High-quality surface smoothening of laser powder bed fusion additive manufacturing AlSi10Mg via intermittent electrochemical polishing

Though the laser powder bed fusion (LPBF) additive manufacturing (AM) AlSi10Mg alloy (LPBF AlSi10Mg) has been utilized for weldability and fatigue resistant property, its high surface roughness limits widespread application. Here, we report the surface roughness reduction of the LPBF AlSi10Mg via electrochemical polishing (ECP). A novel viscous layer formation mechanism is found on LPBF AlSi10Mg surface during the ECP process. An environmentally friendly NaOH based electrolyte was utilized to passivate the LPBF AlSi10Mg surface, resulting in successful ECP of the LPBF AlSi10Mg. Furthermore, the Si phase and its reaction products with electrolyte formed on the polishing surface were found to be a barrier for improving the surface quality of LPBF AlSi10Mg. Therefore, an intermittent removal of the polishing products on AlSi10Mg further improves the polishing effect, i.e., an intermittent electrochemical polishing (IECP) method was utilized to improve the polishing quality of LPBF AlSi10Mg. The surface roughness (Sa) is reduced by 87.7 %, and the corrosion current density (i(corr)) is decreased by 17 folds. The significantly improved polishing effect of IECP is dominated by removing ECP products constantly to enhance dissolution of Al element in AlSi10Mg and fluent dispersion of electrolyte and Al3+ in the metal-electrolyte interface.

Automated summary

The surface roughness of LPBF AlSi10Mg alloy was reduced through electrochemical polishing (ECP), with a novel viscous layer formation mechanism found during the ECP process. An intermittent electrochemical polishing (IECP) method was utilized to further improve the polishing quality. The significantly improved polishing effect of IECP was attributed to the constant removal of ECP products, enhancing the dissolution of Al element and promoting fluent dispersion of electrolyte in the metal-electrolyte interface.