Thermodynamics of Oxygen Solution in Fe–Ni Melts Containing Boron

Fe–Ni alloys are widely used in engineering today. They are sometimes alloyed with boron. Oxygen is a harmful impurity in Fe–Ni alloys. It may be present in dissolved form or as nonmetallic inclusions. The presence of oxygen in Fe–Ni alloys impairs their performance. Research on the thermodynamics of oxygen solutions in Fe–Ni melts containing boron is of considerable interest in order to improve alloy production. The present work offers a thermodynamic analysis of solutions of oxygen in Fe–Ni melts containing boron. The equilibrium constant of the reaction between boron and oxygen dissolved in the melt in such systems is determined. The activity coefficients at infinite dilution and the interaction parameters in melts of different composition are also calculated. When boron reacts with oxygen in Fe–Ni melts, the oxide phase contains not only B₂O₃ but also FeO and NiO. The mole fractions of B₂O₃, FeO, and NiO in the oxide phase are calculated for different boron concentrations in Fe–Ni melts at 1873 K. For iron melts with low boron content, the mole fraction of boron oxide is ~0.1. With increase in the nickel and boron content in the melts, the boron-oxide content in the oxide phase increases. Its mole fraction is close to one for pure nickel. The solubility of oxygen in Fe–Ni melts is calculated as a function of the nickel and boron content. The deoxidizing ability of the boron improve significantly with increase in nickel content in the melt. The curves of oxygen solubility in Fe?Ni melts containing boron pass through a minimum, which is shifted to higher boron content with increase in nickel content in the melt. The boron content at the minima on the curves of oxygen solubility are determined, as well as the corresponding minimum oxygen concentrations.     

Oxygen Solubility in Fe–Co Melts Containing Carbon

In thermodynamic analysis of solutions of oxygen in Fe–Co melts containing carbon, the equilibrium constants of reactions between carbon and oxygen are determined, as well as the activity coefficients at infinite dilution and the interaction parameters in melts of different composition at 1873 K. The dependence of oxygen solubility in such melts on the cobalt and carbon content is calculated. In iron–cobalt melts, carbon has high oxygen affinity. The deoxidizing ability of carbon increase significantly with increase in cobalt content in the melt. In pure cobalt, it is more than an order of magnitude greater than in pure iron. Deoxidation by carbon produces gaseous oxides: carbon monoxide (CO) and dioxide (CO₂). The reaction of carbon and oxygen dissolved in the melt and hence the deoxidizing ability of carbon depend on the total gas pressure above the melt. Decrease in gas pressure significantly improves the reducing properties of carbon. The minimum oxygen concentration for alloys of the same composition is reduced by practically an order of magnitude with tenfold decrease in the total gas pressure. The gas composition above Fe–Co melts and the equilibrium carbon and oxygen concentrations in the melt are calculated with total gas pressures of 1.0, 0.1, and 0.01 atm. The optimal oxygen concentration (1–10 ppm) in Fe–Co melts is reached at carbon concentrations between 0.01 and 1% depending on the total gas pressure (0.01–1 atm). The solubility of oxygen in iron–cobalt melts containing carbon passes through a minimum, which is shifted to lower carbon content with increase in the melt’s cobalt content. Further additions of carbon increase the oxygen concentrations in the melt. With increase in cobalt content, this increase will be sharper.     

Thermodynamics of Fe-P-C in Mn-Based Solutions

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Temperature–Composition Dependence of Thermodynamic Mixing Functions of Co–Cr–Cu–Fe–Ni Melts

Powder Metallurgy and Metal Ceramics - In the framework of the CALPHAD method, a thermodynamic database was developed for calculating the thermodynamic properties of liquid alloys in the...     

Thermodynamics of the oxygen solutions in chromium-containing Ni–Co melts

A thermodynamic analysis of the oxygen solutions in chromium-containing Ni–Co melts at 1873 K has been performed. The equilibrium constants of reactions between chromium and oxygen, the activity coefficients at infinite dilution, and the interaction parameters for melts differing in composition have been determined. The dependences of the oxygen solubility on the cobalt and chromium contents in the melts are calculated. The deoxidizing capacity of chromium slightly decreases as the cobalt content in the melt increases. The composition dependences of the oxygen solubility in the chromium-containing Ni–Co melts have a minimum, which shifts to a high boron content as the cobalt content in the melts increases. The further increase in the chromium addition leads to an increase in the oxygen content in the melt.     

Synthesis of an Aluminum–Erbium Master Alloy from Chloride–Fluoride Melts

Available foreign power-intensive technologies and the absence of domestic production technologies for aluminum–erbium master alloys intended for improving the physicomechanical properties of aluminum alloys make the development of aluminothermic reduction technology of chloride–fluoride melts actual for manufacturing erbium compounds. Thermodynamic analysis of reduction processes is performed for various erbium compounds. Taking into account the physical and chemical properties of erbium compounds, a starting compound, namely, erbium fluoride is found to be preferable. The aluminothermic reduction of the compound from its mixture with sodium fluoride and potassium chloride to form the Al₃Er intermetallic compound is characterized by a high thermodynamic probability. Since data on thermodynamic parameters for erbium complex compound are scanty, they are determined by an indirect method. Experimental data on the aluminothermic preparation of an Al–Er master alloy at temperatures of 750–900°C using melts differing in the ErF₃/NaF ratio and the KCl content are reported; the structure and the phase composition of the prepared master alloy are studied. The phase composition of the flux used for the preparation of the Al–Er master alloy is determined.     

Dissolution of Nitrogen in Liquid Ni–Cr Superalloys

Abstract

The dissolution of nitrogen in liquid Ni–Cr alloys at 1773 and 1873 K over a wide range of composition has been determined by the constant pressure Sieverts' method. The nitrogen dissolution in these alloys is markedly increased with chromium content and decreased with temperature. The chromium effect on the nitrogen dissolution is described in terms of the Wagner's first and second order interaction parameters for both temperatures. © 1998 Canadian Institute of Mining and Metallurgy. Published by Elsevier Science Ltd. All rights reserved.

Résumé

En utilisant la méthode experimentale de Sieverts à pression constante, la dissolution de l'azote dans des alliages liquides Ni–Cr a été determinée pour un large domaine de composition aux températures de 1773 et 1873 K. La dissolution de l'azote augmente fortement avec la teneur en chrome et diminue avec la température. L'effet du chrome sur la dissolution a été decrit en termes de parametres d'interaction suivant le formalisme de Wagner. Ainsi, les coefficients du premier et du deuxième ordre entre l'azote et le chrome dans le nique1liquide ont été determiné pour le deux températures. © 1998 Canadian Institute of Mining and Metallurgy. Published by Elsevier Science Ltd. All rights reserved.     

Thermodynamics of the oxygen solutions in the aluminum-containing Ni–Co melts

A thermodynamic analysis of the oxygen solutions in the aluminum-containing Ni–Co melts has been performed. The equilibrium constants of reactions of aluminum deoxidation of nickel-cobalt melts, the activity coefficients at infinite dilution, and the interaction parameters for the melts differing in composition at 1873 K have been determined for the first time. The dependences of the oxygen solubility on the cobalt and aluminum contents in the melts are calculated. The deoxidizing capacity of aluminum slightly varies as the cobalt content in a melt increases to 20%; at higher cobalt contents in the melts, it increases substantially. The aluminum contents at the minima in the oxygen solubility curves and the oxygen contents corresponding to the aluminum contents have been determined.     

Larson–Miller Failure Modeling of Aluminum in Fire

This article presents a modeling approach based on the Larson–Miller parameter (LMP) for creep rupture to predict failure of aluminum in fire. The modified Larson–Miller model can predict time-dependent tensile rupture or compressive buckling of aluminum plate under combined loading and one-sided heating by fire. The model applies the LMP to determine the failure time and failure temperature of aluminum exposed to fire. Fire structural tests were performed on an aluminum alloy (5083-H116) subjected to different load levels and heat flux conditions (with maximum temperatures of 473 to 688 K (200 to 415 °C)) to validate the Larson–Miller modeling approach. The tests reveal that the Larson–Miller model can accurately predict tensile and compressive failure of aluminum plates (with and without surface insulation) in fire in terms of critical temperature and time.     

Mixing Enthalpies of Sr–Sb Melts

Powder Metallurgy and Metal Ceramics - The mixing enthalpies of Sr–Sb melts were measured by isoperibolic calorimetry at 1230 K over the entire composition range referred to the liquid...     

Strain Partitioning in a Multi-phase V–Ti–Ni Alloy Containing Superelastic Nano-precipitates

Metallurgical and Materials Transactions A - In V45Ti30Ni25 (at. pct), superelastic TiNi and a stable V-rich bcc phase (β) coexist in multiple-phase mixtures with each acting as matrix and...     

Effect of N,Mo, and Si on Local Corrosion Resistance of Unstabilized Cr–Ni and Cr–Mn–Ni Austenitic Steels

Metallurgist - Features of the effect of both individual and combined alloying with nitrogen, molybdenum and silicon of unstabilized cold-worked and heat-treated austenitic Cr–Ni and...