Phase equilibria, phase formation and solidification microstructure in Sm-Fe-Ti alloys via experimental determination and thermodynamic calculation

Phase equilibria in the Sm-Fe-Ti system at 873 and 1073 K as well as solidification microstructure of several Sm-Fe-Ti as-cast alloys were investigated by using the equilibrated alloy method with scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The experimental results reveal that the ternary intermetallic compounds τ 3 -Sm(Fe, Ti) 11 was observed at 873 K and 1073 K, while τ 1 -Sm(Fe, Ti) 12 were found at 1073 K. Meanwhile, two ternary intermetallic compounds τ 2 -Sm 3 (Fe, Ti) 29 and τ 4 -Sm 5 (Fe, Ti) 17 were not detected at 873 K and 1073 K, which were reported in the literature. However, τ 2 -Sm 3 (Fe, Ti) 29 was found in the solidification microstructure of Sm-Fe-Ti as-cast alloys. The solid solubility of the third element in the Fe-Ti and Sm-Fe binary intermetallic compounds was determined at 873 K and 1073 K, respectively, while the composition ranges of τ 1 -Sm(Fe, Ti) 12 and τ 3 -Sm(Fe, Ti) 11 were measured. Furthermore, thermodynamic calculation of the Sm-Fe-Ti system was conducted using the CALPHAD method, integrating the reported assessments of the Sm-Fe, Sm-Ti, and Fe-Ti binary systems. The calculated isothermal sections at different temperatures are consistent with the determined experimental results of the present work and the reported literature. The solidification microstructure of Sm-Fe-Ti as-cast alloys was analyzed through thermodynamic calculation using the Scheil-Gulliver non-equilibrium model. The simulation results demonstrate the good agreement with the present experimental findings, suggesting that self-consistent and reasonable thermodynamic parameters for the Sm-Fe-Ti ternary system were successfully obtained. This work could provide the basis of thermodynamic database of Sm-Fe-Ti-based magnetic alloys.