Controlled cold rolling effect on microstructure and mechanical properties of Ce-modified SAF 2507 super duplex stainless steel

Controlled cold rolling impacts on microstructure and mechanical properties of the rare earth Ce-modified SAF 2507 super duplex stainless steel (SDSS) are investigated towards a better application and development prospective over the pristine SDSS. Rolling was performed at room temperature with the deformation level in a range of 30%-90%. A large amount of dislocations into the ferrite phase turned out, and their density increased with the deformation. While, emergence of dislocation plugs group, ferrite grains get refined to nanometer scale during the deformation process. In addition to deformed bands within austenite, formation of alpha'-martensitic phases and significant increment in their volume fraction are detected and attributed to deformation-induced martensitic transformation. Elongation of the ferrite and austenite microstructures along the deformation direction under the action of high strain also resulted in fibers formation gradually. Correspondingly, significant increase in the strength index while decrement in the plasticity index are observed. Moreover, cold rolling deformation not only affects the tensile fracture morphology but also switches it from a typical ductile to a ductile and quasi-cleavage mixed fracture.