Study of vacancies in the intermetallic compound Ni3Al by positron annihilation

Specimens of the intermetallic compound Ni 3 Al were irradiated by 2 MeV electrons at room temperature or quenched from 900 degrees C to about 1300 degrees C and subsequently annealed isochronally. The behaviour of the vacancies was studied using the positron lifetime. The vacancies annealed out around 215 degrees C. The formation energy of a vacancy was determined to be E v F =1.6+or-0.2 eV. The activation energy for the motion of the vacancy was estimated to be E v M =1.2+or-0.2 eV. The annealing of the vacancies was found to be a second-order reaction.