Microstructural Evolutions of a High Temperature Titanium Alloy Processed by Thermal Mechanical Treatments

TG6 alloy is a new titanium alloy which has been designed to reach the service temperature of 600°C. The microstructural evolutions of TG6 alloy under different thermal mechanical treatments were studied. It was found that lamellar microstructures with basketweave α lamella are obtained for TG6 alloy forged in β field. The evolution mechanism is transformed from dynamic recrystallization to dynamic recovery and the thickness of α lamella increases with increasing forging temperature. The aspect ratio of α lamella decreases firstly and then increases with increasing deformation degree. Grain boundary α lath appears when the deformation degree is less than 40%. The thermal mechanical treatments, including deformation in β field firstly and then deformation in α+β field result in the transformations of the microstructures drastically. The deformation degree in α+β field decides the final microstructure. The deformation degree of 20% in α+β field results in partial globular α phase.