Aluminum alloy for automobile structural member and preparation method thereof

Abstract

The invention provides an aluminum alloy for an automobile structural member and a preparation method of the aluminum alloy. The aluminum alloy for the automobile structural member comprises the following components in percentage by weight: 4.5%-5.5% of Zn, 0.7%-1.4% of Mg, 0.05%-0.25% of Zr, 0-0.05% of Ti, 0-0.3% of Fe, 0-0.3% of Si and the balance of Al. By adjusting the contents of Zn and Mg elements, the strength and good high-temperature extrusion performance of the material under different cooling conditions are ensured; by controlling the contents of Fe and Si elements, the formation of a coarse phase is effectively inhibited, and the cyclic utilization of the material is allowed; through the addition of the Zr element and the optimized heat treatment process, crystal grains are refined, recrystallization is inhibited, and surface coarse grains are eliminated. Finally, the technical effects that the aluminum alloy profile for the automobile structural part is excellent in performance, low in machining cost and environmentally friendly are achieved.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy technology, and more specifically, to an aluminum alloy for automotive structural components and its preparation method. Background Technology

[0002] Aluminum alloys, with their advantages of light weight, high strength, ease of processing and forming, and good corrosion resistance, have been widely used in the automotive, rail transportation, and aerospace industries. Particularly in the automotive industry, with the global energy crisis and increasing environmental awareness, lightweighting has become one of the key technologies for reducing energy consumption, lowering emissions, and improving driving range. Lightweighting, while ensuring the strength and safety performance of the vehicle, aims to improve its power and reduce energy consumption by minimizing its structural weight, thereby increasing its driving range.

[0003] Currently, 6xxx series aluminum alloy extruded profiles are commonly used in automotive body structural components. To improve the lightweighting and application requirements of automotive structural components, a higher-strength, high-formability, and weldable 7xxx series aluminum alloy profile is being developed. This profile possesses mechanical properties that meet the service and lightweighting requirements of automotive structural components, along with good high-temperature formability, enabling the extrusion of profiles with complex cross-sections. It also exhibits good deep-processing bending formability and weldability. To improve the overall performance of the aluminum alloy profile, this project requires optimizing the chemical composition, optimizing the processing technology, and controlling the microstructure. Adjusting the proportions of elements such as Zn, Mg, and Cu can achieve better extrusion formability while maintaining high strength and weldability. Adjusting the content of trace elements such as Zr can refine the microstructure and suppress the formation of coarse grains. Adjusting the extrusion process parameters can optimize the microstructure and improve the material's impact toughness and crumple resistance.

[0004] Currently, there are already published patents related to 7xxx series aluminum alloy profiles for transportation applications. For example, CN108251723A discloses an Al-Zn-Mg alloy profile for rail transit vehicle bodies and its preparation method. The chemical composition of this alloy is: Zn 4.4~4.6%, Zn to Mg mass percentage ratio 3.2~3.5; Cu 0.1~0.15%, Mn 0.3~0.4%, Cr 0.16~0.24%, Ti 0.04~0.08%, Zr 0.12~0.20%, Fe≤0.12%, Si≤0.06%, with the balance being Al. This aluminum alloy profile has a tensile strength greater than 360MPa, does not crack after 30 days of four-point bending stress corrosion, and has a fracture toughness greater than 45MPa. 1 / 2However, this technical solution requires a low Zn content, controlled Fe and Si content, and a three-stage aging process, resulting in high requirements for raw materials and processes, which is not conducive to the low-cost manufacturing and application of aluminum alloys. CN107619976A discloses an Al-Zn-Mg alloy and its preparation method, with the aluminum alloy composition by weight percentage: Zn = 4.0~6.0, Mg = 0.5~2.0, Mn = 0.1~0.5, Cr = 0.05~0.45, Zr = 0.05~0.3, V = 0.1~0.3, Cu, Ti, unavoidable impurity elements wt.% Fe ≤ 0.4, unavoidable impurity elements wt.% Si ≤ 0.4, and the balance being Al and other unavoidable impurity elements. This technical solution requires the addition of V element, which places high demands on cost and casting process. In addition, the above technical solutions do not address the material microstructure, the control of the surface coarse grain layer, or the plastic deformation and welding capabilities of the profiles during subsequent deep processing.

[0005] Therefore, how to develop a new type of aluminum alloy structural component and its processing method to overcome the limitations of existing technologies and achieve comprehensive optimization of the strength, formability, weldability, cost control and environmental adaptability of automotive structural component materials is one of the important technical problems that need to be solved in this field. Summary of the Invention

[0006] The main objective of this invention is to provide an aluminum alloy for automotive structural components and its preparation method, so as to solve the problem that aluminum alloys for automotive structural components in the prior art are difficult to balance high strength and high plasticity.

[0007] To achieve the above objectives, a first aspect of the present invention provides an aluminum alloy for automotive structural components, wherein the aluminum alloy comprises, by weight percentage: 4.5% to 5.5% Zn, 0.7% to 1.4% Mg, 0.05% to 0.25% Zr, 0% to 0.05% Ti, 0% to 0.3% Fe, 0% to 0.3% Si, and the balance being Al.

[0008] Furthermore, by weight percentage, the aluminum alloy composition for automotive structural components includes: 5.0%~5.5% Zn, 0.7%~1.0% Mg, 0.1%~0.2% Zr, 0~0.05% Ti, 0.05~0.25% Fe, 0.05~0.25% Si, with the balance being Al.

[0009] Furthermore, by weight percentage, the aluminum alloy used in automotive structural components also includes: 0~0.3% Cu, 0~0.3% Mn, and 0~0.3% Cr.

[0010] Furthermore, in aluminum alloys used for automotive structural components, the weight ratio of Zn to Mg is (5.1~7.5):1.

[0011] Furthermore, the aluminum alloys used in automotive structural components have a yield strength ≥330MPa, a tensile strength ≥380MPa, and an elongation ≥12.0%.

[0012] The second aspect of the present invention provides a method for preparing the above-mentioned aluminum alloy for automotive structural parts, comprising: step S1, preparing raw materials according to the composition of the aluminum alloy for automotive structural parts, wherein the raw materials are successively melted and cast to obtain a first ingot; step S2, wherein the first ingot is subjected to optional homogenization treatment to obtain a second ingot; step S3, placing the second ingot at a temperature of 420℃~460℃ in an extrusion die at a temperature of 410℃~450℃ and performing extrusion treatment to obtain a first profile; during the extrusion treatment, the exit rate of the first profile is 3mm / s~30mm / s and the exit temperature is 460℃~480℃; step S4, wherein the first profile is successively subjected to quenching treatment and stretching straightening to obtain a second profile; the stretching amount of the stretching straightening is 0.05%~3%; step S5, wherein the second profile is subjected to artificial aging treatment at a holding temperature of 120℃~160℃ and a holding time of 6h~24h to obtain the aluminum alloy for automotive structural parts.

[0013] Furthermore, the homogenization process includes a first-stage process, a second-stage process, and an optional third-stage process performed sequentially; the first-stage process includes: heating the first ingot from 25±10℃ to 380℃~420℃ at a heating rate of 20℃ / h~100℃ / h, and holding it at 380℃~420℃ for 5h~10h; the second-stage process includes: heating the first ingot from 380℃~420℃ to 455℃~500℃ at a heating rate of 20℃ / h~100℃ / h; the third-stage process includes: holding it at 455℃~500℃ for 1h~24h; preferably, the cooling method for the homogenization process is air cooling.

[0014] Furthermore, in step S3, the exit rate of the first profile is 5 mm / s to 15 mm / s.

[0015] Further, in step S4, the quenching treatment is implemented by online quenching or offline quenching; and / or, the stretching amount of the tensile straightening is 0.5%~1.5%; preferably, online quenching is online water quenching or online air quenching; and / or, offline quenching is offline water quenching; more preferably, when the quenching treatment is implemented by offline quenching, before the quenching treatment, step S4 further includes solution treatment of the first profile at a temperature of 465℃~500℃.

[0016] Furthermore, in step S5, the temperature for artificial aging treatment is 130℃~150℃, and the holding time is 6h~24h.

[0017] By applying the technical solution of this invention, the strength and high-temperature extrusion performance of the material under different cooling conditions are ensured by adjusting the content of Zn and Mg elements; the formation of coarse phases is effectively suppressed by controlling the content of Fe and Si elements, allowing for the recycling of the material; and the addition of Zr and optimized heat treatment processes refine the grains and suppress recrystallization, eliminating surface coarse grains. Ultimately, this achieves the goals of improving the strength of aluminum alloy profiles, eliminating the surface coarse grain layer, and improving their bending and welding performance, thus realizing the technical effects of excellent performance, low processing cost, and environmental friendliness in aluminum alloy profiles for automotive structural components. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 This is a microstructure diagram of the aluminum alloy for automotive structural parts obtained in Example 2 of the present invention;

[0020] Figure 2 This is a microstructure diagram of the aluminum alloy for automotive structural parts obtained in Comparative Example 3 of the present invention. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0022] As described in the background section, existing aluminum alloys for automotive structural components suffer from the problem of balancing high strength and high ductility. To address this technical problem, a first aspect of the present invention provides an aluminum alloy for automotive structural components, comprising, by weight percentage: 4.5%~5.5% Zn, 0.7%~1.4% Mg, 0.05%~0.25% Zr, 0~0.05% Ti, 0~0.3% Fe, 0~0.3% Si, with the balance being Al.

[0023] Based on an understanding of the strengthening mechanism of aluminum alloys and consideration of the special performance requirements of automotive structural components, this invention provides the above-mentioned aluminum alloy formulation, wherein:

[0024] Zinc is one of the most important alloying elements in 7xxx series aluminum alloys. It forms the strengthening phase MgZn2 with magnesium (Mg), which is the fundamental reason for the high strength of this type of aluminum alloy. The MgZn2 phase is an effective strengthening phase, significantly increasing the strength of the aluminum alloy through precipitation hardening mechanism. The Zn content is set in the range of 4.5% to 5.5% to balance the material strength and formability. If the Zn content is too low, the amount of MgZn2 phase precipitation will be insufficient, failing to provide sufficient strength; if it is too high, excessive precipitates may form in the alloy, causing the material to become brittle and affecting its weldability and plastic deformation ability. The Zn content within the range provided by this invention ensures that the alloy has sufficient strength while maintaining good plasticity and weldability, meeting the requirements for automotive structural components.

[0025] Magnesium is another key alloying element, also participating in the formation of the MgZn2 strengthening phase. The addition of magnesium can also improve the crack resistance of the alloy, especially for extruded profiles. The Mg content is set between 0.7% and 1.4% to form an effective MgZn2 phase with Zn, while preventing excessive Mg from increasing alloy costs and reducing weldability. Within this range, Mg can effectively improve the tensile strength of the material while maintaining good weld behavior.

[0026] Zirconium in aluminum alloys promotes the formation of dispersed phases such as Al3Zr. These phases refine the grains and inhibit the formation of coarse-grained layers, thereby improving the mechanical properties and surface quality of the material. In this invention, the Zr content is between 0.05% and 0.25% because within this range, zirconium effectively forms fine dispersed phases, achieving optimal grain refining. Excessive Zr, on the other hand, increases costs and may form undesirable coarse compounds, affecting the material's plasticity and processing properties.

[0027] Titanium primarily refines grains by forming compounds such as TiAl3. In aluminum alloys, the addition of trace amounts of Ti can further refine the grains and improve the mechanical properties of the material. In this invention, the upper limit for the Ti content is set at 0.05%, because above this content, the marginal benefit of Ti's grain-refining effect diminishes, while the cost increases significantly. At a content not exceeding 0.05%, Ti can work synergistically with Zr to effectively refine the grains without introducing additional unnecessary costs.

[0028] Iron and silicon are generally considered impurities in aluminum alloys because they can form hard FeAl3 and SiAl4 phases, respectively, which negatively impact the material's plasticity and weldability. By controlling their contents as described above, the negative effects of Fe and Si can be minimized, while simultaneously utilizing their potential benefits in improving the alloy's wear resistance, heat resistance, and corrosion resistance at certain concentrations. Furthermore, the aforementioned ranges for Fe and Si are also based on considerations for material recycling. Even when using recycled materials containing Si and Fe, their negative effects can be controlled through appropriate processes, achieving equivalence in material recycling.

[0029] For aluminum alloys, their room temperature tensile strength depends on the total amount of strengthening phases and the morphology of precipitation. This invention, by controlling the Zn and Mg content, ensures an appropriate amount of MgZn2 precipitation. A high Zn / Mg ratio facilitates MgZn2 precipitation during quenching, avoiding precipitation coarsening and grain boundary precipitation that would lead to strength and toughness loss. The extrusion performance of aluminum alloys depends on their high-temperature strength and rheological properties. Therefore, this invention appropriately adjusts the Zn and Mg content, leveraging the effect of Zn and Mg solid solution on dislocation deformation under high-temperature conditions to facilitate extrusion molding.

[0030] In other words, the aluminum alloy formulation for automotive structural components provided by this invention has the following effects:

[0031] Firstly, based on the comprehensive performance and extrusion performance requirements of automotive structural components, by rationally adjusting the Zn and Mg content and their high ratio in the 7xxx series aluminum alloy, sufficient MgZn2 precipitation and low quenching sensitivity are ensured, achieving aluminum alloy strength under different cooling conditions and exhibiting good high-temperature extrusion performance. Simultaneously, the aluminum alloy provided by this invention does not require the addition of expensive metal elements such as Sc and V, offering advantages such as low cost and simple casting production process, and can be widely used in extruded aluminum profiles for automotive structural components.

[0032] Secondly, by rationally controlling the Fe and Si content in the aluminum alloy, the refractory coarse phases in the alloy are appropriately controlled. This allows for the recycling of the alloy material, achieving the controllable range of Fe / Si impurities and enabling the same-level recycling of the alloy material. Simultaneously, by rationally controlling the Zr content in the aluminum alloy, the full diffusion of trace element Zr is controlled, forming fine Al3Zr and other dispersed phases. This fine dispersed Al3Zr precipitates inhibit recrystallization, thus controlling the coarse grain layer of the profile.

[0033] In summary, through the careful design of the types and contents of the aforementioned elements, the aluminum alloy of this invention, while ensuring high strength, also possesses good plastic deformation capacity and weldability, as well as high tolerance to impurity elements such as Fe and Si. This gives it a significant technical advantage in automotive structural component applications, particularly for the extrusion forming and subsequent deep processing of complex cross-section profiles, such as bending and welding, where the aluminum alloy of this invention exhibits excellent comprehensive performance. Furthermore, by utilizing the possibility of recycled materials, the aluminum alloy of this invention also demonstrates environmental friendliness, reducing the carbon footprint of new material production and promoting resource recycling and low-carbon manufacturing.

[0034] Furthermore, by weight percentage, the aluminum alloy composition for automotive structural components includes: 5.0%~5.5% Zn, 0.7%~1.0% Mg, 0.1%~0.2% Zr, 0~0.05% Ti, 0.05~0.25% Fe, 0.05~0.25% Si, with the balance being Al. This more preferred aluminum alloy formulation allows for more controllable precipitation of the MgZn2 phase and more uniform formation of the Al3Zr phase, thereby further improving the strength, plasticity, and weldability of the resulting composite material.

[0035] To form more alloying strengthening phases or further enhance the alloying effect, thereby significantly optimizing the mechanical properties of the resulting aluminum alloy, the aluminum alloy for automotive structural parts preferably includes, by weight percentage: 0-0.3% Cu, 0-0.3% Mn, and 0-0.3% Cr. In practical applications, the percentage content of Cu can be 0.05%-0.20%, the percentage content of Mn can be 0.20%-0.30%, and the percentage content of Cr can be 0.10%-0.30%.

[0036] Furthermore, in the aluminum alloys used for automotive structural parts, the preferred weight ratio of Zn to Mg is (5.1~7.5):1, which makes the precipitation morphology of the MgZn2 phase more stable and less prone to coarsening or agglomeration during quenching, thereby more effectively strengthening the strength and toughness of the resulting aluminum alloy material.

[0037] In several preferred embodiments, the aluminum alloy used for automotive structural components has a yield strength ≥330 MPa (more preferably 340 MPa~360 MPa), a tensile strength ≥380 MPa (more preferably 385 MPa~410 MPa), and an elongation ≥12.5% ​​(more preferably 13.0%~16.0%). That is to say, the aluminum alloy structural components provided by this invention can effectively balance high strength and high plasticity, and their mechanical properties are superior to those of aluminum alloys in the prior art, thus meeting the performance requirements for aluminum alloys used in automotive structural components.

[0038] The second aspect of the present invention provides a method for preparing the above-mentioned aluminum alloy for automotive structural parts, comprising: step S1, preparing raw materials according to the composition of the aluminum alloy for automotive structural parts, wherein the raw materials are successively melted and cast to obtain a first ingot; step S2, wherein the first ingot is subjected to optional homogenization treatment to obtain a second ingot; step S3, placing the second ingot at a temperature of 420℃~460℃ in an extrusion die at a temperature of 410℃~450℃ and performing extrusion treatment to obtain a first profile; during the extrusion treatment, the exit rate of the first profile is 3mm / s~30mm / s and the exit temperature is 460℃~480℃; step S4, wherein the first profile is successively subjected to quenching treatment and stretching straightening to obtain a second profile; the stretching amount of the stretching straightening is 0.05%~3%; step S5, wherein the second profile is subjected to artificial aging treatment at a holding temperature of 120℃~160℃ and a holding time of 6h~24h to obtain the aluminum alloy for automotive structural parts.

[0039] For the aforementioned aluminum alloys used in automotive structural components, this invention provides a corresponding preparation method. By strictly controlling the parameters in the homogenization treatment, extrusion treatment, and artificial aging treatment processes, the mechanical properties of the resulting aluminum alloys for automotive structural components are comprehensively improved. The optional homogenization treatment can eliminate component segregation within the ingot and promote the uniform distribution of alloying elements. This not only improves the strength and plasticity of the resulting aluminum alloy but also reduces the risk of cracking during heat treatment. In the aluminum alloy preparation process, the appearance of coarse surface grains is closely related to the extrusion process. Based on this, this invention appropriately adjusts parameters such as extrusion temperature and extrusion exit rate to reduce the friction between the extruded material and the extrusion die, suppressing dynamic recrystallization during extrusion. Simultaneously, the lower friction reduces the deformation energy stored in the aluminum alloy, ensuring that the aluminum alloy does not have sufficient driving force for static recrystallization during subsequent solution treatment. Subsequently, quenching is used for rapid cooling after solution treatment to lock in the state of the alloying elements and reduce the precipitation of coarse compounds during cooling. Next, a stretching and straightening process is performed to adjust and correct the microstructure of the aluminum alloy, improving its dimensional stability and eliminating internal stress, thereby improving the overall mechanical properties of the resulting aluminum alloy. Finally, artificial aging treatment is carried out at a holding temperature of 120℃~160℃ for 6h~24h, which promotes the uniform precipitation of strengthening phases such as MgZn2, significantly improving the tensile strength and hardness of the resulting alloy while maintaining good toughness to meet the high strength and durability requirements of automotive structural components.

[0040] In general, the above preparation method optimizes parameters such as extrusion temperature, extrusion exit rate, and solution temperature to ensure fine grains in the extruded profiles and essentially eliminates coarse grains on the profile surface, ultimately yielding aluminum alloys for automotive structural parts with superior comprehensive performance.

[0041] In several typical embodiments, the homogenization treatment includes a first-stage treatment, a second-stage treatment, and an optional third-stage treatment performed sequentially. The first-stage treatment includes heating the first ingot from 25±10℃ to 380℃~420℃ at a heating rate of 20℃ / h~100℃ / h, and holding it at 380℃~420℃ for 5h~10h. The second-stage treatment includes heating the first ingot from 380℃~420℃ to 455℃~500℃ at a heating rate of 20℃ / h~100℃ / h. The third-stage treatment includes holding it at 455℃~500℃ for 1h~24h. In the above preferred embodiment, the multi-stage homogenization heat treatment process minimizes component segregation in the ingot, eliminates casting stress, and improves extrusion formability. For Zr, the multi-stage homogenization heat treatment promotes more complete diffusion, thereby more effectively refining the grains and improving the overall performance of the resulting aluminum alloy structural parts. In practical applications, the cooling method for homogenization is air cooling.

[0042] In the hot extrusion process of step S3, a higher exit rate can significantly improve the production efficiency of the extrusion process. However, excessively high rates may lead to excessive deformation of the material and uneven grain structure, affecting its mechanical properties and subsequent processing performance. Based on this, the exit rate of the first profile is further optimized to be within the range of 5 mm / s to 15 mm / s. This can more effectively balance production efficiency and material quality, ensuring that the resulting aluminum alloy profile maintains good microstructure and mechanical properties under high-speed extrusion conditions. Ultimately, this more effectively balances and improves the tensile strength, yield strength, and elongation of the final aluminum alloy used in automotive structural parts.

[0043] In step S4, the quenching treatment is preferably implemented as online quenching or offline quenching. Furthermore, to more effectively eliminate residual stress generated during extrusion and solution treatment of the profile, thereby further improving its dimensional stability and mechanical properties, the stretching amount during stretching straightening is preferably 0.5% to 1.5%. In practical applications, online quenching is online water quenching or online air quenching; and / or, offline quenching is offline water quenching. And, when the quenching treatment is implemented as offline quenching, to further optimize the overall performance of the resulting aluminum alloy, step S4 further includes solution treatment of the first profile at a temperature of 465°C to 500°C before the quenching treatment.

[0044] In step S5, the holding temperature for artificial aging treatment is further preferably 130℃~150℃, and the holding time is 6h~24h, so as to achieve more complete and more uniform precipitation of MgZn2 phase, while better maintaining the alloy toughness, and promoting the resulting automotive aluminum alloy structural parts material to exhibit superior comprehensive mechanical properties.

[0045] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0046] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0047] Example 1

[0048] A method for preparing aluminum alloy for automotive structural components:

[0049] (1) Prepare aluminum alloy raw materials with the following composition: Zn 5.0%, Mg 0.95%, Zr 0.15%, Ti 0.03%, Fe 0.25%, Si 0.25%, and the remainder is Al (the content and relationship of the above components are shown in Table 1). The above raw materials are smelted and cast in sequence to obtain the first ingot.

[0050] (2) Homogenization treatment: The obtained first ingot was heated from room temperature (25±10℃) to 480℃ at a heating rate of 50℃ / h, held at that temperature for 2h, and then air-cooled to obtain the second ingot.

[0051] (3) Heat the obtained second ingot to 450°C, heat the extrusion die to 440°C, and heat the extrusion cylinder to 440°C. Extrude the ingot, and the profile exit rate during the extrusion process is 10 mm / s, and the profile exit temperature is 470~475°C.

[0052] (4) The extruded profiles are then subjected to online water quenching. After quenching, the profiles are then stretched and straightened by 1.0%.

[0053] (5) The profiles after stretching and straightening are subjected to artificial aging treatment at a temperature of 140℃ for 8 hours.

[0054] Example 2

[0055] A method for preparing aluminum alloy for automotive structural components:

[0056] (1) Prepare aluminum alloy raw materials with the following composition: Zn 5.4%, Mg 0.76%, Zr 0.15%, Ti 0.03%, Fe 0.25%, Si 0.25%, and the remainder is Al (the content and relationship of the above components are shown in Table 1). The above raw materials are smelted and cast in sequence to obtain the first ingot.

[0057] (2) Homogenization treatment: The obtained first ingot was heated from room temperature (25±10℃) to 480℃ at a heating rate of 50℃ / h, held at that temperature for 2h, and then air-cooled to obtain the second ingot.

[0058] (3) Heat the obtained second ingot to 450°C, heat the extrusion die to 440°C, and heat the extrusion cylinder to 440°C. Extrude the ingot, and the profile exit rate during the extrusion process is 10 mm / s, and the profile exit temperature is 470~475°C.

[0059] (4) The extruded profiles are then subjected to online water quenching. After quenching, the profiles are then stretched and straightened by 1.0%.

[0060] (5) The profiles after stretching and straightening are subjected to artificial aging treatment at a temperature of 140℃ for 8 hours.

[0061] The microstructure of the aluminum alloy used in automotive structural parts is shown in the figure. Figure 1 As shown in the figure, this invention, by adjusting the Zr content in the aluminum alloy and optimizing the heat treatment process at different stages, enables the uniform precipitation of Zr-containing dispersed phases, inhibits recrystallization, produces a fine microstructure, and essentially eliminates the coarse grain layer on the profile surface.

[0062] Example 3

[0063] A method for preparing aluminum alloy for automotive structural components:

[0064] (1) Prepare aluminum alloy raw materials with the following composition: Zn 5.4%, Mg 0.76%, Zr 0.2%, Ti 0.03%, Fe 0.1%, Si 0.1%, and the remainder is Al (the content and relationship of the above components are shown in Table 1). The above raw materials are smelted and cast in sequence to obtain the first ingot.

[0065] (2) Homogenization treatment: The obtained first ingot was heated from room temperature (25±10℃) to 480℃ at a heating rate of 50℃ / h, held at that temperature for 2h, and then air-cooled to obtain the second ingot.

[0066] (3) Heat the obtained second ingot to 450°C, heat the extrusion die to 440°C, and heat the extrusion cylinder to 440°C. Extrude the ingot, and the profile exit rate during the extrusion process is 10 mm / s, and the profile exit temperature is 470~475°C.

[0067] (4) The extruded profiles are then subjected to online water quenching. After quenching, the profiles are then stretched and straightened by 1.0%.

[0068] (5) The profiles after stretching and straightening are subjected to artificial aging treatment at a temperature of 140℃ for 8 hours.

[0069] Example 4

[0070] A method for preparing aluminum alloy for automotive structural components:

[0071] The only difference between this embodiment and embodiment 2 is that in step (2), the heat preservation temperature for homogenization is changed to 460°C and the heat preservation time is changed to 20h.

[0072] Example 5

[0073] A method for preparing aluminum alloy for automotive structural components:

[0074] The only difference between this embodiment and embodiment 2 is that in step (4), the quenching method is changed from online water quenching to online air quenching.

[0075] Example 6

[0076] A method for preparing aluminum alloy for automotive structural components:

[0077] The only difference between this embodiment and embodiment 2 is that in step (4), the quenching method is changed from online water quenching to offline water quenching; at the same time, before offline water quenching, a solution treatment step is added to the profile obtained after extrusion, and the solution treatment temperature is 480°C.

[0078] Example 7

[0079] A method for preparing aluminum alloy for automotive structural components:

[0080] The only difference between this embodiment and embodiment 2 is that in step (5), the heat preservation temperature of the artificial aging treatment is changed to 120°C and the heat preservation time is changed to 24h.

[0081] Example 8

[0082] A method for preparing aluminum alloy for automotive structural components:

[0083] The only difference between this embodiment and embodiment 2 is that in step (5), the heat preservation temperature of the artificial aging treatment is changed to 160°C and the heat preservation time is changed to 6h.

[0084] Example 9

[0085] A method for preparing aluminum alloy for automotive structural components:

[0086] The difference between this embodiment and embodiment 2 lies only in step (2), specifically:

[0087] The first ingot was heated from room temperature (25±2℃) to 400℃ at a heating rate of 50℃ / h and held at 400℃ for 8 hours; then the ingot was heated from 400℃ to 500℃ at a heating rate of 30℃ / h and then air-cooled.

[0088] Example 10

[0089] A method for preparing aluminum alloy for automotive structural components:

[0090] The only difference between this embodiment and Embodiment 2 is that the raw material for the aluminum alloy in this embodiment is recycled material, specifically the waste material obtained after testing the aluminum alloy sample for automotive structural parts obtained in Embodiment 2.

[0091] Examples 11 to 15

[0092] The only difference between Examples 11 to 15 and Example 2 is the content of aluminum alloy components, as shown in Table 1.

[0093] Example 16

[0094] A method for preparing aluminum alloy for automotive structural components:

[0095] The only difference between this embodiment and embodiment 2 is that in step (2), the heat preservation temperature for homogenization is changed to 450°C.

[0096] Example 17

[0097] A method for preparing aluminum alloy for automotive structural components:

[0098] The only difference between this embodiment and embodiment 2 is that in step (2), the heat preservation temperature for homogenization treatment is changed to 520°C.

[0099] Example 18

[0100] A method for preparing aluminum alloy for automotive structural components:

[0101] The difference between this embodiment and embodiment 2 lies only in step (3), specifically:

[0102] (3) Heat the obtained second ingot to 470°C, heat the extrusion die to 460°C, and heat the extrusion cylinder to 460°C. Extrude the ingot, and the profile exit rate during the extrusion process is 3 mm / s, and the profile exit temperature is 485~490°C.

[0103] Comparative Example 1

[0104] A method for preparing aluminum alloy for automotive structural components:

[0105] The only difference between this comparative example and Example 2 is the content of aluminum alloy components, as shown in Table 1.

[0106] Comparative Example 2

[0107] A method for preparing aluminum alloy for automotive structural components:

[0108] The only difference between this comparative example and Example 5 is the content of aluminum alloy components, as shown in Table 1.

[0109] Comparative Example 3

[0110] A method for preparing aluminum alloy for automotive structural components:

[0111] The only difference between this comparative example and Example 2 is the content of aluminum alloy components, as shown in Table 1.

[0112] The microstructure of the aluminum alloy used in automotive structural parts is shown in the figure. Figure 2 .Will Figure 2 and Figure 1 In comparison, the aluminum alloy profile of Example 2 has a fine internal structure and the coarse grain layer on the surface is basically eliminated, while the aluminum alloy profile of Comparative Example 3 has obvious coarse surface grains. In addition, the aluminum alloy profiles obtained in each embodiment of the present invention exhibit better bending performance. In the three-point bending test, the profile slice does not crack when bent at 160°, while the aluminum alloy profile of Comparative Example 3, due to its coarse surface grains, causes the profile slice to crack or have an orange peel texture when bent at 160° in the three-point bending test.

[0113] Comparative Example 4

[0114] A method for preparing aluminum alloy for automotive structural components:

[0115] The only difference between this comparative example and Example 2 is the content of aluminum alloy components, as shown in Table 1.

[0116] Although the sample obtained in this comparative example has good mechanical strength, its surface quality is poor, the grains are coarse, and the Zr content is high. The microstructure of the profile contains a large number of insoluble primary Zr phases, which causes the profile slices to crack or have an orange peel texture when bent at 160° in the three-point bending test, making it difficult to use as an aluminum alloy for practical application in automotive structural parts.

[0117] Table 1

[0118]

[0119] The elemental composition of the examples and comparative examples not shown in the table is consistent with that of Example 2.

[0120] Tensile strength, yield strength and elongation were tested according to GB / T 228.

[0121] The aluminum alloy samples obtained from each embodiment and comparative example were subjected to the above tests, and the results are shown in Table 2.

[0122] Table 2

[0123]

[0124] As can be seen from the above description, the embodiments of the present invention achieve the preparation of aluminum alloys for automotive structural components with superior mechanical properties. The resulting aluminum alloy has high strength, eliminates the coarse grain layer on the profile surface, and exhibits good bending and welding performance; its composition does not contain rare and precious metal elements, the process flow is simple, the production cost is low, and high-efficiency processing can be achieved through process optimization. Furthermore, the composition of the resulting aluminum alloy has high tolerance for Fe and Si content, allowing for the recycling of aluminum alloy profiles and achieving low-carbon emission circular reuse and reprocessing.

[0125] In various embodiments, especially embodiments 1 to 6, 9 to 13 (with yield strength ≥340MPa, tensile strength ≥385MPa, and elongation ≥13.0%), superior aluminum alloys were obtained by optimizing the content of each element. Embodiments 11 to 13 further added Cu, Mn, and Cr, thereby forming more alloying strengthening phases in the resulting aluminum alloy structural parts or further enhancing its alloying effect, thus significantly optimizing the mechanical properties of the obtained aluminum alloys.

[0126] Comparing Examples 7 and 8 with Example 2, it can be seen that by optimizing the heat preservation temperature of artificial aging treatment, the uniform precipitation of reinforcing phases such as MgZn2 can be promoted, significantly improving the tensile strength and hardness of the obtained product, while maintaining good toughness, so as to meet the high strength and durability requirements of automotive structural components.

[0127] Comparing Examples 14 and 15 with Example 2, it can be seen that by further optimizing the Zn / Mg ratio in the aluminum alloy formulation, the precipitation morphology of the MgZn2 phase can be made more stable and less prone to coarsening or agglomeration during quenching, thereby more effectively strengthening the strength and toughness of the obtained aluminum alloy material.

[0128] Comparing Examples 16 and 17 with Example 2, it can be seen that by optimizing the heat preservation temperature for homogenization treatment, the grains can be refined more effectively, thereby improving the overall performance of the resulting aluminum alloy structural parts.

[0129] Comparing Example 18 with Example 2, it can be seen that by optimizing the extrusion process conditions, the friction between the extruded material and the extrusion die can be reduced, dynamic recrystallization during the extrusion process can be suppressed, and the mechanical properties of the resulting aluminum alloy can be significantly optimized.

[0130] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0131] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An aluminum alloy for an automobile structural member, characterized by comprising, in mass %, The automobile structural member aluminum alloy comprises, in percentage by weight: 4.5-5.5% of Zn, 0.7-1.4% of Mg, 0.05-0.25% of Zr, 0-0.05% of Ti, 0-0.3% of Fe, 0-0.3% of Si, and the balance of Al.

2. The aluminum alloy for automotive structural members according to claim 1, characterized by The automobile structural member aluminum alloy comprises, in percentage by weight: 5.0-5.5% of Zn, 0.7-1.0% of Mg, 0.1-0.2% of Zr, 0-0.05% of Ti, 0.05-0.25% of Fe, 0.05-0.25% of Si, and the balance of Al.

3. The aluminum alloy for automotive structural members according to claim 1 or 2, characterized by, The automobile structural member aluminum alloy further comprises, in percentage by weight: 0-0.3% of Cu, 0-0.3% of Mn, and 0-0.3% of Cr.

4. The aluminum alloy for automotive structural members according to any one of claims 1 to 3, characterized by, The automobile structural member aluminum alloy has a weight content ratio of Zn to Mg of (5.1-7.5):

1.

5. The aluminum alloy for automotive structural members according to any one of claims 1 to 4, characterized by, The automobile structural member aluminum alloy has a yield strength of ≥330 MPa, a tensile strength of ≥380 MPa, and an elongation of ≥12.0%.

6. A method of producing the aluminum alloy for an automotive structural member according to any one of claims 1 to 5, characterized by, The automobile structural member aluminum alloy comprises, in percentage by weight: 4.5-5.5% of Zn, 0.7-1.4% of Mg, 0.05-0.25% of Zr, 0-0.05% of Ti, 0-0.3% of Fe, 0-0.3% of Si, and the balance of Al. The automobile structural member aluminum alloy comprises, in percentage by weight: 5.0-5.5% of Zn, 0.7-1.0% of Mg, 0.1-0.2% of Zr, 0-0.05% of Ti, 0.05-0.25% of Fe, 0.05-0.25% of Si, and the balance of Al. The automobile structural member aluminum alloy further comprises, in percentage by weight: 0-0.3% of Cu, 0-0.3% of Mn, and 0-0.3% of Cr. The automobile structural member aluminum alloy has a weight content ratio of Zn to Mg of (5.1-7.5):

1. The automobile structural member aluminum alloy has a yield strength of ≥330 MPa, a tensile strength of ≥380 MPa, and an elongation of ≥12.0%. The automobile structural member aluminum alloy comprises, in percentage by weight: 4.5-5.5% of Zn, 0.7-1.4% of Mg, 0.05-0.25% of Zr, 0-0.05% of Ti, 0-0.3% of Fe, 0-0.3% of Si, and the balance of Al.

7. The method of producing an aluminum alloy for an automotive structural member according to claim 6, characterized by, The automobile structural member aluminum alloy comprises, in percentage by weight: 5.0-5.5% of Zn, 0.7-1.0% of Mg, 0.1-0.2% of Zr, 0-0.05% of Ti, 0.05-0.25% of Fe, 0.05-0.25% of Si, and the balance of Al. The automobile structural member aluminum alloy further comprises, in percentage by weight: 0-0.3% of Cu, 0-0.3% of Mn, and 0-0.3% of Cr. The automobile structural member aluminum alloy has a weight content ratio of Zn to Mg of (5.1-7.5):

1. The automobile structural member aluminum alloy has a yield strength of ≥330 MPa, a tensile strength of ≥380 MPa, and an elongation of ≥12.0%. The automobile structural member aluminum alloy comprises, in percentage by weight: 4.5-5.5% of Zn, 0.7-1.4% of Mg, 0.05-0.25% of Zr, 0-0.05% of Ti, 0-0.3% of Fe, 0-0.3% of Si, and the balance of Al.

8. The method of producing an aluminum alloy for an automotive structural member according to claim 6 or 7, characterized in that, The automobile structural member aluminum alloy comprises, in percentage by weight: 5.0-5.5% of Zn, 0.7-1.0% of Mg, 0.1-0.2% of Zr, 0-0.05% of Ti, 0.05-0.25% of Fe, 0.05-0.25% of Si, and the balance of Al.

9. The method of producing an aluminum alloy for automotive structural members according to any one of claims 6 to 8, characterized in that, The automobile structural member aluminum alloy further comprises, in percentage by weight: 0-0.3% of Cu, 0-0.3% of Mn, and 0-0.3% of Cr. The automobile structural member aluminum alloy has a weight content ratio of Zn to Mg of (5.1-7.5):

1. The automobile structural member aluminum alloy has a yield strength of ≥330 MPa, a tensile strength of ≥380 MPa, and an elongation of ≥12.0%. The automobile structural member aluminum alloy comprises, in percentage by weight: 4.5-5.5% of Zn, 0.7-1.4% of Mg, 0.05-0.25% of Zr, 0-0.05% of Ti, 0-0.3% of Fe, 0-0.3% of Si, and the balance of Al. The automobile structural member aluminum alloy comprises, in percentage by weight: 5.0-5.5% of Zn, 0.7-1.0% of Mg, 0.1-0.2% of Zr, 0-0.05% of Ti, 0.05-0.25% of Fe, 0.05-0.25% of Si, and the balance of Al. The automobile structural member aluminum alloy further comprises, in percentage by weight: 0-0.3% of Cu, 0-0.3% of Mn, and 0-0.3% of Cr. The automobile structural member aluminum alloy has a weight content ratio of Zn to Mg of (5.1-7.5):

1. The automobile structural member aluminum alloy has a yield strength of ≥330 MPa, a tensile strength of ≥380 MPa, and an elongation of ≥12.0%. The automobile structural member aluminum alloy comprises, in percentage by weight: 4.5-5.5% of Zn, 0.7-1.4% of Mg, 0.05-0.25% of Zr, 0-0.05% of Ti, 0-0.3% of Fe, 0-0.3% of Si, and the balance of Al. The automobile structural member aluminum alloy comprises, in percentage by weight: 5.0-5.5% of Zn, 0.7-1.0% of Mg, 0.1-0.2% of Zr, 0-0.05% of Ti, 0.05-0.25% of Fe, 0.05-0.25% of Si, and the balance of Al. The automobile structural member aluminum alloy further comprises, in percentage by weight: 0-0.3% of Cu, 0-0.3% of Mn, and 0-0.3% of Cr. The automobile structural member aluminum alloy has a weight content ratio of Zn to Mg of (5.1-7.5):

1. The automobile structural member aluminum alloy has a yield strength of ≥330 MPa, a tensile strength of ≥380 MPa, and an elongation of ≥12.0%. The automobile structural member aluminum alloy comprises, in percentage by weight: 4.5-5.5% of Zn, 0.7-1.4% of Mg, 0.05-0.25% of Zr, 0-0.05% of Ti, 0-0.3% of Fe, 0-0.3% of Si, and the balance of Al. The automobile structural member aluminum alloy comprises, in percentage by weight: 5.0-5.5% of Zn, 0.7-1.0% of Mg, 0.1-0.2% of Zr, 0-0.05% of Ti, 0.05-0.25% of Fe, 0.05-0.25% of Si, and the balance of Al. The automobile structural member aluminum alloy further comprises, in percentage by weight: 0-0.3% of Cu, 0-0.3% of Mn, and 0-0.3% of Cr. The automobile structural member aluminum alloy has a weight content ratio of Zn to Mg of (5.1-7.5):

1. The automobile structural member aluminum alloy has a yield strength of ≥330 MPa, a tensile strength of ≥380 MPa, and an elongation of ≥12.0%. The automobile structural member aluminum alloy comprises, in percentage by weight: 4.5-5.5% of Zn, 0.7-1.4% of Mg, 0.05-0.25% of Zr, 0-0.05% of Ti, More preferably, when the quenching treatment is implemented as an offline quenching, before the quenching treatment, the step S4 further comprises subjecting the first profile to a solid solution treatment at a temperature of 465-500℃.

10. The method of producing an aluminum alloy for automotive structural members according to any one of claims 6 to 9, characterized in that, In the step S5, the holding temperature of the artificial aging treatment is 130-150℃, and the holding time is 6-24h.

Images