Point Defects and Their Properties in the Fe 20 Ni 20 Cr 20 Co 20 Cu 20 High-Entropy Alloy
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Point Defects and Their Properties in the Fe20Ni20Cr20Co20Cu20 High-Entropy Alloy M. A. Kretovaa, R. A. Konchakova, *, N. P. Kobelevb, and V. A. Khonika a
b Institute
Voronezh State Pedagogical University, Voronezh, 394043 Russia of Solid State Physics, Russian Academy of Sciences, Chernogolovka, Moscow region, 142432 Russia *e-mail: [email protected] Received April 27, 2020; revised April 27, 2020; accepted May 1, 2020
The characteristics of interstitial atoms and vacancies in the Fe20Ni20Cr20Co20Cu20 high-entropy alloy have been determined by the molecular dynamics and statics methods. The effect of these defects on elastic moduli has been analyzed. It has been found that interstitial atoms are stable only in the form of dumbbells responsible for a significant diaelastic effect (decrease in the shear modulus). As compared to vacancies, an increase in the concentration of interstitial dumbbells much more rapidly reduces the shear modulus with an increase in the volume. Furthermore, interstitial dumbbells are responsible for the appearance of specific high- and low-frequency modes in the spectrum of the vibrational density of states. The latter modes are related to the observed diaelastic effect. The evolution of the diaelastic effect and vibrational spectrum during the transition of the system to a noncrystalline state has been studied. DOI: 10.1134/S0021364020120097
1. INTRODUCTION High-entropy alloys (HEAs), i.e., systems consisting of five or more components, have been actively studied in the last decade [1] primarily because the uniqueness of their structural state has been recognized. Solid solutions of HEAs usually have a close packed (usually fcc) lattice, where various components are randomly distributed at the sites. Such alloys have a high entropy of mixing ΔSm = R ln n (R is the universal gas constant), which increases with the number of components n and reaches a maximum in the case of the equiatomic composition at a fixed n value [1]. Studies of HEAs are motivated by a fundamentally new composition “design” based on the entropy approach and by a very wide variety of chemical compositions and microstructures. It was found that HEAs have a number of attractive properties (high hardness and strength, high-temperature stability, high failure viscosity at cryogenic temperatures, corrosion resistance, biocompatibility, radiative stability, etc.). For this reason, HEAs are promising materials for various construction and functional applications [1, 2]. The study of HEAs can promote the fabrication of fundamentally new construction and functional metallic materials [3]. A separate problem is the study of high-entropy amorphous alloys beginning six to seven years ago. On one hand, these alloys hold unique properties characteristic of standard amorphous alloys. On the other hand, they have a higher stability to crystallization
(higher activation energies and temperature of crystallization, low growth rate of crystal phases) [4], which is very important for applications. It is specially ment
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