The Effect of Zirconium on the Microstructure and Properties of Cast AlCoCrFeNi_2.1 Eutectic High-Entropy Alloy

To improve the performance of AlCoCrFeNi_2.1 eutectic high-entropy alloys (EHEA) to meet industrial application requirements, Zr_xAlCoCrFeNi_2.1 high-entropy alloys (x = 0, 0.01, 0.05, 0.1) were synthesized through vacuum induction melting. Their microstructures were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). Additionally, the hardness, low-temperature compressive properties, nanoindentation creep behavior, and corrosion resistance of these alloys were evaluated. The results showed that AlCoCrFeNi_2.1 is a eutectic high-entropy alloy composed of FCC and B2 phases, with the FCC phase being the primary phase. The addition of Zr significantly affected the phase stability, promoting the formation of intermetallic compounds such as Ni₇Zr₂, which acted as a bridge between the FCC and B2 phases. Zr addition enhanced the performance of the alloy through solid-solution and dispersion strengthening. However, as the Zr content increased, Ni gradually precipitated from the B2 phase, leading to a reduction in the fraction of the B2 phase. Consequently, at x = 0.1, the microhardness and compressive strength decreased at room temperature. Furthermore, a higher Zr content reduced the sensitivity of the alloy to loading rate changes during creep. At x = 0.05, the creep exponent exceeded 3, indicating that dislocation creep mechanisms dominated. In the Zr_xAlCoCrFeNi_2.1 (where x = 0, 0.01, 0.05, 0.1) alloys, when the Zr content is 0.1, the alloy exhibits the lowest self-corrosion current density of 0.034197 μA/cm² and the highest pitting potential of 323.06 mV, indicating that the alloy has the best corrosion resistance.