Aluminum-silicon alloy based on in-situ reaction modification and additive manufacturing method and application thereof

Abstract

The invention provides an aluminum-silicon alloy additive manufacturing method based on in-situ reaction modification, which comprises the following steps: selecting aluminum-silicon alloy powder with the particle size range of 15-53 microns, carrying out vacuum heat preservation for 2-6 hours at the temperature of 80-150 DEG C, and drying; the aluminum-silicon alloy powder is prepared from the following elements in percentage by mass: 8 to 12 percent of Si, 0 to 1 percent of Mg, 0.01 to 1 percent of Sr and the balance of Al and inevitable impurity elements; and finally, forming and preparing the aluminum-silicon alloy by adopting a selective laser melting process. Silicon phase coarsening is inhibited through Sr metamorphism, Sr and Al / Si in a molten pool are promoted to be subjected to an in-situ reaction through the ultrahigh cooling rate of SLM, a fine nanoscale metastable phase is generated, the elasticity modulus of the fine nanoscale metastable phase is equivalent to that of an aluminum matrix, the fine nanoscale metastable phase can serve as strengthening particles to improve the matrix strength, and stress concentration can be relieved by coordinating local plastic deformation.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal additive manufacturing, and specifically relates to an additively manufactured aluminum-silicon alloy based on in-situ reaction modification, a preparation method and an application thereof. Background Art

[0002] Aluminum-silicon alloys have important application value in aerospace, automotive lightweighting and other fields due to their excellent specific strength, corrosion resistance and good formability. Its typical microstructure is composed of an α-Al matrix and a eutectic silicon phase, in which the morphology, size and distribution of the eutectic silicon play a decisive role in the mechanical properties of the alloy. In traditional cast aluminum-silicon alloys, coarse flaky or needle-shaped eutectic silicon phases (usually 10-50μm in size) easily become crack sources, resulting in a significant decrease in the plasticity of the material, and the tensile strength is difficult to exceed 300MPa. Studies have shown that by refining the eutectic structure (especially reducing the size of the silicon phase to the submicron level and achieving spheroidization), the balance between strength and plasticity can be effectively coordinated, becoming a key way to improve the comprehensive performance of aluminum-silicon alloys.

[0003] At present, the refinement of eutectic structure is mainly achieved through two types of technologies: modification and rapid solidification technology. Modification mainly involves adding Sr, Na or rare earth elements, which changes the nucleation and growth dynamics of the silicon phase, causing it to transform from coarse lamellar to fine fibrous or granular. Among them, Sr modification is most widely used in cast aluminum silicon alloys due to its stable modification effect and good long-term effectiveness. However, the addition of Sr in traditional casting processes requires strict control of the modification temperature (usually 720-750°C) and the addition amount (0.005-0.03wt.%). At high temperatures, Sr is easily oxidized and burned or forms coarse Al4Sr and Al2Si2Sr phases with Al and Si, which in turn deteriorates the mechanical properties. In addition, the segregation problem of Sr elements in the melt is difficult to completely avoid, resulting in localized regional modification failure. On the other hand, rapid solidification technology (such as selective laser melting, SLM) achieves excellent mechanical properties through ultra-high cooling rates (103-10 6K / s) inhibits the coarsening of the silicon phase and can directly achieve a submicron eutectic structure (silicon phase size <100nm); high heating and cooling rates will lead to limited diffusion and movement of metal atoms and alloying elements, inhibiting grain growth and segregation of alloying elements, resulting in fine grains and uniform distribution of alloying elements in the alloy structure after solidification, which can significantly improve the strength and toughness of the material. The tensile strength of SLM-formed aluminum-silicon alloys can reach 400-450MPa, but the elongation is generally less than 8%, and microsegregation, pores and residual stress are easily generated during the rapid solidification process, limiting its scope of engineering application. The performance of SLM-formed aluminum-silicon alloys is closely related to their microstructure. The ultrafine, metastable cellular structure gives it significant strengthening and strain hardening, but due to the strong constraint effect of the Al+Si eutectic on the internal α-Al at the boundary of the cellular structure, there is a strong stress concentration at the boundary of the cellular structure, which leads to premature fracture during the strain hardening stage and exhibits low plasticity.

[0004] It is worth noting that existing research has largely focused on optimizing a single process (modification or rapid solidification), while lacking exploration of the synergistic effects of the two. Traditional Sr modifiers are primarily designed for casting processes. However, the transient high temperatures (>2000K) and extreme non-equilibrium solidification conditions of the melt pool during SLM can cause Sr volatilization or unintended reactions with the melt, leading to modification failure. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art and provide an aluminum-silicon alloy based on in-situ reaction modification. The aluminum-silicon alloy suppresses the coarsening of the silicon phase (refined to 50nm) by Sr modification, and utilizes the ultra-high cooling rate of SLM to promote the in-situ reaction of Sr with Al / Si in the molten pool to generate a fine nano-scale metastable phase, wherein the metastable phase contains an unprecedented Al 16 Si 30 Sr8 phase, the elastic modulus of this phase is comparable to that of the aluminum matrix. It can not only serve as a reinforcing particle to enhance the strength of the matrix, but also relieve stress concentration by coordinating local plastic deformation.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: an additive manufacturing method of aluminum-silicon alloy based on in-situ reaction modification, characterized in that the method comprises the following steps:

[0007] Step 1: Select aluminum-silicon alloy powder with a particle size range of 15-53 μm, keep it in a vacuum at a temperature of 80-150° C. for 2-6 hours, and then dry it; the aluminum-silicon alloy powder is composed of the following elements in mass percentage: Si: 8-12%, Mg: 0-1%, Sr: 0.01-1%, and the balance is Al and unavoidable impurity elements;

[0008] Step 2: Selective laser melting is used to form aluminum-silicon alloy components. The process parameters are: laser power 200-400W, scanning speed 800-1700mm / s, scanning spacing 0.1-0.22mm, layer thickness 30-60μm, energy density 40-100J / mm 3 .

[0009] Preferably, the aluminum-silicon alloy powder is composed of the following elements in percentage by mass: Si: 9.5-10.5%, Mg: 0.3-0.5%, Sr: 0.1-0.5%, and the balance being Al and unavoidable impurity elements.

[0010] Preferably, the aluminum silicon alloy powder is prepared by a method of smelting combined with atomization powder making, wherein during the smelting process, the Sr element is introduced as the Sr raw material in the form of pure Sr, Sr salt or Al-Sr modifier, and the amount of Sr raw material added is calculated according to the Sr content in the Sr raw material. The Sr content in the Sr raw material is not less than 1.2 times the Sr content in the aluminum silicon alloy powder, ensuring that Sr can still play a modifying role and participate in the in-situ reaction after partial volatilization in the SLM molten pool. Sr is extremely easy to oxidize, and the Al-Sr modifier needs to be sealed and isolated from oxygen. Note that when Sr salt is introduced as the Sr raw material, no by-products can be produced during the atomization powder making process. The Sr salt can specifically be SrF2 or SrCl2.

[0011] Preferably, the Sr content in the Sr raw material is 1.2-1.8 times the Sr content in the aluminum-silicon alloy powder.

[0012] Preferably, the laser power is 340-380W, the scanning speed is 1400-1700mm / s, the scanning spacing is 0.13-0.17mm, the layer thickness is 30μm, and the energy density is 45-70J / mm 3 .

[0013] Preferably, the aluminum-silicon alloy component prepared in step 2 has a tensile strength of up to 515 MPa, a yield strength of up to 320 MPa, and an elongation of up to 12.3%.

[0014] The present invention also discloses an aluminum-silicon alloy based on in-situ reaction modification, and an aluminum-silicon alloy prepared according to the above-mentioned additive manufacturing method.

[0015] Preferably, the size of the eutectic silicon phase of the aluminum-silicon alloy is about 50 nm, and a nano-scale metastable phase is evenly distributed at the boundary of the cellular structure, and the metastable phase contains Al 16 Si 30 Sr8 phase, Al 16 Si 30 The average size of the Sr8 phase is about 50 nm.

[0016] The present invention also discloses an application of aluminum-silicon alloy based on in-situ reaction modification. The aluminum-silicon alloy prepared according to the above-mentioned additive manufacturing method is applied to aerospace load-bearing brackets, automobile lightweight structural parts or metal shoe molds.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] Existing research on the refinement of the eutectic structure of aluminum-silicon alloys has mostly focused on the optimization of a single process (modification or rapid solidification), while there is a lack of exploration of the synergistic effect of the two. Although SLM technology can significantly refine the structure through extreme non-equilibrium solidification, its single process still has performance bottlenecks: on the one hand, although the refined eutectic silicon phase can improve strength, the high-density interface may lead to increased brittleness; on the other hand, the improvement of alloy plasticity is limited by the interfacial bonding strength between the silicon phase and the matrix and the uniformity of stress distribution. Sr modification treatment is widely used in traditional casting processes. If it is to be introduced into the SLM process, it is necessary to consider the instantaneous high temperature (>2000K) of the molten pool during the SLM process and the extreme non-equilibrium solidification conditions. This may cause the Sr element to volatilize or react unexpectedly with the melt, producing new effects different from traditional casting processes.

[0019] Existing research on incorporating Sr modification into additive manufacturing processes faces significant challenges: Sr is volatile due to its high vapor pressure, and the Sr addition rate in traditional casting processes is generally 0.005-0.03 wt.%. The transient high temperatures in the melt pool during SLM easily cause the Sr to completely volatilize and become ineffective, making the modification effect difficult to achieve. Therefore, determining the Sr addition rate is crucial for incorporating Sr modification into additive manufacturing. Excessive Sr addition ensures that the modification effect persists even after burnout; however, the excess Sr induces in-situ reactions under the rapid solidification conditions unique to SLM, forming fine metastable phases. Different solidification sequences lead to different microstructural characteristics, which in turn affect the mechanical properties of the cast alloy. To investigate the effect of Sr addition on the solidification behavior of an Al-Si alloy, the solidification process of an Sr-modified Al-Si alloy was simulated using the Scheil-Gulliver solidification model. In the Scheil solidification model, it is assumed that there is a local equilibrium at the solid-liquid interface at the solidification front; the diffusion in the liquid phase is fast enough to reach equilibrium, and there is no diffusion in the solid phase. The Scheil solidification model can be used to obtain the solidification behavior of aluminum-silicon alloys with different Sr contents, including phase transition temperature, solidification sequence, phase transition type and phase volume fraction, and further analyze the evolution of the microstructure; at the same time, a quantitative relationship between alloy composition and solidification microstructure can also be established, which provides a theoretical basis for designing the optimal Sr content. Based on this, the present invention proposes an innovative in-situ reaction modification strategy that combines Sr modification treatment with selective laser melting technology, aiming to achieve a breakthrough in the mechanical properties of aluminum-silicon alloys through a dual mechanism. The specific advantages are as follows:

[0020] (1) Synergistic rapid solidification and modification to achieve deep refinement of eutectic structure: Existing SLM technology relies on a single rapid solidification mechanism, which results in limited refinement of the eutectic silicon phase, and the high-density interface may lead to increased brittleness. The present invention inhibits the coarsening of the silicon phase (refined to 50nm) through Sr modification. Excessive addition of Sr elements during the pre-alloying powder preparation process ensures that Sr can continue to modify the eutectic silicon phase after partial volatilization in the SLM melt pool. At the same time, the rapid solidification characteristics of the SLM process are utilized to further refine the size of the eutectic silicon phase.

[0021] (2) Metastable phase synergistic strengthening: The ultra-high cooling rate of SLM is utilized to promote an in-situ reaction between Sr and Al / Si in the molten pool, generating fine nano-scale metastable phases. The elastic modulus of the in-situ generated nano-phase is comparable to that of the aluminum matrix. It can not only serve as a reinforcing particle to enhance the matrix strength, but also alleviate stress concentration by coordinating local plastic deformation.

[0022] (3) Multi-scale microstructure optimization: Compared with traditional casting processes, the present invention can predict the solidification path (phase transition temperature, sequence, type and phase fraction) of aluminum-silicon alloys with different Sr contents through the Scheil solidification model, reveal the evolution law of their microstructure, and establish a quantitative relationship between alloy composition and microstructure, providing a theoretical basis for optimizing Sr content and multi-scale microstructure design.

[0023] (4) Strong process compatibility, avoiding traditional deterioration defects: In traditional casting, Sr addition requires precise control of temperature and addition amount, which can easily lead to the formation of coarse and brittle phases locally due to segregation. The present invention utilizes the point-by-point melting characteristics of the SLM process and the rapid solidification characteristics of the molten pool to uniformly distribute the Sr element within the micron-scale molten pool, avoiding the problem of macro-segregation.

[0024] (5) Expanding the application potential of aluminum-silicon alloys in additive manufacturing: Existing SLM-formed aluminum-silicon alloys (such as AlSi10Mg) are difficult to meet the needs of high-load-bearing complex structural parts due to insufficient plasticity (elongation <10%). The aluminum-silicon alloy obtained by the present invention has both high strength and high plasticity: the tensile strength is up to 520MPa, the yield strength is up to 320MPa, and the elongation is up to 11%, which is significantly improved compared with the traditional SLM-formed AlSi10Mg alloy (tensile strength 400-450MPa, elongation 5-8%). This allows aluminum-silicon alloys to be used in scenarios such as aerospace thin-walled components and automotive lightweight anti-collision structures, while maintaining the design freedom and lightweight advantages of additive manufacturing.

[0025] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 SEM photograph of the morphology of the aluminum-silicon alloy powder prepared in Example 1 of the present invention.

[0027] Figure 2 Scanning electron microscope photographs of the cross-sectional microstructure of the aluminum-silicon alloy powder in Example 1 of the present invention, (a) is a full-view scanning electron microscope photograph of the cross-sectional microstructure of the aluminum-silicon alloy powder, and (b) is an enlarged view of the area in (a).

[0028] Figure 3 Pore ​​distribution of the deposited sample obtained in Example 1 of the present invention.

[0029] Figure 4 Scanning electron microscope photograph of the microstructure of the component obtained in Example 1 of the present invention.

[0030] Figure 5 Dark field image of the component obtained in Example 1 of the present invention under a transmission electron microscope.

[0031] Figure 6 Image of the component obtained in Example 1 of the present invention under the transmission electron microscope HAADF mode and EDS surface scanning image.

[0032] Figure 7 Solidification path of the aluminum-silicon alloy in Example 1 obtained based on thermodynamic calculations.

[0033] Figure 8 Pore ​​distribution of the component obtained in Comparative Example 1 of the present invention.

[0034] Figure 9 Image of the aluminum-silicon alloy specimen without Sr in Comparative Example 1 of the present invention under the transmission electron microscope HAADF mode and EDS surface scanning image.

[0035] Figure 10 Image of the aluminum-silicon alloy specimen containing trace Sr prepared in Comparative Example 2 of the present invention under the transmission electron microscope HAADF mode and EDS surface scanning image.

[0036] Figure 11 Metallographic photograph of the aluminum-silicon alloy specimen prepared in Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0037] Example 1

[0038] The aluminum-silicon alloy powder is prepared by the existing atomization powder making process. The specific preparation method is as follows:

[0039] S101. Raw material ratio: According to the element ratio of the aluminum-silicon alloy powder to be prepared (Si: 10%, Mg: 0.4%, Sr: 0.3%, and the balance is Al), weigh the raw materials for atomization powder production: high-purity Al (purity ≥ 99.99%), Al-50Si master alloy, high-purity Mg (purity ≥ 99.99%), and Al-50Sr modifier. Considering the volatilization loss of Sr during the atomization powder production process, the actual amount of Sr added to the raw materials is 1.67 times the Sr content in the aluminum-silicon alloy powder. Sr is extremely easy to oxidize, so Sr is introduced using the Al-50Sr modifier, and the Al-50Sr modifier is coated with aluminum foil to prevent oxidation.

[0040] S102, smelting process: The weighed high-purity Al, Al-50Si master alloy, high-purity Mg and Al-50Sr modifier were added to the vacuum induction furnace according to the raw material ratio in S101. The vacuum pump and induction heating were turned on and heated to 850°C. The temperature was kept for 20 minutes to ensure the homogenization of the alloy elements in the melt. The furnace was evacuated to a pressure of 5×10 -1 Pa, and then high-purity argon gas with a purity of 99.999% was filled in until the pressure difference between the inside and outside of the furnace was 0.

[0041] S103, atomization powder production: Remove the stopper rod at the bottom of the crucible and introduce argon gas for atomization at a pressure of 3 MPa. When there is no molten metal in the crucible and the atomizing nozzle is no longer spraying metal spray, wait for a few minutes before turning off the argon gas to prevent the molten metal from clogging the atomizing nozzle. Collect the powder in the cavity to obtain the aluminum-silicon alloy powder. The aluminum-silicon alloy powder is composed of the following elements in percentage by mass: Si: 10%, Mg: 0.4%, Sr: 0.3%, with the remainder being Al and unavoidable impurities. The prepared aluminum-silicon alloy powder has a wide particle size range of approximately 0-200 μm.

[0042] This embodiment discloses an additive manufacturing method for aluminum-silicon alloy based on in-situ reaction modification, which is:

[0043] S201, powder screening and drying: the aluminum silicon alloy powder prepared in S103 is screened to select aluminum silicon alloy powder with a particle size range of 15-53 μm, and then dried in a vacuum drying oven at a drying temperature of 100 ° C for 4 hours; then the dried aluminum silicon alloy powder is filled into the powder bin of the SLM equipment; the morphology of the aluminum silicon alloy powder after screening is as follows Figure 1 As shown, it can be observed that the powder has high sphericity, smooth surface, no adhesion, and no satellite balls, which is conducive to uniform spreading and lays a solid foundation for high-quality printing; the cross-sectional structure of the aluminum-silicon alloy powder is as follows Figure 2 As shown, the cooling rate of gas atomization powder is about 10 4 K / s, therefore, it can be observed that the size of the eutectic silicon phase has been significantly refined compared to the cast aluminum-silicon alloy, but the morphology of the eutectic silicon phase is still short rod-shaped, such as Figure 2As shown in (b), short rod-like eutectic Si is short rod-like eutectic silicon.

[0044] S202. Parts modeling: Use modeling software to draw the three-dimensional graphics of the required parts. After checking that they are correct, export the model into an STL file format suitable for 3D printing and import it into the slicing software.

[0045] Printing parameter settings: spot size 100μm, laser power 340W, scanning speed 1700mm / s, scanning spacing 130μm, layer thickness 30μm, energy density 51.3J / mm 3 The protective atmosphere is high-purity argon, and the oxygen content is controlled to be less than 100ppm during the printing process.

[0046] S203. Preview and Slice: After completing the above settings, use the slicing software's preview function to view the model's slicing effect. After confirming the preview effect is correct, use the slicing software to generate a code file, transfer it to the SLM device (BLTA320 printer) via a USB flash drive, and print it into an aluminum-silicon alloy specimen or component.

[0047] In this embodiment, the microstructure characterization and performance testing of the aluminum-silicon alloy sample are as follows:

[0048] The SLM-formed specimens were polished and the porosity was counted by optical microscopy. The porosity of the samples was detected by Micro CT and was 0.05%. The pore distribution was as follows: Figure 3 The microstructure of the deposited sample was characterized by scanning electron microscopy (SEM). Figure 4 As shown. There are a lot of cellular structures in the microstructure, and the interior is α-Al, the boundary is Al+Si eutectic network, and the size of the cellular structure is about 500nm. Further dark field phase characterization of transmission electron microscopy (TEM) shows that the size of the eutectic silicon phase is about 50nm, as shown Figure 5 The HAADF mode of transmission electron microscopy combined with EDS surface scanning confirmed the presence of a large number of Sr-rich metastable eutectic phases with a size of about 50 nm in the microstructure, as shown in Figure 2. Figure 6 shown. Figure 6 The left side is a low-magnification TEM high-angle annular dark field (HAADF) image, and the right side is a locally enlarged high-magnification HAADF image and the corresponding surface distribution map of Al, Si, and Sr elements. Combining the selected area electron diffraction pattern, high-resolution image, and neutron diffraction, it was determined that the Sr-rich metastable eutectic phase generated by the in-situ reaction is Al 16 Si 30The Sr8 phase has an elastic modulus of 70 GPa, which is comparable to the aluminum matrix. It can not only serve as a reinforcing particle to enhance the matrix strength, but also relieve stress concentration by coordinating local plastic deformation. The solidification process of the aluminum-silicon alloy in Example 1 was simulated using the Scheil-Gulliver solidification model, including phase transition temperature, solidification sequence, and phase volume fraction. The results are shown in Figure 2. Figure 7 As shown in the actual experiment, after adding Sr, the quaternary eutectic reaction Liquid→Al+Si+Mg2Si+Al 16 Si 30 Sr8 generates Al 16 Si 30 Sr8 phase, which is consistent with the microstructure characterization results.

[0049] To verify the effectiveness of Example 1, the yield strength, tensile strength, and elongation of aluminum-silicon alloy samples were tested. Three samples were prepared under the same process conditions. The yield strength, tensile strength, and elongation were measured, and the average and standard deviation were calculated. The specific performance indicators are shown in Table 1.

[0050] Table 1 Mechanical properties of aluminum-silicon alloy samples in Example 1

[0051]

[0052]

[0053] Compared to the aluminum-silicon alloy sample prepared in Comparative Example 1 without Sr, the aluminum-silicon alloy sample prepared in this example exhibited yield strength, tensile strength, and elongation at break increased by 16.6%, 15.3%, and 37.5%, respectively. Furthermore, compared to the aluminum-silicon alloy sample containing trace amounts of Sr prepared in Comparative Example 2, the aluminum-silicon alloy sample prepared in Example 1 exhibited yield strength, tensile strength, and elongation at break increased by 14.0%, 11.8%, and 26.9%, respectively. This demonstrates that the strength and plasticity of additively manufactured components prepared using the modified aluminum-silicon alloy powder of the present invention are significantly superior to those of commercially available AlSi10Mg alloy.

[0054] Example 2

[0055] The aluminum-silicon alloy powder was prepared by the method for preparing the aluminum-silicon alloy powder disclosed in Example 1, except that:

[0056] The actual amount of Sr added to the raw material in S101 is 1.3 times the Sr content in the aluminum-silicon alloy powder.

[0057] The aluminum-silicon alloy powder prepared in S103 is composed of the following elements in percentage by mass: Si: 10.5%, Mg: 0.5%, Sr: 0.5%, and the balance being Al and unavoidable impurity elements.

[0058] The aluminum-silicon alloy specimens were prepared using the additive manufacturing method for aluminum-silicon alloy based on in-situ reaction modification disclosed in Example 1, with the following differences:

[0059] The aluminum-silicon alloy powder used in S201 is prepared in this embodiment;

[0060] In S201, the drying temperature is 80°C and the temperature is kept for 6 hours;

[0061] The process parameters of the selective laser melting method in S202 are: spot size 100 μm, process parameters are laser power 340 W, scanning speed 1400 mm / s, scanning spacing 130 μm, layer thickness 30 μm, and energy density 62.3 J / mm 3 .

[0062] The aluminum-silicon alloy powder in this embodiment may also be composed of the following elements in the following mass percentages: Si: 8%, Mg: 1%, Sr: 1%, with the balance being Al and unavoidable impurity elements. The preparation method employs the aforementioned additive manufacturing method, with the laser power of the selective laser melting method in S202 also being 200 W or 400 W, and the scanning pitch being 100 μm or 220 μm.

[0063] To verify the effectiveness of Example 2, the yield strength, tensile strength, and elongation of aluminum-silicon alloy samples were tested. Three samples were prepared under the same process conditions. The yield strength, tensile strength, and elongation were measured, and the average and standard deviation were calculated. The specific performance indicators are shown in Table 2.

[0064] Table 2 Mechanical properties of aluminum-silicon alloy samples in Example 2

[0065] Sample number Yield strength / MPa Tensile strength / MPa Elongation at break / % 1 311.2 500.7 8.55 2 298.3 498.5 9.70 3 320.0 518.7 9.57 average value 309.8 506.0 9.27 Standard deviation ±10.9 ±11.1 ±0.63

[0066] The aluminum-silicon alloy sample prepared in this example exhibited 12.9% higher yield strength, 13.6% higher tensile strength, and 20.6% higher elongation at break than the Sr-free aluminum-silicon alloy sample prepared in Comparative Example 1. This demonstrates that the additively manufactured components prepared using the modified aluminum-silicon alloy powder of the present invention exhibit superior strength and plasticity to those of commercially available AlSi10Mg alloys.

[0067] Example 3

[0068] The aluminum-silicon alloy powder was prepared by the method for preparing the aluminum-silicon alloy powder disclosed in Example 1, except that:

[0069] The actual amount of Sr added to the raw material in S101 is 1.75 times the Sr content in the aluminum silicon alloy powder.

[0070] The aluminum-silicon alloy powder prepared in S103 is composed of the following elements in percentage by mass: Si: 9.5%, Mg: 0.3%, Sr: 0.2%, and the remainder is Al and unavoidable impurity elements.

[0071] The aluminum-silicon alloy specimens were prepared using the additive manufacturing method for aluminum-silicon alloy based on in-situ reaction modification disclosed in Example 1, with the following differences:

[0072] The aluminum-silicon alloy powder used in S201 is prepared in this embodiment;

[0073] In S201, the drying temperature is 150°C and kept warm for 2 hours;

[0074] The process parameters of the selective laser melting method in S202 are: spot size 100 μm, process parameters are laser power 380 W, scanning speed 1400 mm / s, scanning spacing 130 μm, layer thickness 30 μm, and energy density 69.6 J / mm 3 .

[0075] To verify the effectiveness of Example 3, the yield strength, tensile strength, and elongation of aluminum-silicon alloy samples were tested. Three samples were prepared under the same process conditions. The yield strength, tensile strength, and elongation were measured, and the average and standard deviation were calculated. The specific performance indicators are shown in Table 3.

[0076] Table 3 Mechanical properties of aluminum-silicon alloy samples in Example 3

[0077] Sample number Yield strength / MPa Tensile strength / MPa Elongation at break / % 1 296.2 497.6 13.86 2 282.9 484.3 11.02 3 297.7 504.7 11.92 average value 292.3 495.5 12.27 Standard deviation ±8.1 ±10.4 ±1.45

[0078] The aluminum-silicon alloy sample prepared in this example exhibited 6.5% higher yield strength, 11.2% higher tensile strength, and 61.7% higher elongation at break than the Sr-free aluminum-silicon alloy sample prepared in Comparative Example 1. This demonstrates that the in-situ reaction modification method of the present invention can improve the strength and plasticity of commercial AlSi10Mg alloys, particularly resolving the severe plasticity issues associated with additively manufactured components made from commercial AlSi10Mg alloys.

[0079] Example 4

[0080] The aluminum-silicon alloy powder was prepared by the method for preparing the aluminum-silicon alloy powder disclosed in Example 1, except that:

[0081] The actual amount of Sr added to the raw material in S101 is 1.67 times the Sr content in the aluminum-silicon alloy powder.

[0082] The aluminum-silicon alloy powder prepared in S103 is composed of the following elements in percentage by mass: Si: 12%, Mg: 0.5%, Sr: 0.3%, and the balance being Al and unavoidable impurity elements.

[0083] The aluminum-silicon alloy specimens were prepared using the additive manufacturing method for aluminum-silicon alloy based on in-situ reaction modification disclosed in Example 1, with the following differences:

[0084] The aluminum-silicon alloy powder used in S201 is prepared in this embodiment;

[0085] The process parameters of the selective laser melting method in S202 are: spot size 100 μm, process parameters are laser power 380 W, scanning speed 800 mm / s, scanning spacing 170 μm, layer thickness 60 μm, and energy density 46.6 J / mm 3 .

[0086] To verify the effectiveness of Example 4, the yield strength, tensile strength, and elongation of aluminum-silicon alloy samples were tested. Three samples were prepared under the same process conditions. The yield strength, tensile strength, and elongation were measured, and the average and standard deviation were calculated. Specific performance indicators are shown in Table 4.

[0087] Table 4 Mechanical properties of aluminum-silicon alloy samples in Example 4

[0088] Sample number Yield strength / MPa Tensile strength / MPa Elongation at break / % 1 301.5 492.3 7.65 2 308.3 505.6 9.90 3 311.7 499.3 8.59 average value 307.2 499.1 8.71 Standard deviation ±5.2 ±6.7 ±1.13

[0089] Compared to the Sr-free aluminum-silicon alloy sample prepared in Comparative Example 1, the yield strength, tensile strength, and elongation at break of the aluminum-silicon alloy sample prepared in this example increased by 20.0%, 12.1%, and 14.8%, respectively. This demonstrates that the in-situ reaction modification method of the present invention can simultaneously improve the strength and plasticity of conventional additively manufactured aluminum-silicon alloys.

[0090] Example 5

[0091] The aluminum-silicon alloy powder was prepared by the method for preparing the aluminum-silicon alloy powder disclosed in Example 1, except that:

[0092] The actual amount of Sr added to the raw material in S101 is 1.5 times the Sr content in the aluminum silicon alloy powder.

[0093] The aluminum-silicon alloy powder prepared in S103 is composed of the following elements in percentage by mass: Si: 8%, Mg: 0.4%, Sr: 0.1%, and the balance being Al and unavoidable impurity elements.

[0094] The aluminum-silicon alloy specimens were prepared using the additive manufacturing method for aluminum-silicon alloy based on in-situ reaction modification disclosed in Example 1, with the following differences:

[0095] The aluminum-silicon alloy powder used in S201 is prepared in this embodiment;

[0096] The process parameters of the selective laser melting method in S202 are: spot size 100 μm, process parameters are laser power 340 W, scanning speed 1400 mm / s, scanning spacing 170 μm, layer thickness 30 μm, and energy density 47.6 J / mm 3 .

[0097] To verify the effectiveness of Example 5, the yield strength, tensile strength, and elongation of aluminum-silicon alloy samples were tested. Three samples were prepared under the same process conditions. The yield strength, tensile strength, and elongation were measured, and the average and standard deviation were calculated. Specific performance indicators are shown in Table 5.

[0098] Table 5 Mechanical properties of aluminum-silicon alloy samples in Example 5

[0099] Sample number Yield strength / MPa Tensile strength / MPa Elongation at break / % 1 285.9 470.6 9.39 2 290.6 478.1 9.03 3 275.9 453.0 8.38 average value 284.1 467.2 8.93 Standard deviation ±7.5 ±12.9 ±0.51

[0100] Compared to the Sr-free aluminum-silicon alloy sample prepared in Comparative Example 1, the yield strength, tensile strength, and elongation at break of the aluminum-silicon alloy sample prepared in this example increased by 3.5%, 4.9%, and 17.7%, respectively. This demonstrates that the in-situ reaction modification method of the present invention can improve the plasticity of aluminum-silicon alloys produced by conventional additive manufacturing.

[0101] Comparative Example 1

[0102] The aluminum-silicon alloy specimens without Sr in this comparative example were prepared using the additive manufacturing method of the aluminum-silicon alloy based on in-situ reaction modification disclosed in Example 1, with the following differences:

[0103] In S201, commercial AlSi10Mg alloy powder was used instead of aluminum-silicon alloy powder. This powder contains no Sr and consists of 10.0% Si and 0.4% Mg, with the remainder being Al and unavoidable impurities. All other process conditions remained the same, resulting in Sr-free aluminum-silicon alloy specimens.

[0104] The aluminum-silicon alloy sample without Sr prepared in this comparative example was ground and polished, and the porosity of the aluminum-silicon alloy without Sr was counted by optical microscopy. The porosity of the alloy was detected by Micro CT and was 0.09%. The pore distribution was as follows: Figure 8 As shown. Compared with the pore distribution of the alloy with Sr added in Example 1 ( Figure 3 ), the porosity in the alloy decreases after adding Sr, the average pore size decreases, and the pore aspect ratio is closer to 1. The microstructure of the alloy without Sr addition was observed using transmission electron microscopy HAADF mode. The microstructure is characterized by a cellular structure with α-Al inside and an Al+Si eutectic network at the boundary. The size of the cellular structure is about 500nm, and the size of the boundary eutectic Si particles is about 70nm. Figure 9Compared with the microstructure of the alloy in Example 1, there are no Sr-rich particles, and the eutectic Si particle size is larger than that of the Si particle size in the aluminum-silicon alloy of Example 1.

[0105] To verify the effectiveness of Comparative Example 1, the yield strength, tensile strength, and elongation of Sr-free aluminum-silicon alloy samples were tested. Three samples were prepared under the same process conditions, and the yield strength, tensile strength, and elongation were measured. The average and standard deviation were then calculated. Specific performance indicators are shown in Table 6.

[0106] Table 6 Mechanical properties of aluminum-silicon alloy without Sr in comparative example 1

[0107] Sample number Yield strength / MPa Tensile strength / MPa Elongation at break / % 1 279.3 452.2 7.58 2 276.6 444.1 6.81 3 267.3 440.0 8.39 average value 274.4 445.4 7.59 Standard deviation ±6.3 ±6.2 ±7.90

[0108] The mechanical properties of the aluminum-silicon alloy specimens prepared in this comparative example represent the performance indicators of the most widely used AlSi10Mg alloy. The main problem is that the tensile strength does not exceed 450 MPa and the elongation is generally lower than 8%. When used in aerospace and other fields, the strength and plasticity of the alloy need to be further optimized, especially the plasticity needs to be improved.

[0109] Comparative Example 2

[0110] The aluminum-silicon alloy powder containing a trace amount of Sr in this comparative example was prepared using the preparation method of the aluminum-silicon alloy powder disclosed in Example 1, with the following differences:

[0111] The mass content of Sr in the aluminum-silicon alloy powder prepared in S103 is 0.005%.

[0112] The additive manufacturing method of aluminum-silicon alloy based on in-situ reaction modification disclosed in Example 1 was used to prepare aluminum-silicon alloy specimens containing trace amounts of Sr in this comparative example. The difference is that:

[0113] The aluminum-silicon alloy powder used in S201 is the aluminum-silicon alloy powder containing a trace amount of Sr prepared in this comparative example;

[0114] The process parameters of the selective laser melting method in S202 are: spot size 100 μm, process parameters are laser power 360 W, scanning speed 1300 mm / s, scanning spacing 170 μm, layer thickness 30 μm, and energy density 54.3 J / mm 3 .

[0115] The microstructure of aluminum-silicon alloy containing trace Sr was observed using transmission electron microscopy HAADF mode. Figure 10 As shown; compared with the alloy microstructure in Comparative Example 1, there is no difference in the size of the cellular structure and the size of the eutectic Si particles. Trace Sr element enrichment can be observed by EDS, and only a very small number of Sr-rich particles are observed.

[0116] To verify the effectiveness of Comparative Example 2, the yield strength, tensile strength, and elongation of aluminum-silicon alloy samples containing trace amounts of Sr were tested. Three samples were prepared under the same process conditions, and the yield strength, tensile strength, and elongation were measured. The average and standard deviation were then calculated. Specific performance indicators are shown in Table 7.

[0117] Table 7 Mechanical properties of aluminum-silicon alloy samples containing trace amounts of Sr in Comparative Example 2

[0118] Sample number Yield strength / MPa Tensile strength / MPa Elongation at break / % 1 277.5 464.3 8.40 2 282.0 453.0 7.96 3 285.9 461.0 8.32 average value 281.8 459.4 8.23 Standard deviation ±4.2 ±5.8 ±0.23

[0119] The Si content in Example 5 is 8%. In aluminum-silicon alloys, the Si content is positively correlated with the strength. The mechanical properties of the aluminum-silicon alloy sample prepared in Example 5 are similar to those of the aluminum-silicon alloy sample containing trace Sr prepared in Comparative Example 2. However, the Si content in Comparative Example 2 is 10%, and the strength values ​​of the two are still similar, which is sufficient to illustrate that the addition of 0.1% Sr to the aluminum-silicon alloy in Example 5 has a positive effect on the mechanical properties.

[0120] Comparative Example 3

[0121] The aluminum-silicon alloy powder with a high Sr content in this comparative example was prepared using the method for preparing the aluminum-silicon alloy powder disclosed in Example 1, with the following differences:

[0122] The actual amount of Sr added to the raw material in S101 is 1.25 times the Sr content in the aluminum silicon alloy powder.

[0123] The aluminum-silicon alloy powder with a high Sr content prepared in S103 is composed of the following elements in percentage by mass: Si: 9.3%, Mg: 0.35%, Sr: 1.2%, and the remainder is Al and unavoidable impurity elements.

[0124] The additive manufacturing method of aluminum-silicon alloy based on in-situ reaction modification disclosed in Example 1 was used to prepare aluminum-silicon alloy specimens with a high Sr content in this comparative example. The difference is that:

[0125] The aluminum-silicon alloy powder used in S201 is the aluminum-silicon alloy powder with a high Sr content prepared in this comparative example;

[0126] The process parameters of the selective laser melting method in S202 are: spot size 100 μm, process parameters are laser power 380 W, scanning speed 800 mm / s, scanning spacing 220 μm, layer thickness 30 μm, energy density 72.0 J / mm 3 .

[0127] To verify the effectiveness of Comparative Example 3, the yield strength, tensile strength, and elongation of aluminum-silicon alloy samples with a high Sr content were tested. Three samples were prepared under the same process conditions, and the yield strength, tensile strength, and elongation were measured. The average and standard deviation were then calculated. Specific performance indicators are shown in Table 8.

[0128] Table 8 Mechanical properties of aluminum-silicon alloy samples with high Sr content in comparative example 3

[0129]

[0130]

[0131] Compared to the Sr-free Al-Si alloy sample prepared in Comparative Example 1, the Al-Si alloy sample prepared in this comparative example exhibited yield strength and tensile strength increases of 17.2% and 7.0%, respectively, but a 32.5% decrease in elongation at break. This indicates that excessive Sr addition in this comparative example, while increasing the alloy's strength, further deteriorated its plasticity.

[0132] Comparative Example 4

[0133] The aluminum-silicon alloy additive manufacturing method based on in-situ reaction modification disclosed in Example 1 was used to prepare aluminum-silicon alloy specimens in this comparative example, with the following differences:

[0134] The process parameters of the selective laser melting method in S202 are: spot size 100 μm, process parameters are laser power 180 W, scanning speed 1400 mm / s, scanning spacing 120 μm, layer thickness 30 μm, and energy density 35.7 J / mm 3 .

[0135] Since the printing process parameters are not within the optimal process window, the porosity of the SLM-formed components is high. A large number of holes and unmelted defects can be observed from the metallographic photos, such as Figure 11 shown.

[0136] To verify the effectiveness of Comparative Example 4, the yield strength, tensile strength, and elongation of aluminum-silicon alloy samples were tested. Three samples were prepared under the same process conditions. The yield strength, tensile strength, and elongation were measured, and the average and standard deviation were calculated. Specific performance indicators are shown in Table 9.

[0137] Table 9 Mechanical properties of aluminum-silicon alloy samples in comparative example 4

[0138]

[0139]

[0140] Compared to the Sr-free aluminum-silicon alloy sample prepared in Comparative Example 1, the aluminum-silicon alloy sample prepared in this comparative example exhibited yield strength and tensile strength increases of 10.7% and 7.1%, respectively, but a 16.2% decrease in elongation at break. Although the alloy powder used in this comparative example was the same as that in Example 1, which produced excellent mechanical properties in the sample prepared using this powder in Example 1, the mechanical properties of the sample prepared in this comparative example deteriorated due to the use of an inappropriate additive manufacturing process.

[0141] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent variation made to the above embodiment based on the essence of the invention technology shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for additive manufacturing of aluminum-silicon alloy based on in-situ reaction modification, characterized in that: The method comprises the following steps: Step 1: Select aluminum-silicon alloy powder with a particle size range of 15-53 μm, keep it in a vacuum at a temperature of 80-150° C. for 2-6 hours, and then dry it; the aluminum-silicon alloy powder is composed of the following elements in mass percentage: Si: 8-12%, Mg: 0-1%, Sr: 0.01-1%, and the balance is Al and unavoidable impurity elements; Step 2: Selective laser melting is used to form aluminum-silicon alloy components. The process parameters are: laser power 200-400W, scanning speed 800-1700mm / s, scanning spacing 0.1-0.22mm, layer thickness 30-60μm, energy density 40-100J / mm 3 .

2. The additive manufacturing method according to claim 1, characterized in that: The aluminum-silicon alloy powder is composed of the following elements in percentage by mass: Composition: Si: 9.5-10.5%, Mg: 0.3-0.5%, Sr: 0.1-0.5%, the balance being Al and unavoidable impurity elements.

3. The additive manufacturing method according to claim 1, characterized in that: The aluminum-silicon alloy powder is prepared by a method of smelting combined with atomization powder making. During the smelting process, the Sr element is introduced as the Sr raw material in the form of pure Sr, Sr salt or Al-Sr modifier. The amount of Sr raw material added is calculated based on the Sr content in the Sr raw material. The Sr content in the Sr raw material is not less than 1.2 times the Sr content in the aluminum-silicon alloy powder, ensuring that Sr can still play a modificatory role and participate in the in-situ reaction after partial volatilization in the SLM molten pool.

4. The additive manufacturing method according to claim 3, characterized in that The Sr content in the Sr raw material is 1.2-1.8 times the Sr content in the aluminum-silicon alloy powder.

5. The additive manufacturing method according to claim 1, wherein: The laser power is 340-380W, the scanning speed is 1400-1700mm / s, the scanning spacing is 0.13-0.17mm, the layer thickness is 30μm, and the energy density is 45-70J / mm 3 .

6. The additive manufacturing method according to claim 1, wherein: The aluminum-silicon alloy component prepared in step 2 has a tensile strength of up to 515 MPa, a yield strength of up to 320 MPa, and an elongation of up to 12.3%.

7. An aluminum-silicon alloy based on in-situ reaction modification, characterized in that: An aluminum-silicon alloy prepared by the additive manufacturing method according to any one of claims 1 to 6.

8. The aluminum-silicon alloy according to claim 7, characterized in that: The size of the eutectic silicon phase of the aluminum-silicon alloy is about 50nm, and the nano-scale metastable phase is evenly distributed at the boundary of the cellular structure. The metastable phase contains Al 16 Si 30 Sr8 phase, Al 16 Si 30 The average size of the Sr8 phase is about 50 nm.

9. An application of aluminum-silicon alloy based on in-situ reaction modification, characterized in that: The aluminum-silicon alloy prepared by the additive manufacturing method according to any one of claims 1 to 6 is used in aerospace load-bearing brackets, automobile lightweight structural parts or metal shoe molds.

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