A forging process for aerospace aluminum alloys

Abstract

The application provides a forging process of an aerospace aluminum alloy, and belongs to the technical field of aluminum alloy forging. The process comprises the following steps: after non-isothermal gradient heating of an aluminum alloy ingot by means of induction and radiation combined heating, the ingot enters a holding stage; in the high-temperature large-deformation stage, axial and radial alternating deformation is introduced in the two-up-and-two-down process; then, medium-temperature precision forging is carried out; the forged workpiece is subjected to solid solution treatment, which comprises first-stage solid solution, small-deformation-amount pulse deformation after rapid cooling and second-stage solid solution; 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 carried out in a stress-free state; by combining non-isothermal gradient heating with a pulse heat field, the core structure is preferentially broken under the premise of avoiding grain boundary overburning by using high-deformation resistance of the core structure under a lower temperature, and meanwhile, the surface is ensured to have enough plasticity.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy forging technology, specifically referring to a forging process for aluminum alloys used in aerospace. Background Technology

[0002] High-alloy aluminum alloys typically refer to Al-Zn-Mg-Cu series alloys with Zn content greater than 8wt%, Mg content greater than 2wt%, and often with added elements such as Cu and Zr. These alloys are ideal materials for critical structural components in the aerospace field, such as aircraft wing spars, fuselage frames, and rocket propellant tanks. Through aging precipitation of strengthening phases, such as GP zones, η' phase, and η-MgZn2, they achieve extremely high specific strength, allowing them to meet extremely high load-bearing requirements while reducing structural weight.

[0003] However, while increasing the content of elements such as Zn and Mg brings high strength potential, it also significantly deteriorates the material's machinability, posing a severe challenge to traditional hot working processes, especially forging. Existing forging processes for such high-alloy aluminum alloys mainly suffer from the following limitations:

[0004] 1. Extremely narrow hot working window: The high content of alloying elements results in a large number of low-melting-point eutectic phases (such as Mg(Zn,Cu,Al)2) in the as-cast microstructure. During heating and forging, even slight miscontrol of the temperature, such as exceeding the multi-element eutectic reaction temperature (approximately 475-485℃), can easily lead to overheating and melting of grain boundaries, rendering the product unusable. Conversely, if the temperature is too low, such as as low as 350℃, the alloy's resistance to deformation increases sharply, resulting in poor fluidity and a high risk of forging cracks. This makes the temperature control range of traditional processes extremely narrow, typically only 30-50℃, requiring extremely high equipment and control precision, leading to high production difficulty and low yield.

[0005] 2. High residual stress levels: Due to the poor thermal conductivity and high hardenability of high-alloy aluminum alloys, the significant differences in cooling rates across the cross-sections during quenching after solution treatment introduce extremely high macroscopic residual stress. Furthermore, uneven plastic deformation during forging also accumulates considerable microscopic residual stress. High residual stress not only increases the risk of deformation during subsequent machining but also, during service, superimposes with applied stress, significantly reducing the fatigue life and stress corrosion cracking resistance of components, posing a safety hazard.

[0006] 3. A prominent contradiction exists between strength and toughness / corrosion resistance: While traditional T6 (peak aging) treatment can achieve the highest strength, it often results in lower fracture toughness and stress corrosion resistance of the alloy. T7x (over-aging) treatment, used to improve toughness or corrosion resistance, sacrifices 10-15% of strength. For its application in high-end aerospace fields, how to maintain ultra-high strength while achieving good toughness and corrosion resistance is a core challenge facing current processes.

[0007] To address the aforementioned issues, while some technologies have attempted to locally optimize heating regimes, deformation passes, or heat treatment parameters, these measures are mostly superficial and fragmented improvements. They fail to take a holistic approach, considering the multi-field coupling of "thermal-mechanical-phase transformation," and systematically design an integrated process route. Therefore, developing an innovative forging process that can broaden the hot working window, ensure microstructure uniformity, reduce residual stress, and simultaneously achieve the optimal balance of strength, toughness, and corrosion resistance has become a critical technological bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0008] In order to overcome some of the problems mentioned in the background above, the present invention provides a forging process for aerospace aluminum alloys to at least partially solve the above problems.

[0009] According to the technical solution of the present invention, a forging process for aerospace aluminum alloys is provided, comprising the following steps:

[0010] S1. The aluminum alloy ingot is heated in a non-isothermal gradient manner by a combination of induction and radiation heating, and then enters the heat preservation stage;

[0011] S2. First, a high-temperature large deformation stage is carried out. By introducing alternating axial and radial deformation in the two upsetting and two drawing processes, the workpiece is rotated 55°-65° after each deformation pass, and the total forging ratio is not less than 10; then, medium-temperature precision forging is carried out.

[0012] S3. Perform a solution treatment on the forged workpiece, the solution treatment including a first-stage solution treatment, rapid cooling followed by pulse deformation with small deformation amount and a second-stage solution treatment.

[0013] S4. Perform a two-stage aging treatment on the solution-treated workpiece. In the first stage of aging, apply a hydrostatic pressure of 150-250 MPa, and in the second stage of aging, perform the aging under stress-free conditions.

[0014] Furthermore, during the non-isothermal heating process in step S1, the surface temperature of the aluminum alloy ingot is 420-440℃, and the core temperature is 380-400℃.

[0015] Step S1 also includes introducing a pulsed thermal field during the heat preservation stage, wherein the frequency of the pulsed thermal field is 0.5-2Hz and the temperature amplitude is 15-25℃.

[0016] Furthermore, the duration of the heat preservation stage is calculated using the following formula:

[0017] T=D×k,

[0018] Where T is the holding time (min); D is the effective diameter of the ingot (mm); and k is a constant ranging from 1.2 to 1.4.

[0019] The pulsed thermal field is applied during the last third of the heat preservation stage.

[0020] Furthermore, step S1 includes the following steps:

[0021] Aluminum alloy ingots are loaded into the furnace at room temperature, heated to 250°C at a rate of 75°C / hour, and held at that temperature for 2 hours.

[0022] Then, heat to 400°C at a rate of 110°C / hour, while simultaneously starting induction heating to raise the surface temperature to 430°C before entering the heat preservation stage;

[0023] In the latter third of the heat preservation stage, the power of the pulsed thermal field is controlled by a program to cycle through a temperature amplitude of 20°C at a frequency of 1Hz.

[0024] Furthermore, in the high-temperature large deformation stage, the workpiece is at 410-430℃, and the deformation time for each pass is completed within 3-8 minutes. Between two adjacent passes, the workpiece is returned to the holding furnace for 2-4 minutes to equalize its temperature.

[0025] The intermediate-temperature precision forging stage is carried out at 300-320℃ with a strain rate of 0.01-0.1 s. -1 Precision forging with a variation of 20-30% within the cyclic variation range.

[0026] Furthermore, the solution treatment includes the following steps:

[0027] The first stage of solution treatment is carried out at 475-485℃, and the holding time is calculated as 2.5 min per millimeter of workpiece cross-sectional thickness.

[0028] After rapid cooling to 350-370℃, apply pulse deformation with a deformation amount of 1.5-2.5%;

[0029] The second stage of solution treatment is carried out at 465-475℃, and the holding time is half that of the first stage.

[0030] Furthermore, the two-stage timeliness processing includes the following steps:

[0031] The first-level aging process involves holding the product at 120℃ for 8 hours while applying hydrostatic pressure.

[0032] Secondary aging involves holding the product at 155℃ for 12 hours without applying stress.

[0033] Furthermore, the aluminum alloy comprises, by weight percentage:

[0034] 10.5-12.5% ​​Zn, 2.5-3.5% Mg, 1.8-2.3% Cu, 0.1-0.15% Zr and balance aluminum and impurities.

[0035] Furthermore, the tensile strength fluctuation of the aluminum alloy forgings at different locations on the cross-section does not exceed 5%.

[0036] Furthermore, immediately after the second stage of solution treatment, a quenching process is performed to fix the workpiece from the supersaturated solid solution to room temperature. The quenching process is carried out by water quenching or polymer aqueous solution quenching.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] This invention combines non-isothermal gradient heating with pulsed thermal field to preferentially break the core structure by utilizing the high deformation resistance at a lower core temperature, while ensuring sufficient plasticity at a higher surface temperature, thus avoiding overheating of grain boundaries. This design expands the effective hot working window from about 30-50℃ in traditional processes to over 70-90℃, greatly reducing the difficulty of process control and improving production stability and yield.

[0039] This invention introduces multi-directional, high-density shear strain bands within the material through bidirectional alternating deformation and cyclic control of variable strain rates, providing numerous uniform nucleation points for dynamic recrystallization. This effectively avoids the formation of coarse grain rings, resulting in a uniform and fine recrystallized grain structure in the forging from the surface to the core, significantly reducing grain size inhomogeneity.

[0040] This invention integrates multiple control steps into a coherent and controllable process flow, which can be achieved by upgrading the temperature control system and control software on the basis of existing forging production lines. It does not require expensive investment in new equipment, improves material utilization and production efficiency, and has good technical and economic benefits and industrialization promotion value. Detailed Implementation

[0041] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection.

[0042] This invention provides a forging process for aerospace-grade aluminum alloys, comprising the following steps:

[0043] S1. The aluminum alloy ingot is heated in a non-isothermal gradient manner by a combination of induction and radiation heating, and then enters the heat preservation stage;

[0044] S2. First, a high-temperature large deformation stage is carried out. By introducing alternating axial and radial deformation in the two upsetting and two drawing processes, the workpiece is rotated 55°-65° after each deformation pass, and the total forging ratio is not less than 10; then, medium-temperature precision forging is carried out.

[0045] S3. Perform a solution treatment on the forged workpiece, the solution treatment including a first-stage solution treatment, rapid cooling followed by pulse deformation with small deformation amount and a second-stage solution treatment.

[0046] S4. Perform a two-stage aging treatment on the solution-treated workpiece. In the first stage of aging, apply a hydrostatic pressure of 150-250 MPa, and in the second stage of aging, perform the aging under stress-free conditions.

[0047] In a further embodiment of this example, the surface temperature of the aluminum alloy ingot in step S1 is 420-440°C and the core temperature is 380-400°C during the non-isothermal heating process.

[0048] In a further embodiment of this example, step S1 further includes introducing a pulsed thermal field during the heat preservation stage, wherein the frequency of the pulsed thermal field is 0.5-2Hz and the temperature amplitude is 15-25℃.

[0049] In a further embodiment of this example, the duration of the heat preservation stage is calculated using the following formula:

[0050] T=D×k,

[0051] Where T is the holding time (min); D is the effective diameter of the ingot (mm); and k is a constant ranging from 1.2 to 1.4.

[0052] The pulsed thermal field is applied during the last third of the heat preservation stage.

[0053] In a further embodiment of this example, during the high-temperature large deformation stage, the workpiece is at 410-430℃, and the deformation time for each pass is completed within 3-8 minutes. Between two adjacent passes, the workpiece is returned to the holding furnace for 2-4 minutes to equalize its temperature.

[0054] The intermediate-temperature precision forging stage is carried out at 300-320℃ with a strain rate of 0.01-0.1 s. -1Precision forging with a variation of 20-30% within the cyclic range.

[0055] In a further embodiment of this example, the solution treatment includes the following steps:

[0056] The first stage of solution treatment is carried out at 475-485℃, and the holding time is calculated as 2.5 min per millimeter of workpiece cross-sectional thickness.

[0057] After rapid cooling to 350-370℃, apply pulse deformation with a deformation amount of 1.5-2.5%;

[0058] The second stage of solution treatment is carried out at 465-475℃, and the holding time is half that of the first stage.

[0059] In a further embodiment of this example, the two-stage aging process includes the following steps:

[0060] The first-level aging process involves holding the product at 120℃ for 8 hours while applying hydrostatic pressure.

[0061] Secondary aging involves holding the product at 155℃ for 12 hours without applying stress.

[0062] In a further embodiment of this example, the aluminum alloy comprises, by weight percentage:

[0063] 10.5-12.5% ​​Zn, 2.5-3.5% Mg, 1.8-2.3% Cu, 0.1-0.15% Zr and balance aluminum and impurities.

[0064] In a further embodiment of this example, the tensile strength fluctuation of the aluminum alloy forging obtained by forging at different positions of the cross section does not exceed 5%.

[0065] In a further embodiment of this example, the workpiece is immediately subjected to quenching after the second stage of solution treatment, and the workpiece is fixed to room temperature from the supersaturated solid solution. The quenching treatment is carried out by water quenching or polymer aqueous solution quenching.

[0066] It should be noted that: Step S1 utilizes a temperature gradient to induce pre-dynamic precipitation, forming a high-density nanoscale η' phase within the crystal. These precipitated phases will serve as dislocation pinning points and recrystallization nucleation points during subsequent deformation; Step S2 constructs a high-density deformation band and dislocation cell structure in the material through alternating strain paths and stepwise temperature decreases, providing superior nucleation conditions for subsequent recrystallization; Step S3, through intermittent deformation solution treatment, can promote the dissolution of insoluble crystalline phases through deformation-induced dissolution mechanisms without causing grain growth, thereby increasing solid solubility; Step S4 can achieve the optimal match between strength and toughness by controlling the type, size, and distribution of the precipitated phases.

[0067] The combination of gradient deformation and temperature cycling creates a high-density, uniformly distributed dislocation network. These dislocation structures not only strengthen the matrix but also serve as short-circuit paths for atomic diffusion, accelerating precipitation kinetics during the aging process. The combination of non-isothermal heating and intermittent solid solution treatment optimizes the grain boundary and phase boundary structures, forming an ideal combination of nanoscale grain boundary precipitates and no precipitation band width, which significantly improves the material's resistance to stress corrosion.

[0068] Starting from room temperature loading, aluminum alloy ingots are first slowly heated to 250°C at a rate of ≤80°C / hour using radiant heating, and held at this temperature for 1-2 hours to homogenize the internal temperature and eliminate residual stress. Then, they are heated to 380-400°C at a rate of 100-120°C / hour, while induction heating is simultaneously activated. Due to the "skin effect" of the induced current, the current is highly concentrated on the surface of the aluminum alloy ingot, resulting in rapid and selective heating. By controlling the power of the induction coil, the surface temperature of the aluminum alloy ingot can be precisely raised to the target value of 420-440°C. At this point, the surface of the aluminum alloy ingot is "heated" by the induction coil, while the core temperature is maintained mainly by heat conducted from the surface inwards and by the "baking" effect of the radiant environment. Because heat conduction from the surface inwards takes time, a stable temperature gradient of 430°C (high surface temperature) and 400°C (low core temperature) is actively and controllably established.

[0069] During the latter third of the period of maintaining gradient stability, the power of the induction coil is controlled by the program to make it cycle between "high power" and "low power" at a specific frequency. In the high power half-cycle, the coil outputs additional heat, causing the surface temperature to rise instantaneously, such as by 20°C. In the low power half-cycle, the coil output decreases, and the surface temperature drops back to -20°C under the influence of radiation and internal heat conduction. The surface temperature of the aluminum alloy ingot achieves high-frequency small-amplitude fluctuations (i.e., pulsed thermal field), while the core temperature remains relatively stable due to thermal inertia. This thermal oscillation of the surface can effectively promote atomic diffusion without causing overheating of the core tissue.

[0070] The aluminum alloy ingots selected in the following examples and comparative examples all include components by weight percentage:

[0071] 12% Zn, 3% Mg, 2% Cu, 0.15% Zr and balance aluminum and impurities.

[0072] Example 1

[0073] The ingot is first loaded into the furnace at room temperature and then slowly heated to 250°C at a rate of 75°C / hour and held for 2 hours. Then it is heated to 400°C at a rate of 110°C / hour while induction heating is activated to precisely raise the surface temperature to 430°C and enter the holding stage. In the latter half of the holding stage, the power of the induction coil is controlled by the program to make it cycle between "high power" and "low power" with a temperature amplitude of 20°C at 1Hz.

[0074] In the high-temperature large deformation stage at 420℃, the deformation time for each pass is completed within 5 minutes. Between adjacent passes, the workpiece is returned to the holding furnace for 3 minutes to achieve uniform temperature. After each deformation pass, the workpiece is rotated 60°. The total forging ratio is not less than 12. The medium-temperature precision forging stage is carried out at 310℃ with a strain rate of 0.01-0.1s. -1 Precision forging with a variation of 20-30% within the cyclic range.

[0075] The first stage of solution treatment is performed at 480°C. After the first stage of solution treatment is completed, the workpiece is quickly transferred to the worktable of a press that maintains a constant temperature of 360°C. The transfer time should be as short as possible, less than 30 seconds. Strong air cooling or mist cooling should be used to rapidly reduce the temperature of both the surface and core of the workpiece to the target range of 350-370°C within 3 minutes.

[0076] At a constant temperature of 360°C, a small-scale pulse deformation of 2% is immediately applied to the workpiece. This deformation is not forging, but rather a slight pressing similar to "shaping". After the pulse deformation, the workpiece is quickly transferred to an adjacent solution furnace and immediately heated to the second stage temperature of 470°C at the fastest speed.

[0077] After completing the second stage of solution treatment, quenching is performed immediately to fix the supersaturated solid solution to room temperature. Then, it is held at 120°C for 8 hours while applying a hydrostatic pressure of 200 MPa for first-stage aging treatment. After that, it is held at 155°C for 12 hours and then subjected to second-stage aging treatment without stress to obtain the aluminum alloy.

[0078] Example 2

[0079] The ingot is first loaded into the furnace at room temperature and then slowly heated to 250°C at a rate of 75°C / hour and held for 2 hours. Then it is heated to 395°C at a rate of 110°C / hour while induction heating is activated to precisely raise the surface temperature to 425°C and enter the holding stage. In the latter half of the holding stage, the power of the induction coil is controlled by the program to make it cycle between "high power" and "low power" with a temperature amplitude of 20°C at 1Hz.

[0080] In the high-temperature large deformation stage at 420℃, the deformation time for each pass is completed within 5 minutes. Between adjacent passes, the workpiece is returned to the holding furnace for 3 minutes to achieve uniform temperature. After each deformation pass, the workpiece is rotated 60°. The total forging ratio is not less than 12. The medium-temperature precision forging stage is carried out at 310℃ with a strain rate of 0.01-0.1s. -1 Precision forging with a variation of 20-30% within the cyclic range.

[0081] The first stage of solution treatment is performed at 480°C. After the first stage of solution treatment is completed, the workpiece is quickly transferred to the worktable of a press that maintains a constant temperature of 360°C. The transfer time should be as short as possible, less than 30 seconds. Strong air cooling or mist cooling should be used to rapidly reduce the temperature of both the surface and core of the workpiece to the target range of 350-370°C within 3 minutes.

[0082] At a constant temperature of 360°C, a small-scale pulse deformation of 2% is immediately applied to the workpiece. This deformation is not forging, but rather a slight pressing similar to "shaping". After the pulse deformation, the workpiece is quickly transferred to an adjacent solution furnace and immediately heated to the second stage temperature of 470°C at the fastest speed.

[0083] After completing the second stage of solution treatment, quenching is performed immediately to fix the supersaturated solid solution to room temperature. Then, it is held at 120℃ for 8 hours while applying a hydrostatic pressure of 250MPa for first-stage aging treatment. After that, it is held at 155℃ for 12 hours and then subjected to second-stage aging treatment without stress to obtain the aluminum alloy.

[0084] Example 3

[0085] The ingot is first loaded into the furnace at room temperature and then slowly heated to 250°C at a rate of 75°C / hour and held for 2 hours. Then it is heated to 400°C at a rate of 110°C / hour while induction heating is activated to precisely raise the surface temperature to 430°C and enter the holding stage. In the latter half of the holding stage, the power of the induction coil is controlled by the program to make it cycle between "high power" and "low power" with a temperature amplitude of 20°C at 1Hz.

[0086] In the high-temperature large deformation stage at 420℃, the deformation time for each pass is completed within 5 minutes. Between adjacent passes, the workpiece is returned to the holding furnace for 3 minutes to achieve uniform temperature. After each deformation pass, the workpiece is rotated 58°. The total forging ratio is not less than 12. The medium-temperature precision forging stage is carried out at 310℃ with a strain rate of 0.01-0.1s. -1 Precision forging with a variation of 20-30% within the cyclic range.

[0087] The first stage of solution treatment is performed at 478°C. After the first stage of solution treatment is completed, the workpiece is quickly transferred to the worktable of a press that maintains a constant temperature of 360°C. The transfer time should be as short as possible, less than 30 seconds. Strong air cooling or mist cooling is used to rapidly reduce the temperature of both the surface and core of the workpiece to the target range of 350-370°C within 3 minutes.

[0088] At a constant temperature of 360°C, a small-scale pulse deformation of 2% is immediately applied to the workpiece. This deformation is not forging, but rather a slight pressing similar to "shaping". After the pulse deformation, the workpiece is quickly transferred to an adjacent solution furnace and immediately heated to the second stage temperature of 470°C at the fastest speed.

[0089] After completing the second stage of solution treatment, quenching is performed immediately to fix the supersaturated solid solution to room temperature. Then, it is held at 120°C for 8 hours while applying a hydrostatic pressure of 200 MPa for first-stage aging treatment. After that, it is held at 155°C for 12 hours and then subjected to second-stage aging treatment without stress to obtain the aluminum alloy.

[0090] Example 4

[0091] The ingot is loaded into the furnace at room temperature. It is first slowly heated to 250°C at a rate of 75°C / hour and held for 2 hours. Then it is heated to 400°C at a rate of 110°C / hour while induction heating is activated to precisely raise the surface temperature to 430°C and enter the holding stage.

[0092] In the high-temperature large deformation stage at 420℃, the deformation time for each pass is completed within 5 minutes. Between adjacent passes, the workpiece is returned to the holding furnace for 3 minutes to achieve uniform temperature. After each deformation pass, the workpiece is rotated 60°. The total forging ratio is not less than 12. The medium-temperature precision forging stage is carried out at 310℃ with a strain rate of 0.01-0.1s. -1 Precision forging with a variation of 20-30% within the cyclic variation range.

[0093] The first stage of solution treatment is performed at 480°C. After the first stage of solution treatment is completed, the workpiece is quickly transferred to the worktable of a press that maintains a constant temperature of 360°C. The transfer time should be as short as possible, less than 30 seconds. Strong air cooling or mist cooling should be used to rapidly reduce the temperature of both the surface and core of the workpiece to the target range of 350-370°C within 3 minutes.

[0094] At a constant temperature of 360°C, a small-scale pulse deformation of 2% is immediately applied to the workpiece. This deformation is not forging, but rather a slight pressing similar to "shaping". After the pulse deformation, the workpiece is quickly transferred to an adjacent solution furnace and immediately heated to the second stage temperature of 470°C at the fastest speed.

[0095] After completing the second stage of solution treatment, quenching is performed immediately to fix the supersaturated solid solution to room temperature. Then, it is held at 120°C for 8 hours while applying a hydrostatic pressure of 200 MPa for first-stage aging treatment. After that, it is held at 155°C for 12 hours and then subjected to second-stage aging treatment without stress to obtain the aluminum alloy.

[0096] Comparative Example

[0097] The aluminum alloy ingot is uniformly heated and held at 430℃, then multi-directional forging is performed between 420-350℃, rotating 90° each time. The traditional T6 treatment is then performed, which involves solution treatment at 476℃ for 8 hours, followed by water quenching and single-stage aging treatment at 120℃ for 24 hours to obtain the aluminum alloy.

[0098] The aluminum alloys obtained in Examples 1-4 and the comparative examples were tested experimentally. The test data included mechanical properties and corrosion resistance. The specific testing methods are as follows.

[0099] Mechanical properties were determined by room temperature tensile testing according to ASTM E8 / E8M standards, measuring tensile strength (Rm), yield strength (Rp0.2), and elongation after fracture (A). Plane strain fracture toughness (KIC) was determined according to ASTM E399 standards.

[0100] Corrosion resistance is assessed by exfoliation corrosion (EXCO) testing according to ASTM G34, with ratings of EA (severe exfoliation), EB (moderate exfoliation), EC (minor exfoliation), or ED (no exfoliation). Stress corrosion cracking (SCC) testing is performed according to ASTM G47 to determine the threshold stress intensity factor (KISCC).

[0101] The test results are shown in Table 1 below.

[0102] Table 1 Performance data of the embodiments and comparative examples

[0103]

[0104] In summary, all key performance indicators of the embodiments, including strength, toughness, and corrosion resistance, are significantly better than those of the comparative examples. The huge performance improvement directly proves the synergistic effect and inventiveness of the entire technical solution of gradient heating, bidirectional alternating deformation, intermittent solid solution (including pulse deformation), and synergistic aging. This shows that the process route of the present invention is successful in essence.

[0105] After adjusting the parameters relative to Example 1, Examples 2-4, although each with a different emphasis, all maintained an extremely high level of performance. This demonstrates that the process has a wide window of opportunity, good engineering applicability and stability, rather than being a "laboratory solution" that can only be achieved under extremely specific parameters. The process of this invention achieves ultra-high strength while also taking into account excellent fracture toughness and corrosion resistance, realizing a good match between strength, toughness and corrosion resistance in high-alloy aluminum alloys, and meeting the stringent requirements of the aerospace field for the comprehensive performance of materials.

[0106] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A forging process for aerospace aluminum alloys, characterized in that, Includes the following steps: S1. The aluminum alloy ingot is heated in a non-isothermal gradient manner by a combination of induction and radiation heating, and then enters the heat preservation stage; S2. First, a high-temperature large deformation stage is carried out. By introducing alternating axial and radial deformation in the two upsetting and two drawing processes, the workpiece is rotated 55°-65° after each deformation pass, and the total forging ratio is not less than 10; then, medium-temperature precision forging is carried out. S3. Perform a solution treatment on the forged workpiece, the solution treatment including a first-stage solution treatment, rapid cooling followed by pulse deformation with small deformation amount and a second-stage solution treatment. S4. Perform a two-stage aging treatment on the solution-treated workpiece, wherein a hydrostatic pressure of 150-250MPa is applied during the first-stage aging process, and the second-stage aging is carried out under stress-free conditions; Step S1 includes slowly heating the aluminum alloy ingot to 250°C at a rate of ≤80°C / hour by radiation heating, and holding it at that temperature for 1-2 hours to homogenize the internal temperature and eliminate residual stress in the ingot. Then, it is heated to 380-400°C at a rate of 100-120°C / hour, while simultaneously starting induction heating. By controlling the power of the induction coil, the surface temperature of the aluminum alloy ingot can be precisely raised to the target value of 420-440°C. Step S1 further includes introducing a pulsed thermal field during the heat preservation stage, wherein the frequency of the pulsed thermal field is 0.5-2Hz and the temperature amplitude is 15-25℃. The components of the aluminum alloy, by weight percentage, include: 10.5-12.5% ​​Zn, 2.5-3.5% Mg, 1.8-2.3% Cu, 0.1-0.15% Zr and balance aluminum and impurities.

2. The forging process for aerospace aluminum alloys according to claim 1, characterized in that, During the non-isothermal heating process in step S1, the surface temperature of the aluminum alloy ingot is 420-440℃, and the core temperature is 380-400℃.

3. The forging process for aerospace aluminum alloys according to claim 2, characterized in that, The duration of the heat preservation stage is calculated using the following formula: T=D×k, Where T is the holding time (min); D is the effective diameter of the ingot (mm); and k is a constant ranging from 1.2 to 1.

4. The pulsed thermal field is applied during the last third of the heat preservation stage.

4. The forging process for aerospace aluminum alloys according to claim 3, characterized in that, Step S1 includes the following steps: Aluminum alloy ingots are loaded into the furnace at room temperature, heated to 250°C at a rate of 75°C / hour, and held at that temperature for 2 hours. Then, heat to 400°C at a rate of 110°C / hour, while simultaneously starting induction heating to raise the surface temperature to 430°C before entering the heat preservation stage. In the latter third of the heat preservation stage, the power of the pulsed thermal field is controlled by a program to cycle through a temperature amplitude of 20°C at a frequency of 1Hz.

5. The forging process for aerospace aluminum alloys according to claim 1, characterized in that, During the high-temperature large deformation stage, the workpiece is at 410-430℃, and the deformation time for each pass is completed within 3-8 minutes. Between two adjacent passes, the workpiece is returned to the holding furnace for 2-4 minutes to equalize its temperature. The intermediate temperature precision forging stage is precision forging with a strain rate of 20-30% within a cyclic range of 0.01-0.1s⁻¹ under conditions of 300-320℃.

6. The forging process for aerospace aluminum alloys according to claim 1, characterized in that, The solution treatment includes the following steps: The first stage of solution treatment is carried out at 475-485℃, and the holding time is calculated as 2.5 min per millimeter of workpiece cross-sectional thickness. After rapid cooling to 350-370℃, apply pulse deformation with a deformation amount of 1.5-2.5%; The second stage of solution treatment is carried out at 465-475℃, and the holding time is half that of the first stage.

7. The forging process for aerospace aluminum alloys according to claim 1, characterized in that, The two-stage timeliness processing includes the following steps: The first-level aging process involves holding the product at 120℃ for 8 hours while applying hydrostatic pressure. Secondary aging involves holding the product at 155℃ for 12 hours without applying stress.

8. The forging process for aerospace aluminum alloys according to claim 1, characterized in that, The tensile strength fluctuation of the aluminum alloy forgings at different locations of the cross section does not exceed 5%.

9. The forging process for aerospace aluminum alloys according to claim 6, characterized in that, The second stage of solution treatment is followed immediately by quenching to fix the workpiece from the supersaturated solid solution to room temperature. The quenching process is carried out by water quenching or polymer aqueous solution quenching.

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