CHEN Teng-fei, HUANG Bo-yun, LIU Gen-shan, YU Shu. Effects of Preform Structure on CVD Rate of Carbon/Carbon Composites[J]. Journal of Materials Engineering, 2002, 0(8): 3-5,9.
The influence of needle-punched felt structure on the rate of CVD is investigated by densifying various preforms with different types of carbon fiber or thickness of unit( i.e. non-woven cloth and chopped fiber web). The results show that the needle-punched felts with non-woven cloth fiber of imported carbon fiber B,C can be densified much faster than that of carbon fiber A and the ultimate density of the former is higher than that of the later; To lessen unit thickness, i.e. increasing the number of non-woven cloth and chopped fiber web, can improve the rate of CVD; There is diametrical density gradient in the products densified by pressure gradient CVD and it is necessary to improve the structure of carbon fiber preform to overcome the disavantage of CVD process.
PENG Gui-rong, YANG De-zhuang, HE Shi-yu, LI Dan-ming, JIANG Ll-xiang. Influence of VUV Irradiation on the Surface of Polymers[J]. Journal of Materials Engineering, 2002, 0(8): 6-9.
For the widely use of polymers in aerospace, the surface change of polytetrafluoroethylene (PTFE) and poly (ethylene terephthalate) (PET) in the vacuum ultraviolet (VUV) radiation was investigated. It was shown that PTFE and PET turned to dark brown under the VUV radiation in gas-jet VUV simulator. Carbon enrichment was detected for PTFE and PET after VUV radiation by XPS. Weight loss of both samples of PTFE and PET increased.
ZHANG Jie, ZHAI Jin-fan. Microstructure of the in Situ TiBw/Ti Composite and its Evolution During Hot Deformation[J]. Journal of Materials Engineering, 2002, 0(8): 10-12.
TiB whisker reinforced Ti composite was fabricated in situ by powder metallurgy using Ti and powder. The microstructure of the hot extruded composites was examined by means of SEM and X-ray Diffractometer. As a reactant, the TiB whisker was formed in the composite, and most of the whiskers were oriented in the extruded direction after hot extrusion. After compressive deformation, the TiB whiskers rotate, leading to the breakage of some whiskers. The rotation and breakage of the whiskers become more serious with decreasing deformation temperature.
TU Xiao-lin, WU Shu-sen, WU Guan-zhong. Effect of (NaPO3)n on Refinement of Primary Silicon in Hypereutectic Al-Si Alloys[J]. Journal of Materials Engineering, 2002, 0(8): 13-16.
Grain refinement of primary silicon in Al-Si alloys with (NaPO3)n has been studied. The results show that, the refining effect of (NaPO3)n on primary silicon is superior to that of CuP, and the former can modify eutectic silicon at the same time. The Al-22%Si-1.0%Cu-0.5%Mg-0.5%Mn alloy refined with (NaPO3)n is characterized with tensile strength up to 273 MPa. Effects of phosphorus element on silicon crystal in hypereutectic Al-Si alloys have been studied with Electron Scanning Microscope and Electron-Probe. Moreover, the crystallography and solidification of silicon phase are also discussed. On one side, the primary silicon is refined by AlP, which acts as heterogeneous nuclei; on the other side, when sodium element is added at the same time, phosphorus element is difficult to diffuse in melt, and then enriches the growing faces of silicon phase, which prevents the growth of silicon phase and refines the primary silicon.
ZHONG Zhi-gang, DENG Hai-jin, LI Ming, LI Dong-sheng. Effects of Fe Content on Friction and Wear Properties of Cu-Ceramet Friction Materials[J]. Journal of Materials Engineering, 2002, 0(8): 17-19,23.
The effects of Fe content on friction and wear properties of Cu-cerament friction material has been investigated The results indicate that the wear rate of friction-coupling material decrease rapidiy and that of Cu-ceramet friction material increase slowly with the increase of Fe content from 5% to 20% With increasing Fe content, the hardness of Cu-ceramet friction material and the friction coefficient stability increase However, it is found that the wear of ceramet friction material increase rapidly with Fe content over 20%.
LI Mei-heng, ZHANG Zhong-yuan, SUN Xiao-feng, GONG Sheng-kai, HU Wang-yu, GUAN Heng-rong, HU Zhuang-qi. Failure Mechanism of EB-PVD Thermal Barrier Coating Subjected to Thermal Cycling[J]. Journal of Materials Engineering, 2002, 0(8): 20-23.
Y2O3 partially stabilized ZrO2 ceramic top coat was deposited on NiCrAlY bond coat by electron beam physical vapor deposition (EB-PVD). Thermally cyclic test was performed at 1050℃. It is shown that the as deposited ceramic top coat is relatively dense and the columnar grains formed dense clusters. However there are gaps or holes among grain clusters. With thermal cycling going on, the gaps among columnar grain clusters become larger. The relatively dense gaps interconnect into one another and form microcracks, which extend across and through the top coat gradually. After 200 thermal cycles, the thermally grown oxides (TGO) formed at the interface of bond coat/ceramic top coat is uniform and consist of Al2O3 exclusively. After 300 cycles some NiO and spinels occur in the TGO. According to the microstructure observation, EDS and XRD analysis, the failure mode of EB-PVD thermal barrier coating is put forward.
WANG Yong-kang, XIONG Ren-zhang, LEI Ting-quan, XIA Li-fang, LI Bing-sheng. The Effect of Al Content on the Microstructure of Ti1-XAlXN Coating[J]. Journal of Materials Engineering, 2002, 0(8): 24-25,12.
Ti1-XAlXN coating was deposited by multi-arc ion plating method with cast Ti-Al alloy and hot-press-sintered Ti-Al alloy used as the targets. The microstructure of the coating and the mechanism were studied by SEM、XRD and XTEM. The results show that the TiAlN coating has a polycrystalline columnar structure, it is mainly composed of (Ti,Al)N; The raise of Al content would decrease the formation and the lattice constant of (Ti,Al)N.
ZHANG Xin-ping, YU Si-rong, HE Zhen-ming. Forecast of Primary Crystals Silicons Distribution in Al-16%Si FGM Created by Centrifugal Casting Based on BP Algorithm[J]. Journal of Materials Engineering, 2002, 0(8): 26-29.
The influences of mould temperature, pouring temperature and rotating speed on primary crystal silicons distribution in Al-16%Si FGM created by centrifugal casting were studied by orthodoxy experiment and improved BP algorithm. Under this paper condition, the influence of mould temperature on primary crystal silicons distribution is lager than that of rotating speed, and that of rotating speed is lager than of pouring temperature. The forecasts by BP algorithm and experiment results are in good agreement. BP algorithm is more convenient than experiment and it can forecast the results of experimentation can′t be performed.
GAO Jia-cheng, WANG Yong, ZHENG Shao-hua. Experiment Study on Fe3+ Reduced in Ti-dissolution by Electrolysis Reduction[J]. Journal of Materials Engineering, 2002, 0(8): 30-32.
The basic principles and process of reducing Fe3+ in the Ti dissolution by the electrolysis were introduced The emphasis was put on examining the effect of four factors, which are the concentration of the Fe2+ and H2SO4 in the anolyte respectively, the temperature and the current desity, on the reducing efficiency and the power consumption Through orthogonal test,the best process parameters of reducing the Fe3+ in the Ti dissolution can be obtained,they are current density 200A/m2, Fe2+ concentration 80g/L, H2SO4 concentration 200g/L, electrolysis temperature 40℃, and it takes 1.67 kWh power to reduce 1kg Fe.
ZHANG Guan-li, CUI Guang-zhi. Study of MPI Resin Matrix Composite Materials[J]. Journal of Materials Engineering, 2002, 0(8): 33-34.
The processing of graphite fiber reinforced MPI resin matrix composite materials were discussed. The results of the study indicate that AS4/MPI composite materials flexural and interlaminar shear properties at 371℃ is above 50%at RT, the 2.25% weight loss of composite materials at 371℃ demonstrates its good thermo oxidative stability (TOS).
XU Wei-ping. Friction Stir Welding of Magnesium Alloy MB8[J]. Journal of Materials Engineering, 2002, 0(8): 35-36.
This paper focused on microstructures and mechanical properties in friction stir welding (FSW) at magnesium alloy MB8. This results show that the FSW can achieve high quality welds in magnesium alloys.
YU Yan, CHAI Zhi-gang, SHEN Ying, XU Chang-fu. X-ray Diffraction Examination on the Coexistence Phenomenon of Ordering and Amplitude Modulating Decomposition of Al-Li Alloy Tempering Phase Transformation[J]. Journal of Materials Engineering, 2002, 0(8): 37-38,32.
X-ray diffraction examination was applied to study the phase transformation of Al-2.70%Li (mass fraction) alloy. It was shown that the side peaks exist on both sides of (200) diffraction peak of the base after tempering at 190℃ for 90 min and 120 min; (100) ordering diffraction peak also exist at the same time. This proves that amplitude modulating decomposition and ordering coexist at the beginning of tempering of the alloy.
LIANG Zuo-jian, XU Qing-yan, LIU Bai-cheng. Resent Developments in Modeling and Simulation of Microsegregation[J]. Journal of Materials Engineering, 2002, 0(8): 39-43.
Numerical simulation of microsegregation is an important branch of numerical simulation of material forming process. The significance of research on numerical simulation of microsegregation as well as recent developments was presented. Modeling techniques, characteristics and coupling methods of two types of models, numerical models of microsegregation in grain domain and in interfacial domain were analyzed respectively. The problems of numerical simulation of microsegregation in the present research were pointed out, and research directions in the future were outlined.
CHI Hong-zhong, CHEN Chang-pin, LI Hong-bo, REN Guo-xin. Development in the Research of Magnesium Based Hydrogen Storage Materials[J]. Journal of Materials Engineering, 2002, 0(8): 44-47,29.
From the gas reaction points of view, recent development in new methods and technologies of magnesium based hydrogen storage materials were surveyed. Special attention was focused on the preparation methods including ball mill, nano-amorphous structure materials, combustion synthesis and additives. The absorption-desorption characteristics of the obtained product and the technological conditions of each method was also discussed.
