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EP3788178B1 - Aluminium-copper-lithium alloy having improved compressive strength and improved toughness - Google Patents

Aluminium-copper-lithium alloy having improved compressive strength and improved toughness Download PDF

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Publication number
EP3788178B1
EP3788178B1 EP19726060.7A EP19726060A EP3788178B1 EP 3788178 B1 EP3788178 B1 EP 3788178B1 EP 19726060 A EP19726060 A EP 19726060A EP 3788178 B1 EP3788178 B1 EP 3788178B1
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aluminum alloy
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German (de)
French (fr)
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EP3788178A1 (en
Inventor
Fanny MAS
David BARBIER
Samuel JUGE
Armelle Danielou
Gaëlle POUGET
Nicolas BAYONA-CARRILLO
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Constellium Issoire SAS
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Constellium Issoire SAS
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/12—Alloys based on aluminium with copper as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
    • C22F1/057—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with copper as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/12—Alloys based on aluminium with copper as the next major constituent
    • C22C21/14—Alloys based on aluminium with copper as the next major constituent with silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/12—Alloys based on aluminium with copper as the next major constituent
    • C22C21/16—Alloys based on aluminium with copper as the next major constituent with magnesium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/12—Alloys based on aluminium with copper as the next major constituent
    • C22C21/18—Alloys based on aluminium with copper as the next major constituent with zinc

Definitions

  • the invention relates to aluminum-copper-lithium alloy products, more particularly, such products intended for aeronautical and aerospace construction.
  • Aluminum alloy products are developed to produce high-strength parts intended in particular for the aeronautical and aerospace industries.
  • Aluminum alloys containing lithium are very attractive in this regard, as lithium can reduce the density of aluminum by 3% and increase the modulus of elasticity by 6% for each weight percent of lithium added.
  • their performance with respect to other usage properties must reach that of commonly used alloys, in particular in terms of compromise between static mechanical strength properties (tensile and compression, breaking strength) and damage tolerance properties (toughness, resistance to the propagation of fatigue cracks), these properties generally being contradictory.
  • the elastic limit in compression is an essential property.
  • alloys must also have sufficient corrosion resistance, be able to be shaped according to the usual methods and have low residual stresses so that they can be machined integrally. Finally, they must be obtainable by robust manufacturing processes, in particular, the properties must be able to be obtained on industrial tools for which it is difficult to guarantee temperature homogeneity within a few degrees for large parts.
  • the patent US 5,455,003 describes a process for the manufacture of Al-Cu-Li alloys which exhibit improved mechanical strength and toughness at cryogenic temperature, in particular thanks to suitable work hardening and tempering.
  • the patent US 7,229,509 describes 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, 0.4 max Zr or other grain refiners such as Cr, Ti, Hf, Sc, V.
  • the patent application WO2009/036953 relates to an aluminum alloy product for structural elements having a chemical composition comprising, by weight Cu from 3.4 to 5.0, Li from 0.9 to 1.7, Mg from 0.2 to 0.8, Ag from about 0.1 to 0.8, Mn from 0.1 to 0.9, Zn up to 1.5, and one or more elements selected from the group consisting of: (Zr from 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, the normal and unavoidable impurities.
  • the W0 patent application 2012/085359 A2 relates to a process for the manufacture of aluminum alloy rolled products comprising 4.2 to 4.6% by weight of Cu, 0.8 to 1.30% by weight of Li, 0.3 to 0.8% by weight of Mg, 0.05 to 0.18% by weight of Zr, 0.05 to 0.4% by weight of Ag, 0.0 to 0.5% by weight of Mn, at most 0.20 % by weight of Fe + Si, less than 0.20 % by weight of Zn, at least one element chosen from Cr, Se, Hf and Ti, the amount of said element, if chosen, being from 0.05 to 0.3% by weight for Cr and for Se, 0.05 to 0.5% by weight for Hf and 0.01 to 0.15% by weight for Ti, the other elements at most 0.05% by weight each and 0.15% by weight in total, the balance aluminium, comprising the steps of production, casting, homogenization, rolling with a temperature above 400°C, solution treatment, quenching, traction between 2 and 3.5% and returned.
  • the patent application US2012/0225271Al concerns wrought products 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.% of Li, in which -0.3 Mg - 0.15Cu +1.65 ⁇ Li ⁇ -0.3 Mg-0.15Cu +1.85, from 0.05 to 0.50 by weight.
  • the grain structure controlling element is selected from the group consisting of Zr, Sc, Cr, V, Hf, other earth elements rare, 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, up to 0.10 wt. % of other elements with a total not exceeding 0.35 by weight %.
  • Requirement WO 2013/169901 describes alloys comprising, by weight percent, 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 grain structure control.
  • the alloys advantageously have a Zn to Mg ratio of between 0.60 and 1.67.
  • the patent application FR 3 007 423 A1 relates to an extrados structural element in aluminum, copper and lithium alloy and its method of manufacture.
  • Alloys comprising (in % by weight) 4.2 to 5.2 Cu, 0.9 to 1.2 Li, 0.1 to 0.3 Ag, 0.1 to 0.25 Mg, 0.11 to 0 .18 Zr, 0.01 to 0.15 Ti, optionally up to 0.2 Zn, optionally up to 0.6 Mn, a Fe and Si content less than or equal to 0.1, and other elements at a lower or equal content at 0.05 each and 0.15 in total, remains Al.
  • a first object of the invention is a product based on an aluminum alloy comprising, in percentage by weight, 4.0 to 4.6% by weight of Cu, 0.7 to 1.2% by weight of 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% 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 chosen from among Cr, Sc, Hf, V and Ti, the amount of said element , if chosen, being 0.05 to 0.3% by weight for Cr and for Sc, 0.05 to 0.5% by weight for Hf and for V and 0.01 to 0.15% by weight for Ti, other elements not more than 0.05% by weight each and 0.15% by weight in total and remainder aluminum.
  • Yet another object is an aircraft structural element, preferably an aircraft wing upper surface element.
  • the static mechanical characteristics in tension in other words the breaking strength R m , the conventional yield strength at 0.2% elongation R p0.2 , and the elongation at break A%, are determined by a tensile test according to standard NF EN ISO 6892-1 (2016), the sampling and direction of the test being defined by standard EN 485 (2016).
  • R p0.2 (L) means R p0.2 measured in the longitudinal direction.
  • the compressive yield strength Rc p0.2 was measured at 0.2% compression according to ASTM E9-09 (2016).
  • Rc p0.2 (L) means Rc p0.2 measured in the longitudinal direction.
  • the stress intensity factor (K 1C ) is determined according to standard ASTM E 399 (2012).
  • the stress intensity factor (KQ) is determined according to ASTM E 399 (2012).
  • the ASTM E 399 (2012) standard gives the criteria for determining whether K Q is a valid value of K 1C . For a given specimen geometry, the values of K Q obtained for different materials are comparable with each other provided that the elastic limits of the materials are of the same order of magnitude.
  • the critical stress intensity factor Kc in other words the intensity factor that makes the crack unstable, is calculated from the R-curve.
  • the stress intensity factor KCO is also calculated by assigning the initial crack length at the beginning of the monotonic load, at the critical load. These two values are calculated for a specimen of the required shape.
  • K app represents the K CO factor corresponding to the specimen that was used to perform the R-curve test.
  • K eff represents the Kc factor corresponding to the specimen that was used to perform the R-curve test.
  • structural element or "structural element” of a mechanical construction is used here to mean 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 performed. These are typically elements whose failure is likely to endanger the safety of said construction, its users, its users or others.
  • these structural elements include in particular the elements that make up the fuselage (such as the fuselage skin), the fuselage stiffeners or stringers, the bulkheads, the fuselage (circumferential frames), wings (such as upper or lower wing skin), stiffeners (stringers or stiffeners), ribs and spars) and compound empennage including horizontal and vertical stabilizers (horizontal or vertical stabilizers), as well as floor beams (floor beams), seat tracks (seat tracks) and doors.
  • the fuselage such as the fuselage skin
  • the fuselage stiffeners or stringers such as upper or lower wing skin
  • stiffeners stringers or stiffeners
  • compound empennage including horizontal and vertical stabilizers (horizontal or vertical stabilizers), as well as floor beams (floor beams), seat tracks (seat tracks) and doors.
  • a selected class of aluminum alloys containing in particular specific and critical quantities of lithium, copper, magnesium, silver, manganese and zinc makes it possible to prepare structural elements, in particular wing upper surface plates , having a high elastic limit in compression Rc p0,2 (L), a small difference between elastic limit in compression Rc p0,2 (L) and elastic limit in tensile R p0.2 (L) and a particularly improved apparent stress intensity factor at break K app .
  • the selected alloy composition of the invention also makes it possible to obtain all or part of the aforementioned advantages for a wide range of tempering times (in particular a range of at least 5 hours at a given tempering temperature). Such a composition thus makes it possible to guarantee the robustness of the manufacturing process and therefore to guarantee the final properties of the product during industrial production.
  • the product based on an aluminum alloy according to the invention comprises, in percentage by weight, 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 Cr, Sc, Hf, V and Ti; other elements not more than 0.05% by weight each and 0.15% by weight in total and remainder aluminium.
  • the copper content of the products according to the invention is between 4.0 and 4.6% by weight, preferably between 4.2 and 4.5% by weight and more preferably between 4.2 and 4.4% by weight. .
  • the minimum copper content is 4.25% by weight.
  • the lithium content of the products according to the invention is between 0.7 and 1.2% by weight.
  • the lithium content is between 0.8 and 1.0% by weight; preferably between 0.85 and 0.95% by weight.
  • the copper content and to a lesser extent the lithium content contributes to improving the static mechanical resistance, however, copper having a detrimental effect in particular on the density, it is preferable to limit the copper content to the preferred maximum value of 4.4% by weight.
  • Increasing the lithium content has a favorable effect on the density, however the present inventors have found that for the alloys according to the invention, the preferred lithium content of between 0.85% and 0.95% by weight allows an improvement in the compromise between mechanical strength (yield point in tension and compression) and toughness.
  • a high lithium content, in particular beyond the preferred maximum value of 0.95% by weight can lead to a degradation of toughness.
  • the magnesium content of the products according to the invention is between 0.5% and 0.65% by weight.
  • the magnesium content is at least 0.50% or even at least 0.55% by weight, which simultaneously improves static mechanical strength and toughness.
  • a magnesium content greater than 0.65% by weight can induce a deterioration in toughness.
  • the zinc and silver contents are respectively between 0.25 and 0.45% by weight and 0.15 and 0.30% by weight. Such zinc and silver contents are necessary to guarantee an elastic limit in compression having a value close to that of the elastic limit in tension.
  • the products according to the invention have a difference between the elastic limit in tension R p0.2 (L) and the elastic limit in compression Rc p0.2 (L) less than or equal to 10 MPa, preferably less than or equal to 5 MPa.
  • the presence of silver and zinc makes it possible to obtain a good compromise between the different properties sought.
  • the presence of silver makes it possible to obtain a product in a reliable and robust manner, that is to say that the desired compromise of properties is achieved for a wide range of tempering times, in particular a range of times greater than at 5 a.m., which is compatible with the variability inherent in an industrial manufacturing process.
  • a minimum content of 0.20% by weight of silver is advantageous.
  • a maximum content of 0.27% by weight of silver is advantageous.
  • a minimum content of 0.30% by weight of zinc is advantageous.
  • a maximum content of 0.40% by weight of zinc is advantageous.
  • the Zn content is between 0.30 and 0.40% by weight.
  • the sum of the Zn, Mg and Ag contents comprised between 0.95 and 1.35% by weight, preferentially between 1.00 and 1.30% by weight, more preferentially still between 1.15 and 1.25% in weight.
  • the present inventors have observed that the optimum compromise of properties sought, in particular for wing upper surface structural elements, was only achieved for specific and critical values of the sum of Zn, Mg and Ag.
  • the manganese content is between 0.05 and 0.35% by weight.
  • the Mn content between 0.10 and 0.35% by weight.
  • the manganese content is between 0.2 and 0.35% by weight and preferably between 0.25 and 0.35% by weight.
  • the manganese content is between 0.1 and 0.2% by weight and preferably between 0.10 and 0.20% by weight.
  • the addition of Mn in particular makes it possible to obtain a high tenacity. However, if the Mn content is more than 0.35% by weight, the fatigue life may be significantly reduced.
  • the Zr content of the alloy is between 0.10 and 0.20% by weight. In an advantageous embodiment, the Zr content is between 0.10 and 0.15% by weight, preferably between 0.11 and 0.14% by weight.
  • the sum of the iron content and the silicon content is at most 0.20% by weight.
  • the iron and silicon contents are each at most 0.08% by weight.
  • the iron and silicon contents are at most 0.06% and 0.04% by weight, respectively.
  • a controlled and limited iron and silicon content contributes to the improvement of the compromise between mechanical resistance and damage tolerance.
  • the alloy also contains at least one element which can contribute to the control of the grain size chosen from Cr, Sc, Hf, V and Ti, the amount of said element, if chosen, being from 0.05 to 0.3 % by weight for Cr and for Sc, 0.05 to 0.5 % by weight for Hf and for V and 0.01 to 0.15 % by weight for Ti. In an advantageous embodiment, it is chosen to add between 0.01 and 0.15% by weight of titanium. In a preferred embodiment, the Ti content is between 0.01 and 0.08% by weight, preferably between 0.02 and 0.06% by weight.
  • the content of Cr, Sc, V and Hf is limited to a maximum content of 0.05% by weight, these elements possibly having an unfavorable effect, in particular on the density and being added only to further promote obtaining a substantially non-recrystallized structure if necessary.
  • the Ti is present in particular in the form of TiC particles.
  • AlTiC refining the presence of TiC particles in the refining wire during casting (AlTiC refining), makes it possible to obtain a product having an optimized compromise of properties. .
  • the refining agent has the formula AlTi x C y which is also written AT x C y where x and y are the contents of Ti and C in % by weight for 1% by weight of Al, and x/y > 4
  • the AlTiC refining in the alloy of the present invention allows an improvement in the compromise between the toughness K app LT and the elastic limit in compression R c p0.2 L.
  • the content of the alloying elements prefferably, the addition elements contributing to increase the density such as Cu, Zn, Mn and Ag are minimized and the elements contributing to decreasing the density such as Li and Mg are maximized so as to reach a density less than or equal to 2.73 g/cm 3 and preferably less than or equal to 2.72 g/cm 3 .
  • the content of the other elements is at most 0.05% by weight each and 0.15% by weight in total.
  • the other elements are typically unavoidable impurities.
  • the process for manufacturing the products according to the invention comprises the steps of preparation, casting, homogenization, hot deformation, solution treatment and quenching, traction between 2 and 16% and tempering.
  • a bath of liquid metal is prepared so as to obtain an aluminum alloy of composition according to the invention.
  • the liquid metal bath is then cast in the form of a raw form, preferably in the form of a rolling plate or an extruded billet.
  • the raw form is then homogenized so as to reach a temperature of between 450° C. and 550° and preferably between 480° C. and 530° C. for a period of between 5 and 60 hours.
  • the homogenization treatment can be carried out in one or more stages.
  • the raw form is generally cooled to ambient temperature before being preheated in order to be hot deformed.
  • the hot deformation can in particular be an extrusion or a hot rolling.
  • this is a hot rolling step. Hot rolling is carried out to a thickness preferably between 8 and 50 mm and preferably between 15 and 40 mm.
  • the product thus obtained is then placed in solution by heat treatment making it possible to reach a temperature of between 490 and 530° C. for 15 min to 8 h, then typically quenched with water at room temperature.
  • the product then undergoes cold deformation with a deformation of 2 to 16%. It may be a controlled tensile with a permanent set of 2 to 5%, preferably 2.0% to 4.0%.
  • the cold deformation is carried out in two stages: the product is first cold rolled with a thickness reduction rate of between 8 to 12% then subsequently pulled in a controlled manner with a permanent deformation between 0.5 and 4%.
  • the product is then subjected to a tempering step carried out by heating at a temperature of between 130 and 170° C. and preferably between 140 and 160° C. for 5 to 100 hours and preferably from 10 to 70 hours.
  • the present inventors have found that, surprisingly, the specific and critical contents of the alloy of the present invention make it possible to achieve excellent properties, in particular a compromise between the elastic limit in compression Rc p0.2 (L ) and particularly improved Kapp plane stress toughness.
  • these properties can be obtained, for the alloys of the invention, regardless of the tempering time between 15 h and 25 h at 155° C., which guarantees robustness of the manufacturing process.
  • the granular structure of the products obtained is mostly non-recrystallized.
  • the rate of non-recrystallized granular structure at mid-thickness is preferably at least 70% and preferentially at least 80%.
  • characteristics i) and ii) are obtained for a wide range of tempering times, in particular a range of at least 5 h at a given tempering temperature.
  • Such a composition thus makes it possible to guarantee the robustness of the manufacturing process and therefore to guarantee the final properties of the product during industrial production.
  • the alloy products according to the invention allow in particular the manufacture of structural elements, in particular aircraft structural elements.
  • the preferred aircraft structural element is an aircraft wing upper surface element.
  • the plate was homogenized with a first level of 15 h at 500°C, followed by a second level of 20 h at 510°C.
  • the plate was hot rolled at a temperature 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 put in solution at approximately 510° C for 3h, quenched with water at 20°C.
  • the sheets were then stretched with a permanent elongation of between 2% and 6%.
  • the plates underwent single-stage tempering as indicated in Table 2. Samples were taken at mid-thickness to measure the static mechanical characteristics in tension and compression in the longitudinal direction. The plane stress toughness was also measured at mid-thickness during R-curve tests with CCT specimens 406 mm wide and 6.35 mm thick in the LT direction. The results are presented in Table 2 and in figure 1 .
  • Plates were homogenized at approximately 510°C and then scalped. After homogenization, the plates were hot rolled to obtain sheets having a thickness of 25 mm. The sheets were put in solution for 3 hours at approximately 510° C., quenched in cold water and stretched with a permanent elongation of 3%.
  • the structure of the sheets obtained was mostly non-recrystallized.
  • the rate of non-recrystallized granular structure at mid-thickness was 90%.
  • Plates were homogenized at approximately 510°C and then scalped. After homogenization, the plates were hot rolled to obtain plates having a thickness of 25mm. The sheets were put in solution for 3 hours at approximately 510° C., quenched in cold water and stretched with a permanent elongation of 3%.

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Description

Domaine de l'inventionField of the invention

L'invention concerne les produits en alliages aluminium-cuivre-lithium, plus particulièrement, de tels produits destinés à la construction aéronautique et aérospatiale.The invention relates to aluminum-copper-lithium alloy products, more particularly, such products intended for aeronautical and aerospace construction.

Etat de la techniqueState of the art

Des produits en alliage d'aluminium sont développés pour produire des pièces de haute résistance destinées notamment à l'industrie aéronautique et à l'industrie aérospatiale.Aluminum alloy products are developed to produce high-strength parts intended in particular for the aeronautical and aerospace industries.

Les alliages d'aluminium contenant du lithium sont très intéressants à cet égard, car le lithium peut réduire la densité de l'aluminium de 3 % et augmenter le module d'élasticité de 6 % pour chaque pourcent en poids de lithium ajouté. Pour que ces alliages soient sélectionnés dans les avions, leur performance par rapport aux autres propriétés d'usage doit atteindre celle des alliages couramment utilisés, en particulier en terme de compromis entre les propriétés de résistance mécanique statique (limite d'élasticité en traction et en compression, résistance à la rupture) et les propriétés de tolérance aux dommages (ténacité, résistance à la propagation des fissures en fatigue), ces propriétés étant en général antinomiques. Pour certaines pièces telles que les extrados de voilure, la limite d'élasticité en compression est une propriété essentielle. Ces propriétés mécaniques doivent de plus être de préférence stables dans le temps et présenter une bonne stabilité thermique, c'est-à-dire ne pas être significativement modifiées par un vieillissement à température d'utilisation.Aluminum alloys containing lithium are very attractive in this regard, as lithium can reduce the density of aluminum by 3% and increase the modulus of elasticity by 6% for each weight percent of lithium added. For these alloys to be selected in aircraft, their performance with respect to other usage properties must reach that of commonly used alloys, in particular in terms of compromise between static mechanical strength properties (tensile and compression, breaking strength) and damage tolerance properties (toughness, resistance to the propagation of fatigue cracks), these properties generally being contradictory. For certain parts such as the wing upper surfaces, the elastic limit in compression is an essential property. These mechanical properties must moreover preferably be stable over time and exhibit good thermal stability, that is to say not be significantly modified by aging at the temperature of use.

Ces alliages doivent également présenter une résistance à la corrosion suffisante, pouvoir être mis en forme selon les procédés habituels et présenter de faibles contraintes résiduelles de façon à pouvoir être usinés de façon intégrale. Ils doivent enfin pouvoir être obtenus par des procédés de fabrication robustes, en particulier, les propriétés doivent pouvoir être obtenues sur des outils industriels pour lesquels il est difficile de garantir une homogénéité de température à quelques degrés près pour des pièces de grandes dimensions.These alloys must also have sufficient corrosion resistance, be able to be shaped according to the usual methods and have low residual stresses so that they can be machined integrally. Finally, they must be obtainable by robust manufacturing processes, in particular, the properties must be able to be obtained on industrial tools for which it is difficult to guarantee temperature homogeneity within a few degrees for large parts.

Le brevet US 5,032,359 décrit une vaste famille d'alliages aluminium-cuivre-lithium dans lesquels l'addition de magnésium et d'argent, en particulier entre 0,3 et 0,5 pourcent en poids, permet d'augmenter la résistance mécanique.The patent US 5,032,359 describes a vast family of aluminum-copper-lithium alloys in which the addition of magnesium and silver, in particular between 0.3 and 0.5 percent by weight, makes it possible to increase the mechanical resistance.

Le brevet US 5,455,003 décrit un procédé de fabrication d'alliages Al-Cu-Li qui présentent une résistance mécanique et une ténacité améliorés à température cryogénique, en particulier grâce à un écrouissage et un revenu appropriés. Ce brevet recommande en particulier la composition, en pourcentage en poids, Cu = 3,0 - 4,5, Li = 0,7 - 1,1, Ag = 0 - 0,6, Mg = 0,3-0,6 et Zn = 0 - 0,75.The patent US 5,455,003 describes a process for the manufacture of Al-Cu-Li alloys which exhibit improved mechanical strength and toughness at cryogenic temperature, in particular thanks to suitable work hardening and tempering. This patent recommends in particular the composition, in percentage by weight, Cu = 3.0 - 4.5, Li = 0.7 - 1.1, Ag = 0 - 0.6, Mg = 0.3-0.6 and Zn = 0 - 0.75.

Le brevet US 7,438,772 décrit des alliages comprenant, en pourcentage en poids, Cu : 3-5, Mg : 0,5-2, Li : 0,01-0,9 et décourage l'utilisation de teneur en lithium plus élevées en raison d'une dégradation du compromis entre ténacité et résistance mécanique.The patent US 7,438,772 describes alloys comprising, in weight percent, Cu: 3-5, Mg: 0.5-2, Li: 0.01-0.9 and discourages the use of higher lithium contents due to degradation compromise between toughness and mechanical strength.

Le brevet US 7,229,509 décrit un alliage comprenant (% en poids) : (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, 0,4 max Zr ou d'autres agents affinant le grain tels que Cr, Ti, Hf, Sc, V.The patent US 7,229,509 describes 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, 0.4 max Zr or other grain refiners such as Cr, Ti, Hf, Sc, V.

La demande de brevet US 2009/142222 A1 décrit des alliages comprenant (en % en poids), 3,4 à 4,2% de Cu, 0,9 à 1,4 % de Li, 0,3 à 0,7 % de Ag, 0,1 à 0,6% de Mg, 0,2 à 0,8 % de Zn, 0,1 à 0,6 % de Mn et 0,01 à 0,6 % d'au moins un élément pour le contrôle de la structure granulaire. Cette demande décrit également un procédé de fabrication de produits filés.The patent application US 2009/142222 A1 describes alloys comprising (in % 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 grain structure control. This application also describes a process for the manufacture of extruded products.

La demande de brevet WO2009/036953 concerne un produit en alliage d'aluminium pour les éléments structuraux présentant une composition chimique comprenant, en poids Cu de 3,4 à 5,0, Li de 0,9 à 1,7, Mg de 0,2 à 0,8, Ag d'environ 0,1 à 0,8, Mn de 0,1 à 0,9, Zn jusqu'à 1,5, et un ou plusieurs éléments choisis dans le groupe constitué par: (Zr environ 0,05 à 0,3, Cr 0,05 à 0,3, Ti environ 0,03 à 0,3, Sc environ 0,05 à 0,4, Hf environ 0,05 à 0,4), Fe <0,15, Si <0,5, les impuretés normales et inévitables.The patent application WO2009/036953 relates to an aluminum alloy product for structural elements having a chemical composition comprising, by weight Cu from 3.4 to 5.0, Li from 0.9 to 1.7, Mg from 0.2 to 0.8, Ag from about 0.1 to 0.8, Mn from 0.1 to 0.9, Zn up to 1.5, and one or more elements selected from the group consisting of: (Zr from 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, the normal and unavoidable impurities.

La demande de brevet W0 2012/085359 A2 concerne un procédé de fabrication de produits laminés en alliage à base d'aluminium comprenant 4,2 à 4,6 % en poids de Cu, 0,8 à 1,30 % en poids de Li, 0,3 à 0,8 % en poids de Mg, 0,05 à 0, 18 % en poids de Zr, 0,05 à 0,4 % en poids d'Ag, 0,0 à 0,5% en poids de Mn, au plus 0,20 % en poids de Fe + Si, moins de 0,20 % en poids de Zn, au moins un élément choisi parmi Cr, Se, Hf et Ti, la quantité dudit élément, s'il est choisi, étant de 0,05 à 0,3 % en poids pour Cr et pour Se, 0,05 à 0,5 % en poids pour Hf et de 0,01 à 0, 15 % en poids pour Ti, les autres éléments au plus 0,05% en poids chacun et 0, 15% en poids au total, le reste aluminium, comprenant les étapes d'élaboration, coulée, homogénéisation, laminage avec une température supérieure à 400 °C, mise en solution, trempe, traction entre 2 et 3,5% et revenu.The W0 patent application 2012/085359 A2 relates to a process for the manufacture of aluminum alloy rolled products comprising 4.2 to 4.6% by weight of Cu, 0.8 to 1.30% by weight of Li, 0.3 to 0.8% by weight of Mg, 0.05 to 0.18% by weight of Zr, 0.05 to 0.4% by weight of Ag, 0.0 to 0.5% by weight of Mn, at most 0.20 % by weight of Fe + Si, less than 0.20 % by weight of Zn, at least one element chosen from Cr, Se, Hf and Ti, the amount of said element, if chosen, being from 0.05 to 0.3% by weight for Cr and for Se, 0.05 to 0.5% by weight for Hf and 0.01 to 0.15% by weight for Ti, the other elements at most 0.05% by weight each and 0.15% by weight in total, the balance aluminium, comprising the steps of production, casting, homogenization, rolling with a temperature above 400°C, solution treatment, quenching, traction between 2 and 3.5% and returned.

La demande de brevet US2012/0225271 Al concerne des produits corroyés d'épaisseur au moins 12,7 mm contenant de 3,00 à 3,80 en poids.% de Cu, de 0,05 à 0,35 en poids % de Mg, de 0,975 à 1,385 en poids % de Li, dans lequel -0,3 Mg - 0.15Cu +1,65 ≤ Li ≤ -0,3 Mg-0.15Cu +1,85, de 0,05 à 0,50 en poids. % d'au moins un élément de contrôle de la structure du grain, dans lequel l'élément de contrôle de la structure des grains est choisi dans le groupe constitué de Zr, Sc, Cr, V, Hf, d'autres éléments des terres rares, et des combinaisons de ceux-ci, jusqu'à 1,0 en poids % de Zn, jusqu'à 1,0 en poids % de Mn, jusqu'à 0,12 en poids % de Si, jusqu'à 0,15 en poids % de Fe, jusqu'à 0,15 en poids % de Ti, jusqu'à 0,10 poids. % d'autres éléments avec un total ne dépassant pas 0,35 en poids %.The patent application US2012/0225271Al concerns wrought products 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.% of Li, in which -0.3 Mg - 0.15Cu +1.65 ≤ Li ≤ -0.3 Mg-0.15Cu +1.85, from 0.05 to 0.50 by weight. % of at least one grain structure controlling element, wherein the grain structure controlling element is selected from the group consisting of Zr, Sc, Cr, V, Hf, other earth elements rare, 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, up to 0.10 wt. % of other elements with a total not exceeding 0.35 by weight %.

La demande WO 2013/169901 décrit des alliages comprenant, en pourcentage en poids, 3,5 à 4,4% de Cu, 0,65 à 1,15 % de Li, 0,1 à 1,0 % d'Ag, 0,45 à 0,75% de Mg, 0,45 à 0,75% de Zn et 0,05 à 0,50 % d'au moins un élément pour le contrôle de la structure granulaire. Les alliages ont avantageusement un rapport Zn sur Mg compris entre 0,60 et 1,67. La demande de brevet FR 3 007 423 A1 concerne un élément de structure extrados en alliage de aluminium, cuivre et lithium et son procédé de fabrication. Les alliages comprenant (en % en poids) 4,2 à 5,2 Cu, 0,9 à 1,2 Li, 0,1 à 0,3 Ag, 0,1 à 0,25 Mg, 0,11 à 0,18 Zr, 0,01 à 0,15 Ti, optionnellement jusque 0,2 Zn, optionnellement jusque 0,6 Mn, une teneur de Fe et Si inférieure ou égale 0,1, et des autres éléments à une teneur inférieure ou égale à 0,05 chacun et 0,15 au total, reste Al.Requirement WO 2013/169901 describes alloys comprising, by weight percent, 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 grain structure control. The alloys advantageously have a Zn to Mg ratio of between 0.60 and 1.67. The patent application FR 3 007 423 A1 relates to an extrados structural element in aluminum, copper and lithium alloy and its method of manufacture. Alloys comprising (in % by weight) 4.2 to 5.2 Cu, 0.9 to 1.2 Li, 0.1 to 0.3 Ag, 0.1 to 0.25 Mg, 0.11 to 0 .18 Zr, 0.01 to 0.15 Ti, optionally up to 0.2 Zn, optionally up to 0.6 Mn, a Fe and Si content less than or equal to 0.1, and other elements at a lower or equal content at 0.05 each and 0.15 in total, remains Al.

Il existe un besoin pour des produits en alliage aluminium-cuivre-lithium présentant des propriétés améliorées par rapport à celles des produits connus, en particulier en termes de compromis entre les propriétés de résistance mécanique statique, en particulier la limite d'élasticité en traction et en compression et les propriétés de tolérance aux dommages, en particulier la ténacité, de stabilité thermique, de résistance à la corrosion et d'aptitude à l'usinage, tout en ayant une faible densité.There is a need for aluminum-copper-lithium alloy products having improved properties compared to those of known products, in particular in terms of compromise between the properties of static mechanical strength, in particular the limit tensile and compressive elasticity and the properties of damage tolerance, in particular toughness, thermal stability, corrosion resistance and machinability, while having a low density.

De plus, il existe un besoin pour un procédé de fabrication de ces produits robuste, fiable et économique.In addition, there is a need for a method of manufacturing these products that is robust, reliable and economical.

Objet de l'inventionObject of the invention

Un premier objet de l'invention est un produit à base d'alliage d'aluminium comprenant, en pourcentage en poids, 4,0 à 4,6 % en poids de Cu, 0,7 à 1,2 % en poids de Li, 0,5 à 0,65 % en poids de Mg, 0,10 à 0,20 % en poids de Zr, 0,15 à 0,30 % en poids d'Ag, 0,25 à 0,45 % en poids de Zn, 0,05 à 0,35% en poids de Mn, au plus 0,20 % en poids de Fe + Si, au moins un élément choisi parmi Cr, Sc, Hf, V et Ti, la quantité dudit élément, s'il est choisi, étant de 0,05 à 0,3 % en poids pour Cr et pour Sc, 0,05 à 0,5 % en poids pour Hf et pour V et de 0,01 à 0,15 % en poids pour Ti, autres éléments au plus 0,05% en poids chacun et 0,15% en poids au total et reste aluminium.A first object of the invention is a product based on an aluminum alloy comprising, in percentage by weight, 4.0 to 4.6% by weight of Cu, 0.7 to 1.2% by weight of 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% 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 chosen from among Cr, Sc, Hf, V and Ti, the amount of said element , if chosen, being 0.05 to 0.3% by weight for Cr and for Sc, 0.05 to 0.5% by weight for Hf and for V and 0.01 to 0.15% by weight for Ti, other elements not more than 0.05% by weight each and 0.15% by weight in total and remainder aluminum.

Un second objet de l'invention est un procédé de fabrication d'un produit à base d'alliage d'aluminium dans lequel, successivement,

  1. a) on élabore un bain de métal liquide à base d'aluminium comprenant 4,0 à 4,6 % en poids de Cu ; 0,7 à 1,2 % en poids de Li ; 0,5 à 0,65 % en poids de Mg ; 0,10 à 0,20 % en poids de Zr ; 0,15 à 0,30 % en poids d'Ag ; 0,25 à 0,45 % en poids de Zn ; 0,05 à 0,35% en poids de Mn ; au plus 0,20 % en poids de Fe + Si ; au moins un élément choisi parmi Cr, Sc, Hf, V et Ti, la quantité dudit élément, s'il est choisi, étant de 0,05 à 0,3 % en poids pour Cr et pour Sc, 0,05 à 0,5 % en poids pour Hf et pour V et de 0,01 à 0,15 % en poids pour Ti ; autres éléments au plus 0,05% en poids chacun et 0,15% en poids au total et reste aluminium ;
  2. b) on coule une forme brute à partir dudit bain de métal liquide ;
  3. c) on homogénéise ladite forme brute à une température comprise entre 450°C et 550°C et de préférence entre 480°C et 530°C pendant une durée comprise entre 5 et 60 heures ;
  4. d) on déforme à chaud, préférentiellement par laminage, ladite forme brute homogénéisée ;
  5. e) on met en solution le produit déformé à chaud entre 490 et 530 °C pendant 15 min à 8 h et on trempe ledit produit mis en solution ;
  6. f) on déforme à froid ledit produit avec une déformation de 2 à 16% ;
  7. g) on réalise un revenu dans lequel ledit produit déformé à froid atteint une température comprise entre 130 et 170°C et de préférence entre 140 et 160°C pendant 5 à 100 heures et de préférence de 10 à 70h.
A second object of the invention is a process for manufacturing a product based on an aluminum alloy in which, successively,
  1. a) an aluminum-based liquid metal bath comprising 4.0 to 4.6% by weight of Cu is produced; 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 chosen from Cr, Sc, Hf, V and Ti, the amount of said element, if chosen, being from 0.05 to 0.3% by weight for Cr and for Sc, 0.05 to 0 .5% by weight for Hf and for V and from 0.01 to 0.15% by weight for Ti; other elements not more than 0.05% by weight each and 0.15% by weight in total and remainder aluminum;
  2. b) a raw form is cast from said bath of liquid metal;
  3. c) said raw form is homogenized at a temperature of between 450° C. and 550° C. and preferably between 480° C. and 530° C. for a period of between 5 and 60 hours;
  4. d) hot deforming, preferably by rolling, said homogenized raw shape;
  5. e) the heat-deformed product is dissolved between 490 and 530° C. for 15 min to 8 h and the said solution-dissolved product is quenched;
  6. f) said product is cold deformed with a deformation of 2 to 16%;
  7. g) tempering is carried out in which said cold deformed product reaches a temperature of between 130 and 170° C. and preferably between 140 and 160° C. for 5 to 100 hours and preferably from 10 to 70 hours.

Un autre objet de l'invention est un produit en alliage selon l'invention ou susceptible d'être obtenu selon le procédé de l'invention, d'épaisseur comprise entre 8 et 50 mm ayant, à mi-épaisseur :

  1. i) une limite d'élasticité en compression Rcp0,2(L) ≥ 590 MPa, de préférence Rcp0,2(L) ≥ 595 MPa;
  2. ii) une ténacité Kapp (L-T) ≥ 60 MPa√m, de préférence Kapp (L-T) ≥ 75 MPa√m, avec Kapp (L-T) la valeur du facteur d'intensité de contrainte apparent à la rupture définie selon la norme ASTME561 (2015) mesurée sur des éprouvettes CCT de largeur W=406 mm et d'épaisseur B = 6,35 mm;
  3. iii) ) une différence entre la limite d'élasticité en traction Rp0,2(L) et la limite d'élasticité en compression Rcp0,2(L), Rp0,2(L) - Rcp0,2(L), inférieure ou égale à 10 MPa, de préférence ≤ 5 MPa.
Another object of the invention is an alloy product according to the invention or capable of being obtained according to the process of the invention, with a thickness of between 8 and 50 mm having, at mid-thickness:
  1. i) a compressive yield strength Rc p0.2 (L) ≥ 590 MPa, preferably Rc p0.2 (L) ≥ 595 MPa;
  2. ii) a toughness K app (LT) ≥ 60 MPa√m, preferably K app (LT) ≥ 75 MPa√m, with Kapp (LT) the value of the stress intensity factor apparent at failure defined according to the standard ASTME561 (2015) measured on CCT specimens with width W=406 mm and thickness B=6.35 mm;
  3. iii) ) a difference between the tensile yield strength R p0.2 (L) and the compressive yield strength Rc p0.2 (L), R p0.2 (L) - Rc p0.2 (L ), less than or equal to 10 MPa, preferably ≤ 5 MPa.

Un autre objet encore est un élément de structure d'avion, de préférence un élément extrados d'aile d'avion.Yet another object is an aircraft structural element, preferably an aircraft wing upper surface element.

Description des figuresDescription of figures

  • Figure 1 : Compromis entre la ténacité Kapp L-T et la limite d'élasticité en compression Rcp0.2 L des alliages de l'exemple 1. Figure 1 : Compromise between the toughness K app LT and the elastic limit in compression Rc p0.2 L of the alloys of example 1.
  • Figure 2 : Compromis entre la ténacité Kq L-T et la limite d'élasticité en compression Rcp0.2 L des alliages de l'exemple 2. Figure 2 : Compromise between the toughness K q LT and the elastic limit in compression Rc p0.2 L of the alloys of example 2.
  • Figure 3 : Compromis entre la limite d'élasticité en compression Rcp0.2 L et la limite d'élasticité en traction Rp0.2 L pour les alliages de l'exemple 2. Figure 3 : Compromise between the elastic limit in compression Rc p0.2 L and the elastic limit in tension R p0.2 L for the alloys of example 2.
  • Figure 4 : Compromis entre la ténacité Kapp L-T et la limite d'élasticité en compression Rcp0.2 L des alliages de l'exemple 3. Figure 4 : Compromise between the toughness K app LT and the elastic limit in compression Rc p0.2 L of the alloys of example 3.
Description de l'inventionDescription of the invention

Sauf mention contraire, toutes les indications concernant la composition chimique des alliages sont exprimées comme un pourcentage en poids basé sur le poids total de l'alliage. L'expression 1,4 Cu signifie que la teneur en cuivre exprimée en % en poids est multipliée par 1,4. La désignation des alliages se fait en conformité avec les règlements de The Aluminium Association, connus de l'homme du métier. Lorsque la concentration est exprimée en ppm (parts per million), cette indication se réfère également à une concentration massique.Unless otherwise stated, all indications regarding the chemical composition of the alloys are expressed as a percentage by weight based on the total weight of the alloy. The expression 1.4 Cu means that the copper content expressed in % by weight is multiplied by 1.4. The designation of the alloys is made in accordance with the regulations of The Aluminum Association, known to those skilled in the art. When the concentration is expressed in ppm (parts per million), this indication also refers to a mass concentration.

Sauf mention contraire, les définitions des états métallurgiques indiquées dans la norme européenne EN 515 (1993) s'appliquent.Unless otherwise stated, the definitions of tempers given in European standard EN 515 (1993) apply.

Les caractéristiques mécaniques statiques en traction, en d'autres termes la résistance à la rupture Rm, la limite d'élasticité conventionnelle à 0,2% d'allongement Rp0,2, et l'allongement à la rupture A%, sont déterminés par un essai de traction selon la norme NF EN ISO 6892-1 (2016), le prélèvement et le sens de l'essai étant définis par la norme EN 485 (2016). Rp0,2 (L) signifie Rp0,2 mesuré dans la direction longitudinale.The static mechanical characteristics in tension, in other words the breaking strength R m , the conventional yield strength at 0.2% elongation R p0.2 , and the elongation at break A%, are determined by a tensile test according to standard NF EN ISO 6892-1 (2016), the sampling and direction of the test being defined by standard EN 485 (2016). R p0.2 (L) means R p0.2 measured in the longitudinal direction.

La limite d'élasticité en compression Rcp0,2 a été mesurée à 0,2% de compression selon la norme ASTM E9-09 (2018). Rcp0,2 (L) signifie Rcp0,2 mesuré dans la direction longitudinale. Le facteur d'intensité de contrainte (K1C) est déterminé selon la norme ASTM E 399 (2012). Le facteur d'intensité de contrainte (KQ) est déterminé selon la norme ASTM E 399 (2012). La norme ASTM E 399 (2012) donne les critères qui permettent de déterminer si KQ est une valeur valide de K1C. Pour une géométrie d'éprouvette donnée, les valeurs de KQ obtenues pour différents matériaux sont comparables entre elles pour autant que les limites d'élasticité des matériaux soient du même ordre de grandeur.The compressive yield strength Rc p0.2 was measured at 0.2% compression according to ASTM E9-09 (2018). Rc p0.2 (L) means Rc p0.2 measured in the longitudinal direction. The stress intensity factor (K 1C ) is determined according to standard ASTM E 399 (2012). The stress intensity factor (KQ) is determined according to ASTM E 399 (2012). The ASTM E 399 (2012) standard gives the criteria for determining whether K Q is a valid value of K 1C . For a given specimen geometry, the values of K Q obtained for different materials are comparable with each other provided that the elastic limits of the materials are of the same order of magnitude.

Sauf mention contraire, les définitions de la norme EN 12258 (2012) s'appliquent.Unless otherwise stated, the definitions of EN 12258 (2012) apply.

Les valeurs du facteur d'intensité de contrainte apparent à la rupture (Kapp) et du facteur d'intensité de contrainte à la rupture (Kc) sont telles que définies dans la norme ASTM E561. Une courbe donnant le facteur d'intensité de contrainte effectif en fonction de l'extension de fissure effective, connue comme la courbe R, est déterminée selon la norme ASTM E 561 (ASTM E 561-10-2).The values of apparent stress intensity factor at failure (K app ) and stress intensity factor at failure (K c ) are as defined in ASTM E561. A curve giving the effective stress intensity factor as a function of the effective crack extension, known as the R-curve, is determined according to ASTM E 561 (ASTM E 561-10-2).

Le facteur d'intensité de contrainte critique Kc, en d'autres termes le facteur d'intensité qui rend la fissure instable, est calculé à partir de la courbe R. Le facteur d'intensité de contrainte KCO est également calculé en attribuant la longueur de fissure initiale au commencement de la charge monotone, à la charge critique. Ces deux valeurs sont calculées pour une éprouvette de la forme requise. Kapp représente le facteur KCO correspondant à l'éprouvette qui a été utilisée pour effectuer l'essai de courbe R. Keff représente le facteur Kc correspondant à l'éprouvette qui a été utilisée pour effectuer l'essai de courbe R.The critical stress intensity factor Kc, in other words the intensity factor that makes the crack unstable, is calculated from the R-curve. The stress intensity factor KCO is also calculated by assigning the initial crack length at the beginning of the monotonic load, at the critical load. These two values are calculated for a specimen of the required shape. K app represents the K CO factor corresponding to the specimen that was used to perform the R-curve test. K eff represents the Kc factor corresponding to the specimen that was used to perform the R-curve test.

On appelle ici « élément de structure » ou « élément structural » d'une construction mécanique une pièce mécanique pour laquelle les propriétés mécaniques statiques et/ou dynamiques sont particulièrement importantes pour la performance de la structure, et pour laquelle un calcul de structure est habituellement prescrit ou réalisé. Il s'agit typiquement d'éléments dont la défaillance est susceptible de mettre en danger la sécurité de ladite construction, de ses utilisateurs, des ses usagers ou d'autrui. Pour un avion, ces éléments de structure comprennent notamment les éléments qui composent le fuselage (tels que la peau de fuselage, fuselage skin en anglais), les raidisseurs ou lisses de fuselage (stringers), les cloisons étanches (bulkheads), les cadres de fuselage (circumferential frames), les ailes (tels que la peau de voilure extrados ou intrados (upper or lower wing skin), les raidisseurs (stringers ou stiffeners), les nervures (ribs) et longerons (spars)) et l'empennage composé notamment de stabilisateurs horizontaux et verticaux (horizontal or vertical stabilisers), ainsi que les profilés de plancher (floor beams), les rails de sièges (seat tracks) et les portes.The term "structural element" or "structural element" of a mechanical construction is used here to mean 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 performed. These are typically elements whose failure is likely to endanger the safety of said construction, its users, its users or others. For an airplane, these structural elements include in particular the elements that make up the fuselage (such as the fuselage skin), the fuselage stiffeners or stringers, the bulkheads, the fuselage (circumferential frames), wings (such as upper or lower wing skin), stiffeners (stringers or stiffeners), ribs and spars) and compound empennage including horizontal and vertical stabilizers (horizontal or vertical stabilizers), as well as floor beams (floor beams), seat tracks (seat tracks) and doors.

Selon la présente invention, une classe sélectionnée d'alliages d'aluminium contenant notamment des quantités spécifiques et critiques de lithium, cuivre, magnésium, argent, manganèse et zinc permet de préparer des éléments de structure, en particulier des tôles d'extrados de voilure, présentant une limite d'élasticité en compression Rcp0,2(L) élevée, une faible différence entre limite d'élasticité en compression Rcp0,2(L) et limite d'élasticité en traction Rp0,2(L) et un facteur d'intensité de contrainte apparent à la rupture Kapp particulièrement amélioré. La composition d'alliage sélectionnée de l'invention permet en outre d'obtenir tout ou partie des avantages précités pour une large plage de temps de revenu (notamment une plage d'au moins 5h à une température de revenu donnée). Une telle composition permet ainsi de garantir la robustesse du procédé de fabrication et donc de garantir les propriétés finales du produit lors d'une fabrication industrielle.According to the present invention, a selected class of aluminum alloys containing in particular specific and critical quantities of lithium, copper, magnesium, silver, manganese and zinc makes it possible to prepare structural elements, in particular wing upper surface plates , having a high elastic limit in compression Rc p0,2 (L), a small difference between elastic limit in compression Rc p0,2 (L) and elastic limit in tensile R p0.2 (L) and a particularly improved apparent stress intensity factor at break K app . The selected alloy composition of the invention also makes it possible to obtain all or part of the aforementioned advantages for a wide range of tempering times (in particular a range of at least 5 hours at a given tempering temperature). Such a composition thus makes it possible to guarantee the robustness of the manufacturing process and therefore to guarantee the final properties of the product during industrial production.

Le produit à base d'alliage d'aluminium selon l'invention comprend, en pourcentage en poids, 4,0 à 4,6% en poids de Cu ; 0,7 à 1,2% en poids de Li ; 0,5 à 0,65% en poids de Mg ; 0,10 à 0,20% en poids de Zr ; 0,15 à 0,30% en poids d'Ag ;0,25 à 0,45% en poids de Zn ; 0,05 à 0,35% en poids de Mn ; au plus 0,20% en poids de Fe + Si ; au moins un élément choisi parmi Cr, Sc, Hf, V et Ti ; autres éléments au plus 0,05% en poids chacun et 0,15% en poids au total et reste aluminium.The product based on an aluminum alloy according to the invention comprises, in percentage by weight, 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 Cr, Sc, Hf, V and Ti; other elements not more than 0.05% by weight each and 0.15% by weight in total and remainder aluminium.

La teneur en cuivre des produits selon l'invention est comprise entre 4,0 et 4,6% en poids, préférentiellement entre 4,2 et 4,5% en poids et plus préférentiellement entre 4,2 et 4,4 % en poids. Dans un mode de réalisation avantageux la teneur minimale en cuivre est de 4,25 % en poids.The copper content of the products according to the invention is between 4.0 and 4.6% by weight, preferably between 4.2 and 4.5% by weight and more preferably between 4.2 and 4.4% by weight. . In an advantageous embodiment the minimum copper content is 4.25% by weight.

La teneur en lithium des produits selon l'invention est comprise entre 0,7 à 1,2% en poids. Avantageusement, la teneur en lithium est comprise entre 0,8 et 1,0% en poids; préférentiellement entre 0,85 et 0,95 % en poids.The lithium content of the products according to the invention is between 0.7 and 1.2% by weight. Advantageously, the lithium content is between 0.8 and 1.0% by weight; preferably between 0.85 and 0.95% by weight.

L'augmentation de la teneur en cuivre et dans une moindre mesure de la teneur en lithium contribue à améliorer la résistance mécanique statique, cependant, le cuivre ayant un effet néfaste notamment sur la densité, il est préférable de limiter la teneur en cuivre à la valeur maximale préférée de 4,4 % en poids. L'augmentation de la teneur en lithium a un effet favorable sur la densité, cependant les présents inventeurs ont constaté que pour les alliages selon l'invention, la teneur en lithium préférée comprise entre 0,85 % et 0,95 % en poids permet une amélioration du compromis entre résistance mécanique (limite d'élasticité en traction et en compression) et ténacité. Une forte teneur en lithium, notamment au-delà de la valeur maximale préférée de 0,95 % en poids, peut conduire à une dégradation de la ténacité. La teneur en magnésium des produits selon l'invention est comprise entre 0,5% et 0,65% en poids. Préférentiellement, la teneur en magnésium est au moins de 0,50 % ou même au moins 0,55 % en poids, ce qui améliore simultanément résistance mécanique statique et ténacité. En particulier pour les compositions sélectionnées de la présente invention, une teneur en magnésium supérieure à 0,65% en poids peut induire une dégradation de la ténacité.Increasing the copper content and to a lesser extent the lithium content contributes to improving the static mechanical resistance, however, copper having a detrimental effect in particular on the density, it is preferable to limit the copper content to the preferred maximum value of 4.4% by weight. Increasing the lithium content has a favorable effect on the density, however the present inventors have found that for the alloys according to the invention, the preferred lithium content of between 0.85% and 0.95% by weight allows an improvement in the compromise between mechanical strength (yield point in tension and compression) and toughness. A high lithium content, in particular beyond the preferred maximum value of 0.95% by weight, can lead to a degradation of toughness. The magnesium content of the products according to the invention is between 0.5% and 0.65% by weight. Preferably, the magnesium content is at least 0.50% or even at least 0.55% by weight, which simultaneously improves static mechanical strength and toughness. In particular for the selected compositions of the present invention, a magnesium content greater than 0.65% by weight can induce a deterioration in toughness.

Les teneurs en zinc et en argent sont respectivement comprises entre 0,25 et 0,45% en poids et 0,15 et 0,30 % en poids. De telles teneurs en zinc et argent sont nécessaires pour garantir une limite élastique en compression ayant une valeur proche de celle de la limite élastique en traction. Dans un mode de réalisation avantageux, les produits selon l'invention ont une différence entre la limite d'élasticité en traction Rp0,2(L) et la limite d'élasticité en compression Rcp0,2(L) inférieure ou égale à 10 MPa, de préférence inférieure ou égale 5 MPa.The zinc and silver contents are respectively between 0.25 and 0.45% by weight and 0.15 and 0.30% by weight. Such zinc and silver contents are necessary to guarantee an elastic limit in compression having a value close to that of the elastic limit in tension. In an advantageous embodiment, the products according to the invention have a difference between the elastic limit in tension R p0.2 (L) and the elastic limit in compression Rc p0.2 (L) less than or equal to 10 MPa, preferably less than or equal to 5 MPa.

La présence d'argent et de zinc permet d'obtenir un bon compromis entre les différentes propriétés recherchées. En particulier, la présence d'argent permet d'obtenir un produit de façon fiable et robuste, c'est-à-dire que le compromis de propriétés recherché est atteint pour une large plage de temps de revenu, notamment une plage de temps supérieure à 5h, ce qui est compatible avec la variabilité inhérente à un procédé de fabrication industriel. Une teneur minimale de 0,20 % en poids d'argent est avantageuse. Une teneur maximale de 0,27% en poids d'argent est avantageuse.The presence of silver and zinc makes it possible to obtain a good compromise between the different properties sought. In particular, the presence of silver makes it possible to obtain a product in a reliable and robust manner, that is to say that the desired compromise of properties is achieved for a wide range of tempering times, in particular a range of times greater than at 5 a.m., which is compatible with the variability inherent in an industrial manufacturing process. A minimum content of 0.20% by weight of silver is advantageous. A maximum content of 0.27% by weight of silver is advantageous.

Une teneur minimale de 0,30 % en poids de zinc est avantageuse. Une teneur maximale de 0,40% en poids de zinc est avantageuse. De préférence la teneur en Zn est comprise entre 0,30 et 0,40 % en poids.A minimum content of 0.30% by weight of zinc is advantageous. A maximum content of 0.40% by weight of zinc is advantageous. Preferably the Zn content is between 0.30 and 0.40% by weight.

Avantageusement, la somme des teneurs en Zn, Mg et Ag comprise entre 0,95 et 1,35% en poids, préférentiellement entre 1,00 et 1,30% en poids, plus préférentiellement encore entre 1,15 et 1,25% en poids. Les présents inventeurs ont constaté que le compromis optimum de propriétés recherché, notamment pour des éléments de structure d'extrados de voilure, n'était atteint que pour des valeurs spécifiques et critiques de la somme Zn, Mg et Ag.Advantageously, the sum of the Zn, Mg and Ag contents comprised between 0.95 and 1.35% by weight, preferentially between 1.00 and 1.30% by weight, more preferentially still between 1.15 and 1.25% in weight. The present inventors have observed that the optimum compromise of properties sought, in particular for wing upper surface structural elements, was only achieved for specific and critical values of the sum of Zn, Mg and Ag.

La teneur en manganèse est comprise entre 0,05 et 0,35% en poids. Avantageusement, la teneur en Mn comprise entre 0,10 et 0,35% en poids. Dans un mode de réalisation, la teneur en manganèse est comprise entre 0,2 et 0,35% en poids et préférentiellement entre 0,25 et 0,35% en poids. Dans un autre mode de réalisation, la teneur en manganèse est comprise entre 0,1 et 0,2% en poids et préférentiellement entre 0,10 et 0,20% en poids. L'ajout de Mn permet en particulier l'obtention d'une ténacité élevée. Cependant, si la teneur en Mn est supérieure à 0,35% en poids, la durée de vie en fatigue peut être sensiblement réduite.The manganese content is between 0.05 and 0.35% by weight. Advantageously, the Mn content between 0.10 and 0.35% by weight. In one embodiment, the manganese content is between 0.2 and 0.35% by weight and preferably between 0.25 and 0.35% by weight. In another embodiment, the manganese content is between 0.1 and 0.2% by weight and preferably between 0.10 and 0.20% by weight. The addition of Mn in particular makes it possible to obtain a high tenacity. However, if the Mn content is more than 0.35% by weight, the fatigue life may be significantly reduced.

La teneur en Zr de l'alliage est comprise entre 0,10 et 0,20% en poids. Dans un mode de réalisation avantageux, la teneur en Zr est comprise entre 0,10 et 0,15 % en poids, préférentiellement entre 0,11 et 0,14% en poids.The Zr content of the alloy is between 0.10 and 0.20% by weight. In an advantageous embodiment, the Zr content is between 0.10 and 0.15% by weight, preferably between 0.11 and 0.14% by weight.

La somme de la teneur en fer et de la teneur en silicium est au plus de 0,20 % en poids. De préférence, les teneurs en fer et en silicium sont chacune au plus de 0,08 % en poids. Dans une réalisation avantageuse de l'invention les teneurs en fer et en silicium sont au plus de 0,06 % et 0,04 % en poids, respectivement. Une teneur en fer et en silicium contrôlée et limitée contribue à l'amélioration du compromis entre résistance mécanique et tolérance aux dommages.The sum of the iron content and the silicon content is at most 0.20% by weight. Preferably, the iron and silicon contents are each at most 0.08% by weight. In an advantageous embodiment of the invention, the iron and silicon contents are at most 0.06% and 0.04% by weight, respectively. A controlled and limited iron and silicon content contributes to the improvement of the compromise between mechanical resistance and damage tolerance.

L'alliage contient également au moins un élément pouvant contribuer au contrôle de la taille de grain choisi parmi Cr, Sc, Hf, V et Ti, la quantité dudit élément, s'il est choisi, étant de 0,05 à 0,3 % en poids pour Cr et pour Sc, 0,05 à 0,5 % en poids pour Hf et pour V et de 0,01 à 0,15 % en poids pour Ti. Dans un mode de réalisation avantageux, on choisit d'ajouter entre 0,01 et 0,15 % en poids de titane. Dans un mode de réalisation préféré, la teneur en Ti est comprise entre 0,01 et 0,08% en poids, préférentiellement entre 0,02 et 0,06% en poids. Avantageusement dans les modes de réalisation dans lesquels on choisit d'ajouter du titane, on limite la teneur en Cr, Sc, V et Hf à une teneur maximale de 0,05 % en poids, ces éléments pouvant avoir un effet défavorable, notamment sur la densité et n'étant ajoutés que pour favoriser encore l'obtention d'une structure essentiellement non-recristallisée si nécessaire. D'une manière particulièrement avantageuse, le Ti est présent notamment sous la forme de particules TiC. Contre toute attente, les présents inventeurs ont constaté que, dans le cas particulier du présent alliage, la présence de particules de TiC dans le fil affinant lors de la coulée (affinage AlTiC), permet d'obtenir un produit présentant un compromis de propriétés optimisé. Avantageusement l'affinant a pour formule AlTixCy que l'on écrit aussi ATxCy où x et y sont les teneurs en Ti et C en % en poids pour 1 % en poids de Al, et x/y > 4. En particulier, l'affinage AlTiC dans l'alliage de la présente invention permet une amélioration du compromis entre la ténacité Kapp L-T et la limite d'élasticité en compression Rcp0.2 L.The alloy also contains at least one element which can contribute to the control of the grain size chosen from Cr, Sc, Hf, V and Ti, the amount of said element, if chosen, being from 0.05 to 0.3 % by weight for Cr and for Sc, 0.05 to 0.5 % by weight for Hf and for V and 0.01 to 0.15 % by weight for Ti. In an advantageous embodiment, it is chosen to add between 0.01 and 0.15% by weight of titanium. In a preferred embodiment, the Ti content is between 0.01 and 0.08% by weight, preferably between 0.02 and 0.06% by weight. Advantageously in the embodiments in which it is chosen to add titanium, the content of Cr, Sc, V and Hf is limited to a maximum content of 0.05% by weight, these elements possibly having an unfavorable effect, in particular on the density and being added only to further promote obtaining a substantially non-recrystallized structure if necessary. In a particularly advantageous manner, the Ti is present in particular in the form of TiC particles. Against all expectations, the present inventors have found that, in the particular case of the present alloy, the presence of TiC particles in the refining wire during casting (AlTiC refining), makes it possible to obtain a product having an optimized compromise of properties. . Advantageously, the refining agent has the formula AlTi x C y which is also written AT x C y where x and y are the contents of Ti and C in % by weight for 1% by weight of Al, and x/y > 4 In particular, the AlTiC refining in the alloy of the present invention allows an improvement in the compromise between the toughness K app LT and the elastic limit in compression R c p0.2 L.

Il est possible de sélectionner la teneur des éléments d'alliage pour minimiser la densité. De préférence, les éléments d'additions contribuant à augmenter la densité tels que Cu, Zn, Mn et Ag sont minimisés et les éléments contribuant à diminuer la densité tels que Li et Mg sont maximisés de façon à atteindre une densité inférieure ou égale à 2.73 g/cm3 et de préférence inférieure ou égale à 2.72 g/cm3.It is possible to select the content of the alloying elements to minimize the density. Preferably, the addition elements contributing to increase the density such as Cu, Zn, Mn and Ag are minimized and the elements contributing to decreasing the density such as Li and Mg are maximized so as to reach a density less than or equal to 2.73 g/cm 3 and preferably less than or equal to 2.72 g/cm 3 .

La teneur des autres éléments est au plus de 0,05 % en poids chacun et 0,15% en poids au total. Les autres éléments sont typiquement des impuretés inévitables.The content of the other elements is at most 0.05% by weight each and 0.15% by weight in total. The other elements are typically unavoidable impurities.

Le procédé de fabrication des produits selon l'invention comprend les étapes d'élaboration, coulée, homogénéisation, déformation à chaud, mise en solution et trempe, traction entre 2 et 16% et revenu.The process for manufacturing the products according to the invention comprises the steps of preparation, casting, homogenization, hot deformation, solution treatment and quenching, traction between 2 and 16% and tempering.

Dans une première étape, on élabore un bain de métal liquide de façon à obtenir un alliage d'aluminium de composition selon l'invention.In a first step, a bath of liquid metal is prepared so as to obtain an aluminum alloy of composition according to the invention.

Le bain de métal liquide est ensuite coulé sous forme de forme brute, préférentiellement sous forme de plaque de laminage ou de billette de filage.The liquid metal bath is then cast in the form of a raw form, preferably in the form of a rolling plate or an extruded billet.

La forme brute est ensuite homogénéisée de façon à atteindre une température comprise entre 450°C et 550° et de préférence entre 480 °C et 530°C pendant une durée comprise entre 5 et 60 heures. Le traitement d'homogénéisation peut être réalisé en un ou plusieurs paliers. Après homogénéisation, la forme brute est en général refroidie jusqu'à température ambiante avant d'être préchauffée en vue d'être déformée à chaud. La déformation à chaud peut notamment être une extrusion ou un laminage à chaud. De manière préférée, il s'agit d'une étape de laminage à chaud. Le laminage à chaud est réalisé jusqu'à une épaisseur comprise de préférence entre 8 et 50 mm et de manière préférée entre 15 et 40 mm.The raw form is then homogenized so as to reach a temperature of between 450° C. and 550° and preferably between 480° C. and 530° C. for a period of between 5 and 60 hours. The homogenization treatment can be carried out in one or more stages. After homogenization, the raw form is generally cooled to ambient temperature before being preheated in order to be hot deformed. The hot deformation can in particular be an extrusion or a hot rolling. Preferably, this is a hot rolling step. Hot rolling is carried out to a thickness preferably between 8 and 50 mm and preferably between 15 and 40 mm.

Le produit ainsi obtenu est ensuite mis en solution par traitement thermique permettant d'atteindre une température comprise entre 490 et 530 °C pendant 15 min à 8 h, puis trempé typiquement avec de l'eau à température ambiante.The product thus obtained is then placed in solution by heat treatment making it possible to reach a temperature of between 490 and 530° C. for 15 min to 8 h, then typically quenched with water at room temperature.

Le produit subit ensuite une déformation à froid avec une déformation de 2 à 16 %. Il peut s'agir d'une traction contrôlée avec une déformation permanente de 2 à 5%, préférentiellement de 2,0% à 4,0%. Dans un mode de réalisation avantageux alternatif, la déformation à froid est réalisée en deux étapes : le produit est tout d'abord laminé à froid avec un taux de réduction d'épaisseur compris entre 8 à 12% puis ultérieurement tractionné de façon contrôlée avec une déformation permanente comprise entre 0,5 et 4%.The product then undergoes cold deformation with a deformation of 2 to 16%. It may be a controlled tensile with a permanent set of 2 to 5%, preferably 2.0% to 4.0%. In an alternative advantageous embodiment, the cold deformation is carried out in two stages: the product is first cold rolled with a thickness reduction rate of between 8 to 12% then subsequently pulled in a controlled manner with a permanent deformation between 0.5 and 4%.

Le produit est ensuite soumis à une étape de revenu réalisée par chauffage à une température comprise entre 130 et 170°C et de préférence entre 140 et 160°C pendant 5 à 100 heures et de préférence de 10 à 70h.The product is then subjected to a tempering step carried out by heating at a temperature of between 130 and 170° C. and preferably between 140 and 160° C. for 5 to 100 hours and preferably from 10 to 70 hours.

Les présents inventeurs ont constaté que, de manière surprenante, les teneurs spécifiques et critiques de l'alliage de la présente invention permettent d'atteindre d'excellentes propriétés, notamment un compromis entre la limite d'élasticité en compression Rcp0,2(L) et de ténacité en contraintes planes Kapp particulièrement amélioré. Avantageusement, ces propriétés peuvent être obtenues, pour les alliages de l'invention, quel que soit le temps de revenu entre 15h et 25h à 155°C, ce qui garantit une robustesse du procédé de fabrication.The present inventors have found that, surprisingly, the specific and critical contents of the alloy of the present invention make it possible to achieve excellent properties, in particular a compromise between the elastic limit in compression Rc p0.2 (L ) and particularly improved Kapp plane stress toughness. Advantageously, these properties can be obtained, for the alloys of the invention, regardless of the tempering time between 15 h and 25 h at 155° C., which guarantees robustness of the manufacturing process.

Avantageusement, la structure granulaire des produits obtenus est majoritairement non-recristallisée. Le taux de structure granulaire non-recristallisé à mi-épaisseur est de préférence d'au moins 70% et préférentiellement d'au moins 80%.Advantageously, the granular structure of the products obtained is mostly non-recrystallized. The rate of non-recrystallized granular structure at mid-thickness is preferably at least 70% and preferentially at least 80%.

Les produits obtenus par le procédé selon l'invention, en particulier les produits laminés ayant une épaisseur comprise entre 8 et 50 mm, à mi-épaisseur présentent les caractéristiques suivantes :

  1. i) une limite d'élasticité en compression Rcp0,2(L) ≥ 590 MPa, de préférence Rcp0,2(L) ≥ 595 MPa, avec Rcp0,2(L) la limite d'élasticité en compression mesurée à 0,2% de compression selon la norme ASTM E9 (2018) dans la direction longitudinale;
  2. ii) une ténacité Kapp (L-T) ≥ 60 MPa√m, de préférence Kapp (L-T) ≥ 75 MPa√m, avec Kapp (L-T) la valeur du facteur d'intensité de contrainte apparent à la rupture définie selon la norme ASTME561 (2015) mesurée sur des éprouvettes CCT de largeur W=406 mm et d'épaisseur B = 6,35 mm;
  3. iii) une différence entre la limite d'élasticité en traction Rp0,2(L) et la limite d'élasticité en compression Rcp0,2(L), Rp0,2(L) - Rcp0,2(L), inférieure ou égale à 10 MPa, de préférence ≤ 5 MPa.
The products obtained by the process according to the invention, in particular the rolled products having a thickness of between 8 and 50 mm, at mid-thickness, have the following characteristics:
  1. i) an elastic limit in compression Rc p0,2 (L) ≥ 590 MPa, preferably Rc p0,2 (L) ≥ 595 MPa, with Rc p0,2 (L) the elastic limit in compression measured at 0.2% compression per ASTM E9 (2018) in the longitudinal direction;
  2. ii) a toughness K app (LT) ≥ 60 MPa√m, preferably K app (LT) ≥ 75 MPa√m, with Kapp (LT) the value of the stress intensity factor apparent at failure defined according to the standard ASTME561 (2015) measured on CCT specimens with width W=406 mm and thickness B=6.35 mm;
  3. iii) a difference between the tensile yield strength R p0.2 (L) and the compressive yield strength Rc p0.2 (L), R p0.2 (L) - Rc p0.2 (L) , less than or equal to 10 MPa, preferably ≤ 5 MPa.

Avantageusement, les caractéristiques i) et ii) sont obtenues pour une plage large de temps de revenu, notamment une plage d'au moins 5h à une température de revenu donnée. Une telle composition permet ainsi de garantir la robustesse du procédé de fabrication et donc de garantir les propriétés finales du produit lors d'une fabrication industrielle.Advantageously, characteristics i) and ii) are obtained for a wide range of tempering times, in particular a range of at least 5 h at a given tempering temperature. Such a composition thus makes it possible to guarantee the robustness of the manufacturing process and therefore to guarantee the final properties of the product during industrial production.

Dans un mode de réalisation avantageux, la ténacité est telle que Kapp (L-T) ≥ -0,48 Rcp0,2(L) + 355,2, avec Kapp (L-T) exprimé en MPa√m, la valeur du facteur d'intensité de contrainte apparent à la rupture définie selon la norme ASTM E561 (2015) mesurée sur des éprouvettes CCT de largeur W=406 mm et d'épaisseur B = 6,35 mm, et Rcp0,2(L) exprimé en MPa, la limite d'élasticité en compression mesurée à 0,2% de compression selon la norme ASTM E9 (2018).In an advantageous embodiment, the toughness is such that K app (LT) ≥ -0.48 Rc p0.2 (L) + 355.2, with K app (LT) expressed in MPa√m, the value of the factor d apparent stress intensity at break defined according to ASTM E561 (2015) measured on CCT specimens of width W=406 mm and thickness B = 6.35 mm, and Rc p0.2 (L) expressed in MPa , the compressive yield strength measured at 0.2% compression according to ASTM E9 (2018).

Les produits en alliage selon l'invention permettent en particulier la fabrication d'éléments de structure, notamment d'éléments de structure d'avion. Dans un mode de réalisation avantageux, l'élément de structure d'avion préféré est un élément extrados d'aile d'avion. Ces aspects, ainsi que d'autres de l'invention sont expliqués plus en détails à l'aide des exemples illustratifs et non limitatifs suivants.The alloy products according to the invention allow in particular the manufacture of structural elements, in particular aircraft structural elements. In an advantageous embodiment, the preferred aircraft structural element is an aircraft wing upper surface element. These and other aspects of the invention are explained in more detail using the following illustrative and non-limiting examples.

ExemplesExamples Exemple 1.Example 1.

Dans cet exemple, des plaques de section 406 x 1520 mm en alliage dont la composition est donnée dans le tableau 1 ont été coulées. Les exemples d'alliages 1 et 3-8 ne rentrent pas dans le cadre de l'invention. Tableau 1. Composition en % en poids des alliages n°1 à 8 Alliage Si Fe Cu Mn Mg Zn Ti Zr Li Ag 1 0,02 0,03 4,6 0,32 0,62 0,62 0,03 0,13 0,91 0,01 2 0,02 0,03 4,3 0,31 0,60 0,35 0,03 0,12 0,91 0,24 3 0,03 0,05 4,5 0,34 0,71 0,04 0,04 0,11 1,03 0,21 4 0,03 0,04 4,3 - 0,33 0,03 0,02 0,15 1,13 0,21 5 0,03 0,04 4,2 0,33 0,54 - 0,03 0,13 0,88 0,19 6 0,02 0,04 4,4 0,02 0,21 0,04 0,02 0,14 1,05 0,21 7 0,03 0,04 3,9 - 0,36 - 0,03 0,11 1,31 0,36 8 0,04 0,06 4,1 0,42 0,42 0,02 0,02 0,15 1,18 0,29 In this example, plates with a section of 406 x 1520 mm in an alloy whose composition is given in table 1 were cast. Examples of alloys 1 and 3-8 do not fall within the scope of the invention. Table 1. Composition in % by weight of alloys n°1 to 8 Alloy Whether Fe Cu min mg Zn You Zr Li Ag 1 0.02 0.03 4.6 0.32 0.62 0.62 0.03 0.13 0.91 0.01 2 0.02 0.03 4.3 0.31 0.60 0.35 0.03 0.12 0.91 0.24 3 0.03 0.05 4.5 0.34 0.71 0.04 0.04 0.11 1.03 0.21 4 0.03 0.04 4.3 - 0.33 0.03 0.02 0.15 1.13 0.21 5 0.03 0.04 4.2 0.33 0.54 - 0.03 0.13 0.88 0.19 6 0.02 0.04 4.4 0.02 0.21 0.04 0.02 0.14 1.05 0.21 7 0.03 0.04 3.9 - 0.36 - 0.03 0.11 1.31 0.36 8 0.04 0.06 4.1 0.42 0.42 0.02 0.02 0.15 1.18 0.29

Pour chaque composition, la plaque a été homogénéisée avec un 1er palier de 15h à 500°C, suivi d'un second palier de 20h à 510°C. La plaque a été laminée à chaud à une température supérieure à 440 °C pour obtenir des tôles d'épaisseur 25 mm pour les alliages 2 à 8 et 28 mm pour l'alliage 1. Les tôles ont été mises en solution à environ 510 °C pendant 3h, trempées avec de l'eau à 20 °C. Les tôles ont ensuite été tractionnées avec un allongement permanent compris entre 2% et 6%.For each composition, the plate was homogenized with a first level of 15 h at 500°C, followed by a second level of 20 h at 510°C. The plate was hot rolled at a temperature 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 put in solution at approximately 510° C for 3h, quenched with water at 20°C. The sheets were then stretched with a permanent elongation of between 2% and 6%.

Les tôles ont subi un revenu mono palier tel qu'indiqué dans le tableau 2. Des échantillons ont été prélevés à mi-épaisseur pour mesurer les caractéristiques mécaniques statiques en traction et en compression dans la direction longitudinale. La ténacité en contrainte plane a également été mesurée à mi-épaisseur lors d'essais de courbe R avec des éprouvettes CCT de largeur 406 mm et d'épaisseur 6.35 mm dans la direction L-T. Les résultats sont présentés dans le tableau 2 et à la figure 1.The plates underwent single-stage tempering as indicated in Table 2. Samples were taken at mid-thickness to measure the static mechanical characteristics in tension and compression in the longitudinal direction. The plane stress toughness was also measured at mid-thickness during R-curve tests with CCT specimens 406 mm wide and 6.35 mm thick in the LT direction. The results are presented in Table 2 and in figure 1 .

La structure des tôles obtenues était majoritairement non-recristallisée. Le taux de structure granulaire non-recristallisée à mi-épaisseur était de 90%. Tableau 2. Conditions de traction contrôlée et de revenu et propriétés mécaniques obtenues pour les différentes tôles à mi-épaisseur. Alliage Revenu Allongement permanent lors de la traction contrôlée Rp0,2 (L) Traction (Mpa) Rcp0,2 (L) Compression (Mpa) Kapp (L-T) (MPa√m) 1 15h 155°C 3.0 593 585 71 20h 155°C 3.0 604 610 59 2 15h 155°C 3.0 591 593 76 20h 155°C 3.0 601 599 69 25h 155°C 3.0 613 63 3 15h 155°C 3.3 612 607 60 4 15h 155°C 3.1 619 614 59 20h 155°C 3.1 636 637 55 5 20h 155°C 3.2 574 570 105 25h 155°C 3.2 585 580 79 6 20h 155°C 3.1 628 628 51 7 24h 150°C 4.5 606 590 64 8 24h 150°C 4.0 594 587 72 The structure of the sheets obtained was mostly non-recrystallized. The rate of non-recrystallized granular structure at mid-thickness was 90%. Table 2. Controlled tensile and tempering conditions and mechanical properties obtained for the different plates at mid-thickness. Alloy Revenue Permanent elongation during controlled traction R p0.2 (L) Tensile (Mpa) Rc p0.2 (L) Compression (Mpa) Kapp (LT) (MPa√m) 1 3 p.m. 155°C 3.0 593 585 71 8 p.m. 155°C 3.0 604 610 59 2 3 p.m. 155°C 3.0 591 593 76 8 p.m. 155°C 3.0 601 599 69 25h 155°C 3.0 613 63 3 3 p.m. 155°C 3.3 612 607 60 4 3 p.m. 155°C 3.1 619 614 59 8 p.m. 155°C 3.1 636 637 55 5 8 p.m. 155°C 3.2 574 570 105 25h 155°C 3.2 585 580 79 6 8 p.m. 155°C 3.1 628 628 51 7 24h 150°C 4.5 606 590 64 8 24h 150°C 4.0 594 587 72

Exemple 2Example 2

Dans cet exemple, outre la plaque en alliage 2 de l'exemple 1, une plaque de section 406 x 1520 mm dont la composition est donnée dans le tableau 3 a été coulée. Tableau 3, Composition en % en poids des alliages 2 et 10, Alliage Si Fe Cu Mn Mg Zn Ti Zr Li Ag 2 0,02 0,03 4,3 0,31 0,60 0,35 0,03 0,12 0,91 0,24 10 0,04 0,02 4,3 0,31 0,64 0,33 0,03 0,14 0,90 0,35 In this example, in addition to the alloy plate 2 of example 1, a plate with a section of 406×1520 mm, the composition of which is given in table 3, was cast. Table 3, Composition in % by weight of alloys 2 and 10, Alloy Whether Fe Cu min mg Zn You Zr Li Ag 2 0.02 0.03 4.3 0.31 0.60 0.35 0.03 0.12 0.91 0.24 10 0.04 0.02 4.3 0.31 0.64 0.33 0.03 0.14 0.90 0.35

Les plaques ont été homogénéisées à environ 510 °C puis scalpées. Après homogénéisation, les plaques ont été laminées à chaud pour obtenir des tôles ayant une épaisseur de 25 mm. Les tôles ont été mises en solution 3h à environ 510 °C, trempées à l'eau froide et tractionnées avec un allongement permanent de 3%.Plates were homogenized at approximately 510°C and then scalped. After homogenization, the plates were hot rolled to obtain sheets having a thickness of 25 mm. The sheets were put in solution for 3 hours at approximately 510° C., quenched in cold water and stretched with a permanent elongation of 3%.

La structure des tôle obtenues était majoritairement non-recristallisée. Le taux de structure granulaire non-recristallisé à mi-épaisseur était de 90%.The structure of the sheets obtained was mostly non-recrystallized. The rate of non-recrystallized granular structure at mid-thickness was 90%.

Les tôles ont subi un revenu compris entre 15 h et 50 h à 155 °C. Des échantillons ont été prélevés à mi-épaisseur pour mesurer les caractéristiques mécaniques statiques en traction, en compression dans la direction longitudinale ainsi que la ténacité KQ dans la direction L-T. Les éprouvettes utilisées pour la mesure de ténacité avaient une largeur W=40 mm et une épaisseur B = 20 mm. Les résultats obtenus sont présentés dans le tableau 4 et les figures 2 et 3. Tableau 4 : Conditions de revenu et propriétés mécaniques obtenues pour les tôles 2 et10. Propriétés en traction Propriété en compression Ténacité Différence entre Rp0,2 (MPa) en tension et Rp0,2 (MPa) en compression Alliage Durée de revenu à 155°C Rp0,2 (L) (MPa) Rm (L) (MPa) A (%) Rcp0,2 (L) (MPa) KQ (MPa√m) L-T N°2 10 h 560 598 10 565 -5 15 h 591 617 8.3 593 30,6 -2 20 h 601 625 8.5 599 29,9 2 25 h 613 27,6 30 h 609 632 7.9 615 -6 N°10 10 h 587 620 10 559 28 15 h 604 632 8.5 588 30,7 16 20 h 620 644 8.2 607 25,1 13 25 h 609 24,8 30 h 621 645 7.5 609 12 The sheets were tempered for between 15 h and 50 h at 155°C. Samples were taken at mid-thickness to measure the static mechanical characteristics in tension, in compression in the longitudinal direction as well as the toughness K Q in the LT direction. The specimens used for the toughness measurement had a width W=40 mm and a thickness B=20 mm. The results obtained are presented in Table 4 and the figure 2 and 3 . Table 4: Tempering conditions and mechanical properties obtained for plates 2 and 10. Tensile properties Property in compression Tenacity Difference between Rp 0.2 (MPa) in tension and Rp 0.2 (MPa) in compression Alloy Tempering time at 155°C Rp 0.2 (L) (MPa) Rm (L) (MPa) HAS (%) Rc p0.2 (L) (MPa) K Q (MPa√m) LT #2 10 a.m. 560 598 10 565 -5 3 p.m. 591 617 8.3 593 30.6 -2 8 p.m. 601 625 8.5 599 29.9 2 25 p.m. 613 27.6 30 p.m. 609 632 7.9 615 -6 No. 10 10 a.m. 587 620 10 559 28 3 p.m. 604 632 8.5 588 30.7 16 8 p.m. 620 644 8.2 607 25.1 13 25 p.m. 609 24.8 30 p.m. 621 645 7.5 609 12

Exemple 3Example 3

Dans cet exemple, outre la plaque en alliage 2 de l'exemple 1, une plaque de section 406 x 1700 mm dont la composition est donnée dans le tableau 3 a été coulée en utilisant un affinage AlTiC (fil affinant contenant des germes de type TiC). Tableau 5. Composition en % en poids des alliages 2 et 9. Alliage Si Fe Cu Mn Mg Zn Ti Zr Li Ag 2 0,02 0,03 4,3 0,31 0,60 0,35 0,03 0,12 0,91 0,24 9 0,02 0,04 4,3 0,14 0,61 0,36 0,05 0,13 0,88 0,25 In this example, in addition to the alloy plate 2 of example 1, a plate with a section of 406 x 1700 mm whose composition is given in table 3 was cast using an AlTiC refining (refining wire containing TiC type seeds ). Table 5. Composition in % by weight of alloys 2 and 9. Alloy Whether Fe Cu min mg Zn You Zr Li Ag 2 0.02 0.03 4.3 0.31 0.60 0.35 0.03 0.12 0.91 0.24 9 0.02 0.04 4.3 0.14 0.61 0.36 0.05 0.13 0.88 0.25

Les plaques ont été homogénéisées à environ 510 °C puis scalpées. Après homogénéisation, les plaques ont été laminées à chaud pour obtenir des tôles ayant une épaisseur de 25mm. Les tôles ont été mises en solution 3h à environ 510°C, trempées à l'eau froide et tractionnées avec un allongement permanent de 3%.Plates were homogenized at approximately 510°C and then scalped. After homogenization, the plates were hot rolled to obtain plates having a thickness of 25mm. The sheets were put in solution for 3 hours at approximately 510° C., quenched in cold water and stretched with a permanent elongation of 3%.

Les tôles ont subi un revenu compris entre 15 h et 25 h à 155 °C. Des échantillons ont été prélevés à mi-épaisseur pour mesurer les caractéristiques mécaniques statiques en traction, en compression dans la direction longitudinale ainsi que la ténacité KQ dans la direction L-T. Les éprouvettes utilisées pour la mesure de ténacité avaient une largeur W=40 mm et une épaisseur B = 20 mm. Les critères de validité de K1C ont été remplis pour certains échantillons. Des mesures de ténacité en contraintes planes ont également été obtenues sur des échantillons CCT de largeur 406 mm et d'épaisseur 6.35 mm. Les résultats obtenus sont présentés dans le tableau 6 et à la figure 4. Tableau 6 : Conditions de revenu et propriétés mécaniques obtenues pour les tôles 2 et 9 à mi-épaisseur Propriétés en tension Propriété en compression Ténacité Alliage Durée de revenu à 155°C Rm (L) (MPa) Rp0,2 (L) en tension (MPa) A (%) Rcp0,2 (L) (MPa) KQ L-T (MPa.M1/2) Kapp L-T (MPa.M1/2) N°2 15 h 591 617 8.3 593 30,6 76 20 h 601 625 8.5 599 29,9 69 25 h 613 27,6 63 N°9 15 h 597 622 9.1 599 28,7 84 20 h 603 26,8 80 25 h 602 626 8.5 607 26,9 78 The plates underwent tempering for between 15 h and 25 h at 155°C. Samples were taken at mid-thickness to measure the static mechanical characteristics in tension, in compression in the longitudinal direction as well as the toughness K Q in the LT direction. The specimens used for the toughness measurement had a width W=40 mm and a thickness B=20 mm. K 1C validity criteria were met for some samples. Plane stress toughness measurements were also obtained on CCT samples 406 mm wide and 6.35 mm thick. The results obtained are presented in table 6 and in figure 4 . Table 6: Tempering conditions and mechanical properties obtained for sheets 2 and 9 at mid-thickness Tensile properties Property in compression Tenacity Alloy Tempering time at 155°C Rm (L) (MPa) Rp 0.2 (L) in tension (MPa) HAS (%) Rc p0.2 (L) (MPa) K Q LT (MPa.M 1/2 ) Kapp LT (MPa.M 1/2 ) #2 3 p.m. 591 617 8.3 593 30.6 76 8 p.m. 601 625 8.5 599 29.9 69 25 p.m. 613 27.6 63 No. 9 3 p.m. 597 622 9.1 599 28.7 84 8 p.m. 603 26.8 80 25 p.m. 602 626 8.5 607 26.9 78

Claims (12)

  1. A product based on an aluminum alloy comprising, in percentage by weight,
    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 Cr, Sc, Hf, V and Ti, the amount of said element, if selected, being from 0.05 to 0.3% by weight for Cr and for Sc, 0.05 to 0.5% by weight for Hf and for V and from 0.01 to 0.15% by weight for Ti,
    other elements at most 0.05% by weight each and 0.15% by weight in total, the remainder being aluminum.
  2. The product based on an aluminum alloy according to claim 1 wherein the Cu content is comprised between 4.2 and 4.5% by weight, preferably between 4.2 and 4.4% by weight.
  3. The product based on an aluminum alloy according to claim 1 or claim 2 wherein the Li content is comprised between 0.8 and 1.0% by weight, preferably between 0.85 and 0.95% by weight.
  4. The product based on an aluminum alloy according to any one of claims 1 to 3 wherein the Zn content is comprised between 0.30 and 0.40% by weight.
  5. The product based on an aluminum alloy according to any one of claims 1 to 4 wherein the Mn content comprised between 0.10 and 0.35% by weight.
  6. The product based on an aluminum alloy according to any one of claims 1 to 5 wherein the sum of the Zn, Mg and Ag contents comprised between 0.95 and 1.35% by weight, preferably between 1.00 and 1.30% by weight, more preferably still between 1.15 and 1.25% by weight.
  7. The product based on an aluminum alloy according to any one of claims 1 to 6 wherein the Zr content is 0.10 to 0.15% by weight, preferably between 0.11 and 0.14% by weight.
  8. The product based on an aluminum alloy according to any one of claims 1 to 7 wherein the Ti content is comprised between 0.01 to 0.15% by weight for Ti, preferably between 0.01 and 0.08% by weight, more preferably between 0.02 and 0.06% by weight.
  9. The product based on an aluminum alloy according to claim 8 wherein the Ti is present in particular in the form of particles of TiC.
  10. A method for manufacturing a product based on an aluminum alloy wherein, successively,
    a) a liquid metal bath based on aluminum is prepared comprising 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 Cr, Sc, Hf, V and Ti, the amount of said element, if selected, being from 0.05 to 0.3% by weight for Cr and for Sc, 0.05 to 0.5% by weight for Hf and for V and from 0.01 to 0.15% by weight for Ti; other elements at most 0.05% by weight each and 0.15% by weight in total and the remainder being aluminum;
    b) a crude form is cast from said liquid metal bath;
    c) said crude form is homogenized at a temperature comprised between 450°C and 550°C and preferably between 480°C and 530°C for a period comprised between 5 and 60 hours;
    d) said homogenized crude form is hot-worked, preferably by rolling;
    e) the hot-worked product is solution heat-treated between 490 and 530°C for 15 min to 8 h and said solution heat-treated product is quenched;
    f) said product is cold-worked with a working of 2 to 16%;
    g) ageing is carried out wherein said product reaches a temperature comprised between 130 and 170°C and preferably between 140 and 160°C for 5 to 100 hours and preferably 10 to 70 hours.
  11. The product according to any one of claims 1 to 9 or can be obtained by the method according to claim 10, with a thickness comprised between 8 and 50 mm having, at mid-thickness:
    i) a compressive yield strength Rcp0.2(L) ≥ 590 MPa, preferably Rcp0.2(L) ≥ 595 MPa;
    ii) a toughness Kapp (L-T) ≥ 60 MPa√m, preferably Kapp (L-T) ≥ 75 MPa√m, with Kapp (L-T) the value of the apparent stress intensity factor at rupture defined according to standard ASTM E561 (2015) measured on CCT test specimens of width W = 406 mm and thickness B = 6.35 mm;
    iii) a difference between the tensile yield strength Rp0.2(L) and the compressive yield strength Rcp0.2(L), Rp0.2(L) - Rcp0.2(L), less than or equal to 10 MPa, preferably ≤ 5 MPa.
  12. An aircraft structure element, preferably an aircraft upper wing skin element, comprising a product according to any one of claims 1 to 9 or according to claim 11.
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