Clad 2xxx-series aerospace product

Abstract

To provide an improved rolled composite aerospace product and a method of manufacturing the same.SOLUTION: Provided herein is a rolled composite aerospace product comprising a 2XXX-series core layer and an Al-Cu alloy clad layer coupled to at least one surface of the 2XXX-series core layer, where the Al-Cu alloy clad layer contains an aluminum alloy comprising about 0.06% to 2.8% Cu, and preferably about 0.10% to 1.8% Cu. The rolled composite aerospace product is ideally suitable for structural aerospace parts. Also described herein is a method of manufacturing the rolled composite aerospace product.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of and priority to European Patent Application No. 20172082.2, filed April 29, 2020, the contents of which are incorporated herein by reference in their entirety.

[0002] Described herein is a rolled composite aerospace product comprising a 2XXX series core layer and an aluminum alloy layer joined to at least one surface of the 2XXX series core layer. The rolled composite aerospace product is ideally suited for aerospace structural components. The present disclosure further relates to a method of making the rolled composite aerospace product. [Background technology]

[0003] In the aerospace industry, the AA2024 series of aluminum alloys and its modifications are widely used as highly damage tolerant aluminum alloys, primarily in the T3 condition or its modifications. These aluminum alloy products have a relatively high strength to weight ratio, good fracture toughness, good fatigue properties, and adequate corrosion resistance.

[0004] To improve corrosion resistance, AA2024 series alloy products may be provided as composite products with a relatively thin cladding layer on one or both sides. The cladding layer is usually of higher purity and protects the AA2024 core alloy from corrosion. The cladding essentially comprises unalloyed aluminum. Often, reference is made generally to the 1XXX series of aluminum alloys, which includes the 1000, 1100, 1200, and 1300 subclasses. In practice, however, the 1XXX series aluminum alloys used for the cladding layers are quite pure, with compositions of Si+Fe<0.7%, Cu<0.10%, Mn<0.05%, Mg<0.05%, Zn<0.10%, Ti<0.03%, with the remainder being aluminum.

[0005] Aluminium alloys of the AA2024 series clad with 1XXX series alloys may also be anodised. Anodising increases resistance to corrosion and wear and provides better adhesion than bare metal for paint primers and adhesives. Anodised articles are applied in structural adhesive metal joints such as, for example, wing, horizontal and vertical stabilizer or fuselage skin panels. Further known applications include sandwich constructions where one or more (glass) fibre reinforced layers are placed between aluminium panels or sheets using adhesive bonding, resulting in so-called fibre metal laminates.

[0006] A disadvantage of the 1XXX series alloys as cladding layers is that they are quite soft and susceptible to surface damage during handling of the product. During forming operations, this may result, for example, in mold sticking. Summary of the Invention

[0007] The encompassed embodiments of the invention are defined by the claims, not this summary. This summary is a high-level overview of various aspects of the invention and introduces some of the concepts that are further described in the Detailed Description section below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used alone to determine the scope of the claimed subject matter. The subject matter should be understood by reference to the entire specification, some or all of the drawings, and appropriate portions of the claims.

[0008] Described herein is a rolled composite aerospace product including a 2XXX series core layer and an Al-Cu alloy cladding layer joined to at least one surface of the 2XXX series core layer, where the Al-Cu alloy cladding layer is an aluminum alloy containing 0.06% to 2.8% Cu. Optionally, the Al-Cu alloy cladding layer is an aluminum alloy containing 0.10% to 1.8% Cu. Optionally, the Al-Cu alloy cladding layer is an aluminum alloy containing 0.06% to 2.8% Cu, by weight. Cu: 0.06% to 2.8%, preferably 0.10% to 1.8%, Mg: maximum 1.5%, preferably 0.10% to 1.2%, Mn: maximum 0.5%, preferably 0.10% to 0.5%, Si: max 0.5%, preferably max 0.3%, Fe: 0.4% max. Cr: Maximum 0.25%, V: 0.25% max. Zr: 0.2% max. Ag: Maximum 0.80%, Zn: 0.3% max. Ti: 0.2% max., and The remainder is an aluminum alloy having a composition that includes unavoidable impurities and aluminum.

[0009] Optionally, the Cu content is in the range of 0.2% to 1.5%, preferably 0.5% to 1.6%. Optionally, the Mg content is in the range of 0.20% to 1.2%, preferably 0.20% to 0.9%.

[0010] The Al-Cu aluminum alloy cladding layer can optionally have a corrosion potential of -710 mV or less. Optionally, the Al-Cu alloy cladding layer is joined to at least one surface of the 2XXX series core layer by roll bonding. The Al-Cu alloy cladding layer can have a thickness in the range of 1% to 20%, preferably 1% to 10%, of the total thickness of the rolled composite aerospace product.

[0011] Optionally, the rolled composite aerospace products described herein comprise a 2XXX series core layer and an Al-Cu alloy cladding layer joined to one or both surfaces of the 2XXX series core layer. An intermediate liner can be disposed between the 2XXX series core layer and the Al-Cu alloy cladding layer, and optionally, the intermediate liner is made of a different aluminum alloy than the Al-Cu alloy cladding layer. In some examples, the intermediate liner is made of a 1XXX series aluminum alloy.

[0012] In some cases, the 2XXX series alloy of the core layer (20) may be, in weight percent, as follows: Cu: 1.9% to 7.0%, preferably 3.0% to 6.8%, more preferably 3.2% to 4.95%, Mg: 0.30% to 1.8%, preferably 0.35% to 1.8%, Mn: maximum 1.2%, preferably 0.2% to 1.2%, Si: 0.40% max. Fe: max. 0.40%, Cr: Maximum 0.35%, Zn: Maximum 1.0%, Ti: 0.15% max. Zr: 0.25% max. V: 0.25% max. Li: max 2.0%, Ag: Maximum 0.80%, Ni: max 2.5% and The remainder has a composition that is aluminum and impurities.

[0013] In some cases, the 2XXX series core layer (20) is derived from a 2X24 series alloy. Optionally, at least the 2XXX series core layer (20) is in a T3, T351, T39, T42, T8, or T851 temper. The rolled composite aerospace product (10) can have a total thickness of 0.8 mm to 50.8 mm, preferably 0.8 mm to 25.4 mm.

[0014] Optionally, the rolled composite aerospace product is an aerospace structural part, preferably a fuselage or fuselage component.

[0015] Also described herein is a method for producing a composite aerospace product, comprising the steps of: providing an ingot of a 2XXX series aluminum alloy for forming a core layer of the composite aerospace product; homogenizing the 2XXX series aluminum alloy ingot at a temperature in the range of 400° C. to 510° C. for at least two hours; providing an ingot of an Al-Cu aluminum alloy or a rolled clad liner for forming an outer clad layer on the 2XXX series core aluminum alloy; and optionally homogenizing the ingot of an Al-Cu aluminum clad alloy for forming the outer clad layer at a temperature in the range of at least 400° C., preferably in the range of 400° C. to 510° C. for at least 0.5 hours; roll bonding the Al-Cu aluminum alloy cladding layer to the 2XXX series core alloy, preferably by hot rolling and optionally thereafter by cold rolling, to form a roll bonded product; solution heat treating the roll bonded product at a temperature in the range of 450°C to 510°C; cooling the solution heat treated roll bonded product to below 100°C, preferably to ambient temperature; optionally stretching the solution heat treated and cooled roll bonded product; and aging the cooled roll bonded product.

[0016] Optionally, the method further comprises forming the solution heat treated, cold roll bonded and optionally also stretched product into a product of a predetermined shape with uniaxial or biaxial curvature in a forming process. Optionally, the forming step can be performed after the ageing step. Optionally, the forming and ageing steps are combined in a forming step at elevated temperature, preferably at a temperature in the range of 140° C. to 200° C., for a time preferably in the range of 1 to 50 hours.

[0017] Other objects and advantages of the present invention will become apparent from the following detailed description of non-limiting examples and drawings. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram of a rolled composite aerospace product as is described herein. [Diagram 2] FIG. 1 is a schematic diagram of a rolled composite aerospace product having five distinct layers as described herein. [Diagram 3] 1 is a schematic flow schedule of several embodiments of a process for manufacturing a rolled composite aerospace product. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] As will become apparent hereinafter, unless otherwise indicated, aluminum alloy and temper symbols refer to Aluminum Association symbols in Aluminum Standards and Data and the Registration Records, as published by the Aluminum Association in 2018, and which are frequently updated, and which are well known to those skilled in the art. The temper symbols are also defined in European standard EN515.

[0020] For any description of the alloy composition or preferred alloy composition, all references to percentages are in terms of weight percent unless otherwise indicated.

[0021] The terms "at most" and "at most about," as employed herein, expressly include, but are not limited to, the possibility of zero weight percent of the particular alloying element to which it refers. For example, up to 0.3% Zn may include an aluminum alloy that does not contain Zn.

[0022] As used herein, the meaning of "a," "an," or "the" includes singular and plural references unless the context clearly indicates otherwise.

[0023] All ranges disclosed herein are intended to encompass any and all subranges contained therein. For example, a range stated as "1 to 10" should be considered to include any and all subranges between a minimum value of 1 and a maximum value of 10, inclusive, i.e., all subranges beginning with a minimum value of 1 or greater (e.g., 1 to 6.1) and ending with a maximum value of 10 or less (e.g., 5.5 to 10).

[0024] For purposes of this specification, sheet product or sheeting is to be understood as a rolled product having a thickness of 1.3 mm (0.05 inch) or more and 6.3 mm (0.25 inch) or less. For example, sheet may be 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3.0 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, 3.6 mm, 3.7 mm, 3.8 mm, 3.9 mm, 4.0 mm, 4.1 mm, 4.2 mm, 4.3 mm, 4.4 mm, 4.5 mm, 4.6 mm, 4.7 mm, 4.8 mm, 4.9 mm, 5.0 mm, 5.1 mm, 5.2 mm, 5.3 mm, 5.4 mm, 5.5 mm, 5.6 mm, 5.7 mm, 5.8 mm, 5.9 ...9 mm, 5.1 mm, 5.2 mm, 5.3 mm, 5.4 mm, 5.5 mm, 5.6 mm, 5.7 mm, 5.8 mm, 5.9 mm, 5.9 mm, 5.8 mm, 5.9 mm, 5.9 mm, 5.1 mm , 3.9 mm, 4.0 mm, 4.1 mm, 4.2 mm, 4.3 mm, 4.4 mm, 4.5 mm, 4.6 mm, 4.7 mm, 4.8 mm, 4.9 mm, 5.0 mm, 5.1 mm, 5.2 mm, 5.3 mm, 5.4 mm, 5.5 mm, 5.6 mm, 5.7 mm, 5.8 mm, 5.9 mm, 6.0 mm, 6.1 mm, 6.2 mm, or 6.3 mm thick. See Aluminum Standard and Data, the Aluminum Association, Chapter 5 Terminology, 1997.

[0025] For purposes of this specification, plate stock or plate products should be understood as rolled products having a thickness greater than 6.3 mm (0.25 inches). For example, plate stock or plate products may have a thickness of greater than 6.3, greater than 6.4 mm, greater than 6.5 mm, greater than 6.6 mm, greater than 6.7 mm, greater than 6.8 mm, greater than 6.9 mm, greater than 7.0 mm, greater than 7.1 mm, greater than 7.2 mm, greater than 7.3 mm, greater than 7.4 mm, greater than 7.5 mm, greater than 7.8 mm, greater than 7.9 mm, greater than 8.0 mm, greater than 10.0 mm, greater than 15.0 mm, greater than 20.0 mm, greater than 25.0 mm, greater than 30.0 mm, greater than 35.0 mm, greater than 40.0 mm, greater than 45.0 mm, greater than 50.0 mm, or greater than 100.0 mm. See Aluminum Standard and Data, the Aluminum Association, Chapter 5 Terminology, 1997.

[0026] Provided herein are rolled aerospace products based on 2XXX series alloys and offering an improved balance of corrosion resistance and formability, as well as additional advantages. Specifically, described herein are rolled composite aerospace products including a 2XXX series core layer, the core layer having two faces, an Al-Cu alloy cladding layer joined to at least one face of the 2XXX series core layer, the Al-Cu alloy cladding layer being made of an aluminum alloy containing 0.06%-2.8% Cu as a major alloying component, preferably 0.10%-2.8%, and more preferably 0.10%-1.8% Cu.

[0027] Compared to the 1XXX series alloys, the Al-Cu alloys described herein have several advantages: Al-Cu alloys with a maximum of 2.8%, preferably a maximum of 1.8%, Cu make the aluminum alloy more cathodic; With at least 0.06% Cu, preferably at least 0.10% Cu, more preferably at least 0.20% Cu, the clad layer has a sufficient potential difference with the 2XXX series core alloy to provide very good corrosion resistance, and especially good intergranular corrosion resistance, to the rolled composite aerospace product.

[0028] Al-Cu alloys may have very good formability properties so that rolled composite aerospace products can be formed in forming operations requiring high deformation degrees. The formability properties are comparable to those of some automotive sheet aluminum alloys. Die sticking of the clad layer to the forming die is significantly reduced or even avoided due to the high hardness of the Al-Cu alloy clad layer compared to 1XXX series clad layers. The absence of surface cracks avoids trapping of forming lubricant on the surface. The absence of surface cracks also significantly improves the fatigue performance of the composite aerospace product. Also, the very good resistance to pitting improves fatigue performance, since fatigue is commonly caused by pitting initiation sites. Al-Cu alloys have significantly higher strength than 1XXX series alloys, resulting in a harder surface and corresponding reduction in surface damage, such as scratches, during product handling. Optionally, the Al-Cu alloy clad layer in the T3 condition has a yield strength (Rp) of more than 100 MPa.

[0029] Al-Cu alloys are amenable to anodization and exhibit favorable properties during anodization so that subsequent application of an adhesive bond layer and / or primer layer does not pose problems.

[0030] The Al-Cu alloys are significantly stronger than the 1XXX series alloys such that the overall strength of the composite aerospace product is increased compared to the 1XXX series alloys at the same clad layer thickness. The strength properties also allow for the design of composite aerospace products with reduced clad thickness while reducing weight, good corrosion resistance and improved formability properties as required, or alternatively, maintaining the same thickness while reaching high overall strength.

[0031] Also, industrial-scale scrap recycling of rolled composite aerospace products does not pose any major problems since the 2XXX series alloys have intentional additions of Cu and may have intentional additions of Mn and Mg. The roll-bonded products can be remelted without prior separation of the clad layer(s) from the core layer and processed into new 2XXX series aluminum alloy products.

[0032] Optionally, the Al-Cu aluminum alloy clad layer is bonded to the 2XXX series core layer by roll bonding, preferably by hot rolling, to achieve the required metallurgical bond between the layers. Such roll bonding process is very economical and results in a highly efficient composite product exhibiting the desired properties. When carrying out such roll bonding process to produce a rolled composite product as described in the present invention, it is preferred that both the core layer and the Al-Cu aluminum alloy clad layer(s) are subjected to thickness reduction during roll bonding. Usually, before rolling, especially before hot rolling, the rolled surface of the ingot of both the core layer and the clad layer(s) is stripped to remove segregation areas close to the as-cast surface of the rolled ingot and to enhance the flatness of the product.

[0033] Preferably, the cast ingot or slab of 2XXX alloy core layer is homogenized prior to hot rolling, and / or it may be preheated and hot rolled immediately thereafter. Homogenization and / or preheating of 2XXX series alloys prior to hot rolling is usually carried out at temperatures ranging from about 400°C to 505°C in single or multiple steps. In either case, segregation of alloying elements in the as-cast material is reduced and soluble elements are dissolved. If the treatment is carried out below about 400°C, the resulting homogenization effect is insufficient. If the temperature exceeds about 505°C, melting of phases may occur, resulting in undesirable pore formation. The preferred duration of this heat treatment is between 2 and 30 hours. Longer times are usually detrimental. Homogenization is usually carried out at temperatures above about 480°C. Typical preheat temperatures range from about 430°C to 460°C with soak times ranging up to about 15 hours.

[0034] The Al-Cu aluminum clad alloy may be provided as ingots or slabs for processing into rolled stock using semi-continuous casting techniques for cast products, such as direct chill casting (DC casting), electromagnetic casting (EMC casting), electromagnetic stir casting (EMS casting), and preferably having an ingot thickness in the range of about 300 mm or more, such as 500 mm or 600 mm. Optionally, thinner gauge slabs resulting from continuous casting, such as belt casters or roll casters, may be used to provide the raw material for the Al-Cu aluminum alloy clad liner. Such thinner gauge slabs may have a thickness of up to about 40 mm.

[0035] In some instances, the cast ingot or slab forming the Al-Cu aluminum alloy cladding layer is preheated or homogenized at a temperature of at least 400°C, preferably at least about 450°C, before hot rolling in a single or multiple rolling steps to a thinner gauge forming the rolled clad liner. The temperature should not be too high, typically not exceeding 510°C, and preferably not exceeding 505°C, to avoid melting of phases resulting in possible undesirable pore formation in the ingot. The time at temperature for large commercial size ingots should be at least about 0.5 hours and can be about 1 to 30 hours. Long periods, e.g., 48 hours or more, do not immediately adversely affect the desired properties but are economically unattractive. Homogenization or preheating results in a more homogenous microstructure with phases melting and reduced elemental segregation profile, thereby improving the formability of the alloy for the hot rolling process.

[0036] The rolled composite aerospace product is reduced to the final specification by hot rolling, optionally followed by cold rolling. After the rolled composite product is rolled to the final specification, the rolled composite product is solution heat treated at a temperature in the range of about 450°C to 510°C for a time sufficient for the solution effect to approach equilibrium, with typical soak times ranging from about 5 minutes to 120 minutes. Preferably, the solution heat treatment is at a temperature in the range of about 475°C to 510°C, for example about 495°C. The solution heat treatment (SHT) is typically carried out in a batch furnace or a continuous furnace. The preferred soak times at the indicated temperatures range from about 5 to 35 minutes. However, in clad products, care should be taken against excessively long soak times, since too much copper, especially from the 2XXX core layer, may diffuse into the aluminum alloy clad layer(s), which may have a detrimental effect on the corrosion protection provided by said layer(s). A continuous SHT operation reduces the formation of so-called tensile strain patterns compared to batch annealing. Continuous SHT requires rapid heating of the moving roll-bonded product, with average heating rates greater than 5°C / s, preferably greater than 10°C / s.

[0037] After the solution heat treatment, it is important to cool the composite product to a temperature below 175°C, preferably below about 100°C, and more preferably to ambient temperature quickly enough to prevent or minimize uncontrolled precipitation of secondary phases, such as Al2CuMg and Al2Cu. On the other hand, the cooling rate should not be too high to allow sufficient flatness and low levels of residual stress in the composite product. A suitable cooling rate can be achieved by the use of water, such as water immersion or water jets. Solution heat treatment in this temperature range followed by rapid cooling creates a supersaturated microstructure. The composite product may be further cold worked, for example by stretching to a range of about 0.5-8% of its original length, to relieve residual stress therein and to improve the flatness of the product. Preferably, the stretching is in the range of about 0.5%-6%, more preferably about 0.5%-4%, and most preferably about 0.5%-3%.

[0038] After cooling, the rolled composite aerospace product is usually naturally aged at ambient temperature; alternatively, the composite aerospace product can also be artificially aged. Artificial aging during this process step can be particularly useful for higher specification products.

[0039] In one embodiment, the composition of the Al-Cu aluminum alloy cladding layer is tailored to provide optimal corrosion protection for the 2XXX series core alloy with an open-circuit corrosion value (vs. standard calomel electrode (SCE), also referred to as "corrosion potential") of -710 mV or less (e.g., -750 mV), measured with a 0.1 N calomel electrode on material solution heat treated in a solution of 53 g / L NaCl + 3 g / L H2O2 at 25°C and rapidly cooled. In a preferred embodiment, the corrosion potential of the Al-Cu aluminum alloy cladding layer is in the range of -730 mV to -800 mV, measured after SHT and rapidly cooled, thus when the critical alloying elements are generally in solid solution.

[0040] In one embodiment, the corrosion potential difference between the 2XXX core layer and the Al-Cu aluminum alloy cladding layer, i.e., in the final temper, is in the range of 30 mV to 100 mV to provide sufficient corrosion protection from the anodic cladding layer to the core layer.

[0041] The Al-Cu aluminum alloy cladding layers are typically much thinner than the core, with each Al-Cu aluminum alloy layer comprising 1%-20% of the total thickness of the composite, and more preferably, the Al-Cu alloy cladding layers comprise about 1%-10% of the total thickness of the composite.

[0042] In one embodiment, an Al-Cu aluminum alloy cladding layer is bonded onto one surface or sides of a 2XXX series core layer.

[0043] In one embodiment, an Al-Cu aluminum alloy cladding layer is bonded onto both surfaces or both faces of a 2XXX series core layer that forms the outer surface of the rolled composite aerospace product.

[0044] In one embodiment, an intermediate liner or layer is disposed between the 2XXX series core layer and the Al-Cu aluminum alloy cladding layer, the intermediate liner being made from an aluminum alloy different from the Al-Cu aluminum layer. In some cases, such an aluminum alloy for the intermediate liner can be a 1XXX series alloy. This intermediate liner acts as an additional diffusion barrier for Cu from the core alloy to the outer surface layer formed by the Al-Cu aluminum alloy. It allows to create a difference in Cu content between the various layers and to create a Cu gradient, thereby providing increased galvanic protection to the 2XXX series core alloy, improving the pitting and intergranular corrosion resistance of the 2XXX series core alloy by preferential corrosion of the intermediate liner, while maintaining the hardness and surface properties provided by the Al-Cu aluminum alloy outer layer. The intermediate liner is preferably also roll bonded to the core alloy. Each intermediate liner constitutes 1% to 20% of the total thickness of the composite aerospace product, preferably about 1% to 10% of the total thickness of the composite aerospace product.

[0045] In one embodiment, the rolled composite aerospace product has a total thickness of at least 0.8 mm.

[0046] In one embodiment, the rolled composite aerospace product has a total thickness of at most 2 inches, preferably at most 1 inch, and most preferably at most 12 mm.

[0047] Optionally, the rolled composite aerospace product is a plate product.

[0048] Optionally, the rolled composite aerospace product is a sheet product.

[0049] The Al-Cu aluminum alloy cladding layer has a Cu content in the range of 0.06% to 2.8%. In one embodiment, the upper limit of the Cu content is about 1.8%, preferably about 1.6%. In one embodiment, the lower limit of the Cu content is preferably 0.10%, more preferably 0.20%, and most preferably 0.50%, to provide optimal corrosion protection for the core alloy. The Cu content provides strength to the aluminum alloy cladding layer, allows the corrosion potential to be adjusted to a target range, and allows the grain boundary corrosion resistance to be controlled to an acceptable level for use as an aerospace component.

[0050] Optionally, the Cu content in the cladding layer can be about 0.06%-2.8% (0.1%-2.5%, 0.1%-1.8%, 0.5%-2.0%, 0.5%-1.6%, or 1.0%-1.9%). Optionally, the Cu content in the cladding layer can be about 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0. It can be 6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 25%, 2.6%, 2.7%, or 2.8%.

[0051] In one embodiment, the Al-Cu aluminum alloy cladding layer comprises, in weight percent: Cu: 0.06% to 2.8%, preferably 0.10% to 1.8%, more preferably 0.50% to 1.6%, Mg: maximum 1.5%, preferably 0.10% to 1.2%, more preferably 0.2% to 0.9%, Mn: maximum 0.5%, preferably 0.10% to 0.5%, Si: max 0.5%, preferably max 0.3%, Fe: max 0.4%, preferably max 0.3%, Cr: Maximum 0.25%, V: 0.25% max. Zr: 0.2% max. Ag: max 0.80%, preferably max 0.40%, more preferably max 0.10%; Zn: max 0.3%, preferably max 0.15%, Ti: 0.2% max., and The remainder comes from an aluminum alloy having a composition including unavoidable impurities and aluminum, preferably with each of the unavoidable impurities being a maximum of 0.05% and with a total of a maximum of 0.15%.

[0052] Mg may be added to the Al-Cu aluminum alloy cladding layer in the range of up to about 1.5%, preferably up to about 1.2%, to provide additional strength to the cladding layer through precipitation of Al2CuMg precipitates and / or solid solution hardening. In one embodiment, the upper limit of the Mg content is about 0.9%, more preferably about 0.80%. The preferred lower limit of Mg addition is about 0.10%, more preferably about 0.20%, and most preferably about 0.35%.

[0053] Optionally, the Mg content in the cladding layer can be up to 1.5% (e.g., 0.10%-1.2% or 0.2%-0.9%). Optionally, the Mg content in the cladding layer can be about 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%. , 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%.

[0054] In one embodiment, the Mg content is less than the Cu content in the Al-Cu alloy so that Cu remains the major alloying element.

[0055] Mn may be added to the Al-Cu aluminum alloy clad layer in the range of up to 0.5%, preferably up to 0.4%, to control the grain structure through the formation of dispersoids and which dispersoids immobilize the grain boundaries during homogenization and / or preheating before hot rolling. A preferred lower limit for that purpose is about 0.10%, more preferably about 0.15%. Mn contributes to maintaining a small grain size in the clad layer(s), providing a better surface appearance and fewer surface cracks after subsequent forming operations. The presence of Mn promotes the conversion of β-AlFeSi phase (Al5FeSi) to α-AlFeSi (Al8Fe2Si) and stabilizes the α-AlFeSi phase, thus improving the quality of the anodization of the outer surface of the Al-Cu aluminum alloy clad layer. The presence of Mn also advantageously increases the corrosion potential of Al-Cu aluminum alloys, and the amount of Mn added can be adjusted to optimize the corrosion potential difference between the 2XXX series core alloy and the outer cladding layer(s) depending on the application, thereby enhancing the corrosion resistance of rolled composite aerospace products.

[0056] Optionally, the Mn content in the cladding layer is at most 0.5% (e.g., 0.10%-0.5% or 0.2%-0.4%). Optionally, the Mn content in the cladding layer can be about 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%.

[0057] In another embodiment, the Mn content is max 0.2%, preferably max 0.15%, more preferably max 0.10%, so as not to be intentionally added and to limit the formation of detrimental coarse intermetallic compounds in combination with the presence of Fe.

[0058] Iron is a common impurity and can be present in a range up to about 0.4%. If the Fe content exceeds 0.4%, large Fe-containing intermetallic compounds may form, which may cause vein patterns or cloud the anodized oxide layer. In one embodiment, the Fe content is kept at a maximum of about 0.3%. In one embodiment, the Fe content is at least 0.10%.

[0059] Optionally, the Fe content in the cladding layer is at most 0.4% (e.g., at most 0.3% or 0.06-0.35%). Optionally, the Fe content in the cladding layer can be about 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.25%, 0.3%, 0.35%, or 0.4%.

[0060] Silicon (Si) is a common impurity and may be present in a range up to about 0.5%, preferably kept at a maximum of about 0.3%. More preferred Si levels range up to about 0.20%. In one embodiment, the Si level is at least about 0.05%, preferably at least about 0.07%, to obtain color strength and stability after anodization.

[0061] Optionally, the Si content in the cladding layer is at most 0.5% (e.g., 0.10%-0.5% or 0.15%-0.3%). Optionally, the Si content in the cladding layer can be about 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%.

[0062] Cr may be added up to 0.25% to increase the strength of the aluminum alloy and to control the grain structure. Preferably, it is present up to 0.20%, more preferably up to 0.15%. In one embodiment, Cr is among the inevitable impurities.

[0063] In some cases, the Cr content in the cladding layer can be up to 0.25% (e.g., up to 0.20%, up to 0.09%, up to 0.04%, 0.05%-0.25%, 0.1%-0.25%, or 0.15%-0.2%). Optionally, the Cr content can be 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, or 0.25%.

[0064] V may be added up to a maximum of 0.25% to increase the strength of the aluminum alloy and to control the grain structure. Preferably, it is present at a maximum of 0.20%, more preferably at a maximum of 0.15%. In one embodiment, V is among the unavoidable impurities, preferably at a maximum of only 0.02%, more preferably at a maximum of only 0.01%.

[0065] In some cases, the V content in the cladding layer can be up to 0.25% (e.g., up to 0.20%, up to 0.09%, up to 0.04%, 0.05%-0.25%, 0.1%-0.25%, or 0.15%-0.2%). Optionally, the V content can be 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, or 0.25%.

[0066] Ag can be present in the cladding layer in an amount up to 0.80% (e.g., up to 0.40% or up to 0.15%). In some cases, the Ag content in the cladding layer can be about 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, or 0.8%.

[0067] Zn may be present at up to 0.3%, preferably up to 0.15%, without departing from the advantages described herein. Zn makes the aluminum alloy more anodic and can be used to adjust the corrosion potential to a lower value. In one embodiment, the aluminum alloy contains at least 0.05% Zn. In one embodiment, Zn is among the unavoidable impurities.

[0068] In some examples, the Zn content in the cladding layer can be at most 0.3% (e.g., at most 0.25%, at most 0.20%, at most 0.15%, at most 0.09%, at most 0.04%, 0.05%-0.3%, 0.1%-0.25%, or 0.15%-0.2%). Optionally, the Zn content can be 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, or 0.3%.

[0069] Zr may be added up to 0.2%, preferably up to 0.1%, to control grain structure without departing from the advantages described herein. In a preferred embodiment, Zr is among the unavoidable impurities, preferably only up to 0.02%, more preferably only up to 0.01%. At higher levels, it may form deleterious intermetallic particles in aluminum alloys.

[0070] In some cases, the Zr in the cladding layer can be at most 0.2% (e.g., at most 0.15%, at most 0.1%, 0.05%-0.2%, or 0.05%-0.15%). Optionally, the Zr content can be 0.01%, 0.05%, 0.1%, 0.15%, or 0.2%.

[0071] Ti is a grain refiner during solidification of both the ingot and the weld joint. Ti levels should not exceed about 0.2%, preferably up to a maximum of 0.10%, with a more preferred range of Ti being about 0.005%-0.07%. Ti can be added as the sole element or with either boron or carbon as known in the art, e.g., TiB2, Ti-C, etc., and serves as a casting aid for grain size control.

[0072] In some cases, the Ti content in the cladding layer can be at most 0.2% (e.g., at most 0.15%, at most 0.1%, 0.05%-0.2%, or 0.05%-0.15%). Optionally, the Ti content can be 0.01%, 0.05%, 0.1%, 0.15%, or 0.2%.

[0073] In one embodiment, the Al-Cu aluminum alloy cladding layer is made of an aluminum alloy having a composition, by weight, of 0.06%-2.8%, preferably 0.10%-1.8%, Cu, up to 1.5% Mg, up to 0.5% Mn, up to 0.5% Si, up to 0.4% Fe, up to 0.25% Cr, up to 0.25% V, up to 0.2% Zr, up to 0.3% Zn, up to 0.2% Ti, with the balance being aluminum and impurities, with preferred narrower composition ranges as described and claimed herein.

[0074] In one embodiment, the 2XXX series core layer comprises, in weight percent: Cu: 1.9% to 7.0%, preferably 3.0% to 6.8%, more preferably 3.2% to 4.95%, Mg: 0.30% to 1.8%, preferably 0.35% to 1.8%, more preferably 0.6% to 1.8%, Mn: maximum 1.2%, preferably 0.2% to 1.2%, more preferably 0.25% to 0.9%, Si: max 0.40%, preferably max 0.25%, Fe: max 0.40%, preferably max 0.25%, Cr: max 0.35%, preferably max 0.10%, Zn: max 1.0%, preferably max 0.25%, Ti: maximum 0.15%, preferably 0.01% to 0.10%, Zr: max 0.25, preferably max 0.12%, V: 0.25% max. Li: max 2.0%, Ag: Maximum 0.80%, Ni: max 2.5% and The remainder comes from aluminum alloys having a composition that includes aluminum and impurities, typically present at less than 0.05% each and less than 0.15% in total.

[0075] Optionally, the 2XXX series core layer comprises, by weight percent: Cu: 1.9% to 7.0%, preferably 3.0% to 6.8%, more preferably 3.2% to 4.95%, Mg: 0.30% to 1.8%, preferably 0.6% to 1.8%, more preferably 0.8% to 1.8%, Mn: maximum 1.2%, preferably 0.2% to 1.2%, more preferably 0.25% to 0.9%, Si: max 0.40%, preferably max 0.25%, Fe: max 0.40%, preferably max 0.25%, Cr: max 0.35%, preferably max 0.10%, Zn: max 0.4%, preferably max 0.25%, Ti: maximum 0.15%, preferably 0.01% to 0.10%, Zr: max 0.25, preferably max 0.12%, V: maximum 0.25%, preferably maximum 0.05%, and The remainder comes from an aluminum alloy having a composition including, and preferably consisting of, aluminum and impurities, typically present at less than 0.05% each and less than 0.15% in total.

[0076] The Cu content in the core layer can be 1.9%-7.0% (e.g., 2.0%-7.0%, 3.0%-6.8%, 3.0%-6.0%, or 3.2%-4.95%). Optionally, the Cu content in the core layer can be about 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9 ... It can be 4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6.0%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, or 7.0%.

[0077] The Mg content in the core layer can be 0.30%-1.8% (e.g., 0.35%-1.8% or 0.6%-1.8%). Optionally, the Mg content in the core layer can be about 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, or 1.8%.

[0078] The Mn content in the core layer can be up to 1.5% (eg, 0.2% to 1.2% or 0.25% to 0.9%). Optionally, the Mn content in the core layer can be about 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1.0%, 1.1%, or 1.2%.

[0079] The Si content in the core layer can be at most 0.4% (e.g., at most 0.3%, at most 0.25%, or 0.06-0.35%). Optionally, the Si content in the core layer can be about 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.25%, 0.3%, 0.35%, or 0.4%.

[0080] Optionally, the Fe content in the core layer is at most 0.4% (e.g., at most 0.3%, at most 0.25%, or 0.06-0.35%). Optionally, the Fe content in the core layer can be about 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.25%, 0.3%, 0.35%, or 0.4%.

[0081] The Cr content in the core layer can be at most 0.35% (e.g., at most 0.20%, at most 0.10%, at most 0.09%, at most 0.04%, 0.05%-0.25%, 0.1%-0.25%, or 0.15%-0.2%). Optionally, the Cr content can be 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3% or 0.35%.

[0082] The Zn content in the core layer can be at most 1.0% (eg, at most 0.25%, 0.10% to 1.2%, or 0.2% to 0.9%). Optionally, the Zn content in the core layer can be about 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, or 1.0%.

[0083] The Ti content in the core layer can be at most 0.15% (e.g., at most 0.10%, at most 0.01%, 0.05%-0.2%, or 0.05%-0.15%). Optionally, the Ti content can be 0.01%, 0.05%, 0.1%, or 0.15%.

[0084] The Zr content in the core layer can be at most 0.25% (e.g., at most 0.15%, at most 0.12%, at most 0.1%, 0.05%-0.2%, or 0.05%-0.15%). Optionally, the Zr content can be 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, or 0.25%.

[0085] The V content in the core layer can be up to 0.25% (e.g., up to 0.20%, up to 0.09%, up to 0.04%, 0.05%-0.25%, 0.1%-0.25%, or 0.15%-0.2%). Optionally, the V content can be 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, or 0.25%.

[0086] The Li content in the core layer can be up to 2.0% (e.g., up to 1.5%, 0.10%-1.2%, or 0.2%-0.9%). Optionally, the Li content in the core layer can be about 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.25%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 25%, 20%, 25%, 30%, 35%, 30%, 35%, 40%, 40%, 45%, 50%, 5 ... It can be 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2.0%.

[0087] Ag can be present in the cladding layer in an amount up to 0.80% (e.g., up to 0.40% or up to 0.15%). In some cases, the Ag content in the cladding layer can be about 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, or 0.8%.

[0088] The Ni content in the core layer can be up to 2.5% (e.g., up to 2.0%, up to 1.5%, 0.10%-2.5%, or 0.2%-2.0%). Optionally, the Ni content in the core layer can be about 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, It can be 4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4% or 2.5%.

[0089] In a preferred embodiment, the 2XXX series core layer is derived from an aluminum alloy of the AA2X24 series, where X is equal to 0, 1, 2, 3, 4, 5, 6, 7, or 8. Particularly preferred aluminum alloys are within the composition ranges of AA2024, AA2524, and AA2624.

[0090] In one embodiment, the 2XXX series core layer and metallized on one or both sides with an Al-Cu alloy cladding layer is provided in the T3, T351, T39, T42, T8 or T851 condition.

[0091] The 2XXX series core layers, metallized on one or both sides with an Al-Cu alloy cladding layer, may be provided to the user in a non-solution heat treated condition, e.g., in the "F" temper or in the annealed "O" temper, and then formed, solution heat treated and aged to the required condition, e.g., in the T3, T351, T39, T42, T8 or T851 tempers.

[0092] Also provided is a method of making the rolled composite aerospace products described herein, the method comprising: (a) providing an ingot or rolled stock of a 2XXX series aluminum alloy for forming a core layer of a composite aerospace product; (b) homogenizing the 2XXX series aluminum alloy ingot at a temperature in the range of 400°C to 510°C for at least two hours; (c) providing an ingot or rolled clad liner of an Al-Cu aluminum alloy for forming an outer clad layer on a core 2XXX series aluminum alloy, optionally two ingots or two rolled clad liners of Al-Cu aluminum alloy are provided for forming clad layers on each side of the core 2XXX series aluminum alloy; (d) optionally homogenizing or preheating the Al-Cu aluminum alloy ingot(s) at a temperature in the range of at least about 400°C, preferably at a temperature in the range of about 400°C to 510°C, for at least 0.5 hours; (e) roll bonding the Al-Cu aluminum alloy layer(s) to the 2XXX series core alloy layer, preferably by hot rolling and optionally subsequent cold rolling, to form a roll bonded product; (f) solution heat treating the roll bonded product at a temperature in the range of about 450°C to 510°C in either a batch or continuous operation; (g) cooling the solution heat treated roll bonded product to less than about 100° C., preferably to ambient temperature; (h) optionally stretching the solution heat treated roll bonded product by cold drawing, preferably in the range of about 0.5% to 8% of its original length, preferably in the range of about 0.5% to 6%, more preferably in the range of about 0.5% to 4%, and most preferably in the range of about 0.5% to 3%; (i) ageing the cooled roll bonded product by natural and / or artificial aging. In a preferred embodiment, the ageing is to a 2XXX series core layer in a T3, T351, T39, T42, T8 or T851 temper. The ageing is to an Al-Cu alloy cladding layer in the same temper as the 2XXX series core layer.

[0093] In one embodiment of the method as described herein, in a subsequent processing step (j), the rolled composite aerospace product is formed into a shaped product having at least one of a uniaxial curvature or a biaxial curvature in a forming process at ambient or elevated temperature.

[0094] In an alternative embodiment of the method, after roll bonding of the Al-Cu aluminium alloy(s) to the 2XXX series core alloy in step (e), preferably by hot rolling and optionally subsequent cold rolling to form a roll bonded product, the roll bonded product at ambient or elevated temperature is formed in a forming process into a formed product having at least one of uniaxial or biaxial curvature, followed by solution heat treatment and then aging to final temper.

[0095] The forming process can be by forming operations selected from the group of bending operations, roll forming, stretch forming, aged creep forming, deep drawing, and high energy hydroforming, in particular by explosive forming or electric discharge forming.

[0096] In one embodiment, the high temperature forming process or operation is carried out at a temperature in the range of about 140° C. to 200° C., and preferably the rolled composite aerospace product is held at the forming temperature for a time in the range of about 1 to 50 hours. In a preferred embodiment, the high temperature forming is by an age creep forming operation. Age creep forming is a process or operation that constrains a part into a specific shape during an age heat treatment, allowing the part to relieve stress and creep against a contour, for example a fuselage skin with a single or double curvature.

[0097] In one embodiment, the rolled composite aerospace product described herein after undergoing a solution heat treatment (SHT) and prior to forming into a shape, as disclosed in patent document US-2014 / 036699-A1, which is incorporated herein by reference, is subjected to a post-SHT cold working step that induces at least 25% cold work in the rolled composite aerospace product, and specifically excluded from this disclosure is that the cold working includes cold rolling to a final gauge of the rolled aerospace product.

[0098] One aspect described herein relates to the use of an Al-Cu aluminum alloy as described and claimed herein as a clad layer on one or both surfaces of a 2XXX series aluminum alloy to form a rolled aerospace clad product.

[0099] In a further aspect, provided herein is a welded structure comprising a rolled composite aerospace product as described herein and at least one aluminum alloy reinforcing element joined to the rolled composite aerospace product by a riveting or welding operation.

[0100] The present disclosure also relates to a welded structural member of an aircraft comprising a rolled composite aerospace product as described herein and at least one aluminium alloy reinforcing element, preferably a stringer, joined to the rolled composite aerospace product by a riveting or welding operation, for example by laser beam welding or friction stir welding.

[0101] It also relates to welded fuselage structures in which fuselage panels are joined together by laser beam welding ("LBW") or friction stir welding ("FSW"), for example by butt welding.

[0102] The products described herein also include aircraft or spacecraft whose fuselage is constructed, in whole or in part, from the rolled composite aerospace products described herein that may be incorporated into various structural portions of the aircraft. For example, the various disclosed embodiments may be used to form structural portions in a wing assembly and / or a tail assembly (tail section). The aircraft generally represent commercial passenger or cargo aircraft. In alternative embodiments, the products described herein may also be incorporated into other types of air vehicles. Examples of such air vehicles included manned or unmanned military aircraft, rotorcraft, or even ballistic vehicles.

[0103] The rolled composite aerospace products described herein can be formed into components for aircraft, such as fuselage parts or panels, or wing parts or panels, for example, which can take advantage of the described products. The forming referred to can include bending, stretch forming, machining, and other forming operations known in the art to form panels or other components for aircraft, aerospace, or other vehicles. Forming, including bending or other plastic deformation, can be performed at room temperature or at elevated temperatures. EXAMPLES

[0104] 1 illustrates a rolled composite aerospace product 10 as shown and claimed herein, which is comprised of a three layer construction of a 2XXX series core alloy layer 20 with an Al-Cu aluminum alloy cladding layer 30 on each side of the 2XXX series core alloy. In another embodiment, the 2XXX series core alloy is clad on only one side or on both sides with an Al-Cu aluminum alloy clad liner.

[0105] 2 illustrates the rolled composite aerospace product 10 shown and claimed herein having a five layer structure consisting of a 2XXX series core alloy layer 20 having an Al-Cu aluminum alloy clad layer 30 on each side thereof, with an intermediate liner or clad layer 40 of another different aluminum alloy interposed between the core alloy layer 20 and the Al-Cu aluminum alloy clad layer 30 such that the Al-Cu aluminum alloy clad layer 30 forms the outer layer of the rolled composite aerospace product 10. In one embodiment, the intermediate liner or clad layer 40 is made of an aluminum alloy from the 1XXX series aluminum alloy.

[0106] FIG. 3 is a schematic flow schedule of some embodiments of the process described herein for manufacturing a rolled composite aerospace product. In process step 1, an ingot is cast of a 2XXX series alloy that forms the core alloy of the composite aerospace product, which can be optionally stripped in step 2 to remove segregated areas near the as-cast surface of the rolled ingot and to enhance the flatness of the product. In process step 3, the rolled ingot is homogenized. In parallel in process step 4, an ingot is cast of an Al-Cu aluminum alloy to form at least one cladding layer on the surface of the core alloy of the composite aerospace product, and optionally on both sides of the core alloy. This ingot can also be optionally stripped in step 5. In process step 6, the Al-Cu alloy is preheated to a hot rolling start temperature and then hot rolled in process step 7 to form the liner plate(s), since the cladding layers are usually much thinner than the core. In process step 8, the 2XXX core alloy and a liner plate of Al-Cu aluminum alloy on one or both sides of the core alloy are roll bonded, preferably by hot rolling. Depending on the desired final gauge, the roll bonded product can be cold rolled to the final gauge, e.g., sheet product or thin gauge plate product, in process step 9. In process step 10, the rolled aerospace product is solution heat treated and then cooled in process step 11 and preferably stretched in process step 12.

[0107] In one embodiment, the cooled product is formed in a forming process 13 and in process step 14 is aged, ie, naturally or artificially aged, to a final temper, for example a T3 or T8 temper.

[0108] In one embodiment, the forming process 13 can be combined with aging in process step 14. For example, the forming operation is carried out at a temperature in the range of about 140° C. to 200° C. for a time preferably in the range of about 1 to 50 hours, so as to also effect artificial aging of both the 2XXX series core and the Al-Cu alloy cladding layer(s).

[0109] In one embodiment, the cooled product is aged, either naturally or artificially, to the desired temper in process step 14 and then formed into a shaped product of a desired shape in forming process 13.

[0110] In an alternative embodiment, after roll bonding of the 2XXX series core and Al-Cu aluminum alloy cladding layer(s) to final gauge, the rolled product is formed to a predetermined shape in forming process 13, solution heat treated in process step 15, cooled in process step 11, and subsequently aged to a final temper, e.g., T3 or T8 temper, i.e., naturally or artificially aged, in process step 14.

[0111] Real-life examples Example 1 is a rolled composite aerospace product including a 2XXX series core layer and an Al-Cu alloy clad layer joined to at least one surface of the 2XXX series core layer, wherein the Al-Cu alloy clad layer is an aluminum alloy containing 0.06%-2.8% Cu.

[0112] Example 2 is a rolled composite aerospace product as described in any preceding or subsequent example, wherein the Al-Cu alloy cladding layer is an aluminum alloy containing 0.10%-1.8% Cu.

[0113] In Example 3, the Al-Cu alloy clad layer is Cu: 0.06%~2.8%, Mg: 1.5% max. Mn: 0.5% max. Si: 0.5% max. Fe: 0.4% max. Cr: Maximum 0.25%, V: 0.25% max. Zr: 0.2% max. Ag: Maximum 0.80%, Zn: 0.3% max. Ti: Maximum 0.2% The remainder is an aluminum alloy having a composition with inevitable impurities and aluminum, being a rolled composite aerospace product as described in any preceding or succeeding example.

[0114] Example 4 is a rolled composite aerospace product as described in any preceding or subsequent example, wherein the Cu content is in the range of 0.2% to 1.5%.

[0115] Example 5 is a rolled composite aerospace product as described in any preceding or subsequent example, wherein the Mg content is in the range of 0.20% to 1.2%.

[0116] Example 6 is the rolled composite aerospace product of any preceding or subsequent example, wherein the Al-Cu aluminum alloy cladding layer has a corrosion potential of -710 mV or less.

[0117] Example 7 is the rolled composite aerospace product of any preceding or subsequent example, wherein the Al-Cu alloy cladding layer is joined to the at least one surface of the 2XXX series core layer by roll bonding.

[0118] Example 8 is the rolled composite aerospace product of any preceding or subsequent example, wherein the Al-Cu alloy cladding layer has a thickness in the range of 1% to 20% of the total thickness of the rolled composite aerospace product.

[0119] Example 9 is a rolled composite aerospace product as described in any preceding or subsequent example, comprising a 2XXX series core layer and an Al-Cu alloy cladding layer joined to one or both surfaces of the 2XXX series core layer.

[0120] Example 10 is a rolled composite aerospace product as described in any preceding or subsequent example, wherein an intermediate liner is disposed between the 2XXX series core layer and the Al-Cu alloy clad layer, the intermediate liner being made of a different aluminum alloy than the Al-Cu alloy clad layer.

[0121] Example 11 is a rolled composite aerospace product as described in any preceding or subsequent example, wherein the intermediate liner is made of a 1XXX series aluminum alloy.

[0122] Example 12 shows that the 2XXX series alloy of the core layer is in weight percent Cu: 1.9%~7.0%, Mg: 0.30%~1.8%, Mn: 1.2% max. Si: 0.40% max. Fe: max. 0.40%, Cr: Maximum 0.35%, Zn: Maximum 1.0%, Ti: 0.15% max. Zr: max 0.25, V: 0.25% max. Li: max 2.0%, Ag: Maximum 0.80%, Ni: max 2.5% and The remainder is a rolled composite aerospace product having a composition of aluminum and impurities as described in any preceding or following example.

[0123] Example 13 is a rolled composite aerospace product as described in any preceding or subsequent example, wherein the 2XXX series core layer is derived from a 2X24 series alloy.

[0124] Example 14 is a rolled composite aerospace product as described in any preceding or subsequent example, wherein at least the 2XXX series core layer is in a T3, T351, T39, T42, T8 or T851 temper.

[0125] Example 15 is the rolled composite aerospace product of any preceding or subsequent example, wherein the rolled composite aerospace product has a total thickness of 0.8 mm to 50.8 mm.

[0126] Example 16 is the rolled composite aerospace product of any preceding or subsequent example, wherein the rolled composite aerospace product is an aerospace structural part.

[0127] Example 17 is a method of making a rolled composite aerospace product as described in any preceding or subsequent example, comprising the steps of: providing an ingot of a 2XXX series aluminum alloy for forming the core layer of the composite aerospace product; homogenizing the ingot of the 2XXX series aluminum alloy at a temperature in the range of 400° C. to 510° C. for at least 2 hours; providing an ingot or rolled clad liner of an Al-Cu aluminum alloy for forming an outer clad layer on said 2XXX series core aluminum alloy; Optionally, homogenizing or preheating the ingot of Al-Cu aluminum alloy forming the outer cladding layer at a temperature in the range of at least 400° C. for at least 0.5 hours; roll bonding the Al-Cu aluminum alloy cladding layer to the 2XXX series core alloy to form a roll bonded product, optionally followed by cold rolling; subjecting the roll-bonded product to a solution heat treatment at a temperature in the range of 450°C to 510°C; cooling the solution heat treated roll bonded product to less than 100°C; Optionally, stretching the solution heat treated and cooled roll bonded product and ageing the cooled roll bonded product. The method comprises:

[0128] Example 18 is the method of any preceding or subsequent example, wherein the method further comprises forming the solution heat treated, cooled, and optionally stretched roll-bonded product into a predetermined shaped product having uniaxial or biaxial curvature in a forming process.

[0129] Example 19 is the method of any preceding or subsequent example, wherein a forming step is performed after said aging step.

[0130] Example 20 is the method of any preceding or subsequent example, wherein the forming and aging steps are combined in a forming step at an elevated temperature for a time period ranging from 1 to 50 hours.

[0131] All patents, publications and abstracts cited above are incorporated herein by reference in their entirety. Various embodiments of the invention have been described in the fulfillment of various objectives of the invention. It should be recognized that these embodiments are merely illustrative of the principles of the invention. Numerous modifications and adaptations thereof will be readily apparent to those skilled in the art without departing from the spirit and scope of the invention as defined in the following claims.

Claims

1. A rolled composite aerospace product, comprising a 2xxx series core layer and an Al-Cu alloy clad layer joined to at least one surface of the 2xxx series core layer, the Al-Cu alloy clad layer being an aluminum alloy containing 0.06%-2.8% Cu.

6. Rolled composite aerospace products.

2. The rolled composite aerospace product of claim 1, wherein said Al-Cu alloy cladding layer is of an aluminum alloy containing 0.10% to 1.8% Cu.

3. The Al-Cu alloy clad layer is in weight percent, Cu: 0.06% to 2.8%, Mg: max 1.5%, Mn: max 0.5%, Si: max 0.5%, Fe: max 0.4%, Cr: max 0.25%, V: 0.25% max. Zr: max 0.2%, Ag: max 0.80%, Zn: max 0.3%, Ti: maximum 0.2%; and 3. The rolled composite aerospace product of claim 1 or 2, wherein the remainder is of an aluminium alloy having a composition consisting of inevitable impurities and aluminium.

4. The rolled composite aerospace product of claim 3, wherein said Cu content is in the range of 0.2% to 1.5%.

5. The rolled composite aerospace product according to claim 3 or 4, wherein the Mg content is in the range of 0.20% to 1.2%.

6. The rolled composite aerospace product according to any one of claims 1 to 5, wherein the Al-Cu aluminum alloy cladding layer has a corrosion potential of -710mV or less.

7. The rolled composite aerospace product according to any one of claims 1 to 6, wherein said Al-Cu alloy cladding layer is joined to said at least one surface of said 2XXX series core layer by roll bonding.

8. The rolled composite aerospace product according to any one of claims 1 to 7, wherein said Al-Cu alloy cladding layer has a thickness in the range of 1% to 20% of the total thickness of said rolled composite aerospace product.

9. 9. The rolled composite aerospace product according to any one of claims 1 to 8, comprising a 2XXX series core layer and an Al-Cu alloy cladding layer joined to one or both surfaces of said 2XXX series core layer.

10. The rolled composite aerospace product according to any one of claims 1 to 9, wherein an intermediate liner is disposed between the 2XXX series core layer and the Al-Cu alloy cladding layer, the intermediate liner being made of an aluminum alloy different from the Al-Cu alloy cladding layer.

11. 11. The rolled composite aerospace product of claim 10, wherein said intermediate liner is made from a 1XXX series aluminum alloy.

12. The 2xxx series alloy of the core layer comprises, by weight percent: Cu: 1.9% to 7.0%, Mg: 0.30% to 1.8%, Mn: max 1.2%, Si: maximum 0.40% Fe: max 0.40%, Cr: max 0.35%, Zn: max 1.0%, Ti: max 0.15%, Zr: 0.25 max. V: 0.25% max. Li: max 2.0%, Ag: max 0.80%, Ni: maximum 2.5%; and A rolled composite aerospace product according to any one of claims 1 to 11, having a composition with the remainder being aluminium and impurities.

13. The rolled composite aerospace product according to any one of claims 1 to 12, wherein said 2XXX series core layer is derived from said 2X24 series alloy.

14. The rolled composite aerospace product of any one of claims 1 to 13, wherein at least said 2XXX series core layer is in a T3, T351, T39, T42, T8 or T851 temper.

15. The rolled composite aerospace product according to any one of the preceding claims, wherein the rolled composite aerospace product has a total thickness of 0.8mm to 50.8mm.

16. The rolled composite aerospace product according to any one of claims 1 to 15, wherein the rolled composite aerospace product is an aerospace structural part.

17. A method for producing a rolled composite aerospace product according to any one of claims 1 to 16, comprising the steps of: providing an ingot of a 2xxx series aluminum alloy for forming said core layer of said composite aerospace product; homogenizing said ingot of said 2xxx series aluminum alloy at a temperature in the range of 400°C to 510°C for at least 2 hours; providing an ingot or rolled clad liner of an Al-Cu aluminum alloy for forming an outer cladding layer on said 2xxx series core aluminum alloy; Optionally, homogenizing or preheating the ingot of Al-Cu aluminum clad alloy forming the outer cladding layer at a temperature in the range of at least 400° C. for at least 0.5 hours; roll bonding the Al-Cu aluminum alloy cladding layer to the 2xxx series core alloy to form a roll bonded product, optionally followed by cold rolling; subjecting the roll-bonded product to a solution heat treatment at a temperature in the range of 450°C to 510°C; cooling the solution heat treated roll bonded product to less than 100°C; Optionally, stretching the solution heat treated and cooled roll bonded product and ageing the cooled roll bonded product. The method comprising:

18. 20. The method of claim 17, further comprising forming the solution heat treated, cooled and optionally further stretched roll bonded product into a product of predetermined shape having uniaxial or biaxial curvature in a forming process.

19. 19. The method according to claim 17 or 18, wherein a forming step is carried out after the ageing step.

20. 20. The method of claim 19, wherein the forming and aging steps are combined in a forming step at an elevated temperature for a time in the range of 1 to 50 hours.

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