Microstructure Characteristics Affecting Bendability of Copper Alloys

The bendability of copper alloys varies depending on the annealing temperatures after cold rolling. This study investigated the microstructural factors affecting bendability, with particular focus on the influence of dislocation parameters. Electron backscatter diffraction and X-ray diffraction line profile analysis were used to evaluate the dislocation parameters. It was found that as the annealing temperature increased, bendability improved as a result of enhanced ductility. A decrease in the dislocation density was confirmed as a microstructural change accompanying the rise in the annealing temperature. As dislocation density decreased, the mobility of dislocations increased, leading to improved ductility and consequently better bendability. However, even under low annealing temperature conditions where little decrease in dislocation density occurred, ductility and bendability were still improved. In these low annealing temperature conditions, dislocation rearrangement progressed and the crystallite size increased. The increase in the crystallite size suggests enlargement of the dislocation cell size. It is presumed that the increase in the dislocation cell size enhanced dislocation mobility within the cells, thereby improving ductility and bendability.