Precipitation of α phase in the massive and feathery structures in TiAl alloys during aging in the single α field

Precipitation of α-phase in massive and feathery microstructures was studied during aging in the single α field. It was found that the α-phase mainly precipitated along the γ-plate interfaces as laths in the feathery structure, while it nucleated at various sites in the massive structure in the form of particles and dominantly as plates. Precipitation of α-plates in the massive structure occurred by the diffusional ledge mechanism. The γ_m → α reaction proceeded by the growth of previously nucleated α-precipitates, and chiefly by the development of new α-plates.