Anelastic Damping of Resonant Ultrasound Spectroscopy (RUS) in Ni-rich Solid Solution Alloys at Very High Temperatures

• Applicant: Professor Dr.-Ing. Uwe Glatzel
• Subject Area: Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials ; Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 526145730

The element rhenium (Re) is largely responsible for the outstanding mechanical properties of nickel-base superalloys at high temperatures. As a material for turbine components, these alloys are also exposed to vibration. The resonance ultrasonic spectroscopy (RUS) can be used to precisely determine the orientation-dependent elastic constants until damping occurs. Significant damping sets in, depending on the alloy, at about 1000°C, well below the solidus temperature of ~1350°C. There is currently little knowledge about the composition-dependent damping properties in this temperature and frequency range. At the Chair of Metals and Alloys, a self-made RUS apparatus has been put into operation, with which measurements up to 1500°C are possible. Preliminary work shows that solid solution strengtheners such as Re influence the damping properties of Ni-rich solid solutions at very high temperatures. A high proportion of heavy alloying elements significantly lowers the activation energy and onset temperature of damping. There is evidence that the observed damping is due to defect transport along the alternating strain field. In the proposed project, data will be generated to support this hypothesis. The following three main questions arise. 1) How can damping in resonance ultrasonic spectroscopy in the frequency range 50 - 500 kHz be quantified precisely and reproducibly over a wide temperature range? 2) How do refractory alloying elements such as Re and Ru affect the temperature-dependent damping properties of the Ni-rich solid solution matrix quantitatively? 3) What rules for predicting the temperature-dependent mechanical damping can be determined from these observations? To answer these questions, the experimental setup must be optimized with respect to a minimum base damping of measurement and to the automated evaluation of the resonance peaks. The influence of the process route on the damping properties is to be quantified by further investigations to define standards for the further investigations. The influence of the alloying elements Re and Cr on RUS damping will be determined using single-phase samples. From the quantitative measurements of the damping properties of the samples containing Re and Cr, a model will be derived from which rules for the the design of alloys with optimized damping behavior can be derived.

• DFG Programme: Research Grants