Thermal stability of the omega phase in Zr-containing TiAl alloys

The thermal stability of omega phase in TiAl alloys has been investigated using scanning and transmission electron microscopy and it has been found that Zr has a strong effect in stabilising the omega phase. In Ti–44Al–4Nb–4Zr–0.2Si–1B the omega solvus was determined as just over 900 °C. Increasing additions of Zr to Ti–44Al–4Nb–2Mo resulted in an increase in the volume fraction of omega phase at 700 °C and the omega particle distribution was changed from localised to uniformly distributed omega. In the alloy with 2 at% Zr, omega particles were found uniformly throughout the B2 matrix at 700 °C.