Effects of Ge on microstructure evolution of the Cu-based filler metal and the Cu-20Sn-10Ti-1Ga/diamond brazing mechanism

This research aims to enhance the shear strength of Cu-based composite fillers and improve the interfacial characteristics of brazed diamond joint. The filler is optimized by a two-step melting method. The effects of Ge addition on the thermal analysis, microstructure, mechanical properties of fillers, and interfacial properties of brazed diamond joints were fully investigated. Results showed that a gradual decrement in the melting temperature was recorded via differential thermal analysis (DSC) after addition of different content of Ge. The activation energy required to transform the fillers from solid to liquid state is minimized when the addition amount is 1wt.%. The intermetallic compound and Cu-based solid solution showed a tendency of first refinement and then coarsening with the increase of Ge content. When the addition of Ge is 1wt.%, the microstructure of the fillers is the most obvious refinement. The shear strength of the filler was effectively enhanced when 1 wt.% Ge to the Cu-based composite filler increased by 57% compared to that of the fillers without the addition of Ge. Meanwhile, the thickness of the interfacial layer with 1 wt.% Ge was the highest. Achieved 3.03 μm. And the wear resistance of the brazed diamond samples is the best.