Transformation character of ferrite formation by a ledge mechanism under a mixed-control model |
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| Authors: | Zhen-qing Liu Zhi-gang Yang Zhao-dong Li Chi Zhang |
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| Affiliation: | 1.Key Laboratory of Advanced Materials, Department of Materials Science and Engineering,Tsinghua University,Beijing,China |
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| Abstract: | A mixed-control model was developed to study the transformation character of ferrite formation by a ledge mechanism. A numerical
two-dimensional diffusion-field model was combined to describe the evolution of the diffusion field ahead of the migrating
austenite/ ferrite interface. The calculation results show that the bulk diffusion-controlled model leads to a deviation from
experimental results under large solute supersaturation. In the mixed-control model, solute supersaturation and a parameter
Z together determine the transformation character, which is quantified by the normalized concentration of carbon in austenite
at the austenite/ferrite interface. By comparing with experimental data, the pre-exponential factor of interface mobility,
M
0, is estimated within the range from 0.10 to 0.60 mol·m·J−1·s−1 for the alloys with 0.11wt%–0.49wt% C at 700–740°C. For a certain Fe-C alloy, the trend of the transformation character relies
on the magnitude of M
0 as the transformation temperature decreases. |
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| Keywords: | |
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