Microstructure Evolution and Brazing Mechanism of AgCuTi Alloy Vacuum Brazed Corundum–Mullite Ceramic and Mo Joint

The corundum–mullite ceramic and Mo are successfully joined using AgCuTi filler metal via vacuum brazing. This article investigates the effects of brazing temperature and holding time on the microstructure and mechanical properties of the brazed joints. The interface phase composition of brazed joints includes TiO/Ti3(Cu,Al)3O, Cu(s.s), Ag(s.s), and amorphous Ag–Mo. The TiO phase is first formed on the ceramic base material side, and the continuous diffusion of Ti and Cu from the filler alloy toward the ceramic side promotes the transformation of the TiO phase into Ti3(Cu,Al)3O. An increase in brazing temperature facilitates the metallurgical bonding between the base material and the filler metal, and the homogenization of Ag(s.s) and Cu(s.s) phases in the central region of the brazed joint improves. The holding time significantly affects the interdiffusion and dissolution between the base material and the filler metal. Prolonging the holding time enhances the dissolution and diffusion of the filler metal, gradually increasing the thickness of the brazed seam. Under the brazing conditions of 870 °C and a holding time of 30 min, the brazed joint achieves a maximum shear strength of 65.7 MPa.