The optical observation results of neocrystallization nucleation and growth of fine fully lamellar (FFL) α 2/ γ microstructure of a TiAl based alloy in rapid heating cyclic heat treatment process were reported. The characteristics of α+γ→α transformation under rapid heating conditions were analysed. A model for explaining the nucleation and growth mechanism of FFL α 2/ γ microstructure was proposed. The optical observation results of neocrystallization nucleation and growth of fine fully lamellar (FFL) α 2 / γ microstructure of a TiAl based alloy in rapid heating cyclic heat treatment process were reported. The characteristics of α + γ → α transformation under rapid heating conditions were A model for explaining the nucleation and growth mechanism of FFL α 2 / γ microstructure was proposed.