Thermomagnetic analysis of FeCoCrxNi alloys: Magnetic entropy of high-entropy alloys

Abstract

The equimolar alloy FeCoCrNi, a high-entropy alloy, forms in the face-centered-cubic crystal structure and has a ferromagnetic Curie temperature of 130 K. In this study, we explore the effects of Cr concentration, cold-rolling, and subsequent heat treatments on the magnetic properties of FeCoCrxNi alloys. Cr reductions result in an increase of the Curie temperature, and may be used to tune the TC over a very large temperature range. The magnetic entropy change for a change in applied field of 2T is ΔSm = −0.35 J/(kg K) for cold-rolled FeCoCrNi. Cold-rolling results in a broadening of ΔSm, where subsequent heat treatment at 1073 K sharpens the magnetic entropy curve. In all of the alloys, we find that upon heating (after cold-rolling) there is a re-entrant magnetic moment near 730 K. This feature is much less pronounced in the as-cast samples (without cold-rolling) and in the Cr-rich samples, and is no longer observed after annealing at 1073 K. Possible origins of this behavior are discussed.

Physical Properties of High Entropy Alloys

“…Therefore, the Wiedemann-Franz law is not obeyed in these HEAs. The magnetocaloric properties of some HEA have been tested for possible magnetic refrigeration applications [35]. The magnetic entropy change (ΔS m ) for cold-rolled CoCrFeNi is −0.35 J/kg•K (the change in applied field is 2T).…”

High-entropy alloys: a critical assessment of their founding principles and future prospects

“…These include their use as protective coatings owing to their good corrosion and wear resistance 1,80,84,115,170,171,[219][220][221][222][223][224][225][226][227][228][229][230][231] (see review of laser-deposited HEA coatings by Zhang et al 232 ), as alloys for bulk metallic glasses, 11,[233][234][235][236] and even as materials for hydrogen storage 237 and diffusion barriers. 1,181,182 There has also been interest in their magnetic 1,10,97,[238][239][240][241][242][243] and thermoelectric properties. 244 These properties and applications, and others, are discussed in more detail in the reviews by Zhang et al 14 and Tsai et al 6 The authors consider one of the most promising potential applications for HEAs is as structural materials, and this is addressed specifically in the following text.…”

Structure of some CoCrFeNi and CoCrFeNiPd multicomponent HEA alloys by diffraction techniques

“…The structure and some physical properties have been reported in [37,38] and it was found to be single-phase with some interesting magnetic properties. However, later work showed undoubtedly that it was at least dual-phase with a structure clearly depending on the Pd content [35,36].…”