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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• Manufacturing & Machinery (AREA)
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• Organic Chemistry (AREA)
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• 2021
  • 2021-06-28 FR FR2106909A patent/FR3124409B1/fr active Active
• 2022
  • 2022-06-23 EP EP22741356.4A patent/EP4363141A1/de active Pending
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