Enhancing Strength-Ductility of Cu Foils with Slanted Nanotwinned Microstructure

Nanotwin (nt) strengthening is recently considered as the fifth strengthening mechanism in a certain material. It has been demonstrated that columnar nt-Cu films have excellent mechanical properties and great thermal stability. They can be fabricated by magnetron sputtering. Such a technique is costly because of its low deposition rate. In order to reduce manufacturing expenditure, rotary electroplating was adopted in this current study thanks to its simple and rapid deposition. We are able to produce a new microstructure of nanotwinned copper (nt-Cu) with slanted columnar grains. We found that the slanted columnar microstructure of nt-Cu is attributed to the enhanced mechanical properties. We fabricated the nt-Cu foils using rotary electrodeposition with various current densities and annealed them at some elevated temperatures. The results show that the slanted columnar nt-Cu foils have greater tensile strength and ductility than that of straight columnar counterparts. We suspect that the incline of slant degree leads to the activation of multiple dislocation slip systems. The strengthening effect of slanted grains contributes to the enhanced tensile strength and ductility of the nt-Cu foils, accordingly. As the current density and additive concentration increase, the slant degree between columnar grains and electroplating substrate is more inclined. The current method with high deposition rate is thus potential for mass production of high strength-ductility nt-Cu foils.