Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

ZP Sun and FZ Dai and B Xu and WZ Zhang, ACTA METALLURGICA SINICA- ENGLISH LETTERS, 32, 669-676 (2019).

DOI: 10.1007/s40195-019-00889-0

Coherent second phase often exhibits anisotropic morphology with specific orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening effect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial configuration. The final shape of the ferrite is closely related to the misfit between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content (BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifies that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.

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