6-series high-strength aluminum alloy profile with high extrudability and preparation method of 6-series high-strength aluminum alloy profile

Abstract

The invention belongs to the technical field of aluminum alloy extruded profiles, and relates to a 6-series high-strength aluminum alloy profile with high extrudability and a preparation method of the 6-series high-strength aluminum alloy profile. According to the aluminum alloy profile, the good extrudability of the aluminum alloy profile is kept by limiting the content of Mg and Li, the aluminum alloy profile can be machined into various complex shapes under the low pressure, the design possibility is widened, the production cost is greatly reduced, the production efficiency is greatly improved, and the aluminum alloy profile is particularly important for large-scale industrial production. In addition, the aluminum alloy profile further has excellent mechanical properties including excellent ductility and fatigue resistance, the stable performance under the dynamic load is ensured, and the service life of the product is prolonged. And meanwhile, the composite material also has good corrosion resistance and surface treatment performance, can effectively resist the influence of the external environment, and enhances the durability while keeping attractive appearance.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy extruded profiles, and relates to a 6-series high-strength aluminum alloy profile with high extrudability and a preparation method thereof. Background Art

[0002] Aluminum alloy materials have been regarded as "hope metals" in the engineering field for their series of excellent properties. These properties include low density, high specific strength and specific stiffness, good elasticity, excellent impact resistance, corrosion resistance, wear resistance, high electrical conductivity, thermal conductivity, easy surface coloring, good processing formability, high recycling and regeneration, energy storage and energy saving, etc. In the early days, aluminum alloys were not widely used due to the high price of aluminum and the low price of fuel. However, with the increasing prominence of energy crisis, environmental protection and traffic safety issues in recent years, coupled with the continuous reduction of aluminum alloy production costs, aluminum alloy materials have rapidly entered many industrial fields such as automobiles, aerospace, rail transportation, etc., and have become an important material to promote the development of these industries.

[0003] In particular, 6-series aluminum profiles have become one of the mainstream choices in the industrial field due to their significant advantages in lightweighting, as well as excellent recyclability, extrudability and heat treatability. In the automotive industry, the demand for lightweight body is becoming more and more urgent, and the standards are constantly improving. In order to reduce the effective load area of ​​​​parts while ensuring safe loads, and thus achieve vehicle weight reduction, the requirements for materials are getting higher and higher, especially the requirements for material strength. This trend has prompted the research and development of higher-strength aluminum alloys. However, as the strength of the material increases, its production difficulty and cost also increase significantly. Therefore, the strength of most 6xxx series aluminum profiles on the market is generally lower than 280MPa, which to a certain extent limits its scope of use in high-end applications.

[0004] Faced with this challenge, reducing the high cost and low efficiency in the mass production of ultra-high-strength 6xxx aluminum profiles has become a common concern and urgent problem to be solved within and outside the industry. Through technological innovation and process optimization, finding a more cost-effective production method will not only promote the application of 6xxx aluminum profiles in a wider range of fields, but will also play a positive role in promoting the sustainable development of the entire industry. Summary of the invention

[0005] The purpose of the present invention is to address the above problems existing in the prior art and to propose a 6-series high-strength aluminum alloy profile with high extrudability, which has good extrudability while maintaining ultra-high strength, and a yield strength of ≥360Mpa.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A 6 series high-strength aluminum alloy profile with high extrudability. The aluminum alloy extrusion profile raw material is composed of the following elements in percentage by mass: 0.60-0.90% Mg, 0.70-1.0% Si, 0.30-0.55% Cu, 0.30-0.60% Mn, 0.10-0.20% Cr, 0-0.25% Fe, 0.02-0.10% Li, and the balance is Al and other inevitable impurity elements.

[0008] In the above-mentioned 6-series high-strength aluminum alloy profile with high extrudability, the inevitable impurity elements in the aluminum alloy extruded profile are less than 0.15wt%, wherein the single impurity element is less than 0.05%.

[0009] In the above-mentioned 6-series high-strength aluminum alloy profile with high extrudability, Mg and Li must meet the following conditions:

[0010] 1.45wt%≤Mg+2.5Li+Si effective ≤1.75wt%,

[0011] Among them, Si effective =Si-0.3×(Mn+Fe+Cr).

[0012] In the above-mentioned 6 series high-strength aluminum alloy profile with high extrudability, Si effective The following conditions must be met:

[0013] 0.71≤Mg effective / Si effective ≤1.43;

[0014] Among them, Mg effective =Mg+Li.

[0015] The present invention also provides a method for preparing the above-mentioned 6-series high-strength aluminum alloy profile with high extrudability, the method comprising the following steps:

[0016] S1. Prepare raw materials;

[0017] S2, melting and casting the raw materials into aluminum bars, and then homogenizing them;

[0018] S3, then preheating the aluminum rod, and then hot extruding to obtain an extruded profile;

[0019] S4, then quenching the extruded profile and cooling it to room temperature;

[0020] S5. Finally, the extruded profile is subjected to aging treatment.

[0021] In the above-mentioned method for preparing a 6-series high-strength aluminum alloy profile with high extrudability, the homogenization treatment temperature in step S2 is 450-570° C. and the time is 8-16 hours.

[0022] In the above-mentioned method for preparing a 6-series high-strength aluminum alloy profile with high extrudability, the preheating temperature in step S3 is 500-550°C.

[0023] In the above-mentioned method for preparing a 6-series high-strength aluminum alloy profile with high extrudability, the quenching temperature in step S4 is 520-580°C.

[0024] In the above-mentioned method for preparing a 6-series high-strength aluminum alloy profile with high extrudability, the cooling rate in step S4 is ≥10°C / s.

[0025] In the above-mentioned method for preparing a 6-series high-strength aluminum alloy profile with high extrudability, the aging temperature of the aging treatment in step S5 is 165-200° C. and the time is 4-12 hours.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The aluminum alloy profiles produced by the method for preparing the highly extrudable ultra-high-strength 6-series aluminum alloy and its profiles of the present invention exhibit excellent comprehensive performance and are suitable for multiple high-tech fields. First, the yield strength of the aluminum alloy profile reaches or exceeds 360MPa, which is significantly higher than the strength of most 6-series aluminum profiles on the market. This provides a more robust material option for industries such as automobiles, aerospace, and rail transportation, and helps to achieve lightweight design of car bodies or components while ensuring structural strength, thereby improving fuel efficiency or driving range and reducing carbon emissions.

[0028] 2. The aluminum alloy profile of the present invention maintains good extrudability and can be processed into various complex shapes under relatively low pressure, which not only broadens the design possibilities but also greatly reduces production costs and improves production efficiency, which is particularly important for large-scale industrial production.

[0029] 3. The aluminum alloy profile of the present invention also has excellent mechanical properties, including excellent ductility and fatigue resistance, ensuring stable performance under dynamic loads and extending the service life of the product. At the same time, it also has good corrosion resistance and surface treatment performance, can effectively resist the influence of the external environment, maintain beauty while enhancing durability. DETAILED DESCRIPTION

[0030] The following are specific embodiments of the present invention, which further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0031] The aluminum alloy extruded profile of the present invention is composed of the following elements in percentage by mass: 0.60-0.90% Mg, 0.70-1.0% Si, 0.30-0.55% Cu, 0.30-0.60% Mn, 0.10-0.20% Cr, 0-0.25% Fe, 0.02-0.10% Li, and the balance is Al and other inevitable impurity elements, and the other inevitable impurity elements, individually: ≤0.05%, total: ≤0.15%.

[0032] In the preferred solution, the following conditions must also be met:

[0033] 0.71≤Mg effective / Si effective ≤1.43,

[0034] 1.45wt.%≤Mg+2.5Li+Si effective ≤1.75wt.%

[0035] Among them, Si effective =Si-0.3×(Mn+Fe+Cr),Mg effective =Mg+Li

[0036] Mg and Si are the main additive elements of 6 series alloys. During the aging process, they interact and precipitate to form second phase particles such as GP zone, β”, β' and β phase, strengthening the matrix. According to the latest research, the evolution of precipitation phase of Al-Mg-Si alloy during aging is as follows:

[0037] Supersaturated solid solution → GP zone → β” → β'(B', U1, U2) → β.

[0038] Among them, the β” phase has the best strengthening effect and is the most important strengthening precipitation phase in the peak aging alloy; the β' phase is the main precipitation phase in the alloy when overaging is strong, and its strengthening effect is not as good as the β” phase; the β phase is an equilibrium phase and has a non-coherent relationship with the aluminum matrix, so the strengthening effect is limited.

[0039] Table 1: Information on precipitation phases in 6 series alloys

[0040]

[0041] In the present invention, the main aging precipitation strengthening phases of the 6 series alloy are β' and β" (these two phases precipitate during the aging treatment and have a significant strengthening effect on the material, which is called aging strengthening or precipitation strengthening), wherein the Mg / Si mass ratio in the β' phase is 1.43, and the Mg / Si mass ratio in the β" phase is 0.71. Considering that the excess Mg and Si (not participating in the formation of strengthening precipitation phases) not only have a very limited contribution to the strength improvement, but also increase the difficulty of alloy production, the Mg / Si ratio in the alloy is designed to be within the range of 0.72-1.43. When the Mg / Si ratio is less than 0.72, Si is in excess, and when the Mg / Si ratio is greater than 1.43, Mg is in excess.

[0042] In the preferred embodiment of the present invention, the important parameter of Mg / Si ratio is modified according to the following two points:

[0043] 1. Since Mn, Cr, and Fe are added in the present invention, these three elements will consume a part of Si to form stubborn metal compounds. The amount of Si consumed is estimated according to 0.3*(Mn+Fe+Cr). After removing the consumed part, the remaining Si that can be used to form the aging precipitation phase is equal to the added Si minus 0.3*(Mn+Fe+Cr). effective =Si-0.3*(Mn+Fe+Cr);

[0044] 2. The present invention also adds Li element. Since Li and Mg belong to the same group of elements, they can replace a part of Mg atoms to form aging precipitation phase. Therefore, the effective Mg that can be used to form aging precipitation phase is equal to the sum of Mg and Li. Therefore, Mg is used in the preferred embodiment of the present invention. effective =Mg+Li.

[0045] The added elements Mn and Cr exist in the aluminum alloy in the form of submicron dispersed phase particles. These dispersed phase particles have the effect of hindering recrystallization. In aluminum extrusion, recrystallization often occurs on the surface of the profile to form a relatively coarse surface coarse-grained layer structure, which has a serious negative impact on the deformation cracking, corrosion, surface quality, etc. of the profile product. Therefore, adding Mn, Cr and other elements that inhibit recrystallization has a significant effect on reducing and eliminating the surface coarse-grained layer and improving product performance. In the present invention, Mn and Cr elements are mainly added. If the addition amount is too little, the ability to hinder recrystallization is insufficient, and the surface coarse-grained layer is too thick. If the addition amount is too much, the extrusion pressure is large, which is not conducive to production. The present invention stipulates Mn: 0.30~0.60%; Cr: 0.10~0.20%.

[0046] Li and Mg belong to the same group of elements. When Li is added to the 6 series alloy, it is found that: ① Li replaces part of Mg to participate in the formation of β' and β" strengthening precipitation phases; ② Li significantly refines the precipitation phases and greatly increases the number of precipitation phases, significantly improving the strength of the alloy; ③ According to practical results, within the scope of the present invention, the strengthening effect of Li is about 2.5 times that of Mg and Si, that is, only a small amount of Li is needed to achieve a significant strengthening effect, which can further reduce the degree of alloying and thus improve extrudability. When Li is less than 0.02%, its strengthening ability is not enough to meet the effect described in the present invention. When Li is greater than 0.15%, the cost is too high and the difficulty of melting and casting increases. Therefore, the present invention controls the Li component within the range of 0.02-0.15%.

[0047] Cu is also a major additive element in 6 series aluminum alloys, and it mainly plays a role in supplementary strengthening. However, excessive Cu content will deteriorate the intergranular corrosion performance of the material, while damaging the extrudability of the material and increasing quenching sensitivity. Therefore, in the present invention, Cu is controlled within a moderate range of 0.30-0.55%.

[0048] Examples 1-8 and Comparative Examples 1-3:

[0049] S1. The aluminum alloy profile compositions of Examples 1-8 and Comparative Examples 1-3 are configured as shown in Table 1;

[0050] S2. Add the prepared master alloy raw material into a smelting furnace and smelt it at 775°C to make it completely melt into liquid to form aluminum melt. After it is completely melted into liquid, keep it warm for about half an hour to remove slag and refine the aluminum melt. After the components are adjusted to the required standard, reduce the temperature of the aluminum melt to 715°C, and perform standing, slag removal and casting in sequence to obtain round cast bars, and then perform homogenization treatment at 468°C for 10 hours.

[0051] S2, then preheating the aluminum rod at 520°C, and then using a hot extrusion die to produce an extruded profile;

[0052] S3. The extruded profile is then quenched at 545°C, and then cooled to room temperature at 15°C / s. Finally, the extruded profile is aged at a temperature of 180°C for 8 hours.

[0053] Table 2: Elemental composition of aluminum alloy profiles prepared in Examples 1-8 and Comparative Examples 1-3

[0054]

[0055] Table 3: Performance test results of aluminum alloy profiles prepared in Examples 1-8 and Comparative Examples 1-3

[0056]

[0057]

[0058] The chemical compositions of Examples 1-8 are within the range required by the present invention, and the yield strength R 0.2 The tensile strength Rm and the tensile strength Rm can achieve the effect of the present invention. Further composition optimization design of Examples 5-8 is carried out by separately or jointly controlling Mg+2.5Li+Si effective Mg effective / Si effective As shown in Table 3, in addition to having high mechanical properties, Examples 5-8 also have good extrudability, as shown by the extrusion speed being maintained above 2 mm / s, which expands its applicability in complex structural profiles and improves the efficiency of industrial production.

[0059] By comparing Example 8 with Comparative Example 1, it can be seen that the addition of Li element has a significant effect on improving the strength of the alloy. Comparative Example 1 contains almost no Li, and its strength is significantly lower than that of Example 8 containing 0.09% Li. This shows that even a trace amount of Li can significantly enhance the mechanical properties of the alloy, because Li can replace part of Mg to participate in the formation of strengthening phases, while refining the precipitation phases and increasing the number of precipitation phases, thereby improving the strength of the alloy.

[0060] Since the Mg and Si contents in Comparative Examples 2 and 3 are too low, although the extrusion speed is very high, the strength is insufficient and it is difficult to meet the effect of the present invention.

[0061] In summary, a reasonable ratio of elements such as Mg, Si, and Li is crucial for preparing 6-series aluminum alloys with both high strength and good extrudability. The present invention can maintain or improve the machinability of the alloy while ensuring high strength by precisely controlling the ratio of these key elements to meet the needs of different application scenarios. These findings provide important theoretical basis and technical guidance for the development of high-performance aluminum alloy materials.

[0062] The parts of the embodiments herein that are not exhaustive of the midpoint values ​​of the technical scope claimed for protection by the present invention and the new technical solutions formed by equivalent replacement of single or multiple technical features in the technical solutions of the embodiments are also within the scope claimed for protection by the present invention; at the same time, in all the listed or unlisted embodiments of the scheme of the present invention, each parameter in the same embodiment merely represents an example of its technical solution (i.e., a feasible solution), and there is no strict coordination and limitation relationship between the parameters, wherein the parameters can be replaced with each other without violating the axioms and the claims of the present invention, unless otherwise stated.

[0063] The technical means disclosed in the scheme of the present invention are not limited to the technical means disclosed in the above technical means, but also include technical schemes composed of any combination of the above technical features. The above is a specific implementation of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also regarded as the protection scope of the present invention.

[0064] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A 6-series high-strength aluminum alloy profile with high extrudability, characterized in that: The aluminum alloy extruded profile is composed of the following elements in percentage by mass: 0.60-0.90% Mg, 0.70-1.0% Si, 0.30-0.55% Cu, 0.30-0.60% Mn, 0.10-0.20% Cr, 0-0.25% Fe, 0.02-0.10% Li, and the remainder is Al and other inevitable impurity elements.

2. According to claim 1, a 6-series high-strength aluminum alloy profile with high extrudability, characterized in that: The inevitable impurity elements in the aluminum alloy extruded profile are less than 0.15wt%, of which a single impurity element is less than 0.05%.

3. A 6-series high-strength aluminum alloy profile with high extrudability according to claim 1 or 2, characterized in that: Mg and Li must meet the following conditions: <h2 style=";text-align:left;direction:ltr">1.45wt%≤Mg+2.5Li+Si<h2 style=";text-align:left;direction:ltr"> effective <h2 style=";text-align:left;direction:ltr"> ≤1.75wt%, Among them, Si effective =Si-0.3×(Mn+Fe+Cr).

4. A 6-series high-strength aluminum alloy profile with high extrudability according to claim 3, characterized in that: Si effective The following conditions must be met: 0.71≤Mg effective / And effective ≤1.43; Among them, Mg effective =Mg+Li.

5. A method for preparing a 6-series high-strength aluminum alloy profile with high extrudability as claimed in claim 1 or 2, characterized in that: The method comprises the following steps: S1. Prepare raw materials; S2, melting and casting the raw materials into aluminum bars, and then homogenizing them; S3, then preheating the aluminum rod, and then hot extruding to obtain an extruded profile; S4, then quenching the extruded profile and cooling it to room temperature; S5. Finally, the extruded profile is subjected to aging treatment.

6. The method for preparing a 6-series high-strength aluminum alloy profile with high extrudability according to claim 5, characterized in that: The homogenization temperature in step S2 is 450-570°C and the time is 8-16h.

7. The method for preparing a 6-series high-strength aluminum alloy profile with high extrudability according to claim 5, characterized in that: The preheating temperature in step S3 is 500-550°C.

8. The method for preparing a 6-series high-strength aluminum alloy profile with high extrudability according to claim 5, characterized in that: The quenching temperature in step S4 is 520-580°C.

9. The method for preparing a 6-series high-strength aluminum alloy profile with high extrudability according to claim 5, characterized in that: The cooling rate in step S4 is ≥10°C / s.

10. The method for preparing the 6-series high-strength aluminum alloy profile with high extrudability according to claim 5, characterized in that: The aging temperature of the aging treatment in step S5 is 165-200° C. and the time is 4-12 hours.

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