Tailoring Al-Li Alloy Surface Wettability with a Femtosecond Laser and Its Effect on Bonding Performance

In this study, a femtosecond laser was used to pretreat the surface of the Al-Li alloy, the surface micromorphology, roughness, contact angle, and surface wettability of which were adjusted by changing the laser scanning speed, and the sample was bonded into a single joint with polyether ether ketone (PEEK) adhesive. The mechanism of the laser surface treatment affecting the bonding strength of the Al-Li alloy was explored through tensile and shear experiments. The results indicated that optimizing the laser surface treatment parameters could change the surface roughness and surface micromorphology of the Al-Li alloy, so as to change its surface free energy and bonding strength. Compared with the untreated sample, the bonding strength of the Al-Li alloy increased by 81%, 95%, 107%, 91%, and 78% under the treatment of laser scanning at 25, 20, 15, 10, and 5 mm/s, respectively. As a whole, femtosecond laser etching of the Al-Li alloy surface had an important influence on its wettability and bonding performance.