Large strain concentrations in the austenite-ferrite microstructure can be predicted by unit cell calculations. These analyses provide for explanation of the ductile damage qualitatively. The coupled problem of an interface migration and carbon diffusion during γ―α―transformation in the binary Fe-C-system has been solved by a numerical routine. The transformation kinetics have been evaluated and the results have been compared with schematic TTT-diagrams. When the growth of a ferrite layer is investigated, the variation of the temperature (amount of undercooling) leads to the expected "nose-like" characteristics. The influence of the mechanical driving force on the kinetics has been studied, too. In an Fe-C-alloy with a small amount of carbon almost no hardening will occur. Therefore, the mean stresses that occur due to the transformation at the interface can be reduced, and ΔF_(chem) overbalances ΔF_(mech) Even so, it has been observed that tensile stresses support the transformation and externally applied constraints retard the growth kinetics.
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