Positron studies of vacancy migration behaviour of quenched nickel

In this note we report our present program of Doppler broadening studies in quenched Ni. Specimens of pur Ni were preannealed in a high purity nitrogen atmosphere at 0.9 Tm and quenched into baths of either concentrated HCl at 203 K or liquid nitrogen. In both cases we finf evidence of vacancy clustering at around 630 K. In addition, the sample quenched into HCl shows a recovery stage at around 170 K which is not observed in the liquid nitrogen quenched sample. This indicates interaction of the specimen with the HCl bath and its possible contamination. A conjecture involving contamination of the samples with hydrogen is presented. (author) 15 refs., 2 figs