A micro-nano structure coupling distribution multi-process synergistic regulation method for aluminum alloy plate

Abstract

The application discloses a micro-nano structure coupling distribution multi-process synergistic regulation method of an aluminum alloy plate and belongs to the field of aluminum alloys. The method comprises the following steps: preparing an aluminum alloy, melting the alloy by using a medium-frequency induction furnace under non-vacuum conditions, and pouring the alloy into a water-cooled steel mold for cooling; subsequently, sequentially performing high-temperature heat treatment to optimize solute element distribution, hot rolling deformation, high-temperature heat treatment to regulate micron-scale precipitated phase distribution, room-temperature cold rolling or ultra-low-temperature deep rolling deformation + intermediate annealing + room-temperature cold rolling or ultra-low-temperature deep rolling deformation to a final thickness, short-time high-temperature solid solution + quenching treatment; and finally, performing long-time low-temperature heat treatment to regulate nano solute atom cluster distribution. The method can effectively control the size and distribution of grains and precipitated phases in the alloy, has a significant promoting effect on the forming performance of the alloy, and can greatly improve the coordinated deformation ability of grains of different sizes and different microzones in a stamping deformation process, so that the stamping forming performance of the alloy is excellent; and the method is very suitable for manufacturing of automobile aluminum alloys.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy technology. In particular, it addresses the fact that the forming performance and bending performance of aluminum alloy outer panels for car bodies are still not high enough, and the application status of the automotive industry is constantly improving these performance requirements. It proposes an industrially applicable treatment method to improve the microstructure and properties of Al-Mg-Si-Cu alloy sheets. This treatment method can effectively control the size and distribution of grains and precipitated phases in the alloy, forming a micro-nano structure coupling distribution feature that significantly promotes the forming performance of the alloy. Background Technology

[0002] With the continuous improvement of industrialization, energy crises and environmental problems have become increasingly serious, and energy conservation and emission reduction have become the main theme of future development. Against this backdrop, countries have adopted many measures to address energy consumption and environmental issues, especially in the automotive sector: improving engine efficiency, researching new energy vehicles, and reducing vehicle weight have become recent research hotspots, and major automakers have adopted lightweighting solutions to enhance their competitiveness. Overall, aluminum alloys, due to their lightweight, corrosion resistance, high specific strength, ease of processing, aesthetically pleasing surface, abundant reserves, and recyclability, have become a key material for automotive lightweighting. Furthermore, statistics show that the energy saved by using aluminum alloys in automobiles is 6 to 12 times that of the primary aluminum used to produce those parts. Therefore, the development and application of advanced aluminum alloy sheets for automotive lightweighting has attracted widespread attention from global automakers and researchers, and the amount of aluminum used in automobiles has been increasing year by year in recent years.

[0003] Compared to other aluminum alloy series, 6xxx (Al-Mg-Si-Cu) series aluminum alloys are more widely used in the manufacture of automotive body panels due to their excellent stamping and forming properties, bending performance, and paint hardening increment. Currently, the main alloys used include AA6016, AA6111, and AA6022, each with its own unique properties due to differences in composition. However, compared to traditional automotive steel sheets, 6xxx series aluminum alloys still suffer from higher costs, less formability, bending performance, and lower strength, necessitating the development of new alloys and processes to better meet practical application requirements. Considering that dual-phase or multi-phase synergistic precipitation and synergistic strengthening can effectively improve the paint hardening increment and strength of alloy sheets, our research team recently developed a novel Al-Mg-Si-Cu-Zn alloy with high paint hardening and its preparation method. To better meet practical application needs, while ensuring high paint hardening properties, significantly improving the stamping and bending performance of traditional Al-Mg-Si-Cu alloys and novel Al-Mg-Si-Cu-Zn alloy sheets is key to the further widespread application of 6xxx series aluminum alloys. In particular, developing a hot-working preparation method that ensures the alloy sheets are not only easy to stamp but also possess high paint hardening increments and high resistance to natural weathering would be of great significance for the rapid development of aluminum alloys for lightweight automotive applications. Summary of the Invention

[0004] To better meet the urgent demand for high-performance aluminum alloy sheets in automotive lightweighting, this invention addresses the poor stamping performance of traditional Al-Mg-Si-Cu and novel Al-Mg-Si-Cu-Zn alloy sheets by proposing a multi-process synergistic control method for the coupled micro-nano microstructure distribution of high-formability aluminum alloy sheets. This invention fully utilizes the fact that once a suitable micron-scale precipitate phase forms during hot working, it can significantly promote the fragmentation of the primary iron-rich phase, thereby mitigating the adverse effects of the coarse iron-rich phase distribution. Simultaneously, it can synergistically interact with the coarse iron-rich phase to form a multi-scale dispersed particle distribution characteristic. Therefore, during solution treatment, it can not only induce particle-stimulated nucleation but also prevent recrystallization and grain coarsening, ultimately resulting in a fine-grained alloy. More importantly, once the coarse precipitate phase and the iron-rich phase form a suitable multi-scale dispersed distribution characteristic, it can also induce the alloy to form a microstructure with a special distribution of fine and coarse grains, such as fine... The alloy exhibits a gradient distribution of coarse and fine grains, among other characteristics. Furthermore, after the micron-sized precipitate phase and the primary iron-rich phase synergistically influence the alloy recrystallization process, the melting and diffusion processes of the micron-sized precipitate phase can be controlled to form coupled distribution characteristics of low-concentration and high-concentration solute micro-regions. After further long-term low-temperature heat treatment to regulate solute atom clusters, the alloy matrix can not only have a microstructure with a special distribution of fine and coarse grains, but also, through the precipitation behavior of solute atom clusters, a coupled distribution characteristic of soft and hard micro-regions can be constructed within the alloy sheet. Ultimately, based on the coupling effect of the above-mentioned microstructures, the developed 6xxx series aluminum alloy sheet can exhibit excellent stamping forming performance.

[0005] According to a first aspect of the present invention, a method for synergistic control of the micro-nano microstructure coupling distribution of a highly formable Al-Mg-Si-Cu alloy sheet is provided, wherein the chemical composition and mass percentage content of the Al-Mg-Si-Cu alloy are as follows: Zn: 0-3.7 wt%, Mg 0.6-0.9 wt%, Si 1.0-1.3 wt%, Cu 0.1-0.4 wt%, Fe: 0.1-0.7 wt%, Mn: 0.3-0.7 wt%, Cr ≤ 0.02 wt%, Ti ≤ 0.1 wt%, B ≤ 0.01 wt%, with the balance being Al; characterized by employing the following technical route:

[0006] (1) Configure a highly formable Al-Mg-Si-Cu alloy, then melt the alloy using medium frequency induction under non-vacuum conditions, and cast it into a water-cooled steel mold. Control the cooling rate to be greater than 40℃ / min so that the alloy grain size meets the subsequent control requirements.

[0007] (2) Based on the casting speed of the ingot, the distribution of solute elements is controlled by high-temperature heat treatment of the ingot;

[0008] (3) Preheat at high temperature, and then hot roll with appropriate deformation;

[0009] (4) High-temperature and long-term heat treatment regulates the distribution morphology of micron-scale precipitate phases in the alloy matrix. The precipitate phase size is greater than 0.5 μm and the interparticle spacing is greater than 1 μm.

[0010] (5) Cold rolling at room temperature or deep cold rolling at ultra-low temperature to a certain thickness, and then performing appropriate intermediate annealing treatment. After intermediate annealing, the plate is further cold rolled at room temperature or deep cold rolling at ultra-low temperature to the final thickness.

[0011] (6) High-temperature short-time solution treatment with controlled heating rate, followed by quenching and cooling the solution-treated alloy from the solution treatment temperature to room temperature at a certain cooling rate.

[0012] (7) Transfer the quenched alloy to a heat treatment furnace within 1.5 min for long-term low-temperature heat treatment to regulate the distribution characteristics of solute atomic clusters.

[0013] Based on the above-mentioned synergistic control of multiple processes in micro-nano structures, the developed alloy sheet can be guaranteed to have excellent stamping performance.

[0014] Further, in step (1), the alloy melting process using medium-frequency induction melting under non-vacuum conditions is as follows: First, all recycled aluminum or ordinary aluminum is added to the crucible and melted, with the temperature controlled at 780-880℃. Then, Al-20wt%Fe, Al-10wt%Mn, Al-10wt%Cr, and Al-10wt%Ti master alloys are added respectively. After melting, Al-50wt%Cu and Al-20wt%Si master alloys are added respectively. Then, the melt is stirred at high power for 5 minutes, and subsequently, the temperature is controlled at 720℃. Pure Zn and pure Mg are added separately, and a graphite bell jar is used to press them into the bottom of the melt. After they are completely melted, the bell jar is removed. The power of the medium frequency induction furnace is adjusted to stabilize the temperature of the alloy melt at 740℃. Slag is removed and refining agent is added for degassing and refining. Then, when the temperature of the melt is reduced to 720℃, Al-5wt%Ti-1wt%B grain refiner is added and stirred appropriately. Finally, the melt is held at 720℃ for 9-11 minutes and then poured into a water-cooled steel mold with a cooling rate of more than 50℃ / min.

[0015] Further, in step (2), the process of controlling the distribution of solute elements by high-temperature heat treatment of the ingot is as follows: the heating rate is 10-30℃ / h, the temperature is raised to 450-490℃, and then held for 2-6h, then further raised to 540-565℃, held for 20-50h, and then cooled to room temperature at a rate greater than 30℃ / h.

[0016] Further, in step (3), the high-temperature preheating process is 540-565℃, holding for 1-4 hours, followed by hot rolling treatment with appropriate deformation, specifically: initial rolling temperature: 540-565℃; final rolling temperature: above 300℃, reduction per pass 10-20%, rolling deformation 90-99%.

[0017] Furthermore, in step (4), the high-temperature long-term heat treatment to regulate the distribution morphology of the micron-scale precipitate phase in the alloy matrix specifically includes: 430~510℃ / 20-50h, heating rate greater than 45℃ / h, cooling rate greater than 30℃ / h, ensuring that the size of the formed micron-scale precipitate phase is greater than 0.5μm and the interparticle spacing is greater than 1μm.

[0018] Further, in step (5), if room temperature cold rolling is used to deform to a certain thickness, and appropriate intermediate annealing is performed, and then room temperature cold rolling is performed to the final thickness, the specific process is as follows: the room temperature cold rolling deformation is 30-60%, the reduction per pass is 10-30%, and the corresponding intermediate annealing process is: 400~500℃ / 0.5-2h. The process for further room temperature cold rolling of the plate after intermediate annealing to the final plate is a deformation of 50-80% and a reduction per pass of 10-30%; if The process involves cryogenic deep rolling to a certain thickness, followed by appropriate intermediate annealing, and then cryogenic deep rolling to the final thickness. The specific process is as follows: The cryogenic deep rolling process involves a deformation temperature below -120℃, a deformation amount of 30-60%, and a reduction per pass of 5-10%. The corresponding intermediate annealing process is: 400~480℃ / 0.5-2h. The plate after intermediate annealing is then further cryogenically deep rolled with a deformation amount of 50-80% and a reduction per pass of 5-10%.

[0019] Further, in step (6), the high-temperature short-time solution treatment with controlled heating rate specifically includes: heating rate greater than 100℃ / min, 540-575℃ / 2-10min, and then quenching the solution-treated alloy sample from the solution treatment temperature to room temperature at a cooling rate greater than 200℃ / s.

[0020] Furthermore, in step (7), the quenched sample is transferred to a heat treatment furnace within 1.5 min for long-term low-temperature heat treatment. The specific control parameters include: temperature 60-90℃, time 10-20h, and heating / cooling rate greater than 10℃ / min.

[0021] The application of the high formability Al-Mg-Si-Cu alloy described in this invention in automobiles, especially for the manufacture of complex-shaped parts with high requirements for stamping performance and strength.

[0022] The beneficial effects of this invention are:

[0023] By adopting the above-mentioned technical solution, this invention has the following advantages: This invention not only enables traditional Al-Mg-Si-Cu alloys and novel Al-Mg-Si-Cu-Zn alloy sheets to form suitable micro-nano microstructure coupling distribution characteristics after multi-process synergistic control of hot working, namely, multi-scale dispersed particle distribution characteristics composed of micron-scale precipitated phases and primary iron-rich phases, and microstructure characteristics with special distributions of coarse and fine grains (such as fine grains enclosing coarse grains, fine grains exhibiting gradient distribution characteristics, etc.), but also achieves coupling distribution characteristics of high-concentration solute microregions and low-concentration solute microregions constructed by controlling the distribution of micron-scale precipitated phases, re-dissolution, and precipitation. More importantly, due to the formation of high-concentration and low-concentration solute microregion coupling distribution characteristics, after long-term low-temperature heat treatment, soft and hard microregion coupling distribution characteristics will further form within the alloy matrix. Ultimately, based on the coupling effect of the above-mentioned microstructures, the developed 6xxx series aluminum alloy sheets can exhibit excellent stamping forming performance. This invention can significantly improve the stamping forming performance of alloy sheets, and it plays an important role in promoting the further widespread application of this series of aluminum alloy sheets. This invention is very suitable for the processing and production of aluminum alloy materials for automobiles, as well as for other aluminum alloy material manufacturers with specific requirements for the microstructure and stamping performance of aluminum alloy sheets. Of course, it is also suitable for other technical industries with high requirements for the microstructure and comprehensive performance of other series of aluminum alloy materials. Attached Figure Description

[0024] Figure 1 A flowchart of the multi-process synergistic control method for the coupled distribution of micro-nano microstructure in highly formable aluminum alloys according to the present invention is shown.

[0025] Figure 2 EBSD characterization results of the grain distribution morphology of alloy plate No. 1 prepared in Example 1 after long-term low-temperature heat treatment;

[0026] Figure 3 EBSD characterization results of the grain distribution morphology of the No. 2 alloy plate prepared in Example 1 after long-term low-temperature heat treatment;

[0027] Figure 4 TEM characterization results of the multi-scale dispersed particle distribution characteristics of alloy #1 in the intermediate annealing state in Example 2;

[0028] Figure 5 TEM characterization results of the multi-scale dispersed particle distribution characteristics of alloy #2 in the intermediate annealed state in Example 2;

[0029] Figure 6 TEM characterization results of the multi-scale dispersed particle distribution characteristics of alloy #1 in the intermediate annealing state in Example 3;

[0030] Figure 7TEM characterization results of the multi-scale dispersed particle distribution characteristics of alloy #2 in the intermediate annealing state in Example 3;

[0031] Figure 8 EBSD characterization results of the grain distribution morphology of the No. 1 alloy plate prepared in Example 3 after long-term low-temperature heat treatment;

[0032] Figure 9 EBSD characterization results of grain distribution morphology after long-term low-temperature heat treatment of alloy plate No. 2 prepared in Example 3. Detailed Implementation

[0033] The present invention will be further supplemented and explained below with reference to specific implementation schemes.

[0034] This invention addresses the current research and application status of traditional Al-Mg-Si-Cu alloys and novel Al-Mg-Si-Cu-Zn alloy sheets for automobiles, which still require further improvement in stamping performance and urgently need to significantly reduce production costs. It proposes a multi-process synergistic control method based on micro-nano microstructure coupling distribution. This method not only enables the final alloy sheet to have micro-nano microstructure coupling distribution characteristics, but also exhibits excellent stamping performance. This invention fully utilizes the inevitable compositional segregation that occurs during the traditional casting of aluminum alloys, leading to the formation of coarse precipitates. By controlling the distribution of micron-scale precipitates with appropriate characteristics during hot working, these precipitates can interact with the coarse primary iron-rich phases, effectively promoting their fragmentation during hot working. This results in the formation of multi-scale dispersed particles within the alloy matrix, composed of micron-scale precipitates and primary iron-rich phases. These particles then synergistically interact during subsequent high-temperature solution treatment, creating a microstructure with a unique distribution of fine and coarse grains. Simultaneously, the solution treatment process effectively controls the re-dissolution and diffusion of the micron-scale precipitates, resulting in a coupled distribution of high-concentration and low-concentration solute microregions. Further control through prolonged low-temperature heat treatment allows for the construction of coupled soft and hard microregions within the alloy matrix. Ultimately, based on the construction and synergistic effect of these micro-nano microstructure coupling distributions, the prepared alloy sheet exhibits excellent stamping performance. The method of this invention is very suitable for the manufacture of new aluminum alloys for automobiles, especially for the manufacture of complex shaped parts that have high requirements for stamping performance, strength, surface quality and bending performance.

[0035] The process control method for the heterogeneous microstructure of the high-formability Al-Mg-Si-Cu-Zn alloy system for automobiles according to the present invention uses recycled aluminum or ordinary aluminum, industrial pure Mg, industrial pure Zn, and intermediate alloys such as Al-20wt%Si, Al-50wt%Cu, Al-20wt%Fe, Al-10wt%Mn, Al-10wt%Cr, and Al-10wt%Ti as raw materials. Figure 1 As shown, the following technical approach is adopted:

[0036] Step 101: Prepare an Al-Mg-Si-Cu alloy using recycled aluminum or ordinary aluminum, then melt the alloy using medium frequency induction melting under non-vacuum conditions, and cast it into a water-cooled steel mold. Control the cooling rate to be greater than 40℃ / min so that the alloy grain size meets the subsequent control requirements.

[0037] Step 101: High-temperature and long-term heat treatment of the ingot to control the distribution morphology of micron-scale precipitate phase in the alloy matrix. Specifically, the temperature is 430~510℃ / 20-50h, the heating rate is greater than 45℃ / h, the cooling rate is greater than 30℃ / h, and the size of the precipitate phase controlled is >0.5μm and the interparticle spacing is >1μm.

[0038] Step 102: The high-temperature preheating process is 540-565℃, held for 1-4 hours, followed by hot rolling with appropriate deformation, specifically: initial rolling temperature: 540-565℃; final rolling temperature: above 300℃, reduction per pass 10-20%, rolling deformation 90-99%.

[0039] Step 103: High-temperature long-term heat treatment to regulate the distribution morphology of micron-scale precipitated phases in the alloy matrix specifically includes: 430~510℃ / 20-50h, heating rate greater than 45℃ / h, cooling rate greater than 30℃ / h;

[0040] Step 104: High-temperature long-term heat treatment to regulate the distribution morphology of micron-scale precipitated phases in the alloy matrix specifically includes: 430~510℃ / 20-50h, heating rate greater than 45℃ / h, cooling rate greater than 30℃ / h;

[0041] Step 105: Cold roll at room temperature or deep cold roll at ultra-low temperature to deform to a certain thickness, and perform appropriate intermediate annealing treatment. After intermediate annealing, the sheet is further cold rolled at room temperature or deep cold roll at ultra-low temperature to deform to the final thickness.

[0042] Step 106: High-temperature short-time solution treatment with controlled heating rate, specifically including: heating rate greater than 100℃ / min, 540-575℃ / 2-10min, and then quenching the solution-treated alloy sample from the solution treatment temperature to room temperature at a cooling rate greater than 200℃ / s.

[0043] Step 107: Transfer the quenched sample to a heat treatment furnace within 1.5 min for long-term low-temperature heat treatment to regulate the distribution characteristics of solute atomic clusters. Specifically, the temperature is 60-90℃, the time is 10-20 h, and the heating and cooling rate is greater than 10℃ / min.

[0044] Specifically, the processing steps include the following: First, all pure aluminum is added to the crucible and melted, with the temperature controlled at 780–880°C. Then, Al-20wt%Fe, Al-10wt%Mn, Al-10wt%Cr, and Al-10wt%Ti master alloys are added respectively. After melting, Al-50wt%Cu and Al-20wt%Si master alloys are added respectively. The melt is then stirred at high power for 5 minutes. Subsequently, the temperature is controlled above 720°C, and pure aluminum is added respectively. Zn and pure Mg were added separately, pressed into the bottom of the melt using a graphite bell jar. After complete melting, the bell jar was removed, and the power of the medium-frequency induction furnace was adjusted to stabilize the alloy melt temperature at 740℃. Slag was skimmed off, and refining agents were added for degassing and refining. Then, when the melt temperature was lowered to 720℃, Al-5wt%Ti-1wt%B grain refiner was added and stirred appropriately. Finally, the melt was held at this temperature for 10 minutes and then cast into a water-cooled steel mold, with a cooling rate controlled to be greater than 50℃ / min. The specific chemical composition of the alloy used in this invention is shown in Table 1.

[0045] Table 1 Chemical composition of the alloy of the invention (mass percentage, wt%)

[0046] 1# 0.8 1.2 0.2 0.4 0.5 0 ≤0.02wt% ≤0.1wt% ≤0.01 margin 2# 0.8 1.2 0.2 0.4 0.5 3.0 ≤0.02wt% ≤0.1wt% ≤0.01 margin

[0047] In order to construct the micro-nano structure coupling distribution characteristics, the ingot was subjected to the following multi-process synergistic control treatment: (1) High temperature heat treatment to control the distribution of solute elements: heating rate 10-40℃ / h, raising to 450-500℃, then holding for 2-7h, then further raising to 540-575℃, holding for 20-50h, and then cooling to room temperature at a rate greater than 20℃ / h; (2) High temperature preheating process: 540-575℃, holding for 1-5h, and then hot rolling treatment with appropriate deformation, specifically: initial rolling temperature: 540-575℃; final rolling temperature: above 300℃, reduction per pass 10-30%, rolling deformation 80-99%; (3) High temperature long-term heat treatment to control the distribution morphology of micron-scale precipitates in the alloy matrix, specifically including: 420-520℃

[0048] / 20-50h, heating rate greater than 45℃ / h, cooling rate greater than 30℃ / h, ensuring that the formed micron-scale precipitate phase size is greater than 0.5μm and the particle spacing is greater than 1μm; (4) If room temperature cold rolling deformation is used to a certain thickness, and appropriate intermediate annealing treatment is performed, and then room temperature cold rolling is performed to the final thickness, the specific process is as follows: room temperature cold rolling deformation is 20-60%, pass reduction is 10-30%, the corresponding intermediate annealing process is: 400~510℃ / 0.5-2h, and the plate after intermediate annealing is further cold rolled at room temperature to the final plate, the corresponding process is deformation is 40-80%, pass reduction is 10-30%; If ultra-low temperature deep cold rolling deformation is used to a certain thickness, and appropriate intermediate annealing treatment is performed, and then ultra-low temperature deep cold rolling is performed to the final thickness, the specific process is as follows: ultra-low temperature deep cold rolling deformation process is, The deformation temperature is below -120℃, the deformation amount is 20-60%, the reduction per pass is 5-10%, and the corresponding intermediate annealing process is: 400~510℃ / 0.5-2h. The plate after intermediate annealing is further subjected to ultra-low temperature deep cold rolling process with a deformation amount of 40-80% and a reduction per pass of 5-10%; (5) High temperature short-time solid solution treatment with controlled heating rate, specifically including: heating rate greater than 100℃ / min, 540-575℃ / 1-20min, and then the alloy sample after solid solution treatment is quenched and cooled to room temperature at a cooling rate greater than 200℃ / s from the solid solution treatment temperature; (6) The quenched sample is transferred to the heat treatment furnace within 1.5min for long-term low temperature heat treatment to regulate the distribution characteristics of solute atomic clusters, specifically including: temperature 60-90℃, time 5-20h, heating and cooling rate greater than 10℃ / min. Based on the above-mentioned synergistic control of multiple hot working processes, it can be ensured that the developed alloy sheet can construct micro-nano microstructure coupling distribution characteristics and possess excellent stamping forming performance. The specific implementation method is as follows:

[0049] Example 1

[0050] The invention alloys 1# and 2# were implemented using the following medium-frequency induction melting and casting method: First, all pure aluminum was added to the crucible and melted at a temperature controlled between 780 and 880°C. Then, Al-20wt%Fe, Al-10wt%Mn, Al-10wt%Cr, and Al-10wt%Ti master alloys were added respectively. After melting, Al-50wt%Cu and Al-20wt%Si master alloys were added respectively. The melt was then stirred at high power for 5 minutes. Subsequently, the temperature was controlled above 720°C, and pure Zn and pure Mg were added respectively. During addition, a graphite bell jar was used to press the molten alloy into the bottom of the melt. After the alloys were completely melted, the bell jar was removed, and the power of the medium-frequency induction furnace was adjusted to allow the alloy melt to melt. After the temperature stabilizes again at 740℃, slag is removed and refining agent is added for degassing and refining; then, when the melt temperature drops to about 720℃, Al-5wt%Ti-1wt%B grain refiner is added and stirred appropriately. Finally, after holding at this temperature for 10 minutes, the melt is poured into a water-cooled steel mold on all sides, and the cooling rate is controlled to be greater than 50℃ / min; then, the following multi-process coordinated control is adopted: (1) High temperature heat treatment to control the distribution of solute elements: the heating rate is 10-30℃ / h, raised to 450-490℃, then held for 2-6h, then further raised to 540-565℃, held for 20-50h, and then cooled to room temperature at a rate greater than 30℃ / h; (2) (2) The high-temperature preheating process is 540-565℃, holding for 1-4h, followed by hot rolling with appropriate deformation, specifically: initial rolling temperature: 540-565℃; final rolling temperature: above 300℃, reduction per pass 10-20%, rolling deformation 90-99%; (3) High-temperature long-term heat treatment to regulate the distribution morphology of micron-scale precipitate phase in the alloy matrix specifically includes: 430-470℃ / 20-40h, heating rate greater than 45℃ / h, cooling rate greater than 30℃ / h, ensuring that the formed micron-scale precipitate phase size is greater than 0.5μm and the particle spacing is greater than 1μm; (4) Room temperature cold rolling deformation to a certain thickness, followed by appropriate intermediate annealing, and then The specific process for room temperature cold rolling to the final thickness is as follows: the room temperature cold rolling deformation is 30-60%, the reduction per pass is 10-30%, and the corresponding intermediate annealing process is: 400~500℃ / 0.5-2h. The plate after intermediate annealing is further cold rolled at room temperature to the final plate. The corresponding process is that the deformation is 50-80%, and the reduction per pass is 10-30%. (5) High temperature short-time solid solution treatment with controlled heating rate, specifically including: heating rate greater than 100℃ / min, 540-575℃ / 2-10min, and then quenching and cooling the alloy sample after solid solution treatment from the solid solution treatment temperature to room temperature at a cooling rate greater than 200℃ / s. (6) Quenching the sample in 1.Within 5 minutes, the solute atomic clusters were transferred to a heat treatment furnace for long-term low-temperature heat treatment to regulate their distribution characteristics. Specifically, the temperature was 60-90℃, the time was 10-20h, and the heating and cooling rate was greater than 10℃ / min. Finally, the mechanical properties of alloy plates 1# and 2# in the long-term low-temperature heat treatment state were measured, and the corresponding mechanical properties are shown in Table 2. The EBSD microstructure of alloys 1# and 2# after long-term low-temperature heat treatment is shown in Table 2. Figure 2 and 3 As shown.

[0051] Example 2

[0052] The invention alloys 1# and 2# were implemented using the following medium-frequency induction melting and casting method: First, all pure aluminum was added to the crucible and melted at a temperature controlled between 780 and 880°C. Then, Al-20wt%Fe, Al-10wt%Mn, Al-10wt%Cr, and Al-10wt%Ti master alloys were added respectively. After melting, Al-50wt%Cu and Al-20wt%Si master alloys were added respectively. The melt was then stirred at high power for 5 minutes. Subsequently, the temperature was controlled above 720°C, and pure Zn and pure Mg were added respectively. During addition, a graphite bell jar was used to press the molten alloy into the bottom of the melt. After the alloys were completely melted, the bell jar was removed, and the power of the medium-frequency induction furnace was adjusted to restore the temperature of the alloy melt. After stabilizing at 740℃, slag is removed and refining agent is added for degassing and refining; then, when the melt temperature drops to about 720℃, Al-5wt%Ti-1wt%B grain refiner is added and stirred appropriately. Finally, after holding at this temperature for 10 minutes, the melt is poured into a water-cooled steel mold on all sides, and the cooling rate is controlled to be greater than 50℃ / min; then, the following multi-process coordinated control is adopted: (1) The high-temperature heat treatment process for controlling the distribution of solute elements is: heating rate 10-30℃ / h, raised to 450-490℃, then held for 2-6h, then further raised to 540-565℃, held for 20-50h, and then cooled to room temperature at a rate greater than 30℃ / h; (2) The high-temperature preheating process is , 540-565℃, hold for 1-4h, and then perform hot rolling treatment with appropriate deformation, specifically: initial rolling temperature: 540-565℃; final rolling temperature: above 300℃, reduction per pass 10-20%, rolling deformation 90-99%; (3) high temperature and long time heat treatment to regulate the distribution morphology of micron-scale precipitate phase in alloy matrix specifically includes: 430-470℃ / 20-40h, heating rate greater than 45℃ / h, cooling rate greater than 30℃ / h, to ensure that the size of the micron-scale precipitate phase formed is greater than 0.5μm and the particle spacing is greater than 1μm; (4) use ultra-low temperature deep cold rolling to deform to a certain thickness, and perform appropriate intermediate annealing treatment, and then perform ultra-low temperature deep cold rolling to The specific process for the final thickness is as follows: The ultra-low temperature deep cold rolling process is as follows: the deformation temperature is below -120℃, the deformation amount is 30-60%, the reduction per pass is 5-10%, and the corresponding intermediate annealing process is: 400~480℃ / 0.5-2h. The plate after intermediate annealing is further subjected to ultra-low temperature deep cold rolling process with a deformation amount of 50-80% and a reduction per pass of 5-10%; (5) High temperature short-time solid solution treatment with controlled heating rate, specifically including: heating rate greater than 100℃ / min, 540-575℃ / 2-10min, and then the alloy sample after solid solution treatment is quenched and cooled to room temperature at a cooling rate greater than 200℃ / s from the solid solution treatment temperature; (6) The quenched sample is placed in 1.Within 5 minutes, the solute atomic cluster distribution characteristics were regulated by transferring the material to a heat treatment furnace for long-term low-temperature heat treatment. Specifically, the temperature ranged from 60 to 90°C, the time from 10 to 20 hours, and the heating / cooling rate was greater than 10°C / min. Finally, the mechanical properties of alloy plates #1 and #2 in the long-term low-temperature heat-treated state were measured, and the corresponding mechanical properties are shown in Table 2. The multi-scale precipitate phase distribution characteristics in the matrix of alloys #1 and #2 were regulated by high-temperature long-term heat treatment. Figure 4 and 5 As shown.

[0053] Example 3

[0054] The invention alloys 1# and 2# were implemented using the following medium-frequency induction melting and casting method: First, all pure aluminum was added to the crucible and melted at a temperature controlled between 780 and 880°C. Then, Al-20wt%Fe, Al-10wt%Mn, Al-10wt%Cr, and Al-10wt%Ti master alloys were added respectively. After melting, Al-50wt%Cu and Al-20wt%Si master alloys were added respectively. The melt was then stirred at high power for 5 minutes. Subsequently, the temperature was controlled above 720°C, and pure Zn and pure Mg were added respectively. During addition, a graphite bell jar was used to press the molten alloy into the bottom of the melt. After the alloys were completely melted, the bell jar was removed, and the power of the medium-frequency induction furnace was adjusted to allow the alloy melt to melt. After the temperature stabilizes again at 740℃, slag is removed and refining agent is added for degassing and refining; then, when the melt temperature drops to about 720℃, Al-5wt%Ti-1wt%B grain refiner is added and stirred appropriately. Finally, after holding at this temperature for 10 minutes, the melt is poured into a water-cooled steel mold on all sides, and the cooling rate is controlled to be greater than 50℃ / min; then, the following multi-process coordinated control is adopted: (1) High temperature heat treatment to control the distribution of solute elements: the heating rate is 10-30℃ / h, raised to 450-490℃, then held for 2-6h, then further raised to 540-565℃, held for 20-50h, and then cooled to room temperature at a rate greater than 30℃ / h; (2) (2) The high-temperature preheating process is 540-565℃, holding for 1-4h, followed by hot rolling with appropriate deformation, specifically: initial rolling temperature: 540-565℃; final rolling temperature: above 300℃, pass reduction 10-20%, rolling deformation 90-99%; (3) High-temperature long-term heat treatment to regulate the distribution morphology of micron-scale precipitate phase in the alloy matrix specifically includes: 471-510℃ / 20-40h, heating rate greater than 45℃ / h, cooling rate greater than 30℃ / h, ensuring that the formed micron-scale precipitate phase size is greater than 0.5μm and the particle spacing is greater than 1μm; (4) Room temperature cold rolling deformation to a certain thickness, followed by appropriate intermediate annealing, and then The specific process for room temperature cold rolling to the final thickness is as follows: the room temperature cold rolling deformation is 30-60%, the reduction per pass is 10-30%, and the corresponding intermediate annealing process is: 400~500℃ / 0.5-2h. The plate after intermediate annealing is further cold rolled at room temperature to the final plate. The corresponding process is that the deformation is 50-80%, and the reduction per pass is 10-30%. (5) High temperature short-time solid solution treatment with controlled heating rate, specifically including: heating rate greater than 100℃ / min, 540-575℃ / 2-10min, and then quenching and cooling the alloy sample after solid solution treatment from the solid solution treatment temperature to room temperature at a cooling rate greater than 200℃ / s. (6) Quenching the sample in 1.Within 5 minutes, the solute atomic cluster distribution characteristics were regulated by transferring the material to a heat treatment furnace for long-term low-temperature heat treatment. Specifically, the temperature ranged from 60 to 90°C, the time from 10 to 20 hours, and the heating / cooling rate was greater than 10°C / min. Finally, the mechanical properties of alloy plates #1 and #2 in the long-term low-temperature heat-treated state were measured, and the corresponding mechanical properties are shown in Table 2. The multi-scale precipitate phase distribution characteristics in the matrix of alloys #1 and #2 were regulated by high-temperature long-term heat treatment. Figure 6 and 7 As shown, the EBSD microstructures of alloys #1 and #2 after long-term low-temperature heat treatment are as follows: Figure 8 and 9 As shown.

[0055] Table 2 Summary of tensile properties of pre-aged alloy plates after different heat treatment processes

[0056]

[0057]

[0058] In recent years, the lightweighting process of automobiles has been accelerating, and the comprehensive performance of aluminum alloy materials used in car body panels has been significantly improved. Especially with the addition of Zn as a solute element to traditional Al-Mg-Si-Cu alloys and the application of appropriate hot working processes, the paint hardening increment has been greatly increased, reaching up to 160 MPa or more. However, whether it's traditional 6xxx series aluminum alloys or new Al-Mg-Si-Cu-Zn alloy sheets, their stamping formability and bending performance still need further improvement for widespread application, while the production cost of these alloy sheets also needs to be significantly reduced. Therefore, there is an urgent need to develop a preparation method suitable for these aluminum alloy sheets that can also significantly improve their stamping formability. To further reduce the production cost of these alloys, it is necessary to fully utilize recycled aluminum for casting. However, recycled aluminum generally contains the impurity element Fe, which easily generates dendritic, rod-shaped, or coarse-grained iron-rich phases in the cast alloy. Although these phases can break down during subsequent hot working, it is inevitable that incompletely broken coarse iron-rich phase particles will be distributed within the final alloy matrix, along with residual microcracks and uneven distribution, thus affecting the alloy's plasticity, formability, and bending properties. Therefore, it is necessary to effectively control the size, morphology, and distribution of these phases through multi-process coordinated regulation during subsequent hot working, so that the stamping formability of the alloy sheet can be significantly improved. This invention patent fully utilizes the coarse micron-scale precipitates that can form during the hot working of aluminum alloys. The formation of these phases is highly beneficial for further optimizing the size, morphology, and distribution of the iron-rich phases. The reason is that during the hot working process of the alloy, the micron-scale precipitate phase can interact with the coarse primary iron-rich phase, thereby effectively promoting the fragmentation of the coarse primary iron-rich phase. This results in the formation of multi-scale dispersed particles composed of micron-scale precipitate phase and primary iron-rich phase within the alloy matrix. These particles can then work synergistically to form a microstructure with a special distribution of fine and coarse grains during the subsequent high-temperature solution treatment. At the same time, the re-dissolution and diffusion process of the micron-scale precipitate phase can be effectively controlled during the solution treatment, thereby forming a coupled distribution of high-concentration solute micro-regions and low-concentration solute micro-regions. Subsequently, through long-term low-temperature heat treatment, a coupled distribution of soft and hard micro-regions can be further constructed within the alloy matrix. Finally, based on the construction and synergistic effect of the above-mentioned micro-nano microstructure coupled distribution characteristics, the prepared alloy sheet can exhibit excellent stamping forming performance.

[0059] Based on the microstructure and properties of the alloys prepared in Example 1, it can be seen that the grain distribution of alloys #1 and #2 exhibits obvious heterogeneous characteristics after long-term low-temperature heat treatment, namely, a distribution of fine grains enclosing coarse grains. This is very beneficial for improving the stamping performance of the alloys, mainly because fine and coarse grains have a good coordinated deformation ability. In addition, the solute atom concentration distribution of the alloy plates was also controlled during high-temperature solution treatment, resulting in a coupled distribution of high-concentration and low-concentration solute micro-regions. After long-term low-temperature heat treatment, a coupled distribution of soft and hard micro-regions appeared in the matrix, which further significantly increased the coordinated deformation ability of the alloy matrix. Therefore, alloys #1 and #2 prepared in Example 1 both exhibit stamping performance, especially alloy #2, whose average plastic strain ratio r value can reach 0.739 (as shown in Table 1). Based on Example 1, the cold rolling process in the hot working process was further changed from room temperature cold rolling to ultra-low temperature deep cold rolling deformation. The purpose was to better control the interaction between the micron-scale precipitated phase and the coarse primary iron-rich phase, thereby forming as many multi-scale dispersed particles as possible. Through implementation, it was found that both alloys #1 and #2 formed multi-scale dispersed particles in the intermediate annealing state after cold rolling. However, compared to alloy #2, the coarse particles in the multi-scale dispersed particles were slightly larger. After multi-process hot working synergistic control, the stamping forming performance of the alloy sheet was also quite excellent (as shown in Table 1).

[0060] Based on this, in order to better control the distribution characteristics of multi-scale dispersed particles, as well as the coupled distribution characteristics of high-concentration solute micro-regions and low-concentration solute micro-regions, Example 3 adopted better temperature control during the high-temperature heat treatment process. According to Figure 6 and 7 It can be seen that after intermediate annealing following cold rolling, although multi-scale dispersed particles are still distributed in the alloy matrix, the size of coarse precipitate phases in both alloy matrices increases significantly. This is crucial for further optimization of soft and hard microregions. Finally, after synergistic control of multiple hot working processes, the microstructure of the alloy sheet in the long-term low-temperature heat-treated state changed significantly. Although both still exhibit a fine-grained enclosing coarse-grained structure, the fine-grained structure significantly increased (e.g., ...). Figure 8 and 9 As shown in the figure, the presence of this microstructure significantly increases the coordinated deformation capability of the alloy matrix. Simultaneously, due to the increased size of the coarse precipitated phases and the subsequent heat treatment controlling the distribution characteristics of solute elements and the coupling distribution characteristics of solute atom clusters within the micro-regions, the final alloy sheets exhibit excellent stamping performance. The average plastic strain ratio of alloy #2 reaches 0.747, and it also possesses very low anisotropy (Δr is only -0.04). These properties are significantly higher than those of the current mainstream 6xxx series aluminum alloy sheets internationally (where the average plastic strain ratio is generally around 0.6).

[0061] In summary, this invention, through multi-process synergistic control of hot working on traditional Al-Mg-Si-Cu and novel Al-Mg-Si-Cu-Zn alloy ingots, not only significantly improves the size, morphology, and distribution of the primary iron-rich phase within the alloy matrix, but also fully utilizes the positive influence of multi-scale dispersed particles composed of coarse precipitates and primary iron-rich phases on the alloy recrystallization structure. This results in the alloy sheet exhibiting a heterogeneous microstructure with coupled fine and coarse grain distributions, significantly increasing the alloy sheet's ability to coordinate deformation. Furthermore, by controlling the dissolution of coarse micron-scale precipitates and the element diffusion process through subsequent high-temperature heat treatment, a coupled distribution of high-concentration and low-concentration solute microregions is formed within the alloy matrix. Further control through prolonged low-temperature heat treatment can create a coupled distribution of soft and hard microregions, further enhancing the coordinated deformation ability of the alloy sheet's microstructure. Ultimately, the alloy sheet exhibits excellent stamping performance. All these performance improvements play a crucial role in promoting the faster application of this alloy system in automotive lightweighting processes. Furthermore, this invention also provides guidance for the development, processing, and application of high-formability and high-strength aluminum alloys in other fields. Automobile manufacturers and aluminum alloy processing companies should pay attention to this invention so that it can be promoted and applied in this field as soon as possible.

[0062] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for synergistic control of multiple processes in the coupled distribution of micro-nano microstructure in aluminum alloy sheets, characterized in that... The adjustment steps are as follows: (1) Configure a highly formable Al-Mg-Si-Cu alloy, then melt the alloy using medium frequency induction under non-vacuum conditions, and cast it into a water-cooled steel mold. Control the cooling rate to be greater than 40℃ / min so that the alloy grain size meets the subsequent control requirements. (2) Based on the casting speed of the ingot, the distribution of solute elements is controlled by high-temperature heat treatment of the ingot; (3) Preheat at high temperature, and then perform hot rolling deformation treatment with appropriate deformation amount; (4) High-temperature long-term heat treatment regulates the distribution morphology of micron-scale precipitate phases in the alloy matrix. The precipitate phase size is greater than 0.5 μm and the interparticle spacing is greater than 1 μm. Specifically, the high-temperature long-term heat treatment regulates the distribution morphology of micron-scale precipitate phases in the alloy matrix. Specifically, the high-temperature long-term heat treatment regulates the distribution morphology of micron-scale precipitate phases in the alloy matrix. Specifically, the high temperature is 430~510℃ / 20-50h, the heating rate is greater than 45℃ / h, and the cooling rate is greater than 30℃ / h. (5) Cold rolling at room temperature or deep cold rolling at ultra-low temperature to a certain thickness, and then performing appropriate intermediate annealing treatment. After intermediate annealing, the plate is further cold rolled at room temperature or deep cold rolling at ultra-low temperature to the final thickness. (6) High-temperature short-time solution treatment with controlled heating rate, followed by quenching and cooling the solution-treated alloy from the solution treatment temperature to room temperature at a certain cooling rate. (7) Transfer the quenched alloy to a heat treatment furnace within 1.5 min for long-term low-temperature heat treatment to regulate the distribution characteristics of solute atomic clusters; specifically including: temperature 60-90℃, time 10-20h, heating and cooling rate greater than 10℃ / min; In step (1), the chemical composition and mass percentage content of the Al-Mg-Si-Cu alloy are as follows: Zn: 0~3.7wt%, Mg 0.6~0.9wt%, Si 1.0~1.3wt%, Cu 0.1~0.4wt%, Fe: 0.1~0.7wt%, Mn: 0.3~0.7wt%, Cr≤0.02wt%, Ti≤0.1wt%, B≤0.01wt%, with the balance being Al; In step (2), the process of controlling the distribution of solute elements by high-temperature heat treatment of the ingot is as follows: the heating rate is 10-30℃ / h, the temperature is raised to 450-490℃, and then held for 2-6h. Then the temperature is further raised to 540-565℃ and held for 20-50h. Then the temperature is cooled to room temperature at a rate greater than 30℃ / h.

2. The method for coordinated control of multiple processes in the coupled micro-nano microstructure distribution of Al-Mg-Si-Cu alloy plates according to claim 1, characterized in that, In step (1), the alloy melting process using medium-frequency induction melting under non-vacuum conditions is as follows: First, all recycled aluminum or ordinary aluminum is added to the crucible and melted, with the temperature controlled at 780-880℃. Then, Al-20wt%Fe, Al-10wt%Mn, Al-10wt%Cr, and Al-10wt%Ti master alloys are added respectively. After melting, Al-50wt%Cu and Al-20wt%Si master alloys are added respectively. Then, the melt is stirred at high power for 4-6 minutes. Subsequently, the temperature is controlled above 720℃, and the alloys are added respectively. Pure Zn and pure Mg are added by pressing them into the bottom of the melt using a graphite bell jar. After they are completely melted, the bell jar is removed. The power of the medium-frequency induction furnace is adjusted to stabilize the temperature of the alloy melt at 740℃. Slag is removed, and refining agent is added for degassing and refining. Then, when the temperature of the melt is lowered to 720℃, 20-50 g / kg of Al-5wt%Ti-1wt%B grain refiner is added and stirred appropriately. Finally, the melt is held at 720℃ for 9-11 minutes and then poured into a water-cooled steel mold with a cooling rate of more than 50℃ / min.

3. The method for synergistic control of multi-process coupled distribution of micro-nano structure in Al-Mg-Si-Cu alloy plates according to claim 1, characterized in that, In step (3), the high temperature preheating process is 540-565℃, heat preservation for 1-4h, followed by hot rolling treatment with appropriate deformation, specifically: initial rolling temperature: 540-565℃; final rolling temperature: above 300℃, reduction per pass 10-20%, rolling deformation 90-99%.

4. The method for coordinated control of multi-process micro-nano microstructure coupling distribution of Al-Mg-Si-Cu alloy plates according to claim 1, characterized in that, In step (5), if room temperature cold rolling is used to deform to a certain thickness, and appropriate intermediate annealing is performed, and then room temperature cold rolling is performed to the final thickness, the specific process is as follows: the room temperature cold rolling deformation is 30-60%, the reduction per pass is 10-30%, and the corresponding intermediate annealing process is: 400~500℃ / 0.5-2h. The process for further room temperature cold rolling of the plate after intermediate annealing to the final plate is a deformation of 50-80% and a reduction per pass of 10-30%; if ultra-high temperature cold rolling is used... The material is cold rolled to a certain thickness at low temperature and then subjected to appropriate intermediate annealing. It is then cold rolled again at ultra-low temperature to the final thickness. The specific process is as follows: The ultra-low temperature cold rolling process involves a deformation temperature below -120℃, a deformation amount of 30-60%, and a reduction of 5-10% per pass. The corresponding intermediate annealing process is: 400~480℃ / 0.5-2h. The plate after intermediate annealing is then further cold rolled at ultra-low temperature with a deformation amount of 50-80% and a reduction of 5-10% per pass.

5. The method for coordinated control of multiple processes in the coupled micro-nano microstructure distribution of Al-Mg-Si-Cu alloy plates according to claim 1, characterized in that, In step (6), the high-temperature short-time solution treatment with controlled heating rate specifically includes: heating rate greater than 100℃ / min, 540-575℃ / 2-10min, and then quenching the solution-treated alloy from the solution treatment temperature to room temperature at a cooling rate greater than 200℃ / s.

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