Aluminum-magnesium-silicon alloy for additive manufacturing and preparation method thereof

Abstract

The present invention provides an aluminum-magnesium-silicon alloy for additive manufacturing and a preparation method thereof. The alloy components, by mass percentage, are as follows: Mg: 3-10 wt.%, Si: 1-5 wt.%, Mn: 0.1-2 wt.%, Ti: 0.01-0.5 wt.%, Zr: 0.01-0.5 wt.%, Sr: 0.01-0.2 wt.%, with the total amount of other impurities not exceeding 0.8 wt.%, and the balance being Al. The alloy is produced through ingot melting, powder preparation, laser forming, and aging treatment. The inoculation effect of Ti and Zr synergistically achieves microstructure refinement with the modification effect of Sr. This alloy achieves excellent mechanical properties while exhibiting a relatively low cost advantage, facilitating industrial production and promotion.

Description

Technical Field

[0001] The present invention relates to the field of metal additive manufacturing, and in particular to an aluminum-magnesium-silicon alloy for additive manufacturing and a preparation method thereof. Background Art

[0002] Additive Manufacturing (AM), also known as 3D printing, is a processing method that is completely different from traditional molding processes. AM combines computer-aided design (CAD) with material molding, uses CAD software to deconstruct a two-dimensional image of a three-dimensional model, and then stacks layers to accumulate the molded components. This emerging production method has the advantages of short manufacturing cycle, high material utilization rate, and high product precision, and has good application prospects. Currently, commonly used additive manufacturing technologies include stereolithography (SLA), selective laser melting (SLM), and direct metal deposition (DMD). Among them, selective laser melting uses metal powder as raw material and laser as input energy source. It has fast processing speed, high molding accuracy, and strong complex structure molding capabilities. It is currently widely used in aerospace and other fields.

[0003] Aluminum alloy is currently a widely used alloy material with the characteristics of low density, high specific strength, good plasticity, corrosion resistance, and excellent electrical and thermal conductivity. It has an irreplaceable position in the fields of aerospace, transportation, equipment and instruments. The aluminum alloy prepared by SLM has a uniform microstructure distribution and significant fine grain strengthening. Combined with its lightweight advantage, it is gradually used in important aerospace mechanical structures such as satellite brackets and engine nacelles. However, due to problems such as the manufacturing of printing equipment, the production of alloy powders, and the regulation of process flow, the application range of aluminum alloy parts produced by domestic SLM is relatively small and has not been popularized in the field of large-scale machinery production. Imported printing equipment and metal powders have created relatively high economic costs, making it difficult to replace the traditional low-priced aluminum alloy materials.

[0004] However, the additive manufacturing production model is not suitable for traditional high-strength 2xxx and 7xxx aluminum alloys. Al-Cu and Al-Zn alloys, due to their high solid solubility and the wide solid-liquid temperature range, experience severe cracking during the rapid laser cooling and heating process, resulting in extremely poor component forming performance. Currently, most aluminum alloy powders used in 3D printing are near-eutectic aluminum-silicon alloys with relatively low mechanical properties. The narrow solidification temperature range of the eutectic Si phase and the excellent melt fluidity mitigate the tendency to hot cracking caused by high undercooling during SLM processes. For example, the AlSi10Mg alloy powder disclosed in Chinese patent CN 107716918A exhibits good formability but relatively low mechanical properties. Meanwhile, the mainstream high-strength AlMgScZr alloy powder for additive manufacturing loses the cost advantage traditionally associated with aluminum alloys due to the high price of Sc, making it difficult to widely use in industrial production. Summary of the Invention

[0005] In order to solve the problem that traditional high solid solution and high strength deformed aluminum-magnesium-silicon alloys formed by laser deposition are subject to severe thermal cracking, while high strength aluminum-magnesium-silicon alloys for 3D printing are expensive, the purpose of the present invention is to propose an aluminum-magnesium-silicon alloy for additive manufacturing and a preparation method thereof. By combining the inoculation effect of Ti and Zr with the modification effect of Sr, the fine grain effect of Sc-Zr is replaced to achieve microstructure refinement, thereby reducing the production cost of high strength aluminum-magnesium-silicon alloys for laser additive manufacturing, while achieving excellent mechanical properties and showing a relatively low cost advantage, which is convenient for industrial production and promotion.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides an aluminum-magnesium-silicon alloy for additive manufacturing, wherein the weight percentages of the components in the aluminum-magnesium-silicon alloy are: Mg: 3-10wt.%, Si: 1-5wt.%, Mn: 0.1-2wt.%, Ti: 0.01-0.5wt.%, Zr: 0.01-0.5wt.%, Sr: 0.01-0.2wt.%, and the total amount of other impurities does not exceed 0.8wt.%, and the balance is Al.

[0008] As one embodiment of the present invention, the weight percentage of each component in the aluminum-magnesium-silicon alloy is: Mg: 5-9wt.%, Si: 2-5wt.%, Mn: 0.5-1.5wt.%, Ti: 0.1-0.4wt.%, Zr: 0.1-0.4wt.%, Sr: 0.01-0.03wt.%, and the total amount of other impurities does not exceed 0.8wt.%, and the balance is Al.

[0009] In some embodiments of the present invention, the weight percentages of the components in the aluminum-magnesium-silicon alloy are: Mg: 5-9wt.%, Si: 2-3wt.%, Mn: 0.7-1.5wt.%, Ti: 0.2-0.4wt.%, Zr: 0.1-0.3wt.%, Sr: 0.01-0.03wt.%, and the total amount of other impurities does not exceed 0.8wt.%, and the balance is Al.

[0010] As an embodiment of the present invention, the weight ratio of Mg to Si in the aluminum-magnesium-silicon alloy is 1.72-10:1.

[0011] In the present invention, Mg is the main solid solution strengthening element and its content needs to be relatively high. Mn is added to supplement the alloy and form a double solid solution strengthening of Mg and Mn by adding Mn. While ensuring better mechanical properties, it can avoid excessive content of a single Mg element, thereby reducing the solid-liquid temperature range and reducing the tendency of hot cracking. Si is added to improve the plasticity and toughness of the alloy and avoid cracking during the printing process. Mg and Si can also form Mg2Si precipitation phase in the subsequent aging treatment, so Mg:Si should be greater than 1.72:1. Ti and Zr are grain refining elements and mainly form an initial phase with Al. L12-Al3Zr and L12-Al3Ti phases are generated, and both are coherent with the matrix, so they can serve as nucleation sites for α-Al. However, when the content is too high, the coarse Al3Zr and Al3Zr phases formed will no longer be coherent with α-Al. Therefore, the Ti and Zr content in the alloy should not be higher than 0.2%. Considering that some Ti and Zr will be dissolved in the matrix in the printed state and will precipitate during the heat treatment process without affecting the crystallization process, the Ti and Zr content is designed to be no more than 0.4%; Sr, as a modifier, only needs to be added in trace amounts to be effective, and the content should be controlled at 0.01-0.03%.

[0012] In a second aspect, the present invention provides a method for preparing an aluminum-magnesium-silicon alloy for additive manufacturing, the preparation method comprising the following steps:

[0013] S1. Alloy smelting: mixing aluminum, aluminum-magnesium master alloy, aluminum-silicon master alloy, aluminum-manganese master alloy, aluminum-titanium master alloy, aluminum-zirconium master alloy and aluminum-strontium master alloy according to a certain ratio, smelting and casting into aluminum-magnesium-silicon alloy ingots;

[0014] S2. Powder preparation: remelting the ingot obtained in S1, atomizing it, cooling and solidifying it to form metal powder, and then sieving the powder to obtain aluminum-magnesium-silicon alloy powder for additive manufacturing;

[0015] S3, laser forming: performing selective laser melting forming on the aluminum-magnesium-silicon alloy powder obtained in S2 to obtain a printed alloy;

[0016] S4. Aging treatment: The printed alloy obtained in S3 is subjected to aging treatment to obtain an aluminum-magnesium-silicon alloy for additive manufacturing.

[0017] As an embodiment of the present invention, in step S1, the aluminum is commercially pure aluminum.

[0018] As an embodiment of the present invention, in step S1, the smelting temperature is 750-780° C. The ratio satisfies the weight percentage of each component in the aluminum-magnesium-silicon alloy.

[0019] As an embodiment of the present invention, in step S1, after the alloy is completely melted, the alloy melt is stirred with an electromagnetic stirrer until it is fully mixed and uniformly mixed, and then kept warm and allowed to stand for 30-120 minutes; the stirring time is 20-60 minutes.

[0020] As one embodiment of the present invention, in step S2, before atomization, an alumina conduit is used to guide the melt (i.e., alloy melt) from the smelting furnace. Alumina has a high melting point and can be used to transport molten metal. Using aluminum alloy oxide also avoids the introduction of other metal elements.

[0021] As an embodiment of the present invention, in step S2, the atomization method includes: using high-speed compressed nitrogen gas with a purity of ≥99.995% to impact the molten aluminum-magnesium-silicon alloy, thereby breaking the melt into fine droplets.

[0022] In one embodiment of the present invention, in step S2, the atomization pressure is 8-15 MPa. When the atomization pressure is lower than 8 MPa, the atomized droplets are prone to bag-type breakage due to the low pressure, and the formed powder is prone to forming hollow powder. When the atomization pressure is higher than 15 MPa, the atomized droplets are prone to fragmentation due to the high pressure, and the powder particle size is too small, making it unsuitable for SLM printing.

[0023] As an embodiment of the present invention, in step S2, the screening method is cyclone separation and powder collection. A cyclone separation and powder collection device is used to screen the powder under a high-purity argon atmosphere.

[0024] As an embodiment of the present invention, in step S2, more than 60% of the aluminum-magnesium-silicon alloy powder for additive manufacturing prepared has a particle size range of 20-60 μm.

[0025] As an embodiment of the present invention, in step S2, more than 90% of the aluminum-magnesium-silicon alloy powder for additive manufacturing prepared is spherical or pear-shaped.

[0026] As an embodiment of the present invention, in step S3, in an argon atmosphere, when the oxygen content in the molding chamber is lower than 200ppm, the selective laser melting molding process starts laser printing. The selective laser molding process is carried out in an argon atmosphere, and argon is introduced before printing begins. Laser processing is then started when the oxygen content in the molding chamber is lower than 200ppm. During the molding process, a high-purity argon gas flow is used for directional blowing to prevent metal vapor and oxide inclusions from solidifying and falling back. If the oxygen content in the molding chamber is higher than 200ppm during processing, printing should be stopped immediately and argon should be introduced again until the ambient oxygen content meets the requirements before printing is resumed.

[0027] As one embodiment of the present invention, in step S3, the laser power used in the selective laser melting process is 280-420W and the scanning speed is 1000-2400mm / s. The laser power and scanning speed jointly determine the linear input energy density. When the laser power is less than 280W or the scanning speed is greater than 2400mm / s, the input energy is insufficient to completely melt the metal powder, and unfused voids are likely to form. When the laser power is greater than 420W or the scanning speed is less than 1000mm / s, the linear input energy density is too high, and a large amount of metal vapor escapes, which can easily cause elemental burnout and microstructure coarsening, resulting in a significant decrease in the mechanical properties of the alloy.

[0028] In some embodiments of the present invention, the selective laser melting process uses a laser power of 330-380 W and a scanning speed of 1200-1500 mm / s.

[0029] As an embodiment of the present invention, in step S3, the selective laser melting process uses a scanning pitch of 0.13-0.18 mm, a layer thickness of 40-60 μm, and a substrate preheating temperature of 120-150°C.

[0030] In one embodiment of the present invention, in step S4, the aging treatment temperature is 150-300°C for 1-24 hours. When the aging temperature is below 150°C, the alloy undergoes insignificant age hardening and fails to achieve the desired aging strengthening effect. When the temperature is above 300°C, the grains grow due to the excessive temperature, thereby reducing mechanical properties.

[0031] In some embodiments of the present invention, the aging treatment is performed at a temperature of 170-300° C. for a time of 1-10 h.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) Based on the excellent mechanical properties of Al-Mg-Si alloys, the present invention utilizes the good fluidity of Si to enhance the casting properties of Al-Mg-Si alloys, ensuring that the alloy has good formability under SLM. Simultaneously, the alloy is strengthened by the solid solution of Mg and the precipitation of Mg2Si to provide it with excellent mechanical properties.

[0034] (2) The present invention adds a certain amount of Mn, which, through auxiliary strengthening by Mn, appropriately reduces the addition ratio of the single Mg element, thereby lowering the solid-liquid temperature range of the alloy and reducing hot cracking sensitivity. At the same time, the synergistic effect of Mg and Mn to form the uniform precipitation of Mg5Al8 compounds can improve corrosion resistance, and Al6Mn compounds can hinder the growth of recrystallized grains and refine the structure.

[0035] (3) The Ti and Zr added in the present invention form Al3Ti and Al3Zr coherent with the α-Al matrix, acting as heterogeneous nucleation sites. The Sr modification then hinders grain growth and promotes grain refinement. The combined action of Ti, Zr, and Sr replaces the precious metal Sc, reducing the production cost of laser additive manufacturing of high-strength aluminum-magnesium-silicon alloys.

[0036] (4) This invention proposes a high-strength, low-cost aluminum-magnesium-silicon alloy suitable for selective laser melting. Compared to conventional aluminum-magnesium-silicon alloys, selective laser melting aluminum-magnesium-silicon alloys have an extremely fine grain structure, enabling near-net-shape production of various complex-shaped structural parts and topologically optimized networks, and have broad application prospects in fields such as aerospace. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0038] Figure 1 This is the metallographic structure of the formed alloy in Example 3;

[0039] Figure 2 The grain structure of the formed alloy in Example 1;

[0040] Figure 3 The microstructure of the formed alloy containing microcracks in Comparative Example 1;

[0041] Figure 4 This is a metallographic image of the formed alloy containing pores in Comparative Example 3. DETAILED DESCRIPTION

[0042] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, provide detailed implementation methods and specific operating procedures, and will help those skilled in the art to further understand the present invention. It should be pointed out that the scope of protection of the present invention is not limited to the following embodiments, and a number of adjustments and improvements made under the premise of the concept of the present invention all fall within the scope of protection of the present invention.

[0043] It should be noted that the testing methods of the following examples and comparative examples are the same as those in Example 1.

[0044] Example 1

[0045] Chemical composition and element content of aluminum-magnesium-silicon alloy: Al-7Mg-3Si-0.7Mn-0.2Ti-0.1Zr-0.03Sr (wt.%).

[0046] S1: Alloy smelting: Commercial pure aluminum, aluminum-magnesium master alloy, aluminum-silicon master alloy, aluminum-manganese master alloy, aluminum-titanium master alloy, aluminum-zirconium master alloy and aluminum-strontium master alloy are placed in a smelting furnace at 750°C according to the proportions. The alloys are stirred with an electromagnetic stirrer for 30 minutes until the melt is evenly distributed. The alloys are then kept at this temperature and allowed to stand for 90 minutes before being cast into aluminum-magnesium-silicon alloy ingots.

[0047] S2: Powder preparation: The ingot obtained in S1 is remelted, and the melt is discharged through an alumina tube. High-speed compressed nitrogen is used to impact the molten aluminum-magnesium-silicon alloy to break it into fine droplets. The atomization pressure is 10 MPa, and the purity of the high-pressure nitrogen is ≥99.995%. The metal powder is cooled and solidified to form a metal powder. The powder is sieved by a cyclone separation powder collecting device under a high-purity argon atmosphere to obtain Al-7Mg-3Si-0.7Mn-0.2Ti-0.1Zr-0.03Sr (wt.%) powder for additive manufacturing. More than 90% of the obtained powder is spherical or pear-shaped, and more than 60% of the powder particle size is between 20-53μm.

[0048] S3: Laser forming: In an argon atmosphere, when the oxygen content in the forming chamber is lower than 200 ppm, the powder obtained in S2 is subjected to a selective laser melting forming process with a laser power of 380 W, a scanning speed of 1500 mm / s, a scanning pitch of 0.14 mm, a layer thickness of 50 μm, and a substrate preheating temperature of 120°C to obtain a printed alloy.

[0049] S4: Aging treatment: The printed alloy obtained in S3 is subjected to aging treatment at an aging temperature of 300°C for 1 hour.

[0050] The density ρ of the alloy was measured by the Archimedean method, and the density was calculated by comparing it with the theoretical density. The room temperature tensile properties of the alloy were measured according to GB / T228.1-2021. Through testing, the alloy of this embodiment has excellent forming performance, the sample density is 98.2%, the tensile strength of the printed sample is 443MPa, the yield strength is 349MPa, and the elongation is 11.4%; after aging treatment, the tensile strength of the sample is 481MPa, the yield strength is 373MPa, and the elongation is 7.6%. The grain structure of the formed alloy is as follows Figure 2 As shown, it can be seen that it has an extremely fine grain structure.

[0051] Example 2

[0052] Chemical composition and element content of aluminum-magnesium-silicon alloy: Al-5Mg-2Si-1.5Mn-0.4Ti-0.3Zr-0.01Sr (wt.%).

[0053] S1: Alloy smelting: Commercial pure aluminum, aluminum-magnesium master alloy, aluminum-silicon master alloy, aluminum-manganese master alloy, aluminum-titanium master alloy, aluminum-zirconium master alloy and aluminum-strontium master alloy are placed in a smelting furnace at 770°C according to the proportions. The alloys are stirred with an electromagnetic stirrer for 30 minutes until the melt is evenly distributed. The alloys are then kept at this temperature and allowed to stand for 120 minutes before being cast into aluminum-magnesium-silicon alloy ingots.

[0054] S2: Powder preparation: The ingot obtained in S1 is remelted, and the melt is discharged through an alumina tube. High-speed compressed nitrogen is used to impact the molten aluminum-magnesium-silicon alloy to break it into fine droplets. The atomization pressure is 15 MPa, and the purity of the high-pressure nitrogen is ≥99.995%. The metal powder is cooled and solidified to form a metal powder. The powder is sieved by a cyclone separation powder collection device under a high-purity argon atmosphere to obtain Al-5Mg-2Si-1.5Mn-0.4Ti-0.3Zr-0.01Sr (wt.%) powder for additive manufacturing. More than 90% of the obtained powder is spherical or pear-shaped, and more than 60% of the powder particle size is between 20-60μm.

[0055] S3: Laser forming: In an argon atmosphere, when the oxygen content in the forming chamber is lower than 200 ppm, the powder obtained in S2 is subjected to a selective laser melting forming process with a laser power of 350 W, a scanning speed of 1300 mm / s, a scanning pitch of 0.17 mm, a layer thickness of 40 μm, and a substrate preheating temperature of 150°C to obtain a printed alloy.

[0056] S4: Aging treatment: The printed alloy obtained in S3 is subjected to aging treatment at an aging temperature of 200°C for 10 hours.

[0057] Through testing, the alloy of this embodiment has excellent forming performance, the sample density is 97.1%, the printed sample has a tensile strength of 437MPa, a yield strength of 384MPa, and an elongation of 12.8%; after aging treatment, the sample has a tensile strength of 451MPa, a yield strength of 397MPa, and an elongation of 9.3%.

[0058] Example 3

[0059] Chemical composition and element content of aluminum-magnesium-silicon alloy: Al-9Mg-3Si-1.2Mn-0.2Ti-0.15Zr-0.01Sr (wt.%).

[0060] S1: Alloy smelting: Commercial pure aluminum, aluminum-magnesium master alloy, aluminum-silicon master alloy, aluminum-manganese master alloy, aluminum-titanium master alloy, aluminum-zirconium master alloy and aluminum-strontium master alloy are placed in a smelting furnace at 780°C according to the proportions. The alloys are stirred with an electromagnetic stirrer for 30 minutes until the melt is evenly distributed. The alloys are then kept at this temperature and allowed to stand for 100 minutes before being cast into aluminum-magnesium-silicon alloy ingots.

[0061] S2: Powder preparation: The ingot obtained in S1 is remelted, and the melt is discharged through an alumina tube. High-speed compressed nitrogen is used to impact the molten aluminum-magnesium-silicon alloy to break it into fine droplets. The atomization pressure is 12 MPa, and the purity of the high-pressure nitrogen is ≥99.995%. The metal powder is cooled and solidified to form a metal powder. The powder is sieved by a cyclone separation powder collecting device under a high-purity argon atmosphere to obtain Al-9Mg-3Si-1.2Mn-0.2Ti-0.15Zr-0.01Sr (wt.%) powder for additive manufacturing. More than 95% of the obtained powder is spherical or pear-shaped, and more than 60% of the powder particle size is between 20-50μm.

[0062] S3: Laser forming: In an argon atmosphere, when the oxygen content in the forming chamber is lower than 200 ppm, the powder obtained in S2 is subjected to a selective laser melting forming process with a laser power of 330 W, a scanning speed of 1200 mm / s, a scanning pitch of 0.15 mm, a layer thickness of 40 μm, and a substrate preheating temperature of 140°C to obtain a printed alloy.

[0063] S4: Aging treatment: The printed alloy obtained in S3 is subjected to aging treatment at an aging temperature of 175°C for 2 hours.

[0064] The test results show that the alloy of this embodiment has excellent forming performance, with a sample density of 99.1%. The printed sample has a tensile strength of 426MPa, a yield strength of 388MPa, and an elongation of 11.9%. After aging treatment, the sample has a tensile strength of 430MPa, a yield strength of 401MPa, and an elongation of 10.1%. The metallographic structure of the formed alloy is shown in Figure 2. Figure 1 shown.

[0065] Comparative Example 1

[0066] Chemical composition and element content of aluminum-magnesium-silicon alloy: Al-7Mg-3Si-0.7Mn (wt.%).

[0067] Other experimental conditions are the same as those in Example 1.

[0068] Through testing, the forming performance of the comparative alloy is general, the density of the sample is 96.5%, but there are some micro cracks in the matrix, such as Figure 3 As shown in the figure, the as-printed sample has a tensile strength of 347 MPa, a yield strength of 266 MPa, and an elongation of 7%. After aging treatment, the sample has a tensile strength of 352 MPa, a yield strength of 254 MPa, and an elongation of 8.6%.

[0069] Comparative Example 2

[0070] The alloy composition and production process of this comparative example are basically the same as those of Example 1, with only the aging treatment parameters being changed: aging temperature of 450° C. and time of 12 h.

[0071] Through testing, the comparative alloy has excellent forming performance, the sample density is 99.6%, the printed sample has a tensile strength of 439MPa, a yield strength of 385MPa, and an elongation of 11.1%; after aging treatment, the grains are severely coarsened, the tensile strength of the sample is 326MPa, the yield strength is 288MPa, and the elongation is 13.6%.

[0072] Comparative Example 3

[0073] The alloy composition and production process described in this comparative example are basically the same as those in Example 2, with only some additive manufacturing process parameters changed: the laser power is 450 W, and the scanning speed is 2500 mm / s.

[0074] Through testing, the density of the comparative alloy sample is 96.5%. Due to the high power and fast scanning speed, the alloy has multiple element burnout and unfused pores, such as Figure 4 As shown in the figure, the as-printed sample has a tensile strength of 356 MPa, a yield strength of 303 MPa, and an elongation of 8.1%. After aging treatment, the sample has a tensile strength of 382 MPa, a yield strength of 314 MPa, and an elongation of 7.8%.

[0075] Comparative Example 4

[0076] Chemical composition and element content of aluminum-magnesium-silicon alloy: Al-7Mg-3Si-0.7Mn-0.05Ti-0.05Zr-0.03Sr (wt.%).

[0077] Other experimental conditions are the same as those in Example 1.

[0078] Testing revealed that the density of the comparative alloy sample was 97.4%. The as-printed sample had a tensile strength of 409 MPa, a yield strength of 322 MPa, and an elongation of 12.4%. After aging treatment, the sample had a tensile strength of 440 MPa, a yield strength of 339 MPa, and an elongation of 9.1%.

[0079] Comparative Example 5

[0080] Chemical composition and element content of aluminum-magnesium-silicon alloy: Al-3Mg-7Si-0.7Mn-0.2Ti-0.1Zr-0.03Sr (wt.%).

[0081] Other experimental conditions are the same as those in Example 1.

[0082] Testing showed that the density of the comparative alloy sample was 98.5%. The as-printed sample had a tensile strength of 386 MPa, a yield strength of 294 MPa, and an elongation of 15.8%. After aging treatment, the sample had a tensile strength of 403 MPa, a yield strength of 310 MPa, and an elongation of 12.1%.

[0083] Comparative Example 6

[0084] Chemical composition and element content of aluminum-magnesium-silicon alloy: Al-7Mg-3Si-0.1Mn-0.2Ti-0.1Zr-0.03Sr (wt.%).

[0085] Other experimental conditions are the same as those in Example 1.

[0086] Testing revealed that the density of the comparative alloy sample was 97.7%. The as-printed sample had a tensile strength of 411 MPa, a yield strength of 374 MPa, and an elongation of 12.7%. After aging treatment, the sample had a tensile strength of 423 MPa, a yield strength of 392 MPa, and an elongation of 10.3%.

[0087] In summary, in Comparative Example 1 and Example 1, the Ti and Zr added in the present invention can form Al3Ti and Al3Zr with Al in a coherent lattice with the α-Al matrix, and can play a nucleation role as heterogeneous nucleation sites, and then the modification effect of Sr hinders grain growth and promotes grain refinement; in Comparative Example 4 and Example 1, in Comparative Example 4, Ti≤0.05% and Zr≤0.05%, the content is too low, and during the alloy casting process, Ti and Zr are basically dissolved into the matrix, making it difficult to form primary Al3Zr and Al3Ti as nucleation sites. The amount of Al3Zr and Al3Ti that can form precipitation strengthening after heat treatment is also very limited; in Comparative Example 5 and Example 1, the Si content in Comparative Example 5 is much higher than the Mg content, the main component of the alloy is a near-eutectic Al-Si alloy, and the alloy structure is mainly primary α-Al and eutectic Si structure, resulting in relatively low mechanical properties; in Comparative Example 6 and Example 1, the Mn in Comparative Example 6 is ≤0.1%, the solid-liquid phase temperature difference is not large, and the low content also makes most of it solid-dissolved in the matrix, making it difficult to form a precipitation phase, and it is impossible to form Al6Mn compounds, so it is impossible to refine the structure. Example 1 of the present invention utilizes the solid solution effect of Mg and Mn to replace the solid solution strengthening of a single Mg element. The composite effect of Mn can reduce the content of a single Mg element while ensuring better mechanical properties, thereby reducing the solid-liquid phase temperature difference and improving the alloy's resistance to thermal cracking. The relatively high Mn content also ensures that it can produce a precipitation phase to form a second phase strengthening after aging treatment.

[0088] In Comparative Example 2 and Example 1, the aging temperature of Comparative Example 2 is higher than 300°C, and the grains grow due to the high temperature, thereby reducing the mechanical properties; in Comparative Example 3 and Example 1, the laser power of Comparative Example 3 is higher than 420W, the line input energy density is too high, and a large amount of metal vapor escapes, which easily causes element burnout and microstructure coarsening, resulting in a significant decrease in the mechanical properties of the alloy.

[0089] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. An aluminum-magnesium-silicon alloy for additive manufacturing, characterized in that: The weight percentages of the components in the aluminum-magnesium-silicon alloy are as follows: Mg: 5-9wt.%, Si: 2-5wt.%, Mn: 0.5-1.5wt.%, Ti: 0.1-0.4wt.%, Zr: 0.1-0.4wt.%, Sr: 0.01-0.03wt.%, and the total amount of other impurities does not exceed 0.8wt.%, with the balance being Al; The weight ratio of Mg to Si in aluminum magnesium silicon alloy is 1.72-10:1; The method for preparing the aluminum-magnesium-silicon alloy for additive manufacturing comprises the following steps: S1. Alloy smelting: mixing aluminum, aluminum-magnesium master alloy, aluminum-silicon master alloy, aluminum-manganese master alloy, aluminum-titanium master alloy, aluminum-zirconium master alloy and aluminum-strontium master alloy according to a certain ratio, smelting and casting into aluminum-magnesium-silicon alloy ingots; S2. Powder preparation: remelting the ingot obtained in S1, atomizing it, cooling and solidifying it to form metal powder, and then sieving the powder to obtain aluminum-magnesium-silicon alloy powder for additive manufacturing; The atomization method comprises: using high-speed compressed nitrogen to impact molten aluminum-magnesium-silicon alloy, wherein the nitrogen purity is ≥99.995%; S3, laser forming: performing selective laser melting forming on the aluminum-magnesium-silicon alloy powder obtained in S2 to obtain a printed alloy; S4. Aging treatment: The printed alloy obtained in S3 is subjected to aging treatment to obtain an aluminum-magnesium-silicon alloy for additive manufacturing.

2. The aluminum-magnesium-silicon alloy for additive manufacturing according to claim 1, characterized in that: In step S2, the atomization pressure is 8-15 MPa.

3. The aluminum-magnesium-silicon alloy for additive manufacturing according to claim 1, characterized in that: In step S2, the screening method is cyclone separation to collect powder.

4. The aluminum-magnesium-silicon alloy for additive manufacturing according to claim 1, characterized in that: In step S3, the oxygen content in the molding chamber during the selective laser melting molding is lower than 200 ppm.

5. The aluminum-magnesium-silicon alloy for additive manufacturing according to claim 1, characterized in that: In step S3, the laser power used in the selective laser melting is 280-420 W and the scanning speed is 1000-2400 mm / s.

6. The aluminum-magnesium-silicon alloy for additive manufacturing according to claim 1, characterized in that: In step S3, the selective laser melting process uses a scanning pitch of 0.13-0.18 mm, a layer thickness of 40-60 μm, and a substrate temperature of 120-180°C.

7. The aluminum-magnesium-silicon alloy for additive manufacturing according to claim 1, characterized in that: In step S4, the aging treatment is performed at a temperature of 150-300° C. for 1-24 hours.

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