Microstructure and Properties of Industrially Cast 8021 Battery-Foil Aluminum Alloy with Combined Fe and Ce Additions

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To address the prevalent defects in industrially cast 8021 aluminum alloy for battery foil, including coarse iron-rich phases that sever the matrix and hard-to-remove micrometer-scale inclusions, alloys with different chemical compositions were manufactured on a 100-ton integrated industrial melting and holding production line. The regulatory principles and underlying mechanisms of Fe–Ce composite microalloying on solidification thermal behavior, melt purification efficiency, as-cast microstructure, mechanical properties, and corrosion resistance of the alloy were systematically investigated. The results show that when the mass fractions of Fe and Ce are 1.7% and 0.3%, respectively, the mean intercept length of the α-Al grains of the alloy is reduced by 29% compared with the reference alloy. The acicular iron-rich phases are modified into dispersively distributed short rod-like and granular particles, and the filtration removal efficiency of micro-inclusions in the melt is significantly improved. The ultimate tensile strength of the alloy reaches 94.0 MPa, and the elongation is increased to 44.2%. The corrosion current density in 3.5 wt.% NaCl solution is only 20% of that of the Ce-free reference alloy. Through multi-stage effects including melt purification, grain refinement and second-phase modification induced by joint Fe and Ce additions, the combined addition of Fe and Ce simultaneously improves the metallurgical quality and service performance of the alloy. This work provides theoretical support and engineering references for the stable industrial production of high-performance aluminum foil for lithium-ion battery packaging.