Enthalpy Of Mixing Of Liquid Alloys Thermodynamic Model Studies

The enthalpy of mixing of the liquid alloys is one of the important thermodynamic properties in basic and applied research of the metallurgical process. A theoretical technique to estimate this would be very useful. The molecular interaction volume model (MIVM) was obtained from a physical basis. It is a two-parameter model, which is able to predict the thermodynamic properties in a multicomponent solution system using only the ordinary physical quantities of pure liquid metals and the related binary infinite dilute activity coefficients. The Hoch-Arpshofen model (HAM) was deduced from physical principles, which is an extension of Guggenheim's treatment of solutions, combined with an adaptation of Pauling's ideas of the metallic bond.The relationships between thermodynamic properties and the fundamental physical quantities of constituent elements have been studied based on the MIVM and the HAM which have higher estimate accuracy, clearer physical meaning and less empirical parameters. The research aimed to explore the physical significance, improving the predictive ability and expanding the scope of application of two models. The main works of this paper include the following:According to positive deviation, negative deviation, or mixed-deviation system,346binary systems which complete data were classified. The correlations between infinite dilution partial molar enthalpy of binary liquid alloy systems and bond parameters function have been studied. The results show that the infinite dilution partial molar enthalpies of components and valence electrons have a corresponding relationship. There is a linear relationship between the infinite dilution partial molar enthalpy of two components in binary liquid alloys. Based on the molecular interaction volume model, the infinite dilution partial molar enthalpies of the binary systems have bee calculated.Based on the Hoch-Arpshofen model parameters and the relationship between the potential parameters, calculation of the model parameters has been modified. It improves the prediction accuracy of the enthalpies of mixing multicomponent liquid alloy systems. Combined with the free volume theory, a new method has been obtained to predict the activities of component of ternary liquid alloys. It expands the scope of application of the model. Results for the activities of Fe-Au-Ni, Fe-Cr-Ni, Fe-Co-Cr and Fe-Co-Ni systems at required temperatures are presented by modified Hoch-Arpshofen model. The average relative errors of prediction are11.8%,9.3%,4.9%and8.4%, respectively. It shows that the calculated results are in good agreement with the experimental data except Fe-Au-Ni system, which exhibits strong interaction between unlike atoms. The model provides a simple, reliable and general method for calculating the activities for Fe-based liquid alloys.The mixing enthalpies of the Al-Cu-Ni-Zr quaternary alloys are calculated by the molecular interaction volume model using only the coordination numbers and the binary infinite dilute enthalpies. The average relative error and the average standard deviation of prediction are±19.6% and±7.5kJ/mol, respectively. The calculations by optimal interaction parameters are±14.0% and±4.4kJ/mol. It can be clearly seen that based on the good predicted results of the binary systems, the mixing enthalpies of the Al-Cu-Ni-Zr quaternary system and four ternary systems should be reasonable and reliable relatively. The model will bring certain errors during prediction, which are more obvious in ternary systems, in multicomponents systems maybe due to all kinds of errors counterbalance that results in the predicted effect are good. In comparison with the associated model, the prediction effect of MIVM is of better stability and safety.The liquidus of Ge-In, Ge-Pb, Ge-Si, Ge-Sn, Ge-T1and phase diagrams of Ge-Sb and Ge-Zn systems are calculated by molecular interaction volume model, which only using the infinite activity coefficients of components and the coordination numbers of the constituent elements in liquid alloys. Agreement between the calculated and experimental results indicates the possibility for the efficient application of this method. A method is presented for calculating the separation coefficients and phase equilibrium of Pb-Au, Pb-Sn and Sb-Sn alloys in vacuum distillation based on molecular interaction volume model. By this method, we can evaluate the possibility and extent of distilling separation of a crude metal and an alloy.