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J. Kreyca, E. Kozeschnik:
"Flow Stress Modelling and Microstructure Development during Deformation of Metallic Materials";
Materials Science Forum, 892 (2017), 44 - 49.

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. At
elevated temperatures, rapid stress saturation is typically reached and no stage IV behavior is
observed. This behavior is modelled in the present work, following the concept of state-parameter
based plasticity, evolving dislocation density and subgrain formation as functions of strain rate,
strain and temperature. It is demonstrated that the temperature dependence of state parameters at
different deformation stages is closely related. The present model is compared to 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 the software package MatCalc, offers a powerful tool for flow-curve
simulation.

Large deformation, stage IV / state-parameter

http://dx.doi.org/10.4028/www.scientific.net/MSF.892.44