In-situ synchrotron HEXRD study on the phase transformation mechanisms of the ω-related phases in a Ti4Al3Nb alloy

The ω-related phases in TiAl alloys have various structures and usually precipitate from the βo phase. In the present study, the dissolution and precipitation of the ω”/ωo phases in a Ti4Al3Nb alloy was investigated by means of in-situ synchrotron high energy X-ray diffraction. The results show that the ω” phase dissolves prior to the ωo phase during heating. During cooling, the ωo phase precipitates from βo phase directly. Furthermore, the cooling rates significantly affect the precipitation temperatures of the ω-related phases. The morphology of the two phases was characterized by transmission electron microscopy. The distribution and size of the two phases vary with cooling rates. The nucleation mechanisms of the ω-related phases were also discussed.