A method for preparing a 7-series aluminum alloy with improved parking stability and aging strength

Abstract

The present application relates to the technical field of aluminum alloy processing forming, and particularly relates to a preparation method of 7-series aluminum alloy for improving parking stability and aging strength. The alloy is sequentially added into a smelting furnace, and purification filtering and stretching are carried out. Through precise control of the temperature of the 7-series aluminum alloy extruded profile after extrusion and reasonable stretching treatment, the just extruded profile is cooled to 160-180 DEG C after online quenching, the online quenching is stopped, and then 2%-4% stretching treatment is immediately carried out, and then natural cooling to room temperature is carried out. The yield strength of the obtained profile after natural parking for 30 days is not higher than 18 MPa, and the strength can be increased by more than 25 MPa after artificial aging treatment. In the present application, the process of naturally cooling the profile to room temperature and the stretching treatment are equivalent to short-term pretreatment, the formation of atomic clusters in the parking effect process is inhibited, dislocations are generated by stretching to destroy the atomic cluster structure, and the vacancies formed by quenching are bound, so that the negative effect of natural aging is inhibited, and the subsequent artificial aging performance is not reduced.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy processing and forming technology, specifically relating to a method for preparing 7-series aluminum alloys to improve parking stability and aging strength. Background Technology

[0002] Aluminum alloys are widely used in vehicles, high-speed trains, aerospace, and other fields due to their high strength, good weldability, excellent recyclability, and heat treatability. 7-series aluminum alloys, as a representative of high-strength aluminum alloys, are increasingly used in vehicle lightweighting and aerospace weight reduction. However, high-strength 7-series aluminum alloys exhibit a significant storage effect. When profiles are left to rest naturally after extrusion and quenching, their strength increases significantly over time. This negatively impacts subsequent deep processing of the profiles, such as bending and stamping, reducing product processing accuracy, increasing springback, and lowering surface quality. Furthermore, the mechanical properties of 7-series aluminum alloys fluctuate considerably with the number of days of natural storage. This increase in strength and the fluctuation in strength variation severely affect subsequent deep processing techniques and production cycle time, significantly reducing product yield and production efficiency. In addition, the continuous formation of atomic clusters during natural storage reduces the elements available for precipitate formation during subsequent artificial aging, leading to a decline in the final product performance.

[0003] Currently, there are four main approaches to delaying the natural aging of aluminum alloys: 1. Pre-aging treatment; 2. Pre-deformation treatment; 3. Alloy composition adjustment; and 4. Regression heat treatment. CN109837490B proposes a series of processes including solution quenching, low-temperature pre-aging treatment, pre-stretch deformation, and high-temperature pre-aging treatment to suppress the natural aging effect. CN117512480A patent describes a process where the composite of La and Zn elements interacts with pre-deformation to effectively suppress the formation of room-temperature atomic clusters during natural aging, thereby inhibiting the natural aging effect. CN109487184B's invention patent proposes a synchronous process for the regression forming of artificially aged high-strength aluminum alloys. This invention rapidly heats artificially aged aluminum alloy sheets in a mold using electromagnetic induction, but this method only achieves a short-term reduction in hardness; subsequent natural aging will trigger the re-precipitation of strengthening phases, leading to a renewed increase in strength. These methods often require controlling alloy composition and adding subsequent processes. In addition, the addition of heat treatment processes will lead to increased energy consumption, which will increase the difficulty in actual production. Therefore, how to reduce the parking effect and improve the artificial aging strength is of great significance for the development and production of 7-series aluminum alloys. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing 7-series aluminum alloys that improves storage stability and aging strength. By precisely controlling the temperature of the 7-series aluminum alloy extruded profile after extrusion and by performing reasonable stretching treatment, the extruded profile is cooled to 160-180°C after online quenching and then immediately subjected to 2%-4% stretching treatment. Subsequently, it is allowed to cool naturally to room temperature. After 30 days of natural storage, the yield strength of the obtained profile increases by no more than 18MPa, and after artificial aging treatment, its strength can be increased by more than 25MPa.

[0005] A method for preparing 7-series aluminum alloys to improve parking stability and aging strength, the specific steps of which are as follows:

[0006] (1) Prepare raw materials according to the following mass fraction of aluminum alloy raw materials: Cu: 0-0.25wt%, Mg: 0.7-1.6wt%, Zn: 4.0-5.5wt%, Zr: 0.12-0.30wt%, the content of other individual impurities ≤0.05wt%, the total content of other impurities ≤0.15wt%, and the balance is Al;

[0007] (2) Place Al ingots in a melting furnace. When the Al ingots begin to melt, place them in a pure Zn alloy, an aluminum-copper master alloy with a content of 60%, and an aluminum-zirconium master alloy with a content of 5%. Heat until all are melted, then add pure Mg and stir to obtain molten aluminum.

[0008] (3) After the aluminum liquid is purified and filtered, semi-continuous casting is carried out to obtain a cast rod;

[0009] (4) After homogenization treatment, the casting rod is cooled by strong wind or water mist, and then air-cooled to room temperature after cooling to 80-100℃.

[0010] (5) Extrude the cooled casting rod;

[0011] (6) After extrusion, the profile is quenched online and then stretched immediately, and then naturally cooled to room temperature to obtain 7-series aluminum alloy with improved parking stability.

[0012] (7) The 7-series aluminum alloy with improved parking stability is subjected to aging treatment to obtain a 7-series aluminum alloy with improved parking stability and aging strength.

[0013] Furthermore, the temperature at which all the material is melted in step (2) is 740±10℃.

[0014] Furthermore, the temperature during the purification process in step (3) is 740±10℃; the filtration uses a 30ppi+40ppi ceramic filter plate for dual-stage filtration.

[0015] Furthermore, the semi-continuous casting process described in step (3) employs a casting temperature of 725-740℃, a casting speed of 75-80 mm / min, and a water flow rate of 2.8-3.0 m³ / min for each casting rod. 3 / h, during casting, the melt undergoes online purification and is filtered through a 30ppi+40ppi dual-stage filter before entering the casting tray for semi-continuous casting.

[0016] Furthermore, the homogenization process in step (4) is divided into primary homogenization and secondary homogenization; the primary homogenization regime is: temperature (440±10)℃, time (5±2)h; the secondary homogenization regime is: temperature (470±10)℃, time (14±2)h.

[0017] Furthermore, the temperature of the casting rod during extrusion in step (5) is (480±10)℃.

[0018] Furthermore, the quenching temperature in step (6) is ≥510℃; online quenching is stopped when the surface temperature of the profile cools to (170±10)℃.

[0019] Furthermore, the stretching rate of the stretching treatment described in step (6) is (3±1)%.

[0020] Further, the aging process described in step (7) is a first-level artificial aging process with a temperature of 105°C and a time of (10±2)h, and a second-level artificial aging process with a temperature of 135°C and a time of (22±2)h.

[0021] A 7-series aluminum alloy that improves parking stability and aging strength is prepared using the above method.

[0022] The beneficial effects of this invention are:

[0023] 1. This invention precisely controls the temperature of the extruded profile, allowing it to be cooled to 160-180°C after online quenching, then the online quenching is stopped, followed immediately by stretching and allowing it to cool naturally to room temperature. During this slower natural cooling process, the product undergoes a brief pre-aging treatment. The formation of atomic clusters during this brief pre-aging process significantly reduces the supersaturation of solute atoms in the aluminum matrix, inhibiting the formation of atomic clusters during the resting effect and thus suppressing the negative effects of natural aging. Furthermore, the immediate stretching treatment after stopping quenching eliminates residual stress from quenching while simultaneously disrupting the structure through the interaction between dislocations and atomic clusters, and binding the vacancies formed during quenching. This, combined with pre-aging, suppresses the subsequent natural aging effect, ensuring that the yield strength of the 7-series aluminum alloy obtained by this invention increases by no more than 18 MPa after 30 days of natural resting.

[0024] 2. The natural cooling process and the stretching treatment immediately after stopping quenching during the preparation process of the present invention can effectively suppress the generation of atomic clusters and quenching vacancies. Therefore, a larger number of strengthening phases will be generated during subsequent artificial aging, which increases the strength of the prepared 7-series aluminum alloy by more than 25 MPa.

[0025] 3. The preparation method described in this invention can greatly improve the stability of subsequent 7-series aluminum alloy deep-processed products, increase product processing accuracy, reduce springback, improve surface quality, and improve alloy mechanical properties.

[0026] 4. The method for preparing 7-series aluminum alloys provided by this invention has good market application prospects in automotive lightweighting and aerospace weight reduction. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] A method for preparing 7-series aluminum alloys to improve parking stability and aging strength, the specific steps of which are as follows:

[0030] (1) Prepare aluminum alloy raw materials according to the following proportions: Zn: 4.0wt%, Mg: 0.7wt%, Zr: 0.12wt%, the content of each individual impurity is ≤0.05wt%, the total content of the remaining impurities is ≤0.15wt%, and the balance is Al.

[0031] (2) Place Al ingots in a melting furnace. When the Al ingots begin to melt, place them in a pure Zn alloy, an aluminum-copper master alloy with a content of 60%, and an aluminum-zirconium master alloy with a content of 5%. Heat the mixture to 730°C until all the alloys have melted, then add pure Mg and stir to obtain molten aluminum.

[0032] (3) After purification treatment and 30ppi+40ppi dual-stage filtration of the aluminum liquid, semi-continuous casting is carried out at a casting temperature of 725℃, a casting speed of 75mm / min, and a water flow rate of 2.8m for a single casting rod. 3 / h, to obtain the casting rod;

[0033] (4) After homogenizing the casting rod, use strong wind or water mist to cool it to 100°C and then air cool it to room temperature. First homogenization is carried out: temperature is 430°C and time is 3h; then second homogenization is carried out: temperature is 460°C and time is 12h.

[0034] (5) Extrude the cooled casting rod at a temperature of 470°C.

[0035] (6) After extrusion, the profile is quenched online at a quenching temperature of ≥510℃. When the surface temperature of the profile cools down to 160℃, the online quenching is stopped and then a 2% stretching treatment is immediately performed. After that, it is naturally cooled to room temperature.

[0036] (7) The profile was subjected to a first-level artificial aging treatment at a temperature of 105℃ for 8 hours and a second-level artificial aging treatment at a temperature of 135℃ for 22 hours to obtain 7-series aluminum alloy material.

[0037] Example 2

[0038] A method for preparing 7-series aluminum alloys to improve parking stability and aging strength, the specific steps of which are as follows:

[0039] (1) Prepare aluminum alloy raw materials according to the following proportions: Zn: 4.3wt%, Mg: 0.9wt%, Cu: 0.04wt%, Zr: 0.14wt%; the content of each individual impurity is ≤0.05wt%; the total content of the remaining impurities is ≤0.15wt%; the balance is Al.

[0040] (2) Place Al ingots in a melting furnace. When the Al ingots begin to melt, place them in a pure Zn alloy, an aluminum-copper master alloy with a content of 60%, and an aluminum-zirconium master alloy with a content of 5%. Heat the mixture to 734°C until all the alloys have melted, then add pure Mg and stir to obtain molten aluminum.

[0041] (3) After purification treatment and 30ppi+40ppi dual-stage filtration of the aluminum liquid, semi-continuous casting is carried out at a casting temperature of 728℃, a casting speed of 77mm / min, and a water flow rate of 2.8m for a single casting rod. 3 / h, to obtain the casting rod;

[0042] (4) After homogenizing the casting rod, use strong wind or water mist to cool it to 96°C and then air cool it to room temperature. First homogenization is carried out: temperature is 440°C and time is 5h; then second homogenization is carried out: temperature is 470°C and time is 12h.

[0043] (5) Extrude the cooled casting rod at a temperature of 474℃ during extrusion.

[0044] (6) After extrusion, the profile is quenched online at a quenching temperature of ≥510℃. When the surface temperature of the profile cools down to 164℃, the online quenching is stopped and then a 2.4% stretching treatment is immediately performed, followed by natural cooling to room temperature.

[0045] (7) The profile was subjected to a first-level artificial aging treatment at a temperature of 105℃ for 8 hours and a second-level artificial aging treatment at a temperature of 135℃ for 24 hours to obtain 7-series aluminum alloy material.

[0046] Example 3

[0047] A method for preparing 7-series aluminum alloys to improve parking stability and aging strength, the specific steps of which are as follows:

[0048] (1) Prepare aluminum alloy raw materials according to the following proportions: Zn: 4.5wt%, Mg: 1.1wt%, Cu: 0.08wt%, Zr: 0.16wt%; the content of each individual impurity is ≤0.05wt%; the total content of the remaining impurities is ≤0.15wt%; the balance is Al.

[0049] (2) Place Al ingots in a melting furnace. When the Al ingots begin to collapse, place them in a pure Zn alloy, an aluminum-copper master alloy with a content of 60%, and an aluminum-zirconium master alloy with a content of 5%. Heat the mixture to 738°C until all the alloys have melted, then add pure Mg and stir to obtain molten aluminum.

[0050] (3) After purification treatment and 30ppi+40ppi dual-stage filtration of the aluminum liquid, semi-continuous casting is carried out at a casting temperature of 730℃, a casting speed of 77mm / min, and a water flow rate of 2.9m for a single casting rod. 3 / h, to obtain the casting rod;

[0051] (4) After homogenizing the casting rod, use strong wind or water mist to cool it to 92°C and then air cool it to room temperature. First homogenization is carried out: temperature is 440°C and time is 7h; then second homogenization is carried out: temperature is 480°C and time is 12h.

[0052] (5) Extrude the cooled casting rod at a temperature of 476℃.

[0053] (6) After extrusion, the profile is quenched online at a quenching temperature of ≥510℃. When the surface temperature of the profile cools down to 168℃, the online quenching is stopped and then a 2.7% stretching treatment is immediately performed, followed by natural cooling to room temperature.

[0054] (7) The profile was subjected to a first-level artificial aging treatment at a temperature of 105℃ for 10 hours and a second-level artificial aging treatment at a temperature of 135℃ for 22 hours to obtain 7-series aluminum alloy material.

[0055] Example 4

[0056] A method for preparing 7-series aluminum alloys to improve parking stability and aging strength, the specific steps of which are as follows:

[0057] (1) Prepare aluminum alloy raw materials according to the following proportions: Zn: 4.8wt%, Mg: 1.3wt%, Cu: 0.14wt%, Zr: 0.18wt%; the content of each individual impurity is ≤0.05wt%; the total content of the remaining impurities is ≤0.15wt%; the balance is Al.

[0058] (2) Place Al ingots in a melting furnace. When the Al ingots begin to melt, place them in a pure Zn alloy, an aluminum-copper master alloy with a content of 60%, and an aluminum-zirconium master alloy with a content of 5%. Heat the mixture to 740°C until all the alloys have melted, then add pure Mg and stir to obtain molten aluminum.

[0059] (3) After purification treatment and 30ppi+40ppi dual-stage filtration of the aluminum liquid, semi-continuous casting is carried out at a casting temperature of 734℃, a casting speed of 78mm / min, and a water flow rate of 2.9m for a single casting rod. 3 / h, to obtain the casting rod;

[0060] (4) After homogenizing the casting rod, use strong wind or water mist to cool it to 88°C and then air cool it to room temperature. First homogenization is carried out: temperature is 445°C and time is 5h; then second homogenization is carried out: temperature is 475°C and time is 13h.

[0061] (5) Extrude the cooled casting rod at a temperature of 480℃ during extrusion.

[0062] (6) After extrusion, the profile is quenched online at a quenching temperature of ≥510℃. When the surface temperature of the profile cools down to 170℃, the online quenching is stopped and then a 3.1% stretching treatment is immediately performed, followed by natural cooling to room temperature.

[0063] (7) The profile was subjected to a first-level artificial aging treatment at a temperature of 105℃ for 10 hours and a second-level artificial aging treatment at a temperature of 135℃ for 24 hours to obtain 7-series aluminum alloy material.

[0064] Example 5

[0065] A method for preparing 7-series aluminum alloys to improve parking stability and aging strength, the specific steps of which are as follows:

[0066] (1) Prepare aluminum alloy raw materials according to the following proportions: Zn: 5.0wt%, Mg: 1.4wt%, Cu: 0.18wt%, Zr: 0.20wt%; the content of each individual impurity is ≤0.05wt%; the total content of the remaining impurities is ≤0.15wt%; the balance is Al.

[0067] (2) Place Al ingots in a melting furnace. When the Al ingots begin to melt, place them in a pure Zn alloy, an aluminum-copper master alloy with a content of 60%, and an aluminum-zirconium master alloy with a content of 5%. Heat the mixture to 744°C until all the alloys have melted, then add pure Mg and stir to obtain molten aluminum.

[0068] (3) After purification treatment and 30ppi+40ppi dual-stage filtration of the aluminum liquid, semi-continuous casting is carried out at a casting temperature of 736℃, a casting speed of 78mm / min, and a water flow rate of 2.9m for a single casting rod. 3 / h, to obtain the casting rod;

[0069] (4) After homogenizing the casting rod, use strong wind or water mist to cool it to 86°C and then air cool it to room temperature. First homogenization is carried out: temperature is 449°C and time is 3h; then second homogenization is carried out: temperature is 480°C and time is 13h.

[0070] (5) Extrude the cooled casting rod at a temperature of 484℃ during extrusion.

[0071] (6) After extrusion, the profile is quenched online at a quenching temperature of ≥510℃. When the surface temperature of the profile cools down to 172℃, the online quenching is stopped and then a 3.4% stretching treatment is immediately performed, followed by natural cooling to room temperature.

[0072] (7) The profile was subjected to a first-level artificial aging treatment at a temperature of 105℃ for 12 hours and a second-level artificial aging treatment at a temperature of 135℃ for 20 hours to obtain 7-series aluminum alloy material.

[0073] Example 6

[0074] A method for preparing 7-series aluminum alloys to improve parking stability and aging strength, the specific steps of which are as follows:

[0075] (1) Prepare aluminum alloy raw materials according to the following proportions: Zn: 5.2wt%, Mg: 1.5wt%, Cu: 0.21wt%, Zr: 0.26wt%; the content of each individual impurity is ≤0.05wt%; the total content of the remaining impurities is ≤0.15wt%; the balance is Al.

[0076] (2) Place Al ingots in a melting furnace. When the Al ingots begin to melt, place them in a pure Zn alloy, an aluminum-copper master alloy with a content of 60%, and an aluminum-zirconium master alloy with a content of 5%. Heat the mixture to 748°C until all the alloys have melted, then add pure Mg and stir to obtain molten aluminum.

[0077] (3) After purification treatment and 30ppi+40ppi dual-stage filtration of the aluminum liquid, semi-continuous casting is carried out at a casting temperature of 738℃, a casting speed of 80mm / min, and a water flow rate of 3.0m for a single casting rod. 3 / h, to obtain the casting rod;

[0078] (4) After homogenizing the casting rod, use strong wind or water mist to cool it to 84°C and then air cool it to room temperature. First homogenization is carried out: temperature is 448°C and time is 6h; then second homogenization is carried out: temperature is 480°C and time is 14h.

[0079] (5) Extrude the cooled casting rod at a temperature of 488℃.

[0080] (6) After extrusion, the profile is quenched online at a quenching temperature of ≥510℃. When the surface temperature of the profile cools down to 175℃, the online quenching is stopped and then a 4% stretching treatment is immediately performed. After that, it is naturally cooled to room temperature.

[0081] (7) The profile was subjected to a first-level artificial aging treatment at a temperature of 105℃ for 12 hours and a second-level artificial aging treatment at a temperature of 135℃ for 22 hours to obtain 7-series aluminum alloy material.

[0082] Example 7

[0083] A method for preparing 7-series aluminum alloys to improve parking stability and aging strength, the specific steps of which are as follows:

[0084] (1) Prepare aluminum alloy raw materials according to the following proportions: Zn: 5.5wt%, Mg: 1.6wt%, Cu: 0.25wt%, Zr: 0.30wt%; the content of each individual impurity is ≤0.05wt%; the total content of the remaining impurities is ≤0.15wt%; the balance is Al.

[0085] (2) Place Al ingots in a melting furnace. When the Al ingots begin to melt, place them in a pure Zn alloy, an aluminum-copper master alloy with a content of 60%, and an aluminum-zirconium master alloy with a content of 5%. Heat the mixture to 750°C until all the alloys have melted, then add pure Mg and stir to obtain molten aluminum.

[0086] (3) After purification treatment and 30ppi+40ppi dual-stage filtration of the aluminum liquid, semi-continuous casting is carried out at a casting temperature of 740℃, a casting speed of 80mm / min, and a water flow rate of 3.0m for a single casting rod. 3 / h, to obtain the casting rod;

[0087] (4) After homogenizing the casting rod, use strong wind or water mist to cool it to 80°C and then air cool it to room temperature. First homogenization is carried out: temperature is 450°C and time is 7h; then second homogenization is carried out: temperature is 480°C and time is 16h.

[0088] (5) Extrude the cooled casting rod at a temperature of 490℃ during extrusion.

[0089] (6) After extrusion, the profile is quenched online at a quenching temperature of ≥510℃. When the surface temperature of the profile cools down to 180℃, the online quenching is stopped and then a 4% stretching treatment is immediately performed. After that, it is naturally cooled to room temperature.

[0090] (7) The profile was subjected to a first-level artificial aging treatment at a temperature of 105℃ for 12 hours and a second-level artificial aging treatment at a temperature of 135℃ for 24 hours to obtain 7-series aluminum alloy material.

[0091] Comparative Example 1

[0092] A method for preparing 7-series aluminum alloys to improve parking stability and aging strength, the specific steps of which are as follows:

[0093] (1) Prepare aluminum alloy raw materials according to the following proportions: Zn: 4.0wt%, Mg: 0.7wt%, Zr: 0.12wt%, the content of each individual impurity is ≤0.05wt%, the total content of the remaining impurities is ≤0.15wt%, and the balance is Al.

[0094] (2) Place Al ingots in a melting furnace. When the Al ingots begin to melt, place them in a pure Zn alloy, an aluminum-copper master alloy with a content of 60%, and an aluminum-zirconium master alloy with a content of 5%. Heat the mixture to 730°C until all the alloys have melted, then add pure Mg and stir to obtain molten aluminum.

[0095] (3) After purification treatment and 30ppi+40ppi dual-stage filtration of the aluminum liquid, semi-continuous casting is carried out at a casting temperature of 725℃, a casting speed of 75mm / min, and a water flow rate of 2.8m for a single casting rod. 3 / h, to obtain the casting rod;

[0096] (4) After homogenizing the casting rod, use strong wind or water mist to cool it to 100°C and then air cool it to room temperature. First homogenization is carried out: temperature is 430°C and time is 3h; then second homogenization is carried out: temperature is 460°C and time is 12h.

[0097] (5) Extrude the cooled casting rod at a temperature of 470°C.

[0098] (6) After extrusion, the profile is quenched online at a quenching temperature of ≥510℃. When the surface temperature of the profile cools down to 160℃, the online quenching is stopped and then a 1.8% stretching treatment is immediately performed, followed by natural cooling to room temperature.

[0099] (7) The profile was subjected to a first-level artificial aging treatment at a temperature of 105℃ for 8 hours and a second-level artificial aging treatment at a temperature of 135℃ for 22 hours to obtain 7-series aluminum alloy material.

[0100] Comparative Example 2

[0101] A method for preparing 7-series aluminum alloys to improve parking stability and aging strength, the specific steps of which are as follows:

[0102] (1) Prepare aluminum alloy raw materials according to the following proportions: Zn: 5.5wt%, Mg: 1.6wt%, Cu: 0.25wt%, Zr: 0.30wt%; the content of each individual impurity is ≤0.05wt%; the total content of the remaining impurities is ≤0.15wt%; the balance is Al.

[0103] (2) Place Al ingots in a melting furnace. When the Al ingots begin to melt, place them in a pure Zn alloy, an aluminum-copper master alloy with a content of 60%, and an aluminum-zirconium master alloy with a content of 5%. Heat the mixture to 750°C until all the alloys have melted, then add pure Mg and stir to obtain molten aluminum.

[0104] (3) After purification treatment and 30ppi+40ppi dual-stage filtration of the aluminum liquid, semi-continuous casting is carried out at a casting temperature of 740℃, a casting speed of 80mm / min, and a water flow rate of 3.0m for a single casting rod. 3 / h, to obtain the casting rod;

[0105] (4) After homogenizing the casting rod, use strong wind or water mist to cool it to 80°C and then air cool it to room temperature. First homogenization is carried out: temperature is 450°C and time is 7h; then second homogenization is carried out: temperature is 480°C and time is 16h.

[0106] (5) Extrude the cooled casting rod at a temperature of 490℃ during extrusion.

[0107] (6) After extrusion, the profile is quenched online at a quenching temperature of ≥510℃. When the surface temperature of the profile cools down to 180℃, the online quenching is stopped and then a 4.2% stretching treatment is immediately performed, followed by natural cooling to room temperature.

[0108] (7) The profile was subjected to a first-level artificial aging treatment at a temperature of 105℃ for 12 hours and a second-level artificial aging treatment at a temperature of 135℃ for 24 hours to obtain 7-series aluminum alloy material.

[0109] The natural aging mechanical properties of the 7-series aluminum alloys prepared in Examples 1-7 are shown in Table 1. It can be seen that the yield strength of the 7-series aluminum alloys prepared in Examples 1-7 increases by no more than 18 MPa after natural aging for 30 days. Table 2 shows the artificial aging mechanical properties of the 7-series aluminum alloys prepared in Examples 1-7, and their strength can be increased by more than 25 MPa.

[0110] Table 1. Mechanical properties (wt%) of 7-series aluminum alloys prepared in Examples 1-7 under natural aging conditions.

[0111]

[0112]

[0113]

[0114] Table 2. Artificially aged mechanical properties (wt%) of 7-series aluminum alloys prepared in Examples 1-7

[0115]

[0116] The mechanical properties of 7-series aluminum alloys with different stretching amounts are shown in Table 3. When the stretching amount is less than 2%, the interaction between dislocations and atomic clusters is not fully disrupted, and fewer vacancies are formed by bound quenching, thus failing to significantly improve the storage stability of the aluminum alloy. When the stretching amount is greater than 4%, although the storage stability of the aluminum alloy is significantly improved, the high stretching amount causes severe work hardening of the material, resulting in a serious reduction in the alloy's plasticity.

[0117] Table 3 Mechanical properties (wt%) of 7-series aluminum alloys with different tensile strengths

[0118]

Claims

1. A method for preparing 7000 series aluminum alloys to improve parking stability and aging strength, characterized in that, The specific steps are as follows: (1) Prepare raw materials according to the following mass fraction of aluminum alloy raw materials: Cu: 0-0.18 wt%, Mg: 0.7-1.6 wt%, Zn: 4.0-5.5 wt%, Zr: 0.12-0.20 wt%, the content of other individual impurities ≤0.05 wt%, the total content of other impurities ≤0.15 wt%, and the balance is Al; (2) Place Al ingots in a melting furnace. When the Al ingots begin to melt, add pure Zn, 60% aluminum-copper master alloy and 5% aluminum-zirconium master alloy. Heat until all are melted, then add pure Mg and stir to obtain molten aluminum. (3) After the aluminum liquid is purified and filtered, it is semi-continuously cast to obtain a cast rod; (4) After homogenizing the casting rod, use strong wind or water mist to cool it to 80-100℃ and then air cool it to room temperature. (5) Extrude the cooled cast rod; (6) After extrusion, the profile is subjected to online quenching and then immediately stretched, and then naturally cooled to room temperature to obtain 7000 series aluminum alloy with improved storage stability; the quenching temperature is ≥510℃; online quenching is stopped when the surface temperature of the profile cools to 160-180℃. (7) The 7000 series aluminum alloy with improved parking stability is subjected to aging treatment to obtain a 7000 series aluminum alloy with improved parking stability and aging strength. The temperature of the casting rod during extrusion in step (5) is 470-490℃; The stretching rate of the stretching treatment described in step (6) is 2%-4%; The aging process described in step (7) involves first-level artificial aging at 105℃ for 8-12 hours and second-level artificial aging at 135℃ for 20-24 hours.

2. The method for preparing 7000 series aluminum alloys with improved parking stability and aging strength according to claim 1, characterized in that, The temperature at which all the material is melted in step (2) is 730-750℃.

3. The method for preparing 7000 series aluminum alloy with improved parking stability and aging strength as described in claim 1, characterized in that, The temperature during the purification process in step (3) is 730-750℃; the filtration is a two-stage filtration of 300ppi + 40ppi.

4. The method for preparing 7000 series aluminum alloy with improved parking stability and aging strength as described in claim 1, characterized in that, The semi-continuous casting process described in step (3) uses a casting temperature of 725-740℃, a casting speed of 75-80 mm / min, and a water flow rate of 2.8-3.0 m³ / min per casting rod. 3 / h, during casting, the melt undergoes online purification and is filtered through a 30ppi+40ppi dual-stage filter before entering the casting tray for semi-continuous casting.

5. The method for preparing 7000 series aluminum alloy with improved parking stability and aging strength as described in claim 1, characterized in that, The homogenization process in step (4) is divided into primary homogenization and secondary homogenization. The primary homogenization process is: temperature 430-450℃, time 3-7h. The secondary homogenization process is: temperature 460-480℃, time 12-16h.

6. A 7000 series aluminum alloy for improving parking stability and aging strength, prepared by the method described in any one of claims 1-5.

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