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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.

Beryllium has an extraordinary combination of material properties such as low density, high melting point, high specific heat capacity, high Young's modulus, high hardness and low atomic number. The conventional investigation of the mechanical properties of Be and Be alloys is only possible under difficult conditions due to the material's toxicity and the resulting restrictions on sample manufacturing. These limitations are avoided, at least partly, when using a depth-sensing hardness test, also called nanoindentation, where the resulting contamination with Be dusts is limited to a controllable extent. For this work, technically pure Be from X-ray exit windows of high-performance X-ray tubes was chosen and its mechanical properties were characterized by means of nanoindentation. This contribution will focus in detail on the preparation of the material as well as the following microstructural characterization by means of light microscopy and scanning electron microscopy. The mechanical results of local nanoindentation will be correlated with the microstructure and compared with known values found in the literature.

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.

In this study, a Co-24Cr-8W–3Mo alloy (weight-%) is examined as cast and after hot isostatic pressing in a scanning electron microscope to identify the occurring phases through electron backscatter diffraction and energy dispersive X-ray spectroscopy. Tint etching and heat tinting were used to make the phases distinguishable even in the light microscope and thus be able to quantitatively evaluate the phase fractions without electron microscopy. The impact of hot isostatic pressing was examined in terms of phase fractions, the single phases' chemical composition and macroscopic hardness.