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Interstitial-phase precipitation in iron-base alloys: a comparative study

Description: Recent developments have elucidated the atomistic mechanisms of precipitation of interstitial elements in simple alloy systems. However, in the more technologically important iron base alloys, interstitial phase precipitation is generally not well understood. The present experimental study was therefore designed to test the applicability of these concepts to more complex ferrous alloys. Hence, a comparative study was made of interstitial phase precipitation in ferritic Fe-Si-C and in austenitic phosphorus-containing Fe-Cr-Ni steels. These systems were subjected to a variety of quench-age thermal treatments, and the microstructural development was subsequently characterized by transmission electron microscopy.
Date: June 1, 1982
Creator: Pelton, A.R.
Partner: UNT Libraries Government Documents Department

Computer-assisted analyses of the thermodynamic properties of slags in coal-combustion systems

Description: Equations were developed for the analysis of the thermodynamic properties of molten silicate solutions; the equations take into account the unusual concentration and temperature dependence of the solution properties of ordered systems. For binary systems, these equations were coupled with an optimization computer program to analyze all reliable thermodynamic data, including phase diagrams, free energies and enthalpies of formation of compounds, activities of components, enthalpies of mixing, entropies of fusion, miscibility gaps, etc. In this manner, we analyzed data for five binary systems: CaO-SiO/sub 2/, Na/sub 2/O-SiO/sub 2/, CaO-Al/sub 2/O/sub 3/, Na/sub 2/O-Al/sub 2/O/sub 3/, and Al/sub 2/O/sub 3/-SiO/sub 2/. The results of the binary systems were combined, and an analysis done of three ternary systems: CaO-Al/sub 2/O/sub 3/-SiO/sub 2/, Na/sub 2/O-CaO-SiO/sub 2/, and Na/sub 2/O-Al/sub 2/O/sup 3/-SiO/sub 2/. A tentative analysis of the quaternary system, Na/sub 2/O-CaO-Al/sub 2/O/sub 3/-SiO/sub 2/, was also undertaken. 53 references, 51 figures, 3 tables.
Date: September 1, 1983
Creator: Blander, M. & Pelton, A.D.
Partner: UNT Libraries Government Documents Department

Analyses and predictions of the thermodynamic properties and phase diagrams of silicate systems

Description: Molten silicates are ordered solutions which can not be well represented by the usual polynomial representation of deviations from ideal solution behavior (i.e. excess free energies of mixing). An adaptation of quasichemical theory which is capable of describing the properties of ordered solutions represents the measured properties of binary silicates over broad ranges of composition and temperature. For simple silicates such as the MgO-FeO-SiO{sub 2} ternary system, in which silica is the only acid component, a combining rule generally leads to good predictions of ternary solutions from those of the binaries. In basic solutions, these predictions are consistent with those of the conformal ionic solution theory. Our results indicate that our approach could provide a potentially powerful tool for representing and predicting the properties of multicomponent molten silicates.
Date: July 1, 1992
Creator: Blander, M.; Pelton, A. & Eriksson, G.
Partner: UNT Libraries Government Documents Department

Solidus and liquidus temperatures in the uranium-plutonium-zirconium system

Description: Renewed interest in metallic fuel for nuclear reactors has prompted study of the solidus and liquidus for the uranium-plutonium-zirconium system. These temperatures are of importance in assessing the possibility of fuel melting during abnormal reactor conditions. Data obtained in previous work in this area were found to be inadequate for the needs of the current reactor development effort. A dual effort was undertaken to provide the needed data. These were (1) thermodynamic phase diagram analysis and calculation of the ternary solidus and liquidus surfaces and (2) experimental determination of solidus and liquidus temperatures for selected alloys. The methods used and results obtained are described.
Date: January 1, 1987
Creator: Leibowitz, L.; Veleckis, E.; Blomquist, R.A. & Pelton, A.D.
Partner: UNT Libraries Government Documents Department

Development of models and software for liquidus temperatures of glasses of HWVP products. Final report

Description: In an earlier report [92 Pel] was described the development of software and thermodynamic databases for the calculation of liquidus temperatures of glasses of HWVP products containing the components SiO{sub 2}-B{sub 2}O{sub 3}-Na{sub 2}O-Li{sub 2}O-CaO-MgO-Fe{sub 2}O{sub 3}-Al{sub 2}O{sub 3}-ZrO{sub 2}-{open_quotes}others{close_quotes}. The software package developed at that time consisted of the EQUILIB program of the F*A*C*T computer system with special input/output routines. Since then, Battelle has purchased the entire F*A*C*T computer system, and this fully replaces the earlier package. Furthermore, with the entire F*A*C*T system, additional calculations can be performed such as calculations at fixed O{sub 2}, SO{sub 2} etc. pressures, or graphing of output. Furthermore, the public F*A*C*T database of over 5000 gaseous species and condensed phases is now accessible. The private databases for the glass and crystalline phases were developed for Battelle by optimization of thermodynamic and phase diagram data. That is, all available data for 2- and 3-component sub-systems of the 9-component oxide system were collected, and parameters of model equations for the thermodynamic properties were found which best reproduce all the data. For representing the thermodynamic properties of the glass as a function of composition and temperature, the modified quasichemical model was used. This model was described in the earlier report [92 Pel] along with all the optimizations. With the model, it was possible to predict the thermodynamic properties of the 9-component glass, and thereby to calculate liquidus temperatures. Liquidus temperatures measured by Battelle for 123 CVS glass compositions were used to test the model and to refine the model by the addition of further parameters.
Date: March 1, 1996
Creator: Hrma, P.R.; Vienna, J.D. & Pelton, A.D.
Partner: UNT Libraries Government Documents Department

Thermodynamic analysis of phase equilibria in the iron-zirconium system

Description: Continuing interest in development of metallic fuels for nuclear reactors has prompted an examination of the phase relations of many of the relevant binary and ternary systems of interest. We performed a thermodynamic analysis and optimization of the Fe-Zr system. Overall reasonably good agreement was found with published diagrams, but some significant changes were required to ensure thermodynamic consistency.
Date: September 1, 1992
Creator: Pelton, A. D.; Leibowitz, L. & Blomquist, R. A.
Partner: UNT Libraries Government Documents Department

On the origin of porphyritic chondrules

Description: A computer program for the complex equilibria in a cooling nebular gas was used to explore a possible origin of porphyritic chondrules, the major class of chondrules in chondritic meteorites. It uses a method of accurately calculating the thermodynamic properties of molten multicomponent aluminosilicates, which deduces the silicate condensates vs temperature and pressure of a nebular gas. This program is coupled with a chemical equilibrium algorithm for systems with at least 1000 chemical species; it has a data base of over 5000 solid, liquid, and gaseous species. Results are metastable subcooled liquid aluminoscilicates with compositions resembling types IA and II porphyritic chondrules at two different temperatures at any pressure between 10{sup {minus}2} and 1 (or possibly 10{sup {minus}3} to 5) atm. The different types of chondrules (types I, II, III) could have been produced from the same gas and do not need a different gas for each apparent oxidation state; thus, the difficulty of current models for making porphyritic chondrules by reheating different solids to just below their liquidus temperatures in different locations is not necessary. Initiation of a stage of crystallization just below liquidus is part of the natural crystallization (recalescence) process from metastable subcooled liquidus and does not require an improbably heating mechanism. 2 tabs.
Date: May 1, 1994
Creator: Blander, M.; Unger, L.; Pelton, A. & Ericksson, G.
Partner: UNT Libraries Government Documents Department

A possible origin of EL6 chondrites from a high temperature-high pressure solar gas

Description: Condensates from a gas of ``solar`` composition were calculated to investigate the origins of EL6 chondrites using a free energy minimization program with a data base for the thermodynamic properties of multicomponent molten silicates as well as for other liquids solids, solid solutions and gaseous species. Because of high volatility of silicon and silica, the high silicon content of metal (2.6 mole %) can only be produced at pressures 10{sup {minus}2} atm at temperatures above 1475 K. At 100--500 atm, a liquid silicate phase crystallizes at a temperature where the silicon content of the metal, ferrosilite content of the enstatite and albite concentration in the plagioclase are close to measured values. In pyrometallurgy, liquid silicates are catalysts for reactions in which Si-O-Si bridging bonds are broken or formed. Thus, one attractive mode for freezing in the compositions of these three phases is disappearance of fluxing liquid. If the plagioclase can continue to react with the nebula without a liquid phase, lower pressures of 10{sup {minus}1} to 1 atm might be possible. Even if the nebula is more reducing than a solar gas, the measured properties of EL6 chondrites might be reconciled with only slightly lower pressures (less than 3X lower). The temperatures would be about the same as indicated in our calculations since the product of the silicon content of the metal and the square of the ferrosilite content of the enstatite constitute a cosmothermometer for the mineral assemblage in EL6 chondrites.
Date: May 1, 1994
Creator: Blander, M.; Unger, L.; Pelton, A. & Eriksson, G.
Partner: UNT Libraries Government Documents Department

Analyses and predictions of the thermodynamic properties and phase diagrams of silicate systems

Description: Molten silicates are ordered solutions which can not be well represented by the usual polynomial representation of deviations from ideal solution behavior (i.e. excess free energies of mixing). An adaptation of quasichemical theory which is capable of describing the properties of ordered solutions represents the measured properties of binary silicates over broad ranges of composition and temperature. For simple silicates such as the MgO-FeO-SiO{sub 2} ternary system, in which silica is the only acid component, a combining rule generally leads to good predictions of ternary solutions from those of the binaries. In basic solutions, these predictions are consistent with those of the conformal ionic solution theory. Our results indicate that our approach could provide a potentially powerful tool for representing and predicting the properties of multicomponent molten silicates.
Date: January 1, 1992
Creator: Blander, M. (Argonne National Lab., IL (United States)); Pelton, A. & Eriksson, G. (Ecole Polytechnique, Montreal, PQ (Canada). Dept. of Metallurgy and Materials Engineering)
Partner: UNT Libraries Government Documents Department

Thermodynamic analysis of phase equilibria in the iron-zirconium system

Description: Continuing interest in development of metallic fuels for nuclear reactors has prompted an examination of the phase relations of many of the relevant binary and ternary systems of interest. We performed a thermodynamic analysis and optimization of the Fe-Zr system. Overall reasonably good agreement was found with published diagrams, but some significant changes were required to ensure thermodynamic consistency.
Date: January 1, 1992
Creator: Pelton, A. D. (Ecole Polytechnique, Montreal, PQ (Canada)); Leibowitz, L. & Blomquist, R. A. (Argonne National Lab., IL (United States))
Partner: UNT Libraries Government Documents Department