Effect of Zr on super-elasticity and mechanical properties of Ti–24 at% Nb–(0, 2, 4) at% Zr alloy subjected to aging treatment

β-Type titanium alloys with composition of Ti–24 at% Nb–(0, 2, 4) at% Zr were prepared and subjected to aging treatment for different durations. The addition of Zr suppressed the formation and growth of isothermal ω phase during aging treatment, and therefore the investigated Ti–Nb–Zr alloys with different Zr content performed various deformation mechanisms, mechanical properties and super-elastic effects with the changes of aging time. The isothermal ω phase exerted inhibitory effects on twinning and stress-induced martensitic transformation. Desirable properties were obtained in Ti–Nb–Zr alloy by adding suitable Zr content and processing short time aging treatment. Ti–24 at% Nb–2 at% Zr alloy subjected to aging treatment at 573 K for 7.2 ks exhibited an ultimate tensile strength of 710 MPa, an elongation of 13%, a Youngʹs modulus of 64 GPa, and a super-elastic recovery strain of 4.3%. Ti–24 at% Nb–4 at% Zr alloy subjected to aging treatment at 573 K for 1.8 ks, 3.6 ks, and 7.2 ks performed a low Youngʹs modulus of 62 GPa and ultimate tensile strength around 600 MPa.