Precipitate Phase Evolution of GH4706Alloys under Different Aging Conditions and Its Impact on Mechanical Properties

Abstract: This study systematically investigates the effects of different aging temperatures (600℃ and 650℃) and aging times (3000h、5000h、10000h) on the microstructural evolution, room-temperature tensile properties, and high-temperature stress rupture properties of GH4706 alloy. The results indicate that the microstructure coarsens significantly with increasing aging temperature and time, with the grain size reaching 125 μm after aging at 650℃-10000h. Following high-temperature aging, the grain boundary η phase evolves rapidly from dispersed particles into a continuous network, while the intragranular carbides (primarily MC and M₂₃C₆ types) undergo continuous coarsening. This process is most severe under the 650℃-10000h condition. The study reveals that during room-temperature tensile testing, the elongation after fracture is more sensitive to temperature, whereas the ultimate tensile strength is more sensitive to time. The high-temperature stress rupture performance is critically dependent on the grain boundary condition; M₂₃C₆ carbides and the η phase act synergistically to promote crack initiation and propagation, leading to a drastic reduction in the stress rupture life of the 650℃-10000h sample. In conclusion, the core mechanism behind the performance degradation of GH4706 alloy during high-temperature long-term service is grain boundary embrittlement, induced by the combined effects of the continuous network of grain boundary η phase and the coarsening of carbides, which collectively deteriorate its mechanical properties.