Influence of alloying elements on the dislocation loops created by Zr+ ion or by electron irradiation in α-zirconium

Pure zirconium and four annealed α-zirconium-based alloys (Zr-1760 ppm wt O, Zr-1% Nb-430 ppm O, Zr-1% Nb-1800 ppm O, Zircaloy-4) have been studied by transmission electron microscopy after 500 keV Zr+ ion or 1 MeV electron irradiation performed at high temperature (≥ 4000C). The dislocation loops were found to all have b=1/3a<11anti 20> type Burgers vectors, and were preferentially in {10anti 10} type planes; in the case of electron-irradiated Zr-1760 ppm O, the larger loops were found to be of interstitial type. Alloying elements increase the loop density. The kinetics of loop growth was observed in-situ during 1 MeV electron irradiation between 400 and 7000C: oxygen was found to reduce considerably the growth speed of loops. In-situ annealing at 450 or 5000C after ion irradiation led to a large coalescence of loops in the case of pure zirconium, but modified only slightly the defect structure of the alloys. (orig.)