The combination of different metallic materials enables the design of lightweight structures with tailor-made properties at global as well local scale and offers great potential for advanced solutions especially for the aircraft and automobile sector. Whereas titanium alloys show particular high mechanical strength and good corrosion resistance, aluminium alloys provide a considerable lower density and consequently higher potential for weight savings. However, after conventional fusion joining, e.g. after laser beam welding, heat affected zones, porosity or grain growth may occur and impair the local properties [1, 2]. In contrast, by solid-state joining techniques like co-extrusion these disadvantages can be avoided. Therefore co-extrusion exhibits an attractive solution for long products combining aluminium and titanium based alloys. Current investigations have been focused on the co-extrusion of aluminium and titanium, where titanium is the reinforcing element that is inserted in aluminium profiles. Two different billet variants were examined in the investigations, a titanium-core integrally moulded in the aluminium-billet and titanium-core inserted in a hollow drilled aluminium-billet. Experiments were made with different material combinations, Al99.5 with titanium grade 2 and AlSi1MgMn with Ti6Al4V. Beside mechanical properties of compound the formation of bonding zone are presented.

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The combination of different light alloys enables lightweight solutions with tailor‐made properties at the macroscopic global as well as at the microscopic scale. In this context co‐extrusion by a lateral angular co‐extrusion (LACE) process offers a great potential for advanced profiled structures. While titanium alloys show particular high mechanical strength and good corrosion resistance, aluminium alloys provide a considerable high specific bending stiffness along with low materials costs. The mechanical properties of metallic compounds strongly depend on the bonding mechanisms, which are initiated during processing. In order to enable a rigid adhesive bond between Al and Ti in this study the extrusions were processed by means of a newly developed lateral angular co‐extrusion that is a modified equal channel angular pressing process (ECAP). Latter is known for promoting diffusion bonding by reducing the activation energy. Hence, the study is focused on the general manufacturing of Al–Ti‐compounds by lateral angular co‐extrusion. The second aim of the study was to investigate the development of the bonding zone during processing. Experiments were made with the material combination Al99.5 and titanium grade 2. The bonding zones of the co‐extruded samples were analyzed by scanning electron microscopy and energy dispersive X‐ray analysis. The bond strength was determined by quasi‐static tensile tests. Compared to the as‐extruded condition an intermetallic layer was formed during heat treatment. The layer was characterized by scanning electron microscopy and electron probe micro analysis.

The combination of different metallic materials enables the design of lightweight structures with tailor‐made properties at global as well as local scale and offers great potential for advanced solutions especially for the aircraft and automobile sector. However, after conventional fusion joining, e. g. after laser beam welding, heat affected zones, porosity or grain growth may occur and impair the local properties. In contrast, by solid‐state joining techniques like co‐extrusion these disadvantages can be avoided. Therefore co‐extrusion exhibits an attractive solution for long products combining aluminium and titanium based alloys. Current investigations have been focused on the co‐extrusion of aluminium and titanium, where titanium is the reinforcing element that is inserted in aluminium profiles. In the context of a current research project the formation of the intermetallic layer and the mechanical properties were investigated in detail. In addition to that the influence on the intermetallic layer and the mechanical properties on heat treatment were investigated. The mechanical properties were determined by tensile tests. The intermetallic layers were analysed with light optical microscope, scanning electron microscope and electron probe micro analysis. During the co‐extruding an intermetallic layer with a thickness of 1 μm to 3 μm arises in the bonding zone between aluminium and titanium partner. Alloying elements from the aluminium alloy enrich in this layer. A subsequent heat treatment leads to an age hardening of the aluminium, however, it does not affect the layer thickness. The tensile tests specimen show different failure locations. The heat treatment leads to increased tensile strength values, but also to a decreased yield strength level.

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