Classifications

• • 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
  • C22C21/02—Alloys based on aluminium with silicon 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
• • 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
  • C22F1/05—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 of the Al-Si-Mg type, i.e. containing silicon and magnesium in approximately equal proportions

Definitions

• the present invention relates to a 6XXX series aluminium extrusion alloy, particularly useful for the automotive industry.
• Aluminium alloys are used in the form of extrusions for various applications including automotive usages.
• 6xxx extruded products are usually used after the steps of extrusion, solutioning and quenching and artificial ageing. However, between the end of cooling and artificial ageing, the extruded product is often stored a certain period of time, called period of natural ageing (NA) or floor ageing for manufacturing purposes.
• NA period of natural ageing
• 6xxx alloys suffer from the "negative effect of natural ageing", that is, 6xxx alloys extruded products tend to lose their mechanical properties, measured after final ageing, very rapidly depending on the natural ageing applied. Depending on the duration of this period of natural ageing, it has a negative effect on the mechanical properties of the extruded products after artificial ageing.
• the patent application CN116516218 discloses high-strength and floor ageing effect 6xxx aluminum alloy and a preparation method thereof.
• 6xxx aluminum alloy with high strength and floor ageing effect is consisting of the following components in terms of mass percentage: Mg: 0.70-1.20%; Si: 0.80-1.30%; Cu: ⁇ 0.50%; Mn: ⁇ 0.60%; Cr: ⁇ 0.30%; Zr: ⁇ 0.20%; Sn: 0.05-0.20%; Fe: ⁇ 0.35%; other unavoidable impurity elements, the rest is Al; and the Mg/Si ratio is 0.70-1.00.
• the patent application CN113373331 discloses an aluminum alloy with low extrusion deformation resistance and sufficient strength of the finished product, which is suitable for the production of automobile battery tray products.
• the aluminium alloy has the following weight percentages: Si: 0.7%-0.8%, Fe: ⁇ 0.15%, Cu: 0.03%-0.08%, Mn: 0.08%-0.13%, Mg: 0.6%-0.7 %, Cr: ⁇ 0.05%, Zn: ⁇ 0.05%, Sn: 0.05%-0.10%, Ti: ⁇ 0.03%, single impurity ⁇ 0.05%, total impurities ⁇ 0.15%, the balance is Al.
• the patent application EP3390678 discloses a new high strength 6xxx aluminum alloys and methods of manufacturing these alloys. These 6xxx alloys have the following composition: 0.001 - 0.25 wt. % Cr, 0.4 - 2.0 wt. % Cu, 0.10 - 0.30 wt. % Fe, 0.5 - 2.0 wt. % Mg, 0.005 - 0.40 wt. % Mn, 0.5 - 1.5 wt. % Si, up to 0.15 wt. % Ti, up to 4.0 wt. % Zn, up to 0.2 wt. % Zr, up to 0.2 wt. % Sc, up to 0.25 wt. % Sn, up to 0.1 wt. % Ni, up to 0.15 wt. % impurities, remainder aluminum.
• the patent application CN114703407 discloses high-performance Al-Mg-Si-Cu-Sn aluminum alloy.
• the alloy consists of the following components: Mg: 0.1-1.0%, Si: 0.3-1.2%, Cu: 0.1-0.6 %, Sn: 0.01-0.2%, unavoidable impurities ⁇ 0.02%, the balance is Al.
• a first object of the invention is a manufacturing process for obtaining extrusions made from a 6xxx aluminium alloy, comprising the following successive steps:
• a second object of the invention is an extruded profile made from a 6xxx aluminium alloy comprising in wt.%,
• a third object of the invention is the use of an extruded profile as an automotive component such as a crash box, a bumper, a side impact beam or a side sill, structural and non-structural parts of battery box.
• Metallurgical tempers referred to are designated using the European standard EN-515. Static tensile mechanical characteristics, in other words, the ultimate tensile strength Rm (or UTS), the tensile yield strength at 0.2% plastic elongation Rp0,2 (or TYS), and elongation A% (or E%), are determined by a tensile test according to NF EN ISO 6892-1.
• a first object of the invention is a manufacturing process for obtaining extrusions made from a 6xxx aluminium alloy, comprising the following successive steps:
• the manufacturing process for obtaining extrusions made from an alloy of the composition disclosed in step a) allows to obtain an extrusion whose mechanical strength potential is maintained, in particular there is no loss of strength in the first few hours following step f).
• the addition of Sn maintains the properties of the 6xxx alloys and prevents the effects of natural aging and its negative impact on mechanical properties.
• the homogenization temperature of step b) is preferably from 500°C to 600°C and more preferably from 530°C to 590°C, and even more preferably from 540°C to 580°C.
• the homogenizing comprises two steps treatment, wherein the temperature of the second step is higher than the temperature of the first step.
• the homogenizing two steps treatment b) consists in a first step at a temperature from 500°C to 560°C, preferably from 510°C to 550°C and more preferably from 515°C to 545°C during at most 10 hours, preferably at most 8 hours and even more preferably at most 6 hours, and a second step at a temperature between 540°C and 590°C, preferably from 545°C to 580°C and more preferably from 550°C to 570°C for between 8 and 18 hours, preferably between 10 and 16 hours.
• step b After the homogenizing of step b) the homogenized cast billet is cooled to room temperature.
• the re-heating step before extrusion consists in a pre-heating of the homogenized cast billet, between 400°C and 530°C during a period of less than 1 hour, before performing subsequently the extrusion step d).
• the re-heating step c) comprises re-heating at a temperature between Ts-60°C and Ts, wherein Ts is the solidus temperature of the said aluminium alloy, and quenching until the billet mean temperature reaches a value between 400°C and 480°C in its center while ensuring that the billet surface never goes below a temperature of substantially 400°C.
• the extrusion of step d) is performed immediately after the step of quenching. Immediately corresponds typically to a time period between 1 second to 2 minutes. This time period has to be limited to avoid that the surface temperature of the billet goes below 400°C.
• Quenching step is preferably performed by water spraying.
• Extrusion is carried out at an extrusion rate from 5 m/min to 15 m/min with preferably an entry temperature of the head of the billet from 450°C to 500°C and an entry temperature of the foot of the billet from 400°C to 450°C to obtain an extruded profile.
• the head of the billet is the first part to be extruded and the foot of the billet is the last part to be extruded.
• step e After extrusion the extruded profile is quenched in step e). Quenching can be realized with strong air flow or preferably with a water spray, a water bath and or more preferably through a standing wave.
• the extruding step d) allows to form a solid or hollow extrusion.
• a controlled cold deformation or stretching is applied in a step f).
• the purpose of such stretching is to have a stress-relief and straight extrusion, according to the deformation it underwent during step e).
• the extrusion is stretched, which induces a plastic deformation, preferably of at least 0.1 % and preferentially of at least 0.5 % and preferably of at most 4%, more preferably of at most 2% and even more preferably of at most 1%.
• Natural ageing corresponds to properties changes at room temperature after quenching. It may start immediately after quenching or after an incubation period. Preferably, natural ageing period is for between 1 and 9 hours, more preferably between 2 and 8 hours, even more preferably between 3 and 7 hours and even more and more preferably between 4 and 7 hours.
• the extrusion is artificially final aged in step h).
• the extrusion is aged to a T6 temper.
• the ageing temperature is from 160°C to 180°C for a duration from 5 to 2 hours.
• the extrusion is overaged to a T7 temper.
• an artificial preaging step is done after the natural ageing step g) and before the final artificial ageing step h), at a temperature between for 120°C and 200°C for a duration from 0.5 to 12 hours.
• the final ageing step comprises:
• Said plastic deformation of step ii) is preferably obtained by stretching, or by in any others techniques such as hydro forming or pressing or stamping or bending or roll bending or stretch bending or rotary stretch bending or pulse magnetic forming or flow forming or forging or rolling or drawing or deep drawing or impact or inverse extrusion or punching or blanking.
• Said plastic deformation is preferentially performed at room temperature.
• said plastic deformation is applied uniformly on the said artificially preaged extrusion.
• said plastic deformation is applied locally on the said artificially preaged extrusion,
• Another object of the invention is an extruded profile made from a 6xxx aluminium alloy comprising in wt.%,
• an improved 6xxx aluminium alloy allows to conserve the same mechanical properties throughout the natural ageing process, lasting up to 10 hours after extrusion. Natural ageing can have a very negative effect on extruded profiles, and the longer the natural ageing period, the greater the decrease in mechanical properties.
• Si, Cu and Mg content are carefully adjusted in order to obtain the desired properties of strength, flow stress and the convenient solidus temperature.
• an extruded profile of the invention is made from an aluminium alloy comprising Cr ⁇ 0.18 wt.%, Zr ⁇ 0.16 wt.% and Mn ⁇ 0.57wt.%.
• an extruded profile of the invention is made from an aluminium alloy comprising Si 0.4 - 1.0 wt.%, Mg 0.4 - 0.9 wt.%, preferably Mg 0.4 - 0.83 wt.%, Cu 0.02 - 0.9 wt.%, preferably Cu 0.02 - 0.85 wt.%.
• an extruded profile of the invention is made from an aluminium alloy comprising Si 0.4 - 0.9 wt.%, Mg 0.4 - 1.0 wt.%, Cu 0.02 - 1.1 wt.%, Fe 0.15 - 0.55 wt.%, Mn 0.05 - 0.57 wt.%, Cr 0.06 - 0.15 wt.%, and Zr 0.05 - 0.15 wt.%.
• an extruded profile of the invention is made from an aluminium alloy comprising Si 0.4 - 0.9 wt.%, Mg 0.4 - 0.83 wt.%, Cu 0.02 - 0.85, wt.%, Mn 0.05 - 0.60 wt.%, Cr 0.06 - 0.15 wt.%, Zr 0.05 - 0.15 wt.%, Fe 0.15 - 0.55 wt.%, Sn 0.04 - 0.08 wt.%, Zn ⁇ 0,50 wt.%, V ⁇ 0.10 wt.%, Ti ⁇ 0.10 wt.%, other elements ⁇ 0.05 each and ⁇ 0.15 total, rest aluminium.
• the content of Si is at least 0.4% in weight, or is at least 0.5%, or is at least 0.6%, or is at least 0.7%, or is at least 0.8%, or is at least 0.9%, or is at least 1.0%, or is at least 1.1%, and/or is at most 1.2%, or is at most 1.1%, or is at most 1.0%, or is at most 0.9%, or is at most 0.8%, or is at most 0.7%, or is at most 0.6%, or is at most 0.5%.
• the content of Si is from 0.4% to 1.0% and preferably from 0.4% to 0.9% in weight.
• the content of Mg is at least 0.40% in weight, or is at least 0.45%, or is at least 0.50%, or is at least 0.55%, or is at least 0.60%, or is at least 0.65%, or is at least 0.70%, or is at least 0.75%, and/or is at most 0.83%, or is at most 0.78%, or is at most 0.73%, or is at most 0.68%, or is at most 0.63%, or is at most 0.58%, or is at most 0.53%, or is at most 0.48%.
• the content of Mg is from 0.4% to 0.9% and preferably from 0.4% to 0.83% in weight.
• the content of Cu is at least 0.1% in weight, or is at least 0.2%, or is at least 0.3%, or is at least 0.4%, or is at least 0.5%, or is at least 0.6%, or is at least 0.7%, and/or is at most 0.9%, or is at most 0.8%, or is at most 0.7%, or is at most 0.6%, or is at most 0.5%, or is at most 0.4%, or is at most 0.3%, or is at most 0.2%.
• the content of Cu is from 0.02% to 0.9% and preferably from 0.02% to 0.85% in weight.
• Mn, Cr and/or Zr are added in particular to control the microstructure of the extruded profile.
• the microstructure of the extruded profile is recrystallized or essentially unrecrystallized.
• essentially unrecrystallized microstructure it is meant that the proportion of recrystallized grains is less than 35 %, preferentially less than 30 % and preferably less than 20% through the thickness of the walls the extruded profile.
• the peripheral coarse grain is, per wall side, at most 400 ⁇ m thick, preferably at most 250 ⁇ m thick and most preferably at most 200 ⁇ m thick.
• the peripheral coarse grain (PCG) is a layer of recrystallized grains on the surface of the extruded profile. It is measured in appropriate location of the extruded profile, usually excluding angles and welding zones.
• the content of Cr is at least 0,01% in weight, or is at least 0,02%, or is at least 0,03%, or is at least 0,04%, or is at least 0,05%, or is at least 0,06%, or is at least 0,07%, or is at least 0,08%, or is at least 0,09%, or is at least 0,10%, or is at least 0,11%, or is at least 0,12%, or is at least 0,13%, or is at least 0,14%, or is at least 0,15%, and/or is at most 0,25%, or is at most 0,24%, or is at most 0,23%, or is at most 0,22%, or is at most 0,21%, or is at most 0,20%, or is at most 0,19%, or is at most 0,18%, or is at most 0,17%, or is at most 0,16%, or is at most 0,15%, or is at most 0,14%, or is at most 0,13%, or is at most 0,12%, or is at most 0,11%, or is at most 0,10
• the content of Cr is from 0.01 % to 0.25 % and preferably from 0.06 % to 0.15 % in weight.
• the content of Zr is at least 0,01% in weight, or is at least 0,02%, or is at least 0,03%, or is at least 0,04%, or is at least 0,05%, or is at least 0,06%, or is at least 0,07%, or is at least 0,08%, or is at least 0,09%, or is at least 0,10%, and/or is at most 0,20%, or is at most 0,19%, or is at most 0,18%, or is at most 0,17%, or is at most 0,16%, or is at most 0,15%, or is at most 0,14%, or is at most 0,13%, or is at most 0,12%, or is at most 0,11%, or is at most 0,10%.
• the content of Zr is from 0.01 % to 0.20 % and preferably from 0.05 % to 0.15 % in weight.
• the content of Mn is at least 0,05% in weight, or is at least 0,10%, or is at least 0,15%, and/or is at most 0,80%, or is at most 0,75%, or is at most 0,70%, or is at most 0,65%, or is at most 0,60%, or is at most 0,55%, or is at most 0,50%, or is at most 0,45%, or is at most 0,40%.
• the content of Mn is from 0.05 % to 0.80 % and preferably from 0.05 % to 0.60 % in weight.
• the content of Sn is at least 0.04% in weight, or is at least 0.05%, or is at least 0.06%, or is at least 0.07%, or is at least 0.08%, or is at least 0.09%, or is at least 0.10%, or is at least 0.11%, or is at least 0.12%, or is at least 0.13%, or is at least 0.14%, and/or is at most 0.15%, or is at most 0.14%, or is at most 0.13%, or is at most 0.12%, or is at most 0.11%, or is at most 0.10%, or is at most 0.09%, or is at most 0.08%, or is at most 0.07%, or is at most 0.06%, or is at most 0.05%.
• the Sn content is from 0.04 to 0.08 in weight.
• NA natural ageing
• the content of Fe is at least 0.15% in weight, or is at least 0.20%, or is at least 0.25%, or is at least 0.30%, or is at least 0.35%, or is at least 0.40%, or is at least 0.45%, or is at least 0.50%, and/or is at most 0.55%, or is at most 0.50%, or is at most 0.45%, or is at most 0.40%, or is at most 0.35%, or is at most 0.30%, or is at most 0.25%, or is at most 0.20%.
• the Fe content is from 0.15 to 0.35 wt.% in weight.
• the Zn content is at most 0.50 wt.% in weight, preferably at most 0.40 wt.% or at most 0.30 wt.% or at most 0.20 wt.% or at most 0.10 wt.% or even at most 0.05 wt.%.
• the V content is at least 0.01% in weight, or is at least 0.015%, or is at least 0.02%, and/or is at most 0.20%, or is at most 0.15%, or is at most 0.10%, or is at most 0.05%, or is at most 0.03%.
• Ti is preferably added to control the as-cast grain structure at a content lower than 0,20 wt.%.
• the Ti content is from 0.01 wt.% to 0.07 wt.% and preferably from 0.01 wt.% to 0.05 wt.%.
• the content of other elements is less than 0.05 wt.% each and less than 0.15 wt.% total.
• the other elements are typically unavoidable impurities or incidental elements added in very small quantity such as boron which can be typically added together with Ti in the form of TiB 2 .
• the composition is adjusted so that the calculated solidus temperature using standard thermodynamic database is from 580°C to 610°C, preferably from 585°C to 600°C and more preferably from 588°C to 595°C, and even more preferably from 589°C to 594°C.
• the calculated solidus temperature using standard thermodynamic database is from 580°C to 610°C, preferably from 585°C to 600°C and more preferably from 588°C to 595°C, and even more preferably from 589°C to 594°C.
• the extruded profile may be use as an automotive component such as a crash box, a bumper, a side impact beam or a side sill, structural and non-structural parts of battery box.
• a billet has been cast with two compositions A et B listed in Table 1. Then the billet was homogenized at a temperature of around 520°C for 5 hours and 560°C for 12 hours. The homogenized cast billet was re-heated between 470°C and 490°C and introduced into the container of the extrusion press. The extrusion was then quenched down to room temperature with a cooling device (water standing wave). Then a controlled cold deformation up to 1% was applied to obtain a straight extruded profile.
• Table 1 Chemical composition in weight % Si Fe Mg Cu Mn Ni Cr Zr Ti V Zn Sn Alloy A 0.83 0.19 0.76 0.21 0.53 ⁇ 0.01 0.10 0.14 0.03 0.02 0.02 - Alloy B 0.87 0.19 0.80 0.22 0.55 ⁇ 0.01 0.09 0.13 0.03 0.01 0.02 0.04
• Alloy A is a comparative example and Alloy B is according to the invention.
• the extrusion was then stored at room temperature for times ranging from 0.5h to 12h, corresponding to a natural ageing (NA) from 0.5h to 12h.
• NA natural ageing
• the addition of Sn provides higher mechanical properties after final ageing.
• the addition of Sn reduces the negative impact on the mechanical properties of natural ageing.
• the addition of Sn can resolve the negative effect of natural ageing by allowing a more feasible process window where artificial ageing or a short stabilization treatment can be done to ensure to preserve the hardening potential of the alloy.
• the addition of Sn reduces the effects of natural ageing on mechanical properties.
• the addition of Sn coupled with pre-ageing allows to maintain the mechanical properties of the alloy even after one week.
• thermomechanical ageing step TMA was added, in which the extruded profiles were pre-aged 8h at 140°C, stretched at 4% and final-aged 8h at a temperature of 170°C.
• the addition of Sn and the thermomechanical ageing reduce the effects of natural ageing on mechanical properties, particularly when natural ageing is high. Indeed, we can see that between 0.5h and 6h, the alloy with Sn maintains its mechanical properties, whereas the difference between 0.5h and 6h of natural aging has a more significant impact on the alloy without Sn.

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Citations (6)

• 2024
  • 2024-07-26 EP EP24191070.2A patent/EP4685255A1/fr active Pending
• 2025
  • 2025-07-24 WO PCT/EP2025/071298 patent/WO2026022280A1/fr active Pending

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