Pure aluminum was irradiated at about 90°K using 2-MeV electrons. Isochronal and isothermal annealing studies were carried out. The isochronal anneals were for 10 and 30 min at temperatures 10°C apart. The isothermals were for 64 min at temperatures 20°C apart. The major results were: Stage III occurs by a second-order process with activation energy $E_{\mathrm{III}}=0.62\mathrm{}\pm 0.04$ eV. From the fact that this activation energy agrees well with that observed after quenching, it is concluded that stage III in aluminum occurs by vacancy migration.

• Received 18 August 1967

DOI:https://doi.org/10.1103/PhysRev.165.787