Mössbauer and ultrasonic study of the as-cast high-entropy AlxCuCrCoNiFe alloys

Abstract

Determination of the hyperfine-interaction parameters, acoustic and elastic properties of the high-entropy AlxCuCrCoNiFe alloys (HEAs) (x=1, 1.8) in the as-cast state is carried out with the use of Mössbauer spectroscopy, x-ray diffractometry and high-precision ultrasonic techniques. Wide distributions of both the hyperfine-magnetic fields on iron nuclei (5.0-36.3 T) and the isomer shifts (-0.15-+0.28 mm/s) are detected in the HEAs that is result of multiphase state and inhomogeneous short-range order in the phases. As shown, the as-cast AlxCuCrCoNiFe HEAs are acoustically and elastically inhomogeneous systems. Mean elastic moduli of the as-cast equimolar HEAs ( 172.8 GPa, =65.3 GPa, = 161.8 GPa) and the Debye temperature ( 436 K) exceed ones for the elemental metals composing HEAs. There are the Poisson's ratio =0.312-0.322 and the ratio / = 2.321-2.477. Deviation from equimolar content of Al (x=1.8) results in redistribution of the spin and charge s-electron densities near iron nuclei, increases the elastic moduli and the Debye temperature by approximately 4-5%.