An interpretation of steady state creep

Abstract

Effective stress in steady state creep in aluminum was measured by the strain transient dip test technique with the aim to analyse the creep in terms of two separate kinetic processes driven by different components of the applied stress [sgrave]: the effective stress [sgrave]∗ and the internal stress [sgrave]i (Ahlquist, Gasca-Neri and Nix 1970). The analysis has led to values of’ the apparent activation energy of slip ‘, Q∗, and ‘the apparent activation energy of recovery’, Qi, which generally differ from the apparent activation energy of creep and, therefore, also from the activation enthalpy of lattice self-diffusion, and cannot be correlated with the process controlling dislocation glide velocity and recovery rate, respectively. This supports the contention that if [sgrave]∗ is measured by a dip test technique [sgrave]i, obtained as [sgrave]—[sgrave]∗, cannot be identified with the internal stress taking part in processes other than the dislocation glide. Assuming that the recovery is driven by the applied stress the creep in aluminum can be described in terms of recovery due to dislocation climb as a rate-controlling process.