METHOD FOR MANUFACTURING AN ALUMINIUM ALLOY PART BY ADDITIVE MANUFACTURING AND ALUMINIUM ALLOY PART OBTAINED ACCORDING TO THE METHOD

Abstract

A method for manufacturing an aluminium alloy part by additive manufacturing comprising a step during which a layer of a mixture of powders is melted locally and then solidified, wherein the mixture of powders comprises: —first particles—comprising at least 80 wt % of aluminium and up to 20 wt % of one or more additional elements, and —second particles—of yttria, the volume percentage of second particles in the mixture of powders preferably ranging from 0.5% to 5%.

Claims

1.-11. (canceled)

12. A method for manufacturing an aluminium alloy part by additive manufacturing, comprising a step during which a layer of a mixture of powders is locally melted and then solidified, wherein the mixture of powder comprises: first particles comprising at least 80% by mass aluminium and up to 20% by mass one or more additional elements, and second particles of yttrium oxide.

13. The method according to claim 12, wherein the percentage by volume of second particles in the mixture of powders ranges from 0.5% to 5%

14. The method according to claim 12, wherein the second particles have a largest dimension ranging from 5 nm to 2 μm.

15. The method according to claim 12, wherein the second particles have a largest dimension ranging from 30 nm to 50 nm.

16. The method according to claim 12, wherein the percentage by volume of second particles in the mixture of powders ranges from 1% to 3%.

17. The method according to claim 12, wherein the first particles have a largest dimension ranging from 10 μm to 100 μm.

18. The method according to claim 12, wherein the first particles have a largest dimension ranging from 20 to 65 μm.

19. The method according to claim 1, wherein the additional elements are selected from Cu, Si, Zn, Mg, Fe, Ti, Mn, Zr, Va, Ni, Pb, Bi and Cr.

20. The method according to claim 12, wherein the aluminium alloy is the 7075 alloy, the 2024 alloy, the 2219 alloy or the 6061 alloy.

21. The method according to claim 12, wherein the manufacturing method is a laser selective melting method.

22. The method according to claim 12, wherein the manufacturing method is an electron beam selective melting method.

23. The method according to claim 12, wherein the powder mixture is produced in a 3D dynamic mixer or by mechanosynthesis.

24. An aluminium alloy particle obtained according to the method as defined in claim 12, wherein it comprises yttrium.

25. A part according to claim 24, wherein the part is a heat exchanger.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The present invention will be better understood from a reading of the description of example embodiments given purely by way of indication and in no way limitatively, with reference to the accompanying drawings, on which:

[0049] FIG. 1, previously described, is an Ellingham diagram showing the stabilities of aluminium oxide (Al.sub.2O.sub.3) and yttrium oxide (Y.sub.2O.sub.3),

[0050] FIG. 2 schematically shows a mixture of powders according to a particular embodiment of the method of the invention.

[0051] The various parts shown in the figures are not necessarily shown to a uniform scale, to make the figures more legible.

[0052] The various possibilities (variants and embodiments) must be understood as not being exclusive of one another and may be combined with one another.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0053] The method for manufacturing an aluminium alloy part by additive manufacturing comprises the following successive steps:

[0054] providing a mixture of powders comprising, and preferably consisting of:

[0055] a first powder comprising first particles 10 made from a first material comprising at least 80% by mass aluminium and up to 20% by mass one or more additional elements,

[0056] a second powder comprising second particles 20 made from a second material, the second material being yttrium oxide,

[0057] b) forming a layer of the mixture of powders,

[0058] c) locally melting the layer of the mixture of powders, preferably by sweeping with a laser beam or by sweeping with an electron beam, so as to form a plurality of molten regions,

[0059] d) cooling the plurality melted at step c) so as to form a plurality of solidified regions, this plurality of solidified regions constituting first elements of the parts to be constructed.

[0060] Advantageously, steps b), c) and d) can be repeated at least once so as to form at least one other solidified region on the first solidified region. The method is repeated until the final form of the part is obtained. The first layer of powder mixture is formed on a substrate.

[0061] Adding particles 20 of yttrium oxide to the first particles 10 of interest based on aluminium makes it possible to obtain an equiaxial solidification structure and a final part made from aluminium alloy without cracking.

[0062] Preferably, the first particles 10 are functionalised by the second particles 20 (FIG. 2).

[0063] Preferably, the second particles 20 consist of yttrium oxide.

[0064] The second yttrium oxide powder preferably represents from 0.5% to 5% by volume of the mixture of powders, preferably from 1% to 3%.

[0065] According to an advantageous embodiment, the first particles 10 have a largest dimension ranging from 10 μm to 100 μm and the second particles 20 have a largest dimension ranging from 5 nm to 2 μm and preferably from 10 nm to 400 nm.

[0066] The first particles 10 and the second particles 20 are elements that may be of spherical, ovoid or elongate shape. Preferably, the particles are substantially spherical and the largest dimension thereof is the diameter thereof.

[0067] The first powder is formed by first particles 10 made from a first material. The first material comprises at least 80% by mass aluminium.

[0068] The first particles 10 may comprise up to 20% one or more additional elements (also referred to as alloy elements). These elements are preferably selected from zinc, magnesium, copper, silicon, iron, manganese, titanium, vanadium, bismuth, lead, nickel, zirconium and chromium. The additional element or one of the additional elements is preferably magnesium.

[0069] The alloy is preferably a 7075 aluminium alloy, a 2024 alloy, a 2219 alloy or a 6061 aluminium alloy.

[0070] The mixture of powders provided at step a) is produced upstream of the additive manufacturing method.

[0071] In a preferential embodiment of the invention, the first powder and the second powder are mixed with a 3D dynamic mixer, for example with a Turbula® mixer. Alternatively, it may be a case of a mechanosynthesis method.

[0072] During step c) a sufficiently energetic beam is used for melting at least the first particles 10.

[0073] The layer deposited may be locally melted or totally melted.

[0074] The melting step makes it possible to create molten patterns in the layer of the powder mixture. One or more regions of molten particles may be produced to form the desired pattern. The particles 10 forming the pattern melt completely so as, when solidification takes place (step d), to lead to one or more solidified regions made from an aluminium alloy.

[0075] Advantageously, steps b), c) and d) may be repeated at least once so as to form at least one other solidified region on the first solidified region. The method is repeated until the final form of the part is obtained.

[0076] The non-solidified powders are next discharged and the final part is detached from the substrate.

[0077] The part obtained according to one of these methods can be subjected to an annealing step (heat treatment) for reducing the internal stresses and improving the mechanical properties.

[0078] According to a first variant embodiment, it is a laser melting method on a powder bed (SLM). By way of illustration and non-limitatively, the parameters of the laser melting manufacturing method on powder bed are:

between 50 and 500 W for the laser power;
between 100 and 2000 mm/s for the laser speed;
between 25 and 120 μm for the distance between two vector spaces (“hatch”);
between 15 and 60 μm for the layer thickness.

[0079] According to another variant embodiment, it is an electron beam melting method on powder bed (EBM). By way of illustration and non-limitatively, the parameters of the electron beam melting manufacturing method on powder bed are:

between 50 and 3000 W for the electron beam;
between 100 and 8000 mm/s for the beam speed;
between 50 and 150 μm for the distance between two vector spaces;
between 40 and 60 μm for the layer thickness.

[0080] The machines used for the additive manufacturing methods comprise, for example, a powder delivery system, a device for spreading and homogenising the surface of the powder (roller or blade), a beam (for example an infrared laser beam with a wavelength of approximately 1060 nm), a scanner for directing the beam, and a substrate (also called a plate) that can descend vertically (along a Z axis perpendicular to the powder bed).

[0081] The assembly can be confined in a closed inerted chamber, for controlling the atmosphere, but also for avoiding dissemination of the powders.

[0082] Although this is in no way limitative, the invention particularly finds applications in the energy field, and more particularly heat exchangers, in the aeronautical field, and in the automobile field.

Illustrative and Non-Limitative Examples of an Embodiment

[0083] In this example, a part in the form of a cube with dimensions 10 mm*10 mm*12 mm is manufactured by SLM printing.

[0084] The part is obtained from a mixture of two powders: an aluminium alloy powder and an yttrium oxide powder.

[0085] The granulometry of the aluminium alloy powder (Al6061) is as follows: d.sub.10=27.5 μm, d.sub.50=41.5 μm and d.sub.90=62.7 μm.

[0086] Concerning the Y.sub.2O.sub.3 powder, the granulometry thereof ranges from 30 nm to 50 nm.

[0087] The two powders are mixed in a glove box using: 1200 ml of the aluminium alloy powder to be refined, 24 ml of the yttrium oxide powder (mixture at 2% by volume), and 250 ml of zirconia beads with a diameter of 3 mm, used for homogenising the mixture. The volume of the mixing pot is 6.5 L.

[0088] The filling factor, defined as the ratio of the volume represented by the particles 10, the particles 20 and the zirconia beads to the volume of the mixing pot, is approximately 23%.

[0089] The mixture is passed through a 3D dynamic mixer, for example a Turbula®, for 10 hours.

[0090] The mixture is next coarsely sieved (1 mm) to recover the zirconia beads, and is then used for producing a part by 3D printing.

[0091] By way of illustration, the SLM conditions for obtaining the densest cubes are as follows: laser power, 190-270 W; laser speed: 400-800 mm/s, vector space: 100 μm; layer thickness (powder bed): 20 μm.