Effect of rolling deformation amount on microstructure and properties of 2507 Duplex Stainless Steel

SAF2507 duplex stainless steel samples featuring heterostructured characteristics were fabricated via cold rolling at various reduction rates followed by annealing at 1273K for 1minute. The phase composition, microstructure distribution, and corrosion resistance of SAF2507 alloy were investigated and analyzed using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM),and electrochemical testing.Furthermore, the influence of diverse microstructural states on mechanical properties was evaluated through quasi-static tensile and cyclic loading tests to elucidate the underlying strengthening and toughening mechanisms. The results indicate that increasing the rolling reduction significantly,the grain sizes of ferrite and austenite phases in the heterogeneous samples are significantly refined, and the geometrically necessary dislocationsdensity of the two-phase grains increases significantly.Compared with the coarse-grained sample, the rolled and annealed sample exhibits heterogeneous zone boundary affected regions on both sides of grain boundaries, phase boundaries, and twin boundaries, showing a distinct strain gradient. This leads to heterogeneous deformation-induced (HDI) strengthening and strain hardening during tensile deformation.Consequently, the 90%-1273 specimen exhibited the optimal synergy of mechanical properties,demonstrating better corrosion resistance, with a yield strength of 715MPa, a tensile strength of 939MPa, and a uniform elongation of 24.8%. This microstructural design significantly enhanced strength while maintaining excellent ductility, thereby effectively overcoming the strength-ductility trade-off dilemma typically observed in metallic materials.