Mechanisms in Joining of Dissimilar Materials using Friction Stir Welding

搅拌摩擦焊（FSW）是一种新型焊接技术。该过程由塑性变形驱动，可分为三个阶段：局部塑化、混合和材料固结。为此，使用耐磨工具。由于焊缝温度适中，低于连接方的熔化温度，因此可以连接不同的材料。一般的本金证明已经在文献中提供。然而，对连接过程的基本机理以及对连接质量的影响参数缺乏基本的认识。这些缺失的基本原理阻碍了FSW中与应力相关的焊缝设计。计划的研究项目旨在对不同材料的fsw接头界面层的金相过程有基本的了解。对铝钛接头和铝铜接头采用搭接和对接方式焊接的连接机理进行了分析。因此，对异种材料搅拌摩擦焊接的连接机理有了基本的认识。这是建立搅拌摩擦焊接异种接头界面层连接过程模型的基础。利用收集到的知识，现在应该可以预测有效的连接机制以及关节属性。通过对不同接头的摩擦摩擦焊实施温度控制，可以保持稳定的过程行为。因此，首次可以控制界面层的形成和形貌。这直接影响到有效的连接机制，从而影响到接头的性能。此外，二期工程的数值模型还需要适应和改进温控FSW工况的变化。因此，可以定义不同材料的坚固FSW过程的极限。此外，本文还分析了无损检测方法在检测和量化界面区域形状（界面层、形貌）方面的能力。这样可以在不破坏焊缝的情况下验证所需的接头性能。

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.