Thermodynamic Calculation Of Phase Equilibria In Ag-Cu-Sn-X(X=In,Sb) Alloy Systems

Ag-Cu-Sn based medium temperature brazing materials have good brazing properties and are widely used in the electronics industry.With the rapid development of electronics industry,higher requirements have been put forward for the properties of brazing materials.Green,low-cost and high-performance Ag-Cu-Sn based medium-temperature brazing materials have become a hot research topic.The addition of beneficial alloying elements to brazing alloys is an effective way to enhance the performance of brazing alloys.Research shows that the addition of appropriate amounts of In,Sb and other elements can reduce the melting point of Ag-Cu-Sn-based brazing alloys,thereby reducing the melting range of brazing materials,but also to refine the organization of brazing alloys,to play the role of alloy strengthening,so that brazing materials have excellent fluidity and brazing performance.Phase equilibria and thermodynamic information of the alloy systems are the theoretical basis for studying the properties of brazing materials.Therefore,this work investigates the phase diagram and thermodynamic properties of the Ag-Cu-Sn-X(X=In,Sb)systems,as well as the solidification microstructure and phase transition of the Ag-Cu-SnX(X=In,Sb)alloys.The research contents are as follows:(1)Thermodynamic evaluation of four ternary systems(Ag-Cu-Sn,Ag-Cu-In,Ag-InSn,Cu-In-Sn)for the Ag-Cu-Sn-In system based on literature data.The four ternary systems in the Ag-Cu-Sn-In system were optimized using the CALPHAD method based on the available reasonable six binary systems combined with experimental data on phase equilibria and thermodynamic properties of the ternary systems reported in the literature,and reasonable self-consistent thermodynamic parameters were obtained for each phase in the system,and thermodynamic database of the Ag-Cu-Sn-In system has been also developed.Secondly,to validate the rationality of the thermodynamic database an Ag-Cu-Sn-In as-cast alloys was prepared using arc melting,and the phase transition temperature and microstructure of the Ag-Cu-Sn-In alloy were experiments determined using scanning electron microscopy(SEM)and differential thermal analysis(DTA).Finally,the pseudobinary phase diagram of the Ag-Cu-Sn-In system was calculated using the thermodynamic database optimized in this work,and the equilibrium solidification and non-equilibrium solidification processes of the alloy were simulated using Thermo-Calc software.The calculated results are in general agreement with the experimental results.(2)The Ag-Cu-Sb system is an important ternary system for the Ag-Cu-Sn-Sb system and there is no thermodynamic description of the Ag-Cu-Sb system in the literature.Firstly,the Ag-Cu-Sb system was optimized using the CALPHAD method based on phase diagrams and thermodynamic experimental data published in the literature.Combining the reoptimized Ag-Cu-Sn system with the Ag-Sn-Sb and Cu-Sn-Sb systems already evaluated by our group,a self-consistent database of Ag-Cu-Sn-Sb system was extrapolated in agreement with the experimental results.On this basis,Ag-Cu-Sn-Sb as-cast alloys were prepared by alloying methods,and the phase transition temperature and solidification microstructure of Ag-Cu-Sn-Sb alloys were determined using scanning electron microscopy(SEM)and differential thermal analysis(DTA)experiments.Finally,the pseudo-binary phase diagram of the Ag-Cu-Sn-Sb system was calculated using the thermodynamic database obtained by reasonable extrapolation in this work using Thermo-Calc software,and the equilibrium solidification and non-equilibrium solidification processes of the alloy were simulated.The calculated results are in good agreement with the experimental data.