Microstructure and texture evolution in low carbon steel deformed by differential speed rolling (DSR) method

The study examined the microstructural and textural evolution of low carbon steel samples fabricated using a differential speed rolling (DSR) process with respect to the number of operations. For this purpose, the samples were deformed by up to 4-pass of DSR at room temperature with a roll speed ratio of 1:4 for the lower and upper rolls, respectively. The DSR technique applied to low carbon steel samples resulted in a microstructure composed of ultrafine ferrite grains, approximately 0.4 µm in size, after 4-pass with a high-angle grain boundary fraction of ~65 %. The microstructural features of the ferrite phase indicated the occurrence of continuous dynamic recrystallization, beginning with the formation of a necklace-like structure of ultrafine equiaxed grains around the elongated grains, which were formed in the early stages of deformation, and ending with ultrafine recrystallized grains surrounded by boundaries with high angles of misorientations. In the pearlite phase, the microstructural changes associated with DSR deformation were presented by the occurrence of bending, kinking, and breaking of the cementite lamellar plates. In addition, the evolution of texture after DSR processing was affected by shear deformation and rolling deformation, leading to the formation of a texture composed of fractions of components with shear texture orientations such as {110} 〈001〉 (Goss) and orientations close to {112} 〈111〉, in addition to rolling texture components consisting mainly of α-fiber and γ-fiber.