Indirect extrusion of Cu/Al composite profiles

目前使用铝基复合材料作为导体材料的趋势要求复合材料型材的生产有多种策略。挤压两种或两种以上材料可以在单一成型步骤中生产混杂型材。成功的共挤出要求变形区内的所有材料在整个挤出过程中都能均匀流动。以往的研究表明，通过静液挤压可以生产出宏观上无缺陷的铜/铝复合棒材。因此，材料流动的条件是适宜的，以确保铝和铜的均匀材料流动，从而确保复合挤压。由于在挤压开始时需要向容器中填充静液，因此与直接和间接挤压相比，静液挤压更费力且生产率更低。此外，需要用于静液挤压的坯料具有圆锥形前端，从而显著增加了坯料制备的作用力。相反，间接挤压还导致了与静液挤压相当的均匀的材料流动，但没有上述缺点。然而，与静液挤压相比，不同的应力条件可能会导致不同的材料流动条件，从而影响复合材料的质量。因此，本研究方案的目标是通过间接挤压制备铜/铝复合材料，并根据工艺参数对其性能进行表征。从这一目标中产生的各种基础研究问题必须在项目过程中进行分析。因此，将分析的基础性研究问题包括现有的应力和应变条件、材料流动和摩擦条件对使用间接挤压时材料粘结形成复合材料的影响。

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.