Alloy skin forming die and method

Abstract

The application relates to an alloy skin forming die and method, and belongs to the technical field of metal plastic working, and solves the problems of low profile precision, poor integrity and high cost of an alloy skin in the prior art. The alloy skin forming die comprises an upper die and a lower die, and further comprises a gas quenching die. The alloy skin forming die provided by the application can be used for aluminum alloy local large deformation skin forming, an aluminum alloy local large deformation skin is prepared through a friction stir processing / fluid forming method, the manufactured aluminum alloy local large deformation skin has high precision and good integrity, and the aluminum alloy local deformation capacity can be improved. The alloy skin forming die provided by the application can also be used for aluminum lithium alloy skin forming, an aluminum lithium alloy skin is prepared through a superplasticity / gas quenching forming method, and finally, the aluminum lithium alloy skin not only has high profile precision, but also has high tensile strength performance, the process flow is simple, the processing cost is low, and the aluminum lithium alloy skin has good integrity and consistency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal plastic working, and relates to an alloy skin forming die and method, which are suitable for alloy skin manufacturing. BACKGROUND

[0002] The alloy forming die and method are important contents of part design. Different forming dies and methods have important influences on the manufacturing of complex parts of titanium alloy, aluminum alloy, aluminum-lithium alloy and high-temperature alloy. In the fields of aerospace, aviation and transportation, the overallization and light weight of alloy skin are higher and higher, and the manufacturing precision is higher and higher. Among them, the aluminum alloy local large deformation skin and the aluminum-lithium alloy skin are typical applications.

[0003] The plasticity of aluminum alloy at room temperature is not high, generally not more than 20%, and the high-temperature superplasticity is generally not more than 200%. Compared with titanium alloy superplastic forming, the aluminum alloy superplastic forming capacity is poor, which leads to the difficulty in manufacturing complex and irregular aluminum alloy local large deformation skin. At present, the complex and irregular aluminum alloy local large deformation skin mainly refers to the aluminum alloy local large deformation skin with non-circular arc and plane, irregular curved surface and a minimum circular corner of the bottom generally more than 3 times the thickness of the plate. At present, the preparation method of the skin mainly adopts fine-grained aluminum alloy plate, but the method has high process cost and poor fine-grained effect. The skin manufactured by the cold forming process has low profile precision and needs manual correction, which leads to a long process flow. The direct superplastic inflation forming process leads to serious local thinning of the product.

[0004] Aluminum-lithium alloy is a kind of light metal material. Due to the addition of Li element, the density of the aluminum-lithium alloy is lower than that of ordinary aluminum alloy, and the elastic modulus is higher. The addition of 1% Li element can reduce the density of the aluminum-lithium alloy by 3% and increase the elastic modulus by 6%, and can ensure good hardening effect of the alloy after quenching and artificial aging. In addition, the aluminum-lithium alloy has excellent corrosion resistance, good low-temperature performance and fatigue resistance, and has broad application prospects in the fields of aerospace and other fields such as rail transportation, automobile electronics and nuclear industry. With the wide application of aluminum-lithium alloy structural parts, the research on the manufacturing of aluminum-lithium alloy skin is particularly important. At present, the manufacturing methods of the aluminum-lithium alloy skin mainly include stretching forming, creep aging forming and roll bending forming. However, the forming precision is low, the efficiency is low, the cost is high and other factors greatly hinder the application of the aluminum-lithium alloy skin. SUMMARY

[0005] In view of the above analysis, the application aims to provide an alloy skin forming die and method to solve the problems of low profile precision, poor overallity and high cost of the alloy skin manufactured by the prior art.

[0006] The main purpose of the application is achieved by the following technical scheme.

[0007] In one aspect, the present application provides an alloy skin forming die, comprising an upper die and a lower die; the upper die has an upper die cavity, the upper die cavity has a fluid inlet communicating with the upper die cavity, the lower die has a lower die cavity, the lower die cavity is a groove; the top corner radius r and the bottom corner radius R of the lower die satisfy the relationship R≥0.5×s, r≥2×s, wherein s is the thickness of the alloy sheet; the groove width a and the groove depth b of the lower die cavity satisfy the relationship a≥b; the upper die cavity is square, the length c, the width d, the fluid inlet width e satisfy the relationship c>a, d>e.

[0008] Further, the present application provides an alloy skin forming die, further comprising a gas quenching die, the gas quenching die has a gas quenching die inlet and a gas quenching die outlet, the shape of the protruding part of the gas quenching die is consistent with the shape of the lower die cavity; the gas quenching die has M gas quenching die outlets, and adjacent gas quenching die outlets have a spacing.

[0009] In another aspect, the present application provides an alloy skin forming method, which uses the alloy skin forming die comprising an upper die and a lower die, and prepares an aluminum alloy local large deformation skin by a friction stir processing / fluid forming method, comprising the following steps:

[0010] Step 1: performing friction stir processing on a local area of an aluminum alloy sheet to form a friction stir processing site;

[0011] Step 2: deforming the friction stir processing site under the action of fluid pressure.

[0012] Further, in the step 1, the rotation speed n of the stir head of the friction stir processing is 200 rad / min-1000 rad / min, and the friction stir processing speed v is 50 mm / min-200 mm / min.

[0013] Further, in the step 1, the friction stir processing speed v, the rotation speed n of the stir head and the thickness s of the aluminum alloy sheet 1 satisfy the relationship:

[0014] v=α×n / s

[0015] Wherein, α is a conventional parameter, satisfying 1<α<10;

[0016] s is in mm, n is in rad / min, v is in mm / min, and α is in mm 2 / rad.

[0017] Further, the step 2 comprises:

[0018] Step 21: heating the fluid forming upper die and the fluid forming lower die to a set temperature;

[0019] Step 22: Place the aluminum alloy plate between the fluid forming upper die and the fluid forming lower die, and apply pressure F to compress the aluminum alloy plate;

[0020] Step 23: Pass fluid through the fluid inlet on the fluid forming upper die, and maintain a certain fluid pressure P and time;

[0021] Step 24: Take the aluminum alloy plate out from between the fluid forming upper die and the fluid forming lower die, cut off the process allowance, and clean the surface dirt to obtain the aluminum alloy locally large-deformation skin.

[0022] In another aspect, the application also provides an alloy skin forming method, which adopts the alloy skin forming die, further comprises a gas quenching die, and prepares an aluminum-lithium alloy skin through a superplastic / gas quenching forming method, and comprises the following steps:

[0023] Step 1: Superplastic form the aluminum-lithium alloy plate;

[0024] Step 2: Gas quench the aluminum-lithium alloy plate after superplastic forming.

[0025] Further, the step 1 comprises:

[0026] Step 11: Form n round holes on the top of the aluminum-lithium alloy plate, heat the superplastic forming upper die and the superplastic forming lower die to a preset temperature, and place the aluminum-lithium alloy plate between the superplastic forming upper die and the superplastic forming lower die and keep warm for 10-30 min;

[0027] Step 12: Pass gas between the aluminum-lithium alloy plate and the superplastic forming upper die through the superplastic forming upper die fluid inlet, and the aluminum-lithium alloy plate gradually adheres to the superplastic forming lower die.

[0028] Further, the step 2 comprises:

[0029] Step 21: After the aluminum-lithium alloy plate completely adheres to the cavity of the superplastic forming lower die, remove the superplastic forming upper die, put a hook in the round hole on the top of the aluminum-lithium alloy plate, connect the gas quenching die to the aluminum-lithium alloy plate through the hook, place the gas quenching die above the aluminum-lithium alloy plate, and make the protruding part of the gas quenching die completely placed in the cavity of the superplastic forming lower die;

[0030] Step 22: Move the gas quenching die and the aluminum-lithium alloy plate upward together, and pass gas through the gas quenching die gas inlet at the same time, and the gas is discharged through the gas quenching die gas outlet, so as to form a gas quenching layer between the gas quenching die and the aluminum-lithium alloy plate;

[0031] Step 23: After the aluminum-lithium alloy plate is cooled to room temperature, take the aluminum-lithium alloy plate off the gas quenching die.

[0032] Furthermore, the length of the aluminum-lithium alloy plate is f, there are M gas quenching mold outlets on the gas quenching mold, the spacing between adjacent gas quenching mold outlets is g, the diameter of the gas quenching mold outlet is h, satisfying the relationship g≤f×h / 10, the number of gas quenching mold outlets M≥f / g, and the units of f, g, and h are mm.

[0033] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0034] 1. By employing the alloy skin forming die provided by the present invention, it is possible to form aluminum alloy skins with large local deformations. Furthermore, through the special design of the lower die cavity structure, it is possible to manufacture thin-walled aluminum alloy skins with more complex shapes and greater deformations, such as non-circular arcs, flat surfaces, and irregular curved surfaces. The minimum bottom fillet is generally greater than three times the thickness of the sheet metal, while being less susceptible to cracking during the process, thereby improving the yield rate. The present invention successfully applies a forming die including a gas quenching die to the forming of aluminum alloy skins with large local deformations, successfully manufacturing aluminum-lithium alloy skins with complex, special-shaped curved surfaces such as non-circular arcs, flat surfaces, and irregular curved surfaces, and can achieve the integral forming of parts up to 2 meters in length.

[0035] 2. The alloy skin forming die provided by the present invention can be used for forming aluminum alloy skin with local large deformation. When forming the aluminum alloy skin with local large deformation, the aluminum alloy skin with local large deformation is prepared by the stir friction treatment / fluid forming method. The stir friction treatment of the aluminum alloy locally reduces the processing cost significantly. In combination with fluid forming, the aluminum alloy skin with local large deformation has high precision and good integrity, which can improve the local deformation ability of the aluminum alloy. Compared with the use of fine-grained aluminum alloy plates as a whole, the present invention only stirs the friction treatment on the aluminum alloy locally, and the product cost can be reduced from 2,000 yuan / kg to 1,000 yuan / kg, and the grain size can be reduced from tens of microns. It is reduced to a few microns, with lower cost and better fine-grain effect; compared with the cold forming process, the surface accuracy of the aluminum alloy local large deformation skin manufactured by the present invention is higher, increased from ±1mm to ±0.3mm, no manual correction is required, and the process flow is shorter; compared with direct superplastic inflation forming, the wall thickness uniformity of the aluminum alloy local large deformation skin of the present invention can be increased from ±20% to ±10%, the wall thickness uniformity is better, the weight can be reduced by 10%, and the weight reduction effect is more obvious; due to the local stir friction treatment, aluminum alloy skin with gradient performance can be manufactured according to use requirements, and the performance of the stir friction treated part can be improved by more than 1 times compared with the high-temperature elongation of the part without stir friction treatment.

[0036] 3、The alloy skin forming die provided by the application can also be used for forming the aluminum-lithium alloy skin, when the aluminum-lithium alloy skin is formed, the alloy skin forming die further comprises a gas quenching die, the aluminum-lithium alloy skin is prepared through the superplasticity / gas quenching forming method, the finally prepared aluminum-lithium alloy skin not only has higher profile precision, but also has higher tensile strength performance, the process flow is simple, the processing cost is low, and the aluminum-lithium alloy skin has better integrity and consistency. Compared with the cold forming process, the profile precision of the aluminum-lithium alloy skin manufactured by the application is improved from ±1mm to ±0.3mm, the profile precision is higher, and the size consistency is better; compared with the single superplasticity forming, the tensile strength performance of the aluminum-lithium alloy skin manufactured by the application can be improved by more than 20%, the tensile strength performance is higher, and the part bearing performance is better; compared with the casting process, the weight control of the aluminum-lithium alloy skin manufactured by the application is accurate, the weight reduction effect is better, and the weight is reduced by more than 10%; compared with the heat treatment or shape correction after forming, the application saves the manual correction process, the cost is reduced from 5000 yuan / piece to 4000 yuan / piece, the process flow is simple, and the processing cost is low; compared with the forming+splicing welding scheme, the application can manufacture complex irregular curved surface aluminum-lithium alloy skin such as non-circular arc and plane, can realize the integral forming of the part with a length of 2m, does not need splicing welding, and the prepared aluminum-lithium alloy skin has better integrity and consistency.

[0037] The above technical solutions in the application can also be combined with each other to realize more preferred combination solutions. Other features and advantages of the application will be described in the subsequent description, and some advantages will become apparent from the description or be understood by implementing the application. The objects and other advantages of the application can be realized and obtained from the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0038] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application.

[0039] Figure 1 A schematic diagram for implementing aluminum alloy local large deformation skin friction stir processing / fluid forming by using the alloy skin forming die of the application;

[0040] Figure 2 A schematic diagram for forming an aluminum alloy plate local friction stir processing site when an aluminum alloy local large deformation skin is formed;

[0041] Figure 3 A schematic diagram for the process of aluminum alloy local large deformation skin friction stir processing / fluid forming;

[0042] Figure 4 A schematic diagram for an aluminum alloy local large deformation skin;

[0043] Figure 5 Schematic diagram of aluminum lithium alloy skin superplastic forming before using the alloy skin forming die of the present application;

[0044] Figure 6 Schematic diagram of aluminum lithium alloy skin superplastic forming after using the alloy skin forming die of the present application;

[0045] Figure 7 Schematic diagram of aluminum lithium alloy skin gas quenching before using the alloy skin forming die of the present application;

[0046] Figure 8 Schematic diagram of aluminum lithium alloy skin gas quenching after using the alloy skin forming die of the present application.

[0047] Figure 9 Schematic diagram of aluminum lithium alloy skin;

[0048] Figures: 1-aluminum alloy plate, 2-stir friction processing site, 3-upper die, 4-fluid inlet, 5-lower die, 6-upper die cavity, 7-lower die cavity, 8-gas quenching die, 9-gas quenching die gas inlet, 10-gas quenching die gas outlet, 11-aluminum lithium alloy plate, 12-gas quenching layer, s-aluminum alloy plate thickness, r-lower die top round corner, R-lower die bottom round corner, a-lower die cavity groove width, b-lower die cavity groove depth, c-upper die cavity length, d-upper die cavity width, e-fluid inlet width, f-aluminum lithium alloy plate length, g-distance between adjacent gas quenching die gas outlets, h-diameter of gas quenching die gas outlet, T-aluminum lithium alloy plate thickness, t-gap between aluminum lithium alloy plate and gas quenching die. DETAILED DESCRIPTION

[0049] The preferred embodiments of the present application will be described in detail below with reference to the drawings, wherein the drawings constitute a part of this application and serve to explain the principles of the present application together with the embodiments of the present application, but are not intended to limit the scope of the present application.

[0050] In the fields of aerospace, aviation, transportation, etc., the integration and lightweight degree of alloy skin is getting higher and higher, and the manufacturing precision requirement is also getting higher and higher, among which, aluminum alloy local large deformation skin and aluminum lithium alloy skin are typical applications.

[0051] The plasticity of aluminum alloy at room temperature is not high, generally not more than 20%, and the high-temperature superplasticity is generally not more than 200%, compared with titanium alloy superplastic forming, the superplastic forming capacity of aluminum alloy is poor, which leads to difficulty in manufacturing complex aluminum alloy local large deformation skin. At present, the complex aluminum alloy local large deformation skin mainly refers to the aluminum alloy local large deformation skin with non-circular arc and plane, irregular curved surface, and the minimum circular angle at the bottom is generally more than 3 times the thickness of the plate. At present, the preparation method of the skin mainly adopts fine-grained aluminum alloy plate, but the process cost is high, and the fine-grained effect is poor; the skin manufactured by the cold forming process has low profile precision, and manual correction is required, so that the process flow is long; and the direct superplastic gas inflation forming process leads to serious local thinning of the product.

[0052] At present, the manufacturing methods of aluminum lithium alloy skin mainly include stretching forming, creep aging forming, roll bending forming and the like, but the forming precision is not high, the efficiency is low, the cost is high and the like, which greatly hinders the application of the aluminum lithium alloy skin.

[0053] Based on this, the alloy skin forming die is provided.

[0054] The structure of the upper die and the lower die is shown in Figure 1 、 3 , 5, 6. The upper die 3 is provided with an upper die cavity 6, the side of the upper die cavity 6 is provided with a fluid inlet 4 in communication with the upper die cavity 6, and the lower die 5 is provided with a lower die cavity 7. The lower die cavity 7 is a groove.

[0055] Specifically, the thickness s of the alloy plate, the top corner r and the bottom corner R of the lower die 5, the relationship R is greater than or equal to 0.5 times s, and the relationship r is greater than or equal to 2 times s, the groove width a and the groove depth b of the lower die cavity 7, the relationship a is greater than or equal to b. The upper die cavity 6 is square, the length c, the width d, the width e of the fluid inlet 4, the relationship c is greater than a, and the relationship d is greater than e.

[0056] In the present application, the cavity structure of the lower die is designed, including the top corner, the bottom corner, the cavity depth and the width, and the size of the fluid inlet, which satisfies the relationship, so that the successful forming of the part can be ensured without breaking in the process.

[0057] By using the alloy skin forming die, the forming of the aluminum alloy local large deformation skin can be realized, and through the special design of the cavity structure of the lower die, the aluminum alloy thin-walled skin with more complex shape and larger deformation, such as non-circular arc and plane, irregular curved surface, and the minimum circular angle at the bottom is generally more than 3 times the thickness of the plate, and the skin is not easy to break in the process, and the yield is improved.

[0058] The forming die is successfully applied to the forming of the aluminum alloy local large deformation skin, and based on this, the forming method of the aluminum alloy local large deformation skin is also provided, the alloy skin forming die is adopted, and specifically, the aluminum alloy local large deformation skin is prepared by the friction stir processing / fluid forming method, and the method comprises the following steps:

[0059] Step 1: The local region of the aluminum alloy plate is subjected to friction stir processing to form a friction stir processing site;

[0060] Step 2: Local deformation of the friction stir processing site is performed under the action of fluid pressure.

[0061] Specifically, in the step 1, the proportional relationship between the size of the local region and the overall size of the aluminum alloy plate is determined by the size of the forming region, the size of the forming region is determined according to the actual preparation requirement, the grain can be refined by friction stir processing, and the high temperature elongation of the skin is improved. The length of the friction stir processing site is equal to the groove width a of the lower die cavity 7.

[0062] Wherein the friction stir processing speed v, the rotation speed n of the stirring head and the thickness s of the aluminum alloy plate 1 satisfy the relationship:

[0063] v=α×n / s

[0064] Wherein, α is a conventional parameter, and satisfies 1 < α < 10;

[0065] s is mm, n is rad / min, v is mm / min, and α is mm 2 / rad;

[0066] Satisfying the relationship can improve the grain refinement degree of the local region of the aluminum alloy plate in the friction stir processing process, and is beneficial to improve the high temperature elongation of the skin. In the step 1, the rotation speed n of the stirring head in the friction stir processing is 200 rad / min-1000 rad / min, and the friction stir processing speed v is 50 mm / min-200 mm / min. For example, the rotation speed n of the stirring head in the friction stir processing is 300 rad / min, 400 rad / min, 500 rad / min, 600 rad / min, 700 rad / min, 800 rad / min, 900 rad / min; and the processing speed v is 80 mm / min, 100 mm / min, 150 mm / min, 180 mm / min.

[0067] Specifically, in the step 2, the local deformation of the friction stir processing site is performed by the action of fluid pressure, and the fluid forming process comprises:

[0068] Step 21: heating the fluid forming upper die and the fluid forming lower die to a set temperature;

[0069] Step 22: placing the aluminum alloy plate between the fluid forming upper die and the fluid forming lower die, and applying pressure F to compress the aluminum alloy plate;

[0070] Step 23: passing fluid through the fluid inlet on the fluid forming upper die, and maintaining a certain fluid pressure P and time;

[0071] Step 24: removing the aluminum alloy plate from between the fluid forming upper die and the fluid forming lower die, cutting off the process allowance, and cleaning the surface dirt to obtain the aluminum alloy locally large deformation skin.

[0072] Specifically, in the above step 21, the set temperature is determined by the forming characteristics of the aluminum alloy plate material itself, and within the temperature range required for material forming, the temperature corresponding to the high elongation rate of the material is selected as much as possible. When the fluid is a liquid, 10℃≤T≤40℃, for example, 20℃, 25℃, 30℃, 35℃. When the fluid is a gas, 350℃≤T≤550℃, for example, 400℃, 450℃, 500℃.

[0073] Specifically, in the above step 21, the fluid forming upper die 3 has an upper die cavity 6, and the side of the upper die cavity 6 has a fluid inlet 4 communicating with the upper die cavity. The fluid forming lower die 5 has a lower die cavity 7; the fluid forming lower die 5 has a top round corner r and a bottom round corner R; and the lower die cavity 7 is a groove.

[0074] Specifically, in the above step 22, the applied pressure F, the groove width a of the lower die cavity, and the fluid pressure P have the following relationship: F≥a 2 ×P; wherein F is in N, a is in mm, and P is in MPa. The fluid forming upper die 3 serves as a compression part, the fluid forming lower die 5 serves as a forming surface, the gap of the compression part is equal to the material thickness of the aluminum alloy plate 1, and the forming precision of the part is ensured. The aluminum alloy plate is compressed by applying pressure to the fluid forming upper die 3 through a hydraulic machine.

[0075] Specifically, in the above step 23, the fluid can be a liquid or a gas. The liquid is usually water or oil, and the gas is usually nitrogen or argon. During the fluid pressurization process, the pressure rise rate is generally not greater than 0.1 MPa / min, and the following condition is met: P≥R p ×s / R, so as to ensure that the part can be completely die-bonded under the action of fluid pressure during the forming process. Wherein, P is the fluid pressure, in MPa; R p is the yield strength, in MPa; and s is the thickness of the aluminum alloy plate, in mm.

[0076] Specifically, in the step 24, the process allowance is removed by laser cutting, which greatly reduces the processing time, reduces the processing cost and improves the workpiece quality. By the way of alkaline washing and then acid washing, the oil stains, metal ions and natural oxides and other surface dirt on the surface of the locally large deformed skin of the aluminum alloy are removed, so that the locally large deformed skin of the aluminum alloy has a clean and uniform color surface.

[0077] By the alloy forming die and the friction stir processing / fluid forming method, the locally deformed capacity of the aluminum alloy can be improved, the aluminum alloy complex large deformed skin that cannot be manufactured by conventional processes can be manufactured, the friction stir processing is performed on the aluminum alloy locally, the processing cost is greatly reduced, and the fluid forming is combined to manufacture the aluminum alloy locally large deformed skin with high precision and good integrity.

[0078] The application scope of the alloy skin forming die provided by the application is not limited to the forming of the locally large deformed skin of the aluminum alloy, and can be expanded to the forming of other alloys. Therefore, the application also provides an alloy skin forming die, which further comprises a gas quenching die in addition to the upper die and the lower die.

[0079] Specifically, as shown in the accompanying drawings, Figure 7 The gas quenching die inlet 9 is a horizontal through channel structure, the gas quenching die outlet 10 is vertically communicated with the through direction of the gas quenching die inlet 9, the number of the gas quenching die outlets 10 is M≥f / g, wherein f is the length of the alloy plate, g is the spacing between adjacent gas quenching die outlets, h is the diameter of the gas quenching die outlet, and there is a relationship g≤f×h / 10, the units of f, g and h are m, and the convex part of the gas quenching die 8 is consistent with the shape of the lower die cavity 7.

[0080] The application successfully applies the above-mentioned forming die including the gas quenching die 8 to the forming of the locally large deformed skin of the aluminum alloy and the aluminum lithium alloy skin, based on this, the application also provides a forming method of the aluminum lithium alloy skin, which adopts the alloy skin forming die and further comprises a gas quenching die, specifically, an aluminum lithium alloy skin is prepared by the superplastic / gas quenching forming method, which comprises the following steps:

[0081] Step 1: superplastic forming of the aluminum lithium alloy plate;

[0082] Step 2: gas quenching of the aluminum lithium alloy plate after superplastic forming.

[0083] Specifically, in the step 1, the aluminum lithium alloy plate is superplastically formed, and the superplastic forming process comprises:

[0084] Step 11: n holes are punched on the top of the aluminum-lithium alloy plate 11, the superplastic forming upper die 3 and the superplastic forming lower die 5 are heated to a preset temperature, and the aluminum-lithium alloy plate 11 is placed between the superplastic forming upper die 3 and the superplastic forming lower die 5 and kept for 10-30 min;

[0085] Step 12: gas is introduced between the aluminum-lithium alloy plate 11 and the superplastic forming upper die 3 through the superplastic forming upper die fluid inlet 4, and the aluminum-lithium alloy plate gradually adheres to the superplastic forming lower die 5;

[0086] Specifically, in step 11, the setting temperature is determined by the forming characteristics of the aluminum-lithium alloy plate material itself, and within the temperature range required for material forming, the temperature corresponding to the high elongation rate of the material is selected as much as possible. The preset temperature range is 450-550°C, and exemplary, such as 450°C, 480°C, 500°C, and 550°C. Through the heat preservation operation, the heating temperature of the aluminum-lithium alloy plate is more uniform, and the deformation ability is better. The length of the aluminum-lithium alloy plate is f, in mm, and a hole is punched on the top of the aluminum-lithium alloy plate every 50 mm, and the number of holes n = f / 50.

[0087] Specifically, in step 11, the superplastic forming upper die 3 has an upper die cavity 6, the side of the upper die cavity 6 has a fluid inlet 4 communicating with the upper die cavity 6, and the superplastic forming lower die 5 has a lower die cavity 7; the lower die cavity 7 is a groove.

[0088] Specifically, in step 12, the gas is usually nitrogen or argon, and a certain gas pressure is maintained to make the aluminum-lithium alloy plate 11 and the superplastic forming lower die 5 completely adhere to each other. The gas pressure range is 0.3-3 MPa, and exemplary, such as 0.5 MPa, 1 MPa, 1.5 MPa, 2 MPa, and 2.5 MPa.

[0089] Specifically, in the above step 2, the superplastically formed aluminum-lithium alloy plate is gas quenched, and the gas quenching process includes:

[0090] Step 21: after the aluminum-lithium alloy plate 11 completely adheres to the superplastic forming lower die cavity 7, the superplastic forming upper die 3 is removed, a hook is placed in the hole on the top of the aluminum-lithium alloy plate 11, the gas quenching die 8 is connected to the aluminum-lithium alloy plate 11 through the hook, placed above the aluminum-lithium alloy plate 11, and the protruding part of the gas quenching die 8 is completely placed in the superplastic forming lower die cavity 7;

[0091] Step 22: the gas quenching die 8 and the aluminum-lithium alloy plate 11 are moved upward together, at the same time, gas is introduced through the gas quenching die gas inlet 9, and the gas is discharged through the gas quenching die gas outlet 10, forming a gas quenching layer 12 between the gas quenching die 8 and the aluminum-lithium alloy plate 11;

[0092] Step 23: After the aluminum-lithium alloy plate 11 is cooled to room temperature, the aluminum-lithium alloy plate 11 is taken off from the gas quenching mold 8.

[0093] Specifically, in step 21, the gas quenching mold 8 is provided with a gas quenching mold gas inlet 9 and a gas quenching mold gas outlet 10, and the protruding part of the gas quenching mold 8 has the same shape as the lower mold cavity 7. The protruding part of the gas quenching mold 8 has the same number of round holes as the position of the round hole at the top of the aluminum-lithium alloy plate. The gap between the aluminum-lithium alloy plate 11 and the gas quenching mold 8 is t, which satisfies the relationship t≤0.5×T, where T is the thickness of the aluminum-lithium alloy plate. Satisfying this relationship can ensure that the gas quenching effect is sufficient.

[0094] Specifically, in step 22, the length of the aluminum-lithium alloy plate 11 is f, the gas quenching mold 8 has M gas quenching mold gas outlets 10, the distance between adjacent gas quenching mold gas outlets 10 is g, the diameter of the gas quenching mold gas outlet 10 is h, and the relationship g≤f×h / 10 is satisfied, and the number of gas quenching mold gas outlets 10 M≥a / b, the units of f, g, and h are mm.

[0095] The gas is introduced through the gas quenching mold gas inlet 9, and the gas pressure is P, and the thickness T of the aluminum-lithium alloy plate 11 satisfies the relationship P=γ×T, γ=0.1MPa / mm~0.2MPa / mm, P is in MPa, and T is in mm.

[0096] The gas is usually helium, nitrogen or argon. The greater the gas pressure, the better the mechanical properties of the prepared aluminum-lithium alloy wall plate skin. However, too great a gas pressure can also easily cause the prepared part to deform, so it is necessary to select an appropriate gas pressure to satisfy the above relationship, so as to ensure good gas quenching effect.

[0097] Specifically, in step 23, during the cooling process of the aluminum-lithium alloy plate 11, the continuous introduction of gas is realized through the gas quenching layer 12, which satisfies the relationship described in step 22. The gas is continuously introduced until the aluminum alloy plate is cooled to room temperature, and whether it is cooled to room temperature is detected by an infrared temperature measuring device.

[0098] By using the alloy forming mold and the superplastic / gas quenching forming method of the present application, the aluminum-lithium alloy skin prepared has not only high surface precision, but also high tensile strength performance. The process flow is simple, the processing cost is low, and the aluminum-lithium alloy skin has good integrity and consistency.

[0099] Example 1

[0100] The alloy skin forming mold and method of the present embodiment use an upper mold and a lower mold for the alloy skin forming mold, and the alloy skin is a local large deformation skin of an aluminum alloy. The forming method is a friction stir processing / fluid forming method.

[0101] The alloy skin forming die used includes: fluid forming upper die 3, fluid forming lower die 5. The fluid forming upper die 3 leaves an upper die cavity 6, and the upper die cavity 6 is provided with a fluid inlet 4 communicating with the upper die cavity 6 on the side. The fluid forming lower die 5 leaves a lower die cavity 7. The lower die cavity 7 is a groove. An aluminum alloy plate 1 is selected, and a friction stir processing site 2 is formed by friction stir processing in a local area of the aluminum alloy plate 1. The aluminum alloy plate 1 is clamped between the fluid forming upper die 3 and the fluid forming lower die 5 by the pressure of a hydraulic machine, and the fluid inlet 4 communicating with the upper die cavity 6 is left on the side of the upper die cavity 6. The thickness s of the aluminum alloy plate 1 is selected to be 2mm, the top round corner r of the fluid forming lower die 5 is 4mm, and the bottom round corner R is 2mm, which satisfies the relationship R≥0.5×s, r≥2×s. The groove width a of the lower die cavity 7 is 20mm and the groove depth b is 20mm, which satisfies the relationship a≥b. The width e of the fluid inlet 4 is 6mm, the length c of the upper die cavity 6 is 25mm, and the width d is 10mm, which satisfies the relationship c>a, d>e. It is ensured that the part is not easy to break during forming.

[0102] The aluminum alloy local large deformation skin friction stir processing / fluid forming method of the embodiment is carried out according to the following process steps:

[0103] Step 1: The aluminum alloy plate 1 is subjected to friction stir processing in a local area to form a friction stir processing site 2. The rotation speed n of the stirring head of the friction stir processing is 300 rad / min, and the processing speed v is 180 mm / min. The processing speed v of the friction stir processing and the rotation speed n of the stirring head are related to the thickness s of the aluminum alloy plate 1, and there is a relationship v=α×n / s, α=1.2, which satisfies 1<α<10, s unit is mm, n unit is rad / min, v unit is mm / min, and α unit is mm / rad, as shown in the following formula: 2 Figure 1

[0104] Step 2: Local deformation of the friction stir processing site is carried out under the action of fluid pressure.

[0105] Step 21: The fluid forming upper die 3 and the fluid forming lower die 5 are heated to a set temperature, the fluid is argon, and the set temperature T is 450℃.

[0106] Step 22: The aluminum alloy plate 1 is placed between the fluid forming upper die 3 and the fluid forming lower die 5, and the aluminum alloy plate 1 is pressed tightly by the hydraulic machine. The applied pressure F, the groove width a of the fluid forming lower die 5, and the fluid pressure P in step 23 are all 10MPa, and F is taken as 5000N, which satisfies the relationship F=5000≥a 2 ×P=20 2 ×10=4000, F unit is N, a unit is mm, and P unit is MPa, as shown in the following formula: Figure 2 ​​​

[0107] Step 23: fluid argon is introduced through the fluid inlet 4 connected to the side of the upper die cavity 6, and a certain fluid pressure and time are maintained; the fluid pressure P = 10 MPa, the thickness s = 2 mm of the aluminum alloy plate 1, and the yield strength R p = 8 MPa, the bottom fillet R = 2 mm of the fluid forming lower die 5, and the relationship P = 10 MPa > R p × s / R = 8 × 2 / 3 = 8 MPa, P is in units of MPa, R p is in units of MPa, s is in units of mm, and R is in units of mm, as shown in Figure 3 .

[0108] Step 24: the aluminum alloy plate 1 is taken out from between the fluid forming upper die 3 and the fluid forming lower die 5, the process allowance is cut off by laser cutting, the surface dirt is cleaned by alkaline washing and then acid washing, and the aluminum alloy locally large deformation skin is obtained.

[0109] The profile accuracy of the aluminum alloy locally large deformation skin prepared by this method is ± 0.3 mm, the minimum outer fillet can be smaller than the thickness of the aluminum alloy plate, the wall thickness uniformity is controlled within ± 10%, and the surface roughness Ra is 3.2. Compared with the existing process for preparing the aluminum alloy skin, the structural weight is reduced by more than 10%, and the processing cycle is shortened by 30%. The specific performance indicators of Example 1 are shown in the following table.

[0110] Table 1 Performance indicators of the aluminum alloy locally large deformation skin of Example 1

[0111]

[0112] Example 1-1

[0113] In this embodiment, in step 1, the rotation speed of the friction stir processing stir head is selected as 330 r / min, the processing speed is 180 mm / min, and the other processing conditions are the same as those of Example 1.

[0114] Compared with the prior art, the aluminum alloy locally large deformation skin prepared by this embodiment can further improve the wall thickness uniformity of the aluminum alloy locally large deformation skin to ± 8%, and can reduce the structural weight by more than 12%, which is crucial for aerospace products.

[0115] Example 1-2

[0116] In this embodiment, in step 21, the preset temperature is selected as 500℃, and the other processing conditions are the same as those of Example 1.

[0117] The aluminum alloy partially large deformation skin prepared by the embodiment can further improve the wall thickness uniformity of the aluminum alloy partially large deformation skin, and the wall thickness uniformity is improved by ±5% compared with that of the embodiment 1. The profile accuracy is ±0.2 mm, which can make the structure weight reduce by more than 10% compared with the prior art, which is very important for aerospace products.

[0118] Embodiment 1-3

[0119] In the embodiment, in step 23, argon is introduced through the fluid inlet 4 communicated with the side surface of the upper die cavity 6, and a certain fluid pressure P is maintained, the fluid pressure P = 12 MPa, the thickness s of the aluminum alloy plate 1 = 2 mm, and the yield strength R p = 8 MPa, the bottom fillet R of the fluid forming lower die 5 = 2 mm, and the relationship P = 12 MPa ≥ R p × s / R = 8 × 2 / 3 = 8 MPa, P is in MPa, R p is in MPa, s is in mm, and R is in mm. Other processing conditions are the same as those of the embodiment 1.

[0120] The aluminum alloy partially large deformation skin prepared by the embodiment can further improve the profile accuracy of the aluminum alloy partially large deformation skin to ±0.2 mm compared with that of the embodiment 1, which is very important for aerospace products.

[0121] Embodiment 1-4

[0122] In the embodiment, in step 22, the aluminum alloy plate 1 is placed between the fluid forming upper die 3 and the fluid forming lower die 5, and the aluminum alloy plate 1 is pressed tightly by applying pressure by the hydraulic machine; the applied pressure F, the groove width a of the fluid forming lower die 5, the fluid pressure P in step 23 = 10 MPa, F = 6000 N is taken, and the relationship F = 6000 ≥ a 2 × P = 20 2 × 10 = 4000, F is in N, a is in mm, and P is in MPa. Other processing conditions are the same as those of the embodiment 1.

[0123] The aluminum alloy partially large deformation skin prepared by the embodiment can further improve the profile accuracy of the aluminum alloy partially large deformation skin to ±0.28 mm compared with that of the embodiment 1.

[0124] Embodiment 1-5

[0125] In the embodiment, in step 21: the fluid forming upper die 3 and the fluid forming lower die 5 are heated to a set temperature, the fluid is hydraulic oil, and the set temperature T = 40℃. Other processing conditions are the same as those of the embodiment 1.

[0126] The aluminum alloy partially large deformation skin prepared by the embodiment can further improve the wall thickness uniformity of the aluminum alloy partially large deformation skin, and the wall thickness uniformity is improved by ±8% compared with that of the embodiment 1.

[0127] Comparative example 1

[0128] The forming die is selected, the thickness s of the aluminum alloy plate 1 is 2 mm, the top corner radius r of the fluid forming lower die 5 is 3 mm and the bottom corner radius R is 0.5 mm, and the relationship R≥0.5×s, r≥2×s is not satisfied. The groove width a of the lower die cavity 7 is 20 mm and the groove depth b is 25 mm, which does not satisfy the relationship a≥b. The preparation method is the same as that of the embodiment 1. The width c of the upper die cavity 6 is 15 mm, which does not satisfy c>a.

[0129] The aluminum alloy partially large deformation skin prepared by the comparative example is obviously weaker than that of the embodiment 1, the profile accuracy is ±0.35 mm, and the wall thickness uniformity is controlled within ±15%, which is obviously weaker than that of the embodiment 1.

[0130] Table 2 Performance indicators of the aluminum alloy partially large deformation skin of the comparative example 1 and the embodiment 1 series

[0131]

[0132] Embodiment 2

[0133] The alloy skin forming die and method of the embodiment, the alloy skin forming die further includes a gas quenching die, the alloy skin is an aluminum lithium alloy skin, and the forming method is a superplastic / gas quenching forming method.

[0134] The alloy skin forming die includes a superplastic forming upper die 3, a superplastic forming lower die 5, and a gas quenching die 8.

[0135] The superplastic forming upper die 3 has an upper die cavity 6, and the side of the upper die cavity 6 is provided with a fluid inlet 4 communicating with the upper die cavity 6. The superplastic forming lower die 5 has a lower die cavity 7, which is a groove. The thickness T of the aluminum lithium alloy plate 11 is 2 mm, the top corner radius r of the superplastic forming lower die 5 is 4 mm and the bottom corner radius R is 2 mm, and the relationship R≥0.5×T, r≥2×T is satisfied. The groove width a of the lower die cavity 7 is 20 mm and the groove depth b is 20 mm, and the relationship a≥b is satisfied. The upper die cavity 6 is square, the length c is 25 mm, the width d is 4 mm, the fluid inlet width e is 2 mm, and the relationship c>a, d>e is satisfied.

[0136] The gas quenching die 8 is provided with a gas quenching die gas inlet 9 and a gas quenching die gas outlet 10. The shape of the gas quenching die protruding part is consistent with that of the superplastic forming lower die cavity, and the gas quenching die 8 has the same number of round holes as the position of the top round hole of the aluminum lithium alloy plate.

[0137] When superplastic forming, the aluminum-lithium alloy sheet 11 is located between the superplastic forming upper die 3 and the superplastic forming lower die 5, and when gas quenching, the aluminum-lithium alloy sheet 11 is located between the gas quenching die 8 and the superplastic forming lower die 5. The thickness of the aluminum-lithium alloy sheet 11 is selected as T = 2 mm, the gap between the aluminum-lithium alloy sheet 11 and the gas quenching die 8 is t = 0.5 mm, and the relationship t ≤ 0.5 × T is satisfied. The length of the aluminum-lithium alloy sheet 11 is selected as f = 300 mm, there are M gas quenching die gas outlets 10 on the gas quenching die 8, the spacing between adjacent gas quenching die gas outlets 10 is g = 50 mm, the diameter of the gas quenching die gas outlet 10 is h = 2 mm, the relationship g ≤ f × h / 10 = 300 × 2 / 10 = 60 is satisfied, and the number of gas quenching die gas outlets 10 M ≥ f / g = 5. The units of f, g, and h are mm.

[0138] The aluminum-lithium alloy skin superplastic / gas quenching forming method of the embodiment is performed according to the following process steps:

[0139] Step 1: superplastic forming of the aluminum-lithium alloy sheet;

[0140] Step 11: forming n round holes on the top of the aluminum-lithium alloy sheet, heating the superplastic forming upper die 3 and the superplastic forming lower die 5 to a preset temperature, and placing the aluminum-lithium alloy sheet 11 between the superplastic forming upper die 3 and the superplastic forming lower die 5. The preset temperature is selected as 500 ℃, and the holding time is 15 min. The length of the aluminum-lithium alloy sheet 11 is f = 300 mm, and a round hole is formed on the top of the aluminum-lithium alloy sheet every 50 mm, and the number of round holes n = f / 50 = 6.

[0141] Step 12: passing gas between the aluminum-lithium alloy sheet 11 and the superplastic forming upper die 3 through the superplastic forming fluid inlet 4, and the aluminum-lithium alloy sheet 11 gradually adheres to the superplastic forming lower die 5. The gas selected is nitrogen, and the gas pressure is 1 MPa.

[0142] Step 2: gas quenching of the superplastically formed aluminum-lithium alloy sheet.

[0143] Step 21: after the aluminum-lithium alloy sheet 11 is completely adhered to the superplastic forming lower die cavity 7, the superplastic forming upper die 3 is removed, a hook is placed in the round hole on the top of the aluminum-lithium alloy sheet 11, the gas quenching die 8 is connected to the aluminum-lithium alloy sheet 11 through the hook, the gas quenching die 8 is placed above the aluminum-lithium alloy sheet 11, and the protruding part of the gas quenching die is completely placed in the superplastic forming lower die cavity 7.

[0144] Step 22: Move the gas quenching mold 8 and the aluminum-lithium alloy plate 11 upward together, and at the same time, pass the gas through the gas quenching mold gas inlet 9, and the gas is discharged through the gas quenching mold gas outlet 10, forming a gas quenching layer 12 between the gas quenching mold 8 and the aluminum-lithium alloy plate 11; the gas pressure passed through the gas quenching mold gas inlet 9 is P = 0.2 MPa, the thickness of the aluminum-lithium alloy plate 1 is T = 2 mm, and γ = 0.1 MPa / mm, which satisfies the relationship P = γ × T, γ = 0.1 MPa / mm ~ 0.2 MPa / mm, P is in MPa, and T is in mm. The gas passed through the gas quenching mold gas inlet 9 is argon.

[0145] Step 23: After the aluminum-lithium alloy plate 11 is cooled to room temperature, the aluminum-lithium alloy plate 11 is taken off from the gas quenching mold 8, and an infrared temperature measuring device is used for temperature measurement.

[0146] The aluminum-lithium alloy skin profile accuracy prepared by this method is ±0.3 mm, the tensile strength of the aluminum-lithium alloy skin can reach more than 90% of the aluminum-lithium alloy plate, the surface roughness Ra is 3.2, the structure weight is reduced by more than 10%, and the processing cycle is shortened by 30%. The specific performance indicators of Example 2 are shown in the following table.

[0147] Table 3 Performance indicators of aluminum-lithium alloy skin in Example 2

[0148]

[0149] Example 2-1

[0150] In this embodiment, in step 11, the preset temperature is 515 DEG C, the holding time is 10 min, and the other processing conditions are the same as those in Example 2.

[0151] Compared with the existing process, the aluminum-lithium alloy skin prepared by this embodiment can further improve the tensile strength of the aluminum-lithium alloy skin, which can reach more than 95% of the aluminum-lithium alloy plate, and can reduce the structure weight by more than 5%, which is very important for aerospace products.

[0152] Example 2-2

[0153] In this embodiment, in step 12, the gas passed is nitrogen, and the gas pressure is 2 MPa, and the other processing conditions are the same as those in Example 2.

[0154] Compared with the existing process, the aluminum-lithium alloy skin prepared by this embodiment can further improve the profile accuracy of the aluminum-lithium alloy skin, which can reach ±0.2 mm, and can reduce the structure weight by more than 5%, which is very important for aerospace products.

[0155] Example 2-3

[0156] In this embodiment, in step 22, the gas introduced through the gas inlet 9 of the gas quenching mold is helium, and other processing conditions are the same as in example 2.

[0157] Compared with the existing process, the aluminum-lithium alloy skin prepared by the example can further improve the tensile strength of the aluminum-lithium alloy skin, which can reach more than 95% of the aluminum-lithium alloy sheet, and can reduce the structure weight by more than 5%, which is crucial for aerospace products.

[0158] Example 2-4

[0159] In this embodiment, in step 22, the gas quenching mold 8 and the aluminum-lithium alloy sheet 11 are inverted before being moved upward, and other processing conditions are the same as in example 2.

[0160] Compared with the existing process, the aluminum-lithium alloy skin prepared by the example can further improve the tensile strength of the aluminum-lithium alloy skin, which can reach more than 95% of the aluminum-lithium alloy sheet, and can reduce the structure weight by more than 5%, which is crucial for aerospace products.

[0161] Comparative example 2

[0162] The superplastic / gas quenching forming mold is selected, the thickness of the aluminum-lithium alloy sheet 11 is T=2mm, the gap between the aluminum-lithium alloy sheet 11 and the gas quenching mold 8 is t=1.2mm, which does not satisfy the relationship t≤0.5×T. The length of the aluminum-lithium alloy sheet 11 is f=200mm, the gas quenching mold 8 has M gas quenching mold gas outlets 10, the spacing between adjacent gas quenching mold gas outlets 10 is g=50mm, the diameter of the gas quenching mold gas outlet 10 is h=2mm, which does not satisfy the relationship g≤f×h / 10=200×2 / 10=40 and M≥f / g=4, the units of f, g and h are mm.

[0163] The tensile strength of the aluminum-lithium alloy skin prepared by the example is 510MPa.

[0164] Table 4 lists the properties of the aluminum-lithium alloy skin of comparative example 2 and example 2 series

[0165]

[0166]

[0167] Although the present application is disclosed with reference to the preferred embodiments above, it is not intended to limit the present application, and any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present application, therefore, the protection scope of the present application should be defined by the scope defined by the claims of the present application.

Claims

1. A method for forming an alloy skin, characterized in that: The alloy skin is an aluminum alloy skin with local large deformation and / or an aluminum-lithium alloy skin. The forming method of the aluminum alloy skin with local large deformation is a stir friction treatment / fluid forming method, comprising the following steps: Step 1: performing friction stir treatment on a local area of ​​the aluminum alloy plate to form a friction stir treatment area; Step 2: local deformation of the friction stir treatment area under the action of fluid pressure; The step 2 includes: Step 21: heating the fluid forming upper mold and the fluid forming lower mold to a set temperature; Step 22: placing the aluminum alloy plate between the fluid forming upper die and the fluid forming lower die, and applying pressure F to press the aluminum alloy plate; Step 23: introducing fluid through the fluid inlet on the fluid forming upper mold and maintaining a certain fluid pressure P and time; Step 24: The aluminum alloy plate is removed from between the fluid forming upper die and the fluid forming lower die, the process allowance is cut off, and surface dirt is cleaned to obtain an aluminum alloy skin with a local large deformation; The forming die used in the alloy skin forming method includes an upper die and a lower die; An upper mold cavity is left on the upper mold, a fluid inlet connected to the upper mold cavity is left on the side of the upper mold cavity, and a lower mold cavity is left on the lower mold; The top fillet r and the bottom fillet R of the lower mold have a relationship of R≥0.5×s, r≥2×s, where s is the thickness of the alloy plate; The groove width of the lower mold cavity is a, and the groove depth is b, satisfying: a ≥ b; The upper mold cavity is square, with a length of c and a width of d. The fluid inlet width e satisfies the following conditions: c>a, d>e; The forming die used in the alloy skin forming method further comprises a gas quenching die, the gas quenching die having a gas quenching die air inlet and a gas quenching die air outlet, and the shape of the convex portion of the gas quenching die is consistent with the shape of the lower die cavity; The gas quenching mold has M gas quenching mold outlets, and there is a distance between adjacent gas quenching mold outlets; In step 2, the applied pressure F, the groove width a of the lower mold cavity, and the fluid pressure P are such that F ≥ a 2 ×P, where F is in N, a is in mm, and P is in MPa; In step 2, the fluid pressure increase rate is ≤0.1MPa / min, satisfying P≥R p ×s / R, where P is the fluid pressure in MPa, R p is the yield strength of the aluminum alloy plate, in MPa, and s is the thickness of the aluminum alloy plate, in mm.

2. The alloy skin forming method according to claim 1, characterized in that: In the step 1, the rotation speed n of the stirring head in the friction stir treatment is 200 rad / min to 1000 rad / min, and the friction stir treatment speed v is 50 mm / min to 200 mm / min.

3. The alloy skin forming method according to claim 2, characterized in that: In step 1, the friction stir treatment speed v, the stirring head rotation speed n and the thickness s of the aluminum alloy plate are related as follows: v = α × n / s; Where s is in mm, n is in rad / min, v is in mm / min, and α is in mm 2 / rad, 1<α<10.

4. The alloy skin forming method according to claim 1, characterized in that: The forming method of the aluminum-lithium alloy skin is a superplastic / gas quenching forming method, comprising the following steps: Step 1: superplastic forming the aluminum-lithium alloy plate; Step 2: Gas quenching the superplastic formed aluminum-lithium alloy plate.

5. The forming method according to claim 4, characterized in that: The step 1 comprises: Step 11: Create n circular holes on the top of the aluminum-lithium alloy plate, heat the superplastic forming upper die and the superplastic forming lower die to a preset temperature, place the aluminum-lithium alloy plate between the superplastic forming upper die and the superplastic forming lower die and keep them warm for 10 to 30 minutes; Step 12: Introduce gas between the aluminum-lithium alloy plate and the superplastic forming upper die through the fluid inlet of the superplastic forming upper die, and the aluminum-lithium alloy plate gradually fits toward the superplastic forming lower die.

6. The forming method according to claim 5, characterized in that: The step 2 includes: Step 21: After the aluminum-lithium alloy plate is completely fitted into the superplastic forming lower mold cavity, the superplastic forming upper mold is removed, a hook is placed in the circular hole on the top of the aluminum-lithium alloy plate, and the gas quenching mold is connected to the aluminum-lithium alloy plate via the hook and placed above the aluminum-lithium alloy plate, with the raised portion of the gas quenching mold completely placed in the superplastic forming lower mold cavity; Step 22: The gas quenching mold and the aluminum-lithium alloy plate are moved upward together. At the same time, gas is introduced through the gas inlet of the gas quenching mold and discharged through the gas outlet of the gas quenching mold to form a gas quenching layer between the gas quenching mold and the aluminum-lithium alloy plate. Step 23: After the aluminum-lithium alloy plate cools to room temperature, remove the aluminum-lithium alloy plate from the gas quenching mold.

7. The forming method according to claim 6, characterized in that: The length of the aluminum-lithium alloy plate is f, there are M gas quenching mold air outlets on the gas quenching mold, the spacing between adjacent gas quenching mold air outlets is g, the diameter of the gas quenching mold air outlet is h, and there is a relationship g≤f×h / 10, the number of gas quenching mold air outlets M≥f / g, and the units of f, g, and f are mm.

8. An alloy skin forming die for implementing the alloy skin forming method according to any one of claims 1 to 7, characterized in that: including an upper mold and a lower mold; An upper mold cavity is left on the upper mold, a fluid inlet connected to the upper mold cavity is left on the side of the upper mold cavity, and a lower mold cavity is left on the lower mold; The top fillet r and the bottom fillet R of the lower mold have a relationship of R≥0.5×s, r≥2×s, where s is the thickness of the alloy plate; The groove width of the lower mold cavity is a, and the groove depth is b, satisfying: a ≥ b; The upper mold cavity is square, with a length of c and a width of d. The fluid inlet width e satisfies the following conditions: c>a, d>e.

9. The alloy skin mold according to claim 8, characterized in that: The alloy skin mold further includes an air quenching mold, the air quenching mold having an air quenching mold air inlet and an air quenching mold air outlet, and the shape of the convex portion of the air quenching mold is consistent with the shape of the lower mold cavity; There are M gas quenching mold air outlets on the gas quenching mold, and there is a distance between adjacent gas quenching mold air outlets.

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