Dresden 2014 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 15: Computational Materials Modelling III - Bulk thermodynamics/ Phase Transitions I

MM 15.7: Vortrag

Montag, 31. März 2014, 17:30–17:45, IFW D

First-principles approach to investigate hydrogen cluster formation in austenitic Mn-rich steels — •Aurab Chakrabarty, Robert Spatschek, Tilmann Hickel, and Joerg Neugebauer — Max-Planck Institute for Iron Research, Dusseldorf, Germany

Hydrogen related failure is a well-known problem in high-strength austenitic steels for automotive applications. Experiments provide evidences of reduced ductility and H-induced local plasticity (HELP) upon H charging in these materials. The HELP model provides an explanation for the formation and propagation of cracks in austenitic steel. An important criterion for HELP is segregation of hydrogen to topological defects such as stacking faults and grain boundaries and the mechanism of H-segregation in high-Mn steels is not completely understood yet. We used density functional theory (DFT) total energy calculation to estimate the interactions between H-interstitial atoms in Fe-Mn alloys and the influence of H on stacking faults. We observed enhanced H-H interaction in a hydrogen cluster, i.e. a local hydride phase. Furthermore, a lower solution energy provided by the presence of a stacking fault makes it a favourable site for H-accumulation. The interaction energies and elastic constants calculated using DFT are used in finite-temperature Monte-Carlo and continuum-scale analysis in order to predict a phase-diagram for a temperature driven phase separation of Fe into a dilute and a local hydride phase.