Microstructure and Corrosion Resistance of NiAl-Based High-Entropy Alloys

In this study, the microstructure and corrosion resistance of novel NiAl-based high-entropy alloys (HEAs) were studied. The as-cast structural analysis at the micron-scale and nano-scale revealed that the microstructure comprised hierarchical nano-scale precipitates and a matrix. The size of the nanoprecipitates gradually increases from the inside of the grains to the grain boundaries. Furthermore, x-ray diffraction (XRD) and transmission electron microscopy (TEM) studies revealed that the nano-scale precipitates near the grain boundaries maintained coherent interfaces with an ordered (Cr, Fe)-rich body-centered cubic (BCC) structure and that the matrix was a NiAl BCC structure. The polarisation tests reveal that the Ni₃₅Al₃₅Co₁₀Cr₁₀Fe₁₀ (Ni35(i)) HEA has the highest open-circuit potential and the lowest open-circuit current density, which are − 0.78638 V and 1.094 × 10⁻⁶ A·cm⁻², respectively. Finally, the influence of (Cr, Fe)-rich precipitates near the grain boundaries and the effect of Cr on corrosion resistance were analysed.