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.