AlCoCrFeNi2.1 共晶高熵合金通过软硬双相协同变形，有效克服单相高熵合金 FCC/BCC 结构固有的强塑性倒置瓶颈。 本文针对该合金非平衡凝固条件下组织演变与性能调控的关键科学问题，利用 35 m 落管无容器凝固技术实现了合金的深过冷快速凝固，制备了粒径覆盖 100~2 800 μm 的系列球状试样，系统阐明了粒径对合金微观组织演化与力学性能的耦合调控机制。 研究发现，所有落管样品均保持 FCC+B2 双相结构；随粒径减小，合金组织依次经历径向梯度组织(2 800~1 500 μm，表面初生枝晶+反常共晶至心部规则层片共晶)→枝晶细化碎化(1 200~520 μm)→完全反常共晶(<520 μm)的演变路径；微观结构的演变直接导致力学性能的差异化响应：大粒径试样呈现中心低、外围高的硬度梯度，小粒径试样(1 200~100 μm)硬度随粒径减小线性提升(307~324 HV)。

AlCoCrFeNi2.1 eutectic high-entropy alloys effectively overcome the inherent strength-ductility trade-off bottleneck of single-phase high-entropy alloys with FCC/BCC structures via the coordinated deformation of soft and hard phases. To address the key scientific issues of the microstructure evolution and performance regulation of the alloy under nonequilibrium solidification conditions, this study adopted 35 m drop tube containerless solidification technology to realize deep undercooling and rapid solidification of the alloy. Spherical samples with particle sizes ranging from 100 to 2 800 μm were prepared, and the coupled regulatory mechanism of particle size on the microstructure evolution and mechanical properties of the alloy was systematically clarified. The results show that all the drop-tube samples maintain a dual-phase structure of FCC +B2. With decreasing particle size, the evolution path of the alloy microstructure is as follows: radial gradient structure (2 800~1 500 μm, from primary dendrites+anomalous eutectic on the surface to regular lamellar eutectic in the center)→dendrite refinement and fragmentation (1 200~520 μm)→complete anomalous eutectic (<520 μm). The evolution of the microstructure directly leads to the differential response of the mechanical properties: large samples exhibit ahardness gradient of low center and high periphery, whereas the hardness of small samples (1200~100 μm) increases linearly with decreasing particle size (307~324 HV).