Wagner interaction coefficient between nitrogen and cobalt in liquid steel

Abstract

A simple theory of thermodynamic properties of liquid nitrogen solutions in Fe – Co alloys is proposed. This theory is completely analogous to the theory for liquid nitrogen solutions in alloys of the Fe – Cr system proposed previously by the authors in 2019. The theory is based on lattice model of the Fe – Co solutions. The model assumes FCC lattice. In the sites of this lattice are the atoms of Fe and Co. Nitrogen atoms are located in octahedral interstices. The nitrogen atom interacts only with the metal atoms located in the lattice sites neighboring to it. This interaction is pairwise. It is supposed that the liquid solutions of Fe – Co system are perfect. The initial values for the calculation are the Sieverts law constants for nitrogen solubility in liquid iron and in liquid cobalt. Result of the calculation is value of Wagner interaction coefficient in liquid iron-based alloys at 1873 K \(\varepsilon _{\rm{N}}^{{\rm{Co}}}\) = 1.8. This value is in good agreement with the experimental data obtained by Schenck, Frohberg and Graf, 1958; Maekawa and Nakagawa, 1960.