Excimer laser treatment of aluminium alloys and their potential applications

Although laser surface melting (LSM) of aluminium alloys using high power continuous wave (cw) CO2 and Nd:YAG lasers has shown to produce homogenization/refinement of microstructure, the refined second phase particles still act as preferential sites to initiate localized corrosion. In contrast to a cw laser, an excimer laser with a UV wavelength and nanosecond pulse width, resulting in extremely high cooling rate, is expected to generate a further refinement or completely removal of the second phase particles and hence, improved corrosion performance. This paper reviews our recent investigations on excimer laser surface melting of AA2024-T351 and AA2050-T8 aluminium alloys, in order to gain insight into the microstructure and the resultant corrosion behaviour of the laser-treated surface for different aluminium alloys. In addition, such excimer laser process has been applied as a pretreatment prior to anodizing of the aluminium alloys. The results showed that the excimer laser surface melting of both alloys significantly improved the corrosion performance following anodizing compared with the alloys anodized without prior laser treatment.