Brazing of Al2O3-6061 aluminum alloy based on femtosecond laser surface groove structure

Abstract

The combined use of ceramics and aluminium alloys in the field of new materials will greatly improve the production efficiency of lightweight pieces. However, previous studies showed that the connection between ceramic and aluminium alloys requires pre-metallisation treatment on the ceramic surface before reliable joints can be formed through brazing; this reduces the engineering efficiency. In addition, owing to the mechanical engagement between the metallised layer and the ceramic itself, the resulting strength is insufficient for engineering applications. In this study, femtosecond laser technology was used to roughen the surface of Al2O3 ceramic through a micro-scale periodic structure without destroying nor damaging the ceramic surface structure. With the help of such periodic structure achieved by a femtosecond laser, the oxide layer on the ceramic surface is decreased, the contact area is increased, and the wettability is improved, which further spreads the solder. This eliminates the segregation of Mg and Si elements in the solder on the ceramic side and promotes the formation of a brittle intermetallic compound (MgAl2O4). Through femtosecond laser ablation, the residual stress generated on the ceramic surface and the post-welding thermal stress act simultaneously, resulting in a large pressure at the ceramics joint. It hinders the initiation and propagation of joint cracks effectively, and improves the strength of brazed joints. The average strength of the processed joints was approximately 152% of that of the original joint. On the premise of no surface metallisation, more reliable joints can be formed by faster femtosecond-laser surface treatment.