On the microstructure and mechanical properties of severely cold shape rolled Cu

Processing by severe cold shape rolling of commercially pure Cu up to equivalent strain of 4.5 led to bimodality of structure with significant grain refinement to nano-scale. Microstructure of the processed copper was characterized by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) indicating the ultrafine structure including dislocation tangles, dislocation cells, subgrains, micrograins and nano/ultrafine grains with sharp grain boundaries. The bimodal structure with unequal distribution of grain sizes consisted of nanograins as well as larger grains, formed probably due to an inhomogeneity of deformation. The measurements of the mechanical properties showed an enhancement of microhardness to 114 HV and a high strength of 524 MPa with relatively good ductility that is proposed as a consequence of the bimodal structure.