Fig. 1. Schematic of laser cleaning system

Fig. 2. Schematic of spots overlapping

Fig. 3. Schematics. (a) Welding form; (b) laser welding

Fig. 4. Oxygen content of aluminum alloy surface at single laser cleaning

Fig. 5. Oxygen content of aluminum alloy surface at multiple laser cleaning

Fig. 6. Surface morphology (SEM) and surface energy spectrum analysis (EDS) of 6061 aluminum alloy surface after multiple laser cleaning. (a) P=10 W, N=7; (b) P=15 W, N=5; (c) P=20 W, N=3

Fig. 7. Line scan energy spectrum analysis (P=15 W, N=5). (a) Surface morphology; (b) oxygen, magnesium, alluminum elements change curves along the path E—F

Fig. 8. Surface morphology (SEM) and surface distribution of oxygen of 6061 aluminum alloy after multiple laser cleaning with different laser powers. (a) P=10 W, N=7; (b) P=15 W, N=5; (c) P=20 W, N=3

Fig. 9. Oxygen content of aluminum alloy surface at single laser cleaning with overlap rate of -5%

Fig. 10. Oxygen content of aluminum alloy surface after cleaning with different parameters and overlap ratio of 5%. (a) P=10 W; (b) P=15 W

Fig. 11. Detection results of X-ray non-destructive detector. (a) Weld of the aluminum alloy without pretreatment; (b) weld of the aluminum alloy with oxygen mass fraction of 16.2%; (c) weld of the aluminum alloy with oxygen mass fraction of 9.56%; (d) weld of the aluminum alloy with oxygen mass fraction of 3.23%

Fig. 12. Micrographs of cross-section of weld and corresponding to local enlarged detail. (a) Weld of the aluminum alloy with oxygen mass fraction of 16.2%;(b) weld of the aluminum alloy with oxygen mass fraction of 9.56%; (c) weld of the aluminum alloy with oxygen mass fraction of 3.23%

Fig. 13. Weld morphology of aluminum alloy with oxygen free surface. (a) Cross-sectional morphology; (b) local enlarged detail