Local microstructural evolution, interfacial integrity and rate effects associated with modern joining processes using plastic deformation

该方案考虑了碰撞连接后接合区的组织演变和相应的性能变化。这一过程与高度变形有关。此外，连接以非常高的速度进行。因此，需要对材料在高应变率条件下的行为进行系统的表征，作为模拟连接过程本身的基础。该项目建立在与优先方案面向加工的项目密切合作的基础上，在这些项目中，碰撞连接过程在定制的简化实验装置中进行研究，并在接近工业过程的更现实的加工条件下进行研究。这些合作提供了丰富的样本，允许进行详细的微观结构和微观机械研究。分别采用(技术上)纯铝和钢-铝组合接头，研究了不同的初始组织和表面条件对接头性能的影响。最近的结果详细地记录了特征、波状连接区的形成。此外，还对基础材料的动态材料行为进行了表征，以支持伙伴项目的数值模拟。仔细的显微结构研究表明，连接区域通常由薄层区域组成，这些区域甚至可能在连接过程中短暂融化。随后非常迅速的冷却导致了再结晶、快速凝固的区域。当前和未来的研究重点是了解不同的工艺参数如何影响这些连接区域的特殊形态，如何影响接头的强度和完整性，以及典型的加工窗口如何反过来受到相应的基本微观组织过程的限制。该项目将继续为碰撞连接提供具有明确定义的初始微结构的材料，并表征这些基础材料的动态材料行为。该项目的研究将主要集中在电子显微镜下连接区的微观结构表征，以及用于局部机械表征的补充纳米压痕研究。这里提出的调查还将有助于分析优先方案的两个主要主题(塑性变形连接过程中的粘结机制和高应变率材料行为)。

This project considers microstructural evolution and the corresponding changes of properties in joining zones after collision joining. This process is associated with high degrees of deformation. Moreover, joining occurs at very high velocities. Therefore, the material behavior needs to be characterized systematically under high strain rate conditions as a basis for the simulation of the joining process itself. The project builds on close collaborative work with processing-oriented projects of the Priority Programme, where the collision joining process is studied both in a custom-made, simplified experimental setup, and under more realistic processing conditions close to the industrial process. These collaborations provide a wealth of samples that allow for detailed microstructural and micromechanical investigations. Using joints of (technically) pure aluminum and a combination of steel and aluminum, respectively, the effect of different initial microstructures and surface conditions is investigated. Recent results document in detail the formation of characteristic, wavy joining zones. Moreover, the dynamic material behavior of the base materials is characterized to support numerical simulations in the partner projects. Careful microstructural investigations indicate that the joining zones typically consist of thin regions that may even have briefly melted during joining. The subsequent, very rapid cooling results in recrystallized, rapidly solidified regions. The focus of current and future research is placed on understanding how the special morphology of these joining regions is affected by different processing parameters, how it influences strength and integrity of the joints, and how the typical processing windows are in turn limited by the corresponding fundamental microstructural processes. The project will continue to provide materials with well-defined initial microstructures for collision joining, and to characterize the dynamic material behavior of these base materials. The research of this project will be primarily focused on microstructural characterization of the joining zones by electron microscopy, and on complementary nanoindentation investigations for local mechanical characterization. The investigations propsed here will also contribute to an analysis of two main topics (bonding mechanisms during joining by plastic deformation and high strain rate material behavior) of the Priority Programme.