Skip to ContentSkip to Navigation
Part of University of Groningen
Science LinX Science Linx News

Finding new alloys just became simpler

16 September 2021

In metal alloys, behaviour at the atomic scale affects the material’s properties. However, the number of possible alloys is astronomical. Together with an international team of colleagues, Francesco Maresca, an engineer at the University of Groningen, developed a theoretical model that allows him to rapidly determine the strength of millions of different alloys at high temperatures. Experiments confirmed the model predictions. The findings were published in Nature Communications on 16 September.

The discovery that iron became much stronger with the addition of a little bit of carbon was one of the discoveries that heralded the Industrial Revolution. ‘Tweaking the composition of a base metal by adding different elements, thus creating an alloy, has been important in human history,’ says Francesco Maresca, assistant professor at the Engineering and Technology institute Groningen (ENTEG), at the University of Groningen. As a civil engineer, he likes large structures such as bridges. But he is now studying metals at an atomic scale to find the best alloys for specific applications.

Francesco Maresca
Francesco Maresca

Dislocation

Maresca is particularly interested in high-entropy alloys (HEAs), which were first proposed some twenty years ago. These are complex alloys with five or more elements that can have all kinds of useful properties. But how to find the best one? ‘There are around forty metallic elements that are not radioactive or toxic and are therefore suitable for use in alloys. This gives us roughly 1078 different compositions,’ he explains. It is impossible to test a large fraction of these by simply making them.

This is why Maresca wanted a good theory to describe important properties of HEAs. One of those properties is high-temperature strength, essential in various applications ranging from turbine engines to nuclear power plants. The strength of an alloy depends largely on defects in the crystal structure. ‘Perfect crystals are the strongest, but these do not exist in real life materials.’ A major determinant of strength at high temperatures in body-centred cubic alloys is thought to be a screw dislocation, a dislocation in the lattice structure of a crystal in which the atoms are rearranged into a helical pattern. ‘These dislocations are very hard to model at the atomic scale,’ explains Maresca.

Composition

Another type of defect is edge dislocation, where an extra atomic plane is inserted into part of the crystal structure. Maresca: ‘It was believed that these dislocations have no effect on strength at high temperatures, because that was shown experimentally in pure metals. However, we found that they can determine strength in complex alloys.’ Edge dislocations are much easier to model and Maresca created an atomic-scale model for this dislocation in HEAs, which he then translated into a MATLAB script that could predict the engineering-scale strength of millions of different alloys at high temperatures in a matter of minutes.

Atomistic models shed light on the strengthening mechanisms of dislocations in alloys (panel a). Based on easily accessible input (composition, lattice parameters, elastic constants), an analytical model is formulated that enables the efficient screening over millions of alloys (panel b). The screening provides the prediction of the high-temperature yield strength of millions of high entropy alloys (panel c). | Illustration Francesco Maresca
Atomistic models shed light on the strengthening mechanisms of dislocations in alloys (panel a). Based on easily accessible input (composition, lattice parameters, elastic constants), an analytical model is formulated that enables the efficient screening over millions of alloys (panel b). The screening provides the prediction of the high-temperature yield strength of millions of high entropy alloys (panel c). | Illustration Francesco Maresca

The result is a strength versus temperature relationship for these different alloys. ‘Using our results, you can find which compositions will give you a specific strength at, for example, 1300 Kelvin. This allows you to tweak the properties of such a high-temperature-resistant material.’ The theoretical results can be used to create alloys with new properties, or to find alternative compositions when one element in an alloy becomes scarce. The model was validated by creating two different alloys and testing their predicted ‘yield strength’, the amount of stress they can withstand at high temperatures without irreversible deformation. The importance of edge dislocation in this process was confirmed using different experimental techniques.

Surprise

‘We also made an atomic model for screw dislocations, which was too complicated for the high-throughput analysis used for the edge dislocation,’ says Maresca. This confirmed that screw dislocation was not the most important determinant of yield strength in these alloys. The finding that edge dislocation actually determines a large part of the yield strength of complex HEAs was a major surprise and one that has made a simple, theory-driven discovery of new complex alloys possible.

Reference: Chanho Lee, Francesco Maresca, Rui Feng, Yi Chou, T. Ungar, Michael Widom, Ke An, Jonathan D. Poplawsky, Yi-Chia Chou, Peter K. Liaw, and W. A. Curtin: Strength can be controlled by edge dislocations in refractory high-entropy alloys. Nature Communications, 16 September 2021.

Last modified:16 September 2021 11.49 a.m.
View this page in: Nederlands

More news

  • 11 December 2023

    Join the 'Language and AI' community

    As a part of the Jantina Tammes School, the 'Language and AI' theme is an interdisciplinary initiative that aims to encourage collaboration among academics, PhD candidates, students, and industry representatives who share a keen interest in the...

  • 13 October 2023

    Moniek Tromp appointed Captain of Science of the Top Sector Chemistry

    Prof. Moniek Tromp has been appointed Captain of Science of the Chemistry Top Sector by the Minister of Economic Affairs and Climate Policy. As from 1 July 2023, she succeeded Prof. Bert Weckhuysen from Utrecht University.

  • 12 September 2023

    Art in times of AI

    Leonardo Arriagada Beltran conducted his PhD research on the interface of computer-generated art and the constantly evolving field of Artificial Intelligence (AI). He will defend his Phd thesis on 21 September. His research offers valuable insights...