Microstructure, Corrosion Behaviour and Microhardness of Non-equiatomic Fe_1.5CoNiCrCu _x (0.5 ≤ x ≤ 2.0) High-Entropy Alloys

The microstructure, electrochemical corrosion behaviour and microhardness of Fe_1.5CoNiCrCu_x (x = 0.5, 1.0, 1.5 and 2.0) high-entropy alloys (HEAs) were investigated by X-ray diffraction (XRD), scanning electron microscopy and an electrochemical workstation. The XRD spectra of Fe_1.5CoNiCrCu_x HEAs confirmed the face-centred cubic solid solution structure and that all specimens consisted of an fcc matrix and a Cu-rich fcc phase. The results of electrochemical corrosion tests showed that Fe_1.5CoNiCrCu_0.5 HEAs exhibited low corrosion rates owing to their high corrosion potential and low corrosion current density. The major types of corrosion for Fe_1.5CoNiCrCu_x HEAs belong to localised corrosion and pitting, which is attributed to Cu-rich and Cr-depleted phases in the interdendritic region. The microhardness of Fe_1.5CoNiCrCu_x HEAs increases from 142 HV for alloys with x = 0.5 to 190 HV for alloys with x = 2.0.