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
• • 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
  • C22F1/002—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working by rapid cooling or quenching; cooling agents used therefor

Definitions

• the invention relates to a method for manufacturing a wrought aluminum-magnesium-lithium alloy product, more particularly to a process for manufacturing such a product having an improved property compromise, in particular an improved compromise between yield strength in tension. and toughness of said products.
• the invention also relates to a product that can be obtained by said manufacturing process and its use, said product being intended in particular for aeronautical and aerospace construction.
• Wrought aluminum alloy products are being developed to produce high-strength parts for the aerospace industry and the aerospace industry in particular.
• 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.
• aluminum alloys containing magnesium and lithium simultaneously make it possible to reach particularly low densities and have therefore been extensively studied.
• GB 1,172,736 teaches an alloy containing, in percentage by weight, 4-7% Mg, 1.5-2.6% Li, 0.2-1% Mn and / or 0.05-0.3. % of Zr, remains aluminum. This alloy is useful for producing products with high mechanical strength, good corrosion resistance, low density and high modulus of elasticity. Said products are obtained by a process comprising an optional quenching and then an income.
• the products resulting from the process according to GB 1, 172,736 disclose a tensile strength of from about 440 MPa to about 490 MPa, a tensile yield strength of from about 270 MPa to about 340 MPa and an elongation at break of about 5-8%.
• the international application WO 92/03583 describes a useful alloy for aeronautical structures having a low density and of general formula Mg a LibZn c AgdAlbai, in which a is between 0.5 and 10%, b is between 0.5 and 3%, c is between 0.1 and 5%, d is between 0.1 and 2% and bal indicates that the balance is aluminum.
• This document also discloses a process for obtaining said alloy comprising the steps of: a) casting an ingot of composition described above, b) removing the residual stresses of said ingot by heat treatment, c) homogenizing by heating and maintaining temperature then cool the ingot, d) hot rolling said ingot to its final thickness, e) dissolve and then soaking the product thus laminated, f) pull the product and g) achieve a revenue of said product by heating and maintaining temperature .
• No. 5,431,876 teaches a ternary alloy group of lithium aluminum and magnesium or copper, including at least one additive such as zirconium, chromium and / or manganese.
• the alloy is prepared according to methods known to those skilled in the art including, by way of example, extrusion, dissolution, quenching, traction of the product of 2 to 7% and then income.
• US Pat. No. 6,551,424 discloses a process for producing aluminum-magnesium-lithium alloy rolled products of composition (in% by weight) Mg: 3.0 - 6.0; Li: 0.4 - 3.0; Zn up to 2.0; Mn up to 1.0; Ag up to 0.5; Fe up to 0.3; If up to 0.3; Cu up to 0.3; 0.02 - 0.5 of an element selected from the group consisting of Se, Hf, Ti, V, Nd, Zr, Cr, Y, Be, said method including cold rolling in the length direction and in the sense of width.
• No. 6,461,566 discloses an alloy of composition (in% by weight) Li: 1.5 - 1.9; Mg, 4.1 - 6.0; Zn 0.1 - 1.5; Zr 0.05 - 0.3; Mn 0.01 - 0.8; H 0.9 x 10 "5 - 4.5 x 10 " 5 and at least one element selected from the group Be 0.001 - 0.2; Y 0.001 - 0.5 and Se 0.01 - 0.3.
• the patent application WO 2012/16072 describes a wrought product made of aluminum alloy of composition in% by weight, Mg: 4.0 - 5.0; Li: 1.0-1.6; Zr: 0.05-0.15; Ti: 0.01-0.15; Fe: 0.02 - 0.2; Si: 0.02 - 0.2; Mn: ⁇ 0.5; Cr ⁇ 0.5; Ag: ⁇ 0.5; Cu ⁇ 0.5; Zn ⁇ 0.5; himself ⁇ 0.01; other elements ⁇ 0.05; remains aluminum.
• Said product is in particular obtained according to a manufacturing process comprising in particular successively the casting of the alloy in raw form, its hot deformation and optionally cold, the setting solution and the quenching of the product thus deformed, optionally the cold deformation of the product thus dissolved and quenched and finally the product of the wrought product at a temperature below 150 ° C.
• the metallurgical state obtained for the rolled products is advantageously a T6 or T6X or T8 or T8X state and for the advantageously spun products a T5 or T5X state in the case of quenching on a press or a T6 or T6X or T8 or T8X state.
• Wrought products made of aluminum-magnesium-lithium alloy have a low density and are therefore particularly interesting in the extremely demanding field of aeronautics.
• their performance must be significantly improved compared to that of existing products, in particular their performance in terms of a compromise between the static mechanical strength properties (in particular tensile yield strength limit and in compression, breaking strength) and the properties of damage tolerance (toughness, resistance to the propagation of fatigue cracks), these properties being in general antinomic.
• These alloys 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 without substantial distortion during said machining.
• a first object of the invention is a method of manufacturing a wrought product in which:
• said hot-deformed product is dissolved at a temperature of 360 ° C to 460 ° C, preferably 380-420 ° C, for 15 minutes to 8 hours;
• the hot deformed product thus returned is cold-deformed in a controlled manner so as to obtain a permanent cold deformation of 1 to 10%, preferably of 2 to 6%, more preferably of 3 to 5%, and more preferentially still 4 to 5%.
• the invention also relates to a wrought product that can be obtained according to the method of the invention as well as the use of said wrought product to produce an aircraft structural element.
• Figure 1 Frame for fuselage frame of Example 1
• Figure 2 Yield strength, Rp0,2, as a function of toughness, KQ * for a flat bar 10 mm thick (* all values of KQ are invalid due to criterion P max / PQ ⁇ 1, 10 of ASTM E399)
• Figure 3 Yield strength, Rp0,2, as a function of the stress intensity factor corresponding to the maximum force, K max (evaluated according to ASTM E399) for a 10 mm thick flat bar
• 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, the sampling and the direction of the test being defined by the EN 485-1 standard.
• Increasing the stresses on the product during the Klc toughness test according to ASTM E399 may be indicative of the propensity of the product for delamination.
• delamination ("crackdelamination” and / or "crack divider” in English) a cracking in orthogonal planes at the front of the main crack. The orientation of these planes corresponds to that of non-recrystallized grain boundaries after deformation by milling.
• a weak delamination is the sign of a less fragile planes concerned and minimizes the risk of deflection of crack towards the longitudinal direction during a propagation in fatigue or under monotonic stress.
• EN 12258 Unless otherwise specified, the definitions of EN 12258 apply.
• structural element or “structural element” of a mechanical construction 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 performed.
• 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 fuselage stringers, bulkheads, frames circumferential frames, wings (such as upper or lower wing skin), stiffeners, ribs, floor (fioor beams) and seat rails (seat tracks)) and the empennage composed in particular of horizontal and vertical stabilizers (horizontal or vertical vertical stabilizers), as well as the doors.
• fuselage such as fuselage skin, (skin fuselage), stiffeners or fuselage stringers, bulkheads, frames circumferential frames, wings (such as upper or lower wing skin), stiffeners, ribs, floor (fioor beams) and seat rails (seat tracks)
• empennage composed in particular of horizontal and vertical stabilizers (horizontal or vertical vertical stabilizers), as well as the doors.
• the manufacturing process of the products according to the invention comprises the successive steps of producing a bath of liquid metal so as to obtain an Al-Mg-Li alloy of particular composition, casting said alloy in raw form, optionally the homogenization of said raw form thus cast, the hot deformation of said raw form to obtain a hot deformed product, optionally the separate solution of the product thus deformed hot, the quenching of said hot deformed product, optionally the dressing / planing of the deformed and quenched product, the income of said deformed and quenched product and the controlled cold deformation of the returned product to obtain a permanent cold deformation of 1 to 10%, preferably of 2 to 6%, more preferably of 3 to 5% and more preferably 4 to 5%.
• the manufacturing process therefore consists first of all in the casting of a crude form of Al-Mg-Li alloy of composition, in% by weight: Mg: 4.0 - 5.0; Li: 1.0 -1.8; Zr: 0.05-0.15; Mn: ⁇ 0.6; Ag: ⁇ 0.5; Fe: ⁇ 0.1; Ti: ⁇ 0.15; If: ⁇ 0.05; other elements ⁇ 0.05 each and ⁇ 0.15 in combination; remains aluminum.
• a bath of liquid metal is made and then cast in raw form, typically a rolling plate, a spinning billet or a forging blank.
• the Al-Mg-Li alloy has a Mn content, in% by weight, of 0.2 to 0.6%, preferably of 0.35 to 0.5%, more preferentially of 0.35 to 0.45% and more preferably still 0.35 to 0.40%.
• the alloy products as described above and having the advantageous Mn content have in particular improved static mechanical properties and a low propensity for delamination.
• the raw form of aluminum alloy has a silver content of less than or equal to 0.25% by weight, more preferably a silver content of 0.05% to 0.1% by weight.
• This element contributes in particular to the static mechanical properties.
• the raw form of aluminum alloy has a total content of Ag and Cu less than 0.15% by weight, preferably less than or equal to 0.12%. The control of the maximum content of these two elements in combination makes it possible in particular to improve the resistance to intergranular corrosion of the wrought product.
• the raw form has a zinc content, in% by weight, of less than 0.04%, preferably less than or equal to 0.03%.
• a zinc content in% by weight, of less than 0.04%, preferably less than or equal to 0.03%.
• the raw form of aluminum alloy has a Fe content, in% by weight, of less than 0.08%, preferentially less than or equal to 0.07%, more preferably still less than or equal to 0.06%.
• a minimum Fe content, as well as possibly that of Si can contribute to improving the mechanical properties and in particular the fatigue properties of the alloy. Excellent results have been particularly obtained for an Fe content of 0.02 to 0.06% by weight and / or an Si content of 0.02 to 0.05% by weight.
• the lithium content of the products according to the invention is between 1.0 and 1.8% by weight.
• the raw form of aluminum alloy has a content in Li, in% by weight, of less than 1, 6%, preferably less than or equal to 1.5%, preferentially still less than or equal to 1 , 4%.
• a minimum lithium content of 1.1% by weight and preferably 1.2% by weight is advantageous.
• the present inventors have found that a limited lithium content, in the presence of certain addition elements, makes it possible to very significantly improve the toughness, which largely compensates for the slight increase in density and the decrease in the static mechanical properties.
• the raw form of aluminum alloy has a Zr content, in% by weight, of 0.10 to 0.15%.
• the inventors have indeed found that such a Zr content makes it possible to obtain an alloy having a favorable fiber structure for improved static mechanical properties.
• the raw form of aluminum alloy has a Mg content, in% by weight, of 4.5 to 4.9%. Excellent results have been obtained for alloys according to this embodiment especially with regard to the static mechanical properties.
• the Cr content of the products according to the invention is less than 0.05% by weight, preferably less than 0.01% by weight.
• Such a limited Cr content in combination with the other elements of the alloy according to the invention makes it possible in particular to limit the formation of primary phases during casting.
• the Ti content of the products according to the invention is less than 0.15% by weight, preferably between 0.01 and 0.05% by weight.
• the Ti content is limited in the particular alloy of the present invention in particular to prevent the formation of primary phases during casting.
• the products according to the invention have a maximum content of 10 ppm Na, preferably 8 ppm Na, and / or a maximum content of 20 ppm Ca.
• the raw form of aluminum alloy is substantially free of Se, Be, Y, more preferably said raw form comprises less than 0.01% by weight of these elements taken in combination.
• the raw form of aluminum alloy has a composition, in% by weight:
• Mg 4.0 - 5.0, preferably 4.5 - 4.9;
• Li 1.1, -1.6, preferably 1.2-1.5;
• Zr 0.05-0.15, preferentially 0.10-0.15;
• Fe 0.02 - 0.1, preferably 0.02 - 0.06;
• Mn ⁇ 0.6, preferably 0.2 - 0.6, more preferably still 0.35 - 0.5;
• Ag ⁇ 0.5; preferentially ⁇ 0.25; more preferably still ⁇ 0.1;
• the manufacturing method optionally comprises a homogenization step of the raw form so as to reach a temperature of between 450 ° C. and 550 ° C. and, preferably, between 480 ° C. C and 520 ° C for a period of between 5 and 60 hours.
• the homogenization treatment can be carried out in one or more stages.
• the hot deformation is carried out directly after a simple reheating without performing homogenization.
• the raw form is then hot deformed, typically by spinning, rolling and / or forging, to obtain a deformed product.
• This hot deformation is carried out preferably at an inlet temperature above 400 ° C and advantageously from 420 ° C to 450 ° C.
• the hot deformation is a spinning deformation of the raw form.
• a cold rolling step (which is then optional first stage of cold deformation) for products whose thickness is less than 3 mm. It may be useful to perform one or more intermediate heat treatments, typically carried out at a temperature between 300 and 420 ° C, before or during cold rolling.
• the product deformed hot and, optionally, cold is optionally subjected to separate dissolution at a temperature of 360 ° C to 460 ° C, preferably from 380 ° C to 420 ° C, for 15 minutes to 8 hours.
• the hot deformed product and, optionally, dissolved solution is then quenched.
• Quenching is carried out with water and / or air. It is advantageous to perform quenching in the air because the intergranular corrosion properties are improved.
• a press or quenching on spinning heat
• it is advantageous to carry out quenching on a press (or quenching on spinning heat), preferably quenching on an air press, such quenching in particular making it possible to improve the static mechanical properties .
• it may also be a quench on water press.
• the product is dissolved in spinning heat.
• the hot deformed product and hardened may optionally be subjected to a dressing step or planing according to whether it is a profile or a sheet.
• dressing step or planing a cold deformation step without permanent deformation or with a permanent deformation less than 1%.
• the income is achieved by heating, in one or more steps, at a temperature below 150 ° C, preferably at a temperature of 70 ° C to 140 ° C for 5 to 100 hours.
• the hot deformed product thus obtained is cold-deformed in a controlled manner to obtain a permanent cold deformation of 1 to 10%, preferably of 2 to 6%, more preferably of 3 to 5% and, more preferably still from 4 to 5%.
• the permanent cold deformation is 2 to 4%.
• the Cold deformation can in particular be carried out by traction, compression and / or rolling.
• the cold deformation is performed by traction.
• the metallurgical state obtained for the wrought products corresponds in particular to a T9 state according to the EN515 standard.
• the method of manufacturing a wrought product does not comprise any cold deformation step inducing a permanent deformation of at least 1% between the hot deformation step or, if this step is present, solution and the income stage.
• the combination of the chosen composition, in particular the content of Mg, Li and Mn if the latter is present, and transformation parameters, in particular the order of the steps of the manufacturing process, advantageously makes it possible to obtain wrought products. having a very special improved property compromise, in particular the compromise between mechanical strength and damage tolerance, while having a low density and a good corrosion performance.
• the wrought products according to the invention are preferably spun products such as profiles, rolled products such as sheets or thick plates and / or forged products.
• the subject of the invention is also wrought products that can be obtained according to the process previously described, advantageously such products that are deformed with a cold deformation and greater than 4%. Indeed, such products have quite new and particular characteristics.
• the wrought products obtainable by the process according to the invention advantageously said products with a permanent cold deformation greater than 4%, have, in particular at mid-thickness, for a thickness of between 0.5 and 15 mm.
• the wrought products obtainable by the process according to the invention have, for a thickness of between 0.5 and 15 mm, at least one half-thickness, at least two static mechanical strength properties chosen from properties (i) to (iii) and at least one property of damage tolerance selected from properties (iv) to (v).
• the spun products according to the invention have particularly advantageous characteristics.
• the spun products preferably have a thickness of between 0.5 mm and 15 mm, but products with a thickness greater than 15 mm, up to 50 mm or even 100 mm or more may also have advantageous properties.
• the thickness of the spun products is defined according to EN 2066: 2001: the cross section is divided into elementary rectangles of dimensions A and B; A still being the largest dimension elementary rectangle and B can be considered as the thickness of the elementary rectangle. The sole is the elementary rectangle with the largest dimension A.
• the wrought products according to the invention are advantageously used to produce aircraft structural elements, in particular aircraft.
• Preferred aircraft structural elements include fuselage skin, fuselage frame, stiffener or fuselage rail, or wing skin, sail stiffener, rib, or spar.
• Alloys A and B both have a composition suitable for carrying out the process according to the invention.
• the density of the alloys A and B calculated in accordance with the procedure of The Aluminum Association described on pages 2-12 and 2-13 of "Aluminum Standards and Data", is 2.55.
• Billet diameters of 358 mm were made in the raw forms. They were heated to 430-440 ° C and then hot deformed by spinning on a press in the form of a fuselage frame profile as shown in Figure 1. The products thus spun were quenched in the air (quenching). on press). They then suffered:
• - for products in the final state T6 a two-stage income made for 30 hours at 120 ° C followed by 100 h at 100 ° C .
• - for products in the final state T8 a controlled traction with permanent deformation of 3 or 5% (respectively T8-3% and T8-5%) then a bi-bearing income made for 30h at 120 ° C followed by 1 Oh at 100 ° C;
• T9 for products in final state T9: a bi-bearing income made for 30 hours at 120 ° C followed by 10 h at 100 ° C and then a controlled pull with permanent deformation of 3 or 5% (respectively T9-3% and T9 -5%).
• the mechanical properties, in particular the maximum stress tolerable by the product or breaking strength, Rm, and the yield strength Rp0.2 (stress value for a plastic deformation of 0.2%) of the products in the state T9 are globally significantly higher than those of T8 or T6 products.
• the mechanical properties, in particular Rp0,2 increase with the increase of the controlled traction (T6 ⁇ T8-3% ⁇ T8-5% ⁇ T9-3% ⁇ T9-5%).
• a Mn content of the Al-Mg-Li alloy of approximately 0.4% by weight makes it possible to significantly improve the mechanical strength (Rp0.2 and Rm), in particular in the L direction, of the alloy relative to that of an alloy having a Mn content of about 0.14% by weight (alloy A).
• Billet diameters of 358 mm were made in the raw forms. They were heated to 430-440 ° C and then hot deformed by spinning on a press in the form of a flat bar (100 mm x 10 mm). The products thus spun were quenched in the air (quenching on a press). They then suffered:
• the yield stress (stress value for 0.2% plastic strain, Rp0.2) of the T9 products is significantly higher than that of the T8 or T6 products.
• Rp0,2 increases with the increase of the controlled tensile stress (T6 ⁇ T8-3% ⁇ T8-5% ⁇ T9-3% ⁇ T9-5%).
• An Mn content of the Al-Mg-Li alloy of approximately 0.4% by weight makes it possible to significantly improve the mechanical strength of alloy (Rp0.2 and Rm) with respect to that of a alloy having a Mn content of about 0.14% by weight (alloy A).
• the KQ values have always been invalid according to the ASTM E399 standard, in particular with respect to the criterion Pmax / PQ ⁇ 1, 10. For this, the results are presented in Kmax (stress intensity factor corresponding to the maximum force Pmax).
• the results are reported in Tables 6 and 7 and illustrated in Figures 2 and 3 (test pieces L-T and TL respectively). These results are averages of at least two values.
• the products according to the invention have a satisfactory tenacity regardless of the Mn content of the alloy.
• Figure 2 illustrates the yield strength, Rp0.2, of the products of the present example as a function of toughness, KQ (all KQ values are invalid due to the criterion Pmax / PQ ⁇ 1, 10).
• FIG. 3 illustrates the elastic limit, Rp0.2, of the products of the present example as a function of the stress intensity factor corresponding to the maximum stress, K m ax.

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• 2015
  • 2015-09-29 US US15/514,802 patent/US20170218493A1/en not_active Abandoned
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