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J. Kreyca, E. Kozeschnik:
"Flow stress modeling and microstructure development during deformation of metallic materials";
Talk: MEFORM 2017, Freiberg; 2017-03-15 - 2017-03-16.

A constant strain hardening rate is characteristic for large strain deformation at low temperatures and often observed during wire drawing. This stage of deformation, in the following referred to as stage IV, is determined by the microstructural evolution of dislocation cells. For higher temperatures, stress saturation is reached easily and no stage IV behavior is observed anymore.
This behavior is modelled, following the idea of state-parameter based plasticity, evolving dislocation density and subgrain formation over strain rate, strain and temperature. It is shown that the temperature dependence of different deformation stages is strongly related. The presented model is tested and compared by a series of compression tests carried out on a Gleeble 1500 thermo-mechanical simulator. EBSD micrographs of the same material reveal the microstructural evolution during plastic deformation. It is shown experimentally that the transition from cell forming behavior to subgrain formation correlates well with the disappearance of stage IV and the overall change in the dominant mechanism for overcoming obstacles. In combination with thermally activated yield stress prediction, this model, recently implemented in MatCalc, offers a powerful tool for flow-curve generation.