XU Bin-shi, ZHANG Wei, LIANG Xiu-bing. The Application and Development of Thermal Spray Materials[J]. Journal of Materials Engineering, 2001, 0(12): 3-7.
The development of thermal spray technology and materials is reviewed first. Then, the research of new thermal spray materials is introduced After that, the characteristics and developing directions of the thermal spray materials are discussed also. The purpose is providing the guidance for the development of the thermal spray materials in the future.
ZHANG Shao-qing, CUI Yan, WANG Mei-xuan, SONG ying-gang. Investigation on Reaction Mechanism of SiC Particulate Reinforced Aluminum Matrix Composite Prepared by Pressureless Infiltration[J]. Journal of Materials Engineering, 2001, 0(12): 8-11.
In order to investigate the pressureless infiltration reaction mechanism for a SiC/Al composite, the reaction products structures at the front interface of the SiC preform were identified by means of XPS and TEM. The results of the XPS analysis show that the compounds such as MgO, Al2O3 and ZnO are present at the interfacial region between the infiltrated and uninfiltrated parts of the SiC preform and no nitrogen compound is found. The HRTEM shows that there is only a MgAl2O4 phase existing at the interface between SiC phase and aluminum alloy matrix phase and the MgAl2O4 phase covers almost the whole SiC particulate surface. It is suggested that the exothermic reactions take place between the SiO2 on the surface of SiC particulate and the Al, Mg and Zn elements after the contact of the molten Al with the SiC particulate. Hence the surface tension is decreased, the wettability is increased and the spontaneous infiltration is promoted.
CUI Yan. Optical and Instrument Grade Aluminum Matrix Composites Reinforced with Self-Propagating High-Temperature Synthesized SiC Particle[J]. Journal of Materials Engineering, 2001, 0(12): 12-15.
The reinforcing effects as the reinforcement of high volume fraction optical and instrument SiCp/Al composites were systemically compared, between the novel near-spherical SHS SiC particle with rough surface topography and the common abrasive-grade SiC particle with angular shape and relatively smooth surface. The results show that the SHS SiC particle is more effective than the abrasive-grade SiC particle for strengthening of the aluminium matrix composites, as a result of the local stress concentration extent of Al matrix in the vicinity of the near-spherical geometry particulate is much slighter than that in the vicinity of the pointed end of the common abrasive-grade SiC particle, which will decrease the probability of crack initiation in matrix, in turn improve the strength (including micro-yield strength characterizing the dimension stability of materials).More effective mechanical keying arising from rough topography on the surface of SHS SiC, leads to stronger interface bonding and contributes to higher load transferring efficiency and elastic modulus of composite.
SONG Gui-ming, WU Ying. Thermal Shock Resistance of Carbon Fiber-Reinforced TiC Composites[J]. Journal of Materials Engineering, 2001, 0(12): 16-19.
The thermal shock resistance of hot-pressed TiC composites reinforced by chopped carbon fiber (20vol%) were investigated by evaluating the mechanical and thermophysical properties. The results show that with an addition of chopped carbon fibers, the strength and fracture toughness are increased remarkably, and the elastic modulus and thermal expansion coefficient are decreased, therefore, the thermal stress fracture resistance parameter,R, thermal stress damage resistance parameter,RTV,and thermal stress crack stability parameter, RST, are all increased. The residual strength is decreased significantly when the thermal shock temperature difference,ΔT, is higher than 900℃.The increase of thermal diffusivity of the composites is beneficial to the thermal shock resistance. The strengthening mechanism of Cf/TiC composites is loading transferring, and the toughening mechanisms are crack bridging and fiber pull-out.
PENG Chao-qun, HUANG Bai-yun, HE Yue-hui. Effects of Rapid Heating Induction Heat Treatment on Microstructures and Mechanical Properties of TiAl-based Alloy[J]. Journal of Materials Engineering, 2001, 0(12): 20-23.
The effects of rapid heating, slow cooling heat treatment on microstructures and mechanical properties of a TiAl-based alloy were studied using a GP-30(A) type induction heating machine.The results show that: fine fully-lamellar microstructure of colony size about 50μm and lamellar spacing about 0.12μm can be obtained by using this technology; compression mechanical properties can be raised to a large extent and the best compression mechanical properties can reach the yield stress 745.1MPa, the largest flowstress 1672.2MPa and the compression ratio 19.4%;after induction heat treatment and aging, the compression fracture at room temperature is still typical cleavage fracture.
WU Ping, HE Xin-lai, WANG Xue-min, CAO Bing, YU Dong-you. Grain Boundary Segregation of Boron during Cooling-Isothermal Holding-Cooling Process[J]. Journal of Materials Engineering, 2001, 0(12): 24-28.
The grain boundary segregation of boron in Fe-40%Ni alloy with 10×10-6 and 30×10-6 boron during cooling-isothermal holding-cooling process was investigated by particle tracking autoradiography technique. The results indicate that during cooling-isothermal holding-cooling process cooling from 1150℃ to 1100℃, 1000℃, 900℃, 800℃, 700℃ respectively at 2℃/s and isothermal holding for 2 min and then cooling to 600℃ at 2℃/s, the boron atoms segregate to grain boundaries obviously and the amount of segregating boron atoms first decreases then increases with the isothermal holding temperature decreased, and the lowest point is at about 1000℃ The grain boundary segregation of boron of samples with 10×10-6 boron isothermal holding at temperatures above 800℃ are mainly continuous pit belts with some amount boron precipitates, and that of the other samples are mainly boron precipitates. It is also observed that obvious boron segregation exists on sub-structures and boron depletion zone can be seen. At the intersections of austenitic grain boundaries and sub-grain boundaries, boron atoms preferably segregate to austenitic grain boundaries.
ZHAO Ai-guo, ZHANG Wei-fang, XI Nian-sheng, TAO Chun-hu, HAN Jie-cai, DU Shan-yi. Investigation on Combustion Mode of Al-TiO2-C-Ti-Fe Systems[J]. Journal of Materials Engineering, 2001, 0(12): 29-31,48.
Combustion mode of Al-TiO2-C-Ti-Fe system was studied by means of computer combined with rapid image collecting. The results show that the Al-TiO2-C-Ti system presents typical plane combustion mode. The Al-TiO2-C-Ti-20wt%Fe system exhibits multiple-point undulation combustion mode because of decrease of combustion temperature, the melting of Al and the heat exchange. The undulation degree weakens with the increasing of Fe content. However, an unusual phenomenon was first found that the combustion wave steadily propagated again as plane combustion mode with further increasing of Fe content, i-e. the decreasing of adiabatic temperature (such as Al-TiO2-C-Ti-50wt%Fe system). The possible cause is that the combustion wave with high temperature points is unlikely to be prior to propagate due to the low adiabatic temperature (approaching to 1800K) and the low undulation of temperature at combustion front.
LI Zhi-qiang, HAN Jie-cai, HE Xiao-dong, QU Wei. Self-Propagating High-Temperature Synthesis of Al-Ti-TiO2 System and Reaction Mechanism[J]. Journal of Materials Engineering, 2001, 0(12): 32-35,39.
TiAl/Al2O3 composites were synthesized by SHS method. The effects of Al2O3 content on the SHS process of Al Ti-TiO2 system and the microstructure of products were studied. It is shown that both the combustion temperature and wave velocity increase with increasing Al2O3 content. In addition, the relative density of productsis also improved with more Al2O3 content. The reaction process of Al-Ti-TiO2 system was investigated through thermal differential analysis (DTA).It is concluded that, despite later commencement, the reduction of TiO2 is completed earlier than reactions between Al and Ti due to faster reaction rate resulted from smaller activation energy. TiAl3 formed in early stage as intermediate product and its conversion to TiAl and Ti-3Al is dominating reaction in Al-Ti-TiO2 system.
ZHANG Hu, GAO Wen-li, HE Jian-ping, ZHANG Er-lin, ZENG Shong-yan. Effect of B Content on the Morphology of TiB2 in Ti-50Al-xB Alloys[J]. Journal of Materials Engineering, 2001, 0(12): 36-39.
The microstructure and phase constitution of Ti-50Al-xB(at%)alloys produced by in-situ growing method were investigated by XRD and SEM respectively. The results show that these alloys are composed of TiAl and TiB2 phase, and boron additions to TiAl alloys introduce the refractory compound TiB2 in-variety of morphologies. The morphologies of TiB2 change from convoluted flakes to needles to plates and eventually to particles as the B content increases from 0.4 at% to 1.4 at%. Growth mechanism and evolution of TiB2 morphology were analyzed according to TiB2 crystal structure and growth condition.
CUI Lan, HUO Li-xing, ZHANG Yu-feng, JING Hong-yang, QIAN Yue-dong. A Study on Weld Toughness of Friction Welded Joints of Similar and Dissimilar Materials[J]. Journal of Materials Engineering, 2001, 0(12): 40-42.
The toughness of friction welded joints of similar material 35CrMo and dissimilar material 20CrMo to 35CrMo, 37Mn5 to 35CrMo has been studied- The reason for lower toughness of dissimilar materials welds has been analysed by mean of SEM and metallography. It is shown that welding joints of similar material 35CrMo in rational specification can obtain binding well and finer grain which leads to a weld of higher toughness.
MA Qing-song, CHEN Zhao-hui, ZHENG Wen-wei, HU Hai-feng. Preparation of Complex-Shaped Cf/Si-O-C Parts via Resin Transfer Molding and Pyrolysis[J]. Journal of Materials Engineering, 2001, 0(12): 43-45.
Complex-shaped Cf/SiO C parts were fabricated by resin transfer molding(RTM) and pyrolysis with polysiloxane(PSO) as precursor. According to RTM, the cross-linking and pyrolysis of divinylbenzene(DVB)/PSO, the effects of temperature and time on viscosity of DVB/PSO, the wetting angle between fiber and DVB/PSO, and preparation of TiO2 films used as demoulding agent were studied in this paper.
GAO Yu-kui, YIN Yuan-fa, LI Xiang-bin-and, LIU Tian-qi. Influence of Shot Peening on Fatigue Property for 0Cr13Ni8Mo2Al Steel[J]. Journal of Materials Engineering, 2001, 0(12): 46-48.
The influence of surface residual stress, surface roughness and residual compressive stress field induced by shot peening on fatigue properties of 0Cr13Ni8Mo2Al steel was studied. The results reveal that the shot peening improves the fatigue properties, and the fatigue crack sources are pushed to the region beneath the hardened layer, and fatigue life is significantly increased.
