Improving surface electrochemical polishing quality of additive manufactured AlSi10Mg by reconstituting the Si phase

Novel processing method for various alloying materials using metal laser powder bed fusion (PBF-LB) additive manufacturing (AM) have opened opportunities for fabricating complex parts with desirable mechanical properties due to its flexibility. However, the resulting metal parts often have poor surface roughness. Hybrid machining process based on chemical surface finishing and AM technology is a promising approach for fabricating optical surfaces on AM metals, which affords both optical demands and mechanical performances. Herein, by understanding material segregation and grain structure formation in the PBF-LB AlSi10Mg alloys, a facile method for improving the surface electrochemical polishing (ECP) quality by reconstituting the Si phase using metallurgical heat treatment is developed. After the ECP, the surface roughness decreased by approximately 82.5 % of the heat-treated sample (HT300), while the roughness of the untreated sample (UT) only decreased by 64.4 %. The mechanism of enhancing the electrochemical polishing (ECP) effect through the reconstruction of the Si phase aims to improve the diffusion ability of the electrolyte on the ECP products. This is achieved by increasing the pore size of the Si network on the substrate and coarsening the Si microstructure. Additionally, it promotes the transfer of metal ions near the interface of AlSi10Mg and the electrolyte.