Effect of Mg/Si Ratio on the Bendability and Anisotropic Bend Behavior of Extruded 6000-Series Al Alloy

Extruded Al-Mg-Si profiles applied in the automotive industry are required to achieve an appropriate combination of strength and bendability. In order to investigate the effect of Mg/Si ratio on the bendability and anisotropic bending behavior, AA6005 and AA6061C were extruded to 2 mm thick plates. More Goss texture and anisotropic particle clusters exist in AA6005 alloys with a low Mg/Si ratio, which leads to a high tendency of surface roughing and cracking and to strong anisotropy in their bendability. However, more low-angle grain boundaries, cubic texture and comparatively random distribution of particles exists in AA6061C alloys with a high Mg/Si ratio, which blunts the surface roughing and crack process. The surface undulation is the outcome of the strain-intense localization of several layers of grains in the vicinity of the outer elongated surface. The strain localization and surface undulation lead to shear band initiation near the valleys. Several cooperating micro-mechanisms in AA6005, including grain clusters with Goss and Cubic orientation, heterogeneously nucleated particles and grain boundary spatial arrangements, lead to the grain boundary decohesion along a shear direction. AA6005 shows for predominately intergranular fractures in nature, with some areas exhibiting grain boundary decohesion during bending in the TD. However, AA6061C shows a predominately transgranular in nature, with some areas exhibiting intergranular fracture, which is affected by shear band development.