The effect of through thickness texture variation on the anisotropic mechanical response of an extruded Al-Mn-Fe-Si alloy

There is currently a significant scientific and industrial interest in developing material models for the simulation of plastic deformation of aluminum extrusions relevant to their forming and their response during in service events such as vehicle crash. The objective of this work is to evaluate the effect of through thickness crystallographic texture gradients on material mechanical behaviour. This has been studied using a combination of experiments (i.e. pilot scale extrusions and stress-strain curves with the R-value to characterize plastic anisotropy for different loading directions) and the visco-plastic self-consistent (VPSC) polycrystal plasticity simulations on a model alloy system. Two limiting conditions were examined, i.e. unrecrystallized and fully recrystallized conditions. The results of electron backscatter diffraction (EBSD) characterization show that there is a significant through thickness variation in texture for both cases. However, the implications of the texture gradient on the macroscopic plastic response were relatively minor for the unrecrystallized case but quite significant for the recrystallized case. This was manifested as a strong difference in the contraction of the surface layer compared to the centre of the extrudate, particularly in the case of tests at 45 degrees and 90 degrees to the extrusion direction. This was rationalized in terms of the differences in texture between the surface and the centre using VPSC simulations. Finally, it was proposed that this effect will be explored in future work as it may have important implications on the surface stress state which could affect damage initiation, growth and coalescence, particularly in bending situations.