CUI Chuan-yong, CHEN Yu-xi, GUO Jian-ting, LI Dou-xing, YE Heng-qiang. The Microstructure and Mechanical Property of a Directionally Solidified NiAl-Cr(Mo,Hf) Composite[J]. Journal of Materials Engineering, 2001, 0(1): 3-6.
In situ composite based on the NiAl-Cr(Mo) eutectic system has been successfully produced by Standard Bridgman method and its microstructure was studied using SEM and TEM.The composite was composed of NiAl matrix, Cr(Mo) lamellar and discontinuous Ni2AlHf phase.Fine G-precipitate was cubic in shape and co existed with Heusler phase at NiAl/Cr(Mo) interface.The solidification process of the composite was also discussed.After HIP(1300℃/100MPa/2h) treatment, the Heusler phase at the NiAl and Cr(Mo) interface was reduced greatly and fine G-precipitate disappeared.The compress property from room temperature to elevated temperature and the tensile property at elevated temperature were also investigated.The mechanism responsible for the improved strength was also analyzed.
LI Shu-qin, HUANG Yong, WANG Chang-an, XING Zeng-ping, GUAN Zhen-duo. R-curve Behavior for Si3N4 /BN Fibrous Monolithic Ceramic[J]. Journal of Materials Engineering, 2001, 0(1): 7-9.
R-curves for Si3N4/BN fibrous monolithic ceramic were established by direct measurement of the change of Vickers indentation cracks in length under progressively applied bending stresses. The fracture behavior of the Si3N4/BN fibrous monolithic ceramic was studied. An empirical exponential relation was fitted for the data. The unique steplike shape whiich was possessed of the R-curve of fibrous monolithic ceramic was discussed. Moreover, the mechanism of high fracture toughness of fibrous monolithic ceramic was further explained.
GU Yi-jie, ZHOU Tie-tao, ZHANG Lei, ZHANG Yong-gang, CHEN Chang-qi. The Effect of Natural Aging on the Microstructures of Al-Li-Cu-Mg-Zr Alloy[J]. Journal of Materials Engineering, 2001, 0(1): 10-11,18.
The effect of natural aging on the microstructures of Al-Li-Cu-Mg-Zr alloy was studied by transmission electron microscopy and Vickers hardness tester.It is found that the natural aging before artificial aging may raise the hardness.Analysis indicates that the efficient hardness comes from the increasing number of S particles.There is no effect on δ′ from natural aging before artificial aging.The long natural aging has a little effect on Al-Li-Cu-Mg-Zr alloy.
WANG Yong-kang, LEI Ting-quan, XIA Li-fang, XIONG Ren-zhang. The Oxidation Resistant Behavior of Ti0.5Al0.5N Coating at Elevated Temperature[J]. Journal of Materials Engineering, 2001, 0(1): 12-14.
The elevated temperature oxidation resistant behavior of Ti0.5Al0.5N coating deposited by multi arc ion deposition was studied with AES. The results show that the temperature of the highest oxidation resistant of the TiAlN coating reach 800℃.Mechanisms of oxidation resistant and failure of Ti0.5Al0.5N coating were analyzed with SEM、EDX and XTEM.
ZHENG Jia-gui, JIANG Li-Xin, ZENG Jia-yu, ZHOU Hui, CAI Ya-ping, LUO Si-wei, ZHOU Xin-ming. The Microstructures of Coats for High-voltage Insulated α-Al2O3 Ceramics[J]. Journal of Materials Engineering, 2001, 0(1): 15-18.
The mixed coats of Mn, Ti and Cr were applied to α-Al2O3 insulated ceramics surface,followed by heat treatment under special conditions. The secondary electron emission coefficient, surface resistively, XRD and surface morphology of the samples were observed. It is found that the new phases form because the coats penetrate into and mix with the original α-Al2O3 during the heat treatment, which results in the denser and smoother surface. The surface resisitivity of all the samples decrease, and the decreases in their secondary electron emission coefficient reach 60%~65%. This is helpful for increasing the resistance to surface flashover and the high-voltage breakdown strength of solid insulators in high-vacuum.
NAN Jun-ma, LI Guang-xin, XU Ke-wei, WANG Hong-xing, SONG Li-jian, DOU Xiu-ying. Elevated Temperature Deformation Behaviour and Mechanical Characteristics of Invar Alloy Used for Shadow Mask[J]. Journal of Materials Engineering, 2001, 0(1): 19-21.
Invar alloy is employed as the material of the shadow mask of a color picture or display tube because of its low coefficient of expansion being beneficial to the gain of high clarity.In order to provide the experimental basis for the formation of Invar alloy shadow mask at 200℃, its responses at elevated temperature were observed in the conditions of the static load and uniaxial tension by means of strain gage.The results show that for various annealing treatments at 790~850℃, the stresses is evidently dropped with increasing the heating temperature from about 20 to 180℃, and thereafter is fluctuated in 120~130MPa for the yielding strength and in 300~320MPa for the ultimate strength.The specific elongation is increased with the rise of annealing and heating temperatures, but the elastic modulus is nearly unchanged.
FAN Zhi-kang, SONG Zhong-xiao, LIANG Shu-hua. The Effects of Temperature on Rheological Properties of Electrorheological Fluids[J]. Journal of Materials Engineering, 2001, 0(1): 22-25.
The effects of temperature on shear stress and apparent viscosity of electrorheological(ER) fluids with aluminosilicate,zeolite and BaTiO3 suspensions have been studied. The results show that the effect of temperature has relationship with applied electrical field and the amount of suspension in the ER fluid, but has no relationship with shear rate. With increase in temperature, there are shear stress peaks on the shear stress shear rate curves of the ER fluids with aluminosilicate, zeolite or polymer suspension at strong electrical field. However, shear stress of the ER fluid with BaTiO3 suspension is singly decreased.
GUI Man-chang, WU Jie-jun, YUAN Guang-jiang, WANG Dian-bin. Fabrication Processing and Tensile Strength of Foam of Al/SiCp Composites[J]. Journal of Materials Engineering, 2001, 0(1): 26-27.
A new metallic foam, i e.the foam of SiC particle-reinforced aluminum matrix composite with the porosity of 60%~85% is introduced.The foam is produced by the foaming process with TiH2 blowing agent.The foaming process is controlled easily since the viscosity of composite melts is quite great, without the addition of viscosity increasing agent.Comparing with common foamed aluminum or its alloys, the composite has greater tensile and compression strength.
YIN Li-song, ZHOU Qi-fa. Study of the Preparation and Characteristics of Ultrafine Antimonide-oxide/Kaolin Composite Powder[J]. Journal of Materials Engineering, 2001, 0(1): 28-30,33.
Ultrafine Sb2O3 powders were prepared by ball mill methods; the characteristics of the composite powder was studied by TG,DSC and laser scattering methods.The results show that the beginning temperature of kaolin structure variation becomes low; the beginning temperature of kaolin structure variation is also changed with the quantity of Sb2O3 in the composite powder.The chemical combination reaction of Sb2O3 and kaolin is proceeded at a narrow range of temperature. To Sb2O3,when the quantity of kaolin in the composite powder is large, the active energy E of the chemical combination reaction becomes small, the frequency factor A value becomes large, and the composite reaction is 0 grade reaction.
ZHANG Yun-hui, LI Lei. Optical Characterization of Copper-doped Zinc Sulfide Nanoparticles Synthesized in Microemulsion[J]. Journal of Materials Engineering, 2001, 0(1): 31-33.
ZnS:Cu nanoparticles were prepared in microemulsion at room temperature.X-ray diffraction analysis shows that the diameter of the particles is 3~5nm and the particles are cubic crystallites structure.Ultraviolet absorption demonstrates the increased bandgap due to quantum confinement.A green emission band at 482nm can be observed in PL spectrum.
YAN Feng, WU Kun, ZHAO Min. Study on the Fracture Behavior of SiCw/MB15 Composites[J]. Journal of Materials Engineering, 2001, 0(1): 34-35,14.
The nucleation, propagation of cracks to fracture of SiCw/MB15 composites were observed with tensile loading under SEM.It is discovered that cracks mainly nucleate at clearance between broken whiskers.The whole process of crack formation is that micro-cracks propagated and linked each other in the stress concentration zone of the main crack tip, then combined in the perpendicular direction of main stress to form a macro-crack.
WANG Zhi-hui, HE Ding-yong. The Behavior of the Fatigue Crack Propagation in Austenitic/Ferritic Dissimilar Metal Joints[J]. Journal of Materials Engineering, 2001, 0(1): 36-39.
The E309 type austenitic electrodes was used in welding of 13CrMo44 heat resisting steel to form a dissimilar metal joint. The notched three-point bend specimens (S/W=4) were prepared for the fatigue crack propagation (FCP) test. The relationship between the fatigue crack propagation and the microstructures in the joint was studied. The results show that the path that the fatigue crack propagation takes is in the overheated zone of HAZ, which may be attributed to the low toughness values in the zone. The fatigue crack propagates along the fusion zone at the region 5 25μm to the fusion line. The martensite layer has ability to resist the fatigue crack propagation,which indicates that the trace of FCP is mainly controlled by toughness of the structures. The expression for fatigue crack propagation rate in the fusion zone of the Cr25Ni13/13CrMo44 dissimilar metal joint by Paris equation is as follows:da/dN=7.07×10-13(△K)3.863.
JIN Yao, SUN Ya-fang, SUN Xun-fang, DENG Yong, LIU Hong-jie, TU Yong. Study on Creep Law of Metal[J]. Journal of Materials Engineering, 2001, 0(1): 40-42.
With material internal state varying, creep behavior keeps on changing during creep. A creep law which takes account of damage and hardening influence is proposed. Creep behavior of 12Cr1MoV steel is discussed. Analysis shows that creep rate keeps changing during creep. The secondary stage of creep is merely relative steady stage, and degree of relative steady and duration life fraction depend on applied stress. Different stresses cause the same damage state but different hardening state in conditions of the same exposure time fraction.
YU Gui-lin. Casting Process of Hanging Rack on Aircraft Made of High Setrngth Aluminum Alloy ZL205[J]. Journal of Materials Engineering, 2001, 0(1): 43-44,39.
According to the practical requirement and the structural feature of the hanging rack on a type aircraft and the casting properties of Al alloy ZL205,the sand casting process of the hanging rack made of ZL205 was discussed and analysed.The results show that vertical casting make the parts have a unified property and chemical composition.Chilling with semimetalic mould lining chiller matched with reasonable riser,make the casting have a compact microstructure and high quality;the 1:3:5 cross sectional area ratio of the sprue,runner and gate and the rational fissure with cushion structure make the molten metal fill stably in the mould cavity,that reduce the secondary oxide inclusion and the invading gas;designing the sand core in entirety make the casting have a stable structure.
ZHANG Zheng, CHEN Chi-nan, ZHONG Qun-peng. Failure Analysis of Hanger of Ropeway[J]. Journal of Materials Engineering, 2001, 0(1): 45-46,6.
The analysis of materials and fracture appearance shows that the cracks on the hanger of ropeway are caused by fatigue failure. The stress state of the whole hanger is calculated by the finite element method. Then, the failure of the hanger of ropeway is also determined by the second fatigue chart. The conclusion is the improper design caused the failure of hanger of ropeway.
