Microstructure and fracture properties of carbon/carbon composite and TC4 titanium alloy joints

C/C composites and TC4 titanium alloy were joined using AgCu filler metal at brazing temperature of 820-900°C for 10 min. Interface microstructures and fracture surfaces were investigated by scanning electron microscopy, X-ray diffraction and EDS energy spectrum. The results showed the typical interface microstructure of C/C composite and TC4 brazed joints could be expresses as C/C composite/TiC+C/TiCu/Ag(s.s)+Cu(s.s)+Ti₃Cu₄/ Ti₃Cu₄/TiCu/Ti₂Cu/ Ti₂Cu+Ti(s.s)/TC4. The shear strength of the brazed joints was 38 MPa at 850°C for 10 min. The analysis of fracture surface showed that the situation of fracture surface was related to the orientation of carbon fiber and brazing temperature. When carbon fiber was parallel to the joining surface, the joints were fractured in the composites. When carbon fiber was vertical to the joining surface, the joints were mainly fractured in the C/C composite/filler metal interface with low brazing temperature. Meanwhile, the joints were fractured in the C/C composite/filler metal interface and filler metal/TC4 interface with high brazing temperature.