Influence of surface pre-treatments on porosity and microstructure of laser welding in AlSi10Mg alloys sheets fabricated by selective laser melting

Abstract The surface pre-treatment is of great significance for improving the welding quality of metal materials, especially aluminum alloys. At present, the welding process is introduced to achieve the joining of the selective laser melting (SLM) 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 SLM AlSi10Mg alloys. To clarify the influence of the surface state of the base metal on the hydrogen pore characteristics, the SLM AlSi10Mg alloys sheets were pretreated by chemical cleaning treatment (CCT), mechanical polishing treatment (MPT) and chemical cleaning after mechanical polishing (MPT-CCT) before autogenous laser welding. Subsequently, the hydrogen pore characteristics, microstructure and micro-hardness of the weld joints were investigated. The experimental results show that the autogenous laser welding with MPT-CCT pre-treatment conspicuously reduces the porosity and pore diameter. In addition, TEM results show that MPT-CCT pre-treatment can eliminate most of the broken and discontinuous surface oxide film and Mg enrichment. In summary, the necessity of MPT-CCT surface pre-treatment for SLM aluminum alloy parts is analyzed systematically, which is of great significance to improve the welding quality.