FORMATION OF INTERFACIAL MICROSTRUCTURE IN BRAZING OF SI3N4 WITH TI-ACTIVATED AG-CU FILLER ALLOYS

In the present work, the formation of the interfacial microstructure between the S&N4 and Ti-activated filler alloys has been investigated. It was shown that the brazing process is comparable with the brazing of alumina. At brazing temperatures the AgCuTi tiller alloy is divided into two liquids L1 and L2, where the (Cu.Ti)-rich liquid L2 gathers at the S&N, interface and reacts with it. The concentration of Ti in L2 is high, but due to the strong attractive interaction between Cu and Ti, the activity of Ti in L2 is considerably low. The composition of the liquid L2 remains essentially same regardless of the Cu-content in the braze, and therefore the reaction product in reaction between SisN4 and Cu-containing brazes was in all cases the Ti-Cu-Si-N compound. In the AgTi filler alloys Ti is the only reactive element and it segregates to the S&N, interface with high activity. Consequently, the reaction products are similar to those obtained in reaction between pure Ti and SisN. © 1995.