Microstructure evolution of FGH96 alloys during heat treatment

The microstructure evolution of FGH96 alloys during the heat treatment was studied. The effects of solution temperature and holding time on the grain size, γ′ precipitate size, area fraction, and grain distribution were quantified. The influences of γ′ precipitate and strain storage energy on the grain evolution were analyzed. The results show that, the deformed grains containing a large amount of strain storage energy during heat treatment undergo the static recrystallization and refine the grains, while the dynamic recrystallization grains grow. The uniform fine grain structure can be obtained as the two processes are balanced. After the alloy is held at1060 ℃ for 120 min, the distribution of γ′ precipitate size and grain size are more uniform, and the average grain size is 7.37 μm. The area fraction of the γ′ precipitate decreases with the increase of solution temperature and holding time, while the coarsening and splitting of the primary γ′ precipitate during the subsolvus solution make the area fraction and size of the primary γ′ precipitate increase first and then decrease. The inhomogeneous dissolution of γ′ precipitate leads to the rapid growth of the local grains, forming the mixed crystals.