A mixed-control model was developed to study the transformation character of ferrite formation by a ledge mechanism. A nu- merical two-dimensional diffusion-field model was combined to describe the evolution of the di...A mixed-control model was developed to study the transformation character of ferrite formation by a ledge mechanism. A nu- merical 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/ferfite interface. By comparing with experimental data, thepre-exponential factor of interface mobility, M0, is estimated within the range from 0.10 to 0.60 mol-m·J^-1·s^-1 for the alloys with 0.1 lwt%-0.49wt% C at 700-740℃. For a certain Fe-C alloy, the trend of the transformation character relies on the magnitude of M0 as the transformation temperature decreases.展开更多
基金supported by the National Natural Science Foundation of China (Nos.51171087 and 51071089)the Specialized Research Fund for the Doctoral Program of Higher Education (No.20070003006)
文摘A mixed-control model was developed to study the transformation character of ferrite formation by a ledge mechanism. A nu- merical 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/ferfite interface. By comparing with experimental data, thepre-exponential factor of interface mobility, M0, is estimated within the range from 0.10 to 0.60 mol-m·J^-1·s^-1 for the alloys with 0.1 lwt%-0.49wt% C at 700-740℃. For a certain Fe-C alloy, the trend of the transformation character relies on the magnitude of M0 as the transformation temperature decreases.
