A 6 series high-strength aluminum alloy forged performance part and its preparation method and application

Abstract

The present invention relates to the technical field of aluminum alloy processing and preparation, and in particular to a 6-series high-strength aluminum alloy forged performance part, its preparation method and application. The present invention significantly improves the recrystallization temperature of the material by precisely controlling the content of elements such as Mg, Si, Cu, Fe, Mn, Cr, La, Ce, Sn, and Zn, and effectively avoids the grain growth caused by temperature and deformation during the hot forging process of traditional forgings. At the same time, by adopting a two-stage solid solution process, first a primary solid solution treatment is carried out at a low temperature to ensure that a certain amount of Mg, Si, and Cu elements are dissolved, and at the same time, the low temperature condition reduces the possibility of grain growth; then a secondary solid solution treatment is carried out to promote the dissolution of the remaining Mg and Si elements at a higher temperature in a short time. Due to the short time, the growth of surface grains to form a coarse-grained layer is avoided, thereby reducing the cost of subsequent additional CNC processing. In addition, grain refinement without a coarse-grained layer can significantly improve the fatigue performance and service life of parts.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy processing and preparation, and in particular to a 6 series high-strength aluminum alloy forged performance part and a preparation method and application thereof. Background Art

[0002] In the field of metal processing, especially in automotive manufacturing and forging, aluminum alloys are widely used due to their light weight, high strength, and excellent corrosion resistance, particularly in the manufacture of automotive chassis and other structural parts. As a typical Al-Mg-Si alloy, 6-series aluminum alloys occupy a key position in these applications due to their excellent overall performance. However, during the forging process, traditional 6-series aluminum alloys may experience grain growth due to the influence of temperature and deformation, which can reduce the material's mechanical properties and shorten its service life.

[0003] In existing technologies, the following processes are commonly used to improve the mechanical properties of aluminum alloys: Homogenization: Maintaining the alloy at high temperature for a specified period of time ensures uniform distribution of elements within the alloy. Extrusion: The homogenized aluminum alloy is extruded into the desired shape and size through an extruder. Post-forging solution hardening: The forged aluminum alloy is solution treated and quenched to eliminate internal stresses and improve its mechanical properties. Aging: This further enhances the mechanical properties of the aluminum alloy. These processes work together to optimize the performance of aluminum alloys, making them more suitable for applications in the manufacture of automotive chassis and other structural components.

[0004] However, there are still some problems with the existing technology in this field. First, it is difficult to effectively control the grain growth inside the aluminum alloy profile with the traditional homogenization process and extrusion process, which will affect the mechanical properties and service life of the material. Secondly, there are also problems with the traditional post-forging solution quenching process and aging process. For example, improper control of the time and temperature of the solution treatment and quenching may lead to the generation of internal stress in the material, thereby affecting the mechanical properties. In addition, it is also difficult to control the storage time of the product between offline solution quenching and aging treatment. Long-term storage can easily lead to a decline in material properties.

[0005] Therefore, how to improve the mechanical properties of 6 series aluminum alloy forged performance parts while reducing costs has become a major problem that needs to be solved urgently in current technology. Summary of the Invention

[0006] The purpose of the present invention is to provide a 6 series high-strength aluminum alloy forged performance part that avoids grain growth caused by temperature and deformation during hot forging, and to at least provide a beneficial option or create conditions for solving one or more technical problems existing in the prior art.

[0007] To achieve the above objectives, the present invention adopts the following technical solutions.

[0008] A method for preparing a 6-series high-strength aluminum alloy forged performance part, the specific steps of which are as follows.

[0009] 1) Raw material ratio. The raw materials include Mg, Si, Cu, Fe, Mn, Cr, La, Ce, Sn, Zn and other elements. The elements are mixed according to the following mass percentages: Mg 0.8%-1.2%, Si 0.8%-1.2%, Cu 0.20%-0.60%, Mg / Si ratio is controlled at 0.8-1.2, the sum of Mg, Si and Cu contents (Mg+Si+Cu) is controlled at 2.0%-2.6%; Fe 0.15%-0.40%, the difference between Si and Fe contents (Si-Fe) is controlled at 0.7%-1.0%; Mn 0.4%-0.7%, Cr 0.10%-0.40%, La 0.05%-0.15%, Ce 0.05%-0.15%, the sum of Mn, Cr, La and Ce contents (Mn+Cr+La+Ce) is controlled at 0.7%-1.0%; Sn 0.05%-0.15%; Zn0.20%-0.50%.

[0010] 2) Melting and Casting: The well-proportioned raw materials are placed in a melting furnace for melting at a temperature of 700-750°C to ensure that all elements are completely melted and mixed. The molten aluminum is then refined, degassed, filtered, and cast into aluminum bars.

[0011] 3) Homogenization: The cast aluminum bars undergo three-stage homogenization. Specific parameters are as follows: Level 1 homogenization temperature: 250°C-310°C, holding time: 2-8 hours; Level 2 homogenization temperature: 480°C-540°C, holding time: 6-12 hours; Level 3 homogenization temperature: 550°C-570°C, holding time: 2-8 hours. After homogenization, the aluminum bars require rapid cooling at a cooling rate ≥ 300°C / h.

[0012] 4) Extrusion: extrude the homogenized aluminum alloy material, control the extrusion ratio at 10-30, control the extrusion rod temperature at 400℃-480℃, and the extrusion speed at 4m / min-12m / min. Use water cooling after extrusion, and the surface temperature of the profile after quenching is lower than 100℃.

[0013] 5) Cooling, hot forging the extruded profile into shape and cooling it.

[0014] 6) Solution treatment: The aluminum alloy material after hot forging is subjected to a two-stage solution treatment. The specific parameters are as follows: the first-stage solution temperature is 440℃-480℃, the first-stage solution holding time is 1h-2h, the second-stage solution temperature is 550℃-570℃, the second-stage solution holding time is 0.5h-1.5h, and the heating time from the first-stage solution temperature to the second-stage solution temperature needs to be controlled within 0.5h; after the solution treatment is completed, water cooling and quenching are carried out to ensure that the aluminum alloy material is reduced to within 100℃ within 30 seconds.

[0015] 7) Aging treatment: The aluminum alloy materials after offline solution treatment and quenching are artificially aged. The parts are parked for artificial aging within 14 days after offline solution treatment and quenching. The artificial aging is a two-stage aging process. The first-stage aging temperature is 100℃-120℃, the first-stage aging holding time is 1h-3h, the second-stage aging temperature is 160℃-180℃, and the second-stage aging holding time is 4h-10h.

[0016] Through the above steps, high-performance 6 series high-strength aluminum alloy forging performance parts can be prepared. This material has a refined grain structure, excellent mechanical properties and corrosion resistance, and the preparation process is simple and easy to implement, with good industrial application prospects.

[0017] On the other hand, the present invention also provides the use of the 6 series high-strength aluminum alloy forging performance part described above in the manufacture of automobile chassis.

[0018] The present invention provides a method for preparing a 6-series high-strength aluminum alloy forged performance part. By precisely controlling the content of elements such as Mg, Si, Cu, Fe, Mn, Cr, La, Ce, Sn, and Zn, the recrystallization temperature of the material is significantly increased, effectively avoiding the grain growth caused by temperature and deformation during the hot forging process of traditional forgings. At the same time, by adopting a two-stage solid solution process, a primary solid solution treatment is first carried out at a low temperature to ensure that a certain amount of Mg, Si, and Cu elements are dissolved. At the same time, the low temperature condition reduces the possibility of grain growth. Subsequently, a secondary solid solution treatment is performed to promote the dissolution of the remaining Mg and Si elements at a higher temperature in a short time. Due to the short time, the growth of surface grains to form a coarse-grained layer is avoided, thereby reducing the cost of subsequent additional CNC processing. In addition, the grain refinement without a coarse-grained layer can significantly improve the fatigue performance and service life of the parts. In addition, by adding an appropriate amount of Zn element to adjust the potential of the alloying elements, the corrosion resistance of the material is further improved, avoiding the decrease in corrosion resistance that may be caused by the addition of Cu element. The addition of Sn reacts with the Mg element within the solid-solution aluminum alloy, occupying quenching vacancies and avoiding the effects of solute atomic supersaturation. During artificial aging, the MgSn compound rapidly decomposes, maintaining the material's final strength after aging and avoiding the performance degradation associated with traditional forgings caused by the time between offline solution treatment and artificial aging.

[0019] The present invention provides a method for preparing a 6-series high-strength aluminum alloy forged performance part, which adopts a three-stage homogenization process. By accurately controlling the homogenization temperature, holding time and rapid cooling rate after homogenization at each stage, the Fe phase transformation and element homogenization inside the aluminum alloy material are effectively controlled. In particular, the first-stage low-temperature homogenization process promotes the uniform dispersion and precipitation of Mg2Si particles inside the material. In this way, in the subsequent high-temperature homogenization process, the u phase containing Mn and Cr can nucleate and precipitate on the first precipitated Mg2Si phase, and then the u phase decomposes into dispersed α-Al (MnFe)Si particles, which greatly promotes the uniform distribution of Mn and Cr elements and accelerates the transformation rate of the Fe phase.

[0020] The present invention provides a method for preparing 6-series high-strength aluminum alloy forged performance parts. By precisely controlling the extrusion rod temperature and extrusion speed and requiring water cooling after extrusion, the surface temperature of the profile after quenching is ensured to be lower than 100°C. The grain size and distribution of the aluminum alloy material during the extrusion process are effectively controlled, grain growth is avoided, and the energy inside the grains is reduced, thereby avoiding the grain growth that is likely to occur in the subsequent forging process.

[0021] The present invention provides a method for preparing 6-series high-strength aluminum alloy forged performance parts. After optimizing the composition, it is ensured that artificial aging within 14 days after offline solution treatment and quenching will not affect the performance. The artificial aging is a two-stage aging process. The first stage of low-temperature aging activates quenching vacancies to form a pre-phase structure, and then high-temperature aging is used to quickly increase the material strength to the required level, greatly improving the hardening speed of the aging process. The aging energy consumption can be reduced by lowering the aging temperature or shortening the aging time.

[0022] Compared with the prior art, the present invention mainly solves the following technical problems: 1. It solves the problem that the traditional homogenization process and extrusion process cannot effectively control the grain growth of aluminum alloy materials, thereby affecting the mechanical properties and service life of the materials. 2. It solves the problems existing in the traditional solution quenching process and aging process after forging, such as improper control of the time and temperature of solution treatment and quenching may cause internal stress in the material, thereby affecting the mechanical properties. 3. It solves the problem of grain growth caused by temperature and deformation during hot forging of traditional forgings, which also affects the mechanical properties and service life of the material. 4. It solves the problem of performance degradation caused by changes in the parking time of traditional forgings between offline solution treatment and artificial aging treatment. 5. It solves the problem of slow hardening speed and high energy consumption of traditional forgings during the aging process. 6. It greatly improves the material performance, which helps to promote the continuous lightweight improvement of parts.

[0023] Actual production verification has shown that after offline solution-treatment and two-stage aging, the aluminum alloy material of the present invention has a tensile strength greater than 420 MPa, a yield strength greater than 390 MPa, and an elongation greater than 14%. These performance indicators are significantly superior to those of the prior art, demonstrating that the present invention has significant advantages in improving the mechanical properties of aluminum alloy materials. In summary, compared with the prior art, the present invention not only effectively solves the problems existing in the prior art, but also has higher mechanical properties and lower costs, showing significant advantages. DETAILED DESCRIPTION

[0024] The following further describes the specific embodiments of the present invention to make the technical solutions and beneficial effects of the present invention clearer and more specific. The following embodiments are exemplary and intended to explain the present invention, but are not to be construed as limiting the present invention.

[0025] Additional aspects and advantages of the invention will become apparent from the description which follows, or may be learned by practice of the invention.

[0026] A method for preparing a 6-series high-strength aluminum alloy forged performance part, the specific steps of which are as follows.

[0027] 1) Raw material ratio. The raw materials include Mg, Si, Cu, Fe, Mn, Cr, La, Ce, Sn, Zn and other elements. The elements are mixed according to the following mass percentage: Mg 0.8%-1.2%, Si 0.8%-1.2%, Cu 0.20%-0.60%, Mg / Si ratio is controlled at 0.8-1.2, Mg+Si+Cu content is controlled at 2.0%-2.6%; Fe 0.15%-0.40%, Si-Fe is controlled at 0.7%-1.0%; Mn 0.4%-0.7%, Cr 0.10%-0.40%, La 0.05%-0.15%, Ce 0.05%-0.15%, Mn+Cr+La+Ce is controlled at 0.7%-1.0%; Sn 0.05%-0.15%; Zn 0.20%-0.50%.

[0028] In this invention, the combined addition of Mn, Cr, La, and Ce significantly increases the material's recrystallization temperature, preventing the grain growth caused by temperature and deformation during the hot forging process. This innovation effectively addresses the inability of traditional homogenization and extrusion processes to effectively control grain growth in aluminum alloys, thereby improving the material's mechanical properties and service life.

[0029] In this invention, the addition of Sn reacts with Mg within the solutionized product to occupy quenching vacancies, thus avoiding the effects of solute atomic supersaturation. During artificial aging, the MgSn compound rapidly decomposes, without affecting the material's final strength after aging. This innovation effectively addresses the performance degradation problem associated with the aging period between the offline solutionization and artificial aging of conventional forgings.

[0030] In the present invention, the potential of the alloying elements is adjusted by adding a certain amount of Zn element, thereby promoting further improvement of the corrosion resistance of the material and avoiding the decrease in corrosion resistance that may be caused by the addition of Cu element.

[0031] 2) Melting and Casting: The well-proportioned raw materials are placed in a melting furnace for melting at a temperature of 700-750°C to ensure that all elements are completely melted and mixed. The molten aluminum is then refined, degassed, filtered, and cast into aluminum bars.

[0032] 3) Homogenization: The cast aluminum bars undergo three-stage homogenization. Specific parameters are as follows: Level 1 homogenization temperature: 250°C-310°C, holding time: 2-8 hours; Level 2 homogenization temperature: 480°C-540°C, holding time: 6-12 hours; Level 3 homogenization temperature: 550°C-570°C, holding time: 2-8 hours. After homogenization, the aluminum bars require rapid cooling at a cooling rate ≥ 300°C / h.

[0033] 4) Extrusion: extrude the homogenized aluminum alloy material, control the extrusion ratio at 10-30, control the extrusion rod temperature at 400℃-480℃, and the extrusion speed at 4m / min-12m / min. Use water cooling after extrusion, and the surface temperature of the profile after quenching is lower than 100℃.

[0034] 5) Cooling, hot forging the extruded profile into shape and cooling it.

[0035] 6) Solution treatment: The aluminum alloy material after hot forging is subjected to a two-stage solution treatment. The specific parameters are as follows: the first-stage solution temperature is 440℃-480℃, the first-stage solution holding time is 1h-2h, the second-stage solution temperature is 550℃-570℃, the second-stage solution holding time is 0.5h-1.5h, and the heating time from the first-stage solution temperature to the second-stage solution temperature needs to be controlled within 0.5h; after the solution treatment is completed, water cooling and quenching are carried out to ensure that the aluminum alloy material is reduced to within 100℃ within 30 seconds.

[0036] In this invention, a two-stage solution process is used. The low temperature of the first solution stage ensures a certain amount of Mg, Si, and Cu is dissolved, while the low-temperature energy prevents grain growth. The short, high-temperature second solution stage promotes the dissolution of the remaining Mg and Si. This innovation effectively avoids the problems of traditional post-forging solution quenching and aging processes, such as improper control of the time and temperature of the solution treatment and quenching, which can lead to internal stress in the material and affect mechanical properties.

[0037] 7) Aging treatment: The aluminum alloy materials after offline solution treatment and quenching are artificially aged. The parts are parked for artificial aging within 14 days after offline solution treatment and quenching. The artificial aging is a two-stage aging process. The first-stage aging temperature is 100℃-120℃, the first-stage aging holding time is 1h-3h, the second-stage aging temperature is 160℃-180℃, and the second-stage aging holding time is 4h-10h.

[0038] The present invention significantly increases the hardening speed during the aging process and can reduce aging energy consumption by lowering the aging temperature or shortening the aging time. This innovation effectively reduces the cost of improving the mechanical properties of aluminum alloy materials.

[0039] Through the above steps, high-performance 6-series high-strength aluminum alloy forging performance parts can be produced. This material has a refined grain structure, excellent mechanical properties and corrosion resistance, and the preparation process is simple and easy to implement. It has good industrial application prospects and can better meet the application requirements in automobile chassis manufacturing.

[0040] In order to better reflect the progressiveness of the present invention, the inventors also carried out 3 different embodiments and 10 comparative examples, as shown in Tables 1 to 3. Table 1 shows the raw material ratio table of the 3 embodiments and 10 comparative examples, Table 2 is a comparison table of homogenization and extrusion parameters of the 3 embodiments and 10 comparative examples, and Table 3 shows a comparison table of solid solution and aging parameters of the 3 embodiments and 10 comparative examples.

[0041] Table 1. Comparison of raw materials for 3 examples and 10 comparative examples

[0042] .

[0043] Table 2 Comparison of homogenization and extrusion process parameters of 3 embodiments and 10 comparative examples

[0044] .

[0045] Table 3. Comparison of solution and aging process parameters of 3 embodiments and 10 comparative examples

[0046] .

[0047] It should be noted that the preparation methods for the 6-series high-strength aluminum alloy forged performance parts provided in Examples 1-3 and Comparative Examples 1-10 are identical, except for the differences shown in Tables 1-3. The present invention also conducted performance testing on the 6-series high-strength aluminum alloy forged performance parts produced in Examples 1-3 and Comparative Examples 1-10, and the results are shown in Table 4.

[0048] Table 4. Product performance comparison

[0049] .

[0050] From the performance comparison of the various embodiments and comparative examples, it can be seen that the present invention effectively improves the mechanical properties of aluminum alloy materials while reducing costs by optimizing alloy composition and process parameters. Therefore, it has broad application prospects in application fields such as metal material processing, automobile manufacturing technology, and forging technology.

[0051] Performance test data from Examples 1-3 demonstrate that the 6-series aluminum alloy produced by the present invention exhibits a tensile strength greater than 420 MPa, a yield strength greater than 390 MPa, and an elongation greater than 14%. These performance indicators significantly outperform existing technologies, demonstrating the significant superiority of the present invention in improving the mechanical properties of aluminum alloys.

[0052] It can be seen from Comparative Examples 1-10 that when one or more of the alloy composition and process parameters change, one or more of the product's strength, elongation, intergranular corrosion depth, surface coarse grain layer depth after offline solution and average grain size after offline solution will be cracked. This proves that the technical effect of the present invention is the result of the synergistic effect of alloy composition optimization and process parameter improvement.

[0053] It should also be noted that the above embodiments only represent several implementation methods of the present invention. The descriptions thereof are relatively specific and detailed, but they should not be construed as limiting the scope of the invention. It should be pointed out that a person of ordinary skill in the art can make a number of variations and improvements without departing from the concept of the present invention, and these fall within the scope of protection of the present invention. Any portion not described in the specific embodiments is prior art or common knowledge.

[0054] In describing the present invention, the present invention may be more readily understood by referring to the detailed description of the preferred embodiments of the present invention and the included Examples. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as commonly understood by those of ordinary skill in the art to which the present invention belongs. In the event of a conflict, the definitions in this specification shall prevail.

[0055] As used herein, the term "prepared from" is used synonymously with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0056] In the present invention, when amount, concentration or other value or parameter is expressed as a range, preferred range or a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including a range of "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5" etc. When a numerical range is described in the present invention, unless otherwise stated, the range is intended to include its end value and all integers and fractions within the range.

[0057] In addition, the indefinite articles "a" and "an" before the elements or components of the present invention do not limit the quantity requirement (i.e., the number of times the elements or components appear). Therefore, "a" or "an" should be interpreted as including one or at least one, and elements or components in the singular also include plural forms, unless the number is obviously intended to be singular.

Claims

1. A method for preparing 6 series high-strength aluminum alloy forging performance parts, characterized in that: Here are the steps: 1) Raw material ratio: the raw materials are configured according to the following mass percentages: Mg 0.8%-1.2%, Si 0.8%-1.2%, Cu 0.20%-0.60%, the Mg / Si ratio is controlled within 0.8-1.2, and the sum of the contents of Mg, Si, and Cu is controlled within 2.0%-2.6%; Fe 0.15%-0.40%, and the difference between the contents of Si and Fe is controlled within 0.7%-1.0%; Mn 0.4%-0.7%, Cr 0.10%-0.40%, La 0.05%-0.15%, Ce 0.05%-0.15%, and the sum of the contents of Mn, Cr, La, and Ce is controlled within 0.7%-1.0%; Sn 0.05%-0.15%; Zn 0.20%-0.50%, and the balance is Al; 2) Melting and casting: placing the well-proportioned raw materials into a melting furnace for melting, and then casting the molten aluminum into aluminum bars; 3) Homogenization treatment: The cast aluminum rod is subjected to three-stage homogenization treatment. The specific parameters are as follows: the first-stage homogenization temperature is 250℃-310℃, and the first-stage homogenization holding time is 2h-8h; the second-stage homogenization temperature is 480℃-540℃, and the second-stage homogenization holding time is 6h-12h; the third-stage homogenization temperature is 550℃-570℃, and the third-stage homogenization holding time is 2h-8h; after homogenization, the aluminum rod needs to be rapidly cooled with a cooling rate ≥300℃ / h; 4) Extrusion: extrude the homogenized aluminum alloy material, control the extrusion ratio at 10-30, the extrusion rod temperature at 400℃-480℃, the extrusion speed at 4m / min-12m / min, and use water cooling after extrusion. The surface temperature of the profile after quenching is lower than 100℃. 5) Cooling, hot forging the extruded profile into shape and cooling; 6) Solution treatment: The aluminum alloy material after hot forging is subjected to a two-stage solution treatment. The specific parameters are as follows: the first-stage solution temperature is 440℃-480℃, the first-stage solution holding time is 1h-2h, the second-stage solution temperature is 550℃-570℃, the second-stage solution holding time is 0.5h-1.5h, and the heating time from the first-stage solution temperature to the second-stage solution temperature is controlled within 0.5h; after the solution treatment is completed, water cooling and quenching are carried out; 7) Aging treatment: The aluminum alloy material after offline solid solution and quenching is artificially aged. The artificial aging is a two-stage aging process. The first-stage aging temperature is 100℃-120℃, the first-stage aging holding time is 1h-3h, the second-stage aging temperature is 160℃-180℃, and the second-stage aging holding time is 4h-10h.

2. The method for preparing a 6 series high-strength aluminum alloy forging performance part according to claim 1, characterized in that: In step 1), the raw materials are prepared according to the following mass percentages: Mg 0.85%, Si 1.0%, Cu 0.42%, Fe 0.22%, Si-Fe controlled at 0.78%; Mn 0.47%, Cr 0.18%, La 0.10%, Ce 0.12%, Sn 0.08%, Zn 0.35%, and the balance is Al.

3. The method for preparing a 6 series high-strength aluminum alloy forging performance part according to claim 1, characterized in that: In step 1), the raw materials are prepared according to the following mass percentages: Mg 0.98%, Si 1.05%, Cu 0.51%, Fe 0.30%, Si-Fe controlled at 0.75%; Mn 0.42%, Cr 0.32%, La 0.12%, Ce 0.14%, Sn 0.07%, Zn 0.47%, and the balance is Al.

4. The method for preparing a 6 series high-strength aluminum alloy forging performance part according to claim 1, characterized in that: In step 2), the melting temperature is controlled at 700-750°C, and the molten aluminum is cast into aluminum rods through refining, degassing, filtration and other processes.

5. The method for preparing a 6 series high-strength aluminum alloy forging performance part according to claim 1, characterized in that: In step 7), artificial aging is performed within 14 days after the aluminum alloy material is offline solutionized and quenched.

6. A 6 series high strength aluminum alloy forging performance part, characterized in that: The forged part is made by using the method for preparing a 6 series high-strength aluminum alloy forging performance part as described in any one of claims 1 to 5.

7. Application of the 6 series high-strength aluminum alloy forging performance part as claimed in claim 6 in automobile chassis manufacturing.