Atom probe tomography characterisation of solute clustering in AA6111

A series of ageing treatments have been performed on AA6111 alloy samples for various periods ranging from 4 mins to 2 weeks ageing between room temperature and 180 ºC. The microstructures of these alloy samples have been carefully characterised using atom probe tomography in order to obtain quantitative information about the solute clusters and early-stage precipitates that are formed. Intriguingly, an iso- yield strength regime has been measured for samples aged variously with respect to temperature and duration, generating different precipitate microstructures. Ageing at a higher temperature produced larger early-stage precipitates at lower number density. In contrast, the yield strength of naturally aged samples increased with ageing time at room temperature and initially produced a higher number density of smaller solute clusters followed by a development in the microstructure to a lower number density of early-stage GP zone precipitates. The strengthening effect of different precipitate microstructures formed under different ageing treatments has been addressed.