Design CuZr alloy to control Ti diffusion and reaction layer thickness in C/C-TC4 joins

Brazing C/C composites and Ti6Al4V (TC4) can expand their practical applications, but the too much brittle TiC at C/C side is harmful to joint strength. The key to high-quality brazing joints is to control the excessive diffusion of Ti element from TC4 and TiC reaction layer at C/C. Herein, a new type of CuZr brazing alloy was designed, since Cu element can react with Ti, and Ti element are infinitely miscible in Zr. The interfacial microstructures showed that CuZr alloy reacted with Ti to form Ti 2 Cu + (Zr, Ti) 2 Cu, preventing diffusing Ti and optimizing reaction layer thickness. The effects of brazing temperature and holding time on microstructure changes were analyzed. When the temperature and holding time was insufficient, TiC+ZrC reaction layer was formed not well and inhomogeneous Ti(s, s) and Ti 2 Cu were dispersed in (Zr, Ti) 2 Cu, leading to a relatively low shear strength. Microstructures of continuous TiC+ZrC reaction layer and homogeneous (Zr, Ti) 2 Cu + Ti 2 Cu were optimized as temperature and holding time increased. Optimal microstructure of the joints was brazed at 970 °C for 10 min, which was C/C-TiC+ZrC/Ti 2 Cu + (Zr, Ti) 2 Cu/Ti(s, s)-TC4, and the joint reached the maximum shear strength about 54.2 MPa. • The design of CuZr alloy controls the diffusion of Ti interfacial reaction thickness. • Ti-Cu-Zr reaction phase was revealed by Gibbs free energy analysis method. • The effects of brazing temperature and holding time were investigated in detail. • The shear strength attained to 54.2 MPa by optimizing temperature and holding time.