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      20 February 2012, Volume 0 Issue 2 Previous Issue    Next Issue
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    Sound Velocity Under High Pressure of AD95 Ceramics
    SUN Zhan-feng, XU Hui, PENG Jian-xiang
    2012, 0 (2): 1-4.  
    Abstract ( 646 ( PDF (1078KB)( 352 Citation
    The sound velocity under high pressure and the release path of AD95 ceramics have been studied through the measurement of particle velocity profile by VISAR. Results indicate that AD95 ceramics act very differently with metals during unloading process when the impact stress is 25.86-5742 GPa. The process is evidently divided into two steps; the first is derived from the unloading of the elastic wave, and the second from the shock wave; the ratio of the first step decreases with the increase of impact stress. There is no a clear inflexion between the elastic unloading and the plastic unloading in the second step. The results will lay a foundation of study on dynamic response and compressive damage of ceramics.
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    Preparation and Characterization of PLA/MMT Nanocomposites with Microwave Irradiation
    ZHAO Shan-shan, LI Yuan, CAO Hai-lei, WANG Peng
    2012, 0 (2): 5-8.  
    Abstract ( 817 ( PDF (1416KB)( 305 Citation
    Acidic montmorillonite (H-MMT) was managed to be prepared by treating Na-montmorillonite with H2SO4 under microwave irradiation. The structure and characters of the H-MMT were studied by BET, NH3-TPD and DTA/TG techniques. The results revealed that H-MMT had greater surface area and pore volume, the super acid sites were formed on its surface and the thermal stability was improved. After that, PLA/MMT nanocomposite was synthesized by in situ melt polycondensation under microwave irradiation with H-MMT compounded with SnCl2 as catalyst and nanometer additives. The results showed that H-MMT existed in an exfoliated form in the polymer matrix and had good catalytic effects on elevating the molecular weight of the PLA based nanocomposite, and the mechanical and thermal properties of PLA/MMT nanocomposite were improved.
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    Recrystallization of As-cast AZ31 Magnesium Alloy During High Temperature Compression
    XIAO Kai
    2012, 0 (2): 9-12.  
    Abstract ( 845 ( PDF (2506KB)( 314 Citation
    High temperature compression tests at a temperature range of 200-500℃ with various strain rates 0.001-1s-1 on a conventional as-cast AZ31 were carried out using a Gleeble-1500 dynamic material testing machine. The effects of deformation temperature and strain rate on microstructure evolution of the as-cast AZ31 magnesium alloy were analyzed by introducing temperature-compensated strain rate (Zener-Hollomon parameter, Z value). The results of the microstructure observations indicate that as the volume fraction of DRX grains increased, the size of DRX grain size is decreased. The mean size of the DRX grains decreases and the volume fraction of DRX grains increase with an increase of Z value. The three dimensional graph has been established to provide a clear guideline for forming craft selection.
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    Effect of Microstructure on High Temperature Tensile Properties of TA15 Titanium Alloy
    HE Fei, CHEN Hai-feng, WANG Yu-hui
    2012, 0 (2): 13-15.  
    Abstract ( 693 ( PDF (2087KB)( 347 Citation
    The effect of microstructure on the high tensile properties at 500℃ of TA15 titanium alloy was studied. The results show that the increase of primary α phase content, the strengthening of α phase directional, the thickening of secondary α lamellae or the increase of β grain size can reduce the high temperature tensile at 500℃ of TA15 titanium alloy. The largest decrease of high temperature tensile is more than 90MPa by changing the microstructure. The analyses show that the number of grain boundaries is increasing with primary α phase content, and the descent speed of grain boundary strength is faster than that of the grain with the increase of temperature, resulting in the decrease of high temperature tensile.
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    Friction and Wear Behavior of Al2O3 Ceramic Composite Materials Reinforced with Cr3C2 and (W,Ti)C
    SUN De-ming, XU Chong-hai, YANG Liu-bo, WU Jian-jun
    2012, 0 (2): 16-19.  
    Abstract ( 780 ( PDF (984KB)( 354 Citation
    Ceramic composite materials Al2O3/Cr3C2/(W,Ti)C were fabricated with hot-pressing sintering technique. The physical and mechanical properties were tested, the friction and wear behavior were studied, and the wear trace was investigated by scanning electron microscope (SEM). Results indicate that the ceramic composite material Al2O3/Cr3C2/(W,Ti)C has good mechanical properties, good friction and wear resistance, and especially both the frictional factor and the wear rate decrease about 50% than the monolithic Al2O3 ceramic. The main wear mechanism is the grain-abrasion, and the grain fracture is mostly brittle. The good flexural strength and fracture toughness improve the wear resistance of the ceramic composite material greatly.
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    The Comparison Analysis of Test Result of Ultrasonic Δ Technique and TOFD Method
    SHI Yi-wei, WANG Nai-bo, LU Chao
    2012, 0 (2): 20-24.  
    Abstract ( 549 ( PDF (1542KB)( 291 Citation
    Through the inspection of ultrasonic Δ technique and TOFD method on simulate flaws, concluded signal oscillogram and B/C scan of flaws. The signal characteristics of ultrasonic Δ technique and TOFD method were analyzed and interpreted. The results show that the defects which are perpendicular to the surface can be identified and located effectively, and can overcome surface blind area effectively, and the recognition capibility for defects is not limited by the orientation of them. From the results it can be seen that the achieved flaw sensitivity and probability of detection are substantially better than TOFD method.
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    On the Interfacial Properties of CCF300/QY8911 Composite with Cyclical Hygrothermal Treatments
    ZHANG Li-jun, ZHAO Yan, LUO Yun-feng, DUAN Yue-xin
    2012, 0 (2): 25-29.  
    Abstract ( 975 ( PDF (2175KB)( 292 Citation
    The specimens of CCF300/QY8911 composite are treated with cyclical moisture absorption-desorption processes. The curves of moisture absorption and desorption are drawn and are fitted in the Fick Second Law. Interfacial properties are characterized with the method of the interlaminar shear strength (ILSS), and cross-section and lateral morphologies are observed by SEM. The results indicate that the behaviors of moisture absorption and desorption of specimens are in accordance with Fick Second Law, with the moisture immersion for 14d at 71℃, the samples obtain the saturated moisture absorption contents; Absorption moisture has reversible and irreversible destructive effect on of CCF300/QY8911 composite. Reversible damage on fiber/resin interfaces can be eliminated after desorption processing, which increases the dry ILSS; the increase of hygrothermal cycles can lead to further irreversible damage on the fiber/resin interfaces and make the ILSS of CCF300/QY8911 composite decrease. However, the absorption moisture is the key factor which causes the degradation of ILSS performance.
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    Experimental Study of Acoustic Emission Activity of Alumina Under Compression
    REN Hui-lan, FANG Min-jie, HE Jian-hua
    2012, 0 (2): 30-34.  
    Abstract ( 552 ( PDF (2540KB)( 289 Citation
    Acoustic emission (AE) characteristic of alumina under compressive loading was investigated by experimental method. During three-point-bending test and Brazilian test, advanced multi-channel acoustic emission system was used to detect the failure of alumina. Analyzing the results of acoustic emission, AE energy, AE counts and AE hits changing with loading time reflect the process which is from the growth and evolution of micro-crack to macro-fracture of material. AE parameters are used to determine the location of fracture surface. By micro-macro characteristics, micro-cracks around particles are dominated the brittle fracture of alumina.
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    Study of Fatigue Performance for High Strength Steel 30Cr3SiNiMoVA
    LI Bin, DONG Wan-yuan, WANG Xiao-bing, LIANG Qiang
    2012, 0 (2): 35-40.  
    Abstract ( 743 ( PDF (4729KB)( 498 Citation
    In order to obtain fatigue design data of high strength steel 30Cr3SiNiMoVA, the fatigue test of this steel material have been carried out. In the experiment the material conditional fatigue limit was tested by the up-and-down method, and other fatigue data were done by the group test method under four stress levels for the polished specimen and unpolished specimen of the material, respectively. Then a two-parameter least square method was used to fit the S-N curve, and the probability method was used to obtain the P-S-N curve. By the comparisons between two S-N curves, it is seen that the fatigue life of unpolished samples is lower than that of polished samples under same fatigue load level, so 30Cr3SiNiMoVA’s fatigue life is sensitive to the surface rough state of the specimen, and this sensitivity is increasing with the decreasing of fatigue load, and the fatigue limit of the polished specimen is about 1.4 times of the unpolished specimen. It is suggested that the effective technology should be applied into improving the surface rough state of one type of this material. These data will provided a valuable support for the engineering applications of 30Cr3SiNiMoVA.
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    Joining of SiO2f/SiO2 Composite to TC4, Ti3Al and TiAl
    CHEN Bo, XIONG Hua-ping, MAO Wei, CHENG Yao-yong
    2012, 0 (2): 41-44.  
    Abstract ( 762 ( PDF (1786KB)( 365 Citation
    SiO2f/SiO2 composite was successfully joined to TC4, Ti3Al and TiAl using Ag-Cu-Ti brazing foils at 880℃ for 10min and the sound joints were formed. The microstructures of three kinds of joints showed that a thin reaction layer was formed near the surface of SiO2f/SiO2 matrixes where elements Ti and O were enriched. During the brazing, element Ti in the brazing filler as well as a part of dissolved Ti from base metals together diffused to the surfaces near the composites and reacted with SiO2 and finally formed Ti-O phase. According to the atom ratio of Ti and O, it was deduced that the Ti-O phase should be Ti2O phase. The white microstructures and the grey microstructures existed in the three brazing seam. The former was mostly Ag-based solid solution and the latter mainly contained Ti and Cu that formed Ti-Cu phase.
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    Finite Element Modeling of Residual Stress in the Bonding Interface of Ti/Porcelain
    ZHU Song, DUAN Zhen-zhen, LIU Jie, QIU Xiao-ming, SUN Da-qian
    2012, 0 (2): 45-49.  
    Abstract ( 614 ( PDF (2085KB)( 294 Citation
    The numerical value and distribution of residual stress in the bonding interface of Ti/porcelain and Ti / ZrO2/porcelain have been investigated by finite element method. The results show that the high residual stresses existed in the interface of Ti/porcelain specimen. Porcelain surface tended to produce cracks due to the tensile stress parallel to the surface. Stress concentration in the rim of interface of Ti/porcelain made it a vulnerable area of the bonding and usually led to porcelain collapse or crack, especially at the corner angle of Z-orientation edge. ZrO2 could efficiently protect the surface of Ti from excessive oxidative, lower the degree of stress concentration in the interface, improve the bonding strength of Ti/porcelain and reduce the cracking tendency of porcelain.
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    Effect of High-pressure Torsion on Particle Distribution of SiCp-Al Composites
    LI Xiao, LI Ping, XUE Ke-min, WANG Cheng, ZHANG Kai
    2012, 0 (2): 50-54.  
    Abstract ( 827 ( PDF (2321KB)( 243 Citation
    SiCp-Al matrix composites were fabricated by High-Pressure Torsion.Based on microstructural observations and the quadrat method,the effect of different technological parameters on distribution of SiC particles was studied. The result shows that,SiC particles and Al powder mixtures are directly fabricated into composites by High Pressure Torsion; According to micro structural observations, there is difference of distribution of SiC particles along the distance from the center; the factors(the number of turns, pressure, temperature) could significantly influence the distribution of SiC particles; Combined with quadrat method, the shear strain augments with the number of turns, pressure, the distance from the center increasing, then the distribution of SiC particles is more homogeneous,With temperature increasing, the matrix flow ability becomes better ,which makes the distribution of particles improved.
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    Study on Synthesis and Properties of MDI-50 Type Polyurethane Elastomer
    LI Wan-jie, LIN Yin-lei
    2012, 0 (2): 55-57.  
    Abstract ( 951 ( PDF (633KB)( 344 Citation
    MDI-50, polyol and 3,3′-dichloro-4,4′-diamino-diphenylmethane (MOCA) chain extender were used to prepare MDI-50 type polyurethane elastomer. The effects of the mass fraction of free -NCO in prepolymer and molecular weight of polyol on mechanical properties of the elastomer were studied. The structure and performance were analyzed by means of differential scanning calorimeter (DSC), Thermo gravimetric analysis (TG), Fourier transform infrared (FTIR) spectroscopy and mechanical properties test. And it was compared with TDI-80 type polyurethane elastomer. The results showed that the comprehensive properties of MDI-50 type polyurethane elastomer were better than TDI-80 type polyurethane elastomer. The hardness, tearing strength and tensile intensity of MDI-50 type polyurethane elastomer increased with the increase of the mass content of free -NCO in prepolymer. When the molecular weight of polyol increased, the elongation at break of the elastomer increased.
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    Effects of Cooling Process on Microstructure of As-cast AZ61 Magnesium Alloy
    PENG Jian, SHE Huan, TAO Jian-quan, WANG Xiao-hong, PAN Fu-sheng
    2012, 0 (2): 58-61.  
    Abstract ( 886 ( PDF (2215KB)( 299 Citation
    The liquid solidification process of AZ61 magnesium alloy was divided into two stages of high-temperature melt and solidification. The effects of different cooling rates of each stage on the cast microstructure and the variations of dendrite spacing on the microhardness were investigated. The results show that at the high-temperature melt stage, when the cooling rate increases from 0.65℃/s to 15.9℃/s, the dendrite microstructure is continuously refined and the size becomes more uniform. The primary dendrite is decreased from 230μm to 80μm and the secondary dendrite spacing is decreased from 12.8μm to 9.2μm. At the solidification stage, when the cooling rate increases from 7.8℃/s to 23.0℃/s, the primary dendrite spacing is decreased from 105μm to 73μm and the secondary dendrite spacing is decreased from 10.6μm to 8.8μm. In the two stages, the microhardness value presents increasing trend with the increase of cooling rate. By comparison, the change of cooling rate has a larger impact on the as-cast microstructure of high-temperature melt stage than that the solidification stage.
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    The Preparation and Properties of DSSC CuAl2O4/TiO2 Photoanodes
    HU Zhi-qiang, LIU Xian-qing, HUANG De-feng, GAO Hong
    2012, 0 (2): 63-66.  
    Abstract ( 825 ( PDF (1879KB)( 349 Citation
    CuAl2O4/TiO2 thin film photoanodes were prepared by doping spinel CuAl2O4 nanocrystallineprepared by the citrate method into P25 (degussa, TiO2), and then assembled into Dye-sensitized solar cells(DSSC) and characterized the photoelectric properties. The results showed that performance of DSSC increase when doped CuAl2O4. When the doping amount is 2%(mass fraction), the photoelectric conversion efficiency was 39.1% higher than the pure TiO2 thin film photoanodes.
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    Effect of Re-shot-peening on the Fatigue Life of TC18 Titanium Alloy
    WANG Xin, GAO Yu-kui, WANG Qiang, SONG Ying-gang, LU Feng
    2012, 0 (2): 67-71.  
    Abstract ( 832 ( PDF (2032KB)( 311 Citation
    The effect of re-shot-peening treatment on the residual stress and room temperature fatigue life of initially shot-peened TC18 titanium alloy was investigated. The change of surface residual stress and fatigue life after re-shot-peening were examed by X-ray diffraction and rotating-bending fatigue tester, respectively. The results show that the surface residual stress relaxed in the range of 30%-50% because of pre-fatigue test, and that re-shot-peening successfully recovered the relaxed surface residual compressive stress up to the 50%-70% of the original. Further, compared with the samples excluding re-shot-peening, fatigue life of TC18 titanium alloy can be increased by 75% when re-shot-peened after the suitable pre-fatigue cycle.
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    Influence of Microdefect on Rolling Contact Fatigue Performance of Thermal Spraying Coating
    WANG Shao-yun, LI Guo-lu, WANG Hai-dou, LIU Jin-hai, XU Bin-shi, PIAO Zhong-yu
    2012, 0 (2): 72-76.  
    Abstract ( 744 ( PDF (3406KB)( 287 Citation
    Three kinds of NiCrBSi alloy coatings with different micro-defect types were sprayed on 1045 steel. Rolling contact fatigue (RCF) life of the coating was investigated using a ball-on-disc tester and the map of Weibull distribution failure probability was plotted. SEM was adopted to observe the microstructure and fatigue trace of the coatings. In addition, the contact fatigue life and main failure mode of different coatings were compared and the failure mechanism was investigated as well. The results showed that micro-defects in the coating were mainly composed of micro-pores and micro-cracks. Contact fatigue life of the coating was in inverse proportion to the content of micro-defects. Contact fatigue life of coating were 7.77?105, 8.99?105, 7.81?105 cycle, with the porosity of the coatings 2.5%, 1.3% and 2.1%,respectively. It also can be seen that, when the content of micro-defects was low, the main failure mode of the coating was spalling failure while with the increasing of micro-defects and the decreasing of combined strength the main failure mode changed into the interfacial delimitation failure. The large pores existing in the coatings may result in the early failure of the coating, at the same time increase the wear failure probability.
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    Development and Applications of Electron Beam Cold Hearth Melting
    TIAN Shi-fan, MA Ji-min
    2012, 0 (2): 77-85.  
    Abstract ( 985 ( PDF (2549KB)( 372 Citation
    This paper systematically summarizes the developments of Electron Beam Cold Hearth Melting (EBCHM) technology for nearly 40 years. The main features of the EBCHM including: the improvements in electron beam gun, the evolution of the structural forms of the cold hearth and their functional expanding, the unique capability for elimination of the metallurgical defects of titanium alloys, and the current status and the future trends in the studies and applications of the EBCHM as well, have been sorted out and introduced in a relatively detailed way. It is pointed out that the industrial application of EBCHM in the production of Ti and its alloys has been increased steadily in recent years. The fundamental reason for that is the EBCHM’s capability to eliminate the metallurgical defects in Ti alloys effectively, thus makes it possible to meet the demanding requirements of the rotating aero-engine component. This appears to be the main factor that accelerates the development and optimization of this process.
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    Research Progress of Al-based Amorphous Alloy Materials Prepared by Thermal Spraying Process
    ZHANG Zhi-bin, LIANG Xiu-bing, CHEN Yong-xiong, XU Bin-shi
    2012, 0 (2): 86-90.  
    Abstract ( 950 ( PDF (1062KB)( 360 Citation
    The conventional preparation method of Al-based amorphous alloy consists of the rapid solidification and mechanical alloying technique. The rapid solidification with convenience and rapid cooling rate can produce an amorphous phase and achieve successive production. The mechanical alloying has simple equipments, convenient operation, easy industrialization, relatively wide range of alloy composition, and other advantages. But both methods can only prepare amorphous ribbons, flakes or powders, and the production period is long and the production efficiency is low. Thermal spraying technique is a kind of rising preparation technique, which can produce amorphous coating, and achieve integration of materials preparation and forming to reduce the production period. So it has been the key preparation technique of industrialized application.
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    Thermoplastic Composites Fiber Placement Process Research
    HAN Zhen-yu, LI Yue-hua, FU Hong-ya, SHAO Zhong-xi
    2012, 0 (2): 91-96.  
    Abstract ( 1062 ( PDF (1227KB)( 313 Citation
    The thermoplastic composites, which are known for their weldability, recyclability, chemical resistance, and rapid forming, will become common engineering materials in aerospace industry. There are some physical phenomena during fiber placement process, which involves some fields and cross-fields, such as heat transfer, thermomechanics, crystallization kinetics, Newtonian fluid mechanics and so on. Based on above theories, this article analyses theoretical models of heating process, cooling process, interlaminar bond strength, fiber placement compaction load and thermal residual stress, and discusses the influence factors of final products performance, such as matrix material crystallinity, the degree of inter laminar intimate contact, the degree of interlaminar diffusion and so on. The research achievements and research process are summarized and analyzed in this paper, and some problems which still existed and need to be resolved are discussed. The future development trend of fiber placement is also predicted.
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