First principles study of influence of alloying elements on TiAl: cleavage strength and deformability

The electronic structure and binding energy of a number of TiAl–X alloy systems (X=V, Cr, Mn, or Si) were calculated using the discrete variational cluster method, based on the local density approximation of the density functional theory. The influence of alloying elements on the cleavage strength and the deformability of TiAl was investigated by means of an atomistically uniaxial loading deformation along the [0 0 1] and the [1 1 0] directions, respectively. The results show that both the cleavage strength and the deformability of TiAl depend on the substitution behaviour of alloying atoms in TiAl. In general, the 3d transition atoms V, Cr, and Mn enhance the cleavage strength and the deformability of TiAl due to an increased number of d-electrons contributing to the d–d bonding, while the atom Al and Si reduce the cleavage strength and the deformability of TiAl because of relatively strong hybridization between the p- and d-electrons.