Experimental study and thermodynamic modelling of the ternary system Fe–Ni–Si with re-modelling of the constituent binary systems

Abstract

The present paper reports on the thermodynamic modelling of the complete ternary Fe–Ni–Si system based on key experimental results and information reported in literature. The key experiments were performed to verify phases and phase fractions in selected ternary Fe–Ni–Si alloys using samples in the as-cast state as well as annealed samples. Chemical compositions of the samples were analysed by Energy Dispersive X-Ray Spectroscopy. Microstructure characterization was performed by Scanning Electron Microscopy and Electron Backscatter Diffraction techniques. Phase transformation temperatures were determined by Differential Scanning Calorimetry operated in the Differential Thermal Analysis mode. Calculations performed using proposed thermodynamic description reproduce experimental data well, including data from available literature. In particular, the Fe-rich corner of the Fe–Ni–Si system has been modelled in detail, with emphasis on the A2 and B2 phase fields. The developed ternary database was used to compute phase diagrams and thermodynamic properties of the constituent binary systems as well as selected isothermal and isopleth sections. Due comparison with commercially available and previously modelled thermodynamic descriptions is presented and discussed.