High Temperature Oxidation Resistance of TB8 Titanium Alloy after Equal Channel Angular Pressing and Heat Treatment

In this paper, the metastable β titanium alloy TB8 (Ti-12.76Mo-2.13Nb-2.73Al-0.16Si) was used as the starting material, and the secondary processing method combining equal channel angular pressing (ECAP) and heat treatment was adopted. Moreover, the effects of different processes (800 °C/850 °C solid solution-520 °C aging, ECAP-800 °C/850 °C solid solution-520 °C aging and 800 °C/850 °C solid solution-ECAP-520 °C aging) on the high temperature oxidation resistance of the material were studied with the help of scanning electron microscope (SEM), optical microscope (OM) and X-ray diffractometer (XRD). It was found that the phase composition of the samples after cyclic oxidation at a high temperature of 850 °C for 50 h is similar mainly TiO₂, Al₂O₃, SiO₂, MoO₃ and Nb₂O₅. The grains of the TB8 titanium alloy treated with 850 °C solid solution-ECAP-520 °C aging treatment are obviously refined, and the surface microstructure is the most smooth and compact, forming a continuous Al₂O₃ protective film. The thickness of the oxide layer is the smallest (55.0 μm), which is only 28.45 %-39.29 % of that of other secondary processing titanium alloys. In addition, the average oxidation rate and parabolic rate constant of titanium alloy treated by 850 °C solid solution-ECAP-520 °C aging are the lowest, which are 0.0036 mg·cm^-2·h^-1 and 45.30 mg²·cm^-4·h^-1, respectively. The results show that the TB8 titanium alloy has the best high temperature oxidation resistance after 850 °C solid solution-ECAP-520 °C aging treatment.