Method for making high energy hydroformed structures from 2xxx series alloys

Abstract

The present invention relates to a method for manufacturing an integrated monolithic aluminum structure, the method comprising the following steps: (a) providing an aluminum alloy plate with a predetermined thickness of at least 38.1 mm, wherein the aluminum alloy plate is a 2xxx series alloy provided in a T3 temper, and its composition comprises, in weight %, Cu 3.8-4.5, Mn 0.3‑0.8, Mg1.1‑1.6, Si not higher than 0.15, Fe not higher than 0.20, Cr not higher than 0.10, Zn not higher than 0.25, Ti not higher than 0.15, Ag not higher than 0.10, and remaining aluminum; (b) optionally, pre-processing the aluminum alloy plate into an intermediate processing structure; (c) using a forming surface of a rigid mold to perform high-energy hydraulic forming on the plate or the optional intermediate processing structure, whose contour is consistent with the desired curvature of the integrated integral aluminum structure, and the high-energy forming makes the plate or the intermediate processing structure conform to the contour of the forming surface to at least one of a uniaxial curvature and a biaxial curvature; (d) processing or mechanically grinding the high-energy formed structure into a near-final or final processed integrated integral aluminum structure; (e) aging the final integral aluminum structure to the desired temper.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an integrated monolithic aluminum alloy structure, which can have a complex configuration processed from a sheet material into a near-network shape. More specifically, the present invention relates to a method for manufacturing an integrated monolithic aluminum alloy structure made of a 2xxx series alloy, which can have a complex configuration processed from a sheet material into a near-network shape. The present invention also relates to an integrated monolithic aluminum alloy structure manufactured by the method of the present invention and several intermediate semi-finished products obtained by the method. Background Art

[0002] U.S. Patent No. 7,610,669-B2 (Aleris) discloses a method for manufacturing an integrated monolithic aluminum structure, particularly an aerospace component, comprising the following steps:

[0003] (a) providing an aluminum alloy plate having a predetermined thickness, the plate being stretched after quenching and reaching a first temper selected from T4, T73, T74 and T76, wherein the aluminum alloy plate is made of an AA7xxx series aluminum alloy, and its composition contains, in weight %, 5.0-8.5% Zn, 1.0-2.6% Cu, 1.0-2.9% Mg, <0.3% Fe, <0.3% Si, one or more elements selected from Cr, Zr, Mn, V, Hf, Ti (the total amount of the optional elements does not exceed 0.6%), incidental impurities and residual aluminum,

[0004] (b) forming the alloy sheet by bending to obtain a predetermined formed structure with a pre-processed thickness in the range of 10-220 mm, the alloy sheet being subjected to a first temper selected from T4, T73, T74 and T76 to form a formed structure with a built-in radius,

[0005] (c) heat treating the formed structure, wherein the heat treating comprises artificially aging the formed structure to a second temper selected from T6, T79, T78, T77, T76, T74, T73 or T8,

[0006] (d) machining said formed structure to obtain an integrated monolithic aluminum structure as said aerospace component for an aircraft, wherein said machining of said formed structure occurs after said artificial aging.

[0007] The disclosed method is also applicable to AA5xxx, AA6xxx and AA2xxx series aluminum alloys.

[0008] It is necessary to form an integrated whole aluminum structure with more complex structure from thick plate products. SUMMARY OF THE INVENTION

[0010] As understood herein, unless otherwise specified, aluminum alloy names and temper names refer to the Aluminum Association names in the "Aluminum Standards and Data and the Registration Records" published by the Aluminum Association in 2018, which are well known to those skilled in the art. The temper names are specified in the European standard EN515.

[0011] For any description of alloy compositions or preferred alloy compositions, all references to percentages are by weight unless otherwise stated.

[0012] As used herein, when used to describe a composition range or amount of an alloying addition, the term "about" as understood by those skilled in the art means that the actual amount of the alloying addition may vary from the nominal intended amount due to factors such as standard processing differences.

[0013] As used herein, the terms "not more than" and "not more than about" expressly include, but are not limited to, the possibility that the weight percent of the particular alloy component to which it refers is zero. For example, not more than 0.25% Zn may include an aluminum alloy that does not contain Zn.

[0014] "Unitary" is a term known in the art and is meant to encompass a substantially unitary unit that may be a single piece formed or created without seams or joints and comprises a substantially uniform entity.

[0015] An object of the present invention is to provide a method for manufacturing an integrated monolithic aluminum alloy structure having a complex configuration machined into a near-network shape.

[0016] It is another object of the present invention to provide a method of manufacturing an integrated monolithic 2xxx series aluminum alloy structure having a complex configuration machined from thick gauge plate into a near-network shape.

[0017] The present invention provides a method of manufacturing an integrated monolithic aluminum structure that meets or exceeds these and other objects and further advantages, the method comprising the following process steps:

[0018] - providing an aluminum alloy sheet having a predetermined thickness of at least 31.75 mm (1.25 inches), wherein the aluminum alloy sheet is a 2xxx series alloy provided in a T3 temper, preferably in a T351 temper, and wherein the composition of the 2xxx series alloy comprises, in weight %:

[0019] Cu 3.8%-4.5%,

[0020] Mn 0.3%-0.8%,

[0021] Mg 0.9%-1.6%,

[0022] Si not higher than 0.15%,

[0023] Fe is not more than 0.20%,

[0024] Cr not higher than 0.10%,

[0025] Zn not more than 0.25%,

[0026] Ti not higher than 0.15%,

[0027] Ag not higher than 0.10%,

[0028] Impurities and excess aluminum;

[0029] - Optionally, pre-processing the aluminum alloy sheet into an intermediate processed structure;

[0030] - High energy hydroforming of the plate or intermediate machined structure with a forming surface of a rigid die to a contour at least substantially conforming to a desired curvature of the integrated monolithic aluminum structure, the high energy forming causing the plate or intermediate machined structure to be substantially conformal to the contour of the forming surface, having at least one uniaxial curvature or biaxial curvature;

[0031] - machining or mechanically grinding the high energy formed structure into a near final or final machined integrated monolithic aluminum structure; and

[0032] -Aging the integrated monolithic aluminum structure to a desired temper to develop desired strength and other engineering properties relevant to the intended application of the integrated monolithic aluminum structure.

[0033] As is well known in the art, the T3 temper refers to a 2xxx series starting plate product that has been solution heat treated, cold worked, and naturally aged. The designation Tx51 refers to the stress upon which controlled stretching is dependent after solution heat treatment.

[0034] During the high energy hydroforming of thick gauge aluminum alloy sheet, the degree of deformation in the sheet may vary, for example, in the thickness direction, as well as in the length and width directions, depending on the desired profile of the high energy hydroforming structure having at least uniaxial curvature or biaxial curvature. The present invention has found that when provided in a T3 starting condition and processed and aged to a final T8 condition according to the present invention, the sheet of the claimed 2xxx series alloy composition without intentional addition of silver is almost insensitive to changes in the degree of deformation of at least not more than about 12%. This is an important discovery because when aged to the final temper, such as to the T8 condition, the substantial insensitivity results in more constant mechanical and other engineering properties of the final product in different directions. Another advantage is that Ag-free 2xxx series alloys are much more cost-effective than Ag-containing 2xxx series alloys.

[0035] In one embodiment, the 2xxx series sheet in T3 temper is pre-machined into an intermediate machined structure, for example by turning, grinding and drilling. Preferably, the ultrasonic dead zone is removed from the sheet product. And depending on the final geometry of the integrated monolithic aluminum structure, some material may be removed to create one or more pockets in the sheet and a shape closer to the web in the forming die. This may facilitate forming during a subsequent high energy hydroforming operation.

[0036] In one embodiment of the method according to the invention, the high energy hydraulic forming step is performed by explosive forming. The explosive forming process is a high energy rate plastic deformation process carried out in water or other suitable liquid environment (such as oil) to allow ambient temperature forming of the aluminum alloy plate. The explosive can be concentrated at a single point or distributed over the metal, ideally using a detonating cord. The plate is placed on a die, preferably clamped at the edges. In one embodiment, the space between the plate and the die can be evacuated prior to the forming process.

[0037] The explosive forming process may be equivalently and interchangeably referred to as "explosive deformation", "explosive deformation", "explosive forming" or "high energy hydraulic forming" (HEH) process. The explosive forming process is a metalworking process in which an explosive is used to provide a compressive force (such as a shock wave) to an aluminum sheet for a formed part (such as a mold), also referred to as a "die". Explosive forming is typically performed on materials and structures that are too large to achieve the required compressive force to form such structures using a punch or press. According to one method of explosive forming, an aluminum sheet several inches thick is placed above or near the die, and the space or cavity in between is optionally evacuated by a vacuum pump. The entire apparatus is submerged in a basin or box underwater, and an explosive having a predetermined force potential is detonated at a predetermined distance from the metal workpiece to generate a predetermined shock wave in the water. Thereafter, the water generates a predetermined dynamic pressure on the workpiece for the die at a rate on the order of milliseconds. The die may be made of any material of suitable strength, such as concrete, ductile iron, etc., to withstand the force of the explosive. The yield strength of the die should be higher than the metal workpiece to be formed.

[0038] In one embodiment of the method according to the present invention, the high energy hydraulic forming step is performed by electrohydraulic forming. The electrohydraulic forming process is a high energy rate plastic deformation process preferably carried out in water or other suitable liquid environment (such as oil) to allow ambient temperature forming of aluminum alloy plates. Arc discharge is used to convert electrical energy into mechanical energy to change the shape of the plate product. The capacitor bank transmits a high current pulse through two electrodes that are separated by a small distance when immersed in the fluid. The arc discharge rapidly vaporizes the surrounding fluid, generating a shock wave. The plate is placed above the mold, preferably clamped at the edges. In one embodiment, the space between the plate and the mold can be evacuated prior to the forming process.

[0039] Coolants are preferably used during various pre-machining and machining or mechanical grinding process steps to allow ambient temperature machining of the aluminum alloy sheet or intermediate product. Preferably, wherein pre-machining and machining to a near-final or final machined structure comprises high speed machining, preferably numerically controlled (NC) machining.

[0040] After the high-energy hydroforming step, the obtained structure is solution heat treated and allowed to cool to ambient temperature, depending on the desired final temper. One of the objectives is to heat the structure to a suitable temperature, usually above the solvus temperature, to keep it at that temperature long enough to allow the soluble elements to enter the solid solution, and to cool it quickly enough to keep as many of the elements as possible in the solid solution. The suitable temperature depends on the alloy and is usually in the range of about 460°C-535°C. The solution heat treatment can be carried out in one or more steps. The solid solution formed at high temperature can be kept in a supersaturated state by cooling quickly enough to limit the precipitation of the solute atoms as coarse, incoherent particles.

[0041] Solution heat treatment and subsequent cooling are important in order to obtain an optimal microstructure essentially free of grain boundary precipitates, which can deteriorate corrosion resistance, strength and damage tolerance properties, and to allow as much solute as possible to be available for subsequent aging strengthening.

[0042] In one embodiment of the method according to the invention, the intermediate high-energy hydroformed product is preferably destressed by an operation including a cold compression type operation, otherwise there will be too much residual stress, affecting subsequent processing operations.

[0043] In one embodiment, stress relief by a cold compression type operation is performed by carrying out one or more subsequent high energy hydroforming steps, preferably by applying a milder shock wave than the first high energy hydroforming step that produced the initial high energy hydroformed structure.

[0044] In one embodiment, the high energy formed intermediate structure (optionally also stress relieved) is then sequentially machined or milled to a near final or final machined integrated monolithic aluminum structure and then aged to a desired temper to achieve final mechanical properties.

[0045] In another more preferred embodiment, the high energy formed intermediate structure (optionally also stress relieved) is sequentially aged (naturally or artificially) to the desired temper to obtain the final mechanical properties, and then machined or machined to a near final or final machined integrated monolithic aluminum structure. Thus, the machining operation occurs after the aging operation.

[0046] In both embodiments, the aging to reach the desired temper to obtain the final mechanical properties is selected from T3, T4, T6 and T8. The artificial aging step for T6 and T8 tempering preferably comprises at least one aging step at a temperature in the range of 130°C to 210°C, with an immersion time in the range of 4 to 30 hours.

[0047] In a preferred embodiment, aging to the desired temper to obtain the final mechanical properties is performed by natural aging to a T3 temper, more preferably a T37 or T39 temper, or a T352 temper.

[0048] In a preferred embodiment, aging to the desired temper to obtain final mechanical properties is to a T6 temper.

[0049] In a most preferred embodiment, aging to the desired temper to obtain final mechanical properties is to a T8 temper, more preferably a T852, T87 or T89 temper.

[0050] In one embodiment, the aging (natural or artificial) is to a T354, T654 or T854 temper and represents a combined tension and compression stress relief temper.

[0051] In one embodiment, the final aged near-final or final processed high energy hydroformed integrated monolithic aluminum structure has a tensile yield strength in both the L and LT directions of at least 390 MPa, more preferably at least 400 MPa. In one embodiment, the tensile strength in both the L and LT directions is at least 450 MPa, more preferably at least 460 MPa. These tensile properties are typically achieved when the high energy hydroformed structure is aged to the final T8 temper.

[0052] In one embodiment, the predetermined thickness of the aluminum alloy plate is at least 38.1 mm (1.5 inches). In one embodiment, the predetermined thickness of the aluminum alloy plate is at least 50.8 mm (2.0 inches), and preferably at least 63.5 mm (2.5 inches), and more preferably at least 76.2 mm (3.0 inches).

[0053] In one embodiment, the predetermined thickness of the aluminum alloy plate is at most 127 mm (5 inches), preferably at most 114.3 mm (4.5 inches).

[0054] Cu is the main alloying element in 2xxx series alloys, and for the method according to the present invention, it should be in the range of 3.8%-4.5%. The preferred upper limit of Cu content is about 4.3%. In one embodiment, the upper limit of Cu content is about 4.1%.

[0055] Mn is another important alloying element, and its content should be in the range of 0.30% to 0.8%. In one embodiment, the Mn content is in the range of 0.4% to about 0.8%, preferably 0.4% to about 0.6%.

[0056] Mg is another important alloying element and its content should be in the range of 0.9%-1.6%. The preferred lower limit of Mg content is about 1.10%, more preferably about 1.20%. The preferred upper limit of Mg content is about 1.5%. The preferred upper limit of Mg content is about 1.40%.

[0057] Cr may be present in the range of up to about 0.10%. In one embodiment, there is no intentionally added Cr, which may be present up to about 0.05%, preferably kept below 0.04%.

[0058] An important aspect of the present invention is that the aluminum alloy has no intentional addition of silver (Ag). It is an impurity element and may be present in an amount not greater than about 0.10%, preferably not greater than 0.05%, and more preferably not greater than 0.03%. In a preferred embodiment, the silver content is less than about 0.02%, making the aluminum alloy substantially free of silver. "Substantially free" or "essentially free" means that no intentional additions are made to the chemical composition, but trace amounts of Ag may still enter the alloy product due to impurities and / or leakage from contact with manufacturing equipment. For example, less than 0.01% is an example of a trace amount.

[0059] Zn is an impurity element and may be present in an amount not greater than about 0.25%, preferably not greater than about 0.10%.

[0060] Zr is an impurity element, and may be present in a range of not more than 0.05%, preferably in a range of not more than 0.02%.

[0061] Fe is a common impurity in aluminum alloys, and no more than 0.20% may be tolerated. It is preferably kept at a level of no more than about 0.15%, more preferably no more than about 0.10%, and most preferably no more than about 0.05%.

[0062] Si is also a common impurity in aluminum alloys, and no more than 0.15% may be tolerated. It is preferably maintained at a level of no more than 0.10%.

[0063] Ti can be added to alloy products, especially for the purpose of grain refiner in the casting process of rail vehicles. The addition of Ti should not exceed about 0.15%, preferably not more than 0.06%. The preferred lower limit of Ti addition is about 0.01%. To control grain size, Ti can be added as the sole element or with boron or carbon as casting aids.

[0064] In the 2xxx series aluminum alloy, the remainder consists of aluminum and impurities, typically no more than 0.05% each and no more than 0.15% in total, and preferably no more than 0.02% each and no more than 0.06% in total.

[0065] In a preferred embodiment, there is no intentional addition of lithium (Li) to the 2xxx series alloy at a level greater than about 0.20%, more preferably the Li content is less than about 0.10%, and most preferably the alloy is substantially free of Li. "Substantially free" or "substantially free" means that no intentional additions are made to the chemical composition, but trace amounts of Li may still enter the aluminum alloy product due to impurities and / or leakage from contact with manufacturing equipment. For example, less than about 0.02% or less than about 0.01% are examples of trace amounts.

[0066] In one embodiment, the composition of the 2xxx series aluminum alloy contains, by weight%, Cu 3.8%-4.5%, Mn 0.3%-0.8%, Mg 0.9%-1.6%, Si not higher than 0.15%, Fe not higher than 0.20%, Cr not higher than 0.10%, Zn not higher than 0.25%, Ti not higher than 0.15%, Ag not higher than 0.10%, remaining aluminum and impurities each <0.05% and a total of <0.15%, as described and claimed herein, which preferably has a narrower composition range.

[0067] In another aspect, the invention relates to an integrated monolithic aluminium structure manufactured by the method according to the invention.

[0068] In another aspect, the invention relates to an intermediate semi-finished product formed from an intermediate machined structure prior to a high energy hydroforming operation.

[0069] In another aspect, the invention relates to an intermediate semi-finished product formed from an intermediate (optionally pre-machined) structure which has been high-energy hydroformed by the method according to the invention and which has at least one of a uniaxial curvature or a biaxial curvature.

[0070] In another aspect, the present invention relates to an intermediate semi-finished product formed from an intermediate (optionally pre-machined) structure, which is then high-energy hydraulically formed and has at least one of a uniaxial curvature and a biaxial curvature, and is then stress relieved in a cold compression operation and aged before being machined into a near-final or final-shaped integrated monolithic aluminum structure, and the aging reaches the desired temper to develop the desired strength and other engineering properties associated with the intended application of the integrated monolithic aluminum structure.

[0071] The final integrated integral aluminum structure after aging and processing can be part of structures such as fuselage panels with integrated longitudinal beams, aircraft cockpit, cockpit side windshields, cockpit integral side windshields, cockpit integral front windshields, front bulkheads, door surrounds, front landing gear bays and nose fuselages.

[0072] Another aspect of the present invention relates to the use of a 2xxx series aluminum alloy sheet product in a high-energy hydroforming operation according to the present invention, preferably for the manufacture of aircraft structural components, preferably in T3 temper, with a composition in weight % comprising: Cu 3.8-4.5%, Mn 0.3-0.8%, Mg 0.9-1.6%, Si not higher than 0.15%, Fe not higher than 0.20%, Cr not higher than 0.10%, Zn not higher than 0.25%, Ti not higher than 0.15%, Ag not higher than 0.05%, impurities and residual aluminum, with a gauge length in the range of 31.75 mm-127 mm.

[0073] BRIEF DESCRIPTION OF THE DRAWINGS

[0074] The present invention shall also be described with reference to the accompanying drawings, in which:

[0075] Figure 1 Shown is a flow chart of one embodiment of the method according to the present invention;

[0076] Figure 2 A flow chart showing another embodiment of the method according to the present invention; and

[0077] Figure 3A , 3B 3C are cross-sectional side views of an aluminum sheet according to aspects of the present invention as it passes through various stages of the forming process from a roughly formed metal sheet to a formed, near-finally formed, and finally formed workpiece.

[0078] Figure 1In the method, the method comprises, in sequence: a first process step, which provides a 2xxx series aluminum alloy sheet having a composition described and claimed in a T3 temper, having a predetermined thickness of at least 38.1 mm, with a preferably thicker gauge length. In the next process step, the sheet is pre-processed (which is an optional process step) into an intermediate processed structure, and then high-energy hydraulic forming, preferably by explosive forming or electrohydraulic forming, into a high-energy hydraulic formed structure having at least one of a uniaxial curvature or a biaxial curvature. Preferably, in the next process step, the intermediate product is stress relieved, which is more preferably in an operation involving a cold compression type operation. Thereafter, the high-energy formed structure is processed or mechanically ground to make it a near-final or final processed integrated monolithic aluminum structure, and then the processed integrated monolithic aluminum structure is aged to a desired temper to develop the desired strength and other engineering properties associated with the intended application of the integrated monolithic aluminum structure.

[0079] Alternatively, in an alternative embodiment, the intermediate integrated monolithic aluminum structure is first aged to a desired temper to develop desired strength and other engineering properties associated with the intended application of the integrated monolithic aluminum structure, and then the aged high-energy formed structure is processed or machined into a near-final or final processed integrated monolithic aluminum structure.

[0080] Figure 2 The method shown is similar to Figure 1 The method shown is closely related, except that in this embodiment there is a first high energy hydroforming step, followed by at least a second high energy hydroforming step, the purpose of which is to at least relieve stress, followed by the steps of Figure 1 Ageing and processing in the methods shown.

[0081] Figure 3A , 3B 3C show a series of exemplary figures showing how an aluminum sheet may be formed during an explosive forming process that may be used in the forming process of the present invention. According to explosive forming assembly 80a, tank 82 contains a volume of water 83. Mold 84 defines a cavity 85, and a vacuum line 87 extends from cavity 85 through mold 84 to a vacuum (not shown). Aluminum sheet 86a is held in place in mold 84 by a clamping ring or other retaining device (not shown). The explosive 88 shown is suspended in water 83 by an explosive detonating cord 89, which is connected to a detonator (not shown). As shown in FIG. Figure 3B As shown, explosive 88 (as shown in FIG. 3 a) is detonated in explosive forming assembly 80b, generating shock wave “A” emanating from bubble “B”, shock wave “A” causing aluminum plate 86b to deform into cavity 85 until aluminum plate 86c is driven onto the inner surface of die 84 (e.g., immediately approaching and contacting it), as shown. Figure 3C shown. Example

[0082] In order to demonstrate the principle of the invention, industrially produced plates of three different alloys were tested with regard to the influence of the degree of deformation in the final tempering on their mechanical properties.

[0083] Plates of the three alloys were solution heat treated and stretched to T351 temper using conventional industrial practice. The alloy compositions are listed in Table 1. Alloy 1 is an alloy according to the invention with a gauge length of 33 mm, while alloys 2 and 3 are comparative alloys with gauge lengths of 25 mm and 27 mm, respectively. Samples were cut from all plates and stretched to varying degrees in the L direction to simulate the deformation step after a high-energy hydroforming operation. Afterwards, all samples were artificially aged to the T8 condition and their mechanical properties were tested in the L direction at the mid-thickness point (s / 2) according to the EN2002-1 standard. The results (average of three tested samples) are listed in Table 2.

[0084] Table 1. Alloy composition of the plates tested, all percentages are in weight %, the remainder consisting of aluminum and conventional impurities.

[0085]

[0086] Table 2. Mechanical properties of different alloy samples under T8 conditions as a function of the degree of tension. Rp0.2 is the yield strength, Rm is the tensile strength, and A is the elongation at break.

[0087]

[0088] From the results in Table 2, it can be seen that Alloy 2, as a 2xxx series alloy, has intentionally added silver, which provides almost constant mechanical properties as the degree of stretching increases. This is in line with the expectations of the technician. As expected by the technician, the increase in tensile properties is small as the degree of stretching increases, because under the T8 condition, a higher degree of cold deformation will result in a smaller increase in tensile properties.

[0089] Alloy 3 is closely related to Alloy 2, except without the intentional addition of silver. The yield strength and ultimate tensile strength of this aluminum alloy increase steadily with increasing stretching, while the elongation at break decreases with increasing stretching. When high-energy hydroforming the sheet, the degree of deformation can vary greatly, depending on the geometry of the final structure. Due to the strong dependence of the mechanical properties of Alloy 3 on the degree of stretching, this alloy is not a favorable choice for processing by high-energy hydroforming operations, as it results in large variations in the mechanical properties of the final product in the final temper.

[0090] Surprisingly, Alloy 1 without silver shows a similar trend as Alloy 2, i.e. its mechanical properties remain almost unchanged with increasing degree of stretching. Also in the final T8 temper, the increase in yield strength and tensile strength with increasing degree of stretching is very small.

[0091] Despite the lower Cu content and absence of Ag in Alloy 1 compared to Alloy 2, Alloy 1 exhibits mechanical properties close to those of Alloy 2. Since Alloy 1 is almost insensitive to changes in the degree of deformation, this aluminum alloy is an ideal alloy for processing in high-energy hydroforming operations and provides fairly constant mechanical properties in the final product. At the same time, the absence of silver makes the aluminum alloy more cost-effective than silver-containing 2xxx series alloys.

[0092] Having now fully described the invention, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit or scope of the invention described herein.

Claims

1. A method for manufacturing an integrated monolithic aluminum structure, the method comprising the following steps: - providing an aluminum alloy plate having a predetermined thickness of at least 31.75 mm, wherein: The aluminum alloy plate is a 2xxx series alloy provided in a T3 temper, and wherein the composition of the 2xxx series alloy comprises, in weight percent: Cu 3.8%-4.5%, Mn 0.3%-0.8%, Mg 0.9%-1.6%, Si not more than 0.15%, Fe not more than 0.20%, Cr not more than 0.10%, Zn not more than 0.25%, Ti not more than 0.15%, Ag not more than 0.10%, impurities, and remaining aluminum; -Pre-processing the aluminum alloy sheet into an intermediate processing structure; - High-energy hydroforming of the plate or intermediate processing structure with a forming surface of a rigid die, the contour of which is consistent with the desired curvature of the integrated integral aluminum structure, the high-energy forming makes the plate or intermediate processing structure conform to the contour of the forming surface to at least one of a uniaxial curvature and a biaxial curvature, and relieves the stress of the high-energy formed structure; - Processing or mechanical grinding of high energy formed structures into final machined integrated monolithic aluminum structures; -Aging of the final integrated monolithic aluminum structure to the desired temper.

2. The method of claim 1, wherein: The high energy hydroforming step is performed by explosive forming.

3. The method of claim 1, wherein: The high energy hydroforming step is performed by electrohydraulic forming.

4. The method according to any one of claims 1 to 3, wherein: The high energy hydroforming operation in turn ages the high energy formed structure to the desired temper before machining into the final machined integrated monolithic aluminum structure.

5. The method of claim 1, wherein: After the high energy hydroforming operation, the high energy formed structure is stress relieved by compression forming and thereafter machined and aged to the desired temper of the integrated monolithic aluminum structure.

6. The method of claim 1, wherein: After the high energy hydroforming operation, the high energy formed structure is stress relieved by compression forming in a subsequent high energy hydroforming step and thereafter machined and aged to the desired temper of the integrated monolithic aluminum structure.

7. The method of claim 1, wherein: The predetermined thickness of the aluminum alloy plate is at least 50.8 mm.

8. The method of claim 1, wherein: The predetermined thickness of the aluminum alloy plate is at most 127 mm.

9. The method of claim 1, wherein: Aging of the integrated monolithic aluminum structure is performed to a desired temper selected from T3, T4, T6 and T8.

10. The method of claim 1, wherein: The aging of the integrated monolithic aluminum structure is carried out to T8 tempering.

11. The method of claim 1, wherein: The Cu content of 2xxx series aluminum alloys is 3.8%-4.3%.

12. The method of claim 1, wherein: Pre-machining and final machining involve high-speed machining.

13. Use of a 2xxx series aluminum alloy plate product in the high energy hydraulic forming operation in the method of claim 1, the composition comprising, in weight %, Cu 3.8-4.5, Mn 0.3-0.8, Mg0.9-1.6, Si not higher than 0.15, Fe not higher than 0.20, Cr not higher than 0.10, Zn not higher than 0.25, Ti not higher than 0.15, Ag not higher than 0.05, impurities and residual aluminum, and the gauge length is in the range of 31.75mm-127mm.

14. Use of a 2xxx series aluminum alloy plate product in the high energy hydroforming operation of the method of claim 1 for manufacturing aircraft structural parts, the composition comprising, in weight %, Cu 3.8-4.5, Mn 0.3-0.8, Mg 0.9-1.6, Si not higher than 0.15, Fe not higher than 0.20, Cr not higher than 0.10, Zn not higher than 0.25, Ti not higher than 0.15, Ag not higher than 0.05, impurities and residual aluminum, and the gauge length is in the range of 31.75mm-127mm.

Images