Corrosion behavior of AlCoCrFeNix high entropy alloys. (10th February 2023)

• Record Type: Journal Article
• Authors: Zemanate, Ana Maria; Jorge Júnior, Alberto Moreira; Andreani, Gisele Ferreira de Lima; Roche, Virginie; Cardoso, Kátia Regina
• Is Part Of: Electrochimica acta. Volume 441(2023)
• Publication Date: 2023-02-10
• Subjects: High entropy alloys -- Microstructure -- Corrosion; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2023.141844
• Languages: English
• ISSNs: 0013-4686

Abstract

Highlights: AlCoCrFeNix alloys were elaborated by arc melting and homogenized by heat treatments. Alloys show high hardness, reduced by increasing Ni that induces the soft FCC phase. Corrosion resistance is high, relies on Ni content, phases' composition, and fractions. Heat treatment led to a more homogeneous and less defective oxide film. Resulting oxide film reduced capacitance of alloys, improving corrosion resistance. Abstract: In this study, the effects of three different nickel concentrations on the microstructure, hardness, and corrosion properties of AlCrFeCoNix ( x = 1.0, 1.5, 2.0) high entropy alloys (HEA) were investigated. The alloys were obtained by arc melting from high-purity raw materials and subjected to heat treatment at 1125 °C for 5 h. Microstructural characterization revealed a dendritic morphology for the equimolar and AlCrFeCoNi1.5 alloys, while the AlCrFeCoNi2 alloy presented a hypoeutectic microstructure. Differences in microstructure and chemical composition were observed between the dendritic and interdendritic regions, with clear segregation of Cr in the interdendritic areas. The increase in Ni content and the heat treatment resulted in the formation of the FCC phase, consequently reducing the alloys' hardness. The corrosion properties of HEA were evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy methods in a 3.5% NaCl solution. The results show high resistance to localized corrosion of the alloys, evidenced by the low values of corrosion current densities, and high pitting potentials. The protective film's formation depends on Ni content, which is also related to FCC/BCC ratio and phase compositions. The heat treatment generally results in a more homogeneous, thicker, and less defective oxide film.