A high-performance aluminum-lithium alloy plate forging and shape heat treatment method

Abstract

The application discloses a high-performance aluminum-lithium alloy plate forging and deformation heat treatment method, and belongs to the field of aluminum alloy material processing technology and heat treatment technology, and comprises the following steps: step 1, homogenization treatment; step 2, pre-forging heat treatment; step 3, multi-fire multi-directional forging, forging is respectively along the Z-axis upsetting, Y-axis lengthening and square, along the Y-axis upsetting, then along the X-axis lengthening, along the X-axis upsetting, then along the Z-axis lengthening, and finally, along the Y-axis direction upsetting and shaping to obtain a thick plate; and step 4, deformation heat treatment, the plate obtained in step 3 is subjected to T8 deformation heat treatment. The forging method can effectively improve the directionality and plasticity of the aluminum-lithium alloy, the structure directionality of the aluminum-lithium alloy after being forged by the forging method is weak, the banded structure along the axial direction disappears, the structure grain can be refined, and relatively uniform equiaxed grains are obtained. The structure has good plasticity, can be deformed by a large deformation amount, and is suitable for subsequent T8 deformation heat treatment.

Description

Technical Field

[0001] This invention belongs to the fields of aluminum alloy material processing technology and heat treatment technology, specifically relating to a method for forging and deformation heat treatment of high-performance aluminum-lithium alloy plates. Background Technology

[0002] Third-generation aluminum-lithium alloys are widely used in the aerospace field due to their low density, high strength, high modulus, weldability, good thermal stability, and corrosion resistance. With the development of the aerospace industry, the demand for weight reduction and strengthening of aluminum-lithium alloys is increasing. However, existing forging techniques for aluminum-lithium alloys suffer from severe anisotropy, difficulty in grain refinement, and challenges in heat treatment control. Their strength and toughness cannot yet meet the higher mechanical property requirements of the aerospace industry, thus limiting their widespread application in the aerospace field.

[0003] There are various methods for strengthening and toughening metals, and grain refinement is an effective means of significantly increasing strength without compromising the ductility and toughness of metallic materials. When the grain size is very small, the strengthening effect of grain refinement will far exceed that of processing strengthening or precipitation strengthening. Large plastic deformation is one of the main methods for refining metal grains. Due to its advantages such as simple process, low cost, ability to produce large, dense materials, and performance improvement, it is considered the forging method most likely to be successfully applied industrially.

[0004] To further improve the mechanical properties of alloys beyond deformation strengthening, subsequent heat treatment is required to obtain second-phase strengthening and a more stable microstructure. Deformation heat treatment primarily utilizes the particle-induced recrystallization nucleation mechanism to refine grains. This involves first subjecting the material to high-temperature aging, which precipitates a large number of large-sized second-phase particles, creating a strong deformation zone around them. This provides numerous nucleation sites for subsequent recrystallization annealing, thus refining the grain size.

[0005] Chinese invention patent CN111057975B discloses a method for preparing a superplastic fine-grained aluminum-lithium alloy sheet. This method improves the process plasticity of the aluminum-lithium alloy slab through forging, and then prepares a superplastic fine-grained aluminum-lithium alloy sheet with fine grains and uniform size distribution through processes such as high-temperature rolling, solution quenching, room-temperature rolling, over-aging treatment, low-temperature rolling, and recrystallization annealing. However, the forging method in this method is not comprehensive enough and needs further improvement in terms of plasticity. Summary of the Invention

[0006] To address the aforementioned problems, this invention aims to provide a method for forging and deformation heat treatment of high-performance aluminum-lithium alloy plates.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for forging and deformation heat treatment of high-performance aluminum-lithium alloy plates, comprising multi-stage multi-directional forging and deformation heat treatment, including the following steps:

[0008] Step 1: Homogenization treatment. Heat the blank sample to 420℃~460℃ and hold for 10~16h; continue to heat to 485℃~505℃ and hold for 20h~26h, then air cool to room temperature.

[0009] Step 2: Pre-forging heat treatment: The homogenized ingot is heated to 450℃~490℃ in the furnace and held for 7.5~12h before forging;

[0010] Step 3: Multi-fire multi-directional forging, the forging is upset along the Z-axis, elongated and squared along the Y-axis, upset along the Y-axis, elongated along the X-axis, upset along the X-axis, elongated along the Z-axis, and finally upset and shaped along the Y-axis to obtain a thick plate.

[0011] Step 4: Deformation heat treatment. The sheet material obtained in Step 3 is subjected to T8 deformation heat treatment.

[0012] Preferably, the components and their mass percentages of the aluminum-lithium alloy are as follows: Li 0.7–1.3%, Cu 3.6–4.5%, Mg 0.2–0.8%, Zr 0.06–0.18%, Ag 0.2–0.8%, Zn ≤ 0.25%, Fe < 0.05%, Si < 0.05%, Mn < 0.001%, Ti < 0.001%, H < 0.0001%, with the balance being Al.

[0013] Preferably, step 3, the multi-fire multi-directional forging, includes the following steps:

[0014] Step 31: First forging: Upset the ingot along the Z-axis, then elongate it along the Y-axis and then square it. The Z-axis upsetting ratio is ≥1.5, the Y-axis elongation ratio is ≥1.5, the initial forging temperature is ≥460℃, and the final forging temperature is ≥370℃.

[0015] Step 32: Second forging: Upset the square plate along the Y-axis and then elongate it along the X-axis. The upsetting ratio along the Y-axis is ≥1.5, the elongation ratio along the X-axis is ≥1.5, the initial forging temperature is ≥460℃, the final forging temperature is ≥360℃, and the holding time between passes is ≥0.5h.

[0016] Step 33: Third forging: Upset the square plate along the X-axis and then elongate it along the Z-axis. The upsetting ratio along the X-axis is ≥1.5, the elongation ratio along the Z-axis is ≥1.5, the initial forging temperature is ≥460℃, the final forging temperature is ≥360℃, and the holding time between passes is ≥0.5h.

[0017] Step 34: Fourth forging: Upsetting the block along the Y-axis to form a thick plate, with a Y-axis upsetting ratio ≥2, initial forging temperature ≥460℃, final forging temperature ≥340℃, and holding time between passes ≥0.5h.

[0018] Preferably, the thickness of the thick plate in step 34 is 40 mm.

[0019] Preferably, the T8 deformation heat treatment in step 4 includes the following steps:

[0020] Step 41: Solution treatment, the forged plate is subjected to solution quenching treatment;

[0021] Step 42: Pre-deformation, the quenched sample is pre-deformed on a press;

[0022] Step 43: Artificial aging, the pre-deformed sample is subjected to artificial aging treatment.

[0023] Preferably, the solution temperature in step 41 is 510–520°C, the solution time is 1–2 h, the quenching medium is room temperature water, and the quenching transfer time is <10 s.

[0024] Preferably, the press in step 42 is an 800t press, the pre-deformation amount is 10-30%, and the pre-deformation completion time is <15min.

[0025] Preferably, the aging temperature in step 43 is 155–175°C, and the aging time is 18–26 hours.

[0026] Preferably, the aluminum-lithium alloy sheet prepared by this method has a longitudinal tensile strength >600MPa, a yield strength >550MPa, an elongation >6%, a longitudinal and transverse tensile strength deviation <1%, and a yield strength deviation <3%.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1. The forging method of this invention can effectively improve the directionality and plasticity of the aluminum-lithium alloy of this invention. After forging by the forging method of this invention, the microstructure has weaker directionality, the banded structure along the axial direction disappears, and the microstructure grains can be refined to obtain more uniform equiaxed grains. This microstructure has better plasticity, can undergo larger deformation, and is suitable for subsequent T8 deformation heat treatment.

[0029] 2. The forging and deformation heat treatment method of the present invention can prepare aluminum-lithium alloy plates with low anisotropy and high strength. The longitudinal tensile strength is higher than 600 MPa, the yield strength is higher than 550 MPa, and the elongation is greater than 6%. Compared with its T6 state, the tensile strength is increased by 100-130 MPa and the yield strength is increased by 200-240 MPa. Moreover, the longitudinal and transverse tensile strength deviations are less than 1% and the yield strength deviations are less than 3%. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the forging direction of the aluminum-lithium alloy of the present invention;

[0032] Figure 2 This is a simplified diagram of the deformation heat treatment process for the aluminum-lithium alloy forged plate of the present invention.

[0033] Figure 3 Example 1: Metallographic structure of aluminum-lithium alloy in the forged state;

[0034] Figure 4 This is a microstructure diagram of the aluminum-lithium alloy in the T8 state of Example 1 of the present invention. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, it should not be construed that the scope of the subject matter of the present invention is limited to the following embodiments. All modifications, substitutions and alterations made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention are included within the scope of the present invention.

[0036] The purpose of this invention is to provide a method for forging and heat treating high-performance aluminum-lithium alloy plates, which can solve the problems of severe anisotropy, difficulty in grain refinement, and difficulty in heat treatment control of aluminum-lithium alloys. At the same time, by combining deformation heat treatment method, a high-performance aluminum-lithium alloy with tensile strength higher than 600MPa, yield strength higher than 550MPa, elongation greater than 6%, and longitudinal and transverse tensile strength deviation less than 1% and yield strength deviation less than 3% can be prepared.

[0037] The elements in the aluminum-lithium alloy of this invention are proportioned by mass percentage as follows: Li 0.7-1.3%, Cu 3.6-4.5%, Mg 0.2-0.8%, Zr 0.06-0.18%, Ag 0.2-0.8%, Zn≤0.25%, Fe<0.05%, Si<0.05%, Mn<0.001%, Ti<0.001%, H<0.0001%, with the balance being Al.

[0038] A method for forging and deformation heat treatment of high-performance aluminum-lithium alloy plates involves subjecting aluminum-lithium alloy ingots to a two-stage homogenization heat treatment to form billets, followed by multi-fire, multi-directional forging to obtain plates with uniform microstructure. After solution treatment and quenching, the plates undergo pre-stretch deformation and finally artificial aging to the T8 state. The method includes the following steps:

[0039] Step 1: Homogenization treatment: Heat the blank sample to 420℃~460℃ and keep it at that temperature for 10~16h; continue to raise the temperature to 485℃~505℃ and keep it at that temperature for 20h~26h, then air cool to room temperature.

[0040] Step 2: Pre-forging heat treatment: The homogenized ingot is heated to 450℃~490℃ in the furnace and held for 7.5~12h before forging.

[0041] Step 3: As Figure 1 The diagram shows a multi-fire, multi-directional forging process, where forging is performed in steps.

[0042] Step 31: First forging: upset the ingot along the Z-axis, then elongate it along the Y-axis and then square it. The Z-axis upsetting ratio is not less than 1.5, the Y-axis elongation ratio is not less than 1.5, the initial forging temperature is not less than 460℃, the final forging temperature is not less than 370℃, and the holding time between passes is not less than 8 hours.

[0043] Step 32: Second forging: Upset the square plate along the Y-axis and then draw it along the X-axis. The upsetting ratio is not less than 1.5 and the drawing ratio is not less than 1.5. The initial forging temperature is not less than 460℃ and the final forging temperature is not less than 360℃. The holding time between passes is not less than 0.5h.

[0044] Step 33: Third forging: Upset the square plate along the X-axis and then elongate it along the Z-axis. The upsetting ratio along the X-axis shall not be less than 1.5 and the elongation ratio along the Z-axis shall not be less than 1.5. The initial forging temperature shall not be less than 460℃ and the final forging temperature shall not be less than 360℃. The holding time between passes shall not be less than 0.5h.

[0045] Step 34: Fourth forging: Upset the block along the Y-axis to a thickness of 40mm. The Y-axis upsetting ratio is not less than 2. The initial forging temperature is not less than 460℃, the final forging temperature is not less than 340℃, and the holding time between passes is not less than 0.5h.

[0046] Step 4: Deformation heat treatment: such as Figure 2 The diagram shown is a simplified representation of the high-performance deformation heat treatment process for lithium alloy forged plates. The plates are heat-treated using the "T8 deformation heat treatment" method, which is carried out in the following steps:

[0047] Step 41: Solution treatment. The forged plate is subjected to solution quenching treatment at a temperature of 510-520℃ for 1-2 hours. The quenching medium is room temperature water, and the quenching transfer time is less than 10 seconds.

[0048] Step 42: Pre-deformation. The quenched sample is pre-deformed on an 800t press. The pre-deformation amount is 10-30%, and the pre-deformation completion time is less than 15 minutes.

[0049] Step 43: Artificial aging. The pre-deformed sample is subjected to artificial aging treatment at an aging temperature of 155℃~175℃ for 18~26h.

[0050] Example 1

[0051] The elemental composition (mass percentage) of the aluminum-lithium alloy described in this invention patent is as follows: Li 0.7-1.3%, Cu 3.6-4.5%, Mg 0.2-0.8%, Zr 0.06-0.18%, Ag 0.2-0.8%, Zn≤0.25%, Fe<0.05%, Si<0.05%, Mn<0.001%, Ti<0.001%, H<0.0001%, with the balance being Al.

[0052] Homogenization heat treatment: Heat the blank sample to 460℃ and hold for 16h; continue to heat to 495℃ and hold for 24h, then air cool to room temperature.

[0053] Pre-forging heat treatment: The homogenized ingot is heated to 470℃ in the furnace and held for 7.6 hours before forging.

[0054] First forging: The ingot is upset along the Z-axis, then elongated along the Y-axis and then squared. The Z-axis upsetting ratio is 1.6, the Y-axis elongation ratio is 1.6, the initial forging temperature is 470℃, and the final forging temperature is 372℃.

[0055] Second forging: The square plate is upset along the Y-axis and then drawn along the X-axis. The upsetting ratio is 1.6 and the drawing ratio is 1.6. The initial forging temperature is 468℃ and the final forging temperature is 361℃. The holding time between passes is 1 hour.

[0056] Third forging: The square plate is upset along the X-axis and then elongated along the Z-axis. The X-axis upsetting ratio is 1.6, the Z-axis elongation ratio is 1.6, the initial forging temperature is 466℃, the final forging temperature is 362℃, and the holding time between passes is 1.5h.

[0057] Fourth forging: The square plate is upset along the X-axis, then elongated along the Z-axis and shaped. The X-axis upsetting ratio is 1.6, the Z-axis elongation ratio is 2.5, the initial forging temperature is 467℃, the final forging temperature is 343℃, and the holding time between passes is 1.58h.

[0058] The forged sheet metal is then subjected to T8 heat treatment:

[0059] Solution treatment: The forged plate is subjected to solution quenching treatment at a temperature of 518℃ for 1.5 hours. The quenching medium is room temperature water, and the quenching transfer time is less than 10 seconds.

[0060] Pre-deformation: The quenched sample is pre-deformed on an 800t press with a pre-deformation amount of 20% and a pre-deformation completion time of less than 15 minutes.

[0061] Artificial aging: The pre-deformed sample is subjected to artificial aging treatment at an aging temperature of 162℃ for 24.5h.

[0062] like Figure 3 The figure shows the forged metallographic structure of the alloy in Example 1. As can be seen from the figure, the forged structure of the alloy is relatively equiaxed, the grain size is smaller than that of the homogenized state, the grain structure has no obvious directionality, and there is no banded fiber structure.

[0063] like Figure 4 As shown in the figure, the metallographic structure of the forged plate in the deformed heat-treated state in Example 1 is as follows. It can be seen from the figure that the forged plate structure obtained by the forging and heat treatment method of the present invention does not have obvious directionality.

[0064] Example 2: The alloy ingot after homogenization heat treatment in Example 1 was forged, and the pre-forging heat treatment was the same as in Example 1.

[0065] First forging: The ingot is upset along the Z-axis, then elongated along the Y-axis and then squared. The Z-axis upsetting ratio is 1.5, the Y-axis elongation ratio is 1.5, the initial forging temperature is 465℃, and the final forging temperature is 375℃.

[0066] Second forging: The square plate is upset along the Y-axis and then drawn along the X-axis. The upsetting ratio is 1.5, the drawing ratio is 1.5, the initial forging temperature is 482℃, the final forging temperature is 371℃, and the holding time between passes is 1.1h.

[0067] Third forging: The square plate is upset along the X-axis and then elongated along the Z-axis. The X-axis upsetting ratio is 1.5, the Z-axis elongation ratio is 1.5, the initial forging temperature is 468℃, the final forging temperature is 382℃, and the holding time between passes is 1.5h.

[0068] Fourth forging: The square plate is upset along the X-axis, then elongated along the Z-axis and then shaped. The X-axis upsetting ratio is 1.5, the Z-axis elongation ratio is 2.4, the initial forging temperature is 482℃, the final forging temperature is 340℃, and the holding time between passes is 1.6h.

[0069] The post-forging deformation heat treatment is the same as in Example 1.

[0070] Example 3: Forging was performed using the alloy ingot after homogenization heat treatment as described in Example 1.

[0071] First forging: The ingot is upset along the Z-axis, then elongated along the Y-axis and then squared. The Z-axis upsetting ratio is 1.7, the Y-axis elongation ratio is not less than 1.7, the initial forging temperature is 475℃, and the final forging temperature is 378℃.

[0072] Second forging: The square plate is upset along the Y-axis and then drawn along the X-axis. The upsetting ratio is 1.7, the drawing ratio is 1.7, the initial forging temperature is 470℃, the final forging temperature is 378℃, and the holding time between passes is 1.1h.

[0073] Third forging: The square plate is upset along the X-axis and then elongated along the Z-axis. The X-axis upsetting ratio is 1.7, the Z-axis elongation ratio is 1.7, the initial forging temperature is 476℃, the final forging temperature is 374℃, and the holding time between passes is 1.6h.

[0074] Fourth forging: The square plate is upset along the X-axis, then elongated along the Z-axis and shaped. The X-axis upsetting ratio is 1.5, the Z-axis elongation ratio is 2.4, the initial forging temperature is 470℃, the final forging temperature is 343℃, and the holding time between passes is 1.58h.

[0075] The post-forging deformation heat treatment is the same as in Example 1.

[0076] Example 4: The forged plate from Example 1 was subjected to T8 heat treatment. The specific process is as follows:

[0077] Solution treatment: The forged plate is subjected to solution quenching treatment at a temperature of 518℃ for 1.5 hours. The quenching medium is room temperature water, and the quenching transfer time is less than 10 seconds.

[0078] Pre-deformation: The quenched sample is pre-deformed on an 800t press with a pre-deformation amount of 10% and a pre-deformation completion time of less than 15 minutes.

[0079] Artificial aging: The pre-deformed sample is subjected to artificial aging treatment at an aging temperature of 162℃ for 24.5h.

[0080] Example 5: The forged plate from Example 1 was subjected to T8 heat treatment. The specific process is as follows:

[0081] Solution treatment: The forged plate is subjected to solution quenching treatment at a temperature of 518℃ for 1.5 hours. The quenching medium is room temperature water, and the quenching transfer time is less than 10 seconds.

[0082] Pre-deformation: The quenched sample is pre-deformed on an 800t press with a pre-deformation amount of 30% and a pre-deformation completion time of less than 15 minutes.

[0083] Artificial aging: The pre-deformed specimens were subjected to artificial aging treatment at a temperature of 162℃ for 24.5 hours.

[0084] Comparative Example 1: The forged alloy plate from Example 1 was subjected to T6 heat treatment. The specific process was as follows: the forged plate was subjected to solution quenching at a temperature of 518°C for 1.5 hours, the quenching medium was room temperature water, and the quenching transfer time was less than 10 seconds; the solution-quenched sample was then subjected to artificial aging at a temperature of 162°C for 24.5 hours.

[0085] Comparative Example 2: The alloy ingots from the same batch of homogenized heat-treated materials as in Example 1 were forged.

[0086] First forging: Upsetting the ingot along the Z-axis with a Z-axis upsetting ratio of 2, initial forging temperature of 470℃, and final forging temperature of 376℃;

[0087] Second forging: To elongate the disc along the Z-axis, the elongation ratio is 2, the initial forging temperature is 466℃, the final forging temperature is 370℃, and the holding time between passes is 1 hour.

[0088] Third forging: The billet is upset along the Z-axis and then drawn back along the X-axis. The upsetting ratio is 1.5 and the drawing ratio is 1.6. The initial forging temperature is 470℃ and the final forging temperature is 370℃. The holding time between passes is 1.2h.

[0089] Fourth forging: The forging billet is drawn and shaped along the X-axis with a drawing ratio of 1.5. The initial forging temperature is not lower than 468℃, the final forging temperature is 342℃, and the holding time between passes is 1.4h.

[0090] The post-forging deformation heat treatment is the same as in Example 1.

[0091] Comparative Example 3: The alloy ingots from the same batch of homogenized heat-treated materials as in Example 1 were forged.

[0092] First forging: Upsetting the ingot along the Z-axis with a Z-axis upsetting ratio of 1.5, initial forging temperature of 465℃, and final forging temperature of 380℃;

[0093] Second forging: The round cake is upset along the Z-axis and then squared along the radial direction. The upsetting ratio is 2, the initial forging temperature is 464℃, the final forging temperature is 378℃, and the holding time between passes is 1 hour.

[0094] Third forging: The square plate is upset along the Z-axis, then elongated and shaped along the X-axis. The Z-axis upsetting ratio is 1.5, the X-axis elongation ratio is 1.7, the initial forging temperature is 470℃, the final forging temperature is 364℃, and the holding time between passes is 1.6h.

[0095] The post-forging deformation heat treatment is the same as in Example 1.

[0096] Comparative Example 4: The alloy ingots from the same batch of homogenized heat-treated materials as in Example 1 were forged.

[0097] First forging: The ingot is upset along the Z-axis and then drawn along the Z-axis. The Z-axis upsetting ratio is 1.7 and the drawing ratio is 1.2. The initial forging temperature is 468℃ and the final forging temperature is 378℃.

[0098] Second forging: The round cake is first upset along the Z-axis, then squared along the radial direction, and finally elongated and shaped along the X-axis. The upsetting ratio is 2, the elongation ratio is 1.84, the initial forging temperature is 470℃, the final forging temperature is 382℃, and the holding time between passes is 1 hour.

[0099] The post-forging deformation heat treatment is the same as in Example 1.

[0100] Comparative Example 5: The alloy ingots from the same batch of homogenized heat-treated materials as in Example 1 were forged.

[0101] First forging: First, the ingot is upset along the Z-axis, then drawn along the Z-axis, upset again, then squared along the radial direction and drawn along the X-axis and shaped. The first upsetting ratio is 1.5, the drawing ratio is 1.2, the second upsetting ratio is 1.8, the initial forging temperature is 472℃, and the final forging temperature is 341℃.

[0102] The post-forging deformation heat treatment is the same as in Example 1.

[0103] Comparative Example 6: The forged plate from Example 1 was subjected to T8 heat treatment. The specific process was as follows:

[0104] Solution treatment: The forged plate is subjected to solution quenching treatment at a temperature of 518℃ for 1.5 hours. The quenching medium is room temperature water, and the quenching transfer time is less than 10 seconds.

[0105] Pre-deformation: The quenched sample is pre-deformed on an 800t press with a pre-deformation amount of 5% and a pre-deformation completion time of less than 15 minutes.

[0106] Artificial aging: The pre-deformed sample is subjected to artificial aging treatment at an aging temperature of 162℃ for 24.5h.

[0107] Comparative Example 7: The forged alloy plate from Example 1 was subjected to T8 heat treatment. The specific process was as follows:

[0108] Solution treatment: The forged plate is subjected to solution quenching at a temperature of 519℃ for 1.5 hours. The quenching medium is room temperature water, and the quenching transfer time is less than 10 seconds.

[0109] Pre-deformation: The quenched sample is pre-deformed on an 800t press with a pre-deformation amount of 40% and a pre-deformation completion time of less than 15 minutes.

[0110] Artificial aging: The pre-deformed sample is subjected to artificial aging treatment at an aging temperature of 161℃ for 24 hours.

[0111] Comparative Example 8: The forged alloy plate from Example 1 was subjected to T8 heat treatment. The specific process was as follows:

[0112] Solution treatment: The forged plate is subjected to solution quenching treatment at a temperature of 518℃ for 1.5 hours. The quenching medium is room temperature water, and the quenching transfer time is less than 10 seconds.

[0113] Pre-deformation: The quenched sample is pre-deformed on an 800t press with a pre-deformation amount of 50% and a pre-deformation completion time of less than 15 minutes.

[0114] Artificial aging: The pre-deformed sample is subjected to artificial aging treatment at an aging temperature of 162℃ for 24.5h.

[0115] Comparative Example 9: The forged alloy plate from Example 1 was subjected to T8 heat treatment. The specific process was as follows:

[0116] Solution treatment: The forged plate is subjected to solution quenching treatment at a temperature of 518℃ for 1.5 hours. The quenching medium is room temperature water, and the quenching transfer time is less than 10 seconds.

[0117] Pre-deformation: The quenched sample is pre-deformed on an 800t press with a pre-deformation amount of 30% and a pre-deformation completion time of less than 15 minutes.

[0118] Artificial aging: The pre-deformed sample is subjected to artificial aging treatment at an aging temperature of 162℃ for 24.5h.

[0119] Comparative Example 10: The forged alloy plate from Comparative Example 2 was subjected to T8 heat treatment. The specific process was as follows:

[0120] Solution treatment: The forged plate is subjected to solution quenching treatment at a temperature of 518℃ for 1.5 hours. The quenching medium is room temperature water, and the quenching transfer time is less than 10 seconds.

[0121] Pre-deformation: The quenched sample is pre-deformed on an 800t press with a pre-deformation amount of 30% and a pre-deformation completion time of less than 15 minutes.

[0122] Artificial aging: The pre-deformed sample is subjected to artificial aging treatment at an aging temperature of 162℃ for 24.5h.

[0123] Comparative Example 11: The forged alloy plate from Comparative Example 3 was subjected to T8 heat treatment. The specific process was as follows:

[0124] Solution treatment: The forged plate is subjected to solution quenching treatment at a temperature of 518℃ for 1.5 hours. The quenching medium is room temperature water, and the quenching transfer time is less than 10 seconds.

[0125] Pre-deformation: The quenched sample is pre-deformed on an 800t press with a pre-deformation amount of 30% and a pre-deformation completion time of less than 15 minutes.

[0126] Artificial aging: The pre-deformed sample is subjected to artificial aging treatment at an aging temperature of 162℃ for 24.5h.

[0127] Comparative Example 12: The forged alloy plate from Comparative Example 4 was subjected to T8 heat treatment. The specific process was as follows:

[0128] Solution treatment: The forged plate is subjected to solution quenching treatment at a temperature of 518℃ for 1.5 hours. The quenching medium is room temperature water, and the quenching transfer time is less than 10 seconds.

[0129] Pre-deformation: The quenched sample is pre-deformed on an 800t press with a pre-deformation amount of 30% and a pre-deformation completion time of less than 15 minutes.

[0130] Artificial aging: The pre-deformed sample is subjected to artificial aging treatment at an aging temperature of 162℃ for 24.5h.

[0131] Comparative Example 13: The forged alloy plate from Comparative Example 5 was subjected to T8 heat treatment. The specific process was as follows:

[0132] Solution treatment: The forged plate is subjected to solution quenching treatment at a temperature of 518℃ for 1.5 hours. The quenching medium is room temperature water, and the quenching transfer time is less than 10 seconds.

[0133] Pre-deformation: The quenched sample is pre-deformed on an 800t press with a pre-deformation amount of 30% and a pre-deformation completion time of less than 15 minutes.

[0134] Artificial aging: The pre-deformed sample is subjected to artificial aging treatment at an aging temperature of 162℃ for 24.5h.

[0135] Table 1 lists the different forging and heat treatment schemes in the examples and comparative examples.

[0136]

[0137]

[0138] Table 2 shows the room temperature tensile properties after different forging and heat treatment in the examples and comparative examples.

[0139]

[0140]

[0141]

[0142] As can be seen from Table 1, the forging method of the present invention can ensure that no cracks occur when the pre-deformation deformation reaches 30% during subsequent deformation heat treatment.

[0143] As can be seen from Table 2, the forging and heat treatment methods of the present invention can produce aluminum-lithium alloy forged plates with uniform microstructure, low anisotropy, and high performance.

[0144] Compared with Comparative Example 1, the forging and heat treatment method of the present invention achieves a 100-130 MPa increase in peak tensile strength and a 200-240 MPa increase in yield strength compared with the conventional T6 state.

[0145] Compared with Comparative Examples 2 to 5, the forging and heat treatment method of the present invention yields forged plates with more uniform properties, and the deviations in transverse and longitudinal tensile strength are less than 1%, and the deviations in transverse and longitudinal yield strength are less than 1%.

[0146] Compared with Comparative Example 6, the heat treatment method of the present invention has higher tensile strength and yield strength.

[0147] Compared with Comparisons 7-8, the heat treatment method of the present invention can ensure that a high-strength forged plate will not crack.

[0148] Compared with Comparative Examples 9-13, the forging plate obtained by the forging method of the present invention can undergo a large amount of pre-deformation treatment during deformation heat treatment without cracking.

[0149] The forging and deformation heat treatment method of the present invention solves the problems of severe anisotropy, difficulty in grain refinement, and difficulty in heat treatment control of aluminum-lithium alloys, and prepares high-performance aluminum-lithium alloys with tensile strength higher than 600MPa, yield strength higher than 550MPa, elongation greater than 6%, and longitudinal and transverse tensile strength deviations of less than 1% and yield strength deviations of less than 3%.

[0150] The expected effect of the "multi-fire multi-directional forging" method of the present invention is to obtain aluminum-lithium alloy forging plates with uniform grain size, fine grains, and indistinct fiber orientation, good plasticity, and small deviations in transverse and longitudinal mechanical properties. Moreover, forging plates with this structure are suitable for deformation heat treatment methods with large deformation.

[0151] The expected effect of the "T8 deformation heat treatment" method of the present invention is to obtain aluminum-lithium alloy plates with low anisotropy and high performance, with longitudinal tensile strength higher than 600 MPa and yield strength higher than 550 MPa. Compared with the T6 state, the tensile strength is increased by 100-130 MPa and the yield strength is increased by 200-240 MPa, and the longitudinal and transverse tensile strength deviations are less than 1% and the yield strength deviations are less than 3%.

[0152] The forging and deformation heat treatment method for high-performance aluminum-lithium alloy plates provided by this invention has been described in detail above. Specific examples have been used to illustrate the structure and working principle of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make several improvements and modifications to this invention without departing from the principles of this invention, and these improvements and modifications also fall within the scope of protection of the claims of this invention.

Claims

1. A method for forging and deformation heat treatment of high-performance aluminum-lithium alloy plates, characterized in that: This includes multi-stage, multi-directional forging and deformation heat treatment, comprising the following steps: Step 1: Homogenization treatment. Heat the blank sample to 420℃~460℃ and hold for 10~16h; continue to heat to 485℃~505℃ and hold for 20h~26h, then air cool to room temperature. Step 2: Pre-forging heat treatment: The homogenized ingot is heated to 450℃~490℃ in the furnace and held for 7.5~12h before forging; Step 3: Multi-fire multi-directional forging, the forging is upset along the Z-axis, elongated and squared along the Y-axis, upset along the Y-axis, elongated along the X-axis, upset along the X-axis, elongated along the Z-axis, and finally upset and shaped along the Y-axis to obtain a thick plate. Step 3, the multi-fire multi-directional forging, includes the following steps: Step 31: First forging: Upset the ingot along the Z-axis, then elongate it along the Y-axis and then square it. The Z-axis upsetting ratio is ≥1.5, the Y-axis elongation ratio is ≥1.5, the initial forging temperature is ≥460℃, and the final forging temperature is ≥370℃. Step 32: Second forging: Upset the square plate along the Y-axis and then elongate it along the X-axis. The upsetting ratio along the Y-axis is ≥1.5, the elongation ratio along the X-axis is ≥1.5, the initial forging temperature is ≥460℃, the final forging temperature is ≥360℃, and the holding time between passes is ≥0.5h. Step 33: Third forging: Upset the square plate along the X-axis and then elongate it along the Z-axis. The upsetting ratio along the X-axis is ≥1.5, the elongation ratio along the Z-axis is ≥1.5, the initial forging temperature is ≥460℃, the final forging temperature is ≥360℃, and the holding time between passes is ≥0.5h. Step 34: Fourth forging: Upsetting the block along the Y-axis to form a thick plate, with a Y-axis upsetting ratio ≥2, initial forging temperature ≥460℃, final forging temperature ≥340℃, and holding time between passes ≥0.5h; Step 4: Deformation heat treatment. The plate obtained in Step 3 is subjected to T8 deformation heat treatment. The solution temperature is 510-520℃, the solution time is 1-2h, the quenching medium is room temperature water, the quenching transfer time is <10s, the aging temperature is 155-175℃, and the aging time is 18-26h. The T8 deformation heat treatment in step 4 includes the following steps. Step 41: Solution treatment, the forged plate is subjected to solution quenching treatment; Step 42: Pre-deformation, the quenched sample is pre-deformed on a press; Step 43: Artificial aging, the pre-deformed sample is subjected to artificial aging treatment; The press used in step 42 is an 800t press, with a pre-deformation amount of 10-30% and a pre-deformation completion time of <15min; The components and their mass percentages of the aluminum-lithium alloy are as follows: Li 0.7–1.3%, Cu 3.6–4.5%, Mg 0.2–0.8%, Zr 0.06–0.18%, Ag 0.2–0.8%, Zn≤0.25%, Fe<0.05%, Si<0.05%, Mn<0.001%, Ti<0.001%, H<0.0001%, with the balance being Al.

2. The method for forging and deformation heat treatment of high-performance aluminum-lithium alloy plates according to claim 1, characterized in that: The thickness of the plate in step 34 is 40mm.

3. The method for forging and deformation heat treatment of high-performance aluminum-lithium alloy plates according to claim 1, characterized in that: The aluminum-lithium alloy sheet prepared by this method has a longitudinal tensile strength >600MPa, a yield strength >550MPa, an elongation >6%, a longitudinal and transverse tensile strength deviation <1%, and a yield strength deviation <3%.

Images