSiNi2A Steels in Simulated Tank Water Environment
    HUANG Yi, LIU Hui-cong, ZHU Li-qun, LI Wei-ping, LIU Jian-zhong, YE Xu-bin
    2012, 0 (4): 88-93.  
    Abstract ( 688 ( PDF (1778KB)( 394 Citation
    The environmental conditions of aircraft tank water was simulated to study the corrosion behavior and characteristic of 30CrMnSiNi2A steel by corrosion area, corrosion mass loss rate, content of dissolved oxygen and pH in simulated tank water, corrosion potential of high-strength steel and so on. The results indicated that the corrosion process of 30CrMnSiNi2A steel in the simulated tank water was divided into three states: rapid corrosion stage came from 0h to 24h in which corrosion area was small and corrosion rate was fast; medium corrosion stage came from 24h to 168h in which most of the area was corroded and corrosion rate slowed down; slow corrosion stage came from 168h to 480h in which all of the area was corroded and corrosion rate was slow. With time going on, content of dissolved oxygen gradually reduced at first and then kept steady; pH value rapidly increased at first and then fluctuated within a narrow range; corrosion potential changed as decreasing exponential function. In addition, EIS and Tafel polarization curves indicated that corrosion rate of 30CrMnSiNi2A steel at three characteristic pH(4.2,4.8,5.2) decreased with pH value increasing.
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    Effect of DLC Film Thickness on Properties of DLC/MAO Composite Coating on Magnesium Alloy
    YANG Wei, WANG Ai-ying, KE Pei-ling, DAI Wei, ZHANG Xue-qian
    2012, 0 (4): 94-98.  
    Abstract ( 776 ( PDF (2624KB)( 353 Citation
    Diamond-like carbon (DLC) films with different thickness were deposited using ion beam deposition technique on the coated AZ80 magnesium alloy pretreated by microarc oxidation (MAO), forming the DLC/MAO composite coating. The surface microstructure, mechanical and tribological properties of the four film-substrate systems were studied. The results show that, increasing the thickness of the DLC film, the numbers and aperture of the micropores on the composite coating surface decreased. However, the composite coating surface changed coarse and more grains distributed on the DLC film with the increasing of thickness. As a result, DLC-80min/MAO/AZ80 film-substrate system had the lowest Ra and the maximal H, E and H/E. Compared with the MAO coating, the average values of friction coefficient of the DLC/MAO composite coating decreased. The friction coefficient and wear morphologies of the film-substrate systems with different thickness of DLC film exhibited difference due to the change of surface characteristic. The Fe transfer layer were formed on the wear surface of all the film-substrate systems. The coated Mg alloy was effectively protected for the lubrication characteristic of the surface DLC film.
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