High-strength magnesium alloy composite structural member and method for manufacturing the same

Abstract

This invention discloses a high-strength magnesium alloy composite structural component and its preparation method. The component is composed of a wrought magnesium alloy insert and a semi-solid injected magnesium alloy matrix, forming a diffusion-metallurgical bonding interface between them. The preparation method includes: cleaning and micro-roughening pretreatment of the wrought magnesium alloy insert; preheating the insert to 250°C to 50°C below the solidus temperature under a non-oxidizing atmosphere; preparing a semi-solid slurry with a solid fraction of 30%~90% from the magnesium alloy raw material, and injecting it into the mold cavity of the pre-placed insert under a protective atmosphere; after pressure solidification, opening the mold, removing the component, and performing post-processing. This invention utilizes the mechanical crushing effect of the semi-solid slurry on the pre-oxidized layer on the insert surface to achieve a strong metallurgical bond, significantly reducing shrinkage cavities, residual stress, and deformation, while retaining the high strength and high toughness of the wrought magnesium alloy, making it suitable for lightweight thick-walled structural components.

Description

Technical Field

[0001] This invention relates to the field of metal material forming and composite manufacturing technology, specifically to a high-strength magnesium alloy composite structural component and its preparation method. Background Technology

[0002] Magnesium alloys, as the lightest metallic structural materials, have broad prospects for lightweight applications in aerospace, transportation, and 3C electronic products. Existing magnesium alloy forming processes are mainly divided into three categories: wrought ironing (extrusion, rolling, forging), semi-solid injection molding, and casting (represented by high-pressure die casting). Wrought magnesium alloys possess fine-grained structures, high strength, high ductility, and excellent fatigue properties, but their forming capacity is limited, making it difficult to directly manufacture parts with complex shapes. Semi-solid injection-molded magnesium alloys, on the other hand, have excellent fluidity, enabling high-speed, one-time molding of complex, thin-walled parts with precision features, resulting in high production efficiency. However, their mechanical properties (especially elongation and impact toughness) are lower than wrought alloys, and defects such as shrinkage cavities, porosity, and coarse grains are prone to occur in thick-walled sections, limiting their application in load-bearing structural components.

[0003] Therefore, developing a novel composite structural component and its preparation method that can fully combine the excellent mechanical properties of wrought magnesium alloys with the efficient and complex forming capabilities of semi-solid magnesium alloys, while avoiding the disadvantages of combining dissimilar materials, has significant industrial application value. Summary of the Invention

[0004] The purpose of this invention is to provide a high-strength magnesium alloy composite structural component and its preparation method, overcoming the shortcomings of existing technologies and providing a magnesium-magnesium composite molded structural component and its preparation method with excellent mechanical properties, complex structure, and high reliability. Specifically, it aims to solve the problems of low overall strength and severe shrinkage cavities in traditional die-cast magnesium alloys, and the difficulty in forming complex shapes with wrought magnesium alloys, by achieving a firm bond between high-performance wrought magnesium alloy inserts and semi-solid injection-cast magnesium alloy bodies, thus achieving complementary advantages in material properties and functional integration of the structure.

[0005] To achieve the above objectives, the present invention provides a method for preparing a high-strength magnesium alloy composite structural component, the method comprising: S1. Insert pretreatment: The deformed magnesium alloy is processed into an insert of the required shape, and the surface of the insert to be bonded is cleaned and slightly roughened; S2. Preheating and pre-oxidation: The pretreated insert is placed in a non-oxidizing atmosphere and heated to a preheating temperature T1, wherein the preheating temperature T1 satisfies: 250℃ ≤ T1 ≤ (Ts-50℃), where Ts is the solidus temperature of the deformed magnesium alloy; S3. Semi-solid slurry injection: The magnesium alloy raw material is prepared into a semi-solid slurry, and the semi-solid slurry is injected into the mold cavity pre-placed with a preheated insert under a protective atmosphere; S4. Composite solidification: The injected semi-solid slurry is pressured to coat the insert and fill the cavity, and then pressure is maintained and cooled, so that the slurry and the insert achieve metallurgical bonding through heat conduction, mechanical agitation and diffusion of solid particles; S5. Post-processing: The composite part is removed from the mold and then subjected to subsequent processing or heat treatment.

[0006] Preferably, in step S2, the non-oxidizing atmosphere is an inert gas or a weakly reducing gas, used to form a dense pre-oxidized layer on the insert surface with a thickness of less than 100 nm that can be mechanically broken by the semi-solid slurry.

[0007] Preferably, in step S3, the magnesium alloy raw material is prepared into a semi-solid slurry with a solid content of 30% to 90%. Preferably, in step S4, the holding pressure is 30 MPa to 200 MPa, and the holding time is 1 s to 30 s.

[0008] The present invention also provides a high-strength magnesium alloy composite structural component, which is prepared by the above-described preparation method.

[0009] Compared with the prior art, the present invention has the following outstanding advantages: First, the interface quality is revolutionaryly improved. The semi-solid slurry has a low temperature, resulting in minimal thermal shock to the inserts and virtually avoiding overmelting and grain coarsening on the insert surface. During the molding process, the solid particles in the slurry mechanically scrape and break up the oxide film on the insert surface, effectively removing the oxide layer and exposing fresh metal to promote bonding. Low-temperature molding also reduces the tendency for intermetallic compounds to form.

[0010] Secondly, molding defects are significantly reduced. The semi-solid slurry has high viscosity, fills smoothly, and flows in a laminar state, greatly reducing the risk of gas entrapment. Its paste-like solidification characteristics make solidification shrinkage easier to compensate for through the slurry's own flow, significantly reducing shrinkage defects at interfaces and thick walls. Experimental data show that the composite structural parts prepared using the method of this invention have a maximum shrinkage cavity size of only 2-3 mm, while the shrinkage cavity size of traditional die-cast parts reaches 10-15 mm.

[0011] Third, residual stress and deformation are minimal. The temperature difference between the insert and the slurry is small, the degree of thermal expansion mismatch is reduced, and the shrinkage stress of the paste solidification is small, resulting in significantly lower residual stress and deformation of the molded parts compared to liquid die-cast coated parts.

[0012] Fourth, the perfect inheritance and integration of high performance. This method retains to the maximum extent the original high-performance characteristics of the wrought magnesium alloy insert, such as fine-grain strengthening and work hardening. Simultaneously, through optimized interfacial diffusion, it achieves a strong and tough bond with the semi-solid matrix, truly realizing a synergistic effect of "1+1>2". Taking the composite of AZ80M wrought magnesium alloy insert and AZ91D semi-solid matrix as an example, the overall tensile strength reaches 300-330MPa, and the overall elongation reaches 8-10%, while the tensile strength of traditional die-cast AZ91D parts is only 220-250MPa, and the elongation is about 5%. Under a stress amplitude of 100MPa, the fatigue life of the composite structure of this invention is more than 1.5 times that of traditional die-cast parts. Furthermore, by arranging the insert in local high-stress areas, the local load-bearing capacity can be increased by more than 50%.

[0013] Fifth, the density remains unchanged while the weight reduction effect is significant. The density of the composite structural component of this invention is comparable to that of traditional magnesium alloys, approximately 1.81 g / cm³, but through the insert reinforcement design, the amount of material used can be further reduced while ensuring load-bearing capacity.

[0014] Other features and advantages of the present invention will be described in detail in the following detailed description section. Detailed Implementation

[0015] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0016] Example 1: Composite structural component for automotive steering knuckle This embodiment describes the preparation of a lightweight steering knuckle composite structure for new energy vehicles.

[0017] The base material is AZ91D semi-solid magnesium alloy, and the insert material is AZ80M wrought magnesium alloy bar, which is heat-treated with T5. In terms of structural design, the insert is machined into a reinforcing rib mesh structure and embedded in the high-stress area of ​​the steering knuckle.

[0018] The preparation process is as follows: First, AZ80M magnesium alloy rods are machined into a reinforcing mesh of the designed shape. The bonding surface is then micro-blasted to form a micro-mechanical anchoring structure with a roughness Ra=3.2μm. Next, the insert is heated to 350℃ under an argon protective atmosphere and held for 30 minutes to form a dense pre-oxidized layer approximately 50nm thick on the surface. Then, AZ91D magnesium alloy is heated to a liquidus temperature of 598℃ under a protective atmosphere, stirred, and cooled to 580℃ to obtain a semi-solid slurry with a solid content of 60%. The preheated insert is placed in a mold cavity, and the semi-solid slurry is injected at a pressure of 50MPa to encapsulate the insert, holding the pressure for 15 seconds. Finally, the mold is opened and the insert is removed.

[0019] Performance test results: The overall tensile strength of the composite steering knuckle structure obtained in this embodiment is 310-325 MPa, and the local load-bearing capacity is increased by 55% compared with traditional die-cast steering knuckles. Compared with steel steering knuckles, the weight reduction effect reaches 65%. The fatigue life under a stress amplitude of 100 MPa is 1.8 times that of traditional die-cast parts. Microstructural observation shows that at the bonding interface, the grain size transitions continuously from the deformed magnesium alloy insert to the semi-solid matrix, with no obvious oxide inclusion layer. The maximum shrinkage cavity size is only 2-3 mm, much smaller than the 10-15 mm of traditional die-cast parts.

[0020] This embodiment is particularly suitable for chassis components of new energy vehicles, achieving a perfect combination of lightweight and high strength, while avoiding the shrinkage defects of traditional die-cast thick-walled parts, and meeting the stringent requirements of the steering knuckle as a key safety component of the chassis for fatigue life and reliability.

[0021] Example 2: Composite structural component of UAV frame main beam This embodiment describes the fabrication of a composite structural component for the main beam of a high-end unmanned aerial vehicle (UAV).

[0022] The matrix material is AM60B semi-solid magnesium alloy, and the insert material is ZK60 wrought magnesium alloy thin-walled tube, which is extruded. In terms of structural design, the insert is a continuous hollow tubular structure arranged along the length of the main beam to enhance torsional stiffness.

[0023] The preparation process is as follows: First, ZK60 magnesium alloy is extruded into a hollow tube with a wall thickness of 1.5 mm, and the surface is laser-textured to form a micro-pit array with a depth of 50-100 μm. Then, it is heated to 300℃ in a weakly reducing atmosphere of nitrogen and 5% hydrogen by volume, and held at that temperature for 20 minutes to form a dense pre-oxidized layer with a thickness of about 30 nm. Next, AM60B magnesium alloy is heated to 615℃ and then cooled to 590℃ with stirring to obtain a semi-solid slurry with a solid content of 40%. The pre-treated insert is positioned in the center of the mold cavity, and the semi-solid slurry is injected at a pressure of 40 MPa to completely cover the insert. After natural cooling, the mold is opened and the part is removed, the mounting holes are machined, and the surface is subjected to micro-arc oxidation treatment.

[0024] Performance test results: The overall stiffness of the main beam of the frame manufactured in this embodiment is increased by 40% compared with the traditional cast frame, and the torsional strength reaches 350 N·m / degree. The weight per unit length is only 285 g / m, which is 35% lighter than the aluminum alloy solution. Vibration damping is increased by 30%, effectively reducing flight vibration. The elongation reaches 8-10%, which is better than the 5% of the traditional die-cast magnesium alloy.

[0025] This embodiment addresses the dual requirements of lightweight and high rigidity for UAV structural components, making it particularly suitable for the main load-bearing structures of long-endurance UAVs. The hollow tubular insert design not only provides excellent torsional resistance but also reduces material usage, further lowering weight. Good vibration damping characteristics contribute to improved flight stability and image acquisition quality.

[0026] Example 3: Composite structural component for laptop casing This embodiment describes the fabrication of a composite structure for the A-side shell of a high-end laptop computer.

[0027] The base material is AZ31B semi-solid magnesium alloy, and the insert material is WE43 wrought magnesium alloy sheet, which has undergone rolling processing. In terms of structural design, the inserts are local reinforcing plates, set in the shaft connection area and around the heat dissipation holes to achieve functional zoning optimization of the structure.

[0028] The preparation process is as follows: First, WE43 magnesium alloy is rolled into a 0.8mm thick sheet, stamped, and then the bonding surface is subjected to plasma etching to form a microgroove structure. Next, the insert is heated to 280℃ under an argon protective atmosphere and held for 15 minutes to form a dense pre-oxidized layer approximately 20nm thick. Then, AZ31B magnesium alloy is heated to 630℃ and then cooled to 600℃ with stirring to obtain a semi-solid slurry with a solid content of 70%. Using a multi-gate design, the semi-solid slurry is rapidly injected into the mold cavity containing the insert at a pressure of 30MPa, ensuring that the insert is completely covered and the surface is smooth. After pressure holding and solidification, the mold is opened, the part is removed, and precision polishing is performed. Subsequently, a PVD coating process is used to obtain a high-gloss surface effect.

[0029] Performance test results: The laptop casing produced in this embodiment shows a 50% increase in strength at the hinge connection area and a 25% improvement in heat dissipation performance compared to traditional magnesium alloy casings. The surface roughness reaches Ra≤0.1μm, resulting in excellent appearance quality. The 1.2-meter drop test pass rate reaches 100%. Residual stress is reduced by 60% compared to liquid die-cast parts, effectively preventing deformation and cracking during use.

[0030] This embodiment addresses the comprehensive requirements of 3C products for structural strength, heat dissipation performance, and aesthetic appeal, making it particularly suitable for high-end consumer electronics. By incorporating inserts with varying performance characteristics in different areas, the structure achieves functional zoning optimization: high strength in the hinge area ensures durability, high thermal conductivity around the heat dissipation holes enhances heat dissipation efficiency, and the overall surface maintains a high-gloss finish.

[0031] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0032] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0033] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a high-strength magnesium alloy composite structural component, characterized in that, The preparation method includes: S1. Insert pretreatment: The deformed magnesium alloy is processed into an insert of the required shape, and the surface of the insert to be bonded is cleaned and slightly roughened; S2. Preheating and pre-oxidation: The pretreated insert is placed in a non-oxidizing atmosphere and heated to a preheating temperature T1, wherein the preheating temperature T1 satisfies: 250℃ ≤ T1 ≤ (Ts-50℃), where Ts is the solidus temperature of the deformed magnesium alloy; S3. Semi-solid slurry injection: The magnesium alloy raw material is prepared into a semi-solid slurry, and the semi-solid slurry is injected into the mold cavity pre-placed with a preheated insert under a protective atmosphere; S4. Composite solidification: The injected semi-solid slurry is pressured to coat the insert and fill the cavity, and then pressure is maintained and cooled, so that the slurry and the insert achieve metallurgical bonding through heat conduction, mechanical agitation and diffusion of solid particles; S5. Post-processing: The composite part is removed from the mold and further processed.

2. The preparation method according to claim 1, characterized in that, In step S2, the non-oxidizing atmosphere is an inert gas or a weakly reducing gas, used to form a dense pre-oxidized layer on the insert surface with a thickness of less than 100 nm that can be mechanically broken by the semi-solid slurry.

3. The preparation method according to claim 1, characterized in that, In step S3, the magnesium alloy raw material is prepared into a semi-solid slurry with a solid content of 30% to 90%.

4. The preparation method according to claim 1, characterized in that, In step S4, the holding pressure is 30MPa~200MPa, and the holding time is 1s~30s.

5. A high-strength magnesium alloy composite structural component, characterized in that, The high-strength magnesium alloy composite structural component is prepared by the preparation method described in any one of claims 1-4.