Aluminium alloys that were deliberately underaged exhibited both an enhanced creep resistance at elevated temperatures and high responses to secondary aging at 20 to 65C. These phenomena appeared to be strongly influenced by the presence of vacant lattice sites, and positron annihilation spectroscopy was used to study the roles of solute/vacancy interaction during precipitation in an aged Al-Cu-Mg-Ag alloy.

Role of Vacancies During Creep and Secondary Precipitation in an Underaged Al-Cu-Mg-Ag Alloy. A.Somoza, C.E.Macchi, R.N.Lumley, I.J.Polmear, A.Dupasquier, R.Ferragut: Physica Status Solidi C, 2007, 4[10], 3473-6