Prediction of grain shape evolution during extrusion and annealing of 6xxxx alloy

In the extrusion of aluminum alloys the process chain involves different steps of thermo-mechanical stresses of the material leading to deformation of the grains during plastic forming and several degrees of static recrystallization during cooling. In defective cases, peripheral grain coarsening may occur thus causing profile scrapping. The implementation of a predictive tool able to simulate the whole complex sequence of phenomena involved in the extrusion process, consequently results of considerable interest. Experimental and numerical analysis were performed to investigate the grain shape evolution of 6XXX aluminum alloy during the extrusion process in order to develop a prediction model. A first experimental campaign was carried out in order to investigate the texture deformation modes and retrieve the microstructure evolution model. This model was coupled with the analytical static recrystallization formulations available in literature for the final implementation in a commercial FE code. A unified model was therefore implemented through user-routine, thus carrying the innovation of a model able to simulate grain evolution during the entire process: deformation and following ageing with an integrated approach. A second experimental campaign was used to validate the model on a wide industrial range of Zener-Hollomon values, comparing the experimental and numerical results at the end of the dynamic evolution and of the consequent static recrystallization. The results were analysed also in terms of grain growth effect, although this phenomenon is still not well captured by the model.