Positron studies of solute aggregation in age-hardenable aluminum alloys

The application of the positron annihilation spectroscopy (PAS), specifically lifetime and Doppler broadening (DB) techniques, to the study of age-hardening in Al alloys is presented together with a short discussion of the physical basis of both methods. First, some examples of positron lifetime spectroscopy studies, regarding the kinetics of solute clustering in Al–Cu–Mg and of the transformation of Guinier–Preston zones into semi-coherent η′ precipitates in a commercial Al–Zn–Mg alloy, are given. Secondly, modern applications of DB PAS, making use of a slow positron beam and of two gamma-ray detectors in coincidence, are also described. Results regarding solute–vacancy aggregation in laboratory-prepared Al–Cu and Al–Cu–Mg supersaturated alloys, as well as precipitation phenomena in a commercial alloy of the 7XXX series, are presented as examples.