Microstructure dependence of strength and elongation of electrodeposited Cu foils

Abstract

The mechanical properties of Cu foils are critical for their applications in advanced electronic circuits and batteries. Here we investigated the microstructure dependence of mechanical properties of electrodeposited Cu with 9 μm in thickness. We found the strength of Cu foil increases by reducing the twin thickness. Interestingly, there exists a peak for elongation with decreasing grain size especially along the foil thickness. Microstructure characterizations of deformed Cu foils show that more geometrically necessary dislocations are stored for accommodating the incompatible deformation of more neighboring grains as the grain size decreases. However, as the grain size becomes too small, dislocation density is lowered due to the limited storage room and even grain growth happens. Both evolutions result in an optimal grain size for superior dislocation storage capacity and elongation. Our findings provide a strategic and fundamental guide for developing high-performance Cu foils.