Brazing Mechanism of 70% SiCp/Al Composites with Ti Foam/AlSiMg Filler Metal

To explore suitable filler metal for high-volume fraction SiC_p/Al composites, 70% SiC_p/Al composites were brazed with AlSiMg, AlSiMg6.0Ti and Ti foam/AlSiMg filler metals. The joints were examined using scanning electron microscopy (SEM), energy dispersive spectroscopy, electron probe microanalysis (EPMA), transmission electron microscopy (TEM), x-ray diffraction (XRD), and shear tests to reveal the microstructure evolution and the brazing mechanism. The results showed that the joints brazed with Ti foam/AlSiMg had the highest shear strength (119.0 MPa). The microstructure of the joint consisted mainly of a Ti₇Al₅Si₁₂ interfacial layer, as well as Ti(Al,Si)₃ compounds and a Ti matrix weld that was in-situ reinforced with TiAl nanoparticles. The microstructure evolution of the joints filled with Ti foam/AlSiMg was further studied by subjecting them to different temperatures and holding times. The results indicate that the joints achieved at 700 °C, 60 min and 10 MPa had a complete and dense Ti₇Al₅Si₁₂ interfacial layer, which can improve the interfacial adhesion between the weld seam and the base material. However, with further extension of the holding time, the Ti₇Al₅Si₁₂ interfacial layer gradually broke and loosened, which deteriorated the performance of the joint.