The development of crystallographic texture during porthole die extrusion of Al-Mg-Si alloys

Abstract

The use of hollow aluminum extrusions in internal combustion engine and battery electric powered vehicles has increased significantly in recent years due to lightweighting considerations. It is of interest to understand the evolution of crystallographic texture from a through-process perspective, since the microstructure and texture of the material have a strong influence on plasticity in the final part. In this research, an Al-Mg-Si alloy with Mn and Cr additions to suppress recrystallization was halted mid-extrusion, and the in-die material was extracted for study. The evolution of textures along finite element method (FEM) predicted streamlines were characterized with electron backscatter diffraction (EBSD). Polycrystal plasticity modelling coupled with the FEM simulated deformation history was implemented to predict texture evolution. Streamlines passing near the center of the portholes exhibited axisymmetric double fiber textures, which rotated following the streamlines before shifting to plane strain textures near the die exit. Closer to the weld seam, shear textures developed. It was found that textures could be predicted for streamlines up to 1.4 mm away from the weld seam, where complex deformation modes, significant increase in strain and the possible intervention of alternative mechanisms such as recrystallization and non-octahedral slip inhibit the accuracy of texture prediction.

Keywords

• Crystallographic texture
• Electron backscatter diffraction
• Finite element modelling
• Polycrystal plasticity simulation
• Aluminum alloys
• Porthole die extrusion