Journal
INTERNATIONAL JOURNAL OF MINERALS METALLURGY AND MATERIALS
Volume 19, Issue 5, Pages 428-433Publisher
SPRINGER
DOI: 10.1007/s12613-012-0574-6
Keywords
iron carbon alloys; modeling; ferrite; ledge mechanism; diffusion; interfaces
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Funding
- National Natural Science Foundation of China [51171087, 51071089]
- Specialized Research Fund for the Doctoral Program of Higher Education [20070003006]
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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 degrees 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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