Extrusion of Aluminum Tubes with Axially Graded Wall Thickness and Mechanical Characterization

In this study the indirect extrusion of seamless aluminum tubes with variable wall thickness was investigated. Therefore, an axially moveable stepped mandrel was applied. Investigations revealed that wall thickness transitions can either be graded over the tube length or very sharp. The microstructures in thin-walled and thick-walled tube sections were investigated. The local variation of the extrusion ratio and with that the tube wall thickness, product velocity and product temperature during the process lead to significantly different local microstructures at TB=400 °C. At TB=500 °C the microstructure was homogeneously recrystallized with similar grain size in all different tube sections. Furthermore, the mechanical tube properties were characterized by three point bending tests.