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

Definitions

• the subject of the invention is a process for manufacturing wrought aluminum alloy and magnesium products, also known as aluminum alloy of the 5XXX series according to the Aluminum Association, more particularly Al alloy products. Containing high strength, high toughness and good workability.
• the subject of the invention is also products that can be obtained by said process as well as the use of these products intended for transport and in particular for aeronautical and space construction.
• Wrought aluminum alloy products are developed in particular to produce structural elements intended for the transport industry, in particular for the aeronautical industry and the space industry.
• the performances of the products must be constantly improved and new alloys are developed to present, in particular, a high mechanical resistance, a low density, a high tenacity, an excellent resistance to corrosion and a very good aptitude for the implementation. form.
• the shaping can be carried out hot, for example by creep forming, and the mechanical properties should not decrease at the end of this shaping.
• Al-Mg alloys have been extensively studied in the transport industry, particularly in road and maritime transport, because of their excellent use properties such as weldability, corrosion resistance and formability, especially in the states. little hardened such as the state O and the state Hl 1 1. These alloys, however, have a relatively low mechanical strength for the aerospace industry and the space industry.
• US Pat. No. 5,624,632 describes an alloy of composition 3 - 7% by weight of magnesium, 0.03 - 0.2% by weight of zirconium, 0.2 - 1.2% by weight of manganese, up to 0.15% by weight of silicon and 0.05 - 0, 5% by weight of a dispersoid-forming element in the group scandium, erbium, yttrium, gadolinium, holmium and hafnium.
• US Pat. No. 6,695,935 describes an alloy of composition, in% by weight, Mg 3.5-6.0, Mn 0.4-1.2, Zn 0.4-1.5, Zr 0.25 max., Cr 0.3 max., Ti 0.2 max., Fe 0.5 max., If 0.5 max., Cu 0.4 max, one or more elements in the group: Bi 0.005-0.1, Pb 0.005-0.1, Sn 0.01-0.1, Ag 0.01 -0.5, Se 0.01-0.5, Li 0.01-0.5, V 0.01 - 0.3, Ce 0.01 -0.3, Y 0.01-0.3, and Ni 0.01 -0.3.
• the patent application WO 01/12869 describes an alloy of composition in% by weight 1.0-8.0% Mg, 0.05-0.6% Se, 0.05-0.20% Hf and / or 0.05-0.20% Zr, 0.5-2.0% Cu and / or 0.5-2.0% Zn and in addition 0.1-0.8% by weight of Mn.
• the patent application WO2007 / 020041 describes an alloy of composition, in% by weight, Mg 3.5 to 6.0, Mn 0.4 to 1.2, Fe ⁇ 0.5, Si ⁇ 0.5, Cu ⁇ 0.15, Zr ⁇ 0.5, Cr ⁇ 0.3, Ti 0.03 at 0.2, Se ⁇ 0.5, Zn ⁇ 1.7, Li ⁇ 0.5, Ag ⁇ 0.4, optionally one or more elements forming dispersoids in the group erbium, yttrium, hafnium, vanadium, each ⁇ 0.5% by weight.
• a first object of the invention is a method of manufacturing a wrought aluminum alloy product in which:
• Mn 0.3-0.8; preferably 0.5 - 0.7
• Zr 0.07-0.15, preferably 0.08-0.12;
• the said raw form is homogenized at a temperature of between 370 ° C. and 450 ° C., for a duration of between 2 and 50 hours, such that the time equivalent to 400 ° C. is between 5 and 100 hours,
• a second subject of the invention is a wrought product made of aluminum alloy of composition, in% by weight,
• Mn 0.3 - 0.8, preferably 0.5-0.7;
• Zr 0.07-0.15, preferably 0.08-0.12;
• the static mechanical characteristics in tension in other words the tensile strength R m , the conventional yield stress at 0.2% elongation R P o, 2, and the elongation at break A%, are determined by a tensile test according to standard NF EN ISO 6892-1 (2009), the sampling and the direction of the test being defined by the standard EN 485-1 (2016).
• the toughness under plane stress is determined by means of a curve of the stress intensity factor KR as a function of the effective crack extension Aa s known as the curve R, according to ASTM E 561 (2010).
• the critical stress intensity factor Kc in other words the intensity factor that makes the crack unstable, is calculated from the curve R.
• the stress intensity factor Kco is also calculated by assigning the length from initial crack to critical load, at the beginning of the monotonic charge. These two values are calculated for a specimen of the required form.
• Ka PP represents the Kco factor corresponding to the specimen that was used to perform the R curve test.
• Kefr represents the Kc factor corresponding to the specimen that was used to perform the R curve test. the value of KR for an effective crack extension
• the granular structure of the samples is characterized in the mid-thickness LxTC plane, t / 2, and is quantitatively evaluated after an anodic oxidation and polarized metallographic etching:
• the term "essentially non-recrystallized" is used when the granular structure has no or few recrystallized grains, typically less than 20%, preferably less than 15% and even more preferably less than 10% of the grains are recrystallized;
• recrystallized is used when the granular structure has a large proportion of recrystallized grains, typically more than 50%, preferably more than 60% and more preferably still more than 80% of the grains are recrystallized.
• a "structural element” or “structural element” of a mechanical construction is called a mechanical part for which the static and / or dynamic mechanical properties are particularly important for the performance of the structure and for which a structural calculation is usually prescribed or realized. These are typically elements whose failure is likely to endanger the safety of said construction, its users, its users or others.
• these structural elements include the elements that make up the fuselage (such as fuselage skin, (skin fuselage), stiffeners or stringers, bulkheads, frames circumferential frames, wings (such as upper or lower wing skin), stiffeners, ribs, floor (floor beams) and seat rails (seat tracks)) and the empennage composed in particular of horizontal and vertical stabilizers (horizontal or vertical stabilizers), as well as the doors.
• fuselage such as fuselage skin, (skin fuselage), stiffeners or stringers, bulkheads, frames circumferential frames, wings (such as upper or lower wing skin), stiffeners, ribs, floor (floor beams) and seat rails (seat tracks)
• empennage composed in particular of horizontal and vertical stabilizers (horizontal or vertical stabilizers), as well as the doors.
• the present inventors have found that for a composition according to the invention, it is possible to obtain, by controlling the homogenization conditions, an advantageous wrought product, the mechanical properties of which have a compromise between mechanical strength and toughness useful for aeronautical construction and whose properties are stable after heat treatment corresponding to hot forming conditions.
• an aluminum-based liquid metal bath is produced with a composition, in% by weight, Mg: 3.8-4.2; Mn: 0.3 - 0.8, preferably 0.5-0.7; Se, 0.1-0.3; Zn: 0.1 -0.4; Ti: 0.01 - 0.05, preferably 0.015-0.030; Zr: 0.07-0.15, preferably 0.08-0.12; Cr: ⁇ 0.01; Fe: ⁇ 0.15; If ⁇ 0.1 other elements ⁇ 0.05 each and ⁇ 0.15 in combination, remain aluminum.
• composition according to the invention is remarkable because of a small addition of titanium of 0.01-0.05 and preferably 0.015-0.030% by weight and preferably 0.018-0.024% by weight and absence of chromium addition, the content of which is less than 0.01% by weight.
• High static mechanical properties Rp0.2, Rm
• the addition of Mn, Se, Zn and Zr is necessary to achieve the desired compromise between strength, toughness and hot workability.
• the iron content is kept below 0.15% by weight and preferably below 0.1% by weight.
• the silicon content is kept below 0.1% by weight and preferably below 0.05% by weight.
• the presence of iron and silicon above the maximums indicated has an adverse impact especially on toughness.
• the other elements are impurities, that is to say elements whose presence is not intentional, their presence must be limited to 0.05% each and 0.15% in combination and preferably to 0.03%. each and 0.10% in combination.
• said crude form is homogenized at a temperature of between 370 ° C. and 450 ° C., for a period of between 2 and 50 hours, such that the time equivalent to 400 ° C. is between 5 and 100 hours,
• the homogenization time is between 5 and 30 hours.
• the time equivalent to 400 ° C is between 6 and 30 hours.
• a too low temperature and / or homogenization time do not allow to form dispersoids to control the recrystallization.
• temperature and / or homogenization time are too high, the properties obtained are not stable at the typical hot forming temperature of 300 - 350 ° C, especially since the products recrystallize.
• the hot deformation can be carried out directly after homogenization without cooling to room temperature, the initial temperature of hot deformation to be between 350 and 450 ° C.
• the raw form can be cooled to ambient temperature after homogenization and the raw form can be heated to an initial heat distortion temperature of between 350 and 450 ° C.
• reheating it should be ensured that the time equivalent to 400 ° C during reheating is low, typically less than 10%, compared with the equivalent time at 400 ° C during homogenization.
• the temperature of the metal may in some cases increase, however it should be ensured that the time equivalent to 400 ° C during the hot deformation is low, typically less than 10%, compared with the equivalent time at 400 ° C during homogenization. In any case, it is preferable that the temperature during hot deformation does not exceed 460 ° C and preferably does not exceed 440 ° C.
• the wrought is made by rolling to obtain a sheet. According to this first mode, the final thickness of the sheet obtained is less than 12 mm.
• the wrought is made by extrusion to obtain a profile.
• the heat deformation is typically carried out to a thickness of about 4 mm and then the cold deformation for a thickness of between 0.5 and 4 mm.
• the permanent deformation is typically less than 2%, preferably about 1%.
• an annealing is carried out at a temperature of between 300 ° C. and 350 ° C.
• the duration of the annealing is typically between 1 and 4 hours.
• This annealing mainly has a function of stabilizing the mechanical properties so that they do not evolve during subsequent shaping at a similar temperature.
• the products according to the invention have the advantage of having very stable mechanical properties at this temperature.
• the static mechanical property variation is at most 10% and preferably at most 6% after annealing between 300 and 350 ° C.
• the static mechanical property variation is at most 40% and preferably at most 30% after annealing between 300 and 350 ° C .
• the process according to the invention it is therefore possible in the context of the process according to the invention not to perform stabilization annealing and proceed directly to the shaping, in particular for products whose final thickness is obtained by hot rolling. Thanks to the process according to the invention, the products according to the invention retain a substantially non-recrystallized granular structure after annealing between 300 and 350 ° C.
• the sheets having a thickness of less than 12 mm obtained by the process according to the invention are advantageous, preferably having the following characteristics:
• the sheets with a thickness of less than 4 mm obtained by the process according to the invention have a conventional yield strength measured at 0.2% of elongation in the TL direction of at least 300 MPa, and preferably of at least 320 MPa, these properties being achieved even in the case where the optional annealing step at a temperature between 300 ° C and 350 ° C is performed.
• the sheets according to the invention preferably have advantageous toughness properties, in particular:
• the toughness KR in the direction T-L is greater than that in the direction L-T.
• the products according to the invention can be shaped at a temperature between 300 ° C and 350 ° C to obtain structural elements for aircraft, preferably fuselage elements.
• a conventional yield stress measured at 0.2% LT elongation is at least 250 MPa, and preferably at least 260 MPa and / or
• a conventional yield strength measured at 0.2% elongation in the L direction is at least 260 MPa, and preferably at least 270 MPa.
• Table 1 Composition in% by weight (spectrophotometer analysis of optical spark emissions, S-OES).
• the alloy plate A was homogenized for 5 h at 445 ° C. while the alloy plate B was homogenized for 15 h at 515 ° C.
• the plates thus homogenized were hot rolled directly after homogenization with a hot rolling start temperature of 415 ° C for plate A and 480 ° C for plate B, to obtain sheets having a thickness of 4 mm.
• Table 2 Static mechanical characteristics obtained for the various sheets in the state such as hot rolled (LAC) and in the annealed state (4h at 325 ° C).
• the 4 mm sheets were cold-rolled to a thickness of 2 mm in three passes without intermediate heat treatment, and were then planed. Different Heat treatments were performed after cold rolling. The results of tensile mechanics are shown in Table 3.
• Table 3 Static mechanical characteristics obtained for the different cold-rolled sheets which have undergone annealing under different conditions.
• the granular structure of the sheets was observed after a metallographic attack of anodic oxidation type and under polarized light after cold rolling (LAF) or after cold rolling and annealing for 2 hours at 325 ° C.
• LAF cold rolling
• Table 4 presents the results of the microstructural observations of sheets of composition A and B in the cold rolling raw states and after annealing treatment (2h 325 ° C.).
• the alloy A according to the invention has excellent resistance to recrystallization.
• Example 2
• Table 5 Conditions of transformation of different blocks of alloy A 0 The mechanical properties were measured on the sheets such as rolled or having undergone a treatment. The results are shown in Table 6
• Table 6 Static mechanical characteristics obtained for the various sheets in the state such as hot rolled (LAC) and in the annealed state (4h at 325 ° C).
• the products obtained by the process according to the invention (CD3, CF1, CF2, CF3) have advantageous mechanical characteristics, especially Rp0.2 in the L direction of at least 260 MPa after LAC and after annealing for 4 hours at 325.

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• Chemical & Material Sciences (AREA)
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• Physics & Mathematics (AREA)
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• Crystallography & Structural Chemistry (AREA)
• Heat Treatment Of Steel (AREA)
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• 2016
  • 2016-10-17 FR FR1660049A patent/FR3057476B1/fr active Active
• 2017
  • 2017-10-17 CN CN201780064272.XA patent/CN109844151B/zh active Active
  • 2017-10-17 CA CA3037115A patent/CA3037115A1/fr active Pending
  • 2017-10-17 EP EP17794387.5A patent/EP3526358B1/de active Active
  • 2017-10-17 WO PCT/FR2017/052856 patent/WO2018073533A1/fr active Application Filing
  • 2017-10-17 US US16/342,096 patent/US20190249285A1/en not_active Abandoned
  • 2017-10-17 BR BR112019006323A patent/BR112019006323A2/pt not_active Application Discontinuation
• 2023
  • 2023-01-18 US US18/156,074 patent/US20230151473A1/en active Pending

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