Alloys of the compositional broad class of Al-Mg-Si are medium to high strength, heat-treatable alloys with an excellent workability at elevated temperatures. This makes them suitable for profile extrusion of hollow, complex geometries. Such complex shape, high strength profiles are of important role for crash energy absorbing safety components in automobiles, trains and mobility applications in general, and thus require a high degree of ductility [1]. However, strength and ductility are competing material properties in deforming via dislocation slip [2]. Thus, industrial development and scientific research focusses on enhancing ductility while sustaining strength of Al-Mg-Si alloys
In plane strain deformation, the extrusion process leads to the formation of distinct microstructures and crystallographic textures [3], which range in the bulk from fine grained microstructures with a pronounced \beta-fiber texture to large recrystallized grains with a \{1 0 0\} 〈0 0 1〉 cube component. In most of those microstructures a recrystallized layer of grains forms beneath the surface, which does not relate to the texture formation in the bulk. This sub-surface layer plays an important role in assessing the crash energy absorption, as ductile deformation is often evaluated by three-point profile or plate bending [4]. EBSD investigations reveal how the sub-surface layer and the bulk interact during bending deformation. Subsequently a mechanism is proposed qualitatively for enhancing bending deformation.

[1]    J. Hirsch, Recent development in aluminium for automotive applications, Trans. Nonferrous Met. Soc. China. 24 (2014) 1995–2002.
[2]    R.O. Ritchie, The conflicts between strength and toughness, Nat. Mater. 10 (2011) 817–822.
[3]    J. Humphreys, G.S. Rohrer, A. Rollett, Chapter 3 - Deformation Textures & Chapter 12 - Recrystallization Textures, in: J. Humphreys, G.S. Rohrer, A. Rollett (Eds.), Recryst. Relat. Annealing Phenom. Third Ed., Elsevier, Oxford, 2017: pp. 81–107 & 431–468.
[4]    J. Noder, A. Abedini, C. Butcher, Evaluation of the VDA 238–100 Tight Radius Bend Test for Plane Strain Fracture Characterization of Automotive Sheet Metals, Exp. Mech. 60 (2020) 787–800.