METHOD FOR PRODUCING AN ALUMINIUM ALLOY PART

Abstract

The invention relates to a method for producing a part, comprising the production of successive solid metallic layers (201...20n), each layer being produced by depositing a metal (25) called filler metal, said method being characterized in that the part has a specific grain structure.

The invention also relates to a part obtained by means of this method and an alternative method.

The alloy used in the additive manufacturing method of the invention makes it possible to obtain parts with exceptional properties.

Claims

1. A method for producing a part, comprising production of successive solid metallic layers, which are superimposed on each other, each layer describing a pattern defined using a digital model, each layer being produced by depositing a metal, called filler metal, the filler metal being subjected to a supply of energy so as to become molten and to constitute, upon solidifying, said layer, wherein the filler metal takes the form of a powder , the exposure of which to an energy beam results in a melting followed by a solidification, so as to form a solid layer , wherein the part is produced at a temperature from 25 to 150° C.; wherein the part has a grain structure such that the surface fraction of the equiaxial grains each having an area less than 2.16 .Math.m.sup.2 is less than 44%, optionally less than 40%, optionally less than 36%; and a grain structure such that the surface fraction of columnar grains is greater than or equal to 22%, optionally greater than or equal to 25%, optionally greater than or equal to 30%; and wherein the filler metal is an aluminum alloy comprising at least the following alloy elements: - Zr, in a mass fraction greater than or equal to 0.30%, optionally 0.30-2.50%, optionally 0.40-2.00%, optionally 0.40-1.80%, optionally 0.50-1.60%, optionally 0.60-1.50%, optionally 0.70-1.40%, optionally 0.80-1.20%; - Sc, in a mass fraction less than 0.30 %, optionally less than 0.20%, optionally less than 0.10 %, optionally less than 0.05%; - Mg, in a mass fraction less than 2.00%, optionally less than 1.00%, optionally less than 0.50%, optionally less than 0.30%, optionally less than 0.10%, optionally less than 0.05%; - Zn, in a mass fraction less than 2.00%, optionally less than 1.00%, optionally less than 0.50%, optionally less than 0.30%, optionally less than 0.10%, optionally less than 0.05%; - optionally at least one element selected from: Ni, Mn, Cr and/or Cu, in a mass fraction of 0.50 to 7.00%, optionally of 1.00 to 6.00% each; optionally preferably, in a mass fraction less than 25.00%, optionally less than 20.00%, optionally less than 15.00% in total; - optionally at least one element selected from: Hf, Ti, Er, W, Nb, Ta, Y, Yb, Nd, Ce, Co, Mo, Lu, Tm, V and/or mischmetal, in a mass fraction less than or equal to 5.00%, optionally less than or equal to 3% each, and less than or equal to 15.00%, optionally less than or equal to 12%, optionally less than or equal to 5% in total; - optionally at least one element selected from: Si, La, Sr, Ba, Sb, Bi, Ca, P, B, In and/or Sn, in a mass fraction less than or equal to 1.00%, optionally less than or equal to 0.5%, optionally less than or equal to 0.3%, optionally less than or equal to 0.1%, optionally less than or equal to 700 ppm each, and less than or equal to 2.00%, optionally less than or equal to 1% in total; - optionally Fe, in a mass fraction of 0.50 to 7.00%, optionally of 1.00 to 6.00% according to a first alternative embodiment, or in a mass fraction less than or equal to 1.00%, optionally less than or equal to 0.5%, optionally less than or equal to 0.3%, optionally less than or equal to 0.1%, optionally less than or equal to 700 ppm according to a second alternative embodiment; - optionally at least one element selected from: Ag in a mass fraction of 0.06 to 1.00% and/or Li in a mass fraction of 0.06 to 1.00%; - optionally impurities in a mass fraction less than 0.05% each optionally 500 ppm, and less than 0.15% in total; - remainder being aluminum.

2. A method for producing a part, comprising production of successive solid metallic layers, which are superimposed on each other, each layer describing a pattern defined using a digital model , each layer being produced by depositing a metal, called filler metal, the filler metal being subjected to a supply of energy so as to become molten and to constitute, upon solidifying, said layer, wherein the filler metal takes the form of a powder, the exposure of which to an energy beam results in a melting followed by a solidification, so as to form a solid layer, wherein the part is produced at a temperature from 25 to 150° C.; wherein the part has a grain structure such that surface fraction of the equiaxial grains each having an area less than 2.16 .Math.m.sup.2 is less than 44%, optionally less than 40%, optionally less than 36%; and a grain structure such that surface fraction of columnar grains is greater than or equal to 22%, optionally greater than or equal to 25%, optionally greater than or equal to 30%; wherein the filler metal is an aluminum alloy comprising at least the following alloy elements: - Zr and at least one element selected from: Ti, V, Sc, Hf, Er, Tm, Yb and Lu, in a mass fraction greater than or equal to 0.30%, optionally 0.30-2.50%, optionally 0.40-2.00%, optionally 0.40-1.80%, optionally 0.50-1.60%, optionally 0.60-1.50%, optionally 0.70-1.40%, optionally 0.80-1.20% in total, in the knowledge that Zr represents from 10 to less than 100% of the percentage ranges given hereinabove; - Mg, in a mass fraction less than 2.00%, optionally less than 1.00%, optionally less than 0.50%, optionally less than 0.30%, optionally less than 0.10%, optionally less than 0.05%; - Zn, in a mass fraction less than 2.00%, optionally less than 1.00%, optionally less than 0.50%, optionally less than 0.30%, optionally less than 0.10%, optionally less than 0.05%; - optionally at least one element selected from: Ni, Mn, Cr and/or Cu, in a mass fraction of 0.50 to 7.00%, optionally of 1.00 to 6.00% each; optionally preferably, in a mass fraction less than 25.00%, optionally less than 20.00%, optionally less than 15.00% in total; - optionally at least one element selected from: W, Nb, Ta, Y, Nd, Ce, Co, Mo and/or mischmetal, in a mass fraction less than or equal to 5.00%, optionally less than or equal to 3% each, and less than or equal to 15.00%, optionally less than or equal to 12 %, optionally less than or equal to 5% in total; - optionally at least one element selected from: Si, La, Sr, Ba, Sb, Bi, Ca, P, B, In and/or Sn, in a mass fraction less than or equal to 1.00%, optionally less than or equal to 0.5%, optionally less than or equal to 0.3%, optionally than or equal to 0.1%, optionally less than or equal to 700 ppm each, and less than or equal to 2.00%, optionally less than or equal to 1% in total; - optionally Fe, in a mass fraction of 0.50 to 7.00%, optionally of 1.00 to 6.00% according to a first alternative embodiment, or in a mass fraction less than or equal to 1.00%, optionally less than or equal to 0.5%, optionally less than or equal to 0.3%, optionally less than or equal to 0.1%, optionally less than or equal to 700 ppm according to a second alternative embodiment; - optionally at least one element selected from: Ag in a mass fraction of 0.06 to 1.00% and/or Li in a mass fraction of 0.06 to 1.00%; - optionally impurities in a mass fraction less than 0.05% each optionally 500 ppm, and less than 0.15% in total; - remainder being aluminum.

3. The method according to claim 1 , wherein the part is produced at a temperature optionally from 50 to 130° C., optionally from 50 to 110° C., optionally from 80 to 110° C., optionally from 80 to 105° C.

4. A method for producing a part comprising production of successive solid metallic layers, which are superimposed on each other, each layer describing a pattern defined using a digital model , each layer being produced by depositing a metal, called filler metal, the filler metal being subjected to a supply of energy so as to become molten and to constitute, upon solidifying, said layer, wherein the filler metal takes the form of a powder, the exposure of which to an energy beam results in a melting followed by a solidification, so as to form a solid layer, wherein the filler metal is an aluminum alloy comprising at least the following alloy elements: - Zr, in a mass fraction greater than or equal to 0.30%, optionally 0.30-2.50%, optionally 0.40-2.00%, optionally 0.40-1.80%, optionally 0.50-1.60%, optionally 0.60-1.50%, optionally 0.70-1.40%, optionally 0.80-1.20%; - Sc, in a mass fraction less than 0.30 %, optionally less than 0.20%, optionally less than 0.10 %, optionally less than 0.05%; - Mg, in a mass fraction less than 2.00%, optionally less than 1.00%, optionally less than 0.50%, optionally less than 0.30%, optionally less than 0.10%, optionally less than 0.05%; - Zn, in a mass fraction less than 2.00%, optionally less than 1.00%, optionally less than 0.50%, optionally less than 0.30%, optionally less than 0.10%, optionally less than 0.05%; - optionally at least one element selected from: Ni, Mn, Cr and/or Cu, in a mass fraction of 0.50 to 7.00%, optionally of 1.00 to 6.00% each; optionally preferably, in a mass fraction less than 25.00%, optionally less than 20.00%, optionally less than 15.00% in total; - optionally at least one element selected from: Hf, Ti, Er, W, Nb, Ta, Y, Yb, Nd, Ce, Co, Mo, Lu, Tm, V and/or mischmetal, in a mass fraction less than or equal to 5.00%, optionally less than or equal to 3% each, and less than or equal to 15.00%, optionally less than or equal to 12%, optionally less than or equal to 5% in total; - optionally at least one element selected from: Si, La, Sr, Ba, Sb, Bi, Ca, P, B, In and/or Sn, in a mass fraction less than or equal to 1.00%, optionally less than or equal to 0.5%, optionally less than or equal to 0.3%, optionally less than or equal to 0.1%, optionally less than or equal to 700 ppm each, and less than or equal to 2.00%, optionally less than or equal to 1% in total; - optionally Fe, in a mass fraction of 0.50 to 7.00%, optionally of 1.00 to 6.00% according to a first alternative embodiment, or in a mass fraction less than or equal to 1.00%, optionally less than or equal to 0.5%, optionally less than or equal to 0.3%, optionally less than or equal to 0.1%, optionally less than or equal to 700 ppm according to a second alternative embodiment; - optionally at least one element selected from: Ag in a mass fraction of 0.06 to 1.00% and/or Li in a mass fraction of 0.06 to 1.00%; - optionally impurities in a mass fraction less than 0.05% each optionally 500 ppm, and less than 0.15% in total; - remainder being aluminum; wherein the part is produced at a temperature from more than 250 to less than 350° C., optionally from 280 to 330° C.

5. A method for producing a part comprising the production of successive solid metallic layers, which are superimposed on each other, each layer describing a pattern defined using a digital model , each layer being produced by depositing a metal, called filler metal, the filler metal being subjected to a supply of energy so as to become molten and to constitute, upon solidifying, said layer, wherein the filler metal takes the form of a powder, the exposure of which to an energy beam results in a melting followed by a solidification, so as to form a solid layer, wherein the filler metal is an aluminum alloy comprising at least the following alloy elements: - Zr and at least one element selected from: Ti, V, Sc, Hf, Er, Tm, Yb and Lu, in a mass fraction greater than or equal to 0.30%, optionally 0.30-2.50%, optionally 0.40-2.00 %, optionally 0.40-1.80%, optionally 0.50-1.60%, optionally 0.60-1.50%, optionally 0.70-1.40%, optionally 0.80-1.20% in total, in the knowledge that Zr represents from 10 to less than 100% of the percentage ranges given hereinabove; - Mg, in a mass fraction less than 2.00%, optionally less than 1.00%, optionally less than 0.50%, optionally less than 0.30%, optionally less than 0.10%, optionally less than 0.05%; - Zn, in a mass fraction less than 2.00%, optionally less than 1.00%, optionally less than 0.50%, optionally less than 0.30%, optionally less than 0.10%, optionally less than 0.05%; - optionally at least one element selected from: Ni, Mn, Cr and/or Cu, in a mass fraction of 0.50 to 7.00%, optionally of 1.00 to 6.00% each; optionally preferably, in a mass fraction less than 25.00%, optionally less than 20.00%, optionally less than 15.00% in total; - optionally at least one element selected from: W, Nb, Ta, Y, Nd, Ce, Co, Mo and/or mischmetal, in a mass fraction less than or equal to 5.00%, optionally less than or equal to 3% each, and less than or equal to 15.00%, optionally less than or equal to 12%, optionally less than or equal to 5% in total; - optionally at least one element selected from: Si, La, Sr, Ba, Sb, Bi, Ca, P, B, In and/or Sn, in a mass fraction less than or equal to 1.00%, optionally less than or equal to 0.5%, optionally less than or equal to 0.3%, optionally less than or equal to 0.1%, optionally less than or equal to 700 ppm each, and less than or equal to 2.00%, optionally less than or equal to 1% in total; - optionally Fe, in a mass fraction of 0.50 to 7.00%, optionally of 1.00 to 6.00% according to a first alternative embodiment, or in a mass fraction less than or equal to 1.00%, optionally less than or equal to 0.5%, optionally less than or equal to 0.3%, optionally less than or equal to 0.1%, optionally less than or equal to 700 ppm according to a second alternative embodiment; - optionally at least one element selected from: Ag in a mass fraction of 0.06 to 1.00% and/or Li in a mass fraction of 0.06 to 1.00%; - optionally impurities in a mass fraction less than 0.05% each optionally 500 ppm, and less than 0.15% in total; - remainder being aluminum; wherein the part is produced at a temperature from more than 250 to less than 350° C., optionally from 280 to 330° C.

6. The method according to claim 1 , wherein the aluminum alloy comprises: - Zr, in a mass fraction of 0.50 to 3.00%, optionally of 0.50 to 2.50%, optionally of 0.60 to 1.40%, optionally of 0.70 to 1.30%, optionally of 0.80 to 1.20%, optionally of 0.85 to 1.15%; optionally of 0.90 to 1.10%; - Mn, in a mass fraction of 1.00 to 7.00%, optionally of 1.00 to 6.00%, optionally of 2.00 to 5.00%; optionally of 3.00 to 5.00%, optionally of 3.50 to 4.50%; - Ni, in a mass fraction of 1.00 to 6.00%, optionally of 1.00 to 5.00%, optionally of 2.00 to 4.00%, optionally of 2.50 to 3.50%; - optionally Fe, in a mass fraction less than or equal to 1.00%, optionally less than or equal to 0.50%, optionally less than or equal to 0.30%; and optionally greater than or equal to 0.05, optionally greater than or equal to 0.10%; - optionally Si, in a mass fraction less than or equal to 1.00%, optionally less than or equal to 0.50%; - optionally Cu, in a mass fraction of 1.00 to 5.00%, optionally of 1.00 to 3.00%, optionally of 1.50 to 2.50%.

7. The method according to claim 1 , including, following the formation of the layers, - a thermal treatment optionally at a temperature of at least 100° C. and at most 500° C., optionally from 300 to 450° C.; and/or, - a hot isostatic compression.

8. The method according to claim 1 , wherein addition of La, Bi, Mg, Er, Yb, Y, Sc and/or Zn is avoided, optional mass fraction of each of these elements then being less than 0.05%, and optionally less than 0.01%.

9. The method according to claim 1 , wherein the aluminum alloy also comprises at least one element to refine grains, optionally AlTiC or AlTiB2, according to a quantity less than or equal to 50 kg/ton, optionally less than or equal to 20 kg/ton, optionally less than or equal to 12 kg/ton each, and less than or equal to 50 kg/ton, optionally less than or equal to 20 kg/ton in total.

10. A metallic part obtained with a method according to claim 1, comprising a grain structure such that surface fraction of equiaxial grains each having an area less than 2.16 .Math.m.sup.2 is less than 44%, optionally less than 40%, optionally less than 36%; and such that surface fraction of columnar grains is greater than or equal to 22%, optionally preferably greater than or equal to 25%, optionally greater than or equal to 30%.

11. A powder comprising an aluminum alloy which comprises at least the following alloy elements: - Zr, in a mass fraction of 0.30-1.40 %, optionally preferably 0.40-1.40%, optionally 0.50-1.40%, optionally 0.60-1.40%, optionally 0.70-1.40%, optionally 0.80-1.20%; - Sc, in a mass fraction less than 0.30%, optionally preferably less than 0.20%, optionally preferably less than 0.10%, optionally preferably less than 0.05%; - Mg, in a mass fraction less than 2.00%, optionally less than 1.00%, optionally preferably less than 0.50%, optionally less than 0.30%, optionally less than 0.10%, optionally less than 0.05%; - Zn, in a mass fraction less than 2.00%, optionally preferably less than 1.00%, optionally preferably less than 0.50%, optionally less than 0.30%, optionally less than 0.1%, optionally less than 0.05%; - optionally at least one element selected from: Ni, Mn, Cr and/or Cu, in a mass fraction of 0.50 to 7.00%, optionally preferably of 1.00 to 6.00% each; optionally preferably, in a mass fraction less than 25.00%, optionally preferably less than 20.00%, optionally less than 15.00% in total; - optionally at least one element selected from: Hf, Ti, Er, W, Nb, Ta, Y, Yb, Nd, Ce, Co, Mo, Lu, Tm, V and/or mischmetal, in a mass fraction less than or equal to 5.00%, optionally preferably less than or equal to 3% each, and less than or equal to 15.00%, optionally preferably less than or equal to 12%, optionally less than or equal to 5% in total; - optionally at least one element selected from: Si, La, Sr, Ba, Sb, Bi, Ca, P, B, In and/or Sn, in a mass fraction less than or equal to 1.00%, optionally preferably less than or equal to 0.5%, optionally preferably less than or equal to 0.3%, optionally preferably less than or equal to 0.1%, optionally less than or equal to 700 ppm each, and less than or equal to 2.00%, optionally preferably less than or equal to 1% in total; - optionally Fe, in a mass fraction of 0.50 to 7.00%, optionally preferably of 1.00 to 6.00% according to a first alternative embodiment, or in a mass fraction less than or equal to 1.00%, optionally preferably less than or equal to 0.5%, optionally preferably less than or equal to 0.3%, optionally less than or equal to 0.1%, optionally less than or equal to 700 ppm according to a second alternative embodiment; - optionally at least one element selected from: Ag in a mass fraction of 0.06 to 1.00% and/or Li in a mass fraction of 0.06 to 1.00%; - optionally impurities in a mass fraction less than 0.05% each optionally 500 ppm and less than 0.15% in total; - remainder being aluminum.

12. A powder comprising an aluminum alloy which comprises at least the following alloy elements: - Zr and at least one element selected from: Ti, V, Sc, Hf, Er, Tm, Yb and Lu, in a mass fraction of 0.30-1.40%, optionally preferably of 0.40-1.40%, optionally preferably of 0.50-1.40%, optionally of 0.600-1.4%, optionally of 0.70-1.40%, optionally of 0.80-1.20% in total, in the knowledge that Zr represents from 10 to less than 100% of the percentage ranges given hereinabove; - Mg, in a mass fraction less than 2.00%, optionally preferably less than 1.00%, optionally preferably less than 0.50%, optionally less than 0.30%, optionally less than 0.10%, optionally less than 0.05%; - Zn, in a mass fraction less than 2.00%, optionally preferably less than 1.00%, optionally preferably less than 0.50%, optionally less than 0.30%, optionally less than 0.10%, optionally less than 0.05%; - optionally at least one element selected from: Ni, Mn, Cr and/or Cu, in a mass fraction of 0.50 to 7.00%, optionally preferably of 1.00 to 6.00% each; optionally preferably, in a mass fraction less than 25.00%, optionally less than 20.00%, optionally less than 15.00% in total; - optionally at least one element selected from: W, Nb, Ta, Y, Nd, Ce, Co, Mo and/or mischmetal, in a mass fraction less than or equal to 5.00%, optionally preferably less than or equal to 3% each, and less than or equal to 15.00%, optionally preferably less than or equal to 12%, optionally less than or equal to 5% in total; - optionally at least one element selected from: Si, La, Sr, Ba, Sb, Bi, Ca, P, B, In and/or Sn, in a mass fraction less than or equal to 1.00%, optionally preferably less than or equal to 0.5%, optionally preferably less than or equal to 0.3%, optionally preferably less than or equal to 0.1%, optionally preferably less than or equal to 700 ppm each, and less than or equal to 2.00%, optionally preferably less than or equal to 1% in total; - optionally Fe, in a mass fraction of 0.50 to 7.00%, optionally preferably of 1.00 to 6.00% according to a first alternative embodiment, or in a mass fraction less than or equal to 1.00%, optionally preferably less than or equal to 0.5%, optionally preferably less than or equal to 0.3%, optionally less than or equal to 0.1%, optionally less than or equal to 700 ppm according to a second alternative embodiment; - optionally at least one element selected from: Ag in a mass fraction of 0.06 to 1.00% and/or Li in a mass fraction of 0.06 to 1.00%; - optionally impurities in a mass fraction less than 0.05% each optionally 500 ppm and less than 0.15% in total; - remainder being aluminum.

Description

FIGURES

[0143] FIG. 1 is a diagram illustrating an SLM, or EBM type additive manufacturing method.

[0144] FIG. 2 shows a cracking test specimen as used in the example. Reference 1 corresponds to the face used for metallographic observations, reference 2 to the critical cracking measurement zone, reference 3 to the manufacturing direction.

[0145] FIG. 3 is a test specimen geometry used to perform tensile tests, as used in the examples.

DETAILED DESCRIPTION OF THE INVENTION

[0146] In the description, unless specified otherwise: [0147] aluminum alloys are designated according to the nomenclature established by the Aluminum Association; [0148] the chemical element contents are designated as a % and represent mass fractions.

[0149] FIG. 1 generally describes an embodiment, wherein the additive manufacturing method according to the invention is used. According to this method, the filler material 25 is presented in the form of an alloy powder according to the invention. An energy source, for example a laser source or an electron source 31, emits an energy beam for example a laser beam or an electron beam 32. The energy source is coupled with the filler material by an optical or electromagnetic lens system 33, the movement of the beam thus being capable of being determined according to a digital model M. The energy beam 32 follows a movement along the longitudinal plane XY, describing a pattern dependent on the digital model M. The powder 25 is deposited on a construction slab 10. The interaction of the energy beam 32 with the powder 25 induces selective melting thereof, followed by a solidification, resulting in the formation of a layer 20.sub.i...20.sub.n. When a layer has been formed, it is coated with filler metal powder 25 and a further layer is formed, superimposed on the layer previously produced. The thickness of the powder forming a layer can for example be from 10 to 200 .Math.m. This additive manufacturing mode is typically known as selective laser melting (SLM) when the energy beam is a laser beam, the method being in this case advantageously executed at atmospheric pressure, and as electron beam melting (EBM) when the energy beam is an electron beam, the method being in this case advantageously executed at reduced pressure, typically less than 0.01 bar and preferably less than 0.1 mbar.

[0150] In a further embodiment, the layer is obtained by selective laser sintering (SLS) or direct metal laser sintering (DMLS), the layer of alloy powder according to the invention being selectively sintered according to the digital model selected with thermal energy supplied by a laser beam. In a further embodiment not described by FIG. 1, the powder is sprayed and melted simultaneously by a generally laser beam. This method is known as laser melting deposition.

[0151] Further methods can be used, particularly those known as Direct Energy Deposition (DED), Direct Metal Deposition (DMD), Direct Laser Deposition (DLD), Laser Deposition Technology (LDT), Laser Metal Deposition (LMD), Laser Engineering Net Shaping (LENS), Laser Cladding Technology (LCT), or Laser Freeform Manufacturing Technology (LFMT).

[0152] In an embodiment, the method according to the invention is used for producing a hybrid part comprising a portion obtained using conventional rolling and/or extrusion and/or casting and/or forging methods optionally followed by machining and a rigidly connected portion obtained by additive manufacturing. This embodiment can also be suitable for repairing parts obtained using conventional methods.

[0153] It is also possible, in an embodiment of the invention, to use the method according to the invention for repairing parts obtained by additive manufacturing.

[0154] Following the formation of the successive layers, an unwrought part or part in an as-manufactured temper is obtained.

[0155] According to an embodiment, the yield strength measured at ambient temperature of the part in the as-manufactured temper according to the present invention is less than 450 MPa, preferably less than 400 MPa, more preferably from 200 to 400 MPa, and even more preferably from 200 to 350 MPa.

[0156] According to an embodiment, the yield strength measured at ambient temperature of a part according to the present invention after a thermal treatment not including a solution heat treatment or quenching operation is greater than the yield strength of the same part in the as-manufactured temper. Preferably, the yield strength measured at ambient temperature of a part according to the present invention after a thermal treatment such as that cited hereinabove is greater than 350 MPa, preferably greater than 400 MPa.

[0157] According to an embodiment, the yield strength of the part measured at high temperatures remains high. Indeed, the yield strength measured at 200° C., for a part in the as-manufactured temper or after stress relieving treatment at least of 350° C., remains greater than 50%, preferably greater than 60%, of the yield strength measured at ambient temperature.

[0158] The powder used according to the present invention can have at least one of the following features: [0159] mean particle size from 3 to 100 .Math.m, preferably from 5 to 25 .Math.m, or from 20 to 60 .Math.m. The values given signify that at least 80% of the particles have a mean size within the specified range; [0160] spherical shape. The sphericity of a powder can for example be determined using a morphogranulometer; [0161] good castability. The castability of a powder can for example be determined as per the standard ASTM B213 or the standard ISO 4490:2018. According to the standard ISO 4490:2018, the flow time is preferably less than 50 s; [0162] low porosity, preferably from 0 to 5%, more preferably from 0 to 2%, even more preferably from 0 to 1% by volume. The porosity can particularly be determined by scanning electron microscopy or by helium pycnometry (see the standard ASTM B923); [0163] absence or small quantity (less than 10%, preferably less than 5% by volume) of small, so-called satellite, particles (1 to 20% of the mean size of the powder), which adhere to the larger particles.

[0164] The powder used according to the present invention can be obtained with conventional atomization methods using an alloy according to the invention in liquid or solid form or, alternatively, the powder can be obtained by mixing primary powders before the exposure to the energy beam, the different compositions of the primary powders having an average composition corresponding to the composition of the alloy according to the invention.

[0165] It is also possible to add infusible, non-soluble particles, for example oxides or particles of titanium dibromide TiB.sub.2 or particles of titanium carbide TiC, in the bath before atomizing the powder and/or during the deposition of the powder and/or during the mixing of the primary powders. These particles can serve to refine the microstructure. They can also serve to harden the alloy if they are of nanometric size. These particles can be present according to a volume fraction less than 30%, preferably less than 20%, more preferably less than 10%.

[0166] The powder used according to the present invention can be obtained for example by gas jet atomization, plasma atomization, water jet atomization, ultrasonic atomization, centrifugal atomization, electrolysis and spheroidization, or grinding and spheroidization.

[0167] Preferably, the powder according to the present invention is obtained by gas jet atomization. The gas jet atomization method starts with casting a molten metal through a nozzle. The molten metal is then reached by inert gas jets, such as nitrogen or argon, optionally accompanied by other gases, and atomized into very small droplets which are cooled and solidified by falling inside an atomization tower. The powders are then collected in a can. The gas jet atomization method has the advantage of producing a powder having a spherical shape, unlike water jet atomization which produces a powder having an irregular shape. A further advantage of gas jet atomization is a good powder density, particularly thanks to the spherical shape and the particle size distribution. A further advantage of this method is a good reproducibility of the particle size distribution.

[0168] After the manufacture thereof, the powder according to the present invention can be oven-dried, particularly in order to reduce the moisture thereof. The powder can also be packaged and stored between the manufacture and use thereof.

[0169] The powder according to the present invention can particularly be used in the following applications: [0170] Selective Laser Sintering or SLS; [0171] Direct Metal Laser Sintering or DMLS; [0172] Selective Heat Sintering or SHS; [0173] Selective Laser Melting or SLM; [0174] Electron Beam Melting or EBM; [0175] Laser Melting Deposition; [0176] Direct Energy Deposition or DED; [0177] Direct Metal Deposition or DMD; [0178] Direct Laser Deposition or DLD; [0179] Laser Deposition Technology or LDT; [0180] Laser Engineering Net Shaping or LENS; [0181] Laser Cladding Technology or LCT; [0182] Laser Freeform Manufacturing Technology or LFMT; [0183] Laser Metal Deposition or LMD; [0184] Cold Spray Consolidation or CSC; [0185] Additive Friction Stir or AFS; [0186] Field Assisted Sintering Technology, FAST or spark plasma sintering); or [0187] Inertia Rotary Friction Welding or IRFW.

[0188] The invention will be described in more detail in the example hereinafter.

[0189] The invention is not limited to the embodiments described in the description above or in the examples hereinafter, and can vary widely within the scope of the invention as defined by the claims attached to the present description.

EXAMPLES

Example 1

[0190] A first study was conducted on an alloy A having the composition indicated in Table 1 hereinafter, determined by ICP (Inductively Coupled Plasma) as a mass %. This alloy was obtained in SLM method powder form using gas jet atomization (Ar). The particle size was essentially from 3 .Math.m to 100 .Math.m, D10 was approximately 35 .Math.m, D50 approximately 48 .Math.m and D90 approximately 67 .Math.m.

TABLE-US-00001 Alloy %Mn %Ni %Cu %Zr A 3.52 2.93 1.99 1.53

[0191] Using an EOS290 type SLM machine (supplier EOS), cracking test specimens were produced with a view to studying the sensitivity of this alloy to cracking.

[0192] These test specimens, which are represented in FIG. 2, have a specific geometry having a critical site prone to crack initiation. This critical site has a radius of curvature R. When printing these test specimens, the main laser parameters used were as follows: laser power of 370 W; scanning speed of 1400 mm/s; vector deviation of 0.11 mm; layer thickness of 60 .Math.m. The EOSM290 machine used makes it possible to heat the construction slab with heating elements up to a temperature of 200° C. Cracking test specimens were printed using this machine with a plateau temperature of 50° C., 80° C., 100°, and 200° C. In all cases, the test specimens underwent a post-manufacture stress relief treatment of 4 hours at 300° C.

[0193] After manufacture, the test specimens were mechanically polished to 1 .Math.m on the face shown in FIG. 2 (Reference 1). The total length of the crack present on the critical initiation site of the test specimens was measured using an optical microscope with a magnification factor of X50. The results are summarized in Table 2 hereinafter.

TABLE-US-00002 Alloy Slab heating temperature (°C) Cracking on sample (.Math.m) A 200 1660 A 120 1184 A 100 490 A 80 <50 A 50 <50

[0194] The results of this first study show that a reduction of the slab temperature between 200° C. and 50° C. is advantageous for reducing the cracking sensitivity of alloy A. This result runs counter to several studies from the literature (see the prior art section hereinabove in the present description) which demonstrate a beneficial effect of preheating the construction slab above 150° C., or even above 350° C. on cracking during the SLM method.

[0195] It is worth noting that, in this example, the inventors deliberately placed themselves in conditions conducive to promoting cracking, in order to be able to effectively compare the impact of the construction slab temperature on the sensitivity to cracking. The use of test specimens with less complex shapes would not have made it possible to be sufficiently discriminatory. Therefore, the present example merely serves to demonstrate the impact of the construction slab temperature on the sensitivity to cracking.

[0196] Within the scope of additional tests, not shown here, with compositions according to the invention on another SLM machine which has a heating slab up to a temperature of 500° C., the inventors demonstrated that a slab temperature of 250 to 350° C., and preferably of 280 to 330° C., also made it possible to prevent cracking on the cracking test specimens, without degrading the mechanical performances at ambient temperature and at 200° C. Surprisingly, despite the increase in the slab temperature, there was no decrease in the mechanical properties in the unwrought temper or after a thermal treatment. Without being bound by theory, it seems that, under these conditions, the alloys according to the present invention make it possible to retain a good ability to trap the addition elements in solid solution, and especially Zr. An additional increase in the slab temperature, for example to 400° C. or to 500° C., seems to make it possible to reduce the solidification rate during the SLM method and thus limit the trapping of Zr in solid solution, which seems to degrade the mechanical properties in the unwrought temper, and the ability of the alloys for additional hardness during post-manufacture heat treatments, for example at 400° C. In conclusion, the slab temperature range which seems to maximize cracking sensitivity is located between 150° C. and 250° C.

[0197] Thus, the temperature ranges of the construction slab recommended according to the present invention are either from 25 to 150° C., preferably from 50 to 130° C., more preferably from 80 to 110° C., even more preferably from 80 to 105° C., i.e., at a temperature from more than 250 to less than 350° C., preferably from 280 to 330° C.

Example 2

[0198] A study was conducted in order to determine the influence of the temperature of the construction slab on the mechanical tensile characteristics at ambient temperature and at 200° C. of parts obtained by additive manufacturing. For this, alloy A from example 1 was used.

[0199] Using an EOSM290 type SLM machine (supplier EOS), vertical cylindrical samples relative to the direction of construction (Z direction) were produced in order to determine the mechanical characteristics of the alloy. These samples have a diameter of 11 mm and a height of 46 mm. When printing these samples, the main laser parameters used were as follows: laser power of 370 W; scanning speed of 1400 mm/s; vector deviation of 0.11 mm; layer thickness of 60 .Math.m. Two construction slab temperatures were tested: 100° C. and 200° C.

[0200] In all cases, the samples underwent a post-manufacture stress relief treatment of 4 hours at 300° C.

[0201] The cylindrical samples were machined to obtain tensile test specimens with the following characteristics, as described in Table 3 hereinafter and FIG. 3:

TABLE-US-00003 Test specimen type ø (mm) M (mm) LT (mm) R (mm) Lc (mm) F (mm) TOR 4 4 8 45 3 22 8.7

[0202] In Table 3 hereinabove and FIG. 3, ø represents the diameter of the central portion of the test specimen; M the width of the two ends of the test specimen; LT the total length of the test specimen; R the radius of curvature between the central portion and the ends of the test specimen; Lc the length of the central portion of the test specimen and F the length of the two ends of the test specimen.

[0203] After machining, some test specimens underwent a thermal treatment of 1 h at 400° C. The thermal treatment of 1 h at 400° C. makes it possible to simulate a post-manufacture hot isostatic compression operation or a long-term aging at an operating temperature between 100° C. and 300° C. of the final part.

[0204] The test specimens then underwent a tensile test at ambient temperature (25° C.) as per the standard NF EN ISO 6892-1 (2009-10) and at high temperature (200° C.) as per the standard NF EN ISO 6892-2 (2018). The main results are summarized in Table 4 hereinafter.

TABLE-US-00004 Alloy Construction slab temperature (°C) Duration of thermal treatment at 400° C. (h) Tensile test temperature (°C) RP02 (MPa) A 100 0 25 372 A 100 0 200 284 A 100 1 25 477 A 100 1 200 257 A 200 0 25 406 A 200 0 200 271 A 200 1 25 459 A 200 1 200 246

[0205] Of the two construction slab temperatures tested (100° C. and 200° C.), the temperature of 100° C. seems to be advantageous. Indeed, a construction slab temperature of 100° C. made it possible to obtain better mechanical properties for all the conditions tested except for the tensile test conducted at 25° C. on an as-stress relieved temper (with no post-manufacture thermal treatment at 400° C.).

[0206] However, the softer as-stress relieved temper in the tensile test at 25° C. is also advantageous because it involves lower levels of residual stress during the production of the part with SLM, and lesser final part distortion problems.

[0207] For the two construction slab temperatures tested, the post-manufacture thermal treatment of 1 h at 400° C. enabled a significant increase in the yield strength at 25° C. in relation to the as-stress relieved temper (with no post-manufacture thermal treatment at 400° C.). This type of post-manufacture treatment is advantageous for maximizing the yield strength for applications of parts working at ambient temperature or at a temperature less than 150° C.

[0208] Conversely, for the two construction slab temperatures tested, the post-manufacture thermal treatment of 1 h at 400° C. induced a decrease in the yield strength at 200° C. of approximately 26 MPa in relation to the as-stress relieved temper (with no post-manufacture thermal treatment at 400° C.). An as-stress relieved temper seems to be advantageous for so-called “high-temperature” applications, i.e., for parts working at approximately 200° C., or more generally at temperatures greater than 150° C.

Example 3

[0209] Cracking test specimens, identical to those of example 1, were produced from alloy A described in example 1 and alloys F and H described in Table 5 hereinafter. Alloys F and H were obtained in SLM method powder form using gas jet atomization (Argon). The particle size was essentially from 3 .Math.m to 100 .Math.m, D10 was from 9 to 30 .Math.m, D50 from 25 to 44 .Math.m and D90 from 51 to 64 .Math.m.

TABLE-US-00005 Alloy %Mn %Ni %Cu %Zr F 3.77 2.77 1.90 1.02 H 3.07 4.13 1.94 0.63

[0210] The laser parameters used were the same as those in example 1: laser power of 370 W; scanning speed of 1400 mm/s; vector deviation of 0.11 mm; layer thickness of 60 .Math.m. The construction slab was heated to 200° C. for alloy A and to 100° C. for alloys F and H. The test specimens underwent a post-manufacture stress relief treatment of 4 hours at 300° C.

[0211] As in example 1, the total length of the crack present at the critical initiation site of the cracking test specimens was determined for each alloy.

[0212] Characterizations of the granular structure were also carried out on all the samples with EBSD (Electron Back Scattered Diffraction) using an EDAX camera and OIM (Orientation Imaging Microscopy) software. These characterizations were carried out using a ZEISS Ultra 55 type FEG-SEM with an energy of 15 keV on a 500 .Math.m x 500 .Math.m field with a 0.5 .Math.m pitch.

[0213] Prior to EBSD characterization, all the samples underwent conventional mechanical polishing (emery paper with lubrication with water followed by polishing cloths with diamond suspension) to 1 .Math.m, followed by vibratory polishing with an amplitude of 30% for 6 h, using a 50% dilution of SPM (colloidal silica gel) in water as a lubricant.

[0214] The total surface fraction of grains which each have an area greater than a given threshold value was calculated for all the samples. Several threshold values were used: 2.16 .Math.m.sup.2, 3.24 .Math.m.sup.2, 6.48 .Math.m.sup.2, 8.64 .Math.m.sup.2 and 10.8 .Math.m.sup.2. Th results are shown in Table 6 hereinafter.

TABLE-US-00006 Alloy Slab heating temp (°C) Crack length (.Math.m) Total surface fraction (%) Grains > 2.16 .Math.m.sup.2 Grains > 3.24 .Math.m.sup.2 Grains > 6.48 .Math.m.sup.2 Grains > 8.64 .Math.m.sup.2 Grains > 10.8 .Math.m.sup.2 A 200 1660 56 48 27 22 19 F 100 0 68 62 45 38.5 34 H 100 0 88 80 65 59 55

[0215] The results of Table 6 hereinabove show that a total surface fraction of grains, each having an area greater than 2.16 .Math.m.sup.2, greater than 56%, preferably greater than 60%, and more preferably greater than 64% is advantageous for completely eliminating cracking during the SLM method. In other words, a total surface fraction of fine grains, each having an area greater than 2.16 .Math.m.sup.2, less than 44%, preferably less than 40%, and more preferably less than 36% is advantageous for preventing cracking during the SLM method. These fine grains had an equiaxial structure.

[0216] The results of Table 6 hereinabove show that a total surface fraction of grains, each having an area greater than 3.24 .Math.m.sup.2, greater than 48 %, preferably greater than 52%, and more preferably greater than 57% is advantageous for completely eliminating cracking during the SLM method.

[0217] The results of Table 6 hereinabove show that a total surface fraction of grains, each having an area greater than 6.48 .Math.m.sup.2, greater than 27%, preferably greater than 35%, and more preferably greater than 40% is advantageous for completely eliminating cracking during the SLM method. The results of Table 6 hereinabove show that a total surface fraction of grains, each having an area greater than 8.64 .Math.m.sup.2, greater than 22%, preferably greater than 27%, and more preferably greater than 33%, is advantageous for completely eliminating cracking during the SLM method. The results of Table 6 hereinabove show that a total surface fraction of grains, each having an area greater than 10.8 .Math.m.sup.2, greater than 19%, preferably greater than 25%, and more preferably greater than 30% is advantageous for completely eliminating cracking during the SLM method. The surface fraction of columnar grains measured is 22% for alloy A, 39% for alloy F and 60% for alloy H. This measurement was made with OIM software, considering the grains having a length / width ratio greater than or equal to 3. This result showed that a granular structure with a fraction of columnar grains greater than or equal to 22%, preferably greater than or equal to 25%, and even more preferably greater than or equal to 30% is advantageous for eliminating cracking during the SLM method.

[0218] Columnar grains in the absence of cracks generally have a length less than 500 .Math.m, preferably less than 300 .Math.m, more preferably less than 200 .Math.m, even more preferably less than 150 .Math.m. Columnar grains generally have a width less than 150 .Math.m, preferably less than 100 .Math.m, preferably less than 50 .Math.m, more preferably less than 30 .Math.m, even more preferably less than 20 .Math.m.

[0219] The granular structure to be sought to limit cracking therefore seems to be a structure with a surface fraction of columnar grains greater than 22% and a surface fraction of fine equiaxial grains each with an area < 2.16 .Math.m.sup.2 less than 44%.

[0220] This result runs counter to the prior art on the development of aluminum alloys for the SLM application, which strongly encourages seeking a fine and completely equiaxial structure for eliminating solidification cracks in aluminum alloys during SLM production. This equiaxial structure can particularly be obtained by introducing different types of nuclei or nucleating agents, as illustrated for example in the following patent applications and publication: US2020024700A1; US2018161874A1; Martin et al: September 2017 vol 549 NATURE 365 “3D printing of high-strength aluminium alloys”.

[0221] In additional tests, the inventors demonstrated that the presence of Mg can induce microcracking on samples with a mostly columnar structure. The micro-cracks propagate at the grain boundaries parallel with the columnar grains. The presence of Mg can also result in smoke formation during the SLM method, with a risk of Laser method instability. Thus, in an alternative embodiment of the present invention, the Mg content is preferably less than 2%, preferably less than 1%, and more preferably less than 0.05%.