Resume: The prediction of microstructure during processing needs to characterize the phase transformation occurring during the thermal treatments and their kinetics. In-situ high-energy synchrotron x-ray diffraction experiments performed during temperature variations allow the characterization of the phase evolution. For some transformation conditions, the continuous recording of diffraction diagrams evidences clearly intermediate phases. The quantitative analysis of the diffraction diagrams gives the transformation kinetics of each phase as well as their cell parameters. Transformation kinetics obtained by this method are compared to results obtained by electrical resistivity.
Equipe: Département SI2M : Département SI2M : Microstructures et Contraintes
Resume: We have investigated the microstructure evolutions in the Ti17 near beta titanium alloy during heat treatments. The phase transformation has first been studied experimentally by combining X-ray diffraction analysis, electrical resistivity and microscopy observations. From a series of isothermal treatments. a IT diauram has been determined, which takes into account the different morphologies. Then, a Johnson-Mehl-Avrami-Kolmogorov (JMAK) model has been successfully used to describe the phase transformation kinetics during either isothermal or cooling treatments. Finally, the coupling of the JMAK model to the finite element software ZeBuLoN allowed us to investigate the evolution of the spatial distribution of the different morphologies during the cooling of an aircraft engine shaft disk after forging. (c) 2006 Elsevier B.V. All rights reserved.
Equipe: Département SI2M : Microstructures et Contraintes