AlSi10Mg alloy and laser powder bed melting preparation method thereof

Abstract

The application belongs to the technical field of alloy additive, and particularly relates to an AlSi10Mg alloy and a laser powder bed melting preparation method thereof. The application introduces a crystal seed alloy powder with a mass percentage of Al-2.63Ti-0.66C-0.13B into the AlSi10Mg alloy for modification, and prepares a TM-AlSi10Mg alloy through a laser powder bed melting technology, thereby significantly realizing grain refinement and microstructure optimization. The TM-AlSi10Mg alloy exhibits a bimodal heterogeneous microstructure formed by periodically arranged fine equiaxed crystals and coarse equiaxed crystals, and the average grain size is about 2.8 mu m. The yield strength, tensile strength and elongation of the alloy are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of alloy additive manufacturing, and in particular relates to an AlSi10Mg alloy and a method for preparing the same by laser powder bed melting. Background Art

[0002] With the increasing demand for manufacturing high-performance, complex geometric components, laser powder bed melting (LPBM), as a widely used metal additive manufacturing technology, has attracted increasing attention. However, the application of lightweight aluminum alloys in LBM remains limited, especially in terms of improving mechanical properties. Current research on aluminum alloys mainly focuses on the Al-Si-Mg series alloys, which generally have good processability but relatively poor mechanical properties. In addition, studies have widely verified that the high-temperature crack sensitivity of traditional high-strength aluminum alloys (such as 2xxx and 7xxx series wrought alloys) during LBM hinders their application. Although many studies have shown that elements such as Sc, Zr, Ti, and Ta can be widely added during casting for nucleation, which may help crack suppression, grain refinement, and performance improvement, their use should be avoided due to the high cost and supply risks associated with these key raw materials. Therefore, how to improve the mechanical properties of Al-Si-Mg alloys manufactured by LBM so that they have both excellent strength and plasticity is the problem to be solved by the present invention. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention provides an AlSi10Mg alloy and a laser powder bed melting method for preparing the same. The present invention introduces a new seed alloy into the AlSi10Mg alloy to achieve grain refinement and microstructure optimization of the AlSi10Mg alloy prepared by laser powder bed melting, thereby improving the strength and plasticity of the AlSi10Mg alloy.

[0004] The present invention is specifically implemented through the following technical solutions.

[0005] The present invention provides a laser powder bed melting method for preparing an AlSi10Mg alloy, comprising the following steps:

[0006] The seed alloy powder and the AlSi10Mg alloy powder are uniformly mixed to prepare a mixed powder; the seed alloy powder consists of the following components: 0<Ti≤2.63wt%, 0<C≤0.66wt%, 0<B≤0.13wt%, and the balance is Al, which is 100% in total; in the mixed powder, the mass fraction of the seed alloy powder is 15wt%.

[0007] The dried mixed powder is spread flat on the base plate of the forming chamber to form an alloy powder layer.

[0008] The AlSi10Mg alloy is prepared by layer-by-layer laser scanning and melting of the alloy powder layer under the protection of inert gas.

[0009] Preferably, the seed alloy powder is prepared by a vacuum induction gas atomization process, the average particle size of the seed alloy powder is 9.62 μm, and the seed alloy powder contains Ti(C, B) particles with a particle size of 50 nm to 300 nm. It should be noted that the Ti(C, B) particles are formed by B atoms occupying the C vacancies of the TiC crystal. Because the Ti(C, B) phase is formed by B atoms occupying the C vacancies of the TiC crystal, the Ti(C, B) also retains the structure of the TiC crystal. The TiBC ternary phase is two completely different phases, and the TiBC ternary phase is composed of Ti, B and C.

[0010] Preferably, the AlSi10Mg alloy powder is relatively spherical as a whole, and the average particle size of the AlSi10Mg alloy powder is 30 μm.

[0011] Preferably, in the forming process, the printing of each layer is first completed by the laser beam according to the preset scanning path to form the inner area, and after the inner area is formed, the laser beam is scanned along the inner entity edge of the layer to form the outer contour from inside to outside, and finally the single-layer printing is completed; the step of the single-layer printing is repeated layer by layer until the additive manufacturing of the AlSi10Mg alloy is completed.

[0012] Preferably, in the forming process, the laser scanning path of each layer forms a 67° angle with the laser scanning path of the previous layer.

[0013] Preferably, the laser process parameters used for printing the inner entity and the contour are: the laser power is set to 200 W to 350 W, the laser scanning speed is 600 mm / s to 1800 mm / s, the scanning interval is 0.1 mm, and the powder layer thickness is 0.03 mm.

[0014] Preferably, the composition of the AlSi10Mg alloy powder is: 0 < Si ≤ 9.8 wt%, 0 < Mg ≤ 0.6 wt%, the content of Al is ≥ 89.6 wt%, and the total is 100%.

[0015] Preferably, the AlSi10Mg alloy powder is mixed with the Al-2.63Ti-0.66C-0.13B seed alloy powder. The AlSi10Mg alloy powder and the Al-2.63Ti-0.66C-0.13B seed alloy powder are uniformly mixed by a commercial

[0016] Preferably, the AlSi10Mg alloy powder is dried in a vacuum box at 80°C for 10 hours.

[0017] Preferably, printing is performed on a 6061 aluminum alloy platform, and flowing argon is used in the chamber to minimize oxygen contamination, which is controlled to be below 0.1 vol%.

[0018] The application also provides an AlSi10Mg alloy prepared by the above preparation method, wherein the average grain size of the AlSi10Mg alloy is 2.8 μm, and the microstructure of the AlSi10Mg alloy is a bimodal heterogeneous microstructure formed by periodic arrangement of fine equiaxed crystals (melt pool boundary) and coarse equiaxed crystals (melt pool interior).

[0019] Compared with the prior art, the application has the following beneficial effects:

[0020] The application introduces seed alloy powder into AlSi10Mg alloy powder for modification, prepares mixed powder, and the seed alloy powder is composed of 0 < Ti < 2.63 wt%, 0 < C < 0.66 wt%, 0 < B < 0.13 wt%, and the balance is Al, and the total is 100%. Then the mixed powder is prepared into AlSi10Mg alloy by laser powder bed melting technology. The seed alloy has good refining effect, realizes the refinement of AlSi10Mg alloy grains, significantly improves the strength and plasticity of the alloy, and is beneficial to expand the application of AlSi10Mg alloy in laser powder bed melting technology.

[0021] The seed alloy used in the application has low cost, and the mixing method with AlSi10Mg alloy powder is simple and easy to apply in the production line, and does not produce harmful pollutants. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 In the figure, A is the microstructure of the AlSi10Mg alloy powder of Example 1, and B is the element content distribution diagram obtained by face scanning analysis of the microstructure of A.

[0023] Figure 2 In the figure, A is the X-ray diffraction spectrum of the Al-2.63Ti-0.66C-0.13B seed alloy powder of Example 1.

[0024] Figure 3 In the figure, A is the EBSD reconstruction diagram of the AlSi10Mg alloy of Comparative Example 1, and B is the EBSD reconstruction diagram of the TM-AlSi10Mg alloy of Example 1.

[0025] Figure 4 In the figure, A is the grain size distribution diagram of the AlSi10Mg alloy of Comparative Example 1, and B is the grain size distribution diagram of the TM-AlSi10Mg alloy of Example 1.

[0026] Figure 5 Figure 1 is a microstructure of TM-AlSi10Mg alloy of Example 1; Figure 2 is a bright field image obtained by transmission electron scanning analysis of the microstructure of A in Figure 1; Figure 3 is an element content distribution image obtained by transmission electron scanning analysis of the microstructure of A in Figure 1; Figure 4 is a comparison chart of mechanical properties of TM-AlSi10Mg alloy of Example 1 and AlSi10Mg alloy of Comparative Example 1. Figure 5 Figure 1 is a microstructure of TM-AlSi10Mg alloy of Example 1; Figure 2 is a bright field image obtained by transmission electron scanning analysis of the microstructure of A in Figure 1; Figure 3 is an element content distribution image obtained by transmission electron scanning analysis of the microstructure of A in Figure 1; Figure 4 is a comparison chart of mechanical properties of TM-AlSi10Mg alloy of Example 1 and AlSi10Mg alloy of Comparative Example 1. Figure 5 Figure 1 is a microstructure of TM-AlSi10Mg alloy of Example 1; Figure 2 is a bright field image obtained by transmission electron scanning analysis of the microstructure of A in Figure 1; Figure 3 is an element content distribution image obtained by transmission electron scanning analysis of the microstructure of A in Figure 1; Figure 4 is a comparison chart of mechanical properties of TM-AlSi10Mg alloy of Example 1 and AlSi10Mg alloy of Comparative Example 1.

[0027] Figure 6 Figure 4 is a comparison chart of mechanical properties of TM-AlSi10Mg alloy of Example 1 and AlSi10Mg alloy of Comparative Example 1. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solutions of the present application and to implement them, the present application will be further described below in conjunction with specific examples and drawings, but the examples are not intended to limit the present application. In each of the following examples, the experimental methods and detection methods are conventional methods unless otherwise specified, and the reagents and materials can be purchased on the market unless otherwise specified.

[0029] At present, in the Al-Si alloy prepared by laser powder bed melting, the optimized solidification path and the refined microstructure are the key to realize the enhancement of strength and ductility. However, it is still a major challenge to find an effective nucleating agent to promote significant grain refinement. Traditionally, nano / sub-micron sized ceramic powders (such as TiN, TiCN and LaB6) are usually selected to be added to AlSi10Mg alloy, but this method often leads to the reduction of flowability of the final powder and the agglomeration of ceramic powder, thereby affecting the mechanical properties. In order to explore the suitable grain refining agent, although many researchers have made a lot of explorations, there are more or less technical shortcomings such as high cost, change of alloy composition, poor and unstable effect, and inconsistency with production site technology. Therefore, it is urgent to find a method to improve the mechanical properties of the current AlSi10Mg alloy, to some extent, to break the balance of strength-plasticity.

[0030] The present application provides a laser powder bed melting preparation method of AlSi10Mg alloy, which solves the problems existing in the prior art, introduces a new seed powder into the AlSi10Mg alloy powder, realizes the refinement of the grains, and makes the AlSi10Mg alloy prepared by laser powder bed melting have excellent strength and plasticity, and specifically includes the following steps:

[0031] The seed alloy powder and the AlSi10Mg alloy powder are mixed uniformly to prepare a mixed powder; the seed alloy powder is composed of 0 < Ti ≤ 2.63wt%, 0 < C ≤ 0.66wt%, 0 < B ≤ 0.13wt%, and the balance of Al, with a total of 100%; in the mixed powder, the mass fraction of the seed alloy powder is 15wt%.

[0032] The dry mixed powder is laid on the substrate of the forming cabin to form an alloy powder layer.

[0033] The alloy powder layer is subjected to layer-by-layer laser scanning and fusion forming under the protection of inert gas to obtain an AlSi10Mg alloy, which is named as TM-AlSi10Mg alloy.

[0034] The present application introduces seed alloy powder into AlSi10Mg alloy powder for modification to prepare mixed powder, the seed alloy powder is composed of 0 < Ti < 2.63wt%, 0 < C < 0.66wt%, 0 < B < 0.13wt%, and the balance of Al, totaling 100%. Then the mixed powder is prepared into AlSi10Mg alloy by laser powder bed melting technology, the seed alloy has good refining effect, realizes the refinement of AlSi10Mg alloy grains, significantly improves the strength and plasticity of the alloy (yield strength reaches 302 ± 7.6 MPa, tensile strength is 479.2 ± 1.5 MPa, and elongation is 11.1 ± 0.7%), which is beneficial to expand the application of AlSi10Mg alloy in laser powder bed melting technology. The seed alloy used in the present application has low cost, and the mixing method with AlSi10Mg alloy powder is simple and easy to apply in the production line without producing harmful pollutants. The preparation method of the seed alloy can be prepared according to the scheme disclosed in CN111996424A.

[0035] The content of the present application will be specifically described through the following examples and comparative examples.

[0036] Example 1

[0037] In this example, an Al-2.63Ti-0.66C-0.13B seed alloy modified AlSi10Mg alloy is prepared, which improves the tensile properties of TM-AlSi10Mg alloy and the elongation of AM-AlSi10Mg alloy, so that the aluminum alloy prepared according to the method disclosed in this example can meet the performance requirements in the field of lightweight and high-performance complex part manufacturing. The Al-2.63Ti-0.66C-0.13B seed alloy refers to the seed alloy, the Ti content is 2.63wt%, the C content is 0.66wt%, the B content is 0.13wt%, and the balance is Al, totaling 100%. The prepared alloy is named as TM-AlSi10Mg, and the specific process is as follows:

[0038] (1) The AlSi10Mg alloy powder and the Al-2.63Ti-0.66C-0.13B seed alloy powder are weighed according to the mass percentage. Specifically, the AlSi10Mg alloy powder accounts for 85wt% of the total mass, and the Al-2.63Ti-0.66C-0.13B seed alloy powder accounts for 15wt%. This precise ratio can ensure the uniformity of the composition of the mixed alloy powder, which helps to achieve the expected microstructure and mechanical properties. Then, the weighed AlSi10Mg alloy powder and Al-2.63Ti-0.66C-0.13B seed alloy powder are mixed in a commercial orbital shaker at a fixed oscillation frequency of 50Hz for 100 minutes to ensure sufficient contact and uniform dispersion between the powder particles, thereby forming a mixed powder with consistent composition. Next, the mixed powder is placed in a vacuum box at 80°C for 10 hours of drying treatment before the start of the laser powder bed melting process.

[0039] (2) The mixed powder is spread on the substrate of the forming cabin to form an alloy powder layer. The inert gas (argon) is used to protect the powder from oxygen contamination, which is controlled to be below 0.1vol%.

[0040] (3) The EOS M290 device is used to perform laser scanning on the laid alloy powder to perform layer-by-layer printing forming. During the forming process, the printing of each layer is first completed by the laser beam according to the preset scanning path to form the inner region. After the inner region is formed, the laser beam scans the outer contour from the inside to the outside along the inner solid edge of the layer, and finally completes the printing process of a single layer. By repeating this printing step layer by layer, the additive manufacturing of the TM-AlSi10Mg alloy is completed. The forming process of the above-mentioned printing layer is performed layer by layer, and the laser scanning direction of each layer is kept at an angle of 67° with the laser scanning direction of the upper layer until the laser additive manufacturing of the alloy is completed.

[0041] During the actual printing process, some preparations need to be made:

[0042] Firstly, a three-dimensional model of the part is created using three-dimensional modeling software, and then a planar contour model of each layer is generated by slicing software. Then, the powder is transferred from the powder cylinder to the forming cabin by the scraper, and the laser beam scans and prints according to the model, finally realizing the accumulation forming of the aluminum alloy part. In order to ensure the printing effect, the base plate, powder cylinder and scraper should be cleaned with alcohol before the experiment, and argon gas should be filled in the forming cabin. The laser process parameters used in this embodiment for printing the inner solid plane and contour are: the laser power is set to 300W; the laser scanning speed is 1500mm / s; the scanning interval is 0.1mm; and the powder layer thickness is 0.03mm.​

[0043] As shown in FIG. 1A, the AlSi10Mg alloy powder particles as a whole present a relatively spherical shape, and the average particle size is 30 pm. Although some satellite particles and broken powders can be obviously observed, they are considered to be common defects in the powder preparation process and do not affect the liquidity in the printing process and the printing quality. Figure 1 As shown in FIG. 1B, by performing element energy spectrum analysis on the particle, it can be clearly seen that the particle contains Al, Si and Mg three elements. Figure 1

[0044] FIG. 2 shows the XRD spectrum of the Al-2.63Ti-0.66C-0.13B seed alloy powder used in this embodiment, indicating that the Al-2.63Ti-0.66C-0.13B seed alloy powder is rich in Ti(C,B) particles (formed by B atoms occupying the C vacancies of TiC crystal), and the average particle size is about 50 nm to 300 nm. It is worth noting that because the Ti(C,B) phase is formed by B atoms occupying the C vacancies of TiC crystal, the Ti(C,B) still retains the structure of TiC crystal. TiBC ternary phase is two completely different phases, and TiBC ternary phase is a ternary phase composed of Ti, B and C. Figure 2 Comparative Example 1

[0045] This comparative example prepared an AlSi10Mg alloy preparation method without adding seed crystals, and the specific process was as follows:

[0046] Firstly, the AlSi10Mg alloy powder was placed in a vacuum box at 80°C for 10 hours of drying treatment, so as to obtain dried AlSi10Mg powder.

[0047] Then, the AlSi10Mg powder was laid flat on the substrate of the forming cabin to form an alloy powder layer. Under the protection of inert gas (argon) to minimize oxygen pollution, the control was below 0.1 vol%.

[0048] Finally, the EOS M290 device was used to scan the laid alloy powder with laser to perform layer-by-layer printing forming. During the forming process, the printing of each layer was first completed by the laser beam according to the preset scanning path to form the solid inside the region. After the inside region forming is completed, the laser beam scans the outside contour from inside to outside along the inside solid edge of the layer, and finally completes the printing process of a single layer. By repeating this printing step layer by layer, the additive manufacturing of the TM-AlSi10Mg alloy is completed. The above printing layer forming process is performed layer by layer, and the laser scanning direction of each layer is kept at an angle of 67° with the laser scanning direction of the upper layer, until the laser additive manufacturing of the alloy is completed.

[0049] ​

[0050] During the actual printing process, some preparatory work needs to be done. First, use 3D modeling software to create a 3D model of the part, and then use slicing software to generate a plane contour model of each layer. Next, the scraper transfers the powder from the powder cylinder to the forming chamber, and the laser beam scans and prints according to the model, and finally realizes the stacking formation of the aluminum alloy parts. In order to ensure the printing effect, the substrate, powder cylinder, scraper and other parts should be cleaned with alcohol before the experiment, and argon gas should be filled in the forming chamber. The laser process parameters used for printing the internal solid plane and contour in this comparative example are: the laser power is set to 300W; the laser scanning speed is 1500mm / s; the scanning spacing is 0.1mm; the powder layer thickness is 0.03mm.

[0051] Figure 3 China A and Figure 3 B in the figure shows the EBSD reconstruction images of the AlSi10Mg alloy additive of comparative example 1 of the present invention and the TM-AlSi10Mg of example 1 of the present invention.

[0052] like Figure 3 As shown in Figure A, the AlSi10Mg alloy additive material of Comparative Example 1 of the present invention exhibits a coarse columnar crystal distribution as a whole. This is a typical microstructure in metal additive manufacturing. This is due to the different cooling rates in the molten pool. The grains of the AlSi10Mg alloy grow along the epitaxial direction, forming larger columnar crystals and obvious growth texture. Figure 3 As shown in Figure B, the TM-AlSi10Mg of Example 1 of the present invention exhibits a distinct bimodal heterogeneous structure formed by a periodic arrangement of fine equiaxed crystals (at the melt pool boundary) and coarse equiaxed crystals (inside the melt pool). This is because the faster the cooling rate, the higher the nucleation rate. The Ti(C, B) particles contained in the Al-2.63Ti-0.66C-0.13B seed alloy powder act as a nucleation substrate, significantly increasing the nucleation rate of α-Al in the aluminum alloy and effectively hindering the growth of columnar crystals inside the melt pool.

[0053] Figure 4 In Figure 1, A is the AlSi10Mg alloy prepared in Comparative Example 1, and B is the grain size distribution diagram of TM-AlSi10Mg prepared in Example 1. The average grain size decreases from 12.5 μm to 2.8 μm. This is because the presence of uniformly dispersed Ti(C, B) particles provides more heterogeneous nucleation sites, increases the nucleation rate of α-Al in the aluminum alloy, promotes rapid nucleation and growth of grains, and thus reduces the grain size.

[0054] like Figure 5 As shown in Figure A, the marked Ti(C, B) particles are uniformly dispersed in the Al matrix, while the micron-sized eutectic silicon particles show a random distribution. Figure 5The middle B and C show that the nano-sized eutectic silicon particles form a network structure radiating from the cell boundary inward, forming a certain thickness of the reinforced phase, thereby enhancing the resistance to dislocation movement, to some extent, helping to slow the expansion of the tensile crack.

[0055] Experimental Example

[0056] Test item: tensile mechanical behavior of AlSi10Mg alloy test samples in Comparative Example 1 and TM-AlSi10Mg alloy test samples in Example 1.

[0057] Test process: aluminum alloy standard tensile test samples were prepared according to the preparation method in Example 1 and Comparative Example 1, and the aluminum alloy test samples of Example 1 and Comparative Example 1 were fixed on a material testing machine (Instron 3382) respectively, and tensile test was carried out at room temperature, and the tensile test results are shown in Table 1 and Figure 6

[0058] Table 1: Aluminum alloy tensile strength test results

[0059] Group Yield strength (MPa) Tensile strength (MPa) Elongation (%) Comparative Example 1 254±5.8 381±7.3 4.8±1.2 Example 1 302±7.6 479.2±1.5 11.1±0.7％

[0060] As can be seen from Table 1 and Figure 6 , the mechanical properties of the TM-AlSi10Mg alloy additive prepared by the technical solution provided in the present application are greatly improved compared with the conventional additive manufactured AlSi10Mg alloy, specifically, the yield strength is increased from 254±5.8MPa to 302±7.6MPa, the tensile strength is increased from 381±7.3 to 479.2±1.5, and the elongation is increased from 4.8±1.2% to 11.1±0.7%. It indicates that the new TM-AlSi10Mg alloy additive disclosed in the present application greatly improves the strength and elongation of the aluminum alloy parts.

[0061] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, these modifications and variations are also intended to be included.​

Claims

1. A laser powder bed melting method for preparing AlSi10Mg alloy, characterized in that: The following steps are involved: The seed alloy powder and the AlSi10Mg alloy powder are uniformly mixed to prepare a mixed powder; the seed alloy powder is composed of the following elements: 0<Ti≤2.63 wt%, 0<C≤0.66 wt%, 0<B≤0.13 wt%, and the balance is Al, which is 100% in total; the mass fraction of the seed alloy powder in the mixed powder is 15 wt%; Spreading the dried mixed powder on the base plate of the forming chamber to form an alloy powder layer; Under the protection of inert gas, the alloy powder layer is laser scanned and melted layer by layer to produce AlSi10Mg alloy. The average particle size of the seed alloy powder is 9.62 μm. The seed alloy powder contains Ti(C, B) particles. The Ti(C, B) particles are formed by B atoms occupying the C vacancies of TiC crystals. The particle size of the Ti(C, B) particles is 50 nm~300 nm.

2. The laser powder bed melting method for preparing AlSi10Mg alloy according to claim 1, characterized in that: The average particle size of the AlSi10Mg alloy powder is 30 μm.

3. The laser powder bed melting method for preparing AlSi10Mg alloy according to claim 1, characterized in that: During the forming process, the printing of each layer first completes the solid forming of the internal area by the laser beam according to a preset scanning path. After the solid forming of the internal area is completed, the laser beam scans and forms the external contour from the inside to the outside along the internal solid edge of the layer, and finally completes the single-layer printing; by repeating the single-layer printing steps layer by layer, the additive manufacturing of the AlSi10Mg alloy is completed.

4. The laser powder bed melting method for preparing AlSi10Mg alloy according to claim 3, characterized in that: During the forming process, the laser scanning path of each layer forms an angle of 67° with the laser scanning path of the previous layer.

5. The laser powder bed melting method for preparing AlSi10Mg alloy according to claim 3, characterized in that: The laser process parameters used for printing internal entities and contours are as follows: laser power is set to 200W~350W, laser scanning speed is 600mm / s~1800 mm / s, scanning spacing is 0.1 mm, and powder layer thickness is 0.03 mm.

6. The laser powder bed melting method for preparing AlSi10Mg alloy according to claim 1, characterized in that: The composition of the AlSi10Mg alloy powder is: 0<Si≤9.8 wt%, 0<Mg≤0.6 wt%, and Al content ≥89.6 wt%, which is 100% in total.

7. The AlSi10Mg alloy prepared according to the preparation method according to any one of claims 1 to 6.

8. The AlSi10Mg alloy according to claim 7, characterized in that The average grain size of the AlSi10Mg alloy is 2.8 μm.

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