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 degrees C for 24 h was investigated. Results showed that the cold rolled TNZS-xO alloys possess single beta phase. During the aging process, O could not only effectively suppress the precipitation of omega phase but also retard the formation and decomposition of alpha phase. In addition, the corresponding temperatures of the maximal volume fraction of alpha phase precipitation and the (alpha+beta)/beta 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 to phase and/or alpha phase precipitation and decreased owing to the alpha 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 degrees C, the TNZS-xO alloys exhibit great potential to become a series of new candidates for biomedical applications since they possess high strength (870-1460MPa), 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-6A1-4V alloy and suitable for the use as bio-implant materials. (C) 2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.