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1.
The activity of NiO in NiO?MnO solid solutions has been measured using the cell Ni, NiO |Zr 0.85 Ca 0.15 O 1.85|Ni, [NiO] s.s. in the temperature range 900° to 1200°C for compositions between 0 and 80 mol pct NiO. The activity-composition relationships for MnO have been determined by integration of the Gibbs-Duhem equation, and the partial and integral thermodynamic quantities for the system have been calculated. The system exhibits a positive deviation from ideal behavior with a maximum heat of mixing of 850±150 cals per mole, and a positive excess entropy of mixing of 0.24±0.1 cal per mole °C was detected at the equimolar composition. 相似文献
2.
Wetting of two symmetrical tilt grain boundaries, 77° 〈110〉 and 141° 〈110〉, in synthetic copper bicrystals with a Cu(In) melt was studied in the temperature range 690°990°C. The contact angle at the site of GB intersection with the solid-melt interface was measured. A wetting transition occurred at Tw = 960 ± 6°C for the 77° 〈110〉 grain boundary and at Tw = 930 ± 5°C for the 141° 〈110〉 grain boundary. The contact angle approached zero for this transition. The relative surface energies of the two boundaries were measured using the thermal grooving technique. The energy of the 77° 〈110〉 grain boundary is about 40% lower than that of the 141° 〈110〉 grain boundary. Therefore, it has been shown experimentally that the lower the grain boundary energy, the higher the wetting transition temperature. This is in agreement with the thermodynamic model of wetting transitions on grain boundaries. 相似文献
3.
In the course of scientific development, occasionally a phenomenon is encountered which challenges our understanding and defies
a complete explanation. Such a phenomenon occurs in the formation of Li 5B 4 compound-alloy which is formed by heating ( not cooling). The liquid metallic solution of Li and B which exists at low temperature (300 to 450°C) transforms to a metallic
solid at high temperature (500 to 550°C). Following the transformation to solid, Li 5B 4 compound-alloy formation takes place at 550 ± 2°C, accompanied by a heat release of about 2.2 ± 0.3 kcal per gram of B. The
compound-alloy thus formed is a totally metallic solid existing from room temperature to 1000°C. Above 1000°C, the compound-alloy
sublimes (with Li vaporizing) leaving behind a blackish substance. While these observations are unusual in terms of the wide
composition and temperature ranges in which they occur, they are by no means ‘strange’. They are not inconsistent with the
thermodynamic principles of phase diagrams and can be interpreted once the whole process is fully characterized. 相似文献
4.
A currently available commercial Calphad thermodynamic database was utilized to investigate its applicability to alloy design in the new class of Co-Ni-based γ′-strengthened high-temperature alloys. A simple primary design criterion was chosen: maximize the γ′ solvus temperature in the six-component Co-Ni-Al-Ti-W-Ta system while ensuring no formation of secondary, potentially deleterious phases. Secondary design considerations included the effects of alloying elements on equilibrium γ′ volume fraction and on solidus and liquidus temperatures. The identified composition, Co-30Ni-9Al-3Ti-7W-2Ta-0.1B (expressed in mole percent), representing a conservative estimate of the maximum allowable concentrations of alloying additions Al, Ti, W, and Ta, was subsequently produced and characterized. The experimentally measured γ′ solvus temperature of the new alloy was 1491 ± 3 K (1218 ± 3 °C), about 35 K (35 °C) above any previously reported two-phase γ−γ′ Co-(Ni)-based alloy. No secondary phases were observed in the alloy after annealing at temperatures between 1173 K and 1473 K (900 °C and 1200 °C). Additional alloy compositions with experimentally measured γ′ solvus temperatures in excess of 1533 K (1260 °C) were also identified employing the same basic approach. The efficacy of currently available thermodynamic databases in their application to Co-based γ′-strengthened superalloy development is discussed, including expanding design efforts to include additional alloying elements, as well as specific areas for improvement of future databases. 相似文献
5.
Equilibrium relations involving alloy and oxide phases in the system Fe-Cr-O were determined in the temperature range from
1600 °C to 1825 °C (1873 to 2087 K). Compositions of coexisting alloy and spinel phases were established as a function of
oxygen pressure by equilibrating liquid Fe-Cr alloys with iron chromite (Fe 3-xCr xO 4) solid solutions at 1600 °C and 1700 °C. Combinations of these experimental data and thermodynamic calculations were used
to construct composition-oxygen pressure diagrams for the system at 1600 °C and 1700 °C. Additional runs for selected mixtures
were made at still higher temperatures (1700 °C to 1825 °C), and thermodynamic parameters were derived for spinel-containing
phase assemblages at temperatures up to 1865 °C. The spinel phases occurring in the present system are typically in the high-chromium
range of the solid-solution series Fe 3O 4-Cr 3O 4, i.e., in the range between stoichiometric iron chromite (FeCr 2O 4) and Cr 3O 4. The activities of the various oxide components of the spinel solid solution at 1600 °C were calculated from experimentally
determined parameters for coexisting alloy and spinel phases, as well as by statistical-mechanical modeling of the same spinel
solid solution based on crystal-chemical considerations. The agreement between the two sets of results was excellent. Temperature
variation of parameters characterizing the univariant equilibria spinel + Cr 2O 3 + alloy and spinel + alloy + liquid oxide was established. The univariant curves were found to display temperature maxima
of 1715 °C ± 5 °C and approximately 1865 °C, respectively. In analogy with relations in the Cr-O system, the increase in divalent
chromium of the liquid oxide phase with decreasing oxygen potential was identified as the main cause of the sharp decrease
in liquidus temperatures of chromites in contact with Fe-Cr alloys of high Cr contents.
Formerly Graduate Research Assistant, Department of Metallurgy, The Pennsylvania State University
L.S. DARKEN and ARNULF MUAN, formerly Professors of Geochemistry and Materials Science, The Pennsylvania State University,
University Park, PA 16802, are deceased. 相似文献
6.
The sub-binary systems Al-Ti, Ti-V, and Al-V are reviewed and adopted from the previous assessments, the thermodynamic analysis of the Al-Ti-V ternary system is performed by the CALPHAD approach, and a set of self-consistent thermodynamic parameters of the ternary system are obtained. Furthermore, the isothermal sections of this system at 1073 K, 1173 K, 1273 K, 1373 K, and 1473 K (800 °C, 900 °C, 1000 °C, 1100 °C, and 1200 °C) and the ternary invariant equilibria are calculated and compared with the corresponding experimental data, and all are in good agreement with most of the experimental results. Thus, the optimized thermodynamic parameters in this study may provide more accurate guidance to develop the new alloys involving it. 相似文献
7.
The high temperature regions of the Zr−Mo and Hf−Mo binary phase diagrams have been constructured from temperature-composition
data obtained by gravimetric and pyrometric methods. The liquidus curves were obtained directly from the measurements of saturation
solubilities of molybdenum (single crystal) in liquid Zr and Hf. The solubility results are supported by electron microprobe
analyses which identify the formation of thin (∼10 μm) layers of nearly stoichiometric compounds ZrMo 2 and HfMo 2 on the surface of the single crystal molybdenum below the respective peritectic temperatures 1918±5 and 2206±5°C. These thin
layers and the negligible diffusion zones of Zr and Hf in single crystal molybdenum do not significantly affect the measured
solubilities. The diffusion coefficient of Hf in Mo-single crystal at 2080°C is ∼5×10 −12 m 2 s −1. The melting, solidus, liquidus, eutectic and peritectic temperatures were directly measured by pyrometrically observing
the partial or complete destruction of “black-body” conditions inside an effusion cell with the appearance of a liquid phase
that forms a highly reflecting mirror. The melting points of Zr and Hf metals, 1860±3 and 2228±3°C, respectively, are in good
agreement with previously assessed values. The respective eutectic temperatures peratures and compositions 1551±2°C, 29.0±0.5
at. pct Mo and 1896±3°C, 40.5 at. pct Mo, are considerably more precise and only in fair agreement with previously measured
or estimated values. The liquidus composition at the peritectic temperature for the Zr−Mo binary is precisely fixed at 54.0±1.0
at. pct Mo and that for the Hf−Mo binary is 61 ±3 at. pct Mo. The thermodynamic activities of molybdenum in the liquid Zr−Mo
alloy indicate positive deviations from Raoult's Law.
temporarily attached to the Chemistry Division, Argonne National Laboratory, Argonne IL 60439
This work was performed at Argonne National Laboratory under the auspices of the U.S. Energy Research and Development Administration 相似文献
8.
The phase equilibria and liquidus temperatures in the binary SiO 2-ZnO system and in the ternary Al 2O 3-SiO 2-ZnO system at low Al 2O 3 concentrations have been experimentally determined using the equilibration and quenching technique followed by electron probe
X-ray microanalysis. In the SiO 2-ZnO system, two binary eutectics involving the congruently melting willemite (Zn 2SiO 4) were found at 1448±5 °C and 0.52±0.01 mole fraction ZnO and at 1502±5 °C and 0.71±0.01 mole fraction ZnO, respectively.
The two ternary eutectics involving willemite previously reported in the Al 2O 3-SiO 2-ZnO system were found to be at 1315±5 °C and 1425±25 °C, respectively. The compositions of the eutectics are 0.07, 0.52,
and 0.41 and 0.05, 0.28, and 0.67 mole fraction Al 2O 3, SiO 2, and ZnO, respectively. The results of the present investigation are significantly different from the results of previous
studies. 相似文献
9.
The phase equilibria information on the Pb-Fe-O system is of practical importance for the improvement of the existing thermodynamic database of lead-containing slag systems (Pb-Zn-Fe-Cu-Si-Ca-Al-Mg-O). Phase equilibria of the Pb-Fe-O system have been investigated: (a) in air at temperatures between 1053 K and 1373 K (780 °C and 1100 °C); (b) in equilibrium with metallic lead at temperatures between 1053 K and 1373 K (780 °C and 1100 °C); and (c) at intermediate oxidation conditions for the liquid slag in equilibrium with two solids (spinel + magnetoplumbite), at temperatures between 1093 K and 1373 K (820 °C and 1100 °C). The high-temperature equilibration/quenching/electron probe X-ray microanalysis technique has been used to accurately determine the compositions of the phases in equilibrium in the system. The Pb and Fe concentrations in the phases were determined directly; preliminary thermodynamic modeling with FactSage was used to estimate the ferrous-to-ferric ratios and to present the results in the ternary diagram. 相似文献
10.
To contribute to the curtailment of anthropogenic emission of sulfurous compounds, the susceptibility of manganous oxide for
sulfur under reducing atmospheres (C−O−S system) has been investigated over the temperature range 700 to 900°C (973 to 1173
K). A thermodynamic evaluation of the Mn−S−O system and the C−O−S system was undertaken and the basic, bivariant, and univariant
equilibria in the Mn−S−O system over the temperature range 700 to 1100°C are listed. The kinetic investigation employed thermogravimetry
and an in situ solid electrolyte oxygen probe to follow the sulfidization reaction of spherical MnO pellets under various experimental conditions.
The kinetic evaluation was complemented by X-ray diffraction and krypton B.E.T. surface area analyses. Apparent activation
energy of sulfidization of manganous oxide, under measured oxygen potentials in the C−O−S system, was determined to be 6.26
(±2.0) kcal/gmol (26.2 (±8.4) kJ/gmol), and a comparison with some alternative desulfurization agents in the H−O−S system
is included. 相似文献
11.
The thermodynamic properties of the ternary Bi-In-Zn system were determined with the electromotive force (EMF) method using
a liquid electrolyte. Four different cross sections with constant In/Bi ratios of 1:2, 1:1, 2:1, and 9:1 were applied to measure
the thermodynamic properties of the ternary system in the temperature range between the liquidus temperature of the alloys
and 973 K (700 °C). Zinc was added in steps of 5 at. pct from 5 to 90 pct. The partial free energies of Zn in liquid Bi-In-Zn
alloys were determined as a function of concentration and temperature. The integral Gibbs free energy and the integral enthalpy
of the ternary system at 873 K (600 °C) were calculated by Gibbs–Duhem integration. The ternary interaction parameters were
evaluated using the Redlich–Kister–Muggianu polynomials. 相似文献
12.
Prediction expressions of component activity coefficients of the molecular interaction volume model (MIVM) are suggested for making up for absence of Wagner interaction parameters in Si-based melts. Their effectiveness is verified in liquid Fe-Si-B system at 1823 K (1550 °C). In comparison with experimental data, all errors of ±22 to 56 pct and deviations of ±0.0132 to 0.0318 predicted by MIVM are smaller than those (±53 to 94 pct and ±0.0759 to 0.1010) by the unified interaction parameter formalism. This indicates that the former is better than the later in the system. Accordingly, some interested thermodynamic diagrams and parameters at 1687 K and 1823 K (1414 °C and 1550 °C) are predicted in liquid Si-Al-Fe system, for instance, $ \varepsilon_{\text{Al}}^{\text{Al}} = 2.318 $ , $ \varepsilon_{\text{Fe}}^{\text{Fe}} = 4.297 $ , and $ \varepsilon_{\text{Fe}}^{\text{Al}} = \varepsilon_{\text{Al}}^{\text{Fe}} = - 2.443 $ in the dilute solution at 1687 K (1414 °C). The method of MIVM is able to expand to Si-based multicomponent melt if its sub-binary activity data are available. The reliability of predicted results for the melt is closely dependent upon that of component activities or infinite dilute activity coefficients in its sub-binary systems. 相似文献
13.
The solid + liquid phase equilibria between α-Al and β-AlLi were determined using differential thermal analysis (DTA), metallography,
and chemical analysis. Boron nitride (BN), which was found to be inert to these alloys, was used as the container. These measurements
were carried out in order to resolve the discrepancies reported in the literature. The α-Al+β-AlLi eutectic temperature and
composition were determined to be 600 °C±1 °C and 25.8±0.5 at. pct Li. Using these data and data reported in the literature
concerning the phase equilibria and thermodynamic properties, thermodynamic models for all the phases were obtained by optimization.
The thermodynamic values obtained for the β-AlLi phase describe not only the phase equilibria, but also yield structural defect
data in agreement with measured values. The assessed enthalpies of formation, excess entropies of formation, and entropies
of melting for all the intermetallic phases obtained are compared with empirical correlations when experimental data are not
available. In addition to the stable diagram, a metastable diagram involving the δ′-Al 3Li is also calculated from the thermodynamic models. The calculated diagram is in good agreement with the experimental data. 相似文献
14.
Phase relations and thermodynamic properties of the Cr-O system were studied at temperatures from 1500 °C to 1825 °C. In addition
to Cr and Cr 2O 2, a third crystalline phase was found to be stable in the temperature range from 1650 °C to 1705 °C. The atomic ratio of oxygen
to chromium of this phase, which decomposes upon cooling to form Cr and Cr 2O 3, was determined as 1.33 + 0.02, in good agreement with the formula Cr 3O 4. Temperatures and phase assem blages for invariant equilibria of the Cr-O system were determined as follows: Cr 2O 3 + Cr + Cr 3O 4, 1650 °C ± 2 °C; Cr 3O 4 + Cr + liquid oxide, 1665 °C ± 2 °C; and Cr 3O 4 + Cr 2O 3 + liquid oxide, 1705 °C ± 3 °C. The composition of the liquid oxide phase at the eutectic temperature of 1665 °C was found
to be close to CrO. Relations between oxygen pressure and temperature for the univariant equilibria of the Cr-O system were
established by equilibrating Cr and/or Cr 2O 3 starting materials in H 2-CO 2 mixtures of known oxygen potentials at temper atures from 1500 ΔC to 1825 °C. From this information, the standard free-energy
changes (Δ GΔ) for various reactions were calculated as follows: 2Cr (s) + 3/2O 2 = Cr 2O 3 (s): Δ G ° = -1,092,442 + 237.94 T Joules, 1773 to 1923 K; 3Cr (s) + 2O 2 = Cr 2O 4 (s): Δ G ° =-1,355,198 + 264.64 T Joules, 1923 to 1938 K; and Cr (s) + l/2O 2 = CrO (1): Δ G ° =-334,218 + 63.81 T Joules, 1938 to 2023 K.
Formerly Graduate Research Assistant, The Pennsylvania State University
Formerly Professor 相似文献
15.
The system Cr?Pt has been investigated over the entire composition range by metallography, X-ray diffraction, and electron microprobe studies. There is only one intermediate phase and it has a Cr 3Si(A15)-type crystal structure. The fcc platinum terminal solid solution extends to 71 at. pct Cr at 1530°C and forms a congruent melting maximum at about 1790°C. Atomic ordering within this solid solution range begins at about 17 at. pct Cr and there is a continuous change from the Cu 3Au-type structure to the CuAu-type structure with increasing chromium content. Two eutectic reactions at 1530°C±10°C and at 1500°C ±10°C were indicated and there is evidence of a syntectic reaction at 1580°C±10°C. Platinum is soluble in the bcc chromium terminal solid solution up to about 10 at pct Pt at 1500°C but the solubility decreases rapidly at lower temperatures. 相似文献
16.
U-Mo alloys are being developed as low enrichment uranium fuels under the Reduced Enrichment for Research and Test Reactor (RERTR) Program. In order to understand the fundamental diffusion behavior of this system, solid-to-solid pure U vs Mo diffusion couples were assembled and annealed at 923 K, 973 K, 1073 K, 1173 K, and 1273 K (650 °C, 700 °C, 800 °C, 900 °C, and 1000 °C) for various times. The interdiffusion microstructures and concentration profiles were examined via scanning electron microscopy and electron probe microanalysis, respectively. As the Mo concentration increased from 2 to 26 at. pct, the interdiffusion coefficient decreased, while the activation energy increased. A Kirkendall marker plane was clearly identified in each diffusion couple and utilized to determine intrinsic diffusion coefficients. Uranium intrinsically diffused 5-10 times faster than Mo. Molar excess Gibbs free energy of U-Mo alloy was applied to calculate the thermodynamic factor using ideal, regular, and subregular solution models. Based on the intrinsic diffusion coefficients and thermodynamic factors, Manning’s formalism was used to calculate the tracer diffusion coefficients, atomic mobilities, and vacancy wind parameters of U and Mo at the marker composition. The tracer diffusion coefficients and atomic mobilities of U were about five times larger than those of Mo, and the vacancy wind effect increased the intrinsic flux of U by approximately 30 pct. 相似文献
17.
Phase relations of the Co-Si-Zn ternary system were experimentally investigated and thermodynamically calculated. First, the isothermal sections of the Co-Si-Zn system at 1123 K and 1323 K (850 °C and 1050 °C) were investigated experimentally using scanning electron microscopy coupled with wave-dispersive X-ray spectroscopy and X-ray diffraction. Then the thermodynamic calculation for this system was carried out using the CALPHAD technique. The calculated results and the experimental data are reasonably self-consistent. 相似文献
18.
The iron-manganese phase diagram relevant to phase transformation in the 0 to 5 pct Mn (580° to 911 °C) range has been redetermined.
Phase boundaries at 762° and 822 °C haye been measured. These data have been combined with other relevant experiments and
thermodynamic data to generate an optimal phase diagram. The corresponding To line, relevant to composition-invariant transformations, has also been evaluated. 相似文献
19.
A nonequilibrium version of measuring the electromotive force during a continuous decrease in the temperature at a rate of
5–7 °C/min is used to study the thermodynamic properties of solid solutions of magnesium in aluminum. The studies show that
the abrupt change in the potential of an alloy containing 20–30 mol % Mg at 370–380°C reliably correlates with the decomposition
of the solid solution formed at 450°C. 相似文献
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