Phase transformation of fully lamellar γ-TiAl alloys in α plus γ field

The isothermal phase transformation mechanisms in Ti-46.5Al-2Cr-1.5Nb-1V alloy were studied. The microstructures of the alloy annealed at 1 260 degrees C for different times (2 h, 4 h, 10 h) were observed by using optical microscopy, scanning electron microscopy and transmission electron microscopy. When the annealing time is up to 10 h, the primitive large lamellar grains (more than 600 mu m) transform to small lamellar domains (about 50 mu m) The small lamellar domains formed from one primitive grain have four kinds of fixed orientations and each orientation has a fixed angle. The lamellar spacing and composition of the small lamellar domains are different from those of the primitive lamellar grains.