Stacking fault energy and its influence on high-temperature plastic flow in Zr-Sn alloys

Abstract

Deformed α-zirconium-tin alloys were studied by means of X-ray diffraction and the results were analysed by the line-broadening method. Stacking fault probabilities were estimated and found to be 2·6, 5·6, 7·6 and 10 × 10^-2 in zirconium containing 0, 0·7, 3 and 5 wt.-% tin, respectively. The corresponding fault energies are 240, 116, 85 and 62 mJ/m², respectively. The results are used to show that the unpinning of attractive junctions is a plausible rate-controlling mechanism at high temperatures, as has been previously suggested. The present model calls for the thermally-activatable junction to be a few Burgers vectors long and for the strengthening associated with tin addition to be due to the enhanced stability of the attractive junctions which results from the observed decrease in stacking fault energy. The rate of high-temperature flow in zinc and cadmium and the strengthen- ing of zinc that accompanies the addition of cadmium are also shown to be consistent with this explanation.