Elastic properties of β, α" and ω metastable phases in Ti-Nb alloy from first-principles

The method of pseudopotentials within the generalized gradient approximation has been employed to calculate the phase stability, electronic structure and elastic constants of beta, alpha '' and omega metastable phases in the Ti-25 at.% Nb alloy. The bulk, shear and Young's moduli of those metastable phases are estimated from the theoretical elastic constants by the Voigt-Reuss-Hill averaging method. The results show that the phase stability of those different metastable phases follows the order of alpha '' > omega > beta from the viewpoint of energetic and electronic structure. The bulk moduli of beta, alpha '' and omega phases are close, but the shear and Young's moduli increase with beta, alpha '' and omega phase in that order.