Comparative study of microstructural and corrosion characteristics of AlCrFeCoNi, CrFeCoNi and CrCoNi multicomponent alloys

• Galvanic coupling between BCC and FCC phases induces galvanic corrosion in AlCrFeCoNi. • The synergistic effect of a high fraction of (111) oriented texture and elevated high-angle grain boundary frequency collectively degrades the corrosion resistance of AlCrFeCoNi. • CrCoNi’s superior corrosion resistance across temperatures is attributed to its elevated apparent activation energy. 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.