Effect of extrusion ratios on microstructural evolution, textural evolution, and grain boundary character distributions of pure copper tubes during hydrostatic extrusion

Abstract

This study fabricated Cu tubes by hydrostatic extrusion at various extrusion ratios from 2.7 to 6.5 at ambient temperature and then investigated the effects of the extrusion ratios on the microstructural evolution, textural evolution, and coincidence site lattice (CSL) boundary distribution. The hydrostatic extrusion process affected the grain recovery when the Cu tube was hydrostatically extruded at a certain extrusion ratio, resulting from the decrease in dislocation density calculated by the kernel average misorientation (KAM) values based on EBSD data. The fraction of the low-energy Σ 3 boundaries increased sharply at the highest extrusion ratio, resulting in grain recrystallization, followed by grain growth. The rolling texture components present in microstructure of Cu tubes are a function of the extrusion ratio. This study reports for the first time that the microstructure of Cu tubes can be developed by grain recovery and recrystallization, as well as by increasing the content of the rolling texture components. This is attributed to the heat generated during severe plastic deformation (SPD) at an extrusion ratio of 6.4, and the adiabatic heat plays a key role in dislocations, thus overcoming the obstacles faced during thermal activation and boundary migration under specific conditions of hydrostatic extrusion.