Synergistic effect of crystallographic orientation and porosity: multi-mode corrosion mechanism of additive manufacturing Al-Fe-Mn-Sc-Zr alloy

Additive manufacturing enables precise microstructural control in high-strength aluminum alloys, yet the influence of volumetric energy density (VED) on corrosion mechanisms remains unclear. This study investigates the corrosion behaviour of a PBF-LB Al–Fe-Mn-Sc-Zr alloy across a VED spectrum (38.9∼138.9 J/mm3). We identify a threshold VED of 55.6 J/mm3 that yields optimal corrosion resistance, as evidenced by the lowest corrosion current density (1.29 μA/cm2) and minimal exfoliation-induced roughness. At the lowest VED, severe intergranular attack occurs (depth ∼105 μm), while the highest VED promotes exfoliation due to increased porosity (8.4%). Mechanistically, intergranular corrosion sensitivity is governed by crystallographic orientation, with (111)-oriented grains showing the highest susceptibility, whereas exfoliation corrosion is primarily dictated by porosity and grain size. These findings establish a microstructure-based rationale for corrosion control in additively manufactured aluminum alloys and provide guidelines for optimising PBF-LB parameters.