Extrusion of magnesium alloy hollow profiles with axial variable wall thickness

Abstract

Industrially extruded profiles are characterized by a constant cross section along the length since rigid dies are applied in the process. However, if it would be possible to extrude profiles with cross sections that can be locally adapted (tailored) to the acting forces or stresses this would mean a significant potential for weight and material savings. Hence, in this study the extrusion of magnesium hollow profiles with axial variable wall thickness was investigated. Therefore, a newly developed porthole die was applied and extrusion trials conducted in order to show the feasibility of producing load adapted magnesium hollow profiles with axially variable wall thickness. Billets of magnesium alloy AZ31 were extruded and the required extrusion force was measured vs. process time. After the extrusion tryouts the manufactured hollow profile sections were measured with respect to the obtained wall thickness, inner and outer diameter of the thin-walled and the thick-walled sections, and in the wall thickness transition areas. The feasibility of manufacturing AZ31 hollow profiles with axially variable wall thickness was proven successfully. A maximal wall thickness variation of Δt=1.0 mm was achieved.