Enhanced corrosion resistance and repassivation kinetics associated with Nb-induced hierarchical heterostructures in laser-deposited eutectic high-entropy alloys

Repassivation capability critically governs the resistance of passive alloys to failure under localized film breakdown and dynamic perturbations; however, the concurrent enhancement of pitting corrosion resistance and repassivation ability remains a persistent challenge. This conflict becomes particularly pronounced in the archetypal eutectic high-entropy alloy AlCoCrFeNi 2.1 , where the inherent electrochemical heterogeneity between the dual phases readily provokes micro-galvanic corrosion. In this work, through controlled Nb alloying combined with laser deposition was employed to modify the microstructure of AlCoCrFeNi 2.1 alloy, producing a hierarchical heterogeneous architecture comprising nanoscale FCC/Laves lamellae and BCC/B2 nanocomposite regions. The results demonstrate that Nb alloying increases the Cr 2 O 3 content and introduces Nb-containing oxidized species into the passive film, thereby enhancing its stability and substantially improving the pitting corrosion resistance. Furthermore, the high-density heterointerfaces are accompanied by pronounced local strain heterogeneity, which may provide favorable structural conditions for interfacial reactions during passive-film reconstruction. These findings provide insights into the interplay between microstructural heterogeneity and dynamic passivation behavior in multiphase heterogeneous high-entropy alloys.