A zone melting device for the in situ observation of directional solidification using high-energy synchrotron x rays

Directional solidification (DS) is an established manufacturing process to produce high-performance components from metallic materials with optimized properties. Materials for demanding high-temperature applications, for instance in the energy generation and aircraft engine technology, can only be successfully produced using methods such as directional solidification. It has been applied on an industrial scale for a considerable amount of time, but advancing this method beyond the current applications is still challenging and almost exclusively limited to post-process characterization of the developed microstructures. For a knowledge-based advancement and a contribution to material innovation, in situ studies of the DS process are crucial using realistic sample sizes to ensure scalability of the results to industrial sizes. Therefore, a specially designed Flexible Directional Solidification (FlexiDS) device was developed for use at the P07 High Energy Materials Science beamline at PETRA III (Deutsches Elektronen-Synchrotron, Hamburg, Germany). In general, the process conditions of the crucible-free, inductively heated FlexiDS device can be varied from 6 mm/h to 12 000 mm/h (vertical withdrawal rate) and from 0 rpm to 35 rpm (axial sample rotation). Moreover, different atmospheres such as Ar, N₂, and vacuum can be used during operation. The device is designed for maximum operation temperatures of 2200 °C. This unique device allows in situ examination of the directional solidification process and subsequent solid-state reactions by x-ray diffraction in the transmission mode. Within this project, different structural intermetallic alloys with liquidus temperatures up to 2000 °C were studied in terms of liquid-solid regions, transformations, and decompositions, with varying process conditions.