High-toughness 6XXX aluminum alloy profile for automobile structural parts and preparation method of high-toughness 6XXX aluminum alloy profile

Abstract

A preparation method of a high-strength and high-toughness 6XXX aluminum alloy profile for automobile structural parts comprises the steps of ingredient smelting, casting, homogenization and heating treatment, extrusion forming, online quenching, stretch straightening, aging strengthening and the like, and the high-strength and high-toughness 6XXX aluminum alloy profile for the automobile structural parts is obtained by optimizing the alloy element proportion and adopting the oil-gas lubrication semi-continuous water-cooling casting, gradient heating, air-blast quenching and precise aging processes. The yield strength of the manufactured profile is larger than or equal to 200 MPa, the tensile strength is larger than or equal to 230 MPa, the ductility is larger than or equal to 10%, and no visible crack exists after a 65% total cross section compression test is conducted according to the GB / T 33910-2017 standard. The problems that the strength and toughness of a traditional 6XXX aluminum alloy cannot be achieved at the same time, and the performance and the size precision are opposite are solved, the technology is simple and convenient, the manufacturing cost is low, and the requirements of core structural parts such as automobile bumpers, energy absorption boxes and engine room longitudinal beams are met.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy profile manufacturing technology, specifically to a high-strength and high-toughness 6XXX aluminum alloy profile for automotive structural components and its manufacturing method. Background Technology

[0002] With the continued deepening of global energy conservation and emission reduction policies and the ever-increasing demand for extended driving range in new energy vehicles, lightweighting has become one of the core development directions in the automotive industry. Aluminum alloys, with a density only about one-third that of steel, possess high specific strength, excellent collision energy absorption characteristics, and good recyclability, making them the preferred material to replace traditional steel and achieve vehicle weight reduction. According to publicly available industry data, for every 10% reduction in vehicle weight, fuel consumption per 100 kilometers for gasoline vehicles can decrease by 6%-8%, and the driving range for electric vehicles can increase by 5%-10%. Therefore, the application rate of aluminum alloys in key energy-absorbing structural components such as front and rear bumpers, energy-absorbing boxes, and engine compartment longitudinal beams continues to rise.

[0003] Currently, automakers have set clear and stringent requirements for the material properties of energy-absorbing structural components: on the one hand, they need to meet basic mechanical performance indicators, namely yield strength ≥190MPa, tensile strength ≥230MPa, and elongation ≥10%, to ensure the load-bearing capacity of the energy-absorbing structural components during normal driving and the initial stage of a collision; on the other hand, they need to pass the toughness verification of the "60% full-section compression test" (according to the automotive industry's standard testing), requiring the sample to have regular wrinkles on the surface after compression and no visible cracks, to avoid energy absorption failure due to the fragmentation of the energy-absorbing structural components during a collision, thus ensuring the safety of the occupants.

[0004] However, using traditional 6XXX aluminum alloys as the base material for automotive structural components has a wide range of composition control and relatively loose impurity control precision. However, the yield strength is usually only 170-190MPa and the tensile strength is only 200-210MPa. After the full-section compression test, a large number of cracks are very likely to appear on the surface and in the folds. In severe cases, the parts may even completely break into small pieces, making it impossible to maintain the integrity of the original structure. This is far from meeting the current performance requirements of automotive OEMs for automotive energy-absorbing structural components.

[0005] To address the aforementioned issues, various improvement schemes have been proposed by those skilled in the art. However, in long-term use, these improved schemes have been found to still have significant shortcomings. For example, patent document CN108893659A, entitled "A Processing Method for Aluminum Alloy and Profiles for Automotive Structural Components," improves the mechanical properties of automotive structural components by employing multi-stage homogenization treatment combined with water-cooled quenching after extrusion. However, in long-term application, those skilled in the art have found that this scheme involves numerous steps and a complex process. Furthermore, the samples prepared using this scheme still exhibit non-penetrating cracks after compression, failing to meet the stringent toughness requirements of automotive OEMs for "crack-free full-section compression" in automotive energy-absorbing structural components.

[0006] For example, patent document CN117684054A, entitled "A 6-series energy-absorbing aluminum alloy and its manufacturing method," attempts to improve the mechanical properties of automotive structural components while achieving crack-free profiles after crushing by employing strong water-cooling quenching and aging treatment at 205℃. However, in long-term application, those skilled in the art have discovered a core contradiction between "performance and dimensional accuracy." The strong water-cooling quenching process directly leads to excessive temperature differences between the inner and outer surfaces of the profile, causing a sharp increase in internal stress. Especially when manufacturing thin-walled profiles, bending, twisting, and other dimensional defects are inevitable, resulting in low product dimensional accuracy. This fails to meet the automotive industry's high-precision assembly dimensional requirements for parts, and the produced thin-walled profiles are highly susceptible to penetrating cracks after full-section compression. Furthermore, this method uses both aluminum-titanium-carbon and aluminum-titanium-boron alloys for grain refinement during melting and casting, making the process extremely complex. In addition, the patent document CN119710390A, entitled "A High-Strength High-Energy-Absorbing Aluminum Alloy Material and Its Preparation Method and Application", adopts a multi-stage homogenization process, which also suffers from cumbersome procedures and high production costs.

[0007] The core requirement for high-strength and high-toughness profiles used in automotive lightweighting lies in the balance between "form" and "material": "form" requires high precision in cross-sectional dimensions and geometric tolerances; "material" requires high strength and good plasticity and toughness. However, in existing technologies, ensuring high performance of the "material" relies on high cooling rates; while ensuring high precision of the "form" requires controlling low cooling rates, and the two are often difficult to achieve simultaneously. Therefore, how to meet the requirements of "yield strength ≥200MPa, tensile strength ≥230MPa, elongation ≥10%, and no cracks after full-section compression testing" while simultaneously considering process simplicity and dimensional accuracy, so as to adapt to the high-strength, high-plasticity, and high-toughness application requirements of important energy-absorbing structural components such as front and rear bumpers, energy-absorbing boxes, and engine compartment longitudinal beams, has become an urgent technical problem to be solved in the field of automotive lightweighting. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing a high-strength and high-toughness 6XXX aluminum alloy profile for automotive structural components and its preparation method. The method includes steps such as batching and melting, casting, homogenization heat treatment, extrusion molding, online quenching, tensile straightening, and aging strengthening. By optimizing the alloy element ratio and employing semi-continuous water-cooled casting, gradient heating, air-cooled quenching, and precise aging processes, the resulting profile meets the requirements of yield strength ≥200MPa, tensile strength ≥230MPa, and elongation ≥10%. No visible cracks are observed after a 65% full-section compression test according to GB / T 33910-2017 standard. This invention solves the traditional problem of the incompatibility between strength and toughness and the trade-off between performance and dimensional accuracy in 6XXX aluminum alloys. The process is simple, the manufacturing cost is low, and it is suitable for the needs of core energy-absorbing structural components such as automotive bumpers, energy-absorbing boxes, and engine compartment longitudinal beams.

[0009] The objective of this invention is achieved through the following approach: A high-strength and high-toughness 6XXX aluminum alloy for automotive structural components has the following mass percentage composition: Si: 0.38–0.45%; Fe: ≤0.25%; Cu: 0.06–0.10%; Mn: 0.06–0.10%; Mg: 0.54–0.63%; Cr: ≤0.05%; Zn: ≤0.05%; Ti: ≤0.10%; individual impurities: ≤0.05%; total impurities: ≤0.15%; balance: Al.

[0010] Preferably, the mass percentage of each component in the high-strength and high-toughness 6XXX aluminum alloy is as follows: Si: 0.38-0.42%; Fe: ≤0.15%; Cu: 0.06-0.10%; Mn: 0.06-0.08%; Mg: 0.57-0.60%; Cr: ≤0.03%; Zn ≤0.03%; Ti ≤0.10%; individual impurities ≤0.03%; total impurities ≤0.10%; balance is Al.

[0011] Preferably, the high-strength and high-toughness 6XXX aluminum alloy profiles meet the following performance indicators: yield strength ≥200MPa, tensile strength ≥230MPa, elongation ≥10%; after a 65% (compression height is 65% of the original profile height) full-section compression test according to GB / T 33910-2017 "Aluminum and Aluminum Alloy Extruded Profiles for Automobiles" standard, the profile surface has regular wrinkles and no visible cracks.

[0012] A method for preparing a high-strength and high-toughness 6XXX aluminum alloy profile includes the following steps: 1) Batching and smelting The ingredients are prepared according to the above-mentioned high-strength and high-toughness 6XXX aluminum alloy mass percentage, and after mixing and melting, liquid aluminum alloy is obtained. 2) Casting After refining, settling, slag removal, online degassing, and filtration of the liquid aluminum alloy, high-purity aluminum liquid is obtained; it is then melted and cast to obtain primary aluminum alloy ingots. 3) Homogenization treatment The primary aluminum alloy casting rod is homogenized to obtain a homogenized aluminum alloy casting rod.

[0013] Preferably, in step 3), the homogenization process is as follows: homogenization temperature 560-580℃, heat preservation time 8-10h, and water mist mixing and cooling to room temperature; 4) Extrusion molding The heated aluminum alloy casting rod is placed in a heated extrusion cylinder and extruded through a heated die at a speed of 5-8 m / min. The exit temperature of the extruded profile is controlled to be ≥490℃ to obtain a high-strength and tough 6XXX aluminum alloy profile.

[0014] Preferably, in step 2), the specific method of casting is as follows: high-purity aluminum liquid is formed into aluminum alloy casting rods by using a semi-continuous water-cooled casting method.

[0015] Preferably, in step 2), the refining method is as follows: the refining temperature is 730-750℃, and the refining device with argon gas is inserted into the bottom of the furnace and moved back and forth slowly and evenly for 8-10 minutes, followed by standing for 30-40 minutes; online degassing is performed using a dual-rotor method, with an argon gas flow rate of 3.2-5.5 m³ / h and a rotor speed of 350-550 r / min; during filtration, a double-layer ceramic filter plate with a pore density of 30 ppi and 40 ppi is used; after degassing, the hydrogen content in the aluminum liquid is guaranteed to be ≤0.12 ml / 100 g Al.

[0016] Preferably, in step 4), the heating treatment of the aluminum alloy casting rod is gradient heating: the temperature at the head end of the casting rod is controlled at 470±10℃, and a temperature gradient of -5℃ / 330mm is set from the head end to the tail end of the casting rod; the heating treatment of the extrusion cylinder is: the temperature of the extrusion cylinder is controlled at 430±10℃ and held for 8 to 12 hours; the heating treatment of the mold is: the temperature of the mold is controlled at 490±10℃ and held for 6 to 10 hours; the extrusion speed is 6 to 7 m / min.

[0017] Preferably, the high-strength and high-toughness 6XXX aluminum alloy profile obtained in step 4) further needs to undergo the following treatments in sequence: 4-1) Online quenching treatment High-strength and tough 6XXX aluminum alloy profiles are subjected to online air-cooled quenching treatment with a quenching cooling rate ≥1℃ / s; 4-2) Stretch straightening treatment The high-strength and high-toughness 6XXX aluminum alloy profiles after quenching are subjected to tensile straightening treatment with a stretching amount of 0.8-1.5%. 4-3) Time-efficiency enhancement processing High-strength and high-toughness 6XXX aluminum alloy profiles after stretching and straightening were subjected to artificial aging treatment at an aging temperature of 220±5℃ and a holding time of 5.5±0.5h to obtain high-strength and high-toughness 6XXX aluminum alloy profiles for automotive structural parts.

[0018] Preferably, in step 4-1), the cooling rate of the air-cooled quenching is 1.1 to 1.2 °C / s; in step 4-2), the stretching amount of the stretching straightening treatment is 0.8 to 1.0%; and in step 4-3), the holding time of the aging strengthening treatment is 5.5 h.

[0019] The beneficial effects of this invention are as follows: 1. This invention optimizes the proportions of key strengthening elements such as Mg and Si, and, in conjunction with the extrusion process, achieves precise control over the microstructure of the material. This effectively improves the solid solubility of alloying elements such as Mg and Si in the aluminum matrix, enabling the aluminum alloy to form a stable supersaturated solid solution at a low cooling rate (≥1℃ / s). This effectively suppresses the formation of brittle phases that affect the plasticity and toughness of the material. High plasticity and toughness profiles can be obtained without subsequent strong water-cooling quenching processes. The extrusion process is simple, the obtained profiles have high dimensional accuracy, and the material has good plasticity and toughness, fundamentally solving the contradiction between "high performance requirements and dimensional accuracy requirements".

[0020] 2. This invention achieves homogenization and rapid cooling through precise temperature and time control, effectively eliminating component and microstructure segregation and preventing overheating, thus meeting the microstructure control requirements of subsequent extrusion processes. Simultaneously, this invention sets dedicated heating parameters for the casting rod, extrusion cylinder, and die, effectively preventing uneven extrusion deformation and dimensional deviations in the profile. Precise matching of extrusion speed and exit temperature effectively prevents surface peeling, overheating, or heat loss. Using air-cooled quenching instead of strong water cooling, combined with precise stretching and straightening, eliminates the need for additional shaping and rework processes compared to traditional water-cooled quenching. The straightness, torsion, and dimensional tolerances of the profile exceed automotive industry standards, simplifying the process and reducing manufacturing costs.

[0021] 3. The entire manufacturing process of this invention is continuous and requires no complex equipment investment. It ensures that the profile meets the requirements of yield strength ≥200MPa, tensile strength ≥230MPa, and elongation ≥10%, and exhibits no cracks in the 65% full-section compression test. This fully meets the stringent performance requirements of "impact resistance + crack resistance" for automotive energy-absorbing structural components, balancing strength and toughness. Real-vehicle collision tests have verified that the energy absorption effect is superior to traditional 6XXX alloy profiles, making it perfectly compatible with core structural components such as automotive bumpers, energy-absorbing boxes, and engine compartment longitudinal beams. Its technological advancement and industrialization value are significant. Attached Figure Description

[0022] Figure 1A process flow diagram for preparing high-strength and high-toughness 6XXX aluminum alloy profiles according to the present invention; Figure 2 A process flow diagram for preparing high-strength and tough 6XXX aluminum alloy profiles for automotive structural components according to an embodiment of the present invention; Figure 3 A cross-sectional schematic diagram of a high-strength and tough 6XXX aluminum alloy profile prepared according to an embodiment of the present invention; Figure 4 This is a sample condition diagram of the profile after a full-section compression test and a 10-point rating according to an embodiment of the present invention; Figure 5 This is a diagram showing the condition of a sample of the comparative profile of the present invention after a full-section compression test with a 6-point rating. Figure 6 This is a diagram showing the state of a sample with a score of 0 after a full-section compression test of the comparative profile of this invention. Detailed Implementation

[0023] like Figure 1 As shown, a method for preparing a high-strength and high-toughness 6XXX aluminum alloy profile for automotive structural components includes the following steps: 1) Batching and smelting The raw materials are precisely proportioned according to the following high-strength and high-toughness 6XXX aluminum alloy mass percentages. After the raw materials are mixed evenly, they are sent to a melting furnace for melting to obtain a liquid aluminum alloy with uniform composition: Si: 0.38–0.45%; Fe: ≤0.25%; Cu: 0.06–0.10%; Mn: 0.06–0.10%; Mg: 0.54–0.63%; Cr: ≤0.05%; Zn: ≤0.05%; Ti: ≤0.10%; Individual impurities ≤0.05%; Total impurities ≤0.15%; Balance: Al; Of course, to further improve the performance of the final profile, the following proportions can also be used for melting: Si: 0.38–0.42%; Fe: ≤0.15%; Cu: 0.06–0.10%; Mn: 0.06–0.08%; Mg: 0.57–0.60%; Cr: ≤0.03%; Zn: ≤0.03%; Ti: ≤0.10%; Individual impurities: ≤0.03%; Total impurities: ≤0.10%; Balance: Al.

[0024] 2) Casting The liquid aluminum alloy was processed in sequence as follows: 2-1) Refining: Control the refining temperature to 730-750℃, insert the refining device with argon gas and powder refining agent into the bottom of the furnace and move it back and forth slowly and evenly for 8-10 minutes. 2-2) Let stand: After refining, let stand for 30-40 minutes; 2-3) Slag removal: Removing the slag from the surface of the molten aluminum after refining; 2-4) Online degassing: A dual-rotor system is used, with the argon flow rate controlled at 3.2–5.5 m³ / h and the rotor speed at 350–550 r / min. After degassing, the hydrogen content in the molten aluminum is guaranteed to be ≤0.12 ml / 100 g Al. 2-5) Filtration: High-purity aluminum liquid was obtained by filtration using double-layer ceramic filter plates with pore densities of 30ppi and 40ppi. 2-6) Melting and casting: High-purity aluminum liquid is formed into primary aluminum alloy rods by using a semi-continuous water-cooled casting method (such as a semi-continuous water-cooled casting process with oil and gas lubrication).

[0025] 3) Homogenization treatment The primary aluminum alloy casting rod is homogenized by controlling the homogenization temperature at 560-580℃ and holding time at 8-10h. After the treatment, it is cooled to room temperature by water mist cooling method to obtain the homogenized aluminum alloy casting rod.

[0026] 4) Extrusion molding 4-1) Preheating treatment Aluminum alloy casting rod: The temperature of the aluminum alloy casting rod head is controlled at 470±10℃ using a gradient heating method, with a temperature gradient of -5℃ / 330mm set from the head to the tail of the casting rod. Extrusion cylinder: Temperature controlled at 430±10℃, heat preservation for 8~12h; Mold: Temperature controlled at 490±10℃, heat preservation for 6~10h.

[0027] 4-2) Extrusion The preheated aluminum alloy casting rod is placed in the preheated extrusion cylinder and extruded through the preheated die. The extrusion speed is controlled at 5-8 m / min (preferably 6-7 m / min) to ensure that the exit temperature of the extruded profile is ≥490℃ (preferably 510-530℃) to obtain a preliminary high-strength and tough 6XXX aluminum alloy profile.

[0028] 5) Online quenching treatment: The high-strength and tough 6XXX aluminum alloy profiles that have been initially formed are subjected to online air-cooled quenching treatment, and the cooling rate is controlled to be ≥1℃ / s (preferably 1.1~1.2℃ / s).

[0029] 6) Stretch straightening treatment: After the high-strength and tough 6XXX aluminum alloy profiles are cut by interruption sawing after online quenching, they are immediately subjected to stretch straightening treatment, and the stretching amount is controlled to be 0.8-1.5% (preferably 0.8-1.0%).

[0030] 7) Aging strengthening treatment: After the stretched and straightened profiles are sawed and framed, artificial aging treatment is carried out. The aging temperature is controlled at 220±5℃ and the holding time is 5.5h (preferably 5.5h), to obtain the final high-strength and tough 6XXX aluminum alloy profiles for automotive structural parts.

[0031] The high-strength and high-toughness 6XXX series aluminum alloy profiles for automotive structural parts obtained after the above treatment meet the following performance indicators: yield strength ≥200MPa, tensile strength ≥230MPa, elongation ≥10%; after a 65% full-section compression test according to GB / T 33910-2017 "Aluminum and Aluminum Alloy Extruded Profiles for Automobiles", the profile surface has regular wrinkles and no visible cracks.

[0032] Following the above method, the following are examples and comparisons: I. Components of the Examples and Comparative Examples (as shown in Table 1) Table 1 Alloy composition (mass percentage, %) of the examples and comparative examples

[0033] II. Preparation methods of the examples and comparative examples 1. Preparation methods of Examples 1-9 (1) Batching and smelting: The raw materials are precisely batched according to the mass percentage of the alloy composition in each embodiment in Table 1. After mixing the raw materials, they are put into the smelting furnace and heated to melt into a uniform liquid aluminum alloy.

[0034] (2) Casting: 2-1) Refining: Control the refining temperature to 730-750℃, introduce argon gas and powder refining agent (composition includes NaCl+KCl, etc.) into the bottom of the furnace to refine the liquid aluminum alloy. After refining for 8-10 minutes, let it stand for 30 minutes.

[0035] 2-2) Online degassing: A dual-rotor system is used, with an argon flow rate of 3.2 to 5.5 m³ / h and a rotor speed of 350 to 550 r / min. After degassing, the hydrogen content of the aluminum liquid is ≤0.12 ml / 100 gAl.

[0036] 2-3) Filtration: A 30ppi+40ppi double-layer ceramic filter plate is used for filtration. After degassing, the hydrogen content is less than or equal to 0.12ml / 100gAl.

[0037] 2-4) Melting and casting: Aluminum alloy round casting rods with a diameter of 284 mm and a length of 6 to 6.5 m are prepared by using a semi-continuous water-cooled casting method with oil and gas lubrication.

[0038] (3) Homogenization treatment: Place the casting rod into a homogenizing furnace at a temperature of 560-580℃ and keep it at that temperature for 10 hours. Then, cool it to room temperature with water mist and the cooling rate is ≥220℃ / h.

[0039] (4) Heating of individual components: 4-1) Casting rod: Gradient heating, set the head end temperature to 470±10℃, and set the temperature gradient to decrease by 5℃ every 330mm.

[0040] 4-2) Extrusion cylinder: Heat to 430±10℃ and keep warm for 8~12h.

[0041] 4-3) Mold: Heat to 480-500℃ and keep warm for 8 hours.

[0042] (5) Extrusion molding: Extrusion speed 6m / min, and control the profile exit temperature to 510~530℃.

[0043] (6) Subsequent reinforcement treatment 6-1) Online quenching: air-cooled quenching, cooling rate 1.1~1.2℃ / s.

[0044] 6-2) Stretch straightening: Stretch amount 0.8-1.0%.

[0045] 6-3) Aging enhancement: Temperature 220±5℃, heat preservation for 5.5h.

[0046] 2. Preparation methods of Comparative Examples 1-22 Except for the following differences (as shown in Table 2), the preparation methods of Comparative Examples 1-22 are the same as those of Examples 1-9: Table 2. Detailed list of process differences in the comparative examples

[0047] III. Performance Testing of Profiles Prepared in the Examples and Comparative Examples 1. Performance Testing Methods 1-1) Mechanical property testing: Perform the test according to "Metallic materials tensile testing - Part 1: Room temperature test method", and test the yield strength, tensile strength and elongation.

[0048] 1-2) Full-section compression test: Performed in accordance with GB / T 33910-2017 "Aluminum and Aluminum Alloy Extruded Profiles for Automotive Use", with a compression height of 65% of the original height. The rating criteria are as follows: 10 points: No cracks, surface has regular wrinkles (best); 6 points: Minor cracks, length ≤15mm and do not penetrate the wall thickness (basically qualified); 0 points: Obvious cracks, length > 15mm (unacceptable).

[0049] 1-3) Performance evaluation criteria: Yield strength ≥200MPa, tensile strength ≥230MPa, elongation ≥10%, and full-section compression test ≥6 points meet the requirements for use in automotive structural components.

[0050] 2. Performance Test Results Table 3 Mechanical properties and full-section compression test results of the examples and comparative examples

[0051] As shown in Table 3, in Examples 4, 8, and 5, when the Mg content decreased (compared with Examples 3, 1, and 6 respectively), the mechanical properties of the material further decreased, and the corresponding elongation also decreased accordingly. When Mg and Si were at the lower limit of the target values ​​set by this invention (as in Example 4), the mechanical properties were the lowest, only about 2 MPa higher than the target strength value (≥200 MPa). In Examples 2, 9, and 7, when the Mg content increased (compared with Examples 3, 1, and 6 respectively), the mechanical properties of the material further improved, and the corresponding elongation also increased. When Mg and Si were at the upper limit of the target values ​​within the protection range set by this invention (as in Example 7), the mechanical properties were the highest, about 45 MPa higher than the target strength value (≥200 MPa).

[0052] In Examples 4, 3, and 2, when the Si content decreased (compared to Examples 8, 1, and 9 respectively), the mechanical properties of the material decreased, while the corresponding elongation increased. In Examples 5, 6, and 7, when the Si content increased, the mechanical properties of the material also increased, while the corresponding elongation decreased slightly. In Example 5, when the Si content was at the upper limit of the target value set by this invention and the Mg content was at the lower limit, the corresponding elongation was the lowest, only 10.5%. At this point, cracks appeared in the full-section compressive performance (rating of 6 points), indicating that the full-section compressive performance of the material had reached a critical point.

[0053] When the Si content in Comparative Examples 1 and 2 further decreased and exceeded the composition range set by this invention, the mechanical properties (strength) of the profiles further decreased, and the yield strength was below 200 MPa, failing to meet the strength requirements. When the Si content in Comparative Examples 3 and 4 further increased and exceeded the composition range specified by this invention, the mechanical properties of the materials significantly increased, but local cracks or even overall cracks appeared in the full-section compressive performance, failing to meet the expected toughness requirements. When the Mg content in Comparative Examples 5 and 6 further decreased and exceeded the lower limit of the composition range set by this invention, the strength of the materials further decreased, failing to meet the expected mechanical property requirements (as in Comparative Example 5); compared to Example 5, Comparative Example 6 not only had lower strength, but also a further decrease in elongation to 9.6%, failing to meet the expected high toughness requirements of the product, and the full-section compressive performance rating of the material was 0 points, with obvious cracks appearing. Compared to Example 2, Comparative Example 7 showed an increased Mg content, but its strength decreased instead of increasing, failing to meet requirements. Although the elongation slightly improved, the overall cross-sectional compressive performance rating was 6 points, indicating that increasing Mg content resulted in a decrease in both strength and toughness. In Comparative Example 8, when the Mg content further increased compared to Example 7 and exceeded the upper limit of the composition range set by this invention, the material's strength improved, and the elongation slightly decreased, but the overall cross-sectional compressive performance did not improve; instead, it showed a certain downward trend (crack rating dropped from 10 points to 6 points).

[0054] Compared to Example 1, Comparative Examples 9 and 10 showed a decrease or increase in Cu content, respectively, resulting in a corresponding decrease or increase in the strength properties of the materials. The elongation remained the same or decreased to a certain extent, but obvious cracks appeared in the full-section compressive properties of the materials, with a crack rating of 0.

[0055] Compared to Example 1, Comparative Examples 11 and 12 showed reduced or increased Mn content, respectively. It is evident that as the Mn content increases, the material's strength gradually decreases while its elongation gradually increases. However, regardless of whether the Mn content is below or above the upper or lower limits set by this invention, the material's overall cross-sectional compressive performance did not meet the ideal requirements, resulting in a crack rating of 0. Comparative Examples 13, 14, and 15, compared to Example 1, under lower and higher homogenization temperatures, respectively, underwent tests with extended and shortened holding times. It is evident that in Comparative Example 13, at the lower homogenization temperature, even with extended holding time, the material's strength remained essentially the same as in Example 1, but its elongation significantly decreased, corresponding to an overall cross-sectional compressive performance that did not meet expectations, resulting in a rating of 0. In Comparative Examples 14 and 15, at the higher homogenization temperature, regardless of whether a short or extended holding time was used, both the material's strength and elongation showed a decreasing trend. Experiments revealed that at higher homogenization temperatures, the grain size of the cast slices became significantly coarser, and some areas even exhibited slight remelting grain boundary morphology similar to "overheating." This indicates that higher homogenization temperatures cannot achieve the expected performance of the present invention and may instead have a more negative impact.

[0056] Compared to Example 1, Comparative Example 16 showed a further reduction in quenching cooling rate to 0.7–0.8 °C / s, indicating a slight decrease in strength and a significant increase in elongation. However, the material exhibited obvious cracks after full-section compression, and its toughness did not meet expectations.

[0057] Compared to Example 1, Comparative Examples 17, 18, 19, 20, 21, and 22 had aging temperatures reduced to 210°C and increased to 230°C, respectively, and holding times shortened to 3.5 hours and extended to 6.5 hours, respectively. It is evident that at lower temperatures, material strength increases with increasing aging time, while elongation decreases. Regardless of the comparative example, even with elongation higher than Example 1, the overall cross-sectional compression performance of the product did not meet the expected standard value. At higher temperatures, with a short aging time of 3.5 hours, all mechanical properties met the requirements, but only exceeded the target value by about 1 MPa. Simultaneously, with increasing aging time, material strength decreased sharply and fell below the expected performance requirements. Although elongation increased and overall cross-sectional compression performance was satisfactory, this indicates that the product is highly sensitive to these high-temperature aging conditions, and the material is prone to rapid over-aging, resulting in strength failing to meet usage requirements.

[0058] Based on the experimental data and performance comparison analysis of the above embodiments and comparative examples, it can be seen that the high-strength and tough 6XXX aluminum alloy profiles for automotive structural parts produced by this invention achieve excellent performance: yield strength ≥200MPa. This is achieved by reasonably controlling the proportions of key components such as Si (0.38-0.45%), Mg (0.54-0.63%), Cu (0.06-0.10%), and Mn (0.06-0.10%), and strictly controlling the preparation process parameters such as homogenization treatment (560-580℃, 8-10h), quenching cooling rate (≥1℃ / s), and artificial aging (220±5℃, 5.5h). The material exhibits a tensile strength ≥230MPa and an elongation ≥10%. After a 65% full-section compression test, the surface shows regular wrinkles with no visible cracks or is basically qualified, fully meeting the requirements for high-strength and tough automotive structural components. In contrast, comparative examples with compositions exceeding the limits of this invention or process parameters deviating from the optimized range of this invention all exhibited problems such as insufficient strength, elongation meeting the standard but lacking toughness, and cracking during compression tests. This fully verifies the rationality of the composition ratio and the reliability of the process scheme of this invention, effectively achieving the high-quality preparation goal of high-strength and tough 6XXX aluminum alloy profiles for automotive structural components, and providing solid technical support for the large-scale application of this type of material.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications made to the present invention by those skilled in the art without departing from the spirit of the present invention shall fall within the protection scope of the present invention.

Claims

1. A high-strength and high-toughness 6XXX aluminum alloy for automotive structural components, characterized in that, The mass percentage of each component in the high-strength and high-toughness 6XXX aluminum alloy is as follows: Si: 0.38~0.45%; Fe: ≤0.25%; Cu: 0.06~0.10%; Mn: 0.06~0.10%; Mg: 0.54–0.63%; Cr: ≤0.05%; Zn: ≤0.05%; Ti: ≤0.10%; Single impurity: ≤0.05%; Total impurities ≤ 0.15%; balance Al.

2. The high-strength and high-toughness 6XXX aluminum alloy according to claim 1, characterized in that, The mass percentage of each component in the high-strength and high-toughness 6XXX aluminum alloy is as follows: Si: 0.38~0.42%; Fe: ≤0.15%; Cu: 0.06~0.10%; Mn: 0.06~0.08%; Mg: 0.57~0.60%; Cr: ≤0.03%; Zn≤0.03%; Ti≤0.10%; Individual impurities ≤ 0.03%; total impurities ≤ 0.10%; balance is Al.

3. The high-strength and high-toughness 6XXX aluminum alloy according to claim 1, characterized in that, After being made into profiles from high-strength and high-toughness 6XXX aluminum alloy, the profiles meet the following performance indicators: yield strength ≥200MPa, tensile strength ≥230MPa, elongation ≥10%; after being subjected to a 65% full-section compression test according to GB / T33910-2017 "Aluminum and Aluminum Alloy Extruded Profiles for Automobiles", the profile surface shows regular wrinkles and no visible cracks.

4. A method for preparing profiles using the high-strength and high-toughness 6XXX aluminum alloy as described in claim 1, characterized in that, Includes the following steps: 1) Batching and smelting The high-strength and high-toughness 6XXX aluminum alloy described in claim 1 is used to prepare the raw materials, and after mixing and melting, a liquid aluminum alloy is obtained. 2) Casting After refining, settling, slag removal, online degassing, and filtration of the liquid aluminum alloy, high-purity aluminum liquid is obtained; it is then melted and cast to obtain primary aluminum alloy ingots. 3) Homogenization treatment The primary aluminum alloy casting rod is homogenized to obtain a homogenized aluminum alloy casting rod. 4) Extrusion molding The homogenized aluminum alloy casting rod, extrusion cylinder, and die are heated separately to obtain heated aluminum alloy casting rod, extrusion cylinder, and die; the heated aluminum alloy casting rod is then placed in the heated extrusion cylinder and extruded through the heated die at an extrusion speed of 5-8 m / min, and the exit temperature of the extruded profile is controlled to be ≥490℃ to obtain high-strength and tough 6XXX aluminum alloy profile.

5. The preparation method according to claim 4, characterized in that, In step 2), the specific method of casting is as follows: a semi-continuous water-cooled casting method is used to form high-purity aluminum liquid into aluminum alloy casting rods.

6. The preparation method according to claim 4, characterized in that, In step 2), the refining process is as follows: refining temperature 730-750℃, refining time 8-10 min, and standing for 30-40 min after refining; the online degassing process is as follows: using a dual-rotor system, argon flow rate 3.2-5.5 m³ / h, rotor speed 350-550 r / min; the filtration method is as follows: using a double-layer ceramic filter plate with pore densities of 30 ppi and 40 ppi for filtration; after degassing, the hydrogen content in the aluminum liquid is ≤0.12 ml / 100 g Al.

7. The preparation method according to claim 4, characterized in that, In step 3), the homogenization process is as follows: homogenization temperature 560-580℃, heat preservation time 8-10h, and water mist mixing and cooling to room temperature.

8. The preparation method according to claim 4, characterized in that, In step 4), The heating treatment of the aluminum alloy casting rod is gradient heating: the temperature at the head end of the casting rod is controlled at 470±10℃, and a temperature gradient of -5℃ / 330mm is set from the head end to the tail end of the casting rod; the heating treatment of the extrusion cylinder is: the temperature of the extrusion cylinder is controlled at 430±10℃ and held for 8~12h; the heating treatment of the die is: the temperature of the die is controlled at 490±10℃ and held for 6~10h; the extrusion speed is 6~7m / min.

9. The preparation method according to claim 4, characterized in that, The high-strength and high-toughness 6XXX aluminum alloy profiles obtained in step 4) are further processed in the following manner: 4-1) Online quenching treatment High-strength and tough 6XXX aluminum alloy profiles are subjected to online air-cooled quenching treatment with a quenching cooling rate ≥1℃ / s; 4-2) Stretch straightening treatment The high-strength and high-toughness 6XXX aluminum alloy profiles after quenching are subjected to tensile straightening treatment with a stretching amount of 0.8-1.5%. 4-3) Time-efficiency enhancement processing High-strength and high-toughness 6XXX aluminum alloy profiles after stretching and straightening were subjected to artificial aging treatment at an aging temperature of 220±5℃ and a holding time of 5.5±0.5h to obtain high-strength and high-toughness 6XXX aluminum alloy profiles for automotive structural parts.

10. The preparation method according to claim 4, characterized in that, In step 4-1), the cooling rate of the air-cooled quenching is 1.1 to 1.2 °C / s; in step 4-2), the stretching amount of the stretching straightening treatment is 0.8 to 1.0%; in step 4-3), the holding time of the aging strengthening treatment is 5.5 h.

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