Microstructure, Corrosion Behaviour and Microhardness of Non-equiatomic Fe1.5CoNiCrCux (0.5 ≤ x ≤ 2.0) High-Entropy Alloys

The microstructure, electrochemical corrosion behaviour and microhardness of Fe1.5CoNiCrCux (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 Fe1.5CoNiCrCux 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 Fe1.5CoNiCrCu0.5 HEAs exhibited low corrosion rates owing to their high corrosion potential and low corrosion current density. The major types of corrosion for Fe1.5CoNiCrCux HEAs belong to localised corrosion and pitting, which is attributed to Cu-rich and Cr-depleted phases in the interdendritic region. The microhardness of Fe1.5CoNiCrCux HEAs increases from 142 HV for alloys with x = 0.5 to 190 HV for alloys with x = 2.0.