Additive manufacturing–induced microstructural hierarchy alters dealloying behavior in CoCrFeMnNi high-entropy alloy

Dealloying of high-entropy alloys (HEAs) remains poorly understood, particularly when processed via additive manufacturing. Here, we demonstrate that laser powder bed fusion (LPBF)–induced microstructural hierarchy alters the dealloying pathway of a CoCrFeMnNi HEA in boiling 50 wt% NaOH solution. The wrought alloy exhibits classical dealloying behavior (i.e., selective dissolution of Cr, Fe, Co and Mn), forming a Ni-rich porous film, whereas the LPBF alloy develops a columnar nanoporous layer guided by Ni/Mn-segregated cellular boundaries. Despite Mn being thermodynamically soluble in boiling caustic solution, Mn depletion at these boundaries is locally suppressed due to Ni enrichment, lowering the more reactive element content below the parting limit and promoting possible formation of Ni–Mn spinel oxide. This microstructural confinement also facilitates crack propagation along cell/grain boundaries under combined residual stress and porosity evolution due to dealloying. These findings unveil a unique dealloying–cracking interplay in HEAs, demonstrating that additive manufacturing–induced microstructural hierarchy can redefine corrosion mechanisms in complex concentrated alloys.