EP2981631B1 - Aluminium-copper-lithium alloy sheets for producing aeroplane fuselages - Google Patents

Aluminium-copper-lithium alloy sheets for producing aeroplane fuselages Download PDF

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EP2981631B1
EP2981631B1 EP14719034.2A EP14719034A EP2981631B1 EP 2981631 B1 EP2981631 B1 EP 2981631B1 EP 14719034 A EP14719034 A EP 14719034A EP 2981631 B1 EP2981631 B1 EP 2981631B1
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German (de)
French (fr)
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EP2981631A1 (en
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Juliette CHEVY
Bernard Bes
Frank Eberl
Jean-Christophe Ehrstrom
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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
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D21/00—Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
    • B22D21/002—Castings of light metals
    • B22D21/007—Castings of light metals with low melting point, e.g. Al 659 degrees C, Mg 650 degrees C
    • 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

Definitions

  • the invention relates to rolled products aluminum-copper-lithium alloys, more particularly, such products, their manufacturing processes and use, intended in particular for aeronautical and aerospace construction.
  • Aluminum alloy rolled products are being developed to produce fuselage elements for the aerospace industry and the aerospace industry in particular.
  • Aluminum - copper - lithium alloys are particularly promising for this type of product.
  • the US Patent 5,032,359 discloses a large 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 strength.
  • the US Patent 5,455,003 discloses a process for manufacturing Al-Cu-Li alloys which have improved mechanical strength and toughness at cryogenic temperature, particularly through proper work-hardening and tempering.
  • the US Patent 7,438,772 discloses alloys comprising, in weight percent, Cu: 3-5, Mg: 0.5-2, Li: 0.01-0.9 and discourage the use of higher lithium contents due to degradation compromise between toughness and mechanical strength.
  • the US Patent 7,229,509 discloses an alloy comprising (% by weight): (2.5-5.5) Cu, (0.1-2.5) Li, (0.2-1.0) Mg, (0.2-0, 8) Ag, (0.2-0.8) Mn, 0.4 max Zr or other grain refining agents such as Cr, Ti, Hf, Sc, V.
  • the patent application US 2011/0247730 discloses alloys comprising (% by weight), 2.75 to 5.0% Cu, 0.1 to 1.1% Li, 0.3 to 2.0% Ag, 0.2 to 0.8% Mg, , 50 to 1.5% of Zn, up to 1.0% of Mn, with a Cu / Mg ratio of between 6.1 and 17, this alloy being not very sensitive to wrought iron.
  • composition alloys (in% by weight) Cu 2.8 - 4.0; Li 0.8 - 1.9; Mn 0.2-0.6; Zn 0.20 - 0.80, Zr 0.04 - 0.20, Mg 0.20 - 0.80, Ag 0.1 - 0.7, Si ⁇ 0.10, Fe ⁇ 0.10, Ti ⁇ 0.12.
  • the characteristics required for aluminum sheets for fuselage applications are described for example in the patent EP 1 891 247 .
  • the patent EP 1 966 402 discloses an alloy comprising 2.1 to 2.8% by weight of Cu, 1.1 to 1.7% by weight of Li, 01 to 0.8% by weight of Ag, 0.2 to 0.6% by weight of weight of Mg, 0.2 to 0.6% by weight of Mn, an amount of Fe and Si of less than or equal to 0.1% by weight each, and unavoidable impurities at a content of less than or equal to 0.05 % by weight each and 0.15% by weight in total, the alloy being substantially free of zirconium, particularly suitable for obtaining recrystallized thin sheets.
  • Damage tolerance sizing is the determination of a detectable, limitable fault size that can be guaranteed to not break during a defined time interval. To achieve this dimensioning it is necessary to know the behavior of cracks subjected to a representative load on panels of sufficient size. In addition, in the case of the large damage capability assessment for which the undetected failure of a stiffener is assumed, the width of the crack can be high and it is useful to have accurate data of toughness for very long cracks.
  • the characterization of toughness of the thin sheets is generally carried out on panels with a width of less than or equal to 760 mm by the R curve test.
  • the curve test R is a widely recognized means for characterizing the tenacity properties.
  • the curve R represents the evolution of the critical effective stress intensity factor for the crack propagation as a function of the effective crack extension, under monotonically increasing stress. It allows the determination of the critical load for unstable failure for any configuration relevant to cracked aircraft structures.
  • the values of the effective stress intensity factor and the effective crack extension are actual values as defined in ASTM E561. It is generally believed that the width of the panel should not change the level of the R curve, namely the effective stress intensity factor for a given effective crack growth, but only the valid length of the curve. However, it has been found in the context of the present invention that this hypothesis is not always verified and that in fact the characterization on larger panels, such as panels of width 1220 mm, accounts for certain specific properties. material that can not be deduced from the characterizations performed on smaller panels. Thus the knowledge of the state of the art It is not possible to predict which alloys and which thermomechanical treatments will achieve the most advantageous properties for K app and for the level of the R curve on wide panels, but these properties will influence the dimensioning in damage tolerance.
  • the toughness be high in the L-T direction. Indeed, in some configurations the bending stresses on the fuselage around the axis of the wings become critical, especially for the upper part of the fuselage. The cracks on the plates whose longitudinal direction and also the longitudinal direction of the fuselage are then biased in the L-T direction.
  • Yet another object of the invention is the use of a sheet according to the invention in an aircraft fuselage panel.
  • alloys are in accordance with the regulations of The Aluminum Association, known to those skilled in the art. The density depends on the composition and is determined by calculation rather than by a method of measuring weight. The values are calculated in accordance with the procedure of The Aluminum Association, which is described on pages 2-12 and 2-13 of "Aluminum Standards and Data". Unless otherwise stated, the definitions of the metallurgical states given in the European standard EN 515 apply.
  • the static mechanical characteristics in tension in other words the tensile strength R m , the conventional yield stress 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, the sampling and the direction of the test being defined by the EN 485-1 standard.
  • the mechanical characteristics are measured in full thickness.
  • the term "substantially uncrystallized granular structure” refers to a granular structure such that the degree of recrystallization at 1 ⁇ 2-thickness is less than 30% and preferably less than 10%, and a substantially recrystallized granular structure is called a structure. granular such that the recrystallization rate at 1 ⁇ 2 thickness is greater than 70% and preferably greater than 90%.
  • the recrystallization rate is defined as the surface fraction on a metallographic section occupied by recrystallized grains.
  • 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.
  • the critical stress intensity factor K c in d other words the intensity factor that makes the crack unstable, is calculated from the curve R.
  • the stress intensity factor K CO is also calculated by assigning the crack length initial at the beginning of the monotonic load, at the critical load. These two values are calculated for a specimen of the required form.
  • K app represents the K CO factor corresponding to the specimen that was used to perform the R curve test.
  • K eff represents the K C factor corresponding to the specimen that was used to perform the R curve test.
  • ⁇ a eff (max) represents the crack extension of the last point of the curve R, valid according to the ASTM E561 standard.
  • the crack size at the end of the pre-fatigue cracking stage is W / 3 for M (T) type specimens, where W is the specimen width as defined in ASTM E561.
  • EN 12258 Unless otherwise specified, the definitions of EN 12258 apply.
  • the present inventors have surprisingly found that the toughness measured in the LT direction on 1220 mm wide panels is improved for a precise range of yield strength values in the longitudinal direction R p0,2 (L) while this effect is not observed when the measurement is made on panels of width 760 mm.
  • R p0,2 L
  • there is an optimum range of elastic limit value specific to the width 1220 mm which can not be interpreted by considerations based on the plasticization of the uncracked ligament. , these underlying the validity limits of ASTM E561.
  • the present inventors have therefore established that sheets obtained by a process comprising casting, homogenization, hot rolling and optionally cold rolling, solution-setting, quenching and tempering have the advantageous properties when the composition and the combined so that the yield strength in the longitudinal direction R p0,2 (L) is between 395 and 435 MPa.
  • the sheets have the advantageous properties when the income is made "at the peak".
  • the so-called "peak” income is an income for which the yield strength in the transverse direction R p0,2 (TL) has a value of at least 95%.
  • the yield strength in the transverse direction R p0.2 (TL) obtained for an income having a time equivalent to 155 ° C of 48 h.
  • a "peak" income is preferred.
  • thermal stability is understood to mean the stability of the mechanical properties during a temperature exposure representative of the conditions experienced in civil aviation, this being for example simulated by an aging of 1000 hours at 85 ° C. vs. Therefore, it is chosen to perform, if necessary, an under-income for which the yield strength in the transverse direction R p0.2 (TL) has a value of between 88% and 94% and preferably at least 91% of the value obtained for an income having a time equivalent to 155 ° C of 48 hours.
  • the copper content of the products according to the invention is between 2.6 and 3.0% by weight. In an advantageous embodiment of the invention, the copper content is between 2.8 and 3.0% by weight.
  • the copper content is at most 2.95% by weight and advantageously at most 2.9% by weight.
  • the yield strength R p0.2 (L) is too high to reach the advantageous range under the under- feed conditions according to the invention.
  • the copper content is too low, the minimum static mechanical characteristics are not reached, even for a peak income.
  • the lithium content of the products according to the invention is between 0.5 and 0.8% by weight.
  • the lithium content is between 0.55% and 0.75% by weight.
  • the lithium content is between 0.60% and 0.73% by weight.
  • the addition of lithium can contribute to the increase of the mechanical strength and the toughness, a content that is too high or too low does not make it possible to obtain a high value of tenacity and / or a sufficient limit of elasticity.
  • the magnesium content of the products according to the invention is between 0.2 and 0.7% by weight, preferably between 0.25 and 0.50% by weight and preferably between 0.30 and 0.45% by weight. in weight. In an advantageous embodiment of the invention, the magnesium content is at most 0.4% by weight.
  • the zirconium content is between 0.06 and 0.20% by weight and preferably between 0.10 and 0.18% by weight. When an essentially non-recrystallized granular structure is preferred, the zirconium content is advantageously between 0.14 and 0.17% by weight.
  • the silver content is between 0.1 and 0.4% by weight. In an advantageous embodiment of the invention, the silver content is between 0.2 and 0.3% by weight. In one embodiment of the invention the silver content is between 0.15 and 0.28% by weight.
  • the titanium content is between 0.01 and 0.15% by weight. The addition of titanium helps to control the granular structure, especially during casting.
  • the alloy may optionally contain at least one element selected from Mn, V, Cr, Sc, and Hf, the amount of the element, if selected, being from 0.01 to 0.8% by weight for Mn 0.05 to 0.2% by weight for V, 0.05 to 0.3% by weight for Cr, 0.02 to 0.3% by weight for Sc, 0.05 to 0.5% by weight for Hf.
  • Mn, V, Cr or Sc are not added and their content is less than or equal to 0.05% by weight.
  • the iron and silicon contents are each at most 0.1% by weight.
  • the iron and silicon contents are at most 0.08% and preferably at most 0.04% by weight.
  • a controlled and limited iron and silicon content contributes to the improvement of the compromise between mechanical resistance and damage tolerance.
  • the zinc content is less than 0.2% by weight and preferably less than 0.1% by weight.
  • the zinc content is advantageously less than 0.04% by weight.
  • the unavoidable impurities are maintained at a content of less than or equal to 0.05% by weight each and 0.15% by weight in total.
  • the manufacturing process of the sheets according to the invention comprises steps of production, casting, rolling, dissolution, quenching controlled traction and income.
  • a bath of liquid metal is produced so as to obtain an aluminum alloy of composition according to the invention.
  • the bath of liquid metal is then cast into a form of rolling plate.
  • the rolling plate is then homogenized at a temperature between 450 ° C and 535 ° and preferably between 480 ° C and 530 ° C.
  • the homogenization time is preferably between 5 and 60 hours.
  • the rolling plate is generally cooled to room temperature before being preheated to be hot deformed.
  • Preheating aims to achieve a temperature preferably between 400 and 500 ° C for deformation by hot rolling.
  • the hot rolling and optionally cold rolling is carried out so as to obtain a sheet thickness of 0.5 to 8 mm.
  • Intermediate heat treatments during rolling and / or after rolling can be carried out in some cases. However, preferably, the process does not include intermediate heat treatment during rolling and / or after rolling.
  • the sheet thus obtained is then put in solution by heat treatment between 450 and 535 ° C, preferably for 5 min to 8 h, and then quenched.
  • An income is made comprising heating at a temperature between 130 and 170 ° C and preferably between 150 and 160 ° C for 5 to 100 hours and preferably from 10 to 40h so as to achieve a limit of elasticity in the direction longitudinal R p0.2 (L) between 395 and 435 MPa.
  • a yield strength in the longitudinal direction R p0.2 (L) of 395 and 415 MPa may be preferred in some cases.
  • a yield strength in the longitudinal direction R p0.2 (L) of 415 and 435 MPa may be preferred in some cases.
  • the composition makes it possible to reach the desired longitudinal elasticity limit with a time equivalent to 155 ° C. of less than 48 hours and preferably less than 30 hours.
  • the final metallurgical state is a T8 state.
  • t i is expressed in hours.
  • the present inventors have found in particular that the preferred field of magnesium content makes it possible to limit the duration of the income by reaching a favorable property compromise.
  • a short heat treatment is performed after controlled pulling and before tempering so as to improve the formability of the sheets.
  • the sheets can thus be shaped by a process such as stretch-forming before being returned.
  • the most favorable granular structure depends on the thickness of the products.
  • sheets according to the invention in an aircraft fuselage panel is advantageous.
  • the sheets according to the invention are also advantageous in aerospace applications such as the manufacture of rockets.
  • the granular structure of the samples was characterized from microscopic observation of cross sections after anodic oxidation under polarized light.
  • the granular structure of the sheets was essentially non-recrystallized for all sheets except D # 2 and E # 2 sheets for which the granular structure was essentially recrystallized.
  • the samples were mechanically tested to determine their static mechanical properties as well as their resistance to crack propagation. Tensile yield strength, ultimate strength and elongation at break are given in Table 3.
  • Table 4 summarizes the results of the tenacity tests on CCT test pieces of width 760 mm for these samples. Table 4 results of the R curves for 760 mm wide specimens.
  • Table 5 summarizes the results of the toughness tests for the R curves obtained with CCT specimens of width 12

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Description

Domaine de l'inventionField of the invention

L'invention concerne les produits laminés alliages aluminium-cuivre-lithium, plus particulièrement, de tels produits, leurs procédés de fabrication et d'utilisation, destinés notamment à la construction aéronautique et aérospatiale.The invention relates to rolled products aluminum-copper-lithium alloys, more particularly, such products, their manufacturing processes and use, intended in particular for aeronautical and aerospace construction.

Etat de la techniqueState of the art

Des produits laminés en alliage d'aluminium sont développés pour produire des éléments de fuselage destinés notamment à l'industrie aéronautique et à l'industrie aérospatiale.Aluminum alloy rolled products are being developed to produce fuselage elements for the aerospace industry and the aerospace industry in particular.

Les alliages aluminium - cuivre - lithium sont particulièrement prometteurs pour fabriquer ce type de produit.Aluminum - copper - lithium alloys are particularly promising for this type of product.

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 pour cent en poids, permet d'augmenter la résistance mécanique.The US Patent 5,032,359 discloses a large 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 strength.

Le brevet US 5,455,003 décrit un procédé de fabrication d'alliages Al-Cu-Li qui présentent une résistance mécanique et une ténacité améliorées 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 US Patent 5,455,003 discloses a process for manufacturing Al-Cu-Li alloys which have improved mechanical strength and toughness at cryogenic temperature, particularly through proper 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 teneurs en lithium plus élevées en raison d'une dégradation du compromis entre ténacité et résistance mécanique.The US Patent 7,438,772 discloses alloys comprising, in weight percent, Cu: 3-5, Mg: 0.5-2, Li: 0.01-0.9 and discourage 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 US Patent 7,229,509 discloses an alloy comprising (% by weight): (2.5-5.5) Cu, (0.1-2.5) Li, (0.2-1.0) Mg, (0.2-0, 8) Ag, (0.2-0.8) Mn, 0.4 max Zr or other grain refining agents 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 request for US Patent 2009/142222 A1 discloses 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 controlling the granular structure. This application also describes a process for manufacturing spun products.

La demande de brevet US 2011/0247730 décrit des alliages comprenant (en % en poids), 2.75 à 5.0% de Cu, 0,1 à 1,1 % de Li, 0,3 à 2.0 % de Ag, 0,2 à 0,8% de Mg, 0,50 à 1.5 % de Zn, jusque 1.0% de Mn, avec un rapport Cu/Mg compris entre 6,1 et 17, cet alliage étant peu sensible au corroyage.The patent application US 2011/0247730 discloses alloys comprising (% by weight), 2.75 to 5.0% Cu, 0.1 to 1.1% Li, 0.3 to 2.0% Ag, 0.2 to 0.8% Mg, , 50 to 1.5% of Zn, up to 1.0% of Mn, with a Cu / Mg ratio of between 6.1 and 17, this alloy being not very sensitive to wrought iron.

La demande de brevet CN101967588 décrit des alliages de composition (en % en poids) Cu 2,8 - 4,0 ; Li 0,8 - 1,9 ; Mn 0,2-0,6 ; Zn 0,20 - 0,80, Zr 0,04 - 0,20, Mg 0,20 - 0,80, Ag 0,1 - 0,7, Si ≤ 0.10, Fe ≤ 0.10, Ti ≤ 0.12.The patent application CN101967588 discloses composition alloys (in% by weight) Cu 2.8 - 4.0; Li 0.8 - 1.9; Mn 0.2-0.6; Zn 0.20 - 0.80, Zr 0.04 - 0.20, Mg 0.20 - 0.80, Ag 0.1 - 0.7, Si ≤ 0.10, Fe ≤ 0.10, Ti ≤ 0.12.

La demande de brevet US 2011/209801 concerne des produits corroyé tels que des produits filés , laminés et/ou forgés, en alliage à base d'aluminium comprenant, en % en poids, Cu : 3,0 - 3,9 ; Li : 0,8 - 1,3 ; Mg : 0,6 - 1,0 ; Zr : 0,05 - 0,18 ; Ag : 0,0 - 0,5 ; Mn : 0,0 - 0,5 ; Fe + Si <= 0,20 ; au moins un élément parmi Ti : 0,01-0,15 ; Sc : 0,05 - 0,3 ; Cr : 0,05 - 0,3 ; Hf : 0,05 - 0, 5 ; autres éléments <= 0,05 chacun et <= 0,15 au total, reste aluminium, les produits étant particulièrement utiles pour réaliser des produits épais en aluminium destinés à réaliser des éléments de structure pour l'industrie aéronautique.The request for US Patent 2011/209801 relates to wrought products such as spun, rolled and / or forged products of aluminum-based alloy comprising, in% by weight, Cu: 3.0 - 3.9; Li: 0.8 - 1.3; Mg 0.6 - 1.0; Zr: 0.05-0.18; Ag: 0.0 - 0.5; Mn: 0.0 - 0.5; Fe + Si <= 0.20; at least one of Ti: 0.01-0.15; Sc: 0.05 - 0.3; Cr: 0.05 - 0.3; Hf: 0.05-0.5; other elements <= 0.05 each and <= 0.15 in total, remains aluminum, the products being particularly useful for producing thick aluminum products intended to produce structural elements for the aeronautical industry.

Les caractéristiques nécessaires pour les tôles d'aluminium destinées aux applications de fuselage sont décrites par exemple dans le brevet EP 1 891 247 . Il est souhaitable notamment que la tôle ait une limite d'élasticité élevée (pour résister au flambage) ainsi qu'une ténacité sous contrainte plane élevée, caractérisée notamment par une valeur élevée de facteur d'intensité de contrainte apparent à la rupture (Kapp) élevée et une longue courbe R.The characteristics required for aluminum sheets for fuselage applications are described for example in the patent EP 1 891 247 . In particular, it is desirable for the sheet to have a high yield strength (to withstand buckling) as well as a high plane stress toughness, characterized in particular by a high value of apparent stress intensity factor at break (K app ) high and a long curve R.

Le brevet EP 1 966 402 décrit un alliage comprenant 2,1 à 2,8 % en poids de Cu, 1,1 à 1,7 % en poids de Li, 01 à 0,8 % en poids de Ag, 0,2 à 0,6 % en poids de Mg, 0,2 à 0,6 % en poids de Mn, une quantité de Fe et de Si inférieure ou égale à 0,1 % en poids chacun, et des impuretés inévitables à une teneur inférieure ou égale à 0,05% en poids chacune et 0,15% en poids au total, l'alliage étant sensiblement exempt de zirconium, particulièrement adapté pour l'obtention de tôles minces recristallisées.The patent EP 1 966 402 discloses an alloy comprising 2.1 to 2.8% by weight of Cu, 1.1 to 1.7% by weight of Li, 01 to 0.8% by weight of Ag, 0.2 to 0.6% by weight of weight of Mg, 0.2 to 0.6% by weight of Mn, an amount of Fe and Si of less than or equal to 0.1% by weight each, and unavoidable impurities at a content of less than or equal to 0.05 % by weight each and 0.15% by weight in total, the alloy being substantially free of zirconium, particularly suitable for obtaining recrystallized thin sheets.

Le brevet CN101 967 588 A décrit des tôles en alliage AlCuLiAgMgThe patent CN101 967 588 A describes AlCuLiAgMg alloy sheets

Le dimensionnement en tolérance aux dommages consiste à déterminer une taille de défaut limite, détectables, dont on pourra garantir qu'ils n'entraîneront pas de rupture durant un intervalle de temps défini. Pour réaliser ce dimensionnement il est nécessaire de connaître le comportement des fissures soumises à un chargement représentatif sur des panneaux de taille suffisante. De plus dans le cas de l'évaluation de la capabilité pour les grandes fissures (« large damage capability ») pour laquelle on suppose la rupture non détectée d'un raidisseur, la largeur de la fissure peut être élevée et il est utile de disposer de données précises de ténacité pour des fissures très longues. Or les caractérisations de ténacité des tôles minces sont généralement effectuées sur des panneaux de largeur inférieure ou égale à 760 mm par l'essai de courbe R. L'essai de courbe R est un moyen largement reconnu pour caractériser les propriétés de ténacité. La courbe R représente l'évolution du facteur d'intensité de contrainte effective critique pour la propagation de fissure en fonction de l'extension de fissure effective, sous une contrainte croissant de façon monotone. Elle permet la détermination de la charge critique pour une rupture instable pour toute configuration pertinente à des structures d'aéronef fissurées. Les valeurs du facteur d'intensité de contrainte effective et de l'extension de fissure effective sont des valeurs réelles telles que définies dans la norme ASTM E561. On estime généralement que la largeur du panneau ne devrait pas modifier le niveau de la courbe R, à savoir le facteur d'intensité de contrainte effective pour une croissance de fissure effective donnée, mais uniquement la longueur valide de la courbe. Or il s'est avéré dans le cadre de la présente invention que cette hypothèse n'est pas toujours vérifiée et qu'en fait la caractérisation sur des panneaux plus larges, tels que des panneaux de largeur 1220 mm, rend compte de certaines propriétés spécifiques du matériau ne pouvant être déduites des caractérisations effectuées sur des panneaux moins larges. Ainsi les connaissances de l'état de la technique ne permettent pas de prédire quels alliages et quels traitements thermomécaniques permettront d'atteindre les propriétés les plus avantageuses pour Kapp et pour le niveau de la courbe R sur des panneaux de grande largeur, or ces propriétés influenceront le dimensionnement en tolérance aux dommages.Damage tolerance sizing is the determination of a detectable, limitable fault size that can be guaranteed to not break during a defined time interval. To achieve this dimensioning it is necessary to know the behavior of cracks subjected to a representative load on panels of sufficient size. In addition, in the case of the large damage capability assessment for which the undetected failure of a stiffener is assumed, the width of the crack can be high and it is useful to have accurate data of toughness for very long cracks. The characterization of toughness of the thin sheets is generally carried out on panels with a width of less than or equal to 760 mm by the R curve test. The curve test R is a widely recognized means for characterizing the tenacity properties. The curve R represents the evolution of the critical effective stress intensity factor for the crack propagation as a function of the effective crack extension, under monotonically increasing stress. It allows the determination of the critical load for unstable failure for any configuration relevant to cracked aircraft structures. The values of the effective stress intensity factor and the effective crack extension are actual values as defined in ASTM E561. It is generally believed that the width of the panel should not change the level of the R curve, namely the effective stress intensity factor for a given effective crack growth, but only the valid length of the curve. However, it has been found in the context of the present invention that this hypothesis is not always verified and that in fact the characterization on larger panels, such as panels of width 1220 mm, accounts for certain specific properties. material that can not be deduced from the characterizations performed on smaller panels. Thus the knowledge of the state of the art It is not possible to predict which alloys and which thermomechanical treatments will achieve the most advantageous properties for K app and for the level of the R curve on wide panels, but these properties will influence the dimensioning in damage tolerance.

Par ailleurs, pour certaines applications de fuselage, il est particulièrement important que la ténacité soit élevée dans la direction L-T. En effet, dans certaines configurations les contraintes de flexion sur le fuselage autour de l'axe des ailes deviennent critiques, notamment pour la partie supérieure du fuselage. Les fissures sur les tôles dont la direction longitudinale et également la direction longitudinale du fuselage sont alors sollicitées dans la direction L-T.On the other hand, for some fuselage applications, it is particularly important that the toughness be high in the L-T direction. Indeed, in some configurations the bending stresses on the fuselage around the axis of the wings become critical, especially for the upper part of the fuselage. The cracks on the plates whose longitudinal direction and also the longitudinal direction of the fuselage are then biased in the L-T direction.

Il existe un besoin pour des tôles d'épaisseur 0,5 à 8 mm, en alliage aluminium-cuivre-lithium présentant des propriétés améliorées par rapport à celles des produits connus, en particulier en termes de ténacité mesurée sur des panneaux de grande largeur notamment dans la direction L-T, de propriétés de résistance mécanique statique et de résistance à la corrosion, tout en ayant une faible densité.There is a need for sheets having a thickness of 0.5 to 8 mm, of aluminum-copper-lithium alloy having improved properties compared to those of the known products, in particular in terms of tenacity measured on panels of great width in particular. in the LT direction, static strength properties and corrosion resistance, while having a low density.

Objet de l'inventionObject of the invention

L'objet de l'invention est une tôle d'épaisseur 0,5 à 8 mm en alliage à base d'aluminium comprenant

  • 2,6 à 3,0 % en poids de Cu,
  • 0,5 à 0.8 % en poids de Li,
  • 0,1 à 0,4 % en poids de Ag,
  • 0,2 à 0,5 % en poids de Mg,
  • 0,06 à 0,20 % en poids de Zr,
  • 0,01 à 0,15 % en poids de Ti,
  • optionnellement au moins un élément choisi parmi Mn, V, Cr, Sc, et Hf, la quantité de l'élément, s'il est choisi, étant de 0,01 à 0,8 % en poids pour Mn, 0,05 à 0,2 % en poids pour V, 0,05 à 0,3 % en poids pour Cr, 0,02 à 0,3 % en poids pour Sc, 0,05 à 0,5 % en poids pour Hf,
  • une quantité de Zn inférieure à 0,2 % en poids, une quantité de Fe et de Si inférieure ou égale à 0,1 % en poids chacun, et des impuretés inévitables à une teneur inférieure ou égale à 0,05% en poids chacune et 0,15% en poids au total,
la dite tôle étant obtenue par un procédé comprenant coulée, homogénéisation, laminage à chaud et optionnellement laminage à froid, mise en solution, trempe et revenu, la composition et le revenu étant combinés de façon à ce que la limite d'élasticité dans le sens longitudinal Rp0,2(L) soit comprise entre 395 et 435 MPaThe object of the invention is a sheet of thickness 0.5 to 8 mm of aluminum-based alloy comprising
  • 2.6 to 3.0% by weight of Cu,
  • 0.5 to 0.8% by weight of Li,
  • 0.1 to 0.4% by weight of Ag,
  • 0.2 to 0.5% by weight of Mg,
  • 0.06 to 0.20% by weight of Zr,
  • 0.01 to 0.15% by weight of Ti,
  • optionally at least one element selected from Mn, V, Cr, Sc, and Hf, the amount of the element, if selected, being from 0.01 to 0.8% by weight for Mn, 0.05 to 0.2% by weight for V, 0.05 to 0.3% by weight for Cr, 0.02 to 0.3% by weight for Sc, 0.05 to 0.5% by weight for Hf,
  • an amount of Zn of less than 0.2% by weight, an amount of Fe and Si of less than or equal to 0.1% by weight each, and unavoidable impurities at a content of less than or equal to 0.05% by weight each and 0.15% by weight in total,
said sheet being obtained by a process comprising casting, homogenization, hot rolling and optionally cold rolling, dissolving, quenching and tempering, the composition and the income being combined so that the yield strength in the direction longitudinal R p0,2 (L) is between 395 and 435 MPa

Un autre objet de l'invention est le procédé de fabrication d'une tôle selon l'invention d'épaisseur 0,5 à 8 mm en alliage à base d'aluminium dans lequel, successivement

  • a) on élabore un bain de métal liquide comprenant
    • 2,6 à 3,0 % en poids de Cu,
    • 0,5 à 0.8 % en poids de Li,
    • 0,1 à 0,4 % en poids de Ag,
    • 0,2 à 0,5 % en poids de Mg,
    • 0,06 à 0,20 % en poids de Zr,
    • 0,01 à 0,15 % en poids de Ti,
    • optionnellement au moins un élément choisi parmi Mn, V, Cr, Sc, et Hf, la quantité de l'élément, s'il est choisi, étant de 0,01 à 0,8 % en poids pour Mn, 0,05 à 0,2 % en poids pour V, 0,05 à 0,3 % en poids pour Cr, 0,02 à 0,3 % en poids pour Sc, 0,05 à 0,5 % en poids pour Hf,
    • une quantité de Zn inférieure à 0,2 % en poids, une quantité de Fe et de Si inférieure ou égale à 0,1 % en poids chacun, et des impuretés inévitables à une teneur inférieure ou égale à 0,05% en poids chacune et 0,15% en poids au total,
  • b) on coule une plaque à partir dudit bain de métal liquide
  • c) on homogénéise ladite plaque à une température comprise entre 450°C et 535 °C ;
  • d) on lamine ladite plaque par laminage à chaud et optionnellement à froid en une tôle ayant une épaisseur comprise entre 0.5 mm et 8 mm;
  • e) on met en solution à une température comprise entre 450 °C et 535 °C et on trempe ladite tôle;
  • h) on tractionne de façon contrôlée ladite tôle avec une déformation permanente de 0,5 à 5%,
    la déformation à froid totale après mise en solution et trempe étant inférieure à 15% ;
  • i) on effectue un revenu comprenant un chauffage à une température comprise entre 130 et 170°C et de préférence entre 150 et 160°C pendant 5 à 100 heures et de préférence de 10 à 40h, la composition et le revenu étant combinés de façon à ce que la limite d'élasticité dans le sens longitudinal Rp0,2(L) soit comprise entre 395 et 435 MPa.
Another object of the invention is the method of manufacturing a sheet according to the invention with a thickness of 0.5 to 8 mm of aluminum-based alloy in which, successively
  • a) a bath of liquid metal comprising
    • 2.6 to 3.0% by weight of Cu,
    • 0.5 to 0.8% by weight of Li,
    • 0.1 to 0.4% by weight of Ag,
    • 0.2 to 0.5% by weight of Mg,
    • 0.06 to 0.20% by weight of Zr,
    • 0.01 to 0.15% by weight of Ti,
    • optionally at least one element selected from Mn, V, Cr, Sc, and Hf, the amount of the element, if selected, being from 0.01 to 0.8% by weight for Mn, 0.05 to 0.2% by weight for V, 0.05 to 0.3% by weight for Cr, 0.02 to 0.3% by weight for Sc, 0.05 to 0.5% by weight for Hf,
    • an amount of Zn of less than 0.2% by weight, an amount of Fe and Si of less than or equal to 0.1% by weight each, and unavoidable impurities at a content of less than or equal to 0.05% by weight each and 0.15% by weight in total,
  • b) pouring a plate from said liquid metal bath
  • c) said plate is homogenized at a temperature between 450 ° C and 535 ° C;
  • d) laminating said plate by hot rolling and optionally cold rolling into a sheet having a thickness of between 0.5 mm and 8 mm;
  • e) dissolving at a temperature of between 450 ° C and 535 ° C and quenching said sheet;
  • h) the sheet is controlledly tensile with a permanent deformation of 0.5 to 5%,
    the total cold deformation after dissolution and quenching is less than 15%;
  • i) an income is made comprising heating at a temperature between 130 and 170 ° C and preferably between 150 and 160 ° C for 5 to 100 hours and preferably from 10 to 40h, the composition and the income being combined so that the yield strength in the longitudinal direction R p0,2 (L) is between 395 and 435 MPa.

Encore un autre objet de l'invention est l'utilisation d'une tôle selon l'invention dans un panneau de fuselage pour aéronef.Yet another object of the invention is the use of a sheet according to the invention in an aircraft fuselage panel.

Description des figuresDescription of figures

  • Figure 1 - Courbes R obtenues dans la direction L-T sur des tôles d'épaisseur 4 à 5 mm pour des éprouvettes de largeur 760 mm et 1220 mm. Figure 1 - Curves R obtained in the direction LT on sheets of thickness 4 to 5 mm for specimens of width 760 mm and 1220 mm.
  • Figure 2 - Courbes R obtenues dans la direction L-T sur des tôles d'épaisseur 1,5 à 2,5 mm pour des éprouvettes de largeur 760 mm et 1220 mm. Figure 2 - R curves obtained in the LT direction on sheets of thickness 1.5 to 2.5 mm for specimens of width 760 mm and 1220 mm.
  • Figure 3 - Courbes R obtenues dans la direction L-T sur des tôles E#1 ayant subi différents revenus pour des éprouvettes de largeur 760 mm et 1220 mm. Figure 3 - Curves R obtained in the direction LT on E # 1 plates having undergone different incomes for specimens of width 760 mm and 1220 mm.
  • Figure 4 - Courbes R obtenues dans la direction L-T sur des tôles E#2 ayant subi différents revenus pour des éprouvettes de largeur 760 mm et 1220 mm. Figure 4 - Curves R obtained in the LT direction on E # 2 plates having undergone different incomes for specimens of width 760 mm and 1220 mm.
  • Figure 5- Relation entre la limite d'élasticité dans le sens longitudinal et le facteur d'intensité de contrainte Kapp L-T mesuré sur des échantillons de largeur 1220 mm pour les tôles d'épaisseur 4 à 5 mm. Figure 5 - Relationship between the yield strength in the longitudinal direction and the stress intensity factor K app LT measured on samples with a width of 1220 mm for sheets with a thickness of 4 to 5 mm.
  • Figure 6- Relation entre la limite d'élasticité dans le sens longitudinal et le facteur d'intensité de contrainte Kapp L-T mesuré sur des échantillons de largeur 1220 mm pour les tôles d'épaisseur 1,5 à 2,5 mm. Figure 6 - Relation between the elastic limit in the longitudinal direction and the stress intensity factor K app LT measured on samples with a width of 1220 mm for sheets with a thickness of 1.5 to 2.5 mm.
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. La densité dépend de la composition et est déterminée par calcul plutôt que par une méthode de mesure de poids. Les valeurs sont calculées en conformité avec la procédure de The Aluminium Association, qui est décrite pages 2-12 et 2-13 de « Aluminum Standards and Data ». Sauf mention contraire les définitions des états métallurgiques indiquées dans la norme européenne EN 515 s'appliquent.
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, le prélèvement et le sens de l'essai étant définis par la norme EN 485-1. Dans le cadre de l'invention, les caractéristiques mécaniques sont mesurées en pleine épaisseur.
Dans le cadre de la présente invention, on appelle structure granulaire essentiellement non--recristallisée une structure granulaire telle que le taux de recristallisation à ½ épaisseur est inférieur à 30% et de préférence inférieur à 10% et on appelle structure granulaire essentiellement recristallisée une structure granulaire telle que le taux de recristallisation à ½ épaisseur est supérieur à 70% et de préférence supérieur à 90%. Le taux de recristallisation est défini comme la fraction de surface sur une coupe métallographique occupée par des grains recristallisés.Unless stated otherwise, all the information concerning the chemical composition of the alloys is 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 alloys is in accordance with the regulations of The Aluminum Association, known to those skilled in the art. The density depends on the composition and is determined by calculation rather than by a method of measuring weight. The values are calculated in accordance with the procedure of The Aluminum Association, which is described on pages 2-12 and 2-13 of "Aluminum Standards and Data". Unless otherwise stated, the definitions of the metallurgical states given in the European standard EN 515 apply.
The static mechanical characteristics in tension, in other words the tensile strength R m , the conventional yield stress 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, the sampling and the direction of the test being defined by the EN 485-1 standard. In the context of the invention, the mechanical characteristics are measured in full thickness.
In the context of the present invention, the term "substantially uncrystallized granular structure" refers to a granular structure such that the degree of recrystallization at ½-thickness is less than 30% and preferably less than 10%, and a substantially recrystallized granular structure is called a structure. granular such that the recrystallization rate at ½ thickness is greater than 70% and preferably greater than 90%. The recrystallization rate is defined as the surface fraction on a metallographic section occupied by recrystallized grains.

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. 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. Δaeff(max) représente l'extension de fissure du dernier point de la courbe R, valide selon la norme ASTM E561. Le dernier point est obtenu soit au moment de la rupture brutale de l'éprouvette, soit éventuellement au moment où la contrainte sur le ligament non fissuré excède en moyenne la limite d'élasticité du matériau. Sauf mention contraire, la taille de fissure à la fin du stade de pré-fissurage par fatigue est W/3 pour des éprouvettes du type M(T), dans laquelle W est la largeur de l'éprouvette telle que définie dans la norme 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. The critical stress intensity factor K c , in d other words the intensity factor that makes the crack unstable, is calculated from the curve R. The stress intensity factor K CO is also calculated by assigning the crack length initial at the beginning of the monotonic load, at the critical load. These two values are calculated for a specimen of the required form. K app represents the K CO factor corresponding to the specimen that was used to perform the R curve test. K eff represents the K C factor corresponding to the specimen that was used to perform the R curve test. Δa eff (max) represents the crack extension of the last point of the curve R, valid according to the ASTM E561 standard. The last point is obtained either at the time of the sudden rupture of the test piece, or possibly at the moment when the stress on the uncracked ligament exceeds on average the elastic limit of the material. Unless otherwise stated, the crack size at the end of the pre-fatigue cracking stage is W / 3 for M (T) type specimens, where W is the specimen width as defined in ASTM E561.

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

Des tôles d'épaisseur 0,5 à 8 mm en alliage Al-Cu-Li selon la composition de l'invention permettent, lorsque leur limite d'élasticité dans le sens longitudinal Rp0,2(L) est comprise entre 395 et 435 MPa d'obtenir une ténacité mesurée sur des panneaux de grande largeur notamment dans la direction L-T, particulièrement avantageuse.Sheet thickness 0.5 to 8 mm Al-Cu-Li alloy according to the composition of the invention, when their elastic limit in the longitudinal direction R p0,2 (L) is between 395 and 435 MPa to obtain toughness measured on panels of great width especially in the LT direction, particularly advantageous.

En effet, les présents inventeurs ont constaté de manière surprenante que la ténacité mesurée dans la direction L-T sur des panneaux de largeur 1220 mm est améliorée pour une plage précise de valeurs de limite d'élasticité dans le sens longitudinal Rp0,2(L) alors que cet effet n'est pas observé lorsque la mesure est effectuée sur des panneaux de largeur 760 mm. Ainsi dans le cadre de l'invention il a été observé qu'il existe une plage optimale de valeur de limite d'élasticité spécifique à la largeur 1220 mm, qui ne peut pas être interprétée par des considérations basées sur la plastification du ligament non fissuré, celles-ci sous-tendant les limites de validité de la norme ASTM E561. Les présents inventeurs ont donc établi que des tôles obtenue par un procédé comprenant coulée, homogénéisation, laminage à chaud et optionnellement laminage à froid, mise en solution, trempe et revenu ont les propriétés avantageuses quand la composition et le revenu sont combinés de façon à ce que la limite d'élasticité dans le sens longitudinal Rp0,2(L) soit comprise entre 395 et 435 MPa.Indeed, the present inventors have surprisingly found that the toughness measured in the LT direction on 1220 mm wide panels is improved for a precise range of yield strength values in the longitudinal direction R p0,2 (L) while this effect is not observed when the measurement is made on panels of width 760 mm. Thus within the scope of the invention it has been observed that there is an optimum range of elastic limit value specific to the width 1220 mm, which can not be interpreted by considerations based on the plasticization of the uncracked ligament. , these underlying the validity limits of ASTM E561. The present inventors have therefore established that sheets obtained by a process comprising casting, homogenization, hot rolling and optionally cold rolling, solution-setting, quenching and tempering have the advantageous properties when the composition and the combined so that the yield strength in the longitudinal direction R p0,2 (L) is between 395 and 435 MPa.

Pour certaines compositions selon l'invention, les tôles présentent les propriétés avantageuses lorsque le revenu est réalisé « au pic ». Dans le cadre de la présente invention et pour des raisons de simplification on appelle revenu réalisé « au pic » un revenu pour lequel la limite d'élasticité dans le sens transverse Rp0,2(TL) a une valeur d'au moins 95% de la limite d'élasticité dans le sens transverse Rp0,2(TL) obtenue pour un revenu ayant un temps équivalent à 155 °C de 48 h. Dans le cadre de la présente invention un revenu réalisé « au pic » est préféré. Pour d'autres compositions selon l'invention il peut être nécessaire de réaliser un sous-revenu pour atteindre la limite d'élasticité souhaitée. Cependant si le sous-revenu est trop important, certaines propriétés des tôles, notamment la stabilité thermique, ne sont pas satisfaisante. Par stabilité thermique on entend dans le cadre de la présente invention la stabilité des propriétés mécaniques lors d'une exposition en température représentative des conditions subies dans l'aviation civile, celle-ci étant par exemple simulée par un vieillissement de 1000 heures à 85 °C. On choisit donc d'effectuer si nécessaire un sous-revenu pour lequel la limite d'élasticité dans le sens transverse Rp0,2(TL) a une valeur comprise entre 88% et 94% et de préférence d'au moins 91% de la valeur obtenue pour un revenu ayant un temps équivalent à 155 °C de 48 h.
La teneur en cuivre des produits selon l'invention est comprise entre 2,6 et 3,0 % en poids. Dans une réalisation avantageuse de l'invention, la teneur en cuivre est comprise entre 2,8 et 3,0 % en poids. Dans un mode de réalisation avantageux de l'invention la teneur en cuivre est au plus de 2,95 % en poids et avantageusement au plus de 2,9 % en poids. Lorsque la teneur en cuivre est trop élevée, la limite d'élasticité Rp0,2(L) est trop élevée pour atteindre le domaine avantageux dans les conditions de sous-revenu selon l'invention. Lorsque la teneur en cuivre est trop faible, les caractéristiques mécaniques statiques minimales ne sont pas atteintes, même pour un revenu au pic.
La teneur en lithium des produits selon l'invention est comprise entre 0,5 et 0,8 % en poids. Avantageusement, la teneur en lithium est comprise entre 0,55 % et 0,75 % en poids. De manière préférée, la teneur en lithium est comprise entre 0,60 % et 0,73 % en poids. L'addition de lithium peut contribuer à l'augmentation de la résistance mécanique et de la ténacité, une teneur trop élevée ou trop faible ne permet pas d'obtenir une valeur élevée de ténacité et/ou une limite d'élasticité suffisante.
La teneur en magnésium des produits selon l'invention est comprise entre 0,2 et 0,7 % en poids, de préférence entre 0,25 et 0,50 % en poids et de manière préférée entre 0,30 et 0,45 % en poids. Dans un mode de réalisation avantageux de l'invention la teneur en magnésium est au plus de 0,4 % en poids.
La teneur en zirconium est comprise entre 0,06 et 0,20 % en poids et de préférence entre 0,10 et 0,18% en poids. Lorsqu'une structure granulaire essentiellement non-recristallisée est préférée, la teneur en zirconium est avantageusement comprise entre 0,14 et 0,17 % en poids.
La teneur en argent est comprise entre 0,1 et 0,4 % en poids. Dans une réalisation avantageuse de l'invention, la teneur en argent est comprise entre 0,2 et 0,3 % en poids. Dans un mode de réalisation de l'invention la teneur en argent est comprise entre 0,15 et 0,28 % en poids.
La teneur en titane est comprise entre 0,01 et 0,15 % en poids. L'addition de titane contribue à contrôler la structure granulaire, notamment lors de la coulée.For certain compositions according to the invention, the sheets have the advantageous properties when the income is made "at the peak". In the context of the present invention and for the sake of simplification, the so-called "peak" income is an income for which the yield strength in the transverse direction R p0,2 (TL) has a value of at least 95%. the yield strength in the transverse direction R p0.2 (TL) obtained for an income having a time equivalent to 155 ° C of 48 h. In the context of the present invention a "peak" income is preferred. For other compositions according to the invention it may be necessary to perform a sub-income to achieve the desired yield point. However, if the under-income is too important, certain properties of the sheets, in particular the thermal stability, are not satisfactory. In the context of the present invention, thermal stability is understood to mean the stability of the mechanical properties during a temperature exposure representative of the conditions experienced in civil aviation, this being for example simulated by an aging of 1000 hours at 85 ° C. vs. Therefore, it is chosen to perform, if necessary, an under-income for which the yield strength in the transverse direction R p0.2 (TL) has a value of between 88% and 94% and preferably at least 91% of the value obtained for an income having a time equivalent to 155 ° C of 48 hours.
The copper content of the products according to the invention is between 2.6 and 3.0% by weight. In an advantageous embodiment of the invention, the copper content is between 2.8 and 3.0% by weight. In an advantageous embodiment of the invention, the copper content is at most 2.95% by weight and advantageously at most 2.9% by weight. When the copper content is too high, the yield strength R p0.2 (L) is too high to reach the advantageous range under the under- feed conditions according to the invention. When the copper content is too low, the minimum static mechanical characteristics are not reached, even for a peak income.
The lithium content of the products according to the invention is between 0.5 and 0.8% by weight. Advantageously, the lithium content is between 0.55% and 0.75% by weight. Preferably, the lithium content is between 0.60% and 0.73% by weight. The addition of lithium can contribute to the increase of the mechanical strength and the toughness, a content that is too high or too low does not make it possible to obtain a high value of tenacity and / or a sufficient limit of elasticity.
The magnesium content of the products according to the invention is between 0.2 and 0.7% by weight, preferably between 0.25 and 0.50% by weight and preferably between 0.30 and 0.45% by weight. in weight. In an advantageous embodiment of the invention, the magnesium content is at most 0.4% by weight.
The zirconium content is between 0.06 and 0.20% by weight and preferably between 0.10 and 0.18% by weight. When an essentially non-recrystallized granular structure is preferred, the zirconium content is advantageously between 0.14 and 0.17% by weight.
The silver content is between 0.1 and 0.4% by weight. In an advantageous embodiment of the invention, the silver content is between 0.2 and 0.3% by weight. In one embodiment of the invention the silver content is between 0.15 and 0.28% by weight.
The titanium content is between 0.01 and 0.15% by weight. The addition of titanium helps to control the granular structure, especially during casting.

L'alliage peut optionnellement contenir au moins un élément choisi parmi Mn, V, Cr, Sc, et Hf, la quantité de l'élément, s'il est choisi, étant de 0,01 à 0,8 % en poids pour Mn, 0,05 à 0,2 % en poids pour V, 0,05 à 0,3 % en poids pour Cr, 0,02 à 0,3 % en poids pour Sc, 0,05 à 0,5 % en poids pour Hf. Ces éléments peuvent contribuer à contrôler la structure granulaire. Dans un mode de réalisation de l'invention, on n'ajoute pas de Mn, V, Cr ou Sc et leur teneur est inférieure ou égale à 0,05% en poids.The alloy may optionally contain at least one element selected from Mn, V, Cr, Sc, and Hf, the amount of the element, if selected, being from 0.01 to 0.8% by weight for Mn 0.05 to 0.2% by weight for V, 0.05 to 0.3% by weight for Cr, 0.02 to 0.3% by weight for Sc, 0.05 to 0.5% by weight for Hf. These elements can help control the granular structure. In one embodiment of the invention, Mn, V, Cr or Sc are not added and their content is less than or equal to 0.05% by weight.

De préférence, les teneurs en fer et en silicium sont chacune au plus de 0,1 % en poids. Dans une réalisation avantageuse de l'invention les teneurs en fer et en silicium sont au plus de 0,08 % et préférentiellement au plus de 0,04 % en poids. Une teneur en fer et en silicium contrôlée et limitée contribue à l'amélioration du compromis entre résistance mécanique et tolérance aux dommages.Preferably, the iron and silicon contents are each at most 0.1% by weight. In an advantageous embodiment of the invention, the iron and silicon contents are at most 0.08% and preferably at most 0.04% by weight. A controlled and limited iron and silicon content contributes to the improvement of the compromise between mechanical resistance and damage tolerance.

La teneur en zinc est inférieure à 0,2 % en poids et de préférence inférieure à 0,1 % en poids. La teneur en zinc est avantageusement inférieure à 0,04 % en poids.
Les impuretés inévitables sont maintenues à une teneur inférieure ou égale à 0,05% en poids chacune et 0,15% en poids au total.The zinc content is less than 0.2% by weight and preferably less than 0.1% by weight. The zinc content is advantageously less than 0.04% by weight.
The unavoidable impurities are maintained at a content of less than or equal to 0.05% by weight each and 0.15% by weight in total.

Le procédé de fabrication des tôles selon l'invention comprend des étapes d'élaboration, coulée, laminage, mise en solution, trempe traction contrôlée et revenu.
Dans une première étape, on élabore un bain de métal liquide de façon à obtenir un alliage d'aluminium de composition selon l'invention.
Le bain de métal liquide est ensuite coulé sous une forme de plaque de laminage.
La plaque de laminage est ensuite homogénéisée à une température comprise entre 450°C et 535° et de préférence entre 480 °C et 530°C. La durée d'homogénéisation est de préférence comprise entre 5 et 60 heures.The manufacturing process of the sheets according to the invention comprises steps of production, casting, rolling, dissolution, quenching controlled traction and income.
In a first step, a bath of liquid metal is produced so as to obtain an aluminum alloy of composition according to the invention.
The bath of liquid metal is then cast into a form of rolling plate.
The rolling plate is then homogenized at a temperature between 450 ° C and 535 ° and preferably between 480 ° C and 530 ° C. The homogenization time is preferably between 5 and 60 hours.

Après homogénéisation, la plaque de laminage est en général refroidie jusqu'à température ambiante avant d'être préchauffée en vue d'être déformée à chaud. Le préchauffage a pour objectif d'atteindre une température de préférence comprise entre 400 et 500 °C permettant la déformation par laminage à chaud.
Le laminage à chaud et optionnellement à froid est effectué de manière à obtenir une tôle d'épaisseur 0,5 à 8 mm. Des traitements thermiques intermédiaires pendant le laminage et/ou après le laminage peuvent être effectués dans certains cas. Cependant de manière préférée, le procédé ne comprend pas de traitement thermique intermédiaire pendant le laminage et/ou après le laminage. La tôle ainsi obtenue est ensuite mise en solution par traitement thermique entre 450 et 535 °C, de préférence pendant 5 min à 8 h, puis trempée. Il est connu de l'homme du métier que les conditions précises de mise en solution doivent être choisies en fonction de l'épaisseur et de la composition de façon à mettre en solution solide les éléments durcissants.
La tôle subit ensuite une déformation à froid par traction contrôlée avec une déformation permanente de 0,5 à 5 % et préférentiellement de 1 à 3 %. Des étapes connues telles que le laminage, le planage, le redressage la mise en forme peuvent être optionnellement réalisées après mise en solution et trempe et avant ou après la traction contrôlée, cependant la déformation à froid totale après mise en solution et trempe doit rester inférieure à 15% et de préférence inférieure à 10%. Des déformations à froid élevées après mise en solution et trempe causent en effet l'apparition de nombreuses bandes de cisaillement traversant plusieurs grains, ces bandes de cisaillement n'étant pas souhaitables.
Un revenu est réalisé comprenant un chauffage à une température comprise entre 130 et 170°C et de préférence entre 150 et 160°C pendant 5 à 100 heures et de préférence de 10 à 40h de façon à atteindre une limite d'élasticité dans le sens longitudinal Rp0,2(L) comprise entre 395 et 435 MPa. Dans un mode de réalisation de l'invention dans lequel la structure granulaire est essentiellement recristallisée, une limite d'élasticité dans le sens longitudinal Rp0,2(L) comprise 395 et 415 MPa peut être préférée dans certains cas. Dans un autre mode de réalisation de l'invention dans lequel la structure granulaire est essentiellement non-recristallisée, une limite d'élasticité dans le sens longitudinal Rp0,2(L) comprise 415 et 435 MPa peut être préférée dans certains cas.
De façon avantageuse, la composition permet d'atteindre la limite d'élasticité longitudinale désirée avec un temps équivalent à 155 °C inférieur à 48 h et de manière préférée inférieur à 30 h. De manière préférée, l'état métallurgique final est un état T8.
Le temps équivalent t i à 155 °C. est défini par la formule : t i = ∫ exp − 16400 / T dt exp − 16400 / T ref

Figure imgb0001
où T (en Kelvin) est la température instantanée de traitement du métal, qui évolue avec le temps t (en heures), et Tref est une température de référence fixée à 428 K. ti est exprimé en heures. La constante Q/R = 16400 K est dérivée de l'énergie d'activation pour la diffusion du Cu, pour laquelle la valeur Q = 136100 J/mol a été utilisée. Les présents inventeurs ont constaté en particulier que le domaine préféré de teneur en magnésium permet de limiter la durée du revenu en atteignant un compromis de propriétés favorable.
Dan un mode de réalisation de l'invention, un traitement thermique court est réalisé après traction contrôlée et avant revenu de façon à améliorer la formabilité des tôles. Les tôles peuvent ainsi être mises en forme par un procédé tel que l'étirage-formage avant d'être revenues.After homogenization, the rolling plate is generally cooled to room temperature before being preheated to be hot deformed. Preheating aims to achieve a temperature preferably between 400 and 500 ° C for deformation by hot rolling.
The hot rolling and optionally cold rolling is carried out so as to obtain a sheet thickness of 0.5 to 8 mm. Intermediate heat treatments during rolling and / or after rolling can be carried out in some cases. However, preferably, the process does not include intermediate heat treatment during rolling and / or after rolling. The sheet thus obtained is then put in solution by heat treatment between 450 and 535 ° C, preferably for 5 min to 8 h, and then quenched. It is known to those skilled in the art that the precise conditions of dissolution must be chosen according to the thickness and the composition so as to solubilize the hardening elements.
The sheet then undergoes cold deformation by controlled traction with a permanent deformation of 0.5 to 5% and preferably of 1 to 3%. Known steps such as rolling, planing, straightening and shaping may optionally be carried out after dissolution and quenching and before or after the controlled pull, however total cold deformation after dissolution and quenching must remain less than 15% and preferably less than 10%. High cold deformation after dissolution and quenching cause the appearance of many shear bands passing through several grains, these shear bands being undesirable.
An income is made comprising heating at a temperature between 130 and 170 ° C and preferably between 150 and 160 ° C for 5 to 100 hours and preferably from 10 to 40h so as to achieve a limit of elasticity in the direction longitudinal R p0.2 (L) between 395 and 435 MPa. In one embodiment of the invention in which the granular structure is substantially recrystallized, a yield strength in the longitudinal direction R p0.2 (L) of 395 and 415 MPa may be preferred in some cases. In another embodiment of the invention wherein the granular structure is substantially non-recrystallized, a yield strength in the longitudinal direction R p0.2 (L) of 415 and 435 MPa may be preferred in some cases.
Advantageously, the composition makes it possible to reach the desired longitudinal elasticity limit with a time equivalent to 155 ° C. of less than 48 hours and preferably less than 30 hours. Preferably, the final metallurgical state is a T8 state.
The time equivalent t i at 155 ° C. is defined by the formula: t i = ∫ exp - 16400 / T dt exp - 16400 / T ref
Figure imgb0001
 where T (in Kelvin) is the instantaneous metal processing temperature, which changes with time t (in hours), and T ref is a reference temperature set at 428 K. t i is expressed in hours. The Q / R constant = 16400 K is derived from the activation energy for Cu diffusion, for which Q = 136100 J / mol was used. The present inventors have found in particular that the preferred field of magnesium content makes it possible to limit the duration of the income by reaching a favorable property compromise.
In one embodiment of the invention, a short heat treatment is performed after controlled pulling and before tempering so as to improve the formability of the sheets. The sheets can thus be shaped by a process such as stretch-forming before being returned.

La structure granulaire la plus favorable dépend de l'épaisseur des produits.The most favorable granular structure depends on the thickness of the products.

Les tôles selon l'invention dont l'épaisseur est comprise entre 0,5 et 3,3 mm présentent avantageusement les propriétés suivantes

  • une ténacité en contrainte plane Kapp, mesurée sur des éprouvettes de type CCT760 (2ao = 253 mm), dans la direction L-T d'au moins 120 MPa √m et
  • une ténacité en contrainte plane Kapp, mesurée sur des éprouvettes de type CCT1220 (2ao = 253 mm), dans la direction L-T d'au moins 120 MPa √m.
Les présents inventeurs ont de plus constaté que pour les tôles de l'invention dont l'épaisseur est comprise entre 0,5 et 3,3 mm et de préférence entre 1,0 et 3,0 mm la ténacité en contrainte plane Kapp dans la direction L-T est plus élevée pour les tôles dont la structure est essentiellement recristallisée. Ainsi, les tôles dont l'épaisseur est comprise entre 0,5 et 3,3 mm et de préférence entre 1,0 et 3,0 mm et dont la structure granulaire est essentiellement recristallisée présentent avantageusement les propriétés suivantes :
  • une ténacité en contrainte plane Kapp, mesurée sur des éprouvettes de type CCT760 (2ao = 253 mm), dans la direction L-T d'au moins 140 MPa √m et
  • une ténacité en contrainte plane Kapp, mesurée sur des éprouvettes de type CCT1220 (2ao = 253 mm), dans la direction L-T d'au moins 150 MPa √m.
Les tôles selon l'invention dont l'épaisseur est comprise entre 3,4 et 6 mm et présentent avantageusement les propriétés suivantes
  • une ténacité en contrainte plane Kapp, mesurée sur des éprouvettes de type CCT760 (2ao = 253 mm), dans la direction L-T d'au moins 150 MPa √m et de préférence d'au moins 155 MPa √m et
  • une ténacité en contrainte plane Kapp, mesurée sur des éprouvettes de type CCT1220 (2ao = 253 mm), dans la direction L-T d'au moins 170 MPa √m et de préférence d'au moins 180 MPa √m.
Avantageusement la structure granulaire des tôles dont l'épaisseur est comprise entre 3,4 et 8 mm et de préférence entre 4 et 8 mm est essentiellement non-recristallisée.
La résistance à la corrosion intergranulaire des tôles selon l'invention est élevée. Dans un mode de réalisation préféré de l'invention, la tôle de l'invention peut être utilisée sans placage.The sheets according to the invention, the thickness of which is between 0.5 and 3.3 mm advantageously have the following properties:
  • a Kapp plane strain toughness, measured on specimens of the CCT760 type (2ao = 253 mm), in the LT direction of at least 120 MPa √m and
  • a Kapp plane strain toughness, measured on specimens of the CCT1220 type (2ao = 253 mm), in the LT direction of at least 120 MPa √m.
The present inventors have furthermore found that for the sheets of the invention, the thickness of which is between 0.5 and 3.3 mm and preferably between 1.0 and 3.0 mm, the Kapp plane stress toughness in the LT direction is higher for sheets whose structure is essentially recrystallized. Thus, the sheets whose thickness is between 0.5 and 3.3 mm and preferably between 1.0 and 3.0 mm and whose granular structure is substantially recrystallized advantageously have the following properties:
  • Kapp plane strain toughness, measured on specimens of the CCT760 type (2ao = 253 mm), in the LT direction of at least 140 MPa √m and
  • a Kapp plane stress toughness, measured on specimens of the CCT1220 type (2ao = 253 mm), in the LT direction of at least 150 MPa √m.
The sheets according to the invention, the thickness of which is between 3.4 and 6 mm, advantageously have the following properties:
  • Kapp plane stress toughness, measured on specimens of the CCT760 type (2ao = 253 mm), in the LT direction of at least 150 MPa √m and preferably at least 155 MPa √m and
  • Kapp plane stress toughness, measured on specimens of the CCT1220 type (2ao = 253 mm), in the LT direction of at least 170 MPa √m and preferably at least 180 MPa √m.
Advantageously, the granular structure of the sheets whose thickness is between 3.4 and 8 mm and preferably between 4 and 8 mm is essentially non-recrystallized.
The resistance to intergranular corrosion of the sheets according to the invention is high. In a preferred embodiment of the invention, the sheet of the invention can be used without plating.

L'utilisation de tôles selon l'invention dans un panneau de fuselage pour aéronef est avantageuse. Les tôles selon l'invention sont également avantageuses dans les applications aérospatiales telles que la fabrication de fusées.The use of sheets according to the invention in an aircraft fuselage panel is advantageous. The sheets according to the invention are also advantageous in aerospace applications such as the manufacture of rockets.

ExemplesExamples Exemple 1Example 1

Dans cet exemple, des tôles en alliage Al-Cu-Li ont été préparées. 5 plaques dont la composition est donnée dans le tableau 1 ont été coulées. Les compositions C, et E sont selon l'invention. Tableau 1. Composition en % en poids Référence Cu Li Mg Zr Ag Fe Si Ti A 3,2 0,73 0,68 0,14 0,26 0,03 0,04 0,03 B 3,0 0,70 0,64 0,17 0,27 0,02 0,03 0,03 C 3,0 0,73 0,35 0,15 0,27 0,02 0,03 0,03 D 2,7 0,75 0,58 0,14 0,28 0,03 0,02 0,03 E 2,9 0,73 0,45 0,14 0,29 0,04 0,02 0,03 Les plaques ont été homogénéisées 12 heures à 505 °C. Les plaques ont été laminées à chaud pour obtenir des tôles d'épaisseur comprise entre 4,2 à 6,3 mm. Certaines tôles ont ensuite été laminées à froid jusqu'à une épaisseur comprise entre 1,5 et 2,5 mm. Le détail des tôles obtenues et des conditions de revenu est donné dans le tableau 2. Tableau 2 : détail des tôles obtenues et des conditions de revenu Référence Epaisseur après laminage à chaud (mm) Epaisseur après laminage à froid (mm) Durée de revenu à 155 °C (h) A#1 4.2 - 36 A#2 4.4 1.5 36 B#1 4.6 - 36 B#2 4.4 1.5 36 C#1 4.3 - 24 C#2 4.4 1.5 24 D#1 4.3 - 40 D#2 6.3 2.5 40 E#1 4.3 - 36 E#2 6.3 2.5 36 In this example, sheets of Al-Cu-Li alloy have been prepared. 5 plates whose composition is given in Table 1 were cast. Compositions C and E are according to the invention. Table 1. Composition in% by weight Reference Cu Li mg Zr Ag Fe Yes Ti AT 3.2 0.73 0.68 0.14 0.26 0.03 0.04 0.03 B 3.0 0.70 0.64 0.17 0.27 0.02 0.03 0.03 VS 3.0 0.73 0.35 0.15 0.27 0.02 0.03 0.03 D 2.7 0.75 0.58 0.14 0.28 0.03 0.02 0.03 E 2.9 0.73 0.45 0.14 0.29 0.04 0.02 0.03 The plates were homogenized for 12 hours at 505 ° C. The plates were hot-rolled to obtain sheets having a thickness of between 4.2 and 6.3 mm. Some sheets were then cold rolled to a thickness of between 1.5 and 2.5 mm. The details of the sheets obtained and the income conditions are given in Table 2. Reference Thickness after hot rolling (mm) Thickness after cold rolling (mm) Duration of income at 155 ° C (h) A # 1 4.2 - 36 A # 2 4.4 1.5 36 B # 1 4.6 - 36 B # 2 4.4 1.5 36 C # 1 4.3 - 24 C # 2 4.4 1.5 24 D # 1 4.3 - 40 D # 2 6.3 2.5 40 E # 1 4.3 - 36 E # 2 6.3 2.5 36

Après laminage à chaud et éventuellement à froid, les tôles ont été mises en solution à 505 °C puis défripées, tractionnées avec un allongement permanent de 2% et revenues. Les conditions de revenu ne sont pas toutes identiques car l'augmentation de la limite d'élasticité avec la durée de revenu diffère d'un alliage à l'autre. On a cherché à obtenir une limite d'élasticité « au pic » tout en limitant la durée de revenu. Les conditions de revenu sont données dans le Tableau 2.After hot rolling and possibly cold rolling, the sheets were dissolved at 505 ° C and then de-wracked, stripped with a permanent elongation of 2% and returned. The income conditions are not all the same because the increase of the elasticity limit with the duration of income differs from one alloy to the other. We tried to obtain a "peak" elasticity limit while limiting the duration of income. The income conditions are given in Table 2.

La structure granulaire des échantillons a été caractérisée à partir de l'observation microscopique des sections transversales après oxydation anodique sous lumière polarisée. La structure granulaire des tôles était essentiellement non-recristallisée pour toutes les tôles à l'exception des tôles D#2 et E#2 pour lesquelles la structure granulaire était essentiellement recristallisée.
Les échantillons ont été testés mécaniquement afin de déterminer leurs propriétés mécaniques statiques ainsi que leur résistance à la propagation des fissures. La limite d'élasticité en traction, la résistance ultime et l'allongement à la rupture sont fournis dans le tableau 3. Tableau 3 : Caractéristiques mécaniques exprimées en MPa (Rp0,2, Rm) ou en pourcentage (A%) Référence Rp0,2(L) Rm(L) A%(L) Rp0,2 (TL) Rm(TL) A%(TL) Rp0,2 (TL) 48h 155°C Rp0,2(TL)/ Rp0,2(TL) 48h 155°C (%) A#1 469 513 12,2 439 481 15,8 457 96% A#2 475 522 11,7 441 489 14,0 B#1 431 483 13,5 419 462 16,1 425 99% B#2 431 486 12,9 414 460 17,1 C#1 430 471 13,6 411 455 15,5 434 95% C#2 423 472 12,2 399 451 15,9 D#1 420 462 13,0 384 428 16,3 407 94% D#2 403 437 11,6 371 428 13,9 E#1 453 487 12,5 428 464 15,9 433 99% E#2 433 464 11,4 395 458 11,4 The granular structure of the samples was characterized from microscopic observation of cross sections after anodic oxidation under polarized light. The granular structure of the sheets was essentially non-recrystallized for all sheets except D # 2 and E # 2 sheets for which the granular structure was essentially recrystallized.
The samples were mechanically tested to determine their static mechanical properties as well as their resistance to crack propagation. Tensile yield strength, ultimate strength and elongation at break are given in Table 3. Table 3: Mechanical characteristics expressed in MPa (R <sub> p0,2 </ sub>, R <sub> m </ sub>) or in percentage (A%) Reference R p0.2 (L) R m (L) A% (L) R p0.2 (TL) R m (TL) A% (TL) R p0.2 (TL) 48h 155 ° C R p0.2 (TL) / R p0.2 (TL) 48h 155 ° C (%) A # 1 469 513 12.2 439 481 15.8 457 96% A # 2 475 522 11.7 441 489 14.0 B # 1 431 483 13.5 419 462 16.1 425 99% B # 2 431 486 12.9 414 460 17.1 C # 1 430 471 13.6 411 455 15.5 434 95% C # 2 423 472 12.2 399 451 15.9 D # 1 420 462 13.0 384 428 16.3 407 94% D # 2 403 437 11.6 371 428 13.9 E # 1 453 487 12.5 428 464 15.9 433 99% E # 2 433 464 11.4 395 458 11.4

Le tableau 4 résume les résultats des essais de ténacité sur des éprouvettes CCT de largeur 760 mm pour ces échantillons. Tableau 4 résultats des courbes R pour les éprouvettes de largeur 760 mm. Référence Kapp [MPa√m] Kr60 [MPa√m] Δaeff max [mm] T-L L-T T-L L-T T-L L-T A#1 187 161 247 213 166 80 A#2 160 114 210 151 185 103 B#1 180 178 238 238 171 180 B#2 167 124 223 166 152 144 C#1 182 165 242 219 134 151 C#2 154 127 203 162 165 110 D#1 174 150 230 200 238 163 D#2 147 151 196 201 222 210 E#1 181 159 240 213 241 132 E#2 137 164 181 219 161 214 Le tableau 5 résume les résultats des essais de ténacité pour les courbes R obtenues avec des éprouvette CCT de largeur 1220 mm dans la direction L-T. Tableau 5 résultats des courbes R pour les éprouvettes de largeur 1220 mm dans la direction L-T. Référence Kapp [MPa√m] Kr60 [MPa√m] Δaeff max [mm] A#1 169 202 172 A#2 117 138 247 B#1 176 209 281 B#2 120 145 193 C#1 191 224 237 C#2 120 134 106 D#1 175 206 244 D#2 180 213 244 E#1 159 192 139 E#2 167 196 187 Table 4 summarizes the results of the tenacity tests on CCT test pieces of width 760 mm for these samples. Table 4 results of the R curves for 760 mm wide specimens. Reference Kapp [MPa√m] Kr60 [MPa√m] Δa eff max [mm] TL LT TL LT TL LT A # 1 187 161 247 213 166 80 A # 2 160 114 210 151 185 103 B # 1 180 178 238 238 171 180 B # 2 167 124 223 166 152 144 C # 1 182 165 242 219 134 151 C # 2 154 127 203 162 165 110 D # 1 174 150 230 200 238 163 D # 2 147 151 196 201 222 210 E # 1 181 159 240 213 241 132 E # 2 137 164 181 219 161 214 Table 5 summarizes the results of the toughness tests for the R curves obtained with CCT specimens of width 1220 mm in the LT direction. Reference Kapp [MPa√m] Kr60 [MPa√m] Δa eff max [mm] A # 1 169 202 172 A # 2 117 138 247 B # 1 176 209 281 B # 2 120 145 193 C # 1 191 224 237 C # 2 120 134 106 D # 1 175 206 244 D # 2 180 213 244 E # 1 159 192 139 E # 2 167 196 187

Les courbes R obtenues pour les tôles dont l'épaisseur est de l'ordre de 4 mm sont présentées sur la Figure 1. Les courbes R obtenues pour les tôles dont l'épaisseur est de 1,5 à 2,5 mm sont présentées sur la Figure 2. Les points obtenus après le dernier point valide selon la norme ASTM E561 ont été représentés.
De manière surprenante on constate que Kapp L-T est sensiblement identique pour des éprouvettes de largeur 760 mm et pour des éprouvettes de largeur 1220 mm pour certaines tôles alors que pour d'autres tôles Kapp L-T est plus faible pour des éprouvettes de largeur 760 mm et pour des éprouvettes de largeur 1220 mm.The curves R obtained for the sheets whose thickness is of the order of 4 mm are presented on the Figure 1 . R curves obtained for sheets with a thickness of 1.5 to 2.5 mm are presented on the Figure 2 . The points obtained after the last valid point according to the ASTM E561 standard were represented.
Surprisingly, it can be seen that K app LT is substantially identical for specimens with a width of 760 mm and for specimens with a width of 1220 mm for certain sheets, whereas for other sheets K app LT is weaker for specimens with a width of 760 mm. and for specimens with a width of 1220 mm.

Exemple 2Example 2

Dans cet exemple, on a étudié l'effet des conditions de revenu sur la ténacité de tôles en alliage Al-Cu-Li de composition selon l'invention.In this example, the effect of the income conditions on the toughness of alloy sheets Al-Cu-Li of the composition according to the invention has been studied.

Des tôles en alliage E ont après un traitement identique à celui de l'exemple 1 à l'exception du revenu, subi un revenu de 20h à 155 °C ou de 25 h à 155 °C.Alloy sheets E after treatment identical to that of Example 1 with the exception of income, incured an income of 20h at 155 ° C or 25 h at 155 ° C.

La structure granulaire n'est pas modifiée par ces conditions de revenu.
Les échantillons ont été testés mécaniquement afin de déterminer leurs propriétés mécaniques statiques ainsi que leur résistance à la propagation des fissures. La limite d'élasticité en traction, la résistance ultime et l'allongement à la rupture sont fournis dans le tableau 6. Tableau 6 Caractéristiques mécaniques exprimées en MPa (Rp0,2, Rm) ou en pourcentage (A%) Référence Durée de revenu A 155 °C Rp0,2(L) Rm(L) A%(L) Rp0,2 (TL) Rm(TL) A%(TL) Rp0,2(TL)/ Rp0,2(TL) 48h 155°C (%) E#1 20 h 422 470 13 390 440 16,5 90% E#2 20h 411 450 12,4 374 443 12 E#1 25 h 442 483 12,4 415 456 15,7 96% E#2 25 h 431 466 11,1 391 455 11,7 E#1 36 h 453 487 12,5 428 464 15,9 99% E#2 36 h 433 464 11,4 395 458 11,4 The granular structure is not modified by these income conditions.
The samples were mechanically tested to determine their static mechanical properties as well as their resistance to crack propagation. Tensile yield strength, ultimate strength and elongation at break are given in Table 6. Table 6 Mechanical characteristics expressed in MPa (R <sub> p0,2 </ sub>, R <sub> m </ sub>) or in percentage (A%) Reference Duration of income A 155 ° C R p0.2 (L) R m (L) A% (L) R p0.2 (TL) R m (TL) A% (TL) R p0.2 (TL) / R p0.2 (TL) 48h 155 ° C (%) E # 1 8 pm 422 470 13 390 440 16.5 90% E # 2 20h 411 450 12.4 374 443 12 E # 1 25 h 442 483 12.4 415 456 15.7 96% E # 2 25 h 431 466 11.1 391 455 11.7 E # 1 36 h 453 487 12.5 428 464 15.9 99% E # 2 36 h 433 464 11.4 395 458 11.4

Les courbes R caractérisées pour une largeur d'éprouvette de 760 mm et de 1220 mm dans la direction L-T sont données sur les Figures 3 (épaisseur 4,3 mm) et 4 (épaisseur 2,5 mm) et dans le Tableau 7. Les points obtenus après le dernier point valide selon la norme ASTM E561 ont été représentés. Tableau 7 résultats des courbes R pour les éprouvettes de largeur 760 mm et 1220 mm dans la direction L-T. Référence Durée de revenu à 155°C Eprouvette 760 mm Eprouvette 1220 mm Kapp [MPa√m] Kr60 [MPa√m] Δaeff max [mm] Kapp [MPa√m] Kr60 [MPa√m] Δaeff max [mm] E#1 20 h 168 219 173 180 216 208 E#2 20h 163 216 235 183 216 201 E#1 25 h 160 211 146 170 198 192 E#2 25 h 161 214 193 175 212 205 E#1 36 h 159 213 102 158 190 172 E#2 36 h 164 219 214 167 196 187 The curves R characterized for a specimen width of 760 mm and 1220 mm in the LT direction are given on the Figures 3 (thickness 4.3 mm) and 4 (thickness 2.5 mm) and in Table 7. The points obtained after the last valid point according to ASTM E561 were shown. Table 7 results of the R curves for the specimens of width 760 mm and 1220 mm in the direction LT. Reference Duration of income at 155 ° C 760 mm test tube 1220 mm test tube Kapp [MPa√m] Kr60 [MPa√m] Δa eff max [mm] Kapp [MPa√m] Kr60 [MPa√m] Δa eff max [mm] E # 1 8 pm 168 219 173 180 216 208 E # 2 20h 163 216 235 183 216 201 E # 1 25 h 160 211 146 170 198 192 E # 2 25 h 161 214 193 175 212 205 E # 1 36 h 159 213 102 158 190 172 E # 2 36 h 164 219 214 167 196 187

Les Figures 5 et 6 résument l'ensemble des résultats obtenus.The Figures 5 and 6 summarize all the results obtained.

Claims (12)

  1. Sheet having a thickness from 0.5 to 8 mm made of an aluminium based alloy comprising:
    2.6 to 3.0% by weight of Cu,
    0.5 to 0.8% by weight of Li,
    0.1 to 0.4% by weight of Ag,
    0.2 to 0.5% by weight of Mg,
    0.06 to 0.20% by weight of Zr,
    0.01 to 0.15% by weight of Ti,
    optionally at least one element chosen from among Mn, V, Cr, Sc and Hf, the quantity of the element, if it is chosen, being between 0.01 to 0.8% by weight for Mn, 0.05 to 0.2% by weight for V, 0.05 to 0.3% for Cr, 0.02 to 0.3% by weight for Sc, 0.05 to 0.5% by weight for Hf,
    a quantity of Zn less than 0.2% by weight, a quantity of Fe and Si less than or equal to 0.1% by weight each, the remainder being aluminium, and
    inevitable impurities with a content of less than or equal to 0.05% by weight each and less than or equal to 0.15% total,
    said sheet being obtained by a process including casting, homogenisation, hot rolling and optionally cold rolling, solution heat-treatment, quenching and aging, the composition and the aging being combined such that the yield stress in the longitudinal direction Rp0.2(L) is between 395 and 435 MPa.
  2. Sheet according to claim 1, in which the copper content is between 2.8 and 3.0% by weight and is preferably between 2.8 and 2.9% by weight.
  3. Sheet according to claim 1 or claim 2, in which the lithium content is between 0.55 and 0.75% by weight and is preferably between 0.60 and 0.73% by weight.
  4. Sheet according to any one of claims 1 to 3, in which the silver content is between 0.2 and 0.3% by weight.
  5. Sheet according to any one of claims 1 to 4, in which the magnesium content is between 0.25 and 0.50% by weight and is preferably between 0.30 and 0.45% by weight.
  6. Sheet according to any one of claims 1 to 5, in which aging is performed "at the peak".
  7. Sheet according to any one of claims 1 to 6, with a thickness equal to between 0.5 and 3.3 mm and that has the following properties:
    - fracture toughness in plane strain Kapp, measured on CCT760 type test pieces (2ao = 253 mm) along the L-T direction, equal to at least 120 MPa √m and
    - fracture toughness in plane strain Kapp, measured on CCT1220 type test pieces (2ao = 253 mm) along the L-T direction, equal to at least 120 MPa √m.
  8. Sheet according to claim 7, in which the granular structure is essentially recrystallized and that has the following properties:
    - fracture toughness in plane strain Kapp, measured on CCT760 type test pieces (2ao = 253 mm) along the L-T direction, equal to at least 140 MPa √m and
    - fracture toughness in plane strain Kapp, measured on CCT1220 type test pieces (2ao = 253 mm) along the L-T direction, equal to at least 150 MPa √m.
  9. Sheet according to any one of claims 1 to 6, in which the thickness is between 3.4 and 6 mm and that has the following properties:
    - fracture toughness in plane strain Kapp, measured on CCT760 type test pieces (2ao = 253 mm) along the L-T direction equal to at least 150 MPa √m and preferably equal to at least 155 MPa √m and
    - fracture toughness in plane strain Kapp, measured on CCT1220 type test pieces (2ao = 253 mm) along the L-T direction equal to at least 170 MPa √m and preferably equal to at least 180 MPa √m.
  10. Sheet according to any one of claims 1 to 6, in which the thickness is between 3.4 and 8 mm and preferably between 4 and 8 mm and in which the granular structure is essentially non-crystallised.
  11. Method of manufacturing a Sheet according to any one of claims 1 to 10 with a thickness of 0.5 to 8 mm made of an aluminium based alloy in which the following steps are performed successively:
    a) a molten metal bath is prepared comprising:
    2.6 to 3.0% by weight of Cu,
    0.5 to 0.8% by weight of Li,
    0.1 to 0.4% by weight of Ag,
    0.2 to 0.5% by weight of Mg,
    0.06 to 0.20% by weight of Zr,
    0.01 to 0.15% by weight of Ti,
    optionally at least one element chosen from among Mn, V, Cr, Sc and Hf, the quantity of the element, if chosen, being between 0.01 and 0.8% by weight for Mn, 0.05 to 0.2% by weight for V, 0.05 to 0.3% for Cr, 0.02 to 0.3% by weight for Sc, 0.05 to 0.5% by weight for Hf,
    a quantity of Zn less than 0.2% by weight, a quantity of Fe and Si less than or equal to 0.1% by weight each, the remainder being aluminium, and
    inevitable impurities with a content of less than or equal to 0.05% by weight each and less than or equal to 0.15% total,
    b) a slab is cast starting from said molten metal bath,
    c) said slab is homogenised at a temperature of between 450°C and 535°C;
    d) said slab is hot rolled and optionally cold rolled into a sheet with a thickness of between 0.5 mm and 8 mm
    e) said sheet is solution heat treated at a temperature of between 450°C and 535°C and quenched;
    h) said sheet undergoes controlled stretched with a permanent deformation set of 0.5 to 5%,
    the total cold deformation after solution heat treatment and quenching being less than 15%,
    i) aging is performed comprising heating to a temperature of between 130 and 170°C and preferably between 150 and 160°C for 5 to 100 hours and preferably for 10 to 40 h, the composition and the aging being combined such that the yield stress in the longitudinal direction Rp0.2(L) is between 395 and 435 MPa.
  12. Use of a sheet according to any one of claims 1 to 10, in a fuselage panel for an aircraft.
EP14719034.2A 2013-04-03 2014-04-01 Aluminium-copper-lithium alloy sheets for producing aeroplane fuselages Active EP2981631B1 (en)

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FR1300763A FR3004196B1 (en) 2013-04-03 2013-04-03 ALUMINUM-COPPER-LITHIUM ALLOY SHEETS FOR THE MANUFACTURE OF AIRCRAFT FUSELAGES.
PCT/FR2014/000069 WO2014162068A1 (en) 2013-04-03 2014-04-01 Aluminium-copper-lithium alloy sheets for producing aeroplane fuselages

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CA3032261A1 (en) 2016-08-26 2018-03-01 Shape Corp. Warm forming process and apparatus for transverse bending of an extruded aluminum beam to warm form a vehicle structural component
EP3529394A4 (en) 2016-10-24 2020-06-24 Shape Corp. Multi-stage aluminum alloy forming and thermal processing method for the production of vehicle components
FR3059578B1 (en) * 2016-12-07 2019-06-28 Constellium Issoire METHOD FOR MANUFACTURING A STRUCTURE ELEMENT
US20180291489A1 (en) * 2017-04-11 2018-10-11 The Boeing Company Aluminum alloy with additions of copper, lithium and at least one alkali or rare earth metal, and method of manufacturing the same
DE102017116785B3 (en) * 2017-07-25 2019-01-24 P3 Aero Systems Gmbh Method for checking the radio characteristics of a means of transport
US20190233921A1 (en) * 2018-02-01 2019-08-01 Kaiser Aluminum Fabricated Products, Llc Low Cost, Low Density, Substantially Ag-Free and Zn-Free Aluminum-Lithium Plate Alloy for Aerospace Application
FR3082210B1 (en) * 2018-06-08 2020-06-05 Constellium Issoire THIN SHEETS OF ALUMINUM-COPPER-LITHIUM ALLOY FOR THE MANUFACTURE OF AIRCRAFT FUSELAGES
FR3104172B1 (en) 2019-12-06 2022-04-29 Constellium Issoire Aluminum-copper-lithium alloy thin sheets with improved toughness and manufacturing method

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WO2014162068A1 (en) 2014-10-09
BR112015024820A2 (en) 2017-07-18
CN105102647A (en) 2015-11-25
BR112015024820B1 (en) 2020-05-12
US20160060741A1 (en) 2016-03-03
CA2907807C (en) 2021-06-01
CN105102647B (en) 2017-10-13

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