Experimental thermodynamics, surface and transport properties of liquid Ag-Ge alloys

Highlights: • The new experimental data on the melting temperature and heat of melting of Ag-Ge eutectic alloy were obtained by DSC. • Exothermic and endothermic reactions present in the Ag-Ge system affect the properties of liquid Ag-Ge alloys. • Predicted property datasets of liquid Ag-Ge alloys are compared with literature data to assess data reliability. • Quasi Chemical Approximation (QCA) for regular solution is appropriate to calculate the surface properties of Ag-Ge alloys. -- Abstract: The aim of this study is to correlate the thermodynamics of liquid Ag-Ge alloys with their thermophysical properties such as the surface tension, viscosity, electrical resistivity and microscopic functions. For this purpose the Quasi-Chemical Approximation (QCA) for the regular solution and Faber-Ziman theory have been applied to describe the mixing behaviour of Ag-Ge melts in terms of the energetics and structure. Concerning the Ag-Ge system, the most important is Ag-24.5Ge (in at %) eutectic alloy, widely used as a brazing filler material. The melting temperature and the heat of melting of Ag-Ge eutectic alloy were measured by Differential Scanning Calorimetry (DSC). From a technological point of view, particular attention should be paid to the surface tension, a key property of the joining processes. Accordingly, the QCA and Butler's model calculations have been done and subsequently, the model predicted values were compared to available literature data.