Chair of

High Temperature Materials

Mo-Hf-B and Mo-Zr-B alloys as a new class of refractory alloys are potential candidates in stationary and mobile turbine applications. Due to the high melting points of the constituents high-temperature strength and creep strength are expected up to 1,400 °C. Those high service temperatures, in turn, may result in higher turbine efficiencies and may reduce primary energy consumption.

As a manufacturing route, directional solidification via zone melting as a new processing approach for Mo-Hf-B and Mo-Zr-B results in low oxygen (< 50 ppm) impurities, which is essential to avoid embrittlement of these alloys; moreover the materials possess an anisotropic lamellae-reinforced microstructure.

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With the aid of density functional theory it is possible to adress many questions regarding metals and intermetallics likewise. Not only it is possible to predict the crystal structure of a solid, but also the ability to investigate and explain site preferences within intermetallics like borides and silicides comes in handy. It is also very important to determine the stability of metals and intermetallics and, in doing so, the electronic and phononic properties is investigated. The phase stability of matrix, side phases and precipitations depends on the temperature and the pressure and therefore one uses first principles calculations to investigate the thermodynamic properties of these metals and intermetallic phases at least qualitatively. The elastic properties of the metals and intermetallics can also be predicted to a very good precision.
Density functional theory is therefore the ideal ansatz to investigate metals and intermetallics as it is accurate and fast.

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In cooperation with the Karlsruhe Institute of Technology (KIT), the FlexiDS project aims to investigate the process of directional solidification in various high-temperature materials using in-situ X-ray diffraction. Within this framework, an innovative in-situ sample environment for directional solidification is to be developed and set up at the HEMS (High Energy Material Science) beamline at DESY (Deutsches Elektronen Synchrotron, Hamburg) . This will offer the partners involved completely new research and characterization possibilities through direct observation of the directional solidification process. The Helmholtz-Zentrum-Geesthacht (HZG), which is in charge of this beamline, will support the design, construction and operation of the sample environment.
This text was translated with DeepL

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