Brazing TC4 alloy to Si3N4 ceramic using nano-Si3N4 reinforced AgCu composite filler

A novel particle reinforced AgCu composite filler (abbreviated as AgCuC filler) was developed by introducing nano-Si3N4 particles and micron-Ti particles into AgCu powder filler. Reliable brazing of TC4 alloy to Si3N4 ceramic was achieved by using the AgCuC filler. The interfacial microstructure of TC4/AgCuC/Si3N4 brazed joint was TC4/Ti–Cu intermetallic layers/Ag based composite reinforced by fine particles/TiN + Ti5Si3 layer/Si3N4. The addition of nano-Si3N4 in AgCuC filler improved the interfacial microstructure by suppressing the growth of continuous Ti–Cu intermetallic layers adjacent to TC4 alloy and promoting the formation of Ag based composite reinforced by particle phases in brazing seam. The continuous Ti–Cu intermetallic layers thicken and the TiCu2 particle phases coarsened gradually with an increasing brazing temperature. Brazing defects including micro-cracks and nano-Si3N4 aggregation were generated at higher brazing temperature. The highest average shear strength of 73.9 MPa was achieved when brazed at 880 °C for 10 min, which was higher than that of joints brazed using AgCu filler alone (49.2 MPa).