New Contribution to the Thermodynamics of Fe-Cr Alloys as Base for Ferritic Steels

High chromium ferritic-martensitic steels are commonly used for industrial applications requiring high strength at elevated temperature. Such steels typically contain 9-14 at.% Cr and a few percents of minor alloying elements. In recent studies it has been shown that the Cr solubility limit of the standard Fe-Cr phase diagram in that composition range is significantly underestimated. For the purpose of more reliable engineering and out of physical considerations, we reparameterize the Gibbs free energy so that the correct Cr solubility at low temperature (< 700 K) is reproduced, while leaving the rest of the phase diagram changed only slightly. The mixing enthalpy and heat capacity resulting from the new parameterization are also compared with experiments and found to be in good agreement.