In this article, we investigate the microstructural stability of as-cast and directionally solidified (DS) AlCoCrFeNi_2.1 eutectic high-entropy alloys at elevated temperatures (900 °C to 1100 °C). The microstructure of the as-cast alloy is composed of a lamellar and mesh-like structure consisting of NiAl-rich (B2) and CoCrFeNi-rich (L1₂) phases. Annealing at 900 °C to 1100 °C results in the coarsening of the lamellar or mesh-like structures and the migration of termination. For the as-DS alloy, the solid–liquid interface undergoes a transition from planar to cellular morphology along with the decrease of interlamellar spacing with increasing the withdrawal rates. After the same heat treatment, the stability of DS microstructure is relatively excellent at 6 μm/s where only a little coarsening and migration of the lamellar structure occur. With increasing withdrawal rates, the microstructural degradation, like the coarsening of lamellar or mesh-like structures and the migration of termination, becomes severe because of the decrease of interlamellar spacing. Moreover, an interesting phenomenon is that the coarsening of the lamellar structure occurs along with the thinning of the adjacent lamellae at 1100 °C for the as-cast alloy or the DS alloy at 120 μm/s due to the fine interlamellar spacing. The relevant coarsening and migration mechanisms are discussed. In addition, the precipitate forms at 900 °C in all the experimental alloys and is identified as Ni-rich phase (FCC).

在本文中，我们研究了在高温（900°C至1100°C）下铸态和定向凝固（DS）AlCoCrFeNi _2.1共晶高熵合金的显微组织稳定性。铸态合金的微观结构由层状和网状结构组成，该结构由富NiAl（B2）和富CoCrFeNiNi（L1 ₂）相组成。在900°C至1100°C的温度下退火会导致层状或网状结构的粗化以及终端的迁移。对于as-DS合金，固液界面经历了从平面形态到细胞形态的转变，层间间距的减小伴随着退出速率的增加。相同的热处理后，DS微结构的稳定性是在6相对优异 μm / s，其中仅发生少量的层状结构粗化和迁移。随着退出速率的增加，由于层间距的减小，诸如层状或网状结构的粗化和终端的迁移之类的微观结构退化变得严重。此外，一个有趣的现象是，层状结构的粗大化与相邻薄片的1100处的变薄℃进行铸态合金或在120的DS合金沿发生μ米/秒，由于细层间距。讨论了相关的粗化和迁移机制。此外，所有实验合金中的沉淀物均在900°C时形成，并被确定为富镍相（FCC）。