The interaction between the displacive transformation and the diffusion process during the bainitic type transformation was studied using a phase field model incorporating both processes. A chemical free energy density function was derived to represent thermodynamic properties of low-alloy steels at high supercooling conditions at which the direct transformation from austenite to ferrite at a constant carbon concentration is possible. The results demonstrate that in such conditions both the displacive transformation and diffusional decomposition process may play important roles controlling the transformation kinetics and microstructure. A fast displacive transformation is dominant at the onset of the transformation; however, the diffusion-controlled decomposition can take control over the transformation kinetics and even the ferrite morphology at later stages as a result of the formation of a carbon enriched layer around ferrite grains. Both plate-like and rod-like shapes of ferrite grains can be obtained depending on the thermodynamic conditions and diffusion mobility.

Bainitic transformation, Decomposition, Displacive transformations, Phase field models
dx.doi.org/10.1016/j.commatsci.2019.109079
Computational Materials Science
Department of Mechanical and Aerospace Engineering

Elhigazi, F. (F.), & Artemev, A. (2019). The interaction between the displacive transformation and the diffusion process in the bainitic type transformation. Computational Materials Science, 169. doi:10.1016/j.commatsci.2019.109079