Thermodynamic Modeling of Ni-C, Co-C, and Ni-Co-C Liquid Alloys Using the Modified Quasichemical Model

Abstract

The strong interactions between the metallic elements and C in liquid Ni, Co, and Ni-Co alloys have been thermodynamically analyzed. The liquid solution properties in Ni-C and Co-C systems showed significant asymmetry because of the short-range ordering of C exhibited in the liquid solution. Using the modified quasichemical model in the pair approximation, the Ni-C and Co-C systems were re-optimized to simultaneously reproduce the present experimental results of the C solubility and the reported thermodynamic properties in the liquid phases. In particular, the partial enthalpy data of C in liquid Ni and Co alloys were considered for the first time on the thermodynamic assessment of Ni-C and Co-C liquid solutions. The asymmetric interpolation method was introduced to evaluate the Gibbs free energy in the ternary system based on the binary Gibbs free energies in the Ni-C and Co-C systems. The C solubility data measured in the ternary Ni-Co-C alloy melt over a wide Co concentration range were successfully reproduced without any additional ternary model parameter by considering the short-range ordering of C.

Thermodynamic Assessment of Liquid Fe-Ni-C Alloy Using Modified Quasichemical Model

“…5,6,[11][12][13][14] The values of the coordination numbers selected in the Fe-Ni-C system are listed in Table I. After optimizing the binary Fe-Ni system, the Gibbs free energy of the ternary Fe-Ni-C liquid phase is estimated by merging it with the new MQM parameters in the Fe-C 19 and Ni-C systems. 9 In the ternary system, the Toop-like interpolation method was applied to consider the non-metallic element, with C as the asymmetric component. The Gibbs free energy of all the solid phases have been modeled using compound energy formalism (CEF) in the Fe-Ni system by Xing et al, 15 the Fe-C system by Gustafson, 22 the Ni-C system by Lee, 23 and the Fe-Ni-C system by Gabriel et al 24 with high accuracy.…”

“…As mentioned earlier, the present study only adopted the Gibbs free energy description of the solid solution phases from the previous assessments 15,[22][23][24] and reassessed the liquid solution by the MQM. For the optimization of the liquid solution in this ternary system, the binary MQM parameters of the Fe-C system determined by Shubhank and Kang, 19 and that of the Ni-C system by the authors' recent study, 9 were directly used along with the present Fe-Ni binary parameters. The Toop-like interpolation method with C as the asymmetric component was used because the Fe-C and Ni-C liquid solutions exhibit considerable negative deviation by the strong attraction force between the metal (Fe and Ni) and the gaseous impurity (C).…”

“…18 Thus, the MQM was adopted for the description of asymmetric liquid solution properties in this study. The reassessed Gibbs free energy of the Fe-Ni liquid solution was merged with the recent MQM results 9,19 in the binary Fe-C and Ni-C systems. The C solubility measured in the present study at 1500°C and 1600°C, and the reported partial enthalpy of mixing of C in the ternary Fe-Ni-C system, were simultaneously reproduced for the first time with only one constant ternary MQM parameter.…”

“…Based on the pyrometallurgical extraction process, the Ni-containing alloy scraps and discarded batteries have been utilized as an additional Ni source in the Ni slag-cleaning process. 9,10 The dried Ni-containing concentrates are fed into a Ni flash smelting furnace, and then the smelting slag with shredded scrap can be reduced by cokes and coal in an electric slag-cleaning furnace. Under the reducing condition, the Ni is recovered with other elements, such as Fe, Co, Cu, C, and S. 10 In order to precisely control the distribution ratio of alloying elements and impurities between the FeO x -SiO 2 slag and the liquid alloy, the thermodynamic properties of the liquid Fe-Ni-C alloy have to be understood as one of the core alloy systems.…”

“…However, although the conventional random mixing model based on the ideal configurational entropy has not been able to properly describe the asymmetry of a liquid solution, it has been considered as an ideal solution 15,16 because of its very small enthalpy of a mixing value less than À 5 kJ/mol. On the other hand, in the authors' recent studies, 9,17 it has been shown that the asymmetry of liquid solution can be precisely described by taking into account the shortrange ordering (SRO) using the modified quasichemical model (MQM) in pair approximation. 18 Thus, the MQM was adopted for the description of asymmetric liquid solution properties in this study.…”