Phase transformation of fully lamellar γ-TiAl alloys in α+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 ℃ 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 μm) transform to small lamellar domains (about 50 μm). 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.

The isothermal phase transformation mechanisms in Ti-46.5Al-1.5Nb-1Cr-1V alloy prepared by vacuum arc melting technology were studied. The microstructure of the alloy annealed at 126°C for different time (2 h, 4 h and 10 h) was 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 μm) transform to small lamellar domains (about 50 μm). 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 that of the primitive lamellar grains.