Influence of austenite deformation on ferrite growth in a Fe–C–Mn alloy

The kinetics of ferrite transformation in a Fe–0.2C–2Mn (mass%) alloy after deformation in undercooled austenite region were studied with regard to alloying element-partitioned and partitionless growth. According to the local equilibrium theory of diffusion-controlled growth, partitioned growth controlled by slow Mn diffusion occurs at a low undercooling, whereas partitionless growth at a larger undercooling is the much faster process, which is controlled by carbon diffusion. The alloy with or without deformation was isothermally reacted at temperatures that encompass the two growth modes. The ferrite growth rate at each temperature increases by austenite deformation. The acceleration at higher temperatures is more significant, probably due to the larger contribution of stored deformation energy in the total driving force for ferrite transformation. The transition temperature from partitionless to partitioned growth of ferrite as well as Ae3 temperature increases after austenite deformation, resulting in acceleration of ferrite growth rates between the previous and new transition temperatures by 1–2 orders of magnitude.