XIE Xian-qing, ZHANG-Di, CAI Jian-guo, LIU Jin-shui. Study of Thermal Expansion Behavior of TiC Particulate Reinforced ZA43 Matrix Composite[J]. Journal of Materials Engineering, 2001, 0(8): 3-6.
TiCp/ZA43 composite was fabricated by XDTM and stirring-casting techniques. The microstructure was investigated, and the coefficient of thermal expansion (CTE) of TiCp/ZA43 composite was measured in the range of 50~250℃ with a dilatometer. Theoretical models were employed to calculate the CTE of TiCp/ZA43 in the same temperature range. The influence factors on thermal expansion property were analyzed. It is shown that TiC particles can improve microstructure and thermal expansion property of ZA43 alloy, and the CTE of the composites decreases with the increase of particle volume fraction. The theoretically calculated CTEs are very close to the experimental values. Interfacial thermal stress of TiCp/ZA43 increases rapidly with temperature and slightly with TiC particles content increasing. The influence of thermal stress on CTEs depends on temperature range.
LIU Feng, GUO Xue-feng, YANG Gen-cang. Crystallization of Gels in the SiO2-ZrO2-B2O3 System[J]. Journal of Materials Engineering, 2001, 0(8): 7-10.
The preparation of glasses from gels in the ternary system of SiO2-ZrO2-B2O3 were investigated, by employing sol-gel processing. The crystallization character and high temperature structure stability of these gels were analyzed. Meanwhile, the hydrolyzing engineering parameters were identified, which could make SiO2-ZrO2-B2O3 gel keep less crystalline (1%~3%, vol%) at a temperature of 1500℃ for 30 min. The effect of ZrO2 and B2O3 on the crystallization was demonstrated and explained, respectively. It was found that the crystallization trend of gels is descended with the addition of B2O3.
SHENG Wen-bin, LI Dong, YANG Rui, LIU Yu-yin, GUO Jing-jie, JIA Jun. Study of the Reaction at TiAl Based Alloy/Permanent Mold Interface[J]. Journal of Materials Engineering, 2001, 0(8): 11-13,17.
Ti-48Al-2Cr-2Nb(at%) alloy exhaust valves were formed in permanent mold during centrifugal casting process with Induction Skull Melting (ISM) method, and the reaction at TiAl alloy/permanent mold interface were analyzed by SEM, XRD and EMPA. The results show that the content of Fe on valve surface is about 0.3wt%, which thickness is about 3μm. Certain thick hardness layer exists on the cast valve surface because of the reaction at alloy/mold interface and the powerful heat conduction of the mold, which thickness is more larger than that of Fe-diffusion layer. It is very important to improve the resistance and intensity of the cast surface.
LIU Tong, XIE Zhi-peng, LU Ji-wei, HUANG Yong. The Preparation and Properties of High Fracture Toughness Alumina Ceramics with Elongated Grains[J]. Journal of Materials Engineering, 2001, 0(8): 14-17.
The high fracture toughness alumina ceramics were prepared by hot-pressed sintering using calcined α-alumina powder made from aluminum hydroxide by seeding of wet grinding abrasion powder. The mechanical properties at different sintering temperatures were examined. The maximum fracture toughness reaches 6.70MPa·m1/2, which is one time higher than general. The microstructure of sintered samples was investigated, which showes elongated grain structure The elongated grain structure is considered to play a significant role effect in the increment of fracture toughness.
JIN Yun-xue, ZHANG Er-lin, ZENG Song-yan, ZHU Zhao-jun. Effect of Heat Treatment on Morphology of TiC in Ti-6Al-2C Alloy[J]. Journal of Materials Engineering, 2001, 0(8): 18-21.
Ti 6Al-2C alloy was produced using casting process. The as cast microstructure of alloy and the effect of heat treatment on TiC morphology had been investigated by XRD, SEM, and EPM. TiC in as cast alloy had dendritic shape and gradually transformed into bare branches after heat treated at 1200℃ and water quenched. With increasing holding time, TiC dendrite finally transformed into particles with size of 8~20μm. The dissolving process of dendrite TiC was studied according to C concentration balance in micro-zone and in terms of the studies the granulation model was built. This model indicated that the dissolving and breaking up of dendrite TiC always occur at the root sites of secondary and third dendrite arm where had larger surface curvature corresponding to higher C concentration in Ti matrix. The diffusion of C at high temperature disturbed the C concentration balance, which led to the dendrite TiC to dissolve and break up into particles.
GAO Feng, QU Shao-bo, ZHOU Xin-shan, YANG Zu-pei, TIAN Chang-sheng. The Phase Structure and Dielectric Properties of Klalium Doped PZN-based Ceramics[J]. Journal of Materials Engineering, 2001, 0(8): 22-24,28.
The effect of K+-doped on phase structure and dielectric constant of-PZN-BT-PT ceramics was investigated. The results show that the Curie temperature can be shifted to lower temperature after K+ doped in the ceramics. Dielectric constant will decrease with increasing K+/ additive, but temperature stability can be improved at the same time. Composite sintering can eliminate pyrochlore phase,which existed in K+-doped ceramics. The temperature stability can be improved greatly with combining composite sintering technology to the doping technology.
YANG Su-ling, HAN Ya-fang, LI Sun-hua. The Effect of Composition on Microstructure and Mechanical Properties of a DS Alloy IC6[J]. Journal of Materials Engineering, 2001, 0(8): 25-28.
The effects of alloying elements, Al, Mo, B, C, Nb, Zr, W, Cr, Re et al on the microstructure and mechanical properties were investigated during the development of a Ni3Al base alloy IC6. On the basis of the experimental results, an optimum composition (wt%) range of Ni-(7.5~8.5)Al-(10~14)Mo-(0.02~0.15)B was determined.
LIN Yuan-hua, ZHANG Zhong-tai, TANG Zi-long, ZHANG Feng, CHEN Qing-ming. Preparation of CaAl2O4-based Long Afterglow Luminescent Material and its Luminescent Mechanism[J]. Journal of Materials Engineering, 2001, 0(8): 29-31.
The long afterglow and high brightness of CaAl2O4:Eu,RE(RE:Nd,Dy) luminescent materials were prepared by the solid-sintering method. The luminescent properties were studied, the emission spectra showed that both of the main peaks lie in about 440nm, and the decay curve indicated that the decay process contains the rapid-decaying and slow-decaying processes. The long afterglow mechanism is considered to be that the doped Dy3+ and Nd3+ worked as hole traps, they prolonged the luminescent time and enlarged the brightness The trap depth of CaAl2O4:Eu,Nd is more suitable than that of CaAl2O4:Eu,Dy, and therefore, the luminescent properties of CaAl2O4:Eu,Nd are superior to that of CaAl2O4:Eu,Dy.
LI Guo-lu, JIANG Xin-chang, WEN Ming, CAO Xiao-ming, LÜ Yu-shen. Studies of B4C Particles Reinforced Copper Matrix Composite[J]. Journal of Materials Engineering, 2001, 0(8): 32-35.
The B4C particles containing titanium metal coating reinforced copper matrix composite(B4Cp/(TiB2+TiN)/Cu) was investigated and compared with B4C particles reinforced copper matrix composite(B4Cp/Cu). The experimental results show that the density and conductance of the former were better than which of the later. The wear experimental results show that the wear resistance of the former is better than that of the later. The interface of composites and worn surface were observed and analyzed. The results indicate that the coating modification of B4C particles has improved interfacial bonding property of composite. There is good wettability between the particle and matrix.
LIANG Zhi-yong, DUAN Yue-xin, LIN-Yun, ZHAO Yan, LU Yao, ZHANG Zuo-guang. Rheological Model and Processing Window of Vinyl Ester Resin System for RTM Process[J]. Journal of Materials Engineering, 2001, 0(8): 36-39,47.
The rheological behaviors of vinyl ester resin systems (Ashland 992) for resin transfer molding (RTM) were studied with DSC and viscosity experiments. The rheological model of the resin was established based on Dual-Arrhenius equation and chemical reactive equation. The model was used to simulate rheological behaviors of the resin. The estimated viscosity values of the models were in good agreement with that of the experiments. The low viscosity processing window of the resin for RTM process was determined based on the developed models. The resin system have a 30min/0.4Pa·s processing window at 30℃. The developed viscosity model is important for processing simulation and quality control for RTM processing of high performance composites.
ZHOU Long-jie, HUANG Yong, XIE Zhi-peng, YANG Jin-long. Influence of Coating and Gelcasting on Properties of Silicon Nitride Ceramic[J]. Journal of Materials Engineering, 2001, 0(8): 40-43.
A layer of Y2O3-Al2O3, using as sintering aids, was coated on the surface of Si3N4 particles by precipitation of inorganic salts from a water based solution containing Al(NO3)3, Y(NO3)3 and urea. The electrokinetic and colloidal characteristics of Si3N4 powder was greatly changed by the coating layer. As a result, dispersion of Y2O3-Al2O3 coated Si3N4 powder is greatly increased compared to that of the original powder. Surface coating as well as gelcasting process greatly improves the room temperature bending strength and Weibull modulus of the resulting ceramic bodies.
WANG Wen, ZHOU Yu, YE Feng, JIA De-chang, SONG Gui-ming, LEI Ting-quan. Progress in the Structure and Properties of Ferroelectric SrBi2Ta2O9 Thin Films[J]. Journal of Materials Engineering, 2001, 0(8): 44-47.
The progress in the structure and properties of ferroelectric SrBi2Ta2O9 thin films was reviewed. Special attention was focused on the effect of the chemical composition, crystal orientation, annealing conditions and service temperature on SrBi2Ta2O9 ferroelectric properties. The results show that the SBT thin film with Sr:Bi:Ta=0.8:2.2:2 on the Bi4Ti3O12 buffer, prepared by a rapid thermal annealing, possesses the high remanent polarization, the low coercive filed and the low loss current.
