Strengthening high-nitrogen austenitic stainless steel via constructing multi-scaled heterostructure

High nitrogen austenitic stainless steels (HNASSs) have received widespread attention owing to their outstanding corrosion resistance, excellent weldability and workability. However, these materials usually exhibit insufficient yield strength to satisfy the requirement in service because of their face-centered cubic (fcc) structure. Here, we report a novel material design strategy of constructing both grain-scaled and atomic-scaled heterostructure through applying appropriate thermo-mechanical treatment to improve the comprehensive mechanical properties of HNASS. The optimal comprehensive mechanical properties with a yield strength of 1361 MPa and a uniform elongation of 10.6% are achieved. The results show that the ultrahigh yield strength mainly originates from the lath structure consisting of local chemical order domains (∼490 MPa), and the satisfactory ductility benefits from both deformation twinning and dislocation slip. This work proposes for the first time the strategy to improve mechanical properties of HNASS by introducing the multi-scaled heterostructure, and guides the development of high-performance steels and many other advanced fcc materials.