Beta to alpha transformation kinetics and microstructure of Ti-6Al-4Valloy during continuous cooling

Auteurs :  Nabil KHERROUBA, Mabrouk BOUABDALLAH, Riad BADJI, Denis CARRON, Mounir AMIR
Année : 2016
Domaine : Métallurgie
Type : Article de journal
Revue : Materials Chemistry and Physics
Résumé en PDF :  (résumé en pdf)
Fulltext en PDF :  (.pdf)
Mots clés : Continuous cooling, KJMA model, additivity rule, diffusion, Displacive mechanism

Résumé : 

In the present paper, an approach based on the Kolmogorov-Johnson-Mehl-Avrami (KJMA) model hasbeen developed and applied to study the transformation kinetics of the b phase in Ti-6Al-4V titaniumalloy during cooling. To this purpose, Differential Scanning Calorimetry (DSC) tests have been conductedusing a set of cooling rates ranging from 10 to 50 C/min. This approach allows the kinetics parameters,particularly the activation energy, to be calculated from a single DSC test using a simple linear regression.The microstructural analysis indicates that the microstructure is dominated by the a Widmanstatten €morphology (aW). Microstructural observations along with the calculated values of the Avrami index andof the activation energy suggest that the growth of the aW platelets obeys a mixed mode combining thevanadium diffusion and a displacive mechanism.