Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
  • C22F1/057—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with copper as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/12—Alloys based on aluminium with copper as the next major constituent
  • C22C21/16—Alloys based on aluminium with copper as the next major constituent with magnesium

Definitions

• the invention relates to rolled, extruded or forged products of hardened AlCuMg alloy. and towed, intended for the manufacture of aircraft structural elements, in particular skin panels and airfoil stiffeners, and having, by compared to the products of the prior art used for the same application, a improved compromise between the properties of mechanical strength, formability, toughness, tolerance for damage and residual stresses.
• the designation of alloys and metallurgical states corresponds to the nomenclature of Aluminum Association, taken up by European standards EN 515 and EN 573.
• the wings of large commercial aircraft have a top (or upper surface) made of a skin made from thick alloy sheets 7150 in state T651, or in alloy 7055 in state T7751 or 7449 in state T7951, and stiffeners made from profiles of the same alloy, and a lower part (or lower surface) made of a skin made from thick sheets of alloy 2024 to state T351 or 2324 in state T39, and stiffeners made from profiles of same alloy.
• the two parts are assembled by side members and ribs.
• This alloy is intended more particularly for thin sheets for fuselage and has a toughness and improved crack propagation resistance compared to 2024.
• the applicant's patent application EP 0731185 relates to an alloy, registered subsequently under n ° 2024A, of composition: Si ⁇ 0.25 Fe ⁇ 0.25 Cu: 3.5 - 5 Mg: 1 - 2 Mn ⁇ 0.55 with the relation: 0 ⁇ Mn - 2Fe ⁇ 0.2 Thick sheets of this alloy have both improved toughness and reduced level of residual stresses, without loss on other properties.
• Patents US 5863359 and US 5865914 of Alcoa relate respectively to an aircraft wing comprising an intrados made of an alloy of composition: Cu: 3.6 - 4 Mg: 1 - 1.6 (pref: 1.15 - 1.5) Mn: 0.3 - 0.7 (pref: 0.5 - 0.6) Zr: 0, 05 - 0.25 and preferably Fe ⁇ 0.07 and Si ⁇ 0.05 having both the following properties: R 0.2 (LT)> 60 ksi (414 MPa) and K 1 C (LT)> 38 ksi ⁇ inch (42 MPa ⁇ m) , and a method of manufacturing a lower surface element having a R 0.2 (LT)> 60 ksi comprising the casting of an alloy of the above composition, homogenization between 471 and 482 ° C, hot transformation at a temperature> 399 ° C, solution dissolving above 488 ° C, quenching, work hardening preferably more than 9% cold and at least 1% traction.
• the object of the invention is therefore to provide AlCuMg alloy products in the state cold hardened and deformed, intended for the manufacture of lower surfaces of aircraft wings, and having, compared to similar products of the prior art, a more favorable for all the properties of use: mechanical resistance, speed of crack propagation, toughness, fatigue strength, and stress rate residual.
• the subject of the invention is a rolled, extruded or forged product of AlCuMg alloy, treated by dissolution, quenching and cold traction, intended for the manufacture of aircraft structural elements, of composition (% by weight): Fe ⁇ 0.15 Si ⁇ 0.15 Cu: 3.8 - 4.4 (pref .: 4.0 - 4.3) Mg: 1.0 - 1.5 Mn: 0.5 - 0.8 Zr : 0.08 - 0.15 other elements: ⁇ 0.05 each and ⁇ 0.15 in total, having a ratio R m (L) / R 0.2 (L) of the breaking strength in the direction L at the elastic limit in direction L, greater than 1.25 (and preferably 1.30).
• the chemical composition of the product differs from that of the usual 2024 by a content reduced in iron and silicon, a higher manganese content and an addition of zirconium. Compared to 2034, we have a lower manganese content and a slightly reduced copper content. Compared to the composition of the alloys described in patents US 5863359 and US 5865914, the copper content is higher, which which compensates, for mechanical strength, cold work hardening less high after quenching. Surprisingly, this narrow area of composition (especially with regard to manganese), associated with modifications of the manufacturing range, leads, compared to the prior art, to an improvement significant of the compromise between mechanical strength, elongation and tolerance damage to the operating conditions of a large civil aircraft.
• the manufacturing process involves the casting of plates, in the case where the product to be manufactured is a rolled sheet, or of billets in the case where it is a extruded section or a forged part.
• the plate or billet is scalped, then homogenized between 450 and 500 ° C.
• the hot transformation is then carried out by rolling, spinning or forging. This transformation is preferably carried out at a higher temperature than the temperatures usually used, the outlet temperature being greater than 420 ° C. and preferably at 440 ° C. so as to obtain on the treated product a structure which is not very recrystallized, with a rate recrystallization at quarter thickness less than 20%, and preferably 10%.
• the rolled, extruded or forged semi-finished product is then placed in solution between 480 and 505 ° C., so that this dissolution is as complete as possible, that is to say that the maximum of potentially soluble phases, in particular the precipitates Al 2 Cu and Al 2 CuMg, ie effectively in solid solution.
• the quality of the dissolution can be assessed by differential enthalpy analysis (AED) by measuring the specific energy using the area of the peak on the thermogram. This specific energy should preferably be less than 2 J / g.
• the products according to the invention have significantly improved static mechanical characteristics compared to the 2024-T351 alloy, currently used for the lower surfaces of an aircraft wing, and hardly weaker than those of 2034-T351.
• the high plastic spacing and elongation of the material results in excellent cold formability.
• the toughness, measured by the critical intensity factors of stress in plane stress K c and K co is more than 10% higher than that of 2024 and 2034, and the speed of crack propagation da / dn is clearly improved by compared to these two alloys, in particular for the high values of ⁇ K, and for loadings with variable amplitude.
• the fatigue life times, measured on notched test pieces taken at mid-thickness in the L direction, are also improved by more than 20% compared to 2024 and 2034.
• alloy 2024, 2034 and alloy according to the invention We poured 3 plates of width 1450 mm and thickness 446 mm respectively of alloy 2024, 2034 and alloy according to the invention.
• the chemical compositions (% by weight) of the alloys are given in Table 1: alloy Yes Fe Cu Mg Mn Zr 2024 0.12 0.20 4.06 1.36 0.54 0.002 2034 0.05 0.07 4.30 1.34 0.98 0.104 invention 0.06 0.08 4.14 1.26 0.65 0.102
• the results are given in Table 3: Alloy Thickness K c K c0 2024 40 143.4 105.2 2034 40 128.8 97.8 Invention 40 179.7 122 2034 15 136.4 103.7 Invention 15 173.6 124.3
• the arrow f is measured in the following manner.
• Each bar is machined to mid-thickness and the deflection is measured at mid-length of the bar. This deflection is representative of the level of internal stresses of the sheet and of its ability not to deform during machining.
• the distance 1 between the supports was 180 mm and the length b of the bars 200 mm.
• the machining is a progressive mechanical machining with passes of approximately 2 mm.
• the measurement of the deflection at mid-length is carried out using a comparator with a resolution of one micron.
• the results concerning the arrows and the recrystallization rates are given in Table 6.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Heat Treatment Of Steel (AREA)

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Citations (7)

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• 1999
  • 1999-08-18 FR FR9910682A patent/FR2789406B1/fr not_active Expired - Lifetime
  • 1999-10-13 GB GB9924277A patent/GB2346381A/en not_active Withdrawn
• 2000
  • 2000-01-10 US US09/479,924 patent/US6602361B2/en not_active Expired - Lifetime
  • 2000-02-01 EP EP00420020A patent/EP1026270B1/de not_active Expired - Lifetime
  • 2000-02-01 DE DE60019655T patent/DE60019655T2/de not_active Expired - Lifetime
• 2003
  • 2003-06-19 US US10/464,501 patent/US20030217793A1/en not_active Abandoned

Patent Citations (7)

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