John F. Elliott

Thermodynamics of the Fcc Fe−Ni−C and Ni−C alloys

The activity of carbon in the fcc solid solution of the Fe−Ni−C system has been measured at 800°, 1000°, and 1200°C by comparison with observed values in the Fe−C binary by equilibration with methane-hydrogen mixtures. Defining the lattice ratiozC≡nC/(nFe+nNi−nC), the activity coefficient ΨC≡aC/zC has been determined as a function of temperature and composition. At infinite dilution log ΨC goes through a maximum at about 70 pct Ni in agreement with Smith. The partial molar free energy of carbon in the dilute solution referred to graphite is not a linear function of the base alloy composition, but has a large deviation with maximum at about 60 pct Ni. Similar maxima occur in both ΔHC° and ΔSC°. Linear equations are derived for the activity coefficient of carbon in three composition ranges of Fe−Ni−C alloys; a simplified equation applicable to nickel steels is included. The solubility of graphite in nickel has been determined. The marked deviation from linearity is ascribed to the existence of iron atoms in two electronic states, γ1 and γ2 which differ in energy and are antiferromagnetic and ferromagnetic, respectively.

Activity of carbon and solubility of carbides in the FCC Fe-Mo-C, Fe-Cr-C, and Fe-V-C alloys

The activity of carbon in austenitic Fe-Mo-C, Fe-Cr-C, and Fe-V-C alloys has been studied by equilibration with controlled CH4-H2 atmospheres at temperatures in the range 850° to 1200°C. The observations included a number of compositions in the two-phase fields, γ + carbide. Equations are given for the activity coefficient of carbon as a function of temperature and composition in the austenite field and from these the other thermodynamic properties of the solution may be computed as desired. The phase boundaries γ/γ + carbide were determined by breaks in the isoactivity lines. This was supplemented in the case of Fe-Mo-C alloys by metallographic linear analysis of equilibrated samples. The results confirm certain published phase diagrams and discredit others.

Thermodynamics of the carbides in the system Fe-Cr-C

Phase relations in the Fe-Cr-C system in the temperature range 900 to 1150°C have been studied using metallographic and X-ray methods and the electron microprobe. An isothermal section of the phase diagram at 1000°C is shown. Lattice dimensions of the three carbides were determined for several values of the ratio Cr:(Fe +Cr). The solubilities of the carbides at each temperature were determined by metallographic study of quenched specimens. The distribution of Cr between austenite (γ) and the several carbides was determined by use of the electron microprobe. Data of Wada et al on the activity of carbon were used to calculate activities at the y-phase boundary and the free energy of the several carbides as a function of their chromium content. The data are treated thermodynamically on the basis of assumed random mixing of Cr and Fe atoms in each carbide. While this randomness was not definitely proved, the assumption was shown to be reasonable and the results useful. Extrapolation to 0 and 100 pct Cr gives values for the standard free energy of Cr7C3 and the hypothetical carbides Cr36C, and Fe7C3.

Thermodynamics of austenitic Fe-C alloys

New data on the activity of carbon in austenite have been obtained by CO2/CO equilibration of Fe-C alloys in the temperature range 900° to 1400°C. Equations for the thermodynamic properties of carbon and iron in austenite are obtained from the data combined with selected data from the literature. A slightly modified phase diagram is presented. The stability of cementite is also determined from data published earlier and the results of the present study. Parameters of the various models of the behavior of carbon in austenite taken from the literature are also calculated from the data.

Activities in the liquid Fe-Cr-C(sat), Fe-P-C(sat), and Fe-Cr-P systems at 1600°c

The problem of relating interaction coefficients applicable to conditions of constant chemical potential of one of the solute elements in a solution to the usual interaction coefficients at infinite dilution is treated. The formal relationships are applied to data on the Fe-Cr-C(sat) system at 1600°C and to results presented earlier on the Fe-P-C(sat) system at 1600°C. An alternative treatment for obtaining interaction coefficients for relatively concentrated solutions by a statistical technique is also presented and applied to data on the Fe-Cr-P system. When applicable, the former is considered to be more reliable.

Thermodynamics of the fcc Fe-Mn-C and Fe-Si-C alloys

The activity of carbon in austenitic Fe-Mn-C and Fe-Si-C alloys has been studied by equilibration with controlled CH4-H2 atmospheres at temperatures in the range 848° to 1147°C and for composition up to about 60 pct Mn and 7 pct Si. The activity coefficient of carbon is diminished by manganese and is increased by silicon. Activity coefficients and derived values of the partial molar free energy, enthalpy, and entropy of solution of graphite in the alloy are expressed in mathematical form. The heat of solution of graphite, which is positive in the Fe-C binary alloys, decreases with increasing manganese and increases with increasing silicon concentrations. The partial molar entropy is independent of manganese, but is decreased by silicon.

Coal combustion aerosols and sulfur dioxide: an interdisciplinary analysis.

Coal combustion produces both SO/sub 2/ and submicrometer metal oxides that can react to form irritant aerosols with potential effects on health. Experimental coal combustion studies defined conditions leading to the formation of submicrometer fume and characterized its composition. Effects of temperature and humidity during mixing on the reaction products of SO/sub 2/ and ZnO, which occur in the fume, were determined. These atmospheres produced altered pulmonary function and morphology in guinea pigs. Functional and morphologic changes were correlated. 42 references, 8 figures, 2 tables.

Thermodynamic properties of Na2O-SiO2-CaO melts at 1000 to 1100 °C

AbstractThe thermodynamic properties of Na2O-SiO2 and Na2O-SiO2-CaO melts have been measured using the galvanic cell

The clustering of alumina inclusions

\begin{array}{*{20}c} {O_2 (g), (Na_2 O), Pt} \\ {Na_2 O - WO_3 liq} \\ \end{array} \left| \begin{gathered} Na^ + \hfill \\ \beta - alumina \hfill \\ \end{gathered} \right| \begin{array}{*{20}c} {Pt,(Na_2 O), O_2 (g)} \\ {Na_2 O - SiO_2 - CaO liq} \\ \end{array}