Forging process of aluminum alloy for aerospace

Abstract

The invention provides a forging process of aluminum alloy for aerospace, which belongs to the technical field of aluminum alloy forging, and comprises the following steps: carrying out non-isothermal gradient heating on an aluminum alloy ingot in an induction and radiation composite heating manner, and then entering a heat preservation stage; in the high-temperature large deformation stage, axial and radial alternate deformation is introduced in the two-upsetting and two-drawing process; then medium-temperature precision forging is conducted; solid solution treatment is conducted on the forged workpiece, and the solid solution treatment comprises first-stage solid solution, small-deformation pulse deformation applied after rapid cooling and second-stage solid solution; two-stage aging treatment is conducted on the workpiece subjected to solution treatment, 150-250 MPa hydrostatic pressure is applied in the first-stage aging process, and second-stage aging is conducted in an unstressed state; through the combination of non-isothermal gradient heating and a pulse thermal field, on the premise of avoiding overburning of a grain boundary, a core structure is preferentially crushed by using high deformation resistance of a core at a lower temperature, and meanwhile, enough plasticity is ensured by a higher surface temperature.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aluminum alloy forging, and particularly relates to a forging process of an aluminum alloy for aerospace. BACKGROUND

[0002] Aluminum alloys with high alloy content generally refer to Al-Zn-Mg-Cu series alloys with Zn content greater than 8wt%, Mg content greater than 2wt%, and often added with Cu, Zr and other elements, which are one of ideal materials for key structural parts such as aircraft wing beams, fuselage frames, rocket tanks and the like in the field of aerospace. The aluminum alloys with high alloy content can obtain extremely high specific strength through aging precipitation strengthening phases such as GP zone, η' phase and η phase-MgZn2, so as to meet the extremely high bearing requirements while reducing the structural weight.

[0003] However, the increase of the content of elements such as Zn and Mg not only brings the potential of high strength, but also significantly deteriorates the processing performance of the material, which brings severe challenges to the traditional hot working process, especially the forging process. The existing technology mainly has the following limitations for the forging process of the aluminum alloy with high alloy content: 1. Extremely narrow hot working window: high content of alloy elements leads to a large number of low-melting eutectic phases (such as Mg(Zn,Cu,Al)2) in the as-cast structure. In the heating and forging process, if the temperature control is slightly improper, for example, exceeds the multi-eutectic reaction temperature (about 475-485℃), the grain boundary is easily melted and overburned, causing the product to be scrapped; if the temperature is too low, such as as low as 350℃, the deformation resistance of the alloy increases sharply, the flowability is poor, and forging cracking is easily caused. This makes the temperature control range of the traditional process very narrow, usually only 30-50℃, which requires high equipment and control precision, and has great difficulty in production and low yield.

[0004] 2. High level of residual stress: due to the poor thermal conductivity and high hardenability of the aluminum alloy with high alloy content, the cooling speed difference of the cross section is huge during the quenching process after solid solution treatment, which will introduce extremely high macro residual stress. In addition, the uneven plastic deformation in the forging process will also accumulate considerable micro residual stress. The high residual stress not only increases the deformation risk of subsequent mechanical processing, but also superimposes with the external stress in the service process, significantly reduces the fatigue life and stress corrosion cracking resistance of the part, and constitutes a safety hazard.

[0005] 3. Contradiction between strength and toughness / corrosion resistance is prominent: although the traditional T6 (peak aging) treatment can obtain the highest strength, it often makes the fracture toughness and stress corrosion resistance of the alloy at a low level. In order to improve the toughness or corrosion resistance, the T7x (overaging) treatment is adopted, which will sacrifice 10-15% of the strength. For its application in the high-end field of aerospace, how to maintain ultra-high strength while obtaining good toughness and corrosion resistance is a core problem faced by the existing process.

[0006] To solve the above problems, although the prior art attempts to locally optimize the heating system, deformation pass or heat treatment parameters, these measures are mostly superficial and scattered improvements, and fail to systematically design an integrated process route from the overall perspective of "thermal-mechanical-phase change" multi-field coupling. Therefore, developing an innovative forging process capable of widening the thermal processing window, ensuring the uniformity of the microstructure, reducing the residual stress, and realizing the optimal matching of strength-toughness-corrosion resistance has become a technical bottleneck that urgently needs to be broken through in the field. SUMMARY

[0007] To overcome some of the problems mentioned in the background, the present application provides a forging process for aerospace aluminum alloy to at least partially solve the above problems.

[0008] According to the technical scheme of the present application, a forging process for aerospace aluminum alloy is provided, comprising the following steps: S1. Non-isothermal gradient heating of the aluminum alloy ingot by induction and radiation combined heating, and then entering the holding stage; S2. First, a high-temperature large deformation stage is carried out, by introducing axial and radial alternating deformation in the two-up-two-down process, and rotating the workpiece by 55-65° after each pass deformation, with a total forging ratio not less than 10; then a medium-temperature precision forging is carried out; S3. Solving treatment is carried out on the forged workpiece, which includes first stage solution, small deformation pulse deformation after rapid cooling and second stage solution; S4. Double-stage aging treatment is carried out on the workpiece after solution treatment, wherein a hydrostatic pressure of 150-250 MPa is applied during the first stage aging process, and the second stage aging is carried out in a stress-free state.

[0009] Further, the surface temperature of the aluminum alloy ingot in step S1 during non-isothermal heating is 420-440℃, and the core temperature is 380-400℃; Step S1 further comprises introducing a pulse heat field during the holding stage, the frequency of the pulse heat field is 0.5-2Hz, and the temperature amplitude is 15-25℃.

[0010] Further, the time of the holding stage is calculated by the following formula: T=Dxk, Where T is the holding time, unit: min; D is the effective diameter of the ingot, unit: mm; k is a constant, with a value range of 1.2-1.4; The pulse heat field is applied in the last 1 / 3 stage of the holding stage.

[0011] Further, step S1 comprises the following steps: The aluminum alloy ingot is heated at room temperature, first at a rate of 75°C / hour to 250°C, and kept for 2 hours; Then heated at a rate of 110°C / hour to 400°C, while starting the induction heating, the surface temperature is raised to 430°C, and then enters the holding stage; In the last 1 / 3 of the holding stage, the power of the pulse heat field is controlled by program to make it cycle switch at 1Hz with a temperature amplitude of 20°C.

[0012] Further, in the high-temperature large deformation stage, the workpiece is at 410-430°C, and the deformation time of each pass is completed within 3-8 minutes, and the workpiece returns to the holding furnace for 2-4 minutes between adjacent two passes; The medium-temperature precision forging stage is to perform precision forging with a change amount of 20-30% in the cycle change range at a strain rate of 0.01-0.1s -1 The cycle change range.

[0013] Further, the solution treatment includes the following steps: The first stage solution is carried out at 475-485°C, and the holding time is calculated by multiplying the workpiece cross-sectional thickness by 2.5 minutes per millimeter; After rapid cooling to 350-370°C, pulse deformation with a deformation amount of 1.5-2.5% is applied; The second stage solution is carried out at 465-475°C, and the holding time is half of the first stage holding time.

[0014] Further, the two-stage aging treatment includes the following steps: The first stage aging is at 120°C for 8 hours, while applying hydrostatic pressure; The second stage aging is at 155°C for 12 hours without stress.

[0015] Further, the components of the aluminum alloy include, by weight percentage: 10.5-12.5% of Zn, 2.5-3.5% of Mg, 1.8-2.3% of Cu, 0.1-0.15% of Zr, and the balance of aluminum and impurities.

[0016] Further, the tensile strength of the aluminum alloy forgings obtained by forging fluctuates by no more than 5% at different positions of the cross section.

[0017] Further, quenching treatment is immediately carried out after the second stage solution to fix the workpiece from the supersaturated solid solution to room temperature, and the quenching treatment is carried out by water quenching or polymer aqueous solution quenching.

[0018] Compared with the prior art, the beneficial effects of the present application are: The application combines non-isothermal gradient heating with pulse heat field, under the premise of avoiding grain boundary overburning, preferentially breaks the core organization by using high deformation resistance at a lower temperature in the core, and at the same time, the higher temperature on the surface ensures sufficient plasticity, which widens the effective hot working window from about 30-50 DEG C of the traditional process to more than 70-90 DEG C, greatly reduces the process control difficulty, and improves the production stability and yield. The application introduces multi-directional and high-density shear strain bands in the material by bidirectional alternating deformation and variable strain rate cycle control, and provides a large number of uniform nucleation points for dynamic recrystallization. This effectively avoids the formation of coarse grain rings, so that the forged piece obtains uniform and fine recrystallized grain structure from the surface to the core, and the grain size uniformity is significantly reduced.

[0019] The application integrates multiple control steps into a coherent and controllable process flow, which can be realized by upgrading the temperature control system and control software on the basis of the existing forging production line, without expensive new equipment investment, improves the material utilization and production efficiency, and has good technical and economic benefits and industrialization promotion value. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments; based on the embodiments, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope.

[0021] The embodiment of the application provides a forging process of an aluminum alloy for aerospace, which comprises the following steps: S1. Non-isothermal gradient heating is performed on the aluminum alloy ingot by means of induction and radiation combined heating, and then the ingot enters a holding stage; S2. First, a high-temperature large deformation stage is performed, axial and radial alternating deformation is introduced in the two-up-two-down process, the workpiece is rotated by 55 DEG to 65 DEG after each pass deformation, and the total forging ratio is not less than 10; then a medium-temperature precision forging is performed; S3. The forged workpiece is subjected to solid solution treatment, and the solid solution treatment comprises a first stage solid solution, a small deformation amount pulse deformation after rapid cooling, and a second stage solid solution; S4. The workpiece after the solid solution treatment is subjected to two-stage aging treatment, wherein a hydrostatic pressure of 150-250 MPa is applied in the first-stage aging process, and the second-stage aging is performed in a stress-free state.

[0022] In a further embodiment of the embodiment, the surface temperature of the aluminum alloy ingot in step S1 is 420-440 DEG C, and the core temperature is 380-400 DEG C during the non-isothermal heating process.

[0023] In a further implementation form of the embodiment, the step S1 further comprises introducing a pulsed thermal field during the soaking stage, the pulsed thermal field having a frequency of 0.5-2 Hz and a temperature amplitude of 15-25℃.

[0024] In a further implementation form of the embodiment, the soaking stage time is calculated by the following formula: T=D x k, wherein T is the soaking time, unit: min; D is the effective diameter of the ingot, unit: mm; k is a constant, having a value range of 1.2-1.4; The pulsed thermal field is applied in the last 1 / 3 stage of the soaking stage.

[0025] In a further implementation form of the embodiment, in the high-temperature large deformation stage, the workpiece is under the condition of 410-430℃, and the deformation time of each pass is completed within 3-8 min, and the workpiece returns to the soaking furnace for 2-4 min between adjacent two passes. The medium-temperature precision forging stage is to perform precision forging with a change amount of 20-30% in a cyclic change range at a strain rate of 0.01-0.1 s -1

[0026] In a further implementation form of the embodiment, the solution treatment comprises the following steps: The first stage solution treatment is performed at 475-485℃, and the soaking time is calculated by multiplying the thickness of the workpiece section by 2.5 min per millimeter; After rapid cooling to 350-370℃, a pulsed deformation with a deformation amount of 1.5-2.5% is applied; The second stage solution treatment is performed at 465-475℃, and the soaking time is half of the soaking time of the first stage.

[0027] In a further implementation form of the embodiment, the two-stage aging treatment comprises the following steps: The first stage aging is at 120℃ for 8 hours, while a hydrostatic pressure is applied; The second stage aging is at 155℃ for 12 hours, without stress.

[0028] In a further implementation form of the embodiment, the components of the aluminum alloy include, by weight percentage: 10.5-12.5% of Zn, 2.5-3.5% of Mg, 1.8-2.3% of Cu, 0.1-0.15% of Zr, and the balance of aluminum and impurities.

[0029] In a further implementation form of the embodiment, the tensile strength of the aluminum alloy forgings obtained by forging fluctuates by no more than 5% at different positions of the cross section. ​

[0030] In a further embodiment of the present application, the second stage solutionizing is immediately followed by a quenching treatment to fix the workpiece from the supersaturated solid solution to room temperature, the quenching treatment being by water quenching or polymer solution quenching.

[0031] It should be noted that: step S1 utilizes temperature gradient to induce pre-dynamic precipitation, forming high-density nanometer-scale η' phase in the grains, which will act as dislocation pinning points and recrystallization nucleation points in subsequent deformation; step S2, by alternating changes in strain path and temperature step-down, builds a high-density deformation band and dislocation cell structure in the material, providing superior nucleation conditions for subsequent recrystallization; step S3, by intermittent deformation solution treatment, can promote the dissolution of difficult-to-dissolve crystalline phases under the premise of not causing grain growth, and improve the solid solubility through deformation-induced dissolution mechanism; step S4 can realize the optimal matching of strength and toughness by controlling the type, size and distribution of precipitates.

[0032] Gradient deformation combined with temperature cycling creates a high-density, uniformly distributed dislocation network. These dislocation structures not only strengthen the matrix, but also act as short-circuit paths for atomic diffusion, accelerating the precipitation kinetics during aging. The combination of non-isothermal heating and intermittent solution treatment optimizes the grain boundary and phase boundary structure, forming an ideal combination of nanoscale grain boundary precipitates and no precipitate band width, significantly improving the stress corrosion resistance of the material.

[0033] The aluminum alloy ingot is first slowly heated to 250°C at a rate of ≤ 80°C / hour from room temperature, and is kept for 1-2 hours to homogenize the internal temperature and eliminate the residual stress of the ingot, and then heated to 380-400°C at a rate of 100-120°C / hour, while the induction heating is started. Due to the "skin effect" of the induction current, the current is highly concentrated on the surface layer of the aluminum alloy ingot, thereby rapidly and selectively heating it. By controlling the power of the induction coil, the surface layer temperature of the aluminum alloy ingot can be accurately raised to the target value of 420-440°C. At this time, the surface of the aluminum alloy ingot is "heated" by the induction coil, while the core mainly relies on the heat conduction from the surface to the inside and the "baking" of the radiation environment to maintain the temperature. Since it takes time for heat to conduct from the surface to the inside, a stable gradient of high surface temperature of 430°C and low core temperature of 400°C is formed actively and controllably.

[0034] During the last 1 / 3 of the holding period, the power of the induction coil is controlled to make it switch between "high power-low power" at a certain frequency. In the high power half cycle, the coil outputs extra heat to make the surface layer temperature rise instantaneously, for example, by 20°C. In the low power half cycle, the coil output is reduced, and the surface layer temperature falls back, for example, by -20°C, under the action of radiation and internal heat conduction. The surface layer temperature of the aluminum alloy ingot realizes high-frequency small-amplitude fluctuation (i.e. pulsed heat field), while the core temperature remains relatively stable due to thermal inertia. This thermal shock of the surface layer can effectively promote atomic diffusion without causing overheating of the core.

[0035] The aluminum alloy ingots selected in the following examples and comparative examples each include, by weight percentage: 12% of Zn, 3% of Mg, 2% of Cu, 0.15% of Zr, and the balance of aluminum and impurities.

[0036] Example 1 The ingot is first heated slowly to 250°C at a rate of 75°C / hour and held for 2 hours, and then heated to 400°C at a rate of 110°C / hour while starting the induction heating to precisely raise the surface temperature to 430°C to enter the holding stage. In the second half of the holding stage, the power of the induction coil is controlled to make it switch between "high power-low power" at 1Hz with a temperature amplitude of 20°C.

[0037] The high-temperature large deformation stage is performed at 420°C, and the deformation time of each pass is completed within 5 minutes. The workpiece is returned to the holding furnace for 3 minutes between adjacent two passes. After each pass of deformation, the workpiece is rotated by 60°. The total forging ratio is not less than 12. The medium-temperature precision forging stage is performed at 310°C with a strain rate of 0.01-0.1 s -1 The precision forging is performed with a change amount of 20-30% in the cyclic change range.

[0038] The first stage of solid solution is performed at 480°C. After the completion of the first stage of solid solution, the workpiece is quickly transferred to a press table maintained at a constant temperature of 360°C. The transfer time should be as short as possible, less than 30 seconds. The surface and core temperatures of the workpiece are quickly reduced to the target interval of 350-370°C within 3 minutes by using strong air cooling or mist cooling.

[0039] Immediately after the workpiece is maintained at a constant temperature of 360°C, a pulse deformation with a small deformation amount of 2% is applied to the workpiece. This deformation is not forging, but a slight pressing similar to "shaping". After the pulse deformation, the workpiece is quickly transferred to the adjacent solid solution furnace and immediately heated to the second stage temperature of 470°C at the fastest speed.

[0040] After the second stage of solid solution is completed, quenching is immediately performed to fix the supersaturated solid solution at room temperature, and then first-stage aging treatment is performed at 120 DEG C for 8 hours while applying a hydrostatic pressure of 200 MPa, and second-stage aging treatment is performed at 155 DEG C for 12 hours without stress, to obtain the aluminum alloy.

[0041] Example 2 The ingot is first heated at a rate of 75 DEG C / hour to 250 DEG C and held for 2 hours, and then heated at a rate of 110 DEG C / hour to 395 DEG C while starting induction heating to precisely raise the surface temperature to 425 DEG C to enter the holding stage, and in the latter half of the holding stage, the power of the induction coil is controlled by program to switch the temperature amplitude of 20 DEG C "high power-low power" cycle at 1 Hz.

[0042] The high-temperature large deformation stage is performed at 420 DEG C, and the deformation time of each pass is completed within 5 minutes, the workpiece is returned to the holding furnace for 3 minutes between adjacent two passes, and the workpiece is rotated by 60 DEG after each pass deformation, and the total forging ratio is not less than 12, and the medium-temperature precision forging stage is performed at 310 DEG C at a strain rate of 0.01-0.1 s -1 The precision forging is performed in a cycle change range with a change amount of 20-30%.

[0043] The first stage of solid solution is performed at 480 DEG C, after the first stage of solid solution is completed, the workpiece is quickly transferred to a press workbench maintained at a constant temperature of 360 DEG C, the transfer time should be as short as possible to < 30 seconds, and the surface and core temperatures of the workpiece are quickly reduced to the target interval of 350-370 DEG C within 3 minutes by using strong air cooling or mist cooling.

[0044] At a constant temperature of 360 DEG C, a pulse deformation with a small deformation amount is immediately applied to the workpiece, and the deformation amount is 2%. This deformation is not forging, but a slight pressing similar to "shaping". After the pulse deformation, the workpiece is quickly transferred to the adjacent solid solution furnace, and immediately heated to the second stage temperature of 470 DEG C at the fastest speed.

[0045] After the second stage of solid solution is completed, quenching is immediately performed to fix the supersaturated solid solution at room temperature, and then first-stage aging treatment is performed at 120 DEG C for 8 hours while applying a hydrostatic pressure of 200 MPa, and second-stage aging treatment is performed at 155 DEG C for 12 hours without stress, to obtain the aluminum alloy.

[0046] Example 3 The ingot is first heated slowly to 250°C at a rate of 75°C / hour and held for 2 hours, then heated to 400°C at a rate of 110°C / hour while starting induction heating to precisely raise the surface temperature to 430°C into the holding stage. In the second half of the holding stage, the power of the induction coil is controlled by a program to switch between "high power-low power" at a frequency of 1 Hz with a temperature amplitude of 20°C.

[0047] The high-temperature large deformation stage is performed at 420°C, and the deformation time of each pass is completed within 5 minutes. The workpiece is returned to the holding furnace for 3 minutes between adjacent two passes. The workpiece is rotated by 58° after each pass of deformation. The total forging ratio is not less than 12. The medium-temperature precision forging stage is performed at 310°C with a strain rate of 0.01-0.1 s -1 The precision forging is performed in a cyclic change range with a change amount of 20-30%.

[0048] The first stage solid solution is performed at 478°C. After the first stage solid solution is completed, the workpiece is quickly transferred to a press workbench maintained at a constant temperature of 360°C. The transfer time should be as short as possible, less than 30 seconds. The surface and core temperatures of the workpiece are quickly reduced to the target interval of 350-370°C within 3 minutes by using strong air cooling or mist cooling.

[0049] Immediately after the workpiece is transferred to the adjacent solid solution furnace, it is immediately heated to the second stage temperature of 470°C at the fastest speed.

[0050] After the second stage solid solution is completed, quenching is immediately performed to fix the supersaturated solid solution to room temperature. Then, first aging treatment is performed at 120°C for 8 hours while applying a hydrostatic pressure of 200 MPa. Second aging treatment is performed at 155°C for 12 hours without stress to obtain an aluminum alloy.

[0051] Example 4 The ingot is first heated slowly to 250°C at a rate of 75°C / hour and held for 2 hours, then heated to 400°C at a rate of 110°C / hour while starting induction heating to precisely raise the surface temperature to 430°C into the holding stage.

[0052] The high-temperature large deformation stage is performed at 420°C, and the deformation time of each pass is completed within 5 minutes. The workpiece is returned to the holding furnace for 3 minutes between adjacent two passes. The workpiece is rotated by 58° after each pass of deformation. The total forging ratio is not less than 12. The medium-temperature precision forging stage is performed at 310°C with a strain rate of 0.01-0.1 s -1The finish forging is varied by 20-30% in the range of the cycle.

[0053] The first stage solid solution is performed at 480°C, and after the first stage solid solution is completed, the workpiece is quickly transferred to a press workbench maintained at a constant temperature of 360°C. The transfer time should be as short as possible, <30 seconds, and the workpiece surface and core temperature are quickly reduced to the target interval of 350-370°C within 3 minutes by using strong air cooling or mist cooling.

[0054] At a constant temperature of 360°C, a pulse deformation of a small deformation amount is immediately applied to the workpiece, and the deformation amount is 2%. This deformation is not forging, but a slight pressing similar to “shaping”. After the pulse deformation, the workpiece is quickly transferred to the adjacent solid solution furnace and immediately heated to the second stage temperature of 470°C at the fastest speed.

[0055] After the second stage solid solution is completed, quenching is immediately performed, the supersaturated solid solution is fixed to room temperature, and then first aging treatment is performed at 120°C for 8 hours while applying a hydrostatic pressure of 200 MPa, and second aging treatment is performed at 155°C for 12 hours without stress, to obtain an aluminum alloy.

[0056] Comparative Example The aluminum alloy ingot is uniformly heated at 430°C and then multi-directionally forged between 420-350°C, with each rotation of 90°, and then a conventional T6 treatment is performed, i.e., solid solution at 476°C for 8 hours and then water quenching, and then single-stage aging treatment at 120°C for 24 hours, to obtain an aluminum alloy.

[0057] The aluminum alloys obtained in the above Examples 1-4 and Comparative Example are subjected to experimental detection, and the detection data include mechanical properties and corrosion resistance, and the detection methods are specifically as follows.

[0058] The mechanical properties are measured by room temperature tensile test according to ASTM E8 / E8M standard, to determine the tensile strength (Rm), yield strength (Rp0.2) and elongation after fracture (A). The plane strain fracture toughness (KIC) is measured according to ASTM E399 standard.

[0059] The corrosion resistance is measured by EXCO test according to ASTM G34 standard, and the rating is EA (severe exfoliation), EB (moderate exfoliation), EC (slight exfoliation) or ED (no exfoliation). The stress corrosion cracking (SCC) test is performed according to ASTM G47 standard, to measure the threshold stress intensity factor (KISCC).

[0060] The detection results are shown in Table 1 below.

[0061] Table 1 Performance data table of Examples and Comparative Example

[0062] In summary, all the key performance indicators of the examples, including strength, toughness, and corrosion resistance, are significantly better than the comparative examples. The significant improvement in performance directly proves the synergistic effect and creativity of the whole set of technical solutions of gradient heating, bidirectional alternating deformation, intermittent solid solution (including pulse deformation), and simultaneous aging. This shows that the process route of the present application is successful in nature.

[0063] Examples 2-4 adjust the parameters relative to Example 1, and although the performance is focused on different aspects, the overall performance is at a very high level. This proves that the process window is wide, has good engineering applicability and stability, and is not a "laboratory solution" that can only be realized under extremely specific parameters. The process of the present application achieves ultra-high strength while considering excellent fracture toughness and corrosion resistance, realizes the good matching of strength, toughness, and corrosion resistance of high-alloy aluminum alloys, and meets the stringent requirements of the aerospace field for the comprehensive performance of materials.

[0064] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A wrought process for aerospace aluminum alloys, characterized in that, The method comprises the following steps: S1. Non-isothermal gradient heating of an aluminum alloy ingot by means of induction and radiation combined heating, and then entering a holding stage; S2. First, a high-temperature large deformation stage is performed, axial and radial alternating deformation is introduced in a two-up-two-down process, the workpiece is rotated by 55-65° after each pass, and the total forging ratio is not less than 10; then a medium-temperature finish forging is performed; S3. The workpiece after forging is subjected to a solid solution treatment, which comprises a first stage solid solution, a small deformation amount pulse deformation after rapid cooling, and a second stage solid solution; S4. The workpiece after the solid solution treatment is subjected to a two-stage aging treatment, wherein a hydrostatic pressure of 150-250 MPa is applied during the first-stage aging, and the second-stage aging is performed in a stress-free state.

2. The wrought process for aerospace aluminum alloys of claim 1 wherein, The surface temperature of the aluminum alloy ingot in step S1 is 420-440°C during the non-isothermal heating process, and the core temperature is 380-400°C; Step S1 further comprises introducing a pulse heat field during the holding stage, the frequency of the pulse heat field is 0.5-2 Hz, and the temperature amplitude is 15-25°C.

3. The wrought process for aerospace aluminum alloys of claim 2, wherein, The time of the holding stage is calculated by the following formula: T=D×k, wherein T is the holding time, unit: min; D is the effective diameter of the ingot, unit: mm; k is a constant, the value range is 1.2-1.4; The pulse heat field is applied in the last 1 / 3 stage of the holding stage.

4. The wrought process for aerospace aluminum alloys of claim 3, wherein, Step S1 comprises the following steps: The aluminum alloy ingot is heated to 250°C at a rate of 75°C / hour and held for 2 hours; Then heated to 400°C at a rate of 110°C / hour, while starting induction heating, the surface temperature is raised to 430°C and then enters the holding stage; In the last 1 / 3 stage of the holding stage, the power of the pulse heat field is controlled by the program to switch the temperature amplitude of 20°C at 1 Hz.

5. The wrought process for aerospace aluminum alloys of claim 1 wherein, In the high-temperature large deformation stage, the workpiece is at a temperature of 410-430°C, and the deformation time of each pass is completed within 3-8 minutes, and the workpiece is returned to the holding furnace for 2-4 minutes between adjacent two passes; The medium temperature finish forging stage is to carry out finish forging with a change amount of 20-30% in a cyclic change range at a strain rate of 0.01-0.1 s -1 Finish forging with a change amount of 20-30% in a cyclic change range.

6. The wrought process for aerospace aluminum alloys of claim 1 wherein, The solid solution treatment comprises the following steps: The first stage solid solution is performed at 475-485°C, and the holding time is calculated by multiplying the thickness of the workpiece section by 2.5 min per mm; After rapid cooling to 350-370°C, a pulse deformation with a deformation amount of 1.5-2.5% is applied; The second stage solid solution is performed at 465-475°C, and the holding time is half of the first stage holding time.

7. The wrought process for aerospace aluminum alloys of claim 1 wherein, The two-stage aging treatment comprises the following steps: The first-stage aging is performed at 120°C for 8 hours while applying a hydrostatic pressure; The second-stage aging is performed at 155°C for 12 hours without stress.

8. The wrought process for aerospace aluminum alloys of claim 1 wherein, The composition of the aluminum alloy comprises, by weight percentage: 10.5-12.5% Zn, 2.5-3.5% Mg, 1.8-2.3% Cu, 0.1-0.15% Zr, and the balance of aluminum and impurities.

9. The wrought process for aerospace aluminum alloys of claim 1 wherein, The tensile strength of the aluminum alloy forging at different positions of the cross section fluctuates by not more than 5%.

10. The wrought process for aerospace aluminum alloys of claim 6, wherein, The second stage solutioning is followed immediately by quenching to fix the workpiece from the supersaturated solution to room temperature, the quenching being by water quenching or polymer aqueous solution quenching.

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