Abstract
The creep deformation behavior of aged AZ91 magnesium alloy under the cyclic stress reduction has been investigated in the temperature range 353-383 K. The microstructural evolution of the AZ91 magnesium alloy at different heat treatment conditions has been studied using optical microscopy and scanning electron microscopy. The minimum strain rate, (epsilon) over dotmin, was found to be higher under cyclic stress reduction condition than that under static creep condition for the same maximum stress. Cyclic creep acceleration is interpreted using the interaction of moving dislocations with the existing beta-phase (Mg17Al12) precipitates. The mean value of the activation energy of secondary creep stage was found to be equal to that quoted for lattice self-diffusion of magnesium mechanism.