Effect of brazing temperature on interfacial microstructure and properties of Ti60/Si₃N₄ brazed joints

In order to study the effect of brazing temperature on the microstructure and mechanical properties of Ti60/Si₃N₄ joints, Ag-28Cu eutectic alloy was used to braze Ti60 alloy and Si₃N₄ ceramic at the temperature range from 870℃ to 910℃ for 10 min. The microstructure of the brazed joint was analyzed by Scanning Electron Microscope and Energy Dispersive Spectrometer. The typical interfacial microstructure was Ti60/Ti-Cu intermetallic layer/Ag(s,s)+Cu(s,s)/Ti-Cu intermetallic layer/Ti₅Si₃+TiN/Si₃N₄. The evolution process of the brazed joint was analyzed. The results showed that the thickness of Ti-Cu intermetallic layer next to Ti60 alloy and the Ti₅Si₃+TiN layer on Si₃N₄ ceramic side increased gradually with the increasing of brazing temperature. Meanwhile, the content of Ag(s,s) and Cu(s,s) decreased. In addition, Ti-Cu compound was formed in Ti₅Si₃+TiN layer by the reaction between element Ti which diffused to Si₃N₄ ceramic side and element Cu in the liquid phase. The shear test indicated that the highest shear strength of 61.7 MPa was obtained with the brazing technological parameter of 880℃+10 min.