Evolution of mixed cementite morphologies during non-cooperative eutectoid transformation in Fe–C steels

• Published in: Computational materials science 2015-10, Vol.108, p.342-347
• Main Authors: Ankit, Kumar, Mittnacht, Tobias, Mukherjee, Rajdip, Nestler, Britta
• Format: Article
• Language: English
• Subjects: Carbon; Cementite; Coarsening; Divorced eutectoid; Eutectoid temperature; Materials science; Microstructure; Morphology; Non-cooperative growth; Phase-field method; Transformations
• ISSN: 0927-0256; 1879-0801
• DOI: 10.1016/j.commatsci.2015.03.002

[Display omitted] •Extension of the theory for a random distribution of preexisting cementite.•Numerical studies reveal overlapping eutectoid transformation modes.•Amended theory explains mixed cementite morphologies in transformed microstructure. We numerically investigate the characteristics of concurrent carbon redistribution pathways, as the ferrite–austenite front evolves during an isothermal eutectoid transformation starting from a random distribution of preexisting cementite particle. By analyzing the influence of initial interparticle spacing, arrangement and undercooling (below A1 temperature) on the curvature-driven coarsening, we generalize the present criteria of non-cooperative eutectoid transformation. We also propose plausible mechanisms that result in mixed cementite morphologies (spherical and non-spherical) in the transformed microstructure. For the chosen set of parameters, the present phase-field simulations suggest a strong competition between the cooperative, non-cooperative and coarsening regimes, as the transformation proceeds. The predominance of one or more of the three regimes during the intermittent stages, which depend on the local conditions, determine the cementite size distribution in the transformed microstructure.