Activation parameters and deformation mechanisms of ultrafine-grained copper under tension at moderate temperatures

Mechanical properties, characteristic features of deformation behavior, the activation energy for plastic deformation, strain rate sensitivity and activation volume of ultrafine-grained (UFG) and conventional coarse-grained (CG) copper have been studied by tension in the temperature interval of 293–573 K and in the strain rate interval of 1.3×10−2–3.0×10−5 s−1. It is found that both the properties and the activation parameters differ significantly in UFG and CG copper suggesting the different deformation mechanisms. Plastic flow is shown to be controlled by grain boundary diffusion in the case of UFG copper. Considering the thermal activation analysis data and deformation relief appearing on the pre-polished surface of the test samples, the significant contribution of grain boundary sliding to the overall deformation during plastic flow of UFG copper at moderate temperatures is supposed.