Influence of the Initial Microstructure on the Kinetics of Microstructural Evolutions During Ageing in the Titanium Alloy Ti17Wednesday (28.09.2016) 11:45 - 12:00 Part of:
Nicolas Maury1,2, Moukrane Dehmas1,3, Benoît Denand1,3, Elisabeth Aeby-Gautier1,3, Benoît Appolaire4, Claude Archambeau-Mirguet2, Jérôme Delfosse5, Philippe Emile2
1Institut Jean Lamour, UMR 7198 CNRS-Université de Lorraine, Parc de Saurupt, CS 50840, 54011 Nancy Cedex, France
2Airbus Operations S.A.S., 316 route de Bayonne, 31060 Toulouse, France
3LABoratory of EXcellence Design of Alloy Metals for low-mAss Structures (“DAMAS” Labex), Université de Lorraine, France
4LEM ONERA-CNRS, 29 avenue de la Division Leclerc, 92322 Châtillon, France
5Airbus Group Innovations, 12 rue Pasteur, BP-76, 92152 Suresnes, France
Titanium alloys are increasingly used in the aeronautical industry due to their high strength-to-rate ratio. For β-metastable alloys in particular, a very good combination of strength and ductility is obtained for a bimodal microstructure consisting of "primary" α precipitates as well as "secondary" α precipitates. In this study, the influence of the "primary" α grain microstructure on the precipitation kinetics and sequences of "secondary" α phase during ageing has been investigated. Several initial microstructures, consisting of "primary" α grains with different fractions, morphologies, sizes, densities and spatial distributions have been designed. The influence of the heating rate on the decomposition of the β-metastable phase was studied essentially by in-situ electrical resistivity and by in-situ high energy synchrotron X-ray diffraction. The influence of the heating rate on the decomposition sequence of the β-metastable phase and the transformation domains is confirmed whatever the initial microstructure. Moreover, it is shown that the initial microstructure influences the precipitation kinetics and therefore the resulting microstructures. These results are summarized in continuous heating transformation diagrams.