MODELING OF THE DYNAMIC TRANSFORMATION ABOVE THE AE3 TEMPERATURE

Abstract

The dynamic precipitation of ferrite during austenite deformation above the Ae3 temperature, was first reported by Yada et al. in the 1980s. These observations were later confirmed for a wide range of steel compositions and processing conditions. The aim of this work is to clarify the mechanism by which ferrite formation takes place above the Ae3 temperature. To that end, a simple model for ferrite growth as a result of the movement of disconnections under applied stress is established. This motion, opposed by the back stress, increases the Gibbs energy as a result of deformation of ferrite above Ae3. Preliminary calculation suggests that the dynamic transformation is possible near the Ae3 temperature for large stress. The results are discussed in terms of experiments using a deformation dilatometer.