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Due to the high operation temperatures, microstructural changes will occur in tungsten when used as plasma-facing material in future fusion reactors. In drawn tungsten wires, potassium doping has proven to prevent such undesired changes effectively. This strategy has been adapted to thin cold-rolled tungsten sheets containing 80 ppm potassium. Their texture evolution during annealing is investigated using electron backscatter diffraction. In the as-rolled condition, a strong cube texture is present with a volume fraction of 67.0 % deviating maximal 15° from the rotated cube orientation. This texture intensifies strongly during isochronal annealing for 2 h at temperatures between 1000 °C and 1300 °C; the higher the temperature, the higher the rotated cube fraction. The volume fraction of 94.8 % obtained after 2 h at 1300 °C does not change significantly during further annealing. These are remarkably strong textures for a body-centered cubic metal compared e.g. to commonly reported high volume fractions of 30 % for Goss orientations in silicon steels. Reliable quantification of such strong texture components requires analysis of orientations individually.

Pure tungsten is considered as armor material for the most critical parts of fusion reactors (i.e. the divertor and the first wall), among other reasons due to its high melting point (3422 °C) and recrystallization temperature. The thermal stability of a pure tungsten plate warm-rolled to a high plastic strain by 90% thickness reduction was investigated by isothermal annealing for up to 190 h in the temperature range between 1100 °C and 1250 °C. Vickers hardness testing allowed tracking the changes in mechanical properties caused by recovery and recrystallization. The hardness evolution could be rationalized in terms of a logarithmic recovery kinetics and a Johnson–Mehl–Avrami–Kolmogorov recrystallization kinetics accounting for an incubation time of recrystallization. The observed time spans for recrystallization and the corresponding recrystallization activation energy for this highly deformed plate suggest that large plastic deformations (e.g. applied during shaping) are only suitable to produce tungsten components to be used at relatively low temperatures (up to 900 °C for a 2 years lifespan). Higher operation temperatures will lead to fast degradation of the microstructure during operation.

Many physical and mechanical properties of crystalline materials depend strongly on their internal structure, which is typically organized into grains and domains on several length scales. Here we present dark-field X-ray microscopy; a non-destructive microscopy technique for the three-dimensional mapping of orientations and stresses on lengths scales from 100 nm to 1 mm within embedded sampling volumes. The technique, which allows ‘zooming’ in and out in both direct and angular space, is demonstrated by an annealing study of plastically deformed aluminium. Facilitating the direct study of the interactions between crystalline elements is a key step towards the formulation and validation of multiscale models that account for the entire heterogeneity of a material. Furthermore, dark-field X-ray microscopy is well suited to applied topics, where the structural evolution of internal nanoscale elements (for example, positioned at interfaces) is crucial to the performance and lifetime of macro-scale devices and components thereof., The internal structure of materials determines many of their physical and mechanical properties. Here, the authors have developed a non-destructive X-ray microscopy technique for layer-by-layer mapping of crystallographic orientations and stresses to obtain a three-dimensional reconstruction of a material.

Mit einem ballistischen Plastometer wurden dynamische Stauchversuche bei Umformgeschwindigkeiten ϕ zwischen 103 s−1 und 104 s−1 sowie verschiedenen Temperaturen durchgefuhrt. Die Anlage ist zur Aufnahme von Flieskurven geeignet. Im Anschlus an den Verformungsvorgang kann die Probe abgeschreckt werden, so das Strukturuntersuchungen (Licht- und Elektronenmikroskopie, rontgenografische Methoden usw.) am Deformationszustand des Werkstoffes moglich sind. Die Verformung geteilter Proben gestattet die Einbeziehung visioplastischer Methoden in die Auswertung. Die Ergebnisse von dynamischen Stauchversuchen an Kupfer und Aluminium werden vorgestellt und mit bei quasistatischer Verformung ermittelten Resultaten verglichen. Compression tests at high strain rates using a ballistic testing system Dynamic compression tests at strain rates ϕ between 103 s−1 and 104 s−1 and high temperatures were performed by means of a ballistic testing system. The equipment allows the determination of stress strain curves. Because the specimen can be quenched immediately after the deformation process, microstructural investigations (optical microscopy, TEM, X-ray analysis etc.) are possible. The compression of cutted specimens allows the application of visioplastic methods. In the present work the results of dynamic compression tests of Copper and Aluminium are presented and compared with such of quasistatic tests.