Magnetic properties, electrical resistivity, and hardness of high-entropy alloys FeCoNiPd and FeCoNiPt

TL;DR

This study investigates the magnetic, electrical, and hardness properties of FeCoNiPd and FeCoNiPt high-entropy alloys, revealing their soft ferromagnetic nature, metallic resistivity, and high hardness, with minimal effects from heat treatment.

Contribution

It provides experimental and theoretical insights into the physical properties of FeCoNiPd and FeCoNiPt HEAs, highlighting their potential for designing soft ferromagnetic alloys with high hardness.

Findings

Curie temperatures are 955 K and 851 K for FeCoNiPd and FeCoNiPt.

Both HEAs are soft ferromagnets with metallic resistivity.

Vickers hardness is 188 HV for both alloys.

Abstract

We report the magnetic properties, electrical resistivity, and Vickers microhardness of as-cast and annealed high-entropy alloys (HEAs) FeCoNiPd and FeCoNiPt with the face-centered cubic structure. The heat treatment at 800 $^{\circ}$C does not largely affect the physical properties in each HEA. The values of the Curie temperature and the saturation moment at 50 K are 955 K and 1.458 $\mu_\mathrm{B}$/f.u. for the annealed FeCoNiPd, and 851 K and 1.456 $\mu_\mathrm{B}$/f.u. for the annealed FeCoNiPt, respectively. Each HEA is a soft ferromagnet and shows metallic resistivity. The electronic structure calculations of both HEAs support the ferromagnetic ground states. The comparisons between experimental and theoretical values are made for the Curie temperature, the saturation moment, and the residual resistivity. The Vickers microhardness of annealed FeCoNiPd and FeCoNiPt are both 188 HV. The hardness vs. valence electron count (VEC) per atom plot of these HEAs does not largely deviate from an expected universal relation forming a broad peak at VEC$\sim$6.8. This study would give some hints on designing a soft ferromagnetic HEA with high hardness.