Pressure-induced magnetovolume effect in CoCrFeAl high-entropy alloy

Lei Liu,Elena Bykova,Minjie Dong,Lajos K Varga,Shuo Huang,Jan-Erik Rubensson,Bjarne S G Almqvist,Peter Lazor,Sergey Ivanov,Dongzhou Zhang,Bela Varga,Levente Vitos

doi:10.1038/s42005-019-0141-9

Abstract

High-entropy alloys (HEAs) composed of multiple-principal elements with (nearly) equimolar ratio establish a new conceptual framework for alloy design and hold a promise for extensive applications in industry, akin to the controlled expansion alloys (CEAs), such as Invar alloys. Spontaneously, one question emerges - would it be possible to synthesize a novel class of alloys combining the virtues of both CEAs and HEAs? Here, we report the pressure-induced magnetovolume effect in the body-centered-cubic CoCrFeAl HEA coupled with magnetic phase transitions from ferromagnetic to paramagnetic, and to non-magnetic states, originating from the successive collapses of local magnetic moments of Co and Fe. The observed magnetovolume anomalies, occurring in a progressive way, tailor appreciably the coefficient of thermal expansion of CoCrFeAl. These results further strengthen HEAs’ anticipated potential for designing multifunctional materials in virtue of their multiple outstanding properties, and reveal possible routes for their future synthesis.

Highlights

High-entropy alloys (HEAs) composed of multiple-principal elements with equimolar ratio establish a new conceptual framework for alloy design and hold a promise for extensive applications in industry, akin to the controlled expansion alloys (CEAs), such as Invar alloys
Bearing the prominent properties of Invar alloys and HEAs in mind, an interesting question arises—is it possible to synthesize materials, which possess combined merits of both classes of these extraordinary alloys? In the present study, by employing the techniques of in situ high-pressure X-ray diffraction (XRD) and ab initio calculation, we report the observation of the magnetovolume effect in CoCrFeAl HEA
The composition of the synthesized sample was analyzed by energy-dispersive X-ray fluorescence spectroscopy (EDS) method, and the results indicated the average composition is Co0.249Cr0.228Fe0.240Al0.282 (Supplementary Fig. 1), close to the nominal composition

Summary

Introduction

High-entropy alloys (HEAs) composed of multiple-principal elements with (nearly) equimolar ratio establish a new conceptual framework for alloy design and hold a promise for extensive applications in industry, akin to the controlled expansion alloys (CEAs), such as Invar alloys. Van Schilfgaarde et al.[16] considered that the usual thermal expansion was counteracted by a gradual volume decrease during the continuous transformation of the direction of magnetic moment—from the parallel to the non-collinear configuration. Both the 2γ and the non-collinear models attribute the Invar effect to the mutual dependence on magnetism and volume, the so-called magnetovolume effect. The results of this study show that the newly-emerged HEAs exhibit intriguing and potentially useful properties worth to be investigated further They reveal the future possibility of designing promising Invar high-entropy alloys (IHEAs), which combine outstanding properties of Invar alloy and HEAs

Methods

Results

Conclusion