Indirect extrusion of Cu/Al composite profiles

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The current trend towards the use of aluminum based composites as conductor material requires manifold strategies fort he production of composite profiles. The extrusion of two or more materials enables the production of hybrid profiles in a single forming step. The successful co-extrusion demands a homogenous flow of all materials in the deformation zone along the complete extrusion process. Previous studies have shown that macroscopically defect-free Cu/Al composite bars can be produced by hydrostatic extrusion. Thus, the conditions for the material flow is suitable to ensure a homogenous material flow for Al and Cu and thereby a composite extrusion. Due to the necessary filling of the container with a hydrostatic fluid at the beginning of the extrusion the hydrostatic extrusion is more laborious and less productive compared to the direct and indirect extrusion. Furthermore, it is necessary that the billets for the hydrostatic extrusion have a conical frontend whereby the effort for the billet preparation is significantly increased. In contrast the indirect extrusion also leads to a homogenous material flow comparable to the hydrostatic extrusion but without the aforementioned disadvantages. However it is possible that the different stress conditions compared to the hydrostatic extrusion result in different conditions for the material flow and are thus influencing the quality of the composite. Therefore, the objective of the present research proposal is the production of Cu/Al composites by indirect extrusion and the characterization of the resulting properties in dependence of the process parameters. Various fundamental research questions arise from this objective that have to be analyzed during the course of the project. So amongst others the fundamental research question that will be analyzed are the influence of the present stress and strain conditions, the material flow and the friction conditions on the bonding of the materials to form a composite if the indirect extrusion is used.