Surface degradation mechanisms in a eutectic high entropy alloy at microstructural length-scales and correlation with phase-specific work function

High entropy alloys represent a new paradigm of structural alloy design consisting of (near) equal proportions of constituent elements resulting in a number of attractive properties. In particular, eutectic high entropy alloys offer a remarkable combination of high strength and good ductility from the synergistic contribution of each phase in the eutectic, thereby circumventing the strength-ductility trade-off in conventional structural materials. In the present study, wear and corrosion behavior were evaluated for the AlCoCrFeNi 2.1 eutectic high entropy alloy consisting of BCC (B2), and FCC (L1 2 ) lamellae. A transition from adhesive to oxidative wear was observed in reciprocating wear analysis. The L1 2 phase with lower hardness preferentially deformed during the wear test. The ratio of hardness to modulus was almost two times higher for the B2 phase as compared to L1 2 . The overall corrosion resistance of the eutectic high entropy alloy was comparable to 304 stainless steel in 3.5 wt% NaCl solution. However, detailed microscopy revealed preferential dissolution of the B2 phase. Phase-specific scanning kelvin probe analysis showed relatively higher electropositivity for the B2 phase as compared with L1 2 , supporting the selective corrosion and higher coefficient of friction of B2.