Discovery of a FeCoNiPdCu High‐Entropy Alloy with Excellent Magnetic Softness

Abstract

The authors report on the discovery of a magnetically soft high‐entropy alloy of composition FeCoNiPdCu, which performs comparably to the best commercial soft magnets for static and low‐frequency applications. Properly heat‐treated FeCoNiPdCu develops nanostructure that can be viewed as a two‐phase bulk nanocomposite of randomly intermixed FeCoNi magnetic domains and PdCu nonmagnetic “spacers”, both of 2–5 nm cross dimensions. Due to the nanometric size, the FeCoNi domains are magnetically single‐domain particles, and since the particles are exchange‐coupled across the boundaries, exchange averaging of magnetic anisotropy takes place, resulting in an almost vanishing coercive field and excellent magnetic softness. The formation of a two‐phase nanostructure favorable for the exchange averaging of magnetic anisotropy is a consequence of specific values of the binary mixing enthalpies for the chosen elements. Though high‐entropy alloys are generally considered to be random solid solutions of multiple elements on a topologically ordered crystal lattice, clustering of the atoms into preferential chemical environments on a nanoscale essentially determines their magnetic properties. Experimentally, the magnetic properties of the FeCoNiPdCu high‐entropy alloy are compared to the commercial, magnetically soft non‐oriented silicon electrical steel.

Fast mechanical synthesis, structure evolution, and thermal stability of nanostructured CoCrFeNiCu high entropy alloy

“…(5) In-situ HT XRD results show that the annealing at 1000 °C for 5.5 h and SPS consolidation at 1000 °C result in the formation of the CoCrFeNiCu HEA alloy with a single fcc 2 Cu-depleted phase. (6) The melting points for the Cu-rich and Cu-depleted HEAs were found to have the values of 1118 °C and 1288 °C, respectively, as calculated by Calphad approach and of 1115 °C and 1365 °C as a determined by DSC method. (7) During SPS at 1000 °C under applied pressure of 50 MPa, the formation of the CoCrFeNiCu 0.5 HEA with fcc single phase is thermodynamically more favorable than the equiatomic one.…”

“…The ability of retaining these properties depends on the structural stability in different environments such as corrosive media, high/low temperature, high load/high speed and other extreme conditions. High entropy alloys (HEAs) show excellent properties in some respects, such as high strength and corrosion resistance, outstanding mechanical properties including yield strength, creep properties, fracture toughness, and promising magnetic properties [1][2][3][4][5][6].…”

The (110) and (320) surfaces of a Cantor alloy

“…It has already led to the identification of superconductivity in refractory Ta 34 Nb 33 Hf 8 Zr 14 Ti 11 HEA 4 and more recently to magnetically soft transition metal HEAs in the FeCoNiPdCu system which performs comparatively to the best commercial soft magnets. 5 In literature, the majority of the studies remains devoted to the characterisation of the mechanical properties depending on the microstructure and composition. Among the variety of alloys, several refractory-based HEAs appear as potential candidates for applications in transport or aerospace industries due to their high melting temperature combined with high hardness.…”

Mechanical and Magnetic Properties of the High-Entropy Alloys for Combinatorial Approaches

“…Nowadays, most of the electronics and computational devices facilitate magnetism and magnetic materials as the smart functional materials [71]. The excellent mechanical properties of high-entropy alloys can improve the reliability of these modern devices [72][73][74].…”