Mechanisms in Joining of Dissimilar Materials using Friction Stir Welding

搅拌摩擦焊是一种新型的连接技术。该过程由塑性变形驱动，可分为三个阶段：材料的局部塑化、混合和固结。为此，使用了耐磨工具。由于焊缝温度适中，低于连接伙伴的熔化温度，因此可以连接不同的材料。文献中已经提供了原则的一般证明。然而，关于连接过程的机理以及影响连接质量的参数的基本知识仍然缺乏。这些缺失的基本原理妨碍了FSW中与应力相关的焊缝设计。计划中的研究项目旨在对异种材料搅拌摩擦焊接头界面层的金相过程有一个基本的了解。分析了铝-钛和铝-铜搭接对接焊接接头的连接机理。因此，可以对搅拌摩擦焊接异种材料的连接机理有一个基本的了解。这是对搅拌摩擦焊接异种接头界面层(连接)过程进行建模的基础。现在应该利用收集到的知识来预测有效的连接机制以及联合属性。通过对异种接头的搅拌摩擦焊实施温度控制，可以保持稳定的过程行为。因此，第一次可以控制界面层的形成和形貌。这直接影响到有效的加入机制，从而影响到联合的性质。此外，二期工程的数值模型还必须根据温控搅拌摩擦焊的变化条件进行调整和改进。由此，可以定义用于不同材料的健壮的FSW工艺的极限。此外，还分析了无损检测方法检测和量化界面区域(界面层、地形)形状的能力。这允许在不破坏焊缝的情况下验证所需的连接特性。

Friction Stir Welding (FSW) is an innovative joining technology. The process, which is driven by plas-tic deformation, can be divided into three phases: local plastification, mixture, and consolidation of the material. For this purpose, wear resistant tools are used. Due to the moderate temperatures of the weld seam, which are below the melting temperature of the joining partners, dissimilar materials can be joined. The general proof of principal is already supplied in the literature. Yet, fundamental knowledge about the mechanisms of the joining process as well as the influencing parameters on the joint quality is missing. These missing fundamentals prohibit a stress-related de-sign of a weld seam in FSW. The planned research project aims at the fundamental understanding of the metallographical process-es at the interface layer of FSW-joints of dissimilar materials. Analyses of the joining mechanisms of aluminum-titanium and aluminum-copper joints, which were welded in overlap- and butt-joint configura-tion, were carried out. Therefore, a fundamental knowledge of the joining mechanisms of friction stir welded dissimilar materials can be derived. This is the basis for modeling the (joining)processes at the interface layer of friction stir welded dissimilar joints. The effective joining mechanisms as well as the joint properties should now be made predictable using the gathered knowledge. By implementing a temperature control for the FSW of dissimilar joints, a stationary process behavior can be main-tained. Hence, the formation of the interface layer and the topography can be controlled for the first time. This directly influences the effective joining mechanisms and as a consequence the joint proper-ties. Furthermore, the numerical models of the second project phase have to be adapted and im-proved concerning the changed conditions of the temperature controlled FSW. Hereby, the limits for a robust FSW process for dissimilar materials can be defined. In addition, methods for non-destructive testing are analyzed regarding their ability to detect and quantify the shape of the interface area (interface layer, topography). This allows to verify the desired joint properties without destroying the welds.