Influence of heat treatment on microstructure and creep properties of hot continuous rolled Ti-6Al-4V alloy

The influence of heat treatments on microstructure and creep behavior of hot rolled (HR) Ti-6Al-4V alloy is investigated. Results show that the microstructure of HR alloy consists of needle-like β phase distributed within stripe-like α phase. After long term aging (LTA), significant amount of particle-like β phase precipitates within α phase. After solution treatment at 940 °C and aging, the microstructure of the alloy consists of the “basket weave” structure with high volume fraction and the equiaxed α phase. Under the condition of the applied stress of 575 MPa at 400 °C, creep lifetimes of HR alloy treated by long term aging and solution treatment at 940 °C increase from 72 h to 230 h and 548 h, respectively. During the creep, deformation mechanism of HR alloy solution treated at 940 °C is significant amount of 〈a+c〉 dislocations with wave-like feature activated on pyramidal plane of α phase. Deformation mechanism of HR-LTA alloy is the slip of 〈c〉 dislocation with hook-like feature activated on cylindrical plane of α phase, and dense dislocations may be concentrated to form the subgrains due to the occurrence of dynamic recrystallization.