|Previous Session||Next Session|
|Return To Program Contents Page|
Session Chairpersons: P.R. Taylor, University of Idaho, Dept. of Metallurgical & Mining Engineering, Moscow, ID 83844-3024; J.R. Groza, Chemical Engineering and Materials Science Dept., University of California at Davis
ZIRCONIUM CARBIDE SYNTHESIS IN A HIGH TEMPERATURE PLASMA REACTOR: Patrick R. Taylor, Banqiu Wu and Edgar E. Vidal, University of Idaho, Department of Metallurgical & Mining Engineering, Moscow, ID 83844-3024
Zirconium carbide powder has been synthesized from zircon concentrate and methane using a high temperature plasma reactor. A non-transferred DC plasma torch was used as heat source. A high temperature filter consisting of graphite felt was designed, built and operated to separate the zirconium carbide from silicon carbide during the process. Characterization of the collected powders was done by wet chemical analysis using Atomic Absorption (AA), Scanning and Transmission Electron Microscopy (SEM and TEM) and X-Ray Diffraction (XRD). It was found that the zirconium carbide purity was around 95% with silicon carbide being the primary impurity. The powders had particle sizes between 30 and 80 nm. Based on the XRD pattern a lattice parameter of 4.6932A was calculated for the zirconium carbide. The effect of several experimental variables is presented as well as a mathematical model that describes the temperature and velocity profiles in the reactor.
PRECIPITATES ROLE IN SUPERPLASTICITY OF HIGH PERFORMANCE COPPER ALLOYS: Ken R. Anderson, Joanna R. Groza, Chemical Engineering and Materials Science Dept. University of California at Davis, A.T. Dumitrescu, Metallurgical Research Institute, Bucharest, Romania
High strength, high thermal conductivity copper alloys are in continuous demand for a variety of applications such as actively cooled structures, electric and electronic parts, molding tools or welding electrodes. The goal of the present work is to understand the interrelationship between processing and microstructure of these alloys to promote superplastic behavior. Chemistry and processing variations were applied to achieve precipitation of different dispersoids in the copper matrix. High temperature, high strain rate deformation was performed to characterize the superplastic behavior. Precipitate identification and microstructural studies were correlated to mechanical properties.
MECHANICAL PROPERTIES AND MICROSTRUCTURAL CHARACTERIZATION OF THE COMMERCIAL ALUMINUM ALLOY 6063 UNDER DIFFERENT HOMOGENIZING THERMAL TREATMENTS: J.R. Rendon, C.V.G Venalum, Puerto Ordaz, Venezuela, B. Hidalgo, Universidad de Oriente, Cumana, Venezuela, Mokka N. Rao, Universidad Nacional Experimental de Guayana, Puerto Ordaz, Venezuela
Cylinders of commercial aluminum alloy 6063 were homogenized under different conditions. The experimental results indicate that the general mechanical behavior as related to curves of 0.2% yield strength, ultimate tensile strength, and ductility versus homogenizing process is the same in both cases. These mechanical properties as compared to those required by plant specifications, tend to be better with increasing values of %Mg2Si in the alloy, as expected. The electron microscopy investigations revealed that in both homogenizing processes the resulting microstructure consist of significant spheroidizing of the alpha phase (AlFeSi) and fine - needle type structures of the beta phase. The alpha phase was also present in a Chinese scripture type structure. Furthermore, the slow cooling within the furnace resulted in the nucleation and growth of Mg2Si precipitates generally along the grain boundaries.
THE FIRST EXPERIENCE WITH FORMATION OF "NATURAL" METAL-MATRIX COMPOSITE BY THE APPROPRIATE THERMO-MECHANICAL TREATMENT OF POLYCRYSTALLINE METALS: A. Korbel, W. Bochniak, F. Ciura, H. Dybiec, K. Piela, The Department of Structure & Mechanics of Solids, Academy of Mining and Metallurgy, Mickiewicza 30, 30-059 Krakow, Poland
The progress in understanding of the nature of strain localization in metallic materials and in particular understanding of the role of external (deformation conditions) and internal (material substructure) factors in the development of the tendency toward concentration of plastic flow within transgranular shear bands has laid at the background of the pointed in the title idea. Following this idea, a practical possibility of replacement a homogeneous in a micro scale mode of deformation by transgrasnular shear bands gives a chance to change the arrangement of dislocation substructure in the material from that typical for homogeneous deformation into a long wavelength (transgranular), pseudo-periodic dislocation walls. The presence or formation of such a substructure in a thermodynamically unstable matrix may result in formation of the products of phase transformation along shear bands, giving rise to a composite like structure. The experimental verification of the idea is the main aim of the work. The spectrum of different materials undergoing (post or during shear banding) different phase transformations: precipitation from supersaturated solid solution in Al-base alloys, martensitic transformation in Fe-Ni alloy, austenite-ferrite and austenite perlite transformation in the plain carbon steel and - transformation in Cu-Zn brass has been studied by use of the optical and electron microscopy. The effect of this way induced structures on some mechanical properties (strength of materials, shape memory effect in Fe-Ni alloy) is also shown in the work.
3:40 pm BREAK
STUDIES ON GROWTH MECHANISMS AND CHARACTERISTIC FACTORS FOR THE HYDROTHERMAL PREPARATION OF A-QUARTZ CRYSTAL POWDERS: Kee Jeung Lee, Kyung Won Seo, Young Mok, Department of Chemical Engineering, Ajou University, 5 Wonchon-Dong, Paldal Gu, Suwon 442-749 Korea; Hyo Shin Yu, Korea Institute of Geology, Mining & Materials, Resources Utilization & Materials Division, 30 Kajung-Dong, Yusung Gu, Taejon, 305-350, Korea
In this study the characteristic factors and formation mechanisms for the hydrothermal preparation of -quartz crystal powders were investigated to find the optimum synthetic conditions. The degree of -quartz crystal face development depended on the relative growth rate of a particular form that varies considerable with the degree of supersaturation, the reaction temperature, the concentration of mineralizers, and the presence of seed crystals in the feedstock. Alkali hydroxides and alkali halides were found to be effective in the reactions as mineralizers, which added in order to increase the solubility of the feedstock. The fine quartz crystal powders were obtained in the temperature range of 250-500°C and pressure range of 100-300 atm. As the concentration of mineralizers increased, the particle size of crystalline powders became smaller with lower reaction temperatures. The fractional size distribution of synthetic crystal powders was depended on the hydrothermal conditions. As the reaction time and the amount of seed crystals increased, the width of particle size distribution became narrower. The weight mean particle size was in the range of 1 to 10µm. The characterization of the products were carried out using XRD, SEM, PSA, FTIR, Raman Spectrometer.
THE INTRAGRANULAR FERRITE PLATE AND ITS NUCLEATING INCLUSIONS IN HAZ OF X-60 PIPE STEEL: Jiang Guo Chang, Zhu Yu Ru, Guo Shu Qiang, Xu Jian Lun, Department of Materials, Shanghai University, 149 Yan Chang Road, Shanghai 200072, China; Wang Yue Qlang, Pan Li Ying, Yu Di Wei, Bao Shan Iron & Steel Corporation
To improve the HAZ toughness of X-60 pipe steel the intragranular ferrite plate (IFP) technology was used. The characteristics of IFP is claimed to be much fine ferrite plates appear inside the original austenite grains. By means of a suitable Re, Zr, Ti additions in a bath with a higher initial oxygen potential, and a good control over the peak temperature as well as the cooling rate during welding simulation, one get a%IFP in volume over 50%, and the toughness goes up from 55J to 160J. It was found that the inclusions most effective on nucleating IFP are some deformable complex silicates which either entrapping Re, Zr, Ti oxides or containing these elements. The more the evenly distributed and effectively nucleating inclusions, the more the % IFP in volume, and the finer the microstructure of the HAZ, so the better the relevant toughness. Generally, these silicates behave as fine spheres along a line. The present authors revealed that these fine spheres result from the remelting of the silicates due to temperature raising up in the process of welding simulation. These silicates used to get a higher sulfur capacity, so MnS deposits might be observed on the periphery of the silicates. IFP was proved to be directly rooted in the [Mn] depleting zone which locates beside MnS deposits.
ZIRCONIUM PURIFICATION IN THE PROCESS OF METAL RAW MATERIALS IODINATION: Z.B. Moukhametshina, V.I. Adamovich, A.M. Chekmarev, Mendeleev University of Chemical Technology of Russia, Miusskaya sq., 9, Moscow 125047, Russia
The process of various zirconium alloys iodination by the iodine vapor was investigated. The nature of impurities, conditions of iodination, iodine flow rate, and zirconium tetraiodide condensation rate effect on the metal impurities transfer process was analyzed, both qualitative and quantitative correlations were established. Impurities were classified according to their transfer extent. Another classification of impurities transport dependence on iodination process temperature was also offered Obtained results were compared with impurities transport data in the process of iodide refining available in literature. Some impurities transport mechanisms and iodide-refined metals improvement possibility by means of iodination conditions control were discussed.
|Previous Session Next Session|
|Search||Technical Program Contents||1997 Annual Meeting Page||TMS Meetings Page||TMS OnLine|