METHOD FOR MANUFACTURING AN ALUMINIUM ALLOY PART BY ADDITIVE MANUFACTURING FROM A POWDER MIXTURE CONTAINING ZrSi2 PARTICLES

Abstract

Method for manufacturing an aluminium alloy part by additive manufacturing comprising a step in which a layer of a mixture of powders is locally melted then solidified, wherein the mixture of powders comprises: first particles comprising at least 80 wt. % aluminium and up to 20 wt. % one or more additional elements, and second particles of ZrSi.sub.2, the mixture of powders comprising 1.8 wt. % to 4 wt. % second particles.

Claims

1. Method for manufacturing an aluminium alloy part by additive manufacturing comprising a step in which a layer of a mixture of powders is locally melted then solidified, wherein the mixture of powders comprises: first particles comprising at least 80 wt. % aluminium and up to 20 wt. % one or more additional elements, and second particles of ZrSi.sub.2, the mixture of powders comprising 1.8 wt. % to 4 wt. % second particles.

2. Method according to claim 1, wherein the mixture of powders comprises 1.9 wt. % to 2.5 wt. % second particles.

3. Method according to claim 1, wherein the second particles have a larger size ranging from 50 nm to 5000 nm.

4. Method according to claim 1, wherein the second particles have a larger size ranging from 100 nm to 1000 nm.

5. Method according to claim 1, wherein the second particles have a larger size ranging from 400 nm to 600 nm.

6. Method according to claim 1, wherein the first particles have a larger size ranging from 10 μm to 120 μm.

7. Method according to claim 1, wherein the first particles have a larger size ranging from 20 μm to 65 μm.

8. 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.

9. Method according to claim 1, wherein the aluminium alloy is alloy 7075, alloy 6061, alloy 2219 or alloy 2024.

10. Method according to claim 1, wherein the manufacturing method is a selective laser melting process.

11. Method according to claim 1, wherein the manufacturing method is a selective electron beam melting process.

12. Method according to claim 1, wherein the mixture of powders is produced in a 3D dynamic mixer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The present invention will be better understood from the description of exemplary embodiments, given by way of illustration only and not in any way limiting, with reference to the accompanying drawings in which:

[0059] FIG. 1 is an image obtained by scanning electron microscope (SEM) of particles of aluminium alloy 6061.

[0060] FIG. 2 is an image obtained by scanning electron microscope (SEM) of aluminium particles and 1.9 wt. % ZrSi.sub.2 particles in a particular embodiment of the invention.

[0061] FIG. 3 is an image obtained by an optical microscope in the YZ plane (Z being the construction axis and Y the axis perpendicular to the displacement of the laser in the horizontal plane) of a part made from particles of an aluminium alloy 6061.

[0062] FIG. 4 is an image obtained by optical microscope in the YZ plane of a part made from a mixture of particles of aluminium alloy 6061 and 1.9 wt. % ZrSi.sub.2 particles in a particular embodiment of the invention.

[0063] FIG. 5 is an image in electron backscatter diffraction (EBSD) in the YZ plane of a part made from aluminium alloy 6061 particles.

[0064] FIG. 6 is an image in electron backscatter diffraction (EBSD) in the YZ plane of a part made from a mixture of particles of an aluminium alloy 6061 and 1.9 wt. % ZrSi.sub.2 particles, according to a particular embodiment of the invention.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0065] The method for manufacturing an aluminium alloy part by additive manufacturing comprises the following successive steps: [0066] providing a mixture of powders comprising, and preferably consisting of: [0067] a first powder comprising first particles 10 made from a first material comprising at least 80 wt. % aluminium and up to 20 wt. % of one or more additional elements, [0068] a second powder comprising second particles 20 of a second material, the second material being ZrSi.sub.2, [0069] b) forming a layer of the mixture of powders, [0070] c) locally melting the layer of the mixture of powders, preferably by laser beam scanning or by electron beam scanning, so as to form successively a plurality of melted areas, [0071] d) cooling the plurality of areas melted in step c) so as to form a plurality of solidified areas, this plurality of solidified areas consisting of the first elements of the parts to be constructed.

[0072] Advantageously, steps b), c) and d) can be repeated at least once so as to form at least one other solidified area on the first solidified area. The method is repeated until the final form of the part is obtained. The first layer of the mixture of powders is formed on a substrate.

[0073] The addition of ZrSi.sub.2 particles 20 to the aluminium-based first particles 10 of interest makes it possible to obtain a substantially equiaxed solidification structure and a crack-free final aluminium alloy part.

[0074] Preferably, the first particles 10 are functionalised by the second particles 20, for example by electrostatic grafting.

[0075] Preferably, the second particles 20 consist of ZrSi.sub.2.

[0076] The second ZrSi.sub.2 powder preferably represents from 1.8 wt. % to 4 wt. % of the mixture of powders. In other words, the mixture of powders comprises from 1.8 wt. % to 4 wt. % second particles and from 96 wt. % to 98.2 wt. % first particles. The second ZrSi.sub.2 powder represents, even more preferably, 1.9 wt. % to 2.5 wt. % of the mixture of powders. In other words, the mixture of powders comprises 1.9 wt. % to 2.5 wt. % second particles and 97.5 wt. % to 98.1 wt. % first particles.

[0077] According to an advantageous embodiment, the first particles 10 have a larger size ranging from 10 μm to 120 μm and preferably from 20 μm to 65 μm.

[0078] Advantageously, the second particles 20 have a larger size ranging from 50 nm to 5000 nm and, preferably from 100 nm to 1000 nm, even more preferably from 400 nm to 600 nm.

[0079] The first particles 10 and the second particles 20 may be for example, elements which can have a spherical, ovoid or elongated form. Preferably, the particles are substantially spherical and their largest dimension is their diameter.

[0080] The first powder is formed by first particles 10 made from a first material. The first material comprises at least 80 wt. % aluminium, and preferably at least 90 wt. % aluminium.

[0081] The first particles 10 can comprise up to 20% and preferably up to 10 wt. % of 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.

[0082] Preferably, the alloy is aluminium alloy 7075, alloy 2024, alloy 2219 or aluminium alloy 6061.

[0083] The mixture of powders provided in step a) is made upstream of the additive manufacturing process.

[0084] In a preferred embodiment of the invention, the first powder and the second powder are mixed in the 3D dynamic mixer, for example with a Turbula® mixer. Alternatively, it could be a method for mechanosynthesis.

[0085] During step c), a beam of sufficient energy is used to melt at least the first particles 10.

[0086] The deposited layer can be melted locally or totally.

[0087] The melting step makes it possible to create melted patterns in the layer of the mixture of powders. One or more areas of melted particles can be made to form the desired pattern. The particles 10 forming the pattern melt completely so that during the solidification (step d), one or more solidified areas of an aluminium alloy are formed.

[0088] Advantageously, steps b), c) and d) may be repeated at least once so as to form at least one other solidified area on the first solidified area. The method is repeated until the final form of the part is obtained.

[0089] The non-solidified powders are then evacuated and the final part is detached from the substrate.

[0090] The part obtained, according to one of these methods, may be subjected to an annealing step (heat treatment) to reduce internal stresses and improve the mechanical properties.

[0091] According to a first embodiment, the method is a Powder Bed Laser Fusion (FBLF) process, also known as Powder Bed Fusion (PBF) and erroneously as selective laser melting (SLM). By way of illustration and in a non-limiting manner, the parameters of the powder bed laser fusion manufacturing method are: [0092] between 50 and 500 W for the laser power, [0093] between 100 and 2000 mm/s for the laser speed, [0094] between 25 and 120 μm for the distance between two vector spaces (hatch), [0095] between 15 and 60 μm for the layer thickness.

[0096] According to another embodiment, the method is an electron beam melting (EBM) process on a powder bed. By way of illustration and in a non-limiting manner, the parameters of the EBM manufacturing process on a powder bed are: [0097] between 50 and 3000 W for the electron beam, [0098] between 100 and 8000 mm/s for the beam speed, [0099] between 50 and 200 μm for the distance between two vector spaces, [0100] between 30 and 150 μm for the layer thickness.
The depositing machines used for 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 about 1060 nm), a scanner for directing the beam, and a substrate (also referred to as a tray) which can be lowered vertically (according to a Z-axis perpendicular to the powder bed).

[0101] The assembly can be confined in a thermally closed and inerted enclosure to control the atmosphere, but also to avoid the dissemination of the powders.

[0102] Although this is by no means limiting, the invention can be applied in particular in the field of aeronautics and in the automotive field.

Illustrative and Non-Limiting Examples of an Embodiment

[0103] In this example, cube-shaped parts with dimensions 10 mm*10 mm*10 mm are manufactured by SLM printing.

[0104] The part is obtained from a mixture of two powders: an aluminium alloy powder and a ZrSi.sub.2 powder.

[0105] The particle size of the aluminium alloy powder (Al6061), measured by a particle size laser on a Malvern Panalytical Mastersizer 2000 device, is as follows: d.sub.10=27.5 μm, d.sub.50=41.5 μm and d.sub.90=62.7 μm. The powder is observed by SEM (FIG. 1).

[0106] With regard to the ZrSi.sub.2 powder, its particle size is about 500 nm.

[0107] The mixture of the two powders is made in a glove box from: 1200 mL aluminium alloy powder to be refined, 17 mL ZrSi.sub.2 powder (mixture at 1.4% by volume, which represents 1.9 wt. %), and 250 mL of 5 mm diameter zirconia beads, used for homogenising the mixture. The volume of the mixing pot is 6.5 L.

[0108] The filling rate, defined as the ratio of the volume represented by particles 10, particles 20 and zirconia beads to the volume of the mixing pot, is approximately 23%.

[0109] The mixture is passed through a 3D dynamic mixer, for example the Turbula®, for 10 h.

[0110] The mixture is then returned to the glove box to be screened coarsely (1 mm) to recover the zirconia beads.

[0111] The mixture of powders was observed by SEM (FIG. 2). The aluminium alloy particles 6061 appear in grey and the particles of ZrSi.sub.2 in white.

[0112] The mixture of powder is then used to manufacture parts by 3D printing.

[0113] For example, the SLM conditions that make it possible to obtain the densest cubes are as follows: laser power: 189-270 W; laser speed: 400-800 mm/s, vector space: 100 μm; layer thickness (powder bed): 20 μm.

[0114] For comparison, an aluminium part is made without adding ZrSi.sub.2 powders.

[0115] The part manufactured solely with aluminium powder (FIG. 3) has cracks. The part obtained with the mixture of powders containing 1.9 wt. % ZrSi.sub.2 powder is a dense part (>99%) without cracks (FIG. 4).

[0116] The part manufactured without adding ZrSi.sub.2 powder and the one manufactured with 1.9 wt. % ZrSi.sub.2 were characterised by backscattered electron diffraction (FIGS. 5 and 6 respectively): the addition of 1.9 wt. % ZrSi.sub.2 leads to a refinement of the microstructure, making it possible to avoid the problem of hot cracking.

REFERENCES

[0117] 1. Stemmer et al “Thermodynamic considerations in the stability of binary oxides for alternative gate dielectrics in complementary metal-oxide-semiconductors” J. Vac. Sci. Technol. B 22 (2004), 791. [0118] 2. Clouet et al “Nucleation of Al 3 Zr and Al 3 Sc in aluminum alloys: From kinetic Monte Carlo simulations to classical theory”, Phys. Rev. B 69 (2004), 064109. [0119] 3. Knipling et al “Nucleation and Precipitation Strengthening in Dilute Al—Ti and Al—Zr Alloys” Metal and Mat Trans A 38 (2007), 2552-2563.