Modelling of the diffusional austenite-ferrite transformation

ABSTRACT

The austenite-ferrite transformation is the key metallurgical tool to tailor properties of low alloyed steels and remains an active area of research. Models have yet to be developed with truly predictive capabilities for phase transformations in multi-component commercial steels. This review provides a critical analysis of the various austenite-to-ferrite diffusional transformation model approaches that have been significantly broadened over the past decade by modelling at different length scales, i.e. classical macro-scale models have been augmented with simulations at the meso-scale and atomistic scale. Both semi-empirical and fundamental models are reviewed with an emphasis on polygonal ferrite formation in low and medium carbon steels. Formation of ferrite with more complex morphologies (i.e. irregular/bainitic/Widmanstätten ferrite) is also discussed. In particular, approaches to describe the interaction of alloying elements with the austenite-ferrite interface are critically analysed. The paper concludes with an outlook on the proposed austenite-ferrite transformation modelling work for the next decade.

KEYWORDS:

• Steel
• austenite
• ferrite
• nucleation
• diffusion
• interfaces
• solute drag
• multi-scale modelling‌

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1 Following Howe et al. [53] we have used the term ‘displacive’ to refer to transformations that involve a shape change. This should not be confused with the unfortunately common use of the term ‘displacive’ to refer to ‘diffusionless’ transformations.