EP4363141A1 - Method for manufacturing a 6061 aluminium alloy part by additive manufacturing - Google Patents

Method for manufacturing a 6061 aluminium alloy part by additive manufacturing

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Publication number
EP4363141A1
EP4363141A1 EP22741356.4A EP22741356A EP4363141A1 EP 4363141 A1 EP4363141 A1 EP 4363141A1 EP 22741356 A EP22741356 A EP 22741356A EP 4363141 A1 EP4363141 A1 EP 4363141A1
Authority
EP
European Patent Office
Prior art keywords
aluminum alloy
zirconium
particles
heat treatment
powder
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP22741356.4A
Other languages
German (de)
French (fr)
Inventor
Mathieu OPPRECHT
Jean-Paul Garandet
Guilhem Roux
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Original Assignee
Commissariat a lEnergie Atomique CEA
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Commissariat a lEnergie Atomique CEA, Commissariat a lEnergie Atomique et aux Energies Alternatives CEA filed Critical Commissariat a lEnergie Atomique CEA
Publication of EP4363141A1 publication Critical patent/EP4363141A1/en
Pending legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/20—Direct sintering or melting
    • B22F10/28—Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/60—Treatment of workpieces or articles after build-up
    • B22F10/64—Treatment of workpieces or articles after build-up by thermal means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y10/00—Processes of additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y40/00—Auxiliary operations or equipment, e.g. for material handling
    • B33Y40/20—Post-treatment, e.g. curing, coating or polishing
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/0408—Light metal alloys
    • C22C1/0416—Aluminium-based alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/047—Making non-ferrous alloys by powder metallurgy comprising intermetallic compounds
    • 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
    • C22F1/04—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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/16—Metallic particles coated with a non-metal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/17—Metallic particles coated with metal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • B22F2998/10—Processes characterised by the sequence of their steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
    • B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
    • B22F9/082—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying atomising using a fluid
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
    • C22C32/001—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides
    • C22C32/0015—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides with only single oxides as main non-metallic constituents
    • C22C32/0036—Matrix based on Al, Mg, Be or alloys thereof

Definitions

  • the present invention relates to the general field of the manufacture of aluminum alloy 6061 parts.
  • the invention relates to a method of manufacturing an aluminum alloy part and a part thus obtained.
  • the invention is particularly interesting since it makes it possible to improve the mechanical resistance of an aluminum alloy 6061 chemically modified by the addition of zirconium.
  • the invention finds applications in numerous industrial fields, and in particular in the automobile and aeronautical fields or else for the structural reinforcement of aluminum alloys.
  • the raw material is in the form of powders and the shaping of the alloy is done in the liquid process, by melting the powder particles then solidifying the liquid phase thus formed, during cooling.
  • FLLP powder bed laser fusion
  • aluminum alloys having a solidification according to a columnar structure are subject to the problem of hot cracking.
  • the heat treatment conventionally applied is the so-called T6 treatment.
  • This treatment is broken down into 3 steps: re-dissolving (for example around 530°C for 5 hours), quenching and tempering (for example at 175°C for 9 hours).
  • the re-dissolution step makes it possible to return the Mg and Si elements to solid solution so that they are trapped during quenching.
  • tempering at 175°C precipitates the hardening b" phase, rich in Mg and Si ([3], [4], [5]).
  • the last known point concerns the growth kinetics of the AbSc and AhZr phases in an Al-rich environment.
  • the growth kinetics of the AbSc phase was studied by numerical simulation ([9]). A good correlation is demonstrated: after 2 hours at 400°C the size of the particles is around 3-4 nm.
  • these Zr-Si precipitates form more easily than AhZr, as evidenced by their more negative enthalpy of formation than that of the AhZr phase, regardless of the Zr/Si precipitate that forms ([11]).
  • the enthalpy of formation of the AhZr phase is -27kJ/mol, against -77kJ/mol for the SiZr2 phase, - 61kJ/mol for SiZr3, -57kJ/mol for ShZr, -88kJ/mol for ShZrs .
  • An object of the present invention is to propose a process for the additive manufacturing of parts in aluminum alloy 6061 chemically modified by the addition of zirconium making it possible to remedy at least in part the drawbacks of the prior art and making it possible to obtain a part having good mechanical properties.
  • the present invention proposes a method for manufacturing a part in aluminum alloy 6061 chemically modified by adding zirconium comprising the following steps: i) printing a part by Powder Bed Laser Fusion (FLLP) (or by Anglo-Saxon terminology Laser Powder Bed Fusion (LPBF)), from a powder comprising particles of aluminum alloy 6061 and zirconium, the zirconium representing at least 0.7% by mass relative to the total mass of the aluminum alloy, ii) performing a heat treatment on the printed aluminum alloy part, the heat treatment being carried out at a temperature of at least 350°C.
  • FLLP Powder Bed Laser Fusion
  • LPBF Laser Powder Bed Fusion
  • the temperature of the heat treatment in step ii) is between 380°C and 420°C, preferably between 390°C and 410°C.
  • the duration of the heat treatment in step ii) is between 1 hour and 3 hours, preferably between 1 hour 30 minutes and 2 hours 30 minutes.
  • the temperature of the heat treatment in stage ii) is between 395° C. and 405° C. and the duration of the heat treatment in stage ii) is between 1h50 and 2h10. For example, we will choose a temperature of 400°C and a duration of 2 hours.
  • the invention differs fundamentally from the prior art by the implementation of a particular heat treatment on the part printed by additive manufacturing.
  • annealing at such temperatures makes it possible to improve the mechanical properties of the printed part and in particular the elastic response of the material.
  • a heat treatment at 400° C. for 2 hours makes it possible to improve the elastic response of the material up to at 340 MPa.
  • Obtaining AUZr nanoparticles requires a large thermal budget. For example, annealing at 300°C does not allow the precipitation of hardening AhZr particles within a reasonable annealing time. For a heat treatment at a temperature of 350° C., a period of several tens of hours is necessary to form AhZr nanoparticles.
  • Such a thermal budget may turn out to be too large for other particles. This surplus can have negative effects.
  • a temperature of 400°C appears to be too high to promote the formation and preservation of b" (rich in Si and Mg). Due to the good mobility of Mg and Si in FCC aluminium, the b'' will grow and very quickly transform into Mg Si. However, these phases are known to be non-hardening for aluminium.
  • a treatment at 400° C. is also not sufficient to bring the elements Mg and Si back into solution, a key step for the formation of the b'' according to the treatment T6.
  • the heat treatment at a temperature of at least 350° C., and preferably of at least 380° C. allows a marked improvement in the mechanical properties whereas non-hardening Mg Si forms during tempering. .
  • Zr-Si intermetallics were formed during heat treatment for our Al-Mg-Si-Zr alloy. Due to their size (typically greater than 20 nm), such precipitates do not allow the improvement of the mechanical properties.
  • a particular point related to the high temperatures encountered in the AM process is that the Mg evaporates preferentially, thus leaving Si in excess with respect to its stoichiometry with respect to the Mg, capable of forming the ZrSi intermetallics observed in the matrix.
  • These Zr-Si precipitates, having a more negative enthalpy of formation than that of the AhZr phase, form more easily than the latter.
  • materials resulting from AM have very high dislocation densities (typically greater than 10 14 nr 2 ), which strongly contributes to the value of the elastic limit. Nevertheless, at a high temperature, conventionally at least greater than 0.7 times the melting temperature T f , this dislocation density can decrease by mutual annihilation. Thus, in the case of the method of the present invention, implementing high temperature annealing, a drop in hardness was expected, which, against all expectation, was not observed.
  • the heat treatment according to the invention therefore brings into play numerous physico-chemical phenomena, each leading to contradictory tendencies. Nevertheless, at the end of the process, the part obtained has good mechanical properties and in particular a strong elastic response.
  • the zirconium is added to the 6061 alloy powders in the form of particles of YSZ, ZrÜ2, ZrSh or a mixture thereof.
  • the zirconium represents from 0.7 to 6% by mass relative to the total mass of the aluminum alloy.
  • the zirconium represents at most 4% relative to the total mass of the aluminum alloy.
  • the zirconium represents from 0.7% to 1.4% by mass relative to the total mass of the aluminum alloy.
  • step i) can comprise the following steps: a) supplying a powder comprising particles of aluminum alloy
  • step b) depositing a layer of powder on a solid substrate or on an underlying layer of powder, c) locally melting the layer of powder deposited by scanning a laser beam, so as to form a molten pool, d ) cooling the molten bath so as to solidify it, repeating the cycle comprising steps b), c) and d) several times, whereby a printed aluminum alloy part is formed, the zirconium being added before step c) , and preferably before step b).
  • the powder provided in step a) comprises the aluminum alloy particles functionalized with particles containing Zr; which makes it possible to easily modify the mass ratio between the powders when mixing the powder,
  • the zirconium is added during a liquid atomization step prior to step c), and preferably prior to step b).
  • the method according to the invention implementing both an FLLP printing step and a particular heat treatment, has many advantages:
  • T6 conventional treatment
  • the invention also relates to a part in aluminum alloy 6061 chemically modified by adding zirconium and obtained by such a process.
  • the zirconium represents at least 0.7% by mass, and preferably from 0.7 to 1.4% by mass relative to the total mass of the aluminum alloy.
  • the size of the equiaxed grains is less than 1 ⁇ m, and preferably less than 0.8 ⁇ m, for example 0.7 ⁇ m. These grains form a continuous equiaxed zone at the bottom of the fusion pool.
  • the heat-treated part comprises AUZr nanoparticles having a size between 1 and 6 nm and preferably between 2 and 5 nm.
  • the elastic stress of the part is between 300 and 400 MPa, preferably greater than or equal to 330 MPa, for example between 330 and 350 MPa.
  • the part is a heat exchanger.
  • Figure 1 is a graph representing the evolution of the hardness of the alloy 6061+1,2mass% Zr printed by laser fusion on a powder bed as a function of time and tempering temperature (175°C, 300°C and 400°C).
  • FIG. 2A is a diffraction photograph obtained with a transmission electron microscope (TEM) of a part manufactured according to a particular embodiment of the invention: a 6061 + 1.2 mass % Zr alloy, printed by FLLP and heat-treated at 400°C for 2 hours (orientation relationship [100]AI // [100]AI3ZG).
  • TEM transmission electron microscope
  • Figures 2B, 2C and 2D are shots obtained by transmission electron microscopy of a printed part manufactured according to a particular embodiment of the invention.
  • FIG. 2E is an image obtained by high-resolution transmission electron microscopy of a printed part manufactured according to a particular embodiment of the invention, confirming the coherence of nano-AUZr with aluminum.
  • Figures 2F and 2G are shots obtained by transmission electron microscopy of a printed part manufactured according to a particular embodiment of the invention.
  • FIGS. 2H and 21 are snapshots representing EDS analyses, confirming the presence of precipitates rich in Al and Zr (AhZr).
  • FIG. 3A is a snapshot of a part manufactured according to a particular embodiment of the invention (alloy 6061+1.2 mass % Zr, printed by FLLP and heat-treated at 400° C. for 2 hours).
  • Figures 3B, 3C and 3D are EDS analyses, respectively Si, Mg and Zr, of a grain of the alloy of Figure 3A.
  • the method for manufacturing a part in aluminum alloy 6061 chemically modified by adding zirconium by additive manufacturing comprises the following successive steps: i) printing a part in aluminum alloy 6061 chemically modified by additive manufacturing, from zirconium and a powder comprising 6061 aluminum alloy particles, the zirconium representing at least 0.7% by mass relative to the total mass of the aluminum alloy, ii) performing a heat treatment on the alloy part printed aluminium, the heat treatment being carried out at a temperature of at least 350°C.
  • the zirconium preferably represents from 0.7% to 1.4% by mass, and even more preferably from 0.9 to 1.3% by mass relative to the total mass of the alloy, for example from 1.1 % to 1.3% by mass relative to the total mass of the alloy.
  • the aluminum 6061 particles have a larger dimension ranging from 10 ⁇ m to 120 ⁇ m and the particles containing Zr have a larger dimension ranging from 5 nm to 6000 nm and, preferably, from 10 nm to 1000 nm, even more preferably from 60 nm to 400 nm.
  • the 6061 aluminum alloy particles are substantially spherical and their largest dimension is their diameter.
  • the Zr is added in the form of particles containing Zr to the powder comprising particles of aluminum alloy 6061.
  • the particles containing Zr are particles of yttria-stabilized zirconia (or YSZ for “Yttria-Stabilized Zirconia”), of ZrÜ2 or of ZrSh. It can also be one of their mixtures. For example, it may be a mixture of YSZ and ZrÜ2, or even a mixture of YSZ, ZrÜ2 and ZrSh.
  • the 6061 alloy particles are functionalized by the particles containing Zr.
  • the 6061 aluminum particles and the particles containing Zr can be mixed with the 3D dynamic mixer, for example with a Turbula ® mixer. Alternatively, it could be a mechanosynthesis process.
  • the aluminum alloy part is printed by additive manufacturing.
  • the deposition machines used for additive manufacturing processes include, for example, a powder supply system (“Powder delivery System”), a device for spreading and homogenizing the surface of the powder (“Roller”) or "Blade”), a beam (for example an infrared laser beam at a wavelength of approximately 1064nm), a scanner to direct the beam, and a substrate (also called plate) which can descend vertically (along a Z axis perpendicular to the powder bed).
  • Step i) is advantageously carried out by laser fusion on a powder bed. It may comprise the following steps: a) providing a powder of aluminum alloy 6061 particles, b) depositing the powder so as to form a layer of powder, c) locally melting the layer of powder, by sweeping a laser beam, so as to form a molten bath, d) cooling the molten bath to solidify it, the solidified molten bath constituting the first elements of the parts to be built.
  • the zirconium is added before step c) and preferably before step b).
  • Zr can be added by grafting or inclusion.
  • a sufficiently energetic beam is used to melt the particles.
  • a molten bath is thus obtained comprising a first surface and a second surface.
  • the first surface is in contact with a solid substrate or with the underlying layer of powders.
  • the second surface is a free surface interfacing with the atmosphere of the manufacturing chamber.
  • the two surfaces delimit a volume, called fusion pool.
  • the deposited layer can be locally melted or completely melted. It is possible to form a melted zone or a plurality of melted zones.
  • the melting step makes it possible to create melted patterns in the layer of the mixture of powders.
  • One or more areas of fused particles can be made to form the desired pattern.
  • the particles forming the pattern melt completely so as to lead, during solidification (step d), to one or more zones solidified in an aluminum alloy.
  • the molten bath is cooled at a cooling rate Vr so as to solidify it.
  • the cooling rate Vr at the start of solidification at the level of the first surface of the molten bath is:
  • Vfrns ⁇ W 9.10 s -4 10 s fî) with w the mass percentage of zirconium relative to the total mass of aluminum alloy, and
  • Vr min 10 6 K/s.
  • Such a cooling rate at the pool bottom influences the formation of an equiaxed structure.
  • the cooling rate increases from the bottom of the molten pool (also called the bottom of the melting pool) towards the center of the molten pool, i.e. it is weaker at the bottom where the equiaxed growth is observed.
  • a cooling rate Vr at the start of solidification for example, less than 10 7 K/s at the level of the first surface of the molten bath
  • a particular chemical composition in Zr at least 0.7% mass
  • a number of germination events (AhZr particles) in the available volume and time associated with this 3D printing process greater than 10 5 , preferably greater than 10 6 .
  • This promotes an equiaxed solidification structure over the entire surface at the bottom of the melting pool with grain sizes of less than lpm, preferably 0.7 pm (mean diameter).
  • the cooling rate at the start of solidification is greater than 2 ⁇ 10 6 K/s at the level of the first surface of the solidification front (ie at the level of the first surface of the molten bath).
  • Steps b), c) and d) are repeated at least once so as to form at least one other solidified zone on the first solidified zone.
  • the process is repeated until the final shape of the part is obtained, the first layer of powder mixture being formed on a substrate (also called a plate).
  • the parameters of the process for manufacturing the part printed by laser fusion on a powder bed are:
  • the assembly can be confined in a thermally closed and inerted enclosure, to control the atmosphere, but also to prevent the dissemination of powders.
  • the unsolidified powders are then evacuated and the final part is detached from the substrate.
  • the part thus printed has a continuity of equiaxed grains having a size of less than 1 pm, for example 0.7 pm at the bottom of the melting pools.
  • the part is then subjected to heat treatment (step ii).
  • the heat treatment is carried out at a temperature of at least 350°C.
  • the temperature is preferably below 420°C.
  • the temperature is between 380°C and 420°C, and preferably between 390°C and 410°C and even more preferably between 395°C and 405°C.
  • the duration of the heat treatment is advantageously between 1 hour and 3 hours.
  • a duration of between 1h30 and 2h30 and even more preferably between 1h50 and 2h10 will be chosen.
  • the heat treatment consists of a step at a temperature of between 380° C. and 420° C., preferably for a period of between 1 hour and 3 hours.
  • a temperature of between 390° C. and 410° C. and a duration of between 1 hour 30 minutes and 2 hours 30 minutes will be chosen. Even more advantageously, a temperature of between 395° C. and 405° C. and a duration of between 1 h 50 and 2 h 10 will be chosen.
  • the part thus obtained (after the printing and heat treatment steps) has a fine microstructure and good mechanical properties.
  • the size of the AUZr particles of the part is between 1 and 6 nm and preferably between 2 and 5 nm.
  • the elastic stress of a part obtained by such a process is advantageously between 300 and 400 MPa, preferably greater than 330 MPa.
  • the invention particularly finds applications for structural reinforcement.
  • the invention finds applications in the field of energy, and more particularly, heat exchangers, in the field of aeronautics and in the field of automobiles.
  • an AI6061 aluminum alloy powder with a size between 20 and 63 ⁇ m is chemically modified, by adding 1.8% by mass of ZrÜ2 by dry process. This addition corresponds to a contribution of 1.2 wt% of Zr in the printed part.
  • the powder can be printed in a laser powder bed fusion (FLLP) machine.
  • FLLP laser powder bed fusion
  • the FLLP conditions used are: - Laser power: 216 W,

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Plasma & Fusion (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Powder Metallurgy (AREA)

Abstract

The invention relates to a method for manufacturing a 6061 aluminium alloy part, which is chemically modified by adding zirconium, comprising the following steps: i) printing a 6061 aluminium alloy part by additive manufacturing, in particular by laser powder bed fusion, from a powder comprising 6061 aluminium alloy particles and zirconium, wherein the zirconium contributes for at least 0.7% by weight relative to the total weight of the aluminium alloy, ii) performing a heat treatment on the printed aluminium alloy part, the heat treatment being performed at a temperature of at least 350°C.

Description

PROCEDE DE FABRICATION D'UNE PIECE EN ALLIAGE D'ALUMINIUM 6061 PAR METHOD FOR MANUFACTURING A 6061 ALUMINUM ALLOY PART BY
FABRICATION ADDITIVEADDITIVE MANUFACTURING
DESCRIPTIONDESCRIPTION
DOMAINE TECHNIQUE TECHNICAL AREA
La présente invention se rapporte au domaine général de la fabrication de pièce en alliage d'aluminium 6061. The present invention relates to the general field of the manufacture of aluminum alloy 6061 parts.
L'invention concerne un procédé de fabrication d'une pièce en alliage d'aluminium et une pièce ainsi obtenue. The invention relates to a method of manufacturing an aluminum alloy part and a part thus obtained.
L'invention est particulièrement intéressante puisqu'elle permet d'améliorer la résistance mécanique d'un alliage d'aluminium 6061 modifié chimiquement par l'ajout de zirconium. The invention is particularly interesting since it makes it possible to improve the mechanical resistance of an aluminum alloy 6061 chemically modified by the addition of zirconium.
L'invention trouve des applications dans de nombreux domaines industriels, et notamment dans les domaines de l'automobile et de l'aéronautique ou encore pour le renforcement structural d'alliages d'aluminium. The invention finds applications in numerous industrial fields, and in particular in the automobile and aeronautical fields or else for the structural reinforcement of aluminum alloys.
ÉTAT DE LA TECHNIQUE ANTÉRIEURE PRIOR ART
Dans un procédé de fusion laser sur lit de poudre (FLLP), la matière première se présente sous forme de poudres et la mise en forme de l'alliage se fait elle en voie liquide, en faisant fondre les particules des poudres puis en solidifiant la phase liquide ainsi formée, lors du refroidissement. In a powder bed laser fusion (FLLP) process, the raw material is in the form of powders and the shaping of the alloy is done in the liquid process, by melting the powder particles then solidifying the liquid phase thus formed, during cooling.
Au moins pour certaines nuances d'intérêt industriel, des alliages d'aluminium ayant une solidification selon une structure colonnaire sont sujets au problème de fissuration à chaud. At least for certain grades of industrial interest, aluminum alloys having a solidification according to a columnar structure are subject to the problem of hot cracking.
Classiquement, pour résoudre le phénomène de fissuration à chaud, il est connu de modifier chimiquement la composition de l'alliage d'aluminium afin de favoriser au moins localement une croissance de type équiaxe. Pour ce faire une manière de procéder est de revêtir les poudres d'aluminium avec d'autres particules contenant du zirconium. Dans le cas de l'ajout de particules contenant du Zr, il a été montré que l'ajout de Zircone Yttriée (YSZ) à des particules d'alliage d'aluminium permet de raffiner l'alliage d'aluminium et de complètement supprimer les fissures ([1], [2]). Conventionally, to resolve the hot cracking phenomenon, it is known to chemically modify the composition of the aluminum alloy in order to promote, at least locally, growth of the equiaxed type. To do this, one way of proceeding is to coat the aluminum powders with other particles containing zirconium. In the case of the addition of particles containing Zr, it has been shown that the addition of Yttria Zirconia (YSZ) to aluminum alloy particles makes it possible to refine the aluminum alloy and to completely remove the cracks ([1], [2]).
Pour améliorer la résistance mécanique d'un alliage d'aluminium imprimé par fusion laser sur lit de poudre, il est possible de mettre en œuvre un traitement thermique adapté. To improve the mechanical resistance of an aluminum alloy printed by laser fusion on a powder bed, it is possible to implement a suitable heat treatment.
Par exemple, pour améliorer la résistance de l'alliage 6061, le traitement thermique classiquement appliqué est le traitement dit T6. Ce traitement se décompose en 3 étapes : une remise en solution (par exemple autour de 530°C pendant 5h), une trempe et un revenu (par exemple à 175°C pendant 9h). L'étape de remise en solution permet de remettre en solution solide les éléments Mg et Si afin qu'ils soient piégés lors de la trempe. Puis le revenu à 175°C permet de faire précipiter la phase b" durcissante, riche en Mg et Si ([3], [4], [5]). For example, to improve the resistance of the 6061 alloy, the heat treatment conventionally applied is the so-called T6 treatment. This treatment is broken down into 3 steps: re-dissolving (for example around 530°C for 5 hours), quenching and tempering (for example at 175°C for 9 hours). The re-dissolution step makes it possible to return the Mg and Si elements to solid solution so that they are trapped during quenching. Then tempering at 175°C precipitates the hardening b" phase, rich in Mg and Si ([3], [4], [5]).
Ces phases évoluent avec le temps (ou la température) en précipités moins durcissants b' et Mg Si. Un revenu à haute température (typiquement supérieur à 300°C) est particulièrement néfaste pour les propriétés mécaniques. L'étude de l'évolution de la dureté avec la température et le temps de revenu montre que, pour une température comprise entre 350 et 420°C, la dureté chute y compris pour des temps de revenu courts. Cette diminution est associée à la précipitation de gros précipités Mg Si non durcissants ([5]). These phases evolve with time (or temperature) into less hardening b′ and MgSi precipitates. Tempering at high temperature (typically above 300° C.) is particularly harmful for the mechanical properties. The study of the evolution of hardness with temperature and tempering time shows that, for a temperature between 350 and 420°C, the hardness drops even for short tempering times. This decrease is associated with the precipitation of large non-hardening MgSi precipitates ([5]).
De même, il a été observé qu'un recuit très long, même à basse température, détériore la dureté de l'alliage 6061 ([6]). Similarly, it has been observed that a very long annealing, even at low temperature, deteriorates the hardness of the 6061 alloy ([6]).
Ainsi, il est connu de la littérature qu'une température de revenu trop haute (supérieure à 300°C) ainsi qu'un temps trop long sont néfastes aux propriétés d'un alliage Al-Mg-Si. Thus, it is known from the literature that too high a tempering temperature (greater than 300° C.) as well as too long a time are detrimental to the properties of an Al-Mg-Si alloy.
L'autre point connu de la littérature concerne les alliages d'aluminium contenant du Zr piégé en solution solide. A partir d'une certaine température, il est possible de faire précipiter des nano-particules d'AUZr durcissantes dans la matrice aluminium. A titre illustratif, de précédents auteurs ont montré qu'un traitement à 400°C permet la précipitation de nanoparticules d'AUZr durcissantes dans un alliage Al-Mg-Zr imprimé par FLLP ([7]). Ces nano-précipités possèdent deux avantages : durcir la matrice d'environ 40%, et améliorer la tenue en température de l'alliage, grâce à la faible diffusivité du Zr dans les solides Al-Mg. The other known point in the literature concerns aluminum alloys containing Zr trapped in solid solution. From a certain temperature, it is possible to precipitate hardening AUZr nano-particles in the aluminum matrix. By way of illustration, previous authors have shown that a treatment at 400°C allows the precipitation of hardening AUZr nanoparticles in an Al-Mg-Zr alloy. printed by FLLP ([7]). These nano-precipitates have two advantages: harden the matrix by around 40%, and improve the temperature resistance of the alloy, thanks to the low diffusivity of Zr in Al-Mg solids.
Il a également été démontré qu'un traitement à 400°C pendant 2h permet de précipiter des nanoparticules d'AUZr de taille comprise entre 2 et 5nm. Celles- ci permettent de nettement améliorer la résistance mécanique d'un alliage de type 5083 chimique modifié (Al-Mg-Mn-Fe + Zr) ([8]). It has also been demonstrated that a treatment at 400° C. for 2 hours makes it possible to precipitate AUZr nanoparticles of size between 2 and 5 nm. These make it possible to significantly improve the mechanical strength of a chemically modified 5083 type alloy (Al-Mg-Mn-Fe + Zr) ([8]).
Le dernier point connu porte sur la cinétique de croissance des phases AbSc et AhZr dans un environnement riche en Al. La cinétique de croissance de la phase AbSc a été étudiée par simulation numérique ([9]). Une bonne corrélation est mise en évidence : après 2h à 400°C la taille des particules avoisine les 3-4nm. The last known point concerns the growth kinetics of the AbSc and AhZr phases in an Al-rich environment. The growth kinetics of the AbSc phase was studied by numerical simulation ([9]). A good correlation is demonstrated: after 2 hours at 400°C the size of the particles is around 3-4 nm.
Il est également connu que des intermétalliques Zr-Si précipitent lorsqu'ils constituent les éléments d'addition d'un alliage base aluminium ([10]). De tels précipités ne permettent pas l'amélioration des propriétés mécaniques des pièces en alliage d'aluminium. It is also known that Zr-Si intermetallics precipitate when they constitute the addition elements of an aluminum base alloy ([10]). Such precipitates do not allow the improvement of the mechanical properties of aluminum alloy parts.
De plus, ces précipités Zr-Si se forment plus facilement que les AhZr, comme en témoigne leur enthalpie de formation plus négative que celle de la phase AhZr, quel que soit le précipité Zr/Si qui se forme ([11]). A titre illustratif, l'enthalpie de formation de la phase AhZr est de -27kJ/mol, contre -77kJ/mol pour la phase SiZr2, - 61kJ/mol pour SiZr3, -57kJ/mol pour ShZr, -88kJ/mol pour ShZrs. Moreover, these Zr-Si precipitates form more easily than AhZr, as evidenced by their more negative enthalpy of formation than that of the AhZr phase, regardless of the Zr/Si precipitate that forms ([11]). By way of illustration, the enthalpy of formation of the AhZr phase is -27kJ/mol, against -77kJ/mol for the SiZr2 phase, - 61kJ/mol for SiZr3, -57kJ/mol for ShZr, -88kJ/mol for ShZrs .
Ainsi, de nombreux phénomènes physico-chimiques co-existent lors du traitement thermique d'un alliage AI6061 modifié chimiquement par l'ajout de zirconium. Thus, many physico-chemical phenomena co-exist during the heat treatment of an AI6061 alloy chemically modified by the addition of zirconium.
EXPOSÉ DE L'INVENTION DISCLOSURE OF THE INVENTION
Un but de la présente invention est de proposer un procédé de fabrication additive de pièces en alliage d'aluminium 6061 modifié chimiquement par ajout de zirconium permettant de remédier au moins en partie aux inconvénients de l'art antérieur et permettant d'obtenir une pièce ayant de bonnes propriétés mécaniques. Pour cela, la présente invention propose un procédé de fabrication d'une pièce en alliage d'aluminium 6061 modifié chimiquement par ajout de zirconium comprenant les étapes suivantes : i) imprimer une pièce par Fusion Laser sur Lit de Poudre (FLLP) (ou en terminologie anglo-saxonne Laser Powder Bed Fusion (LPBF)), à partir d'une poudre comprenant des particules en alliage d'aluminium 6061 et de zirconium, le zirconium représentant au moins 0,7% massique par rapport à la masse totale de l'alliage d'aluminium, ii) réaliser un traitement thermique sur la pièce en alliage d'aluminium imprimée, le traitement thermique étant réalisé à une température d'au moins 350°C. An object of the present invention is to propose a process for the additive manufacturing of parts in aluminum alloy 6061 chemically modified by the addition of zirconium making it possible to remedy at least in part the drawbacks of the prior art and making it possible to obtain a part having good mechanical properties. For this, the present invention proposes a method for manufacturing a part in aluminum alloy 6061 chemically modified by adding zirconium comprising the following steps: i) printing a part by Powder Bed Laser Fusion (FLLP) (or by Anglo-Saxon terminology Laser Powder Bed Fusion (LPBF)), from a powder comprising particles of aluminum alloy 6061 and zirconium, the zirconium representing at least 0.7% by mass relative to the total mass of the aluminum alloy, ii) performing a heat treatment on the printed aluminum alloy part, the heat treatment being carried out at a temperature of at least 350°C.
Avantageusement, la température du traitement thermique à l'étape ii) est comprise entre 380°C et 420°C, de préférence entre 390°C et 410°C. Advantageously, the temperature of the heat treatment in step ii) is between 380°C and 420°C, preferably between 390°C and 410°C.
Avantageusement, la durée du traitement thermique à l'étape ii) est comprise entre lh et 3h, de préférence entre lh30 et 2h30. Advantageously, the duration of the heat treatment in step ii) is between 1 hour and 3 hours, preferably between 1 hour 30 minutes and 2 hours 30 minutes.
De manière très avantageuse, la température du traitement thermique à l'étape ii) est comprise entre 395°C et 405°C et la durée du traitement thermique à l'étape ii) est comprise entre lh50 et 2hl0. Par exemple, on choisira une température de 400°C et une durée de 2h. Very advantageously, the temperature of the heat treatment in stage ii) is between 395° C. and 405° C. and the duration of the heat treatment in stage ii) is between 1h50 and 2h10. For example, we will choose a temperature of 400°C and a duration of 2 hours.
L'invention se distingue fondamentalement de l'art antérieur par la mise en œuvre d'un traitement thermique particulier sur la pièce imprimée par fabrication additive. The invention differs fundamentally from the prior art by the implementation of a particular heat treatment on the part printed by additive manufacturing.
En particulier, les inventeurs ont montré qu'un recuit à de telles températures permettait d'améliorer les propriétés mécaniques de la pièce imprimée et notamment la réponse élastique du matériau. A titre d'exemple, par rapport à un matériau AI6061 + l,2%massique Zr brut de fabrication FLLP ayant une limite élastique de 241 MPa, un traitement thermique à 400°C pendant 2h permet d'améliorer la réponse élastique du matériau jusqu'à 340 MPa. In particular, the inventors have shown that annealing at such temperatures makes it possible to improve the mechanical properties of the printed part and in particular the elastic response of the material. By way of example, compared to an AI6061 + 1.2% Zr material as manufactured FLLP having an elastic limit of 241 MPa, a heat treatment at 400° C. for 2 hours makes it possible to improve the elastic response of the material up to at 340 MPa.
De plus, avec de telles températures de recuit, les inventeurs ont remarqué une absence de grossissement de grains au cours du recuit. La fine microstructure, induite par le procédé FLLP et la modification chimique de l'alliage, est conservée et contribue à la limite élastique. Moreover, with such annealing temperatures, the inventors noticed an absence of grain growth during the annealing. The thin microstructure, induced by the FLLP process and the chemical modification of the alloy, is preserved and contributes to the elastic limit.
En outre, même s'il peut induire une réorganisation de la répartition des dislocations au sein du matériau, un tel recuit permet de préserver la densité de dislocations initiale. C'est un point intéressant car les densités de dislocations très élevées dans les matériaux bruts de FLLP contribuent à la limite élastique. Furthermore, even if it can induce a reorganization of the distribution of the dislocations within the material, such annealing makes it possible to preserve the initial density of dislocations. This is an interesting point because the very high dislocation densities in the FLLP raw materials contribute to the elastic limit.
Ces résultats n'étaient pas du tout évidents car la limite élastique dans un alliage contenant du magnésium, du silicium et du zirconium est le résultat de plusieurs mécanismes contradictoires. These results were not at all obvious because the yield point in an alloy containing magnesium, silicon and zirconium is the result of several contradictory mechanisms.
L'obtention de nanoparticules d'AUZr nécessite un budget thermique important. Par exemple, un recuit à 300°C ne permet pas la précipitation de particules AhZr durcissant dans un délai de recuit raisonnable. Pour un traitement thermique à une température de 350°C, une durée de plusieurs dizaines d'heures est nécessaire pour former des nanoparticules d'AhZr. Obtaining AUZr nanoparticles requires a large thermal budget. For example, annealing at 300°C does not allow the precipitation of hardening AhZr particles within a reasonable annealing time. For a heat treatment at a temperature of 350° C., a period of several tens of hours is necessary to form AhZr nanoparticles.
Un tel budget thermique peut s'avérer trop important pour d'autres particules. Ce surplus peut avoir des effets négatifs. A titre illustratif, une température de 400°C apparaît comme trop élevée pour favoriser la formation et la conservation de b" (riches en Si et Mg). Du fait de la bonne mobilité du Mg et du Si dans l'aluminium FCC, les b'' vont grossir et très rapidement se transformer en Mg Si. Or, ces phases sont connues comme étant non durcissantes pour l'aluminium. Such a thermal budget may turn out to be too large for other particles. This surplus can have negative effects. By way of illustration, a temperature of 400°C appears to be too high to promote the formation and preservation of b" (rich in Si and Mg). Due to the good mobility of Mg and Si in FCC aluminium, the b'' will grow and very quickly transform into Mg Si. However, these phases are known to be non-hardening for aluminium.
Par ailleurs, un traitement à 400°C n'est également pas suffisant pour remettre en solution les éléments Mg et Si, étape clé pour la formation des b'' selon le traitement T6. Moreover, a treatment at 400° C. is also not sufficient to bring the elements Mg and Si back into solution, a key step for the formation of the b'' according to the treatment T6.
Ainsi, contre tout attente, le traitement thermique à une température d'au moins 350°C, et de préférence d'au moins 380°C permet une nette amélioration des propriétés mécaniques alors que des Mg Si non durcissants se forment au cours du revenu. Thus, against all expectations, the heat treatment at a temperature of at least 350° C., and preferably of at least 380° C., allows a marked improvement in the mechanical properties whereas non-hardening Mg Si forms during tempering. .
Même si la littérature témoigne de l'effet néfaste des traitements thermiques à haute température (supérieure à 300°C) pour les alliages Al-Mg-Si, les inventeurs ont constaté une amélioration importante de la contrainte élastique en lien avec l'ajout de Zr et ce malgré l'apparition de Mg2Si. Even if the literature testifies to the harmful effect of heat treatments at high temperature (above 300°C) for Al-Mg-Si alloys, the inventors have observed a significant improvement in the elastic stress in connection with the addition of Zr, despite the appearance of Mg2Si.
De plus, des intermétalliques Zr-Si se sont formés pendant le traitement thermique pour notre alliage Al-Mg-Si-Zr. De par leur taille (typiquement supérieure à 20nm), de tels précipités ne permettent pas l'amélioration des propriétés mécaniques. Un point particulier lié aux températures élevées rencontrées dans le procédé de FA est que le Mg s'évapore préférentiellement, laissant ainsi du Si en excès par rapport à sa stœchiométrie vis-à-vis du Mg, susceptible de former les intermétalliques ZrSi observés dans la matrice. Ces précipités Zr-Si, ayant une enthalpie de formation plus négative que celle de la phase AhZr, se forment plus facilement que ces derniers. In addition, Zr-Si intermetallics were formed during heat treatment for our Al-Mg-Si-Zr alloy. Due to their size (typically greater than 20 nm), such precipitates do not allow the improvement of the mechanical properties. A particular point related to the high temperatures encountered in the AM process is that the Mg evaporates preferentially, thus leaving Si in excess with respect to its stoichiometry with respect to the Mg, capable of forming the ZrSi intermetallics observed in the matrix. These Zr-Si precipitates, having a more negative enthalpy of formation than that of the AhZr phase, form more easily than the latter.
Par conséquent, il n'était pas évident qu'assez de Zr soit encore disponible pour former des nanoparticules d'AUZr, participant à l'amélioration des propriétés mécaniques. Contre tout attente, une quantité significative de nanoparticules de AhZr se forme, permettant l'amélioration des propriétés mécaniques de l'alliage 6061+Zr imprimé et traité thermiquement à une température d'au moins 350°C. Consequently, it was not evident that enough Zr was still available to form AUZr nanoparticles, contributing to the improvement of the mechanical properties. Against all expectations, a significant amount of AhZr nanoparticles are formed, allowing the improvement of the mechanical properties of the 6061+Zr alloy printed and heat-treated at a temperature of at least 350°C.
Par ailleurs, il est connu que les matériaux issus de la FA ont des densités de dislocation très élevées (typiquement supérieures à 1014nr2), ce qui contribue fortement à la valeur de la limite élastique. Néanmoins, à une température élevée, de façon conventionnelle au moins supérieure à 0,7 fois la température de fusion Tf, cette densité de dislocations peut diminuer par annihilation mutuelle. Ainsi, dans le cas du procédé de la présente invention, mettant en œuvre un recuit à haute température, une chute de dureté était attendue, ce qui, contre toute attente, n'a pas été observé. Furthermore, it is known that materials resulting from AM have very high dislocation densities (typically greater than 10 14 nr 2 ), which strongly contributes to the value of the elastic limit. Nevertheless, at a high temperature, conventionally at least greater than 0.7 times the melting temperature T f , this dislocation density can decrease by mutual annihilation. Thus, in the case of the method of the present invention, implementing high temperature annealing, a drop in hardness was expected, which, against all expectation, was not observed.
Le traitement thermique selon l'invention met donc en jeu de nombreux phénomènes physico-chimiques, chacun menant à des tendances contradictoires. Néanmoins, à l'issue du procédé la pièce obtenue présente de bonnes propriétés mécaniques et notamment une forte réponse élastique. The heat treatment according to the invention therefore brings into play numerous physico-chemical phenomena, each leading to contradictory tendencies. Nevertheless, at the end of the process, the part obtained has good mechanical properties and in particular a strong elastic response.
Avantageusement, le zirconium est ajouté aux poudres d'alliage 6061 sous forme de particules de YSZ, de ZrÜ2, de ZrSh ou un de leurs mélanges. Avantageusement, le zirconium représente de 0,7 à 6 % massique par rapport à la masse totale de l'alliage d'aluminium. Avantageusement, le zirconium représente au plus 4% par rapport à la masse totale de l'alliage d'aluminium. De préférence, le zirconium représente de 0,7% à 1,4% massique par rapport à la masse totale de l'alliage d'aluminium. Advantageously, the zirconium is added to the 6061 alloy powders in the form of particles of YSZ, ZrÜ2, ZrSh or a mixture thereof. Advantageously, the zirconium represents from 0.7 to 6% by mass relative to the total mass of the aluminum alloy. Advantageously, the zirconium represents at most 4% relative to the total mass of the aluminum alloy. Preferably, the zirconium represents from 0.7% to 1.4% by mass relative to the total mass of the aluminum alloy.
Avantageusement, l'étape i) peut comprendre les étapes suivantes : a) fournir une poudre comprenant des particules en alliage d'aluminiumAdvantageously, step i) can comprise the following steps: a) supplying a powder comprising particles of aluminum alloy
6061, b) déposer une couche de poudre sur un substrat solide ou sur une couche de poudre sous-jacente, c) faire fondre localement la couche de poudre déposée par balayage d'un faisceau laser, de manière à former un bain fondu, d) refroidir le bain fondu de manière à le solidifier, répéter plusieurs fois le cycle comprenant les étapes b), c) et d) moyennant quoi on forme une pièce en alliage d'aluminium imprimée, le zirconium étant ajouté avant l'étape c), et de préférence avant l'étape b). 6061, b) depositing a layer of powder on a solid substrate or on an underlying layer of powder, c) locally melting the layer of powder deposited by scanning a laser beam, so as to form a molten pool, d ) cooling the molten bath so as to solidify it, repeating the cycle comprising steps b), c) and d) several times, whereby a printed aluminum alloy part is formed, the zirconium being added before step c) , and preferably before step b).
Le procédé peut être mis en œuvre quel que soit le moyen d'ajout du zirconium : The process can be implemented regardless of the means of adding the zirconium:
- par greffage : la poudre fournie à l'étape a) comprend les particules en alliage d'aluminium fonctionnalisées par des particules contenant du Zr ; ce qui permet de pouvoir facilement modifier le rapport massique entre les poudres au moment du mélange de poudre, - By grafting: the powder provided in step a) comprises the aluminum alloy particles functionalized with particles containing Zr; which makes it possible to easily modify the mass ratio between the powders when mixing the powder,
- par inclusion: le zirconium est ajouté lors d'une étape d'atomisation en voie liquide préalablement à l'étape c), et de préférence préalablement à l'étape b). - by inclusion: the zirconium is added during a liquid atomization step prior to step c), and preferably prior to step b).
Le procédé selon l'invention, mettant en œuvre à la fois une étape d'impression FLLP et un traitement thermique particulier, présente de nombreux avantages : The method according to the invention, implementing both an FLLP printing step and a particular heat treatment, has many advantages:
- être simple à mettre en œuvre en comparaison avec un traitement classique (T6) ; en effet, avec le procédé selon l'invention aucune trempe n'est nécessaire, et le temps total et le budget énergétique du traitement thermique restent faibles comparés à ceux du T6, - be simple to implement compared to conventional treatment (T6); indeed, with the method according to the invention, no quenching is necessary, and the total time and the energy budget of the heat treatment remain low compared to those of the T6,
- être peu coûteux, et donc intéressant d'un point de vue industriel,- be inexpensive, and therefore interesting from an industrial point of view,
- pouvoir stocker/manipuler facilement les poudres, - be able to easily store/handle powders,
- pouvoir utiliser les paramètres classiquement utilisés dans les procédés de fabrication additive. - be able to use the parameters conventionally used in additive manufacturing processes.
La modification chimique de l'alliage 6061, l'impression par FLLP de la pièce et la mise en œuvre de ce traitement thermique particulier (notamment pour des températures autour de 400°C pendant environ 2h) conduisent à l'obtention d'un effet synergique. On obtient ainsi une pièce comprenant de très petites tailles de grains, des quantités de dislocations importantes et des nanoprécipités. De telles caractéristiques ne pourraient pas être obtenues ave un autre procédé de fabrication additive, avec un alliage 6061 sans zirconium ou avec un autre traitement thermique. The chemical modification of the 6061 alloy, the FLLP printing of the part and the implementation of this particular heat treatment (in particular for temperatures around 400°C for approximately 2 hours) lead to the obtaining of an effect synergistic. A part is thus obtained comprising very small grain sizes, large quantities of dislocations and nanoprecipitates. Such characteristics could not be obtained with another additive manufacturing process, with a 6061 alloy without zirconium or with another heat treatment.
L'invention concerne également une pièce en alliage d'aluminium 6061 modifié chimiquement par ajout de zirconium et obtenue par un tel procédé. Le zirconium représente au moins 0,7% massique, et de préférence de 0,7 à 1,4 % massique par rapport à la masse totale de l'alliage d'aluminium. The invention also relates to a part in aluminum alloy 6061 chemically modified by adding zirconium and obtained by such a process. The zirconium represents at least 0.7% by mass, and preferably from 0.7 to 1.4% by mass relative to the total mass of the aluminum alloy.
La taille des grains équiaxes est inférieure à 1 pm, et préférentiellement inférieure à 0,8 pm, par exemple de 0,7 pm. Ces grains forment une zone équiaxe continue en fond de piscine de fusion. The size of the equiaxed grains is less than 1 μm, and preferably less than 0.8 μm, for example 0.7 μm. These grains form a continuous equiaxed zone at the bottom of the fusion pool.
La pièce traitée thermiquement comprend des nanoparticules d'AUZr ayant une taille comprise entre 1 et 6nm et de préférence entre 2 et 5nm. The heat-treated part comprises AUZr nanoparticles having a size between 1 and 6 nm and preferably between 2 and 5 nm.
Avantageusement, la contrainte élastique de la pièce est comprise entre 300 et 400MPa, préférentiellement supérieure ou égale à 330 MPa, par exemple entre 330 et 350MPa. Advantageously, the elastic stress of the part is between 300 and 400 MPa, preferably greater than or equal to 330 MPa, for example between 330 and 350 MPa.
Avantageusement, la pièce est un échangeur thermique. Advantageously, the part is a heat exchanger.
D'autres caractéristiques et avantages de l'invention ressortiront du complément de description qui suit. Il va de soi que ce complément de description n'est donné qu'à titre d'illustration de l'objet de l'invention et ne doit en aucun cas être interprété comme une limitation de cet objet. Other characteristics and advantages of the invention will emerge from the additional description which follows. It goes without saying that this additional description is only given by way of illustration of the object of the invention and should in no way be interpreted as a limitation of this object.
BRÈVE DESCRIPTION DES DESSINS BRIEF DESCRIPTION OF DRAWINGS
La présente invention sera mieux comprise à la lecture de la description d'exemples de réalisation donnés à titre purement indicatif et nullement limitatif en faisant référence aux dessins annexés sur lesquels : The present invention will be better understood on reading the description of exemplary embodiments given purely for information and in no way limiting with reference to the appended drawings in which:
La figure 1 est un graphique représentant l'évolution de la dureté de l'alliage 6061+1, 2massique% Zr imprimé par fusion laser sur lit de poudre en fonction du temps et de la température de revenu (175°C, 300°C et 400°C). Figure 1 is a graph representing the evolution of the hardness of the alloy 6061+1,2mass% Zr printed by laser fusion on a powder bed as a function of time and tempering temperature (175°C, 300°C and 400°C).
La figure 2A est un cliché de diffraction obtenu au microscope électronique à transmission (MET) d'une pièce fabriquée selon un mode de réalisation particulier de l'invention : un alliage 6061 + l,2massique % Zr, imprimée par FLLP et traitée thermiquement à 400°C pendant 2h (relation d'orientation [100]AI // [100]AI3ZG). FIG. 2A is a diffraction photograph obtained with a transmission electron microscope (TEM) of a part manufactured according to a particular embodiment of the invention: a 6061 + 1.2 mass % Zr alloy, printed by FLLP and heat-treated at 400°C for 2 hours (orientation relationship [100]AI // [100]AI3ZG).
Les Figures 2B, 2C et 2D sont des clichés obtenus par microscopie électronique à transmission d'une pièce imprimée fabriquée selon un mode de réalisation particulier de l'invention. Figures 2B, 2C and 2D are shots obtained by transmission electron microscopy of a printed part manufactured according to a particular embodiment of the invention.
La figure 2E est un cliché obtenu par obtenue microscopie électronique à transmission en haute résolution d'une pièce imprimée fabriquée selon un mode de réalisation particulier de l'invention, confirmant la cohérence des nanos-AUZr avec l'aluminium. FIG. 2E is an image obtained by high-resolution transmission electron microscopy of a printed part manufactured according to a particular embodiment of the invention, confirming the coherence of nano-AUZr with aluminum.
Les figures 2F et 2G sont des clichés obtenus par microscopie électronique à transmission d'une pièce imprimée fabriquée selon un mode de réalisation particulier de l'invention, Figures 2F and 2G are shots obtained by transmission electron microscopy of a printed part manufactured according to a particular embodiment of the invention,
Les figure 2H et 21 sont des clichés représentant des analyses EDS, confirmant la présence de précipités riche en Al et Zr (AhZr). FIGS. 2H and 21 are snapshots representing EDS analyses, confirming the presence of precipitates rich in Al and Zr (AhZr).
La figure 3A est un cliché d'une pièce fabriquée selon un mode de réalisation particulier de l'invention (alliage 6061 + l,2massique % Zr, imprimée par FLLP et traitée thermiquement à 400°C pendant 2h). Les figures 3B, 3C et 3D sont des analyses EDS, respectivement Si, Mg et Zr, d'un grain de l'alliage de la figure 3A. FIG. 3A is a snapshot of a part manufactured according to a particular embodiment of the invention (alloy 6061+1.2 mass % Zr, printed by FLLP and heat-treated at 400° C. for 2 hours). Figures 3B, 3C and 3D are EDS analyses, respectively Si, Mg and Zr, of a grain of the alloy of Figure 3A.
EXPOSÉ DÉTAILLÉ DE MODES DE RÉALISATION PARTICULIERS DETAILED DISCUSSION OF PARTICULAR EMBODIMENTS
Le procédé de fabrication d'une pièce en alliage d'aluminium 6061 modifié chimiquement par ajout de zirconium par fabrication additive comprend les étapes successives suivantes : i) imprimer une pièce en alliage d'aluminium 6061 modifié chimiquement par fabrication additive, à partir de zirconium et d'une poudre comprenant des particules en alliage d'aluminium 6061, le zirconium représentant au moins 0,7% massique par rapport à la masse totale de l'alliage d'aluminium, ii) réaliser un traitement thermique sur la pièce en alliage d'aluminium imprimée, le traitement thermique étant réalisé à une température d'au moins 350°C. The method for manufacturing a part in aluminum alloy 6061 chemically modified by adding zirconium by additive manufacturing comprises the following successive steps: i) printing a part in aluminum alloy 6061 chemically modified by additive manufacturing, from zirconium and a powder comprising 6061 aluminum alloy particles, the zirconium representing at least 0.7% by mass relative to the total mass of the aluminum alloy, ii) performing a heat treatment on the alloy part printed aluminium, the heat treatment being carried out at a temperature of at least 350°C.
Le zirconium représente, de préférence, de 0,7% à 1,4% massique, et encore plus préférentiellement de 0,9 à 1,3% massique par rapport à la masse totale de l'alliage, par exemple de 1,1% à 1,3% massique par rapport à la masse totale de l'alliage. The zirconium preferably represents from 0.7% to 1.4% by mass, and even more preferably from 0.9 to 1.3% by mass relative to the total mass of the alloy, for example from 1.1 % to 1.3% by mass relative to the total mass of the alloy.
Selon un mode de réalisation avantageux, pour l'ajout de zirconium par greffage, les particules d'aluminium 6061 ont une plus grande dimension allant de 10pm à 120pm et les particules contenant du Zr ont une plus grande dimension allant de 5nm à 6000nm et, de préférence, de lOnm à lOOOnm, encore plus préférentiellement de 60nm à 400nm. According to an advantageous embodiment, for the addition of zirconium by grafting, the aluminum 6061 particles have a larger dimension ranging from 10 μm to 120 μm and the particles containing Zr have a larger dimension ranging from 5 nm to 6000 nm and, preferably, from 10 nm to 1000 nm, even more preferably from 60 nm to 400 nm.
De préférence, les particules d'alliage d'aluminium 6061 sont sensiblement sphériques et leur plus grande dimension est leur diamètre. Preferably, the 6061 aluminum alloy particles are substantially spherical and their largest dimension is their diameter.
Avantageusement, le Zr est ajouté sous forme de particules contenant du Zr à la poudre comprenant des particules en alliage d'aluminium 6061. Advantageously, the Zr is added in the form of particles containing Zr to the powder comprising particles of aluminum alloy 6061.
De préférence, les particules contenant du Zr sont des particules de zircone yttriée (ou YSZ pour « Yttria-Stabilized Zirconia »), de ZrÜ2 ou de ZrSh. Il peut également s'agir d'un de leurs mélanges. Par exemple, il peut s'agir d'un mélange de YSZ et de ZrÜ2, ou encore un mélange de YSZ, de ZrÜ2 et de ZrSh. Avantageusement, les particules d'alliage 6061 sont fonctionnalisées par les particules contenant du Zr. Les particules d'aluminium 6061 et les particules contenant du Zr peuvent être mélangées au mélangeur dynamique 3D, par exemple avec un mélangeur Turbula®. Alternativement, il pourrait s'agir d'un procédé de mécano- synthèse. Preferably, the particles containing Zr are particles of yttria-stabilized zirconia (or YSZ for “Yttria-Stabilized Zirconia”), of ZrÜ2 or of ZrSh. It can also be one of their mixtures. For example, it may be a mixture of YSZ and ZrÜ2, or even a mixture of YSZ, ZrÜ2 and ZrSh. Advantageously, the 6061 alloy particles are functionalized by the particles containing Zr. The 6061 aluminum particles and the particles containing Zr can be mixed with the 3D dynamic mixer, for example with a Turbula ® mixer. Alternatively, it could be a mechanosynthesis process.
Lors de l'étape i), on imprime la pièce en alliage d'aluminium par fabrication additive. Les machines de dépôt utilisées pour les procédés de fabrication additive comprennent, par exemple, un système d'alimentation en poudre (« Powder delivery System »), un dispositif d'étalement et d'homogénéisation de la surface de la poudre (« Roller » ou « Blade »), un faisceau (par exemple un faisceau laser infrarouge à une longueur d'onde de 1064nm environ), un scanner pour diriger le faisceau, et un substrat (aussi appelé plateau) qui peut descendre verticalement (selon un axe Z perpendiculaire au lit de poudre). During step i), the aluminum alloy part is printed by additive manufacturing. The deposition machines used for additive manufacturing processes include, for example, a powder supply system (“Powder delivery System”), a device for spreading and homogenizing the surface of the powder (“Roller”) or "Blade"), a beam (for example an infrared laser beam at a wavelength of approximately 1064nm), a scanner to direct the beam, and a substrate (also called plate) which can descend vertically (along a Z axis perpendicular to the powder bed).
L'étape i) est avantageusement réalisée par fusion laser sur lit de poudre. Elle peut comprendre les étapes suivantes : a) fournir une poudre de particules en alliage d'aluminium 6061, b) déposer la poudre de manière à former une couche de poudre, c) faire fondre localement la couche de poudre, par balayage d'un faisceau laser, de manière à former un bain fondu, d) refroidir le bain fondu pour le solidifier, le bain fondu solidifié étant constitutif des premiers éléments des pièces à construire. Step i) is advantageously carried out by laser fusion on a powder bed. It may comprise the following steps: a) providing a powder of aluminum alloy 6061 particles, b) depositing the powder so as to form a layer of powder, c) locally melting the layer of powder, by sweeping a laser beam, so as to form a molten bath, d) cooling the molten bath to solidify it, the solidified molten bath constituting the first elements of the parts to be built.
Le zirconium est ajouté avant l'étape c) et de préférence avant l'étape b). L'ajout de Zr peut être réalisé par greffage ou inclusion. The zirconium is added before step c) and preferably before step b). Zr can be added by grafting or inclusion.
Lors de l'étape c), on utilise un faisceau suffisamment énergétique pour faire fondre les particules. On obtient ainsi un bain fondu comprenant une première surface et une deuxième surface. La première surface est en contact avec un substrat solide ou avec la couche de poudres sous-jacente. La deuxième surface est une surface libre faisant interface avec l'atmosphère de la chambre de fabrication. Les deux surfaces délimitent un volume, appelé piscine de fusion. La couche déposée peut être localement fondue ou totalement fondue. Il est possible de former une zone fondue ou une pluralité de zones fondues. During step c), a sufficiently energetic beam is used to melt the particles. A molten bath is thus obtained comprising a first surface and a second surface. The first surface is in contact with a solid substrate or with the underlying layer of powders. The second surface is a free surface interfacing with the atmosphere of the manufacturing chamber. The two surfaces delimit a volume, called fusion pool. The deposited layer can be locally melted or completely melted. It is possible to form a melted zone or a plurality of melted zones.
L'étape de fusion permet de créer des motifs fondus dans la couche du mélange de poudres. Une ou plusieurs zones de particules fondues peuvent être réalisées pour former le motif désiré. Les particules formant le motif fondent complètement de manière à conduire, lors de la solidification (étape d), à une ou plusieurs zones solidifiées en un alliage d'aluminium. The melting step makes it possible to create melted patterns in the layer of the mixture of powders. One or more areas of fused particles can be made to form the desired pattern. The particles forming the pattern melt completely so as to lead, during solidification (step d), to one or more zones solidified in an aluminum alloy.
Lors de l'étape d), on refroidit le bain fondu à une vitesse de refroidissement Vr de manière à le solidifier. Avantageusement, la vitesse de refroidissement Vr en début de solidification au niveau de la première surface du bain fondu est : During step d), the molten bath is cooled at a cooling rate Vr so as to solidify it. Advantageously, the cooling rate Vr at the start of solidification at the level of the first surface of the molten bath is:
- inférieure à une valeur Vrmax définie selon l'équation (1) suivante : - less than a Vr max value defined according to the following equation (1):
Vfrnsæ = W 9.10s -4 10s fî) avec w le pourcentage massique de zirconium par rapport à la masse totale d'alliage d'aluminium, et Vfrnsæ = W 9.10 s -4 10 s fî) with w the mass percentage of zirconium relative to the total mass of aluminum alloy, and
- strictement supérieure à une valeur minimale Vrmm telle que- strictly greater than a minimum value Vr mm such that
Vrmin = 106 K/s. Vr min = 10 6 K/s.
Une telle vitesse de refroidissement en fond de piscine influence la formation d'une structure équiaxe. Such a cooling rate at the pool bottom influences the formation of an equiaxed structure.
La vitesse de refroidissement augmente en partant du fond du bain fondu (aussi appelé fond de la piscine de fusion) vers le centre du bain fondu, i.e. elle est plus faible au fond là où la croissance équiaxe est observée. The cooling rate increases from the bottom of the molten pool (also called the bottom of the melting pool) towards the center of the molten pool, i.e. it is weaker at the bottom where the equiaxed growth is observed.
La combinaison d'une vitesse de refroidissement Vr en début de solidification (par exemple, inférieure à 107 K/s au niveau de la première surface du bain fondu) et d'une composition chimique particulière en Zr (au moins 0,7% massique) permet un nombre d'évènements de germination (particules d'AhZr) dans le volume et le temps disponibles liés à ce procédé d'impression 3D supérieur à 105, préférentiellement supérieur à 106. Ceci favorise une structure de solidification équiaxe sur l'intégralité de la surface en fond de piscine de fusion avec des tailles de grain faisant moins de lpm, préférentiellement 0,7pm (diamètre moyen). The combination of a cooling rate Vr at the start of solidification (for example, less than 10 7 K/s at the level of the first surface of the molten bath) and of a particular chemical composition in Zr (at least 0.7% mass) allows a number of germination events (AhZr particles) in the available volume and time associated with this 3D printing process greater than 10 5 , preferably greater than 10 6 . This promotes an equiaxed solidification structure over the entire surface at the bottom of the melting pool with grain sizes of less than lpm, preferably 0.7 pm (mean diameter).
Avantageusement, la vitesse de refroidissement en début de solidification est supérieure à 2xl06 K/s au niveau de la première surface du front de solidification (i.e. au niveau de la première surface du bain fondu). Advantageously, the cooling rate at the start of solidification is greater than 2×10 6 K/s at the level of the first surface of the solidification front (ie at the level of the first surface of the molten bath).
Les étapes b), c) et d) sont répétées au moins une fois de manière à former au moins une autre zone solidifiée sur la première zone solidifiée. Le procédé se répète jusqu'à obtenir la forme finale de la pièce, la première couche de mélange de poudres étant formée sur un substrat (aussi appelé plateau). Steps b), c) and d) are repeated at least once so as to form at least one other solidified zone on the first solidified zone. The process is repeated until the final shape of the part is obtained, the first layer of powder mixture being formed on a substrate (also called a plate).
A titre illustratif et non limitatif, les paramètres du procédé de fabrication de la pièce imprimée par fusion laser sur lit de poudre sont : By way of illustration and not limitation, the parameters of the process for manufacturing the part printed by laser fusion on a powder bed are:
- entre 50 et 500W pour la puissance laser, - between 50 and 500W for the laser power,
- entre 100 et 2000 mm/s pour la vitesse laser, - between 100 and 2000 mm/s for the laser speed,
- entre 25 et 120pm pour la distance entre deux espaces vecteurs (« hatch » en terminologie anglo-saxone), - between 25 and 120pm for the distance between two vector spaces (“hatch” in Anglo-Saxon terminology),
- entre 15 et 60pm pour l'épaisseur de couche. - between 15 and 60pm for the layer thickness.
L'ensemble peut être confiné dans une enceinte thermiquement fermée et inertée, pour contrôler l'atmosphère, mais aussi pour éviter la dissémination des poudres. The assembly can be confined in a thermally closed and inerted enclosure, to control the atmosphere, but also to prevent the dissemination of powders.
Les poudres non solidifiées sont ensuite évacuées et la pièce finale est détachée du substrat. The unsolidified powders are then evacuated and the final part is detached from the substrate.
La pièce ainsi imprimée présente une continuité de grains équiaxes ayant une taille inférieure à lpm, par exemple 0,7pm en fond des piscines de fusion. The part thus printed has a continuity of equiaxed grains having a size of less than 1 pm, for example 0.7 pm at the bottom of the melting pools.
La pièce est ensuite soumise à un traitement thermique (étape ii). The part is then subjected to heat treatment (step ii).
Le traitement thermique est réalisé à une température d'au moins 350°C. La température est, de préférence, inférieure à 420°C. The heat treatment is carried out at a temperature of at least 350°C. The temperature is preferably below 420°C.
Selon un mode de réalisation avantageux, la température est comprise entre 380°C et 420°C, et de préférence entre 390°C et 410°C et encore plus préférentiellement entre 395°C et 405°C. Pour de telles températures, la durée du traitement thermique est, avantageusement, comprise entre lh et 3h. De préférence, on choisira une durée comprise entre lh30 et 2h30 et encore plus préférentiellement entre lh50 et 2hl0. According to an advantageous embodiment, the temperature is between 380°C and 420°C, and preferably between 390°C and 410°C and even more preferably between 395°C and 405°C. For such temperatures, the duration of the heat treatment is advantageously between 1 hour and 3 hours. Preferably, a duration of between 1h30 and 2h30 and even more preferably between 1h50 and 2h10 will be chosen.
Par exemple, le traitement thermique consiste en une étape à une température comprise entre 380°C et 420°C, de préférence pendant une durée comprise entre lh et 3h. For example, the heat treatment consists of a step at a temperature of between 380° C. and 420° C., preferably for a period of between 1 hour and 3 hours.
Selon un mode de réalisation particulièrement avantageux, on choisira une température comprise entre 390°C et 410°C et une durée comprise entre lh30 et 2h30. De manière encore plus avantageuse, on choisira une température comprise entre 395°C et 405°C et une durée comprise entre lh50 et 2hl0. According to a particularly advantageous embodiment, a temperature of between 390° C. and 410° C. and a duration of between 1 hour 30 minutes and 2 hours 30 minutes will be chosen. Even more advantageously, a temperature of between 395° C. and 405° C. and a duration of between 1 h 50 and 2 h 10 will be chosen.
La pièce ainsi obtenue (après les étapes d'impression et de traitement thermique) présente une fine microstructure et de bonnes propriétés mécaniques. The part thus obtained (after the printing and heat treatment steps) has a fine microstructure and good mechanical properties.
La taille des particules d'AUZr de la pièce est comprise entre 1 et 6nm et de préférence entre 2 et 5nm. The size of the AUZr particles of the part is between 1 and 6 nm and preferably between 2 and 5 nm.
La contrainte élastique d'une pièce obtenue par un tel procédé est, avantageusement, comprise entre 300 et 400MPa, préférentiellement supérieure à 330 MPa. The elastic stress of a part obtained by such a process is advantageously between 300 and 400 MPa, preferably greater than 330 MPa.
Bien que cela ne soit aucunement limitatif, l'invention trouve particulièrement des applications pour le renforcement structural. Notamment, l'invention trouve des applications dans le domaine de l'énergie, et plus particulièrement, des échangeurs thermiques, dans le domaine de l'aéronautique et dans le domaine de l'automobile. Although this is in no way limiting, the invention particularly finds applications for structural reinforcement. In particular, the invention finds applications in the field of energy, and more particularly, heat exchangers, in the field of aeronautics and in the field of automobiles.
Exemple illustratif et non limitatif d'un mode de réalisation : Illustrative and non-limiting example of an embodiment:
Tout d'abord, une poudre d'alliage d'aluminium AI6061 de taille comprise entre 20 et 63 pm est modifiée chimiquement, en ajoutant l,8%massique de ZrÜ2 par voie sèche. Cet ajout correspond à un apport de l,2wt% de Zr dans la pièce imprimée. First, an AI6061 aluminum alloy powder with a size between 20 and 63 μm is chemically modified, by adding 1.8% by mass of ZrÜ2 by dry process. This addition corresponds to a contribution of 1.2 wt% of Zr in the printed part.
Une fois cette étape réalisée, la poudre peut être imprimée dans une machine de fusion laser sur lit de poudre (FLLP). Dans cet exemple, les conditions FLLP utilisées sont : - Puissance laser : 216 W, Once this step is done, the powder can be printed in a laser powder bed fusion (FLLP) machine. In this example, the FLLP conditions used are: - Laser power: 216 W,
- Vitesse laser : 700mm/s, - Laser speed: 700mm/s,
- Espace vecteur : lOOpm, - Vector space: lOOpm,
- Epaisseur de couche (lit de poudre) : 20pm. Plusieurs températures et temps de recuit ont été étudiés (Figure 1). Les pièces obtenues avec un traitement thermique à 400°C possèdent de bonnes propriétés mécaniques, notamment pour une durée de traitement comprise entre lh et 3h. - Layer thickness (powder bed): 20µm. Several annealing temperatures and times were studied (Figure 1). The parts obtained with a heat treatment at 400° C. have good mechanical properties, in particular for a treatment time of between 1 hour and 3 hours.
En appliquant un post-traitement thermique à l'alliage imprimé par FLLP, les inventeurs ont constaté la précipitation de particules d'AUZr de taille proche de 2-3nm pour un traitement de 400°C pendant 2h (Figures 2A à 21). Celles-ci sont cohérentes avec la matrice. By applying a thermal post-treatment to the alloy printed by FLLP, the inventors observed the precipitation of AUZr particles with a size close to 2-3 nm for a treatment at 400° C. for 2 hours (FIGS. 2A to 21). These are consistent with the matrix.
Ce procédé permet une nette amélioration de la réponse élastique du matériau avec un gain de lOOMPa supplémentaire pour cet alliage 6061+1.2massique% Zr par rapport à la valeur obtenue sur le matériau brut de fabrication. Un alliage Al-Mg-Si-Zr (AI6061+1.2% massique Zr) imprimé par FLLP et traité thermiquement à 400°C pendant 2h a été caractérisé par EDS. Il a ainsi été observé que, d'une part, des particules de Mg2Si non durcissantes se forment au cours du revenu et, d'autre part, des intermétalliques Zr-Si se sont formés pendant le traitement à 400°C pendant 2h pour notre alliage (figures 3A 3D). This process allows a marked improvement in the elastic response of the material with an additional gain of 1000 Pa for this 6061+1.2 mass% Zr alloy compared to the value obtained on the raw material of manufacture. An Al-Mg-Si-Zr alloy (Al6061+1.2 mass % Zr) printed by FLLP and heat-treated at 400°C for 2h was characterized by EDS. It has thus been observed that, on the one hand, non-hardening Mg2Si particles form during tempering and, on the other hand, Zr-Si intermetallics are formed during the treatment at 400°C for 2h for our alloy (Figures 3A 3D).
REFERENCES REFERENCES
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Claims

REVENDICATIONS
1. Procédé de fabrication d'une pièce en alliage d'aluminium 6061 modifié chimiquement par ajout de zirconium comprenant les étapes suivantes : i) imprimer une pièce en alliage d'aluminium 6061 par fusion laser sur lit de poudre, à partir d'une poudre comprenant des particules en alliage d'aluminium 6061 et de zirconium, le zirconium représentant au moins 0,7% massique et au plus 6% massique par rapport à la masse totale de l'alliage d'aluminium, ii) réaliser un traitement thermique sur la pièce en alliage d'aluminium imprimée, le traitement thermique étant réalisé à une température comprise entre 380°C et 420°C. 1. Process for manufacturing a part in aluminum alloy 6061 chemically modified by adding zirconium, comprising the following steps: i) printing a part in aluminum alloy 6061 by laser melting on a powder bed, from a powder comprising particles of aluminum alloy 6061 and zirconium, the zirconium representing at least 0.7% by mass and at most 6% by mass relative to the total mass of the aluminum alloy, ii) carrying out a heat treatment on the printed aluminum alloy part, the heat treatment being carried out at a temperature between 380°C and 420°C.
2. Procédé selon la revendication 1, caractérisé en ce que l'étape i) comprend les étapes suivantes : a) fournir une poudre comprenant des particules en alliage d'aluminium2. Method according to claim 1, characterized in that step i) comprises the following steps: a) supplying a powder comprising particles of aluminum alloy
6061, b) déposer une couche de poudre sur un substrat solide ou sur une couche de poudre sous-jacente, c) faire fondre localement la couche de poudre déposée par balayage d'un faisceau laser, de manière à former un bain fondu, d) refroidir le bain fondu de manière à le solidifier, répéter plusieurs fois le cycle comprenant les étapes b), c) et d) moyennant quoi on forme une pièce en alliage d'aluminium imprimée, le zirconium étant ajouté avant l'étape c), et de préférence avant l'étape b). 6061, b) depositing a layer of powder on a solid substrate or on an underlying layer of powder, c) locally melting the layer of powder deposited by scanning a laser beam, so as to form a molten pool, d ) cooling the molten bath so as to solidify it, repeating the cycle comprising steps b), c) and d) several times, whereby a printed aluminum alloy part is formed, the zirconium being added before step c) , and preferably before step b).
3. Procédé selon la revendication précédente, caractérisé en ce que la poudre fournie à l'étape a) comprend les particules en alliage d'aluminium fonctionnalisées par des particules contenant du Zr ou en ce que le zirconium est ajouté à l'alliage d'aluminium lors d'une étape d'atomisation en voie liquide préalablement à l'étape b). 3. Method according to the preceding claim, characterized in that the powder provided in step a) comprises aluminum alloy particles functionalized with particles containing Zr or in that zirconium is added to the alloy of aluminum during a liquid atomization step prior to step b).
4. Procédé selon l'une des revendications précédentes, caractérisé en ce que le zirconium est ajouté sous forme de particules de YSZ, de ZrÜ2, de ZrSh ou un de leurs mélanges. 4. Method according to one of the preceding claims, characterized in that the zirconium is added in the form of particles of YSZ, ZrÜ2, ZrSh or a mixture thereof.
5. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que le zirconium représente de 0,7 à 1,4 % massique par rapport à la masse totale de l'alliage d'aluminium. 5. Method according to any one of the preceding claims, characterized in that the zirconium represents from 0.7 to 1.4% by mass relative to the total mass of the aluminum alloy.
6. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que la température du traitement thermique à l'étape ii) est comprise entre 390°C et 410°C. 6. Process according to any one of the preceding claims, characterized in that the temperature of the heat treatment in step ii) is between 390°C and 410°C.
7. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que la durée du traitement thermique à l'étape ii) est comprise entre lh et 3h, de préférence entre lh30 et 2h30. 7. Method according to any one of the preceding claims, characterized in that the duration of the heat treatment in step ii) is between 1 hour and 3 hours, preferably between 1 hour 30 minutes and 2 hours 30 minutes.
8. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que la température du traitement thermique à l'étape ii) est comprise entre 395°C et 405°C et la durée du traitement thermique à l'étape ii) est comprise entre lh50 et 2hl0. 8. Method according to any one of the preceding claims, characterized in that the temperature of the heat treatment in step ii) is between 395°C and 405°C and the duration of the heat treatment in step ii) is between lh50 and 2hl0.
9. Pièce en alliage d'aluminium 6061, obtenue par le procédé selon l'une quelconque des revendications 1 à 8, le zirconium représentant au moins 0,7% massique par rapport à la masse totale de l'alliage d'aluminium, la pièce comprend des particules d'AUZr, la taille des particules d'AhZr de la pièce étant comprise entre 1 et 6nm. 9. Part in aluminum alloy 6061, obtained by the process according to any one of claims 1 to 8, the zirconium representing at least 0.7% by mass relative to the total mass of the aluminum alloy, the part comprises AUZr particles, the size of the AhZr particles of the part being between 1 and 6 nm.
10. Pièce en alliage d'aluminium 6061 selon la revendication 9, caractérisé en ce que la taille des particules d'AUZr est comprise entre 2 et 5nm. 10. Aluminum alloy 6061 part according to claim 9, characterized in that the size of the AUZr particles is between 2 and 5 nm.
11. Pièce en alliage d'aluminium 6061 selon l'une des revendications 9 et 10, caractérisé en ce que la contrainte élastique de la pièce est comprise entre 300 et 400MPa, préférentiellement supérieure ou égale à 330MPa. 11. Aluminum alloy 6061 part according to one of claims 9 and 10, characterized in that the elastic stress of the part is between 300 and 400 MPa, preferably greater than or equal to 330 MPa.
EP22741356.4A 2021-06-28 2022-06-23 Method for manufacturing a 6061 aluminium alloy part by additive manufacturing Pending EP4363141A1 (en)

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US11802321B2 (en) * 2015-03-17 2023-10-31 Elementum 3D, Inc. Additive manufacturing of metal alloys and metal alloy matrix composites
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FR3096056B1 (en) * 2019-05-13 2021-06-04 Commissariat Energie Atomique METHOD OF MANUFACTURING AN ALUMINUM ALLOY PART BY ADDITIVE MANUFACTURING FROM A MIXTURE OF POWDERS CONTAINING YTTRIA ZIRCONIA

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