LIU Rong-jun, ZHANG Chang-rui, ZHOU Xin-gui, CAO Ying-bin, LIU Xiao-yang. Preparation and Characterization of Chemical Vapor Deposited Dense SiC Surface Coatings[J]. Journal of Materials Engineering, 2005, 0(4): 3-6.
The effects of deposition temperatures and diluent gas flow rates on the microstructures and crystal structures of the chemical vapor deposited (CVD) SiC coatings were studied. The results showed that dense SiC coatings can be deposited at 1100℃ and Ar flow rates less than 400 mL/min. The as-deposited coatings density was 3.204 g/cm3, its micro-hardness and elastic modulus were HV4459.2 and 471GPa respectively. The CVD SiC coatings showed that superior polishiability and its surface roughness was 0.429nm after optically polishing.
WU Hui-qiang, FENG Ji-cai, HE Jing-shan, ZHOU Li. Structure and Crack Forming Susceptibility of TiAl Based Alloy Joints by Electron Beam Welding[J]. Journal of Materials Engineering, 2005, 0(4): 7-10.
Micro-structural characterization and evolution mechanism of electron beam welded Ti-48Al-2Cr-2Nb alloy (atom fraction/%) joints were investigated. The results showed that the welded microstructure exhibited columnar and dendritic structure as ribbing pattern. Micro-structural constituents in the fusion zone were a massive gamma structure and some amount of lamellar structure consisting of alternating platelets of α2 and γ. Analysis of weld cracking susceptibility was also performed. The major contributing factor to the susceptibility to solid state cracking was micro-structural change in the weld metal for the suppression of the α phase decomposition leading producing more retained α2 brittle phase. The thermally induced stresses, the difference of α2/γ both phases thermal expansion coefficient and transformation stress also played an important role in crack forming mechanism.
LI Shu-qing, HE Ding-yong, JIANG Jian-min, QIN Hao. Influence of Cr Element on Abrasive Wearing of Arc Spraying TiB2 Coatings[J]. Journal of Materials Engineering, 2005, 0(4): 11-14,25.
The wear resistant coatings on Q235 substrate were prepared from a cored wire by arc spraying. The cored wire contained TiB2 ceramic enveloped by a low carbon steel. The different contents of Cr element were added to the cored wire to improve performance of the coating. The properties of the coating were measured, wear mechanism was analyzed, and their microstructures were observed. The results showed that the abrasive wear resistance of the coating was significantly improved by adding Cr, and the optimum content of Cr was 11%～15%. The phase distribution of the coatings was uniform and dispersive after adding Cr.
LIANG Zi-qing, TANG Bang-ming, LI Yan-liang, YI Xiao-su. Research on Compatibility of Tackifier and Resin[J]. Journal of Materials Engineering, 2005, 0(4): 15-17,41.
The solubility of the tackifier in the RTMable resin was tested. The influence of tackifier contents on the bending strength, bending modulus,impact strength and glass transition temperature Tg were also studied. The results showed that the tackifier dosage in the process had no negative effect on the resin castings.
XU Yong-gang, LI Ning, YU Xue-yong, SHEN Bao-luo, QIU Shao-yu, ZOU Hong. Effects of Ambient Temperature and Magnetic Field on Damping Capacity of Fe-13Cr-2.5Mo Damping Alloy[J]. Journal of Materials Engineering, 2005, 0(4): 18-20,45.
The damping capacity of Fe-13Cr-2.5Mo alloy at varying ambient temperatures and alternate-current magnetic field were measured with improved reversal torsion machine. The microstructure was observed with scanning electronic microscope. The results showed that the damping value resulted from both ferromagnetic and un-ferromagnetic parts. The former contributed to about 80%~90% and the latter 10%~20% at 23℃. As the ambient temperature increased from 23℃ to 550℃, the damping capacity decreased slowly to 60%~70% of that at 23℃ finally. Compared with the specimen water-cooled at 900℃, the damping-maximum torsion strain of the furnace-cooled at 1100℃ was much lower, which meaned that its damping reaction to the environmental noise was more intensive. The grain size, carbide precipitation and microscopic residual stress were the main reason that the damping-maximum torsion strain amplitude was higher when the alloy was heated at 900℃ for 2h and water-cooled.
SUO Jun, CHEN Zhao-hui, HAN Wei-min, ZHENG Wen-wei. Influence of Process Parameters on Pyro-joining of Ceramic Materials via Preceramic Silicone Resin[J]. Journal of Materials Engineering, 2005, 0(4): 21-25.
The joining of graphite, ceramic SiC and Cf/SiC composites via preceramic silicone resin (SR) at high temperature (800~1400℃) was studied. The influence of curing and pyrolysis process of silicone resin, solution concentration and pyrolysis temperature,on joining properties was discussed especially. The results showed that the curing process of SR was accomplished by Si-OH. Different influences of solution concentration and pyrolysis temperature appeared according to the different materials to be joined.
LIU Hai-lin, MA Xiao-yan, LIANG Guo-zheng, LU Ting-li, GE Qiang. Study on E-51/DDS System Modified by Silsesquioxane Based on (3-glycidoxypropyl) Trimethoxysilane[J]. Journal of Materials Engineering, 2005, 0(4): 26-29,54.
The E-51 epoxy resin modified by adding 3-glycidoxypropyl polyhedral silsesquioxane cage and using equivalent 4,4′-diaminodiphenyl sulfone (DDS) as the curing agent were studied. The FTIR spectrum, gelation characteristics and differential scanning calorimetry (DSC) were used to study the curing behavior and kinetics of the composites.The mechanical properties of the systems were also considered. The results showed that the cured reaction had lower activation energy Ea=48.7kJ/mol. The heat deformation temperature (HDT), thermal decomposition temperature and glass transition temperature (Tg) of the composite were 200℃, 442℃ and 245℃, and were 31℃, 58℃ and 20℃ respectively higher than that of E-51/DDS system under the same curing condition. This composite had higher thermal residue, which can be as high as 25% at 800℃. The flexural and impact strength were basically unchanged at the same time.
JIN Fang-wei, REN Zhong-ming, WANG Hui, XU Kuang-di. Effect of High Magnetic Field on Solidification Microstructure of Al-18Si Alloy and Its Mechanism[J]. Journal of Materials Engineering, 2005, 0(4): 30-32.
The solidification behavior of hypereutectic Al-18Si alloy was researched in a homogeneous high magnetic field. The experiment results showed that segregation of the primary silicon crystal in hypereutectic Al-18Si alloys was remarkable under a high magnetic field. In order to explain the segregation mechanism of primary silicon, a model of quantum theory was established. The model demonstrated that some silicon atoms, after getting additional energy in the magnetic field,was made a spiral movement along the magnetic field direction, this resulted in the segregation of primary silicon crystal in Al-18Si alloy. Additional energy obtained by silicon atom was 1.854×10-22J in 10T magnetic field.
ZHONG Fei, SHI Yao-wu, LI Xiao-yan, GONG Shui-li, CHEN Li. Study on Fracture Toughness of Laser-welded Joint for BT20 Titanium Alloy[J]. Journal of Materials Engineering, 2005, 0(4): 33-37.
Fracture toughness test on Ti alloy BT20 and laser-welded joints was carried out.Meanw-hile, hardness distribution and microstructure of the alloy and welded joints were investigated. Fracture test indicated that brittle unstable fracture occured after ductile crack initiation and slow propagation for all the compact tension (CT) specimens, except one welded joint specimen was brittle crack initiation. Fracture toughness of base metal was obviously higher than that of welded joint, and rolling directions had no obvious effect on fracture toughness of base metal. Fracture toughness of heat-affected zone(HAZ) was between the base metal and weld metal. Postweld heat treatment not only not improved the fracture toughness of welded joint, but also had the trend of deterioration. Addition of activating agent had no obvious effect on fracture toughness of weld metal, but it improved the length of ductile crack propagation.
LIU Yong, YIN Zhong-da, ZHU Jing-chuan, JIANG Yue. Influence of Processing Factors on Stress Relaxation Behavior of TC4 Alloy[J]. Journal of Materials Engineering, 2005, 0(4): 38-41.
The stress relaxation behavior characters of TC4 alloy and influence of processing factors were studied. The results showed that the stress relaxed very fast at the first stage, while slowly at the second stage, and the residual stress approached a limit after a long relaxation time. Stress relaxation was characterized with stress relaxation limit and stress relaxation rate. The higher temperature resulted in higher stress relaxation rate and lower relaxation limit. Different initial stress gave the same relaxation limit at same temperature.
WEI Hong-liang, YANG Xiao-guang, YU Hui-chen. Constitutive Modeling and Parameter Identification of Mechanical Behavior for GH4169 Alloy at High Temperature[J]. Journal of Materials Engineering, 2005, 0(4): 42-45.
Tests concerning monotonic loading,symmetric and unsymmetric cycling were carried out at high temperatures in GH4169 used for turbine disk. The results showed that the material had a distinct characteristic of cyclic softening and mean stress relaxation. The Chaboche type viscoplastic constitutive model modified by Ohno/Wang was adopted to model the mechanical behaviors. The Levenberg-Marquadt nonlinear optimization strategy was introduced briefly. Combing the material test data and utilizing the strategy, parameters of the constitutive model were identified. The model was implemented into ABAQUS and the material tests were numerically simulated. Some good agreement between test data and calculated curves was achieved.
TANG Bang-ming, LIANG Zi-qing, YI Xiao-su. Investigation of Processing Properties of Resin Film Used in Composite Resin Film Infusion Technology[J]. Journal of Materials Engineering, 2005, 0(4): 46-49.
The manufacturing processing of resin film used in resin film infusion technology was briefly analyzed. Based on the measurement of viscosity-temperature relationship of resin systems, tensile sheer test was conducted to investigate the transition temperature range from cohesion failure to interface failure, and shear load-displacement behavior.The results showed that the transition of failure behavior from cohesion to mixture or interface was the key which dominated the relationships between shear strength and test temperature. The temperature lower limit for the resin film manufacturing was determined by results of tensile sheer test.
WANG Hai-jun, CAI Jiang, HAN Zhi-hai. Study on Erosion Wear of WC-Co Coatings Prepared by Supersonic Plasma Spray and HVOF Spray[J]. Journal of Materials Engineering, 2005, 0(4): 50-54.
The WC-12Co coatings were sprayed by different supersonic thermal spraying processes of supersonic plasma spraying (HEPJet) and two kind of high velocity oxy-fuel spraying (HVOF)(JP-5000, DJ-2700).The contrast tests of porosity, micro-hardness, bonding strength, erosion of 30° jet or 90° jet angle were carried out, and SEM morphology of coatings was analyzed. The results showed that main properties of the WC-Co coatings by the supersonic plasma spray were equivalent to that of coating by JP-5000, and better than that of coating by DJ-2700. At 30° jet angles, erosion wear behavior of WC-Co coating presented the characteristics of micro-cutting and scale exfoliation; at 90° jet angles, the coatings presented the fatigue desquamation due to the upright wallop of particles on the coating surface.
YU Jia, WANG Zhen-qing, ZHANG Bo-ming, WANG Dian-fu, ZHANG Bao-yan, CHEN Xiang-bao. Building of Cure Kinetic Model in Modified Bismeleimide Resin During Curing Process[J]. Journal of Materials Engineering, 2005, 0(4): 55-59.
The simulating calculation of composite curing process was carried out by means of cure kinetic model. Taking modified BMI resin for example, two methods of Least-square and Malek were used to deal with experimental data obtained by different scanning calorimetry(DSC).Correct cure kinetic model was selected and determined ,the processing parameter of curing process was defined further.
ZHANG Yu-di, ZHOU Xin-gui, ZHANG Chang-rui. Development and Application of Cf/SiC Ceramic Matrix Composites[J]. Journal of Materials Engineering, 2005, 0(4): 60-63.
The several fabrication processes of Cf/SiC ceramic matrix composite(CMC) were introduced.The advantage and disadvantage of every process was analyzed.The discussion was put emphasis on development and application of Cf/SiC composite,such as aeronautic turbine engine,thermal protective system,optical structure and mirror,brake system and so on.Some current problems that lie in study of Cf/SiC composites were analyzed,it was put forward that how to improve the oxygenation resistance of Cf/SiC composites is still an important research and development direction in the future.
