Isothermal tensile deformation behaviors and fracture mechanism of Ti-26Al-20Nb-0,5Mo alloy at different phase regions

In this paper, the microstructure evolution, the deformation behavior and the fracture mechanism of the Ti-26Al-20Nb-0.5Mo alloy have been systematically investigated during tensile test. Results show that increase in tensile temperature leads to decrease in strength and increase in ductility. Under the deformation temperature of room temperature and 600 °C, there were no change in the microstructure of the samples, and the movement of dislocations plays a very important role. With increase of deformation temperature, the spheroidization degrees of the lamellar orthorhombic phase increases and the volume fraction of that decreases. Particularly the deformation temperature rising to 950 °C, the morphology of some equiaxed α₂ phases had been flattened into an ellipsoidal shape and the lamellar orthorhombic phase had been spheroidized completely during the deformation process. The deformation mechanism was mainly based on merged of grains and grown at this moment. Moreover, the fracture changes from brittle fracture to ductile fracture with increase of deformation temperature. At the tensile temperatures of 750 °C and 950 °C, the dimples around the holes are very different, and the fractographs are wave feature and fish scale features, respectively. The reason for this feature is mainly related to the spheroidization degree of the lamellar during the tensile deformation process.