Effects of Ga and In on the properties of cadmium-free Ag-Cu-Zn filler metal

Melting temperature,spreadability,mechanical properties and the microstructures of joints brazed with silver-base filler metals including different amounts of Ga and/or In were studied respectively in this paper,and the results show that the melting temperature of the silver-base filler metals is decreased,spreadability of the silver-base filler metals is improved,and the microstructures of silver-base filler metals are refined obviously with the addition of Ga and/or In.Using copper and brass plates as base metal and brazing with flame method,the mechanical properties of the lap-joint and butt joint were also examined and analyzed respectively,and the results indicate that the fracture position of two kinds of brazed joints occurred on the base metal,except for the lap-joint of brass,which shows better mechanical properties of the joints brazed with the silver-based filler metals including Ga.For the lap-joint of brass,the tensile strength gradually increased with the increase of Ga content,while the addition of In has little effect on mechanical properties.It is also found that the best comprehensive properties of cadmium-free Ag-Cu-Zn filler metals are obtained when Ga content is about 3.0 wt.% and In content is between 1.5 wt.% and 2.0 wt.%.