The activation energy of the β → α/ω phase transformation increased monotonously with the application of a continuous heating process to a Ti-15Mo-2.7Nb-3Al-0.2Si alloy. Precipitation behaviour of the alloy aged at different temperatures were analysed with scanning electron microscopy, electron backscattered diffraction and transmission electron microscopy. Selected-area diffraction patterns of the ω, ω/α and α phases in the alloy aged at different temperatures indicated that the type of phase transformation was influenced by the precipitation process. Precipitate-free zones in the alloy aged at 450 °C for 8 h were harmful to the mechanical performance. Fine α precipitates with an obvious texture were obtained in the alloy aged at 500 °C. A good combination of tensile properties with an ultimate tensile strength of 1310 MPa and an elongation of 13.5% were obtained due to the expected microstructure and texture of the precipitates that transformed in the specimen when it was aged at 500 °C for 8 h. The size of the precipitates increased with increasing aging temperature. Furthermore, the amount of precipitates and their degree of texture decreased substantially in the alloy aged at 600 °C. The investigation of the tensile properties and fractures also revealed a correlation between the mechanical properties and precipitation behaviour in the Ti-15Mo-2.7Nb-3Al-0.2Si alloy aged at different temperatures.

In this study, the microstructural evolution of a Ti-15Mo medical alloy was investigated, when the in situ cyclic tensile strain had 2% amplitude and the tension–compression cyclic deformation had 1%, 2%, and 3% amplitude. The Vickers hardness and wear resistance of the alloy were also optimized due to the grain-refining effect after cyclic deformation and annealing. The twinning-induced plasticity (TWIP) was considered the main deformation mechanism of the Ti-15Mo alloy during the tensile–compressive cycle deformation with suitable strain amplitude. The {332} twins and boundaries were the main contributors to the grain refinement. The optimal microstructure, hardness, and wear resistance were obtained in the alloy deformed by tension–compression cyclic strain with a 3% strain amplitude. The wear resistance of the annealed alloy in Hank’s solution was excellent in contrast to the original Ti-15Mo alloy due to its reasonable microstructure and hardness. It is clear that abundant twins were formed and retained in the coarse grains of the original alloy after cyclic deformation and annealing, which provided the expected refined grains and performance.

The purpose of this investigation was to determine the extent to which a combination of pre-deformation and aging procedures could enhance the corrosion and wear resistance of the Ti-15Mo alloy for biomedical materials. The initial grains were refined with {332} twins and other defects after the pre-deformation, increasing the amount of precipitation nucleation and forming finer α phases during aging. The finer precipitates with numerous boundaries are beneficial in forming a thicker passivation film in phosphate-buffered saline (PBS) solution, and the corrosion resistance of the 20% pre-deform plus aged alloy is improved by 4.23 times. The result indicates that the corrosion passivation behavior and film structure of the biomedical Ti-15Mo alloy are significantly influenced by its microstructure. The worn track and debris of the alloy after pre-tension and aging gradually decreases with the increase in pre-deformation rates, caused by the increase in the hardness and wear resistance. The mechanism of corrosion and wear resistance in PBS solution were revealed, which showed the pre-tension and aging processes that were performed on the Ti-15Mo alloy. This study proposes that pre-tension with {332} twins contributed to precipitation refinement, which would enhance the passivation behaviors and wear resistance of the biomedical β titanium alloy.