Artificial aging method of 6xxx aluminum alloy and 6xxx aluminum alloy subjected to artificial aging

Abstract

The invention provides an artificial aging method of a 6xxx aluminum alloy and the 6xxx aluminum alloy subjected to artificial aging, and relates to the technical field of aluminum alloy heat treatment, and the artificial aging method comprises the following steps: carrying out first artificial aging treatment on the 6xxx aluminum alloy; wherein the 6xxx aluminum alloy is a 6xxx aluminum alloy in a natural aging state; performing second artificial aging treatment on the 6xxx aluminum alloy subjected to the first aging treatment; third artificial aging treatment is conducted on the 6xxx aluminum alloy obtained after second aging treatment, and the 6xxx aluminum alloy obtained after artificial aging is obtained; according to the method, dissolution of atomic clusters formed in the natural aging period is promoted through the first artificial aging treatment, and inhibition on formation of a precipitated phase is relieved; forming of fine and compact precipitated phase nucleation points is promoted through second artificial aging treatment; finally, a precipitated phase is accelerated to form dynamics through third artificial aging treatment, and the content of the precipitated phase is rapidly increased; therefore, the strength of the alloy after artificial aging is improved, and the plasticity of the alloy after artificial aging is ensured.

Description

Technical Field

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

[0002] 6xxx series (Al-Mg-Si(-Cu) series) aluminum alloys have the advantages of good corrosion resistance, light weight, and good formability, and are ideal materials for automotive panels. To meet the requirements of the automotive industry for low-cost and short-process production, 6xxx Al alloy sheets are generally supplied to automotive OEMs after solution quenching heat treatment in aluminum factories. During this period, due to factors such as storage and transportation, the Al-Mg-Si(-Cu) alloy sheets need to be stored at room temperature for a long time, that is, they undergo natural aging. Subsequently, the naturally aged Al-Mg-Si(-Cu) alloy is stamped and formed in the automotive OEM, and the strength is increased during the painting baking process to meet the use requirements. The painting baking process of the automobile is equivalent to a short-time artificial aging treatment, with a temperature generally of 170~180°C and a time generally not exceeding 40 min. However, the time for the Al-Mg-Si(-Cu) alloy to reach the peak strength at the same temperature is generally more than 10 h. Obviously, it is difficult to obtain an effective strength increase with such a short-time painting baking treatment. In addition, a large number of atomic clusters will be formed during the natural aging process of the Al-Mg-Si(-Cu) alloy sheets. These atomic clusters have poor strengthening ability and will inhibit the formation of precipitation phases during artificial aging, resulting in more difficult strength increase during the painting 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) alloys for automotive panels.

[0003] To solve the problems of difficult strength increase of Al-Mg-Si(-Cu) alloy sheets in a short time during painting baking and the further inhibition of strength increase by the negative effect of natural aging, some automotive OEMs have adopted the method of increasing the baking treatment temperature. For example, Ford Motor in North America increased the baking temperature to 220°C, significantly improving the strength of the alloy. On the one hand, at this high temperature, the atomic clusters formed during natural aging will quickly dissolve, weakening the inhibitory effect on the formation of precipitation phases; on the other hand, the kinetics of precipitation phase formation is accelerated at high temperature, and a large number of them can be formed in a short time. However, such a high temperature also leads to coarse precipitation phase sizes and a decrease in the coherent degree of the interface with the aluminum matrix, resulting in serious stress and strain concentration, deteriorating the plasticity of the alloy and making it difficult to ensure service safety.

[0004] In summary, there is still a lack of a method that can increase the strength of 6xxx aluminum alloys in a short time and maintain good plasticity. Summary of the Invention

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

[0006] To solve the above problems, the present invention provides a method for artificial aging of 6xxx aluminum alloy, including the following steps: First artificial aging treatment: Perform the first artificial aging treatment on the 6xxx aluminum alloy to dissolve the atomic clusters in the 6xxx aluminum alloy and obtain the 6xxx aluminum alloy after the first aging treatment; Among them, the 6xxx aluminum alloy is a naturally aged 6xxx aluminum alloy; Second artificial aging treatment: Perform the second artificial aging treatment on the 6xxx aluminum alloy after the first aging treatment to form precipitation phase nucleation points and obtain the 6xxx aluminum alloy after the second aging treatment; Third artificial aging treatment: Perform the third artificial aging treatment on the 6xxx aluminum alloy after the second aging treatment to form precipitation phases and obtain the 6xxx aluminum alloy after artificial aging.

[0007] Further, in the step of the first artificial aging treatment: the temperature of the first artificial aging treatment is 200 - 230 °C, and the holding time is 5 - 10 min.

[0008] Further, in the step of the first artificial aging treatment, the naturally aged 6xxx aluminum alloy is obtained by the following preparation method: Prepare a 6xxx aluminum alloy ingot and process it into a 6xxx aluminum alloy plate; then perform solution treatment, quenching treatment and natural aging treatment on the 6xxx aluminum alloy plate in sequence.

[0009] By mass fraction, the chemical composition of the 6xxx aluminum alloy ingot is: Mg 0.5 - 1.0 wt%, Si 0.6 - 1.1 wt%, Cu 0.5 - 0.9 wt%, and the balance is aluminum; 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.

[0010] Further, the step of the second artificial aging treatment specifically includes: Cool the 6xxx aluminum alloy after the first artificial aging treatment to 170 - 180 °C and hold for 10 - 15 min.

[0011] Further, in the step of the second artificial aging treatment, the furnace cooling method is adopted during cooling; among them, the cooling rate is ≥20 °C / min.

[0012] Further, the steps of the third artificial aging treatment specifically include: heating the 6xxx aluminum alloy after the second artificial aging treatment to 200-230°C and holding for 10-15 min.

[0013] Further, in the second artificial aging treatment step, the furnace heating method is adopted during heating; wherein, the heating rate ≥ 20°C / min.

[0014] On the other hand, the present invention provides a 6xxx aluminum alloy after artificial aging. In the 6xxx aluminum alloy after artificial aging, the precipitated phases include GP zones and β″ phases; the volume fraction of the precipitated phases ≥ 1.3%; the average diameter of the precipitated phases ≤ 8 nm.

[0015] Further, the yield strength of the 6xxx aluminum alloy after artificial aging at room temperature is 270-320 MPa, the tensile strength is 330-360 MPa, and the elongation is 17-25%; Preferably, the 6xxx aluminum alloy after artificial aging is prepared by using the artificial aging method described in any one of the above.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: 1. On the one hand, the present invention provides an artificial aging method for 6xxx aluminum alloy, including the following steps: performing a first artificial aging treatment on the 6xxx aluminum alloy to dissolve the atomic clusters in the 6xxx aluminum alloy and obtaining the 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 nucleation points of precipitated phases and obtaining the 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 precipitated phases and obtaining the 6xxx aluminum alloy after artificial aging; based on the above method, by high-temperature aging treatment (the first artificial aging treatment), the dissolution of atomic clusters formed during natural aging is promoted, thereby reducing the inhibition of atomic clusters on the formation of precipitated phases; then, by low-temperature aging treatment (the second artificial aging treatment), the formation of fine and dense nucleation points of precipitated phases is promoted; finally, by high-temperature aging treatment (the third artificial aging treatment), the precipitation phase formation kinetics is accelerated, and the content of precipitated phases is rapidly increased in a short time; wherein, the fine and dense precipitated phases can effectively hinder the movement of dislocations, thereby improving the strength of the alloy after artificial aging, and the fine size of the precipitated phases and good coherency can relieve the strain concentration during the deformation process, thereby ensuring the plasticity of the alloy after artificial aging.

[0017] 2. On the other hand, the present invention provides a 6xxx aluminum alloy after artificial aging, which is prepared by the above artificial aging method. In the 6xxx aluminum alloy after artificial aging, the precipitated phase is coherent with the aluminum matrix; wherein, the precipitated phase includes GP zones and β″ phases; the volume fraction of the precipitated phase ≥ 1.3%; the average diameter of the precipitated phase ≤ 8 nm; the yield strength of the 6xxx aluminum alloy after artificial aging at room temperature is 270 - 320 MPa, the tensile strength is 330 - 360 MPa, and the elongation is 17 - 25%; compared with the traditional method of solution quenching and natural aging followed by single-stage artificial aging, the strength and hardness of the alloy after multi-stage artificial aging (treatment of high-temperature artificial aging, low-temperature artificial aging, and high-temperature artificial aging) of the present invention are significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. The drawings in the following description are only exemplary, and for those of ordinary skill in the art, without creative efforts, other implementation drawings can be obtained by extending the provided drawings.

[0019] Figure 1 It is the precipitated phase microstructure diagram of the 6xxx aluminum alloy after artificial aging in Example 1 of the present invention; Figure 2 It is the precipitated phase microstructure diagram of the 6xxx aluminum alloy after artificial aging in Comparative Example 1 of the present invention; Figure 3 It is the precipitated phase microstructure diagram of the 6xxx aluminum alloy after artificial aging in Comparative Example 2 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. The drawings in the following description are only exemplary, and for those of ordinary skill in the art, without creative efforts, other implementation drawings can be obtained by extending the provided drawings.

[0021] To overcome the deficiencies of the prior art, the present invention provides an artificial aging method for 6xxx aluminum alloy, comprising the following steps: First artificial aging treatment: performing a first artificial aging treatment on the 6xxx aluminum alloy to dissolve the atomic clusters in the 6xxx aluminum alloy and obtain the 6xxx aluminum alloy after the first aging treatment; wherein, the 6xxx aluminum alloy is a naturally aged 6xxx aluminum alloy; Specifically, this step is as follows: Place the 6xxx aluminum alloy in a furnace at 200 - 230 °C (for aging treatment), and keep it warm for 5 - 10 minutes. Among them, the naturally aged 6xxx aluminum alloy is obtained by the following preparation method: Prepare a 6xxx aluminum alloy ingot and process it into a 6xxx aluminum alloy sheet; then perform solution treatment, quenching treatment, and natural aging treatment on the 6xxx aluminum alloy sheet in sequence; among them, by mass fraction, the chemical composition of the 6xxx aluminum alloy ingot is: Mg 0.5 - 1.0 wt%, Si 0.6 - 1.1 wt%, Cu 0.5 - 0.9 wt%, and the balance is aluminum. The temperature of the solution treatment is 530 - 560 °C, and the time of the solution treatment is 10 minutes - 1 hour; the medium for the quenching treatment is room temperature water; during the natural aging treatment, the 6xxx aluminum alloy sheet can be cold - formed at any time point.

[0022] Second artificial aging treatment: Perform a second artificial aging treatment on the 6xxx aluminum alloy after the first aging treatment to form precipitation phase nucleation points and obtain the 6xxx aluminum alloy after the second aging treatment. Specifically, this step is as follows: Cool the 6xxx aluminum alloy after the first artificial aging treatment to 170 - 180 °C and keep it warm for 10 - 15 minutes; among them, during the cooling process, the furnace - cooling method is adopted, and the cooling rate ≥ 20 °C / min.

[0023] Third artificial aging treatment: Perform a third artificial aging treatment on the 6xxx aluminum alloy after the second aging treatment to form precipitation phases and obtain the 6xxx aluminum alloy after artificial aging.

[0024] Specifically, this step is as follows: Heat the 6xxx aluminum alloy after the second artificial aging treatment to 200 - 230 °C and keep it warm for 10 - 15 minutes; among them, during the heating process, the furnace - heating method is adopted; the heating rate ≥ 20 °C / min.

[0025] Based on the above - mentioned method, through high - temperature aging treatment (the first artificial aging treatment), the dissolution of atomic clusters formed during natural aging is promoted, thereby reducing the inhibition of atomic clusters on the formation of precipitation phases; then through low - temperature aging treatment (the second artificial aging treatment), the formation of fine and dense precipitation phase nucleation points is promoted; finally, through high - temperature aging treatment (the third artificial aging treatment), the precipitation phase formation kinetics is accelerated, and the precipitation phase content is rapidly increased in a short time; among them, the fine and dense precipitation phases can effectively hinder the movement of dislocations, thereby improving the strength of the alloy after artificial aging, and the fine size and good coherency can relieve the strain concentration during the deformation process, thereby ensuring the plasticity of the alloy after artificial aging.

[0026] When cooling and heating, the rate is greater than or equal to 20 °C / min, which can shorten the time of artificial aging and control the total time of three-stage artificial aging within 40 min; preferably, the total time of three-stage artificial aging is controlled within 30 min, so as to rapidly improve the strength of the alloy and maintain good plasticity in a short time.

[0027] On the other hand, the present invention provides a 6xxx aluminum alloy after artificial aging, which is prepared by using the artificial aging method of any one of the above; in the 6xxx aluminum alloy after artificial aging, the precipitation phases include GP zones and β″ phases with good coherency with the aluminum matrix; the yield strength of the 6xxx aluminum alloy after artificial aging at room temperature is 270~320 MPa, the tensile strength is 330~360 MPa, and the elongation is 17~25%.

[0028] The present invention will be further described below in conjunction with specific examples and comparative examples.

[0029] In the examples and comparative examples, the naturally aged 6xxx aluminum alloy was obtained by the following preparation method: preparing a 6xxx aluminum alloy ingot and processing it into a 6xxx aluminum alloy plate with a thickness of 3 mm; then performing a solution treatment at 550±5 °C for 30 min, and after quenching to room temperature, naturally aging the 6xxx aluminum alloy plate for 7 days to obtain the naturally aged 6xxx aluminum alloy; wherein, by mass fraction, the chemical composition of the 6xxx aluminum alloy ingot is Al-0.8Mg-0.9Si-0.7Cu.

[0030] Example 1 This example provides an artificial aging method for 6xxx aluminum alloy, including the following steps: First artificial aging treatment: placing the naturally aged 6xxx aluminum alloy in a furnace at 220 °C and holding for 5 min to obtain the 6xxx aluminum alloy after the first artificial aging treatment; Second artificial aging treatment: cooling the 6xxx aluminum alloy after the first artificial aging treatment in the furnace at a rate of 20 °C / min to 180 °C, and holding for 15 min to obtain the 6xxx aluminum alloy after the second artificial aging treatment; Third artificial aging treatment: heating the 6xxx aluminum alloy after the second artificial aging treatment in the furnace at a rate of 20 °C / min to 220 °C, and holding for 10 min to obtain the 6xxx aluminum alloy after artificial aging.

[0031] Testing the precipitation phases of the 6xxx aluminum alloy after artificial aging obtained in this example, the results are as Figure 1As shown, it can be seen that the precipitated phases are fine and dense, with a diameter of only about 5 nm and a volume fraction of about 1.6%, and are dispersed in the aluminum matrix. Judging from their morphology, the precipitated phases include GP zones and β″ phases with good coherency with the aluminum matrix. Tensile tests were carried out on the 6xxx aluminum alloy obtained in this example, and 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. Among them, the yield strength at room temperature is 290 MPa, the tensile strength is 350 MPa, and the elongation is 20%.

[0032] Example 2 This example provides an artificial aging method for 6xxx aluminum alloy, including the following steps: First artificial aging treatment: Place the naturally aged 6xxx aluminum alloy in a furnace at 200 °C and hold for 5 min to obtain the 6xxx aluminum alloy after the first artificial aging treatment; Second artificial aging treatment: Cool the 6xxx aluminum alloy after the first artificial aging treatment in the furnace at a rate of 20 °C / min to 170 °C, and hold for 10 min to obtain the 6xxx aluminum alloy after the second artificial aging treatment; Third artificial aging treatment: Heat the 6xxx aluminum alloy after the second artificial aging treatment in the furnace at a rate of 20 °C / min to 200 °C, and hold for 10 min to obtain the artificially aged 6xxx aluminum alloy.

[0033] Tensile tests were carried out on the artificially aged 6xxx aluminum alloy obtained in this example, and 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. Among them, the yield strength at room temperature is 270 MPa, the tensile strength is 330 MPa, and the elongation is 24%.

[0034] Example 3 This example provides an artificial aging method for 6xxx aluminum alloy, including the following steps: First artificial aging treatment: Place the naturally aged 6xxx aluminum alloy in a furnace at 230 °C and hold for 9 min to obtain the 6xxx aluminum alloy after the first artificial aging treatment; Second artificial aging treatment: Cool the 6xxx aluminum alloy after the first artificial aging treatment in the furnace at a rate of 40 °C / min to 180 °C, and hold for 14 min to obtain the 6xxx aluminum alloy after the second artificial aging treatment; Third artificial aging treatment: Heat the 6xxx aluminum alloy after the second artificial aging treatment in the furnace at a rate of 40 °C / min to 230 °C, and hold for 14 min to obtain the artificially aged 6xxx aluminum alloy.

[0035] The artificially aged 6xxx aluminum alloy obtained in this example was subjected to a tensile test, and 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. Among them, the yield strength at room temperature is 315 MPa, the tensile strength is 350 MPa, and the elongation is 17%.

[0036] Comparative Example 1 This comparative example provides an artificial aging method for 6xxx aluminum alloy, including the following steps: The naturally aged 6xxx aluminum alloy was placed in a furnace at 180 °C and kept warm for 30 min to obtain the artificially aged 6xxx aluminum alloy.

[0037] The precipitation phases of the artificially aged 6xxx aluminum alloy obtained in this comparative example are as Figure 2 shown. It can be seen that the precipitation phases are fewer, and the volume fraction is only about 0.5%. The artificially aged 6xxx aluminum alloy obtained in this comparative example was subjected to a tensile test, and the test results are shown in Table 1. It can be seen that the yield strength at room temperature is 180 MPa, the tensile strength is 310 MPa, and the elongation is 26%. In this comparative example, due to only single-stage aging at 180 °C, the atomic clusters formed during natural aging cannot be fully dissolved at too low a temperature, and the lack of a third-stage high-temperature artificial aging process leads to slow precipitation phase formation. Therefore, the content of precipitation phases is insufficient, and the strength of the alloy after artificial aging is much lower than that of Example 1.

[0038] Comparative Example 2 This comparative example provides an artificial aging method for 6xxx aluminum alloy, including the following steps: The naturally aged 6xxx aluminum alloy was placed in a furnace at 220 °C and kept warm for 30 min to obtain the artificially aged 6xxx aluminum alloy.

[0039] The precipitation phases of the artificially aged 6xxx aluminum alloy obtained in this comparative example are as Figure 3 shown. It can be seen that the size of the precipitation phases is significantly higher than that of Example 1 (the diameter is about 10 nm, which is twice that of the precipitation phases in Example 1). The artificially aged 6xxx aluminum alloy obtained in this comparative example was subjected to a tensile test, and the test results are shown in Table 1. It can be seen that the yield strength at room temperature is 300 MPa, the tensile strength is 340 MPa, and the elongation is 10%. In this comparative example, due to only single-stage aging at 220 °C, the formation process of fine and dense nucleation points of precipitation phases at 180 °C is lacking, and the nucleation rate of precipitation phases at high temperature is low, and atomic diffusion is intense, resulting in larger precipitation phase sizes. Therefore, although the strength of the alloy after artificial aging is comparable to that of Example 1, the plasticity is much lower than that of Example 1.

[0040] Comparative Example 3 This comparative example provides an artificial aging method for 6xxx aluminum alloy, including the following steps: First artificial aging treatment: Place the naturally aged 6xxx aluminum alloy in a furnace at 180 °C and hold for 15 min to obtain the 6xxx aluminum alloy after the first artificial aging treatment; Second artificial aging treatment: Heat the 6xxx aluminum alloy after the first artificial aging treatment in the furnace at a rate of 20 °C / min to 220 °C, and hold for 10 min to obtain the artificially aged 6xxx aluminum alloy.

[0041] Tensile tests were carried out on the artificially aged 6xxx aluminum alloy obtained in this comparative example. The test results are shown in Table 1. It can be seen that the yield strength at room temperature is 250 MPa, the tensile strength is 320 MPa, and the elongation is 22%. Due to the lack of the first-stage aging in the three-stage artificial aging of Example 1, the step of dissolving the natural aging clusters and inhibiting the formation of precipitation phases during artificial aging, the strength of the alloy after artificial aging in Comparative Example 3 is lower than that in Example 1.

[0042] Comparative Example 4 This comparative example provides an artificial aging method for 6xxx aluminum alloy, including the following steps: First artificial aging treatment: Heat the naturally aged 6xxx aluminum alloy at a rate of 20 °C / min to 220 °C and hold for 5 min to obtain the 6xxx aluminum alloy after the first artificial aging treatment; Second artificial aging treatment: Cool the 6xxx aluminum alloy after the first artificial aging treatment in the furnace at a rate of 20 °C / min to 180 °C, and hold for 15 min to obtain the artificially aged 6xxx aluminum alloy.

[0043] Tensile tests were carried out on the artificially aged 6xxx aluminum alloy obtained in this comparative example. The test results are shown in Table 1. It can be seen that the yield strength at room temperature is 200 MPa, the tensile strength is 320 MPa, and the elongation is 25%. Due to the lack of the third-stage aging in the three-stage artificial aging of Example 1, resulting in insufficient precipitation phase formation kinetics and difficult to fully form during aging, the strength of the alloy after artificial aging in Comparative Example 4 is lower than that in Example 1.

[0044] Comparative Example 5 This comparative example provides an artificial aging method for 6xxx aluminum alloy, including the following steps: First artificial aging treatment: Place the naturally aged 6xxx aluminum alloy in a furnace at 185 °C and hold for 5 min to obtain the 6xxx aluminum alloy after the first artificial aging treatment; Second artificial aging treatment: The 6xxx aluminum alloy after the first artificial aging treatment is cooled in the furnace at a rate of 20 °C / min to 180 °C, and after holding for 15 min, the 6xxx aluminum alloy after the second artificial aging treatment is obtained; Third artificial aging treatment: The 6xxx aluminum alloy after the second artificial aging treatment is heated in the furnace at a rate of 20 °C / min to 220 °C, and after holding for 10 min, the artificially aged 6xxx aluminum alloy is obtained.

[0045] Tensile tests were carried out on the artificially aged 6xxx aluminum alloy obtained in this comparative example. The test results are shown in Table 1. It can be seen that the yield strength at room temperature is 255 MPa, the tensile strength is 300 MPa, and the elongation is 20%. In this comparative example, due to the relatively low temperature of the first artificial aging treatment, it is difficult for the natural aging clusters to dissolve sufficiently and the precipitates to form sufficiently. Therefore, the strength of the alloy after artificial aging is lower than that of Example 1.

[0046] Comparative Example 6 This comparative example provides an artificial aging method for 6xxx aluminum alloy, including the following steps: First artificial aging treatment: The naturally aged 6xxx aluminum alloy is heated to 220 °C at a rate of 20 °C / min and held for 5 min to obtain the 6xxx aluminum alloy after the first artificial aging treatment; Second artificial aging treatment: The 6xxx aluminum alloy after the first artificial aging treatment is cooled in the furnace at a rate of 20 °C / min to 180 °C, and after holding for 15 min, the 6xxx aluminum alloy after the second artificial aging treatment is obtained; Third artificial aging treatment: The 6xxx aluminum alloy after the second artificial aging treatment is heated in the furnace at a rate of 20 °C / min to 250 °C, and after holding for 10 min, the artificially aged 6xxx aluminum alloy is obtained.

[0047] Tensile tests were carried out on the artificially aged 6xxx aluminum alloy obtained in this comparative example. The test results are shown in Table 1. It can be seen that the yield strength at room temperature is 280 MPa, the tensile strength is 320 MPa, and the elongation is 15%. In this comparative example, due to the too high temperature of the third artificial aging treatment, the precipitates form too fast and coarsen too violently, resulting in lower strength and plasticity of the alloy after artificial aging.

[0048] Comparative Example 7 This comparative example provides an artificial aging method for 6xxx aluminum alloy, including the following steps: First artificial aging treatment: The naturally aged 6xxx aluminum alloy is heated to 220 °C at a rate of 20 °C / min and held for 5 min to obtain the 6xxx aluminum alloy after the first artificial aging treatment; Second artificial aging treatment: The 6xxx aluminum alloy after the first artificial aging treatment is cooled in the furnace at a rate of 20 °C / min to 130 °C, and after holding for 15 min, the 6xxx aluminum alloy after the second artificial aging treatment is obtained; Third artificial aging treatment: The 6xxx aluminum alloy after the second artificial aging treatment is heated in the furnace at a rate of 20 °C / min to 250 °C, and after holding for 10 min, the 6xxx aluminum alloy after artificial aging is obtained.

[0049] Tensile tests were carried out on the 6xxx aluminum alloy after artificial aging obtained in this comparative example. The test results are shown in Table 1. It can be seen that the yield strength at room temperature is 260 MPa, the tensile strength is 310 MPa, and the elongation is 22%. In this comparative example, due to the too low temperature of the second artificial aging treatment, the nucleation points of the precipitation phase were not fully formed, and the strength of the alloy after artificial aging is low.

[0050] Table 1 Mechanical properties of 6xxx aluminum alloy in the examples and comparative examples

[0051] In summary, compared with the traditional artificial aging (or painting baking) process, through the synergistic effect of three-stage artificial aging at high temperature, low temperature, and high temperature, the present invention effectively improves the rapid strengthening ability of 6xxx aluminum alloy in a short time and maintains good plasticity.

[0052] It is easy for those skilled in the art to understand that, on the premise of no conflict, the advantageous technical features of the above various methods can be freely combined and superimposed.

[0053] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. The above is only the preferred implementation manner of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can still be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. An artificial aging method for 6xxx aluminum alloy, characterized in that, It includes the following steps: The first artificial aging treatment: Perform the first artificial aging treatment on the 6xxx aluminum alloy to dissolve the atomic clusters in the 6xxx aluminum alloy and obtain the 6xxx aluminum alloy after the first aging treatment; Among them, the 6xxx aluminum alloy is a naturally aged 6xxx aluminum alloy; The second artificial aging treatment: Perform the second artificial aging treatment on the 6xxx aluminum alloy after the first aging treatment to form precipitation phase nucleation points and obtain the 6xxx aluminum alloy after the second aging treatment; The third artificial aging treatment: Perform the third artificial aging treatment on the 6xxx aluminum alloy after the second aging treatment to form precipitation phases and obtain the 6xxx aluminum alloy after artificial aging.

2. The artificial aging method of the 6xxx aluminum alloy according to claim 1, characterized in that, In the step of the first artificial aging treatment: The temperature of the first artificial aging treatment is 200 - 230 °C, and the holding time is 5 - 10 min.

3. The artificial aging method of the 6xxx aluminum alloy according to claim 1, characterized in that, In the step of the first artificial aging treatment, the naturally aged 6xxx aluminum alloy is obtained by the following preparation method: Prepare a 6xxx aluminum alloy ingot and process it into a 6xxx aluminum alloy plate; then perform solution treatment, quenching treatment, and natural aging treatment on the 6xxx aluminum alloy plate in sequence.

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

5. The artificial aging method of the 6xxx aluminum alloy according to claim 1, characterized in that, The step of the second artificial aging treatment specifically includes: Cool the 6xxx aluminum alloy after the first artificial aging treatment to 170 - 180 °C and hold for 10 - 15 min.

6. The artificial aging method of 6xxx aluminum alloy according to claim 5, characterized in that, In the second artificial aging treatment step, the furnace cooling method is used during cooling; Among them, the cooling rate ≥ 20 °C / min.

7. The artificial aging method of 6xxx aluminum alloy according to claim 1, characterized in that, The step of the third artificial aging treatment specifically includes: Heat the 6xxx aluminum alloy after the second artificial aging treatment to 200 - 230 °C and hold for 10 - 15 min.

8. The artificial aging method of 6xxx aluminum alloy according to claim 7, characterized in that, In the third artificial aging treatment step, the furnace heating method is used during heating; Among them, the heating rate ≥ 20 °C / min.

9. An artificially aged 6xxx aluminum alloy, characterized in that, The 6xxx aluminum alloy after artificial aging is prepared by the artificial aging method described in any one of claims 1 - 8; in the 6xxx aluminum alloy after artificial aging, the precipitation phases include GP zones and β″ phases; The volume fraction of the precipitation phases ≥ 1.3%; the average diameter of the precipitation phases ≤ 8 nm.

10. The 6xxx aluminum alloy after artificial aging according to claim 9, characterized in that, The yield strength of the 6xxx aluminum alloy after artificial aging at room temperature is 270 - 320 MPa, the tensile strength is 330 - 360 MPa, and the elongation is 17 - 25%.

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