Aluminum alloy, preparation method of aluminum alloy, alloy part and application of alloy part

Abstract

The invention discloses an aluminum alloy, a preparation method of the aluminum alloy, an alloy part and application of the alloy part, and the aluminum alloy comprises the following metals in percentage by mass: 0.7%-0.9% of Mg, 0.9%-1.3% of Si, 0.5%-0.7% of Cu, 0.1%-0.3% of Mn, 0.1%-0.5% of Sc, 0%-0.4% of Zr and the balance of aluminum. According to the aluminum alloy disclosed by the invention, Zr and Sc in a certain mass ratio are added, and a crystal phase and a precipitated phase generated in the aluminum alloy are further dispersed and refined by utilizing a composite effect of Zr and Sc, so that the aluminum alloy achieves relatively high strength and ductility.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and in particular to an aluminum alloy, a method for preparing the aluminum alloy, an alloy part, and applications of the alloy part. Background Art

[0002] Aluminum alloy is made by adding some alloying elements to pure aluminum. For example, adding Si element to pure aluminum to develop Al-Si alloy, adding Mg element to pure aluminum to develop Al-Mg alloy, adding Si element and Mg element to pure aluminum at the same time to develop Al-Si-Mg aluminum alloy, adding Si, Mg and Cu elements to pure aluminum at the same time to develop Al-Si-Mg-Cu alloy, etc.

[0003] 6 series aluminum alloy is a typical Al-Si-Mg(-Cu) alloy that can be strengthened by heat treatment. It has the advantages of medium-high strength, good corrosion resistance and weldability, no tendency to stress corrosion cracking, and excellent formability and processing performance. It is the most commonly used deformed aluminum alloy on the market. However, the existing 6 series aluminum alloy has low strength and elongation. When meeting the demand for lightweight, it is difficult to meet the high load-bearing requirements of large structural parts. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the first object of the present invention is to provide an aluminum alloy having higher strength and elongation.

[0005] The second object of the present invention is to provide a method for preparing an aluminum alloy.

[0006] The third object of the present invention is to provide an aluminum alloy part.

[0007] A fourth object of the present invention is to provide an application of an aluminum alloy part.

[0008] The aluminum alloy according to the embodiment of the first aspect of the present invention includes: in terms of mass percentage, the following metals: 0.7% to 0.9% Mg, 0.9% to 1.3% Si, 0.5% to 0.7% Cu, 0.1% to 0.3% Mn, 0.1% to 0.5% Sc, 0% to 0.4% Zr, and the balance is aluminum.

[0009] According to the aluminum alloy of the embodiment of the present invention, by adding Zr and Sc in a certain mass ratio, the composite effect of Zr and Sc is utilized to further disperse and refine the crystalline phase and precipitation phase generated in the aluminum alloy, so that the aluminum alloy has higher strength and elongation. For example, the room temperature tensile strength of the aluminum alloy of the embodiment of the present invention is not less than 590MPa, the yield strength is not less than 530MPa, the elongation is greater than 10%, and the mechanical properties are comparable to those of Al-Zn super-hard aluminum alloys.

[0010] According to some embodiments of the present invention, the following metals are included, in terms of mass percentage: 0.7% to 0.8% Mg, 0.9% to 1.1% Si, 0.5% to 0.6% Cu, 0.1% to 0.15% Mn, 0.1% to 0.3% Sc, 0.1% to 0.3% Zr, and the balance is aluminum.

[0011] According to some embodiments of the present invention, the aluminum alloy further includes the following metals: at least one of Fe, Ti and Zn, and the sum of the mass percentages of Fe, Ti and Zn is less than 0.2% by mass.

[0012] According to the second aspect of the present invention, the method for preparing an aluminum alloy includes: pretreatment of raw materials, low-temperature rolling and aging treatment, wherein the temperature of the low-temperature rolling is T1, wherein T1 satisfies: -20℃≤T1≤25℃; the temperature of the aging treatment is T2, wherein T2 satisfies: 80℃≤T2≤120℃; the duration of the interval between the low-temperature rolling and the aging treatment is Δt1, wherein Δt1 satisfies: Δt1≤30min.

[0013] According to some embodiments of the present invention, the raw materials include: 99.9 wt. % high purity Al, industrial pure Mg, Al-Sc alloy, Al-Cu alloy, Al-Mn alloy, Al-Si and Al-Zr alloy.

[0014] According to some embodiments of the present invention, the pretreatment of the raw materials includes: melting 99.9wt.% high-purity Al, industrial pure Mg, Al-Sc alloy, Al-Cu alloy, Al-Mn alloy, Al-Si and Al-Zr alloy, degassing, deslagging, and casting to obtain ingots.

[0015] According to some embodiments of the present invention, the pretreatment of the raw material further comprises:

[0016] The ingot is homogenized and annealed, wherein the homogenized annealing comprises:

[0017] Insulation treatment: Insulating the ingot at 480° C. to 540° C. for 16 h to 32 h;

[0018] Water quenching: the ingot is water quenched.

[0019] According to some embodiments of the present invention, the heat preservation treatment includes:

[0020] Primary heat preservation treatment: the ingot is kept at 480° C. to 500° C. for 12 h to 20 h;

[0021] Secondary heat preservation treatment: the ingot is heated to 520°C to 540°C and kept warm for 4h to 12h.

[0022] According to some embodiments of the present invention, the interval between the homogenization annealing and the low-temperature rolling is Δt2, wherein the Δt2 satisfies: Δt2≤60min.

[0023] According to some embodiments of the present invention, the low-temperature rolling is performed multiple times, the reduction amount of a single low-temperature rolling is 3%-25%, and the total reduction amount of the multiple low-temperature rolling is 55%-65%.

[0024] According to the alloy part of the third aspect of the present invention, the alloy part includes: the aluminum alloy according to the first aspect of the present invention, or the alloy part prepared by the preparation method of the second aspect of the present invention.

[0025] According to the application of the alloy part of the embodiment of the fourth aspect of the present invention, the alloy part is applied to a vehicle body, a main frame, a door, a subframe, a crossbeam, or a battery housing.

[0026] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0028] Figure 1 is a schematic diagram of a method for preparing an aluminum alloy according to an embodiment of the present invention;

[0029] Figure 2 is a schematic diagram of pretreatment of raw materials according to an embodiment of the present invention;

[0030] Figure 3 is a schematic diagram of homogenization annealing according to an embodiment of the present invention;

[0031] Figure 4 This is the metallographic photograph of the cast structure of the aluminum alloy after adding the Sc element (a);

[0032] Figure 5 is a transmission photograph of the ingot after low-temperature rolling and aging treatment (b);

[0033] Figure 6 is the shape and size of the tensile specimen (unit: mm);

[0034] Figure 7 It is the shape and size of the tensile specimen at another angle (unit: mm). DETAILED DESCRIPTION

[0035] Reference below Figure 1-Figure 7An aluminum alloy according to an embodiment of the first aspect of the present invention is described.

[0036] like Figure 1-Figure 7 As shown, the aluminum alloy according to the embodiment of the first aspect of the present invention includes the following metals, in percentage by mass: 0.7% to 0.9% Mg, 0.9% to 1.3% Si, 0.5% to 0.7% Cu, 0.1% to 0.3% Mn, 0.1% to 0.5% Sc, 0% to 0.4% Zr, and the balance is aluminum.

[0037] Specifically, aluminum alloy is an aluminum alloy formed by adding a certain mass percentage of Mg, Si, Cu, Mn, Sc and Zr to aluminum. The role of Mg, Si and Cu is to form the main strengthening crystal phases Mg2Si, Al4Cu2Mg8Si7(Q), nano-Si and a small amount of Al2Cu phases during aging, so that the strength of the aluminum alloy can be improved through aging treatment.

[0038] Among them, the density of Mg is much smaller than that of aluminum, about 67% of aluminum. Therefore, adding a small amount of Mg to the aluminum alloy, that is, Mg in the range of 0.7% to 0.9% M, can significantly reduce the density of the aluminum alloy, making the final aluminum alloy lighter. The addition of Mg can increase the specific strength (ratio of strength to density) of the aluminum alloy, which helps to improve the casting performance and plastic processing performance of the aluminum alloy.

[0039] Si is beneficial to enhance the hardness and strength of aluminum alloy, especially tensile strength and yield strength, so that aluminum alloy can withstand higher mechanical loads. At the same time, Si's high melting point (1414℃) and high temperature resistance enable aluminum alloy to maintain good mechanical properties at higher temperatures and help reduce the thermal expansion coefficient (CTE) of aluminum alloy.

[0040] Cu can significantly improve the tensile strength, yield strength and hardness of aluminum alloys through solid solution strengthening mechanism, which is beneficial to improve the cutting performance of aluminum alloys, making aluminum alloys easier to cut, reducing tool wear and improving processing efficiency. At the same time, the addition of Cu can improve the electrical conductivity of aluminum alloys.

[0041] Mn increases the hardness and strength of aluminum alloys through the solid solution strengthening mechanism, and is also beneficial to improving the corrosion resistance of aluminum alloys. That is, Mn reduces the corrosion rate of aluminum alloys in harsh environments by forming a protective oxide film, thereby extending the service life of aluminum alloys. In addition, Mn can improve the processing properties of aluminum alloys, reduce the temperature and processing difficulty of aluminum alloy processing deformation, enable aluminum alloys to maintain good stability and uniformity during thermal deformation, and reduce the formation of cracks and cracks. Adding a small amount of Mn is beneficial to reducing and eliminating the influence of Fe that may be introduced during alloy smelting, and avoiding the formation of coarse needle-shaped Al5FeSi phase in aluminum alloys, which may deteriorate the strength and plasticity of aluminum alloys.

[0042] The addition of 0.1% to 0.5% Sc element not only inhibits grain growth through the composition supercooling and crystallization phases Al3Sc and AlSc2Si2 formed at the solid-liquid boundary front, but also significantly increases the nucleation rate and refines the grains through the heterogeneous nucleation of Al3Sc. Figure 4 As shown in the figure, the formation of Al3Sc phase will simultaneously reduce the segregation of Sc elements at the front of the Al3Sc / liquid Al interface, delaying grain growth, and transforming the dendrite structure of the Sc-containing aluminum alloy into a morphology similar to equiaxed crystals. The refined ɑ-Al grains increase the grain boundary area of ​​the aluminum alloy, and the formation of AlSc2Si2 consumes the Si element. Therefore, compared with the alloy without the addition of Sc element, the crystallized and precipitated Si particles, flaky Mg2Si, needle-like Q phase and granular Al2Cu phase in the aluminum alloy are greatly refined and dispersed, so that the aluminum alloy maintains good plasticity while improving strength.

[0043] Because Zr and Sc have similar chemical properties, but the price of Zr is significantly lower than that of Sc. Therefore, by replacing part of the rare earth element Sc with 0%-0.4% Zr, when adding a low content (0.1%-0.5%) of rare earth Sc, not only can the use of rare earth element Sc be reduced and the cost be reduced, but also the composite effect of Zr and Sc (the composite addition of Zr and Sc can effectively refine the grain size of α-Al, and grain refinement helps to improve the mechanical properties of aluminum alloys; in the α-Al matrix, the addition of Zr and Sc promotes the precipitation of a large number of Al (Sc-xZrx) nanoparticles, and the precipitation phase of these Al (Sc-xZrx) nanoparticles acts as a strengthening phase, which strengthens the aluminum alloy by hindering dislocation movement, thereby improving the tensile strength, yield strength and hardness of the aluminum alloy), further dispersing and refining the crystalline phase and precipitation phase generated in the solidification and aging of the aluminum alloy, so that the aluminum alloy can achieve higher strength and elongation.

[0044] According to the aluminum alloy of the embodiment of the present invention, by adding Zr and Sc in a certain mass ratio, the composite effect of Zr and Sc is utilized to further disperse and refine the crystalline phase and precipitation phase generated in the aluminum alloy, so that the aluminum alloy achieves higher strength and elongation. For example, the room temperature tensile strength of the aluminum alloy of the embodiment of the present invention is not less than 590MPa, the yield strength is not less than 530MPa, the elongation is greater than 10%, and the mechanical properties are comparable to those of Al-Zn super-hard aluminum alloys.

[0045] According to some embodiments of the present invention, the following metals are included in percentage by mass: 0.7% to 0.8% Mg, 0.9% to 1.1% Si, 0.5% to 0.6% Cu, 0.1% to 0.15% Mn, 0.1% to 0.3% Sc, 0.1% to 0.3% Zr, and the balance is aluminum. Thus, while meeting the requirements of strength and ductility of aluminum alloys, the content of each element is reduced, which is conducive to reducing the cost of aluminum alloys.

[0046] According to some embodiments of the present invention, the aluminum alloy further comprises the following metals: at least one of Fe, Ti and Zn, and the sum of the mass percentages of Fe, Ti and Zn is less than 0.2% by mass percentage. Among them, Ti can be used as an effective grain refiner, and by forming fine precipitation phases such as Al3Ti, it effectively hinders the growth of grains, thereby refining the microstructure of the aluminum alloy and improving the strength and toughness of the aluminum alloy. The addition of an appropriate amount of Ti can improve the fluidity of the aluminum alloy, help the aluminum alloy liquid to better fill complex molds, reduce casting defects, and improve the quality of castings. Excessive addition of Ti can also have negative effects, such as the formation of coarse Ti compounds, resulting in a decrease in the mechanical properties and casting properties of the aluminum alloy and an increase in cost. When Zn and Mg are added together as the main alloying elements, the strength of the aluminum alloy can be significantly improved, especially the tensile strength and yield strength. The strengthening phases formed by Zn and Mg in the aluminum alloy, such as MgZn (η phase) and AlMgZn (T phase), are precipitated during the aging treatment, and the aluminum alloy is significantly strengthened through the precipitation hardening mechanism. In addition, an appropriate amount of Zn can also improve the fluidity of the aluminum alloy.

[0047] The sum of the mass percentages of Fe, Ti and Zn is controlled within 0.2% to reduce the formation of coarse needle-shaped Al5FeSi phase in the aluminum alloy, so as to avoid deteriorating the strength and plasticity of the aluminum alloy, avoid excessive Ti from forming coarse Ti compounds, resulting in a decrease in the mechanical properties and casting properties of the aluminum alloy, and avoid problems such as excessive Zn content increasing internal stress and reducing intergranular corrosion resistance.

[0048] Reference Figure 1 , according to the method for preparing aluminum alloy of the second embodiment of the present invention, comprising: pretreatment of raw materials, low temperature rolling and aging treatment. Low temperature rolling is beneficial to reducing energy consumption and improving the quality and performance of aluminum alloy. Low temperature rolling helps to refine the grains, and grain refinement can significantly enhance the mechanical properties of aluminum alloy, such as improving the strength and toughness of aluminum alloy. Aging treatment is to change the mechanical properties of aluminum alloy through a specific temperature control process, such as improving strength, hardness, stabilizing size or improving resistance to stress corrosion cracking.

[0049] Among them, the temperature of low-temperature rolling is T1, wherein T1 satisfies: -20℃≤T1≤25℃. Therefore, processing is carried out in the optimal temperature range of multiple metal structure transformations, and deformation heat is fully utilized to maintain or slightly increase the temperature of the metal material during low-temperature rolling. In addition, the composite effect of Zr and Sc is sensitive to temperature. High temperature can easily cause the precipitated strengthening phase to aggregate and grow or dissolve into the matrix again, reducing the number and uniformity of the strengthening phase distribution, thereby reducing the hardness and strength of the aluminum alloy. Therefore, the low-temperature rolling of the ingot is to optimize the composite effect of Zr and Sc under the condition of suppressing the recovery recrystallization of the aluminum alloy, so that a large number of dislocations, subgrained structures and fine dispersed second phases of the precipitated part are generated in the aluminum alloy, so as to achieve the purpose of dislocation strengthening, and provide a large number of dispersed heterogeneous nucleation particles for subsequent aging treatment.

[0050] The temperature of the aging treatment is T2, where T2 satisfies: 80℃≤T2≤120℃. In this way, the aluminum alloy can achieve the best balance between mechanical properties and processability, and improve the strength of the aluminum alloy. Figure 1 and Figure 5 As shown, after low-temperature rolling, the aluminum alloy is aged at 80℃-120℃, so that under the action of strain energy and heterogeneous nucleation, a large number of fine and dispersed flaky or needle-shaped Mg2Si, Al4Cu2Mg8Si7(Q), and a small amount of Al2Cu phase are quickly precipitated from the aluminum alloy, which releases some dislocations to increase the plasticity of the aluminum alloy and further improves the strength of the aluminum alloy by utilizing the interaction between dislocations and various second phases.

[0051] The interval between low temperature rolling and aging treatment is Δt1, where Δt1 satisfies: Δt1≤30min. Controlling the interval between low temperature rolling and aging treatment is conducive to ensuring that the aluminum alloy fully exerts the aging hardening effect and reduces the parking effect.

[0052] According to the method for preparing aluminum alloy of an embodiment of the present invention, the metal material is subjected to pretreatment, low-temperature rolling and aging treatment to obtain an aluminum alloy with higher strength and elongation. In particular, the introduction of low-temperature large plastic deformation (low-temperature rolling) in the heat treatment process (aging treatment) can make full use of the combined effects of fine grain strengthening, dispersion strengthening and dislocation strengthening to form an aluminum alloy. In particular, in order to ensure that the alloy fully exerts the aging hardening effect and reduces the parking effect, the interval time between homogenization metamorphism, low-temperature large plastic deformation and low-temperature aging should be shortened as much as possible.

[0053] Further, the raw materials include: 99.9wt.% high-purity Al, industrial pure Mg, Al-Sc alloy, Al-Cu alloy, Al-Mn alloy, Al-Si and Al-Zr alloy. Therefore, the use of processed intermediate alloys (i.e., Al-Sc alloy, Al-Cu alloy, Al-Mn alloy, Al-Si and Al-Zr alloy) reduces the requirements for raw material processing temperature and other conditions, which is conducive to shortening the preparation time of aluminum alloy and improving the preparation efficiency of aluminum alloy.

[0054] Furthermore, refer to Figure 2 The pretreatment of raw materials includes: melting 99.9wt.% high-purity Al, industrial pure Mg, Al-Sc alloy, Al-Cu alloy, Al-Mn alloy, Al-Si and Al-Zr alloy, degassing, deslagging, and casting to obtain ingots. As a result, the temperature required for fully melting Al, Mg, Al-Sc alloy, Al-Cu alloy, Al-Mn alloy, Al-Si and Al-Zr is relatively low, which reduces the requirements for preparation equipment and the cost of raw material processing. Degassing and deslagging the melted raw materials are beneficial to increasing the purity of the raw materials and reducing impurities in the ingots, so as to improve the purity of the aluminum alloy finally prepared, thereby improving the quality of the aluminum alloy and enhancing the market competitiveness of the aluminum alloy.

[0055] In addition, refer to Figure 1 and Figure 3 , the pretreatment of raw materials also includes:

[0056] The ingot is homogenized and annealed. The homogenization annealing includes:

[0057] Insulation treatment: keep the ingot at 480℃~540℃ for 16h~32h;

[0058] Water quenching: The ingot is water quenched.

[0059] Therefore, the ingot is kept warm to allow the Cu-containing phase (such as Al2Cu and Q phase), Mg2Si, Si and Q phase to be fully dissolved, and then the ingot is quickly cooled by water quenching to refine the grain structure of the ingot and improve the hardness, strength and wear resistance of the aluminum alloy.

[0060] Further, the heat preservation treatment includes:

[0061] Primary insulation treatment: keep the ingot at 480℃~500℃ for 12h~20h;

[0062] Secondary insulation treatment: raise the temperature of the ingot to 520℃~540℃ and continue to keep it warm for 4h~12h.

[0063] The purpose of keeping warm at 480-500℃ is to dissolve the low-melting-point Cu-containing phase (such as Al2Cu and Q phase) to avoid overburning to form a homogeneous phase; the purpose of keeping warm at 520-540℃ is to promote the full solid solution of the divorced primary phase or eutectic phase Mg2Si, Si and Q phase formed by crystallization, reduce the splitting effect of coarse crystals on the matrix, increase the plasticity of the aluminum alloy, and prepare for subsequent low-temperature rolling and aging treatment.

[0064] According to some specific embodiments of the present invention, the interval between homogenization annealing and low temperature rolling is Δt2, wherein Δt2 satisfies: Δt2≤60min. Controlling the time interval between homogenization annealing and low temperature rolling can reduce the storage effect of the aluminum alloy, reduce the deformation resistance during subsequent low temperature rolling, and enhance the hardening effect of subsequent aging treatment.

[0065] According to some specific embodiments of the present invention, the low temperature rolling is performed multiple times, the reduction amount of a single low temperature rolling is 3%-25%, and the total reduction amount of multiple low temperature rolling is 55%-65%. Therefore, the reduction amount of the low temperature rolling can meet the rolling of the alloy, and is conducive to saving energy and reducing energy loss.

[0066] The aluminum alloy prepared by the preparation method according to the embodiment of the present invention has good mechanical properties. When the elongation is greater than 10%, the yield strength and tensile strength of the aluminum alloy reach 530 MPa and 590 MPa or more, respectively.

[0067] The embodiments of the present invention are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention. In addition, if not explicitly stated, all reagents used in the following embodiments are commercially available, or can be synthesized according to this article or known methods, and the reaction conditions not listed are also easily available to those skilled in the art.

[0068] Example 1

[0069] The composition of the aluminum alloy in this embodiment is as follows by mass percentage: 0.85% Mg, 1.2% Si, 0.70% Cu, 0.22% Mn, 0.52% Sc, the total amount of impurity elements such as Fe, Ti, Zn, etc. is less than 0.2%, and the balance is Al. The mass percentage of rare earth Sc is 0.5%.

[0070] 99.9wt.% high-purity Al, industrial pure Mg and five intermediate alloys of Al-2wt.%Sc, Al-50wt.%Cu, Al-10wt.%Mn, Al-10wt.%Si and Al-10wt.%Zr are used as raw materials. After melting, degassing and slag removal, ingots with the above composition are cast. The ingot is homogenized annealed, kept at 500℃ for 12h, heated to 520℃ and kept for 12h before water quenching. The homogenized material is low-temperature rolled at -20℃-25℃, with a single reduction of 3-25% and a total deformation of 63.5%. After low-temperature rolling, aging treatment is carried out, that is, after keeping at 120℃ for 5h, water quenching.

[0071] Example 2

[0072] The steps in this embodiment are the same as those in Embodiment 1, except that:

[0073] The composition of the aluminum alloy is as follows by mass percentage: 0.90% Mg, 1.0% Si, 0.58% Cu, 0.30% Mn, 0.33% Sc, 0.21% Zr, the total amount of impurity elements such as Fe, Ti, and Zn is less than 0.2%, and the balance is aluminum. The mass percentage of rare earth Sc is 0.33%.

[0074] The total deformation of low temperature rolling is 58.9%.

[0075] The aging treatment is to keep the temperature at 80℃ for 24h and then quench in water.

[0076] Example 3

[0077] The steps in this embodiment are the same as those in Embodiment 1, except that:

[0078] The composition of the aluminum alloy is as follows by mass percentage: 0.71% Mg, 1.30% Si, 0.50% Cu, 0.15% Mn, 0.13% Sc, 0.39% Zr, the total amount of impurity elements such as Fe, Ti, and Zn is less than 0.2%, and the balance is aluminum. The mass percentage of rare earth Sc is 0.13%.

[0079] The total deformation of low temperature rolling is 55.6%.

[0080] Homogeneous annealing is carried out by keeping the temperature at 480°C for 20 hours, heating to 540°C for 4 hours, and then water quenching.

[0081] Comparative Example 1

[0082] The steps are the same as those in Example 1, except that:

[0083] The composition of the aluminum alloy is as follows by mass percentage: 0.89% Mg, 0.86% Si, 0.56% Cu, 0.19% Mn, 0.49% Zr, the total amount of impurity elements such as Fe, Ti, and Zn is less than 0.2%, and the balance is aluminum. The mass percentage of rare earth Sc is 0%.

[0084] The total deformation of low temperature rolling is 58.6%.

[0085] Homogeneous annealing is carried out by keeping the temperature at 480°C for 20 hours, heating to 540°C for 4 hours, and then water quenching.

[0086] Comparative Example 2

[0087] The steps are the same as those in Example 1, except that:

[0088] The material composition is consistent with that of Example 1, and the composition of the aluminum alloy is as follows by mass percentage: 0.85% Mg, 1.2% Si, 0.70% Cu, 0.22% Mn, 0.52% Sc, the total amount of impurity elements such as Fe, Ti, and Zn is less than 0.2%, and the balance is Al. The mass percentage of rare earth Sc is 0.5%.

[0089] The aging treatment is to heat the solution at 540℃ for 20min, quench in water, and then heat the aging at 175℃ for 7h, and then quench in water. The time interval between the 540℃ heat preservation and the 175℃ heat preservation is less than 30s-60s.

[0090] Performance Testing

[0091] 1. Metallographic electron microscope test

[0092] Equipment: The metallographic electron microscope used is Olympus-GX71.

[0093] Test method: Cut 10×10(5~10)mm aluminum alloys from the aluminum alloys of Examples 1-3 and Comparative Examples 1-2 of the present invention. 3 The sample is ground with 400#~1200# sandpaper until there are no scratches on the surface. Then polish it with electrolyte until it is bright and dry it with a hair dryer. The electrolyte is perchloric acid alcohol solution (perchloric acid: alcohol = 1:9). Then use 0.5% HF aqueous solution to corrode for 3~10s or use a coating solution with fluoroboric acid: water = 1:24 for anodic coating at -25℃. During anodic coating, the negative pole of the power supply is connected to the stainless steel and the positive pole is connected to the sample. The voltage is set to 20V, the current is about 2A, and the time is 3min.

[0094] 2. Transmission electron microscopy tissue test

[0095] Equipment: The transmission electron microscopes include FEI's Talos F200X and Themis Z Double Cs Corrector double spherical aberration-field emission transmission electron microscope.

[0096] Test method: The voltage used for characterization is 200kV. For aluminum alloys, unless otherwise specified, the shooting axis is along the aluminum <100> Direction. The TEM sample process is as follows: use wire cutting to cut a 10mm×0.5mm disc sample, water-grind to about 50μm, and use a puncher to obtain a 3mm small disc. Then use a Gatan 691 ion thinning instrument to perforate or use an ion double-spray device to thin to micropores in a double-spray electrolyte of 70% HNO3+30CH3OH at a temperature of about -25℃.

[0097] 3. Room temperature tensile test

[0098] Equipment: The tensile test was carried out on a SHIMADZY AUTO GRAPHAG-X 5KN universal mechanical testing machine.

[0099] Test method: The plate after aging treatment was selected as the research object, and the sampling tensile direction was the rolling direction. According to the international tensile standard (ASTM E8M-04), the tensile strain rate was 1×10 -3 s -1 , the number of parallel samples shall not be less than 3.

[0100] Table 1 shows the yield strength, tensile strength and elongation of the aluminum alloys of Examples 1-3 and Comparative Examples 1-2.

[0101] Table 1 Mechanical properties of Examples 1-3 and Comparative Examples 1-2

[0102] serial number Yield strength(MPa) Tensile strength(MPa) Elongation(%) Example 1 543 615 14.8％ Example 2 554 624 15.3％ Example 3 538 595 13.0％ Comparative Example 1 520 584 11.5％ Comparative Example 2 422 572 18.7％

[0103] According to the alloy part of the embodiment of the third aspect of the present invention, the alloy part includes: the aluminum alloy according to the embodiment of the first aspect of the present invention, or the alloy part prepared by the preparation method of the embodiment of the second aspect of the present invention.

[0104] The alloy parts according to the embodiments of the present invention are made by aluminum alloy or the preparation method, which is beneficial to improving the quality of the alloy parts, thereby increasing the service life of the alloy parts and improving the market competitiveness of the alloy parts.

[0105] According to the application of the alloy part of the embodiment of the fourth aspect of the present invention, the alloy part is applied to a vehicle body, a main frame, a door, a subframe, a crossbeam, or a battery housing.

[0106] The application of the alloy parts according to the embodiments of the present invention has the advantages of excellent weldability, corrosion resistance, thermal cracking resistance, etc., which enriches the application fields of the alloy parts and improves the market competitiveness of the alloy parts.

[0107] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

[0108] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. An aluminum alloy, characterized in that: Calculated by mass percentage, the following metals are included: 0.7% to 0.9% Mg, 0.9% to 1.3% Si, 0.5% to 0.7% Cu, 0.1% to 0.3% Mn, 0.1% to 0.5% Sc, 0% to 0.4% Zr, and the balance is aluminum.

2. The aluminum alloy according to claim 1, characterized in that Calculated by mass percentage, the following metals are included: 0.7% to 0.8% Mg, 0.9% to 1.1% Si, 0.5% to 0.6% Cu, 0.1% to 0.15% Mn, 0.1% to 0.3% Sc, 0.1% to 0.3% Zr, and the balance is aluminum.

3. The aluminum alloy according to claim 1 or 2, characterized in that: The following metals are also included: at least one of Fe, Ti and Zn, and the sum of the mass percentages of Fe, Ti and Zn is less than 0.2% by mass.

4. The method for preparing an aluminum alloy according to any one of claims 1 to 3, characterized in that: include: Raw material pretreatment, low temperature rolling and aging treatment, The temperature of the low temperature rolling is T1, wherein T1 satisfies: -20°C≤T1≤25°C; The temperature of the aging treatment is T2, wherein T2 satisfies: 80°C≤T2≤120°C; The duration of the interval between the low-temperature rolling and the aging treatment is Δt1, wherein the Δt1 satisfies: Δt1≤30min.

5. The preparation method according to claim 4, characterized in that: The raw materials include: 99.9wt.% high-purity Al, industrial-purity Mg, Al-Sc alloy, Al-Cu alloy, Al-Mn alloy, Al-Si and Al-Zr alloy.

6. The preparation method according to claim 5, characterized in that: The pretreatment of the raw materials includes: 99.9wt.% high-purity Al, industrial pure Mg, Al-Sc alloy, Al-Cu alloy, Al-Mn alloy, Al-Si and Al-Zr alloy are melted, degassed and deslaged, and then cast to obtain an ingot.

7. The preparation method according to claim 6, characterized in that: The pretreatment of the raw materials also includes: The ingot is homogenized and annealed, wherein the homogenized annealing comprises: Insulation treatment: Insulating the ingot at 480° C. to 540° C. for 16 h to 32 h; Water quenching: the ingot is water quenched.

8. The method for preparing the aluminum alloy according to claim 7, characterized in that: The heat preservation treatment comprises: Primary heat preservation treatment: the ingot is kept at 480° C. to 500° C. for 12 h to 20 h; Secondary heat preservation treatment: the ingot is heated to 520°C to 540°C and kept warm for 4h to 12h.

9. The method for preparing the aluminum alloy according to claim 7, characterized in that: The duration of the interval between the homogenization annealing and the low-temperature rolling is Δt2, wherein the Δt2 satisfies: Δt2≤60min.

10. The preparation method according to claim 4, characterized in that: The low temperature rolling is performed multiple times, the reduction amount of a single low temperature rolling is 3%-25%, and the total reduction amount of the multiple low temperature rolling is 55%-65%.

11. An alloy part, characterized in that: The alloy part comprises: An aluminum alloy according to any one of claims 1 to 3, or an alloy part made by the preparation method according to any one of claims 4 to 10.

12. Use of the alloy part according to claim 11, characterized in that: The alloy parts are applied to vehicle bodies, vehicle frames, vehicle doors, sub-frames, cross beams, or battery housings.

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