Abstract: Effect of solution temperature on microstructure (including grain and γ′ phase) and mechanical properties of the GH4720Li alloy was investigated by means of optical microscope(OM), field emission scanning electron microscope(FESEM) and mechanical tensile tester. The results show that the volume fraction of primary γ′ decreases, the diameter of tertiary γ′ increases and the average grain size increases with the solution temperature increasing. When the solid solution temperature exceeds 1120 ℃, the primary γ′ phase is rapidly dissolved, the grain grows rapidly, the grain size distribution inhomogeneity increases. The solid solution temperature has a parabolic linear relationship with the strength, and the strength peak is at 1130 ℃. As the solution temperature increases, the plasticity of the alloy decreases, and when the solution temperature exceeds 1100 ℃, the plasticity decreases faster. Stress-rupture tensile test under 680 ℃/830 MPa shows that the duration increases with the increase of solid solution temperature; when the solution temperature exceeds 1100 ℃, the duration increases obviously, but when the solution temperature exceeds 1130 ℃, the duration remains basically unchanged. As the solution temperature increases, the persistent plasticity decreases, but it decreases slowly below 1110 ℃, and rapidly or is even substandard above 1110 ℃. Furthermore, the relationship between solid solution temperature, microstructure and mechanical properties is discussed. The results provide a theoretical reference for the selection of solid solution heat treatment process for GH4720Li alloy disc.

Key words: GH4720Li alloy, solution temperature, grain structure, γ′ phase, mechanical properties