Thermodynamic assessment of the Co-Mo system

Abstract

Experimental thermochemical and phase diagram data for the Co-Mo system were assessed. A consistent thermodynamic description, using a Redlich-Kister model for the solution phases and sublattice and line-compound models for the intermetallics, was obtained, and it agreed well with the critically evaluated experimental data. Several variations of the sublattice model for the and phases were compared with the traditional models used for these phases in other systems. Measured data indicate an abrupt decrease of the terminal Mo solubility in the fcc (Co) phase with decreasing temperature. This behavior was reproduced well by inclusion of the magnetic contribution to the Gibbs energy of the fcc phase. Addition of the magnetic term also led to the prediction of a fcc (Co) miscibility gap, and a high-temperature stability region of the paramagnetic cph (Co) phase.