Influence of oxygen addition and aging on the microstructure and mechanical properties of a β-Ti-29Nb–13Ta–4Mo alloy

Abstract

In this work, theoretical composition design and thermo-mechanical treatments were combined in order to improve the mechanical compatibility of a metastable β-type Ti–29Nb–13Ta–4Mo (wt%) alloy. Also, the influence of Mo and O alloying elements were investigated. By applying cold rolling and low temperature aging (673K during 20 and 100 min) different behaviours in microstructure and mechanical properties were identified. Alloys with Ultimate Tensile strength-UTS = 854 MPa and Elastic Modulus = 65 GPa were successfully fabricated. The microstructure responsible for that behaviour consisted mainly of β-matrix and ω-precipitation obtained via cold rolling plus short-time aging at low temperature, i.e. 673K for 20 min. These precipitates increase the strength of the material by hindering the motion of dislocations while the β-matrix with relatively high content of β-stabilizers (such, Mo) gives rise to the observed low elastic modulus. By extending aging time (100 min), a higher UTS is reached, but a slight increase in Elastic Modulus is also observed. The addition of oxygen increased mechanical and physical properties by favouring ω-phase formation. Whereas, Mo content increased β-stability, and in solution treated condition, only β-phase could be observed.