Thermodynamic modeling of multicomponent MX phases (M= Nb,Ti,V; X=C,N) in steel

Abstract

The microstructure and properties of micro-alloyed steels are controlled by small concentrations of the elements Nb, Ti, V. In combination to C and N they form so-called FCC-structured carbonitride phase, producing a miscibility gap with FCC-Fe. In the present work, we review and assessed the available thermodynamic modeling of the MX phases in the framework of applied Calphad to computational thermodynamics and kinetics. Within this work, it was found that binary alloy system such as Fe-Nb, Nb-C and Nb-N as well as ternary M-(C,N) (M standing for metal) needed to be re-optimized in order to get accurate descriptions for multicomponent extensions with relevance for simulations in micro-alloyed steels. The reassessed description is edited in an open-source multi-component thermodynamic database (mc_fe_MX) and used to calculate physical interfacial energy which can be used for predictive precipitation simulation.