Effect of grain refinement by ECAP on creep of pure Cu

The creep behavior of pure, initially coarse-grained Cu of 99.99% purity was investigated at a temperature of 473 K in tension and compression in dependence on predeformation by ECAP (route BC) at ambient temperature. Static recrystallization during heating to test temperature generates a microcrystalline structure; its homogeneity increases with increasing ECAP-predeformation. The high-angle boundaries are sufficiently closely spaced to exert a significant influence on work hardening and quasi-stationary deformation where generation and loss of free dislocations are at approximate balance. This influence is quantitatively interpreted in terms of control of deformation resistance shifting from low- to high-angle boundaries as predeformation increases and creep stress decreases. The microcrystalline structure created by the thermomechanical treatment consisting of ECAP and static recrystallization leads to favorable combination of relatively high creep resistance and high ductility at 473 K with fracture strains in the order of 0.5.