Thermodynamics and surface properties of Fe-V and Fe-Ti liquid alloys

A simple statistical mechanical model, based on a quasi-lattice approximation in which one assumes the formation of complexes, has been used to study bulk properties, such as free energy of mixing, the thermodynamic activity and enthalpy of mixing, in liquid Fe - V and Fe - Ti alloys. The energetics and its effect on the alloying behavior of the liquid alloys has been investigated with the aim of correlating bulk phenomena with surface effects. The analysis shows that, assuming the formation of intermetallic complexes of the form Fe2V and FeTi in the liquid. alloys, one can explain the energetics of the bulk alloys. Our results for the bulk calculations indicate that Fe-V and Fe-Ti both exhibit a significant tendency for compound formation. From a perusal of the diffusion coefficient D, we observe the same trend towards compound formation, as demonstrated by the chemical short-range order parameter (CSRO) close to the assumed stoichiometric composition. Furthermore, using the model calculations in the bulk, we study some surface properties. Our calculations indicate that Fe segregates to the surface at all bulk compositions in Fe - V and Fe - Ti liquid, though the segregation effect is more pronounced in the former alloy. The reason for this is that Fe-Ti is a more ordered system than Fe - V and, thus, the driving force for surface segregation in these alloys is their energetics.