In situ consume excessive Ti element and form fine Ti based compounds as reinforcements for strengthening C/C-TC4 joints

Brazing C/C composites to TC4 is often associated with the problems of excessive Ti and high residual stress, which results in low-strength joints. To overcome these problems, AgCu brazing alloy incorporated with Si3N4 or SiO2 particles was used to join the C/C composites to TC4 alloy. The effect of Si3N4 or SiO2 particles on the microstructure and mechanical properties of brazed joints was investigated in detail. Results show that Si3N4 or SiO2 particles can react with Ti element from TC4, which is beneficial to inhibit too many brittle compounds at the C/C side. Meanwhile, it can in situ form the homogeneous distribution of fine-grained Ti based compounds during the brazing process. Due to their fine size, uniform distribution, and favorable cohesion with the matrix, the in situ Ti based compounds as reinforcements have excellent reinforcing effects in the brazing seam. Finite element analyze was adopted to investigate the residual stress state of the joins, and the result shows that the addition of silicide particles can reduce the residual stress obviously. The highest average shear strength reached about 45 MPa for Si3N4 and 41 MPa for SiO2 particles additions, which was higher than that of joints brazed using pure AgCu.