Comparison of a copper processed by asymmetric unidirectional rolling (AUR) and cross rolling (ACR): Strain distribution, microstructure, texture, and mechanical properties

Abstract

In this work, the effect of strain path on the strain distribution, microstructural evolution, crystallographic texture, and mechanical behavior of electrolytic tough-pitch copper was investigated by simulation and experimental procedures. The asymmetric unidirectional and cross rolling processes with a thickness reduction of 90% were performed at room temperature. The asymmetric cross-rolling (ACR) gives much better through-thickness uniformity of shear strain distribution compared to the asymmetric unidirectional-rolling (AUR). The average equivalent strain of AUR and ACR after 90% rolling reduction was 3.99 ± 1.22 and 3.66 ± 0.26, respectively. Both AUR and ACR processes improved the particle distribution in the matrix. However, the particle distribution of the AUR sample was slightly more uniform compared to the ACR sample. The shape of primary grains in the AUR copper was straight while that in the ACR sample was zigzag. The average dislocation density of the AUR sheet was larger than that of the ACR sample (2.41 × 1016 m−2 vs. 2.31 × 1016 m−2). The major recrystallization mechanism in the AUR and ACR samples was discontinuous and continuous dynamic recrystallization, respectively. The main deformation textures (Copper, S, and Brass components, and α and β fibers) were weak in both samples due to the domination of recrystallization and shear textures in the cold-rolled copper. The recrystallization texture components in the upper region were stronger than in the lower region. The uniformity of the microhardness profile of the ACR sample was more than that of the AUR sample. The AUR sample had a larger strength and a smaller ductility compared to the ACR sample. The results showed that the strain path of asymmetric rolling was effective on the strain-hardening behavior of copper during the tensile test. The fractograph of the ACR sheet exhibited ductile dimples. However, the fractograph of the AUR sample revealed many ductile shear dimples and flat surfaces.