• A novel decarburization treatment effectively controls carbon content and prevents δ-ferrite formation in low-density steels.
• Decreasing carbon content transforms full austenite to a dual-phase austenite/ferrite structure, while (Ti,V)C carbides remain stable.
• Carbon loss reduces strength due to weakened solid solution strengthening, but alters work hardening behavior.
• Deformation mechanisms shift from dislocation planar glide in austenite to cross-slip and dislocation cell formation in ferrite at higher strains.