On the stress sensitivity parameter in high temperature creep of Al-3 wt% Mg

Abstract

Stress dependence of creep rates, internal and effective stress, as well as the apparent instantaneous strain associated with sudden stress changes during the steady-state creep of Al-3 wt% Mg were studied. The transition in stress exponentn is attributed to the change in the stress dependence of dislocation density and does not necessarily correspond to the change in the creep mechanism. The effective stress exponentn ^* is considered as the identifying parameter for the process controlliag the creep mechanism. The absence of the instantaneous plastic strain upon stress changes during creep shows that creep is mainly controlled by viscous glide motion of dislocations.