Corrosion behavior of a high-entropy AlCrFeNiMn alloy in a high-temperature supercritical CO2 environment

• The AM-HEA alloy had a duplex microstructure with α region surrounded by B2 phase. • S-CO 2 corrosion caused dual structure and less surface product in α region. • The B2 region consisted of Mn-rich granular and flocculent layer after corrosion. • A compact Al 2 O 3 film was formed in the B2 region to protect AM-HEA from corrosion. • The inward diffusion of C into the B2 matrix resulted in the formation of Cr carbides. A high-entropy AlCrFeNiMn alloy (AM-HEA) was corroded in a high-temperature supercritical CO 2 environment at 500 °C and 25 MPa. The AM-HEA has a duplex structure with Ni,Al-enriched α region domains surrounded by Fe,Cr-enriched B2 region domains. The B2 region experienced severe corrosion, leading to the formation of large-faceted Mn-rich oxides on the exterior and flocculent oxides in the interior. Conversely, the Ni,Mn-rich domains showed minimal corrosion. A uniform, thin Al 2 O 3 layer developed as a subsurface layer on both structures, enhancing the corrosion resistance of the AM-HEA.