A combined characterization of clusters in naturally aged Al-Cu-(Li,Mg) alloys using small-angle neutron and X-ray scattering and atom probe tomography

A new methodology for the characterization of solute clusters leading to compositional fluctuations is presented and discussed. The methodology makes use of contrast variation arising from a combination of small-angle scattering using neutrons and X-rays, and adapts a model for solute correlation to extract the chemistry and length scale of clustered states after quench and after natural ageing. In three subsets of the Al-Cu system, Cu-rich clusters are reported for all cases. The presence of Mg strongly enhances Cu clustering in the naturally aged state and results in more than double the number of clusters in the complex Al-Cu-Li-Mg system. The results are compared with those obtained using atom probe tomography.