Stability of γ′ phase in FGH95 superalloy

The microstructure of γ′ phase in HIPFGH95 superalloy was investigated by use of SEM and TEM. The results show that the microstructure is a mixture of recrystal grains and original dendrite crystals after the heat treatment. The undissolved particles of γ′ phase during the solution treatment distribute in the grain boundaries. Meanwhile, there are three different sizes of γ′ particles within the recrystal grains. Among them, the big and square γ′ particles exhibit arrays of every 8 particles, which are formed from the spitted single γ′ particles precipitated during the cooling procedure from 1160°C. Moreover, which would decompose to form finer γ′ precipitates, at the same time, the cube γ′ particles disappear with the growth of finer γ′ precipitates.