Influence of oxygen content on the microstructure and mechanical properties of cold rolled Ti-32.5Nb-6.8Zr-2.7Sn-xO alloys after aging treatment

The influence of oxygen (O) content on the microstructure and mechanical properties of cold rolled Ti-32.5Nb-6.8Zr-2.7Sn-xO (TNZS-xO; x = 0, 0.3, 0.6; mass%) alloys after aging at temperature range from 350 to 600 °C for 24 h was investigated. Results showed that the cold rolled TNZS-xO alloys possess single β phase. During the aging process, O could not only effectively suppress the precipitation of ω phase but also retard the formation and decomposition of α phase. In addition, the corresponding temperatures of the maximal volume fraction of α phase precipitation and the (α+β)/β transus temperatures of the TNZS-xO alloys were all increased with the increasing of O content. For mechanical properties, it was found that the strength and Young's modulus of the TNZS-xO alloys increased owing to the ω phase and/or α phase precipitation and decreased owing to the α phase decomposition. However, the elongation showed the opposite change tendency with the above mentioned strength. The mechanical properties of TNZS-xO alloys can be controlled over a wide range by subjecting to aging treatment and/or changing their O content. When aged at or below 450 °C, the TNZS-xO alloys exhibit great potential to become a series of new candidates for biomedical applications since they possess high strength (870-1460 MPa), low Young's modulus (45.1-75.6 GPa), high strength-to-modulus ratio (0.018-0.02) and appropriate elongation (7.2%-14.9%), which are superior to those of Ti-6Al-4 V alloy and suitable for the use as bio-implant materials.