Evaluation Model for Viscosity of Fe–Ni–Cr Alloys Using Gibbs Free Energy of Mixing and Geometric Methods

Abstract

Purpose of this investigation is to predict the viscosity of liquid Fe–Ni, Fe–Cr, Ni–Cr and Fe–Ni–Cr alloys at 1873 K. The activation energies of binary alloys were calculated by the mixing Gibbs energies, and the proposed activation energies of pure Fe, Ni and Cr are 72657, 66721 and 74517 J/mol. Geometric models (Kohler, Toop and Chou models) were used to predict the excess activation energies of ternary alloys. The iso-viscosity curves of Fe–Ni–Cr alloy are calculated by three geometric models (Kohler, Toop and Chou models) from sub-binary systems. Ni can decrease the viscosity in the whole range, while Fe has a two-sided effect. Cr can result in the decrease of the viscosity at the Ni-rich corner and Fe-rich corner. The effects of Ni and Cr on viscosities of Fe–Ni–Cr alloys are consistent with the measured results. But when Cr exceeds 20 in mole%, the addition of Cr will cause the rise of the viscosity. The evaluated values by the Chou model are the biggest and have a much more reasonable low viscosity region. Comparison between the evaluated results and experimental values of the Fe–Ni–Cr ternary alloys were investigated. The average errors between the measured results and predicted values by Kohler, Toop and Chou model are below 5%, indicating that evaluated viscosities of Fe–Ni–Cr ternary alloys by three models (Kohler, Toop and Chou) can reproduce the measured results quite well.