Finished Project


FOR 1509 Microtructural interaction and switsching in ferroelectrics

The purpose of this project is to establish multiscale laminate- and homogenization-based models for the interactions between the grain, defect,polarization and dislocation microstructures in ferroelectric single- and polycrystals during technological processes. These involve in particular single-, multi- and polycrystal-based modeling. At the single-crystal level, laminatebased mixture models for energetic and dissipative processes associated with the polarization, defect and dislocation microstructures and their evolution will be developed. These will then be embedded in multigrain-based grain boundary interaction models for the investigation of the eect of graingrain interactions on the polarization and defect microstructures. Finally, the single-grain model will be embedded into an orientation-distributionfunction-based single- and multi-grain-based texture model for the grain microstructure at the specimen and technological level. FOR 1509

SFB 761

In this project a number of macroscopic phenomenological and microscopic physical models (e.g., phase field models) were developed for dislocation-based microstructure, deformation processes and inhomogeneous flow in fcc materials and in particular in high Mn steels. In the planned third phase, the microscopic physical models will be extended to multiphase, chemically inhomogeneous systems with mass transport, in particular to pursue applications with respect to the material class Fe-xMn-yC-zAl for Mn steels. SFB 761

SPP 1713

The projekt is concerned with the formulation, comparison and application of phase-field-based chemomechanical models for metallic alloys undergoing phase transitions, dislocation-mediated finite deformation, and failure. On the methodological side, this is based for example on generalization and further development of existing approaches such as WBM (Wheeler-Böttinger-McFadden) and KKS (Kim-Kim-Suzuki) for chemical homogenization to large-deformation chemome-chanics. These will be compared with existing chemomechanical models for small deformation in the context for example of benchmark simulations and the modelling of excess interface energy. In addi-tion, models based on both artificial and physical (i.e., sublattice- and element-site-fraction-based) chemical order parameters will be extended to finite-deformation chemomechanics, facilitating cou-pling to CALPHAD. Likewise, the modelling of dislocation processes and failure will be included via the generalization of phase-field microelasticity for defects and phase-field fracture to finite defor-mation. Principle applications of the proposed method and model developments include the model-ling of precipitation, dislocation-solute interaction, and dislocation-precipitate interaction. Of par-ticular interest in this regard are Fe-Mn-C-Al-based low-density steel kappa-carbides. SPP 1713