Microstructures and mechanical properties of Cf/SiC composite and TC4 alloy joints brazed with (Ti-Zr-Cu-Ni)+W composite filler materials

In this study, carbon fiber reinforced SiC (Cf/SiC) composite was joined to TC4 alloy using (Ti-Zr-Cu-Ni)+W mixed powders as composite filler material at proper process parameters. The interfacial microstructures and evolution mechanism of Cf/SiC composite/(Ti-Zr-Cu-Ni)+W/TC4 alloy joints were investigated based on scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). The mechanical properties of the brazed joints were measured by the mechanical testing machine. The results showed that Ti and Zr elements in the interlayer can react with the brazed material, the brazed joint mainly consisted of Ti3SiC2, Ti5Si3, (Ti, Zr)C, Ti2Cu, Cu10Zr7, Ti(Cu, Ni) and Ti(s,s) reaction products. The diffusion-reaction layer was formed between the interlayer and TC4 alloy due to the element interdiffusion. The brazing parameters had a distinct effect on the interfacial reaction between Cf/SiC composite and filler material, which affected the shear strength of the brazed joints. Adding the appropriate W powder was beneficial for relaxing the residual thermal stress and reinforcing the brazed joints. The maximum shear strength of the brazed joints was 166 MPa at room temperature and 96 MPa at 800 °C high temperature acquired at 930 °C for 20 min using (Ti-Zr-Cu-Ni)+15 vol.%W composite filler material.