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.
Highlights
NICKEL and cobalt are critical raw materials for high-tech products and emerging industries
To verify the asymmetric property of the binary and ternary liquid solutions, the C solubility was measured over the wide range of melt composition from pure Ni to Ni-57.5 mass pct Co alloy by the equilibration and quenching method
The liquid Ni alloy is in equilibrium with graphite at high temperature, and the face centered cubic (FCC) solid solution has limited carbon solubility in the Ni-rich side at low temperature
Summary
NICKEL and cobalt are critical raw materials for high-tech products and emerging industries.
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