In situ natural ageing of Al-Cu-(Mg) alloys: The effect of In and Sn on the very early stages of decomposition

The influence of trace elements (0.01 at.% In/Sn) on the decomposition process of Al-Cu-(Mg) alloys during the very early stages of natural ageing has been investigated in situ by small angle X-ray scattering supported with differential scanning calorimetry and hardness measurements. In the binary Al-Cu alloy quenched-in vacancies are bound to In or Sn, resulting in a suppressed Cu clustering process. In Al-Cu-Mg room temperature hardening occurs much faster due to Mg entering the clusters. However, the influence of In or Sn is negligible. Cu and Mg possibly form complexes with quenched-in vacancies before they can reach a trace element atom.