Effects of Preoxidation on Microstructure and Characteristics of Carbon/Carbon Composite–Ti₃Al Joints Prepared by Transient Liquid Phase Diffusion Bonding

In order to promote the molten metal penetration into the carbon/carbon (C/C) composite, a sequence of annular gaps is designed and prepared on the C/C surface. These gaps are created on the C/C surface under preoxidation conditions at 600–660 °C. The oxidized C/C composite is joined to Ti₃Al via transient liquid phase (TLP) diffusion bonding at 880 °C with AgCuNiLi foil as an intermediate layer. The study investigates the effects of preoxidation temperature on the microstructure and characteristics of C/C composite and C/C–Ti₃Al joints. The results show that a sequence of annular gaps with appropriate size can be established between the carbon fiber and pyrolytic carbon layer, while carbon fiber is barely oxidized after oxidation at 630 °C for 30 min. During the bonding process, the molten metal seeps through the C/C gaps, and a permeation layer composed of TiC, Ag (s, s), and C/C composite can be formed. The production of a permeation layer can enhance the bonding strength of the C/C–Ti₃Al joint, and the maximum shear strength (42.12 MPa) of the joint can be 22% greater than the initial C/C–Ti₃Al joint.