Relationship between Nb concentration and stability of α, ω, β phases in Ti-Nb alloys

The effect of Nb content on the lattice parameters and relative stability of α, β and ω phases in Ti_1-xNb_x (0<x≤0·30) alloys was investigated using the exact muffin-tin orbitals method in combination with the coherent potential approximation. For ω phase, the value of a increases and c/a decreases almost linearly with increasing Nb concentration. Whereas in the case of α phase, the lattice constant a and the value of c/a increase with the increasing Nb content. The critical Nb concentration for the complete stabilisation of β phase at 0 K is 26 at-%. An approximate composition range in which the ω phase exist is between 17 and 26 at-%Nb. The Nb addition enhances the stability of β phase relative to ω and α.