Thermodynamic modeling and experimental validation of the Fe-Al-Ni-Cr-Mo alloy system

NiAl-type precipitate-strengthened ferritic steels have been known as potential materials for the steam turbine applications. In this study, thermodynamic descriptions of the B2-NiAl type nano-scaled precipitates and body-centered-cubic (BCC) Fe matrix phase for four alloys based on the Fe-Al-Ni-Cr-Mo system were developed as a function of the alloy composition at the aging temperature. The calculated phase structure, composition, and volume fraction were validated by the experimental investigations using synchrotron X-ray diffraction and atom probe tomography. With the ability to accurately predict the key microstructural features related to the mechanical properties in a given alloy system, the established thermodynamic model in the current study may significantly accelerate the alloy design process of the NiAl-strengthened ferritic steels.

► Thermodynamic descriptions of four Fe-AI-Ni-Cr-Mo alloys were developed.
► Experimentally studied by synchrotron X-ray diffraction and atom probe tomography.
► Alloy with a low AI/Ni ratio contains FCC phase.
► The calculated results are in good agreements with those measured experimentally.
► The established model accelerates the design of NiAI-strengthened ferritic steels.