Effect of Zr, Hf, and Sn additives on elastic properties of α₂-Ti₃Al phase by first-principles calculations

Abstract

First-principles calculations within density functional theory have been carried out to investigate α₂ phase in the Ti₃Al based alloy with Zr, Hf, and Sn (6.25at%) elements doped. The lattice constants, total energies and elastic constants were calculated for the supercells. The formation enthalpies, bulk modulus, shear modulus, Young’s modulus, and intrinsic hardness were investigated. The ductility of the doped α₂ phases was analyzed by the Cauchy pressure, G/B and Poisson’s ratio. The results show that the substitution of Ti(6 h) by Zr, Hf, and the substitution of Al(2n) by Sn can make the doped α₂ phase more stable. The inflexibility and hardness of α₂ phase can be enhanced by doping with Zr and Hf, while Sn brings the opposite effect. Sn is more powerful to improve the ductility of the doped α₂ phase than Hf, but Zr can increase the brittleness. The densities of states (DOS and PDOS) and the difference charge density are obtained to reveal the underlying mechanism of the effect of alloying elements.

Keywords

α²-Ti₃Al / neutral element / ambient ductility / first-principles

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