Grain refinement of micrometer-scale Cu foils through accumulative cyclic deformation

The microstructure evolution of the 190 mu m-thick Cu foils subjected to repeatedly bending loading was investigated. Wefound that the grains in the micron-scale foil were refined into subgrains with a size of about 0.5 mu mthrough a removal of twin boundaries and an introduction of a high frequency of high angle boundaries (> 15 degrees) with accumulative cyclic deformation. With increasing strain rate (loading frequency), the grains are completely refined into well-defined fine grains with high angle boundaries. Such the microstructure refinement induced by accumulative cyclic deformation may provide a potential strategy for grain refinement of small-scale materials.