Dependence of strain rate sensitivity upon deformed microstructures in nanocrystalline Cu

摘要

The creep behavior of nanocrystalline copper was experimentally characterized with nanoindentation using two sequential regimes,i.e., loading and holding. Significantly enhanced strain rate sensitivity was found within an unusually narrow range of creep rate in theholding regime, which is attributed to the deformed microstructure generated during the loading regime. By quantitatively analyzing thecreep rate and rate sensitivity exponent of NC Cu in the holding regime, both the grain boundary sliding (GBS) and dislocation activitiesare found to be responsible for the observed abnormal behavior, with the contribution of GBS decreasing with increasing grain size andincreasing with decreasing loading strain rate. These findings provide a potential way of adjusting the mechanical properties of nano-crystalline metals by pre-straining.