Omega phase in as-cast high-Nb-containing TiAl alloy

The omega phase in as-cast high-Nb-containing TiAl alloy exhibits particles with sizes on the nano- or microscale within the B2 matrix. Omega particles are transformed from the B2 phase by heterogeneous nucleation on the B2/gamma boundaries or homogeneous nucleation within the B2 phase. After annealing at 900 degrees C, the omega particles disappear and transform into B2 phase. The transformation is rapidly initiated, but is difficult to complete. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.