Indirect extrusion of Cu/Al composite profiles

目前的趋势是使用铝基复合材料作为导体材料，这需要多种策略来生产复合型材。两种或更多种材料的挤出使得能够在单个成形步骤中生产混合型材。成功的共挤出要求所有材料在变形区中沿整个挤出过程沿着均匀流动。已有研究表明，采用静液挤压可以获得无宏观缺陷的Cu/Al复合材料棒材。因此，材料流动的条件适合于确保Al和Cu的均匀材料流动，从而确保复合挤出。由于在挤出开始时必须用静压流体填充容器，与直接和间接挤出相比，静压挤出更费力且生产率更低。此外，用于静液压挤压的坯料必须具有锥形前端，由此显著增加坯料制备的努力。相比之下，间接挤出也导致与静液压挤出相当的均匀材料流，但没有上述缺点。然而，与静液压挤压相比，不同的应力条件可能导致材料流动的不同条件，从而影响复合材料的质量。因此，本研究建议的目的是通过间接挤压生产Cu/Al复合材料，并根据工艺参数表征所得性能。各种基础研究问题产生于这个目标，必须在项目过程中进行分析。因此，除其他外，将分析的基本研究问题是当前应力和应变条件，材料流动和摩擦条件对材料粘合的影响，以形成复合材料，如果使用间接挤压。

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.