Interface microstructure and fracture behavior of aluminum/titanium laser fusion-brazing under different Si element contents

This research successfully achieved the butt joining of aluminum/titanium dissimilar metals using laser welding-brazing technology with filler wires containing different Si content (pure Al, AlSi5, AlSi12). The study investigated the influence of Si content on weld formation, interfacial intermetallic compound (IMC), mechanical properties, and fracture behavior of joints. The results indicated that as the Si content increased, thickness of interfacial IMC gradually decreased while Si aggregation occurred along the IMC layer. The IMC layer transformed from Ti-Al binary phases (TiAl₃) to Ti-Al-Si ternary phases (Ti(Al,Si)₃) with the addition of Si. The tensile strength of joints gradually increased with the increment of Si content, reaching a maximum of 197.69 MPa when AlSi12 was adopted. When the joint was subjected to tensile force, thicker IMC layer formed at the upper part of interface became the weak zone of the joint's mechanical properties, prone to crack initiation, leading to brittle fracture of the joint and ultimately affecting its tensile strength. Due to the increased Si content, the reduced thickness of the IMC layer mitigated the negative effects of its microstructure on the tensile mechanical properties of the joint, shifting the fracture path from the brazing interface to the heat-affected zone of the aluminum base material.