Process chains for co-extrusion and heat treatment of asymmetrical compounds made of alumini-um and titanium

• Applicants: Professor Dr.-Ing. Axel von Hehl; Dr.-Ing. Florian Nürnberger, since 7/2014
• Subject Area: Metallurgical, Thermal and Thermomechanical Treatment of Materials
• Term: from 2013 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 239636403

The aim of the new applied project is to develop process chains for manufacturing com-pound profiles with continuous bonded reinforcing elements, including the necessary relationships of materials science and production technology.Based on the state of research and preliminary work these relationships to be developed jointly can be narrowed as follows:1. Formation of a material bond by co-extrudingIn order to avoid clamping and tearing of the reinforcing element, the frictional contact is only re-stricted on the region of the die. For this, the rigid reinforcing element is fed in cleaned and pre-heated condition from outside into the bale chamber and dragged from the extruded aluminium profile. The required deflection of the extruded profile for lateral feeding can be achieved by using an ECAP die that also enables the production of asymmetric compound profiles. Compared to the precursor project an oxide-free diffusion layer shall be achieved by means of the cleaning and pre-heating device that is completely purged with inert gas.Thus, a deeper understanding of the co-extrusion of compounds by means of ECAP has to be developed in consideration of the pressing parameters as well as the surface conditions of the externally fed reinforcing elements and its pre-heating conditions.2. Development of the dimensional and shape changes along the process chainDue to the asymmetry of the compound profiles and the very different thermal expansion coeffi-cients significant dimensional and shape changes can be expected. Information about distortion compensation approaches for extruded compound profiles could not be found in the literature.Therefore, in order to find suitable distortion compensation approaches a deeper insight has to be gained regarding the development of the dimensional and shape changes during extrusion and heat treatment.3. Evolution of the bonding zone and bond properties during heat treatmentThe results of the first project phase show that the bond strength largely depends on the bonding zone caused by diffusion. Additionally, the strength of aluminium as the weaker of the two materials has to be considered as well. Therefore, the heat treatment is a significant process step for adjusting the final bond properties. Works, which deal with modelling of the bond properties during heat treatment, are not known.Hence, depending on the heat treatment conditions an indepth insight into the evolution and modi-fication of the bonding zone has to be gained that enables a modelling of the resulting bond properties.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr.-Ing. Mirko Schaper, until 7/2014