Coincidence Doppler broadening and 3DAP study of the pre-precipitation stage of an Al–Li–Cu–Mg–Ag alloy

Abstract Pre-precipitation solute clustering in Al–Li–Cu–Mg–Ag and Al–Cu–Mg–Ag alloys has been investigated by coincidence Doppler broadening (CDB) spectroscopy of positron annihilation and three-dimensional atom probe (3DAP) analysis. Although Ag–Mg co-clusters form in the Al–Cu–Mg–Ag alloy in the early stage of aging, no evidence for the co-cluster formation was obtained from the Li containing alloy using 3DAP. While CDB spectra indicated that vacancies are associated with Ag after aging for 15 s in the Al–Cu–Mg–Ag alloy, vacancy–Ag association is suppressed in the Li containing alloy. Based on the 3DAP and CDB results, the reasons for the completely different clustering behaviors observed in these two similar alloys are discussed.