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

beta-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 omega 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 omega 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 Young's 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 Young's modulus of 62 GPa and ultimate tensile strength around 600 MPa. (C) 2012 Elsevier B.V. All rights reserved.