Role of intermetallic networks in developing high-performance austenitic steel

Austenitic steels are renowned for exceptional ductility and toughness, yet their widespread application is hindered by low strength. Enhancing their strength while preserving ductility is crucial for scientific and industrial purposes. In this study, we successfully fabricated heterostructured austenitic steels via stepwise controllable precipitation and recrystallization and break the strength-ductility trade-off. Initial precipitation induces nonshearable B₂ nanoprecipitates within the austenitic matrix, and subsequent partial recrystallization introduces intermetallic B₂ networks along deformation bands. Advanced characterizations verify that the dense nanoprecipitates in the matrix confer high strength, while the networks accommodate strain through nanoparticle formation and anisotropic plastic deformation of the B₂ phase, as well as the stacking faults and mechanical twins within austenite. Collectively, these mechanisms contribute to a high yield strength of 1200 MPa and good ductility of 25%, exceeding previous high-performance austenitic steels. This work can provide insights into the design of strong and ductile austenitic steels and the processing-microstructure-property relationship of heterostructured materials.