TRANSFORMATION MECHANISM OF FINE FULLY LAMELLAR MICROSTRUCTURE IN TiAl ALLOYS

The fine fully lamellar (FFL) microstructure and intermedium microstructures in the process of forming FFL microstructure were examined under optical and transmission electronic microscopes. Based on the observation results, the transformation mechanism of FFL microstructure was analyzed and proposed as that the fine γ/α lamellar colonies form at the high temperature in the α single phase region through the precipitating of the α plates on the four equivalent habit planes {111}γ, in each γ matrix grain and then evolve to the γ/α2 lamellar colonies of the FFL microstructure.