The early stages of Si or Mg containing clusters in Al-Mg-Si alloys are experimentally extremely difficult to observe and atom probe tomography (APT) is the only possible imaging technique. A new strategy for the measurement of the as-quenched condition and the initial stages of natural aging has been applied. To hinder uncontrolled natural aging of the as-quenched condition sample preparation has been performed by cryogenic focused ion beam (FIB). Moreover, a new direct cryogenic transfer method of the samples into the APT analysis chamber has been utilized. Samples for the as-quenched condition, long term natural aging and different cryo-FIB sample preparation strategies have been successfully measured.
The quantification of early stage clustering is still difficult due to the spatial noise of the APT data. Additionally surface migration of Si during the experiment is known to generate artifacts in the vicinity of poles. Adjusting experimental parameters is known to keep this problem at a minimum, but still makes the overall interpretation difficult.
The data is corrected for artifacts and the effect of natural aging as well as the influence of cryo-FIB damage on clustering will be discussed within the framework of a customized APT data analysis.