Unique Microstructure established by the combination of Additive Manufacturing and Equal Channel Angular Pressing

铝（Al）合金的特殊强度密度比为减轻部件的重量提供了巨大的潜力。为了扩大这些合金的应用范围，用它们代替高强钢，可以采用各种技术来提高铝合金的强度。铝合金的快速制造为组织的系统设计和力学性能的改善提供了巨大的潜力。通过激光粉末床熔合（L-PBF）制备的AlSi12合金显示出由细小Si网络组成的粗晶Al基体，与传统铸造部件相比具有更高的强度。通过剧烈塑性（SPD）变形，可以获得具有特殊机械性能的独特微观结构。然而，在某些SPD技术（如搅拌摩擦加工和搅拌摩擦焊接）中，由于加工温度高，Si网络的粗化和团聚可能会对这些合金的强度产生不利影响。首次研究了等通道角挤压/挤压（ECAE/P）对增材制造铝合金力学性能和微观组织的影响，表明该方法能够提高合金的强度和延展性。由于较低的ECAP处理温度，硅电池在ECAP过程中只受到拉伸，而不会溶解。UFG微结构只在细胞内形成。从而形成了一种独特的异质结构。对现有技术的分析表明，目前还没有系统的研究ECAP对增材制造（AM）铝合金微观组织演变和力学性能的影响。因此，本研究的主要目的是进一步深入了解ECAP作为后处理对L-PBF铝合金显微组织和力学行为的影响。为了探索初始组织（即AM组织与铸造组织）对合金力学性能的影响，特别是合金的循环变形行为和最终组织，将研究一种参考铸态合金。如果硅含量增加到超过共晶相的水平，则应用程序可以获得相关性和连接性。这也可能导致在本提案中获得更多增材制造领域的知识。在这方面，将采用LB-PBF制备过共晶Al-Si合金（AlSi20和AlSi50）。然后，对过共晶Al-Si合金进行最多4道次的ECAP。

The exceptional strength-to-density ratio of Aluminum (Al) alloys offers a great potential for reducing the weights of components. In order to broaden the applications of these alloys and replace high-strength steels with them, various techniques can be employed to enhance the strength of Al alloys. The rapid manufacturing of Al alloys provides a great potential for a systematic design of microstructure and consequently the improvement of mechanical properties. AlSi12 alloy fabricated via laser powder bed fusion (L-PBF) shows a coarse-grained Al matrix consisting of fine Si networks with higher strength in comparison to the conventionally casted parts. A unique microstructure with exceptional mechanical properties can be achieved by severe plastic (SPD) deformation. However, coarsening and agglomeration of Si networks due to the high processing temperature during some SPD techniques such as friction stir processing and friction stir welding may adversely affect the strength of these alloys. The very first study on the effect of equal channel angular extrusion/pressing (ECAE/P) on the mechanical properties and microstructure of additively manufactured Al alloys reveals that this SPD method is capable of enhancing both strength and ductility of these alloys. Due to the low ECAP processing temperature, the Si-cells only get stretched during ECAP, they are not dissolved. The UFG microstructure only forms within the cells. Thus, a unique heterostructure is finally formed. The analysis of the current state-of-the-art verifies that there are no systematic investigations on the influence of ECAP on the microstructural evolutions and mechanical properties of Al alloys fabricated via additive manufacturing (AM). Therefore, the primary motivation of the present proposal is to complement the in-depth understanding of the impact of ECAP as a post-processing treatment on the microstructure and mechanical behavior of L-PBF Al alloys. A reference as-cast alloy will be investigated in order to explore the impact of the initial microstructure (i.e. AM microstructure versus as-cast counterpart) on the mechanical properties, especially the cyclic deformation behavior and final microstructure of the alloys. The application could gain relevance and connectivity if the Si content would be increased to a level exceeding the eutectic phase. This may also lead to the acquisition of more knowledge in the field of additive manufacturing in the present proposal. In this regard, hypereutectic Al-Si alloys (AlSi20 and AlSi50) will be fabricated employing LB-PBF. Then, ECAP up to 4 passes will also be carried out on hypereutectic Al-Si alloys.