Enhanced grain refinement of commercial pure copper using the ECAE of Al–Cu–Al tri-layer composite

Equal channel angular extrusion (ECAE) is a promising technique for production of ultrafine grained (UFG) materials of few hundred nanometers size. In this research, the grain refinement of copper strip is accelerated to ultrafine range by sandwiching it between two aluminum strips and then subjecting the three strips to ECAE process simultaneously. After passing the aluminum–copper–aluminum laminated billet through ECAE die up to 8 passes, tensile properties of the copper layer are evaluated. The optical, scanning and transmission electron microscopes, differential scanning calorimeter, and X-ray diffraction were used to characterize the microstructural changes. The results show that the yield stress of the middle layer (Cu) is increased significantly by about eight times after application of four consecutive passes of ECAE and then it is slightly decreased when more ECAE passes are applied. An ultrafine grain within the range of 150 to 200 nm is obtained in the Cu layer.