Microstructural Evolution and Kinetics for Post-dynamic Transformation in a Plain Low Carbon Steel

The post-dynamic transformation (post-DT), which could occur during isothermal holding after hot deformation, was investigated by using both dilatometry method and optical microstructural observation in a plain low carbon steel. The results indicates that the kinetics of post-DT at deformation temperature between Ae3 and Ar3 can be well described by the Avrami equation: X=1−exp(−ktn), but the n value is lower than that of the corresponding static transformation due to the early impingement of formed ferrite grains. Furthermore, the ferrite-to-austenite re-transformation was measured by dilatometry during the isothermal holding after hot deformation above Ae3 temperature, which suggests that dynamic transformation can indeed occur even above Ae3.