Microstructural evolution and mechanical characterization of Nb-interlayer-inserted Ti–6Al–4V/Si3N4 joints brazed with AuNiTi filler

Abstract The interfacial microstructure evolution and mechanical behavior of Ti–6Al–4V/Si3N4 joints with insertion of a 2 mm-thick Nb interlayer were studied by brazing with Au96.5Ni3Ti0.5 (mass%) alloy as a heat- and corrosion-resistant filler. When the joints were brazed at 1323 K with holding times of 0, 5, and 10 min, multilayered Au4Ti, Au2Ti, AuTi, AuTi3, and Au2Nb3 intermetallic compounds were formed at the Ti–6Al–4V/Nb interface, whereas two distinct regions consisting of Au2Nb3 layer and Au–Ni solid solution were predominantly developed at the Nb/Si3N4 interface. Joints brazed with a 0 min holding time fractured, with initiation at the reaction-layer/Si3N4 interface and propagation into the Si3N4 with a concave morphology because of large residual stress; the joints exhibited a maximum average room-temperature bending strength of 53 MPa.