O. Schulz¹, A. Schulze¹, A. E. Tekkaya¹, L. Kertsch², M. Zapara²
1 Institute of Forming Technology and Lightweight Components, TU Dortmund University
2 Fraunhofer Institute for Mechanics of Materials IWM

The mechanical properties of extruded profiles depend significantly on the resulting microstructure. Therefore, in this approach, the mapping of the microstructure is included in numerical simulation to ensure a more accurate prediction of the product properties. For the development of a feasible and efficient numerical approach to predict the microstructure, first an experimental database is created. The widely used aluminum alloys AA6060 and AA6082 are characterized and the microstructure analyzed by hot upsetting and hot extrusion on an experimental downscaled press. To accelerate the grain size determination, a script is developed to calculate the size based on the line intersection method as well as estimating the grain size distribution. The evaluation of homogenized microstructure using the script shows a deviation in the mean grain size of 7 % in comparison to using the intersection line method of DIN EN ISO 643. Considering the human error and possible deviations resulting from different scientists counting valid grain boundaries, this deviation is acceptable in regards to the acceleration.
Hot upsetting specimens of AA6082 do not show recrystallization, whereas in the case of AA6060 static recrystallization is observed even at rather small strains of φ = 0.8, strain rates $\dot{φ}$ = 1.0, and a holding time of 15 seconds. In combination with initial microstructure analysis, a numerical model is calibrated.