Berlin 2008 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 43: Phase Transitions IV

MM 43.5: Vortrag

Donnerstag, 28. Februar 2008, 17:00–17:15, H 0107

An ab-initio study of the phase transitions in the interstitial Fe-C solid solutions — •Alexander Udyansky, Martin Friák, and Jörg Neugebauer — Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Str. 1, 402 37, Düsseldorf, Germany

The Fe-C system constitutes the backbone of the steel industry that has long been altering our daily life. The Fe-C phase diagram is very rich in different phases exhibiting both low-carbon concentration, like ferrite or martensite, and high-carbon content, as e.g. austenite or cementite. An important prerequisite for the nucleation and formation of the latter is the existence of regions in the Fe matrix with diffusion-enhanced carbon concentration. In order to gain a detailed insight into properties of the high-C regions we have theoretically determined the formation energies, magnetic moments, and structural properties of selected interstitial Fe-C solid solutions employing density functional theory (DFT) in the generalized gradient approximation (GGA). The interstitial solid solutions have been modeled using the super-cell approach. Both magnetic and structural phase transformations induced by increasing carbon concentration are predicted and the very strong interplay between the C-content and both structural and magnetic degrees of freedom is found and analyzed.