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 filler metal consisting of an aluminium alloy comprising at least the following alloying elements: Zr, in a mass fraction of 0.60 to 1.40%, Mn, in a mass fraction of 2.00 to 5.00%, Ni, in a mass fraction of 1.00 to 5.00%, Cu, in a mass fraction of 1.00 to 5.00%.

The invention also relates to a part obtained by means of the 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 filler metal is an aluminum alloy comprising at least the following alloy elements: Zr, in a mass fraction of 0.60 to 1.40%, optionally of 0.70 to 1.30%, optionally of 0.80 to 1.2%, optionally of 0.85 to 1.15%; optionally of 0.90 to 1.10%; Mn, in a mass fraction 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 5.00%, optionally of 2.00 to 4.00%, optionally of 2.50 to 3.50%; 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%; optionally at least one element selected from: Hf, Cr, 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%, optionally less than or equal to 3.00% each, and less than or equal to 15.00%, optionally less than or equal to 12.00%, optionally less than or equal to 5.00% in total; optionally at least one element selected from: Fe, Si, Mg, Zn, Sc, 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 0.50%, optionally less than or equal to 0.30%, optionally less than or equal to 0.10%, optionally less than or equal to 700 ppm each, and less than or equal to 2.00%, optionally less than or equal to 1.00% in total; optionally at least one element selected from: Ag in a mass fraction of 0.06 to 1.00%, 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 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 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% in total, wherein Zr represents from 10 to less than 100% of the percentage ranges given hereinabove; Mn, in a mass fraction 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 5.00%, optionally of 2.00 to 4.00%, optionally of 2.50 to 3.50%; 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%; optionally at least one element selected from: Cr, W, Nb, Ta, Y, Nd, Ce, Co, Mo and/or mischmetal, in a mass fraction less than or equal to 5%, optionally less than or equal to 3.00% each, and less than or equal to 15.00%, optionally less than or equal to 12.00%, optionally less than or equal to 5.00% in total; optionally at least one element selected from: Fe, Si, Mg, Zn, 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 0.50%, optionally less than or equal to 0.30%, optionally less than or equal to 0.10%, optionally less than or equal to 700 ppm each, and less than or equal to 2.00%, optionally less than or equal to 1.00% in total; optionally at least one element selected from: Ag in a mass fraction of 0.06 to 1.00%, 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 addition of La, Bi, Mg, Er, Yb, Y, Sc and/or Zn is avoided, an optional mass fraction of each of these elements then being less than 0.05%, and optionally less than 0.01%.

4. 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.

5. 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.

6. The method according to claim 1 wherein the part is manufactured either at a temperature from 25 to 150° C., optionally from 50 to 130° C., optionally from 80 to 110° C., or at a temperature from more than 250 to less than 350° C., optionally from 280 to 330° C.

7. A metal part obtained by a method according to claim 1.

8. A powder comprising an aluminum alloy comprising at least the following alloy elements; Zr, in a mass fraction 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 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 5.00%, optionally of 2.00 to 4.00%, optionally of 2.50 to 3.50%; 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%; optionally at least one element selected from: Hf, Cr, 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%, optionally less than or equal to 3.00% each, and less than or equal to 15.00%, optionally less than or equal to 12.00%, optionally less than or equal to 5.00% in total; optionally at least one element selected from: Fe, Si, Mg, Zn, Sc, 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 0.50%, optionally less than or equal to 0.30%, optionally less than or equal to 0.10%, optionally less than or equal to 700 ppm each, and less than or equal to 2.00%, optionally less than or equal to 1.00% in total; optionally at least one element selected from: Ag in a mass fraction of 0.06 to 1.00%, 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.

9. A powder comprising 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 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% in total, in the knowledge that Zr represents from 10 to less than 100% of the percentage ranges given hereinabove; Mn, in a mass fraction 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 5.00%, optionally of 2.00 to 4.00%, optionally of 2.50 to 3.50%; 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%: optionally at least one element selected from: Cr, 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 3.00% each, and less than or equal to 15.00%, optionally less than or equal to 12.00%, optionally less than or equal to 5.00% in total; optionally at least one element selected from Fe, Si, Mg, Zn, 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 0.50%, optionally less than or equal to 0.30%, optionally less than or equal to 0.10%, optionally less than or equal to 700 ppm each, and less than or equal to 2.00%, optionally less than or equal to 1.00% in total; optionally at least one element selected from: Ag in a mass fraction of 0.06 to 1.00%, 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

[0092] FIG. 1 is a diagram illustrating an SLM, or EBM type additive manufacturing method.

[0093] 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.

[0094] FIG. 3 is a graph showing the results of the statistical analysis based on the experiment plan of example 1, in order to determine the effects of the addition elements Ni, Cu and Zr on cracking. The y-axis represents the crack length in μm and the x-axis the mass percentage.

[0095] FIG. 4 is a test specimen geometry used to perform tensile tests, as used in Example 2.

DETAILED DESCRIPTION OF THE INVENTION

[0096] In the description, unless specified otherwise: [0097] aluminum alloys are designated according to the nomenclature established by the Aluminum Association; [0098] the chemical element contents are designated as a % and represent mass fractions.

[0099] 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.1 . . . 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 μm. During manufacture, the powder bed can be heated. 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.

[0100] 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.

[0101] 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).

[0102] 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.

[0103] 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.

[0104] Following the formation of the successive layers, an unwrought part or part in an as-manufactured temper is obtained.

[0105] Preferably, the yield strength 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.

[0106] Preferably, the yield strength 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 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.

[0107] The powder according to the present invention can have at least one of the following features: [0108] mean particle size from 3 to 100 μm, preferably from 5 to 25 μm, or from 20 to 60 μm. The values given signify that at least 80% of the particles have a mean size within the specified range; [0109] spherical shape. The sphericity of a powder can for example be determined using a morphogranulometer; [0110] 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; [0111] 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); [0112] 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.

[0113] The powder 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.

[0114] 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%.

[0115] The powder 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.

[0116] 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.

[0117] 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.

[0118] The powder according to the present invention can particularly be used in the following applications: [0119] Selective Laser Sintering or SLS; [0120] Direct Metal Laser Sintering or DMLS; [0121] Selective Heat Sintering or SHS; [0122] Selective Laser Melting or SLM; [0123] Electron Beam Melting or EBM; [0124] Laser Melting Deposition; [0125] Direct Energy Deposition or DED; [0126] Direct Metal Deposition or DMD; [0127] Direct Laser Deposition or DLD; [0128] Laser Deposition Technology or LDT; [0129] Laser Engineering Net Shaping or LENS; [0130] Laser Cladding Technology or LCT; [0131] Laser Freeform Manufacturing Technology or LFMT; [0132] Laser Metal Deposition or LMD; [0133] Cold Spray Consolidation or CSC; [0134] Additive Friction Stir or AFS; [0135] Field Assisted Sintering Technology, FAST or spark plasma sintering); or [0136] Inertia Rotary Friction Welding or IRFW.

[0137] The invention will be described in more detail in the example hereinafter.

[0138] 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

[0139] A study was conducted on four alloys (B, C, D and E) as part of a three-variable Taguchi type experiment plan (% Ni, % Cu and % Zr). The compositions, determined by ICP (Inductively Coupled Plasma) as a mass %, are given in Table 1 hereinafter. These four alloys were obtained in SLM method powder form using gas jet atomization (Ar). The particle size was essentially from 3 μm to 100 μm, D10 was from 8 to 10 μm, D50 from 24 to 28 μm and D90 from 48 to 56 μm.

TABLE-US-00001 TABLE 1 Alloy % Mn % Ni % Cu % Zr B 3.57 0.00 1.97 1.30 C 3.52 2.00 3.84 1.26 D 3.53 0.00 3.85 1.02 E 3.56 1.94 1.97 1.00

[0140] Using an EOS290 type SLM machine (supplier EOS), cracking test specimens were produced with a view to studying the sensitivity of these alloys to cracking.

[0141] These test specimens, which are represented in FIG. 2, have a specific geometry having a critical site prone to crack initiation. 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 μm. 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 200° C. In all cases, the test specimens underwent a post-manufacture stress relief treatment of 4 hours at 300° C. After manufacture, the test specimens were mechanically polished to 1 μm 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 TABLE 2 Slab heating temperature Crack length Alloy (° C.) (μm) B 200 1456 C 200 1609 D 200 1051 E 200 543

[0142] A statistical analysis of the results from this experiment plan was conducted in the form of graphs of the main effects of the addition elements, as shown in FIG. 3. This graph shows how a factor (here the addition element content) affects the response observed (here the crack length measured on the cracking samples). For this, the mean response for each factor level is calculated and positioned on the graph and a line joins the points of each of the factor levels. When the line is horizontal, there is no main effect (i.e., each factor level affects the measured response in the same way). When the line is not horizontal, there is a main effect (therefore, the two factor levels affect the measured response differently). The greater the slope of this line, the greater the main effect.

[0143] The graph in FIG. 3 shows that, on the composition ranges studied, a 1% decrease in Ni induces an increase in the mean cracking length of 90 μm; a 1% decrease in Cu induces a decrease in the mean cracking length of 175 μm and a 1% decrease in Zr induces a decrease in the mean cracking length of 2724 μm.

[0144] The results of this example show that on the composition ranges studied, Zr has a predominant effect on cracking. More specifically, a decrease in the Zr content is preferable to limit the sensitivity to cracking.

[0145] 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 addition elements 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 addition elements on the sensitivity to cracking.

Example 2

[0146] A study was conducted on 6 alloys A, F, G, H, I and J. The compositions of the 6 alloys, determined by ICP (Inductively Coupled Plasma) as a mass %, are given in Table 3 below. These 6 alloys were obtained in SLM method powder form using gas jet atomization (Ar). The particle size was essentially from 3 μm to 100 μm, D10 was from 8 to 36 μm, D50 from 24 to 48 μm and D90 from 48 to 67 μm.

TABLE-US-00003 TABLE 3 Alloy % Mn % Ni % Cu % Zr A 3.52 2.93 1.99 1.53 F 3.77 2.77 1.90 1.02 G 2.89 2.44 1.90 0.40 H 3.07 4.13 1.94 0.63 I 3.97 2.51 1.95 0.66 J 3.94 4.00 1.92 0.34

[0147] Cracking test specimens (identical to that from example 1) and cylindrical test specimens (according to the explanations given hereinafter) were produced from the alloys of Table 3 hereinabove.

[0148] 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 μm. The manufacturing slab heating temperature was 100° C. In all cases, the samples underwent a post-manufacture stress relief treatment of 4 hours at 300° C.

[0149] The cylindrical samples were machined to obtain tensile test specimens with the following characteristics, as described in Table 4 hereinafter and FIG. 4.

TABLE-US-00004 TABLE 4 Test specimen Ø M LT R Lc F type (mm) (mm) (mm) (mm) (mm) (mm) TOR 4 4 8 45 3 22 8.7

[0150] In Table 4 hereinabove and FIG. 4, 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.

[0151] The test specimens then underwent a tensile test at ambient temperature (25° C.), in the as-stress relieved temper (with no additional thermal treatment other than stress relief) as per the standard NF EN ISO 6892-1 (2009-10). The main results are shown in Table 5 hereinafter.

TABLE-US-00005 TABLE 5 RP02 measured at Slab heating 25° C. in MPa on as- temperature Crack length stress relieved Alloy (° C.) (μm) temper A 100 490 372 F 100 0 303 G 100 0 184 H 100 0 267 I 100 0 235 J 100 0 245

[0152] The results of Table 5 hereinabove show that, for a manufacturing slab temperature of 100° C., a Zr content less than or equal to 1.3% (alloys F to J) made it possible to eliminate cracking completely on the cracking test specimens.

[0153] The results of Table 5 also show that an RP02 value in the as-stress relieved temper less than 400 MPa, and preferably less than 370 MPa, would be advantageous for limiting the sensitivity to cracking.

Example 3

[0154] A similar study to that in example 2 was conducted on 5 alloys. The compositions of these 5 alloys, determined by ICP (Inductively Coupled Plasma) as a mass %, are given in Table 6 hereinafter.

[0155] These 5 alloys were obtained in SLM method powder form using gas jet atomization (Ar). The particle size was essentially from 3 μm to 100 μm, D10 was from 8 to 36 μm, D50 from 24 to 48 μm and D90 from 48 to 67 μm.

TABLE-US-00006 TABLE 6 Alloy % Mn % Ni % Cu % Zr F 3.77 2.77 1.90 1.02 G 2.89 2.44 1.90 0.40 H 3.07 4.13 1.94 0.63 I 3.97 2.51 1.95 0.66 J 3.94 4.00 1.92 0.34

[0156] 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 μm. The construction slab was heated to a temperature of 100° C.

[0157] In all cases, the samples underwent a post-manufacture stress relief treatment of 4 hours at 300° C.

[0158] The cylindrical samples were machined to obtain similar tensile test specimens to that in example 2 hereinabove.

[0159] 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.

[0160] 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 temperatures (200° C.) as per the standard NF EN ISO 6892-2 (2018). The main results are shown in Table 7 hereinafter.

TABLE-US-00007 TABLE 7 Duration Construction of thermal slab treatment Tensile test temperature at 400° C. temperature RP02 Alloy (° C.) (h) (° C.) (MPa) F 100 0 25 303 G 100 0 25 184 H 100 0 25 267 I 100 0 25 235 J 100 0 25 245 F 100 1 25 420 G 100 1 25 187 H 100 1 25 291 I 100 1 25 291 J 100 1 25 222 F 100 0 200 270 G 100 0 200 179 H 100 0 200 242 I 100 0 200 218 J 100 0 200 235 F 100 1 200 238 G 100 1 200 175 H 100 1 200 208 I 100 1 200 211 J 100 1 200 192

[0161] According to Table 7 hereinabove, in the as-stress relieved temper (with no post-manufacture thermal treatment other than stress relief), all of the alloys tested have a yield strength at 25° C. less than 310 MPa, which is beneficial for the processability of the alloys by limiting the level of residual stress during manufacture. The best mechanical properties at ambient temperature after thermal treatment of 1 h at 400° C. are obtained for alloy F (RP02 of 420 MPa) followed by alloys H and I (291 MPa). The poorest performances are obtained for alloys G and J, 187 and 222 MPa, respectively. These results show the positive impact of the Zr content on mechanical performances after hardening treatment. A minimum Zr content of 0.6% is thus required to obtain a minimum RP02 of 250 MPa after thermal treatment of 1 h at 400° C.

[0162] For the tensile tests at 200° C., the results of Table 7 hereinabove show that, for all the alloys tested, the as-stress relieved temper is advantageous in relation to the temper with a post-manufacture thermal treatment of 1 h at 400° C.

[0163] The thermal treatment of 1 h at 400° C. makes it possible to simulate the effect of very long-term aging at 200° C. The best performances at 200° C. after thermal treatment of 1 h at 400° C. were obtained for alloy F followed by alloys H and I. The poorest performances are once again obtained for alloys G and J (RP02<200 MPa).

[0164] A minimum Zr content of 0.6% thus seems to be preferably to obtain a good thermal stability of the mechanical properties at 200° C.

[0165] Within the scope of additional tests, not shown here, with the 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.

[0166] 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., i.e., at a temperature from more than 250 to less than 350° C., preferably from 280 to 330° C.