Sponsored by: EPD Process Fundamentals Committee, MSD Thermodynamics & Phase Committee, Japan Institute of Metals
Program Organizers: Prof. R.Y. Lin, University of Cincinnati; Prof. Y. Austin Chang, University of Wisconsin-Madison; Prof. R. Reddy, University of Navada-Reno and Dr. C.T. Liu, Oak Ridge NL
Wednesday, AM Room: B2
February 7, 1995 Location: Anaheim Convention Center
Session Chairperson: Y. Iguchi, Dept. Metallurgy, Tohoku Univ., Sendai, JAPAN; Michael J. Koczak, Department of Materials Engineering, Drexel University, Philadelphia, PA 19104
8:30 am Invited
EFFECTS OF INTERGRANULAR NANODISPERSIONS OF HIGH TEMPERATURE PROPERTIES OF CERAMIC MATRIX COMPOSITES: K. Niihara, T. Ohji, N. Kusunose and K. Akamatsu, The Research Institute of Scientific and Industrial Research, Osaka University,8-1 Mihogaoka, Ibaraki, Osaka 567, Japan
Ceramic based nanocomposites, in which nano-sized ceramics and metals were dispersed within matrix grains and/or at grain boundaries, were fabricated by an usual powder metallurgical method. The striking finding in the nanocomposite systems is that the mechanical properties such as fracture toughness, strength and creep resistance are significantly improved by the nano-sized dispersions. Specifically, the creep rates of alumina/silicon carbide, magnesia/silicon carbide and silicon nitride/silicon carbide composites were 3 to 4 orders improved by the nano-sized dispersions. In this presentation, the process-structure-properties reaction will be first described, and finally the roles of intergranular nanodispersions in the creep resistance improvement will be discussed.
8:55 am Invited
CMC'S RESEARCH IN EUROPE AND THE FUTURE POTENTIALS OF CMC'S IN INDUSTRY: M.Van de Voorde, European Commission-Joint Research Center, P.O. Box 2, 1755ZG Petten, The Netherlands
CMC's have been developed for high Temperature Applications in Aerospace and Military Industries. In general, the CMC's were capable to withstand high temperatures (up to 1700deg.C) in an inert atmosphere for short durations. Great efforts are being given to pinpoint spin-off technologies i.e. applications in aero engines, modern fossil fuel power plants, gas-turbines, petrochemistry etc. In these applications, the CMC's have to operate at up to 1400deg.C, in corrosive environments for long durations. In addition, the CMC's process should become cost effective. The development of such CMC's will provoke a breakthrough for this new group of materials. The paper will 1) give an overview of the CMC's research in Europe; processing-characterization of physical, chemical and engineering properties at H.T.; 2) pinpoint the R & D needs to achieve the potential growth; 3) evaluate the market potentials; and 4) review the industrial applications.
9:20 am Invited
HIGH TEMPERATURE MECHANICAL BEHAVIOR OF MGO-BASED NANOCOMPOSITES: Y. H. Choa, K. Niihara, The Research Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567, Japan
MgO/SiC nanocomposites were found to exhibit the excellent high fracture strength and toughness even at high-temperatures. These significant improvements of mechanical properties were contributed to the dispersion of nano-sized second phase. In this presentation, the effects of micro-sized SiC particulate dispersions on the fracture strength, toughness, Young's modulus, and effective surface energy up to 1400deg.C were investigated.
COMPLEX OXIDE FILMS FORMED DURING THERMAL OXIDATION OF LIQUID ALUMINUM ALLOYS: Y.Iguchi, T.Narushima, M.Maruyama, T.Shiozawa Department of Metallurgy, Tohoku University, Sendai 980-77, Japan; H.Arashi, Department of Machine Intelligence and System Engineering, Tohoku University, Sendai 980-77, Japan
Oxidation behavior of liquid aluminum alloys is important in the view point of crack formation during continuous casting of aluminum alloys or syntheses of ceramic matrix composites. In the present work, the in situ observation system for thermal oxidation using Raman spectroscopy was constructed, and oxide films formed on liquid pure Al and Al-Mg alloys (Mg contents =1 and 4 mass%) were analyzed at room temperature to 1273 K in dry oxygen with this system. Oxidation films formed on the specimens depended on the composition of alloys. In situ Raman spectra of the surface of a liquid Al-4 mass% Mg indicated the formation of MgO$B!&(BAl2O3 (spinel) as oxidation products, while e$B&A(B-Al2O3 and MgO$B!&(BAl2O3 (spinel) were observed on a liquid Al-1mass%Mg alloy. It was suggested that the formation of MgO film affected oxidation behavior of these alloys. The oxidation mechanisms were discussed thermodynamically.
10:10 am BREAK
10:45 am Invited
IN-SITU PROCESSING TECHNIQUES FOR FUNCTIONAL GRADED MATERIALS: Michael J. Koczak, Department of Materials Engineering, Drexel University, Philadelphia, PA 19104
It is now widely recognized that Functionally Graded Materials (FGMs) are of interest for structural and electronic applications. The properties of FGMs are controlled by the size and volume fraction of the reinforcement phase, as well as the microstructure and properties of the matrix/reinforcement interface. Traditionally, FGMs have been produced by such processing techniques as powder metallurgy, preform infiltration, spray deposition and various casting technologies, i.e. squeeze casting, rheocasting and compocasting. In the last decade, new in situ processing, analysis and evaluation technologies have emerged. For processing FGMs, in-situ techniques can be applied and involve a chemical reaction resulting in the formation of very fine thermodynamically stable reinforcing ceramic phases during processing, e.g. DIMOXTM, XDTM, and reactive gas infiltration (RGI) and can be combined with densification techniques, e.g. reactive infiltration, centrifugal casting, SHS rolling approaches. The application of new processing and analysis approaches should low for more cost-effective productions of FGM for wear and structural applications. The author acknowledges from the Office of Naval Research - Materials Division.
LAYERED METAL MATRIX COMPOSITES: Li Lu, Dept. Mechanical & Production Engineering, The National University of Singapore, 10 Kent Ridge Crescent, Singapore 0511
Metal matrix composite (MMC) with composition of Al-4.5wt.%Cu reinforced by 10wt.%TiB2 or 15wt.%SiC particulate has been successfully fabricated using powder metallurgy technique. Disk and beam shaped specimens were prepared with (a) layered structure containing ductile Al-4.5wt.%Cu with brittle Al-4.5%Cu/TiB2 or 4.5wt.%Cu/SiC layers, and (b) homogenous constituent with composition of Al4.5wt%Cu/10wt.%TiB2. The normal direction of the layers in the layered specimens, being built through three ductile-brittle-ductile alternating layers was parallel to the axis of the disk specimen for the beam specimens, the layers were built through brittle-ductile-brittle sequence. The brittle layer consisted of Al-4.5%Cu with fixed amount of reinforcement. Fracture toughness testing revealed an increase for layered composites although the total amount of the reinforcement was the same for all disk specimens. The increase in the fracture toughness is due to the existence of ductile layers which manifests a strong influence on delaying the occurrence of fracture. It acts as a barrier to resist the propagation of crack and hence increases the fracture toughness of the layered MMC specimens. Delamination in the beam specimens were observed due to shear stresses. Fracture surface of both disk and beam specimens wer characterized using the SEM.
PHASE RELATIONS IN THE Sm2O3-CeO2-CuO SYSTEM INVOLVING THE N-TYPE SUPERCONDUCTOR Sm2 x Cex CU04 y: Zhivu Qiao, Weidong Zhuang, Shoukun Wei, Lin Cheng, Jingkui Liang. Department of Pllysical Chemistry, University of Science and Technology Beijing, Beijing 100083, China
The subsolidus phase relations in the Sm2O3-CeO2-CuO system involving the
n-type Sm2-x Cex Cu04-y superconductor were investigated by x-ray diffraction
at 1000deg.C in air. The system can be divided into two ternary phase regions
and three binary phase regions. the solid solution Sm2, CexCuO4 y was found to
be the only ternary phase, and the maximum solid solubility was confirmed to be
x=0.20. The solid solution crystallizes in a tetragonal unit cell, space group
I4/mmm. The c value of the solid solution is smaller than that of Sm2CuO4, but
the a value is larger than that of Sm2CuO4. The average valence of copper ion
of the solid solution decreases linearly with the increase Ce content.
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