Vacancy-solute aggregates which formed in Al-4.38Cu-1.62wt%Mg were studied by using 2 different positron annihilation techniques (lifetime spectroscopy, 2-detector Doppler broadening spectroscopy), plus differential scanning calorimetry. The results showed that the Cu concentration in the environment of a vacancy increased when the aging temperature was increased from 20 to 60C. Structural transformations which produced a re-ordering of the chemical species in contact with vacancies, and an energetic stabilization of the solute aggregates, occurred at room temperature after aging at 180C.

Vacancy-Solute Aggregates in Al-Cu-Mg Alloys Studied by Positron Annihilation Techniques. M.Biasini, G.Ferro, P.Folegati, G.Riontino: Physical Review B, 2001, 63[9], 092202 (4pp)