Evolution of microstructural homogeneity in copper processed by high-pressure torsion

Disks of coarse-grained pure Cu were processed by high-pressure torsion (HPT) and the microhardness and microstructural parameters were used to reveal the evolution of homogeneity. It is shown that the microstructures at the centers of the disks are significantly refined by HPT and an essentially homogeneous microstructure is achieved at strains above 15. An analysis demonstrates that microstructural homogeneity is achieved most readily in materials having either high or low, rather than intermediate, stacking fault energies.