Phase stability, mechanical properties and electronic structure of TiAl alloying with W, Mo, Sc and Yb: First-principles study

• There is a phase transition for TiAl from L10 to B2 structure when the concentrations of W and Mo are about 10.50 at.% and 11.50 at.%, respectively. However, there is no phase transition for L10 TiAl with Sc and Yb.
• The brittle/ductile transition are predicted for TiAl with W, Mo, Sc and Yb. It is found that W and Mo can effectively improve the ductility of TiAl due to the phase transition.
• The density of states is also used to analysis the mechanical properties, which is consistent with brittle/ductile transition map of TiAl based alloys.

The phase stability and site preference of alloying elements W, Mo, Sc and Yb in L10 and B2 TiAl alloys were investigated using first-principles calculations. It is found that there will be a phase transition from L10 to B2 structure when the concentrations of W and Mo are about 10.50 at.% and 11.50 at.%, respectively. However, there is no phase transition for L10 TiAl with Sc and Yb. The elastic constants, bulk modulus, shear modulus, Poisson's ratio and hardness of TiAl alloys are also systematically presented. Based on Pugh ratio, the brittle/ductile transition are predicted for TiAl with W, Mo, Sc and Yb. It is found that W and Mo can effectively improve the ductility of TiAl due to the phase transition. Finally, the density of states is also used to analysis the mechanical properties, which is consistent with brittle/ductile transition map of TiAl based alloys.