Wrought product made of 2XXX aluminum alloy featuring an improved static-toughness compromise and manufacturing method.

Abstract

Aluminum alloy rolled product of the 2xxx series having a thickness of at least 50 mm, comprising in % by weight, Cu 4.5 – 4.9; Mg 0.5 – 0.6; Mn 0.2 – 0.4; Zn 0 - 0.1; Ti 0.02-0.07; Ag 0.1-0.4; Zr 0.08-0.15; Si 0 – 0.15; Fe 0 – 0.15; Inevitable impurities ≤0.05 each and ≤0.15 in total, remainder aluminum, such that, at mid-thickness, the granular structure of said product comprises at mid-thickness a surface fraction of recrystallized grains of 50% to 80%. The rolled product is obtained by a manufacturing process comprising a controlled hot rolling step such that the hot rolling exit temperature is between 410°C and 445°C. (Shorthand figure: Fig. 1)

Description

Title of the invention: Wrought product in 2XXX aluminum alloy having an improved static-toughness compromise and its manufacturing method. Technical field

[0001] The present invention relates to a wrought product of 2XXX aluminum alloy having a thickness greater than or equal to 50 mm, preferably from 90 mm to 160 mm, having improved properties with respect to the static-toughness trade-off and a manufacturing method for improving the static-toughness trade-off while maintaining excellent resistance to stress corrosion cracking. Prior art

[0002] Aeronautical applications generally require a very specific set of properties. In wing structure applications, the spar is generally made of 7xxx alloy because a good static-toughness compromise is sought for sheets with a thickness greater than or equal to 50 mm, preferably from 90 mm to 160 mm. However, there is a demand for products that are not very sensitive to crack deflection, allowing good fatigue cracking behavior to be achieved.

[0003] Among aluminum alloys, 2XXX alloys perform well in fatigue cracking.

[0004] EP1641952 discloses an alloy having improved strength and ductility, comprising Cu 3.5 - 5.8 wt%, Mg 0.1 - 1.8 wt% Mn 0.1 - 0.8 wt% Ag 0.2 - 0.8 wt% Ti 0.02 - 0.12 wt% and optionally one or more elements selected from the group consisting of Cr 0. 1 - 0.8 wt%, Hf 0.1 - 1.0 wt%, Sc 0.03 - 0.6 wt%, and V 0.05 - 0.15 wt%, remainder aluminum and other incidental elements and impurities, and wherein the alloy is essentially free of zirconium.

[0005] US 5,376,192 discloses a wrought aluminum alloy comprising about 2.5-5.5 wt% copper, about 0.10-2.3 wt% magnesium, about 0.1-1 wt% silver, up to 0.05 wt% titanium, and the balance aluminum, wherein the amount of copper and magnesium is kept below the solid solubility limit of copper and magnesium in aluminum.

[0006] US Patents US 5,630,889, US 5,665,306, US 5,800,927 and US 5,879,475 disclose substantially vanadium-free aluminum-based alloys comprising about 4.85-5.3 wt.% copper, about 0.5-1 wt.% magnesium, about 0.4-0.8 wt.% manganese, about 0.2-0.8 wt.% silver, up to about 0.25 wt.% zirconium, up to about 0.1 wt.% of silicon, and up to 0.1% by weight of iron, the remainder being aluminum, incidental elements and impurities.

[0007] WO2006 / 019946 discloses a 2000 series aluminum alloy, the alloy being consisting essentially of about 3.0-4.0 wt. % copper, about 0.4-1.1 wt. % magnesium, up to about 0.8 wt. % silver, up to about 1.0 wt. % Zn, up to about 0.25 wt. % Zr; up to about 0.9 wt. % Mn; up to about 0.5 wt. % Fe; and up to about 0.5 wt. % Si, the remainder being essentially aluminum, impurities and accessory elements, the copper and magnesium being present in a ratio of about 3.6 to 5 parts copper to about 1 part magnesium. The alloy can be used in wrought or cast products, including those used in aerospace applications, particularly structural members in the form of thin or heavy sheet, extrusions and forgings, and offers an improved combination of strength and damage tolerance.

[0008] WO2020 / 123096 discloses 2xxxx aluminum alloys which comprise 0.08 at 0.20 wt% Ti. The new 2xxx aluminum alloys according to WO2020 / 123096 may exhibit an improvement in at least two properties including, for example, strength, fracture toughness, elongation and corrosion resistance.

[0009] WO2022 / 129806 discloses a method for thermomechanical treatment of products wrought in 2000 series aluminum alloy comprising, in % by weight, Cu 3.5 -5.8; Mg 0.2 - 1.5; Mn < 0.9; Fe < 0.15; Si < 0. 15; Zr < 0.25; Ag < 0.8; Zn < 0.8; Ti 0.02-0.15; unavoidable impurities < 0.05 each and < 0.15 in total; remainder of aluminum, allowing an improvement in the resistance to stress corrosion. It comprises an annealing composed of two sequences. The first sequence is defined by a maximum temperature Tlmax of 130°C to 180°C and by a holding time at a temperature between 130°C and 180°C which is equivalent to an equivalent time calculated at 160°C between 10 h and 80 h. The second sequence is defined by a temperature T2°c (t) lower than Tlmax and a holding time t2 at a temperature between 100°C and 130°C, which is equivalent to an equivalent time calculated at 160°C such that it is between 0.3% and 15% of the equivalent time calculated for the first sequence.

[0010] WO2023 / 028070 discloses a method comprising artificially aging a 2xxx aluminum alloy in at least two stages. In one embodiment, the first aging stage comprises aging a 2xxx aluminum alloy at a first temperature between 300°F (150°C) and 450°F (230°C) and for a first aging time between 4 and 120 hours, and aging the 2xxx aluminum alloy at a second temperature for a second aging time of between 30 minutes and 120 hours, with the second temperature being 20°F to 150°F lower than the first temperature. The new two-stage artificial aging step may facilitate an improved combination of properties, such as an improved combination of two or more of strength, ductility, fracture toughness, and corrosion resistance.

[0011] There is a need for thick products with a thickness greater than or equal to 50 mm, preferably between 90 mm and 160 mm, made of 2XXX alloy, having at mid-thickness both a tensile yield strength Rpo.2(L) and a compressive yield strength Rpco 2(L) in the high L direction, a high toughness Klc (LT) in the LT direction, as well as a low tendency to crack bifurcation and good corrosion resistance. Statement of the invention

[0012] The invention relates to a method for manufacturing wrought products made of 2xxx series aluminum alloy comprising the following steps: (a) An aluminum alloy plate is cast, comprising in % by weight, Cu 4.5 - 4.9, Mg 0.5 - 0.6 Mn 0.2 - 0.4, Zn 0-0.1, Ti 0.02-0.07, Ag 0.1-0.4, Zr 0.08-0.15, preferably 0.10 - 0.13 or 0.10 - 0.12,. If 0-0.15, Fe 0-0.15, Unavoidable impurities <0.05 each and <0.15 in total, remainder aluminum, (b) Said plate is homogenized at a temperature of 480°C to 540°C for 4 to 80 hours, preferably 10 to 60 hours, (c) Optionally, said homogenized plate is heated. Preferably, heating during step (c) is carried out at a temperature of 410°C to 480°C. (d) hot-deforming said homogenized plate by rolling to obtain an intermediate product having a thickness greater than or equal to 50 mm, preferably 90 mm to 160 mm. During step (d) the hot rolling outlet temperature is 410°C to 445°C, preferably 420°C to 440°C. (e) said intermediate product is dissolved, (f) quenching said intermediate product in solution with water, (g) said intermediate product in solution and quenched is pulled in a controlled manner with a permanent deformation of 3 to 6%, (h) said intermediate product thus dissolved, quenched and pulled is tempered by heating from 100 to 180°C for 5 to 100 hours. Preferably the total equivalent time ttoteq at 160 °C of the tempering carried out is 10 to 90 hours, preferably 13 to 40 hours. The total equivalent time ttoteq at 160 °C is defined by the formula: where T c( t ) corresponds to the change in temperature expressed in °C as a function of time t during tempering.

[0013] In a preferred embodiment, during step (h) the tempering is carried out in two stages, a first stage at a temperature of 140°C to 180°C for a duration of 10h to 100 h, preferably 10h to 40h and a second stage at a temperature of 100°C to 130°C for a duration of 10h to 50h, preferably 15h to 30h. Preferably, the first stage is carried out at a temperature of 160°C + / - 5°C for a duration of 18h + / - 5h and the second stage at a temperature of 120°C + / - 5°C for a duration of 20h + / - 10h, preferably 20h + / - 2h.

[0014] In a preferred embodiment, during step (d) the hot rolling inlet temperature is from 380°C to 460°C.

[0015] The invention also relates to a rolled product of 2xxx series aluminum alloy having a thickness of at least 50 mm, preferably from 90 mm to 160 mm, comprising in wt%, Cu 4.5 - 4.9, Mg 0.5 - 0.6, preferably from 0.50 to 0.60 Mn 0.2 - 0.4, Zn 0 - 0.1, preferably 0-0.05 Ti 0.02-0.07, Ag 0.1-0.4, Zr 0.08-0.15, preferably 0.10 - 0.13 or 0.10 - 0.12, Si 0-0.15 Fe 0-0.15 Unavoidable impurities <0.05 each and <0.15 in total, remainder aluminum, and such that at mid-thickness, the grain structure of said product comprises a surface fraction of recrystallized grains of 50% to 80%, preferably 50% to 75%, the surface fraction of recrystallized grains is measured by EBSD and where a grain is considered recrystallized if it has a misorientation of at least 7° with the neighboring grain and the orientation of said grain has an extent of less than 2.5°, also called Grain Orientation spread (GOS).

[0016] According to a preferred embodiment, the rolled product has a texture such that the volume fraction of Copper component {112} <111> is greater than 4%, preferably 5% and / or the volume fraction of brass component {110} < 112> is greater than 7%, preferably 8% and / or the volume fraction of S component {123} <634> is greater than 9%, preferably 11%. Preferably, the sum of the mid-thickness volume fractions of the copper texture components {112} <111> , brass {110} <112> and S {123} <634> is greater than 20%.

[0017] According to a preferred embodiment, the rolled product has, at mid-thickness, a tensile strength in the L direction, Rp0.2 (L) and a compressive strength in the L direction, Rpc0.2 (L) each of at least 435 MPa. Preferably, the rolled product has, at mid-thickness, a toughness Klc (LT) measured according to the ASTM E399 standard greater than or equal to 40 MPa / Vm.

[0018] The invention also relates to a structural element manufactured from a product according to the invention and / or obtained according to the method of the invention. Said structural element being intended for aerospace applications. Preferably, the structural element may be a spar in an aircraft wing, preferably an integral spar.

[0019] The invention also relates to an armor element manufactured from a product according to the invention and / or obtained according to the method of the invention. Said armor element may be an armor plate, preferably an integral armor plate, intended for example for an armored vehicle. Figures

[0020] [Fig.l] represents the Rp02 (L)-Klc (LT) compromise at mid-thickness of the different sheets tested in example 1.

[0021] [Fig.2] represents the evolution of the stress in the L direction according to the position in the thickness of the sheet.

[0022] [Fig. 3] represents the evolution of the stress corrosion life as a function of the stress applied for a product according to the invention. Detailed description of the invention

[0023] Unless otherwise stated, all information regarding the chemical composition of alloys is expressed as a percentage by weight based on the total weight of the alloy. The designation of alloys is made in accordance with the regulations of The Aluminium Association, known to those skilled in the art. The definitions of the metallurgical conditions are given in the European standard EN 515. Unless otherwise stated, the definitions of the standard NF EN 12258-1 relating to aluminium and aluminium alloy products apply.

[0024] Unless otherwise stated, the static mechanical characteristics, in other words The ultimate strength Rm, the tensile yield strength Rp0>2 and the elongation at break A% are determined by a tensile test according to EN 10002-1 or NF EN ISO 6892-1. The compressive yield strength Rpc0.2 is determined according to ASTM E9-19, where the compressive yield strength Rpc0 2 corresponds to the stress corresponding to an offset of 0.2%. The location at which the pieces are taken and their direction are defined by EN 485-1. The stress intensity factor (Kq) is determined according to ASTM E 399-23. ASTM E 399 gives the criteria for determining whether KQ is a valid value of KiC. For a given specimen geometry, the KQ values ​​obtained for different materials are comparable to each other as long as the yield strengths of the materials are of the same order of magnitude.Unless otherwise stated, stress corrosion studies were performed according to ASTM G47-22 (2022) and G49-85 (2023) in the Short Traverse (CT) direction. Stress corrosion tests are performed under constant load using a device according to [Fig.3] of ASTM G49-85 (2023).

[0025] Here, the term "structural element" or "structural element" of a mechanical construction refers to a mechanical part for which the static and / or dynamic mechanical properties are particularly important for the performance of the structure and for which a structural calculation is usually prescribed or carried out. These are typically elements whose failure is likely to endanger the safety of said construction, its users, its users or others.

[0026] The products according to the invention are capable of being obtained by a process comprising the steps of casting, homogenization, hot rolling, solution treatment, quenching, controlled traction and tempering.

[0027] The inventors found that by adapting the composition of the product and controlling the hot rolling outlet temperature, it was possible to improve the RpO.2(L) - Klc(LT) compromise, so as to obtain at mid-thickness a tensile yield strength RpO.2(L) in the L direction of at least 435 MPa and a toughness Klc(LT) in the LT direction of at least 40 MPa.'Vm, while obtaining a compressive yield strength in the L direction of at least 435 MPa, good stress corrosion resistance, as well as lower residual stress levels at mid-thickness.

[0028] An aluminum alloy plate according to the invention is cast.

[0029] The alloy according to the invention is an aluminum alloy of the 2xxx series comprising in percentage by weight Cu: 4.5-4.9; Mg: 0.5-0.6; Mn: 0.2-0.4; Zn: 0-0.1; Ti 0.02-0.07; Ag: 0.1-0.4; Zr 0.08-0.15; Si: 0-0.1; Fe: 0-0.1; unavoidable impurities <0.05 each and <0.15 in total, remainder aluminum.

[0030] The copper content of the alloy according to the invention is from 4.5% to 4.9%. Preferably the copper content is at least 4.6%, or preferably 4.65% or 4.70% so as to obtain sufficient mechanical characteristics. Preferably, the maximum copper content is 4.85% or preferably 4.80% by weight so as to obtain sufficient toughness properties. In a preferred embodiment, the Cu content is 4.65% to 4.85% by weight.

[0031] The magnesium content is from 0.5 to 0.6% by weight. Preferably the magnesium content is at least 0.50% by weight or 0.55% by weight so as to obtain sufficient mechanical characteristics, in particular the mid-thickness yield strength. Preferably the magnesium content is at most 0.60% by weight to obtain a sufficient level of toughness. In a preferred embodiment, the Mg content is from 0.50% to 0.60% by weight.

[0032] The silver content is from 0.1 to 0.4% by weight, preferably from 0.10 to 0.40% by weight. Preferably, the silver content is at least 0.15%, or 0.20% or 0.25% or 0.30% so as to obtain sufficient mechanical characteristics. Preferably the silver content is at most 0.40% or 0.38% or 0.35% or 0.30% by weight. In a preferred embodiment of the invention, the silver content is from 0.15 to 0.30% by weight. In another preferred embodiment of the invention, the silver content is from 0.30 to 0.40% by weight.

[0033] The manganese content is from 0.2 to 0.4%, preferably from 0.20 to 0.40%. Preferably, the manganese content is at least 0.25%, or even more preferably at least 0.30%. Preferably, the manganese content is at most 0.35%. In a preferred embodiment, the Mn content is from 0.25% to 0.35% by weight.

[0034] The zirconium content is from 0.08% to 0.15%. Preferably, the zirconium content is at least 0.09% or 0.10% by weight. The inventors have found that the addition of Zr makes it possible to improve the RpO.2(L) - K1C (L) compromise in combination with the hot rolling exit temperature. Preferably, the zirconium content is at most 0.14%, or 0.13% by weight. In a preferred embodiment, the Zr content is from 0.10% to 0.13% by weight and even more preferably from 0.10% to 0.12%.

[0035] The zinc content is less than 0.1% by weight. Preferably the zinc content is less than or equal to 0.05% by weight, or even 0.04% by weight.

[0036] The alloy also contains from 0.02 to 0.07% by weight of Ti, preferably from 0.02 to 0.06% by weight and even more preferably from 0.02% to 0.05% in order in particular to control the grain size during casting. A titanium content of less than or equal to 0.07% makes it easier to recycle the alloy according to the invention. A low titanium content of less than or equal to 0.07%, preferably less than or equal to 0.05% makes it possible to increase the quantity of scrap (from the product according to the invention) used for the development of new products. Indeed, it is advantageous to maintain a low titanium content in the scraps in order to allow the subsequent refining of new products, refining carried out using a refining agent containing Ti, such as TiB2 or TiC.

[0037] It is preferable to limit the content of unavoidable impurities in the alloy so as to achieve the most favorable damage tolerance properties. The unavoidable impurities include iron and silicon, these elements having a content of less than or equal to 0.15% by weight each, preferably less than or equal to 0.12% by weight each, or even less than or equal to 0.10% by weight each. Preferably, the iron and silicon content is less than or equal to 0.08% or 0.07% or 0.06% or 0.05% by weight each. In a preferred embodiment according to the invention, the iron content is 0 to 0.12% or 0 to 0.10% or 0 to 0.08% or 0.03 to 0.12%, or 0.03 to 0.10% or 0.04 to 0.06%. In a preferred embodiment according to the invention, the silicon content is 0 to 0.12% or 0 to 0.10% or 0 to 0.08% or 0.03 to 0.12%, or 0.03 to 0.10% or 0.04 to 0.06%.

[0038] The other elements considered as impurities have a content less than or equal to 0.05% by weight each and 0.15% by weight in total. The remainder corresponds to aluminum.

[0039] The plate is cast by conventional casting techniques such as semi-continuous casting. The plate has a substantially parallelepiped shape. The plate preferably has a thickness of 300 mm or more, for example 400 mm, 500 mm or 600 mm or any other intermediate values. After casting, the plate is generally scalped to eliminate segregation zones near the surface while maintaining a substantially parallelepiped shape.

[0040] The cast plate is then homogenized. The homogenization treatment is carried out at a temperature of 480°C to 540°C for 4 to 80 hours, preferably from 10 to 60 hours or from 20 to 50 hours. Preferably, the homogenization temperature is from 495°C to 540°C for 5 to 60 hours, preferably from 15 to 50 hours. The homogenization can be carried out according to one or more stages, at least one stage of which is carried out at a temperature of 510°C to 540°C for 1 to 30 hours, preferably from 5 to 25 hours.

[0041] After homogenization, the plate is generally cooled to room temperature before being preheated to a temperature of 410°C to 480°C for hot rolling deformation. The preheating makes it possible to reach a hot rolling inlet temperature preferably of 380°C to 460°C and preferably of 400°C to 460°C and even more preferably of 420°C to 450°C allowing the deformation of the plate. However, it is also possible to roll the homogenized plate directly without prior preheating if it is not cooled and has a sufficient temperature, preferably of 380°C to 460°C and preferred from 400°C to 460°C and even more preferably from 420°C to 450°C allowing the deformation of the plate.

[0042] The hot deformation is carried out by hot rolling so as to obtain a sheet with a final thickness of at least 50 mm. Preferably, the final thickness is at least 75 mm or 90 mm. Preferably, the sheet has a final thickness less than or equal to 200 mm, preferably less than or equal to 180 mm or 160 mm or 130 mm. In a preferred embodiment of the invention, the final thickness is from 90 mm to 160 mm, or even from 90 mm to 130 mm.

[0043] The hot rolling conditions are chosen such that the final hot deformation temperature is from 410°C to 445°C, preferably from 420°C to 440°C and even more preferably from 430°C to 440°C. To achieve this hot rolling exit temperature, the skilled person has various technical solutions available. Mention may be made of the use of reheating and / or cooling boxes to achieve the exit temperature of at least 410°C. Heated rolling cylinders or the rolling scheme or the waiting times between passes may also be used.

[0044] The sheet thus rolled is then solution-treated, preferably by a heat treatment of 490 to 530°C for 15 min to 8 h, then quenched in water, typically water at room temperature, preferably below 40°C.

[0045] The product then undergoes a controlled traction of 3 to 6% and preferably at least 4.5%, typically around 5%.

[0046] Tempering is then carried out at a temperature of 100 to 180°C for 5 to 100 hours, preferably 120 to 170°C for 20 to 70 hours. Preferably, the income is achieved in at least two stages according to the conditions of patent application WO2022 / 129806: - a first sequence whose temperature expressed in °C is described by a function f fc depending on time t, such that the maximum temperature reached Tf'ux csl between 130°C and 180°C and the holding time tl at a temperature between 130°C and 180°C is such that the equivalent time is between 10h and 80h, equivalent time ^|J^œcalculated at the temperature of 160°C according to the formula r 136000 / 1 1 ri :” 8314 ' + 273 ~ 160 % 27371 - and a second sequence whose temperature expressed in °C is described by a function t) dependent on time t whose temperature is such that is less than Tf™-* and whose holding time t2 expressed in hours at a tem- temperature between 100°C and 130°C is such that the equivalent duration calculated at the temperature of 160°C according to the formula .s.. » r = | dt.exp 136000 / i 1 y 8,314 ' + 273 " 160 4 2737 is between 0.3% and 15% of the equivalent duration ^^calculated for the first sequence.

[0047] Preferably, the tempering is carried out in two stages, a first stage at a temperature of 140°C to 180°C for a duration of 10h to 100h, preferably 10h to 40h, and a second stage at a temperature of 100°C to 130°C for a duration of 10h to 50h, preferably 15h to 30h. In a preferred embodiment, the first stage is carried out at a temperature of 160°C + / - 5°C for a duration of 18h + / -5h and the second stage at a temperature of 120°C + / -5°C for a duration of 20h + / -10h, preferably 20h + / -2h in order to improve the resistance to stress corrosion.

[0048] Preferably the tempering is such that the total equivalent time t toteq at 160°C is from 10 to 90 hours. Preferably, the total equivalent time ttoteq at 160°C is at least 13 hours, preferably from 13 to 40 hours. It may be advantageous to aim for total equivalent time durations ttoteq at 160°C of 13 to 25 hours in order to improve the stress corrosion resistance.

[0049] The total equivalent time ttoteq at 160 °C is defined by the formula: fr 13W00 / 1 1 xi JI -8,.314 V (S) +2 / 3 -rz / a / 3 where the temperature expressed in °C is described by a function Tc ( t ) depending on time t. The function Tc {l) corresponds to the instantaneous tempering treatment temperature, which changes with time t (in hours). In the particular case of a plateau, the function T c ( t ) is constant for the duration of the plateau. ttoteq is expressed in hours. The constant Q / R = 16360 K is derived from the activation energy for Cu diffusion, Q = 136000 J / mol. The formula giving t_toteq takes into account the heating and cooling phases.

[0050] The preferred metallurgical states for the sheets are the T8 states, more particularly T84 or T86.

[0051] The inventors found that by maintaining a hot rolling exit temperature of 410°C to 445°C, in combination with the selected composition, it was possible to improve the mid-thickness compromise Rpo.2 (L) - K[c(LT), while maintaining good quarter-thickness properties and good resistance to bi crack furcation. Indeed, by maintaining a hot rolling exit temperature of 410°C to 445°C, in combination with the selected composition, it is possible to obtain at mid-thickness a tensile yield strength Rp0.2(L) and a compressive yield strength Rpc0.2(L) in the L direction, both of at least 435 MPa and a toughness Kk (LT) in the LT direction of at least 40 MPa.'Vm, as well as good fatigue cracking behavior and good corrosion resistance.

[0052] The inventors attribute this improvement to the mid-thickness granular microstructure obtained on the solution-treated and tempered product, which comprises a surface fraction of recrystallized grains at mid-thickness of 50% to 80%, preferably 50% to 75%. The inventors have in fact found that it is important for the structure to be predominantly recrystallized, i.e. to have a surface fraction of recrystallized grains of at least 50%, without however obtaining a completely recrystallized microstructure. It is in fact important to have a surface fraction of recrystallized grains of less than 80%, preferably less than 75%, and preferably less than 70%.

[0053] The measurement of recrystallized surface fraction can be measured by EBSD. Preferably, the observation is made in the L-TC plane of the product. According to the invention, a grain is considered to be recrystallized if it has a misorientation of at least 7° with the neighboring grain and the orientations within said grain (also called GOS for Grain Orientation Spread) have an extent of less than 2.5°.

[0054] The inventors have also found that by maintaining a hot rolling temperature at the outlet of 410°C to 445°C, in combination with the selected composition, a favorable texture is obtained at mid-thickness to optimize the compromise at mid-thickness Rp02 (L) - Kic (LT). This texture is such that the volume fraction of the Copper component {112} <111> is greater than 4%, preferably 5% and / or the volume fraction of Brass component {110} <112> is greater than 7%, preferably 8% and / or the volume fraction of component S {123} <634> is greater than 9%, preferably 11%. Preferably, the sum of the volume fractions at mid-thickness of the Copper {112} texture components <111> , Brass {110} <112> , and S {123} <634> is greater than 20%, preferably 25%, or even 30%.

[0055] Texture quantification can be done from global measurements by X-ray diffraction or from local measurements by electron backscatter diffraction (EBSD, Electron BackScatter Diffraction) in a scanning electron microscope (SEM). It is then possible to access, via the calculation of the crystal orientation distribution function (COD), the volume fractions of the different components present in the texture.

[0056] The FDOC can be calculated by the spherical harmonics method from the measured pole figures (preferably at least 4 pole figures). The sample size is adapted to the grain size of the material. Preferably, if an RX measurement is used, the sample size is chosen so as to be able to analyze at least 3000 grains, preferably 5000. If the EBSD technique is used, the sample size is chosen so as to be able to analyze at least about a hundred grains, preferably at least 200 grains.

[0057] It is possible to simplify the information contained in the FDOC. This is commonly done in the art to describe selected aspects of the distribution of orientations in the material. An example of this practice is the calculation of the volume fraction of crystallites that have a specific orientation. To do this, reference orientations are defined as well as an angle of maximum misorientation around these orientations. The FDOC is then integrated into the domain thus defined, which makes it possible to deduce the relative volume of orientations contained in this domain compared to the total volume.

[0058] The present inventors used a tolerance of 15° around the orientations “copper”, “brass”, “S” in order to describe the texture obtained. The crystallographic orientations “copper”, “brass”, “S” are known to those skilled in the art and described for example in the reference document by UF Kocks, CN Tomé, and H.-R. Wenk, “Texture and anisotropy: preferred orientations in polycrystals and their effect on materials properties”. Cambridge University Press, 2000.

[0059] The orientations “copper”, “brass”, “S” are reproduced in the table below. Name Indices Bunge (cpi,O>, <p2) Kocks (W,0,0) Cuivre {112} <m>90,35,45 0,35,45 Brass {110} <112> 35.45.0 55.45.0 S {123} <634 > 59.37.63 149.37.27

[0060] The inventors found that by maintaining an outlet hot rolling temperature of 410°C to 445°C, in combination with the selected composition, the residual stresses in absolute values ​​were minimized at mid-thickness in the tempered state.

[0061] The rolled product according to the invention, with a thickness greater than or equal to 50 mm, preferably between 90 mm and 160 mm, has at mid-thickness a tensile yield strength Rp0.2(L) and a compressive yield strength Rpc0.2(L) in the L direction, both of at least 435 MPa. The product has a toughness Klc (LT) in the LT direction of at least 40 MPa.'Vm.

[0062] According to the invention, the term “tensile and compressive properties in the L direction” means rolling at mid-thickness tensile or compression tests carried out from test pieces taken from the sheet at a position centered on the mid-thickness of the sheet and which can integrate a part of the thickness of the sheet between a quarter thickness and three-quarter thickness. Similarly, according to the invention, toughness properties Kic in the LT direction at mid-thickness are understood to mean toughness tests carried out from CT test pieces taken from the sheet at a position centered on the mid-thickness of the sheet and which can integrate a part of the thickness of the sheet between a quarter thickness and three-quarter thickness.

[0063] The product according to the invention has a combination of strength and toughness properties that makes it particularly suitable for structural elements for the aerospace industry (aeronautics and space). For aeronautical applications, a representative structural element manufactured from the product according to the invention comprises a spar, preferably an integral spar or any other similar parts machined from thick wrought sections. An integral spar is used when the spar is machined in one piece from a sheet according to the invention. The spar can be used in an aircraft wing box.

[0064] The product according to the invention is also of interest for armor applications. The product according to the invention is particularly interesting as an armor plate used on armored vehicles, in particular on military vehicles such as tracked or wheeled combat vehicles, armored personnel carriers, armored support systems, amphibious assault systems, advanced amphibious assault vehicles or armed robotic vehicles. Preferably, the armor plate is one of the integral armor plates, i.e. machined in one piece from a sheet according to the invention. Examples

[0065] Example 1

[0066] Two compositions A and B (Table 1) were obtained by conventional semi-continuous casting. Composition B corresponds to the composition of the invention. The other composition A differs from the invention by the absence of zirconium. For each composition, two trays are available.

[0067] [Table 1] - Chemical composition by weight % Si Fe Cu Mn Mg Zn Ti Ag Zr A Ref 0.04 0.08 4.63 0.31 0.56 0.006 0.03 0.37 0.00 B Invention 0.04 0.08 4.71 0.30 0.57 0.003 0.03 0.36 0.11

[0068] The trays thus cast were homogenized for 5 hours at 495°C + 18 hours at 525°C, scalped to a thickness of approximately 416 mm and then reheated before being hot rolled for reach a final thickness of approximately 101 mm. Taking into account the rise and fall times, the total homogenization time between 480°C and 540°C is approximately 42 hours. For each composition, we sought to test the mechanical properties obtained depending on whether the hot rolling exit temperature is 430°C to 440°C or less than 410°C. For this purpose, the plates were reheated between 410°C and 480°C and then hot rolled in such a way as to obtain the target temperatures. According to Table 2, the plates for which an exit temperature above 430°C is targeted have a hot rolling entry temperature above 4 10°C and the plates for which an exit temperature below 410°C is targeted have a hot rolling entry temperature below 410°C. This is one example among others to obtain the target hot rolling exit temperature.Indeed, there are other ways to reach the desired exit temperature; for example, one can adapt the rolling pattern by making, for example, larger reduction passes in order to heat the metal. It is also possible to carry out intermediate reheating or, on the contrary, carry out waiting times to ensure that the metal cools.

[0069] The hot-rolled sheets were then solution-treated for 5 hours at 524°C and then quenched in water at room temperature. They were then stretched so as to achieve a residual plastic deformation of approximately 5% to reach a final thickness of approximately 98.5 ± 5 mm. The sheets then underwent a two-stage tempering of X h 160°C + 20 h 120°C with X = 18 h, 36 h and 54 h. The total equivalent time at 160°C taking into account the rising and falling phases is respectively 20.411, 38.5 h and 56.4 h. The sheets thus treated were then tested so as to measure the elastic limit, the breaking load, the elongation as well as the toughness. Tensile specimens were taken at mid-thickness in the rolling direction L. Toughness specimens were also taken at mid-thickness and measured in the direction LT.The toughness specimens used are CT20W40 specimens (thickness B=20 mm, width W=40 mm according to the nomenclature of the ASTM E399 standard).

[0070] [Table 2] Mechanical characteristics T -1- LAC inlet T -1- LAC outlet Tempering X h 160°C + 20h 120°C Total Tequ at 160°C Rp0.2 (L) t / 2 Rm (L) t / 2 A% (L) t / 2 K1C (LT) t / 2 °c °CX (h) hour MPa MPa % MPa.^m Al Ref 389 385 18 20.4 429 452 13.6 41.2 36 38.5 426 450 13.2 40.6 54 56.4 427 453 12.2 39.9 A-2 Ref 442 435 18 20.4 428 452 14.3 43.9 36 38.5 428 452 12.6 43.8 54 56.4 427 453 11.7 43.5 Bl Ref 393 392 18 20.4 433 456 12.9 39.7 36 38.5 430 454 13.4 38.9 54 56.4 428 453 12.1 37.9 B-2 Inv. 444 434 18 20.4 442 466 13.4 45.0 36 38.5 442 466 12.7 43.8 54 56.4 440 466 11.4 43.2

[0071] It is noted (see [Fig.l]) that the B-2 sheets according to the invention have the best compromise Rp0.2 (L) - Klc (LT). The inventors have noted that the combined choice of the chemical composition and the hot rolling exit temperature between 410°C and 445°C makes it possible not only to increase the toughness but also the yield strength. Indeed, an increase in the yield strength of approximately 10 MPa and in the toughness of approximately 5 MPa are observed for a composition containing Zr if the hot rolling exit temperature is between 410°C and 445°C ([Fig.l]). For a composition not containing Zr, only an increase in the toughness is observed.

[0072] A texture measurement by X-ray diffraction was carried out on each of the sheets at mid-thickness. The present inventors used a tolerance of 15° for each of the orientations considered. The volume fraction in % of the brass, copper and S orientations, representative of the compression components, as well as the cube, Goss, CG 26.5 orientations representative of the components parallel to the direction <100> is given in Table 3.

[0073] [Table 3] - volume fraction in % of texture orientations Cube {001}<10 0> Goss {011}<10 0> CG26.5 {021}<10 0> Copper {112}<11 1> Brass {110}<ll 2> S {123}<63 4> Sum of components Copper + Brass +S % % % % % % % Al 5.8 3.3 7.3 2.8 5.9 7.8 16.5 A-2 5.7 2.1 4.1 2.2 5.1 6.7 14.0 Bl 4.8 2.5 6.2 2.8 5.8 7.7 16.2 B-2 5.7 2.1 4.1 5.5 9.0 13.0 27.5

[0074] The inventors have found that a product having a volume fraction of Copper component {112}< 111> greater than 4% is beneficial and / or a Brass component {110}<l 12> greater than 7% and / or an S component {123} <634> greater than 9%. A sum of volume fractions of the copper texture components {112} <111> , brass {110}<l 12> and S {123} <634> greater than 20% improves the static-toughness compromise.

[0075] The surface fraction of recrystallized grains was determined at mid-thickness for each of the tested sheets (Table 4). This measurement was made by EBSD measurement. The observations were made on a scanning microscope of the FEG-SEM Ultra type (Zeiss) under a voltage of 20 kV and a working distance of approximately 12 mm. The acquisition of the images is made using a Hikari EDAX camera with an acquisition step of approximately 0.75 pm.

[0076] A grain is considered recrystallized if it has a misorientation of at least 7° with the neighboring grain and the orientation of said grain has an extent of less than 2.5°, also called Grain Orientation spread (GOS).

[0077] [Table 4] Recrystallized fraction at mid-thickness determined by EBSD Recrystallized surface fraction at t / 2% Al 91 A-2 95 Bl 92 B-2 62

[0078] It is noted that the B-2 sheet according to the invention has a recrystallized surface fraction at mid-thickness lower than the other sheets. The surface fraction of recrystallized grains is equal to 62%. The inventors attribute the better behavior of the B-2 sheet to a “predominantly recrystallized” mid-thickness granular structure, that is to say that the structure is not 100% recrystallized. This is referred to as a majori structure formally recrystallized according to the invention such that the surface fraction of recrystallized grains at mid-thickness is 50% to 80%.

[0079] The residual stresses were evaluated on each of the sheets. The measurement of residual stresses is carried out according to the “bar method”. Two full-thickness bars are taken, in the L and TL directions, by sawing from each of the sheets. The sampling dimensions are: - for the bar in L direction: 450mm (L direction) x 35mm (TL direction) x thickness - for the bar in TL direction: 35mm (L direction) x 450mm (TL direction) x thickness. The bars are then machined to obtain a bar 440 mm long, 30 mm wide and e thick (thickness of the sheet after tempering).

[0080] The method comprises the following steps: - Initial measurement of the deformation on the lower face of the bar: the bar is positioned on two supports approximately 435 mm apart so that an L-TL surface is in contact with the supports. Using a strain gauge glued to this face, halfway along the L-TL surface, the initial deformation is measured. - Machining of the bar in successive passes to remove 4 mm of its thickness until reaching a final thickness of approximately 6 mm. During each machining step, heating is limited to 5°C so as to avoid any influence of the machining conditions on the deflection measurements taken. - Measurement of the deformation at the end of each machining pass using the deformation gauge. From the deformation measurements made on each of the bars in the L and TL directions, it is possible to calculate the evolution of the residual stresses present in the sheet as a function of the position in the thickness of the sheet in the L direction. The calculation principle is well known. The principle is for example recalled on page 37 and following of Nicolas Chobaut's thesis "Measurements and modelling of residual stresses during quenching of thick heat treatable aluminum components in relation to their precipitation State" 2015- Ecole Polytechnique Fédérale de Lausannne (https: / / doi.org / 10.5075 / epfl-thesis-6559).

[0081] The evolution of the stress in the L direction according to the position in the thickness of the sheet is shown in [Fig.2]. It is observed that the sheet B-2 according to the invention has, at mid-thickness, the lowest residual stresses in absolute values.

[0082] Stress corrosion tests were carried out on the products obtained according to the invention. The stress corrosion tests consisted of testing the B-2 sheets in the short transverse direction after tempering for 36h 160°C + 20h 120°C (total equivalent time at 160°C: 38.5h) and 18h ​​160°C + 20h 120°C (total equivalent time at 160°C: 20.4h). The corrosion tests are carried out according to ASTM G44, with devices for testing the product under constant load according to ASTM G49-85 (2019) recommendations.

[0083] The test consisted of determining, for different stresses between approximately 200 MPa and 330 MPa, the number of days of testing without a break appearing. It is noted that an aging of 18h 160°C + 20h 120°C makes it possible to increase the resistance to stress corrosion ([Fig.3]). Income X h 160°C + 20h 120°C Stress CSC (MPa) TC Number of days before failure B-2 18h 201 27 238 19 278 14 319 6 36h 225 9 238 7 279 5 321 4< / m>

Claims

Claims

1. A method of manufacturing wrought products of 2xxx series aluminum alloy comprising the following steps: (a) An aluminum alloy plate is cast comprising in % by weight, Cu 4.5 - 4.9, Mg 0.5 - 0.6 Mn 0.2 - 0.4 Zn 0-0.1 Ti 0.02-0.07 Ag 0.1-0.4 Zr 0.08-0.15 Si 0-0.15 Fe 0-0.15 Unavoidable impurities <0.05 each and <0.15 in total, remainder aluminium, (b) Said plate is homogenised at a temperature of 480°C to 540°C for 4 to 80 hours, preferably from 10 to 60 hours, (c) Optionally, said homogenized plate is heated, (d) said homogenized plate is hot-deformed by rolling to obtain an intermediate product having a thickness greater than or equal to 50 mm, preferably from 90 mm to 160 mm, (e) said intermediate product is dissolved, (f) quenching said intermediate product in solution with water, (g) said intermediate product in solution and quenched is pulled in a controlled manner with a permanent deformation of 3 to 6%, (h) said intermediate product thus in solution, quenched and pulled is tempered by heating from 100 to 180°C for 5 to 100 hours, preferably the total equivalent time ttoteq at 160°C is 10 to 90 hours, preferably 13 to 40 hours, the total equivalent time tfeteq at 160°C is defined by the formula: ff 136000 z 1. 1 vf = JA 273 “ 160 + 273 / 1 where T c( t ) corresponds to the change in temperature expressed in °C as a function of time t during tempering. characterized in that in step (d) the hot rolling outlet temperature is 410°C to 445°C, preferably 420°C to 440°C.

2. Manufacturing method according to claim 1 such that during step (h) the tempering is carried out in two stages, a first stage at a temperature of 140°C to 180°C for a duration of 10h to 100 h, preferably 10h to 40h and a second stage at a temperature of 100°C to 130°C for a duration of 10h to 50h, preferably 15h to 30h.

3. Manufacturing method according to claim 2 such that the first stage is carried out at a temperature of 160°C + / - 5°C for a duration of 18h + / - 5h and the second stage at a temperature of 120°C + / - 5°C for a duration of 20h + / - 10h, preferably 20h + / - 2h.

4. Manufacturing method according to any one of claims 1 to 3 such that reheating is carried out during step (c) at a temperature of 410°C to 480°C.

5. A manufacturing method according to any one of claims 1 to 4 such that in step (d) the hot rolling inlet temperature is 380°C to 460°C.

6. Rolled product of 2xxx series aluminum alloy having a thickness of at least 50 mm, preferably from 90 mm to 160 mm, comprising in % by weight, Cu 4.5 - 4.9 Mg 0.5 - 0.6 Mn 0.2 - 0.4 Zn 0-0.1 Ti 0.02-0.07 Ag 0.1-0.4 Zr 0.08-0.15 Si 0-0.15 Fe 0-0.15 Unavoidable impurities <0.05 each and <0.15 in total, remainder aluminum, characterized in that, at mid-thickness, the grain structure of said product comprises a surface fraction of recrystallized grains of 50% to 80%, preferably of 50% to 75%, the surface fraction of recrystallized grains is measured by EBSD and where a grain is considered as recrystallized if it has a misorientation of at least 7° with the neighboring grain and the orientation of said grain has an extent of less than 2.5°, also called Grain Orientation spread (GOS).

7. Rolled product according to claim 6 characterized in that the volume fraction of Copper component {112} <111> is greater than 4%, preferably 5% and / or the volume fraction of brass component {110} <112> is greater than 7%, preferably 8% and / or the volume fraction of component S {123} <634> is greater than 9%, preferably 11%.

8. Rolled product according to claim 7 characterized in that the sum of the volume fractions at mid-thickness of the copper texture components {112} <111> , brass {110} <112> and S {123} <634> is greater than 20%.

9. Rolled product according to one of claims 6 to 8 characterized in that the Mg content in % by weight is from 0.50 to 0.

60.

10. Rolled product according to one of claims 6 to 9 characterized in that the Zn content in % by weight is less than 0.

05.

11. Rolled product according to one of claims 6 to 10 characterized in that, at mid-thickness, the tensile yield strength in the L direction, Rp0.2 (L) and the compressive yield strength in the L direction, Rpco,2 (L) is each at least 435 MPa.

12. Rolled product according to one of claims 6 to 11 characterized in that at mid-thickness the toughness K[c (LT) measured according to standard ASTM E399 is greater than or equal to 40 MPa.'Vm.

13. Structural element for aerospace applications manufactured from a product according to claims 6 to 12 or obtained according to one of claims 1 to 5, said structural element preferably being a spar for an aircraft wing, preferably an integral spar.

14. Armor element manufactured from a product according to claims 6 to 12 or obtained according to one of claims 1 to 5, said element is preferably an armor plate, preferably an integral armor plate, intended for example for an armored vehicle.