VARIATION IN SUBGRAIN STRUCTURE OVER THE CROSS SECTION IN AN EXTRUDED ALUMINIUM PROFILE � MEASURED BY EBSD

During extrusion of aluminium alloys the material experiences a complex flow pattern through the extrusion die. In the case of a flat extruded profile, the centre material deforms in plain strain compression, while the material close to the surface is exposed to a combination of plain strain compression and severe shear deformation. This difference in deformation conditions over the cross section often results in a recrystallized surface layer during extrusion of AA6xxx-alloys. The reason for this might be explained by the variation in microstructure evolution over the profile cross section, giving rise to a different driving pressure for subsequent recrystallization. The present work applies the electron backscattering diffraction technique (EBSD) in combination with a field emission SEM (FESEM) to measure the variations in subgrain size and misorientations over the cross section of an extruded profile. An Al-0,5Mn-0,2Mg-0,21Sc-0,15Zr-0,15Si-0,2Fe alloy was investigated.