Commercial sheets need effective pretreatment to eliminate work hardening and anisotropy, and improve their forming properties to meet the requirement of micro-forming process. Compared with the traditional heat treatment, the electropulsing treatment (EPT) process has some advantages of performance improvement and consumes less energy and is environmentally friendly. It is a potential pretreatment method or process for sheets of micro-forming. In this paper, the effect of EPT on copper sheets with varying thicknesses and different grain sizes is studied. Electropulsing can significantly improve the plasticity of cold-rolled sheet, and plasticity improvement effect was better than that of heat treatment. The mechanical properties of copper sheets with different thicknesses which undergo electropulsing show the same size effect as that of samples without electric pulse. After EPT of copper sheets with different grain sizes, the flow stress difference decreased, which weakened Hall-Petch effect. As the thickness of copper sheets decreased, the threshold of current density for plasticizing effect increased. Based on the analysis of the dislocation motion induced by electropulsing, the mechanism of electropulsing to improve the plasticity of copper sheet was presented, which provides a reference for future research on the pretreatment process for micro-forming materials.

This study investigated the relationship between the Σ3 boundaries, dislocation slip, and plasticity in pure nickel wires after grain boundary (GB) modification. Both quasi in situ tensile tests and simulations were employed. During plastic deformation, twins surrounded by Σ3 boundaries may exhibit a good deformation coordination. With an increase in strain, the slip systems corresponding to the maximum Schmid factor and the actual activated slip systems remain unchanged. Even sub-grains can maintain the dominant slip system of their origin matrix grains. Slip systems with slip planes (111) and (1−1−1) are the most active. Moreover, random boundaries have strong hindering effects on dislocations, and the nearby stress accumulates continuously with an increase in strain. In contrast, Σ3 boundaries demonstrate weak blocking effects and can release the nearby stress due to their unique interfacial structures, which is favorable for improving plasticity. They are more penetrable for dislocations or may react with the piled dislocations. In addition, some Σ3 boundaries can improve their geometrical compatibility factor with an increase in the strain, which enhances the deformation coordination of the grains. The research results provide a better understanding of the plasticizing mechanism for face-centered cubic (fcc) materials after grain boundary modification.