WANG Da-yong, FENG Ji-cai, WANG Pan-feng. Microstructures and Mechanical Properties of Al-Li Alloy Friction Stir Welds with a Cylinder-shape and Non-whorl Pin[J]. Journal of Materials Engineering, 2004, 0(3): 3-6,10.
Friction stir welded 5 mm thick, Al-Li alloy rolled sheet, metallurgical, hardness and tensile strength measurements were performed. The results demonstrate that there exist three distinct zones in the FSW joint:the weld nugget zone (WNZ), and the thermal-mechanically affected zone (TMAZ),and the heat-affected zone (HAZ).The microstructures in WNZ take on scale shape.Under the thermal cycle,the microstructures in HAZ occur recovery and generate the bar-shape recovery structure.The microstructures in TMAZ consist of the equiaxed grains, and the grain size of the microstructures at the retreating side is bigger than that at the advancing side. The tensile test results confirm that the highest tensile strength of Al-Li FSW joints welded with a cylinder-shape and non-thread pin is 296MPa(under the welding speed υ=40mm/min),and the highest elongation percentage is 8.6%(under the welding speed υ=80mm/min).The hardness measurements show that the weld is softened, and the softened scope of both the advancing and the retreating sides are almost the same. But the soften degree of the material at the retreating side is higher than that at the retreating side.
GUO Xing-zhong, YANG Hui, WANG Jian-wu, CAO Ming. The Material Properties Characterization of SiC Powder Surface-modified by Polyethylene Glycol[J]. Journal of Materials Engineering, 2004, 0(3): 7-10.
The surface modification of industrial SiC powders were carried out by polyethylene glycol (PEG 200), and the effects of PEG weight and liquid media on the flow characteristics, adsorption, thermal analysis and morphology of the modified powder were analyzed by TG, IR and SEM.The results show, when the content of PEG 200 is 5%(mass fraction) and liquid media is alcohol, the modified powder has better flow characteristics;the adsorption content on SiC powder surface increases with PEG content,it is not effected by liquid medias; the PEG on SiC powder surface can be burned out at 0~500℃;the particles in the modified powder has better dispersive and of uniformly blocky; the sintering characteristics of the silicon carbon product with the modified SiC can be improved.
LI Ju, GUAN Qiao, SHI Yao-wu, GUO De-lun, DU Yu-xiao, SUN Yong-chun. Strain Field of Gas Tungsten Arc Welding with a Spot Heat Sink on Titanium Alloy Thin Plate[J]. Journal of Materials Engineering, 2004, 0(3): 11-14,48.
The longitudinal strain field pattern and the longitudinal strain developing history were studied numerically and experimentally for both the conventional Gas Tungsten Arc Welding(GTAW) and Dynamically Controlled Low Stress No-Distortion (DC-LSND) GTAW welding of a titanium alloy. Results show that high tensile effect generated by heat sink with sharp cooling and contraction of weld metals is acting in the zone between the arc and the trailing heat sink during DC-LSND GTAW welding, which increase tensile plastic strain of weld and decrease compress plastic strain in the zone near to the weld. All of these phenomena mitigate the incompatible strain in the weld and the zone nearby. With the selected welding parameters, residual tensile incompatible strain can be reached in the weld during DC-LSND GTAW welding.
JIN Xiao-ou, ZHAO Hui-jie, HE Shi-yu. Fatigue Behavior of Peak-aged 2A12 Alloy in Vacuum[J]. Journal of Materials Engineering, 2004, 0(3): 15-17,20.
The fatigue behaviors of peakaged 2A12 alloy in air and vacuum at room temperature were investigated using a tension-compresion fatigue testing machine. The effect of vacuum on the fatigue behavior was studied by means of Scanning Electron Microscopy (SEM). The results show that, the fatigue life is noticeably improved in vacuum than that in air, and the S-N curve shift to the right in vacuum. Under lower cyclic stresses, the fatigue cycles to failure in vacuum is increased 2 or 3 times. Both the fractures in air and vacuum are transgranular. Tyre-like patterns and fatigue striations are observed in some local areas of fatigue fractures in air, and more areas with the fatigue striations exist under lower cyclic stresses. However, little fatigue striations exist and tyre-like patterns in vacuum. The reason for the effect of vacuum on the fatigue behavior of peakaged 2A12 alloy is discussed.
QI Hong-yu, WEN Wei-dong, SUN Lian-wen. Fatigue Research on Composite Laminate with a Hole[J]. Journal of Materials Engineering, 2004, 0(3): 18-20.
T300/KH304, which is recently studied in aviation, is a high capability composite material. To predicate the fatigue life of an aero-engine structure mode by this composite, the notched laminates were mainly investigated. Based on the fatigue model laminates and average stress criterion of static strength for the composite material laminates with a circular hole, a new fatigue model of composite material laminates was presented.According to the experiment data of static strength and fatigue of notched laminates,the stress correct factor β was presented. The fatigue analysis and tests were carried under the difference stress levels. In the future this method could be used for the predication of S-N curve of other composite materials plate with a circular hole.
HOU Feng-yan, WANG Wei, LIU Jia-chen, GUO He-tong. Effect of Dispersibility of ZrO2 Nanoparticles in the Ni-ZrO2 Composite Coatings on Microstructures and Properties of Composite Coatings[J]. Journal of Materials Engineering, 2004, 0(3): 21-23,27.
The effects of ZrO2 nanoparticles in the Ni-ZrO2 composite coatings existed in monodispersed or agglomerated on microstructures and properties of composite coatings were studied. The Ni-ZrO2 composite coatings were prepared with and without dispersant(MZS) under DC electrodeposition condition. The morphology of the coating was examined by SEM and the texture of the matrix nickel were detected by XRD. It is found that zirconia nanoparticles are monodispered into matrix nickel with dispersant, but zirconia nanoparticles are agglomerated without dispersant. The dispersibility of ZrO2 nanoparticles in the Ni-ZrO2 composite coatings can affect the preferred orientation of the matrix metal remarkably. The result show that the hardness of Ni-ZrO2 composite coatings can be improved because of good dispersibility of ZrO2 nanoparticles in the composite coatings
ZHANG Sheng-hui, XIA Hua, YANG Wei, ZHAO Shun-ping, HAN Li-xiong. Preparation and Characterization of Kaolinite-pNA Intercalation Compound[J]. Journal of Materials Engineering, 2004, 0(3): 24-27.
A kaolinite-para nitroaniline intercalation compound was prepared by displacement method using a kaolinite-methanol intercalation compound as an intermediate. The product was characterized by powder X-ray diffractometry(PXRD) and Fourier-transformed infrared spectroscopy((FTIR).)The basal spacing of kaolinite-para nitroaniline intercalation compound was 1.48nm. The apparent intercalation of the product was 81.0%. The IR spectrum of the kaolinite-para nitroaniline intercalation compound indicated the presence of hydrogen bonding between the inner-surface hydroxyls of the kaolinite and the nitro groups of para nitroanilines, meanwhile between the siloxane oxygen and the amino groups of para nitroanilines. On the basis of the basal spacing of the kaolinite-para nitroaniline intercalation compound, the para nitroanilines appeared to be in an approximately perpendicular position, with the nitro groups of para nitroanilines facing the gibbsitic sheets.
CAO Jing-xia, HUANG Xu, LI Zhen-xi. High Cycle Fatigue Properties and Fracture Features of TA15 Titanium Alloy[J]. Journal of Materials Engineering, 2004, 0(3): 28-30,34.
The high cycle fatigue properties and fracture features of TA15 titanium alloy were investigated.The results show that there is great influence of the morphology and amount of the secondary α phase in the transformed β microstructure on the fatigue properties. The spherical secondary α phases in the transformed β microstructure decrease the crack propagation resistance, while the great deal of plate-like secondary α phases, which lead to crack deflection, effectively decrease the crack propagating rate and improve the fatigue strength.
ZHENG Wen-wei, CHEN Zhao-hui, YAO Jun-tao. Study of SiC Fillers into Three-dimensional Braided Carbon Fiber Preform by Ultrasonic Infiltration[J]. Journal of Materials Engineering, 2004, 0(3): 31-34.
SiC fillers were introduced into three-dimensional braided carbon fiber preform((3D-BCf)) by ultrasonic infiltration in order to shorten the fabrication cycles of Cf/SiC composites through precursor-infiltration-pyrolysis (PIP). Effects of diameter of SiC fillers and mass ratio of SiC/EtOH on volume fraction of introduced SiC fillers in 3D-BCf were investigated. The results show that the highest volume fraction (16.4%) of SiC fillers can be achieved by ultrasonic infiltration when the diameter of SiC fillers is 0.4μm and the mass ratio of SiC/EtOH is 1:1, which can shorten the densification cycles of Cf/SiC composites.
ZHAN Mei-yan, CHEN Zhen-hua, XIA Wei-jun. Effects of High Temperatures on the Hardness and Microstructure of Spray-deposited Heat-resistant 8009 Aluminum Alloy[J]. Journal of Materials Engineering, 2004, 0(3): 35-37,41.
The effects of high temperatures on the hardness and microstructure of spray-deposited heat-resistant 8009 aluminum alloy were studied. The hardness was determined. Optical microscopy,scanning and transmission electron microscopy(SEM,TEM) were performed on the as-rolled and annealed samples. The results show that there are no obvious decrease in hardness of samples after annealed at 580℃×2h,540℃×100h,600℃×1.5h. The special heat-resistant property of 8009 can be attributed to the fine dispersions Al12(Fe,V)3Si.
SHEN Xing, YUAN Shen-fang, WANG Xin-wei. Research on the Reduction Behavior of PLZT Piezoelectric Ceramics at High Temperature[J]. Journal of Materials Engineering, 2004, 0(3): 38-41.
To develop the RAINBOW piezoelectric actuator with ultra-high displacement, the reduction behavior of PLZT piezoelectric ceramics was researched by experiments.The phase constitutions and microstructures of reduced samples were studied by XRD and SEM methods. And the illustration of the reduction process and mechanism were also put forward.It was found that PLZT was easily reduced and the thickness of reduced layer had a linear relationship with the reduction time; The optimal conditions for PLZT were determined to be 950℃ for 1~1.5 hours; Reduced PLZT was composed of reduced and unreduced layer obviously and the reduced layer was transgranularly fractured while the unreduced ceramic was intergranularly fractured; Metallic lead and refractor oxides (PbO,ZrO2,TiO2,etc.)were found in the reduced layer, however, the crystal structure of PLZT was not found.
YE Lei, MAO Wei, XIE Yong-hui, LI Xiao-hong. Research on TLP Diffusion Bonded Joint Microstructure of Directionally Solidfied Superalloy IC10[J]. Journal of Materials Engineering, 2004, 0(3): 42-44.
TLP diffusion bonding of the IC10 directional-solidfication superalloy was studied. The interlayer was made of IC10 base metal in additional of a certain contant of B. Microstructure in the bonding seam and base metal differed with bonding time was researched and the difference of the shape and size of the γ′ phase in the bonding seam and base metal was analyzed.
LI Ying, SU Bin. Abnormal Yield Behavior and Deformation Mechanism of Nickel Base Single Crystal Superalloy[J]. Journal of Materials Engineering, 2004, 0(3): 45-48.
Nickel base single crystal superalloy is a key material blade for turbine engine blade having high thrust-weight ratio. A comprehensive description is given to the abnormal yield stress of nickel base single crystal superalloy. Meanwhile, the deformation mechanism of nickel base single crystal superalloy is discussed.
