The microstructures of Ti-46Al, Ti-46Al-0.3B, Ti-46Al-0.5B, Ti-46Al-2Fe, Ti-46Al-2Fe-0.3B, and Ti-46Al-2Fe-0.5B alloys solidified on water-cooled copper crucible were investigated. It is found that the as-cast alloys possess a typical columnar structure, and the mean diameters of the columnar grains decrease significantly as the addition of Fe or B. The mean columnar diameter in Ti-46Al-2Fe-0.5B is found to be the smallest among these alloys. B addition can increase the constitutional supercooling in front of the solid-liquid interface, which refines the columnar structure and the dendritic structure. Moreover, Fe addition can enhance the refining effect of boron on the columnar structure of TiAl-based alloys