Theoretical and numerical investigations on grain boundary migration due to inverse pinning

Effective interface energies of various homo-and hetero-interfaces of iron were calculated with an aid of phase-field modeling, taking into account geometric constraints by competition among grains or interfaces. Calculated effective interface energies for ¤/£, ¤/¤, and £/£ interfaces are 0.56, 0.44 and 0.37 J/m 2 , respectively. Using two simple geometric models for nucleation on or off an interface in the matrix, the optimal shape of a nucleus at a given radius and undercooling, a critical radius and an energy barrier for nucleation for each possible circumstance were numerically calculated. It is found that, although the energy barrier for £-phase nucleation in homogeneous ¤-phase matrix is more than three orders of magnitude greater than that for homogeneous solidification of ¤-phase, the £ nucleation on a ¤/¤ grain boundary in the solidifying matrix suppresses the energy barrier, increasing a nucleation rate. Furthermore, it is found that the £-phase nucleation on an existing £ nucleus halves undercooling needed with smaller critical radius. This suggests that, once £ nucleation is initiated, then following £ nucleation is promoted by doubled driving force, enabling multiple £ nucleation as in chain reaction. These findings are sufficient to explain experimentally observed phenomena during the ¤-£ massive-like phase transformation even if other factors such as solute re-distribution or transformation is neglected.

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Concurrent γ-Phase Nucleation as a Possible Mechanism of δ-γ Massive-like Phase Transformation in Carbon Steel: Numerical Analysis Based on Effective Interface Energy

Yoshiya

Watanabe

Nakajima

et al. 2015

Mater. Trans.

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How to produce a desired bimodal microstructure for optimized mechanical properties: Investigation of the mechanisms of abnormal grain growth in pulsed electro-deposited nickel

Kerger

Rathmann

Marx

2015

International Journal of Materials Research

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Mechanical properties of metallic materials are often optimized by a specific heat treatment to adjust a required grain size. Thereby solute atoms, impurities or precipitates play an important role due to their retarding forces on the grain boundary movement. However, they not only stabilize small grain sizes during a heat treatment, it is also suggested that they introduce abnormal grain growth whereby for a small amount of grains the grain size increases tenfold and more. On the one hand abnormal grain growth impedes the adjustment of a required grain size; on the other hand it can be used to introduce bimodal grain structures which are known to combine opposing mechanical properties such as a high toughness and a high ductility. Therefore, the mechanisms of abnormal grain growth are investigated by varying the content of additives during the deposition process. Particle pinning is suggested as the mechanism responsible for abnormal grain growth at least in the initial stage, while a second phase may introduce extraordinary cubic grains growing abnormally in the late stage.

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Theoretical and numerical investigations on grain boundary migration due to inverse pinning

Cited by 2 publications

References 14 publications

Concurrent γ-Phase Nucleation as a Possible Mechanism of δ-γ Massive-like Phase Transformation in Carbon Steel: Numerical Analysis Based on Effective Interface Energy

Concurrent γ-Phase Nucleation as a Possible Mechanism of δ-γ Massive-like Phase Transformation in Carbon Steel: Numerical Analysis Based on Effective Interface Energy

How to produce a desired bimodal microstructure for optimized mechanical properties: Investigation of the mechanisms of abnormal grain growth in pulsed electro-deposited nickel

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Theoretical and numerical investigations on grain boundary migration due to inverse pinning

Cited by 2 publications

References 14 publications

Concurrent &gamma;-Phase Nucleation as a Possible Mechanism of &delta;-&gamma; Massive-like Phase Transformation in Carbon Steel: Numerical Analysis Based on Effective Interface Energy

Concurrent &gamma;-Phase Nucleation as a Possible Mechanism of &delta;-&gamma; Massive-like Phase Transformation in Carbon Steel: Numerical Analysis Based on Effective Interface Energy

How to produce a desired bimodal microstructure for optimized mechanical properties: Investigation of the mechanisms of abnormal grain growth in pulsed electro-deposited nickel

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Product

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Concurrent γ-Phase Nucleation as a Possible Mechanism of δ-γ Massive-like Phase Transformation in Carbon Steel: Numerical Analysis Based on Effective Interface Energy

Concurrent γ-Phase Nucleation as a Possible Mechanism of δ-γ Massive-like Phase Transformation in Carbon Steel: Numerical Analysis Based on Effective Interface Energy