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 degrees C for 10 min, which was higher than that of joints brazed using AgCu filler alone (49.2 MPa). (C) 2015 Elsevier Ltd. All rights reserved.