Microstructure and mechanical properties of pure copper plate processed by novel dynamic offsets and shear force adjustment rolling

Abstract

Asymmetric rolling is beneficial for grain refinement and properties improvement through mass production of metals. This study introduces a novel asymmetric rolling technology, known as dynamic offsets and shear force adjustment (DS) rolling. DS rolling not only achieves roll offset and differential speed/diameter, but maintains a constant offset angle in multiple passes. And rolling mechanics model, finite element model, and rolling experiment is established. The results indicate the advantages of DS rolling in reducing the vertical rolling force with increasing offset angles. Moreover, it is observed that the vertical rolling force initially decreases and subsequently increases as the roll-to-diameter ratio increases. DS rolling enhances both average strain and core strain compared to symmetrical rolling, consequently promoting uniformity in strain distribution and permeability into the core region. The shear stress is the primary factor contributing to the increase in equivalent strain during DS rolling. The adjustment of roller diameter ratio and offset angle allows for control over the shear stress level. DS rolling enhances mechanical properties and refines the grain structure. Notably, at an offset angle of 9°, DS rolling results in a substantial increase in microhardness on the upper surface, center, and lower surface of Cu by 3.31 %, 8.40 %, and 8.19 %, respectively, when compared to symmetrical rolling. Furthermore, DS rolling exhibits an enhanced tensile strength and elongation, yielding improvements of 5.12 % and 38.9 % compared to symmetrical rolling, respectively. Additionally, DS rolling leads to a reduction in grain size by 5.77 %, 17.3 %, and 21.7 % on the upper surface, center, and lower surface, respectively.

Keywords

• Dynamic offsets
• Rolling force model
• Finite element model
• Microstructure
• Mechanical properties
• Pure copper