Phase evolution and mechanical properties of novel FeCoNiCuMox high entropy alloys

Abstract

In this work, the effect of Mo addition on phase evolution and mechanical properties of as-cast FeCoNiCuMox (molar ratio X = 0.2, 0.4, 0.6, 0.8, 1) high entropy alloy systems (HEAs) have been investigated. It has been found that with increasing Mo concentration, atomic size difference (δ), geometrical parameter (∧) and enthalpy of mixing (ΔHmix) of this multi-component alloy systems decrease. However, the mixing entropy (ΔSmix), electronegativity difference (ΔX), d-orbital energy level parameter (Md‾), root mean square residual strain (RMS) and critical parameter (Ω) increases which clearly indicates the formation of the solid solution with no intermetallic compounds. X-ray diffraction and scanning electron microscope analysis also confirm that FCC solid solution phases are formed at X = 0.2 to 0.6. Further, on increasing the Mo concentration beyond 13 at % (X > 0.6), FCC1 and FCC2 phase were detected due to large positive enthalpy of mixing between Cu and others (Fe, Co, Ni, and Mo) elements. Moreover, the segregation of Cu in the FeCoNiCuMox (X = 0.8 and 1) alloy can be well predicted via φ and λ parameters. The Compressive strength and hardness were found to increase with Mo concentration in FeCoNiCuMox HEAs due to solid solution strengthening.