Two Al_xCoCrFeNi (x = 0.75, 1.25) high entropy alloys (HEAs) were prepared and annealed with different temperatures (800, 1000 and 1200 °C) and holding times (2 h, 4 h and 8 h) using furnace cooling. Effects of annealing treatment details on the microstructure and hardness of the HEAs were investigated. It was found that the σ-phase did not form in the Al_0.75CoCrFeNi alloy for whatever annealing temperatures or holding times. The σ-phase was produced at 610 °C and dissolved at 930 °C in the Al_1.25CoCrFeNi alloy. After dissolution, the σ-phase could reappear when this alloy furnace cooled from higher annealed temperature (1200 °C for 4 h) or longer duration time (1000 °C for 8 h). The reason is that the redistribution of Cr element in the post-holding stage or furnace cooling stage was sufficient to precipitate σ-phase. The formation and dissolution of σ-phase and their influences on the hardness in the HEAs were analyzed and discussed thoroughly.

制备了两种 Al _x CoCrFeNi ( x = 0.75, 1.25) 高熵合金 (HEA)，并使用炉冷在不同温度（800、1000和 1200 °C）和保温时间（2 小时、4 小时和 8 小时）下进行退火。研究了退火处理细节对 HEA 显微组织和硬度的影响。发现无论退火温度或保温时间如何，都不会在 Al _0.75 CoCrFeNi 合金中形成 σ 相。σ 相在 610 °C 下产生并在 930 °C 下溶解在 Al _1.25钴铬铁镍合金。溶解后，当该合金炉从更高的退火温度（1200°C 持续 4 小时）或更长的持续时间（1000°C 持续 8 小时）冷却时，σ 相会重新出现。原因是后保温阶段或炉冷阶段Cr元素的重新分布足以析出σ相。深入分析和讨论了 σ 相的形成和溶解及其对 HEAs 硬度的影响。