Phonon behavior in a random solid solution: a lattice dynamics study on the high-entropy alloy FeCoCrMnNi

Shelby R Turner (1, 2, 3) , Stéphane Pailhès (3) , Frédéric Bourdarot (4) , Jacques Ollivier (1) , Yvan Sidis (5) , John-Paul Castellan (5, 6) , Jean-Marc Zanotti (5) , Quentin Berrod (7) , Florence Porcher (5) , Alexei Bosak (8) , Michael Feuerbacher (9) , Helmut Schober (1) , Marc de Boissieu (2) , Valentina M Giordano (3)

1 ILL - Institut Laue-Langevin
2 SIMaP - Science et Ingénierie des Matériaux et Procédés
3 ILM - Institut Lumière Matière [Villeurbanne]
4 MDN - Magnétisme et Diffusion Neutronique
5 LLB - UMR 12 - Laboratoire Léon Brillouin
6 KIT - Karlsruher Institut für Technologie
7 STEP - Synthèse, Structure et Propriétés de Matériaux Fonctionnels
8 ESRF - European Synchrotron Radiation Facility [Grenoble]
9 PGI - Peter Grünberg Institut

High-Entropy Alloys (HEAs) are a new family of crystalline random alloys with four or more elements in a simple unit cell, at the forefront of materials research for their exceptional mechanical properties. Their strong chemical disorder leads to mass and force-constant fluctuations which are expected to strongly reduce phonon lifetime, responsible for thermal transport, similarly to glasses. Still, the long range order would associate HEAs to crystals with a complex disordered unit cell. These two families of materials, however, exhibit very different phonon dynamics, still leading to similar thermal properties. The question arises on the positioning of HEAs in this context. Here we present an exhaustive experimental investigation of the lattice dynamics in a HEA, Fe 20 Co 20 Cr 20 Mn 20 Ni 20 , using inelastic neutron and X-ray scattering. We demonstrate that HEAs present unique phonon dynamics at the frontier between fully disordered and ordered materials, characterized by long-propagating acoustic phonons in the whole Brillouin zone.

Mots clés: Phonon dynamics; High entropy alloy HEA; Inelastic scattering

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Shelby R Turner, Stéphane Pailhès, Frédéric Bourdarot, Jacques Ollivier, Yvan Sidis, et al.. Phonon behavior in a random solid solution: a lattice dynamics study on the high-entropy alloy FeCoCrMnNi. Nature Communications, 2022, 13 (1), pp.7509. ⟨10.1038/s41467-022-35125-4⟩. ⟨hal-04281463⟩