Thermodynamics of Si and Ti in Solid Fe at 1273 K

Abstract

Equilibrium experiments were carried out with solid Fe and liquid Ag to investigate the interactions between Si and Ti in solid Fe. The thermodynamic properties of Si in γ-Fe and α-Fe phases were studied by determining the distribution equilibrium of Si in the Fe and the Ag phases. Using the activity coefficient and the self-interaction parameter of Si in solid Fe, the interaction parameter of Si and Ti in both the solid Fe phases— γ-Fe and α-Fe—was determined as follows:
ε_Si^Ti = 460 ± 78 in γ-Fe, ε_Si^Ti = 350 ± 7 in α-Fe
The analysis results for Si and Ti in the solid Fe phase showed reasonable agreement with previous research in α-Fe region. Furthermore, the influence of the interaction between Si and Ti in the solid Fe phases on the formation of secondary inclusions such as Ti-based inclusions was discussed. It was concluded that, during solidification, the interactions among solutes such as Si and Ti should be properly considered because the formation of not only the secondary inclusions but also ferrites may depend on the thermodynamic properties of the solutes.