Size effects in tensile testing of thin cold rolled and annealed Cu foils

Thin copper foils of varying thickness were tested in tension at room temperature. The thickness of the samples was between 10 and 250 μm, length and width were scaled according to the thickness. Two types of samples were tested: as-received samples and annealed samples. The microstructure of the foils was determined in detail by means of several methods. If samples of the same processing condition were compared, there was a clear dependence of the mechanical behavior on the thickness of the foils in the tensile test. When the thickness was reduced from 250 to 10 μm, the fracture strain decreased for the as-received foils from approximately 20% to 0.2% and for the samples with heat treatment from 35% to 15%. It has to be stressed that this size effect occurred in the absence of considerable strain gradients and for samples with a comparable microstructure.