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Molybdenum is part of many modern everyday items and, to some extent, also necessary for their production. Besides its high melting point of 2620 °C, molybdenum exhibits good electrical and thermal conductivity and a low coefficient of thermal expansion at the same time. However, pure molybdenum has low ductility at room temperature. The ductile-brittle transition which is typical of body-centred cubic metals occurs at around room temperature, depending on the processing state. Thus, components partly fracture along the grain boundaries due to brittle failure. The decisive reason for this are, inter alia, impurities which segregate at grain boundaries. In order to analyze individual grain boundaries, a load is applied in compression direction to micropillars in the size range of a few micrometres. This allows a targeted study of the mechanical properties, complemented by atom probe experiments analysing the chemical structure. The micrometre-scale analyses enable the determination and correlation of the mechanical with the chemical properties of a single grain boundary with the aim of better understanding the relationship between segregations and deformation behaviour in the grain boundary region.

The characteristics of grain boundaries and their influence on the mechanical properties have become key issues in recent research on structural materials. Especially in molybdenum, grain boundary segregation plays a significant role regarding ductility and strength. In this study as-sintered conditions of technically pure as well as boron and carbon doped molybdenum were mechanically characterized by bending tests and correspondingly analyzed by atom probe tomography to understand the differences in mechanical behavior after alloying. Strategies for improving the ductility of molybdenum are discussed with special focus on grain boundary segregation.

High-performance materials play a dominant role in modern society. Without them, modern manufacturing and transportation technologies would, for instance, be impossible. In order to purposefully improve and optimize the potential of these materials based on their properties, a multi-scale understanding of the interaction of microstructural elements and mechanical properties is essential. Such understanding can be achieved by the specific analysis of the interaction of microstructural components such as interfaces, crystal structures, precipitates, and other defects in the material, as well as of their impact on the underlying deformation processes in complex alloys. For this purpose, not only a precise metallographic preparation of the individual microstructural constituents is performed but also, and in particular, rate- and temperature-dependent plastic deformation processes are determined. On the one hand, this is done on a local scale using micromechanical examination methods such as nanoindentation or uniaxial micropillar-compression experiments. On the other hand, experiments on the global scale with compression and tensile tests are performed. These mechanical characteristics are subsequently correlated with structural and chemical high-resolution analyses based on electron microscopy and atom probe tomography methods. Thus, reliable mechanistic models of the dominating deformation mechanisms of high-performance materials can be created based on these examinations – even under harsh conditions such as elevated temperatures or aggressive environment. This targeted correlative interaction of metallography, high-resolution microstructural analysis, and mechanical deformation experiments is demonstrated by the examples of the refractory metals Mo and Cr as well as on a Mo-Hf-C alloy.