Research results improve the usability of high-performance materials in engines

The research provides important foundations for the design of more robust and safer engine components in civil aviation and contributes to further improving flight safety in the long term.

The study was led by Prof. Benoit Merle from the Institute of Materials Engineering (Department of Mechanical Behavior of Materials) at the University of Kassel. An intermetallic phase (Ni₃Si) was investigated, which serves as a model material for so-called nickel-based superalloys that are used in aircraft engines.

A special feature of these materials is the so-called yield stress anomaly: unlike ordinary metals, they initially become firmer as temperatures rise. This effect is crucial for the mechanical reliability of engines, as they are operated at extremely high temperatures (> 1000°C) for efficiency reasons, which would lead to softening in conventional metals.

Until now, however, it was unclear whether this central mechanism is also maintained under shock-like loads, such as those that can occur during bird strikes, debris impacts or hard landings. Using novel nanoindentation experiments - a method in which mechanical properties are measured in the nanometer range - the Kassel team was able to show that the yield stress anomaly persists even at high loading speeds and even extends into higher temperature ranges. The fact that this finding has now been confirmed improves the potential applications of these materials in engines.

The work was carried out in collaboration with Prof. George M. Pharr from Texas A&M University (USA), an internationally leading and highly cited expert in the field of nanomechanics of materials. The project was funded by the European Research Council (ERC) as part of the EU's Horizon 2020 research program (Grant Agreement No. 949626).

The results were published in the renowned international journal Acta Materialia: Merle et al: "High strain rate persistence of the strength anomaly in the _L12 intermetallic compound _Ni3Sievidenced by nanoindentation testing" (2025)
https://doi.org/10.1016/j.actamat.2024.120598

What does this mean in summary?

• Unlike ordinary metals, nickel-based superalloys initially become stronger as temperatures rise.
• Until now, however, it was unclear whether this central mechanism also remains intact under shock-like loads.
• The Kassel research team has shown that the yield stress anomaly is also maintained at high loading rates.
• This finding improves the application possibilities of these materials in engines.