Direct influence of recovery behaviour on mechanical properties in oxygen-free copper processed using different SPD techniques: HPT and ECAP

Oxygen-free copper of 99.95 wt.% purity was severely deformed at room temperature by two modes of severe plastic deformation, equal-channel angular pressing (ECAP) and high-pressure torsion (HPT). ECAP was performed using 4, 16 and 24 passes, and HPT was performed using 1/2, 1 and 10 turns. The results show that while recovery occurs during both ECAP and HPT processing, copper shows a faster recovery rate with HPT processing than ECAP. The occurrence of recovery was observed at an equivalent strain exceeding ∼12 that led to an enhancement in the uniform plastic deformation. The influence of recovery behaviour on the mechanical properties was investigated using X-ray diffraction, microhardness and tensile testing.