Porosity, microstructure and mechanical property of welded joints produced by different laser welding processes in selective laser melting AlSi10Mg alloys

The welding process has been recently introduced to join of the materials fabricated by powder bed fusion (PBF) additive manufacturing (AM) to meet the requirement for the large parts and their repair in service. However, one of the main issues is the high susceptibility to the hydrogen pores occurred during fusion welding of the PBF aluminum (Al) alloys. Autogenous laser welding of a selective laser melting (SLM) AlSi10Mg alloy was firstly carried out in comparison with the casting AlSi10Mg alloy to examine the hydrogen pore characteristics. Singlepass welding with filler powders and laser melting deposition (LMD) welding were then performed on SLM AlSi10Mg alloys to reduce the hydrogen pores. The porosity, microstructure, microhardness and tensile property of the welded joints were investigated. As a result, a high susceptibility to hydrogen pores of SLM AlSi10Mg alloys is occurred in the weld metal (WM) of the welded joint produced by autogenous laser welding and singlepass laser welding due to the high hydrogen content pre-existing in the base metal (BM). However, LMD welding has been shown to effectively reduce the pore size and the porosity generated in the WM of SLM AlSi10Mg alloys. The laser welding of SLM AlSi10Mg alloys produces lower hardness and ultimate tensile strength (UTS) than that of the BM. However, the LMD welding of SLM AlSi10Mg alloys achieves higher hardness and UTS than those of the autogenous laser welding and single-pass laser welding, which is attributed to the refined microstructures and the reduced hydrogen pores in the WM.

Automated summary

The susceptibility to hydrogen pores in the welded joints of SLM AlSi10Mg alloys was investigated through different welding methods. It was found that autogenous laser welding and single-pass laser welding had a high sensitivity to hydrogen pores, while LMD welding effectively reduced the size and porosity of the pores. SLM AlSi10Mg alloys exhibited lower hardness and ultimate tensile strength in laser welding compared to LMD welding, which can be attributed to the refined microstructures and reduced hydrogen pores in the welded metal.