The effect of weak boundary layers on adhesion properties of laser pretreated aluminum alloy EN-AW 6082 surfaces

Kurzfassung

This study investigates the influence of the laser ablation regimes and the material removal mechanisms on the morphologies, topographies, and chemistries of laser-formed surface structures on the aluminum alloy EN-AW 6082. The characteristics of these surface structures are correlated to the adhesion and durability of joints bonded adhesively with PA6. X-ray photoelectron spectroscopy showed that the chosen laser ablation regimes have almost no influence on surface chemistries while microscopic analysis indicated that the surface structures are affected significantly. The adhesion properties and durability of the adhesive bonded joints studied by single lap shear and aging tests are strongly affected by the ablation regimes. Optimal initial lap shear strengths and aging resistances were obtained for a single step laser treatment, while multi-step treatments provided no further benefits. A failure analysis revealed that the micro- and nanostructures developed in melt ejection regime of laser ablation can act as weak boundary layers (WBLs) on metal substrates and affect adversely the adhesion and durability of the joints.