Effects of laser parameters on morphological change and surface properties of aluminum alloy in masked laser surface texturing

The masked laser surface texturing process was used to produce micro-pattern arrays. Using mesh grids as masks, the surface of the workpieces were selectively ablated and hundreds of micro-patterns were simultaneously generated by a single laser irradiation. The effects of laser energy intensity and number of laser pulses on surface morphologies and properties were investigated. It was found that it is more efficient to control the number of laser pulses than the laser energy intensity to form a uniform micro pattern array and to control the pattern shape. In addition, hardness values of the material surface can be selectively increased by adjusting laser parameters. When the laser energy intensity increased, the hardness of the hole region which was directly affected by the laser irradiation increased. When the surface was irradiated repeatedly by the multiple laser pulses, however, the increase in hardness was much pronounced in the masked bar region adjacent to the ablation zone. The structural changes of the patterned surface and the work hardening effect due to laser shock loading were superimposed to increase the hardness of the masked region. The contact angle decreased with increasing laser energy intensity and number of laser pulses. This is mainly due to an increase in surface heterogeneity at high laser energy intensities and an increase in bar width at multiple laser pulses condition.