Effect of brazing temperature on microstructure and mechanical properties of Si_3N_4/Si_3N_4 joints brazed with Ag-Cu-Ti + Mo composite filler

摘要

Mo particles have been introduced into Ag-Cu-Ti brazing alloy for the joining of Si_3N_4 ceramic. Effect of brazing temperature on microstructure and mechanical properties of the joints were investigated. The result shows that a continuous reaction layer which is composed of TiN and Ti_5Si_3 was formed at the Si_3N_4/braze interface. The central part of the joint was composed of Ag-based solid solution, Cu-based solid solution, Mo particles, and Cu-Ti intermetallic compounds. By increasing the brazing temperature, both the thickness of the reaction layer and amount of Cu-Ti intermetallic compounds in the joint increased, being beneficial for the joint strength. Whereas, the reaction between Ti and Si_3N_4 ceramic proceeded excessively and more Cu-Ti intermetallic compounds were precipitated in the joint while elevating the brazing temperature to 950 °C, leading to deterioration of the bending strength. The maximal bending strength reached 429.4 MPa at 900 °C for 5 min when the Si_3N_4 ceramic was brazed with Ag-Cu-Ti + Mo composite filler.