Influence of surface roughness on morphology of aluminum alloy after pulsed-laser irradiation

The objective of this study is to investigate the influence of surface roughness on the morphology of aluminum 6061-T6 alloy after irradiation with a Nd: YAG pulsed laser. The test specimen was prepared by a polishing process using a diamond paste (1 μm) and emery polishing papers (#100, #220, #600, #2400) to obtain different initial surface roughness. After irradiation with ten pulsed-laser shots, the surface morphology was examined by using scanning electron microscopy (SEM), optical microscopy (OM), and atomic force microscopy (AFM). The diameter of the melted zone increased with the surface roughness because the multiple reflections and absorption of the laser beam occurred on the surface because of the surface roughness, so that the absorptance of the laser beam changed. This result was verified using the relative absorptance calculated from the diameter of the melted zone with the surface roughness and the diameter increased with the average surface roughness.