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
• • 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
• • 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
  • C22C21/18—Alloys based on aluminium with copper as the next major constituent with zinc

Definitions

• the present invention generally relates to thick plates of Al-Cu-Li alloy and in particular such products used in the aeronautical and aerospace industry.
• Products, especially thick rolled products, typically at least 50 mm thick, of aluminum alloy are developed to produce by cutting, surfacing or mass machining of high strength parts intended in particular for the aeronautical industry. , the aerospace industry or mechanical engineering.
• Aluminum alloys containing lithium are very interesting in this respect, since lithium can reduce the density of aluminum by 3% and increase the modulus of elasticity by 6% for each weight percent of lithium added.
• their performance compared to other properties of use must reach that of commonly used alloys, in particular in terms of a compromise between the static mechanical strength properties (yield strength, resistance to rupture) and the properties of damage tolerance (toughness, resistance to initiation and propagation of fatigue cracks), these properties being in general antinomic.
• these properties must in particular be obtained at quarter and at mid-thickness.
• These products must also have sufficient corrosion resistance, be able to be shaped according to the usual processes and have low residual stresses so that they can be machined integrally.
• No. 5,032,359 discloses a broad 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.
• US Pat. No. 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, Se, V, especially having KJC toughness ( L)> 37.4 MPaVm for a limit of elasticity R p o, 2 (L)> 448.2 MPa (products with a thickness greater than 76.2 mm) and in particular a tenacity KJC (L)> 38.5 MPaVm for a yield strength R p o , 2 (L)> 489.5 MPa (products less than 76.2 mm thick).
• the AA2050 alloy comprises (% by weight): (3.2-3.9) Cu, (0.7-1.3) Li, (0.20-0.6) Mg, (0.20-0 7) Ag, 0.25max. Zn, (0.20-0.50) Mn, (0.06-0.14) Zr and AA2095 (3.7-4.3) Cu, (0.7-1.5) Li, (0.25-0.8) Mg, (0.25-0.6) Ag, 0.25max. Zn, 0.25 max. Mn, (0.04-0.18) Zr.
• AA2050 alloy products are known for their quality in terms of static strength and toughness, especially for thick rolled products and are selected in some aircraft.
• the interval between two operations of control of the structure depends on the speed and the way the cracks propagate in the materials used for the structure and it is advantageous to use products for which the cracks spread slowly and predictably.
• the improvement of the propagation properties of fatigue cracks thus concerns in particular the speed of propagation and the direction of propagation.
• the patent application WO2009103899 thus describes a substantially unrequistallized laminated product comprising in% by weight: 2.2 to 3.9% by weight of Cu, 0.7 to 2.1% by weight of Li; 0.2 to 0.8% by weight of Mg; 0.2 to 0.5% by weight of Mn; 0.04 to 0.18% by weight of Zr; less than 0.05%) by weight of Zn and, optionally, 0.1 to 0.5% by weight of Ag, the remainder being aluminum and unavoidable impurities, having a low propensity for crack bifurcation when a fatigue test in the direction of LS.
• Crack bifurcation, crack deflection, crack rotation, or crack branching are terms used to express the propensity for the propagation of a crack to deviate from the expected plane of fracture perpendicular to the load applied during a stress test. fatigue or tenacity.
• the crack bifurcation occurs at the microscopic scale ( ⁇ 100 ⁇ ), at the mesoscopic scale (100-1000 ⁇ ) or at the macroscopic scale (> 1 mm), but it is only considered harmful if the direction of the crack remains stable after bifurcation (macroscopic scale).
• crack bifurcation is used here for the macroscopic crack bifurcation during fatigue or toughness testing in the LS direction, from the S direction to the L direction which occurs for rolled products whose thickness is from minus 50 mm.
• a laminated aluminum lithium alloy product for aeronautical applications, particularly for fully machined parts, having improved fatigue crack propagation properties and having a low propensity for crack bifurcation.
• a first object of the invention is a laminated product having a thickness of at least 50 mm of aluminum alloy comprising, in% by weight, 2.2 to 3.9% Cu, 0.7 to 1.8% Li, 0.1 to 0.8% Mg, 0.1 to 0.6% Mn; 0.01 to 0.15% of Ti, at least one element selected from Zn and Ag, the amount of said element if it is chosen being 0.2 to 0.8% for Zn and 0.1 to 0.5% for Ag, optionally at least one element selected from Zr, Cr, Se, Hf, and V, the amount of said element if it is chosen being 0.04 to 0.18% for Zr, 0.05 to 0.3% for Cr and Se, 0.05 to 0.5% for Hf and for V, less than 0.1% of Fe, less than 0.1% of Si remains aluminum and unavoidable impurities, of a content less than 0 , 05% each and 0.15% in total; characterized in that its granular structure is predominantly recrystallized between 1 ⁇ 4 and 1 ⁇ 2 thickness.
• a second object of the invention is a method of manufacturing a sheet according to the invention, comprising:
• step b) the controlled traction of said sheet with a permanent deformation of 1 to 7%
• step c) the income of said sheet by heating between 130 ° C and 160 ° C for 5 to 60 hours, characterized in that the sum of the content of elements Zr, Cr, Se, Hf, and V is less than 0.08 % by weight and / or in that in step b) the homogenization temperature is at least 520 ° C for a period of at least 20 hours and in step c) the outlet temperature hot rolling is less than 390 ° C.
• Yet another object of the invention is the use of a sheet according to the invention for producing an aircraft wing spar or an airplane wing rib.
• Figure 1 Schematic of the CT specimen used for fatigue crack propagation tests. The dimensions are given in mm.
• Figure 5 Different modes of crack propagation on the test piece CT according to Figure 1, having a rear face (1), a lower face (22) and an upper face (21). Directions S and L are indicated.
• Figure 5a low propensity for crack bifurcation and fracture by the rear face (1)
• 5b high propensity for crack bifurcation and fracture by the lower face (22)
• 5c low propensity for crack bifurcation, fracture by the upper face (21) but distance d on which the crack is neither in the initial direction S nor in the direction L of at least 5 mm.
• the cracking rate (da / dN) is determined according to ASTM E 647.
• the stress intensity factor (KJC) is determined according to ASTM E 399.
• rolled products with a thickness of at least 50 mm in aluminum-copper-lithium-magnesium-manganese alloy have advantageous properties when the granular structure is predominantly recrystallized between the 1 ⁇ 4 and the 1 ⁇ 2 thickness.
• the fatigue crack propagation resistance is improved while the compromise between mechanical strength and toughness is not significantly degraded.
• granular structure predominantly recrystallized between the 1 ⁇ 4 and 1 ⁇ 2 thickness is meant a granular structure whose recrystallization rate is at least 50% between 1 ⁇ 4 and 1 ⁇ 2 thickness that is to say at least 50% of grains between 1 ⁇ 4 and 1 ⁇ 2 thickness are recrystallized.
• the recrystallization rate between 1 ⁇ 4 and 1 ⁇ 2 thickness is at least 55%.
• the thickness of the products according to the invention is between 80 and 130 mm.
• the products according to the invention have a copper content of between 2.2 and 3.9% by weight.
• the copper content is at least 2.8% by weight and preferably at least 3.2% by weight.
• the maximum copper content is 3.8% by weight.
• the products according to the invention have a lithium content of between 0.7 and 1.8% by weight.
• the lithium content is at least 0.8% by weight and preferably at least 0.9% by weight.
• the maximum lithium content is 1.5% by weight, preferably 1.1%, and most preferably 0.95% by weight.
• the products according to the invention have a magnesium content of between 0.1 and 0.8% by weight.
• the magnesium content is at least 0.2% by weight and preferably at least 0.3% by weight.
• the maximum magnesium content is 0.7% by weight and preferably 0.6% by weight.
• the products according to the invention have a manganese content of between 0.1 and 0.6% by weight.
• the manganese content is at least 0.2% by weight and preferably at least 0.3% by weight.
• the maximum content of manganese is 0.5% by weight and preferably 0.4% by weight.
• the products according to the invention contain at least one element chosen from Zn and Ag, the quantity of said element, if it is chosen, being 0.2 to 0.8% for Zn and 0.1 to 0.5% for Ag, these elements being particularly useful for hardening the alloy. Preferably, only one of these elements is added, the second being maintained at a content of less than 0.05% by weight.
• the products according to the invention contain at least one element chosen from Zr, Cr, Se, Hf, and V, the quantity of said element, if it is chosen being 0.04 to 0.18% and preferably 0.04 to 0.15% for Zr, 0.05 to 0.3% for Cr and Se, 0.05 to 0.5% for Hf and V.
• These elements contribute to the control of the granular structure.
• the predominantly recrystallized granular structure according to the invention is obtained by a selection of the transformation parameters, in particular the conditions of homogenization and hot rolling.
• the sum of the content of the elements Zr, Cr, Se, Hf, and V is preferably at least 0.08% by weight.
• the Zr content in this first embodiment is from 0.08 to 0.10% by weight.
• the predominantly recrystallized granular structure according to the invention is obtained by limiting the content of elements acting on the control of the granular structure.
• the sum of the content of elements Zr, Cr, Se, Hf, and V is less than 0.08% by weight.
• the Zr content is 0.04 to 0.07 wt.%, And preferably 0.05 to 0.07 wt.%.
• there is no addition of Zr the Zr content is less than 0.05% by weight, preferably less than 0.04% by weight and more preferably still lower. to 0.02% by weight.
• the products according to the invention contain 0.01 to 0.15% by weight of titanium, this element being especially useful for the control of the granular structure during casting.
• the titanium content is between 0.01 and 0.05% by weight.
• the content of iron and silicon impurities must be limited to avoid degradation of the properties of fatigue and toughness.
• the products according to the invention contain less than 0.1% Fe and less than 0.1% Si.
• the iron content is less than 0.08% by weight and preferably less than 0%. 06% by weight.
• the silicon content is less than 0.07% by weight and preferably less than 0.05% by weight.
• the other elements present are unavoidable impurities whose content is less than 0.05% by weight each and 0.15% by weight in total.
• An element not selected from Cr, Se, Hf, V, Ag and Zn thus has a content of less than 0.05% by weight and preferably less than 0.03% by weight. If the Zr is not chosen, its content is less than 0.04% by weight and preferably less than 0.02% by weight.
• the products according to the invention have satisfactory properties in terms of compromise between mechanical strength and toughness and very advantageous properties in terms of crack propagation speed in fatigue and in terms of sensitivity to crack deflection.
• the products according to the invention also have advantageous properties in terms of propensity for crack bifurcation.
• the macroscopic crack bifurcation during fatigue tests in the L-S direction from the S direction to the L direction was evaluated in two ways.
• a first method at least 6 test pieces LS CT, of thickness 10 mm and total width 50 mm (40 mm between the axis of the holes and the rear face of the test piece) made according to FIG. 1 are fatigue tested.
• at a maximum load of at least 3000 N, and a load ratio of R 0.1, covering the range of ⁇ in the course of the test from 10 to 40 MPaVm, where ⁇ is the variation of the factor of stress intensity in a load cycle.
• ⁇ is the variation of the factor of stress intensity in a load cycle.
• FIG. 5c shows an example of evaluation of this distance: when the crack deviates, it does not immediately join the direction L and thus the distance d can be measured. It is considered that the crack is in the direction S or in the direction L when it does not deviate from this direction by more than 10 °.
• the method of manufacturing a sheet of predominantly recrystallized granular structure with a thickness of at least 50 mm according to the invention comprises the steps of casting, homogenization, hot rolling, dissolution, quenching, controlled pulling and tempering.
• An alloy containing controlled quantities according to the invention of alloying elements is cast in the form of a plate.
• the plate is homogenized at a temperature of at least 490 ° C.
• the homogenization time is at least 12 hours.
• the homogenization can be carried out in one or more stages.
• the homogenization comprises at least one step whose temperature is at least 520 ° C. and preferably at least 530 ° C., the duration during which the temperature is greater than 520 ° C. C being at least 20 hours and preferably at least 30 hours.
• a hot rolling step is performed after reheating if necessary to obtain sheets having a thickness of at least 50 mm.
• the hot rolling exit temperature is less than 390 ° C., preferably less than 380 ° C.
• the combination, in particular, of the conditions of the homogenization step and the hot rolling step of the first embodiment makes it possible to obtain a final structure after income that is predominantly recrystallized, especially for products whose sum of the content of the Zr elements. , Cr, Se, Hf, and V is at least 0.08% by weight.
• the inventors have found that the conditions according to this first embodiment make it possible to reduce the propensity for crack bifurcation.
• the sum of the content of elements Zr, Cr, Se, Hf, and V is less than 0.08% by weight and the hot rolling output temperature is preferably at least 400. ° C and preferably at least 420 ° C.
• the sheets are dissolved by heating between 490 and 540 ° C, preferably for 15 minutes to 4 hours, the dissolution parameters depending on the thickness of the product.
• the product then undergoes controlled traction with a permanent deformation of between 1% and 7% and preferably between 2% and 6%.
• the income is carried out at a temperature between 130 ° C and 170 ° C and preferably at a temperature between 140 ° C and 160 ° C for a period of 5 to 60 hours, resulting in a T8 state.
• the yield is preferably between 140 and 160 ° C for 12 to 50 hours.
• the products according to the invention are advantageously used in aeronautical construction.
• the use of the products according to the invention for producing an aircraft wing spar or an airplane wing rib is particularly advantageous.
• the use of the products according to the invention for the production of an aircraft wing spar is preferred, advantageously for the lower part, that is to say in connection with the underside of the wing, d a welded spar.
• Plate A was homogenized in two 36-hour increments at 504 ° C and then 48 hours at 530 ° C.
• Plates B and C were homogenized in two 8 hour increments at 496 ° C and then 34 hours at 530 ° C.
• Plate D was homogenized for 12 hours at 505 ° C.
• the plate E was homogenized in two stages 8h at 500 ° C. and then 36 hours at 527 ° C.
• Plate A was hot rolled to a 100 mm thick sheet, hot roll inlet temperature was 410 ° C, and hot roll output temperature was 361 ° C.
• Plate B was hot rolled to a sheet thickness of 102 mm, hot roll inlet temperature was 406 ° C and hot roll output temperature was 350 ° C.
• Plate C was hot rolled to a 102 mm thick sheet, hot roll inlet temperature was 410 ° C, and hot roll output temperature was 360 ° C.
• Plate D was hot rolled to a 100 mm thick sheet, hot roll inlet temperature was 505 ° C, and hot roll output temperature was 520 ° C.
• Plate E was hot rolled to a 100 mm thick sheet, the hot rolling inlet temperature was 481 ° C and the hot rolling exit temperature was 460 ° C.
• the sheets thus obtained were dissolved for 2 hours at 525 ° C. and quenched with cold water.
• the sheets thus dissolved and quenched were controlled in a controlled manner, with a permanent elongation of 4% and were tempered for 18 hours at 155 ° C. (A, B, C and E) or 24 hours at 155 ° C. (D).
• KJC Stress intensity factor measured at 1 ⁇ 4 thickness (T / 4) and at mid-thickness (T / 2) determined according to ASTM E 399.
• Fatigue crack propagation tests on L-S specimens were performed on samples from sheets C and E. The tests were performed according to ASTM E647. These tests are carried out on CCT test specimens, with central crack, width 100 mm and thickness 6.35 mm.
• Figure 2 shows the crack propagation rate results for the samples tested with the CCT test specimen. The results are summarized in Table 5 below.
• Figures 3a and 3b show, respectively, the samples from sheets A and D after the fatigue test.
• the samples from the sheet A according to the invention have a progressive crack bifurcation with in 4 cases out of 6 (Cl, C2, Bl, A2) a rupture by the rear face of the test piece.
• the distance d on which the crack is neither in the initial direction S nor in the direction L is at least 15 mm for all the samples coming from the sheet A, because in no case does the crack join the direction L.
• the predominantly recrystallized product according to the invention has a particularly advantageous fatigue crack propagation.
• the samples thus obtained were dissolved for 2 hours at 525 ° C. and then quenched with cold water and were tempered.
• Samples F and G are mainly recrystallized.

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• Chemical & Material Sciences (AREA)
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• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Heat Treatment Of Steel (AREA)
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• Laminated Bodies (AREA)

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• 2016
  • 2016-02-03 FR FR1650850A patent/FR3047253B1/fr active Active
• 2017
  • 2017-02-03 BR BR112018014770-2A patent/BR112018014770B1/pt active IP Right Grant
  • 2017-02-03 CN CN201780009624.1A patent/CN108603253B/zh active Active
  • 2017-02-03 CA CA3012956A patent/CA3012956C/fr active Active
  • 2017-02-03 US US16/074,661 patent/US20190040508A1/en not_active Abandoned
  • 2017-02-03 WO PCT/FR2017/050255 patent/WO2017134405A1/fr active Application Filing
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• 2023
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