Etude expérimentale et modélisation des cinétiques de transformation de phase dans un alliage de titane

Auteur : Nabil KHERROUBA
Année : 2017
Domaine : Métallurgie
Type : Thèse de doctorat
Etablissement : Ecole nationale polytechnique d'Alger
Résumé en PDF :  (résumé en pdf)
Fulltext en PDF :  (.pdf)
Mots clés : Ti-6Al-4V, KM-JMA, additivity, nucleation – growth

Résumé :

The aim of this thesis is to experimentally study and to model the kinetics of α + β → β → αII phase transformations in Ti-6Al-4V alloy for isothermal and non-isothermal conditions. To this purpose, several technics have been performed (DSC, SEM, optical microscopy, in-situ electrical resistivity and XRD). The KM-JMA equation has been used to describe the kinetics of phase transformations during isothermal holdings. An approach based on the additivity rule has been developed to adapt the KM-JMA equation to non-isothermal phase transformations and is compared to the one using the fictitious time. Kinetics parameters (n, k and Q) have been determined using this approach and discussed based on the microstructural analysis. Mechanisms of the α + β → β → α phase transformations have been discussed by considering the microstructural analysis and the kinetics parameters already determined. Finally, the βm → αII phase transformation kinetics in isothermal conditions has been simulated with the MatCalc software and modelled using both the nucleation – growth theory and the KM-JMA equation.