Interfacial microstructure and mechanical properties of Si3N4/Invar joints using Ag–Cu–In–Ti with Cu foil as an interlayer

Abstract Si 3 N 4 and Invar alloy brazed joints were achieved using two types of Ag-based interlayers: a Ag–Cu–In–Ti foil and a Ag–Cu–In–Ti/Cu/Ag–Cu multi-interlayer. The results showed that when only using a single Ag–Cu–In–Ti filler, the wave-shaped Fe 2 Ti + Ni 3 Ti intermetallic compounds are concentrated in the middle of the brazing seam. When adding Cu as the interlayer, the dissolution of the Cu interlayer formed a large number of Cu(s,s) blocks of different sizes in the brazing seam, which hindered the concentrated distribution of Fe 2 Ti + Ni 3 Ti intermetallic compounds in the brazing seam. As a result, Fe 2 Ti and Ni 3 Ti were dispersedly distributed in the brazing seam, increasing the shear strength of the brazed joint. The shear strength of brazed joints was increased by 82 % compared to joints brazed with a single Ag–Cu–In–Ti filler when the Cu interlayer was added.