Thermodynamic Analysis of Steels by Incorporating First-Principles Calculations into the CALPHAD Approach

Abstract

A thermodynamic analysis of the Fe−M−P (M = Nb, Ti) ternary system has been performed by combining first-principles calculations with the CALPHAD approach. Because of the lack of experimental information available, thermodynamic properties of orthorhombic anti-PbCl2-type FeMP were evaluated using the Full Potential Linearized Augmented Plane Wave method, and the estimated values were introduced into a CALPHAD-type thermodynamic analysis. Applying this procedure, the phase diagrams of the Fe−M−P ternary phase diagrams whose contents are uncertain so far were calculated with a high degree of probability. Phase diagrams for high-purity ferritic stainless steels obtained following the same procedure are also presented.