Abstract:The microstructure and properties of the novel GH4198 alloy were studied under various solution heat treatment regimes using advanced characterization techniques such as electron probe microanalysis, metallographic microscopy, and field emission scanning electron microscope. The results indicate that as the solution temperature increases from 1100 °C to 1150 °C, the primary γ' phase dissolves into the matrix, the grain size increases from ASTM 9.5 to 3, and the size of the secondary γ' phase increases. The tensile properties are greatly affected by the solution temperature: the optimum tensile strength is obtained at 850 °C and low-temperature tensile strength drops when the solution temperature increases from 1120 °C to 1140 °C. At the sub-solvus temperature of 1120 °C, as the solution cooling rate increases from 10 °C/min to 450 °C/min, the volume fraction and the size of the primary γ' phase remain unchanged, the size of the secondary γ' phase decreases, and the microhardness increases. The possible explanations for the improvement of mechanical properties are also discussed.