Effect Of Deformation Degree On Microstructure And Properties Of Deformation Zone Of Turbine Disk Forging For Advanced Aero-Engine

GH4720Li superalloy is the main material of turbine disk forgings for advanced aeroengines.It is a nickel-based superalloy that can resist oxidation,corrosion and creep at high temperatures above 750 ℃,and can work for a long time under mechanical stress.It is widely used in hot end components of various types of aeroengines.However,due to the high alloying,small hot working temperature range and low yield of GH4720 Li superalloy,the alloy forgings are prone to uneven microstructure and unstable performance in the deformation zone during the deformation process,and even serious problems such as cracking of the disc forgings increase the difficulty and cost of producing qualified disc forgings.According to the different uses of aero-engines,it is necessary to configure engine turbine disks with different degrees of deformation,which not only meets the requirements of safe use,but also can be selected on demand to reduce costs.In view of the above problems,the influence of deformation degree on the microstructure and properties of the deformation zone of turbine disk forgings is studied,which provides a reference for the production of turbine disk forgings for multi-purpose and multi-model advanced aeroengines.It is of great significance to promote the rapid development of China ’s aviation industry.Using GH4720 Li alloy rod billet as the initial material,the deformation zone of GH4720 Li alloy with different hot deformation degree was studied.The grain refinement mechanism and the precipitation law of the second phase in each deformation zone of the disk forging were analyzed.The analysis results show that the grain size and secondary γ ’phase particle size of each deformation zone of GH4720 Li alloy bar gradually decrease and the hardness gradually increases with the increase of deformation degree under different deformation degrees.When the deformation degree is low,the grain size and size distribution of each deformation zone of the forging are not uniform,and some of them grow up.The secondary γ ’ phase is mainly coarse flake,the particle size of γ ’ phase is extremely uneven,and sunflower-like γ / γ ’ eutectic phase appears in some deformation zones.The hardness of forgings is obviously different from that of difficult deformation zone to large deformation zone.When the deformation degree is higher,the grain size of the forging is greatly reduced and the grain size of each deformation zone is more uniform.The secondary γ ’ phase is mainly a relatively uniform and fine spherical shape;the hardness of each deformation zone is relatively uniform.Aiming at the problem of uneven microstructure and properties of GH4720 Li superalloy during forging,heat treatment experiments of deformation zones with different deformation degrees were carried out on the forgings,and the influence of heat treatment on the microstructure and properties of the deformation zone of the alloy forgings was studied.The experimental results show that : GH4720 Li alloy samples with different deformation degrees after heat treatment,with the increase of deformation degree,the grain size of each deformation zone of the sample gradually decreases,and the particle size and hardness of the secondary γ ’ phase gradually increase.For the samples with lower deformation degree,the grains are reduced to different degrees compared with the forgings,and the grain size gap in each deformation zone is gradually reduced.The particle size of the secondary γ ’phase increases slightly,changing from flake to sphere,the sunflower-like γ / γ ’ eutectic phase disappears,and no precipitation occurs in some grains.The hardness of the samples is relatively close,and there is no significant difference in the hardness of each deformation zone.The grains of the samples with higher deformation degree grow slightly,and the grain size of each deformation zone remains uniform.The particle size of the primary γ ’ phase in each deformation zone of the sample is greatly reduced,and the particle size of the secondaryγ ’ phase is greatly increased,and it still maintains a relatively uniform spherical shape.The hardness of the sample increases steadily,and the hardness of each deformation zone is not much different and remains at a high level.When the aero-engine is working in the take-off,landing and troposphere stages,the aero-engine inhales small particles suspended in the air,which is easy to cause the wear behavior of the turbine disk in high temperature and high speed operation,thus reducing the life of the engine.By analyzing the recrystallization mechanism of the alloy,the effect of deformation degree on the wear properties of the deformation zone of GH4720 Li superalloy at high temperature was studied.The results show that the recrystallization mechanism of GH4720 Li alloy hot deformed forgings at high strain rate in γ single phase region is discontinuous dynamic recrystallization.The deformed forgings contain a large number of substructures and twin boundaries,and the dislocation density at the recrystallized grain boundaries is very high.After heat treatment,the forgings are dominated by substructures and twin boundaries,but the number of twin boundaries decreases,and the dislocation density at the recrystallized grain boundaries also decreases to a certain extent.The main source of strengthening after hot deformation is the combination of fine grain strengthening and precipitation strengthening phase,while the main source of further strengthening after heat treatment is the complete precipitation of γ ’ phase.With the increase of deformation degree,the wear resistance of the alloy is stronger.