To cite this version:Borge Forbord, Williams Lefebvre, Frederic Danoix, Hakon Hallem, Knut Marthinsen. Three Dimensional Atom Probe investigation on the formation of Al3(Sc,Zr)-dispersoids in aluminium alloys. Scripta Metallurgica, Elsevier, 2004, 51, pp.333-337. 10 Abstract. Three Dimensional Atom-Probe (3DAP) has been applied in order to study the nucleation of small, spherical and coherent Al 3 (Sc,Zr)-dispersoids. The results indicate that Al 3 (Sc,Zr) in the beginning of the nucleation process mainly consist of Al and Sc, while Zr enters the dispersoids at a later stage, i.e relatively Zr-rich shells seem to form around Sc-rich cores.

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Three-dimensional atom probe and field ion microscopy have been used to determine the composition of precipitates formed in several types of aluminium-based alloys. Special attention has been paid to local magnification artefacts, which are often suspected to strongly disrupt the precipitates' apparent composition. The charge state of Al ions has been used to identify the nature of precipitates (lower or higher evaporation field than the matrix) and also to determine the origin of Al ions observed in 3D reconstructions. The use of a cluster identification method, which allows erosion concentration profiles to be drawn, has revealed the importance of trajectory overlaps in the measurement of the precipitates' composition. By applying this method to low-evaporation-field precipitates in a 7XXX alloy, good agreement was found between atom probe measurements and observations in transmission electron microscopy and small angles X-ray scattering.

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