Aluminum-copper-lithium alloy with improved compressive strength and improved toughness

Abstract

An aluminum-copper-lithium alloy having improved compressive strength and improved toughness. The invention relates to a product based on an aluminum alloy comprising, in weight percent, 4.0 to 4.6% by weight of Cu, 0.7 to 1.2% by weight of Li, 0.5 to 0.65% by weight of Mg, 0.10 to 0.20% by weight of Zr, 0.15 to 0.30% by weight of Ag, 0.25 to 0.45% by weight of Zn, 0.05 to 0.35% by weight of Mn, at most 0.20% by weight of Fe + Si, at least one element selected from the group consisting of Cr, Sc, Hf, V and Ti, the amount of said element (if selected) being 0.05 to 0.3% by weight for Cr and Sc, 0.05 to 0.5% by weight for Hf and V, and the balance being aluminum and unavoidable impurities. 0.01 to 0.15 wt% for Ti; the other elements are each at most 0.05% by weight and a total of at most 0.15% by weight, the remainder being aluminum. The invention also relates to a method for obtaining such a product and to the use thereof for aircraft structural elements.

Description

[0001] This application is a divisional application of patent application No. 201980029413.3, entitled "Aluminum-Copper-Lithium Alloy with Improved Compressive Strength and Improved Toughness". The original application was filed on April 24, 2019, with a priority date of May 2, 2018, and corresponds to international application PCT / FR2019 / 050965. Invention Field

[0002] This invention relates to products made of aluminum-copper-lithium alloys, and more specifically, such products are intended for use in aerospace and aviation constructions. Existing technology

[0003] Develop aluminum alloy products to manufacture high-strength parts, particularly for the aerospace and aviation industries.

[0004] In this regard, lithium-containing aluminum alloys are of great interest because for every 1% by weight of lithium added, the density of aluminum decreases by 3% and the elastic modulus increases by 6%. For these alloys selected for aircraft applications, their properties related to other service characteristics must be comparable to those of commonly used alloys, particularly in the trade-offs between static mechanical strength properties (tensile and compressive yield strength, ultimate tensile strength) and damage tolerance properties (toughness, resistance to fatigue crack propagation), which are often mutually exclusive. For certain components, such as upper wing skin, compressive yield strength is an important characteristic. Furthermore, these mechanical properties should preferably be stable over time and possess good thermal stability, i.e., these mechanical properties should not change significantly due to aging at operating temperatures.

[0005] These alloys must also possess sufficient corrosion resistance to be formed using conventional methods and have low residual stress, allowing for full machining. Finally, they must be achievable through robust manufacturing methods, particularly ensuring their properties can be obtained on industrial equipment where it is difficult to guarantee temperature uniformity within a few degrees for large parts.

[0006] US Patent 5,032,359 describes a large class of aluminum-copper-lithium alloys in which the addition of magnesium and silver, particularly 0.3 to 0.5% by weight of magnesium and silver, allows for improved mechanical strength.

[0007] US Patent 5,455,003 discloses a method for manufacturing an Al-Cu-Li alloy, which exhibits improved mechanical strength and improved toughness at low temperatures, particularly due to appropriate work hardening and revenu. The patent specifically recommends the following composition: by weight percentage, Cu = 3.0–4.5, Li = 0.7–1.1, Ag = 0–0.6, Mg = 0.3–0.6, and Zn = 0–0.75.

[0008] US Patent 7,438,772 describes an alloy comprising, by weight percentage: Cu: 3-5, Mg: 0.5-2, Li: 0.01-0.9, and higher lithium content is not recommended due to the reduced trade-off between toughness and mechanical strength.

[0009] US Patent 7,229,509 discloses an alloy comprising (by weight %): (2.5-5.5) Cu, (0.1-2.5) Li, (0.2-1.0) Mg, (0.2-0.8) Ag, (0.2-0.8) Mn, and up to 0.4% Zr or other grain refiners (such as Cr, Ti, Hf, Sc, V).

[0010] Patent application US 2009 / 142222 A1 discloses an alloy comprising (by weight%): 3.4 to 4.2% Cu, 0.9 to 1.4% Li, 0.3 to 0.7% Ag, 0.1 to 0.6% Mg, 0.2 to 0.8% Zn, 0.1 to 0.6% Mn, and 0.01 to 0.6% of at least one element for controlling granular structure. The application also discloses a method for manufacturing extruded products.

[0011] Patent application WO2009 / 036953 relates to an aluminum alloy product for structural components, the chemical composition of which comprises, by weight, Cu 3.4 to 5.0, Li 0.9 to 1.7, Mg 0.2 to 0.8, Ag about 0.1 to 0.8, Mn 0.1 to 0.9, Zn up to 1.5, and one or more elements selected from the following: (Zr about 0.05 to 0.3, Cr 0.05 to 0.3, Ti about 0.03 to 0.3, Sc about 0.05 to 0.4, Hf about 0.05 to 0.4), Fe < 0.15, Si < 0.5, and conventional and unavoidable impurities.

[0012] Patent application WO 2012 / 085359 A2 relates to a method for manufacturing rolled products made of an aluminum-based alloy, said aluminum-based alloy comprising 4.2 to 4.6 wt% Cu, 0.8 to 1.30 wt% Li, 0.3 to 0.8 wt% Mg, 0.05 to 0.18 wt% Zr, 0.05 to 0.4 wt% Ag, 0.0 to 0.5 wt% Mn, and up to 0.20 wt% Fe+. Si, less than 0.20 wt% Zn, at least one element selected from Cr, Se, Hf and Ti, wherein the amount of said element (if selected) is 0.05 to 0.3 wt% for Cr and Se, 0.05 to 0.5 wt% for Hf, 0.01 to 0.15 wt% for Ti, and other elements are each at most 0.05 wt% and total at most 0.15 wt%, with the remainder being aluminum; the method includes preparation, casting, homogenization, rolling at a temperature above 400°C, solution heat treatment, quenching, stretching 2% to 3.5%, and a tempering step.

[0013] Patent application US2012 / 0225271 A1 relates to a forged product with a thickness of at least 12.7 mm, containing 3.00 to 3.80 wt% Cu, 0.05 to 0.35 wt% Mg, 0.975 to 1.385 wt% Li, wherein -0.3 Mg - 0.15Cu + 1.65 ≤ Li ≤ -0.3 Mg - 0.15Cu + 1.85, and 0.05 to 0.50 wt% of at least one grain structure controlling element, wherein the grain structure controlling element is selected from Zr, Sc, Cr, V, Hf, other rare earth elements and combinations thereof, up to 1.0 wt% Zn, up to 1.0 wt% Mn, up to 0.12 wt% Si, up to 0.15 wt% Fe, up to 0.15 wt% Ti, and up to 0.10 wt% other elements, the total amount of which does not exceed 0.35 wt%.

[0014] Application WO 2013 / 169901 discloses an alloy comprising, by weight percentage, 3.5 to 4.4% Cu, 0.65 to 1.15% Li, 0.1 to 1.0% Ag, 0.45 to 0.75% Mg, 0.45 to 0.75% Zn, and 0.05 to 0.50% of at least one element for controlling the granular structure. Advantageously, the ratio of Zn to Mg in the alloy is 0.60 to 1.67.

[0015] There is a need for aluminum-copper-lithium alloy products that offer improved performance compared to known products, particularly in terms of the trade-off between static mechanical strength properties (especially tensile and compressive yield strength) and damage tolerance properties (especially toughness, thermal stability, corrosion resistance, and machinability), while also having low density.

[0016] Furthermore, a robust, reliable, and economical method for manufacturing these products is needed. Summary of the Invention

[0017] The first object of the present invention is an aluminum alloy-based product comprising, by weight percentage: 4.0 to 4.6 wt% Cu, 0.7 to 1.2 wt% Li, 0.5 to 0.65 wt% Mg, 0.10 to 0.20 wt% Zr, 0.15 to 0.30 wt% Ag, 0.25 to 0.45 wt% Zn, 0.05 to 0.35 wt% Mn, up to 0.20 wt% Fe + Si, at least one element selected from Cr, Sc, Hf, V and Ti, wherein the amount of said element (if selected) is 0.05 to 0.3 wt% for Cr and Sc, 0.05 to 0.5 wt% for Hf and V, 0.01 to 0.15 wt% for Ti, each of the other elements is up to 0.05 wt% and the total is up to 0.15 wt%, and the remainder is aluminum.

[0018] A second objective of this invention is a method for manufacturing products based on aluminum alloys, wherein, sequentially,

[0019] a) Prepare an aluminum-based liquid metal pool comprising: 4.0 to 4.6 wt% Cu; 0.7 to 1.2 wt% Li; 0.5 to 0.65 wt% Mg; 0.10 to 0.20 wt% Zr; 0.15 to 0.30 wt% Ag; 0.25 to 0.45 wt% Zn; 0.05 to 0.35 wt% Mn; up to 0.20 wt% Fe + Si; at least one element selected from Cr, Sc, Hf, V and Ti, wherein the amount of said element (if selected) is 0.05 to 0.3 wt% for Cr and Sc, 0.05 to 0.5 wt% for Hf and V, and 0.01 to 0.15 wt% for Ti; other elements each up to 0.05 wt% and the total amount up to 0.15 wt%, the remainder being aluminum;

[0020] b) Casting the rough product from the molten metal pool;

[0021] c) Homogenize the crude product at a temperature of 450°C to 550°C, preferably 480°C to 530°C, for 5 to 60 hours;

[0022] d) The homogenized rough product is hot-deformed, preferably by rolling;

[0023] e) The heat-deformed product is solution heat-treated at 490 to 530°C for 15 min to 8 h, and the solution-heat-treated product is then quenched.

[0024] f) The product is subjected to cold deformation with a deformation rate of 2% to 16%;

[0025] g) Tempering is performed, wherein the cold-deformed product is brought to a temperature of 130 to 170°C, preferably 140 to 160°C, for 5 to 100 hours, preferably 10 to 70 hours.

[0026] Another object of the present invention is an alloy product of the present invention, or an alloy product obtainable by the method of the present invention, having a thickness of 8 to 50 mm and having the following properties at a medium thickness:

[0027] i) Compressive yield strength Rc p0.2 (L) ≥ 590 MPa, preferably Rc p0.2 (L) ≥ 595 MPa;

[0028] ii) Toughness K app (LT) ≥ 60 MPa√m, K is preferred app (LT) ≥ 75 MPa√m, where Kapp (LT) is the value of the apparent stress intensity factor at fracture as defined in standard ASTM E561 (2015), which was measured on a CCT specimen with a width W = 406 mm and a thickness B = 6.35 mm.

[0029] iii) Tensile yield strength Rp 0.2 (L) and compressive yield strength Rc p0.2 The difference Rp between (L) 0.2 (L) - Rc p0.2 (L) less than or equal to 10 MPa, preferably ≤ 5 MPa.

[0030] Another objective is an aircraft structural component, preferably an aircraft upper wing skin element. Attached Figure Description

[0031] Figure 1 Toughness K of the alloy in Example 1 app LT and compressive yield strength Rc p0.2 A compromise between L.

[0032] Figure 2 Toughness K of the alloy in Example 2 q LT and compressive yield strength Rcp0.2 A compromise between L.

[0033] Figure 3 The compressive yield strength Rc of the alloy in Example 2 p0.2 L and tensile yield strength R p0.2 A compromise between L.

[0034] Figure 4 Toughness K of the alloy in Example 3 app LT and compressive yield strength Rc p0.2 A compromise between L. Detailed Implementation

[0035] Unless otherwise stated, all indications relating to the chemical composition of the alloy are expressed as a weight percentage based on the total weight of the alloy. The expression 1.4 Cu means the copper content expressed as a percentage by weight multiplied by 1.4. The alloy name conforms to the conventions known to those skilled in the art of the Aluminum Association. When the concentration is expressed in ppm (parts per million), the indication also refers to mass concentration.

[0036] Unless otherwise stated, the metallurgical condition definition given in European Standard EN 515 (1993) shall apply.

[0037] The static mechanical characteristics of tension, in other words, the ultimate tensile strength R m Conventional yield strength R at 0.2% elongation p0.2 Elongation at break (A%) was determined by tensile testing according to standard NF EN ISO 6892-1 (2016), with sampling and testing directions as defined in standard EN 485 (2016). p0.2 (L) refers to R measured in the longitudinal direction. p0.2 .

[0038] Compressive yield strength Rc p0.2 Measured according to standard ASTM E9-09 (2018) at 0.2% compression. Rc p0.2 (L) refers to Rc measured in the longitudinal direction. p0.2 .

[0039] Stress intensity factor (K) 1C ) Measured according to standard ASTM E 399 (2012).

[0040] Stress intensity factor (K) Q ) Determined according to standard ASTM E 399 (2012). Standard ASTM E 399 (2012) provides the allowable determination of K. Q Is it K?1C The standard for the effective value. For a given specimen geometry, K is obtained for different materials. Q The values ​​are comparable to each other, provided that the yield strength of the materials is on the same order of magnitude.

[0041] Unless otherwise stated, the definitions of standard EN 12258 (2012) shall apply.

[0042] Apparent stress intensity factor (K) at fracture app ) and stress intensity factor (K) at fracture c The value of ) is as defined in standard ASTM E561.

[0043] The curve of the effective stress intensity factor as a function of effective crack propagation is given, called the R curve, which is measured according to the standard ASTM E 561 (ASTM E 561-10-2).

[0044] Calculate the critical stress intensity factor K from the R curve C That is, the strength factor that destabilizes the crack. Furthermore, the stress intensity factor K is calculated by allocating the initial crack length at the start of a single load to the critical load. CO Calculate these two values ​​for a specimen with the desired shape. K app The factor K represents the sample used for R-curve testing. CO K eff The factor K represents the sample used for R-curve testing. C .

[0045] Such mechanical parts are referred to herein as “structural elements” or “structural components” of a mechanical construction. The static and / or dynamic mechanical properties of these parts are particularly important to the performance of the structure and typically require or are subject to structural calculations. These are often elements whose failure could jeopardize the construction, its users, consumers, or the safety of others. In the case of aircraft, these structural elements specifically include components constituting the fuselage (e.g., fuselage skin), fuselage stringers, bulkheads, circumferential frames, wings (e.g., upper or lower wingskin), stringers or stiffeners, ribs, and spars, as well as the tail section, particularly composed of horizontal and vertical stabilizers, and floor beams, seat tracks, and doors.

[0046] According to the present invention, a class of aluminum alloys containing, in particular specific and critical amounts, lithium, copper, magnesium, silver, manganese, and zinc allows for the fabrication of structural components, especially upper wing skins, which possess high compressive yield strength Rcp. 0.2 (L), compressive yield strength Rcp 0.2 (L) and tensile yield strength Rp 0.2 The small difference between (L) and the particularly improved apparent stress intensity factor K at fracture. app The alloy composition selected in this invention also allows for the attainment of all or part of the aforementioned advantages over a wide range of tempering times (particularly within the range of at least 5 hours at a given tempering temperature). Therefore, this composition ensures the robustness of the manufacturing process and thus the final performance of the product during industrial manufacturing.

[0047] The aluminum alloy-based product of the present invention comprises, by weight percentage, 4.0 to 4.6 wt% Cu; 0.7 to 1.2 wt% Li; 0.5 to 0.65 wt% Mg; 0.10 to 0.20 wt% Zr; 0.15 to 0.30 wt% Ag; 0.25 to 0.45 wt% Zn; 0.05 to 0.35 wt% Mn; up to 0.20 wt% Fe + Si; at least one element selected from Cr, Sc, Hf, V and Ti; other elements each up to 0.05 wt% and totaling up to 0.15 wt%, with the remainder being aluminum.

[0048] The copper content of the product of the present invention is 4.0 to 4.6% by weight, preferably 4.2 to 4.5% by weight, and more preferably 4.2 to 4.4% by weight. In an advantageous embodiment, the minimum copper content is 4.25% by weight.

[0049] The lithium content of the product of the present invention is 0.7 to 1.2 by weight. Advantageously, the lithium content is 0.8 to 1.0 by weight; preferably 0.85 to 0.95 by weight.

[0050] Increasing the copper content, and to a lesser extent, the lithium content, helps improve static mechanical strength; however, copper has a detrimental effect, particularly on density, and the copper content is preferably limited to a maximum of 4.4 wt%. Increasing the lithium content has a beneficial effect on density; however, the inventors have observed that for the alloys of the present invention, a lithium content of 0.85 to 0.95 wt% allows for a better trade-off between mechanical strength (tensile strength and compressive yield strength) and toughness. High lithium content, particularly above the preferred maximum of 0.95 wt%, can lead to reduced toughness.

[0051] The magnesium content of the product of the present invention is from 0.5% to 0.65% by weight. Preferably, the magnesium content is at least 0.50% by weight or even at least 0.55% by weight, which simultaneously improves static mechanical strength and toughness. In particular, for the composition selected in the present invention, a magnesium content greater than 0.65% by weight may lead to a decrease in toughness.

[0052] The zinc and silver contents are 0.25 to 0.45% by weight and 0.15 to 0.30% by weight, respectively. These zinc and silver contents are necessary to ensure that the compressive yield strength is close to the tensile yield strength. In an advantageous embodiment, the tensile yield strength Rp of the product of the present invention is... 0.2 (L) and compressive yield strength Rcp 0.2 The difference between (L) is less than or equal to 10 MPa, preferably less than or equal to 5 MPa.

[0053] The presence of silver and zinc allows for a good compromise between various desired properties. In particular, the presence of silver allows for a reliable and robust way of obtaining products, i.e., achieving the desired performance compromises over a wide range of tempering times, especially those greater than 5 hours, which is compatible with the inherent variability of industrial manufacturing methods. A minimum silver content of 0.20% by weight is advantageous. A maximum silver content of 0.27% by weight is advantageous.

[0054] A minimum zinc content of 0.30% by weight is advantageous. A maximum zinc content of 0.40% by weight is advantageous. Preferably, the Zn content is 0.30 to 0.40% by weight.

[0055] Advantageously, the total content of Zn, Mg, and Ag is 0.95 to 1.35% by weight, preferably 1.00 to 1.30% by weight, and still more preferably 1.15 to 1.25% by weight. The inventors have observed, particularly for upper wing skin structural elements, that only specific and critical values ​​of the total content of Zn, Mg, and Ag achieve the desired optimal performance trade-off.

[0056] The manganese content is 0.05 to 0.35 wt%. Advantageously, the Mn content is 0.10 to 0.35 wt%. In one embodiment, the manganese content is 0.2 to 0.35 wt%, and preferably 0.25 to 0.35 wt%. In another embodiment, the manganese content is 0.1 to 0.2 wt%, and preferably 0.10 to 0.20 wt%. In particular, the addition of Mn allows for high toughness. However, if the Mn content is greater than 0.35 wt%, fatigue life can be significantly reduced.

[0057] The alloy has a Zr content of 0.10 to 0.20% by weight. In an advantageous embodiment, the Zr content is 0.10 to 0.15% by weight, preferably 0.11 to 0.14% by weight.

[0058] The sum of the iron and silicon content is at most 0.20% by weight. Preferably, the iron and silicon content is each at most 0.08% by weight. In an advantageous embodiment of the invention, the iron and silicon content are at most 0.06% by weight and 0.04% by weight, respectively. Controllable and limited iron and silicon content helps to improve the trade-off between mechanical strength and damage tolerance.

[0059] The alloy also contains at least one element selected from Cr, Sc, Hf, V, and Ti, which helps control grain size, in amounts of 0.05 to 0.3 wt% for Cr and Sc, 0.05 to 0.5 wt% for Hf and V, and 0.01 to 0.15 wt% for Ti. In an advantageous embodiment, 0.01 to 0.15 wt% titanium is optionally added. In a preferred embodiment, the Ti content is 0.01 to 0.08 wt%, preferably 0.02 to 0.06 wt%. Advantageously, in embodiments where titanium is optionally added, the contents of Cr, Sc, V, and Hf are limited to a maximum of 0.05 wt%, these elements can have a particularly adverse effect on density, and their addition is only to further promote the formation of a substantially non-recrystallized structure (if desired). In a particularly advantageous manner, Ti is present, in particular, in the form of TiC particles. Unexpectedly, the inventors have observed that, in certain cases of the alloy of the present invention, the presence of TiC particles in the grain refiner bar during casting (AlTiC refinement) allows for the acquisition of a product with an optimal performance trade-off. Advantageously, the refiner has the formula AlTi x Cy It is also written as AT x C y Where x and y are the contents of Ti and C in weight percent for 1 wt% Al, and x / y > 4. In particular, the AlTiC refinement of the alloy of the present invention allows for improved toughness K. app LT and compressive yield strength R c A compromise between p0.2 and L.

[0060] The content of alloying elements can be selected to minimize density. Preferably, the addition of elements that contribute to increasing density (e.g., Cu, Zn, Mn, and Ag) is minimized, while elements that contribute to decreasing density (e.g., Li and Mg) are maximized, to achieve a density of less than or equal to 2.73 g / cm³. 3 And preferably less than or equal to 2.72 g / cm³ 3 The density.

[0061] The content of each of the other elements is at most 0.05% by weight and the total content is at most 0.15% by weight. The other elements are usually unavoidable impurities.

[0062] The method of manufacturing the product of the present invention includes preparation, casting, homogenization, hot deformation, solution heat treatment and quenching, stretching by 2 to 16%, and tempering steps.

[0063] In the first step, a liquid metal pool is prepared to obtain an aluminum alloy having the composition of the present invention.

[0064] The molten metal is then cast into rough product form, preferably in the shape of rolled ingots or extruded billets.

[0065] The crude product is then homogenized to a temperature of 450°C to 550°C, preferably 480°C to 530°C, for 5 to 60 hours. The homogenization process can be carried out in one or more stages.

[0066] After homogenization, the crude product is typically cooled to room temperature and then preheated for heat deformation. Heat deformation can be, in particular, extrusion or hot rolling. Preferably, it is a hot rolling step. Hot rolling is performed to a preferred thickness of 8 to 50 mm, and more preferably 15 to 40 mm.

[0067] The product thus obtained is then subjected to solution heat treatment at a temperature of 490 to 530°C for 15 minutes to 8 hours, and then typically quenched with water at room temperature.

[0068] The product is then cold-formed at a rate of 2 to 16%. This can be a controlled stretching with a permanent deformation of 2 to 5%, preferably 2.0% to 4.0%. In an alternative advantageous embodiment, the cold forming is performed in two steps: first, the product is cold-rolled with a thickness reduction of 8% to 12%, and then stretched in a controlled manner with a permanent deformation rate of 0.5% to 4%.

[0069] The product is then subjected to a tempering step by heating at a temperature of 130 to 170°C, preferably 140 to 160°C, for 5 to 100 hours, preferably 10 to 70 hours.

[0070] The inventors have observed, unexpectedly, that specific content and critical content of the alloys of the present invention allow for excellent properties, particularly the compressive yield strength Rc. p0.2 (L) and plane stress toughness K app A particularly improved compromise between these. Advantageously, these properties can be obtained in the alloys of the present invention regardless of the tempering time of 15 h to 25 h at 155 °C, which ensures the robustness of the manufacturing method.

[0071] Advantageously, the resulting product has a predominantly non-recrystallized granular structure. The proportion of non-recrystallized granular structure at the intermediate thickness is preferably at least 70% and more preferably at least 80%.

[0072] Products obtained by the method of the present invention, particularly rolled products with a thickness of 8 to 50 mm, have the following characteristics at medium thickness:

[0073] i) Compressive yield strength Rc p0.2 (L) ≥ 590 MPa, preferably Rc p0.2 (L) ≥ 595 MPa, where the compressive yield strength Rc p0.2 (L) Measured in the longitudinal direction under 0.2% compression according to standard ASTM E9 (2018);

[0074] ii) Toughness K app (LT) ≥ 60 MPa√m, K is preferred app (LT) ≥ 75 MPa√m, where K is the value of the apparent stress intensity factor at fracture as defined in standard ASTM E561 (2015). app (LT) was measured on a CCT specimen with a width W = 406 mm and a thickness B = 6.35 mm;

[0075] iii) Tensile yield strength R p0.2 (L) and compressive yield strength Rc p0.2 The difference R between (L) p0.2(L) - Rc p0.2 (L) less than or equal to 10 MPa, preferably ≤ 5 MPa.

[0076] Advantageously, features i) and ii) are obtained at a given tempering temperature over a wide range of tempering times, particularly at least 5 hours. Therefore, this composition allows for ensuring the robustness of the manufacturing process and thus the final performance of the product during industrial manufacturing.

[0077] In a favorable implementation, resilience makes K app (LT) ≥ -0.48 Rc p0.2 (L) + 355.2, where K app (LT), expressed in MPa√m, is the value of the apparent stress intensity factor at fracture as defined in standard ASTM E561 (2015), measured on a CCT specimen with width W = 406 mm and thickness B = 6.35 mm; and Rc p0.2 (L), expressed in MPa, is the compressive yield strength measured at 0.2% compression according to standard ASTM E9 (2018).

[0078] The alloy products of this invention particularly allow for the manufacture of structural components, especially aircraft structural components. In an advantageous embodiment, the preferred aircraft structural component is the upper wing skin component.

[0079] These and other aspects of the invention will be explained in more detail using the following illustrative and non-limiting examples.

[0080] Example

[0081] Example 1.

[0082] In this embodiment, a plate with a cross-section of 406 × 1520 mm made of an alloy is cast, the composition of which is listed in Table 1.

[0083] Table 1. Composition of alloys N°1 to 8, in weight %

[0084]

[0085] For each composition, the sheets were homogenized in a first stage at 500°C for 15 h, followed by a second stage at 510°C for 20 h. The sheets were then hot-rolled at temperatures above 440°C to obtain sheets with a thickness of 25 mm for alloys 2 to 8 and 28 mm for alloy 1. The sheets were then solution-treated at approximately 510°C for 3 h and water-quenched at 20°C. The sheets were then stretched with a permanent elongation of 2% to 6%.

[0086] The thin plates were subjected to single-stage tempering as shown in Table 2. Samples were taken at intermediate thickness to measure the static mechanical properties under tension and compression in the longitudinal direction. Plane stress toughness at intermediate thickness in the LT direction was also measured during R-curve testing using CCT specimens that were 406 mm wide and 6.35 mm thick. The results are shown in Table 2 and... Figure 1 .

[0087] The resulting thin plates are mostly non-recrystallized. The proportion of non-recrystallized granular structures at medium thickness is 90%.

[0088] Table 2. Controlled tensile and tempering conditions and the mechanical properties obtained for each sheet at medium thickness.

[0089]

[0090] Example 2

[0091] In this embodiment, in addition to the alloy plate 2 of Example 1, a plate with a cross-section of 406×1520 mm was also cast, the composition of which is given in Table 3.

[0092] Table 3. Composition of Alloys 2 and 10, in weight %

[0093]

[0094] The sheet is homogenized at approximately 510°C and then peeled. After homogenization, the sheet is hot-rolled to obtain a sheet with a thickness of 25 mm. The sheet is then solution-treated at approximately 510°C for 3 hours, quenched in cold water, and stretched with a permanent elongation of 3%.

[0095] The resulting thin plate has a predominantly non-recrystallized structure. At medium thickness, the proportion of non-recrystallized granular structure is 90%.

[0096] The sheet metal was tempered at 155°C for 15 to 50 hours. Samples were taken at medium thicknesses to measure the static mechanical properties under tension and compression in the longitudinal direction and the toughness K in the LT direction. Q The specimens used for toughness measurement had a width W = 40 mm and a thickness B = 20 mm. The results are shown in Table 4 and... Figure 2 and Figure 3 .

[0097] Table 4: Tempering conditions and mechanical properties obtained for plates 2 and 10.

[0098]

[0099] Example 3

[0100] In this embodiment, in addition to the plate of alloy 2 in Example 1, a plate with a cross section of 406×1700 mm was cast using AlTiC refinement (grain refinement rod containing TiC nuclei), and the composition of the plate is shown in Table 3.

[0101] Table 5. Composition of Alloys 2 and 9, in weight %

[0102]

[0103] The sheet was homogenized at approximately 510°C and then peeled. After homogenization, the sheet was hot-rolled to obtain a sheet with a thickness of 25 mm. The sheet was then solution-treated at approximately 510°C for 3 h, quenched in cold water, and stretched with a permanent elongation of 3%.

[0104] The sheet was tempered at 155°C for 15 to 25 hours. Samples were taken at medium thickness to measure the static mechanical properties under tension and compression in the longitudinal direction and the toughness K in the LT direction. Q The specimens used for toughness measurement had a width W = 40 mm and a thickness B = 20 mm. Some samples conformed to K... 1C The validity criteria were established. Planar stress toughness measurements were also obtained on CCT samples that were 406 mm wide and 6.35 mm thick. The results are shown in Table 6 and... Figure 4 .

[0105] Table 6: Tempering conditions for plates 2 and 9 and mechanical properties obtained at medium thicknesses

[0106]

Claims

1. A rolled product with a thickness of 8 to 50 mm, comprising the following elements in percentage terms: 4.0 to 4.6% by weight of Cu, 0.85 to 0.95% by weight of Li 0.5 to 0.65% by weight of Mg, 0.10 to 0.20% by weight of Zr, 0.15 to 0.30% by weight of Ag, 0.25 to 0.45% by weight of Zn, 0.05 to 0.35% by weight of Mn, At most 0.20% by weight of Fe + Si, At least one element selected from Cr, Sc, Hf, V, and Ti, and if selected, the amount of said element is 0.05 to 0.3 wt% for Cr and Sc, 0.05 to 0.5 wt% for Hf and V, and 0.01 to 0.15 wt% for Ti. The other elements each comprise at most 0.05% by weight and the total amount comprises at most 0.15% by weight, with the remainder being aluminum. And it has the following characteristics at a medium thickness: i) Compressive yield strength Rc p0.2 (L) ≥ 590 MPa, preferably Rc p0.2 (L) ≥ 595 MPa, where Rc p0.2 (L) represents the compressive yield strength measured in the longitudinal direction under 0.2% compression according to ASTM E9 (2018); ii) Toughness K app (LT) ≥ 75 MPa√m, where K app (LT) is the apparent stress intensity factor at fracture, as defined in ASTM E561 (2015), measured on a CCT specimen with a width W = 406 mm and a thickness B = 6.35 mm. iii) Tensile yield strength R p0.2 (L) and compressive yield strength Rc p0.2 The difference R between (L) p0.2 (L) - Rc p0.2 (L) less than or equal to 10 MPa, preferably ≤ 5 MPa.

2. The aluminum alloy-based product according to claim 1, wherein the Cu content is 4.2 to 4.5% by weight, preferably 4.2 to 4.4% by weight.

3. The aluminum alloy-based product according to claim 1 or 2, wherein the Zn content is 0.30 to 0.40 by weight.

4. The aluminum alloy-based product according to any one of claims 1 to 3, wherein the Mn content is 0.10 to 0.35 by weight.

5. The aluminum alloy-based product according to any one of claims 1 to 4, wherein the total content of Zn, Mg and Ag is 0.95 to 1.35% by weight, preferably 1.00 to 1.30% by weight, more preferably 1.15 to 1.25% by weight.

6. The aluminum alloy-based product according to any one of claims 1 to 5, wherein the Zr content is 0.10 to 0.15% by weight, preferably 0.11 to 0.14% by weight.

7. The aluminum alloy-based product according to any one of claims 1 to 6, wherein the Ti content is 0.01 to 0.15% by weight of Ti, preferably 0.01 to 0.08% by weight, more preferably 0.02 to 0.06% by weight.

8. The aluminum alloy-based product according to claim 7, wherein Ti is present, in particular, in the form of TiC particles.

9. A method for manufacturing an aluminum alloy-based product, wherein, In turn, a) Preparing an aluminum-based liquid metal pool comprising: 4.0 to 4.6 wt% Cu; 0.85 to 0.95 wt% Li; 0.5 to 0.65 wt% Mg; 0.10 to 0.20 wt% Zr; 0.15 to 0.30 wt% Ag; 0.25 to 0.45 wt% Zn; 0.05 to 0.35 wt% Mn; up to 0.20 wt% Fe + Si; at least one element selected from Cr, Sc, Hf, V and Ti, wherein, if selected, the amount of said element is 0.05 to 0.3 wt% for Cr and Sc, 0.05 to 0.5 wt% for Hf and V, and 0.01 to 0.15 wt% for Ti; other elements each up to 0.05 wt% and the total up to 0.15 wt%, the remainder being aluminum; b) Casting the rough product from the molten metal pool; c) Homogenize the crude product at a temperature of 450°C to 550°C, preferably 480°C to 530°C, for 5 to 60 hours; d) The homogenized rough product is hot-deformed, preferably by rolling; e) The heat-deformed product is solution heat-treated at 490 to 530°C for 15 min to 8 h, and the solution-heat-treated product is then quenched. f) The product is subjected to cold deformation with a deformation rate of 2% to 16%; g) Tempering is performed, wherein the product is brought to a temperature of 130 to 170°C, preferably 140 to 160°C, for 5 to 100 hours, preferably 10 to 70 hours.

10. The product obtained by the method of claim 9, having a thickness of 8 to 50 mm, and having the following characteristics at a moderate thickness: i) Compressive yield strength Rc p0.2 (L) ≥ 590 MPa, preferably Rc p0.2 (L) ≥ 595 MPa; ii) Toughness K app (LT) ≥75 MPa√m, where K app (LT) is the value of the apparent stress intensity factor at fracture as defined in standard ASTM E561 (2015), which was measured on a CCT specimen with a width W = 406 mm and a thickness B = 6.35 mm. iii) Tensile yield strength R p0.2 (L) and compressive yield strength Rc p0.2 The difference R between (L) p0.2 (L) - Rc p0.2 (L) less than or equal to 10 MPa, preferably ≤ 5 MPa.

11. An aircraft structural element, preferably an aircraft upper wing skin element, comprising the product according to any one of claims 1 to 8 or according to claim 10.

Images