Properties and welding interface characterization of new-type Au-Ag-Ge brazing alloy

According to Au-Ag-Ge phase diagram,two new-type brazing alloys Au-19.25Ag-12.80Ge and Au-21.06Ag-13.09Ge(mass fraction,%) were prepared.The melting characteristic and microstructure of the alloys were analyzed by using differential thermal analyzers and Sirion 200 field emission scanning electron microscope,and the wettability with pure Ni was also studied.The results show that,Au-19.25Ag-12.80Ge brazing alloy is better,its melting temperature range is 446.76-494.40 ℃,and the temperature interval between the solidus and the liquidus is 47.64 ℃.When the brazing temperature is in the range of 510-550 ℃,the alloy has a good spreadability and wettability with Ni.Interface structure observation reveals that there is one continuous intermetallic layer between the brazing alloy and the base metal Ni when welding.X-ray energy spectrum analysis results show that the intermetallic layer is Ge3Ni5,and because of its brittleness,the overthick intermetallic layer will decrease the shear strength of the welding joint,therefore,the welding technology should be controlled so as to gain an ideal welding interface structure.