Microstructure and mechanical properties of BN-Si₃N₄ and AlON joints brazed with Ag-Cu-Ti filler alloy

AlON was successfully brazed to BN-Si₃N₄ using a Ag-Cu-Ti filler alloy. SEM, TEM and XRD studies revealed that a TiN + TiB₂ + Ti₅Si₃ reaction layer formed adjacent to the BN-Si₃N₄ while a (Cu,Al)₃Ti₃O layer formed adjacent to the AlON. In addition, Ag-Cu eutectic, Cu(s,s) and AlCu₂Ti were observed in the brazing filler. The effect of brazing temperature on the microstructure and mechanical properties of the joints was investigated. As the brazing temperature increased, the reaction layers became thicker, while the thickness of the brazing seam decreased. Meanwhile, the amount and the size of AlCu₂Ti intermetallic compounds decreased. The shear strength of the joints first increased and then dropped with increasing the brazing temperature. A joint with a maximum strength of 94 MPa was obtained when it was brazed at 850 °C for 15 min.