A processing technique for improving the structure uniformity of a deformed zone of GH4720Li alloy

Abstract

The application discloses a processing technology for improving the structure uniformity of a GH4720L i alloy deformation area, and comprises the following steps: heating an electric resistance furnace to an initial temperature of gradient heating and holding treatment; placing a GH4720L i alloy rod blank in the electric resistance furnace to perform the gradient heating and holding treatment; after the gradient heating and holding treatment is completed, controlling the GH4720L i alloy rod blank to perform forging at an optimal initial forging temperature to obtain a GH4720L i alloy forge piece; and sequentially performing solid solution treatment, primary aging treatment and secondary aging treatment on the GH4720L i alloy forge piece, so that the GH4720L i alloy forge piece with uniform structure is obtained after the secondary aging treatment is completed. The GH4720L i alloy forge piece obtained by using the processing technology has relatively uniform grain size and hardness in each deformation area, and has good high-temperature wear resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of GH4720Li alloy processing technology. Specifically, it is a processing technology for improving the uniformity of the deformed zone structure of GH4720Li alloy. BACKGROUND

[0002] GH4720Li is a new type of high-performance deformed high-temperature alloy for turbine disks, which has a very high degree of alloying, with the sum of Al and Ti element content reaching 7.5wt%, and the number of main strengthening phase γ' reaching about 40%, thus having excellent high-temperature mechanical properties and a higher use temperature, and can be used to manufacture high-performance turbine disk parts for aircraft engines. However, due to the high alloying, small hot working temperature range and low yield of GH4720Li high-temperature alloy, the alloy forgings are prone to have uneven deformed zone structure and unstable performance during deformation, and even cracking of the forgings.

[0003] The manufacture of turbine disks using GH4720Li generally goes through the hot working processes of free forging (billet breaking), die forging (pre-forging), isothermal forging (final forging), heat treatment, etc. CN115852281A discloses a pre-forging heating process for GH4720Li alloy, which performs gradient heating on the billet before forging to ensure uniform temperature of the core and outer surface of the billet during heating, prevent the billet from cracking due to thermal stress, and promote the precipitation of primary γ' phase and secondary γ' phase of GH4720Li alloy processed using the process, and the grains are relatively uniform and small.

[0004] During forging, due to the characteristics of high alloy content, high thermal deformation resistance, poor plasticity and narrow deformable temperature range of GH4720Li, the deformation degree of each part is different during upsetting, and the surface and edge of the forgings are prone to have coarse grains, and the grains in each deformed zone of the forgings are prone to be uneven in size and second phase, which eventually leads to uneven hardness of each deformed zone of the forgings. Increasing the deformation degree helps to break and refine the grains, making the grains uniform, and the strength and hardness of the forgings are improved, but when the deformation degree is designed unreasonably and exceeds the bearing capacity of the forgings, the forgings will crack.

[0005] In addition, during heat treatment of GH4720Li alloy, grain nucleation, recrystallization and growth often occur again, and heat treatment can effectively adjust the size of the grains, and solid solution treatment helps to dissolve and homogenize the γ' phase in the alloy, which is beneficial to improving the mechanical properties of the alloy.

[0006] However, there is still no effective method to improve the uniformity of the entire cross-section deformed zone structure of GH4720Li alloy. SUMMARY

[0007] To this end, the technical problem to be solved by the present application is to provide a processing technology for improving the uniformity of the deformed zone structure of GH4720Li alloy, and the grain size and hardness of each deformed zone of the GH4720Li alloy forgings processed using the technology are relatively uniform, and the high-temperature wear resistance is good.

[0008] To solve the above technical problems, the present application provides the following technical solutions.

[0009] A processing technology for improving the uniformity of the deformed zone structure of GH4720Li alloy, comprising the following steps:

[0010] Step A: heating the resistance furnace to the initial temperature of the gradient heating and holding treatment;

[0011] Step B: placing the GH4720Li alloy bar blank in the resistance furnace for gradient heating and holding treatment;

[0012] Step C: after the gradient heating and holding treatment is completed, controlling the GH4720Li alloy bar blank at the initial forging temperature for forging, to obtain the GH4720Li alloy forgings;

[0013] Step D: sequentially performing solid solution treatment, primary aging treatment and secondary aging treatment on the GH4720Li alloy forgings, and after the secondary aging treatment is completed, the GH4720Li alloy forgings with uniform structure are obtained.

[0014] The processing technology for improving the uniformity of the deformed zone structure of GH4720Li alloy described above, in step A, the initial temperature of the gradient heating and holding treatment is 800-850℃; and the heating rate of the resistance furnace is 20-30℃ / min.

[0015] The processing technology for improving the uniformity of the deformed zone structure of GH4720Li alloy described above, in step A, the initial temperature of the gradient heating and holding treatment is 800℃; and the heating time of the resistance furnace is 30min.

[0016] The processing technology for improving the uniformity of the deformed zone structure of GH4720Li alloy described above, in step B, the specific method of the gradient heating and holding treatment is:

[0017] Step (B-1), placing the GH4720Li alloy bar blank in the resistance furnace at a temperature of 800-850℃ for 60-70min;

[0018] Step (B-2), continuing to heat at a heating rate of 3-4℃ / min to 900-950℃, and holding at 900-950℃ for 60-70min;

[0019] Step (B-3), continue to heat up to 1000-1050℃ at a heating rate of 10-15℃ / min, and keep the temperature at 1000-1050℃ for 20-30min;

[0020] Step (B-4), continue to heat up to 1130-1150℃ at a heating rate of 10-15℃ / min, and keep the temperature at 1130-1150℃ for 20-30min.

[0021] The above-mentioned processing technology for improving the uniformity of the deformed zone structure of GH4720Li alloy, in step B, the specific method of gradient heating and holding treatment is:

[0022] Step (B-1), place the GH4720Li alloy bar in an electric resistance furnace at a temperature of 800℃ for 60min;

[0023] Step (B-2), continue to heat up to 900℃, the heating time is 30min, and keep the temperature at 900℃ for 60min;

[0024] Step (B-3), continue to heat up to 1000℃ at a heating rate of 10℃ / min, and keep the temperature at 1000℃ for 20min;

[0025] Step (B-4), continue to heat up to 1140℃ at a heating rate of 10℃ / min, and keep the temperature at 1140℃ for 20min.

[0026] The above-mentioned processing technology for improving the uniformity of the deformed zone structure of GH4720Li alloy, in step C, the initial forging temperature is 1130-1150℃, the final forging temperature is 1080-1100℃, and the total deformation is 48-73%.

[0027] The above-mentioned processing technology for improving the uniformity of the deformed zone structure of GH4720Li alloy, in step C, the initial forging temperature is 1140℃, the final forging temperature is 1080℃, and the total deformation is 73%.

[0028] The above-mentioned processing technology for improving the uniformity of the deformed zone structure of GH4720Li alloy, in step D, during solid solution treatment, the GH4720Li alloy forging is kept at 1060-1080℃ for 3-4h, and then cooled to room temperature by oil cooling; during the first aging treatment, the GH4720Li alloy forging is kept at 650-680℃ for 6-8h, and then air-cooled to room temperature; during the second aging treatment, the GH4720Li alloy forging is kept at 760-780℃ for 6-8h, and then air-cooled to room temperature.

[0029] The processing technology for improving the uniformity of the deformed zone structure of the GH4720Li alloy, in step D, during the solution treatment, the GH4720Li alloy forge piece is placed at 1060℃ for 4 hours, and then cooled to room temperature by oil cooling; during the first aging treatment, the GH4720Li alloy forge piece is placed at 650℃ for 8 hours, and then air-cooled to room temperature; during the second aging treatment, the GH4720Li alloy forge piece is placed at 760℃ for 8 hours, and then air-cooled to room temperature.

[0030] The processing technology for improving the uniformity of the deformed zone structure of the GH4720Li alloy, in step A, the initial temperature of the gradient heating and holding treatment is 800℃; the heating time of the electric resistance furnace is 30 minutes.

[0031] In step B, the specific method of the gradient heating and holding treatment is:

[0032] Step (B-1), the GH4720Li alloy bar blank is placed in an electric resistance furnace at a temperature of 800℃ for 60 minutes;

[0033] Step (B-2), continue to heat to 900℃, the heating time is 30 minutes, and hold at 900℃ for 60 minutes;

[0034] Step (B-3), continue to heat to 1000℃ at a heating rate of 10℃ / min, and hold at 1000℃ for 20 minutes;

[0035] Step (B-4), continue to heat to 1140℃ at a heating rate of 10℃ / min, and hold at 1140℃ for 20 minutes;

[0036] In step C, the initial forging temperature is 1140℃, the final forging temperature is 1080℃, and the total deformation is 73%;

[0037] In step D, during the solution treatment, the GH4720Li alloy forge piece is placed at 1060℃ for 4 hours, and then cooled to room temperature by oil cooling; during the first aging treatment, the GH4720Li alloy forge piece is placed at 650℃ for 8 hours, and then air-cooled to room temperature; during the second aging treatment, the GH4720Li alloy forge piece is placed at 760℃ for 8 hours, and then air-cooled to room temperature.

[0038] The microstructure and mechanical properties of GH4720Li superalloy are controlled by controlling heating temperature, heating rate and deformation degree. The heating rate before forging directly affects the success of forging. If the heating rate is slow, the disadvantage is that the production process consumes too much time, leading to grain growth, affecting the stability of the microstructure and properties of the disk forgings. If the heating rate is too fast, the actual temperature in the furnace will not be "synchronized" with the heating rate, and the rapid heating will lead to a large temperature difference between the surface and the core of the workpiece, resulting in a large thermal stress, which will cause the workpiece to crack during the forging deformation process, causing serious loss. Therefore, in step B, the GH4720Li alloy billet is heated at a gradient to prevent the billet from cracking due to thermal stress.

[0039] In step C, 1140°C is the most suitable initial forging temperature for GH4720Li alloy forging. Because the alloying degree of GH4720Li alloy is relatively high, the original bar needs to be heated before being forged into a disk forging to reduce the stress of the alloy bar and improve the formability. If the initial forging temperature is too low, the alloy will have poor plasticity and be difficult to deform, and cracking may occur during the forging process. If the initial forging temperature is too high, the billet may be overheated or even burned, damaging the microstructure of the alloy. Experiments show that when the bar is heated to 1140°C, the γ' phase has completely dissolved in the matrix. At this time, the pinning effect of γ' phase and carbide on the grain boundary is greatly weakened, so the grains will grow to some extent, and the resistance to deformation of the forging will also decrease, which is more conducive to forming. The deformation degree of GH4720Li alloy billet is between 50% and 80%. Experiments show that the higher the deformation degree, the better the uniformity of the microstructure of the forging. At a deformation degree of 73%, the grains in each deformation zone are fully broken and uniform in size. Due to the pinning effect of the primary γ' phase on the grain boundary, the grains are prevented from growing too much. Although the grains in the large deformation zone grow, the size is relatively uniform, forming an equiaxed grain structure. Therefore, the microstructure of the forging is uniform and the hardness is relatively average. During the forging process, the mold can be preheated and an appropriate lubricant can be selected to improve the uniformity of the microstructure of the difficult-to-deform zone of the forging.

[0040] In step D, the microstructure and performance of the GH4720Li alloy forging after hot deformation are not up to the requirements of the turbine disk of the aero-engine, and in order to make the disk forging meet the final requirements, the forging needs to be heat treated so that the comprehensive mechanical properties of the workpiece after heat treatment are further improved. The solution treatment of GH4720Li is generally to heat it to the gamma single-phase region, keep it at a certain temperature for a period of time, and then cool it to room temperature. This process is mainly to obtain a saturated solid solution, so as to prepare for the subsequent aging process to obtain a gamma' phase with appropriate size, regular shape and uniform distribution. Aging treatment of the alloy can make a certain amount of dispersed second phase in the alloy, so that the alloy has high strength. The chemical formula of the gamma' phase in the GH4720Li alloy is Ni3(Al, Ti), and the dissolution temperature is about 1040 DEG C. In order to ensure the sufficient dissolution of the gamma' phase, the solution treatment is carried out at 1060 DEG C in step E. Using oil cooling can not only ensure that the forging has a suitable cooling rate to obtain fine and uniform grains, but also prevent stress cracking of the forging surface due to the rapid cooling speed caused by contacting air.

[0041] The technical scheme of the present application has the following beneficial technical effects:

[0042] 1. In the present application, GH4720Li alloy is subjected to different degrees of forging, and GH4720Li alloy forgings with different degrees of deformation are obtained. With the increase of the degree of deformation, the degree of fragmentation of the grains grown during hot working increases gradually, the grain size of each deformation zone of the forging gradually decreases, the grain boundary gradually increases, the solute atoms rapidly enrich in the primary gamma' phase through the grain boundary, the nucleation and growth of the secondary gamma' phase become easier, the number of the secondary gamma' phase increases, and the size gradually decreases from coarse lamellar to uniform and fine spherical, the sunflower-shaped gamma / gamma' eutectic phase decreases, and the uniformity of the microstructure and the hardness of the forging increase.

[0043] 2. The solution treatment and the two aging treatments make the re-nucleation and re-crystallization in the forging. For the grains with large size in the forgings with low degree of deformation during forging, the solution treatment and the two aging treatments can reduce the size and gradually reduce the difference in the grain size of each deformation zone of the forgings with low degree of deformation, effectively improving the problem of non-uniform grain size in each deformation zone of the alloy forgings with low degree of deformation during forging. For the forgings with high degree of deformation, the solution treatment and the two aging treatments further reduce the particle size of the primary gamma' phase in each deformation zone and further increase the particle size of the secondary gamma' phase. This series of changes improves the uniformity of the microstructure and the hardness of each deformation zone of the forgings with low degree of deformation, further improves the hardness of the forgings with high degree of deformation, and maintains the hardness of the large deformation zone of the forgings with high degree of deformation at a high level.

[0044] 3. In the hot working process, the GH4720Li alloy forge piece occurs discontinuous dynamic recrystallization, and appears spherical tertiary γ' phase, reduces the dislocation density at the twin boundary and recrystallization grain boundary of the forge piece, promotes the complete precipitation of γ' phase, makes the small size γ' phase controlled in the range of 50nm-200nm and uniformly dispersed in the matrix. The reduction of dislocation density, the complete precipitation of γ' phase and the uniform distribution of small size γ' phase make the alloy forge piece further strengthened, and improves the mechanical properties and high temperature wear resistance of the forge piece.

[0045] 4. The control GH4720Li alloy bar in the present application is heated under the specific gradient heating and holding treatment condition, and is deformed by forging under the forging pressure condition that the initial forging temperature is 1130-1150℃, the final forging temperature is 1080-1100℃, and the total deformation is 48-73%, and finally is sequentially subjected to solid solution treatment, primary aging treatment and secondary aging treatment, so that the GH4720Li alloy forge piece with good uniformity of the structure in each deformation zone, especially in the large deformation zone, can be obtained; this is because: the specific gradient heating and holding treatment condition in the present application can ensure that the temperature of the heart and the outer surface of the GH4720Li alloy bar blank is uniform, and the temperature of each part of the blank is uniform during the heating process, not only can the cracking problem caused by the temperature stress in the heating process be avoided, but also the consistent grain growth degree of each part of the blank after heating can be ensured, which provides favorable conditions for the uniformity of the grain size in each deformation zone in the subsequent forging deformation process; and the forging pressure condition in the present application can make each part of the forge piece fully deform and occur complete dynamic recrystallization, so as to ensure the uniformity of the grain size in each deformation zone, and the heat in the heart of the forge piece can be effectively transferred to the outer surface of the forge piece under the forging pressure condition in the present application, so as to make up for the insufficient reduction of the temperature of the outer surface of the forge piece, and further ensure the uniformity of the grain size in each deformation zone; when the GH4720Li alloy is subjected to the above gradient heating and holding treatment and forging treatment, and then is subjected to the solid solution treatment, primary aging treatment and secondary aging treatment condition in the present application, the number, size, morphology and distribution of the primary precipitated phase γ', the secondary precipitated phase γ'' and the tertiary precipitated phase γ''' in each deformation zone of the forge piece can be effectively controlled, so that the three kinds of precipitated phases play a synergistic regulation role, and finally the grain size in each deformation zone of the forge piece after heat treatment tends to be more uniform, especially the GH4720Li alloy forge piece with good uniformity of the structure in the large deformation zone can be obtained, and the forge piece has good comprehensive mechanical properties, and the high temperature wear resistance can meet the service life requirements of the turbine disc. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 a The OM microstructure of the GH4720Li high-temperature alloy ingot in the embodiment of the present application;

[0047] Figure 1 bThe microstructure SEM graph of the GH4720Li high-temperature alloy ingot in the embodiment of the application;

[0048] Figure 2 The heating process scheme graph of the GH4720Li high-temperature alloy in the embodiment of the application;

[0049] Figure 3 The technical roadmap of the embodiment of the application;

[0050] Figure 4a The macroscopic morphology of the actual forging with a deformation degree of 48% in the embodiment of the application;

[0051] Figure 4b The macroscopic morphology of the actual forging with a deformation degree of 58% in the embodiment of the application;

[0052] Figure 4c The macroscopic morphology of the actual forging with a deformation degree of 67% in the embodiment of the application;

[0053] Figure 4d The macroscopic morphology of the actual forging with a deformation degree of 73% in the embodiment of the application;

[0054] Figure 5a The research observation point schematic diagram of the forging section after corrosion with a deformation degree of 48% in the embodiment of the application;

[0055] Figure 5b The research observation point schematic diagram of the forging section after corrosion with a deformation degree of 58% in the embodiment of the application;

[0056] Figure 5c The research observation point schematic diagram of the forging section after corrosion with a deformation degree of 67% in the embodiment of the application;

[0057] Figure 5d The research observation point schematic diagram of the forging section after corrosion with a deformation degree of 73% in the embodiment of the application;

[0058] Figure 6a The microstructure OM graph of the difficult deformation area of the forging with a deformation degree of 48% in the embodiment of the application;

[0059] Figure 6b The microstructure SEM graph of the difficult deformation area of the forging with a deformation degree of 48% in the embodiment of the application;

[0060] Figure 6c The grain size distribution graph of the difficult deformation area of the forging with a deformation degree of 48% in the embodiment of the application;

[0061] Figure 6d The gamma prime phase particle size distribution graph of the difficult deformation area of the forging with a deformation degree of 48% in the embodiment of the application;

[0062] Figure 7a The microstructure OM diagram of the small deformation area of the forging with a deformation degree of 48% in the embodiment of the application;

[0063] Figure 7b The microstructure SEM diagram of the small deformation area of the forging with a deformation degree of 48% in the embodiment of the application;

[0064] Figure 7c The grain size distribution diagram of the small deformation area of the forging with a deformation degree of 48% in the embodiment of the application;

[0065] Figure 7d The distribution diagram of the γ' phase particle size of the small deformation area of the forging with a deformation degree of 48% in the embodiment of the application;

[0066] Figure 8a The microstructure OM diagram of the large deformation area of the forging with a deformation degree of 48% in the embodiment of the application;

[0067] Figure 8b The microstructure SEM diagram of the large deformation area of the forging with a deformation degree of 48% in the embodiment of the application;

[0068] Figure 8c The grain size distribution diagram of the large deformation area of the forging with a deformation degree of 48% in the embodiment of the application;

[0069] Figure 8d The distribution diagram of the γ' phase particle size of the large deformation area of the forging with a deformation degree of 48% in the embodiment of the application;

[0070] Figure 9 The relationship between the grain size and the hardness of the different deformation areas of the forging with a deformation degree of 48% in the embodiment of the application;

[0071] Figure 10a The microstructure OM diagram of the difficult deformation area of the forging with a deformation degree of 58% in the embodiment of the application;

[0072] Figure 10b The microstructure SEM diagram of the difficult deformation area of the forging with a deformation degree of 58% in the embodiment of the application;

[0073] Figure 10c The grain size distribution diagram of the difficult deformation area of the forging with a deformation degree of 58% in the embodiment of the application;

[0074] Figure 10d The distribution diagram of the γ' phase particle size of the difficult deformation area of the forging with a deformation degree of 58% in the embodiment of the application;

[0075] Figure 11 a The microstructure OM diagram of the small deformation area of the forging with a deformation degree of 48% in the embodiment of the application;

[0076] Figure 11 bThe microstructure SEM diagram of the small deformation area of the forging with the deformation degree of 58% in the embodiment of the application;

[0077] Figure 11 c The grain size distribution diagram of the small deformation area of the forging with the deformation degree of 58% in the embodiment of the application;

[0078] Figure 11 d The distribution diagram of the γ' phase particle size of the small deformation area of the forging with the deformation degree of 58% in the embodiment of the application;

[0079] Figure 12a The microstructure OM diagram of the large deformation area of the forging with the deformation degree of 58% in the embodiment of the application;

[0080] Figure 12b The microstructure SEM diagram of the large deformation area of the forging with the deformation degree of 58% in the embodiment of the application;

[0081] Figure 12c The grain size distribution diagram of the large deformation area of the forging with the deformation degree of 58% in the embodiment of the application;

[0082] Figure 12d The distribution diagram of the γ' phase particle size of the large deformation area of the forging with the deformation degree of 58% in the embodiment of the application;

[0083] Figure 13 The relationship diagram between the grain size and the hardness of the different deformation areas of the forging with the deformation degree of 58% in the embodiment of the application;

[0084] Figure 14a The microstructure OM diagram of the difficult deformation area of the forging with the deformation degree of 67% in the embodiment of the application;

[0085] Figure 14b The microstructure SEM diagram of the difficult deformation area of the forging with the deformation degree of 67% in the embodiment of the application;

[0086] Figure 14c The grain size distribution diagram of the difficult deformation area of the forging with the deformation degree of 67% in the embodiment of the application;

[0087] Figure 14d The distribution diagram of the γ' phase particle size of the difficult deformation area of the forging with the deformation degree of 67% in the embodiment of the application;

[0088] Figure 15a The microstructure OM diagram of the small deformation area of the forging with the deformation degree of 67% in the embodiment of the application;

[0089] Figure 15b The microstructure SEM diagram of the small deformation area of the forging with the deformation degree of 67% in the embodiment of the application;

[0090] Figure 15c The grain size distribution diagram of the small deformation area of the forging with the deformation degree of 67% in the embodiment of the application;

[0091] Figure 15d The distribution diagram of the grain size of the forged piece with a deformation degree of 67% in the small deformation area in the embodiment of the application;

[0092] Figure 16a The OM microstructure diagram of the forged piece with a deformation degree of 67% in the large deformation area in the embodiment of the application;

[0093] Figure 16b The SEM microstructure diagram of the forged piece with a deformation degree of 67% in the large deformation area in the embodiment of the application;

[0094] Figure 16c The distribution diagram of the grain size of the forged piece with a deformation degree of 67% in the large deformation area in the embodiment of the application;

[0095] Figure 16d The distribution diagram of the γ' phase particle size of the forged piece with a deformation degree of 67% in the large deformation area in the embodiment of the application;

[0096] Figure 17 The relationship between the grain size and the hardness of the forged piece with a deformation degree of 67% in different deformation areas in the embodiment of the application;

[0097] Figure 18a The OM microstructure diagram of the forged piece with a deformation degree of 73% in the difficult deformation area in the embodiment of the application;

[0098] Figure 18b The SEM microstructure diagram of the forged piece with a deformation degree of 73% in the difficult deformation area in the embodiment of the application;

[0099] Figure 18c The distribution diagram of the grain size of the forged piece with a deformation degree of 73% in the difficult deformation area in the embodiment of the application;

[0100] Figure 18d The distribution diagram of the γ' phase particle size of the forged piece with a deformation degree of 73% in the difficult deformation area in the embodiment of the application;

[0101] Figure 19a The OM microstructure diagram of the forged piece with a deformation degree of 73% in the small deformation area in the embodiment of the application;

[0102] Figure 19b The SEM microstructure diagram of the forged piece with a deformation degree of 73% in the small deformation area in the embodiment of the application;

[0103] Figure 19c The distribution diagram of the grain size of the forged piece with a deformation degree of 73% in the small deformation area in the embodiment of the application;

[0104] Figure 19d The distribution diagram of the γ' phase particle size of the forged piece with a deformation degree of 73% in the small deformation area in the embodiment of the application;

[0105] Figure 20a Microstructure OM of large deformation area of the forging with 73% deformation in the embodiment of the present application;

[0106] Figure 20b SEM microstructure of large deformation area of the forging with 73% deformation in the embodiment of the present application;

[0107] Figure 20c Distribution diagram of grain size of large deformation area of the forging with 73% deformation in the embodiment of the present application;

[0108] Figure 20d Distribution diagram of γ' phase particle size of large deformation area of the forging with 73% deformation in the embodiment of the present application;

[0109] Figure 21 Relationship between grain size and hardness of different deformation areas of the forging with 73% deformation in the embodiment of the present application;

[0110] Figure 22a Microstructure OM of difficult deformation area of the sample with 48% deformation after heat treatment in the embodiment of the present application;

[0111] Figure 22b SEM microstructure of difficult deformation area of the sample with 48% deformation after heat treatment in the embodiment of the present application;

[0112] Figure 22c Distribution diagram of grain size of difficult deformation area of the sample with 48% deformation after heat treatment in the embodiment of the present application;

[0113] Figure 22d Distribution diagram of γ' phase particle size of difficult deformation area of the sample with 48% deformation after heat treatment in the embodiment of the present application;

[0114] Figure 23a Microstructure OM of small deformation area of the sample with 48% deformation after heat treatment in the embodiment of the present application;

[0115] Figure 23b SEM microstructure of small deformation area of the sample with 48% deformation after heat treatment in the embodiment of the present application;

[0116] Figure 23c Distribution diagram of grain size of small deformation area of the sample with 48% deformation after heat treatment in the embodiment of the present application;

[0117] Figure 23d Distribution diagram of γ' phase particle size of small deformation area of the sample with 48% deformation after heat treatment in the embodiment of the present application;

[0118] Figure 24a Microstructure OM of large deformation area of the sample with 48% deformation after heat treatment in the embodiment of the present application;

[0119] Figure 24b Microstructure SEM of large deformation area of the sample with deformation degree of 48% after heat treatment in the embodiment of the present application;

[0120] Figure 24c Distribution diagram of grain size of large deformation area of the sample with deformation degree of 48% after heat treatment in the embodiment of the present application;

[0121] Figure 24d Distribution diagram of γ' phase particle size of large deformation area of the sample with deformation degree of 48% after heat treatment in the embodiment of the present application;

[0122] Figure 25 Relationship diagram of grain size and hardness of different deformation areas of the sample with deformation degree of 48% after heat treatment in the embodiment of the present application; Figure 26a Microstructure OM of difficult deformation area of the sample with deformation degree of 58% after heat treatment in the embodiment of the present application;

[0123] Figure 26b Microstructure SEM of difficult deformation area of the sample with deformation degree of 58% after heat treatment in the embodiment of the present application;

[0124] Figure 26c Distribution diagram of grain size of difficult deformation area of the sample with deformation degree of 58% after heat treatment in the embodiment of the present application;

[0125] Figure 26d Distribution diagram of γ' phase particle size of difficult deformation area of the sample with deformation degree of 58% after heat treatment in the embodiment of the present application;

[0126] Figure 27a Microstructure OM of small deformation area of the sample with deformation degree of 58% after heat treatment in the embodiment of the present application;

[0127] Figure 27b Microstructure SEM of small deformation area of the sample with deformation degree of 58% after heat treatment in the embodiment of the present application;

[0128] Figure 27c Distribution diagram of grain size of small deformation area of the sample with deformation degree of 58% after heat treatment in the embodiment of the present application;

[0129] Figure 27d Distribution diagram of γ' phase particle size of small deformation area of the sample with deformation degree of 58% after heat treatment in the embodiment of the present application;

[0130] Figure 28a Microstructure OM of large deformation area of the sample with deformation degree of 58% after heat treatment in the embodiment of the present application;

[0131] Figure 28b Microstructure SEM of large deformation area of the sample with deformation degree of 58% after heat treatment in the embodiment of the present application;

[0132] Figure 28c The grain size distribution diagram of the large deformation area of the sample with a deformation degree of 58% after heat treatment in the embodiment of the application;

[0133] Figure 28d The γ' phase particle size distribution diagram of the large deformation area of the sample with a deformation degree of 58% after heat treatment in the embodiment of the application;

[0134] Figure 29 The relationship between the grain size and hardness of different deformation areas of the sample with a deformation degree of 58% after heat treatment in the embodiment of the application;

[0135] Figure 30a The microstructure OM diagram of the difficult deformation area of the sample with a deformation degree of 67% after heat treatment in the embodiment of the application;

[0136] Figure 30b The microstructure SEM diagram of the difficult deformation area of the sample with a deformation degree of 67% after heat treatment in the embodiment of the application;

[0137] Figure 30c The grain size distribution diagram of the difficult deformation area of the sample with a deformation degree of 67% after heat treatment in the embodiment of the application;

[0138] Figure 30d The γ' phase particle size distribution diagram of the difficult deformation area of the sample with a deformation degree of 67% after heat treatment in the embodiment of the application;

[0139] Figure 31 a The microstructure OM diagram of the small deformation area of the sample with a deformation degree of 67% after heat treatment in the embodiment of the application;

[0140] Figure 31 b The microstructure SEM diagram of the small deformation area of the sample with a deformation degree of 67% after heat treatment in the embodiment of the application;

[0141] Figure 31 c The grain size distribution diagram of the small deformation area of the sample with a deformation degree of 67% after heat treatment in the embodiment of the application;

[0142] Figure 31 d The γ' phase particle size distribution diagram of the small deformation area of the sample with a deformation degree of 67% after heat treatment in the embodiment of the application;

[0143] Figure 32a The microstructure OM diagram of the large deformation area of the sample with a deformation degree of 67% after heat treatment in the embodiment of the application;

[0144] Figure 32b The microstructure SEM diagram of the large deformation area of the sample with a deformation degree of 67% after heat treatment in the embodiment of the application;

[0145] Figure 32cThe grain size distribution diagram of the large deformation area of the sample with a deformation degree of 67% after heat treatment in the embodiment of the application;

[0146] Figure 32d The distribution diagram of the gamma prime phase particle size of the large deformation area of the sample with a deformation degree of 67% after heat treatment in the embodiment of the application;

[0147] Figure 33 The relationship between the grain size and hardness of different deformation areas of the sample with a deformation degree of 67% after heat treatment in the embodiment of the application; Figure 34a The OM microstructure diagram of the difficult deformation area of the sample with a deformation degree of 73% after heat treatment in the embodiment of the application;

[0148] Figure 34b The SEM microstructure diagram of the difficult deformation area of the sample with a deformation degree of 73% after heat treatment in the embodiment of the application;

[0149] Figure 34c The grain size distribution diagram of the difficult deformation area of the sample with a deformation degree of 73% after heat treatment in the embodiment of the application;

[0150] Figure 34d The distribution diagram of the gamma prime phase particle size of the difficult deformation area of the sample with a deformation degree of 73% after heat treatment in the embodiment of the application;

[0151] Figure 35a The OM microstructure diagram of the small deformation area of the sample with a deformation degree of 73% after heat treatment in the embodiment of the application;

[0152] Figure 35b The SEM microstructure diagram of the small deformation area of the sample with a deformation degree of 73% after heat treatment in the embodiment of the application;

[0153] Figure 35c The grain size distribution diagram of the small deformation area of the sample with a deformation degree of 73% after heat treatment in the embodiment of the application;

[0154] Figure 35d The distribution diagram of the gamma prime phase particle size of the small deformation area of the sample with a deformation degree of 73% after heat treatment in the embodiment of the application;

[0155] Figure 36a The OM microstructure diagram of the large deformation area of the sample with a deformation degree of 73% after heat treatment in the embodiment of the application;

[0156] Figure 36b The SEM microstructure diagram of the large deformation area of the sample with a deformation degree of 73% after heat treatment in the embodiment of the application;

[0157] Figure 36c The grain size distribution diagram of the large deformation area of the sample with a deformation degree of 73% after heat treatment in the embodiment of the application;

[0158] Figure 36d Figure 6 is a distribution diagram of the γ' phase particle size of the sample with a deformation degree of 73% after heat treatment in an embodiment of the present application;

[0159] Figure 37 Figure 7 is a relationship between the grain size and the hardness of different deformation zones of the sample with a deformation degree of 73% after heat treatment in an embodiment of the present application; Figure 38 Figure 8 is a comparison diagram of the normal temperature hardness and the high temperature hardness of the large deformation zone with different deformation degrees in an embodiment of the present application;

[0160] Figure 39a Figure 9 is a high temperature friction coefficient diagram of the large deformation zone with different deformation degrees in an embodiment of the present application;

[0161] Figure 39b Figure 10 is a wear amount diagram of the large deformation zone with different deformation degrees in an embodiment of the present application. DETAILED DESCRIPTION

[0162] The first part is the preparation and research method of GH4720Li high temperature alloy material

[0163] 1.1 Microstructure and chemical composition of GH4720Li high temperature alloy ingot

[0164] The GH4720Li alloy used in this embodiment is a deformed high temperature alloy with a high alloying degree of Ni element as a matrix, and a uniformized consumable ingot of difficult-to-deform nickel-based high temperature alloy GH4720Li is obtained by adopting a triple melting process of vacuum induction melting, electroslag remelting and vacuum consumable remelting (VIM+ESR+VAR), Figure 1 a 、The original microstructure of the GH4720Li alloy ingot bar is obtained by Figure 1 b It is known that the grain size of the alloy in the ingot state is uneven, and obvious strip-shaped structure appears. It is known from Figure 1 a that a large amount of primary γ' phase exists in the ingot state, and smaller primary γ' phase and secondary γ' phase exist in the grain interior. Table 1-1 shows the chemical composition of the GH4720Li high temperature alloy. Figure 1 b

[0165] Table 1-1 Chemical composition table of deformed high temperature alloy (mass fraction / %)

[0166]

[0167] 1.2 Forging process

[0168] GH4720Li high-temperature alloy belongs to difficult-to-deform high-temperature alloy because of its high alloying, narrow forging temperature range and poor plasticity. The heating temperature and deformation degree have great influence on the microstructure and properties of the alloy during the forging process. Through experiments, the deformation temperature of GH4720Li high-temperature alloy is determined to be between 1130°C and 1150°C; and the deformation degree of the alloy is determined to be 50% to 80%.

[0169] 1.2.1 Development of heating process scheme

[0170] Because the deformation temperature range of GH4720Li high-temperature alloy is narrow, in order to determine the best initial forging temperature of the alloy, four φ47x100mm high-temperature alloy bars were cut from the ingot and divided into four groups. After being heated at room temperature for 30min and reaching 800°C, the four bars were directly loaded into the resistance furnace at 800°C and kept for 60min. Then, the temperature was raised from 800°C to 900°C for 30min and kept for 60min. Next, the temperature was raised from 900°C to 1000°C for 10min and kept for 20min. Finally, the temperature was raised from 1000°C to 1140°C for 14min and kept for 20min before the bars were subjected to forging experiments with different deformation degrees. The evolution law of the microstructure and properties of GH4720Li high-temperature alloy forgings with different deformation degrees was observed and analyzed, and the heating process scheme of GH4720Li high-temperature alloy is shown in Table 1-1. Figure 2

[0171] 1.2.2 Deformation degree process scheme

[0172] In order to study the influence law of different deformation degrees of GH4720Li high-temperature alloy on the microstructure and properties, four φ47x100mm bars were selected and divided into four groups. After being heated at room temperature for 30min and reaching 800°C, the four bars were directly loaded into the resistance furnace at 800°C and kept for 60min. Then, the temperature was raised from 800°C to 900°C for 30min and kept for 60min. Next, the temperature was raised from 900°C to 1000°C for 10min and kept for 20min. Finally, the four groups of samples were heated to the best initial forging temperature and subjected to upsetting experiments with deformation degrees of 50%, 60%, 70% and 80%. The evolution law of the microstructure and properties of GH4720Li high-temperature alloy forgings in each deformation zone with different deformation degrees was observed and analyzed.

[0173] Table 1-2 Deformation degree process scheme

[0174]

[0175] 1.3 Heat treatment

[0176] ​Generally, the comprehensive mechanical properties of high-temperature alloy forgings do not reach their optimal service state after hot deformation. Only through heat treatment can stable grain structure and mechanical properties be obtained. Therefore, heat treatment is essential for such alloy forgings. GH4720Li alloy was heat-treated using solution treatment and two aging treatments. After heat treatment, the comprehensive mechanical properties of the specimens were related not only to grain size but also to factors such as the size, morphology, content, and distribution of the second phase. Solution treatment achieved the dissolution and homogenization of the γ' phase in the alloy, obtaining a homogeneous solid solution. In GH4720Li high-temperature alloy, heat treatment is a key factor affecting its microstructure and properties; selecting an appropriate heat treatment method can better unleash its greater potential.

[0177] Through experiments, the heat treatment process schemes shown in Table 1-3 were preliminarily determined, namely, the optimal solution treatment temperature is 1060℃, holding time is 4 hours, and oil cooling is used; the first aging treatment temperature is 650℃, holding time is 8 hours, and air cooling is used; the second aging treatment temperature is 760℃, holding time is 8 hours, and air cooling is used. The microstructure and hardness evolution of each deformation zone of the GH4720Li high-temperature alloy samples after heat treatment were observed and analyzed.

[0178] Table 1-3 Heat Treatment Process Scheme

[0179]

[0180] 1.4 High-temperature hardness and high-temperature friction and wear tests

[0181] To investigate the high-temperature hardness and wear performance of the deformed zone of GH4720Li superalloy under different deformation degrees, GH4720Li superalloy samples with the same deformation zone size of 30mm×30mm×5mm were selected. An HVT-1000 high-temperature vacuum hardness tester provided by Lanzhou Zhongke Kaihua Technology Development Co., Ltd. was used to simulate the hardness of each deformation zone under different deformation degrees at high temperatures under the turbine disk operating temperature. An HVT-1000 high-temperature friction and wear testing machine also provided by Lanzhou Zhongke Kaihua Technology Development Co., Ltd. was used to simulate the friction and wear performance of each deformation zone under different deformation degrees at high temperatures under the turbine disk operating temperature. By weighing the material before and after friction and wear, the different densities were compared. The mass removed by wear was used to represent the influence of wear particles on the material surface. The friction coefficient and wear amount of the alloy at high temperatures were analyzed. Combined with the wear characteristic mechanism of the alloy, the anti-friction and wear performance of the material was analyzed. The parameters for high-temperature wear are shown in Table 1-4, namely, the experimental temperature is 700℃, the friction and wear load is set to 10N, the motor speed is set to 1000r / min, the wear material is Si3N4, and the wear test duration is 30min.

[0182] Table 1-4 Abrasion wear process parameters

[0183]

[0184] 1.5 Test characterization methods

[0185] 1.5.1 Metallographic structure observation

[0186] In this embodiment, a Zeiss Primotech optical microscope produced in Germany is used to observe and analyze the samples after etching at multiple magnifications, and the influence of the degree of deformation on the microstructure and properties of the deformed zone of GH4720Li alloy is explored.

[0187] 1.5.2 SEM / EBSD analysis

[0188] In this embodiment, a Phenom LE field emission electron microscope (SEM) produced by Phenom Company in the Netherlands is used to analyze the distribution and content of precipitates in each deformed zone. The prepared samples are tested and analyzed for grain orientation and recrystallization in each deformed zone using Velocity TM Plus electron backscatter diffraction (EBSD) produced by EDAX Company.

[0189] 1.5.3 TEM analysis

[0190] In this embodiment, a JEM-F200 field emission transmission electron microscope produced by Japan Electron is used to analyze and observe the microstructure of the thin section samples in each deformed zone.

[0191] 1.5.4 Hardness testing

[0192] In this embodiment, a HR-150A Rockwell hardness tester produced by Laizhou Huayin Test Instrument Co., Ltd. is used to measure the Rockwell hardness of the samples, with units of HRC, repeated 7 times and the maximum and minimum values are removed to obtain the average value.

[0193] 1.5.5 Average grain size and distribution statistics

[0194] In this embodiment, the grain boundary distribution photographs of the samples are collected using a metallographic microscope, and the diameter of each grain in the field of view of the alloy forging metallographic photograph is measured using ImageJ software, thereby obtaining the distribution range and average grain size of the grain size in each deformed zone. On this basis, using the ASTM grading method, combined with the grain size test results, the influence of the degree of deformation on the microstructure and properties of the deformed zone of the alloy is explored.

[0195] 1.5.6 γ' phase content statistics

[0196] In this embodiment, scanning electron microscope is used to collect the distribution of γ' phase of the sample, and Imageproplus software is used to count and analyze the distribution of γ' phase in the field of view of the collected sample scanning electron microscope photos.

[0197] 1.6 Technical route

[0198] The technical route of this embodiment is shown in Figure 3 .

[0199] Evolution of microstructure and properties of GH4720Li alloy forgings in different deformation degrees in the second part

[0200] Due to the high alloying of GH4720Li alloy, small heat treatment temperature range, low yield, and the problem of easy crack in disc forging process, it is more difficult to prepare high-quality disc forging products, and the cost is also increased. GH4720Li alloy is a Ni-based precipitation strengthened wrought superalloy, its main component is high γ' phase, with the increase of heating temperature, its composition will gradually dissolve in the matrix, and at a certain temperature, it will all dissolve in the matrix. Due to the difficulty in controlling the uniformity of the microstructure of the forgings, it is generally used to complete the final forging before the γ' phase is dissolved. Therefore, for wrought superalloy, the grain size, size and distribution of the second phase of forgings with different deformation degrees are different, and the grain size, size and distribution of the second phase of forgings with different deformation degrees are also different. At present, although some researchers have studied the grain size and size of the second phase of GH4720Li alloy with different deformation degrees, most of the experimental studies are carried out on thermal simulation testing machine, and there is a certain deviation between the experimental environment and the actual mass production, especially in the study of the influence law of the microstructure and properties of forgings with different deformation degrees in different deformation zones.

[0201] Therefore, this part studies the influence law of the microstructure and properties of GH4720Li alloy forgings with different deformation degrees, systematically analyzes the grain size, size and distribution law of the second phase of forgings with different deformation degrees, and elaborates the influence of deformation degree on the deformation zone of GH4720Li alloy forgings.

[0202] 2.1 Deformation process experiment of different deformation degrees

[0203] During the hot deformation of GH4720Li high-temperature alloy bars, the metal expands and flows outwards as the height decreases. Based on the degree of deformation, the bar can be divided into three deformation zones along its plane of symmetry: The first zone is near the end face of the bar, where the outward flow resistance of particles caused by friction increases with distance from the center of the end face. Additionally, during hot deformation, the upper and lower end faces cool rapidly due to contact with the mold, resulting in significant resistance to deformation. Therefore, this zone experiences the least deformation and is called the "difficult-to-deform zone." The second zone is located in the middle of the bar, where the frictional force from the end face is minimal, and its stress condition is favorable for forming, resulting in the largest deformation; this zone is called the "large deformation zone." The third zone is located on the outer periphery of the bar. Due to the circumferential tensile stress caused by the radial flow expansion of the metal in the second zone, the bar bulges; this zone is called the "small deformation zone."

[0204] Uneven deformation is a significant factor affecting forging quality. The circumferential tensile stress on the sides of the specimen can cause longitudinal cracks on the surface; especially in areas prone to deformation, insufficient deformation can lead to coarse grains, resulting in inconsistent forging properties. This has a substantial impact on the forging quality of high-temperature alloys like GH4720Li, which have high requirements for grain size.

[0205] To investigate the influence of deformation degree on the microstructure and properties of GH4720Li alloy forgings in large-scale free forging processes, hot deformation experiments with deformation degrees of 50% to 80% were conducted on the billets under the same heating process. Since the reduction amount cannot be precisely controlled by the free forging hammer, the actual deformation degree of the billet after hot deformation deviates from the designed deformation degree. The specific deformation parameters are shown in Table 2-1. Figures 4a-4d The macroscopic morphology of forgings with different degrees of deformation is shown.

[0206] Table 2-1 Deformation Degree Process Scheme

[0207]

[0208] Depend on Figures 4a-4d It can be seen that the deformation degree of the bar blanks used in the experiment ranged from 48% to 73%. Figures 4a-4c It can be seen that the forgings with the three degrees of deformation exhibited varying degrees of instability. As the degree of deformation increased, the area of ​​the difficult-to-deform zone became smaller and smaller, while the area of ​​the difficult-to-deform zone became smaller and smaller. Figure 4d It can be seen that there are almost no obvious undeformed areas. Although the forgings with small deformation degrees showed instability and large areas that were difficult to deform, none of the forgings with the four deformation degrees showed cracks or fissures. This has reference value for the production and research of turbine disks for various types and applications of aero-engines.

[0209] Figures 5a-5d This diagram illustrates the observation points for the study of corrosion on the cross-sections of forgings with four different deformation degrees. As shown in the figure, the areas of the difficult-to-deform and small-deformation zones gradually decrease with increasing deformation degree, while the area of ​​the large-deformation zone gradually increases with increasing deformation degree. To investigate the influence of deformation degree on the microstructure and properties of GH4720Li alloy forgings, a systematic and detailed study was conducted on various locations along the cross-sections of alloy forgings with four different deformation degrees. Analysis revealed that forgings with the same deformation degree exhibited almost identical microstructure and properties in the same deformation zone, with no significant differences or changes. However, the microstructure and properties of different deformation zones within the same deformation degree showed significant differences. Therefore, studying the influence of deformation degree on the microstructure and properties of the deformation zone of GH4720Li alloy forgings is of significant value for understanding turbine disks of different aircraft models.

[0210] 2.2 Evolution of microstructure and properties in the difficult-to-deform zone of forgings with different deformation degrees

[0211] Figures 6a-6d The microstructure and size distribution of the difficult-to-deform region in a forging with a deformation degree of 48% are shown. In this region, the grains are coarse, with the largest grain size being 103.7 μm, the smallest 27.3 μm, and the average grain size being 55.3 μm. The grain size is mainly distributed in the range of 37.8-63.5 μm, with a small portion distributed below 37.8 μm and above 63.5 μm. The secondary γ' phase is distributed in a lamellar form within the γ matrix. The largest γ' phase grain size is 373.3 nm, the smallest is 179.8 nm, and the average grain size is approximately 248.9 nm. The grain size is mainly distributed in the range of 195-275 nm, with a small portion distributed below 195 nm and above 275 nm.

[0212] Figures 10a-10d The image shows the microstructure and size distribution of the difficult-to-deform zone in a forging with a deformation degree of 58%. Figures 10a-10d As shown, under 58% deformation, the grain size of the difficult-to-deform region of the forging is mainly distributed in the range of 18.9–37.8 μm, with a small portion distributed below 18.9 μm and above 37.8 μm. The largest grain size is 63.1 μm, the smallest is 13.2 μm, and the average grain size is 28.2 μm. The γ' phase grain size is mainly distributed in the ranges of 155–215 nm and 275–315 nm, with a small portion distributed below 155 nm, 215–275 nm, and above 315 nm. The largest γ' phase grain size is 353.6 nm, the smallest is 137.5 nm, and the average grain size is approximately 205.6 nm.

[0213] Figures 14a-14dThe microstructure and size distribution of the difficult-to-deform zone in the forging with a deformation degree of 67% are shown. At 67% deformation, the microstructure of the difficult-to-deform zone is relatively uniform, with grain sizes mainly distributed in the range of 15.9–26.7 μm, and a small portion distributed below 15.9 μm and above 26.7 μm. The largest grain size is 33.4 μm, the smallest is 11.3 μm, and the average grain size is 20.3 μm. The secondary γ' phase grain size is mainly distributed in the range of 115–215 nm, with a small portion distributed above 215 nm. The γ' phase grain size distribution is uneven, with the largest grain size being 314.1 nm, the smallest being 118.1 nm, and the average grain size being approximately 183.2 nm.

[0214] Figures 18a-18d The image shows the microstructure and size distribution of the difficult-to-deform zone in a forging with a deformation degree of 73%. Figures 18a-18d As shown, under 73% deformation, the grain size of the difficult-to-deform region of the forging is mainly distributed in the range of 13.3–31.8 μm, with a small portion distributed below 13.3 μm and above 31.8 μm. The largest grain size is 34.3 μm, the smallest is 9 μm, and the average grain size is 19.7 μm. The secondary γ' phase grain size is mainly distributed in the range of 95–135 nm, with a small portion distributed below 95 nm and above 135 nm. The size distribution of the γ' phase grain size is very concentrated and uniform, with the largest γ' phase grain size being 135.2 nm, the smallest being 94.7 nm, and the average grain size being approximately 113.9 nm.

[0215] From the above results, for the difficult deformation zone, the smaller the degree of deformation, the more uneven the grain, and the larger the grain size. This is mainly due to the experimental use of the bar in the heating process, the first γ' phase dissolution leads to the weakening of the pinning effect of grain boundary, leading to rapid grain growth, and when the degree of deformation is low, the grain crushing effect on the difficult deformation zone of the bar is not obvious, so among the four degrees of deformation forgings, the grain size of the difficult deformation zone of the forging with a deformation degree of 48% is the largest and uneven. Although the grain size of the difficult deformation zone of the forging with a deformation degree of 58% is still relatively large, it is smaller than that of the difficult deformation zone of the forging with a deformation degree of 48%, and it is a nearly equiaxed crystal organization. With further increase of the degree of deformation, the grain is further crushed, and the grain size is also smaller and more uniform. The difficult deformation zone of the forgings with a deformation degree of 67% and 73% forms an equiaxed crystal organization. The secondary γ' phase in the difficult deformation zone of the forging with a deformation degree of 48% is mainly distributed in the γ matrix in the form of sheets. The secondary γ' phase in the difficult deformation zone of the forging with a deformation degree of 58% is distributed in the γ matrix in the form of sheets and spheres, and the size of the γ' phase is obviously smaller than that in the difficult deformation zone of the forging with a deformation degree of 48%, but there are still a large number of γ / γ' eutectic phases in the form of sunflowers, indicating that Al, Ti and other elements are enriched between the dendrites, affecting the uniformity of the organization and performance of the forging. For the difficult deformation zone of the forgings with a deformation degree of 67% and 73%, the γ' phase is mainly distributed in the γ matrix in the form of spheres, and only a small amount of sheet-shaped γ' phase is distributed at the grain boundary.

[0216] 2.3 Evolution of microstructure and properties of small deformation zone of forgings with different degrees of deformation

[0217] Figures 7a-7d The microstructure and size distribution of the small deformation zone of the forging with a deformation degree of 48% are shown in FIG. 2. The largest grain size of the small deformation zone is 88.9 μm, the smallest grain size is 20.8 μm, the average grain size is 40.4 μm, and the grain size is mainly distributed in the range of 26.7-53.4 μm, a small part is distributed below 26.7 μm and above 53.4 μm. The secondary γ' phase is distributed in the γ matrix in the form of sheets and spheres, the maximum particle size of the γ' phase is 273.6 nm, the minimum particle size is 115.4 nm, the average particle size is about 188.9 nm, and the particle size is mainly distributed in two interval ranges, i.e. 135-175 nm and 195-215 nm, a small part is distributed below 135 nm, 175-195 nm and above 215 nm, and the size of the secondary γ' phase is extremely uneven

[0218] Figures 11 a-11 d The microstructure and size distribution of the small deformation zone of the forging with a deformation degree of 58% are shown in FIG. 3. As Figures 11 a-11 dThe maximum grain size of the small deformation zone is 31.1 μm, the minimum grain size is 16.4 μm, the average grain size is 23.8 μm, the grain size is mainly distributed in the interval range of 18.9-31.8 μm, and a small part is distributed below 18.9 μm. The maximum particle size of the secondary γ' phase is 294.7 nm, the minimum particle size is 97.1 nm, the average particle size is about 182.9 nm, the particle size is mainly distributed in the interval range of 155-195 nm, a small part is distributed below 155 nm and above 195 nm, and other ranges are also relatively uniform except for most of the distribution.

[0219] Figures 15a-15d The microstructure and size distribution diagram of the small deformation zone of the forging with a deformation degree of 67% are shown. Under the deformation degree of 67%, the grain size is mainly distributed in the interval range of 11.2-18.9 μm, a small part is distributed below 11.2 μm and above 18.9 μm, the maximum grain size is 21.7 μm, the minimum grain size is 8.4 μm, and the average grain size is 18.9 μm. The γ' phase particle size is mainly distributed in the interval range of 135-215 nm, a small part is distributed above 215 nm, the maximum particle size of the γ' phase is 254.6 nm, the minimum particle size is 137.9 nm, and the average particle size is about 178.7 nm.

[0220] Figures 19a-19d The microstructure and size distribution diagram of the small deformation zone of the forging with a deformation degree of 73% are shown. Under the deformation degree of 73%, the grain size is mainly distributed in the interval range of 13.3-26.7 μm, a small part is distributed below 13.3 μm and above 26.7 μm, the maximum grain size is 27.9 μm, the minimum grain size is 9.1 μm, and the average grain size is 17.2 μm. The γ' phase particle size is mainly distributed in the interval range of 75-95 nm, a small part is distributed below 75 nm and above 95 nm, the maximum particle size of the γ' phase is 116.3 nm, the minimum particle size is 70 nm, and the average particle size is about 85.5 nm.

[0221] From the above results, it can be seen that the grain size of the small deformation zone is smaller than that of the difficult deformation zone in the forgings with different deformation degrees. For the forging with a deformation degree of 48%, the grain in the small deformation zone is still coarse and uneven, and the grains are elongated. Although the grain size of the small deformation zone of the forging with a deformation degree of 58% is refined, there is still a serious uneven structure, and the grains have obvious fine crystal bands, and the grains are elongated. For the small deformation zone of the forgings with a deformation degree of 48% and 58%, there are a large number of sunflower-shaped γ / γ' eutectic phases in the interdendritic (mainly in the form of flaky γ' phase enriched at the grain boundary and small spherical γ' phase gathered in the grain for the forging with a deformation degree of 58%), which indicates that Al, Ti and other elements are enriched in the interdendritic, affecting the uniformity of the structure and properties of the forgings. For the forgings with a deformation degree of 67% and 73%, the grains in the small deformation zone are more fully broken than those in the difficult deformation zone, so the grain size is more uniform and smaller; the secondary γ' phase of the forgings with two deformation degrees is mainly spherical and distributed in the γ matrix, and the size of the γ' phase is more concentrated and uniform than that in the difficult deformation zone.

[0222] 2.4 Evolution of the microstructure and properties of the large deformation zone of the forgings with different deformation degrees

[0223] Figures 8a-8d The microstructure and size distribution of the large deformation zone of the forging with a deformation degree of 48% are shown in the figure. The grain size of the large deformation zone is mainly distributed in the range of 26.7-44.9 μm, a small part is below 26.7 μm and above 53.4 μm, the largest grain size is 47.3 μm, the smallest grain size is 8.3 μm, and the average grain size is 28.9 μm. The secondary γ' phase is mixedly distributed in the γ matrix in the form of flaky and spherical, and the size of the γ' phase is mixedly distributed in the range of 155-175 nm, 195-235 nm, 255-295 nm, and the distribution is extremely uneven, among which the maximum particle size of the γ' phase is 369.6 nm, the minimum particle size is 155.1 nm, and the average particle size is about 249.3 nm.

[0224] Figures 12a-12dFigure 6 is a microstructure and size distribution diagram of a large deformation zone of a forging with a deformation degree of 58%. The grain size of the large deformation zone is mainly distributed in the range of 15.9-37.8 μm, a small part is distributed below 15.9 μm and above 37.8 μm, the largest grain size is 56.1 μm, the smallest grain size is 12 μm, and the average grain size is 26 μm. The primary γ' phase gradually increases and grows in the difficult deformation zone and the small deformation zone, which is mainly because as the grain is refined, the grain boundary increases, and the solute atoms quickly enrich in the primary γ' phase through the grain boundary. The secondary γ' phase particle size is mainly distributed in the range of 115-175 nm, a small part is distributed below 115 nm and above 175 nm, the largest γ' phase particle size is 292.7 nm, the smallest γ' phase particle size is 102.7 nm, the average γ' phase particle size is about 179.1 nm, the γ' phase is mainly spherical and distributed in the γ matrix, but there is still a small amount of flaky γ' phase distributed near the primary γ' phase.

[0225] Figures 16a-16d Figure 7 is a microstructure and size distribution diagram of a large deformation zone of a forging with a deformation degree of 67%. The grain size of the forging is mainly distributed in the range of 13.3-26.7 μm, a small part is distributed below 13.3 μm and above 26.7 μm, the largest grain size is 29.2 μm, the smallest grain size is 10.9 μm, and the average grain size is 17.9 μm. The secondary γ' phase is spherical and distributed in the γ matrix, the γ' phase particle size is mainly distributed in the range of 115-175 nm, a small part is distributed below 115 nm and above 175 nm, the largest γ' phase particle size is 226 nm, the smallest γ' phase particle size is 94.7 nm, and the average γ' phase particle size is about 143.9 nm.

[0226] Figures 20a-20d Figure 8 is a microstructure and size distribution diagram of a large deformation zone of a forging with a deformation degree of 73%. The grain size of the forging is mainly distributed in the range of 13.3-22.5 μm, a small part is distributed below 13.3 μm and above 22.5 μm, the largest grain size is 24.1 μm, the smallest grain size is 11.1 μm, and the average grain size is 16.9 μm. The secondary γ' phase is spherical and distributed in the γ matrix, the γ' phase particle size is mainly distributed in the range of 75-115 nm, a small part is distributed below 75 nm and above 115 nm, the largest γ' phase particle size is 133.9 nm, the smallest γ' phase particle size is 66 nm, and the average γ' phase particle size is about 95.3 nm.

[0227] For the large deformation zone, the grains in the forgings with deformation degrees of 48% and 58% are uniformly distributed in an equiaxed crystal structure. The grain size is reduced compared to the less deformable and smaller deformation zones, but the grain size is still relatively large. This is mainly due to insufficient fragmentation of the grown grains caused by the smaller deformation degree. As the deformation degree increases to 67% and 73%, the grains in the large deformation zone are fully fragmented, resulting in a more uniform and finer grain size, exhibiting an equiaxed crystal structure. Because the large deformation zone is located in the core of the forging, the cooling rate is slow, and the billet has residual heat from forging, leading to grain growth. This results in the grain size in the large deformation zone of the forgings with deformation degrees of 67% and 73% being slightly larger than the grain size in the smaller deformation zone at the same deformation degree. However, due to the pinning effect of the primary γ' phase on the grain boundaries, excessive grain growth is limited. Therefore, the overall grain structure is a uniform and fine equiaxed crystal structure, with a more uniform γ' phase grain size distribution, which strengthens the matrix. The residual heat from machining in the large deformation zone also led to a certain degree of coarsening of the γ' phase in the forging with a deformation degree of 48%. The γ' phase grain size was relatively small, and it grew significantly in the deformation zone, which was similar to that of the difficult-to-deform zone at the same deformation degree. As the deformation degree increased, the lamellar secondary γ' phase distributed in the γ matrix gradually decreased until it disappeared, while the spherical secondary γ' phase gradually increased.

[0228] 2.5 Hardness evolution in different deformation zones of forgings with different degrees of deformation

[0229] Figure 9 The relationship between grain size and hardness in different deformation zones of a forging with a deformation degree of 48% is shown. Figure 9 As shown, the hardness of the difficult-to-deform region is 40.3 HRC, the hardness of the small deformation region is 43.6 HRC, and the hardness of the large deformation region is 44.3 HRC. (Combined with...) Figure 9 The changes in grain size and hardness reveal that from the difficult-to-deform region to the large-deformation region, the hardness gradually increases as the average grain size decreases. The lower hardness in the difficult-to-deformation region is mainly due to the rapid grain growth caused by the primary dissolution of the γ' phase at higher temperatures. Because the deformation is relatively small, the grains in the difficult-to-deformation and small-deformation regions are not effectively broken up, resulting in lower hardness. While the grains in the large-deformation region undergo some breakage, the effect is not significant, and the grains remain relatively large.

[0230] Figure 13 The relationship between grain size and hardness in different deformation zones of a forging with a deformation degree of 58% is shown. The hardness of the difficult-to-deform zone is 44.5 HRC, the hardness of the small deformation zone is 44.9 HRC, and the hardness of the large deformation zone is 45.5 HRC. (Combined with...) Figure 13The change of the grain size and hardness of the forging with the deformation degree of 67% can be known from the figure, that is, the average grain size gradually decreases from the difficult deformation zone to the large deformation zone, and the hardness gradually increases, but the increasing amplitude is small. The main reason is that with the increase of the deformation degree, the microstructure of each deformation zone is close under the large deformation degree, so the hardness change is not obvious.

[0231] Figure 17 The relationship between the grain size and the hardness of the forging with the deformation degree of 73% in different deformation zones is shown in the figure. The hardness of the difficult deformation zone is 47.2HRC, the hardness of the small deformation zone is 47.6HRC, and the hardness of the large deformation zone is 47.7HRC. The change of the grain size and hardness of the forging can be known from the figure, that is, the average grain size gradually decreases from the difficult deformation zone to the large deformation zone, and the hardness gradually increases. Figure 17 Figure 17

[0232] Figure 21 The relationship between the grain size and the hardness of the forging with the deformation degree of 73% in different deformation zones is shown in the figure. The hardness of the difficult deformation zone is 47.2HRC, the hardness of the small deformation zone is 47.6HRC, and the hardness of the large deformation zone is 47.7HRC. The change of the grain size and hardness of the forging can be known from the figure, that is, the average grain size gradually decreases from the difficult deformation zone to the large deformation zone, and the hardness gradually increases. Figure 21

[0233] 2.6 Summary of this part

[0234] (1) The grain size of the GH4720Li alloy bar gradually decreases as the deformation degree increases under different deformation degrees. When the deformation degree is low, the grain size and size distribution of each deformation zone of the forging are uneven, and some of them grow. When the deformation degree is high, the grain size of the forging is greatly reduced and the grain size of each deformation zone gradually becomes uniform.

[0235] (2) The γ' phase size of the GH4720Li alloy bar gradually decreases as the deformation degree increases under different deformation degrees. When the deformation degree is low, the secondary γ' phase of each deformation zone of the forging is mainly coarse flake, and the γ' phase particle size is extremely uneven, and some deformation zones appear sunflower-shaped γ / γ' eutectic phase. When the deformation degree is high, the secondary γ' phase of the forging is mainly uniform and small spherical.

[0236] ​​​(3) GH4720Li alloy bar under different deformation degree, with the increase of deformation degree, the hardness of each deformation zone of the forging gradually increased. Lower deformation degree, the forging from the difficult deformation zone to the large deformation zone, the hardness has obvious difference. Higher deformation degree, the hardness of each deformation zone of the forging gradually tends to be the same.

[0237] The third part of GH4720Li alloy forging under different deformation degree after heat treatment of the organization and performance influence law

[0238] For precipitation strengthening type nickel-based superalloy GH4720Li alloy, grain size, size distribution and γ' phase morphology, size, distribution of high temperature alloy organization uniformity and comprehensive mechanical properties have a crucial influence, and heat treatment can adjust the morphology, size and distribution of GH4720Li alloy, so that the organization and performance meet the qualified product use requirements.

[0239] In order to study the influence law of deformation degree on the microstructure and properties of the deformation zone after heat treatment, 1060℃ / 4h / OC / +650℃ / 8h / AC+760℃ / 8h / AC was selected to heat treat the forgings with the above four deformation degrees, and the influence law of grain size, size distribution and γ' phase morphology, size and distribution on the performance of the deformation zone with different deformation degree after heat treatment was studied.

[0240] 3.1 Evolution of microstructure and properties of difficult deformation zone of forgings with different deformation degrees after heat treatment

[0241] Figures 22a-22d The microstructure and size distribution of the difficult deformation zone of the specimen with 48% deformation degree after heat treatment. The grain size of the forging with 48% deformation degree after heat treatment is mainly distributed in the range of 22.5-44.9μm, a small part is distributed below 22.5μm and above 44.9μm, the maximum grain size is 53.2μm, the minimum grain size is 13.9μm, and the average grain size is 28.9μm. The γ' phase particle size is mainly distributed in the range of 215-295nm, a small part is distributed below 215nm and above 295nm, the maximum particle size of γ' phase is 327nm, the minimum particle size is 171.9nm, the average particle size is about 244.4nm, which has no obvious change compared with the γ' phase size of the forging before heat treatment, and the γ' phase is unevenly distributed in the form of sheet and sphere in the γ matrix.

[0242] Figures 26a-26d The microstructure and size distribution of the difficult deformation zone of the forging with 58% deformation degree after heat treatment. As Figures 26a-26dThe microstructure and size distribution of the difficult-to-deform region of the 58% deformed forged piece after heat treatment are shown. The grain size of the difficult-to-deform region of the 58% deformed forged piece after heat treatment is mainly distributed in the range of 15.9-26.7 μm, with a small part being less than 15.9 μm and more than 26.7 μm. The maximum grain size is 30.2 μm, the minimum grain size is 13.2 μm, and the average grain size is 27 μm. The secondary γ' phase particle size is mainly distributed in the range of 175-255 nm, with a small part being less than 175 nm and more than 255 nm. The maximum γ' phase particle size is 300 nm, the minimum particle size is 116.8 nm, and the average particle size is about 211.9 nm. The secondary γ' phase particle size has no obvious change compared with that before heat treatment, and the γ' phase is unevenly distributed in the γ matrix in the form of a sphere.

[0243] Figures 30a-30d The microstructure and size distribution of the difficult-to-deform region of the 67% deformed forged piece after heat treatment are shown. The grain size of the difficult-to-deform region of the 67% deformed forged piece after heat treatment is mainly distributed in the range of 15.9-37.8 μm, with a small part being less than 15.9 μm and more than 37.8 μm. The maximum grain size is 45.7 μm, the minimum grain size is 15.6 μm, and the average grain size is 25.9 μm. The secondary γ' phase particle size is mainly distributed in the range of 215-315 nm, with a small part being less than 215 nm and more than 315 nm. The maximum γ' phase particle size is 348.9 nm, the minimum particle size is 205.4 nm, and the average particle size is about 266 nm.

[0244] Figures 34a-34d The microstructure and size distribution of the difficult-to-deform region of the 73% deformed forged piece after heat treatment are shown. The grain size of the difficult-to-deform region of the 73% deformed forged piece after heat treatment is mainly distributed in the range of 15.9-26.7 μm, with a small part being less than 15.9 μm and more than 26.7 μm. The maximum grain size is 30 μm, the minimum grain size is 15.1 μm, and the average grain size is 21.6 μm. The secondary γ' phase particle size is mainly distributed in the range of 195-275 nm, and the average γ' phase particle size is about 247.6 nm.

[0245] Compared with the forging before heat treatment, the grains in the difficult deformation zone of the forgings with deformation degree of 48% and 58% were homogenized and refined after heat treatment. This is because after heat treatment, the grains re-nucleate, recrystallize and grow, effectively adjusting the size of the grains, but there are still a small amount of mixed crystal organization. The primary γ' phase significantly increases and grows, the pinning effect on the grain boundary is enhanced, and the secondary γ' phase significantly decreases and does not fully dissolve. The grain size in the difficult deformation zone of the forgings with deformation degree of 67% and 73% is larger than that of the forgings before heat treatment. This is because during heat treatment, the primary γ' phase dissolves and decreases, reducing the pinning effect on the grain boundary, resulting in the growth of the grain size. The secondary γ' phase in the difficult deformation zone is significantly reduced compared with that before heat treatment, and the secondary γ' phase significantly grows and is uniformly distributed in the γ matrix in spherical shape.

[0246] 3.2 Evolution of microstructure and properties of small deformation zone of heat treated forgings with different deformation degrees

[0247] Figures 23a-23d The figure is the microstructure and size distribution of the small deformation zone of the forging with deformation degree of 48% after heat treatment. After heat treatment, the grain size of the forging with deformation degree of 48% is mainly distributed in the range of 18.9-37.8 μm, a small part is distributed below 18.9 μm and above 37.8 μm, the largest grain size is 52.3 μm, the smallest grain size is 12.4 μm, and the average grain size is 26.8 μm. The γ' phase particle size is mainly distributed in the range of 175-295 nm, a small part is distributed below 175 nm and above 295 nm, the largest particle size of γ' phase is 313.6 nm, the smallest particle size is 159.2 nm, the average particle size is about 228.3 nm, the γ' phase is approximately spherical and extremely unevenly distributed in the γ matrix.

[0248] Figures 27a-27d The figure is the microstructure and size distribution of the small deformation zone of the forging with deformation degree of 58% after heat treatment. After heat treatment, the grain size of the forging with deformation degree of 58% is mainly distributed in the range of 15.9-26.7 μm, a small part is distributed below 15.9 μm and above 26.7 μm, the largest grain size is 31.3 μm, the smallest grain size is 13 μm, and the average grain size is 25.9 μm. The γ' phase particle size is mainly distributed in the range of 175-275 nm, a small part is distributed below 175 nm and above 275 nm, the largest particle size of γ' phase is 313.5 nm, the smallest particle size is 150 nm, the average particle size is about 223.8 nm, the γ' phase size is significantly reduced compared with the forging, but there is no significant change compared with the difficult deformation zone after heat treatment, the γ' phase is spherical and extremely unevenly distributed in the γ matrix.

[0249] Figures 31 a-31 dThe microstructure and size distribution of the small deformation area of the 67% deformed forging after heat treatment. The grain size of the 67% deformed forging after heat treatment mainly distributes in the range of 18.9-37.8 μm, with a small part below 18.9 μm and above 37.8 μm. The maximum grain size is 46 μm, the minimum grain size is 16.4 μm, and the average grain size is 27 μm. The γ' phase particle size mainly distributes in the range of 195-255 nm, with a small part below 195 nm and above 255 nm. The maximum γ' phase particle size is 326.2 nm, the minimum γ' phase particle size is 136.8 nm, and the average γ' phase particle size is about 231.6 nm.

[0250] Figures 35a-35d The microstructure and size distribution of the small deformation area of the 73% deformed forging after heat treatment. The grain size of the 73% deformed forging after heat treatment mainly distributes in the range of 15.9-26.7 μm, with a small part below 15.9 μm and above 26.7 μm. The maximum grain size is 28.9 μm, the minimum grain size is 14.1 μm, and the average grain size is 20.1 μm. The primary γ' phase increases significantly after heat treatment, and the grain size still shows a decreasing trend compared to the difficult deformation area of the heat-treated forging. The γ' phase particle size mainly distributes in the range of 195-255 nm, with a small part below 195 nm and above 255 nm. The maximum γ' phase particle size is 312 nm, the minimum γ' phase particle size is 148.1 nm, and the average γ' phase particle size is about 223.8 nm.

[0251] Compared with before heat treatment, the grain size of the small deformation area of the 48% and 58% deformed forgings after heat treatment is not significantly improved, and there is a large amount of mixed crystal structure, but the grain size is significantly refined. The primary γ' phase increases significantly and grows, and the pinning effect on the grain boundary is enhanced. The secondary γ' phase is significantly reduced and decreased, and is not fully analyzed. The grain size of the small deformation area of the 67% and 73% deformed forgings after heat treatment is larger than before heat treatment. The primary γ' phase dissolves into the matrix, which weakens the pinning effect on the grain boundary, resulting in the growth of the grain size. The size of the secondary γ' phase is significantly larger than before heat treatment, and the γ' phase is spherical and uniformly distributed in the γ matrix.

[0252] 3.3 Evolution of microstructure and properties of the large deformation area of heat-treated forgings with different deformation degrees

[0253] Figures 24a-24dFigure 6 is a microstructure and size distribution diagram of a large deformation zone of a forged piece with a deformation degree of 48% after heat treatment. The grain size of the large deformation zone of the forged piece with a deformation degree of 48% after heat treatment is relatively uniform, and the size is mainly distributed in the range of 18.9-31.8 μm, a small part is distributed below 18.9 μm and above 31.8 μm, the largest grain size is 52.7 μm, the smallest grain size is 12.3 μm, and the average grain size is 25.5 μm. After heat treatment, the primary γ' phase in the forged piece increases and grows, and the pinning effect on the grain boundary is enhanced, the secondary γ' phase particle size is mainly distributed in the range of 195-315 nm, a small part is distributed below 195 nm and above 315 nm, the largest γ' phase particle size is 327 nm, the smallest γ' phase particle size is 130.6 nm, the average γ' phase particle size is about 249.2 nm, the γ' phase in the forged piece after heat treatment is significantly reduced, the γ' phase size has no obvious change, and the γ' phase is spherical and dispersedly distributed in the γ matrix.

[0254] Figures 28a-28d Figure 7 is a microstructure and size distribution diagram of a large deformation zone of a forged piece with a deformation degree of 58% after heat treatment. The grain size of the large deformation zone of the forged piece with a deformation degree of 58% after heat treatment is relatively uniform, and the size is mainly distributed in the range of 15.9-31.8 μm, a small part is distributed below 15.9 μm and above 31.8 μm, the largest grain size is 43.5 μm, the smallest grain size is 12.2 μm, and the average grain size is 23.3 μm. Compared with the size and content of the primary γ' phase in the difficult deformation zone and the small deformation zone, there is no obvious change, but during the heat treatment process, the primary γ' phase in the large deformation zone has obvious cracks, which may be produced during the process of the primary γ' phase dissolving into the matrix. The secondary γ' phase particle size is mainly distributed in the range of 155-255 nm, a small part is distributed below 155 nm and above 255 nm, the largest γ' phase particle size is 329.4 nm, the smallest γ' phase particle size is 146.1 nm, the average γ' phase particle size is about 219.9 nm, compared with the difficult deformation zone, the secondary γ' phase particle size in the large deformation zone does not change obviously, but the distribution is more uniform, compared with the forged piece before heat treatment, the γ' phase size grows obviously, but the γ' phase is significantly reduced and is spherical and dispersedly distributed in the γ matrix.

[0255] Figures 32a-32dFigure 6 is a microstructure and size distribution diagram of a large deformation zone of the forged piece with a deformation degree of 67% after heat treatment. The grain size of the large deformation zone of the forged piece with a deformation degree of 67% after heat treatment is relatively uniform, mainly distributed in the range of 15.9-31.8 μm, a small part is distributed below 15.9 μm and above 31.8 μm, the largest grain size is 34.2 μm, the smallest grain size is 15.5 μm, and the average grain size is 23.3 μm. The grain size is larger than that of the forged piece, which is caused by the recrystallization and growth of the grain during heat treatment. The secondary γ' phase particle size is mainly distributed in the range of 155-275 nm, a small part is distributed below 155 nm and above 275 nm, the largest γ' phase particle size is 309.8 nm, the smallest γ' phase particle size is 151.1 nm, and the average γ' phase particle size is about 211.6 nm.

[0256] Figures 36a-36d Figure 7 is a microstructure and size distribution diagram of a large deformation zone of the forged piece with a deformation degree of 73% after heat treatment. The grain size of the large deformation zone of the forged piece with a deformation degree of 73% after heat treatment is relatively uniform, mainly distributed in the range of 13.3-22.5 μm, a small part is distributed below 13.3 μm and above 22.5 μm, the largest grain size is 24.6 μm, the smallest grain size is 12.8 μm, and the average grain size is 17.6 μm. The grain size is larger than that of the forged piece, which is mainly caused by the dissolution of the primary γ' phase into the matrix, the pinning effect of the grain boundary is weakened, and the grain size is increased. Compared with the difficult deformation zone and the small deformation zone, the average grain size of the large deformation zone is obviously reduced. The secondary γ' phase particle size is mainly distributed in the range of 175-275 nm, a small part is distributed below 175 nm and above 275 nm, the largest γ' phase particle size is 304.6 nm, the smallest γ' phase particle size is 160.2 nm, and the average γ' phase particle size is about 232.2 nm.

[0257] Compared with before heat treatment, the grains of the large deformation zone of the forged pieces with deformation degrees of 48% and 58% are refined after heat treatment, which is because the grains are recrystallized and grown after heat treatment, and the size of the grains is effectively adjusted. The size and content of the primary γ' phase of the large deformation zone of the forged pieces with deformation degrees of 67% and 73% do not change obviously after heat treatment compared with before heat treatment, while the secondary γ' phase particle size of the large deformation zone of the forged pieces with deformation degrees of 67% and 73% is obviously reduced after heat treatment compared with the difficult deformation zone and the small deformation zone under the same deformation degree, the spheroidization phenomenon is more obvious, and the secondary γ' phase is more uniformly distributed in the matrix, and the secondary γ' phase is more obviously grown than the forged piece before heat treatment.

[0258] 3.4 Hardness evolution of each deformation zone of the forged pieces with different deformation degrees after heat treatment

[0259] Figure 25 The relationship between the grain size and hardness of different deformation zones of the sample with a deformation degree of 48% is shown in the figure. The hardness of the difficult deformation zone is 44.3 HRC, the hardness of the small deformation zone is 44.6 HRC, and the hardness of the large deformation zone is 45.3 HRC. Figure 29 The relationship between the grain size and hardness of different deformation zones of the sample with a deformation degree of 58% is shown in the figure. The hardness of the difficult deformation zone is 44.5 HRC, the hardness of the small deformation zone is 44.9 HRC, and the hardness of the large deformation zone is 46.8 HRC. Figure 33 The relationship between the grain size and hardness of different deformation zones of the sample with a deformation degree of 67% is shown in the figure. The hardness of the difficult deformation zone is 44.5 HRC, the hardness of the small deformation zone is 44.9 HRC, and the hardness of the large deformation zone is 45.5 HRC. Figure 37 The relationship between the grain size and hardness of different deformation zones of the sample with a deformation degree of 73% is shown in the figure. The hardness of the difficult deformation zone is 44.5 HRC, the hardness of the small deformation zone is 44.9 HRC, and the hardness of the large deformation zone is 45.5 HRC. According to the above changes in grain size and hardness, it can be seen that for all the forged pieces with different deformation degrees, after heat treatment, the average grain size gradually decreases and the hardness gradually increases from the difficult deformation zone to the large deformation zone.

[0260] 3.5 Summary of this section

[0261] (1) After heat treatment, the grain size of the GH4720Li alloy forgings with different deformation degrees gradually decreases as the deformation degree increases. For the samples with lower deformation degree, the grain size decreases to different degrees compared with the forged pieces, and the difference between the grain sizes of different deformation zones gradually decreases. For the samples with higher deformation degree, the grain size slightly increases, and the grain size of different deformation zones remains uniform.

[0262] (2) After heat treatment, the γ' phase particle size of the GH4720Li alloy forgings with different deformation degrees gradually increases as the deformation degree increases. For the samples with lower deformation degree, the secondary γ' phase particle size of different deformation zones slightly increases, and the γ / γ' eutectic phase disappears, and part of the grains appears unprecipitated. For the samples with higher deformation degree, the primary γ' phase particle size of different deformation zones decreases significantly; the secondary γ' phase particle size increases significantly and remains uniform spherical.

[0263] (3) After heat treatment, the hardness of the GH4720Li alloy forgings with different deformation degrees gradually increases as the deformation degree increases. For the samples with lower deformation degree, the hardness of the samples is relatively close, and there is no significant difference in the hardness of different deformation zones. For the samples with higher deformation degree, the hardness of the samples increases steadily, and the hardness of different deformation zones is not significantly different and remains at a high level.

[0264] The fourth part is the high temperature hardness and high temperature wear resistance test of GH4720Li alloy forgings

[0265] GH4720Li alloy can be used to manufacture aero-engine turbine disk. Aero-engine turbine disk needs to have high high temperature hardness and wear resistance, so this part tests the high temperature hardness and high temperature wear resistance of GH4720Li alloy forgings with different deformation degrees. Since the performance of the large deformation area of GH4720Li alloy turbine disk after heat treatment is relatively good, this part selects the sample of the large deformation area after heat treatment as the research object.

[0266] Figure 38 The figure is the room temperature hardness and high temperature hardness of the large deformation area with different deformation degrees. As shown in the figure, the samples of the large deformation area after heat treatment with four deformation degrees are selected as the research object, with the increase of the deformation degree, the room temperature hardness and the high temperature hardness at 700℃ are gradually increased, while the high temperature hardness is lower than the room temperature hardness with the same deformation degree, because when the temperature rises, the binding force between metal atoms and grains is weakened, and the small defects and vacancies in the lattice become more active. These factors lead to the increase of plasticity and toughness of the material, but the hardness decreases. Therefore, the hardness of GH4720Li alloy at high temperature is indeed lower than that at room temperature, which is the typical behavior of this nickel-based high temperature alloy at high temperature.

[0267] Figures 39a-39b The figure is the high temperature friction coefficient and wear amount of different deformation degrees. According to the query, GH4720Li alloy aero-engine turbine disk can be serviced stably at 650℃-750℃, so this experiment studies the high temperature hardness and high temperature wear resistance at 700℃. The friction coefficient includes the running-in wear stage, the transition stage and the stable wear stage. In the running-in wear stage, the friction ball at the front end of the friction rod contacts with the sample, because the surface of the sample is rough, the friction coefficient changes greatly, in the transition stage, the contact area between the friction ball and the sample surface tends to be stable, in the stable wear stage, the friction coefficient tends to be stable.

[0268] The friction coefficient of the sample with 48% deformation is initially about 0.6-0.7, is in the running-in wear stage and transition stage for the first 4 minutes, has a large variation range, then enters a stable wear stage, and gradually tends to be stable at about 0.45 during the stage, and the wear amount is 5.6 mg. The friction coefficient of the sample with 58% deformation is initially about 0.5-0.6, is in the running-in wear stage and transition stage for the first 4 minutes, has a large variation range, then enters a stable wear stage, and gradually tends to be stable at about 0.4 during the stage, and the wear amount is 4.9 mg. The friction coefficient of the sample with 67% deformation is initially about 0.45-0.5, is in the running-in wear stage and transition stage for the first 3 minutes, has a large variation range, then enters a stable wear stage, and gradually tends to be stable at about 0.35 during the stage, and the wear amount is 3.7 mg. The friction coefficient of the sample with 73% deformation is initially about 0.45-0.5, is in the running-in wear stage and transition stage for the first 3 minutes, has a large variation range, then enters a stable wear stage, and gradually tends to be stable at about 0.32 during the stage, and the wear amount is 2.7 mg.

[0269] The samples with the four deformation degrees are in the running-in wear stage and transition stage at the initial stage of friction, and have a large variation range of the friction coefficient, because the friction ball directly contacts the sample surface at the initial stage of friction, and is two-body wear, then different hard wear debris is generated under the action of shear force and normal load due to friction on the sample, at this time, three-body wear between the friction ball, the wear debris and the sample is changed, and thus the friction coefficient has a certain fluctuation. With the increase of the deformation degree, the friction coefficient gradually increases, the time in the running-in wear stage and transition stage is shorter, and the wear amount gradually decreases.

[0270] From the above results, it can be seen that the hardness of the GH4720Li alloy under high temperature is lower than that under normal temperature; with the increase of the deformation degree, the friction coefficient, the wear amount and the time in the running-in wear stage and transition stage are gradually reduced, and the wear resistance is better.

[0271] In the prior art, there are some methods for improving the performance of GH4720Li alloy forgings by pre-forging gradient heating and improving the forging process, such as the method disclosed in CN115852281A. CN115852281A is a patent previously applied by the subject group of the present invention. Although this patent also uses the gradient heating treatment method of the present embodiment to treat GH4720Li alloy forgings, it performs two forging processes after gradient heating treatment. The purpose is to solve the technical problem of cracking of forgings during forging. It is found through experiments that the uniformity of the deformed zone structure of GH4720Li alloy forgings obtained by using the technical solution of this patent is not good, and the mechanical properties and high-temperature wear resistance of turbine discs prepared from such forgings cannot be satisfied.

[0272] Similarly, the method disclosed in the paper "Effect of Gradient Heating Process on Forming Properties of Free Forging GH4720Li High-temperature Alloy" by Li Jingnan et al. In this paper, forgings obtained by gradient heating process and furnace temperature rising process were subjected to forging with various degrees of deformation. The conclusion is that forgings obtained by gradient heating process are less likely to crack than forgings obtained by furnace temperature rising process. The gradient heating method in the method disclosed in this paper is different from the present embodiment, and the alloy forgings are not subjected to post-forging heat treatment. It is found through experiments that the uniformity of the deformed zone structure of GH4720Li alloy forgings obtained by using the same gradient heating process and deformation degree as in this paper is also not ideal, and the mechanical properties and high-temperature wear resistance of turbine discs prepared from such forgings cannot be satisfied.

[0273] The paper "Effect of heat treatment process parameters on the microstructure and properties of GH4720Li superalloy" by Zhang Wei et al. discloses a method of gradient heating and post-forging heat treatment for GH4720Li alloy. The main technical problem solved by this method is to improve the hardness of GH4720Li alloy forgings. Compared with the gradient heating method provided in this paper, the gradient heating method in the present embodiment is simpler and more convenient. The maximum hardness of GH4720Li alloy forgings obtained by using the method in this paper is 47HRC (deformation degree of 79%), and the maximum hardness of GH4720Li alloy forgings obtained by post-forging heat treatment in the present embodiment is 46.8HRC (large deformation zone at a deformation degree of 58%). The difference between the two is not big. In addition, the method provided in this paper does not consider the uniformity of the structure of different deformed zones under different forging deformation degrees.

[0274] In the embodiment, the pre-forging heat treatment, the forging treatment and the post-forging heat treatment interact and synergistically affect the uniformity of the deformed zone structure of the GH4720Li alloy forgings. When the pre-forging heating condition, the forging pressure condition (deformation degree of 73%), the temperature and time condition of the solid solution treatment and the twice aging treatment in the embodiment are adopted, the uniformity of the deformed zone structure of the GH4720Li alloy forgings can reach an ideal state. If the pre-forging heat treatment in the embodiment is not adopted or the pre-forging heat treatment mode in the embodiment is changed or the forging condition is changed or the post-forging heat treatment mode is changed, no matter how the parameters or treatment modes of other processes are adjusted, the uniformity of the deformed zone structure of the GH4720Li alloy forgings is far from the uniformity of the deformed zone structure of the GH4720Li alloy forgings processed in the embodiment.

Claims

1. A processing technology for improving the uniformity of the structure of the deformed zone of GH4720Li alloy, characterized in that, Comprising the following steps: Step A: heating the resistance furnace to the initial temperature of the gradient heating and holding treatment; Step B: placing the GH4720Li alloy bar in the resistance furnace for the gradient heating and holding treatment; Step C: after the gradient heating and holding treatment is completed, controlling the GH4720Li alloy bar at the initial forging temperature for forging, to obtain a GH4720Li alloy forge piece; Step D: sequentially performing solid solution treatment, primary aging treatment and secondary aging treatment on the GH4720Li alloy forge piece, and after the secondary aging treatment is completed, a GH4720Li alloy forge piece with uniform structure is obtained; In step B, the specific method of the gradient heating and holding treatment is as follows: Step (B-1), placing the GH4720Li alloy bar in the resistance furnace at a temperature of 800-850℃ for 60-70min; Step (B-2), continuing to heat at a heating rate of 3-4℃ / min to 900-950℃, and holding at 900-950℃ for 60-70min; Step (B-3), continuing to heat at a heating rate of 10-15℃ / min to 1000-1050℃, and holding at 1000-1050℃ for 20-30min; Step (B-4), continuing to heat at a heating rate of 10-15℃ / min to 1130-1150℃, and holding at 1130-1150℃ for 20-30min; In step C, the initial forging temperature is 1130-1150℃, the final forging temperature is 1080-1100℃, and the total deformation is 48-73%; In step D, for the solid solution treatment, the GH4720Li alloy forge piece is placed at 1060-1080℃ for 3-4h, and then cooled to room temperature by oil cooling; for the primary aging treatment, the GH4720Li alloy forge piece is placed at 650-680℃ for 6-8h, and then air-cooled to room temperature; for the secondary aging treatment, the GH4720Li alloy forge piece is placed at 760-780℃ for 6-8h, and then air-cooled to room temperature.

2. The process for improving the microstructure homogeneity of the deformed zone of GH4720Li alloy according to claim 1, characterized in that, In step A, the initial temperature of the gradient heating and holding treatment is 800-850℃, and the heating rate of the resistance furnace is 20-30℃ / min.

3. The process for improving the microstructure homogeneity of the deformed zone of GH4720Li alloy according to claim 2, characterized in that, In step A, the initial temperature of the gradient heating and holding treatment is 800℃, and the heating time of the resistance furnace is 30min.

4. The process for improving the microstructure homogeneity of the deformed zone of GH4720Li alloy according to claim 1, characterized in that, In step B, the specific method of the gradient heating and holding treatment is as follows: Step (B-1), placing the GH4720Li alloy bar in the resistance furnace at a temperature of 800℃ for 60min; Step (B-2), continuing to heat to 900℃ for 30min, and holding at 900℃ for 60min; Step (B-3), continuing to heat at a heating rate of 10℃ / min to 1000℃, and holding at 1000℃ for 20min; Step (B-4), continuing to heat at a heating rate of 10℃ / min to 1140℃, and holding at 1140℃ for 20min.

5. The process for improving the microstructure homogeneity of the deformed zone of GH4720Li alloy according to claim 1, characterized in that, In step C, the initial forging temperature is 1140℃, the final forging temperature is 1080℃, and the total deformation is 73%.

6. The process for improving the microstructure homogeneity of the deformed zone of GH4720Li alloy according to claim 1, characterized in that, In step D, during the solution treatment, the GH4720Li alloy forge piece is placed at 1060℃ for 4 hours, and then cooled to room temperature by oil cooling; during the first aging treatment, the GH4720Li alloy forge piece is placed at 650℃ for 8 hours, and then air-cooled to room temperature; during the second aging treatment, the GH4720Li alloy forge piece is placed at 760℃ for 8 hours, and then air-cooled to room temperature.

7. The process for improving the microstructure homogeneity of the deformed zone of GH4720Li alloy according to claim 1, characterized in that, In step A, the initial temperature of the gradient heating and holding treatment is 800℃; the heating time of the electric resistance furnace is 30 minutes; In step B, the specific method of the gradient heating and holding treatment is as follows: Step (B-1), the GH4720Li alloy bar blank is placed in an electric resistance furnace at a temperature of 800℃ for 60 minutes; Step (B-2), continue to heat to 900℃ at a heating time of 30 minutes, and hold at 900℃ for 60 minutes; Step (B-3), continue to heat to 1000℃ at a heating rate of 10℃ / min, and hold at 1000℃ for 20 minutes; Step (B-4), continue to heat to 1140℃ at a heating rate of 10℃ / min, and hold at 1140℃ for 20 minutes; In step C, the initial forging temperature is 1140℃, the final forging temperature is 1080℃, and the total deformation is 73%; In step D, during the solution treatment, the GH4720Li alloy forge piece is placed at 1060℃ for 4 hours, and then cooled to room temperature by oil cooling; during the first aging treatment, the GH4720Li alloy forge piece is placed at 650℃ for 8 hours, and then air-cooled to room temperature; during the second aging treatment, the GH4720Li alloy forge piece is placed at 760℃ for 8 hours, and then air-cooled to room temperature.

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