为了探索共晶高熵合金在增材制造过程中的快速凝固行为，本工作研究了冷却速率等凝固条件对共晶高熵合金相面积分数、相成分、晶粒形貌及力学性能的影响规律。通过铜模浇铸和选区激光熔化(SLM)分别制备Ni_43.5Co₁₉Cr₁₀Fe₁₀Al₁₅Ti₂Mo_0.5共晶高熵合金，采用SEM、EBSD及TEM对其凝固行为进行了分析，并测试了对应凝固条件下的力学性能。结果表明，在冷却速率最低的铸态试样心部，fcc领先相较多且形成等轴晶，而B2相的相面积分数为16.9%。在冷却速率更快的铸态试样表层，fcc领先相明显减少，B2相面积分数增加至23.0%。同时，铸态试样中各个区域B2相中Al元素浓度均为23.2% (原子分数，下同)。然而，在冷却速率最大的SLM试样中，B2相的面积分数最小，垂直于打印方向的统计结果为15.8%，且B2相中Al元素浓度降低至16.5%。SLM试样中B2相面积分数的下降是由于过快的冷却速率引起溶质截留，形成过饱和固溶体，导致达到共晶成分的液相减少。此外，扫描速率较大时，温度梯度较大，SLM试样普遍由柱状晶组成；当扫描速率降低至500 mm/s时，由于温度梯度减小，发生了柱状晶-等轴晶转变。SLM试样的力学性能优于铸态试样，平均室温抗拉强度达(1320.5 ± 4.5) MPa，平均断裂延伸率达到(25.8 ± 2.2)%。

Eutectic high-entropy alloys (EHEAs) have exhibited excellent mechanical properties. However, their rapid solidification behaviors during additive manufacturing processes still require further investigation. In the present study, Ni_43.5Co₁₉Cr₁₀Fe₁₀Al₁₅Ti₂Mo_0.5 EHEA via copper mold casting and selective laser melting (SLM) were produced to study the influence of solidification conditions, such as cooling rate, on the phase area fraction, phase composition, grain morphology, and mechanical properties of the alloy. SEM, EBSD, TEM, and tensile testing were used to systematically analyze the solidification behaviors and mechanical properties of this EHEA. The center of the as-cast specimen has the lowest cooling rate, a large amount of fcc primary phase appears and forms equiaxed crystals, with a B2 phase area fraction of 16.9%. As the cooling rate increases, the amount of fcc primary phase decreases, and the area fraction of the B2 phase increases to 23.0% on the surface of the as-cast specimen. Meanwhile, the concentration of Al in the B2 phase of each region in the as-cast specimen is 23.2% (atomic fraction, the same below). However, with the continuous increase in the cooling rate, the area fraction of B2 phase tends to reach its lowest value in the SLM specimen, with only 15.8% in edge-on orientation, and the concentration of Al in the B2 phase decreases to 16.5%. The decrease in the area fraction of the B2 phase in SLM samples is due to solute trapping caused by the high cooling rate, resulting in the formation of a supersaturated solid solution and a reduction in the amount of liquid phase available for forming eutecticphase. In addition, during the SLM process, a high scanning rate results in a large temperature gradient, which promotes the formation of columnar crystals. Reducing the scanning rate to 500 mm/s causes a columnar-to-equiaxed transition due to the decrease in temperature gradient. The mechanical properties of the SLM specimens are superior to those of the as-cast specimens, with a room-temperature ultimate tensile strength of (1320.5 ± 4.5) MPa and a fracture elongation of (25.8 ± 2.2)%.