Nano-scale twinned Cu with ultrahigh strength prepared by direct current electrodeposition

An equiaxed grained nanotwinned Cu was firstly prepared by direct current electroplating using composite gelatin and poly-2-sulfur-2-propane sodium sulfonate additive, whose microstructure was similar to that prepared by pulse electroplating. This equiaxed grained nanotwinned Cu exhibited an ultrahigh tensile strength of 764 MPa, about 40% higher than that of columnar grained nanotwinned Cu. It suggested that the ultrahigh strength of Cu can be achieved through a microstructure of fine equiaxed grained nanotwin rather than large columnar grained nanotwin. It was thought that the grain growth along preferred orientation could be prevented through the dynamic competitive adsorption of poly-2-sulfur-2-propane sodium sulfonate and gelatin, which well explained the microstructural modification from columnar grain into equiaxed grain after SPS addition. The preparation of nt-Cu with ultrahigh strength by direct current electroplating has a potential application in production of ultrathin Cu foil used in lithium ion battery.