An Ultrastrong and Ductile Duplex Lightweight Steel with Dual-Nanoprecipitation

In this study, a duplex lightweight steel with the compositions of Fe-30Mn-9Al-1C-1V-5Ni (wt.%) was designed, and its microstructure and mechanical properties were analyzed after simple rolling and heat treatment. The microstructure of duplex lightweight steel consists of austenite and B2 phases, with the dual-nanoprecipitation of L′1₂ type long-range ordered domains and VC carbides within the austenite. The steel exhibits an ultra-high strength-ductility combination, with a yield strength of 1316 ± 16 MPa, a tensile strength of 1458 ± 11 MPa, and a total elongation of 11.7 ± 1.2%. Its high strength is primarily attributed to hetero-deformation induced (HDI) strengthening, solid solution strengthening, and precipitation strengthening. Meanwhile, the substantial dislocation accumulation in both austenite and B2 phases, coupled with the HDI hardening from intense heterogeneous deformation near grain/phase boundaries, collectively confers the steel with excellent ductility.