Nb effects on the structural and mechanical properties of TiAl alloy: Density-functional theory study

Nb can improve the oxidation resistance of TiAl; however, the reported concomitant effects on the mechanical properties are controversial. Therefore, the effect of different Nb additions (0∼20.83 at.% Nb) on the lattice distortion as well as dislocation nucleation and mobility of TiAl were examined by density-functional theory calculations to solve the puzzle. The calculation of the formation energy and c/a ratio showed that Nb slightly decreases the phase stability and enhances the anisotropy. The variation of shearing energy barrier demonstrates an interesting staged strengthening effect of Nb on TiAl. Further analyses of the charge density difference and the partial density of states reveal that the physical origination is the electronic anisotropy, which is correlated with the Nb content and distribution.