Microstructure characterization and corrosion resistance of eutectic and near-eutectic AlCoCrFeNi high-entropy alloys
Zhipeng Yuan, Zhikang Yang, Yifan Lu, Ting Yuan, Yiyou Tu, Zenglei Ni, Leyu Wei, Syed Raza Ali Raza
Abstract
Corrosion resistance of high-entropy alloys (HEAs) are critical challenges in the development of advanced structural materials, particularly for applications in harsh environments. With the growing demand for such materials across various industries, understanding the influence of nickel (Ni) content on the microstructure and properties of AlCoCrFeNi-based HEAs has become a key issue in addressing these engineering challenges. Therefore, the design and optimization of HEAs to enhance their performance in corrosive environments is crucial for practical applications. In this paper, systematic experiments were performed to investigate the corrosion resistance of AlCoCrFeNi2.1 and AlCoCrFeNi2.2 HEAs. A detailed analysis of phase evolution and its impact on the material properties was conducted using X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). To evaluate electrochemical performance, Micro-Vickers hardness tests, electrochemical measurements, and equivalent circuit modeling were employed. The results indicate that the FCC/B2 phase ratio, controlled by Ni content, plays a critical role in determining the hardness and corrosion resistance of the alloys. Specifically, AlCoCrFeNi2.2, with a higher fraction of the FCC phase, exhibited superior corrosion resistance, while AlCoCrFeNi2.1, dominated by the B2 phase, demonstrated higher hardness. Corrosion was primarily attributed to the preferential dissolution of the B2 phase, with localized pitting identified as the dominant corrosion mechanism. This study provides valuable insights for optimizing the composition and enhancing the performance of AlCoCrFeNi-based HEAs in corrosive environments.