The production and annealing of point defects in β-CuZn

Abstract

Ordered β-brass was irradiated with 1.5 MeV electrons at 20°K and then annealed. Three prominent decay stages occur at 40, 65 and 90°K with respective energies of about 0.03, 0.05 and 0.1 eV. These stages are similar to those which occur in pure metals and are therefore believed to arise from correlated interstitial—vacancy recombination. A stage occurs in the range of 100–150°K which is believed to arise from either uncorrelated interstitial migration or from the release of trapped interstitials. A long decay stage begins at 150°K and continues until it joins the thermal equilibrium curve above room temperature. It has a varying activation energy with about 0.4 eV at 200°K. The annealing goes well below the pre-irradiated value at 180°K and a similar effect is observed after irradiation at 78°K. This enhanced ordering is assigned to the vacancy. After quenching an unirradiated sample to − 14°C, transferring quickly to liquid nitrogen and then annealing, two stages are seen; one from −50 to about 0°C with an activation energy of 0.45 ± 0.05 eV and one in the range of 10–120°C with an activation energy ranging from 0.6 to 0.7 eV, the location of the latter stage depending upon the quench temperature. The lower temperature stage is assigned to the vacancy and the upper stage to vacancies trapped at antiphase domain boundaries. On the basis of these assignments it is understandable that the high vacancy mobility inhibits the retention of quenched-in disorder in this system.