A TEM analysis of the Si3N4/Si3N4 joint brazed with a Cu-Zn-Ti filler metal

Si₃N₄ ceramic was joined to itself using a filler alloy of (CuZn)85Ti15 at 1123–1323 K for 15 min. TEM observation showed that a reaction zone of TiN and/or Ti₂N exists at the interface between the ceramic and filler alloy, and the center of the joint is composed of Cu-Zn solid solution in which there are Cu₂TiZn and Ti₅Si₃ reaction phases. With increasing brazing temperature, both the thickness of the reaction zone and the amount and size of the Ti₅Si₃ phase increase, while the amount and size of the Cu₂TiZn phase decrease. When the brazing temperature reached 1323 K, the Cu₂TiZn phase disappeared. When the brazing temperature is lower than 1223 K, the interfacial reaction zone is mainly composed of Ti₂N, which has a cylindrical shape and orientates randomly in the zone. There is a crystal orientation relationship between the Ti₂N in the reaction zone and the Cu in the Cu-Zn solid solution, which is: {110}_Ti2N//{420}_Cu, 001_Ti2N//001_Cu. When the brazing temperature is higher than 1223 K, the interfacial zone is composed of TiN, which has a plate shape crossing each other.