Abstract Ternary Al55Fe40Nb5 alloy was rapidly solidified in 3 m drop tube to investigate its solidification evolution and mechanical properties at high cooling rates and undercoolings. The microstructure of this alloy was composed of the primary FeAl dendrite, the (FeAl + Nb(Fe, Al)2) eutectic and the composite of FeAl, FeAl2 and Nb(Fe, Al)2 phases. As the alloy droplet diameter varied from 1200 to 80 μm, the growth morphology of primary FeAl phase evolved from coarse dendrite to refined dendrite, and finally into equiaxed grain. Meanwhile, the eutectic and the composite exhibited a regular to anomalous microstructure transition, and the Nb(Fe, Al)2 phase changed from aggregation growth to uniform distribution. Consequently, the homogenous reticulate-shaped particulate structure formed. The microscopic structures of the three intermetallic compound phases were explored by HRTEM technique. Under the influences of large undercooling and cooling rate, the grain refinement of primary phase and the homogenous distribution of three phases led to the increase of Vickers microhardness for this rapidly solidified alloy.

中文翻译：

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自由落体条件下三元Al-Fe-Nb合金的显微组织演变及力学性能

摘要 三元Al55Fe40Nb5 合金在3 m 下降管中快速凝固，以研究其在高冷却速率和过冷度下的凝固演变和力学性能。该合金的显微组织由初生 FeAl 枝晶、(FeAl + Nb(Fe, Al)2) 共晶和 FeAl、FeAl2 和 Nb(Fe,Al)2 相的复合相组成。随着合金液滴直径从 1200 μm 变化到 80 μm，初生 FeAl 相的生长形态从粗枝晶演变为细枝晶，最后演变为等轴晶。同时，共晶和复合材料呈现规则到异常的显微组织转变，Nb(Fe, Al)2 相从聚集生长转变为均匀分布。因此，形成了均质的网状颗粒结构。通过HRTEM技术探索了三种金属间化合物相的微观结构。在大过冷度和冷却速度的影响下，初生相晶粒细化和三相均匀分布导致该快速凝固合金的维氏显微硬度增加。