A single-phase ScTiZrHf high-entropy alloy with thermally stable hexagonal close-packed structure

Abstract

High-entropy alloys forming non-cubic crystal structures are intriguing systems for both scientific and functional viewpoints. Hexagonal-structured HEAs are among them. In this work, we have fabricated a single-phase hexagonal close-packed phase in ScTiZrHf system. To verify its structural stability, we anneal the alloy samples at 973 K for a long time from 15 up to 140 h. Structural analysis reveals that the HEA retains its single-phase structure after the thermal treatment. To characterize the material, we examine its electron-transport and magnetic properties over a wide temperature range. The alloy electrical resistivity has purely metallic temperature dependence, while its absolute values are rather high. The thermal conductivity in this material is very low. The analysis of the transport properties reveals a noticeable lattice contribution (≈ 50% ) in total thermal conductivity probably caused by a strongly defected crystal structure. The alloy magnetization demonstrates complicated temperature dependence, which is well described by a superposition of Curie–Weiss and valence-electron contributions. Based on this suggestion, we fit experimental magnetization data and extract the electron density of states (DOS) at the Fermi level as ≈1eV−1. To address the properties of interatomic interaction in the system, we perform ab-initio molecular dynamics simulations of the liquid phase. The data obtained indicate unambiguously the absence of strong chemical interaction between alloy components as well as the nearly additive character of the liquid mixture that supports the results obtained experimentally.