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.

Zero‐Magnetostriction Magnetically Soft High‐Entropy Alloys in the AlCoFeNiCux (x = 0.6–3.0) System for Supersilent Applications

“…These values are in the same range as the resistivity of the non‐oriented electrical steel (silicon steel Fe 97 Si 3 , type M270‐35A), a commonly used commercial magnetically soft material, where ρ 2K = 30 µΩ cm and ρ 400K = 46 µΩ cm. [ 13 ] This similarity indicates that the eddy‐current losses in the AlCoFeNiCu x HEAs should be about the same as in the silicon steel, confirming their usefulness as soft magnets.…”

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.…”

A novel high-entropy alloy with an exceptional combination of soft magnetic properties and corrosion resistance

“…Compared with the reported representative magnetic HEAs with or without antiferromagnetic Cr element (Fig. 3c), such as FeCoCrNi [21], Fe 40 Co 40 Ni 10 Cr 10 [37], AlCoCrFeNi [20], CoCrFeNiTiAl [38], TiVCrNiZrFe 10 [39], AlCoCuFeNi 0.5 [40], FeCoNiMnAl [41], FeCoNiPdCu [42], AlCoCrFeNi [43] HEA exhibited far better soft magnetic properties.…”