The positron annihilation lifetime spectra of the under-aged and peak-aged Al-Li-Cu-Mg-Zr alloys were measured in the range from cryogenic to room temperature. The positron annihilation lifetime spectra show that the defect behaviours between two samples in the whole process of temperature rising are similar
but amount of the recovered vacancies is much greater in the peak-aged sample than in the under-aged one
and the average open space of defects in the peak-aged one is larger. With the particle δ’(Al3Li) growing in aging
the bulk election density in the alloy is increased and the strength enhanced.