Iron and Steel

This project addresses the sensitivity of ultra-high strength cold rolled steels to hydrogen embrittlement. It is focussed on the interplay of hydrogen with retained austenite under cyclic loading conditions. The project combines state-of-the-art characterization techniques with test setups that are as close as possible to reality. The underlying mechanisms will additionally be investigated, combining ab initio methods for the hydrogen uptake and release by the austenite with continuum simulations for hydrogen distribution in the microstructure. [more]
The computational design of high strength steels such as FeMn alloys often faces a combination of challenges: (1) the treatment of chemical complexity, (2) the treatment of magnetic disorder, in particular, in the paramagnetic state, and (3) the treatment of structural defects. Moreover, the interplay of these degrees of freedom also needs to be accounted for. In this project we particularly focus on this kind of coupling of different degrees of freedom, since we believe it is decisive to understand some of the phenomena observed in FeMn alloys. [more]
The diffusion mechanisms in ordered binary alloys are more complicated than in materials with only one atom species. Several mechanisms, including, e.g., triple defect jump cycles, have been suggested in the literature. Within this project, we resolve which of them is energetically most favorable in FeAl and use the calculated barriers for large scale simulations. [more]
The aim of this project is to resolve the interplay of real space structure and electronic states in combination with magnetic disorder for iron-based superconductors.  We apply a combination of density-functional theory calculations and effective tight-binding models for the electronic energy dispersion. [more]
The stability and concentration of extended defects is closely related to their atomic structure, which can already be complex for planar defects in pure elements or chemically ordered phases, such as Laves phases. In the case of multi-component alloys with off-stoichiometric compositions, the chemical degree of freedom adds another level of complexity. Particularly fascinating becomes the interplay of local chemistry and planar defects, however, if defect structures and/or compositions are created that would not be present otherwise. [more]
Hydrogen embrittlement is a persistent mode of failure in modern structural materials. The processes related to HE span various time and spatial scales. Thus we are establishing multiscale approaches that are based on the parameters and insights obtained by accurate ab initio calculations in order to simulate HE at the continuum level. [more]
Understanding hydrogen-assisted embrittlement of advanced high-strength steels is decisive for their application in automotive industry. Ab initio simulations have been employed in studying the hydrogen trapping of Cr/Mn containing iron carbides and the implication for hydrogen embrittlement. [more]
Eutectic Ti-Fe alloys exhibit a high strength (~1000 MPa), excellent ductility, and sufficient corrosion resistance making them promising candidates for numerous aerospace and automotive applications. Dual-phase Fe-Ti eutectics are composed of a rather brittle FeTi intermetallic phase with the B2 structure and a softer and more ductile β-Ti(Fe) alloy with varying Ti concentrations. [more]

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