Influence of Nb concentration on the structure, stability, and electronic and mechanical properties of D0(22) Al3Ti by first-principles calculations and updates experiments

摘要

The crystal structure, stability, and electronic and mechanical properties of D0(22) Al3Ti-Al3Nb pseudobinary solid solution were systematically investigated by a first-principles method and experiment. The calculated formation energies demonstrated that all the Al-3(Ti1-xNbx) (0 <= x <= 1) solid solutions considered are thermodynamically stable and that the stability decreases monotonously with increasing Nb concentration. Lattice parameter a of Al-3(Ti1-xNbx) exhibits strong negative deviation from a linear composition dependence, while the trend is reversed for lattice parameter c. Study of the mechanical properties (including the bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and Debye temperature) reveals that Nb atom substitution in Al3Ti enhances the mechanical stability and strength. The analysis of calculated electronic structures reveals that the metallic behavior of Al-3(Ti1-xNbx) depends on the Nb concentration. Experimentally, Al-3(Ti1-xNbx) was synthesized and was characterized by means of X-ray diffraction and scanning electron microscopy. Rietveld refinement results confirmed that the lattice parameters are in the range of our previous calculated values. The differences between the calculated and experimental lattice parameters are also discussed in detail.