Effect of asymmetric cross-rolling on the microstructure, texture, and mechanical anisotropy of Fe–0.07C steel

Abstract

In this study, the impact of asymmetric cross-rolling on the microstructure, crystallographic texture, and tensile anisotropy of a low-carbon steel sheet was evaluated. In the microstructures of the cross-rolled sheets, elongated α grains appeared in TD–ND and RD–ND sections, while equiaxed and irregular grains were seen in the RD–TD plane of the sheets. The results indicated that the asymmetric cross-rolling weakens the texture and γ-fiber due to the change in the path of strain during the deformation. The high increasing rate of hardness from 50 to 75% thickness reduction was related to the elimination of ⟨100⟩∥ND (with a low elastic modulus (129 GPa)) in the 75% cross-rolled sheet. Compared with the as-received sheet, the average yield and tensile strengths after 75% cross-rolling were increased to 620.9 and 705.6 MPa, respectively, due to strain hardening. As the cross-rolling strain increased, the rate of increase in strength decreased. For all samples (except 75% cross-rolled sheet), the maximum yield and tensile strengths were obtained along transverse direction owing to the presence of strong 〈111〉∥TD and 〈110〉∥TD texture. The anisotropy results indicated that large-strain asymmetric cross-rolling decreased the mechanical anisotropy degree of low-carbon steel. With an increase in imposed strain to 50% and 75%, the fracture gradually changed from fully ductile to a combination of fully ductile and shear ductile types. The presence of uniform dimples in the 0°-loaded and 45°-loaded sheets for 25% and 50% cross-rolled samples demonstrated the comparable rate of nucleation and growth of microvoids, which led to similar behavior of stress–strain curves after the necking for these sheets.