Effect of cyclic stress reduction on the creep behaviour of Al-40 wt%Zn alloy

The effect of cyclic stress reduction on the creep behaviour of A1-40 wt% Zn alloy during transformation was investigated. The influence of cyclic stress reduction of increasing amplitudes (18–47%) and frequencies (0.12–0.29 Hz) was systematically examined at various deformation temperatures (573–633 K). Both transient and steady state creep parameters, ββ, n   and εs·, were found to be higher under cyclic stress reduction condition than under the static condition for the same peak stress. Increasing temperature increased all the measured parameters. Increasing frequency and cyclic stress reduction increased the parameters n   and εs· but decreased ββ. The frequency was found to be more effective than the cyclic stress reduction amplitude. Activation energies for the transformation temperature region around 603 K, which were found to be independent on either frequency or amplitude of cyclic stress reduction but depend on the temperature range, characterized a dislocation mechanism involving grain boundary sliding or grain migration.