Creep processes in pure aluminium processed by equal-channel angular pressing

It is suggested that creep of pure aluminium processed by equal-channel angular pressing (ECAP) occurs by diffusion-controlled movement of intragranular dislocations and by grain boundary sliding. The contribution of grain boundary sliding is increasingly higher with increasing number of ECAP passes. The coexistence of a dislocation process and grain boundary sliding may explain the observed decrease of the creep resistance with increasing number of ECAP passes. This is because high-angle boundaries are necessary in order to achieve grain boundary sliding. Therefore, an increase in the fraction of high-angle boundaries with increasing number of ECAP passes will essentially lead to increasing contribution of grain boundary sliding to the total creep strain, as it was observed experimentally.