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To study the vacuum arc remelting process and improve the homogenization and cleanliness level of large-sized superalloy ingot， numerical simulation and industrial experiment were carried out to investigate the evolution of molten pool， solidification characteristics and inclusion distribution in a ϕ690 mm GH4738 superalloy ingot during vacuum arc remelting. The results show that as the melting progresses， the simulated molten pool morphology changes from a "shallow flat" shape to a "shallow U " shape. After melting for 500 minutes， the depth of the molten pool and the width of the mushy zone tend to stabilize， with maximum molten pool depth and mushy zone width being 200.88 mm and 72.38 mm respectively. During stable melting， the cooling rate at the surface and center of the casting ingot is 0.126K / s and 0.009 K/s， respectively， and after the height of the ingot is exceeds 0.4 m， the cooling rate of the casting ingot is basically stable.The trajectories of six particle size inclusions in the molten pool were simulated. Large size inclusions （>20 μm） were subjected to the fluid flow and buoyancy to move helically in the molten pool and were eventually trapped at the ingot sidewalls， while small size inclusions （≤10 μm） entered the molten pool and then moved inward along the bottom of the pool， eventually remaining inside the ingot， which is basically consistent with the detection value of the industrial ingot.

The high temperature deformation behavior of vacuum powder forging FGH95 alloy was studied by Gleeble-3800 thermal simulation testing machine. The hot compression test was carried out at the deformation temperature of 1090-1170 ℃ and the strain rate of 0.01-10 s−1. The flow stress-strain curves under the corresponding conditions were obtained. The effects of deformation conditions on the microstructure evolution of vacuum powder forging FGH95 alloy were analyzed by EBSD. After considering the influence of temperature，strain rate and strain on the flow behavior of the alloy，the Arrhenius equation was selected to establish the constitutive model of vacuum powder forging FGH95 alloy，and the parameters of vacuum powder forging FGH95 alloy were obtained. The relationship between material parameters and strain was fitted and the obtained constitutive equation was verified.The results show that the flow stress of FGH95 alloy prepared by vacuum powder forging process decreases with the increase of temperature and increases with the increase of strain rate. The size of recrystallized grains in the deformed microstructure decreases with the increase of temperature and increases with the decrease of strain rate. The error between the predicted value and the experimental value of the flow stress of the vacuum powder forging FGH95 alloy is 6.33%，and the predicted value is in good agreement with the experimental value.

The FGH4095 superalloys prepared by hot isostatic pressing + extrusion + isothermal forging were quenched with the different quenching transfer time, and the microstructure and mechanical properties of the treated superalloys were analyzed. The results show that, the quenching transfer time has little effect on the grain size, primary γ′ phase, and tertiary γ′ phase of the FGH4095 superalloys, but influences the size distribution of the secondary γ′ phase. The average size of the secondary γ′ phase with the quenching transfer time of 30 s is 142.9 nm, and that of the secondary γ′ phase is 161 nm with the quenching transfer time of 40 s. The shorter the quenching transfer time, the faster the quenching cooling rate of the FGH4095 superalloys, and the smaller the average size of the secondary γ′ phase. The yield strength of the FGH4095 superalloys at room temperature with the quenching transfer time of 30 s is better than that of FGH4095 superalloys with quenching transfer time of 40 s, and the tensile strength at room temperature is similar to that of FGH4095 superalloys with quenching transfer time of 40 s. The yield strength, tensile strength, endurance life, and endurance ductility of the FGH4095 alloys with the quenching transfer time of 30 s at 650 ℃ are higher than those of the FGH4095 superalloys with the quenching transfer time of 40 s. The shorter the quenching transfer time, the greater the number of the secondary γ′ phase, the smaller the size, the higher critical shear stress impeding the dislocation movement, the higher the tensile strength and the longer the endurance life of the FGH4095 superalloys.

The different heat transfer conditions in each region of the vacuum arc remelting superalloy ingot lead to significant difference in the morphology and size distribution of carbide in the ingot. Based on industrial vacuum arc remelting GH4742 alloy as a raw material, using metallographic and scanning electron microscopic analysis quantitative analysis method to study the ingot different position distribution of the carbide precipitation behavior and microstructure, supplemented by MeltFlow-VAR simulation software, the solidification process of remelting different cooling rate and local solidification time on the influence of carbide were analyzed. The results show that Nb and Ti elements are enriched in the carbide precipitates of GH4742 alloy, and the segregation degree of Nb element is the largest. The area of the precipitated phase is decreased from the center to the edge, and the morphology is changed from skeleton-like and cursive to interconnected fine strips. As the cooling rate increases, the dendrites become more slender and compact, and the dendrite spacing decreases. The area of precipitated phase is linearly related to the secondary dendrite spacing. Increasing the cooling rate can reduce the dendrite spacing, thus the area of precipitated phase is reduced effectively.

The solution temperature and aging temperature of GH4720Li superalloy are the critical factors in determining its microstructure stability and mechanical properties. However, the matching of solution temperature, primary aging temperature, and second aging temperature greatly influences the final microstructure and mechanical properties, and the mechanism was rarely studied. In this paper, the effects of solution temperature, aging temperature, and other process parameters on the grain size, precipitated phase, and mechanical properties of GH4720Li superalloy were systematically studied by orthogonal experiment, and a set of optimal heat treatment process parameters were found. The results show that the sample was solution treated in the temperature range of 1060 °C ∼ 1120 °C. When the solution temperature was 1160 °C ∼ 1100 °C, although the primary γ ′ phase gradually dissolved, the secondary γ ′ phase gradually increased, and the primary γ ′ phase was pinned at the grain boundary to hinder the grain growth, and the hardness of the alloy gradually increases. When the solution temperature exceeded 1100 °C, the primary γ ′ phase dissolved in large quantities, the grains grew up rapidly, and the hardness of the alloy decreased. The sample was subjected to two-stage aging treatment in the temperature range of 650 °C ∼ 770 °C and 760 °C ∼ 880 °C. As the aging temperature increased, the primary γ ′ phase of the sample gradually grew, and the ability to pin the grain boundary weakened. The volume fraction of the secondary γ ′ phase of the sample gradually decreased and coarsened, resulting in grain growth and a gradual decrease in the hardness of the sample. When the samples were treated by 1100 °C/OC × 4 h + 650°C /AC × 8 h + 760 °C/AC × 8 h, the grain size of the sample was the smallest, the average grain size was 4.5 μ m, the distribution of γ ′ phase was the most uniform, and the mechanical properties are the best, reaching 47 HRC.