Microstructure, phase formation, and properties of melt-quenched CoCr0.8Cu0.64FeNi high-entropy alloy

Abstract

This paper explores the CoCr_0.8Cu_0.64FeNi high-entropy alloy. Different criteria, such as the valence electron concentration, the Ω parameter, and the atomic size difference δ, are used to estimate the phase composition of the alloy. As-cast samples of the alloy are made by melting the components in a high-temperature Tamman furnace in an argon flow and solidifying them in a copper mold. The weight loss during the ingot production is minimal, and the average cooling rate is about 10² K/s. Melt-quenched samples are made by remelting the cast ingot and rapidly cooling the melt droplets on the inner surface of a fast rotating (about 8000 rpm) hollow copper cylinder. The cooling rate, estimated from the film thickness, is about 10⁶ K/s. X-ray diffraction is used to analyze the structure of the samples on a DRON-2.0 diffractometer with monochromatic Cu K_α radiation. Magnetometry is used to measure the magnetic
properties of the samples at room temperature. The results confirm the theoretical predictions that the structure of the alloy, in both states, is an FCC solid solution. The lattice parameters in the as-cast and melt-quenched states are 0.3593 nm and 0.3589 nm, respectively. The results also show that the CoCr_0.8Cu_0.64FeNi alloy is a soft magnetic material, but its coercivity and microhardness increase after quenching due to internal stresses.