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
  • C22F1/047—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 magnesium 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
• • 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
  • C22C21/06—Alloys based on aluminium with magnesium 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
  • C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
  • C22C21/08—Alloys based on aluminium with magnesium as the next major constituent with silicon
• • 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

Definitions

• the invention relates to method of manufacturing Al-Mg-Sc sheet products.
• the Al-Mg-Sc sheet products obtained by this method are ideally for use in aerospace applications, and the like.
• aluminium alloy designations and temper designations refer to the Aluminium Association designations in Aluminium Standards and Data and the Registration Records, as published by the Aluminium Association in 2011 and are well known to the person skilled in the art.
• US Patent No. 5,624,632 discloses an aluminium alloy product, the composition is substantially zinc-free and lithium-free, and has 3% to 7% Mg, 0.05% to 0.2% Zr, 0.2% to 1.2% Mn, up to 0.15% Si, and 0.05% to 0.5% of a dispersoid-forming element selected from the group consisting of: Sc, Er, Y, Gd, Ho or Hf, balance aluminium and inevitable impurities.
• the aluminium alloy product is said to be especially suited for applications where damage tolerance is required.
• US Patent No. 6,139,653 discloses aluminium alloy consisting of 4% to 8% Mg, 0.05% to 0.6% Sc, 0.1 to 0.5% Mn, 0.05% to 2% Cu or Zn, 0.05% to 0.20% Hf or Zr, and the balance aluminium and incidental impurities. It further discloses an aluminium alloy consisting of 4% to 8% Mg, 0.05% to 0.6% Sc, 0.05-2% Cu or Zn, 0.05-0.20% Hf or Zr, and the balance aluminium and incidental impurities.
• US Patent No. 6,531,004 discloses a weldable, corrosion-resistant aluminium alloy having 5% to 6% Mg, 0.05% to 0.15% Zr, 0.05% to 0.12% Mn, 0.01% to 0.2% Ti, 0.05% to 0.5% by total of Sc and Tb, and at least 0.1% to 0.2% Cu or 0.1 % to 0.4% Zn, the balance being aluminium and unavoidable contaminants not exceeding 0.1 % Si. It is reported in this document that in the sensitised condition due to the low Mn-content an improved corrosion resistance is obtained.
• Part of the invention is that a feedstock for rolling is being provided and having a gauge in the range of 4 mm to 30 mm and being made from an aluminium alloy having at least 2.5% to 6% Mg and 0.05% to 1% Sc, and preferably also having at least Zr in a range of 0.03% to 0.4%.
• the feedstock is prior to cold rolling not being subjected to a thermal or thermo-mechanical process at temperature in the range of 325°C to 450°C, for example as part of a pre-heat cycle or homogenisation cycle, so as to avoid the formation of coarse Al 3 (Sc,Zr) precipitates that do not dissolve in any further processing steps and having a detrimental effect on the mechanical properties.
• Suitable feedstock can be obtained for example by continuous casting techniques, e.g. roll casting, belt casting or strip casting, having favourable high cooling rates and resulting in as-cast strip in a gauge range of 4 mm to 30 mm, e.g. about 10 mm or about 15 mm. This continuous cast strip can be coiled and stored for subsequent cold rolling in accordance with this invention.
• the size of the dispersoids should be as fine as possible, viz. these dispersoids should be smaller than 20 nm, and more preferably smaller than 15 nm.
• the feedstock is free from any Al 3 (Sc,Zr) dispersoids having a size larger than 20 nm, and preferably is free from any such dispersoids larger than 15 nm.
• the cold rolling can be carried out in one or more cold deformation steps depending on the starting gauge and the desired final gauge.
• each cold rolling step introduces a gauge reduction of maximum 35%.
• the desired final gauge after cold rolling is in the range of about 0.8 mm to 6 mm, and preferably in the range of 0.8 mm to 5 mm.
• the cold rolling is carried out at ambient temperature.
• the cold rolling to final gauge is carried out using at least one cold rolling step at a sub-zero temperature.
• Preferably all cold rolling steps leading to the final gauge of the sheet product have been carried out at sub-zero temperature. It has been found that cold rolling at sub-zero temperatures lead an increased ductility compared to cold rolling at ambient temperature. Also the strength of the sheet product can be increased. Furthermore, it may lead to improved surface quality and to less edge cracking during rolling.
• a processing temperature of the sheet product is meant of less than -25°C, and typically in a range of -200°C to -25°C, and more preferably in the range -200°C to -40°C.
• Cooling to the rolling temperature can be done by placing or spraying cold media onto the sheet using liquid nitrogen or dry ice and which are preferred, but it should be understood that also other types of cooling liquids (dry ice/ethanol, dry ice/acetone, liquid nitrogen/solvent, and the like) or gases can be used.
• cooling liquids dry ice/ethanol, dry ice/acetone, liquid nitrogen/solvent, and the like
• gases gases can be used.
• a cold rolling process and apparatus can be used as disclosed in international patent application WO-02/087803-A1 published on 07 November 2002 and incorporated herein in its entirety by reference.
• the sheet products are annealed at a temperature in a range of about 225°C to 400°C.
• the annealing temperature is at least 250°C and more preferably at least 275°C.
• a preferred upper-limit for the annealing temperature is about 375°C, and more preferably 325°C.
• Annealing that these temperatures are to be carried out typically for several hours in the range of about 1.5 to 16 hours, for example for about 2 hours or about 8 hours.
• the annealing results in the formation of the fine, densely-distributed Al 3 (Sc,Zr) precipitates in a nanostructured matrix.
• the formation of the fine, densely-distributed Al 3 (Sc,Zr) precipitates having a size of less than 12 nm is believed to contribute to the observed enhancement in the ductility of the nanostructured alloy sheet as measured by an improvement in the uniform tensile elongation.
• the aluminium sheet product can be formed into a panel, for example a complex curved shape of a structural panel of an aircraft, e.g. fuselage panel or a wing stringer, using a roll forming operation, a stretch-forming operation or a creep-forming operation.
• a panel for example a complex curved shape of a structural panel of an aircraft, e.g. fuselage panel or a wing stringer, using a roll forming operation, a stretch-forming operation or a creep-forming operation.
• the aluminium alloy has a composition of, in wt.%,
• inevitable impurities are present in a range of each up to 0.05% and in total up to 0.25%.
• Iron can be present in a range of up to about 0.40% and preferably is kept to a maximum of about 0.25%.
• a typical preferred iron level would be in the range of up to 0.12%, for example about 0.03% or about 0.05%.
• Silicon can be present in a range of up to about 0.25% and preferably is kept to a maximum of about 0.2%.
• a typical preferred Si level would be in the range of up to 0.12%, for example at a level of about 0.04%.
• zinc can be present up to about 0.4%.
• Zn can be present as a strengthening element in a range of about 0.4% to 2%.
• a relatively high amount of Zn also has a positive effect of the corrosion resistance of the aluminium alloy.
• a more preferred upper-limit for the Zn-content is about 0.7%.
• Cu can be present in the AlMgSc-alloy as strengthening element in a range up to about 2%. However, in applications of the alloy product where the corrosion resistance is a very critical engineering property, it is preferred to maintain the Cu at a low level of 0.25% or less, and preferably at a level of 0.1 % or less, and more preferably at a level of 0.04% or less.
• Li can be present in the AlMgSc alloy in a range of up to about 3% to provide the product with a low density, high strength, good weldability, and a very good natural ageing response. If purposively added, the preferred Li level is in the range of 0.5 to 3%, and more preferably in a range of about 0.8 to 2%. In an alternative embodiment there is no purposive addition of Li and should be kept at impurity level of maximum 0.05%, and more preferably the aluminium alloy is lithium-free.
• the AlMgSc alloy preferably has one or more elements selected from the group consisting of Zr 0.03% to 0.4%, Cr 0.03% to 0.4%, and Ti 0.005% to 0.3%.
• the preferred alloying element is Zr.
• a preferred range of the Zr addition is about 0.05% to 0.2%.
• one or more elements selected from the group of (erbium, dysprosium, gadolinium, and hafnium) can be added whereby the total amount, if added, is in a range of 0.03% to 0.3%.
• the listed elements can be added to substitute in part the Sc in the AlMg alloy.
• Ti may be added to the AlMgSc alloy as strengthening element or for improving the corrosion resistance or for grain refiner purposes.
• the aluminium alloy consisting of, in wt. %:
• the aluminium alloy has a chemical composition within the ranges of AA5024.
• the aluminium alloy product manufactured with this invention is especially suited for aerospace application, particularly fuselage skin, and for lower wing sections, upper wing sections, stringers, spars, pressure bulkheads of many airplanes.
• AlMgSc-alloy of composition 3% Mg, 0.6% Mn, 0.3% Sc, 0.15% Zr, 0.15% Fe, 0.05% Ti, 0.05% Si had been produced by strip casting and having a gauge of 10 mm.
• Table 1 Tensile properties of the sheet materials. Tensile properties Rolling practice Annealing Rp [MPa] Rm [MPa] Ag [%] A [%] Previous HR+CR 2h@320°C 365 429 5.1 6.3 Invention RT Rolling 2h@320°C 384 428 7.2 9.0 Cryorolling 2h@320°C 382 429 7.5 10.6

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• Chemical & Material Sciences (AREA)
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• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
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• Crystallography & Structural Chemistry (AREA)
• Metal Rolling (AREA)

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Citations (8)

• 2011
  • 2011-07-13 EP EP11173741A patent/EP2546373A1/fr not_active Withdrawn
• 2012
  • 2012-06-15 WO PCT/EP2012/061397 patent/WO2013007471A1/fr active Application Filing

Patent Citations (8)

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