The Puzzle of Radiation-Resistant Alloys
Refractory high-entropy alloys are materials made from multiple high-melting-point metals in roughly equal proportions. Those containing tungsten exhibit minimal changes in mechanical properties when exposed to continuous radiation and could be used to shield the crucial components of future nuclear reactors. Now Jesper Byggmästar and his colleagues at the University of Helsinki have performed atomic simulations that explore the uncertain origins of this radiation resistance [1]. The findings could help scientists design novel materials that are even more robust than these alloys in extreme environments.
The researchers studied a tungsten-based refractory high-entropy alloy using state-of-the-art simulations guided by machine learning. In particular, they modeled the main mechanism by which radiation can disrupt such an alloy’s atomic structure. In this mechanism, the incoming radiation causes one atom in the alloy to displace another atom, forming one or more structural defects. The team determined the threshold energy needed to induce such displacements and its dependence on the masses of the two involved atoms.
Surprisingly, the researchers found that the tungsten alloy’s average threshold displacement energy is much lower than that of any of the material’s constituent pure metals, suggesting that the alloy is comparatively prone to defect creation. They also found that the threshold energy depends strongly on the masses of the involved atoms and that, in many cases, a particularly low value applies when a heavy atom—such as tungsten—displaces a light atom. According to the team, these findings suggest that the material’s radiation resistance cannot be explained by its robustness to radiation-induced defect formation. To fully solve the mystery, scientists will need to investigate other processes, particularly the ways in which the created defects diffuse through the alloy.
–Ryan Wilkinson
Ryan Wilkinson is a Corresponding Editor for Physics Magazine based in Durham, UK.
References
- J. Byggmästar et al., “Threshold displacement energies in refractory high-entropy alloys,” Phys. Rev. Mater. 8, 115406 (2024).