Thermodynamic modelling of the Ag–Cu–Ti ternary system

Abstract

Abstract The Ag–Cu–Ti system is important for brazing applications, particularly for ceramic joining. This system is characterized by numerous intermetallics in the Cu–Ti binary and the existence of a miscibility gap in the liquid phase. For applications, knowledge of the phase equilibria, invariant reactions in the temperature range of interest and thermodynamic activity values (mainly of Ti) are important. Thermodynamic model parameters for all the stable phases in the Ag–Cu, Cu–Ti and Ag–Ti systems, previously obtained using the Calphad method and available in the literature are used. A new thermodynamic description for the ternary interaction parameter of the liquid is obtained from experimental informations. Ti2Cu and Ti2Ag which have the same crystallographic structure were modelled as a single phase. The same was done for TiCu and TiAg. Finally, solid solubility of Ag in the Ti–Cu intermetallics is taken into account. The parameters obtained in this assessment are later used for the calculation of selected sections that can be useful for research and applications in the field of joining with Ti-activated Ag–Cu braze.