Beschreibung
This dissertation presents investigations, utilizing the phase-field method (PFM), of the microsegregation phenomenon of high manganese steel grades and of the peritectic phase transformation with and without mechanical elasticity for binary alloys based on the Fe-Mn and the Fe-C systems. For the case of the microsegregation investigations, several simulations under directional solidification conditions were performed for different cooling rates. The secondary dendrite arm spacing (SDAS) was determined for each simulation and the results were compared with an analytical model and with experimental results for different alloys presented in the literature. Frequency distributions of chemical composition were determined based on the numerical results from 2-D phase-field simulations, experimental results from the literature for a similar alloy, analytical models from the literature and 1-D DICTRA simulation. A comparison of the frequency distributions of chemical composition was performed and the results have shown that PFM is able to describe more precisely the microsegregation than the others method. For the case of simulations of the peritectic phase transformations, two different numerical models were developed and utilized here for isothermal and directional solidification conditions. One does not include in its formulation the elastic effect and the other one considers the elasticity in its mathematical formulation. The two stages of the phase transformation, the peritectic reaction and the peritectic transformation, were simulated for both numerical models. Kinetic aspects of phase transformation and the level of stress caused by the volume contraction due to the phase transformation from delta ferrite to gamma was investigated also with the present model.
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Shaker Verlag GmbH
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52353 Düren
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