High-Entropy alloys as high temperature materials? Microstructure, mechanical properties, oxidation and corrosion behaviour.

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Modifications of the alloy Al8Cr17Co17Cu8Fe17Ni33 will be investigated. This alloy turned out to be the most promising high entropy alloy up to now. It solidifies in a simple fcc solid solution and an ordered phase with L12 structure. The phase fractions and hence the alloys properties will be adjusted by additions of Ti, Ta and/or W. In order to better understand the formation of the phases it is important to investigate the high entropy alloys in detail in the as-cast state and after heat treatments. The microstructure and the mechanical properties will be correlated. A major aim of the project is the investigation of the thermal stability of the microstructure under mechanical load. The corrosion and oxidation resistance of these alloys are important for future application and will therefore be investigated. The following methods will be used in the project: X-ray diffraction, scanning and transmission electron microscopy, 3-dimensional atom probe, micro hardness testing, mechanical tests (e.g. hot tension and creep testing). The results will be discussed in terms of models using the already acquired knowledge about phase formation in high entropy alloys. Finally conclusions will be drawn concerning the suitability of high entropy alloys for the application as refractory materials.