Achieving superior strength-ductility synergy of 2205 duplex stainless steel via dual-heterogeneous structure design

The trade-off between strength and ductility remains a persistent obstacle in the development of advanced structural materials. In the present study, a novel dual-heterogeneous structure with a bimodal grain distribution in both ferrite and austenite phases was fabricated via cold rolling and partial recrystallization annealing on solution-treated 2205 duplex stainless steel (DSS). The processed steel exhibited superior mechanical properties, with the yield strength increasing from 586 MPa to 903 MPa, and the ultimate tensile strength from 796 MPa to 1082 MPa, while maintaining a high total elongation of 35.3%. Based on in-situ electron backscatter diffraction (EBSD) and scanning electron microscope (SEM) analyses, the microstructural deformation behavior and strengthening mechanisms of the dual-heterostructured 2205 DSS were elucidated. The outstanding combination of strength and ductility was ascribed to the synergistic effects of grain refinement, dislocation strengthening, and hetero-deformation induced (HDI) strengthening. Moreover, the high ductility in DSS was attributed to the co-activation of cross-slip systems in ferrite {110} and {112} along with the single-slip systems in austenite {111}. These findings provide a new strategy for the design and development of high-strength and ultra-high-strength DSSs.