Enhancing Al₂O₃-7A52 brazed joints by femtosecond laser surface machining of periodic alumina structure

In this study, we propose a method that utilizes femtosecond laser surface machining technology to enhance the quality of ceramic-aluminium alloy joints while minimizing residual stress. The present study investigates the impact of the periodic structure of Al2O3 surface, which is machined using femtosecond laser, on the properties of Al2O3-7A52 brazed joint. Various surface periodic structures, including shallow grooves, deep grooves and micro-convex platform, were created on the surface of Al2O3 using femtosecond laser technology. The joint strengths of these different periodic structures are 44.6, 49.1 and 41.1 MPa, respectively, making 129%, 142% and 119% of the shear strength observed in the original planar ceramic-aluminium alloy joint. By machining ceramic surfaces with femtosecond lasers, a periodic structure can be created that enhances the bonding area between the ceramics and solder. This increased surface area improves the wettability of the solder to the ceramic surface, encouraging diffusion reactions at the joint interface. Ultimately, this leads to the creation of a solid bond with the ceramic interface, facilitated by the formation of spinel (MgAl2O4).