Microstructure and properties of AgCuGa brazing filler metal

A novel Ag-Cu-Ga（Ag≤50 wt. %） brazing filler metal was developed. The melting characteristics,brazing performance and microstructure of Ag-Cu-Ga brazing filler metal were investigated. The results indicated when the mass fraction of Ga in AG-Cu-GA alloy was 5%,its melting temperature was 771 ～ 786 ℃. The melting point was moderate and the temperature difference between solid and liquid phase was small.The as-cast microstructure of AG-55Cu-5GA alloy was mainly composed of rich Cu phase,rich Ag phase and Ag-Cu-Ga eutectic phase,which determined its good process ability. The Ag-55Cu-5Ga strip with a thickness of 0. 1 mm had optimal clean ability and collapsibility,which had good spreading performance on copper and nickel sheet,but had obvious shrinkage on stainless steel. The tensile samples of brazed joints failed in parent metal,and the strength of brazed joints was higher than that of parent metal. Through analysis of the interface microstructure,it was founded that diffusion layer,copper-based solid solution in large quantities and a small amount of fine sand eutectic microstructure were formed in the brazed joint,which improved tensile strength of the brazed joint to some extent. By comprehensive analysis,Ag-55Cu-5Ga brazing filler metal was probably a alternative to AgCu28 eutectic brazing filler metal to meet sealing requirements of the vacuum electronic device.