Vacancies and self-interstitials in copper--gold alloys

Enhanced diffusion was measured in copper-gold alloys containing 10, 15, 20, and 25 at. percent Au during neutron and during electron irradiations in the temperature range between 60 and 2000C, after plastic deformation at -1960C, and after quenching from 3500C. It was found that the ordering rate during irradiation in a Cu3Au alloy is initially determined by a vacancy and with increasing degree of order by an interstitialcy diffusion mechanism. The resulting migration activation energies of vacancies and self-interstitials were 1.04 and 0.68 eV, respectively. This is the first time that a vacancy migration energy could be derived from an irradiation experiment. The migration activation energy of vacancies was also determined after quenching from 3500C and a value of 1.0 eV was found in agreement with the one obtained from the irradiation experiment. The annihilation of only vacancy-type defects in stage III is excluded on the basis of the low ordering rate observed in this stage