Formation of precipitates and their effects on the mechanical properties in a Fe–Mn–Al–C austenitic low-density steel

κ-carbides serve as a strengthening phase in Fe-Mn-Al-C austenitic low-density steels, enhancing yield strength but reducing the work hardening rate due to slip plane softening effect. To address this issue, this study introduces strong carbide-forming elements Ti and V to regulate carbon distribution and then control κ-carbide precipitation. Without Ti and V addition, κ-carbides uniformly precipitate in the matrix after aging, with an average size of 10.8 ± 6.2 nm and a volume fraction of 7.4 ± 3.4%. The addition of Ti and V leads to the formation of (Ti, V)C carbides at high temperatures, which act as carbon sinks, reducing the matrix carbon content and thereby suppressing the homogeneous precipitation of κ- carbides. As a result, the κ-carbides precipitate at the edge of the (Ti, V)C carbides, with an average radius of 9.7 ± 8.5 nm and a volume fraction of 3.2 ± 2.8%. Compared to the uniform precipitation of κ-carbides in low-density steel without Ti/V additions, this modified precipitation behavior preserves the work-hardening rate and increases the tensile strength from 1004 MPa to 1096 MPa. TEM analysis reveals that both steels exhibit planar slip deformation, but the Ti/V-modified steel shows narrower slip band spacing and more intense plastic deformation. This study establishes a novel microalloying strategy for optimizing precipitate distribution and mechanical properties in low-density steels.