Abstract: Based on the composition of powder metallurgy René88DT alloy, GH4096 alloy was prepared by using a new deformation process. The coarsening of the γ′ phase and the precipitation behavior of the grain boundary precipitated phase in the solution treated and aged GH4096 alloy during long-term thermal exposure between 700-900 ℃ were studied. The results show that the GH4096 alloy has good microstructure stability during thermal exposure at 700 ℃. The size of the intragranular γ′ particles is stable at about 70 nm, and no precipitated phase is observed at the grain boundaries. The secondary γ′ phases begin to grow by a coalescence process, and the discontinuous phases begin to precipitate on the grain boundaries after exposure at 750 ℃ for 500 h, however, the growth rate of γ′ phase and the precipitation rate of grain boundary precipitates are relatively low. When the exposure temperature is above 800 ℃, The coarsening rate of γ′ phase and the precipitation and growth rate of grain boundary precipitates are obviously accelerated. After long-term thermal exposure, the relationship between the size of the secondary γ′ phase and Larsen Miller parameter is approximately linear, and the main precipitates are M₃B₂ and μ phase.

Key words: GH4096 alloy, thermal exposure, microstructure evolution