Microstructural evolution of Si3N4/Ti6Al4V joints brazed with nano-Si3N4 reinforced AgCuTi composite filler

A novel nano-Si3N4 particle reinforced AgCuTi composite filler (AgCuTiC) was used to braze Ti6Al4V and Si3N4 ceramic in the study and brazing cycles that peak at 880 °C for 0-20 min. Effects of holding time on interfacial microstructure and mechanical property were studied by scanning electron microscopy, energy dispersive spectrometer, transmission electron microscopy, and universal testing machine. TiN and Ti5Si3 were identified as the main product of the reaction between Si3N4 and Ti. The interfacial microstructure evolved considerably with joining time, eventually leading to a high degree of inhomogeneity across the length of the joint, and the maximal shear strength of 78.3 MPa was obtained when the joint was brazed at 880 °C for 10 min. A limited number of Si3N4/Si3N4 and Ti6Al4V/Ti6Al4V joints using AgCuTiC with different content of Ti particles were also studied to clarify the influences of diffusion and dissolution behaviors of element Ti on interfacial microstructure. In terms of characterizing the interfacial phases, efforts were made to understand the microstructural evolution mechanism of Si3N4/Ti6Al4V brazed joints.