In-situ X-ray diffraction evidence of dynamic transformation of austenite to ferrite during hot compression test in the single austenite phase field

Dynamic transformation (DT) of austenite to ferrite can take place in the single austenite phase field during thermomechanical processing as shown in the literature. However, despite significant progress on this topic, limited real-time evidence of DT has been published. To address this concern, an in-situ X-ray diffraction measurement was carried out on a pipeline steel before, during and after hot compression. The appearance of ferrite peaks is evident during deformation and these peaks disappear after 9 s of isothermal holding. This work provides an in-situ evidence of both forward and backward dynamic transformation complemented with energy calculations to validate the observations. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.