Microstructural evolution and mechanical characterization of Nb-interlayer-inserted Ti-6Al-4V/Si_3N_4 joints brazed with AuNiTi filler

摘要

The interfacial microstructure evolution and mechanical behavior of Ti-6Al-4V/Si_3N_4 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 Au_4Ti, Au_2Ti, AuTi, AuTi_3, and Au_2Nb_3 intermetallic compounds were formed at the Ti-6Al-4V/Nb interface, whereas two distinct regions consisting of Au_2Nb_3 layer and Au-Ni solid solution were predominantly developed at the Nb/Si_3N_4 interface. Joints brazed with a 0 min holding time fractured, with initiation at the reaction-layer/Si_3N_4 interface and propagation into the Si_3N_4 with a concave morphology because of large residual stress; the joints exhibited a maximum average room-temperature bending strength of 53 MPa.