Positron Lifetime Study in Al-Li Alloys

Abstract
Light alloys such as Al-Li binary alloys are very important from the technological point of view due to their mechanical properties. The Al-rich side of the Al-Li binary alloy for Li concentrations between 5% and 25% atomic contains at room temperature a two-phase region formed by the α terminal solid solution and the ordered metastable δ'-phase Al₃Li. We present a systematic positron lifetime study for Li content below and above 5at% (the appearance of δ'-phase) in the Al-rich side of the binary alloy to investigate the influence of Li content and also the influence of Zr addition. We also present the study of the formation and dissolution of δ' precipitates, the recovery behaviour of an electron irradiated alloy, aging studies to monitor Li losses, and the Li influence on the nucleation of defects in quenched alloys. The technique has proved to be very sensitive to Li-rich zones in the α solid solution and to the growth and dissolution of δ' precipitates due to the high positron affinity for Li in an Al matrix.