First-principles calculations of the site preference, phase stability and brittle versus ductile behaviors of TiAl intermetallic alloyed with ternary elements

Abstract

Effects of site preference, phase stability and brittle versus ductile behaviors of W, Mo, La and Ce in TiAl have been investigated by using the first-principles calculations. The results show that transition elements W and Mo can effectively stabilize B2 phase except rare earth elements La or Ce. Elastic modulus show that the ductility can be improved for ternary elements addition and there is a plastic transition from intrinsic brittleness to intrinsic ductility with W and Mo addition due to phase transition. The competitive mechanisms between the opening of microcracks and dislocation emission show the increased ductility is mainly due to the energetic dislocation but suppressed cracks. Finally, electronic density of states and charge density show that weakened covalent interactions of TiAl for W, Mo, La and Ce addition are the essential reasons for the transformation from brittleness to ductility.