Exceptional high-temperature corrosion resistance of multi-component alloys via modulating Al and Nb

The chemical compatibility of metallic materials with thermal transfer/storage media, which often involves aggressive working conditions (i.e., high-temperature, corrosive environments), challenges the safe operations of advanced and sustainable energy-related infrastructures. Here, we report the corrosion-oxidation behaviors of three multi-component alloys (MCAs) when exposed to a corrosive heavy-liquid metal condition (i.e., molten Pb at 650 ℃ with 10⁻⁶ wt% oxygen dissolved). The two compositions, Al_0.36Cr_0.67FeNi_0.98 (HAl11) and Al_0.27Cr_0.71FeNi_1.16Nb_0.17 (HAl8^Nb), show excellent corrosion-resistance via passivating a protective oxide scale on the alloy surface. Further characterizations of the oxide layers differentiate their corrosion-oxidation mechanisms: a protective Al₂O₃ oxide layer (with Cr and Fe segregation outmost) formed on HAl11 and a duplex oxide layer (outward growth of FeCr₂O₄/Cr₂O₃ layer plus inward growth of an Al₂O₃ layer) with internal oxidation on HAl8^Nb. Adding Nb improved the corrosion-oxidation resistance (“Nb-doping effect”) by enhancing the outward diffusion of metallic elements and promoting the rapid establishment of an alumina scale. Besides, the presence of AlNbO₄, which was predicted by thermodynamics calculation, lying between the spinel and Al₂O₃ formation, was also confirmed by experimental observations. Our findings advance the mechanistic understanding of MCAs’ performances in extreme conditions and provide novel strategies for designing corrosion-resistant alloys targeting aggressive application environments.