Oxygen content and morphology of laser cleaned 5083 aluminum alloy and its influences on weld porosity

In this paper, laser cleaning of the 5083 alloy was used to remove the native oxide film and modify the morphological defects. The effects of oxygen content changes and surface morphology evolution on weld porosity after pretreatment with different energy densities (E) was studied. After laser cleaning, the oxygen element first decreases and then increases. With 3.5–35 J/cm2, the surface oxygen content drops by more than 60% compared with the untreated sample. It is the lowest with 17.5 J/cm2, a decrease of 75%. The main oxide are Al2O3 before and after laser cleaning. Untreated specimens have morphological defects such as scratches, superficial damage, and bulge. As E increased, the morphological defects were modified by the crater, gradually for fusion, and finally formed a striation morphology. The micromorphology after laser cleaning did not significantly affect the penetration and weld width. However, observation of the keyhole behavior reveals the micromorphology can affect the keyhole stability to regulate the process porosity. The change trend of the hydrogen porosity of the weld is consistent with the oxygen content. With 17.5 J/cm2, the hydrogen porosity of the weld is 0.9%.