Correlation study of self-annealing-induced recrystallization and grain growth mechanism in copper foil

Abstract

Copper foils demonstrate a tendency for self-annealing, which adversely impacts the stability of the products. The self-annealing induced recrystallization of copper foil is closely related to the grain growth mode. When copper foil grows in equiaxed grain mode, resulting in a decrease in tensile strength from 780 MPa to 330 MPa. Conversely, the columnar grain copper foil exhibits excellent room-temperature stability in mechanical properties. The mechanism of copper foil room temperature self-annealing behavior was put forward. It was found that the internal stress generated in the process of preparing copper foils is the key factor driving the recrystallization of equiaxed grains. This internal stress originates from nanocrystals and high-density dislocations, with the latter arising from the doping of organic elements. The initial high stress values and the plasticity of dislocations contributed to a noteworthy decrease in residual stress. As dislocation plasticity ensues, the anchoring of interstitial atoms gives rise to dislocation loops. The interaction between dislocation loops and coincident twin boundaries induces the formation of twin steps. The quantity of twins of equiaxed copper foil increases greatly after self-annealing. Conversely, the initial dislocation density of columnar grain copper foil is an order of magnitude lower than that of equiaxed grains.