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This study presents the differences in microstructure and corrosion behavior among AlCrFeCoNi (high-entropy alloy), CrFeCoNi (medium-entropy alloy), and CrCoNi (medium-entropy alloy). CrFeCoNi and CrCoNi exhibit a single-phase face-centered cubic (FCC) structure, whereas AlCrFeCoNi consists of an island-like FCC structure and a dendritic structure. The latter comprises radiating dendritic body-centered cubic (BCC) phases and interdendritic FCC phases. In AlCrFeCoNi, the (111) crystallographic orientation displays the highest texture intensity at 19.5 %. In 3.5 wt% NaCl solution, CrCoNi shows a lower corrosion current density I corr of 0.056 μA·cm −2 and a higher polarization resistance R p of 146.1 Ω·cm 2 . Additionally, its film resistance R f reaches the highest value of 1.246 × 10⁶ Ω·cm 2 , indicating that CrCoNi possesses the strongest corrosion resistance and the best passivation behavior. In U-bending immersion corrosion tests at various temperatures, AlCrFeCoNi exhibits a lower mixing enthalpy ΔH mix of –12.32 kJ/mol and a valence electron concentration VEC of 7.2, which together contribute to a gradual reduction in corrosion rate during thermal exposure. Additionally, its dual-phase microstructure leads to galvanic corrosion, resulting in progressive pitting. CrCoNi maintains the highest apparent activation energy across the temperature range, confirming its superior corrosion resistance.
Xu et al. (Thu,) studied this question.