Effects of deep cold rolling on the evolution of microstructure, microtexture, and mechanical properties of 2507 duplex stainless steel

A commercial ferritic and austenitic duplex stainless steel was severely cold rolled at room temperature from 50% to 87.5% thickness reduction. The microstructure and microtexture evolutions of the cold-rolled steel were investigated by scanning electron microscopy, X-ray diffraction, transmission electron microscopy and electron backscattered diffraction. The results revealed that both constituent phases were severely deformed and morphologically elongated along the rolling direction. The plastic strain was preferentially partitioned into austenite phase during cold rolling due to the involvement of multiple deformation modes. As the deformation strain increased, the twin-matrix lamellae gradually rotated to coincide with the rolling plane, after which the localized shear deformation contributed to the formation of "eye" shaped domains composed of nanotwins/ fragmented fine structures. After 87.5% cold rolling, austenite phase was constituted by Brass {110}< 112 >, Goss {110}< 001 >, and S {123}< 634 > textures, and the formation of both deformation twins and shear bands leaded to a continuous texture transition from the Copper {112}< 111 > to the near-Goss and Brass orientations. A strong alpha-fiber (< 110 >//RD) accompanied with weak gamma-fiber (< 111 >//ND) texture was dominated in ferrite. Cold rolling significantly improved the strength of duplex stainless steel at the sacrifice of ductility. With the increasing of deformation strain, the fracture manner of the material changed from a mixture of ductile and brittle fracture to typical brittle fracture.