Classifications

• • 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
  • C22C21/10—Alloys based on aluminium with zinc 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
• • 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 a new manufacturing process for rolled, spun or forged products made of high tenacity and high fatigue strength aluminum alloy, especially Al-Zn-Cu-Mg type alloy, and products obtained by this method, including structural elements made from such products and intended for the construction of aircraft. It is based on the introduction of barium in an aluminum-based liquid alloy.
• Patent FR 1 507 664 (Metallgesellschaft Aktiengesellschaft) states that in Al-Si type casting alloys with a Si content between 5 and 14%, the addition of strontium and / or barium (Ba) at a rate of 0.001 to 2% leads to obtaining a fine eutectic structure; this effect is reinforced by the simultaneous addition of beryllium (Be).
• Patent EP 1 230 409 B1 (RUAG Components) teaches that the addition of barium (between 0.1 and 0.8%) to aluminum alloys with a silicon content of at least 5% improves their performance. thixotropic forming ability.
• US Patent 4,711,762 proposes the addition of strontium (Sr), antimony (Sb) and / or calcium (Ca) to an Al-Zn-Cu type alloy.
• Sr strontium
• Sb antimony
• Ca calcium
• Patent GB 505 728 (L'Electrique) mentions an aluminum-based alloy intended for the manufacture of drawn wire and containing Zn 5 - 6.5%, Mg 2 - 3.5%, Si 0.15 - 0.5%, Mn 0.25 - 1%, Mo 0.20 - 0.60%, Co 0.20 - 0.60%, K 0 - 0.12%, Ba 0 - 0.25%, Sb 0 - 0.1%, WO - 0.50%, Ni 0 - 1%, Ti 0 - 0.40%, in which the barium is introduced in the form of chloride to smooth the dirt; this barium content in the resulting metal product would also have a hardening effect.
• US Pat. No. 4,631,172 discloses an aluminum-based alloy used as a sacrificial anode containing 3.2% Zn, 1.5% magnesium, 0.02% indium, , 01% tin and / or calcium and barium, the latter in a content of between 0.002% and 1.0%.
• Another composition contains Zn 2.5%, Mg 2.5%, In 0.02%, Ca and / or Ba 0.005 - 1.0%, Si 0.004 - 1.0%.
• Patent Application JP 61 096052 A discloses a sacrificial anode aluminum alloy composition Zn 1 - 10%, Mg
• CH 328 148 discloses the introduction of a barium hydride in a zinc-aluminum alloy with at least 40% zinc.
• US Patent 3,310,389 mentions the presence of barium, calcium and / or strontium in a total content of up to 0.2% in an aluminum-based alloy containing Cu 2.2 - 2.7% , Mg 1.3 - 1.7%, Si 0.12 - 0.25%, Fe 0.9 - 1.2%, Ni 0.9 - 1.4%, Ti 0.02 - 0.15% .
• the patent RU 2 184 167 discloses an aluminum-based alloy for structural application in aeronautical construction of composition Cu 3.0 - 3.8%, Li 1.4 - 1.7% , Zr 0.0001 - 0.04%, Sc 0.16 - 0.35%, Fe
• UK Patent No. 1,678,080 discloses an aluminum-based alloy of composition Cu 5.0 - 5.5%, Cr 0.1 - 0.4%, Mn 0.2 - 0 , 6%, Zr 0.1 - 0.4%, Ti 0.1 - 0.4%, Cd 0.05 - 0.25%, Sr or Ba 0.01 - 0.1%.
• the subject of the invention is a process for manufacturing wrought products made of aluminum alloy of the Al-Cu, Al-Cu-Mg or Al-Zn-Cu-Mg type with high tenacity and fatigue resistance, comprising casting of a raw form (such as a spinning billet, forge billet or a rolling plate) and the hot deformation of said raw form, said method being characterized in that 0.005 to 0 are introduced into said alloy , 1% barium.
• a raw form such as a spinning billet, forge billet or a rolling plate
• the invention also relates to a structural element for aircraft construction, made from a rolled product, spun or forged alloy Al-Cu type, Al-Cu-Mg or Al-Zn-Cu-Mg which contains between 0.005 and 0.1% of barium.
• a product or structural element obtainable by the process according to the present invention, can be advantageously used in applications which require a high tenacity and / or a high resistance to fatigue, such as for example wing elements. extrados or intrados (wing skin), stiffeners, longitudinal members, or ribs, or elements for bulkheads (bulkheads). Description of figures
• FIG. 1 shows the morphology of the Al-Fe-Cu type phases in the casting state after selective dissolution of the matrix in a 7449 alloy (scanning electron micrographs with a field effect gun (FEG). SEM):
• FIG. 2 shows the morphology of Al-Fe-Cu type phases:
• Figure 3 shows the morphology of Al-Fe-Cu type phases in a sample that shows both morphologies:
• Alloy 7449 (with added barium) with coexistence within the same structure of an unmodified form ("without Ba”, on the left) and a modified form ("with Ba”, on the right) of the AlFeCu phase ( If) (magnification: see the bar corresponding to 10 ⁇ m in the left base of the legend).
• Figures 4 and 5 show the morphology of Al-Fe-Cu type phases in a 7449 alloy with barium added. Note the morphology “sea urchin-shaped” ( Figure 4) and “broccoli-shaped” ( Figure 5) eutectic compounds. Alloy 7449 (with added barium) according to the invention (magnification: see the bar at the bottom left of FIG. 4 which represents 1 ⁇ m). Sample P4078-1 # 37.
• FIG. 6 shows the morphology of Al-Fe-Cu phases in the form of platelets in a 7449 alloy according to the state of the art.
• FIG. 7 gives a comparison of the toughness K app measured on a CCT type specimen of width 406 mm and thickness 6.35 mm (taken at a quarter thickness). according to Ro.2 (L). Alloy 7449. It is noted that the products according to the invention
• the static mechanical characteristics i.e., the ultimate strength R m , the yield point R p0 , 2, and the elongation at break A, are determined by a tensile test according to EN 10002-1 standard, the location and direction of specimen collection being defined in EN 485-1.
• Fatigue strength is determined by ASTM E 466 test, fatigue crack propagation speed (so-called da / dn test) according to ASTM E 647, and critical stress intensity factor Kc, Kco or K app. according to ASTM E 561.
• the term "spun product” includes so-called “stretched” products, that is, products that are made by spinning followed by stretching.
• wrought product a product having undergone a deformation operation after its solidification
• this deformation operation may be, without this list being exhaustive, rolling, forging, spinning, drawing and drawing.
• structural element or “structural element” of a mechanical construction a mechanical part whose failure is likely to endanger the security of the said construction, its users, its users or others.
• these structural elements include the elements that make up the fuselage (such as fuselage skin (fuselage skin in English), stiffeners or stringers, bulkheads, fuselage (circumferential frames), wings (such as wing skin), stiffeners (stiffeners), ribs (ribs) and spars) and empennage including horizontal stabilizers and vertical stabilizers (horizontal or vertical stabilizers) as well as the floor beams, the seat tracks and the doors: here we call the "integral structure” the structure of a part of an airplane that has been designed so as to ensure as much continuity as possible of the material over as large a dimension as possible in order to reduce the number of mechanical points of assembly.An integral structure may be manufactured either by machining in the mass, either by using shaped parts obtained for example by spinning, forging or molding, or by welding structural elements made of
• the present invention can be applied to all Al-Cu, Al-Cu-Mg or Al-Zn-Cu-Mg type hardening wrought aluminum alloys. More particularly, the Al-Cu type alloys to which the present invention may be applied are alloys comprising between 1 and 7% Cu, and more particularly between 3 and 5.5% Cu.
• the invention can be applied to alloys of the Al-Cu-Mg type comprising between 1 and 7% of Cu and between 0.2 and 2% of Mg, and more particularly between 3.5 and 5.5% of Cu and between 1 and 2% Mg, it being understood that the content of iron and silicon must not exceed 0.30% for each of these elements.
• These alloys may contain other alloying elements and impurities up to about 3% in total. Among these elements are manganese, lithium, zinc.
• the alloy may also contain the usual additions of zirconium, titanium or chromium.
• the process according to the invention can advantageously be applied to alloys of the Al-Mg-Cu type or alloys of the 2xxx series, in particular to those conventionally used in aeronautical construction: 2024, 2024A, 2056, 2022, 2023, 2139, 2124, 2224, 2324, 2424, 2524 and their variants.
• the so-called free-cutting alloys which include additions of Pb, Bi or Sb in order to obtain easy splitting chips such as 2004, 2005 and 2030 are excluded here.
• the alloys of Al-Zn-Cu-Mg type to which the present invention can be applied are alloys comprising between 4 and 14% of zinc, and more particularly between 7 and 10.5% of zinc, between 1 and 3% of Cu , and more particularly between 1.4 and 2.5% of Cu, and between 1 and 3% of Mg, and more particularly between 1.7 and 2.8% of Mg, it being understood that the content of iron and silicon must not exceed 0.30% for each of these elements.
• These alloys can contain other alloying elements and impurities up to 2% in total. Among these elements is manganese.
• the alloy may also contain the usual additions of zirconium, titanium or chromium.
• the process according to the invention can advantageously be applied to alloys of the 7xxx series, in particular to those conventionally used in aeronautical construction: 7010, 7050, 7055, 7056, 7150, 7040, 7075, 7175, 7475, 7049, 7149, 7249 , 7349, 7449 and their variants.
• the method according to the invention comprises casting a raw form, such as a rolling plate, a spinning billet or a forge billet, by any known method. This raw form is then deformed hot, for example by rolling, spinning or forging.
• the invention is not applicable to products produced by fast solidification, ie with a solidification rate typically greater than 600 ° C / min, which lead to a significantly different microstructure.
• the process may comprise other stages of thermal or mechanical treatment, the more often homogenization, cold deformation, dissolution, artificial or natural aging, intermediate or final annealing.
• These eutectic phases may be of Al-Fe-Cu type (in alloys with addition of barium) or Al-Fe-Si-Cu (in alloys without addition of barium). It is observed that in the presence of barium, silicon seems to disappear precipitates.
• the properties of the product which are improved by the process according to the invention are in particular the tenacity, the fatigue strength, and the resistance to the propagation of cracks da / dn with a high stress intensity factor ⁇ K. This effect is particularly pronounced in a non-recrystallized structure.
• an alloy of barium with silicon is added.
• An alloy of Si (70%) - Ba (30%) is suitable; this product is commercially available.
• the silicon content of the alloy can be between 50% and 90%.
• Other alloys of the same type containing in addition iron up to a content of 20% are also applicable to the invention, the silicon content can then vary between 30% and 90% and the barium content can then vary between 10 and 40%.
• barium is added in metallic form or, preferably, in the form of an intermetallic compound or alloy with one or more of the constituents of the aluminum alloy in question.
• an Al-Ba or Zn-Ba type alloy is suitable.
• These intermetallic compounds or alloys can be obtained directly by reducing the barium oxide BaO with aluminum or zinc according to known methods.
• the amounts of barium used are very small, preferably less than 0.1% and even more preferentially less than 0.05%. A value between 0.005% and 0.03% may be suitable.
• account must be taken of the relatively low solubility of this alloy in liquid aluminum.
• the second embodiment is particularly advantageous when it is applied to an aluminum alloy which has a relatively high silicon content, for example of the order of 0.10%.
• the metal barium is expensive.
• the first embodiment uses a less expensive barium alloy, but leads to the increase of the silicon content and possibly iron in the aluminum alloy. However, it is surprising to note that this increase in the silicon content and possibly iron does not degrade the toughness or the resistance to fatigue. This is due to the fact that silicon and possibly iron are not incorporated in the same way: the morphology of the phases is significantly modified.
• Such a semi-finished product or structural element has a yield strength R p o.2 (L) greater than 600 MPa.
• the product according to the invention is more resistant to exfoliation corrosion (EXCO test), determined on test pieces taken at mid-thickness, than a corresponding product without barium.
• EXCO test exfoliation corrosion
• the product according to the invention can have many possible uses, and it is particularly advantageous to use said product as a structural element in aircraft construction, and especially as an extrados wing element, as part of lower sails, as a sail-skin element, as a stiffener, as a spar, as a rib or as an element for bulkheads.
• the method according to the invention has several advantages.
• the mode of introduction of barium according to the invention avoids the use of hydrides, which increase the residual hydrogen content, may cause pores in the solidified metal.
• Barium neutralizes the detrimental effect of residual silicon in aluminum-based structural hardening alloys, resulting in improved toughness, including Kic and K app .
• Barium also improves resistance to corrosion, including exfoliating corrosion.
• Al-Zn-Cu-Mg were cast under similar conditions, one with added barium as a parent alloy containing about 28% Ba and 72% Si (added at a liquid metal temperature of about 75 %). C), one without adding barium.
• the liquid metal was treated with an Ar + Cl 2 mixture. The casting temperature was
• the alloy was refined with 0.8 kg / t AT5B and cast at 685 ° C with a speed of 65 mm / min in rolling plates. After cooling and scalping, the plates were homogenized at 463 ° C. and hot-rolled at a temperature between 420 and 410 ° C. The sheets obtained were dissolved for 6 hours at 120 ° C. and then for 17 hours at room temperature. 150 ° C. The final product was thus metallurgical T351.
• the silicon content of the type 7449 aluminum alloy increases from 0.04% to 0.09% and that of Fe increases from 0.03% to 0.06%
• the microstructure of the sample with added barium shows eutectic compounds "in the shape of sea urchins" ( Figure 4) or "broccoli-shaped” (see Figure 5).
• the microstructure of the barium-free sample added revealed eutectic compounds in the form of platelets ( Figure 6).
• the static mechanical characteristics were measured in the T79 state on a sheet of thickness 40 mm.
• Exfoliation corrosion resistance (EXCO) results obtained on mid-thickness specimens show that the 7449 barium alloy (EXCO: EA performance) is more resistant to exfoliating corrosion than the barium-free reference product (performance EXCO: EB). The resistance to stress corrosion is also slightly improved.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Forging (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)
• Powder Metallurgy (AREA)
• Prevention Of Electric Corrosion (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)
• Continuous Casting (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)

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• 2004
  • 2004-06-25 FR FR0406957A patent/FR2872172B1/fr not_active Expired - Fee Related
• 2005
  • 2005-06-22 CA CA002570618A patent/CA2570618A1/fr not_active Abandoned
  • 2005-06-22 AT AT05778801T patent/ATE417136T1/de not_active IP Right Cessation
  • 2005-06-22 DE DE602005011619T patent/DE602005011619D1/de active Active
  • 2005-06-22 US US11/571,189 patent/US20070243097A1/en not_active Abandoned
  • 2005-06-22 CN CNB2005800212752A patent/CN100564571C/zh not_active Expired - Fee Related
  • 2005-06-22 WO PCT/FR2005/001572 patent/WO2006010817A1/fr active Application Filing
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