Impact-resistant low-anisotropy wrought magnesium alloy material for vehicle body structure and preparation method thereof

Abstract

The invention provides an impact-resistant low-anisotropy wrought magnesium alloy material for a vehicle body structure and a preparation method thereof, and relates to the technical field of metal materials, the impact-resistant low-anisotropy wrought magnesium alloy material comprises, by mass, 4.5%-7.5% of Zn, 0.3%-0.8% of Mn, 0.2%-1% of Sn, 0.3%-1.0% of RE and the balance Mg, and RE is at least one of Ce and La. Through an optimally designed Zn-Mn-Sn-RE multi-element alloy system, the magnesium alloy material prepared by the method has high strength and high plasticity, the yield strength can reach 220 MPa or above, the tensile strength can reach 260 MPa or above, the ductility can reach 15% or above, and the harsh requirements of vehicle body structural parts for material performance are met.

Description

Technical Field

[0001] This invention relates to the field of metallic materials technology, and in particular to a deformable magnesium alloy material with low anisotropy and impact resistance for vehicle body structures and its preparation method. Background Technology

[0002] With the global automotive industry's increasing demands for lightweighting, energy conservation, emission reduction, and safety, the development and application of lightweight, high-strength metallic materials has become a key trend in the industry. Magnesium alloys, as the lightest engineering metal structural material, possess advantages such as low density, high specific strength, high specific stiffness, good shock absorption, and ease of recycling. They have enormous application potential in the automotive field, especially in body structural components, crash beams, and seat frames, where they can significantly reduce overall vehicle weight, thereby improving fuel economy or the driving range of electric vehicles.

[0003] Traditional commercial magnesium alloys (such as the AZ and ZK series) still have some inherent drawbacks when applied to automotive structural components subjected to complex stress states. First, most magnesium alloys lack sufficient room-temperature plasticity and impact toughness, especially at high strength, making them prone to brittle fracture and limiting their application in crash safety components. Second, magnesium alloys have a close-packed hexagonal crystal structure, which leads to strong texture during deformation, resulting in significant anisotropy in mechanical properties, particularly a marked difference between tensile and compressive yield strength. This anisotropy makes the mechanical response of components during service unpredictable, posing a significant challenge to structural design and potentially reducing the actual load-bearing capacity and safety of components. To address these issues, researchers have explored alloying and process optimization. For example, adding rare earth elements can weaken texture and improve plasticity, but this is costly and may adversely affect strength; hot working processes such as extrusion and rolling can refine grains and improve strength, but often exacerbate the anisotropy problem. Therefore, there is an urgent need in this field for a new type of magnesium alloy material and its corresponding preparation method, which can simultaneously possess high impact toughness, high strength, excellent plasticity and low mechanical property anisotropy, in order to meet the stringent requirements of modern automotive body structural components for lightweight, high safety and performance reliability. Summary of the Invention

[0004] The purpose of this invention is to provide a deformable magnesium alloy material with low impact resistance and low anisotropy for vehicle body structure and its preparation method, so as to solve the technical problems of insufficient impact toughness, difficulty in balancing strength and plasticity, and significant anisotropy of mechanical properties when existing magnesium alloys are applied to vehicle body structural parts.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A deformable magnesium alloy material with low anisotropy and impact resistance for vehicle body structure is composed of the following components by mass percentage: Zn 4.5%–7.5%, Mn 0.3%–0.8%, Sn 0.2%–1%, RE 0.3%–1.0%, with the balance being Mg, wherein RE is at least one of Ce and La.

[0006] Preferably, the magnesium alloy material has a room temperature impact toughness of not less than 30 J / cm², a yield strength of not less than 220 MPa, a tensile strength of not less than 260 MPa, an elongation of not less than 15%, and the ratio of its tensile yield strength to its compressive yield strength is in the range of 0.8 to 1.2.

[0007] A method for preparing impact-resistant, low-anisotropy wrought magnesium alloy material for vehicle body structures includes the following steps: S1. Batching: Mg ingots, Zn ingots, Mg-Sn master alloy, Mg-RE master alloy, Mg-Mn master alloy, and Mg-Zn-Mn primary waste are quantitatively prepared according to mass percentage. The above materials are preheated and dried. S2. Melting: The preheated Mg ingot and alloying elements are placed in a crucible for melting, and smelting and refining are carried out under a protective atmosphere. S3. Casting: Casting the refined alloy molten metal into alloy ingots; S4. Homogenization treatment: The alloy billet is subjected to solution treatment or homogenization heat treatment. S5. Surface treatment: Peeling off the outer skin of the homogenized alloy billet; S6. Hot extrusion: Hot extrusion of the peeled alloy billet to form deformed magnesium alloy components; S7. Aging treatment: Aging heat treatment is performed on deformed magnesium alloy components.

[0008] Preferably, the ingredients in step S1 also include Mg-Zn-Mn primary waste material with a weight ratio of no more than 50%.

[0009] Preferably, the preheating conditions in step S1 are to keep warm at 120℃~200℃ for 3h~6h.

[0010] Preferably, the melting and refining in step S2 are carried out at 720°C, with a 2% SF6+CO2 mixed gas introduced as a protective atmosphere. During refining, argon gas is introduced for blowing and stirring for 3 to 5 minutes, followed by standing at 670°C for 40 minutes.

[0011] Preferably, the alloying elements are added in the following order in step S2: Al, Zn, Mn, Sn, and RE.

[0012] Preferably, the homogenization process in step S4 is carried out at a temperature of 400℃~450℃ for 8h~24h.

[0013] Preferably, the temperature of hot extrusion in step S6 is 300℃~380℃, the forward speed of the extrusion rod is 0.2 mm / s~1.0 mm / s, and the extrusion ratio is not less than 10.

[0014] Preferably, the aging treatment in step S7 is carried out at a temperature of 120°C to 200°C for 30 min to 120 min.

[0015] The beneficial effects of this invention are: 1. Through the optimized design of the Zn-Mn-Sn-RE multi-element alloy system, the magnesium alloy material prepared by this invention has both high strength and high plasticity. Its yield strength can reach more than 220 MPa, its tensile strength can reach more than 260 MPa, and its elongation can reach more than 15%, which meets the stringent requirements of the vehicle body structural components for material performance.

[0016] 2. The impact toughness of the alloy material of this invention is not less than 30 J / cm², which is much higher than that of traditional magnesium alloys, enabling it to absorb more energy when a vehicle collides, thereby improving the passive safety of the vehicle body structure.

[0017] 3. By synergistically controlling the alloy composition and preparation process, this invention effectively weakens the texture of the material, making its tensile and compressive yield strength ratio between 0.8 and 1.2, exhibiting excellent low anisotropy or near isotropic characteristics, and improving the service stability and predictability of the component under complex stress conditions.

[0018] 4. The preparation method of the present invention has a clear process route, controllable parameters, good repeatability, and allows up to 50% of the same grade of primary waste material to be recycled, which significantly reduces production costs. Detailed Implementation

[0019] To facilitate understanding of the present invention, a more complete description will be provided below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0021] Example 1 This embodiment proposes a deformable magnesium alloy material with low impact resistance and low anisotropy for vehicle body structure. The components and their mass percentage content in this material are Zn 4.5%, Mn 0.3%, Sn 0.2%, Ce 0.3%, and the balance is Mg.

[0022] The preparation steps for this material are as follows: S1. Using Mg ingots, Zn ingots, Mg-Sn master alloys, Mg-RE master alloys, Mg-Mn master alloys, and Mg-Zn-Mn primary waste as raw materials, calculate the batching according to the mass percentage, and dry the raw materials at 120℃ for 6 hours. S2. The dried raw materials are put into the melting furnace, melted and refined under a protective atmosphere, and alloy billets are prepared by a semi-continuous casting process. S3. Perform solution treatment on the ingot at a temperature of 400℃ for 8 hours. S4. The solution-treated and peeled billet is hot-extruded. The extrusion temperature is set at 300℃, the extrusion bar forward speed is 1.0 mm / s, and the extrusion ratio is 10. S5. The final measured tensile strength of the material is 280 MPa, yield strength is 220 MPa, elongation is 15%, and V-notch impact energy is 31 J / cm².

[0023] Example 2 This embodiment proposes a deformable magnesium alloy material with low impact resistance and low anisotropy for vehicle body structure. The components and their mass percentage content in this material are Zn 7.5%, Mn 0.8%, Sn 1.0%, Ce 1.0%, and the balance is Mg.

[0024] The preparation steps for this material are as follows: S1. Using Mg ingots, Zn ingots, Mg-Sn master alloys, Mg-RE master alloys, Mg-Mn master alloys, and Mg-Zn-Mn primary waste as raw materials, calculate the batching according to the mass percentage, and dry the raw materials at 200℃ for 3 hours. S2. The dried raw materials are put into the melting furnace, melted and refined under a protective atmosphere, and alloy billets are prepared by a semi-continuous casting process. S3. Perform solution treatment on the ingot at a temperature of 450℃ for 20 hours. S4. The solution-treated and peeled billet is hot-extruded. The extrusion temperature is set at 380℃, the extrusion bar forward speed is 0.2 mm / s, and the extrusion ratio is 20. S5. The final measured tensile strength of the material is 360 MPa, yield strength is 260 MPa, elongation is 25%, and V-notch impact energy is 36 J / cm².

[0025] Example 3 This embodiment proposes a deformable magnesium alloy material with low impact resistance and low anisotropy for vehicle body structure. The components and their mass percentage content in the material are: Zn 5.0%, Mn 0.5%, Sn 0.3%, rare earth elements Ce 0.3% and La 0.5%, and the balance is Mg.

[0026] The preparation steps for this material are as follows: S1. Using Mg ingots, Zn ingots, Mg-Sn master alloys, Mg-RE master alloys, Mg-Mn master alloys, and Mg-Zn-Mn primary waste as raw materials, calculate the proportion of raw materials according to mass percentage, and dry the raw materials at 150℃ for 5 hours. S2. The dried raw materials are put into the melting furnace, melted and refined under a protective atmosphere, and alloy billets are prepared by a semi-continuous casting process. S3. Perform solution treatment on the ingot at a temperature of 420℃ for 10 hours. S4. The solution-treated and peeled billet is hot-extruded. The extrusion temperature is set at 350℃, the extrusion bar forward speed is 0.4 mm / s, and the extrusion ratio is 10. S5. The final measured tensile strength of the material is 300 MPa, yield strength is 230 MPa, elongation is 16%, and V-notch impact energy is 32 J / cm².

[0027] Example 4 This embodiment proposes a deformable magnesium alloy material with low impact resistance and low anisotropy for vehicle body structure. The components and their mass percentage content in this material are Zn 6.0%, Mn 0.4%, Sn 0.5%, Ce 0.5%, and the balance is Mg.

[0028] The preparation steps for this material are as follows: S1. Using Mg ingots, Zn ingots, Mg-Sn master alloys, Mg-RE master alloys, Mg-Mn master alloys, and Mg-Zn-Mn primary waste as raw materials, calculate the batching according to the mass percentage, and dry the raw materials at 180℃ for 4 hours. S2. The dried raw materials are put into the melting furnace, melted and refined under a protective atmosphere, and alloy billets are prepared by gravity casting process using metal molds. S3. The ingot is subjected to solution treatment at a temperature of 430℃ for 16 hours. S4. The solution-treated and peeled billet is hot-extruded. The extrusion temperature is set at 340℃, the extrusion bar forward speed is 0.8 mm / s, and the extrusion ratio is 16. S5. The final measured tensile strength of the material is 320 MPa, yield strength is 245 MPa, elongation is 22%, and V-notch impact energy is 31 J / cm².

[0029] Example 5 This embodiment proposes a deformable magnesium alloy material with low impact resistance and low anisotropy for vehicle body structure. The components and their mass percentage content in this material are Zn 6.5%, Mn 0.3%, Sn 0.5%, rare earth elements Ce 0.3% and La 0.7%, and the balance is Mg.

[0030] The preparation steps for this material are as follows: S1. Using Mg ingots, Zn ingots, Mg-Sn master alloys, Mg-RE master alloys, Mg-Mn master alloys, and Mg-Zn-Mn primary waste as raw materials, calculate the batching according to the mass percentage, and dry the raw materials at 160℃ for 4 hours. S2. The dried raw materials are put into the melting furnace, melted and refined under a protective atmosphere, and alloy billets are prepared by gravity casting process using metal molds. S3. The ingot is subjected to solution treatment at a temperature of 450℃ for 16 hours. S4. The solution-treated and peeled billet is hot-extruded. The extrusion temperature is set at 360℃, the extrusion bar forward speed is 0.4 mm / s, and the extrusion ratio is 20. S5. The final measured tensile strength of the material is 330 MPa, yield strength is 240 MPa, elongation is 18%, and V-notch impact energy is 35 J / cm².

[0031] Comparative Example 1 This comparative example provides a magnesium alloy material, formulated according to the commonly used AZ31B alloy, with a chemical composition (wt.%) of Al 3.0%, Zn 1.0%, Mn 0.4%, and the balance being Mg.

[0032] The preparation steps for this material are as follows: S1. Dry the raw materials at 150℃ for 4 hours; S2. Alloy billets are prepared using a semi-continuous casting process; S3. Treat the ingot at 420℃ for 16 hours. S4. Hot extrusion of the peeled billet, with the extrusion temperature set at 380℃, the extrusion bar forward speed at 1.0 mm / s, and the extrusion ratio at 20. S5. The final measured tensile strength of the material is 240 MPa, the yield strength is 160 MPa, the elongation is 10%, and the V-notch impact energy is only 6 J / cm².

[0033] Comparative Example 2 This comparative example provides a magnesium alloy material, formulated according to the commonly used AZ31B alloy, with a chemical composition (wt.%) of *Zn 6.0%, Zr 0.4%, and the balance being Mg.

[0034] The preparation steps for this material are as follows: S1. Dry the raw materials at 150℃ for 4 hours; S2. Alloy billets are prepared using a semi-continuous casting process; S3. Treat the ingot at 420℃ for 16 hours. S4. Hot extrusion is performed on the stripped billet. The extrusion temperature is set to 350℃, the extrusion bar forward speed is 0.6 mm / s, and the extrusion ratio is 20. S5. The final measured tensile strength of the material is 320 MPa, the yield strength is 240 MPa, the elongation is 15%, and the V-notch impact energy is only 12 J / cm².

[0035] The magnesium-based material formulations and contents in Examples 1-5 and the comparative examples are shown in Table 1. The specific process parameters are shown in Table 2. The various properties of the final products are shown in Table 3.

[0036] Among them, the room temperature tensile and compression tests were conducted in accordance with the standard GB / T 228.1-2010, and the room temperature Charpy pendulum impact test was conducted in accordance with the standard GB / T 229-2020.

[0037] Table 1: Formulation Content Table Table 2: Process Parameter Table Table 3: Product Performance Table A comparative analysis of the data from five examples and two comparative examples yielded the following conclusions: The core advantage of the magnesium alloy materials prepared in Examples 1-5 lies in their excellent impact resistance. All materials prepared in these examples achieved a V-notch impact energy of over 31 J / cm², with the highest reaching 36 J / cm². In contrast, conventional commercial magnesium alloys, such as Comparative Example 1 (AZ31B alloy), had an impact energy of only 6 J / cm², and Comparative Example 2 (ZK60A alloy) only 12 J / cm². This demonstrates that the combination of the alloy formulation and preparation process of this invention improves the impact toughness of the material by 2.5 to 6 times compared to traditional alloys, successfully overcoming the key technical bottleneck of poor impact toughness in traditional wrought magnesium alloys.

[0038] The magnesium alloy materials prepared in Examples 1-5 significantly improved impact toughness while maintaining high strength and good ductility. In terms of strength, the tensile strength of Examples 1-5 ranged from 28 MPa to 360 MPa, and the yield strength ranged from 220 to 260 MPa, reaching the level of high-strength magnesium alloys, comparable to the ZK60A alloy in Comparative Example 2, and significantly superior to the AZ31B alloy in Comparative Example 1. Regarding ductility, the elongation of the magnesium alloy materials prepared in Examples 1-5 all reached 15% or more, with a maximum of 22%, meeting the basic requirements for plasticity in deformation processing and structural applications, and also superior to Comparative Example 1 and Comparative Example 2.

[0039] Comparing the chemical compositions of Examples 1-5 with Comparative Examples 1 and 2, it can be found that Examples 1-5 adopted a Mg-Zn-Mn-Sn-RE (Ce / La) alloy system. By adding appropriate amounts of Sn and RE (Ce, La) and eliminating Al or Zr elements in traditional alloys, the microstructure and second-phase morphology of the alloy were effectively controlled, thereby greatly improving the toughness and plasticity of the material while ensuring strength.

[0040] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0041] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A wrought magnesium alloy material with low impact resistance and low anisotropy for use in vehicle body structures, characterized in that, It is composed of the following components in mass percentage: Zn 4.5%–7.5%, Mn 0.3%–0.8%, Sn 0.2%–1%, RE 0.3%–1.0%, with the balance being Mg, wherein RE is at least one of Ce and La.

2. The magnesium alloy material according to claim 1, characterized in that, The magnesium alloy material has a room temperature impact toughness of not less than 30 J / cm², a yield strength of not less than 220 MPa, a tensile strength of not less than 260 MPa, an elongation of not less than 15%, and the ratio of its tensile yield strength to its compressive yield strength is in the range of 0.8 to 1.

2.

3. A method for preparing a deformable magnesium alloy material with low impact resistance and low anisotropy for vehicle body structures as described in claim 1 or 2, characterized in that, Includes the following steps: S1. Batching: Mg ingots, Zn ingots, Mg-Sn master alloy, Mg-RE master alloy, Mg-Mn master alloy, and Mg-Zn-Mn primary waste are quantitatively prepared according to mass percentage. The above materials are preheated and dried. S2. Melting: The preheated Mg ingot and alloying elements are placed in a crucible for melting, and smelting and refining are carried out under a protective atmosphere. S3. Casting: Casting the refined alloy molten metal into alloy ingots; S4. Homogenization treatment: The alloy billet is subjected to solution treatment or homogenization heat treatment. S5. Surface treatment: Peeling off the outer skin of the homogenized alloy billet; S6. Hot extrusion: Hot extrusion of the peeled alloy billet to form deformed magnesium alloy components; S7. Aging treatment: Aging heat treatment is performed on deformed magnesium alloy components.

4. The method according to claim 3, characterized in that, The ingredients in step S1 also include Mg-Zn-Mn primary waste, which accounts for no more than 50% by weight.

5. The method according to claim 3 or 4, characterized in that, The preheating conditions in step S1 are to keep the temperature at 120℃~200℃ for 3h~6h.

6. The method according to claim 3, characterized in that, The melting and refining in step S2 are carried out at 720°C, and a 2% SF6+CO2 mixed gas is introduced as a protective atmosphere. During refining, argon gas is introduced for blowing and stirring for 3 to 5 minutes, and then the mixture is kept at 670°C for 40 minutes.

7. The method according to claim 3, characterized in that, The order in which the alloying elements are added in step S2 is Al, Zn, Mn, Sn, and RE.

8. The method according to claim 3, characterized in that, The homogenization process in step S4 is carried out at a temperature of 400℃~450℃ for 8h~24h.

9. The method according to claim 3, characterized in that, In step S6, the temperature of hot extrusion is 300℃~380℃, the forward speed of the extrusion rod is 0.2 mm / s~1.0 mm / s, and the extrusion ratio is not less than 10.

10. The method according to claim 3, characterized in that, The aging process in step S7 is carried out at a temperature of 120℃ to 200℃ for 30 min to 120 min.

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