Thermodynamic modeling of Fe–Ce–Bi system and explanation of interfacial reaction in Fe-45 at%–Ce/Bi couple

Knowledge of phase equilibria of Fe–Ce–Bi is important for understanding respective effects of rare earth, low melting point elements, e.g. Bi, and the interaction between rare earth and low melting point elements in cast iron. By using a CALPHAD approach, the Ce–Bi binary system was assessed on the basis of reported thermodynamic and phase-equilibrium data and then extrapolated to Fe–Ce–Bi ternary system combined with the Fe–Ce and Fe–Bi binary systems assessed in literatures. Meanwhile, the interfacial reaction between Bi and Fe-45 at%–Ce alloy at 773 K was investigated to verify the reliability of thermodynamic calculations. It was clearly observed that a reaction layer containing CeBi2, Fe and liquid (Bi) exists in the couple, indicating the reaction path liquid (Bi)/CeBi2+Fe/Fe-45 at%–Ce in this couple. The reaction path was further explained using a recently reported model by adopting the thermodynamics assessed herein.