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A. Jacob, E. Povoden-Karadeniz, E. Kozeschnik:
"Thermodynamic modeling of Fe-Cr-Ni and its implication for the calculation of multicomponent system";
Poster: 46. Calphad International Conference, St. Malo; 2017-06-11 - 2017-06-16.

Thermodynamic open-licensed Fe-base database (mc_fe [1]) is predictinga too low
equilibrium phase fraction of ferrite in duplex stainless steel,e.g. steel grade 2205
compared to experiments[2]. Since the Fe-Cr-Ni system is highly governing phase
relations in stainless steels, a revision of the Fe-Cr system and associated extension to
Fe-Cr-Ni is made. The presented Fe-Crre-assessmentshows an improvement of mixing
behaviour and phase boundaries of all phases in the system. In the framework of
application of duplex steels, the austenitic-ferritic transformation is reproducedcorrectly.
The present thermodynamic modelling of the Fe-Cr-Ni system is based on available
experimental data and ab initio data of the enthalpy of mixing of bcc and fcc [3]. Reassessment
ofalloy phase stabilities in Fe-Cr-Ni does not solve the stability problem of
ferrite in the multi-component extension. Additional stabilising / destabilising interactions in
Mn-, Mo-, and Si-containing subsystems were deciphered, which required re-adjustments.
As a result, the revised mc_fe delivers correct stabilities of the high-temperature deltaferrite
phase of various stainless steels, and composition-dependent austenite / ferrite
fractions in duplex and super duplex steel grades.

Thermodynamic modelling