Phase discretization induced nonlinear corrosion response mechanism of Al-Co-Cr-Fe-Ni high-entropy alloys prepared by laser cladding

This study employed cable-type welding wire laser cladding (CTWW-LC) technology to fabricate Al-Co-Cr-Fe-Ni high-entropy alloy (HEA) coatings with different dilution rates, systematically investigating the influence mechanism of the dual-phase (BCC/FCC) structure on corrosion behavior. Through microstructural characterization, electrochemical testing, and analysis of the passive film composition, the quantitative regulatory laws of phase spacing and phase proportion on corrosion properties were revealed. The results indicate that in the areas where the two phases are very close to each other, the difference in the potentials of the two phases can cause significant local corrosion of the BCC phase. Moreover, the proportion of the FCC phase exhibits a threshold effect: when it is below about 16.58 %, isolated FCC lamellae trigger a “cathodic discretization” effect, accelerating the dissolution of the BCC matrix and increasing the corrosion current density to 8.874 × 10⁻⁶ A/cm². However, as the proportion of the FCC phase increases, the corrosion resistance gradually recovers due to the enhanced continuity of the dual-phase structure. This study reveals the quantitative mechanisms of phase interface effect and nonlinear response of phase proportion in dual-phase HEAs, providing a theoretical basis for the compositional design and process optimization of high-entropy alloy coatings in extreme environments.