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

铝（Al）合金的优异强度密度比为减轻部件重量提供了巨大的潜力。为了拓宽铝合金的应用范围，替代高强度钢，可以采用各种方法提高铝合金的强度。铝合金的快速制造为系统设计组织结构和提高力学性能提供了巨大的潜力。通过激光粉末床熔合（L-PBF）制备的AlSi 12合金显示出由细Si网络组成的粗晶Al基体，与常规铸造零件相比具有更高的强度。通过剧烈塑性（SPD）变形可以获得具有优异机械性能的独特微观结构。然而，由于在一些SPD技术例如摩擦搅拌加工和摩擦搅拌焊接期间的高加工温度导致的Si网络的粗化和团聚可能不利地影响这些合金的强度。关于等通道转角挤压/压制（ECAE/P）对增材制造铝合金的机械性能和微观结构的影响的第一项研究表明，这种SPD方法能够提高这些合金的强度和延展性。由于ECAP加工温度较低，硅电池在ECAP过程中仅被拉伸，而不会溶解。UFG微结构仅在细胞内形成。因此，最终形成独特的异质结构。通过对现有研究成果的分析，发现目前还没有系统研究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，本提案的主要动机是补充ECAP作为后处理对L-PBF Al合金的微观结构和力学行为的影响的深入理解。将研究参考铸态合金，以探索初始显微组织（即AM显微组织与铸态对应物）对机械性能的影响，特别是合金的循环变形行为和最终显微组织。如果Si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通性。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制造过共晶Al-Si合金（AlSi 20和AlSi 50）。然后，还将对过共晶Al-Si合金进行多达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.