Phase, Microstructure and Corrosion Behaviour of Al_0.3FeCoNiCr_x High-Entropy Alloys via Cr Addition

The microstructure evolution of Al_0.3FeCoNiCr_x (x = 0, 0.3, 0.5, 1, 1.5) high-entropy alloys (HEAs) were studied using X-Ray diffraction technique and scanning electron microscope equipped with energy dispersive spectrometer. The short-term and long-term corrosion behaviours of these alloys in 3.5 wt.% NaCl solution were studied by electrochemical impedance spectroscopy, potentiodynamic polarisation measurement, immersion test and corrosion morphology analysis. The results show that all the designed HEAs present single-phase FCC structure, and the increase in Cr content changes the microstructural morphology from cellular to a typical dendritic-interdendritic state. Without the influence of phase transformation, the corrosion resistance of Al_0.3FeCoNiCr_x HEAs gradually increases with the increase in Cr content. Our designed alloys exhibit excellent corrosion resistance compared to the existing HEAs in the AlFeCoNiCr composition system.