Vacancy-solute aggregates formed in the alloy Al-Cu(4.38 wt%)-Mg(1.62 wt%) after age-hardening thermal treatments were studied by positron lifetime spectroscopy, 2-detectors Doppler broadening spectroscopy and by differential scanning calorimetry (DSC). When the temperature of aging is raised from 20 degreesC to 60 degreesC, the concentration of Cu associated vacancies is increased. A re-ordering of the chemical species bound to vacancies and an energetic stabilization of the solute aggregates are observed at room temperature after aging at 180 degreesC from the average positron lifetime as well as on DSC thermograms.