Investigation of the interfacial behavior and mechanical properties of B₄C/1060 Al brazed joints

The brazing connection of multi-layer B₄C/1060Al/B₄C was achieved by using Al-Si-Mg-Bi active brazing filler metal. The effects of brazing temperature and holding time on the microstructure and shear strength of brazed joints were systematically studied. The optimal brazing process was determined as 650 ℃×20 min. At this time, the shear strength of the joint was 63 MPa, and the phase composition of the joint was B₄C/α-Al+Al₂Si+AlB₂+Al₄C₃/Al. With the increase of brazing temperature and the extension of holding time, the shear strength of the brazed joint first increases and then decreases, and all joints under different process parameters exhibit brittle fracture characteristics. Specifically, under the process of 610 ℃×20 min, fracture failure occurs at the interface between B₄C ceramic and the brazing filler metal layer, while under 650 ℃×20 min, the fracture position shifts to the interface between 1060Al and the brazing filler metal layer. It is concluded that excessively high brazing temperature or overly long holding time leads to excessive generation of brittle phase Al₄C₃ in the interfacial region, accompanied by significant accumulation of internal stress, which ultimately causes the deterioration of the mechanical properties of the brazed joint.