The microstructural stability and property evolution of high-temperature titanium alloys under long-term high-temperature conditions has been a critical scientific issue in the field of advanced titanium alloys. In this work, we systematically investigated the precipitation behavior of silicides and ordered α₂ phase, which are closely related to the microstructural stability of Ti65 high-temperature alloy, during thermal exposure at 650 °C for different periods of time. Furthermore, the effects of thermal exposure on mechanical properties were evaluated using room temperature and high temperature tensile tests, and subsequently, the correlation between the microstructural thermal stability and the mechanical characteristics was discussed. The results reveal that (Ti, Zr)₆Si₃ silicides initially precipitate within the residual β film and then start to precipitate in the α platelet. A large number of fine spherical α₂ precipitates were formed inside the α platelet after a short thermal exposure. The number density of ordered α₂ decreased significantly after 1000 h due to Ostwald ripening. The precipitation of silicides and ordered α₂ phases during thermal exposure improves the tensile strength but deteriorates the ductility, and the room-temperature ductility is slightly restored due to α₂ ripening after long-time thermal exposure. Ti65 high-temperature titanium alloy consistently maintains favorable room-temperature tensile properties throughout long-term thermal exposure.

The crystallographic orientations of grain boundary α phase and matrix β phase are two main factors determining the mechanical properties of β forging TC17 alloy. Microstructure and texture evolution of three height reduction pancakes were mainly investigated in this present work by optical microscopy (OM), scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD) combined with Schmid factor analysis and X-ray diffraction (XRD). The results revealed that all pancakes of three height reduction exhibited similar < 001>//forging direction(FD) fiber texture component of β matrix phase whose intensity significantly increased with the increase of height reduction from 20–50%. While the height reduction was up to 70%, intensity basically remained unchanged, but a new texture component (< 011>//FD) was formed possibly due to dynamic recrystallization. The recrystallized grains representing the undeformed or slightly deformed grains affect the texture component of β matrix. Tensile properties of β forging TC17 alloy demonstrated relatively obvious anisotropy. The angle of 45° between forging direction and longitudinal direction indicated the highest strength and lowest ductility, while the longitudinal direction showed higher strength than forging direction. The orientation diversity of grain boundary α phase increased with the increase of height reduction. The specific crystallographic features of grain boundary α phase caused by forging texture affect effective slip length. In addition, their Schmid factor varied significantly with loading direction, possibly leading to tensile anisotropy.