Phase-field Modeling of Structural Elongation and Alignment of (α+γ) Microstructure in Fe–0.4C Alloy during Thermomagnetic Treatment

Abstract

During last decade, the phase-field method has emerged across many fields in materials science as the powerful tool to simulate and predict the complex microstructure developments. In this study, the microstructure changes of g precipitation in polycrystalline a phase during thermomagnetic treatment in Fe-0.4C alloy are modeled using the phase-field method. Using phase-field simulation, the model reasonably represents microstructure changes in Fe-0.4C system quantitatively. In particular, it is shown that the structural elongation and alignment of the (aϩg) two-phase microstructure is influenced by the anisotropic carbon diffusion induced by the magnetic energy at the initial stage of the g phase formation. Modeling of microstructure developments with the framework of the phase-field method is shown to be a very effective strategy to predict and analyze complex microstructure formation.

Structural control of Fe-based alloys through diffusional solid/solid phase transformations in a high magnetic field

“…The effects of a magnetic field on carbon diffusivity have been reported by Nakamichi et al [45] and Ohtsuka and Hao [46] and they both found that carbon diffusivity is retarded by a magnetic field, but they did not find any anisotropy of diffusivity. Koyama and Onodera [47] have modeled the structural change and carbon distribution for the lath martensite to austenite transformation in a magnetic field using the phase-field method. They found that the carbon distribution is affected by a magnetic field and results in the formation of an elongated structure.…”

Phase-field modeling of microstructure evolutions in magnetic materials

“…Since the magnetic energy E d suppresses phase decomposition along the direction of magnetic moment, composition modulation along the direction of external magnetic field does not progress [57]. [69]. The microstructure change in the upper row demonstrates the temporal evolution of the phase field that represents the polycrystalline grain structure, where the gray and white regions indicate the α ferrite phase and γ austenite phase, respectively.…”

“…The following simulation is an attempt at modeling this complex microstructure change by the phasefield method. Figure 5 shows the two-dimensional simulation of phase transformation and microstructure development in Fe-0.4 mass%C at 1023K with an external magnetic field along the vertical direction [69]. The sequence of phase transformation and microstructure changes with isothermal aging is represented in figures 5(a)-(d).…”

Phase field simulation of spinodal decomposition under external magnetic field

“…The coupled simulations have been performed in several real magnetic material systems, for example, Ni 2 MnGa ferromagnetic shape memory alloys [30], FePt nanogranular thin films [31], Co-Sm-Cu rare-earth magnets [32], Fe-Cr-Co alloys [33], and Fe-C steels [34]. In the above studies, the micromagnetic approach was used directly under the assumption of ''strongenough'' external magnetic field.…”