Effect of Si3N4-particles addition in Ag–Cu–Ti filler alloy on Si3N4/TiAl brazed joint

A novel composite filler alloy was developed by introducing Si3N4p (p = particles) into Ag–Cu–Ti filler alloy. The brazing of Si3N4 ceramics and TiAl intermetallics was carried out using this composite filler alloy. The typical interfacial microstructure of brazed joints was: TiAl/AlCu2Ti reaction layer/Ag(s,s) + Al4Cu9 + Ti5Si3p + TiNp/TiN + Ti5Si3 reaction layer/Si3N4. Effects of Si3N4p content in composite filler alloy on the interfacial microstructure and joining properties were investigated. The distribution of Ti5Si3p and TiNp compounds in Ag-based solid solution led to the decrease of the mismatch of the coefficient of thermal expansion (CTE) and the Youngʹs modulus between Si3N4 and TiAl substrate. The maximum shear strength of 115 MPa was obtained when 3 wt.% Si3N4p was added in the composite filler alloy. The fracture analysis showed that the addition of Si3N4p could improve the mechanical properties of the joint.