A semi-solid injection formed high-toughness Mg-Al-Si-Sn series magnesium alloy formed piece, and a preparation method and application thereof

Abstract

This invention discloses a high-strength and high-toughness Mg-Al-Si-Sn magnesium alloy forming part by semi-solid injection molding, its preparation method, and its application, belonging to the field of metal material processing technology. The forming part uses a Mg-Al magnesium alloy as the matrix, with added Si and Sn; by total mass, the Si content is 0.1wt.%–1.2wt.%, and the Sn content is 0.2wt.%–5wt.%. Its microstructure includes dispersed Mg2Si and Mg2Sn phases. The preparation method includes: dehumidifying and drying the raw material; semi-solid injection molding at a barrel temperature of 555–625℃ and a nozzle temperature of 570–640℃; and aging heat treatment at 120–200℃ for 1–12 hours. This invention, through the synergistic design of composition and process, obtains fine and dispersed composite reinforcing phases, significantly improving the strength and plasticity of thin-walled magnesium alloy forming parts, and is suitable for automotive structural parts, consumer electronics housings, lightweight aerospace components, etc.

Description

Technical Field

[0001] This invention relates to the field of metal material processing technology, and in particular to a semi-solid injection molded high-strength and high-toughness Mg-Al-Si-Sn alloy forming part, its preparation method and application. Background Technology

[0002] Magnesium alloys, due to their low density, high specific strength, excellent damping performance, and good electromagnetic shielding properties, are considered important metallic materials for achieving lightweight structural materials and are widely used in the automotive, consumer electronics, and aerospace industries. Thixomolding (semi-solid injection molding) is a near-net-shape forming method that combines plastic injection molding technology with semi-solid metal processing technology. It involves heating and screw shearing to form a thixotropic solid-liquid two-phase slurry, which is then injected and solidified under a protective atmosphere. This process offers advantages such as fewer oxide inclusions, fewer porosity defects, lower forming temperature, and higher dimensional accuracy.

[0003] Currently, magnesium alloys used in industrial semi-solid injection molding are mainly traditional magnesium-aluminum die-casting alloys such as AZ91D and AM60B. However, these traditional magnesium alloys were originally developed for high-pressure die casting processes, and their alloy composition design and microstructure control were not specifically optimized for semi-solid injection molding. This results in limited potential for improving mechanical properties, difficulty in effectively controlling the morphology of the second phase, and insufficient microstructure stability. Therefore, developing a novel magnesium alloy material suitable for semi-solid injection molding to achieve microstructure refinement and improve the overall mechanical properties of the material is of great significance for promoting the development of magnesium alloy semi-solid injection molding technology. Existing modification routes (Mg-Al-Zn / US20140023547A1, Mg-Al-Ca / US20140238192A1, Mg-Al-RE / CA2366610C, multi-element alloying / WO2024129170A1) still have problems such as coarse strengthening phases, difficulty in morphology control, low dispersion, high cost, or limited room temperature performance improvement. Therefore, developing a new Mg-Al alloying scheme suitable for semi-solid injection molding is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a high-strength and high-toughness Mg-Al-Si-Sn alloy molded part formed by semi-solid injection molding, its preparation method and application. Through the synergy of composition and process, a certain amount of Si and Sn is introduced into the Mg-Al magnesium alloy matrix. Under the conditions of semi-solid injection molding and subsequent heat treatment, fine and dispersed Mg2Si and Mg2Sn reinforcing phase particles are finally formed in the alloy structure, thereby improving the high strength and toughness at room temperature.

[0005] To achieve the above objectives, the present invention provides a high-strength and high-toughness Mg-Al-Si-Sn alloy molded part formed by semi-solid injection molding, which uses Mg-Al magnesium alloy as the matrix and adds Si and Sn; Based on total mass, the Si content is 0.1wt.%-1.2wt.% and the Sn content is 0.2wt.%-5wt.%.

[0006] Preferably, the microstructure of the molded part includes dispersed Mg2Si phase and Mg2Sn phase; wherein the particle size distribution D90 of the Mg2Si phase is 0.5-5μm and the particle size distribution D90 of the Mg2Sn phase is 10-500nm.

[0007] This invention also provides a method for preparing a high-strength and high-toughness Mg-Al-Si-Sn alloy molded part by semi-solid injection molding, comprising the following steps: Step S1: Dehumidify and dry the raw materials; Step S2: Place the raw material in a semi-solid injection molding equipment. Under the protection of an inert atmosphere, a semi-solid slurry is formed by the shearing and propulsion of the screw and the thermal effect of the barrel. Then, injection molding is performed to obtain the molded part. The barrel is heated to 555-625℃, and the nozzle temperature during injection molding is 570-640℃. Step S3: Perform aging heat treatment on the formed part to obtain a thin-walled formed part of Mg-Al-Si-Sn high-strength and high-toughness magnesium alloy; wherein the aging heat treatment temperature is 120-200℃ and the holding time is 1-12h.

[0008] Preferably, in step S1, the drying temperature is 80-120℃ and the drying time is 1-5h.

[0009] Preferably, in step S1, the raw material is any one of the following forms: Form (a): Mg-Al-Si-Sn magnesium alloy particles, with Mg-Al magnesium alloy particles as the matrix, and Si and Sn pre-included in the matrix particles in an alloyed form; Form (b): A mixture of Mg-Al magnesium alloy particles with Si source materials and Sn source materials; Form (c): A mixture of form (a) and form (b).

[0010] Preferably, the Mg-Al magnesium alloy is an AZ-based magnesium alloy or an AM-based magnesium alloy.

[0011] Preferably, when the raw material is in form (a), before the Mg-Al magnesium alloy batching and casting, Si particles and Sn particles are directly added to the alloy liquid and stirred, and Mg-Al-Si-Sn magnesium alloy particles are cast. The particle size of Si particles is 0.1-1 mm, and the particle size of Sn particles is 0.1-5 mm.

[0012] Preferably, when the raw material is in form (b), the Si source material is one or more of metallic silicon powder, silicon-containing master alloy, Mg-Si master alloy, and Al-Si master alloy; the Sn source material is one or more of metallic tin powder, tin-containing master alloy, Mg-Sn master alloy, and Al-Sn master alloy; and both the Si source material and the Sn source material are introduced through one or more combinations of premixing, synchronous main feeding, and side feeding. The particle size of metallic silicon powder is 0.5-10μm, and the particle size of metallic tin powder is 0.5-100μm.

[0013] Preferably, in step S2, the material cylinder adopts a segmented temperature control method, including a preheating section and a heating section connected to the nozzle; wherein, the temperature of the preheating section is 450~480℃, the temperature of the heating section is 610~620℃, and the temperature of the nozzle is 600~615℃.

[0014] The present invention also provides the application of the above-mentioned molded parts in the manufacture of automotive structural parts, consumer electronics housings or aerospace lightweight components.

[0015] Therefore, the semi-solid injection molded high-strength and high-toughness Mg-Al-Si-Sn magnesium alloy molded part, its preparation method, and its application provided by the present invention have the following beneficial effects: (1) Significantly improve the strength level of materials This invention employs targeted alloying design on Mg-Al magnesium alloys to form finely dispersed Mg2Si and Mg2Sn reinforcing phase particles during semi-solid injection molding and subsequent heat treatment. The Mg2Si phase exhibits high hardness, high elastic modulus, and good thermal stability, while the Mg2Sn phase provides strong precipitation strengthening through aging. The synergistic effect of these two phases significantly improves the tensile strength and yield strength of thin-walled molded parts. The room temperature tensile strength of the thin-walled molded parts produced by this invention can reach 270-360 MPa, and the yield strength can reach 170-250 MPa, overcoming the limitation of limited strength improvement in existing Mg-Al magnesium alloys used for semi-solid injection molding.

[0016] (2) Formation of fine and uniform granular reinforcing phase, synergistic improvement of strength and plasticity This invention suppresses the formation of coarse-grained second phases of traditional Mg2Si and Mg2Sn by controlling the range of alloying element content and the semi-solid process parameter window, promoting the refinement and dispersion of the strengthening phase. The particle size D90 of the Mg2Si phase is controlled at 0.5-5 μm, and the particle size D90 of the Mg2Sn phase is controlled at 10-500 nm. Simultaneously, compared with the network-like β-Mg commonly found in existing technologies... 17 Al12 Regarding phase morphology, this invention can refine, disperse, and homogenize the β phase morphology in the alloy, while also reducing the grain size of the α-Mg matrix. This makes it less likely to form obvious local stress concentration areas during stress, thereby improving strength while maintaining good plasticity and achieving a synergistic improvement in high strength and high toughness.

[0017] (3) Good process compatibility This invention does not simply follow the traditional die-casting magnesium alloy composition system, but rather incorporates the process characteristics of heating, screw shearing, and rapid solidification during semi-solid injection molding. The addition of Sn effectively improves the fluidity of the semi-solid slurry, reduces filling resistance, and allows the slurry to smoothly fill thin-walled complex cavities, reducing casting defects such as porosity and cold shuts, and improving the density and dimensional accuracy of the molded parts.

[0018] (4) It helps to improve organizational stability Thanks to improved fluidity and control of the solidification path of alloy components, this invention facilitates obtaining a more stable microstructure evolution path during semi-solid forming, enabling the strengthening phase and matrix microstructure to maintain a better state of refinement and homogenization during shearing and solidification, thereby improving the consistency and stability of the material microstructure.

[0019] (5) Low cost, short process, suitable for industrial production This invention eliminates the need for expensive rare earth elements, utilizes widely available raw materials, and can employ a simple process by directly mixing commercially available Mg-Al alloy particles with Si / Sn powder. The combination of semi-solid injection molding and aging heat treatment achieves near-net-shape forming and performance control, significantly shortening the production process and reducing manufacturing costs. Therefore, it shows promising application prospects in lightweight structural components, electronic product housings, and other magnesium alloy products requiring high specific strength.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1 Microstructure (optical microscope) of the Mg-Al-Si-Sn magnesium alloy thin-walled formed part obtained in Example 1 of the present invention. Figure 2 Microstructure (optical microscope) of the Mg-Al-Si-Sn magnesium alloy thin-walled formed part obtained in Example 2 of the present invention. Figure 3 Microstructure (optical microscope) of the Mg-Al-Si-Sn magnesium alloy thin-walled formed part obtained in Example 3 of the present invention. Figure 4Comparison of room temperature mechanical properties of magnesium alloy thin-walled formed parts obtained in Examples 1-3 and Comparative Examples 1-2 of this invention. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims and are all within the protection scope of the present invention.

[0023] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0024] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0025] Unless otherwise specified, the reagents, instruments, and equipment used in this invention are all commonly used by those skilled in the art, and the testing standards all use national or international standards commonly used in the field, without further explanation.

[0026] Without departing from the spirit of this invention, those skilled in the art may make equivalent substitutions or combinations of optimizations for raw material type and grade, silicon / tin source introduction method, composition control range, barrel temperature field and solid fraction window, screw shearing and residence time, and injection molding parameters, all of which should fall within the protection scope of this invention.

[0027] Example 1 This embodiment provides a high-strength and high-toughness magnesium alloy thin-walled formed part with AZ91D alloy as the matrix and Si and Sn added, and its preparation method: (1) Raw materials and ingredients This embodiment uses form (a) of raw material, namely Mg-Al-Si-Sn series magnesium alloy particles.

[0028] The particles were produced by directly adding 0.5 mm Si and 1.0 mm Sn particles to the molten alloy before casting the Mg-Al magnesium alloy batch, stirring the mixture, casting it into ingots, and then mechanically cutting it to obtain irregular particles. Chemical composition analysis showed that the alloy particles consisted of approximately 9.1 wt.% Al, approximately 1.0 wt.% Si, approximately 1.0 wt.% Sn, with the balance being Mg and unavoidable impurities (with industrially unavoidable impurities present within permissible limits).

[0029] (2) Preparation method Step S1, Raw material pretreatment: Place the above Mg-Al-Si-Sn alloy chips in a vacuum drying oven and dry them at 100°C for 3 hours to remove surface-adsorbed moisture and volatiles, and prevent oxidation inclusions and pores from forming during subsequent forming processes.

[0030] Step S2, Semi-solid Injection Molding: The dried raw material is placed in the hopper of the semi-solid injection molding machine (Thixomolding machine) and molding is performed under the protection of an argon inert atmosphere. The barrel adopts a segmented temperature control method, with a preheating section and a heating section set along the screw conveying direction, and a heating section set at the front end of the barrel / nozzle. This ensures the stable formation of the semi-solid slurry while providing the necessary heat and shear conditions for the in-situ reaction / conversion process, and keeps the slurry in a semi-molten state suitable for thin-wall filling before injection. The preheating section temperature is 450℃, the heating section temperature is 615℃, the nozzle temperature is 610℃, and the screw speed is set to 150rpm. Through the shearing propulsion of the screw and the thermal effect of the barrel, the raw material forms a semi-solid slurry with thixotropic properties in the semi-solid temperature range. The residence time of the semi-solid slurry in the barrel is 1 minute. Subsequently, the semi-solid slurry is injected into the mold cavity at an injection speed of 80 mm / s, the mold temperature is controlled at 215℃, and after filling, it is held under pressure and solidified to obtain a thin-walled molded part.

[0031] Step S3, Aging Heat Treatment: Place the above-mentioned formed part into a heat treatment furnace and perform aging heat treatment under a protective atmosphere of nitrogen. The aging temperature is 150℃ and the holding time is 4 hours. After the holding time is completed, cool the part to room temperature with the furnace to obtain the final Mg-Al-Si-Sn system high strength and toughness magnesium alloy thin-walled formed part.

[0032] Samples of the obtained thin-walled formed parts were taken, and after grinding, polishing, and etching, their microstructure was observed using an optical microscope (OM). Figure 1 As shown in the figure, it can be clearly seen that two types of granular second phases of different sizes are dispersed in the matrix: the larger particles are Mg2Si phase and the smaller particles are Mg2Sn phase. Both reinforcing phases are evenly distributed without obvious agglomeration or segregation.

[0033] Tensile specimens were cut from thin-walled formed parts according to GB / T228.1-2021 standard and subjected to uniaxial tensile tests at room temperature (25℃) at a tensile rate of 1 mm / min. The test results are as follows: Figure 4 As shown, the tensile properties are: tensile strength 310MPa, yield strength 225MPa, elongation after fracture 6.4%, and elastic modulus 55GPa.

[0034] The thin-walled molded part obtained in this embodiment can be directly used as a laptop shell, which has a significant weight reduction effect, as well as excellent impact resistance and appearance quality.

[0035] Example 2 This embodiment provides a high-strength and high-toughness magnesium alloy thin-walled formed part with AM60B alloy as the matrix and Si and Sn added, and its preparation method: (1) Raw materials and ingredients This embodiment uses form (b) of raw materials. The matrix material is commercial AM60B magnesium alloy particles with a particle size of 2-4 mm. The Si source is metallic Si powder with an average particle size of 2 μm, and the Sn source is metallic Sn powder with an average particle size of 2 μm. According to the target composition, the Si content is 0.8 wt.% and the Sn content is 1.5 wt.%.

[0036] (2) Preparation method Step S1, Raw material pretreatment and mixing: AM60B particles, Si powder and Sn powder are dried at 110℃ for 2 hours, and then mixed in a V-type mixer for 2 hours under argon protection to obtain uniformly mixed raw materials.

[0037] Step S2, Semi-solid injection molding: Same as step S2 in Example 1, except for the process parameters: preheating section temperature 480℃, heating section temperature 620℃, nozzle temperature 615℃, screw speed 180rpm, barrel dwell time 1.5 minutes, mold temperature 225℃.

[0038] Step S3 is the same as step S3 in Example 1, except that the aging temperature is 180°C, the holding time is 4.5 hours, and the protective atmosphere is argon.

[0039] Samples of the obtained thin-walled formed parts were taken, and after grinding, polishing, and etching, their microstructure was observed using an optical microscope (OM). Figure 2 As shown, fine and dispersed Mg2Si phase (D90 approximately 2.8 μm) and Mg2Sn phase were formed, and the two phases were uniformly distributed.

[0040] Tensile specimens were cut from thin-walled formed parts according to GB / T228.1-2021 standard and subjected to uniaxial tensile tests at room temperature (25℃) at a tensile rate of 1 mm / min. The test results are as follows: Figure 4As shown, the tensile properties are: tensile strength 274 MPa, yield strength 180 MPa, elongation after fracture 8.1%, and elastic modulus 48 GPa.

[0041] The thin-walled formed part obtained in this embodiment is used as a structural component for an automotive dashboard bracket, meeting the requirements of lightweight and high toughness.

[0042] Example 3 This embodiment provides a high-strength and high-toughness magnesium alloy thin-walled formed part with AZ91D alloy as the matrix and Si and Sn added, and its preparation method: (1) Raw materials and ingredients This embodiment uses form (b) of raw materials. The matrix material is commercial AZ91D magnesium alloy particles with a particle size of 2-4 mm. The Si source is metallic Si powder with an average particle size of 2 μm, and the Sn source is metallic Sn powder with an average particle size of 2 μm. According to the target composition, the Si content is 0.8 wt.% and the Sn content is 1.2 wt.%.

[0043] (2) Preparation method Step S1, Raw material pretreatment and mixing: AZ91D particles, Si powder and Sn powder are dried at 90℃ for 4 hours, and then mixed for 2 hours under argon protection using a V-type mixer to obtain uniformly mixed raw materials.

[0044] Step S2, semi-solid injection molding: Same as step S2 in Example 1, except for the process parameters: preheating section temperature 470℃, heating section temperature 620℃, nozzle temperature 610℃, screw speed 160rpm, dwell time 1.5 minutes, mold temperature 235℃.

[0045] Step S3 is the same as step S3 in Example 1, except that the aging temperature is 150℃ and the heat preservation time is 3.5 hours.

[0046] Samples of the obtained thin-walled formed parts were taken, and after grinding, polishing, and etching, their microstructure was observed using an optical microscope (OM). Figure 3 As shown, fine and dispersed Mg2Si phase (D90 approximately 3.3 μm) and Mg2Sn phase were formed, and the two phases were uniformly distributed.

[0047] According to GB / T228.1-2021 standard, tensile specimens were cut from thin-walled formed parts and subjected to uniaxial tensile tests at room temperature (25℃) with a tensile rate of 1 mm / min.

[0048] Test results are as follows Figure 4 As shown, the tensile properties are: tensile strength 308 MPa, yield strength 220 MPa, elongation after fracture 6.7%, and elastic modulus 54 GPa.

[0049] The thin-walled molded part obtained in this embodiment is used in the preparation of a laptop casing, which meets the requirements of lightweight and high toughness.

[0050] Comparative Example 1 This comparative example uses the same preparation method as Example 3, taking the AZ91D alloy without added Si and Sn as an example for comparison: (1) Raw materials and ingredients This comparative example uses commercially available AZ91D magnesium alloy particles with a particle size of 2-4 mm.

[0051] (2) Preparation method Step S1, Raw material pretreatment and mixing: Dry AZ91D particles at 90°C for 4 hours, and mix them for 2 hours under argon protection using a V-type mixer to obtain uniformly mixed raw materials.

[0052] Step S2, semi-solid injection molding: Same as step S2 in Example 1, except for the process parameters: preheating section temperature 470℃, heating section temperature 620℃, nozzle temperature 610℃, screw speed 160rpm, dwell time 1.5 minutes, mold temperature 235℃.

[0053] Step S3 is the same as step S3 in Example 1, except that the aging temperature is 150℃ and the heat preservation time is 3.5 hours.

[0054] According to GB / T228.1-2021 standard, tensile specimens were cut from thin-walled formed parts and subjected to uniaxial tensile tests at room temperature (25℃) with a tensile rate of 1 mm / min.

[0055] Test results are as follows Figure 4 As shown, the tensile properties are: tensile strength 245MPa, yield strength 160MPa, elongation after fracture 5.8%, and elastic modulus 44GPa.

[0056] Comparative Example 2 This comparative example uses the same preparation method as Example 2, taking AM60B alloy without added Si and Sn as an example for comparison: (1) Raw materials and ingredients This embodiment uses commercially available AM60B magnesium alloy particles with a particle size of 2-4 mm.

[0057] (2) Preparation method Step S1, Raw material pretreatment and mixing: Dry AM60B particles at 110℃ for 2 hours, and mix them for 2 hours under argon protection using a V-type mixer to obtain uniformly mixed raw materials.

[0058] Step S2, Semi-solid injection molding: Same as step S2 in Example 1, except for the process parameters: preheating section temperature 480℃, heating section temperature 620℃, nozzle temperature 615℃, screw speed 180rpm, barrel dwell time 1.5 minutes, mold temperature 225℃.

[0059] Step S3 is the same as step S3 in Example 1, except that the aging temperature is 180°C, the holding time is 4.5 hours, and the protective atmosphere is argon.

[0060] Tensile specimens were cut from thin-walled formed parts according to GB / T228.1-2021 standard and subjected to uniaxial tensile tests at room temperature (25℃) at a tensile rate of 1 mm / min. The test results are as follows: Figure 4 As shown, the tensile properties are: tensile strength 230MPa, yield strength 140MPa, elongation after fracture 10.8%, and elastic modulus 42GPa.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A high-strength and high-toughness Mg-Al-Si-Sn alloy molded part by semi-solid injection molding, characterized in that: Using Mg-Al magnesium alloy as the base, Si and Sn are added. Based on the total mass, the content of Si is 0.1wt.%-1.2wt.% and the content of Sn is 0.2wt.%-5wt.%.

2. The semi-solid injection molded high-strength and high-toughness Mg-Al-Si-Sn alloy molded part according to claim 1, characterized in that: The microstructure of the molded part includes dispersed Mg2Si and Mg2Sn phases; wherein the particle size distribution D90 of the Mg2Si phase is 0.5-5μm, and the particle size distribution D90 of the Mg2Sn phase is 10-500nm.

3. The method for preparing a high-strength and high-toughness Mg-Al-Si-Sn alloy molded part by semi-solid injection molding as described in any one of claims 1-2, characterized in that, Includes the following steps: Step S1: Dehumidify and dry the raw materials; Step S2: Place the raw material in a semi-solid injection molding equipment. Under the protection of an inert atmosphere, a semi-solid slurry is formed by the shearing and propulsion of the screw and the thermal effect of the barrel. Then, injection molding is performed to obtain the molded part. The barrel is heated to 555-625℃, and the nozzle temperature during injection molding is 570-640℃. Step S3: Perform aging heat treatment on the formed part to obtain a thin-walled formed part of Mg-Al-Si-Sn high-strength and high-toughness magnesium alloy; wherein the aging heat treatment temperature is 120-200℃ and the holding time is 1-12h.

4. The method for preparing a high-strength and high-toughness Mg-Al-Si-Sn alloy molded part by semi-solid injection molding according to claim 3, characterized in that, In step S1, the drying temperature is 80-120℃ and the drying time is 1-5h.

5. The method for preparing a high-strength and high-toughness Mg-Al-Si-Sn alloy molded part by semi-solid injection molding according to claim 3, characterized in that, In step S1, the raw material is any one of the following forms: Form (a): Mg-Al-Si-Sn magnesium alloy particles, with Mg-Al magnesium alloy particles as the matrix, and Si and Sn pre-included in the matrix particles in an alloyed form; Form (b): A mixture of Mg-Al magnesium alloy particles with Si source materials and Sn source materials; Form (c): A mixture of form (a) and form (b).

6. The method for preparing a high-strength and high-toughness Mg-Al-Si-Sn alloy molded part by semi-solid injection molding according to claim 5, characterized in that, Mg-Al series magnesium alloys are either AZ series magnesium alloys or AM series magnesium alloys.

7. The method for preparing a high-strength and high-toughness Mg-Al-Si-Sn alloy molded part by semi-solid injection molding according to claim 5, characterized in that, When the raw material is in form (a), before the Mg-Al magnesium alloy batching and casting, Si particles and Sn particles are directly added to the alloy liquid and stirred, and Mg-Al-Si-Sn magnesium alloy particles are obtained by casting. The particle size of Si particles is 0.1-1 mm, and the particle size of Sn particles is 0.1-5 mm.

8. The method for preparing a high-strength and high-toughness Mg-Al-Si-Sn alloy molded part by semi-solid injection molding according to claim 5, characterized in that, When the raw material is in form (b), the Si source material is one or more of the following: metallic silicon powder, silicon-containing master alloy, Mg-Si master alloy, and Al-Si master alloy; the Sn source material is one or more of the following: metallic tin powder, tin-containing master alloy, Mg-Sn master alloy, and Al-Sn master alloy; and both the Si source material and the Sn source material are introduced through one or more combinations of premixing, synchronous main feeding, and side feeding. The particle size of metallic silicon powder is 0.5-10μm, and the particle size of metallic tin powder is 0.5-100μm.

9. The method for preparing a high-strength and high-toughness Mg-Al-Si-Sn alloy molded part by semi-solid injection molding according to claim 5, characterized in that, In step S2, the material cylinder adopts a segmented temperature control method, including a preheating section and a heating section connected to the nozzle; wherein, the temperature of the preheating section is 450~480℃, the temperature of the heating section is 610~620℃, and the temperature of the nozzle is 600~615℃.

10. The application of a semi-solid injection molded high-strength and high-toughness Mg-Al-Si-Sn alloy molded part as described in any one of claims 1-2 in the preparation of automotive structural parts, consumer electronics housings or aerospace lightweight components.

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