Algorithms for atom probe tomography characterisations optimization of RPV steels at the atomic scale
Résumé
The Atom Probe Tomography (APT) is commonly used to characterize the nanostructure of RPV steels. The evolution of the mechanical properties is relatively well correlated with the nanostructure characteristics studied by this technique (mainly the density and the size of the solute clusters). Nevertheless, APT is subject to sampling problems, the volumes analyzed being much smaller than the elementary volume representative of the mechanical properties, and to possible instrumental aberrations. The results given by complex data processing used to detect and characterize small solute clusters may also differ between laboratories.Within the development of these useful algorithms, it is possible to check the reliability of the parameters chosen for the characterization of nanostructure of RPV steels, in particular solute clusters. The first algorithm is based on maximum separation method (MSM) and permits to compare different order to optimize the choice of this parameter. The second one proposes a sensibility analysis of the MSM parameters. The last one is a visualization of the microstructures with the local concentration method.The first applications have been done on model alloys thermally aged and will be presented.
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