Mechanical and microstructural characteristics of polycrystalline copper rolled asymmetrically to a high deformation level

Highlights: • Normal force and torques in symmetric and asymmetric rolling were determined experimentally and calculated; • Detailed characteristics of microstructure and mechanical properties were determined; • Effect of rolling asymmetry on grain refinement and intra-grain fragmentation was found; • Texture change due to a shear stress component, induced by rolling asymmetry, was documented; • It was shown that modification of material microstructure depends both on asymmetry ratio and rolling gap geometry. -- Abstract: The paper presents mechanical characteristics of the symmetric and asymmetric rolling processes as well as microstructure and material modifications of asymmetrically rolled polycrystalline copper. Mechanical aspects of the rolling process were examined experimentally and studied using the Finite Element Method. It was confirmed that the rolling normal force is reduced and distribution of torques between two work rolls are strongly modified in asymmetric rolling process, as compared with the symmetric one. The microstructure characteristics of asymmetrically rolled polycrystalline copper were examined using the EBSD technique, optical metallography and X-ray diffraction. It was found that asymmetric rolling leads to a grain refinement, an important modification of selected microstructure parameters, a slight modification of mechanical characteristics, a texture rotation around transverse direction and a homogenization of the shear strain and texture. It has to be underlined that an important contribution of the present work consists in a detailed study of the mechanical characteristics, related with material microstructure examination, for asymmetric and symmetric rolling processes. Experimental determination of the rolling normal force and distribution of torques between two work rolls is accompanied by theoretical predictions. Another interesting result is that microstructure modifications depend not only on the asymmetry ratio, but also on the way of inducing rolling asymmetry (modification of rolling gap geometry in the present case case).