Al-driven peculiarities of local coordination and magnetic properties in single-phase Alx-CrFeCoNi high-entropy alloys

Abstract

Modern design of superior multi-functional alloys composed of several principal components requires in-depth studies of their local structure for developing desired macroscopic properties. Herein, peculiarities of atomic arrangements on the local scale and electronic states of constituent elements in the single-phase face-centered cubic (fcc)- and body-centered cubic (bcc)-structured high-entropy Alx-CrFeCoNi alloys (x = 0.3 and 3, respectively) are explored by element-specific X-ray absorption spectroscopy in hard and soft X-ray energy ranges. Simulations based on the reverse Monte Carlo approach allow to perform a simultaneous fit of extended X-ray absorption fine structure spectra recorded at K absorption edges of each 3d constituent and to reconstruct the local environment within the first coordination shells of absorbers with high precision. The revealed unimodal and bimodal distributions of all five elements are in agreement with structure-dependent magnetic properties of studied alloys probed by magnetometry. A degree of surface atoms oxidation uncovered by soft X-rays suggests different kinetics of oxide formation for each type of constituents and has to be taken into account. X-ray magnetic circular dichroism technique employed at L2.3 absorption edges of transition metals demonstrates reduced magnetic moments of 3d metal constituents in the sub-surface region of in situ cleaned fcc-structured Al0.3-CrFeCoNi compared to their bulk values. Extended to nanostructured versions of multicomponent alloys, such studies would bring new insights related to effects of high entropy mixing on low dimensions.

Inner relaxations in equiatomic single-phase high-entropy cantor alloy

“…Moreover, the spectra of all elements in the Cantor alloy are very similar to those of pure Co and Ni foils shown in Ref. [59].…”

“…The EXAFS spectra of pure metallic foils collected in transmission mode at the K edges of other constituents at the same beamline can be found in Ref. [59].…”

“…In the current study, we followed the same procedure as described previously in Ref. [59]. The number of atomic configurations simultaneously considered in the EA was 32, and the largest allowed displacement of atoms from their initial position was 0.4 Å, which is sufficient to describe both static and thermal disorder.…”

“…Recently, we have employed the element-specific EXAFS technique in conjunction with the reverse Monte Carlo (RMC) based analysis to reveal key peculiarities of individual atom distributions on the local scale up to several coordination shells in AlxCrFeCoNi [59]. The interatomic distances between different nearest-neighbor pairs and quantitative estimations of local atomic structure relaxations were found.…”

Validation of moment tensor potentials for fcc and bcc metals using EXAFS spectra

“…To our knowledge, this is the first time a machine-learning potential for materials was validated using experimental EXAFS spectra. The employed approach is scalable to multicomponent alloys where EXAFS spectra can be independently measured for each element [45,46,47].…”