Interfacial microstructure and performance of nano-diamond film/Ti-6Al-4V joint brazed with AgCuTi alloy

• CVD nano-diamond film and Ti-6Al-4V were successfully brazed using AgCuTi filler.
• The highest shear strength of joints reached 25 MPa.
• The mechanism of microstructure evolution of brazed joint was illuminated.

The CVD nano-diamond film and Ti-6Al-4V alloy were successfully brazed with AgCuTi active brazing filler. The interfacial microstructure was investigated by SEM, EDS, XRD and TEM. Typical interfacial microstructure of brazed joint was conformed as Ti-6Al-4V/diffusion layer/Ti2Cu + TiCu + Ti3Cu4/Ag(s,s) + Cu(s,s) + Ti2Cu3/TiCu + TiC/nano-diamond film. The effects of brazing temperature on interfacial microstructure and mechanical properties of the brazed joints were analyzed. With the increasing brazing temperature, the thickness of reaction layers adjacent to Ti-6Al-4V substrate and nano-diamond film increased obviously. Moreover, the Ti2Cu3 phase coarsened and aggregated in brazing seam at higher temperature. The joint was formed by the diffusion and reactions between atoms, and the microstructure evolution of brazed joint was discussed. In addition, a slight graphitization of nano-diamond film occurred during brazing process, and the highest shear strength can reach 25 MPa when the joint was brazed at 880 °C for 10 min. Finally, the fracture positions and fractographs of brazed joints were also discussed.

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