Microstructure and mechanical properties of Si_3N_4 ceramic and (TiB + Y_2O_3)/Ti matrix composite joints brazed with AgCu/Cu foam/AgCu multilayered filler

摘要

Silicon nitride ceramics (Si3N4) and (TiB + Y2O3)/titanium matrix composites (TMCs) were brazed using a multilayered filler consisting of AgCu foils and Cu foam. The microstructure and formation mechanism of the TMCs/Si3N4 joint were studied. The results showed that the TMCs/Si3N4 joint consisted of TMCs/TiCu + TiCu2/Ag(s, s) + Cu(s, s)/TiCu + Ti5Si3 + TiN/Si3N4 ceramic. The reaction layer consisting of TiN and Ti5Si3 formed first on the Si3N4 ceramic side is crucial for the joining the TMC and Si3N4. The influence of brazing temperature on the microstructure evolution and mechanical performance of the TMCs/Si3N4 joint was discussed. Element diffusion was intensified by increasing the brazing temperature, which reduced the Cu(s, s) and enlarged the Ti-Cu compounds. At 820 degrees C, the Ag-Cu eutectic structure was uniformly distributed into the brazing seam, which improved the performance of the joint. The shear strength reached a maximum of approximately 165.0 MPa. At higher brazing temperatures, the Cu foam collapsed, the Ti-Cu intermetallics increased, the brittleness was aggravated, and the shear strength of the joint decreased.