Effect of Zr addition on mechanical and shape memory properties of Ti-5Mo-3Sn alloys

Abstract

The effects of Zr addition on the mechanical, shape memory and superelastic properties of Ti-5Mo-3Sn (mol%) based alloys were investigated with Zr content up to 24 mol%. The parent bcc phase was stabilized with increasing Zr content, and the volume fraction of the ω phase seemed independent of the Zr content. The ultimate tensile strength and fracture strain increased with increasing Zr content up to 6 mol%Zr, however, the alloy became brittle with further addition of Zr content over 8 mol%. Young's modulus was low around 37∼38 GPa when Zr content was 2∼6 mol%. Shape memory effect was confirmed when Zr content was less than 5 mol%, and the superelasticity appeared in 6 mol%Zr-added alloy with the good shape recovery strain of 4.3%. When the Zr addition exceeded 6 mol%, the slip deformation occurred. The slip stress was raised by Zr addition with a rate of 9.5 MPa/mol%Zr in the alloys containing 2∼6 mol%Zr. It is concluded for Ti-5Mo-3Sn based alloys that Zr addition is effective to improve the mechanical properties without degradation of lattice transformation strain, and that good room-temperature superelasticity appears in the Ti-5Mo-3Sn-6Zr alloy.