RU2783714C1 - Cladded product based on 2xxx series alloy for aerospace equipment - Google Patents

Abstract

FIELD: composite materials.

SUBSTANCE: invention relates to composite products used in aerospace engineering. The composite product contains a core layer of the 2XXX series alloy and a cladding layer of the 6XXX series aluminum alloy connected to at least one surface of the core layer of the 2XXX series alloy, wherein the 6XXX series aluminum alloy contains, wt. %: Si from 0.3 to 1.0, Mg from 0.3 to 1.1, Mn from 0.04 to 1.0, Fe from 0.03 to 0.4, Cu up to 0.10 inclusive, Cr up to inclusive 0.25, V up to 0.2 inclusive, Zr up to 0.2 inclusive, Zn up to 0.5 inclusive, Ti up to 0.15 inclusive, unavoidable impurities, quantity each of which is less than 0.05, less than 0.15 in total, the rest is aluminum. The invention also relates to a method for manufacturing a rolled composite product for aerospace equipment.

EFFECT: invention is aimed at creating a cladded product containing a 2XXX series alloy with an improved balance of corrosion resistance and formability.

20 cl, 2 dwg

Description

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit and priority of European Patent Application No. 19193108.8, filed August 22, 2019, titled CLAD 2XXX-SERIES AEROSPACE PRODUCT, the contents of which are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to an aerospace composite rolled product comprising a 2XXX series alloy core layer and an aluminum alloy layer bonded to at least one surface of the 2XXX series alloy core layer. The rolled composite product is ideal for the manufacture of structural parts for aerospace engineering. The present invention also relates to a method for manufacturing a rolled composite product for aerospace applications.

BACKGROUND OF THE INVENTION

In the aerospace industry, AA2024 series aluminum alloy and its modifications are widely used as an aluminum alloy with high damage resistance in the main T3 state or its modifications. Products made from these aluminum alloys have a relatively high strength-to-weight ratio and exhibit good toughness, good fatigue performance and adequate corrosion resistance.

For many decades, to improve corrosion resistance, the AA2024 series alloy product can be made as a composite product with a relatively thin cladding layer on one or both sides. The cladding layer is usually of higher purity to protect the AA2024 series core alloy from corrosion. The cladding includes substantially unalloyed aluminium. Generally, reference is made to 1XXX series aluminum alloys in general, which include subclasses 1000 type, 1100 type, 1200 type, and 1300 type. Si+Fe<0.7%, Cu<0.10%, Mn<0.05%, Mg<0.05%, Zn<0.10%, Ti<0.03% and balance: aluminium.

In addition, AA2024 series aluminum alloy clad with 1XXX series alloy can be anodized. Anodizing increases resistance to corrosion and wear and provides better adhesion of primers and adhesives than bare metal. Anodized products are used in the process of joining metal parts using structural adhesives, for example, in wing skin panels, horizontal tail, vertical tail or fuselage. Another known application is a layered structure where one or more fibre-reinforced (fiberglass) layers are placed between aluminum panels or sheets using an adhesive bond, resulting in a so-called fibre-metal laminate. WO-2017/183965-A1 (Fokker) discloses a process for anodizing an aluminum alloy to apply a porous anodic oxide coating in preparation for the subsequent application of an adhesive tie layer and/or a primer layer.

A disadvantage of the 1XXX series alloy as a cladding layer is that these alloys are very soft and susceptible to surface damage during product handling. In addition, during the molding operation, this can lead to, for example, sticking to the matrix.

DESCRIPTION OF THE INVENTION

As will be described later in this document, unless otherwise noted, aluminum alloy designations and heat treatment designations refer to designations given by the Aluminum Manufacturers Association in aluminum standards and data and registry entries published by the Aluminum Manufacturers Association in 2018 and are well known. a person skilled in the art. Heat treatment status designations are also given in the European standard EN515.

For any description of alloy compositions or preferred alloy compositions, all references to percentages are by weight unless otherwise indicated.

In the context of this document, the terms "up to and including about" explicitly include, among other things, the possibility of zero weight percent of the particular alloying component to which they refer. For example, up to and including 0.20% Zn may include aluminum alloy without Zn.

For the purposes of the present invention, a sheet product or sheet material is understood to mean a rolled product having a thickness of not less than 1.3 mm (0.05 inch) and not more than 6.3 mm (0.25 inch), and thick sheet material or thick sheet product should be understood as a rolled product having a thickness of more than 6.3 mm (0.25 inches). See also Aluminum Standards and Data, Aluminum Manufacturers Association, Chapter 5, Terminology, 1997.

It is an object of the present invention to provide a clad aerospace rolled product containing a 2XXX series alloy with an improved balance of corrosion resistance and formability.

This and other objectives and additional advantages are achieved or exceeded by the present invention providing a rolled aerospace composite product comprising a 2XXX series alloy core layer, the core layer having two facets, and a 6XXX series aluminum alloy clad layer bonded at least with one surface layer of the core from an alloy of the 2XXX series, and the aluminum alloy of the 6XXX series contains, in wt.%,

Si from 0.3% to 1.0%,

Mg from 0.3% to 1.1%,

Mn from 0.04% to 1.0%,

Fe from 0.03% to 0.4%,

Cu up to and including 0.10%,

Cr up to and including 0.25%,

V up to and including 0.2%,

Zr up to and including 0.2%,

Zn up to and including 0.5%,

Ti up to and including 0.15%,

unavoidable impurities, the amount of each is less than 0.05%, total less than 0.15%, balance: aluminum.

The 6XXX series alloy has very good formability characteristics, in particular flexibility and tensile formability, so that a rolled aerospace composite product can be formed in forming operations requiring a high degree of deformation. Formability characteristics are comparable to the formability characteristics of some sheet aluminum alloys for automotive applications. Adhesion of the cladding layer to the shaped matrix is significantly reduced or even eliminated due to the increased hardness of the cladding layer compared to the cladding layer of the 1XXX series. The 6XXX series alloy has a very good surface quality, in particular after molding into a desired shaped article. The absence of surface cracks prevents any molding lubricants from penetrating into the surface. The absence of surface cracks also greatly enhances the fatigue performance of the rolled aerospace composite product. In addition, very good pitting resistance improves fatigue performance, as fatigue is usually caused by the presence of pitting. The 6XXX series alloy has a significantly higher strength than the 1XXX series alloys, resulting in a harder surface and correspondingly less surface damage such as scratches when handling the product. The 6XXX series alloy is significantly stronger than the 1XXX series alloys so that the overall strength of the composite aerospace product is increased compared to the 1XXX series alloy for the same cladding layer thickness. It also allows aerospace composite rolled products to be produced with a thinner cladding thickness, resulting in a reduction in weight and still providing the required good corrosion resistance and improved formability. The 6XXX series alloy is very well anodized, so there are no problems with the subsequent application of an adhesive tie layer and / or a primer layer.

In one embodiment, a 6XXX series aluminum alloy cladding layer achieves a hardness of at least 55 HB when brought to a T4 heat treatment condition. In one embodiment, a 6XXX series aluminum alloy cladding layer achieves a hardness of at least 60 HB and preferably at least 65 HB when brought to a T4 heat treatment condition.

In one embodiment, a 6XXX series aluminum alloy cladding layer is bonded to the core layer by roll bonding, and preferably by hot rolling, to provide the desired metallurgical bond between the layers. This roll bonding process is very economical and results in a very efficient composite product with desired properties. In carrying out said rolling bonding process to obtain a rolled composite product according to the present invention, it is preferable that both the core layer and the 6XXX series aluminum alloy cladding layer(s) experience a reduction in thickness during the rolling bonding process. As a rule, before rolling, in particular before hot rolling, the surface layer is removed from the rolled faces of the ingots of the core layer and the cladding layer(s) in order to remove segregation zones near the surface immediately after the casting of the rolled ingot and increase the flatness of the product.

Preferably, the cast ingot or slab of the 2XXX alloy core layer is homogenized prior to hot rolling and/or it may be preheated immediately prior to hot rolling. The homogenization and/or preheating of 2XXX series alloys prior to hot rolling is typically carried out at a temperature in the range of 400°C to 505°C. The segregation of alloying elements in the material immediately after casting is reduced, and the dissolution of soluble elements also occurs. If the processing takes place at a temperature below about 400° C., the resulting homogenization effect is insufficient. If the temperature is above about 505°C, eutectic melting may occur, which leads to undesirable pore formation. The time of this heat treatment is preferably 2 to 30 hours. The use of longer time intervals usually does not cause any harm. Homogenization is usually carried out at temperatures above 480°C. The usual preheat temperature is in the range from about 430°C to about 460°C, and the holding time is in the range up to and including about 15 hours. Homogenization can be carried out in one step or several steps of temperature increase in order to avoid the onset of melting.

In one embodiment of the present invention, the cast ingot or slab forming the 6XXX series aluminum alloy cladding has been homogenized prior to hot rolling to a smaller gauge to form a suitable cladding for rolling with the 2XXX series alloy core layer to the desired gauge. The surface layer of the rolled faces of a 6XXX series alloy ingot or slab can be stripped to remove segregation zones near the surface immediately after the rolled ingot is cast and to increase the flatness of the product. Homogenization results in a finer and more uniform grain structure and results in an increase in the formability of the alloy layer in the final rolled aerospace composite product. It will dissolve most of the coarse phases, and also complete the conversion of the beta-AlFeSi phase to the alpha-AlFeSi phase, which will improve the anodizing performance of the 6XXX series alloy. The homogenization heat treatment is preferably carried out at a temperature of at least 480°C for at least about 0.5 hours, preferably in the range of about 1 to about 30 hours, typically for about 6 to about 20 hours. Preferably, the homogenization temperature is in the range from about 500°C to about 590°C, preferably in the range from 510°C to 580°C. In one embodiment, the homogenization is carried out at a temperature of not more than 570°C. As is known to those skilled in the art, homogenization can be carried out in one or more temperature raising steps in order to avoid the onset of melting.

The gauge of a rolled aerospace composite product is reduced to a final gauge by hot rolling, optionally followed by cold rolling, as is common in the art. After the rolled composite product has been rolled to a final gauge, the product is typically subjected to a solution heat treatment (SHT) at a temperature in the range of about 450°C to about 505°C for a time sufficient to so that the effects of the solution come close to equilibrium, with typical soak times ranging from 5 to 120 minutes. Preferably, the heat treatment for solid solution (SHT) takes place at a temperature in the range from 475°C to 500°C, for example, at about 495°C. The solution heat treatment is usually carried out in a batch or continuous furnace. Preferred holding times at this temperature range from about 5 minutes to about 35 minutes. However, in the case of clad products, attention should be paid to too long a holding time, since, in particular, too much copper from the 2XXX series alloy core layer can diffuse into the 6XXX series aluminum alloy cladding layer(s), which may adversely affect the corrosion protection provided by the specified layer(s). After solution heat treatment (SHT), it is important that the rolled composite product be cooled sufficiently rapidly to 175°C or below, preferably 100°C or below, and more preferably to ambient temperature to prevent or minimize uncontrolled flashing. , such as Al ₂ CuMg and Al ₂ Cu, in a 2XXX series core alloy. On the other hand, cooling rates should not be too high in order to achieve sufficient flatness and low levels of residual stresses in the rolled composite product. Suitable cooling rates can be achieved with water, for example by immersion in water or cooling with water jets. Solid solution heat treatment in this temperature range provides a recrystallized microstructure of the 6XXX series alloy layer. In the case of a 6XXX series aluminum alloy used in accordance with the present invention, there will be a minimum proportion of undissolved Mg ₂ Si and Si coarse particles after SHT, in particular at a temperature in the range from 475°C to 500°C, for example, at a temperature of about 495°C, which has a positive effect on the strength, formability and corrosion resistance of the cladding layer of aluminum alloy series 6XXX. The change in microstructure at ambient temperature (room temperature) changes the 6XXX series aluminum alloy layer from the W state (immediately after quenching) to the T4 state. In this state, the 6XXX series aluminum alloy cladding layer exhibits improved formability compared to the non-recrystallized state.

The composite article may be subjected to additional cold working, such as stretching in the range of 0.5% to 8% of its original length, to relieve residual stresses in it and improve the flatness of the article. Preferably, the stretch is in the range of 0.5% to 6%, more preferably 0.5% to 4%, and most preferably 0.5% to 3%.

After cooling, the rolled aerospace composite product is naturally aged, typically at ambient temperatures, and alternatively, the aerospace composite product may also be artificially aged.

The 6XXX series aluminum alloy layer or layers are typically thinner than the core, with the thickness of each 6XXX series aluminum alloy layer being between 1% and 20% of the total thickness of the composite material. More preferably, the thickness of the 6XXX series aluminum alloy layer is from about 1% to about 10% of the total thickness of the composite material.

In one embodiment, the 6XXX series aluminum alloy layer is bonded to one surface or face of the 2XXX series alloy core layer.

In one embodiment, the 6XXX series aluminum alloy layer is bonded to both surfaces or faces of the 2XXX series alloy core layer, thereby forming the outer surface of the rolled aerospace composite product.

In one embodiment, the rolled aerospace composite product has an overall thickness of at least 0.8 mm.

In one embodiment, the rolled aerospace composite product has an overall thickness of no more than 50.8 mm (2 inches), preferably no more than 25.4 mm (1 inch), and most preferably no more than 12 mm.

In one embodiment, the rolled aerospace composite product is a thick sheet product.

In one embodiment, the rolled aerospace composite product is a sheet product.

The 6XXX series aluminum alloy cladding layer consists of an aluminum alloy having a composition comprising, in wt. %: Si 0.3% to 1.0%, Mg 0.3% to 1.1%, Mn 0.04% to 1.0%, Fe 0.03% to 0.4%, Cu up to and including 0.10%, Cr up to and including 0.25%, V up to and including 0.2%, Zr up to and including 0.2%, Zn up to and including 0.5%, Ti up to and including 0.15%, unavoidable impurities , the amount of each of which is less than 0.05%, in total less than 0.15%, the balance: aluminum.

Si and Mg are the most important alloying elements of the 6XXX series alloy and provide the required level of strength and formability, in particular tensile formability, of aluminum. The Si content should be in the range of 0.3% to 1.0%. The preferred lower limit for the Si content is 0.40%. The preferred upper limit for the Si content is 0.9% and more preferably 0.75%. The Mg content should be in the range of 0.3% to 1.1%. The preferred lower limit for the Mg content is 0.40% and more preferably 0.45%. The preferred upper limit for the Mg content is 0.90% and more preferably 0.80%. These ranges of Si and Mg, together with other alloying elements, will provide a tensile strength in the range of about 110 to about 125 MPa after about 1 month of natural aging after SHT and rapid cooling, which will then only gradually increase with long natural aging, resulting in to a very stable set of strength level indicators in the T4 condition. Preferably, the 6XXX series alloy contains Si in excess of Mg, as this will provide improved aging kinetics and the formation of an optimized structure for precipitation of Mg ₂ Si particles. This will provide higher levels of aging strength both after artificial aging and in particular in the first month of natural aging after solution heat treatment, for example in the range of 475° C. to 500° C., and rapid cooling.

Mn is also an important alloying element of the 6XXX series alloy used for the cladding layer(s) and should be in the range of 0.04% to 1.0%. The preferred lower limit for the Mn content is 0.20% and preferably 0.25%. The preferred upper limit for the Mn content is 0.90% and preferably 0.80%. In one embodiment, the upper limit of the Mn content is 0.7%. Mn will increase the strength of the aluminum alloy in the T4 or T6 heat treatment state after solution heat treatment and rapid cooling. The Mn will help keep the grain size in the cladding layer(s) small, resulting in a better surface appearance and fewer surface cracks after the forming operation. The presence of Mn improves the quality of anodization of the outer surface of the 6XXX series alloy layer, since it promotes the transformation of the beta-AlFeSi (Al ₅ FeSi) phase into the alpha-AlFeSi (Al ₈ Fe ₂ Si) phase and stabilizes the alpha-AlFeSi phases. The presence of Mn will also favorably increase the corrosion potential of the 6XXX series aluminum alloy, and the amount of Mn added can be controlled to reduce and optimize the corrosion potential difference between the core alloy and the cladding layer(s) depending on the application, thus improving corrosion resistance. rolled composite product for aerospace engineering.

In one embodiment of the 6XXX series aluminum alloy, the Cu content is up to and including 0.10%, preferably up to and including 0.05%, and more preferably up to and including 0.03% to increase corrosion resistance.

Fe is an effective element for increasing strength and reducing crystal grain. An Fe content of less than 0.03% may not have a sufficient effect, while, on the other hand, an Fe content of more than 0.4% may lead to the formation of many coarse-grained intermetallic compounds, in particular in the presence of high amounts of Mn, which may reduce tensile formability. and corrosion resistance of aluminum alloy. Therefore, the Fe content is in the range of 0.03% to 0.4%, preferably 0.1% to 0.3%. In a preferred embodiment, the Fe content is less than 0.25%. In a preferred embodiment, the Fe/Mn ratio is less than 1.8 to provide a balance between good corrosion resistance and good anodizing quality.

Cr can be added up to and including 0.25% to improve the strength of the aluminum alloy and reduce the crystal grain. Preferably, its content is up to and including 0.20%, and more preferably up to and including 0.15%. In one embodiment, Cr is among the unavoidable impurities.

Zn may be present up to and including 0.5% and preferably up to and including 0.25% without derogating from the advantages of the present invention. In one embodiment, Zn is among the unavoidable impurities.

V may be added up to and including 0.2% and preferably up to and including 0.1% without derogating from the advantages of the present invention. In a preferred embodiment, V is among the unavoidable impurities and is preferably present in an amount of only up to and including 0.02%, and more preferably only up to and including 0.01%, since it can prevent complete recrystallization of the rolling stock after solution heat treatment and quenching. In addition, it may form harmful intermetallic particles in the aluminum alloy.

Zr can be added up to and including 0.2% and preferably up to and including 0.1% without derogating from the advantages of the present invention. In a preferred embodiment, Zr is among the unavoidable impurities and is preferably present in an amount of only up to and including 0.02% and more preferably only up to and including 0.01%, since it can prevent complete recrystallization of the rolling stock after solution heat treatment and quenching. In addition, it may form harmful intermetallic particles in the aluminum alloy.

Grain refiners such as Ti, TiB ₂ , Ti-C or the like are generally added at a total Ti content of up to and including 0.15%, preferably up to and including 0.10%, and more preferably from 0.005% to 0.05%.

The remainder is aluminum and unavoidable impurities, each of which is less than 0.05%, and their total amount is less than 0.15%.

In one embodiment, the 6XXX series alloy layer consists of an aluminum alloy having the following composition in wt. %: Si 0.3% to 1.0%, Mg 0.3% to 1.1%, Mn 0.04% to 1.0%, Fe 0.03% to 0.4%, Cu up to and including 0.10%, Cr up to and including 0.25%, V up to and including 0.2%, Zr up to and including 0.2%, Zn up to and including 0.5%, Ti up to and including 0.1%, unavoidable impurities , the amount of each of which is less than 0.05%, less than 0.15% in total, the balance: aluminum, and preferably the composition ranges are narrower, as described and stated in this document.

In one embodiment, the composition of the 6XXX series aluminum alloy cladding layer is adjusted or set so that it has a free corrosion potential value (relative to the Standard Calomel Electrode (SCE), also referred to as "corrosion potential") -710 mV or less (e.g. -750 mV) to provide optimum corrosion protection for the 2XXX series core alloy, measured on solution heat treated and quenched material in a solution containing 53 g/l NaCl and H ₂ O ₂ at a concentration of 3 g/l, at a temperature of 25° C. with a 0.1 N calomel electrode. after hard melt heat treatment and quenching, when the key alloying elements are essentially in solid solution.

In one embodiment, the corrosion potential difference between the 2XXX series alloy core layer and the 6XXX series aluminum alloy cladding layer, i. e. in the final state of heat treatment, is in the range from 30 to 100 mV to provide sufficient protection against corrosion from the anode cladding layer to the core layer.

In one embodiment, the 2XXX series alloy core layer is made from an aluminum alloy having the following composition in wt. %:

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 up to and including 1.2%, preferably 0.2% to 1.2%, more preferably 0.2% to 0.9%,

Si up to and including 0.40%, preferably up to and including 0.25%,

Fe up to and including 0.40%, preferably up to and including 0.25%,

Cr up to and including 0.35%, preferably up to and including 0.10%,

Zn up to and including 1.0%,

Ti up to and including 0.15%, preferably from 0.01% to 0.10%,

Zr up to and including 0.25, preferably up to and including 0.12%,

V up to and including 0.25%,

Li up to and including 2.0%

Ag up to and including 0.80%,

Ni up to and including 2.5%,

residue: aluminum and impurities. As a rule, such impurities are present in an amount of less than 0.05% each, less than 0.15% in total.

In another embodiment, the 2XXX series alloy core layer is made from an aluminum alloy having the following wt % composition:

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 0.8% to 1.8%,

Mn up to and including 1.2%, preferably 0.2% to 1.2%, more preferably 0.2 to 0.9%,

Si up to and including 0.40%, preferably up to and including 0.25%,

Fe up to and including 0.40%, preferably up to and including 0.25%,

Cr up to and including 0.35%, preferably up to and including 0.10%,

Zn up to and including 0.4%,

Ti up to and including 0.15%, preferably from 0.01% to 0.10%,

Zr up to and including 0.25, preferably up to and including 0.12%,

V up to and including 0.25%,

residue: aluminum and impurities. As a rule, such impurities are present in an amount of less than 0.05% each, less than 0.15% in total.

In a preferred embodiment, the 2XXX series alloy core layer is made from an AA2X24 series aluminum alloy where X is 0, 1, 2, 3, 4, 5, 6, 7 or 8. A highly preferred aluminum alloy is selected from AA2024, AA2524 and AA2624 alloys. .

In one embodiment, the 2XXX series alloy core layer is provided in T3, T351, T39, T8, or T851 temper.

The 2XXX series alloy core layer can be provided to the user in a non-solution heat-treated state, such as post-cast heat-treatment state or annealed heat-treated state, and then formed and subjected to solution heat-treatment and aging by the user to a desired state, such as T3 heat-treatment state. , T351, T39, T8 or T851.

The present invention also relates to a method for manufacturing a rolled aerospace composite product according to the present invention, said method including the following steps:

(a) providing a 2XXX series aluminum alloy ingot or rolled stock to form the core layer of an aerospace composite product;

(b) homogenizing the ingot of the specified aluminum alloy series 2XXX at a temperature in the range from 400°C to 505°C for at least 2 hours;

(c) providing a 6XXX series aluminum alloy ingot or rolled cladding to form an outer cladding layer on a 2XXX series aluminum alloy core; optionally two ingots or two rolled 6XXX series aluminum alloy claddings are provided to form a cladding layer on each side of the 6XXX series aluminum alloy core;

(d) homogenizing the 6XXX series aluminum alloy ingot(s) at a temperature in the range of at least 480°C for at least 0.5 hour, preferably at a temperature in the range of 500°C to 590°C, prior to hot rolling in rolling cladding;

(e) rolling joining the 6XXX series aluminum alloy layer(s) with the 2XXX series alloy core layer to form a roll-bonded article, preferably by hot rolling, optionally followed by cold rolling;

(f) solution heat treatment of the rolled product at a temperature in the range of 450°C to 505°C;

(g) cooling the solution-treated rolled product to a temperature below 100° C., preferably to ambient temperature;

(h) optionally stretching the solution-treated rolled product, preferably by cold stretching, in the range of 0.5% to 8% of its original length, preferably in the range of 0.5% to 6%, more preferably 0, 5% to 4% and most preferably 0.5% to 3%; and

(i) aging the cooled rolled product through natural aging and/or artificial aging. In a preferred embodiment, the 2XXX series alloy core layer is aged to a T3, T351, T39, T8, or T851 heat treated condition. The 6XXX series alloy cladding layers will be in a T4 heat treatment if they are naturally aged only, and in a T6 heat treatment if they are artificially aged.

In one embodiment of the method of the present invention, in the following processing steps, the aerospace rolled composite product is formed during a molding process at ambient or elevated temperature to produce a desired molded product having at least one of uniaxial curvature or biaxial curvature.

In an alternative embodiment of the method, after rolling joining the 6XXX series aluminum alloy(s) with the 2XXX series core alloy to form a rolled product, preferably by hot rolling, optionally followed by cold rolling, said rolled aerospace product according to the present invention is formed during a molding process at ambient or elevated temperature to obtain a desired shaped product having at least one of uniaxial curvature or biaxial curvature, followed by solution heat treatment and subsequent aging to obtain the final state of heat treatment.

The molding can be carried out by a molding operation selected from the group consisting of: bending, profiling, draw molding, aging plastic deformation molding, deep drawing, and high energy hydroforming, in particular explosive molding or electro-hydraulic molding. The 6XXX series aluminum alloy used for the rolled aerospace composite product according to the present invention provides the required flexibility also after natural and/or artificial aging. In addition, it also has the required tensile formability for these forming operations.

In one embodiment, the elevated temperature molding operation is carried out at a temperature in the range of 140°C to 200°C, and preferably the aerospace article is maintained at the molding temperature for a time period in the range of 1 to 50 hours. To optimize the strength of the 6XXX series alloy cladding layer, a molding temperature in the range of 150°C to 170°C is preferred. In a preferred embodiment, the elevated temperature molding is carried out by an aging plastic deformation molding operation. Aged plastic deformation molding is a process or operation of shaping a component during an aging heat treatment to relieve stresses present inside the component and shape the contour, such as in the case of single or double curvature fuselage shells.

In one embodiment (excluded from the present invention), the rolled aerospace composite article of the present invention, after solution heat treatment (SHT) and prior to shaping, is subjected to a post-SHT cold working step that includes at least 25 % cold working of a rolled aerospace composite product, and in particular, cold working includes cold rolling of a rolled aerospace product to a final gauge as disclosed in US-2014/036699-A1, the contents of which are incorporated herein document through a link.

In one aspect of the present invention, the use of a 6XXX series aluminum alloy as described and claimed herein is provided as a cladding layer on one or both surfaces of a 2XXX series aluminum alloy aerospace rolled product.

In a further aspect of the present invention, there is provided a welded structure comprising a rolled aerospace composite product according to the present invention and at least one aluminum alloy stiffener attached to the rolled aerospace composite product by a riveting or welding operation.

In yet another aspect, the present invention relates to a welded aircraft structural member comprising a rolled aerospace composite product according to the present invention and at least one aluminum alloy stiffener, preferably a stringer, attached to the rolled aerospace composite product by a riveting operation. or welding, for example by laser welding or friction welding. In addition, the present invention also relates to fuselage welded structures in which fuselage panels are joined to each other by laser beam welding (LBW) or friction stir welding (FSW), for example, using butt welds.

The present invention also includes an aircraft or spacecraft, the fuselage of which is wholly or partly constructed from a rolled aerospace composite product according to the present invention, which can be incorporated into various structural parts of the aircraft. For example, the various disclosed embodiments may be used to form wing assemblies and/or tail structures. The aircraft is usually a commercial passenger or cargo aircraft. In alternative embodiments, the present invention may also be applied to other types of aircraft. Examples of such aircraft have included manned and unmanned military aircraft, rotary wing aircraft, or even ballistic aircraft.

The aerospace composite rolling product of the present invention may be formed into an aircraft element, such as a fuselage component or panel, or such as a wing component or panel, and said aircraft can take advantage of the present invention as described. Said molding may include bending, stretch molding, machining, and other molding operations known in the art for molding panels or other components of aircraft, aerospace vehicles, or other vehicles. Molding, including bending or other plastic deformation, can be carried out at room temperature or elevated temperatures.

DESCRIPTION OF GRAPHICS

Hereinafter, the present invention will be described with reference to the accompanying drawings, where:

in fig. 1 is a schematic diagram showing embodiments of the present invention;

in fig. 2 is a schematic flow of operations for several embodiments of the method for manufacturing a rolled composite aerospace product according to the present invention.

In FIG. 1 shows an embodiment of a rolled composite aerospace product 10 having a three-layer structure consisting of a 2XXX series alloy core layer 20, on each side of which is a 6XXX series aluminum alloy cladding layer 30, as described and claimed herein.

In FIG. 2 is a schematic flow of operations for several embodiments of the method according to the present invention for the manufacture of a rolled aerospace composite product. In step 1 of the process, an ingot is cast from a 2XXX series alloy forming the core alloy of a composite aerospace product, from which the surface layer may optionally be stripped in step 2 to remove segregation zones near the surface immediately after casting the rolled ingot and increase the flatness of the product. In step 3 of the process, the rolled ingot is homogenized. In parallel, in step 4 of the process, an ingot is cast from a 6XXX series alloy to form at least one cladding layer on the core alloy surface of the composite aerospace product, and optionally on both faces of the core alloy. In addition, in step 5, this ingot may optionally be stripped of its surface layer. In process step 6, the 6XXX series alloy is homogenized and then hot rolled in process step 7 to form the overlay(s) plate(s), with the cladding layer typically being much thinner than the core. In step 8 of the process, the 2XXX series core alloy and the 6XXX series alloy cover plate on one or both sides of the core alloy are joined by rolling, preferably by hot rolling. Depending on the desired final gauge, the rolled product may be cold rolled in process step 9 to obtain a final gauge, such as a sheet product or thin sheet product. In process step 10, the aerospace rolled product is solution heat treated, then cooled in process step 11, and preferably stretched in process step 12.

In one embodiment, the cooled article is formed during the molding process 13 and subjected to aging, i. e. natural or artificial aging, at the stage 14 of the method to obtain the final state of the heat treatment, for example T3 or T8.

In one embodiment, the molding process 13 and the aging process step 14 can be combined, for example, the molding operation is carried out at a temperature in the range of 140°C to 200°C, and preferably for a time in the range of 1 to 50 hours, resulting in artificial aging of both the 2XXX series alloy core and the 6XXX series alloy cladding layer(s) also occurs.

In one embodiment, the cooled article is subjected to aging in step 14 of the process, i. e. natural or artificial aging, to obtain the desired state of heat treatment, and then molded in the process 13 molding to obtain a molded product with a given shape.

In an alternative embodiment, after the 2XXX series alloy core and 6XXX series alloy cladding layer(s) have been rolled into final gauge, the rolled product is formed in a molding process 13 into a predetermined shape, after which said molded product is heat treated. into a solid solution at the stage

15 of the method and cooled in step 11 of the method, and then subjected to aging, i.e. natural or artificial aging, at the stage 14 of the method to obtain the final state of the heat treatment, for example T3 or T8.

The present invention is not limited to the previously described embodiments, which may vary widely within the scope of the present invention as defined by the appended claims.

Claims (43)

1. Rolled composite product for aerospace engineering, containing a core layer of a 2XXX series alloy and a cladding layer of a 6XXX series aluminum alloy bonded to at least one surface of a 2XXX series alloy core layer, wherein the 6XXX series aluminum alloy contains, in wt.% : Si 0.3% to 1.0%, Mg 0.3% to 1.1%, Mn 0.04% to 1.0%, Fe 0.03% to 0.4%, Cu up to and including 0.10%, Cr up to and including 0.25%, V up to and including 0.2%, Zr up to and including 0.2%, Zn up to and including 0.5%, Ti up to and including 0.1%, unavoidable impurities, the amount of each of which is less than 0.05%, the total is less than 0.15%, the rest is aluminum. 2. Rolled composite product for aerospace engineering according to claim 1, characterized in that the aluminum alloy of the 6XXX series has a Si content in the range from 0.4% to 0.9%. 3. Rolled composite product for aerospace engineering according to claim 1 or 2, characterized in that the aluminum alloy of the 6XXX series has a Mg content in the range from 0.40% to 0.90%. 4. Rolled composite product for aerospace technology according to any one of paragraphs. 1-3, characterized in that the 6XXX series aluminum alloy has a Mn content in the range of 0.25% to 1.0%, and preferably in the range of 0.30% to 0.90%. 5. Rolled composite product for aerospace engineering according to any one of paragraphs. 1-4, characterized in that the 6XXX series aluminum alloy cladding layer is bonded by rolling to at least one surface of the 2XXX series alloy core layer. 6. Rolled composite product for aerospace technology according to any one of paragraphs. 1-5, characterized in that the 6XXX series aluminum alloy cladding layer has a thickness in the range from 1% to 20% and preferably from 1% to 10% of the total thickness of the rolled composite product for aerospace engineering. 7. Rolled composite product for aerospace engineering according to any one of paragraphs. 1-6, consisting of a 2XXX series alloy core layer and a 6XXX series aluminum alloy clad layer bonded to one surface of the 2XXX series alloy core layer. 8. Rolled composite product for aerospace technology according to any one of paragraphs. 1-6, consisting of a 2XXX series alloy core layer and a 6XXX series aluminum alloy clad layer bonded to both surfaces of the 2XXX series alloy core layer. 9. Rolled composite product for aerospace technology according to any one of paragraphs. 1-8, characterized in that the alloy of the 2XXX series of the core layer has the following composition in wt.%: 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 up to and including 1.2%, preferably from 0.2% to 1.2%, Si up to and including 0.40%, Fe up to and including 0.40%, Cr up to and including 0.35%, Zn up to and including 1.0%, Ti up to and including 0.15%, Zr up to and including 0.25%, V up to and including 0.25%, Li up to and including 2.0% Ag up to and including 0.80%, Ni up to and including 2.5%, the rest is aluminum and impurities. 10. Rolled composite product for aerospace technology according to any one of paragraphs. 1-9, characterized in that the core layer of the 2XXX series alloy is made of the 2×24 series alloy. 11. Rolled composite product for aerospace technology according to any one of paragraphs. 1-10, characterized in that the 2XXX series alloy core layer has a heat treatment state of T3, T351, T39, T8, or T851. 12. Rolled composite product for aerospace technology according to any one of paragraphs. 1-11, characterized in that the 6XXX series alloy cladding layer has a heat treatment state of T4 or T6. 13. Rolled composite product for aerospace technology according to any one of paragraphs. 1-12, characterized in that said rolled composite product for aerospace engineering has a total thickness of 0.8 mm to 50.8 mm and preferably 0.8 mm to 25.4 mm. 14. Rolled composite product for aerospace technology according to any one of paragraphs. 1-13, characterized in that said rolled composite product for aerospace engineering is a thick sheet product. 15. Rolled composite product for aerospace technology according to any one of paragraphs. 1-13, characterized in that said rolled composite product for aerospace engineering is a sheet product. 16. Rolled composite product for aerospace technology according to any one of paragraphs. 1-15, characterized in that said rolled composite product for aerospace engineering is a structural part of aerospace engineering and preferably an aircraft fuselage. 17. A method of manufacturing a rolling composite product for aerospace technology according to any one of paragraphs. 1-16, including the following steps: (a) providing a 2XXX series aluminum alloy ingot to form 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 505°C for at least 2 hours; (c) providing a 6XXX series aluminum alloy ingot or rolled cladding to form an outer cladding layer on a 2XXX series aluminum alloy core; (d) homogenizing a 6XXX series aluminum alloy ingot at a temperature in the range of at least 480°C, preferably 500°C to 590°C, for at least 0.5 hour; (e) rolling joining a 6XXX series aluminum alloy with a 2XXX series core alloy to form a roll-bonded article, preferably by hot rolling, optionally followed by cold rolling; (f) solution heat treatment of the rolled product at a temperature in the range of 450°C to 505°C; (g) cooling the solution-treated rolled product to a temperature below 100° C., preferably to ambient temperature; (h) optionally stretching the cooled solution-treated rolled product; and (i) aging the 2XXX series core alloy of the cooled rolled product to give a T3, T351, T39, T8, or T851 heat treatment condition. 18. The method according to claim 17, characterized in that said method further comprises molding a cooled, solution-heat-treated product joined by rolling, and optionally stretching during molding to obtain a product of a predetermined shape. 19. The method according to claim. 17 or 18, characterized in that step (j) molding is carried out after the aging step (i). 20. The method according to claim 18, characterized in that step (j) of molding and step (i) of aging are combined into a molding step at an elevated temperature, preferably at a temperature in the range from 140°C to 200°C and preferably for a time of range from 1 to 50 hours.

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