Wagner interaction coefficient between nitrogen and chromium in liquid nickel-based alloys

Abstract

The authors propose a simple theory of thermodynamic properties of nitrogen solutions in liquid Ni–Cr alloys. This theory is completely analogous to the theory for liquid nitrogen solutions in alloys of the Fe–Cr and Fe –Mn systems proposed previously by the authors in 2019 and 2020. The theory is based on lattice model of the Ni–Cr solutions. The model assumes FCC lattice. In the sites of this lattice are the atoms of Ni and Cr. 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 assumed that the energy of this interaction depends neither on the composition nor on the temperature. It is supposed that the solutions in the Ni–Cr system are perfect. Within the framework of the proposed theory, a relation is obtained that expresses the Wagner interaction coefficient between nitrogen and chromium in liquid nickel-based alloys. The right-hand part of the appropriate formula is a function of ratio of the Sieverts law constants for solubility of nitrogen in liquid chromium and nickel. The values of these constants for the temperature of 1873 K are assumed to be K′(Cr) = 15,2; K′(Ni) = 0,0015 wt. %. An estimate is obtained for the Wagner interaction coefficient in nickel-based alloys = 21,4. This corresponds to the value of the Langenberg interaction coefficient = –0,105, wich is very close to the experimental estimates = –0,108 for the temperature of 1873 K (Surovoi et al., 1971) and = –0,11 for the temperature of 1823 K (Stomakhin at al., 1965).