Effect of Brazing Fillet on the Microstructure and Mechanical Properties of Vacuum Brazing Stainless Steel Joints

The enhancement mechanism of the fillet on brazing joints is of great significance for vacuum brazing technology. Although a lot of research on the enhancement mechanism of the fillet has been carried out, some key components of a comprehensive systematic enhancement mechanism for brazing fillets have yet to be established. In this paper, the enhancement mechanism for brazing fillets of SS304/pure copper brazing joints was studied by both experimental and numerical simulations. The SEM and tensile experiments were used to characterize the microstructure and shear strength of the brazing joints. The results show that the brazing joints, using 60 µm thick pure copper filler metal, exhibit a good microstructure in the brazing seam; however, its mechanical properties are lower than those found in specimens with a thickness of 90 µm. The fracture behaviors of brazing joints were also investigated, the fracture of the brazing seam was a fracture of mode II due to shear stress, while the fracture of the brazing fillet was caused by a combination of tensile stress and shear stress (mode I and mode II).