Effects of transition metals in a binary-phase TiAl-Ti ₃Al alloy: From site occupancy, interfacial energetics to mechanical properties

We have systematically investigate interfacial energetics and mechanical properties of the binary TiAl-Ti ₃Al 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 ₃Al 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 ₃Al interface. On the other hand, V, Cr, and Mn are shown to increase the interface energy and thus destabilize the TiAl/Ti ₃Al 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 ₃Al alloy among all these transition metals, consistent with the experimental results.