We have systematically investigate interfacial energetics and mechanical properties of the binary TiAl–Ti 3 Al alloy with the transition metals, using a first-principles method in combination with empirical criterions. V, Cr, Nb, Mo, Ta, W, and Re prefer to occupy the TiAl/Ti 3 Al interface, and increase the cleavage energy γ cl while decrease the unstable stacking fault energy γ us , leading to an increase of the ratio of γ cl /γ us , which suggests these transition metals can improve the ductility of the TiAl/Ti 3 Al interface. On the other hand, V, Cr, and Mn are shown to increase the interface energy and thus destabilize the TiAl/Ti 3 Al interface, which are beneficial to the ductility of the alloy in term of the microstructure. Therefore, V, Cr, and Mn with lower density should be the good choices of alloy elements for the binary TiAl–Ti 3 Al alloy among all these transition metals, consistent with the experimental results.