Project group A focuses on the modelling of the Fe-Mn-C system. Based on the ab initio modelling, new models will be conceptualized for this material system, going up to the point of microstructure mechanics.
In project area A the ab initio-based investigations for the prediction of the mechanical properties of high manganese steels are continued and extended to medium manganese steels. A new challenge resulting from the extension of the alloy concept is the treatment of the interaction of different phases (austenite, ferrite and κ-carbide) in the same material. The theoretical work is focused on questions of strenghtening and hydrogen embrittlement.
The large number of ab initio questions that arise in this group of topics are dealt with by the subprojects in close co-operation and with different emphases. While in A1 the chemical aspects (e.g., binding analysis) are in the foreground, in A2 the perspective dominates the physical mechanisms (e.g., magnon-phonon interaction). Accordingly, A1 primarily analyzes enthalpies, local ordering and point defects, as are important for the fitting of hydrogen atoms. In A2, however, mainly excitation processes, kinetics, and extended defects, such as segregation kinetics at phase boundaries, are in the foreground. The thermodynamic description of the very extensive Fe-Mn-Al-C system using the Calphad method is being pursued in A3, with a particular focus on the thermodynamic description of the k-phase. Mechanism maps allow the selection of the prevailing deformation mechanism; in A5 they will be extended to segregation processes and structural influences. A detailed description of microstructure mechanics in a continuum mechanical model is given in A7, with a focus on the interaction of different phases and the influence of hydrogen on plastic behavior. In A9, a cross-scale description of hydrogen in steels is made, which is based on ab initio data and operations at the mesoscopic level (micro-) cracking is to be predicted.