ω-Assisted refinement of α phase and its effect on the tensile properties of a near β titanium alloy

In this work, the phase transformation sequence during the continuous heating process (3 °C/min) was investigated in a near β titanium alloy. The results show that the staring formation of ω phase is about 267 °C, and the ending precipitation temperature about 386 °C during the heating process. When the heating temperature is greater than 485 °C, there are no ω phase detected within the β matrix. Combined with the microstructural characterization, it is found that ω phase facilitates the nucleation of α phase nearby the ω/β interface and has a great effect on the refinement for α phase. As compared with the specimens directly aged, the specimens with ω-assisted refinement of α phase possess high tensile strength, but there is no yield stage detected on their stress-strain curve. Combined with the analyses of the fracture morphology, the specimens with ω-assisted refinement of α phase present a brittle fracture. This is mainly ascribed to its relatively lager width of grain boundaries and the absence of widmanstätten α precipitates.