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International audienceWe have studied the correlation between field evaporated atoms during an atom probe tomography experiment. The evaporated atoms have been shown to be highly correlated both in time and in space. This correlation can be explained by the dynamic distribution of the electric field at the surface of the sample. The evaporation sequence follows the distribution of zones where the electric field intensity is higher. The distance of correlation between successively evaporated atoms corresponds to the mean size of these zones and the time of correlation corresponds to the mean time necessary to evaporate the entire zone

Modern wide field-of-view atom probes permit observation of a wide range of crystallographic features that can be used to calibrate the tomographic reconstruction of the analyzed volume. In this study, methodologies to determine values of the geometric parameters involved in the tomographic reconstruction of atom probe data sets are presented and discussed. The influence of the tip to electrode distance and specimen temperature on these parameters is explored. Significantly, their influence is demonstrated to be very limited, indicating a relatively wide regime of experimental parameters space for sound atom probe tomography (APT) experiments. These methods have been used on several specimens and material types, and the results indicate that the reconstruction parameters are specific to each specimen. Finally, it is shown how an accurate calibration of the reconstruction enables improvements to the quality and reliability of the microscopy and microanalysis capabilities of the atom probe.

This article addresses gaps in definitions and a lack of standard measurement techniques to assess the spatial resolution in atom probe tomography. This resolution is known to be anisotropic, being better in the depth than laterally. Generally the presence of atomic planes in the tomographic reconstruction is considered as being a sufficient proof of the quality of the spatial resolution of the instrument. Based on advanced spatial distribution maps, an analysis methodology that interrogates the local neighborhood of the atoms within the tomographic reconstruction, it is shown how both the in-depth and the lateral resolution can be quantified. The influences of the crystallography and the temperature are investigated, and models are proposed to explain the observed results. We demonstrate that the absolute value of resolution is specimenspecific. 2/23

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The pair-correlation function applied to 3D Atom Probe reconstructed volumes has been used to study the influence of a pre-ageing treatment (363K) on the early stages of precipitation at 458K in an Al-Mg-Si 6016 alloy. Mg-Si short-range positive pair correlation (clustering) is shown to form after a pre-ageing treatment. The hetero-atomic clusters are thought to act as preferential nucleation sites and lead to a finer dispersion of precipitates after ageing.

a b s t r a c tThe influence of artificial ageing on the corrosion behaviour of the recently developed 2050 Al-Cu-Li aluminium alloy in chloride-containing solutions was studied. Corrosion tests showed that artificial ageing changed the corrosion morphology of the alloy from intergranular to intragranular and decreased the corrosion potential of the alloy. Transmission electron microscopy observations combined with small-angle X-ray scattering measurements were used to establish a link between the distribution of T 1 precipitates and the corrosion behaviour.⇑ Corresponding author. Tel.: +33 (0)5 34 32 34 07; fax: +33 (0)5 34 32 34 98.