Mechanochemical and environmental factors in intergranular corrosion of additively manufactured AlSi10Mg

The mechanochemical origin of intergranular corrosion (IGC) in AlSi10Mg additively manufactured by laser-based powder bed fusion (PBF-LB) has been investigated using electrochemical, microstructural, and stress analyses. A combined framework of electrochemical and microstructural characterizations, along with the residual stress analysis, has been employed to correlate the microstructural heterogeneity with corrosion performance. It is found that melt pool boundaries (MPBs) are characterized by a fine grain size, which results in increased susceptibility to the IGC attack. Scanning electrochemical microscopy measurements show that IGC initiates within MPBs, where fine grains and the microgalvanic difference between the Si-rich network and the Al matrix generate localized electrochemical activity. Electrochemical data reflect the IGC trends, with MPBs yielding a higher corrosion current density, lower charge-transfer resistance, and deeper IGC attack. An aggressive peroxide-enriched environment induces oxide film breakdown and deeper IGC penetration, diminishing the influence of variations in PBF-LB parameters. These findings demonstrate that IGC in AlSi10Mg produced by additive manufacturing arises from the combined influence of melt pool structures, residual stresses, and electrolyte chemistry.