Experimental investigation and numerical prediction of the peripheral coarse grain (PCG) evolution during the extrusion of different AA6082 aluminum alloy profiles

Peripheral Coarse Grain (PCG) is an undesirable defect that may occur in the extrusion of medium-strength Al-Mg-Si aluminum alloys. This phenomenon usually degrade extruded profiles in mechanical, crash, corrosion, fracture and surface quality properties thus precluding their applicability in the automotive sector. In this work, an experimental campaign was carried out involving the extrusion of two different AA6082 profiles in a wide range of process parameters. The microstructural analysis of these profiles was conducted in order to investigate the impact of die design and process parameters on PCG occurrence. According to this analysis, it was detected a clear influence of the ram speed and of highly dynamic recrystallized (DRX) zones on the PCG. The modeling for the PCG evaluation was then developed and implemented into the commercial FEM code Qform Extrusion® for the simulation of the extrusion process together with the DRX and the PCG predictions. The numerical results were further compared to the collected experimental data thus proving the reliability of the proposed model.