LAUSR

Abstract Eutectic high entropy alloys, with lamellar arrangement of solid-solution phases, offer a unique combination of high strength and elongation to overcome the strength-ductility trade-off seen in conventional alloys. However, there is very limited understanding of the passivation mechanisms in these complex alloys. Here, localized corrosion behavior of AlCoCrFeNi2.1 eutectic high entropy alloy was evaluated in NaCl solution using scanning vibrating electrode technique (SVET). Overall, the AlCoCrFeNi2.1 alloy showed very similar corrosion current density to 304 stainless steel in NaCl solution. The microstructure of the eutectic alloy consisted of L12/B2 lamellar structure with L12 containing higher fraction of Cr, Co and Fe, while B2 had higher concentration of Al and Ni. For both un-polarized and polarized conditions, preferential dissolution of the B2 phase was found to be the predominant corrosion initiation mechanism. This was attributed to the higher content of Cr and Co in the L12 matrix. The B2 phase was anodic with respect to the L12 matrix in the localized micro-galvanic cells formed in the microstructure. Tactical partitioning of constituent elements maybe used as an effective design strategy for developing corrosion resistant eutectic alloys with excellent mechanical properties.