Abstract
The reactivity of the surface of multicomponent metals such as High Entropy Alloys (HEAs) is rapidly gaining importance for corrosion and catalytic applications, but the mechanisms of surface segregation in these complex materials are poorly understood. Here we investigate with ab initio calculations the segregation thermodynamics in the magnetic Cr-Mn-Fe-Co-Ni HEA in vacuum, in the presence of O at the surface, and in the oxide phase. We predict a weak segregation of Ni for Cr-, Mn-, and Fe-rich alloys in vacuum and a very strong segregation of Cr and Mn upon exposure to O.
Highlights
High Entropy Alloys (HEAs) [1,2,3,4] are complex metallic solid solu tions with five or more principal elements in non-dilute concentrations that possess superior mechanical and structural properties with respect to conventional metals [5,6,7,8,9,10,11,12,13,14,15]
We address the fundamentals of surface segregation for the prototypical Cr-Mn-Fe-Co-Ni HEA [2,37] with first principles calculations
The first principles calculations were performed within the frame work of Density Functional Theory (DFT), using the plane-wave pro jector augmented wave (PAW) method [44,45] as implemented in VASP 5.4 [46,47,48] and the exact muffin-tin orbital (EMTO) method [49,50,51]
Summary
High Entropy Alloys (HEAs) [1,2,3,4] are complex metallic solid solu tions with five or more principal elements in non-dilute concentrations that possess superior mechanical and structural properties with respect to conventional metals [5,6,7,8,9,10,11,12,13,14,15]. Recent studies observed a seemingly uniform distribution of elements in high-entropy nanotubes [27], nanoparticles [28,29,30,31], and nanoporous structures [32], hinting that surface segregation may be negligible in the in vestigated HEAs at least in non-reactive conditions. This stands in stark contrast with common bimetallic alloys, such as PtPd, CoCr [33], Ag3Pd [34], where segregation is commonly reported.
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