Preparation method for high-strength aluminum alloy additive manufacturing

Abstract

The invention belongs to the technical field of additive manufacturing, and relates to a selective laser melting forming preparation method of an AlMgScZr high-strength aluminum alloy, which specifically comprises additive manufacturing forming process parameters and a heat treatment process of the high-strength aluminum alloy. Relates to a preparation method for high-strength aluminum alloy additive manufacturing. The optimal and reasonable additive manufacturing forming process parameters are determined by adjusting and optimizing the laser power and the scanning speed; by adjusting the heating temperature and the heat preservation time of heat treatment, a strengthening phase is fully separated out from an aluminum alloy matrix, so that the mechanical property of the alloy is improved, and the optimal heat treatment process of the high-strength aluminum alloy is determined.

Description

Technical Field

[0001] The present invention belongs to the technical field of additive manufacturing, and relates to a method for preparing an AlMgScZr high-strength aluminum alloy by selective laser melting forming, specifically including the additive manufacturing forming process parameters and heat treatment process of the high-strength aluminum alloy. It relates to a preparation method for additive manufacturing of high-strength aluminum alloy. Background Art

[0002] Due to the increasing requirements for lightweight design and manufacturing of aeroengines, the additive manufacturing technology of high-strength aluminum alloys has received extensive attention. Although the mechanical properties of traditional additive manufacturing aluminum alloys AlSi7Mg and AlSi10Mg are higher than those of traditional manufacturing aluminum alloys, the maximum tensile strength can only reach about 320 MPa, which cannot meet the needs of weight reduction of aeroengine parts. Compared with the traditional AlSi7Mg and AlSi10Mg alloys, the new AlMgScZr high-strength aluminum alloy has better mechanical properties, and the tensile strength after heat treatment reaches more than 500 mPa. Therefore, under the same service load requirements, the weight reduction design of parts can be effectively realized. Summary of the Invention

[0003] Object of the Invention

[0004] To provide a preparation method for additive manufacturing of high-strength aluminum alloy, ensuring that the alloy obtains a high density and enabling the alloy to have high-strength performance indicators through heat treatment.

[0005] Technical Solution

[0006] In order to achieve the above object, a preparation method for additive manufacturing of high-strength aluminum alloy is provided. The high-strength aluminum alloy has the grade of AlMgScZr and is characterized by the following steps:

[0007] S1: Take a certain amount of AlMgScZr metal powder and screen it with an 80-mesh - 120-mesh sieve;

[0008] S2: Place the powder described in S1 in a vacuum drying oven and dry it under a certain vacuum degree, temperature and holding time to remove the moisture in the powder;

[0009] S3: Place the aluminum alloy substrate for forming in the forming chamber of the additive manufacturing forming equipment and level it;

[0010] S4: Load the powder described in S2 into the additive manufacturing forming equipment. After filling the powder loading bin, the equipment is evacuated to prepare for additive manufacturing printing and forming;

[0011] S5: Turn on the laser. Before preparing for additive manufacturing forming, the substrate needs to be preheated to an appropriate temperature.

[0012] S6: Prepare specimens with density and test bars for tensile property testing using appropriate additive manufacturing forming process parameters; the additive manufacturing forming process parameters are: solid laser power = 370 W, scanning speed = 1000 mm / s. Laser overlap zone width: 0.10 mm to 0.30 mm; process parameters of the support part: laser power: 300 W to 370 W, laser scanning speed: 2500 mm / s to 3600 mm / s;

[0013] S7: Take out the additive manufacturing formed specimens and test bars described in S6 from the additive manufacturing equipment, clean the powder, and then perform annealing heat treatment together with the bottom substrate; the annealing heat treatment regime is: heat to 280 °C ± 10 °C in an air furnace, hold for 2 h to 4 h, then cool in the furnace to 100 °C ± 20 °C, and then air cool to room temperature;

[0014] S8: Wire cut the specimens and test bars after the heat treatment described in S7 to separate the specimens with density and test bars for tensile property from the bottom substrate;

[0015] S9: After polishing the specimen with density described in S8 with 1000# sandpaper, measure the density by the drainage method;

[0016] S10: Divide the test bars for tensile property described in S8 into two groups, transverse and longitudinal, and machine them according to certain dimensional specifications;

[0017] S11: Perform room temperature tensile property testing on the machined test bars described in S10, and record the values of tensile strength, yield strength, and elongation for the transverse and longitudinal directions respectively.

[0018] In a possible embodiment, in the AlMgScZr powder in the step S1, the mass percentages of its chemical components are: Al: the balance, Mg: 3.9 to 5.1, Sc: 0.1 to 0.9, Zr: 0.1 to 0.5, Mn: 0.2 to 0.8, Fe ≤ 0.4, Ti ≤ 0.2, Si ≤ 0.4 requirements.

[0019] In a possible embodiment, in the step S1, the powder is screened using a sieve mesh of 80 to 120 meshes to remove impurities such as large particles and black slag of the powder.

[0020] In a possible embodiment, in the step S2, the powder vacuum drying process regime is that the vacuum degree is maintained at 0.1 MPa to 0.5 MPa, and heat is kept at 80 °C to 130 °C for 4 h to 6 h;

[0021] In a possible embodiment, in the step S3, the runout of the substrate leveling does not exceed 0.03 mm;

[0022] In a possible embodiment, the aluminum alloy substrate grade in the step S3 is pure aluminum or 2024 aluminum alloy;

[0023] In a possible embodiment, in the step S4, the oxygen content of the additive manufacturing forming equipment should be reduced to less than 0.01% before printing and manufacturing can be carried out;

[0024] In a possible embodiment, in the step S5, the substrate heating temperature is 60°C - 80°C.

[0025] In a possible embodiment, in the step S6, the number of density specimens is 6, the specimen size specification is 10mm × 10mm × 10mm, the number of transverse tensile property test bars is 3, and the number of longitudinal ones is 3, and their size specification is φ14mm × 80mm;

[0026] In a possible embodiment, in the step S9, the density values of 6 groups of specimens are detected respectively and then the average value is taken.

[0027] The beneficial effects of this application are as follows:

[0028] The technical key of the present invention is to prepare a new type of high-strength aluminum alloy material by using the additive manufacturing process method. For an AlMgScZr alloy material with a specific composition, the optimal and reasonable additive manufacturing forming process parameters are determined by adjusting and optimizing the laser power and scanning speed; by adjusting the heating temperature and holding time of the heat treatment, strengthening phases are fully precipitated in the aluminum alloy matrix, thereby improving the mechanical properties of the alloy, and the optimal heat treatment process of the high-strength aluminum alloy is determined.

[0029] The AlMgScZr high-strength aluminum alloy is prepared by using the additive manufacturing forming technology, and the forming process parameters and heat treatment process system are determined. The density of the prepared high-strength aluminum alloy components is above 98%; through reasonable annealing heat treatment, Al 3 (Sc, Zr) strengthening phases are fully precipitated, significantly improving the mechanical properties of the AlMgScZr alloy. Its tensile strength exceeds 520 MPa, and the internal metallurgical quality is good, without excessive pores and cracks. While the tensile strength of the traditional AlSi 10Mg and AlSi7Mg alloys after additive manufacturing forming and heat treatment does not exceed 320 mPa. Therefore, the mechanical properties of the new type of high-strength aluminum alloy are significantly better than those of traditional aluminum alloy materials, providing technical support for the lightweight design of aero-engine parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the method flow chart of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0031] The present invention will be further described below in conjunction with embodiments. The following descriptions only cover some embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0032] Table 1 Influence of scanning speed on density;

[0033] Table 2 Influence of annealing heat treatment temperature on mechanical properties;

[0034] Table 3 Influence of annealing holding time on mechanical properties;

[0035] S1: Take a certain amount of AlMgScZr metal powder and screen it with an 80-mesh to 120-mesh sieve to remove impurities such as large particles and black slag in the powder. The chemical composition mass percentages of the AlMgScZr powder are as follows: Al: the balance, Mg: 3.9 - 5.1, Sc: 0.1 - 0.9, Zr: 0.1 - 0.5, Mn: 0.2 - 0.8, Fe ≤ 0.4, Ti ≤ 0.2, Si ≤ 0.4.

[0036] S2: Place the powder described in S1 in a vacuum drying oven, keep the vacuum degree at 0.1 MPa to 0.5 MPa, the drying temperature at 80 °C to 130 °C, and hold for 4 h to 6 h. Through drying and heating, the moisture in the powder is effectively removed to prevent pore defects from occurring due to the influence of moisture during the forming process.

[0037] S3: Place an aluminum alloy substrate with the grade 2024 for forming in the forming chamber of the additive manufacturing equipment, and level it. After leveling, the runout of the substrate plane does not exceed 0.03 mm. Detecting the runout of the substrate installation plane before forming is to ensure that the forming surface of the substrate is as horizontal as possible with the equipment reference plane, and the forming accuracy in the height direction (Z-axis direction) during the additive manufacturing layer-by-layer stacking process is controllable.

[0038] S4: Load the powder described in S2 into the additive manufacturing equipment. After filling the powder bin, the equipment evacuates the air to ensure that the oxygen content in the bin drops below 0.01% before additive manufacturing printing and forming can be carried out;

[0039] S5: Before starting the laser for additive manufacturing, it is necessary to preheat the substrate to 80 °C in advance. During the additive manufacturing forming process, due to the rapid melting and rapid solidification and cooling of the metal powder, there are large internal stresses in the high-strength aluminum alloy parts, which are prone to serious deformation and even cracking problems. Preheating the substrate before additive manufacturing forming can effectively reduce the internal stress of the parts during the additive manufacturing forming process and ensure successful printing in one pass. If the preheating temperature is too high, it will have a greater impact on precision optical components such as lasers, and long cooling times are required when taking the parts; if the preheating temperature is too low, the effect of reducing internal stress cannot be effectively exerted.

[0040] S6: Prepare density specimens and tensile property test bars using appropriate additive manufacturing forming process parameters. The number of density specimens is 6, with the specimen size specification being 10 mm × 10 mm × 10 mm. For the tensile property test bars, there are 3 transverse ones and 3 longitudinal ones, with the size specification being φ14 mm × 80 mm. The additive manufacturing forming process parameters are as follows: Laser power for the solid part = 370 W, scanning speed = 1000 mm / s. Laser overlap zone width: 0.10 mm to 0.30 mm; For the support part, the process parameters are laser power: 300 W to 370 W, laser scanning speed: 2500 mm / s to 3600 mm / s;

[0041] In the present invention, process optimization is carried out by adjusting the scanning speed parameter. Through the density detection of the manufactured parts, a reasonable scanning speed = 1000 mm / s is determined. The specific results are shown in Table 1. There are differences between the process parameters of the support and those of the solid part, mainly because the support part has no high requirements for density and mechanical properties, and only ensuring the forming of the solid part is sufficient.

[0042] S7: Take out the additive manufacturing formed specimens and test bars described in S6 from the additive manufacturing equipment. After cleaning the powder, perform annealing heat treatment together with the bottom substrate. The annealing heat treatment system is as follows: Heat in an air furnace to 280 °C ± 10 °C, hold for 2 h to 4 h, then cool with the furnace to 100 °C ± 20 °C, and then air cool to room temperature. The heat treatment process parameters directly affect the mechanical properties of the additively manufactured high-strength aluminum alloy. The specific test results are shown in Table 2 and Table 3.

[0043] S8: Wire cut the specimens and test bars after the heat treatment described in S7, and separate the density specimens and tensile property test bars from the bottom substrate;

[0044] S9: After polishing the density specimens described in S8 with 1000# sandpaper, use the drainage method to detect the density of 6 groups of specimens and take the average value;

[0045] S10: Divide the tensile property test bars described in S8 into two groups, transverse and longitudinal, and perform machining according to certain size specifications;

[0046] S11: Perform room temperature tensile property detection on the machined test bars described in S10, and record the tensile strength, yield strength, and elongation values of the transverse and longitudinal directions respectively.

[0047] Table 1

[0048] Scanning speed mm / s Density % 800 96.0 900 96.3 1000 96.8 1100 96.3 1200 96.3 1300 95.6

[0049] Table 2

[0050]

[0051] Table 3

[0052]

[0053] Those skilled in the art can understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as the general understanding of those of ordinary skill in the art to which the present invention pertains. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with their meaning in the context of the prior art, and will not be interpreted in an idealized or overly formal sense unless defined as such here. The specific embodiments described above have further elaborated on the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method for additive manufacturing of high-strength aluminum alloy, characterized in that, it includes the following steps: Step S1: Take a certain amount of AlMgScZr metal powder and screen it using a sieve. Step S2: Place the powder described in Step S1 in a vacuum drying oven and dry it under a certain vacuum degree, temperature, and holding time to remove the moisture in the powder. Step S3: Place a formed aluminum alloy substrate in the forming chamber of the additive manufacturing equipment and level it. Step S4: Load the powder described in Step S2 into the additive manufacturing equipment. After filling the powder loading bin, the equipment evacuates to prepare for additive manufacturing printing and forming. Step S5: Before starting the laser to prepare for additive manufacturing and forming, the substrate needs to be preheated to a suitable temperature in advance. Step S6: Use appropriate additive manufacturing and forming process parameters to prepare a density specimen and a tensile property test bar; the additive manufacturing and forming process parameters are: solid laser power = 370 W, scanning speed = 1000 mm / s; laser overlap zone width: 0.10 mm to 0.30 mm; laser power for the support part process parameters: 300 W to 370 W, laser scanning speed: 2500 mm / s to 3600 mm / s. Step S7: Take out the additive manufacturing and forming specimen and test bar described in Step S6 from the additive manufacturing equipment. After cleaning the powder, perform annealing heat treatment together with the bottom substrate; the annealing heat treatment system is: heat to 280°C ± 10°C in an air furnace, hold for 2 h to 4 h, then cool with the furnace to 100°C ± 20°C, and then air cool to room temperature. Step S8: Use wire cutting to process the specimen and test bar after heat treatment described in Step S7, and separate the density specimen and the tensile property test bar from the bottom substrate. Step S9: After polishing the density specimen described in Step S8 with sandpaper, measure the density using the drainage method. Step S10: Divide the tensile property test bars described in Step S8 into two groups, transverse and longitudinal, and machine them according to certain size specifications. Step S11: Perform room temperature tensile property tests on the machined test bars described in Step S10, and record the tensile strength, yield strength, and elongation values of the transverse and longitudinal directions respectively.

2. The method according to claim 1, characterized in that, in the AlMgScZr powder in Step S1, the mass percentages of its chemical components are Al: the balance, Mg: 3.9 to 5.1, Sc: 0.1 to 0.9, Zr: 0.1 to 0.5, Mn: 0.2 to 0.8, Fe ≤ 0.4, Ti ≤ 0.2, Si ≤ 0.

4.

3. The method according to claim 2, characterized in that, in Step S1, the powder is screened using an 80-mesh to 120-mesh sieve to remove large particles and black slag in the powder.

4. The method according to claim 3, characterized in that, in Step S2, the powder vacuum drying process system is that the vacuum degree is maintained at 0.1 MPa to 0.5 MPa; keep warm at 80°C to 130°C for 4 h to 6 h.

5. The method according to claim 4, characterized in that, In the substrate leveling step S3, the bounce amount does not exceed 0.03 mm.

6. The method according to claim 5, wherein, in the step S3, the aluminum alloy substrate grade is pure aluminum or 2024 aluminum alloy.

7. The method according to claim 6, wherein, in the step S4, the oxygen content of the additive manufacturing forming equipment is reduced to less than 0.01% before printing and manufacturing can be carried out.

8. The method according to claim 7, wherein, in the step S5, the substrate heating temperature is 60°C - 80°C.

9. The method according to claim 8, wherein, in the step S6, the number of density specimens is 6, the specimen size specification is 10 mm × 10 mm × 10 mm, the number of transverse tensile property test bars is 3, the number of longitudinal test bars is 3, and their size specification is φ14 mm × 80 mm.

10. The method according to claim 9, wherein, in the step S9, the density values of 6 groups of specimens are respectively detected and then averaged.

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