Microstructure evolution of Al2O3/Al2O3 joint brazed with Ag–Cu–Ti + B + TiH2 composite filler

Al2O3/Al2O3 joint was achieved using Ag–Cu–Ti + B + TiH2 composite fillers at 900 °C for 10 min. The evolution mechanism of interface during brazing was discussed. Effects of Ti and B atoms content on microstructure of joints were investigated. Results show that a continuous and compact reaction layer Ti3(Cu,Al)3O forms at Al2O3/brazing alloy interface. Ti(Cu,Al) precipitates near Ti3(Cu,Al)3O layer. In situ synthesized TiB whiskers evenly distribute in Ag and Cu based solid solution. The higher content of B powders in composite fillers increases TiB whiskers content, but decreases the thickness of Ti3(Cu,Al)3O layer, while the higher TiH2 powders content thickens Ti3(Cu,Al)3O layer. Ag and Cu based solid solutions become uniform and fine with the increasing of TiB whiskers content. Ti(Cu,Al) intermetallics content increase and they gradually distribute from Al2O3 side to the central of brazing alloy, but the content of Cu based solid solution decreases when the TiH2 content increases.