硼化物被广泛应用于铸造TiAl合金的晶粒细化中，已经有许多中不同结构的硼化物被报道过了。本文主要阐述了利用透射电子显微镜和第一性原理计算对TiAl合金中的细小硼化物进行观察和计算的工作。结果显示，大多半硼化物是一硼化物TiB且具有B27结构。在含有Nb和Mn的TiAl合金中，所有的TiB都是B27结构，且富Nb贫Mn。在含有Nb和Ta的TiAl合金中，则发现有B27与Bf共生的现象，硼化物中既富Nb也富Ta。第一性原理计算得出Ta、Mn、Nb对TiB晶型结构的合金化效应不同，Nb有助稳定B27不利于Bf，Ta强稳定B27和Bf，Mn则强烈破坏B27和Bf的形成。共生的B27和Bf结构的原子结构和界面已经被像差矫正电镜测定。

Borides have been widely used in cast TiAl alloy for grain refinement and a variety of stoichiometry and crystal structure of borides were reported. Here the effects of alloying elements Nb, Ta, and Mn on the structural stability of fine boride precipitates in TiAl alloys have been studied combining transmission electron microscopy (TEM) and first-principles calculations. The results show that most boride particles have the TiB stoichiometry. In the alloy containing Nb and Mn, all the TiB particles have the B27 structure and are highly enriched with Nb but depleted with Mn. In the alloy containing Nb and Ta, however, the intergrowth of Bf and B27 structure has been observed, and the TiB particles are enriched with both Nb and Ta. First-principles calculations reveal different effects of Nb, Ta, and Mn on the structural stability of TiB polymorphs. Nb stabilizes B27 but destabilizes Bf. Ta strongly stabilizes both B27 and Bf structures. Mn strongly destabilizes both B27 and Bf structures. In the TiB particles with the intergrowth of the B27 and Bf structures, the atomic structure of the interface have been determined using aberration-corrected TEM.