Influence of surface pretreatment on porosity and microstructure of laser welding in AlSi10Mg alloys sheets fabricated by laser powder bed fusion

Surface pretreatment is of great significance for improving the welding quality of metal materials, especially aluminum alloys. At present, the welding process is introduced to join the laser powder bed fusion (LPBF) AlSi10Mg alloys or their repair during manufacturing or service. However, the high susceptibility of hydrogen pores is one of the most important problems encountered in the fusion welding process of LPBF AlSi10Mg alloys. To clarify the influence of the surface state of the base metal on the hydrogen pore characteristics, the LPBF AlSi10Mg sheets were pretreated by chemical cleaning treatment (CCT), mechanical polishing treatment (MPT), and chemical cleaning treatment after mechanical polishing treatment (MPT-CCT) before laser welding. Subsequently, the hydrogen pore characteristics, microstructure, and micro-hardness of the welded joints were investigated. The experimental results show that laser welding with MPT-CCT significantly reduces the porosity and pore diameter. In addition, MPT-CCT can eliminate most of the broken and discontinuous surface oxide film and Mg enrichment. In summary, the necessity of MPT-CCT for LPBF AlSi10Mg alloys is analyzed systematically, which is of great significance to improve the welding quality.