Enhanced Mechanical Properties of Multilayered Cu with Modulated Grain Size Distribution

A bulk multilayered copper with nano-sized grains (NG) as hard layer and ultrafine grains (UFG) as soft layer with the thickness ratio of about 10:1 is synthesized by electrodeposition. Microstructural studies by scanning electron microscope (SEM) and transmission electron microscope (TEM) reveal the alternating growth of well-defined layers with either nano-grains or ultrafine-grains. Tensile tests reveal that the layered nanostructured Cu exhibits an enhanced ductility of near 17.5% and high ultimate tensile strength of about 700MPa. The multilayered Cu exhibits a higher ductility without obvious loss of strength compared to the monolithic nano-grained Cu. The enhanced ductility is primarily attributed to two effects including the increased strain hardening ability and the effective adjustment to the local stress concentration brought by the periodic existence of the UFG layer in the NG matrix.