Simulation of Extrusion Processes of Aluminum Profiles with Modeling of Microstructure

"Numerical simulation of extrusion processes offers an efficient method for tool design and optimization of geometries and properties of extruded parts. However, until now there are few systematic investigations about influences of material model and different parameters e.g. for friction and thermal processes on calculated local and global responses. Since extrusion processes are essentially influenced by friction between billet and extrusion tools, new friction tests were performed in this work to develop a reliable friction model. Compression and torsion tests were performed at different temperatures and velocities to calibrate the material model for extrusion simulations. Extrusion processes for circular rods and U-profiles were conducted at TU Berlin with backward and forward extrusion for different extrusion ratios, billet temperatures, product velocities and cooling conditions. This work focuses on numerical simulations of the extrusion tests with the FE code HyperXtrude. Based on the calculated distributions of local strain, strain rate and temperature the recrystallized volume fraction and grain sizes were calculated with empirical models and compared with the experimental results from optical micrographs and EBSD scans. The calculated total and friction forces and temperatures were compared with the experimental results and the deviations between experiment and simulation were analyzed.INTRODUCTION Extruded aluminum components are widely used in vehicle constructions due to light weight and manufacturing consideration. Local mechanical properties in the components are inhomogeneous as a consequence of the spatial distribution of microstructure which is influenced by numerous factors like material composition, temperature, tool design, friction, extrusion ratio and speed during the extrusion process. For the optimization of the extrusion process with regard to all these factors numerical simulation can be an essential tool. Based on results of finite element simulations of the extrusion process the microstructure in the extruded components can be predicted and then the resulting mechanical properties can be numerically determined instead of by costly trial and error methods. The aim of the work presented in this paper is the development of a numerical method for the simulation of extrusion processes with modeling of microstructure."