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Abstract
A quantitative experimental study of precipitation kinetics in complex situations is presented, using a variety of experimental tools: small-angle X-ray scattering, transmission electron microscopy and differential scanning calorimetry. In addition, a modelling approach is developed to describe the evolution of precipitate population during these complex situations. The response of AA7108 aluminium alloy in the T4 and T7 conditions to welding and more simple non-isothermal treatments is evaluated. It is shown that the variety of phenomena encountered, which encompass precipitate dissolution and coarsening, can be appropriately described by a simple model based on the discretization of the precipitate size distribution and on simple evolution laws. Second, a consistent model for both isothermal and non-isothermal precipitation is developed on an Fe–Cu alloy, and a method is devised for the independent calibration of all physical parameters involved by the model. Last, a quantitative study of the microstructure of AA2024 aluminium friction stir welds is presented, and is shown to explain the occurrence of strain localisation when these welds are mechanically loaded.
Acknowledgements
All the staff of the ESRF/D2AM beam line is gratefully acknowledged for providing the facilities for the SAXS experiments. Hydro Automotive Structures is acknowledged for providing the 7108.50 material and for financial support; ARCELOR Research S.A., as well as ONERA, are acknowledged for financial support. Dr. Claudio Dalle-Donne of DLR-Köln (Germany) is acknowledged for providing the FSW welds. The DGA of the French Ministry of Defence is acknowledged for financial support. Some of this work is part of a French scientific programme (CPR Précipitation), in collaboration with Arcelor, Pechiney, CNRS, CEA, INPG, INSA Lyon, Université de Rouen, Université Aix-Marseille III.
Dr. Pierre Vacher is gratefully acknowledged for providing access to the SeptD image correlation software of LMeca laboratory (Annecy, France). Prof. Y. Bréchet, Dr. P. Maugis, Dr. M. Perez are warmly thanked for fruitful discussions.