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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
  • B21B2003/001—Aluminium or its alloys

Definitions

• the invention relates to sheets of thicknesses less than 12.7 mm rolled from aluminum-copper-lithium alloys, offering improved toughness, and methods of making them. These sheets are intended in particular for aeronautical and aerospace construction.
• Aluminum alloy rolled products have been developed to produce fuselage elements intended in particular for the aeronautical industry and the aerospace industry.
• Aluminum - copper - lithium alloys are particularly promising for manufacturing this type of product.
• EP 1966402 describes an alloy comprising 2.1 to 2.8% by weight of Cu, 1.1 to 1.7% by weight of Li, 0.1 to 0.8% by weight of Ag, 0, 2 to 0.6% by weight of Mg, 0.2 to 0.6% by weight of Mn, an amount of Fe and Si less than or equal to 0.1% by weight each, and inevitable impurities at a content less than or equal to 0.05% by weight each and 0.15% by weight in total, the alloy being substantially free of zirconium, particularly suitable for obtaining recrystallized thin sheets.
• Patent FR3014448 describes a rolled and / or forged product, the thickness of which is between 14 and 100 mm, in aluminum alloy of composition, in% by weight, Cu: 1.8 - 2.6 Li: 1, 3 - 1.8 Mg: 0.1 - 0.5 Mn: 0.1 - 0.5 and Zr ⁇ 0.05 or Mn ⁇ 0.05 and Zr 0.10 - 0.16 Ag: 0 - 0.5 Zn ⁇ 0 , 20 Ti: 0.01 - 0.15 Fe: ⁇ 0.1 Si: ⁇ 0.1 15 other elements ⁇ 0.05 each and ⁇ 0.15 in total, remainder aluminum whose density is less than 2.670 g / cm3, characterized in that at mid-thickness the volume fraction of the grains having a brass texture is between 25 and 40% and the texture index is between 12 and 18.
• EP 2981632 describes a process for manufacturing a thin sheet of thickness 0.5 to 3.3 mm with an essentially non-recrystallized structure in an aluminum-based alloy in which, successively, a) a bath of liquid metal comprising, 2.6 to 3.4 wt% Cu, 0.5 to 1.1 wt% Li, 0.1 to 0.4 wt% Ag, 0.2 to 0, 8% by weight Mg, 0.11 to 0.20
• % by weight of Zr 0.01 to 0.15% by weight of Ti, optionally at least one element chosen from Mn, V, Cr, Sc, and Hf, the amount of the element, if it is chosen, being 0.01 to 0.8 wt% for Mn, 0.05 to 0.2 wt% for V, 0.05 to 0.3 wt% for Cr, 0.02 to 0.3 wt% for weight for Sc, 0.05 to 0.5% by weight for Hf, an amount of Zn less than 0.6% by weight, an amount of Fe and Si less than or equal to 0.1% by weight each, and impurities unavoidable at a content of less than or equal to 0.05% by weight each and 0.15% by weight in total; b) casting a plate from said bath of liquid metal; c) said plate is homogenized at a temperature between 450 ° C and 515 ° C; d) said plate is rolled by hot rolling into a sheet having a thickness between 4 and 12 mm; e) said sheet is rolled by cold rolling into
• Patent EP2981631 describes a sheet of thickness 0.5 to 8 mm made of an aluminum-based alloy comprising, 2.6 to 3.0% by weight of Cu, 0.5 to 0.8% by weight of Li, 0, 1 to 0.4 wt% Ag, 0.2 to 0.7 wt% Mg, 0.06 to 0.20 wt% Zr, 0.01 to 0.15 wt% Ti, optionally at least one element chosen from Mn, V, Cr, Sc, and Hf, the amount of the element, if it is chosen, being from 0.01 to 0.8% by weight for Mn, 0.05 to 0.2 wt% for V, 0.05 to 0.3 wt% for Cr, 0.02 to 0.3 wt% for Sc, 0.05 to 0.5 wt% for Hf, an amount of Zn less than 0.2% by weight, an amount of Fe and Si less than or equal to 0.1% by weight each, and inevitable impurities at a content of less than or equal to 0.05% by weight each and 0 , 15% by weight in total, said sheet being obtained
• microstructure is completely non-recrystallized or completely recrystallized.
• Application PCT / FR2019 / 051269 describes a process for manufacturing a thin sheet made of an aluminum-based alloy comprising, in% by weight, 2.3 to 2.7% of Cu, 1.3 to 1.6% of Li, 0.2 to 0.5% of Mg, 0.1 to 0.5% of Mn, 0.01 to 0.15% of Ti, an amount of Zn less than 0.3, an amount of Fe and Si less than or equal to 0.1% each, and inevitable impurities at a content of less than or equal to 0.05% by weight each and 0.15% by weight in total, in which in particular the inlet temperature of hot rolling being between 400 ° C and 445 ° C and the hot rolling outlet temperature being less than 300 ° C.
• the object of the invention proposes to solve this problem.
• the first object of the invention relates to a method of manufacturing a sheet with a thickness of between 0.5 and 12.7 mm made of an aluminum-based alloy in which, successively a) a liquid metal bath is produced including
• a plate is cast from said bath of liquid metal; c) said plate is homogenized at a temperature between 490 ° C and 535 ° C; d) the said homogenized plate is rolled by hot rolling and optionally by cold rolling in a sheet having a thickness between 0.5 and 12.7 mm, the hot rolling inlet temperature being between 400 ° C and 460 ° C and the hot rolling outlet temperature being less than 300 ° C, preferably less than 290 ° C; e) said sheet is dissolved at a temperature between 450 ° C and 535 ° C for at least 5 min, preferably at least 10 min with an average rate of heating of said sheet of at least about 17
• a third object of the invention relates to the use of a thin sheet according to the second object of the invention in a fuselage panel for an aircraft.
• Figure 2 shows the relationship between the grain size measurements in the L direction as a function of the thicknesses of the sheets processed in Example 1.
• Figure 3 shows an example of the granular structure of Example C-2-28 which corresponds to a reference example of Example 1.
• Figure 4 shows an example of the granular structure of Example A-2-25 which corresponds to an example according to the invention of Example 1.
• Figure 5 shows an example of the granular structure of Example E-1-48 which corresponds to an example according to the invention of Example 1.
• the static mechanical properties in tension in other words the tensile strength Rm, the conventional yield strength at 0.2% elongation Rp0.2, and the elongation at break A%, are determined by a tensile test according to standard NF EN ISO 6892-1 (2016), the sampling and direction of the test being defined by standard EN 485-1 (2016).
• the critical stress intensity factor KC in other words terms the intensity factor which makes the unstable crack, is calculated from the curve R.
• the stress intensity factor KCO is also calculated by assigning the initial crack length at the onset of the monotonic load, to the critical load. These two values are calculated for a specimen of the required shape.
• Kapp represents the KCO factor corresponding to the test piece which was used to perform the curve test R.
• Keff represents the KC factor corresponding to the test piece which was used to perform the curve test R.
• Aaeff (max) represents the crack extension of the last point of the R curve, valid according to ASTM E561. The last point is obtained either at the time of sudden rupture of the specimen, or possibly at the time when the stress on the uncracked ligament exceeds on average the elastic limit of the material.
• the crack size at the end of the fatigue pre-cracking stage is W / 3 for type M (T) specimens, where W is the width of the specimen as defined in the ASTM standard. E561 (ASTM E561-10-2).
• an essentially recrystallized granular structure is called a granular structure such that the rate of recrystallization at 1 ⁇ 2 thickness is greater than 70% and preferably greater than 90%.
• the recrystallization rate is defined as the surface fraction on a metallographic section occupied by recrystallized grains.
• a characteristic specified by a value preceded by the term “approximately” means that this characteristic can be between +/- 10% of the value disclosed.
• the term “thin sheet” is understood to mean a sheet with a thickness of between 0.5 mm and 12.7 mm.
• the present inventors have obtained thin sheets, preferably between 0.5 to 8 mm, and even more preferably between 1.2 mm and 6.5 mm, exhibiting an advantageous compromise between mechanical strength and toughness by using the method according to the invention which comprises in particular the combination of
• the thin sheets thus obtained have particularly advantageous properties, in particular as regards the toughness in the T-L direction.
• a liquid metal bath is produced, the composition of which is as follows:
• the copper content of the products according to the invention is between 2.2 and 2.7% by weight.
• the copper content is between 2.45% and 2.55% by weight in order to increase the toughness value in the T-L direction.
• the copper content is preferably between 2.20 and 2.35% by weight in order to improve the aging behavior.
• the Cu content is at least 2.25% by weight and preferably at least 2.27% by weight.
• the copper content is at most 2.30% by weight.
• the copper content is between 2.20 and 2.30% by weight and preferably between 2.25 and 2.30% by weight.
• the lithium content of the products according to the invention is between 1.3 and 1.6% by weight.
• the lithium content is between 1.35 and 1.55% by weight and preferably between 1.40% and 1.50% by weight.
• a minimum lithium content of 1.35% by weight and preferably 1.40% by weight is advantageous.
• a maximum lithium content of 1.55% by weight and preferably 1.50% by weight is advantageous, in particular for improving the compromise between toughness and mechanical strength.
• the addition of lithium can contribute to the increase in mechanical strength and toughness, too high or too low a content does not allow to obtain a very high toughness value in the TL direction and / or a limit of sufficient elasticity.
• the addition of lithium makes it possible to reduce the density.
• the density of the products according to the invention is less than 2.65.
• the silver content of the products according to the invention is less than or equal to 0.1% by weight.
• the silver content is less than or equal to 0.05% by weight and even more preferably less than or equal to 0.01% by weight.
• the product has too high an industrial cost. Reducing the silver content to levels below 0.1% by weight is of economic interest.
• the magnesium content of the products according to the invention is between 0.2 and 0.5% by weight and preferably between 0.25 and 0.45% by weight and preferably between 0.25 and 0.35%. in weight.
• a minimum magnesium content of 0.25% by weight is advantageous.
• a maximum magnesium content of 0.45% by weight and preferably 0.40% by weight and preferably 0.35% by weight or even 0.30% by weight is advantageous.
• the manganese content is between 0.1 and 0.5% by weight, preferably between 0.2 and 0.4% by weight and preferably between 0.25 and 0.35% by weight.
• a minimum manganese content of 0.2% by weight and preferably 0.25% by weight is advantageous.
• a maximum manganese content of 0.4% by weight and preferably 0.35% by weight or even 0.33% by weight is advantageous.
• the titanium content is between 0.01 and 0.15% by weight.
• the iron and silicon contents are each at most 0.1% by weight.
• the iron and silicon contents are at most 0.08% and preferably at most 0.04% by weight. Controlled and limited iron and silicon content helps improve the trade-off between mechanical strength and damage tolerance.
• the zinc content is less than or equal to 0.3% by weight, preferably less than 0.2% by weight and preferably less than 0.1% by weight.
• the zinc content is advantageously less than 0.04% by weight.
• the unavoidable impurities are kept at a content of less than or equal to 0.05% by weight each and 0.15% by weight in total.
• the process for manufacturing thin sheets according to the invention then comprises steps of casting, homogenization, hot and optionally cold rolling, dissolving, controlled traction, quenching and tempering.
• the elaborate liquid metal bath is cast in a rolling plate form.
• the rolling plate is then homogenized at a temperature between 490 ° C and 535 ° C.
• the homogenization time is between 5 and 60 hours.
• the homogenization temperature is at least 500 ° C. In one embodiment, the homogenization temperature is less than 515 ° C.
• the rolling plate After homogenization, the rolling plate is generally cooled to room temperature before being preheated with a view to being hot-deformed.
• the objective of preheating is to achieve a hot rolling inlet temperature of between 400 and 460 ° C and preferably between 420 ° C and 445 ° C and even more preferably between 420 ° C and 440 ° C allowing deformation by hot rolling.
• Hot rolling is carried out so as to obtain a sheet of thickness typically from 3 to 12.7 mm, preferably 4 to 12.7 mm.
• the hot rolling outlet temperature is less than 300 ° C and preferably less than 290 ° C in order to control the energy stored in the sheet. This makes it possible to obtain a grain size according to the invention if the conditions for the rate of rise in dissolution are also achieved according to the invention.
• the sheet obtained can optionally be cold rolled in particular to obtain a final thickness of between 0.5 and 4 mm.
• the final thickness is at most 8.0 mm, more preferably at most 7.0 mm and even more preferably at most 6.5 mm.
• the final thickness is at least 0.8 mm and preferably at least 1.2 mm.
• the sheet thus obtained is then placed in solution between 450 and 535 ° C, preferably between 450 and 525 ° C, for at least 5 min, preferably at least 10 min.
• the dissolution time is advantageously between 5 min to 8 h, even more preferably between 10 min and 1 h.
• the average rate of heating of the sheet during the solution must be at least about 17 ° C / min in the temperature range between 300 ° C and 400 ° C, preferably at least about 19 ° C / min, and even more preferably at least about 25 ° C / min.
• the control of the average heating rate of the sheet between 300 ° C and 400 ° C is necessary to control the final grain size of the product according to the invention.
• the average sheet heating rate between 300 ° C and 400 ° C can be calculated by measuring the temperature rise temperature of the sheet using a thermocouple placed on the surface of the sheet.
• the average sheet heating rate between 300 ° C and 400 ° C is calculated by making a linear regression between 300 ° C and 400 ° C of the temperature of the metal as a function of the heating time to go from 300 ° C to 400 ° C. It is particularly important to control the average heating rate between 300 ° C and 400 ° C. It is well known to those skilled in the art that the average heating speed is influenced by the thermal conditions of the furnace (temperature of the air inside the furnace, furnace technology), but also by the load (quantity and position of the sheets in the oven) and the thickness of the product.
• the sheet thus placed in solution is then soaked in water.
• the quenching is carried out by quenching in water at room temperature.
• the sheet then undergoes cold deformation by controlled traction with a permanent deformation of 0.5 to 6% and preferably from 3 to 5%.
• Known steps such as rolling, leveling, straightening and shaping can optionally be carried out after dissolving and quenching and before or after controlled traction, however the total cold deformation after dissolving and quenching must remain less than 15% and preferably less than 10%.
• High cold deformations after solution and quenching indeed cause the appearance of numerous shear bands crossing several grains, these shear bands not being desirable.
• cold rolling is not carried out after dissolving.
• Tempering is carried out comprising heating at a temperature between 130 and 170 ° C and preferably between 140 and 160 ° C and preferably between 145 and 155 ° C for 5 to 100 hours and preferably 10 to 50 hours in order to 'obtain an elastic limit in the direction TL, R0.2 (TL) of between 350 MPa and 380 MPa, preferably between 350 MPa and 370 MPa, and even more preferably between 355 MPa and 365 MPa.
• TL TL
• Tempering kinetics consist in cutting out several blanks after dissolving, quenching and cold deformation and evaluating the elastic limit in the TL direction for different tempering times at a given temperature. It is thus possible to determine for a given temperature how the yield strength changes with the tempering time and to choose a tempering time which makes it possible to obtain a yield strength of between 350 MPa and 380 MPa.
• the final metallurgical state is a T8 state.
• a short heat treatment is carried out after controlled traction and before tempering so as to improve the formability of the sheets.
• the sheets can thus be shaped by a process such as stretch-forming before being returned. Examples of short heat treatments are described in patents EP2766503 or EP 2984195.
• the tempering kinetics to determine the duration of tempering necessary to reach an elastic limit in the TL direction, R0.2 (TL) between 350 MPa and 380 MPa must be carried out on blanks having undergone this short treatment.
• the thin sheets obtained by the process according to the invention have a characteristic grain size, preferably sheets with a thickness between 0.8 and 8.0 mm, even more preferably between 1.2 mm and 6.5. mm.
• the average grain size in the thickness measured by the method of intercepts on an L / TC cut in the direction L according to the ASTM E112 standard and expressed in pm is less than 56t + 250, where t is the thickness of the sheet expressed in mm, preferably less than 56t + 200 and more preferably less than 56t + 150.
• the granular structure of the sheets is advantageously essentially recrystallized.
• the thin sheets obtained by the process according to the invention have a toughness in the T-L direction which is particularly advantageous.
• favorable performance of the thin sheets according to the invention with regard to toughness are obtained when the lithium content is between between 1.40 and 1.50% by weight, the copper content is between 2.45 and 2.55% by weight and the magnesium content is between 0.25 and 0.35% by weight.
• favorable performance of the thin sheets according to the invention as regards the resistance to aging, preferably for a thickness between 1.2 mm and 6.5 mm, are obtained when the lithium content is between 1.40 and 1.50% by weight, the copper content is between 2.20 and 2.35% by weight , preferred between 2.20 and 2.30% by weight and the magnesium content is between 0.25 and 0.35% by weight.
• the resistance to intergranular corrosion of the sheets according to the invention is high.
• the sheet of the invention can be used without plating.
• the granular structure of the samples was characterized from the microscopic observation of cross sections after anodic oxidation, under polarized light on L / TC sections. The granular structure of the sheets was recrystallized.
• Figure 3, Figure 4, and Figure 5 show the observed granular structures of samples C-2-28, A-2-25 and E-1-48. Average grain sizes across thickness measured by the intercept method according to ASTM E112 are shown in Table 5. Typically, grain structure is not affected by tempering conditions. It is therefore expected that the grain sizes are identical whatever the tempering conditions performed for a given processing condition. The measured grain sizes are shown in Figure 2.
• references A-2-25, B-2-25 and E1-48 are produced according to the invention.
• the references A1-34, A-2-34, B1-34, B-2-34, C1-28 are products outside the invention which have been described in application PCT / FR2019 / 051269. These products do not make it possible to achieve a Kapp toughness value greater than 145 MPa.m 1/2 in the TL direction.
• a grain size in the L direction of less than 56t + 250 is obtained in particular if the hot rolling outlet temperature is less than 300 ° C and if the metal heating rate between 300 and 400 ° C during setting. solution is greater than or equal to 17 ° C / min.
• Example Fl-48 shows that despite hot rolling conditions respecting an outlet temperature of less than 300 ° C and tempering conditions making it possible to reach a value of R0.2 (TL) of between 350 MPa and 380 MPa , this product does not make it possible to achieve a toughness value Kapp greater than 145 MPa.m 1/2 in the TL direction.
• the E1-48 sheet obtained according to the invention shows after aging a toughness Kapp in the TL direction greater than 135 MPa.m 1/2 .

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• Chemical & Material Sciences (AREA)
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• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Heat Treatment Of Steel (AREA)
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• 2019
  • 2019-12-06 FR FR1913889A patent/FR3104172B1/fr active Active
• 2020
  • 2020-11-30 EP EP20829623.6A patent/EP4069875A1/de active Pending
  • 2020-11-30 US US17/778,179 patent/US20220349040A1/en active Pending
  • 2020-11-30 WO PCT/FR2020/052226 patent/WO2021111069A1/fr not_active Ceased
  • 2020-11-30 CA CA3163347A patent/CA3163347A1/fr active Pending
  • 2020-11-30 CN CN202080083779.1A patent/CN114746566A/zh active Pending

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