Strain-hardening resilience via the cooperation of geometrically necessary dislocations and deformation twins in a strong and ductile lightweight high-entropy steel

In the net-zero era, the burgeoning demands within engineering applications require materials that are not only lighter and stronger but also ductile. A robust strain hardening, crucial for achieving high strength and ductility, is challenging due to limited dislocation density evolution. This study discovers a cooperative strain-hardening strategy in a newly designed high-entropy steel (HES) with a density of 6.82 g/cm3. 3 . In this lightweight HES, the duplex microstructure of compositionally complex austenite and D03 3 intermetallic compounds facilitates the interplay between geometrically necessary dislocations (GNDs) and deformation twins (DTs) during plastic deformation. It generates a strain-hardening resilience during deformation and yields a very high dislocation density of 6.62 x 1015 15 m-2, 2 , contributing to strain hardening of over 900 MPa and a large elongation of 47%. The resilient strain hardening achieved by the GND-DT cooperative strategy can be applied to various heterostructured alloys, offering a pathway for strong and ductile lightweight materials.