Synthesis, characterizations, and magnetic properties of FeCoNiTi-based high-entropy alloys

The present report describes the effect of Mn, Cr, and Al on phase formation, magnetic, and hardness behavior of FeCoNiTi-based high-entropy alloys (HEAs). The selected HEAs are synthesized through mechanical alloying (MA). A single solid solution of fcc and mixture of fcc + R-phase are evolved for synthesized FeCoNiTiCr and FeCoNiTiMn HEAs respectively. However, mixture of fcc and bcc and minor fraction of R-phase are evolved for synthesized FeCoNiTiAl HEA. After annealing at 700 °C, a new bcc phase is evolved for FeCoNiTiMn HEA. On the other hand, there is no such phase formation that has been observed for FeCoNiTiCr and FeCoNiTiAl HEAs. All the synthesized HEAs exhibit ferromagnetic characteristics. The synthesized FeCoNiTiAl HEA possesses better semi-hard magnetic characteristics (Ms = 53.67 emu/g, Hc = 88.0 Oe) as compared to the synthesized FeCoNiTiCr (Ms = 24.17 emu/g, Hc = 151.6 Oe) and FeCoNiTiMn (Ms = 18.04 emu/g, Hc = 32.0 Oe) HEAs. After annealing at 700 °C, the magnetic characteristics changed dramatically. For annealed FeCoNiTiCr HEA, the value of Ms decreased to 1.83 emu/g from 24.17 emu/g. However, for annealed FeCoNiTiMn and FeCoNiTiAl HEAs, the saturation magnetization increased to 41.29 emu/g from 18.40 emu/g and 70.04 emu/g from 53.67 emu/g respectively. The 700 °C annealed FeCoNiTiMn HEA possesses better semi-hard magnetic characteristics along with better hardness (164 ± 4 HV) as compared to the synthesized and annealed FeCoNiTiCr and FeCoNiTiAl HEAs.