Effects of Thermal Exposure Temperature on Room-Temperature Tensile Properties of Ti65 Alloy

As a critical material for high-temperature components of aero-engines, the mechanical properties of Ti65 alloy, subjected to high-temperature and long-term thermal exposure, directly affect its service safety. The room-temperature tensile properties of the Ti65 alloy after thermal exposure to temperatures ranging from 450 °C to 650 °C for 100 h were investigated. The results indicate that as the thermal exposure temperature increases, the strength of Ti65 alloy initially increases and then decreases, while ductility exhibits a decreasing trend. The strength of the thermally exposed alloy positively correlates with the size and content of the <i>α</i>₂ phase. The ductility of the thermally exposed alloy is comprehensively influenced by the surface oxidation behavior, <i>α</i>₂ phase, and silicides. After the prolonged thermal exposure, stress concentration at the crack tips within the oxide layer was enhanced with the increased thickness of the surface TiO₂ oxide layer, leading to premature fracture due to reduced alloy ductility. Furthermore, the <i>α</i>₂ phase in the matrix promotes the planar slip of dislocations, while silicides at the <i>α</i>/<i>β</i> phase boundaries hinder dislocation motion, causing dislocation pile-ups. Both behaviors facilitate crack nucleation and deteriorate alloy ductility.