IMPROVEMENT OF ADHESIVE BONDING STRENGTH IN SEALED ANODIZED ALUMINUM THROUGH EXCIMER-LASER PREBEND TREATMENT

The feasibility of using an excimer laser as a prebend treatment of se aled anodized aluminium alloys has been demonstrated. Irradiation of s ealed chromic acid anodized aluminium by means of pulsed ultraviolet l aser (193 nm wavelength, energy density of 0.2-7 J cm(-2) per pulse an d duration of 24 ns) improved bonding strength by more than 100% compa red to that of the sealed anodized but non-treated alloy (using modifi ed epoxy adhesive). The influence of laser treatment on the sealed ano dic layer was investigated by various techniques, including scanning e lectron microscopy, X-ray diffraction and Fourier transform-infrared s pectroscopy. Various phenomena, such as morphological changes, ablatio n, crater formation, melting, gas evaporation, water removal and cryst allization, were observed following the laser treatment. The magnitude of these changes was found to depend on both laser-beam energy densit y and number of pulses.