Microstructural evolution in a Cu-Zr alloy processed by a combination of ECAP and HPT

A Cu-0.1% Zr alloy was processed by equal-channel angular pressing (ECAP) for up to 8 passes and the samples processed through 4 and 8 passes were then sectioned into disks and further processed by high-pressure torsion (HPT) for 5 turns. Measurements were taken for the microhardness distributions on cross-sectional planes of the ECAP billets and on the HPT disks and the microstructures were examined using transmission electron microscopy and electron back-scatter diffraction. The results demonstrate that a combination of ECAP and HPT leads to additional grain refinement, higher hardness values and a larger fraction of boundaries having high angles of misorientation. The minimum average grain sizes recorded in these experiments were similar to 280 and similar to 260 nm at the center and edge of a disk, respectively, after processing through 8 passes of ECAP and 5 turns of HPT. The results contrast with an earlier report using high-purity Cu where a combination of ECAP and HPT gave a mixture of ultrafine and coarse grains due to the occurrence of dynamic recrystallization during the torsional straining. (C) 2013 Elsevier B.V. All rights reserved.