EVALUATION OF THERMODYNAMICS AND THERMOPHYSICAL PROPERTIES OF BINARY LIQUID Fe-Me (Me = Pd, Ni, Co, Mn, V) SYSTEMS

Abstract

A theoretical investigation of the energetics of mixing and the thermophysical property via viscosity of liquid Fe-Pd, Fe-Mn, Fe-Ni, Fe-Co and Fe-V alloys were analyzed within the frame of Flory’s model based on the Quasi-Lattice Theory of liquid mixtures (QLT). The thermodynamic and thermophysical properties of the selected Fe-based systems were determined at different temperatures. The thermodynamic properties such as free energy of mixing, heat of mixing and entropy of mixing were used to study the nature, stability and bonding of the selected Fe-based system while viscosity has one of the most important thermophysical properties also study the fluid flow process of the selected Fe based systems. Comparative analysis of experimental and calculated viscosity of the selected Fe-based binary alloys were determined by seven (7) different theoretical models which incorporate different physical parameters such as enthalpy of mixing, densities, molar volumes of alloys and atomic radius of metals. The models used are Moelwyn- Hughes (MH), Koslov-Romannov-Petrov (KRP), Iida and Morita model (IUM), Kucharski model (KUK), Gasior model (G), Sato model (SATO) and Kaptay model (K). Maximum deviations between experimental and theoretical values were evaluated in relative percentage to ascertain the average error. The average deviation, the absolute deviation and the ranking of different models were taken in order to identify the most suitable model for predicting viscosity. The theoretical results obtained were compared with available experimental data for both thermodynamic and thermophysical properties, since the negative interaction of molecules increases viscosity, the heat of mixing were used as basic parameter in estimating viscosity. The heat of mixing of all the selected systems confirmed negative deviations to the Raoult’s law with a weakly interacting system showing the interaction of unlike pairs of atoms. Hence, the viscosity models predicted Fe-Co and Fe-Ni alloys to be more segregating due to the negative deviations from the viscosity experimental data while the models predicted Fe-Pd, Fe-Mn and Fe- V systems deviate positively from the viscosity additivity and also confirm a compound forming systems. The best performing models in predicting the concentration dependence of viscosity for liquid binary alloys were established has Kaptay model showed a strong ability in describing the cohesion interaction and fluid flow of viscosity of liquid alloys and was ranked first among others.