Beta to alpha transformation kinetics and microstructure of Ti-6Al-4V alloy during continuous cooling
Résumé
In the present paper, an approach based on the Kolmogorov-Johnson-Mehl-Avrami (KJMA) model has been developed and applied to study the transformation kinetics of the beta phase in Ti-6Al-4V titanium alloy during cooling. To this purpose, Differential Scanning Calorimetry (DSC) tests have been conducted using a set of cooling rates ranging from 10 to 50 degrees 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 alpha Widmanstatten morphology (alpha(W)). Microstructural observations along with the calculated values of the Avrami index and of the activation energy suggest that the growth of the alpha(W) platelets obeys a mixed mode combining the vanadium diffusion and a displacive mechanism. (C) 2016 Elsevier B.V. All rights reserved.