B. Striewe, N. Grittner, A. von Hehl, M. Hunkel, O. Stelling, M. Schaper, H.-W. Zoch, Fr.-W. Bach
May 2, 2013
The combination of different metallic materials enables the design of lightweight structures with tailor-made properties. In contrast to conventional joining methods, for example fusion welding, by co-extrusion no degradation occurs in the materials structure in the form of heat affected zones or pore formation. Therefore, co-extrusion exhibits an attractive alternative for joining aluminium and titanium based alloys. The performed extrusion experiments were focused on the co-extrusion of aluminium (EN AW-6082) and titanium (TiAl6V4), where titanium is the reinforcing element that is inserted in aluminium profiles. During co-extruding an intermetallic layer with a thickness of 1 to 3 µm arises in the bonding zone between aluminium and titanium. In this layer an enrichment of elements of the aluminium alloy, such as silicon, was observed. The formation of the intermetallic layer and the strength of the compounds were examined at various positions after the co-extrusion and after subsequent heat treatment. The investigation of the intermetallic layer was performed with light optical microscope, scanning electron microscope and electro probe micro analysis. The mechanical properties were determined by tensile tests. The heat treatment led to the intended hardening of the aluminium alloy. However, the layer thickness did not change. The tensile tests specimen showed different failure locations. The heat treatment led to increased tensile strength values, but also to a decreased yield strength level.