Influence Of Process Fluctuations On Weld Seam Properties In Aluminum Alloy Extrusion

The quality of weld seams produced during extrusion of hollow profiles is a big issue in the extrusion industry. The presented investigations deal with the characterization of extruded weld seams for the alloys AlMgSi0.5 (EN AW-6060), AlMgSi1 (EN AW-6082) and AlZn4.5Mg1 (EN AW-7020). Mictrostructural analysis and material properties have been analyzed with respect to variations in billet temperature, extrusion speed, subsequent cooling and heat treatment. The alloys show distinct differences in recrystallization behavior and microstructure of the weld seams and the surrounding base material.The AlMgSi0.5 alloy shows a fully recrystallized microstructure while the AlZn4.5Mg1 and the AlMgSi1 exhibit different degrees of a partially recrystallized structure leading to substantial differences in grain size between the three alloys. This behavior results in a different dependency of the material properties on process parameter changes. As already stated by previous investigations, this influence is especially fatal to the material properties transverse to the extrusion direction for non-or partially recrystallizing alloys.