The homogeneity of multi-textured micro-pattern arrays in a laser shock surface patterning process and its effect on the surface properties of aluminum alloy

In this study, a laser shock surface patterning process was performed to effectively implement hundreds of micro patterns on a metallic surface through a single laser beam irradiation. Micro-pattern arrays of rectangular, hexagonal, circular, and mesh shapes of various sizes were successfully transferred to the workpiece, and a multi-textured surface structure was realized. In order to improve the homogeneity of the micro-pattern array, it was most effective to increase the thickness of the ablation layer. In the case of the thicker ablation layer, it seems that more uniform pressure was transferred to the material because the ablation layer was in a relatively rigid state due to the reduced level of self-deformation. Since the laser shock surface patterning process exerts a strong shock loading along with plastic deformation on the material surface, the hardness value increased mainly around the area subjected to the shock load. The better the homogeneity of the micro-pattern array, the less the deviation in the hardness value. Therefore, it is important to ensure micro-pattern uniformity in order to achieve uniform surface properties. Changes in the contact angle were also observed under various process conditions. After surface patterning, the contact angle increased as the amount of air trapped in the bar region increased. As the laser intensity increased, it was observed that the geometric surface changes were sharp, and the surface structure changed. As a result, the contact between the air and the water droplets decreased, and the contact angle decreased.