Simulation of Ferrite Formation in Fe-C Alloys Based on a Three-Dimensional Mixed-Mode Transformation Model |
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Authors: | S M C Van Bohemen C Bos J Sietsma |
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Affiliation: | (1) Tata Steel Research Development & Technology, 1970 CA IJmuiden, The Netherlands;(2) Department of Materials Science and Engineering, Delft University of Technology, 2628 CD Delft, The Netherlands |
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Abstract: | A three-dimensional mixed-mode (MM) transformation model accounting for both soft impingement and hard impingement was developed
that calculates the growth kinetics of ferrite grains in an austenite matrix. The simulations are compared to the kinetics
of ferrite formation in high-purity Fe-C alloys for which phase-transformation kinetics were measured isothermally by dilatometry
at several temperatures in the range of 973 K to 1043 K (700 °C to 770 °C). The interface mobility is obtained from the best
fit of the data at 1023 K (750 °C) for which the nucleus density N is estimated from the final microstructure. Subsequently, the experimental ferrite kinetics in Fe-0.36C at the other temperatures
are simulated. The values of N extracted from the fits can be described with a nucleation model. The significance of the MM calculations is rationalized
by comparing the results for Fe-0.17C with simulations assuming purely diffusion-controlled (DC) and purely interface-controlled
(IC) growth. Comparison of simulated fraction curves for Fe-0.57C with the three models demonstrates that the transformation
in high-carbon steels is essentially DC. |
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