Dual-phase microstructures arising out of eutectic reactions offer several advantages: ease of casting, composite properties and tunable characteristic length scale of the phases. Eutectic high entropy alloys (EHEA) with a multi-component solution phase and a hard intermetallic phase are candidate materials to identify alternate high-temperature materials. Alloying elements can be chosen to improve the resistance to lamellar microstructure degradation and coarsening. In this work, we present the CALPHAD guided design of a hypo-eutectic high entropy alloy CoCrFeNiTa_0.395 with primary dendritic FCC phase and fine eutectic (FCC solution + Laves phase) microstructure possessing good high-temperature mechanical properties. The primary FCC phase fraction is 0.42 ± 0.02. The interlamellar spacing of the eutectic is 0.69 ± 0.12 μm. The alloy exhibited a balanced yield strength of 1303 ± 18 MPa, a fracture strength of 2237 ± 23 MPa and a fracture strain of 0.3 under room temperature compression testing. The mechanism for change in the lamellar morphology during deformation at temperatures beyond 0.8 T_E is explained schematically. Strain field distribution obtained by FEM simulation correlates well with the observed microstructure gradients in the deformed samples. The formation of nano-scale precipitates in the low strain rate deformation is attributed to thermal effects. High-temperature precipitation of two types of precipitates (L1₂ ordered and Ni₃Ta type) in the FCC-solution phase extended the useable temperature range of this alloy.

由共晶反应产生的双相微观结构提供了几个优点：易于铸造、复合性能和相的可调特征长度尺度。具有多组分溶液相和硬金属间相的共晶高熵合金 (EHEA) 是识别替代高温材料的候选材料。可以选择合金元素来提高对层状微观结构退化和粗化的抵抗力。在这项工作中，我们展示了亚共晶高熵合金 CoCrFeNiTa _0.395的 CALPHAD 引导设计具有初级枝晶 FCC 相和细共晶（FCC 溶液 + Laves 相）显微组织，具有良好的高温机械性能。主要 FCC 相分数为 0.42 ± 0.02。共晶的层间距为 0.69 ± 0.12 μm。该合金在室温压缩试验中表现出 1303±18 MPa 的平衡屈服强度、2237±23 MPa 的断裂强度和 0.3 的断裂应变。在超过 0.8 T _{E 的}温度下变形过程中层状形态变化的机制被示意性地解释。通过有限元模拟获得的应变场分布与变形样品中观察到的微观结构梯度非常相关。低应变率变形中纳米级析出物的形成归因于热效应。FCC 溶液相中两种析出物（L1 ₂有序和Ni ₃ Ta 型）的高温析出扩大了该合金的可用温度范围。