Effect of stacking-fault energy on thermal activation of attractive junctions in change-in-stress creep of FCC metals

Abstract

Change-in-stress creep experiments involving increments as well as decrements of stress have been conducted on Ag, Au, Cu, Ni, Pb, Pd and Pt at temperatures at and below room temperature. The activation volumes (v) evaluated from the flow parameter, B (given by B=(Δ ln ε/Δτ)=v/kT) obtained by making stress increments, were found to be in the range 10² to 10⁴ b³, indicating the rate-controlling mechanism to be the intersection of glide and forest dislocations. The value of the flow parameter was found to be higher for creep following stress decrements than increments, the difference being a decreasing function of stress and temperature. The results were analysed in terms of the model, earlier suggested for aluminium, based on the formation of attractive junctions on stress decrement which causes a change in the number of elements participating in the activation event. The stacking-fault widths and energies evaluated for these metals based on the above model are found to be in good agreement with the reported values.