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Titre: TEM Study of High-Temperature Precipitation of Delta Phase in Inconel 718 Alloy
Auteur(s): Moukrane Dehmas, Jacques Lacaze, Aliou Niang et Bernard Viguier
Journal: Advances in Materials Science and Engineering
Année: 2011
Volume: 2011
Pages: 9
DOI: 10.1155/2011/940634
ISSN: 1687-6822
Résumé: Inconel 718 is widely used because of its ability to retain strength at up to 650 degrees C for long periods of time through coherent metastable gamma `' Ni(3)Nb precipitation associated with a smaller volume fraction of gamma' Ni(3)Al precipitates. At very long ageing times at service temperature, gamma `' decomposes to the stable Ni(3)Nb delta phase. This latter phase is also present above the gamma `' solvus and is used for grain control during forging of alloy 718. While most works available on delta precipitation have been performed at temperatures below the gamma `' solvus, it appeared of interest to also investigate the case where delta phase precipitates directly fromthe fccmatrix free of gamma `' precipitates. This was studied by X-ray diffraction and transmission electron microscopy (TEM). TEM observations confirmed the presence of rotation-ordered domains in delta plates, and some unexpected contrast could be explained by double diffraction due to overlapping phases.
Projet: Département SI2M : Microstructures et Contraintes

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