Influence of Nb content on mechanical behavior and microstructure of Ti–Nb alloys

Abstract

The effect of Nb content on the mechanical behavior of Ti-(20, 25, 30) at.% Nb alloys has been investigated. Results show that the storage modulus, the tensile strength and elongation at room temperature decrease with increasing Nb content. The Ti-20Nb and Ti-25Nb alloys show double-yielding behavior and they exhibit higher work hardening rate than the Ti-30Nb alloy. The Ti-20Nb alloy deforms by stress-induced β → α″ transformation and the reorientation of the α″ phase. While the Ti-25Nb alloy deforms by stress-induced martensitic transformation and deformation bands that are devoid of ω phase. The Ti-30Nb alloy, which has the highest β phase stability, deforms in a localized mode mainly by dislocation slip. The “marble-like” deformation microstructure previously reported in “gum metal” was observed in severely deformed Ti-25Nb and Ti-30Nb alloys.