Microstructure and mechanical properties of brazed joints between titanium alloy and aluminum matrix composites

Ultrasonic-assisted brazing of two dissimilar materials, 55%SiC_p/Al composite and TC4 titanium alloy, using Zn-based filler metal was investigated. The microstructure and constituent phases of the joints were examined by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) analysis and the shear strength of the joints was tested. The results show that metallurgical bond is obtained between titanium alloy and 55%SiC_p/Al composite by the ultrasonic-assisted brazing. The oxide films disappear entirely in the composite side of the joint. A number of smaller SiC particles migrate into the brazing seam by the ultrasonic wave. Only TiAl₃ phase (a thickness of about 2-4 μm) is formed in the interfacial area of the titanium alloy side of the joint. The maximum shear strength of 167 MPa has been attained for the bond made at 420℃. It is found that the fracture occurs at the interface region between TiAl₃ phase and 55%SiC_p/Al composite in the joint.