Artificial aging method for 6xxx aluminum alloy and 6xxx aluminum alloy after artificial aging

Abstract

The present invention provides an artificial aging method for a 6xxx aluminum alloy and the artificially aged 6xxx aluminum alloy, relating to the technical field of aluminum alloy heat treatment. The method comprises the following steps: performing a first artificial aging treatment on the 6xxx aluminum alloy, wherein the 6xxx aluminum alloy is a naturally aged 6xxx aluminum alloy; performing a second artificial aging treatment on the 6xxx aluminum alloy after the first aging treatment; and performing a third artificial aging treatment on the 6xxx aluminum alloy after the second aging treatment to obtain the artificially aged 6xxx aluminum alloy. The method promotes the dissolution of atomic clusters formed during the natural aging process through the first artificial aging treatment, thereby alleviating the inhibition on the formation of precipitates; then promotes the formation of fine and dense precipitate nucleation points through the second artificial aging treatment; and finally accelerates the kinetics of precipitate formation through the third artificial aging treatment, thereby rapidly increasing the precipitate content. This improves the strength of the artificially aged alloy and ensures the plasticity of the artificially aged alloy.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum alloy heat treatment, and in particular relates to an artificial aging method for 6xxx aluminum alloy. Background Art

[0002] 6xxx series (Al-Mg-Si(-Cu) series) aluminum alloys offer excellent corrosion resistance, lightweight, and formability, making them ideal for automotive sheet metal. To meet the automotive industry's demand for low-cost, short-process production, 6xxx Al alloy sheets are typically solution-hardened and heat-treated at aluminum mills before being supplied to automotive OEMs. During storage and transportation, these sheets are stored at room temperature for extended periods, a process known as natural aging. The naturally aged Al-Mg-Si(-Cu) alloys are then stamped and formed at the OEM, where they undergo a paint bake process to achieve enhanced strength to meet operational requirements. The paint bake process in automotive applications is equivalent to a short-term artificial aging treatment, typically at 170-180°C for no more than 40 minutes. However, Al-Mg-Si(-Cu) alloys typically reach peak strength in over 10 hours at the same temperature. Clearly, achieving effective strength improvement in such a short paint bake process is difficult. In addition, Al-Mg-Si(-Cu) alloy sheets form a large number of atomic clusters during the natural aging process. These atomic clusters have poor strengthening capabilities and inhibit the formation of precipitates during artificial aging, making it more difficult to increase strength during the coating and baking process. This phenomenon is called the negative effect of natural aging, or the parking effect. The above factors have become the main obstacles restricting the use of Al-Mg-Si(-Cu) alloy in automotive sheets.

[0003] To address the difficulty of increasing the strength of Al-Mg-Si(-Cu) alloy sheets during coating and baking in a short period of time, and the negative effects of natural aging that further inhibit strength improvement, some automobile OEMs have adopted the method of increasing the baking treatment temperature. For example, Ford Motor Company in North America increased the baking temperature to 220°C, significantly improving the strength of the alloy. On the one hand, at such high temperatures, the atomic clusters formed during natural aging will quickly dissolve, weakening the inhibitory effect on the formation of precipitates; on the other hand, the kinetics of precipitate formation are accelerated at high temperatures, allowing large quantities to form in a short period of time. However, such high temperatures also lead to coarse precipitates and reduced interface coherence with the aluminum matrix, which in turn causes severe stress and strain concentration, resulting in deterioration of the alloy's plasticity and difficulty in ensuring service safety.

[0004] In summary, there is still a lack of methods that can improve the strength of 6xxx aluminum alloys while maintaining good plasticity in a short period of time. Summary of the Invention

[0005] Therefore, the present invention provides an artificial aging method for 6xxx aluminum alloy and the artificially aged 6xxx aluminum alloy, which can solve the problem in the prior art that it is difficult to increase the strength of 6xxx aluminum alloy and maintain good plasticity in a short period of time.

[0006] In order to solve the above problems, the present invention provides an artificial aging method for 6xxx aluminum alloy, comprising the following steps:

[0007] First artificial aging treatment: performing a first artificial aging treatment on the 6xxx aluminum alloy to dissolve atomic clusters in the 6xxx aluminum alloy and obtain a first-aged 6xxx aluminum alloy;

[0008] Wherein, the 6xxx aluminum alloy is a naturally aged 6xxx aluminum alloy;

[0009] Second artificial aging treatment: performing a second artificial aging treatment on the 6xxx aluminum alloy after the first aging treatment to form precipitation nucleation sites and obtain a 6xxx aluminum alloy after the second aging treatment;

[0010] Third artificial aging treatment: The 6xxx aluminum alloy after the second aging treatment is subjected to a third artificial aging treatment to form a precipitate phase to obtain an artificially aged 6xxx aluminum alloy.

[0011] Furthermore, in the first artificial aging treatment step: the temperature of the first artificial aging treatment is 200-230° C., and the holding time is 5-10 minutes.

[0012] Furthermore, in the first artificial aging step, the naturally aged 6xxx aluminum alloy is prepared by the following preparation method:

[0013] A 6xxx aluminum alloy ingot is prepared and processed into a 6xxx aluminum alloy plate; and the 6xxx aluminum alloy plate is then subjected to a solid solution treatment, a quenching treatment, and a natural aging treatment in sequence.

[0014] The chemical composition of the 6xxx aluminum alloy ingot is, by mass fraction, Mg 0.5-1.0 wt %, Si 0.6-1.1 wt %, Cu 0.5-0.9 wt %, and aluminum balance; and / or

[0015] The temperature of the solution treatment is 530-560° C., and the time of the solution treatment is 10 min-1 h; and / or

[0016] The medium for the quenching treatment is room temperature water.

[0017] Furthermore, the second artificial aging treatment step specifically includes:

[0018] The 6xxx aluminum alloy after the first artificial aging treatment is cooled to 170-180° C. and kept at this temperature for 10-15 minutes.

[0019] Furthermore, in the second artificial aging treatment step, the temperature is lowered along with the furnace; wherein the rate of the temperature reduction is ≥20°C / min.

[0020] Furthermore, the third artificial aging treatment step specifically includes: heating the 6xxx aluminum alloy after the second artificial aging treatment to 200-230° C. and keeping the temperature for 10-15 minutes.

[0021] Furthermore, in the second artificial aging treatment step, the temperature is raised along with the furnace;

[0022] The heating rate is ≥20°C / min.

[0023] In another aspect, the present invention provides an artificially aged 6xxx aluminum alloy, wherein the precipitated phase comprises a GP zone and a β″ phase; the volume fraction of the precipitated phase is ≥1.3%; and the average diameter of the precipitated phase is ≤8 nm.

[0024] Furthermore, the yield strength of the artificially aged 6xxx aluminum alloy at room temperature is 270-320 MPa, the tensile strength is 330-360 MPa, and the elongation is 17-25%;

[0025] Preferably, the artificially aged 6xxx aluminum alloy is prepared by any of the artificial aging methods described above.

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

[0027] 1. In one aspect, the present invention provides an artificial aging method for a 6xxx aluminum alloy, comprising the following steps: performing a first artificial aging treatment on the 6xxx aluminum alloy to dissolve atomic clusters in the 6xxx aluminum alloy and obtain a 6xxx aluminum alloy after the first aging treatment; wherein the 6xxx aluminum alloy is a naturally aged 6xxx aluminum alloy; performing a second artificial aging treatment on the 6xxx aluminum alloy after the first aging treatment to form precipitation phase nucleation points and obtain a 6xxx aluminum alloy after the second aging treatment; performing a third artificial aging treatment on the 6xxx aluminum alloy after the second aging treatment to form precipitation phases and obtain an artificially aged 6xxx aluminum alloy; based on The above method promotes the dissolution of atomic clusters formed during natural aging through high-temperature aging treatment (first artificial aging treatment), thereby reducing the inhibition of atomic clusters on the formation of precipitates; then promotes the formation of fine and dense precipitate nucleation points through low-temperature aging treatment (second artificial aging treatment); finally, accelerates the kinetics of precipitate formation through high-temperature aging treatment (third artificial aging treatment), rapidly increasing the precipitate content in a short period of time; among them, the fine and dense precipitates can effectively hinder dislocation movement, thereby improving the strength of the alloy after artificial aging, while the small precipitate size and good coherence can alleviate strain concentration during deformation, thereby ensuring the plasticity of the alloy after artificial aging.

[0028] 2. In another aspect, the present invention provides an artificially aged 6xxx aluminum alloy prepared using the artificial aging method described above. In the artificially aged 6xxx aluminum alloy, the precipitates are coherent with the aluminum matrix; the precipitates comprise GP zones and β″ phases; the volume fraction of the precipitates is ≥1.3%; and the average diameter of the precipitates is ≤8 nm. The artificially aged 6xxx aluminum alloy exhibits a yield strength of 270-320 MPa, a tensile strength of 330-360 MPa, and an elongation of 17-25% at room temperature. Compared to conventional solution quenching and natural aging followed by single-stage artificial aging, the strength and hardness of the alloy obtained by the multi-stage artificial aging method (high-temperature artificial aging, low-temperature artificial aging, and high-temperature artificial aging) are significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. The drawings described below are merely exemplary. Those skilled in the art can, without inventive effort, derive other implementation drawings based on the provided drawings.

[0030] Figure 1 is a precipitated phase structure diagram corresponding to the 6xxx aluminum alloy after artificial aging in Example 1 of the present invention;

[0031] Figure 2 is a precipitated phase structure diagram corresponding to the 6xxx aluminum alloy after artificial aging in Comparative Example 1 of the present invention;

[0032] Figure 3 This is the precipitation phase organization diagram corresponding to the 6xxx aluminum alloy after artificial aging in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0033] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. The drawings described below are merely exemplary. Those skilled in the art can, without inventive effort, derive other implementation drawings based on the provided drawings.

[0034] To overcome the deficiencies of the prior art, the present invention provides an artificial aging method for a 6xxx aluminum alloy, comprising the following steps:

[0035] First artificial aging treatment: performing a first artificial aging treatment on the 6xxx aluminum alloy to dissolve atomic clusters in the 6xxx aluminum alloy and obtain a first-aged 6xxx aluminum alloy; wherein the 6xxx aluminum alloy is a naturally aged 6xxx aluminum alloy;

[0036] The specific steps are as follows: placing the 6xxx aluminum alloy in an aging furnace at 200-230°C for 5-10 minutes;

[0037] The naturally aged 6xxx aluminum alloy is prepared by the following method: preparing a 6xxx aluminum alloy billet and processing it into a 6xxx aluminum alloy plate; then sequentially subjecting the 6xxx aluminum alloy plate to a solid solution treatment, a quenching treatment, and a natural aging treatment; wherein the chemical composition of the 6xxx aluminum alloy billet is, by mass fraction, Mg 0.5-1.0 wt%, Si 0.6-1.1 wt%, Cu 0.5-0.9 wt%, and the balance aluminum;

[0038] The temperature of the solution treatment is 530~560℃, and the time of the solution treatment is 10min~1h; the medium of the quenching treatment is room temperature water; during the natural aging treatment, the 6xxx aluminum alloy plate can be cold formed at any time point.

[0039] Second artificial aging treatment: performing a second artificial aging treatment on the 6xxx aluminum alloy after the first aging treatment to form precipitation nucleation sites and obtain a 6xxx aluminum alloy after the second aging treatment;

[0040] This step specifically comprises: cooling the 6xxx aluminum alloy after the first artificial aging treatment to 170-180°C and keeping the temperature therefor for 10-15 minutes; wherein, the cooling is carried out in a furnace-based cooling manner, and the cooling rate is ≥20°C / min.

[0041] Third artificial aging treatment: The 6xxx aluminum alloy after the second aging treatment is subjected to a third artificial aging treatment to form a precipitate phase to obtain an artificially aged 6xxx aluminum alloy.

[0042] This step specifically comprises: heating the 6xxx aluminum alloy after the second artificial aging treatment to 200-230°C and keeping the temperature therefor for 10-15 minutes; wherein, the heating is carried out in a furnace-based heating manner; and the heating rate is ≥20°C / min.

[0043] Based on the above method, a high-temperature aging treatment (the first artificial aging treatment) is used to promote the dissolution of atomic clusters formed during natural aging, thereby reducing the inhibition of atomic clusters on the formation of precipitates. A low-temperature aging treatment (the second artificial aging treatment) is then used to promote the formation of fine and dense precipitate nucleation sites. Finally, a high-temperature aging treatment (the third artificial aging treatment) is used to accelerate the kinetics of precipitate formation and rapidly increase the precipitate content in a short period of time. Among them, the fine and dense precipitates can effectively hinder dislocation movement, thereby improving the strength of the alloy after artificial aging, while the small size and good coherence can alleviate strain concentration during deformation, thereby ensuring the plasticity of the alloy after artificial aging.

[0044] The cooling rate and the heating rate are greater than or equal to 20°C / min, which can shorten the artificial aging time and control the total time of the three-stage artificial aging to within 40 minutes; preferably, the total time of the three-stage artificial aging is controlled within 30 minutes, thereby quickly improving the strength of the alloy and maintaining good plasticity in a short time.

[0045] In another aspect, the present invention provides an artificially aged 6xxx aluminum alloy prepared by any of the aforementioned artificial aging methods; in the artificially aged 6xxx aluminum alloy, the precipitated phase includes a GP zone and a β″ phase that are well coherent with the aluminum matrix; the artificially aged 6xxx aluminum alloy has a yield strength of 270 to 320 MPa, a tensile strength of 330 to 360 MPa, and an elongation of 17 to 25% at room temperature.

[0046] The present invention is further described below with reference to specific examples and comparative examples.

[0047] In the examples and comparative examples, a naturally aged 6xxx aluminum alloy is obtained by the following preparation method: a 6xxx aluminum alloy ingot is prepared and processed into a 6xxx aluminum alloy plate with a thickness of 3 mm; then, a solid solution treatment is performed at 550±5°C for 30 minutes, and after quenching to room temperature, the 6xxx aluminum alloy plate is naturally aged for 7 days to obtain a naturally aged 6xxx aluminum alloy; wherein, the chemical composition of the 6xxx aluminum alloy ingot is Al-0.8Mg-0.9Si-0.7Cu, calculated by mass fraction.

[0048] Example 1

[0049] This embodiment provides a method for artificial aging of a 6xxx aluminum alloy, comprising the following steps:

[0050] First artificial aging treatment: placing the naturally aged 6xxx aluminum alloy in a furnace at 220° C. and holding the temperature for 5 minutes to obtain a first artificial aging treated 6xxx aluminum alloy;

[0051] Second artificial aging treatment: cooling the 6xxx aluminum alloy after the first artificial aging treatment to 180°C at a rate of 20°C / min in a furnace, and holding the temperature for 15 minutes to obtain the 6xxx aluminum alloy after the second artificial aging treatment;

[0052] Third artificial aging treatment: The 6xxx aluminum alloy after the second artificial aging treatment is heated to 220° C. in a furnace at a rate of 20° C. / min and kept at that temperature for 10 minutes to obtain the artificially aged 6xxx aluminum alloy.

[0053] The precipitation phase of the artificially aged 6xxx aluminum alloy obtained in this embodiment was tested, and the results are as follows: Figure 1 As shown, the precipitated phase is small and dense, with a diameter of only approximately 5 nm and a volume fraction of approximately 1.6%, dispersed within the aluminum matrix. Its morphology indicates that the precipitated phase includes GP zones and β″ phases that are well coherent with the aluminum matrix. The 6xxx aluminum alloy obtained in this example was subjected to tensile testing. The test results, shown in Table 1, demonstrate that the alloy obtained in this example still exhibits excellent strength and ductility, with a yield strength of 290 MPa at room temperature, a tensile strength of 350 MPa, and an elongation of 20%.

[0054] Example 2

[0055] This embodiment provides a method for artificial aging of a 6xxx aluminum alloy, comprising the following steps:

[0056] First artificial aging treatment: placing the naturally aged 6xxx aluminum alloy in a furnace at 200° C. and holding the temperature for 5 minutes to obtain a first artificial aging treated 6xxx aluminum alloy;

[0057] Second artificial aging treatment: cooling the 6xxx aluminum alloy after the first artificial aging treatment to 170°C at a rate of 20°C / min in a furnace, and holding the temperature for 10 minutes to obtain the 6xxx aluminum alloy after the second artificial aging treatment;

[0058] Third artificial aging treatment: The 6xxx aluminum alloy after the second artificial aging treatment is heated to 200° C. in a furnace at a rate of 20° C. / min and kept at that temperature for 10 minutes to obtain the artificially aged 6xxx aluminum alloy.

[0059] The artificially aged 6xxx aluminum alloy obtained in this example was subjected to a tensile test. The test results are shown in Table 1. It can be seen that the alloy obtained in this example still has good strength and plasticity, wherein the yield strength at room temperature is 270 MPa, the tensile strength is 330 MPa, and the elongation is 24%.

[0060] Example 3

[0061] This embodiment provides a method for artificial aging of a 6xxx aluminum alloy, comprising the following steps:

[0062] First artificial aging treatment: placing the naturally aged 6xxx aluminum alloy in a furnace at 230° C. and holding the temperature for 9 minutes to obtain a first artificially aged 6xxx aluminum alloy;

[0063] Second artificial aging treatment: cooling the 6xxx aluminum alloy after the first artificial aging treatment to 180°C at a rate of 40°C / min in a furnace, and holding the temperature for 14 minutes to obtain the 6xxx aluminum alloy after the second artificial aging treatment;

[0064] Third artificial aging treatment: The 6xxx aluminum alloy after the second artificial aging treatment is heated to 230° C. in a furnace at a rate of 40° C. / min and kept at that temperature for 14 minutes to obtain the artificially aged 6xxx aluminum alloy.

[0065] The artificially aged 6xxx aluminum alloy obtained in this example was subjected to a tensile test. The test results are shown in Table 1. It can be seen that the alloy obtained in this example still has good strength and plasticity, wherein the yield strength at room temperature is 315 MPa, the tensile strength is 350 MPa, and the elongation is 17%.

[0066] Comparative Example 1

[0067] This comparative example provides an artificial aging method for a 6xxx aluminum alloy, comprising the following steps:

[0068] The naturally aged 6xxx aluminum alloy is placed in a furnace at 180° C. and kept at this temperature for 30 minutes to obtain an artificially aged 6xxx aluminum alloy.

[0069] The precipitates of the artificially aged 6xxx aluminum alloy obtained in this comparative example are as follows: Figure 2 As shown, the precipitate phase is relatively small, with a volume fraction of only approximately 0.5%. The 6xxx aluminum alloy obtained in this comparative example was subjected to tensile testing after artificial aging. The test results are shown in Table 1, showing a yield strength of 180 MPa, a tensile strength of 310 MPa, and an elongation of 26% at room temperature. Because this comparative example only underwent a single-stage aging at 180°C, the low temperature prevented the full dissolution of atomic clusters formed during natural aging. Furthermore, the lack of a third-stage, high-temperature artificial aging process slowed the formation of precipitates. Consequently, the precipitate content was insufficient, and the strength of the artificially aged alloy was significantly lower than that of Example 1.

[0070] Comparative Example 2

[0071] This comparative example provides an artificial aging method for a 6xxx aluminum alloy, comprising the following steps:

[0072] The naturally aged 6xxx aluminum alloy is placed in a furnace at 220° C. and kept at this temperature for 30 minutes to obtain an artificially aged 6xxx aluminum alloy.

[0073] The precipitation phase of the 6xxx aluminum alloy after artificial aging obtained in this comparative example is as follows Figure 3 As shown, the size of the precipitates is significantly larger than that of Example 1 (approximately 10 nm in diameter, twice the size of the precipitates in Example 1). The artificially aged 6xxx aluminum alloy obtained in this comparative example was subjected to tensile testing. The test results, shown in Table 1, show a room temperature yield strength of 300 MPa, a tensile strength of 340 MPa, and an elongation of 10%. Because this comparative example only underwent a single-stage aging at 220°C, it lacked the formation of fine, dense nucleation sites for the precipitates at 180°C. The low nucleation rate of the precipitates at high temperatures leads to intense atomic diffusion, resulting in larger precipitates. Therefore, while the strength of the artificially aged alloy is comparable to that of Example 1, its plasticity is much lower than that of Example 1.

[0074] Comparative Example 3

[0075] This comparative example provides an artificial aging method for a 6xxx aluminum alloy, comprising the following steps:

[0076] First artificial aging treatment: placing the naturally aged 6xxx aluminum alloy in a furnace at 180° C. and holding the temperature for 15 minutes to obtain a first artificial aging treated 6xxx aluminum alloy;

[0077] Second artificial aging treatment: The 6xxx aluminum alloy after the first artificial aging treatment is heated to 220°C at a rate of 20°C / min and kept at this temperature for 10 minutes to obtain the artificially aged 6xxx aluminum alloy.

[0078] The artificially aged 6xxx aluminum alloy obtained in this comparative example was subjected to tensile testing. The test results, shown in Table 1, show a yield strength of 250 MPa, a tensile strength of 320 MPa, and an elongation of 22% at room temperature. Due to the lack of the first stage of the three-stage artificial aging process in Example 1, the natural aging clusters cannot be dissolved, inhibiting the formation of precipitates during artificial aging. Therefore, the strength of the artificially aged alloy in Comparative Example 3 is lower than that in Example 1.

[0079] Comparative Example 4

[0080] This comparative example provides an artificial aging method for a 6xxx aluminum alloy, comprising the following steps:

[0081] First artificial aging treatment: heating the naturally aged 6xxx aluminum alloy to 220°C at a rate of 20°C / min and holding the temperature for 5 minutes to obtain a first artificially aged 6xxx aluminum alloy;

[0082] Second artificial aging treatment: The 6xxx aluminum alloy after the first artificial aging treatment is cooled to 180°C at a rate of 20°C / min in a furnace and kept at this temperature for 15 minutes to obtain the artificially aged 6xxx aluminum alloy.

[0083] The artificially aged 6xxx aluminum alloy obtained in this comparative example was subjected to tensile testing. The test results, shown in Table 1, show a yield strength of 200 MPa, a tensile strength of 320 MPa, and an elongation of 25% at room temperature. Due to the lack of the third stage of artificial aging in Example 1, the precipitate phase formation dynamics were insufficient, making it difficult to fully form during the aging period. Therefore, the strength of the artificially aged alloy in Comparative Example 4 was lower than that in Example 1.

[0084] Comparative Example 5

[0085] This comparative example provides an artificial aging method for a 6xxx aluminum alloy, comprising the following steps:

[0086] First artificial aging treatment: placing the naturally aged 6xxx aluminum alloy in a furnace at 185° C. and holding the temperature for 5 minutes to obtain a first artificial aging treated 6xxx aluminum alloy;

[0087] Second artificial aging treatment: cooling the 6xxx aluminum alloy after the first artificial aging treatment to 180°C at a rate of 20°C / min in a furnace, and holding the temperature for 15 minutes to obtain the 6xxx aluminum alloy after the second artificial aging treatment;

[0088] Third artificial aging treatment: The 6xxx aluminum alloy after the second artificial aging treatment is heated to 220° C. in a furnace at a rate of 20° C. / min and kept at that temperature for 10 minutes to obtain the artificially aged 6xxx aluminum alloy.

[0089] The artificially aged 6xxx aluminum alloy obtained in this comparative example was subjected to tensile testing. The test results, shown in Table 1, show a yield strength of 255 MPa, a tensile strength of 300 MPa, and an elongation of 20% at room temperature. In this comparative example, due to the relatively low temperature of the first artificial aging treatment, the natural aging clusters were not fully dissolved, and the precipitation phase was not fully formed. Therefore, the strength of the artificially aged alloy was lower than that of Example 1.

[0090] Comparative Example 6

[0091] This comparative example provides an artificial aging method for a 6xxx aluminum alloy, comprising the following steps:

[0092] First artificial aging treatment: heating the naturally aged 6xxx aluminum alloy to 220°C at a rate of 20°C / min and holding the temperature for 5 minutes to obtain a first artificially aged 6xxx aluminum alloy;

[0093] Second artificial aging treatment: cooling the 6xxx aluminum alloy after the first artificial aging treatment to 180°C at a rate of 20°C / min in a furnace, and holding the temperature for 15 minutes to obtain the 6xxx aluminum alloy after the second artificial aging treatment;

[0094] Third artificial aging treatment: The 6xxx aluminum alloy after the second artificial aging treatment is heated to 250° C. in a furnace at a rate of 20° C. / min and kept at this temperature for 10 minutes to obtain the artificially aged 6xxx aluminum alloy.

[0095] The artificially aged 6xxx aluminum alloy obtained in this comparative example was subjected to tensile testing. The test results, shown in Table 1, show a yield strength of 280 MPa, a tensile strength of 320 MPa, and an elongation of 15% at room temperature. In this comparative example, due to the excessively high temperature of the third artificial aging treatment, the precipitation phase formed too quickly and the coarsening was too intense, resulting in low strength and ductility of the artificially aged alloy.

[0096] Comparative Example 7

[0097] This comparative example provides an artificial aging method for a 6xxx aluminum alloy, comprising the following steps:

[0098] First artificial aging treatment: heating the naturally aged 6xxx aluminum alloy to 220°C at a rate of 20°C / min and holding the temperature for 5 minutes to obtain a first artificially aged 6xxx aluminum alloy;

[0099] Second artificial aging treatment: cooling the 6xxx aluminum alloy after the first artificial aging treatment to 130°C at a rate of 20°C / min in a furnace, and holding the temperature for 15 minutes to obtain the 6xxx aluminum alloy after the second artificial aging treatment;

[0100] Third artificial aging treatment: The 6xxx aluminum alloy after the second artificial aging treatment is heated to 250° C. in a furnace at a rate of 20° C. / min and kept at this temperature for 10 minutes to obtain the artificially aged 6xxx aluminum alloy.

[0101] The artificially aged 6xxx aluminum alloy obtained in this comparative example was subjected to tensile testing. The test results, shown in Table 1, show a yield strength of 260 MPa, a tensile strength of 310 MPa, and an elongation of 22% at room temperature. In this comparative example, the second artificial aging treatment temperature was too low, resulting in insufficient nucleation sites for the precipitation phase, resulting in low strength of the artificially aged alloy.

[0102] Table 1 Mechanical properties of 6xxx aluminum alloys in Examples and Comparative Examples

[0103]

[0104] In summary, compared with the traditional artificial aging (or coating and baking) process, the present invention effectively improves the rapid strengthening ability of 6xxx aluminum alloy in a short period of time and maintains good plasticity through the synergistic effect of high temperature, low temperature, and high temperature three-stage artificial aging.

[0105] It is easy for those skilled in the art to understand that, under the premise of no conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0106] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention. The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and variations without departing from the technical principles of the present invention, and such improvements and variations shall also be considered within the scope of protection of the present invention.

Claims

1. A method for artificial aging of a 6xxx aluminum alloy, characterized in that: It consists of the following steps: First artificial aging treatment: performing a first artificial aging treatment on the 6xxx aluminum alloy to dissolve atomic clusters in the 6xxx aluminum alloy and obtain a first-aged 6xxx aluminum alloy; The 6xxx aluminum alloy is a naturally aged 6xxx aluminum alloy; the temperature of the first artificial aging treatment is 200-230° C., and the holding time is 5-10 minutes; Second artificial aging treatment: performing a second artificial aging treatment on the 6xxx aluminum alloy after the first aging treatment to form precipitation nucleation sites and obtain a second-aged 6xxx aluminum alloy; wherein the 6xxx aluminum alloy after the first artificial aging treatment is cooled to 170-180° C. and held at this temperature for 10-15 minutes; Third artificial aging treatment: The 6xxx aluminum alloy after the second artificial aging treatment is subjected to a third artificial aging treatment to form a precipitate phase to obtain an artificially aged 6xxx aluminum alloy; wherein the 6xxx aluminum alloy after the second artificial aging treatment is heated to 200-230° C. and maintained at this temperature for 10-15 minutes.

2. The artificial aging method of 6xxx aluminum alloy according to claim 1, characterized in that In the first artificial aging step, the naturally aged 6xxx aluminum alloy is prepared by the following preparation method: A 6xxx aluminum alloy ingot is prepared and processed into a 6xxx aluminum alloy plate; and the 6xxx aluminum alloy plate is then subjected to a solid solution treatment, a quenching treatment, and a natural aging treatment in sequence.

3. The artificial aging method of 6xxx aluminum alloy according to claim 2, characterized in that: The chemical composition of the 6xxx aluminum alloy ingot is, by mass fraction, Mg 0.5-1.0 wt %, Si 0.6-1.1 wt %, Cu 0.5-0.9 wt %, and aluminum balance; and / or The temperature of the solution treatment is 530-560° C., and the time of the solution treatment is 10 min-1 h; and / or The medium for the quenching treatment is room temperature water.

4. The artificial aging method of 6xxx aluminum alloy according to claim 1, characterized in that In the second artificial aging treatment step, the temperature is lowered along with the furnace; Among them, the cooling rate is ≥20℃ / min.

5. The artificial aging method of 6xxx aluminum alloy according to claim 1, characterized in that: In the third artificial aging treatment step, the temperature is raised along with the furnace; The heating rate is ≥20°C / min.

6. An artificially aged 6xxx aluminum alloy, characterized in that: The artificially aged 6xxx aluminum alloy is prepared by the artificial aging method according to any one of claims 1 to 5; in the artificially aged 6xxx aluminum alloy, the precipitated phase includes GP zone and β″ phase; The volume fraction of the precipitated phase is ≥1.3%; and the average diameter of the precipitated phase is ≤8 nm.

7. The artificially aged 6xxx aluminum alloy of claim 6, wherein: The yield strength of the artificially aged 6xxx aluminum alloy at room temperature is 270-320 MPa, the tensile strength is 330-360 MPa, and the elongation is 17-25%.

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