Low temperature electron irradiation of α-brass; defect annealing and assignment

Abstract

α-CuZn (30%) was irradiated at 20 K with 1 MeV and 1.5 MeV electrons and isochronally annealed. Following 1 MeV irradiation two electrical resistivity annealing steps were observed, one centered at 100 K with energy of 0.25 ± 0.05 eV and one centered at 255 K with an energy of 0.8 to 0.9 eV. The 100 K step does not go below the pre-irradiated value while the 255 K step does and they are assigned as Cu interstitials and vacancies, respectively. Following 1.5 MeV irradiation, the above two steps appear and, in addition two other steps, a small step at 75 K and a broad step from 120–210 K which falls below the pre-irradiated value. These steps are assigned to Zn interstitials.

These annealing stages are discussed in relation to those of pure Cu and the evidence indicates that the interpretation of Stage III of pure Cu as an interstitial-type defect cannot satisfy the observations on α-CuZn. Since a different type of explanation is required for α-CuZn such an explanation may be applicable to pure Cu also.

The large decrease in electrical resistivity which occurs in the 255 K annealing stage indicates that α-brass can be fully ordered by appropriate irradiation technique and that the critical temperature lies in the range of 240 to 250 K.