The Effect of Annealing on the Microstructure and Properties of the ZrxAlCoCrFeNi2.1 High-Entropy Alloy

Abstract

The Zr_xAlCoCrFeNi_2.1 eutectic high-entropy alloys (x=0, 0.01, 0.05, 0.1) were prepared using the vacuum electric furnace melting method and subjected to annealing at 600°C for 12 hours. The microstructural changes of the alloys with zirconium addition were analyzed using X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. Additionally, the Vickers hardness and room temperature compressive properties of the Zr_xAlCoCrFeNi_2.1 alloys were tested.The results indicate that AlCoCrFeNi_2.1 is a eutectic high-entropy alloy, primarily composed of FCC and B2 phases, with the FCC phase being dominant. As the zirconium content increases, nickel elements gradually precipitate from the B2 phase, forming Ni₇Zr₂ (Laves phase), which distributes in a network structure between the FCC and B2 phases. This structural change significantly enhances the hardness and compressive strength of the alloy.However, excessive zirconium leads to the coarsening of phases in the alloy, reducing the precipitation strengthening effect and resulting in a decrease in hardness and compressive performance. Overall, the main strengthening mechanisms of the alloy with increasing zirconium content are the precipitation strengthening from the hard Laves phase and the solid solution strengthening working in synergy.In summary, an appropriate amount of zirconium addition can effectively improve the properties of the Zr_xAlCoCrFeNi_2.1 alloy, while excessive zirconium can negatively impact the mechanical properties of the alloy.