Positron annihilation lifetime technique was one of the most important nuclear non-destructive techniques. It was used to study the thermal vacancies in one of the most important engineering aluminum alloys – the 2024 Al-alloy. Quenching experiments were usually performed on thin specimens to ensure a uniform quenching rate throughout the specimen. The specimens were prepared with dimensions of 0.15 x 1.5 x 1.5 cm3. After grinding, polishing and etching, samples of 2024 were homogenized (12h, 673K) and annealed (1.5h), before being quenched in water (277K). Positron lifetime measurements followed. From such measurements, it was possible to deduce the vacancy formation enthalpy, which in combination with the results of self-diffusion measurements, gives a value for migration enthalpy of the vacancy. These were very important quantities in the study of the annealing of irradiation induced defects. The use of the quenching technique in the positron annihilation study has the advantage that it allows a distinction between vacancy and dislocation.

Thermal Vacancies and Self-Diffusion Energy in 2024 Al-Alloy by Positron Annihilation Lifetime Technique. E.A.Badawi, M.A.Abdel-Rahman, M.S.Abdallah: Physica Status Solidi C, 2009, 6[11], 2349–51