High-strength Al-Zn-Mg alloy with excellent comprehensive performance and preparation method thereof

Abstract

A high-strength Al-Zn-Mg alloy with excellent comprehensive performance and a preparation method thereof, belonging to the field of non-ferrous metal materials and their preparation. In terms of mass fraction, the Al-Zn-Mg alloy comprises the following components: 5.5%≤Zn≤7.9%, 1.2%≤Mg≤2.5%, 0<Cu≤0.6%, 0.05%≤Zr≤0.25%, 0.05%≤Cr≤0.3%, 0.05%≤Mn≤0.5%, 0.02%≤Ti≤0.10%, the remainder being Al and other unavoidable impurities, and the mass percentage content ratio of Zn to Mg is 3.4≤Zn / Mg≤5.3. At the same time, the preparation method thereof is also disclosed: melt casting-homogenization process-extrusion-solid solution and aging process. The method optimizes and controls the content ratio of main alloying elements and micro-alloying elements, and combines the preparation method to prepare Al-Zn-Mg alloy with excellent mechanical properties, corrosion resistance and welding properties. The method has the advantages of simple preparation method, high yield, low energy consumption, low pollution, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of nonferrous metals and their preparation, and in particular to a high-strength Al-Zn-Mg alloy with excellent comprehensive performance and a preparation method thereof. The product exhibits excellent mechanical properties, corrosion resistance and welding properties, and is suitable for use as a structural material for transportation equipment such as automobiles, railway vehicles and airplanes. Background Art

[0002] Al-Zn-Mg alloys are heat-treatable and strengthened aluminum alloys. They are widely used in high-speed rail, automobile and aerospace fields because of their low density, high mechanical properties, corrosion resistance and welding properties. Cu, Zr, Cr, Mn and other elements in Al-Zn-Mg alloys are the main micro-alloying elements of the alloy. On the one hand, the Cu element can reduce the potential of the grain boundary of the Al-Zn-Mg alloy and improve the stress corrosion resistance. On the other hand, the Cu element is beneficial to improve the mechanical properties of the alloy. However, when the Cu content is greater than 0.4wt.%, the corrosion performance of the alloy decreases. Micro-alloying elements Zr, Cr, and Mn combine with Al to form a tiny compound phase, which can inhibit recrystallization to obtain a fibrous structure and control quenching sensitivity. Zr, Cr, and Mn elements can be added together or separately as micro-alloying elements. Zr is the preferred alloying element, and its maximum value should not exceed 0.2wt.%. The Cr element content should be less than 0.3wt.%. When the Cr content is high, a coarse intergranular insoluble phase will be formed in the alloy, resulting in a decrease in the mechanical properties of the alloy. Although Cr is not as effective as Zr as an element that inhibits recrystallization, adding Cr alone or in combination will also inhibit recrystallization. The maximum addition amount of Mn is 0.8wt.%, and the optimal addition amount of Mn is 0.05-0.4wt.%. When Mn is combined with Zr, the Mn+Zr content should be less than 0.4wt.%. Fe and Si elements, as inevitable impurities in Al-Zn-Mg alloys, can combine with Al to form Al-Fe-Si compound phases. Since this compound phase is easy to become the starting point of cracks during the stress process of the alloy, the content of Fe and Si in Al-Zn-Mg alloys should be strictly controlled, wherein the Fe content should be less than 0.2wt.%, and the Si content should be less than 0.1wt.%.

[0003] Generally, the strength or corrosion resistance of Al-Zn-Mg alloys can be improved through deformation and heat treatment processes, but it is difficult to achieve both strength and corrosion resistance, and the improvement of one property requires the sacrifice of another. In addition, trace amounts of Cu can effectively improve the strength of the alloy during the production of Al-Zn-Mg alloys, but the Cu element will seriously affect the welding performance of the alloy.

[0004] The ratio of main elements and the type, content and ratio of trace elements in Al-Zn-Mg alloys seriously affect the performance. The optimization design of alloy composition is an important way to develop high-performance Al-Zn-Mg alloys. Therefore, how to obtain high-performance Al-Zn-Mg alloys with higher mechanical properties, corrosion resistance and welding performance by adjusting the ratio of main elements and trace elements is a technical problem to be solved in this field. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a high-strength Al-Zn-Mg alloy with excellent comprehensive performance and a preparation method thereof, and the product exhibits excellent mechanical properties, corrosion resistance and welding properties. By regulating the content of the main alloy elements and trace elements and adopting a specific preparation process, the microstructure state of the Al-Zn-Mg alloy is regulated, thereby obtaining an Al-Zn-Mg alloy with excellent comprehensive performance.

[0006] The high-strength Al-Zn-Mg alloy with excellent comprehensive performance provided by the present invention comprises main alloying elements Zn and Mg, one or more of microalloying elements Cu, Zr, Cr, Mn, Ti, Fe and Si, and the balance is Al and unavoidable impurities.

[0007] Calculated by mass fraction, the high-strength Al-Zn-Mg alloy with excellent comprehensive performance includes the following components and the mass percentage of each component is: 5.5%≤Zn≤7.9%, 1.2%≤Mg≤2.5%, 0<Cu≤0.6%, 0.05%<Zr≤0.25%, 0.05%<Cr≤0.3%, 0.05%<Mn≤0.5%, 0.02%≤Ti≤0.10%, and the balance is Al and other inevitable impurities.

[0008] Furthermore, the content of a single impurity is less than 0.05%, and the total content of impurities does not exceed 0.3%, wherein the Fe content is less than 0.2%, and the Si content is less than 0.2%.

[0009] Furthermore, for the above-mentioned high-strength Al-Zn-Mg alloy with excellent comprehensive properties, 3.4≤Zn / Mg≤5.3, 0<Zr+Cr+Mn≤0.9%.

[0010] The high-strength Al-Zn-Mg alloy with excellent comprehensive performance has a yield strength of 450-550 MPa, a tensile strength of 470-570 MPa and an elongation of 15-23%.

[0011] The preparation method of the Al-Zn-Mg alloy with excellent comprehensive performance and high strength of the present invention comprises: melting-casting-homogenization process-extrusion-solid solution and aging process. The specific preparation method comprises the following steps:

[0012] 1. Smelting: Prepare pure aluminum, pure zinc, pure magnesium, pure copper, Al-10Cr, Al-10Zr, Al-10Mn and Al-5Ti-B as raw materials, wherein the mass purity of aluminum is ≥99.98%, and the mass purity of pure zinc, pure magnesium and pure copper is ≥99.98%. Under protective atmosphere conditions, heat pure aluminum to 700-730℃ to form an aluminum melt. Put pure copper, Al-10Cr, Al-10Zr, Al-5Ti-B and Al-10Mn into the melt, heat the solution to 730-750℃ to completely melt the alloy, and keep it warm for 5-8 minutes under stirring conditions. Under protective atmosphere conditions, add pure zinc and pure magnesium to the melt, stir until pure zinc and pure magnesium are completely melted, then degas, deslag and cast to obtain an ingot.

[0013] 2. Ingot homogenization treatment: The ingot is heated to 460-520°C at a heating rate of 3-20°C / min, kept at this temperature for 12-36 hours, and then taken out of the furnace and air-cooled to obtain the alloy after homogenization treatment.

[0014] 3. Extrusion: After homogenization, the alloy is subjected to extrusion treatment to remove the surface oxide skin and obtain an extruded alloy billet. During the extrusion process, the extrusion ratio is 10-40; the extrusion temperature is 460-540°C; the extrusion speed is 2mm / s-5mm / s; and the cooling rate after extrusion is greater than 30°C / s.

[0015] 4. Solution treatment and aging treatment: The extruded alloy billet is subjected to solution treatment and aging treatment to obtain a high-strength Al-Zn-Mg alloy with excellent comprehensive performance. The solution treatment process is: temperature 450-485℃, holding time 0.5-3 hours, room temperature water quenching; the aging process is: temperature 100-225℃, holding time 10-72 hours, air cooling after leaving the furnace.

[0016] In the above step 1, the protective atmosphere is an argon atmosphere.

[0017] In the above step 1, the master alloy and the pure metal are added into the melt by bell-jar pressing.

[0018] In the above step 1, the stirring method is mechanical stirring, and the degassing is to introduce argon atmosphere into the melt, and the degassing time is 20-40 minutes.

[0019] In the above step 1, the casting temperature is 720° C. to 735° C. and the casting speed is 200 to 400 mm / min.

[0020] The present invention optimizes and controls the content ratio of the main alloying elements and the microalloying elements, and prepares an Al-Zn-Mg alloy with excellent mechanical properties, corrosion properties and welding properties through a reasonable preparation method. The preparation method of the present invention is simple, has a high yield, low energy consumption, low pollution, is widely used in industrial production, and can realize industrialized mass production of Al-Zn-Mg alloys. DETAILED DESCRIPTION

[0021] The following non-limiting embodiments may enable a person skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0022] The test methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0023] The percentages used in the following examples are by mass unless otherwise specified.

[0024] An Al-Zn-Mg alloy with excellent comprehensive performance and high strength, characterized in that: its components include Al, Zn, Mg, Cu, Zr, Cr, Mn, Zr, and Ti, wherein the mass percentage of Zn is 5.5%-7.9%, the mass percentage of Mg is 1.2%-2.5%, the mass percentage ratio of Zn to Mg is 3.4≤Zn / Mg≤5.3, the mass percentage of Cu is 0-0.6%, the mass percentage of Zr is 0.05%-0.25%, the mass percentage of Cr is 0.05%-0.3%, the mass percentage of Mn is 0.05%-2.5%, and the mass percentage of Ti is 0.02%-0.1%;

[0025] The above-mentioned method for preparing the Al-Zn-Mg alloy with excellent comprehensive performance and high strength comprises the following steps:

[0026] (1) Melting: Prepare pure aluminum, pure zinc, pure magnesium, pure copper, Al-10Cr, Al-10Zr, Al-10Mn and Al-5Ti-B as raw materials, wherein the mass purity of aluminum is ≥99.98%, and the mass purity of pure zinc, pure magnesium and pure copper is ≥99.98%. Under protective atmosphere conditions, heat pure aluminum to 700-730℃ to form aluminum melt. Put pure copper, Al-10Cr, Al-10Zr, Al-5Ti-B and Al-10Mn into the melt, heat the solution to 730-750℃ to completely melt the alloy, and keep it warm for 5-8 minutes under stirring conditions. Under protective atmosphere conditions, pure zinc and pure magnesium are added to the melt and stirred until the pure zinc and pure magnesium are completely melted, followed by degassing with argon gas for 20-40 minutes, and finally slag removal and casting, wherein the casting temperature is 720°C to 735°C and the casting speed is 200 to 400 mm / min.

[0027] (2) Ingot homogenization treatment: The ingot is heated to 460-520°C at a heating rate of 3-20°C / min, kept at this temperature for 12-36 hours, and then taken out of the furnace and air-cooled.

[0028] (3) Extrusion: After homogenization, the alloy is subjected to extrusion treatment to remove the surface oxide skin and obtain an extruded alloy billet. During the extrusion process, the extrusion ratio is 10-40; the extrusion temperature is 460-540°C; the extrusion speed is 2mm / s-5mm / s; and the cooling rate after extrusion is greater than 30°C / s.

[0029] (4) Solution treatment and aging treatment: The extruded alloy billet is subjected to solution treatment and aging to obtain a high-strength Al-Zn-Mg alloy with excellent comprehensive performance. The solution treatment process is as follows: temperature 450-485°C, holding time 0.5-3 hours, room temperature water quenching; the aging process is as follows: temperature 100-225°C, holding time 10-72 hours, and air cooling after exiting the furnace.

[0030] Example 1

[0031] An Al-Zn-Mg alloy with excellent comprehensive performance and high strength, the composition of which includes by mass percentage: Zn: 5.5%, Mg: 1.6%, Cu: 0.2%, Zr: 0.12%, Cr: 0.2%, Mn: 0.4%, Ti: 0.03%, and the balance is Al and inevitable impurities. The process of preparing the alloy is:

[0032] (1) Melting: Prepare pure aluminum, pure zinc, pure magnesium, pure copper, Al-10Cr, Al-10Zr, Al-10Mn and Al-5Ti-B as raw materials, wherein the mass purity of aluminum is ≥99.98%, and the mass purity of pure zinc, pure magnesium and pure copper is ≥99.98%. Under protective atmosphere conditions, heat pure aluminum to 700°C to form an aluminum melt. Put pure copper, Al-10Cr, Al-10Zr, Al-5Ti-B and Al-10Mn into the melt, heat the solution to 730°C to completely melt the alloy, and keep it warm for 6 minutes under stirring conditions. Under protective atmosphere conditions, add pure zinc and pure magnesium to the melt, stir until pure zinc and pure magnesium are completely melted, then degas with argon gas for 30 minutes, finally remove slag and cast, wherein the casting temperature is 720°C and the casting speed is 200mm / min.

[0033] (2) Ingot homogenization treatment: The ingot was heated to 460°C at a heating rate of 3°C / min, kept at this temperature for 36 hours, and then taken out of the furnace and air-cooled.

[0034] (3) Extrusion: After homogenization, the alloy is subjected to extrusion treatment to remove the surface oxide skin and obtain an extruded alloy billet. During the extrusion process, the extrusion ratio is 20; the extrusion temperature is 460°C; the extrusion speed is 2 mm / s; and the cooling rate after extrusion is greater than 30°C / s.

[0035] (4) Solution treatment and aging treatment: The extruded alloy billet is subjected to solution treatment and aging to obtain a high-strength weldable Al-Zn-Mg alloy. The solution treatment process is: temperature 450°C, holding time 3 hours, room temperature water quenching; the aging process is: temperature 205°C, holding time 24 hours, and air cooling after leaving the furnace.

[0036] The performance test was carried out on the high-strength Al-Zn-Mg alloy with excellent comprehensive performance obtained by the above preparation method, and the yield strength of the high-strength Al-Zn-Mg alloy with excellent comprehensive performance was 472 MPa, the tensile strength was 495 MPa, and the elongation was 18.5%.

[0037] Example 2

[0038] An Al-Zn-Mg alloy with excellent comprehensive performance and high strength, the composition of which includes by mass percentage: Zn: 6%, Mg: 1.8%, Cu: 0.3%, Zr: 0.2%, Cr: 0.2%, Mn: 0.5%, Ti: 0.03%, and the balance is Al and inevitable impurities. The process of preparing the alloy is:

[0039] (1) Melting: Prepare pure aluminum, pure zinc, pure magnesium, pure copper, Al-10Cr, Al-10Zr, Al-10Mn and Al-5Ti-B as raw materials, wherein the mass purity of aluminum is ≥99.98%, and the mass purity of pure zinc, pure magnesium and pure copper is ≥99.98%. Under protective atmosphere conditions, heat pure aluminum to 730°C to form an aluminum melt. Put pure copper, Al-10Cr, Al-10Zr, Al-5Ti-B and Al-10Mn into the melt, heat the solution to 750°C to completely melt the alloy, and keep it warm for 5 minutes under stirring conditions. Under protective atmosphere conditions, add pure zinc and pure magnesium to the melt, stir until pure zinc and pure magnesium are completely melted, then degas with argon gas for 20 minutes, finally remove slag and cast, wherein the casting temperature is 735°C and the casting speed is 400mm / min.

[0040] (2) Ingot homogenization treatment: The ingot was heated to 520°C at a heating rate of 10°C / min, kept at this temperature for 24 hours, and then taken out of the furnace and air-cooled.

[0041] (3) Extrusion: After homogenization, the alloy is subjected to extrusion treatment to remove the surface oxide skin and obtain an extruded alloy billet. During the extrusion process, the extrusion ratio is 30; the extrusion temperature is 540°C; the extrusion speed is 5 mm / s; and the cooling rate after extrusion is greater than 30°C / s.

[0042] (4) Solution treatment and aging treatment: The extruded alloy billet is subjected to solution treatment and aging to obtain a high-strength weldable Al-Zn-Mg alloy. The solution treatment process is as follows: temperature 485°C, holding time 0.5 hour, room temperature water quenching; the aging process is as follows: temperature 225°C, holding time 10 hours, and air cooling after exiting the furnace.

[0043] The performance test was carried out on the high-strength Al-Zn-Mg alloy with excellent comprehensive performance obtained by the above preparation method, and the yield strength of the high-strength Al-Zn-Mg alloy with excellent comprehensive performance was 494 MPa, the tensile strength was 515 MPa, and the elongation was 17.6%.

[0044] Example 3

[0045] An Al-Zn-Mg alloy with excellent comprehensive performance and high strength, the composition of which includes by mass percentage: Zn: 6.3%, Mg: 1.9%, Cu: 0.2%, Zr: 0.15%, Cr: 0.2%, Mn: 0.4%, Ti: 0.03%, and the balance is Al and inevitable impurities. The process of preparing the alloy is:

[0046] (1) Melting: Prepare pure aluminum, pure zinc, pure magnesium, pure copper, Al-10Cr, Al-10Zr, Al-10Mn and Al-5Ti-B as raw materials, wherein the mass purity of aluminum is ≥99.98%, and the mass purity of pure zinc, pure magnesium and pure copper is ≥99.98%. Under protective atmosphere conditions, heat pure aluminum to 720°C to form an aluminum melt. Put pure copper, Al-10Cr, Al-10Zr, Al-5Ti-B and Al-10Mn into the melt, heat the solution to 750°C to completely melt the alloy, and keep it warm for 6 minutes under stirring conditions. Under protective atmosphere conditions, add pure zinc and pure magnesium to the melt, stir until pure zinc and pure magnesium are completely melted, then use argon gas for degassing, the degassing time is 40 minutes, and finally remove slag and cast, wherein the casting temperature is 735°C and the casting speed is 300mm / min.

[0047] (2) Ingot homogenization treatment: The ingot is heated to 500°C at a heating rate of 15°C / min, kept at this temperature for 24 hours, and then taken out of the furnace and air-cooled.

[0048] (3) Extrusion: After homogenization, the alloy is subjected to extrusion to remove the surface oxide skin and obtain an extruded alloy billet. During the extrusion process, the extrusion ratio is 20; the extrusion temperature is 540°C; the extrusion speed is 3 mm / s; and the cooling rate after extrusion is greater than 30°C / s.

[0049] (4) Solution treatment and aging treatment: The extruded alloy billet is subjected to solution treatment and aging to obtain a high-strength weldable Al-Zn-Mg alloy. The solution treatment process is as follows: temperature 465°C, holding time 1 hour, room temperature water quenching; the aging process is as follows: temperature 200°C, holding time 36 hours, and air cooling after exiting the furnace.

[0050] The performance test of the high-strength Al-Zn-Mg alloy with excellent comprehensive performance obtained by the above preparation method was carried out, and the yield strength of the high-strength Al-Zn-Mg alloy with excellent comprehensive performance was 505MPa, the tensile strength was 527MPa, and the elongation was 19.4%.

[0051] Example 4

[0052] An Al-Zn-Mg alloy with excellent comprehensive performance and high strength, the composition of which includes by mass percentage: Zn: 7.5%, Mg: 2.3%, Cu: 0.2%, Zr: 0.15%, Cr: 0.2%, Mn: 0.4%, Ti: 0.03%, and the balance is Al and inevitable impurities. The process of preparing the alloy is:

[0053] (1) Melting: Prepare pure aluminum, pure zinc, pure magnesium, pure copper, Al-10Cr, Al-10Zr, Al-10Mn and Al-5Ti-B as raw materials, wherein the mass purity of aluminum is ≥99.98%, and the mass purity of pure zinc, pure magnesium and pure copper is ≥99.98%. Under protective atmosphere conditions, heat pure aluminum to 710°C to form an aluminum melt. Put pure copper, Al-10Cr, Al-10Zr, Al-5Ti-B and Al-10Mn into the melt, heat the solution to 740°C to completely melt the alloy, and keep it warm for 5-8 minutes under stirring conditions. Under protective atmosphere conditions, add pure zinc and pure magnesium to the melt, stir until pure zinc and pure magnesium are completely melted, then use argon gas for degassing, the degassing time is 25 minutes, and finally remove slag and cast, wherein the casting temperature is 730°C and the casting speed is 250mm / min.

[0054] (2) Ingot homogenization treatment: The ingot was heated to 520°C at a heating rate of 5°C / min, kept at this temperature for 12 hours, and then taken out of the furnace and air-cooled.

[0055] (3) Extrusion: After homogenization, the surface oxide skin of the alloy is removed and then extruded to obtain an extruded alloy billet. During the extrusion process, the extrusion ratio is 20; the extrusion temperature is 500°C; the extrusion speed is 4 mm / s; and the cooling rate after extrusion is greater than 30°C / s.

[0056] (4) Solution treatment and aging treatment: The extruded alloy billet is subjected to solution treatment and aging to obtain a high-strength weldable Al-Zn-Mg alloy. The solution treatment process is: temperature 475°C, holding time 2 hours, room temperature water quenching; the aging process is: temperature 155°C, holding time 24 hours, and air cooling after leaving the furnace.

[0057] The performance test was carried out on the high-strength Al-Zn-Mg alloy with excellent comprehensive performance obtained by the above preparation method, and the yield strength of the high-strength Al-Zn-Mg alloy with excellent comprehensive performance was 518 MPa, the tensile strength was 539 MPa, and the elongation was 21%.

[0058] Example 5

[0059] An Al-Zn-Mg alloy with excellent comprehensive performance and high strength, the composition of which includes, by mass percentage, Zn: 7.9%, Mg: 2.5%, Cu: 0.15%, Zr: 0.15%, Cr: 0.25%, Mn: 0.3%, Ti: 0.03%, and the balance is Al and inevitable impurities. The process of preparing the alloy is the same as that of Example 1.

[0060] The performance test was carried out on the high-strength Al-Zn-Mg alloy with excellent comprehensive performance obtained by the above preparation method, and the yield strength of the high-strength Al-Zn-Mg alloy with excellent comprehensive performance was 526 MPa, the tensile strength was 555 MPa, and the elongation was 19.2%.

[0061] Example 6

[0062] An Al-Zn-Mg alloy with excellent comprehensive performance and high strength, wherein the composition includes, by mass percentage, Zn: 7.9%, Mg: 2.5%, Zr: 0.15%, Cr: 0.25%, Mn: 0.3%, Ti: 0.03%, and the balance is Al and unavoidable impurities, and the difference from Example 5 is that the alloy does not contain copper. The process of preparing the alloy is the same as that of Example 1.

[0063] The performance test of the high-strength Al-Zn-Mg alloy with excellent comprehensive performance obtained by the above preparation method was carried out, and the yield strength of the high-strength Al-Zn-Mg alloy with excellent comprehensive performance was 524 MPa, the tensile strength was 552 MPa, and the elongation was 16.8%.

[0064] The above technical scheme explains the technical idea of ​​the present invention, which cannot be used to limit the protection scope of the present invention. Any changes and modifications made to the above technical scheme based on the technical essence of the present invention without departing from the content of the technical scheme of the present invention shall fall within the protection scope of the technical scheme of the present invention.

Claims

1. A high-strength Al-Zn-Mg alloy with excellent comprehensive performance, characterized in that: Measured in mass percentage, the Al-Zn-Mg alloy with excellent comprehensive performance and high strength includes main alloying elements and micro-alloying elements, the main alloying element is Al-Zn-Mg, the micro-alloying elements include one or more of Cu, Zr, Cr, Mn, Ti, Fe, and Si, and the balance is Al and unavoidable impurities; Among them, the mass ratio of the micro-alloying elements meets the condition (1), and the mass ratio of the main alloying elements meets the condition (2): 0<Cu≤0.6%, 0.05%<Zr≤0.25%, 0.05%<Cr≤0.3%, 0.05%<Mn≤0.5%, 0.02%≤Ti≤0.10%, Fe<0.2%, Si<0.2% (1) 5.5%<Zn≤7.9%, 1.2%<Mg≤2.5%, the balance is Al; (2); 0<Zr+Cr+Mn≤0.9%, the mass percentage of a single impurity is less than 0.05%, and the total mass percentage of impurities does not exceed 0.3%; The high-strength Al-Zn-Mg alloy with excellent comprehensive performance has a yield strength of 450-550 MPa, a tensile strength of 470-570 MPa, and an elongation of 15-23%.

2. The method for preparing the Al-Zn-Mg alloy with excellent comprehensive performance and high strength according to claim 1, characterized in that: include: Melting-homogenization process-extrusion-solidification and aging process; specifically includes the following steps: S1. Melting and casting: according to the designed Al-Zn-Mg alloy composition with excellent comprehensive performance and high strength, prepare the components of the alloy, prepare pure aluminum, pure zinc, pure magnesium, pure copper, Al-10Cr, Al-10Zr, Al-10Mn and Al-5Ti-B as raw materials, wherein the mass purity of aluminum is ≥99.98%, and the mass purity of pure zinc, pure magnesium and pure copper are all ≥99.98%, heat to 730-750℃, melt and cast to obtain alloy ingots; S2. Ingot homogenization treatment: The ingot is heated to 460-520°C at a heating rate of 3-20°C / min, kept at this temperature for 12-36 hours, and then air-cooled to obtain a homogenized alloy; S3. Extrusion: After the homogenization treatment, the alloy ingot is subjected to extrusion treatment after removing the surface oxide skin, the extrusion ratio is 10-40, the extrusion temperature is 460-540°C, the extrusion speed is 2mm / s-5mm / s, and the cooling rate after extrusion is greater than 30°C / s to obtain an extruded alloy billet; S4. Solution treatment and aging treatment: The extruded alloy billet is subjected to solution treatment and aging treatment. Aging process: temperature 100-225°C, insulation time 10-72 hours, air cooling after being taken out of the furnace, to obtain a high-strength Al-Zn-Mg alloy with excellent comprehensive performance.

3. The method for preparing the Al-Zn-Mg alloy with excellent comprehensive performance and high strength according to claim 2, characterized in that: In step S1, smelting includes the following steps: Under protective atmosphere conditions, pure aluminum is heated to 700-730°C to form aluminum melt; Under protective atmosphere, pure copper, Al-10Cr, Al-10Zr, Al-5Ti-B and Al-10Mn are put into the melt, the solution is heated to 730-750℃ to completely melt the alloy, and then kept warm for 5-8 minutes under stirring conditions; Under protective atmosphere conditions, pure zinc and pure magnesium are added into the melt, stirred until the pure zinc and pure magnesium are completely melted, and then degassed and deslaged.

4. The method for preparing the Al-Zn-Mg alloy with excellent comprehensive performance and high strength according to claim 3, characterized in that: Argon is used for degassing, and the introduction time is 20-40 minutes; the stirring method is mechanical stirring.

5. The method for preparing the Al-Zn-Mg alloy with excellent comprehensive performance and high strength according to claim 2, characterized in that: In S1, the casting step is: at a casting temperature of 720° C. to 735° C. and a casting speed of 200 to 400 mm / min, and finally a shearing treatment is performed.

6. The method for preparing the Al-Zn-Mg alloy with excellent comprehensive performance and high strength according to claim 2, characterized in that: In the above-mentioned S4, the solution treatment process is as follows: temperature 450-485° C., holding time 0.5-3 hours, and water quenching at room temperature.