WANG Xiao-dong, LI Ting-ju, JIN Jun-ze. Research on Feeding Mechanism during Metal Solidification under Rotating Electromagnetic Field[J]. Journal of Materials Engineering, 2001, 0(11): 3-5,12.
Solidification process of the melt with electromagnetic field action was studied.Based on theory analysis of metal solidification and hydrodynamics, momentum convection generated by rotating electromagnetic field do not improve feeding obviously.Mechanism of counteraction of center shrinkage cavities formed by electromagnetic force is heat and mass transport which is increased by momentum convection, temperature tends to be well distributed, and temperature gradient in radial direction decrease, solid phase ratio of melt in the center portion increase to the characteristic one in a short time, and solidifying velocity increases at the last stage of solidification.The center portion of melt is solidified quickly, so the forming of center shrinkage cavities is counteracted.
HE Peng-fei, C. Yuan, R Stern, W. J. Clegg. Cracking of Porous Ceramics under Thermal Shock[J]. Journal of Materials Engineering, 2001, 0(11): 6-8.
Cracking of porous ceramics under thermal shock has been investigated by water quenching experimental method. The materials used in this study were dense and porous alumina Slip casting slurries of alumina dispersed in water using an ammonium polyacrylate-dispersing agent have produced samples. The experimental observations show that the porosity modifies the way in which cracking initiation, giving only multiply penetrating cracks for porous materials rather spalling and penetrating cracks for dense materials. In addition, under same thermal shock condition, crack density for the porous materials is larger than that for the dense materials, but crack length for the porous materials is shorter than that for the dense materials.
SHENG Wen-bin, YANG Rui, LIU Yu-yin, XU Dong-sheng, LI Dong. Analysis of Overflow Critical Value for TiAl Base Alloy Melt during Centrifugal Casting Process[J]. Journal of Materials Engineering, 2001, 0(11): 9-12.
The method combining theoretical analysis with experimental verification was adopted, and pressure distribution of TiAl based alloy poured in permanent mould during the process of centrifugal casting was analyzed. The expression of extra pressureitem and the relations between maximum angular velocity ω0max(r/min) and melt high H, pouring basin diameter D0 were concluded. It provided theoretical guiding for actual casting process. Experimental results show that the pressure acting on cavity consisted of static pressure and extra pressure during the process of centrifugal casting. The static pressure was determined by melt height, while the extra pressure was controlled by metal liquid density and rotating angular velocity. Pouring basin height and diameter should follow certain functional relation, and it was ideal when metal liquid was as high as half of pouring basin height. Also, it showed that the value of maximum angular velocity increased with the increasing of metal liquid height and pouring basin diameter.
SUN Jian-fei, XIE Zhuang-de, SHEN Jun, ZHOU Bi-de, LI Qing-chun. Microstructure and Tensile Properties of a Rapidly Solidified High Silicon Aluminum Alloy[J]. Journal of Materials Engineering, 2001, 0(11): 13-16.
An Al-17Si-6Fe-4.5Cu-0.5Mg alloy was manufactured by rapid solidification/powder metallurgy(RS/PM) process and followed by T6 temper. Microstructure and tensile properties of the extruded and T6 tempered alloys were studied by means of modern measuring techniques. The results show that the second phases in the microstructure of the alloy were obviously refined by this process, through T6 temper coarsening of the second phases occurred and a new phase precipitated in the matrix; the tensile properties of the alloy were characterized by high strength, low ductility and improved heat resistance.
LIANG Hui, XU Ting-xian, YANG De-an, DONG Xiang-hong. Research on the Metallization for the Surface of Bismaleimide-glass Fibre Composite[J]. Journal of Materials Engineering, 2001, 0(11): 17-20.
Bismaleimide-glass fibre composite surface is chemically pretreated for subsequent metallization on the surface. The metallization processes include the surface pretreatment, copper electroless plating, copper electroplating, and nickel electroplating. The results of the experiment show that the surface toughening process is very important for the coating quality. Appropriate roughness of the surface, and the improvement for the surface water wettable can promote a good adhesion of the coating on the surface.
LIN Cheng-xin, GU Nan-ju, ZHAO Lian-cheng. Behavior Analysis of Fe-17Mn-5Si-10Cr-5Ni Alloy Pipe-joints[J]. Journal of Materials Engineering, 2001, 0(11): 21-24,16.
The shape memory effect and connecting behaviors of pipe-joint made form Fe 17Mn-5Si-10Cr-5Ni shape memory alloy were studied systematically. The results show that the recovery ratio reduces with increasing per strain and the maximal recovery strain appears when pre strain is 4%～6%. When pre-strain is 4.5%~8%, the connecting of pipe-joint shows bigger tight force and higher pressure-resistance sealing ability. The shape memory effect, tight force and pressure resistance sealing ability of the pipe joint can improve remarkably with thermal-mechanical training. The recovery ratio and recovery strain reduces with increasing thickness of pipe joint With a reasonable range in thickness of pipe-joint, the tight force and pressure-resistance sealing ability in connecting of pipe joint are higher. With increasing length of jointing, in the connecting of pipe joint the tight force reduces and the pressure resistance sealing ability increases. Pipe-joint structure can change the pressure-resistance sealing ability greatly and with the different structure there is severalfold diversity of pressure-resistance sealing ability in connecting of pipe-joint.
WANG Lu, LI Xue-li, WANG Fu-chi, LIU Guo-quan. Study on Surface Fractal Dimension of Functionally Gradient Materials[J]. Journal of Materials Engineering, 2001, 0(11): 25-27.
Fractal dimension(Df) of ZrO2/NiCrAl functionally gradient materials(FGMs) which was prepared by plasma spraying technology was investigated. The results show that Df displays curvilinear variety with NiCrAl content increased, and it can be found there is a good corresponding relation between fraction dimension and bending strength. When NiCrAl content is around 30%, there is the percolation phenomena, and the bending strength is obviously increased. The studies set up the relationship between fractal dimension and macroscopical properties.
DONG Xiang-hong, WANG Yu-guo, WANG Yu-lin, WAN Yi-zao. Friction and Wear Behaviors of 3-D Carbon Fiber/Epoxy Composites[J]. Journal of Materials Engineering, 2001, 0(11): 28-30.
The friction and wear behaviors of three-dimensionally braided carbon fibers(C3D/EP) composites prepared by RTM process were studied using a ring-on-block tester and the wear mechanism was discussed. The results show that fiber volume fraction, contact pressure and sliding velocity have obvious effects on the friction coefficient and the width of wear scar of the C3D/EP composites. From the scanning electron micrographs of the wear scars, it is believed that wear is primarily due to a combination of adhesion and fatigue The wear mechanism of the C3D/EP composites differs depending on contact pressure and sliding velocity.
QI Xue-gui, CHEN Ze-shao, WANG Guan-zhong. Study of the Relationship between Temperature Field and Diamond Film Growth in Hot-filament CVD Reactors[J]. Journal of Materials Engineering, 2001, 0(11): 31-34,16.
Heat and mass transfer affect growth rate and properties of diamond films in hot filament chemical vapor deposition reactors. Thermal transfer in three ways(conduction, convection and radiation) was analyzed and the temperature fields were also numerically calculated in this paper. Conduction is the dominant mechanism in gas-phase thermal transfer, while the temperature field on the substrate surface is determined mainly by radiation from the filament. The growth rate and microstructure of the diamond film prepared by HFCVD method is related to the temperature field on the substrate surface Large-area temperature field of high uniformity, which benefits to the growth of diamond film in large scale, can be obtained by using multi-filaments.
YAO Ping-ping, XIONG Xiang, HAN Juan. The Formation Mechanism of Chip on the Powder Metallurgy Brake Material for Airplane under Braking[J]. Journal of Materials Engineering, 2001, 0(11): 35-37.
The formation mechanism of several kinds of chips on the powder metallurgy brake material for airplane under braking, the action of chips in monitoring and forecasting of the powder metallurgy brake material for airplane using condition were studied in this paper. The results show that there are four kinds of chips, and the formation mechanism of each kind chip was analyzed Plate chip is created by the expanding of surface cracks; block chip is created by the spread of inter and outer cracks;strip chip is the results of the grooving There are two kinds of ball chips:solid ball and hollow ball, which are created at high temperature.
CHEN Meng-cheng, CHEN Xing-yao, GAO Yang, LI Jian-ping, LI Wei-guang. The Study on Thermal Shock Test of Thermal Barrier Coatings[J]. Journal of Materials Engineering, 2001, 0(11): 38-40.
The requirement of high-temperature coatings has been improved with research and production of advanced engine. Thermal barrier coatings which has been applied in blades and vanes is a new type coating Thermal shock test has been performed on the TBCs which are prepared by EB PVD. The morphology, composition and phase transformation of the TBCs samples is analyzed by SEM, EDXS and XRD.
XU Jian-xiang, LIU Jun-neng. Study of Wave Absorbing Material for S Air Duct[J]. Journal of Materials Engineering, 2001, 0(11): 41-42.
On the basis of optimum programming,a favorable structure of the wave absorbing material was studied and determined.The wave absorbing material was developed for S air duct of glass fiber reinforced composite.
ZHAI Hua-zhang, LI Jian-bao, Huang Yong. Development, Application and Industrialization of Nano-Materials, Nano-Science &-Technology[J]. Journal of Materials Engineering, 2001, 0(11): 43-48.
Nano science & technology(Nano ST) has become a strategic commanding point of science and technology of the 21st century Some the hottest development of nano materials and Nano ST were reviewed. The applications of Nano ST in some fields such as electronics, biology,national defense and advanced ceramics were described in detail, and the industrialization status of Nano ST in our country was also introduced.
