Study of the Mixing Behavior of Some Compound Forming Binary Liquid Alloys (Bi-Pb, Cu-In etc)

Abstract

Alloys are produced by combining two or more metals, and they often develop from their liquid states. Only a small number of metals are used in their pure form; the majority of applications use alloys instead because they have distinctive qualities above and beyond those of the component metals. In the study of liquid science, it is essential to comprehend the properties of liquid alloys because most solid alloys are produced by cooling them from the corresponding liquid states. Liquid alloys are regarded as disordered materials because they lack long-range atomic or magnetic organization. Because disordered materials show a wide range of atomic configurations, this topic is of significant interest to both theoretical and experimental researchers. They have long sought to comprehend the anomalies in the mixing properties of liquid alloys in order to fully comprehend alloying behavior. Theoretical methods can reduce the amount of time and effort necessary and are quite useful in forecasting the mixing properties. So, we have created focused on a theoretical model to study how alloys behave when they are molten. Commonly, the effectiveness of binary alloy production is assessed based on observed thermo-physical characteristics that depart from the ideal mixing state. Departures from ideality manifest as asymmetries in thermodynamic and structural characteristics away from equiatomic composition and are typically attributed to one or more of the following: the size effect, different electronegativity, interactions between solute and solvent atoms, complex formation, or a combination of these factors. The binary liquid alloys can be divided into two categories symmetric and asymmetric, based on the symmetry of the curves reflecting the thermodynamic and microscopic functions. Numerous theoretical approaches have been devised and implemented to examine the thermodynamic and structural properties of binary systems. The Complex Formation Model (CFM) is founded on a fundamental theoretical model. This model makes it possible to express the energetics of a system in terms of the interaction parameters that reproduce the system's thermodynamic properties, as well as the ordering and phase separation processes that are observed in liquid binary alloys. The CFM makes the assumption that, if compounds are formed in the solid state at one or more stoichiometric compositions, then it follows that they are very likely to exist in the liquid state at those same compositions. The alloying behavior of binary solutions can be investigated by making the assumption that complexes are present near to melting points. The molten alloy is considered to be composed of a ternary mixture of A and B atoms, as well as a number of chemical complexes A_p B_q in chemical equilibrium with one another. In this case, p and q are both pairs of small integers that stand for stoichiometric indices of the complex. In the present work, we have examined and explained the mixing behavior of two liquid binary alloys based on Bi, such as Bi-Mg at 975 K and Bi-Pb at 700 K, as well as two In-based alloys, such as Cu-In at 1073 K and In-Pb at 673 K, using the CFM framework. For the aforementioned liquid alloys at a given temperature, the thermodynamic properties, such as free energy of mixing (G_M ), enthalpy of mixing (H_M ), and entropy of mixing (S_M ), structural properties, such as concentration fluctuation in long wave length limit (S_cc (0)) and chemical short range order parameter (α_1 ), and transport property, such as ratio of diffusion coefficients (D_M/D_id ), have been examined. We have calculated the interaction energy parameters 〖(Ψ〗_ij,i,j=1,2,3,i≠j), the energy of complex formation (χ), and the number of complexes (n_3 ) for this purpose. These parameters are used to compute the free energy of mixing (G_M/RT) for each system. Enthalpy of mixing (H_M/RT) and entropy of mixing (S_M/R) have been calculated using these parameters and their temperature coefficients ((∂Ψ_ij)⁄(∂T and ∂χ⁄(∂T ))). Comparing the thermodynamic characteristics of the selected systems, it can be seen that they are in very well agreement with the experimental data reported in the literature. The Bi-Mg system is the most interactive, followed by the Cu-In and Bi-Pb systems, according to a comparison of structural properties (S_cc (0) and α_1 ), the ratio of diffusion coefficients (D_M/D_id ) using the same interaction parameters, and thermodynamic properties. The analysis of these mixing characteristics in the In-Pb liquid alloy, however, shows that segregation does occur in this alloy. We have also used the Budai-Benko-Kaptay (BBK) model to study the viscosity of the selected liquid alloys. For the liquid alloys of Bi-Pb and In-Pb, symmetric viscosity isotherms have been reported; however, Bi-Mg and Cu-In exhibits asymmetry. Within the framework of the updated Butler model, the surface properties of the aforementioned binary alloys, such as surface concentration (c_i^s ) and surface tension (σ), have been investigated. Theoretical analyses show that the component in binary liquid alloys whose surface concentration values are higher than the corresponding ideal values segregates across the surface. It is found that the interaction parameters depend on temperature rather than concentration. To optimize the values of interaction parameters at high temperatures, temperature coefficients and their values at a certain temperature are used. The mixing characteristics of Bi-Pb liquid alloys at 900 K, 1100 K, 1300 K, and 1500 K have been investigated using these optimized values of interaction parameters. The compound-forming propensity of binary liquid systems diminishes with increase in temperature, according to the high temperature investigation of Bi-Pb liquid alloy. The properties of binary liquid alloys at the needed temperature can be carried using this expanded CFM, which is expected to be highly helpful in future work.