Bubble formation in Zr alloys under heavy ion implantation

We report here the results of a study conducted to examine the effect of Kr ion irradiation on bubble formation in Zr alloys. We used the HVEM/Tandem facility at Argonne National Laboratory to irradiate several Zr alloys, including Zircaloy-2 and Zircaloy-4, at temperatures from 300 to 800 C and to doses up to 2 × 10¹⁶ion.cm^-2. Both in-situ irradiation of thin foils as well as irradiation of bulk samples with an ion implanter were used in this study. For the thin foil irradiations, a distribution of small bubbles in the range of 30-100 angstrom was found, at all temperatures with the exception of the Cr-rich Valloy where bubbles of 130 angstrom were found. The irradiation of bulk samples at high temperature (700-800 C) produced large faceted bubbles (up to 300 angstrom) after irradiation to 2 × 10¹⁶ion.cm^-2. The results are examined in the context of existing models for bubble formation and growth in other metals.