Ultrahigh-strength aluminum alloy material and processing method therefor, and extrusion component

Abstract

The present application provides an ultrahigh-strength aluminum alloy material and a processing method therefor, and an extrusion component. The ultrahigh-strength aluminum alloy material, on the basis that the mass of aluminum alloy material is 100 wt.%, comprises: 0.8-1.2 wt.% of Si; 0.1-0.3 wt.% of Fe; 0.3-0.7 wt.% of Cu; 0.4-0.8 wt.% of Mn; 0.8-1.2 wt.% of Mg; 0.05-0.2 wt.% of Cr; 0.01-0.1 wt.% of Ti; 0.01-0.2 wt.% of V; and the balance of Al.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the priority to and benefits of Chinese Patent Application No. 202310532228.4, filed on May 11, 2023, the entire contents of which are incorporated herein by reference.FIELD

[0002] The present application relates to the technical field of metal materials, and more particularly to an ultra-high strength aluminum alloy material and a processing method therefor, and an extruded part.BACKGROUND

[0003] Aluminum alloy extruded profiles have been widely used in the automotive industry. However, at present, the automotive industry mainly utilizes medium-strength 6000 series aluminum profiles. The 6000 series aluminum profiles belong to an aluminum-magnesium-silicon alloy series, which have superior characteristics, such as excellent processability, superior welding characteristics and electroplating properties, good corrosion resistance, high toughness, no deformation after processing, dense and defect-free material structure, ease of polishing, ease of coloring, excellent oxidation effects, etc.

[0004] Currently, the 6000 series aluminum profiles for automobiles mainly involve alloys such as 6061 aluminum profiles, 6063 aluminum profiles and 6082 aluminum profiles. The 6061 aluminum profiles have a yield strength of not less than 240 MPa, a tensile strength of not less than 260 MPa, an elongation of not less than 7%, and a bending angle of not less than 40°. The 6063 aluminum profiles have a yield strength of not less than 170 MPa, a tensile strength of not less than 215 MPa, an elongation of not less than 6%, and a bending angle of not less than 120°. The 6082 aluminum profiles have a yield strength of not less than 250 MPa, a tensile strength of not less than 290 MPa, an elongation of not less than 6%, and a bending angle of not less than 80°. With the continuously increasing demands for automotive lightweighting, high-strength aluminum profiles used in automobiles have a yield strength of not less than 350 MPa, a tensile strength of not less than 400 MPa, an elongation of not less than 10%, and a bending angle of not less than 60°. Therefore, the properties of conventional 6000 series aluminum profiles can no longer meet the development requirements of automotive industry.

[0005] Therefore, there is an urgent need to redesign alloy composition and preparation process parameters of conventional 6000 series aluminum alloy materials to significantly improve mechanical properties and material toughness of 6000 series aluminum profiles, providing better material selection solutions for automotive lightweight design.SUMMARY

[0006] The present application is intended to solve at least one of the technical problems in the related art to some extent.

[0007] To this end, the present application provides an ultra-high strength aluminum alloy material and a processing method therefor, and an extruded part. By optimizing alloy composition and preparation process for conventional 6000 series aluminum profiles, an ultra-high strength 6000 series aluminum alloy with excellent comprehensive performance is obtained, achieving a tensile strength of 400 MPa or more while maintaining high toughness.

[0008] In order to achieve the above-mentioned objective, according to a first aspect of the present application, an ultra-high strength aluminum alloy material is provided. The aluminum alloy material includes 0.8 to 1.2 wt.% of Si, 0.1 to 0.3 wt.% of Fe, 0.3 to 0.7 wt.% of Cu, 0.4 to 0.8 wt.% of Mn, 0.8 to 1.2 wt.% of Mg, 0.05 to 0.2 wt.% of Cr, 0.01 to 0.1 wt.% of Ti, 0.01 to 0.2 wt.% of V, and a balance of Al, based on a mass of the aluminum alloy material of 100 wt.%.

[0009] In some embodiments, the aluminum alloy material includes 0.8 to 1.1 wt.% of Si, 0.1 to 0.2 wt.% of Fe, 0.3 to 0.5 wt.% of Cu, 0.4 to 0.6 wt.% of Mn, 0.8 to 1.1 wt.% of Mg, 0.1 to 0.2 wt.% of Cr, 0.05 to 0.1 wt.% of Ti, and 0.01 to 0.1 wt.% of V.

[0010] In some embodiments, the aluminum alloy material further includes inevitable impurities. A total impurity content is ≤ 0.15 wt.%, and a content of a single impurity is ≤ 0.05 wt.%.

[0011] In some embodiments, a ratio of Mg / Si in the aluminum alloy material is in a range of 0.8 to 1.5.

[0012] In some embodiments, a ratio of Mg / Si in the aluminum alloy material is in a range of 1.0 to 1.2.

[0013] According to a second aspect of the present application, a method for forming an extruded part from the aluminum alloy material according to any one of the above-mentioned embodiments is provided. The method includes preparing raw materials according to a recipe of the aluminum alloy material, and subjecting the raw materials to smelting, casting, homogenization heat treatment, extrusion shaping and aging treatment to obtain the extruded part. A metal structure of the extruded part is subjected to a strict constraint.

[0014] In some embodiments, the homogenization heat treatment is performed at a temperature of 500 to 580 °C and heat preservation for 5 to 20 h.

[0015] In some embodiments, in the extrusion shaping, hot extrusion is performed, followed by stretching and straightening of the extruded part after cooling. Process parameters for the hot extrusion are an extrusion outlet temperature of 530 to 580 °C, and an extrusion ratio of ≥ 20.

[0016] In some embodiments, process parameters for the aging treatment are heat preservation at 160 to 200 °C for 6 to 20 h, followed by air cooling to room temperature.

[0017] In some embodiments, the strict constraint on the metal structure of the extruded part is a grain morphology of the extruded part being a fibrous structure along an extrusion direction.

[0018] According to a third aspect of the present application, an extruded part formed by the method according to any one of the above-mentioned embodiments is provided.

[0019] In some embodiments, the extruded part has a yield strength of at least 350 MPa, a tensile strength of at least 400 MPa, an elongation of at least 10% and a bending angle of at least 60°.

[0020] The present application solves the problem that conventional 6000 series aluminum profiles face a difficulty in achieving both strength and toughness. On the one hand, by optimizing the composition of conventional 6000 series aluminum alloy material, the strengthening mechanism of conventional 6000 series aluminum profiles, which relies on nano-sized Mg 2 Si precipitated phases, is altered. The present application promotes the transformation of nano-sized Mg 2 Si precipitated phases into Q-phases (Mg-Si-Cu) with better strengthening effect, thus significantly improving the strength of the material. In addition, in the present application, by controlling the content of inevitable impurities, the influence of impurities on corrosion resistance and toughness of aluminum alloy is reduced, and the optimization of the strength, corrosion resistance and high toughness of aluminum alloy material is realized. On the other hand, on the basis of optimizing the composition of the aluminum alloy material, the present application improves the processing method of conventional 6000 series aluminum alloys. The relatively high extrusion temperature is utilized to dissolve alloying elements such as Mg, Si and Cu into an aluminum alloy matrix, ensuring the high strength of the extruded part formed from the aluminum alloy material. With a relatively large extrusion ratio, compounds and coarse grains formed during the casting process can be broken down, improving the toughness of the extruded part.

[0021] Additional aspects and advantages of the present application will be set forth, in part, in the following description, and in part will be apparent from the following description, or learned by practice of the present application.BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above-mentioned and / or additional aspects and advantages of the present application will be apparent and readily understood from the following description of embodiments taken in conjunction with the accompanying drawings, in which: FIG. 1 is a schematic diagram showing a method for forming an extruded part from an aluminum alloy provided in an embodiment of the present application; FIG. 2 is a schematic diagram showing a grain morphology of a metal structure of an extruded part provided in Example 1 of the present application; FIG. 3 is a schematic diagram showing a grain morphology of a metal structure of an extruded part provided in Comparative Example 1 of the present application; FIG. 4 is a schematic diagram showing a tensile test sample for a metal material provided in an embodiment of the present application. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present application more clear, the present application will be further described in detail with reference to embodiments below. Obviously, embodiments described are part of the embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those ordinarily skilled in the art belong to the scope of the protection of the present application.

[0024] The present application provides an ultra-high strength aluminum alloy material and a processing method therefor, and an extruded part. By optimizing alloy composition and preparation process for conventional 6000 series aluminum alloy profiles, an ultra-high strength 6000 series aluminum alloy with excellent comprehensive performance is obtained, achieving a tensile strength of 400 MPa or more while maintaining high toughness.

[0025] To achieve the above-mentioned objective, the present application is implemented through the following aspects: By controlling a content and a recipe of alloying elements such as Mg, Si, Cu and Mn, and strictly controlling process parameters, the density and strengthening capability of Q phase (Mg-Si-Cu) nano-sized precipitation strengthening phase within an extruded part formed from an aluminum alloy material are improved, thus significantly improving the strength of the extruded part. Through a strict control of impurity elements in the aluminum alloy material, a control of trace elements such as Mn, Cr and V, and a strict constraint on a metal structure of the extruded part, the toughness of the extruded part is improved, enabling the aluminum alloy material of the present application and the extruded part formed from the aluminum alloy material to have comprehensive performance of ultra-high strength and high toughness.

[0026] According to a first illustrative embodiment, composition of an aluminum alloy includes: 0.8 to 1.2 wt.% of Si, for example, it may be 0.8 wt.%, 0.9 wt.%, 1.0 wt.% and 1.2 wt.%, but is not limited to the listed values, and other unlisted values within this numerical range are also applicable; 0.1 to 0.3 wt.% of Fe, for example, it may be 0.1 wt.%, 0.2 wt.%, 0.25 wt.% and 0.3 wt.%, but is not limited to the listed values, and other unlisted values within this numerical range are also applicable; 0.3 to 0.7 wt.% of Cu, for example, it may be 0.3 wt.%, 0.4 wt.%, 0.5 wt.% and 0.6 wt.%, but is not limited to the listed values, and other unlisted values within this numerical range are also applicable; 0.4 to 0.8 wt.% of Mn, for example, it may be 0.4 wt.%, 0.5 wt.%, 0.6 wt.% and 0.8 wt.%, but is not limited to the listed values, and other unlisted values within this numerical range are also applicable; 0.8 to 1.2 wt.% of Mg, for example, it may be 0.8 wt.%, 0.9 wt.%, 1.0 wt.% and 1.2 wt.%, but is not limited to the listed values, and other unlisted values within this numerical range are also applicable; 0.05 to 0.2 wt.% of Cr, for example, it may be 0.05 wt.%, 0.08 wt.%, 0.1 wt.%, 0.12 wt.%, 0.15 wt.%, 0.18 wt.%, 0.2 wt.%, but is not limited to the listed values, and other unlisted values within this numerical range are also applicable; 0.01 to 0.1 wt.% of Ti, for example, it may be 0.01 wt.%, 0.04 wt.%, 0.06 wt.%, 0.08 wt.% and 0.1 wt.%, but is not limited to the listed values, and other unlisted values within this numerical range are also applicable; 0.01 to 0.2 wt.% of V, for example, it may be 0.01 wt.%, 0.04 wt.%, 0.1 wt.%, 0.15 wt.% and 0.2 wt.%, but is not limited to the listed values, and other unlisted values within this numerical range are also applicable; and a balance of Al, based on a mass of the aluminum alloy of 100 wt.%. The aluminum alloy further includes inevitable impurities, in which a total impurity content is ≤ 0.15 wt.%, and a content of a single impurity is ≤ 0.05 wt.%.

[0027] In the present application, manganese (Mn), chromium (Cr), titanium (Ti) and vanadium (V) are main trace additive elements in 6000 series aluminum alloys, primarily used to control grain size. Mn and Cr are used to optimize grain size of material in an extruded state, and Ti is mainly used to optimize grain size of aluminum alloy cast bar. Contents of Mn and Cr need to be strictly controlled, otherwise, it is easy to form a mixed structure of recrystallization and non-recrystallization in the structure, leading to a decrease in the toughness of the material. During a process of forming an extruded part from the aluminum alloy material, Mn and Cr elements can form dispersed phases such as Al 6 Mn and Al-Cr-Mn during the homogenization of the aluminum alloy cast bar. These dispersed phases control grain morphology during the extrusion of the aluminum alloy material, preventing the abnormal growth of grains and the appearance of surface coarse grain layers. However, if Mn and Cr elements are added in excess, they will combine with Fe element during the casting process to form micron-sized Al-Fe-Mn-Si compounds. These compounds not only cannot optimize the grain size, but also are likely to become crack sources during the deformation of material, thus significantly reducing the toughness of material. Therefore, the contents of Mn and Cr elements need to be limited. The content of Ti element needs to ensure that the extruded part formed from the aluminum alloy material does not crack during the casting process and that grain size of ingot meets requirements. The addition of V element has effects of refining recrystallization structures and increasing recrystallization temperature during the process of forming the extruded part from the aluminum alloy material. In the present application, controlled composition ranges for Mn, Cr, Ti and V are respectively as follows: 0.4 to 0.6 wt.% of Mn, 0.1 to 0.2 wt.% of Cr, 0.05 to 0.1wt.% of Ti, and 0.01 to 0.1wt.% of V.

[0028] According to a second illustrative embodiment, composition of an aluminum alloy includes 0.8 to 1.1 wt.% of Si, 0.1 to 0.2 wt.% of Fe, 0.3 to 0.5 wt.% of Cu, 0.4 to 0.6 wt.% of Mn, 0.8 to 1.1 wt.% of Mg, 0.1 to 0.2 wt.% of Cr, 0.05 to 0.1 wt.% of Ti, 0.01 to 0.1 wt.% of V, and a balance of Al, based on a mass of the aluminum alloy of 100 wt.%. The aluminum alloy further includes inevitable impurities, in which a total impurity content is ≤ 0.15 wt.%, and a content of a single impurity is ≤ 0.05 wt.%.

[0029] According to a third illustrative embodiment, composition of an aluminum alloy include 1 wt.% of Si, 0.1 wt.% of Fe, 0.4 wt.% of Cu, 0.6 wt.% of Mn, 1 wt.% of Mg, 0.1 wt.% of Cr, 0.02 wt.% of Ti, 0.02 wt.% of V, and a balance of Al, based on a mass of the aluminum alloy of 100 wt.%. The aluminum alloy further includes inevitable impurities, in which a total impurity content is ≤ 0.15 wt.%, and a content of a single impurity is ≤ 0.05 wt.%.

[0030] In some embodiments, a ratio of Mg / Si in the composition of aluminum alloy is in a range of 0.8 to 1.5. Optionally, a ratio of Mg / Si in the composition of aluminum alloy material is in a range of 1.0 to 1.2. Mg and Si are main strengthening elements in 6000 series aluminum alloys. The higher the Mg and Si contents, the higher the strength of the alloy. However, if the contents of Mg and Si are too high, it is easy to form a large number of coarse Mg 2 Si phases in the structure. Once these phases are formed, they cannot be eliminated by subsequent processing, thus significantly reducing the toughness of the material. Therefore, the contents of Mg and Si need to be controlled within the following ranges: 0.8 to 1.2 wt.% of Mg, and 0.8 to 1.2 wt.% of Si.

[0031] According to a second aspect of the present application, a method for forming an extruded part from the aluminum alloy according to any one of the above-mentioned embodiments is provided. The method includes preparing raw materials according to a composition recipe of the aluminum alloy, and subjecting the raw materials to smelting, casting, homogenization heat treatment, extrusion shaping and aging treatment to obtain the extruded part. A metal structure of the extruded part is subjected to a strict constraint.

[0032] The homogenization heat treatment is performed at a temperature of 500 to 580 °C and heat preservation for 5 to 20 h. Optionally, the homogenization heat treatment is performed at a temperature of 550 to 580 °C and heat preservation for 8 to 12 h. The homogenization heat treatment is also referred to as homogenizing heat treatment. In the present application, a main purpose of the homogenization heat treatment is to eliminate coarse Mg 2 Si phases formed during the casting process and to promote the transformation of elongated AlFeSi phases into rounded AlFeMnSi phases. Since a crystallization process is a non-equilibrium process and the material has a relatively high degree of alloying, other compounds such as a Cu-containing phases may form in the structure, in addition to the Mg 2 Si phases. Therefore, single-stage or multi-stage homogenization heat treatment is employed to promote the dissolution of different types or the same types of phases. In the homogenization heat treatment, both the temperature and heat preservation time (it may also be referred to as soaking time or holding time) for the homogenization heat treatment are critical. Illustrative temperatures for the homogenization heat treatment are 500 °C, 510 °C, 530 °C, 550 °C and 580 °C, but are not limited to the listed values. Other unlisted values within the range of 500 to 580 °C are also applicable. The heat preservation time is 5 h, 8 h, 10 h, 14 h, 18 h and 20 h, but are not limited to the listed values. Other unlisted values within the range of 5 to 20 h are also applicable.

[0033] In the extrusion shaping, hot extrusion is performed, followed by stretching and straightening of the extruded part after cooling. Process parameters for the hot extrusion are an extrusion outlet temperature of 530 to 580 °C, and an extrusion ratio of ≥ 20. Optionally, process parameters for the hot extrusion are an extrusion outlet temperature of 530 to 550 °C, and an extrusion ratio of ≥ 20. On the one hand, the relatively high extrusion temperature allows alloying elements such as Mg, Si and Cu to dissolve into an aluminum alloy matrix, ensuring the high strength of the aluminum alloy material. If the extrusion temperature is too low, such as below 530 °C, it cannot ensure that a sufficient amount of Mg, Si and Cu elements dissolve into the aluminum alloy matrix, resulting in a decrease in the strength of the material. If the temperature is too high, such as above 580 °C, defects such as cracking and overburning may occur during the extrusion of the aluminum alloy material to form the extruded part. On the other hand, with a relatively large extrusion ratio, such as at least 20, compounds and coarse grains formed during the casting process can be broken down, improving the toughness of the material. If the extrusion ratio is too small, such as less than 20, compounds and coarse grains formed during the casting process cannot be broken, resulting in a decrease in the toughness of the material.

[0034] In the present application, the extrusion shaping is used to improve properties of the material. A relatively high temperature needs to be maintained during the extrusion process to allow the material to have relatively high mechanical properties and excellent metal structures. Especially, during the extrusion process, it needs to dissolve Mg 2 Si particles generated during the casting process, and thus a high temperature needs to be maintained during the entire extrusion process. In addition, online quenching intensity of the material needs to be increased to ensure relatively high mechanical properties of the material in subsequent stages. The higher the quenching intensity, the greater the content of alloying elements dissolved in the matrix and the greater the vacancy concentration, resulting in improved strength and better plasticity after the subsequent aging. Therefore, in the present application, the process parameters for the extrusion shaping are the extrusion outlet temperature of 530 to 580 °C and the extrusion ratio of ≥ 20. After extrusion, water cooling or water mist cooling is applied, followed by the stretching and straightening of the extruded part.

[0035] Process parameters for the aging treatment are heat preservation at 160 to 200 °C for 6 to 20 h, followed by air cooling to room temperature. Optionally, process parameters for the aging treatment are the heat preservation at 180 to 200 °C for 10 to 20 h. In the present application, the aging treatment is the final key process to improve the strength of 6000 series aluminum alloys. Before the aging treatment, the higher the content of solute atoms and the greater the vacancy concentration in the matrix available for aging, the better the mechanical properties after aging. Aging can be single-stage or multi-stage aging. The single-stage aging is easy to produce, and the multi-stage aging is easy to improve the comprehensive performance, but it may reduce production efficiency. Therefore, single-stage aging treatment is selected in the present application, and the single-stage aging treatment is performed at a temperature of 160 to 200 °C for 6 to 20 h. For example, the temperature may be 160 °C, 170 °C, 180 °C, 190 °C, 200 °C, etc., but is not limited to the listed values, and the time may be 6 h, 7 h, 8 h, 9 h, 10 h, 14 h, 18 h, 20 h, etc., but is not limited to the listed values.

[0036] In the above structure constraint, a grain morphology of the extruded part is a fibrous structure along an extrusion direction. The strict constraint on the metal structure of the extruded part is the grain morphology of the extruded part being the fibrous structure along the extrusion direction, improving the strength and toughness of the extruded part. The strict constrain on the metal structure of extruded part is achieved through the composition of the aluminum alloy and the method for forming the extruded part.

[0037] In some embodiments, according to a third aspect of the present application, an extruded part formed by the method according to any one of the above-mentioned embodiments is provided. The extruded part has a yield strength of at least 350 MPa, a tensile strength of at least 400 MPa, an elongation of at least 10% and a bending angle of at least 60°.

[0038] The extruded part formed in this embodiment may be a part for a vehicle. Many different types of parts can be formed by an extrusion process, such as front and rear anti-collision beam parts, body-in-white parts, suspension parts or chassis parts. After the extrusion process, the method may include an optional heat treatment process or other finishing processes.Example 1

[0039] An ultra-high strength aluminum alloy was provided. Composition of the aluminum alloy includes 0.8 wt.% of Si, 0.1 wt.% of Fe, 0.4 wt.% of Cu, 0.6 wt.% of Mn, 1.2 wt.% of Mg, 0.1 wt.% of Cr, 0.02 wt.% of Ti, 0.01 wt.% of V, and a balance of Al and inevitable impurities, based on a mass of the aluminum alloy of 100 wt.%.

[0040] A processing method is shown in FIG. 1. Raw materials were prepared according to a composition recipe of the aluminum alloy, and the raw materials were subjected to melting and casting to obtain a round aluminum bar. The aluminum bar was subjected to homogenization heat treatment, and the homogenization heat treatment was performed at a temperature of 550 °C for 12 h. The aluminum bar was subjected to extrusion after preheating, and process parameters for the extrusion were an extrusion ratio of 20 and an extrusion outlet temperature of 530 °C. After extrusion, water cooling was applied. An extruded part was subjected to stretching and straightening, followed by artificial aging treatment. Process parameters for the aging treatment were a temperature of 180 °C and a time of 10 h. A metal structure of the extruded part was subjected to a strict constraint. A grain morphology of the extruded part was a fibrous structure along an extrusion direction, improving strength and toughness of the extruded part. The grain morphology of the metal structure of the extruded part in this example is shown in FIG. 2. In Comparative Example 1, a metal structure of an extruded part was not subjected to a strict constraint, and a grain morphology of the metal structure of the extruded part is shown in FIG. 3.

[0041] For Examples 2 to 20 and Comparative Examples 1 to 18, mass percentage contents of Si, Cu, Mg, Mn, Cr and Ti in aluminum alloy compositions and process parameters were adjusted according to Table 1, and other technical features were the same as those in Example 1. Metal structures of extruded parts of Examples 2 to 20 were also subjected to a strict constraint, that is, grain morphologies of the extruded parts were fibrous structures along an extrusion direction. Metal structure of extruded parts of Comparative Examples 2 to 18, like Comparative Example 1, were not subjected to a strict constraint. Automotive anti-intrusion beams were prepared according to the aluminum alloy compositions and processing methods provided in individual Examples and Comparative Examples. Specimens taken from the cross-section of automotive anti-intrusion beam as shown in FIG. 4 were tested for mechanical properties including yield strength, tensile strength and elongation in accordance with the ASTM E8 / E8M-21 test method (Standard Test Methods for Tension Testing of Metallic Materials). A bending angle was tested according to VDA-238 standard. The test results are also shown in Table 1 below. Table 1. Aluminum alloy material compositions, processing methods and mechanical properties test results of extruded partsChemical Composition (wt.%)Preparation ProcessMechanical PropertiesSiCuMgMnCrTiMg / Si ratioHomogeni -zation heat treatmentExtrusion Temperature (°C)Cooling MethodAging TreatmentYield Strength (MPa)Tensile Strength (MPa)Elongation (%)Bending Angle (°)JudgmentExample 10.80.41.20.60.10.021.5550°C / 12h530Water Cooling180°C / 10h3504001370QualifiedExample 210.410.60.10.021.0550°C / 12h530Water Cooling180°C / 10h3604051365QualifiedExample 31.20.410.60.10.020.8550°C / 12h530Water Cooling180°C / 10h3654101161QualifiedComparative Example 10.70.410.60.10.021.4550°C / 12h530Water Cooling180°C / 10h3203701470UnqualifiedComparative Example 21.30.410.60.10.020.8550°C / 12h530Water Cooling180°C / 10h3704151040UnqualifiedExample 410.310.60.10.021.0550°C / 12h530Water Cooling180°C / 10h3504011268QualifiedExample 510.510.60.10.021.0550°C / 12h530Water Cooling180°C / 10h3654101064QualifiedExample 610.710.60.10.021.0550°C / 12h530Water Cooling180°C / 10h3704181062QualifiedComparative Example 310.210.60.10.021.0550°C / 12h530Water Cooling180°C / 10h3403801470UnqualifiedComparative Example 410.810.60.10.021.0550°C / 12h530Water Cooling180°C / 10h380430845UnqualifiedExample 710.40.80.60.10.020.8550°C / 12h530Water Cooling180°C / 10h3554031367QualifiedExample 810.41.20.60.10.021.2550°C / 12h530Water Cooling180°C / 10h3754161062QualifiedComparative Example 510.40.70.60.10.020.7550°C / 12h530Water Cooling180°C / 10h3453901470UnqualifiedComparative Example 610.41.30.60.10.021.3550°C / 12h530Water Cooling180°C / 10h380420955UnqualifiedExample 910.410.40.10.021.0550°C / 12h530Water Cooling180°C / 10h3584031360QualifiedExample 1010.410.80.10.021.0550°C / 12h530Water Cooling180°C / 10h3634081368QualifiedComparative Example 710.410.30.10.021.0550°C / 12h530Water Cooling180°C / 10h3503951255UnqualifiedComparative Example 810.410.90.10.021.0550°C / 12h530Water Cooling180°C / 10h365410750UnqualifiedExample 1110.410.60.050.021.0550°C / 12h530Water Cooling180°C / 10h3584051363QualifiedExample 1210.410.60.20.021.0550°C / 12h530Water Cooling180°C / 10h3634081368QualifiedComparative Example 910.410.60.020.021.0550°C / 12h530Water Cooling180°C / 10h3554001050UnqualifiedComparative10.410.60.30.021.0550°C / 12h530Water180°C / 10h365410845UnqualifiedExample 10CoolingExample 1310.410.60.20.011.0550°C / 12h530Water Cooling180°C / 10h3554011262QualifiedExample 1410.410.60.20.11.0550°C / 12h530Water Cooling180°C / 10h3654101368QualifiedComparative Example 1110.410.60.20.0051.0550°C / 12h530Water Cooling180°C / 10h335395950UnqualifiedComparative Example 1210.410.60.20.21.0550°C / 12h530Water Cooling180°C / 10h368410855UnqualifiedExample 1510.410.60.10.021.0500°C / 12h530Water Cooling180°C / 10h3504001061QualifiedExample 1610.410.60.10.021.0580°C / 12h530Water Cooling180°C / 10h3654201062QualifiedComparative Example 1310.410.60.10.021.0490°C / 12h520Water Cooling180°C / 10h330390950UnqualifiedComparative Example 1410.410.60.10.021.0590°C / 12h530Water Cooling180°C / 10h360395640UnqualifiedExample 1710.410.60.10.021.0550°C / 12h550Water Cooling180°C / 10h3654101365QualifiedExample 1810.410.60.10.021.0550°C / 12h580Water Cooling180°C / 10h3704151368QualifiedComparative Example 1510.410.60.10.021.0550°C / 12h520Water Cooling180°C / 10h3303701355UnqualifiedComparative Example 1610.410.60.10.021.0550°C / 12h590Water Cooling180°C / 10h / / / / Un-extrudableExample 1910.410.60.10.021.0550°C / 12h530Water Cooling160°C / 20h3554051365QualifiedExample 2010.410.60.10.021.0550°C / 12h530Water Cooling200°C / 6h3604081262QualifiedComparative Example 1710.410.60.10.021.0550°C / 12h530Water Cooling150°C / 20h3403901468UnqualifiedComparative Example 1810.410.60.10.021.0550°C / 12h530Water Cooling210°C / 6h3303701470Unqualified

[0042] From the data in Table 1, it can be seen that by comparing Examples 1 to 20 with Comparative Examples 1 to 18, the following results can be found.

[0043] From the comparison between Example 1 to 3 and Comparative Example 1 to 2, it can be seen that when the Si content is relatively low, the amount of strengthening phases in the extruded part decreases, causing the strength of the extruded part to fail to meet the requirement of tensile strength of at least 400 MPa in the present application. When the Si content is relatively high, excess Si may precipitate within the extruded part in a form of elemental Si, reducing the bending angle of the extruded part, and causing the toughness of the extruded part to fail to meet the requirement of at least 350 MPa in the present application.

[0044] From the comparison between Example 4 to 6 and Comparative Example 3 to 4, it can be seen that, similar to Si, when the Cu content is relatively low, the amount of strengthening phases in the extruded part decreases, causing the strength of the extruded part to fail to meet the requirements of the present application. However, when the Cu content is relatively high, excess Cu may improve the strength of the material, but reduce the elongation and bending angle of the extruded part, causing the toughness of the extruded part to fail to meet the requirements of the present application.

[0045] From the comparison of Examples 7 to 8 and Comparative Examples 5 to 6, it can be seen that when the Mg content is relatively low, the amount of strengthening phases in the extruded part decreases, causing the strength of the extruded part to fail to meet the requirements of the present application. However, when the Mg content is relatively high, excess Mg may improve the strength of the material, but reduce the elongation and bending angle of the extruded part, causing the toughness of the extruded part to fail to meet the requirements of the present application.

[0046] From the comparison of Examples 9 to 10 and Comparative Examples 7 to 8, it can be seen that when the Mn content is relatively low, the amount of dispersed phases in the extruded part decreases, leading to poor control of the fibrous structure and a consequent decrease in the bending angle of the extruded part, which does not meet the requirements of the present application. However, when the Mn content is relatively high, excess Mm leads to the formation of coarse Al-Fe-Mn phases during the casting process, which cannot be fully broken down during the extrusion process, which not only decreases the bending angle of the extruded part, but also decreases the elongation of the extruded part, causing the toughness of the extruded part to fail to meet the requirements of the present application.

[0047] From the comparison of Examples 11 to 12 and Comparative Examples 9 to 10, it can be seen that similar to Mn, Cr forms dispersed phases to control the metal structure. When the Cr content is relatively low, the amount of dispersed phases in the extruded part decreases, leading to poor control of the fibrous structure and a consequent decrease in the bending angle of the extruded part, which does not meet the requirements of the present application. However, when the Cr content is relatively high, excess Cr leads to the formation of coarse Al-Fe-Cr phases during the casting process, which cannot be fully broken down during the extrusion process, which not only decreases the bending angle of the extruded part, but also decreases the elongation of the extruded part, causing the toughness of the extruded part to fail to meet the requirements of the present application.

[0048] From the comparison between Examples 13 to 14 and Comparative Examples 11 to 12, it can be seen that when the Ti content is relatively low, it may lead to coarse ingot grain size and coarse grain boundary compounds such as Mg 2 Si phases and Al-Fe-Mn-Si, causing the strength and bending angle of the extruded part to decrease and fail to meet the requirements of the present application. However, when the Ti content is relatively high, excess Ti may lead to solid solution strengthening and improve the strength of extruded part, but it may also cause a decrease in the elongation and bending angle of extruded part, causing the toughness to fail to meet the requirements of the present application.

[0049] From the comparison between Example 15 to 16 and Comparative Example 13 to 14, it can be seen that when the homogenization heat treatment temperature is relatively low, it may lead to incomplete homogenization of aluminum bars (incomplete dissolution of Mg 2 Si, and incomplete transformation of elongated Al-Fe-Si compounds into rounded Al-Fe-Mn-Si phases), which not only decreases the strength of the extruded part, but also decreases the elongation and bending angle of the extruded part, resulting in failure to meet the requirements of the present application. When the homogenization heat treatment temperature is relatively high, it may lead to overburning of aluminum bars, which may decrease the elongation and bending angle of extruded part, causing the toughness of extruded part to fail to meet the requirements of the present application.

[0050] From the comparison between Examples 17 to 18 and Comparative Examples 15 to 16, it can be seen that when the extrusion outlet temperature for the extruded part is relatively low, it may lead to incomplete dissolution of Mg 2 Si into the extruded part during the extrusion process, decreasing the bending angle of the extruded part and failing to meet the requirements of the present application. When the extrusion outlet temperature is relatively high, it may cause the extruded part to be difficult to weld at an outlet of an extrusion die and cannot be extruded normally.

[0051] From the comparison between Examples 19 to 20 and Comparative Examples 17 to 18, it can be seen that when the artificial aging treatment temperature for the extruded part is relatively low, it may lead to insufficient density of precipitated phases during the artificial aging treatment, and the extruded part is in an under-aged state, thus decreasing the strength of the extruded part, resulting in failure to meet the requirements of the present application. When the artificial aging treatment temperature is relatively high, it may lead to the growth of precipitated phases and the loss of semi-coherent relationship with aluminum matrix during the artificial aging treatment, and the extruded part is in an under-aged state, which may decrease the strength of the extruded part, resulting in failure to meet the requirements of the present application.

[0052] Reference throughout the description of the present application to "an embodiment," "some embodiments," "an example," "a specific example," or "some examples," means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. The schematic expressions of the above-mentioned terms throughout this specification are not necessarily referring to the same embodiment or example. Moreover, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0053] Although the embodiments of the present application have been shown and described above, it is to be understood that the above embodiments are illustrative and cannot be construed as limiting the present application, and those skilled in the art may make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Examples

example 1

[0039]An ultra-high strength aluminum alloy was provided. Composition of the aluminum alloy includes 0.8 wt.% of Si, 0.1 wt.% of Fe, 0.4 wt.% of Cu, 0.6 wt.% of Mn, 1.2 wt.% of Mg, 0.1 wt.% of Cr, 0.02 wt.% of Ti, 0.01 wt.% of V, and a balance of Al and inevitable impurities, based on a mass of the aluminum alloy of 100 wt.%.

[0040]A processing method is shown in FIG. 1. Raw materials were prepared according to a composition recipe of the aluminum alloy, and the raw materials were subjected to melting and casting to obtain a round aluminum bar. The aluminum bar was subjected to homogenization heat treatment, and the homogenization heat treatment was performed at a temperature of 550 °C for 12 h. The aluminum bar was subjected to extrusion after preheating, and process parameters for the extrusion were an extrusion ratio of 20 and an extrusion outlet temperature of 530 °C. After extrusion, water cooling was applied. An extruded part was subjected to stretching and straightening, follo...

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the priority to and benefits of Chinese Patent Application No. 202310532228.4, filed on May 11, 2023, the entire contents of which are incorporated herein by reference.FIELD

[0002] The present application relates to the technical field of metal materials, and more particularly to an ultra-high strength aluminum alloy material and a processing method therefor, and an extruded part.BACKGROUND

[0003] Aluminum alloy extruded profiles have been widely used in the automotive industry. However, at present, the automotive industry mainly utilizes medium-strength 6000 series aluminum profiles. The 6000 series aluminum profiles belong to an aluminum-magnesium-silicon alloy series, which have superior characteristics, such as excellent processability, superior welding characteristics and electroplating properties, good corrosion resistance, high toughness, no deformation after processing, dense and defect-free material structure, ease of polishing, ease of coloring, excellent oxidation effects, etc.

[0004] Currently, the 6000 series aluminum profiles for automobiles mainly involve alloys such as 6061 aluminum profiles, 6063 aluminum profiles and 6082 aluminum profiles. The 6061 aluminum profiles have a yield strength of not less than 240 MPa, a tensile strength of not less than 260 MPa, an elongation of not less than 7%, and a bending angle of not less than 40°. The 6063 aluminum profiles have a yield strength of not less than 170 MPa, a tensile strength of not less than 215 MPa, an elongation of not less than 6%, and a bending angle of not less than 120°. The 6082 aluminum profiles have a yield strength of not less than 250 MPa, a tensile strength of not less than 290 MPa, an elongation of not less than 6%, and a bending angle of not less than 80°. With the continuously increasing demands for automotive lightweighting, high-strength aluminum profiles used in automobiles have a yield strength of not less than 350 MPa, a tensile strength of not less than 400 MPa, an elongation of not less than 10%, and a bending angle of not less than 60°. Therefore, the properties of conventional 6000 series aluminum profiles can no longer meet the development requirements of automotive industry.

[0005] Therefore, there is an urgent need to redesign alloy composition and preparation process parameters of conventional 6000 series aluminum alloy materials to significantly improve mechanical properties and material toughness of 6000 series aluminum profiles, providing better material selection solutions for automotive lightweight design.SUMMARY

[0006] The present application is intended to solve at least one of the technical problems in the related art to some extent.

[0007] To this end, the present application provides an ultra-high strength aluminum alloy material and a processing method therefor, and an extruded part. By optimizing alloy composition and preparation process for conventional 6000 series aluminum profiles, an ultra-high strength 6000 series aluminum alloy with excellent comprehensive performance is obtained, achieving a tensile strength of 400 MPa or more while maintaining high toughness.

[0008] In order to achieve the above-mentioned objective, according to a first aspect of the present application, an ultra-high strength aluminum alloy material is provided. The aluminum alloy material includes 0.8 to 1.2 wt.% of Si, 0.1 to 0.3 wt.% of Fe, 0.3 to 0.7 wt.% of Cu, 0.4 to 0.8 wt.% of Mn, 0.8 to 1.2 wt.% of Mg, 0.05 to 0.2 wt.% of Cr, 0.01 to 0.1 wt.% of Ti, 0.01 to 0.2 wt.% of V, and a balance of Al, based on a mass of the aluminum alloy material of 100 wt.%.

[0009] In some embodiments, the aluminum alloy material includes 0.8 to 1.1 wt.% of Si, 0.1 to 0.2 wt.% of Fe, 0.3 to 0.5 wt.% of Cu, 0.4 to 0.6 wt.% of Mn, 0.8 to 1.1 wt.% of Mg, 0.1 to 0.2 wt.% of Cr, 0.05 to 0.1 wt.% of Ti, and 0.01 to 0.1 wt.% of V.

[0010] In some embodiments, the aluminum alloy material further includes inevitable impurities. A total impurity content is ≤ 0.15 wt.%, and a content of a single impurity is ≤ 0.05 wt.%.

[0011] In some embodiments, a ratio of Mg / Si in the aluminum alloy material is in a range of 0.8 to 1.5.

[0012] In some embodiments, a ratio of Mg / Si in the aluminum alloy material is in a range of 1.0 to 1.2.

[0013] According to a second aspect of the present application, a method for forming an extruded part from the aluminum alloy material according to any one of the above-mentioned embodiments is provided. The method includes preparing raw materials according to a recipe of the aluminum alloy material, and subjecting the raw materials to smelting, casting, homogenization heat treatment, extrusion shaping and aging treatment to obtain the extruded part. A metal structure of the extruded part is subjected to a strict constraint.

[0014] In some embodiments, the homogenization heat treatment is performed at a temperature of 500 to 580 °C and heat preservation for 5 to 20 h.

[0015] In some embodiments, in the extrusion shaping, hot extrusion is performed, followed by stretching and straightening of the extruded part after cooling. Process parameters for the hot extrusion are an extrusion outlet temperature of 530 to 580 °C, and an extrusion ratio of ≥ 20.

[0016] In some embodiments, process parameters for the aging treatment are heat preservation at 160 to 200 °C for 6 to 20 h, followed by air cooling to room temperature.

[0017] In some embodiments, the strict constraint on the metal structure of the extruded part is a grain morphology of the extruded part being a fibrous structure along an extrusion direction.

[0018] According to a third aspect of the present application, an extruded part formed by the method according to any one of the above-mentioned embodiments is provided.

[0019] In some embodiments, the extruded part has a yield strength of at least 350 MPa, a tensile strength of at least 400 MPa, an elongation of at least 10% and a bending angle of at least 60°.

[0020] The present application solves the problem that conventional 6000 series aluminum profiles face a difficulty in achieving both strength and toughness. On the one hand, by optimizing the composition of conventional 6000 series aluminum alloy material, the strengthening mechanism of conventional 6000 series aluminum profiles, which relies on nano-sized Mg 2 Si precipitated phases, is altered. The present application promotes the transformation of nano-sized Mg 2 Si precipitated phases into Q-phases (Mg-Si-Cu) with better strengthening effect, thus significantly improving the strength of the material. In addition, in the present application, by controlling the content of inevitable impurities, the influence of impurities on corrosion resistance and toughness of aluminum alloy is reduced, and the optimization of the strength, corrosion resistance and high toughness of aluminum alloy material is realized. On the other hand, on the basis of optimizing the composition of the aluminum alloy material, the present application improves the processing method of conventional 6000 series aluminum alloys. The relatively high extrusion temperature is utilized to dissolve alloying elements such as Mg, Si and Cu into an aluminum alloy matrix, ensuring the high strength of the extruded part formed from the aluminum alloy material. With a relatively large extrusion ratio, compounds and coarse grains formed during the casting process can be broken down, improving the toughness of the extruded part.

[0021] Additional aspects and advantages of the present application will be set forth, in part, in the following description, and in part will be apparent from the following description, or learned by practice of the present application.BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above-mentioned and / or additional aspects and advantages of the present application will be apparent and readily understood from the following description of embodiments taken in conjunction with the accompanying drawings, in which: FIG. 1 is a schematic diagram showing a method for forming an extruded part from an aluminum alloy provided in an embodiment of the present application; FIG. 2 is a schematic diagram showing a grain morphology of a metal structure of an extruded part provided in Example 1 of the present application; FIG. 3 is a schematic diagram showing a grain morphology of a metal structure of an extruded part provided in Comparative Example 1 of the present application; FIG. 4 is a schematic diagram showing a tensile test sample for a metal material provided in an embodiment of the present application. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present application more clear, the present application will be further described in detail with reference to embodiments below. Obviously, embodiments described are part of the embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those ordinarily skilled in the art belong to the scope of the protection of the present application.

[0024] The present application provides an ultra-high strength aluminum alloy material and a processing method therefor, and an extruded part. By optimizing alloy composition and preparation process for conventional 6000 series aluminum alloy profiles, an ultra-high strength 6000 series aluminum alloy with excellent comprehensive performance is obtained, achieving a tensile strength of 400 MPa or more while maintaining high toughness.

[0025] To achieve the above-mentioned objective, the present application is implemented through the following aspects: By controlling a content and a recipe of alloying elements such as Mg, Si, Cu and Mn, and strictly controlling process parameters, the density and strengthening capability of Q phase (Mg-Si-Cu) nano-sized precipitation strengthening phase within an extruded part formed from an aluminum alloy material are improved, thus significantly improving the strength of the extruded part. Through a strict control of impurity elements in the aluminum alloy material, a control of trace elements such as Mn, Cr and V, and a strict constraint on a metal structure of the extruded part, the toughness of the extruded part is improved, enabling the aluminum alloy material of the present application and the extruded part formed from the aluminum alloy material to have comprehensive performance of ultra-high strength and high toughness.

[0026] According to a first illustrative embodiment, composition of an aluminum alloy includes: 0.8 to 1.2 wt.% of Si, for example, it may be 0.8 wt.%, 0.9 wt.%, 1.0 wt.% and 1.2 wt.%, but is not limited to the listed values, and other unlisted values within this numerical range are also applicable; 0.1 to 0.3 wt.% of Fe, for example, it may be 0.1 wt.%, 0.2 wt.%, 0.25 wt.% and 0.3 wt.%, but is not limited to the listed values, and other unlisted values within this numerical range are also applicable; 0.3 to 0.7 wt.% of Cu, for example, it may be 0.3 wt.%, 0.4 wt.%, 0.5 wt.% and 0.6 wt.%, but is not limited to the listed values, and other unlisted values within this numerical range are also applicable; 0.4 to 0.8 wt.% of Mn, for example, it may be 0.4 wt.%, 0.5 wt.%, 0.6 wt.% and 0.8 wt.%, but is not limited to the listed values, and other unlisted values within this numerical range are also applicable; 0.8 to 1.2 wt.% of Mg, for example, it may be 0.8 wt.%, 0.9 wt.%, 1.0 wt.% and 1.2 wt.%, but is not limited to the listed values, and other unlisted values within this numerical range are also applicable; 0.05 to 0.2 wt.% of Cr, for example, it may be 0.05 wt.%, 0.08 wt.%, 0.1 wt.%, 0.12 wt.%, 0.15 wt.%, 0.18 wt.%, 0.2 wt.%, but is not limited to the listed values, and other unlisted values within this numerical range are also applicable; 0.01 to 0.1 wt.% of Ti, for example, it may be 0.01 wt.%, 0.04 wt.%, 0.06 wt.%, 0.08 wt.% and 0.1 wt.%, but is not limited to the listed values, and other unlisted values within this numerical range are also applicable; 0.01 to 0.2 wt.% of V, for example, it may be 0.01 wt.%, 0.04 wt.%, 0.1 wt.%, 0.15 wt.% and 0.2 wt.%, but is not limited to the listed values, and other unlisted values within this numerical range are also applicable; and a balance of Al, based on a mass of the aluminum alloy of 100 wt.%. The aluminum alloy further includes inevitable impurities, in which a total impurity content is ≤ 0.15 wt.%, and a content of a single impurity is ≤ 0.05 wt.%.

[0027] In the present application, manganese (Mn), chromium (Cr), titanium (Ti) and vanadium (V) are main trace additive elements in 6000 series aluminum alloys, primarily used to control grain size. Mn and Cr are used to optimize grain size of material in an extruded state, and Ti is mainly used to optimize grain size of aluminum alloy cast bar. Contents of Mn and Cr need to be strictly controlled, otherwise, it is easy to form a mixed structure of recrystallization and non-recrystallization in the structure, leading to a decrease in the toughness of the material. During a process of forming an extruded part from the aluminum alloy material, Mn and Cr elements can form dispersed phases such as Al 6 Mn and Al-Cr-Mn during the homogenization of the aluminum alloy cast bar. These dispersed phases control grain morphology during the extrusion of the aluminum alloy material, preventing the abnormal growth of grains and the appearance of surface coarse grain layers. However, if Mn and Cr elements are added in excess, they will combine with Fe element during the casting process to form micron-sized Al-Fe-Mn-Si compounds. These compounds not only cannot optimize the grain size, but also are likely to become crack sources during the deformation of material, thus significantly reducing the toughness of material. Therefore, the contents of Mn and Cr elements need to be limited. The content of Ti element needs to ensure that the extruded part formed from the aluminum alloy material does not crack during the casting process and that grain size of ingot meets requirements. The addition of V element has effects of refining recrystallization structures and increasing recrystallization temperature during the process of forming the extruded part from the aluminum alloy material. In the present application, controlled composition ranges for Mn, Cr, Ti and V are respectively as follows: 0.4 to 0.6 wt.% of Mn, 0.1 to 0.2 wt.% of Cr, 0.05 to 0.1wt.% of Ti, and 0.01 to 0.1wt.% of V.

[0028] According to a second illustrative embodiment, composition of an aluminum alloy includes 0.8 to 1.1 wt.% of Si, 0.1 to 0.2 wt.% of Fe, 0.3 to 0.5 wt.% of Cu, 0.4 to 0.6 wt.% of Mn, 0.8 to 1.1 wt.% of Mg, 0.1 to 0.2 wt.% of Cr, 0.05 to 0.1 wt.% of Ti, 0.01 to 0.1 wt.% of V, and a balance of Al, based on a mass of the aluminum alloy of 100 wt.%. The aluminum alloy further includes inevitable impurities, in which a total impurity content is ≤ 0.15 wt.%, and a content of a single impurity is ≤ 0.05 wt.%.

[0029] According to a third illustrative embodiment, composition of an aluminum alloy include 1 wt.% of Si, 0.1 wt.% of Fe, 0.4 wt.% of Cu, 0.6 wt.% of Mn, 1 wt.% of Mg, 0.1 wt.% of Cr, 0.02 wt.% of Ti, 0.02 wt.% of V, and a balance of Al, based on a mass of the aluminum alloy of 100 wt.%. The aluminum alloy further includes inevitable impurities, in which a total impurity content is ≤ 0.15 wt.%, and a content of a single impurity is ≤ 0.05 wt.%.

[0030] In some embodiments, a ratio of Mg / Si in the composition of aluminum alloy is in a range of 0.8 to 1.5. Optionally, a ratio of Mg / Si in the composition of aluminum alloy material is in a range of 1.0 to 1.2. Mg and Si are main strengthening elements in 6000 series aluminum alloys. The higher the Mg and Si contents, the higher the strength of the alloy. However, if the contents of Mg and Si are too high, it is easy to form a large number of coarse Mg 2 Si phases in the structure. Once these phases are formed, they cannot be eliminated by subsequent processing, thus significantly reducing the toughness of the material. Therefore, the contents of Mg and Si need to be controlled within the following ranges: 0.8 to 1.2 wt.% of Mg, and 0.8 to 1.2 wt.% of Si.

[0031] According to a second aspect of the present application, a method for forming an extruded part from the aluminum alloy according to any one of the above-mentioned embodiments is provided. The method includes preparing raw materials according to a composition recipe of the aluminum alloy, and subjecting the raw materials to smelting, casting, homogenization heat treatment, extrusion shaping and aging treatment to obtain the extruded part. A metal structure of the extruded part is subjected to a strict constraint.

[0032] The homogenization heat treatment is performed at a temperature of 500 to 580 °C and heat preservation for 5 to 20 h. Optionally, the homogenization heat treatment is performed at a temperature of 550 to 580 °C and heat preservation for 8 to 12 h. The homogenization heat treatment is also referred to as homogenizing heat treatment. In the present application, a main purpose of the homogenization heat treatment is to eliminate coarse Mg 2 Si phases formed during the casting process and to promote the transformation of elongated AlFeSi phases into rounded AlFeMnSi phases. Since a crystallization process is a non-equilibrium process and the material has a relatively high degree of alloying, other compounds such as a Cu-containing phases may form in the structure, in addition to the Mg 2 Si phases. Therefore, single-stage or multi-stage homogenization heat treatment is employed to promote the dissolution of different types or the same types of phases. In the homogenization heat treatment, both the temperature and heat preservation time (it may also be referred to as soaking time or holding time) for the homogenization heat treatment are critical. Illustrative temperatures for the homogenization heat treatment are 500 °C, 510 °C, 530 °C, 550 °C and 580 °C, but are not limited to the listed values. Other unlisted values within the range of 500 to 580 °C are also applicable. The heat preservation time is 5 h, 8 h, 10 h, 14 h, 18 h and 20 h, but are not limited to the listed values. Other unlisted values within the range of 5 to 20 h are also applicable.

[0033] In the extrusion shaping, hot extrusion is performed, followed by stretching and straightening of the extruded part after cooling. Process parameters for the hot extrusion are an extrusion outlet temperature of 530 to 580 °C, and an extrusion ratio of ≥ 20. Optionally, process parameters for the hot extrusion are an extrusion outlet temperature of 530 to 550 °C, and an extrusion ratio of ≥ 20. On the one hand, the relatively high extrusion temperature allows alloying elements such as Mg, Si and Cu to dissolve into an aluminum alloy matrix, ensuring the high strength of the aluminum alloy material. If the extrusion temperature is too low, such as below 530 °C, it cannot ensure that a sufficient amount of Mg, Si and Cu elements dissolve into the aluminum alloy matrix, resulting in a decrease in the strength of the material. If the temperature is too high, such as above 580 °C, defects such as cracking and overburning may occur during the extrusion of the aluminum alloy material to form the extruded part. On the other hand, with a relatively large extrusion ratio, such as at least 20, compounds and coarse grains formed during the casting process can be broken down, improving the toughness of the material. If the extrusion ratio is too small, such as less than 20, compounds and coarse grains formed during the casting process cannot be broken, resulting in a decrease in the toughness of the material.

[0034] In the present application, the extrusion shaping is used to improve properties of the material. A relatively high temperature needs to be maintained during the extrusion process to allow the material to have relatively high mechanical properties and excellent metal structures. Especially, during the extrusion process, it needs to dissolve Mg 2 Si particles generated during the casting process, and thus a high temperature needs to be maintained during the entire extrusion process. In addition, online quenching intensity of the material needs to be increased to ensure relatively high mechanical properties of the material in subsequent stages. The higher the quenching intensity, the greater the content of alloying elements dissolved in the matrix and the greater the vacancy concentration, resulting in improved strength and better plasticity after the subsequent aging. Therefore, in the present application, the process parameters for the extrusion shaping are the extrusion outlet temperature of 530 to 580 °C and the extrusion ratio of ≥ 20. After extrusion, water cooling or water mist cooling is applied, followed by the stretching and straightening of the extruded part.

[0035] Process parameters for the aging treatment are heat preservation at 160 to 200 °C for 6 to 20 h, followed by air cooling to room temperature. Optionally, process parameters for the aging treatment are the heat preservation at 180 to 200 °C for 10 to 20 h. In the present application, the aging treatment is the final key process to improve the strength of 6000 series aluminum alloys. Before the aging treatment, the higher the content of solute atoms and the greater the vacancy concentration in the matrix available for aging, the better the mechanical properties after aging. Aging can be single-stage or multi-stage aging. The single-stage aging is easy to produce, and the multi-stage aging is easy to improve the comprehensive performance, but it may reduce production efficiency. Therefore, single-stage aging treatment is selected in the present application, and the single-stage aging treatment is performed at a temperature of 160 to 200 °C for 6 to 20 h. For example, the temperature may be 160 °C, 170 °C, 180 °C, 190 °C, 200 °C, etc., but is not limited to the listed values, and the time may be 6 h, 7 h, 8 h, 9 h, 10 h, 14 h, 18 h, 20 h, etc., but is not limited to the listed values.

[0036] In the above structure constraint, a grain morphology of the extruded part is a fibrous structure along an extrusion direction. The strict constraint on the metal structure of the extruded part is the grain morphology of the extruded part being the fibrous structure along the extrusion direction, improving the strength and toughness of the extruded part. The strict constrain on the metal structure of extruded part is achieved through the composition of the aluminum alloy and the method for forming the extruded part.

[0037] In some embodiments, according to a third aspect of the present application, an extruded part formed by the method according to any one of the above-mentioned embodiments is provided. The extruded part has a yield strength of at least 350 MPa, a tensile strength of at least 400 MPa, an elongation of at least 10% and a bending angle of at least 60°.

[0038] The extruded part formed in this embodiment may be a part for a vehicle. Many different types of parts can be formed by an extrusion process, such as front and rear anti-collision beam parts, body-in-white parts, suspension parts or chassis parts. After the extrusion process, the method may include an optional heat treatment process or other finishing processes.Example 1

[0039] An ultra-high strength aluminum alloy was provided. Composition of the aluminum alloy includes 0.8 wt.% of Si, 0.1 wt.% of Fe, 0.4 wt.% of Cu, 0.6 wt.% of Mn, 1.2 wt.% of Mg, 0.1 wt.% of Cr, 0.02 wt.% of Ti, 0.01 wt.% of V, and a balance of Al and inevitable impurities, based on a mass of the aluminum alloy of 100 wt.%.

[0040] A processing method is shown in FIG. 1. Raw materials were prepared according to a composition recipe of the aluminum alloy, and the raw materials were subjected to melting and casting to obtain a round aluminum bar. The aluminum bar was subjected to homogenization heat treatment, and the homogenization heat treatment was performed at a temperature of 550 °C for 12 h. The aluminum bar was subjected to extrusion after preheating, and process parameters for the extrusion were an extrusion ratio of 20 and an extrusion outlet temperature of 530 °C. After extrusion, water cooling was applied. An extruded part was subjected to stretching and straightening, followed by artificial aging treatment. Process parameters for the aging treatment were a temperature of 180 °C and a time of 10 h. A metal structure of the extruded part was subjected to a strict constraint. A grain morphology of the extruded part was a fibrous structure along an extrusion direction, improving strength and toughness of the extruded part. The grain morphology of the metal structure of the extruded part in this example is shown in FIG. 2. In Comparative Example 1, a metal structure of an extruded part was not subjected to a strict constraint, and a grain morphology of the metal structure of the extruded part is shown in FIG. 3.

[0041] For Examples 2 to 20 and Comparative Examples 1 to 18, mass percentage contents of Si, Cu, Mg, Mn, Cr and Ti in aluminum alloy compositions and process parameters were adjusted according to Table 1, and other technical features were the same as those in Example 1. Metal structures of extruded parts of Examples 2 to 20 were also subjected to a strict constraint, that is, grain morphologies of the extruded parts were fibrous structures along an extrusion direction. Metal structure of extruded parts of Comparative Examples 2 to 18, like Comparative Example 1, were not subjected to a strict constraint. Automotive anti-intrusion beams were prepared according to the aluminum alloy compositions and processing methods provided in individual Examples and Comparative Examples. Specimens taken from the cross-section of automotive anti-intrusion beam as shown in FIG. 4 were tested for mechanical properties including yield strength, tensile strength and elongation in accordance with the ASTM E8 / E8M-21 test method (Standard Test Methods for Tension Testing of Metallic Materials). A bending angle was tested according to VDA-238 standard. The test results are also shown in Table 1 below. Table 1. Aluminum alloy material compositions, processing methods and mechanical properties test results of extruded partsChemical Composition (wt.%)Preparation ProcessMechanical PropertiesSiCuMgMnCrTiMg / Si ratioHomogeni -zation heat treatmentExtrusion Temperature (°C)Cooling MethodAging TreatmentYield Strength (MPa)Tensile Strength (MPa)Elongation (%)Bending Angle (°)JudgmentExample 10.80.41.20.60.10.021.5550°C / 12h530Water Cooling180°C / 10h3504001370QualifiedExample 210.410.60.10.021.0550°C / 12h530Water Cooling180°C / 10h3604051365QualifiedExample 31.20.410.60.10.020.8550°C / 12h530Water Cooling180°C / 10h3654101161QualifiedComparative Example 10.70.410.60.10.021.4550°C / 12h530Water Cooling180°C / 10h3203701470UnqualifiedComparative Example 21.30.410.60.10.020.8550°C / 12h530Water Cooling180°C / 10h3704151040UnqualifiedExample 410.310.60.10.021.0550°C / 12h530Water Cooling180°C / 10h3504011268QualifiedExample 510.510.60.10.021.0550°C / 12h530Water Cooling180°C / 10h3654101064QualifiedExample 610.710.60.10.021.0550°C / 12h530Water Cooling180°C / 10h3704181062QualifiedComparative Example 310.210.60.10.021.0550°C / 12h530Water Cooling180°C / 10h3403801470UnqualifiedComparative Example 410.810.60.10.021.0550°C / 12h530Water Cooling180°C / 10h380430845UnqualifiedExample 710.40.80.60.10.020.8550°C / 12h530Water Cooling180°C / 10h3554031367QualifiedExample 810.41.20.60.10.021.2550°C / 12h530Water Cooling180°C / 10h3754161062QualifiedComparative Example 510.40.70.60.10.020.7550°C / 12h530Water Cooling180°C / 10h3453901470UnqualifiedComparative Example 610.41.30.60.10.021.3550°C / 12h530Water Cooling180°C / 10h380420955UnqualifiedExample 910.410.40.10.021.0550°C / 12h530Water Cooling180°C / 10h3584031360QualifiedExample 1010.410.80.10.021.0550°C / 12h530Water Cooling180°C / 10h3634081368QualifiedComparative Example 710.410.30.10.021.0550°C / 12h530Water Cooling180°C / 10h3503951255UnqualifiedComparative Example 810.410.90.10.021.0550°C / 12h530Water Cooling180°C / 10h365410750UnqualifiedExample 1110.410.60.050.021.0550°C / 12h530Water Cooling180°C / 10h3584051363QualifiedExample 1210.410.60.20.021.0550°C / 12h530Water Cooling180°C / 10h3634081368QualifiedComparative Example 910.410.60.020.021.0550°C / 12h530Water Cooling180°C / 10h3554001050UnqualifiedComparative10.410.60.30.021.0550°C / 12h530Water180°C / 10h365410845UnqualifiedExample 10CoolingExample 1310.410.60.20.011.0550°C / 12h530Water Cooling180°C / 10h3554011262QualifiedExample 1410.410.60.20.11.0550°C / 12h530Water Cooling180°C / 10h3654101368QualifiedComparative Example 1110.410.60.20.0051.0550°C / 12h530Water Cooling180°C / 10h335395950UnqualifiedComparative Example 1210.410.60.20.21.0550°C / 12h530Water Cooling180°C / 10h368410855UnqualifiedExample 1510.410.60.10.021.0500°C / 12h530Water Cooling180°C / 10h3504001061QualifiedExample 1610.410.60.10.021.0580°C / 12h530Water Cooling180°C / 10h3654201062QualifiedComparative Example 1310.410.60.10.021.0490°C / 12h520Water Cooling180°C / 10h330390950UnqualifiedComparative Example 1410.410.60.10.021.0590°C / 12h530Water Cooling180°C / 10h360395640UnqualifiedExample 1710.410.60.10.021.0550°C / 12h550Water Cooling180°C / 10h3654101365QualifiedExample 1810.410.60.10.021.0550°C / 12h580Water Cooling180°C / 10h3704151368QualifiedComparative Example 1510.410.60.10.021.0550°C / 12h520Water Cooling180°C / 10h3303701355UnqualifiedComparative Example 1610.410.60.10.021.0550°C / 12h590Water Cooling180°C / 10h / / / / Un-extrudableExample 1910.410.60.10.021.0550°C / 12h530Water Cooling160°C / 20h3554051365QualifiedExample 2010.410.60.10.021.0550°C / 12h530Water Cooling200°C / 6h3604081262QualifiedComparative Example 1710.410.60.10.021.0550°C / 12h530Water Cooling150°C / 20h3403901468UnqualifiedComparative Example 1810.410.60.10.021.0550°C / 12h530Water Cooling210°C / 6h3303701470Unqualified

[0042] From the data in Table 1, it can be seen that by comparing Examples 1 to 20 with Comparative Examples 1 to 18, the following results can be found.

[0043] From the comparison between Example 1 to 3 and Comparative Example 1 to 2, it can be seen that when the Si content is relatively low, the amount of strengthening phases in the extruded part decreases, causing the strength of the extruded part to fail to meet the requirement of tensile strength of at least 400 MPa in the present application. When the Si content is relatively high, excess Si may precipitate within the extruded part in a form of elemental Si, reducing the bending angle of the extruded part, and causing the toughness of the extruded part to fail to meet the requirement of at least 350 MPa in the present application.

[0044] From the comparison between Example 4 to 6 and Comparative Example 3 to 4, it can be seen that, similar to Si, when the Cu content is relatively low, the amount of strengthening phases in the extruded part decreases, causing the strength of the extruded part to fail to meet the requirements of the present application. However, when the Cu content is relatively high, excess Cu may improve the strength of the material, but reduce the elongation and bending angle of the extruded part, causing the toughness of the extruded part to fail to meet the requirements of the present application.

[0045] From the comparison of Examples 7 to 8 and Comparative Examples 5 to 6, it can be seen that when the Mg content is relatively low, the amount of strengthening phases in the extruded part decreases, causing the strength of the extruded part to fail to meet the requirements of the present application. However, when the Mg content is relatively high, excess Mg may improve the strength of the material, but reduce the elongation and bending angle of the extruded part, causing the toughness of the extruded part to fail to meet the requirements of the present application.

[0046] From the comparison of Examples 9 to 10 and Comparative Examples 7 to 8, it can be seen that when the Mn content is relatively low, the amount of dispersed phases in the extruded part decreases, leading to poor control of the fibrous structure and a consequent decrease in the bending angle of the extruded part, which does not meet the requirements of the present application. However, when the Mn content is relatively high, excess Mm leads to the formation of coarse Al-Fe-Mn phases during the casting process, which cannot be fully broken down during the extrusion process, which not only decreases the bending angle of the extruded part, but also decreases the elongation of the extruded part, causing the toughness of the extruded part to fail to meet the requirements of the present application.

[0047] From the comparison of Examples 11 to 12 and Comparative Examples 9 to 10, it can be seen that similar to Mn, Cr forms dispersed phases to control the metal structure. When the Cr content is relatively low, the amount of dispersed phases in the extruded part decreases, leading to poor control of the fibrous structure and a consequent decrease in the bending angle of the extruded part, which does not meet the requirements of the present application. However, when the Cr content is relatively high, excess Cr leads to the formation of coarse Al-Fe-Cr phases during the casting process, which cannot be fully broken down during the extrusion process, which not only decreases the bending angle of the extruded part, but also decreases the elongation of the extruded part, causing the toughness of the extruded part to fail to meet the requirements of the present application.

[0048] From the comparison between Examples 13 to 14 and Comparative Examples 11 to 12, it can be seen that when the Ti content is relatively low, it may lead to coarse ingot grain size and coarse grain boundary compounds such as Mg 2 Si phases and Al-Fe-Mn-Si, causing the strength and bending angle of the extruded part to decrease and fail to meet the requirements of the present application. However, when the Ti content is relatively high, excess Ti may lead to solid solution strengthening and improve the strength of extruded part, but it may also cause a decrease in the elongation and bending angle of extruded part, causing the toughness to fail to meet the requirements of the present application.

[0049] From the comparison between Example 15 to 16 and Comparative Example 13 to 14, it can be seen that when the homogenization heat treatment temperature is relatively low, it may lead to incomplete homogenization of aluminum bars (incomplete dissolution of Mg 2 Si, and incomplete transformation of elongated Al-Fe-Si compounds into rounded Al-Fe-Mn-Si phases), which not only decreases the strength of the extruded part, but also decreases the elongation and bending angle of the extruded part, resulting in failure to meet the requirements of the present application. When the homogenization heat treatment temperature is relatively high, it may lead to overburning of aluminum bars, which may decrease the elongation and bending angle of extruded part, causing the toughness of extruded part to fail to meet the requirements of the present application.

[0050] From the comparison between Examples 17 to 18 and Comparative Examples 15 to 16, it can be seen that when the extrusion outlet temperature for the extruded part is relatively low, it may lead to incomplete dissolution of Mg 2 Si into the extruded part during the extrusion process, decreasing the bending angle of the extruded part and failing to meet the requirements of the present application. When the extrusion outlet temperature is relatively high, it may cause the extruded part to be difficult to weld at an outlet of an extrusion die and cannot be extruded normally.

[0051] From the comparison between Examples 19 to 20 and Comparative Examples 17 to 18, it can be seen that when the artificial aging treatment temperature for the extruded part is relatively low, it may lead to insufficient density of precipitated phases during the artificial aging treatment, and the extruded part is in an under-aged state, thus decreasing the strength of the extruded part, resulting in failure to meet the requirements of the present application. When the artificial aging treatment temperature is relatively high, it may lead to the growth of precipitated phases and the loss of semi-coherent relationship with aluminum matrix during the artificial aging treatment, and the extruded part is in an under-aged state, which may decrease the strength of the extruded part, resulting in failure to meet the requirements of the present application.

[0052] Reference throughout the description of the present application to "an embodiment," "some embodiments," "an example," "a specific example," or "some examples," means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. The schematic expressions of the above-mentioned terms throughout this specification are not necessarily referring to the same embodiment or example. Moreover, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0053] Although the embodiments of the present application have been shown and described above, it is to be understood that the above embodiments are illustrative and cannot be construed as limiting the present application, and those skilled in the art may make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Examples

example 1

[0039]An ultra-high strength aluminum alloy was provided. Composition of the aluminum alloy includes 0.8 wt.% of Si, 0.1 wt.% of Fe, 0.4 wt.% of Cu, 0.6 wt.% of Mn, 1.2 wt.% of Mg, 0.1 wt.% of Cr, 0.02 wt.% of Ti, 0.01 wt.% of V, and a balance of Al and inevitable impurities, based on a mass of the aluminum alloy of 100 wt.%.

[0040]A processing method is shown in FIG. 1. Raw materials were prepared according to a composition recipe of the aluminum alloy, and the raw materials were subjected to melting and casting to obtain a round aluminum bar. The aluminum bar was subjected to homogenization heat treatment, and the homogenization heat treatment was performed at a temperature of 550 °C for 12 h. The aluminum bar was subjected to extrusion after preheating, and process parameters for the extrusion were an extrusion ratio of 20 and an extrusion outlet temperature of 530 °C. After extrusion, water cooling was applied. An extruded part was subjected to stretching and straightening, follo...

Claims

1. An ultra-high strength aluminum alloy material, comprising: 0.8 to 1.2 wt.% of Si; 0.1 to 0.3 wt.% of Fe; 0.3 to 0.7 wt.% of Cu; 0.4 to 0.8 wt.% of Mn; 0.8 to 1.2 wt.% of Mg; 0.05 to 0.2 wt.% of Cr; 0.01 to 0.1 wt.% of Ti; 0.01 to 0.2 wt.% of V; and a balance of Al, based on a mass of the aluminum alloy material of 100 wt.%.

2. The aluminum alloy material of claim 1, comprising: 0.8 to 1.1 wt.% of Si; 0.1 to 0.2 wt.% of Fe; 0.3 to 0.5 wt.% of Cu; 0.4 to 0.6 wt.% of Mn; 0.8 to 1.1 wt.% of Mg; 0.1 to 0.2 wt.% of Cr; 0.05 to 0.1 wt.% of Ti; and 0.01 to 0.1 wt.% of V.

3. The aluminum alloy material of claim 1 or 2, further comprising inevitable impurities, wherein a total impurity content is ≤ 0.15 wt.%, and a content of a single impurity is ≤ 0.05 wt.%.

4. The aluminum alloy material of claim 3, wherein a ratio of Mg / Si in the aluminum alloy material is in a range of 0.8 to 1.5.

5. The aluminum alloy material of claim 3, wherein a ratio of Mg / Si in the aluminum alloy material is in a range of 1.0 to 1.2.

6. A method for forming an extruded part from the aluminum alloy material of any one of claims 1 to 5, comprising: preparing raw materials according to a recipe of the aluminum alloy material, and subjecting the raw materials to smelting, casting, homogenization heat treatment, extrusion shaping and aging treatment to obtain the extruded part; wherein a metal structure of the extruded part is subjected to a strict constraint.

7. The method of claim 6, wherein the homogenization heat treatment is performed at a temperature of 500 to 580 °C and heat preservation for 5 to 20 h.

8. The method of claim 6 or 7, wherein in the extrusion shaping, hot extrusion is performed, followed by stretching and straightening of the extruded part after cooling; wherein process parameters for the hot extrusion are: an extrusion outlet temperature of 530 to 580 °C, and an extrusion ratio of ≥ 20.

9. The method of any one of claims 6 to 8, wherein process parameters for the aging treatment are: heat preservation at 160 to 200 °C for 6 to 20 h, followed by air cooling to room temperature.

10. The method of any one of claims 6 to 9, wherein the strict constraint on the metal structure of the extruded part is: a grain morphology of the extruded part being a fibrous structure along an extrusion direction.

11. An extruded part, formed by the method of any one of claims 6 to 10.

12. The extruded part of claim 11, wherein the extruded part has a yield strength of at least 350 MPa, a tensile strength of at least 400 MPa, an elongation of at least 10% and a bending angle of at least 60°.

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