Pressurizing heat treatment method for rapidly enabling aluminum alloy to obtain isometric crystal structure

Abstract

The invention discloses a pressurized heat treatment method for rapidly enabling an aluminum alloy to obtain an isometric crystal structure. The method comprises the following steps that a heat treatment furnace is heated to the heat treatment temperature; the rolled aluminum alloy plate is placed in a heat treatment furnace, heat preservation is conducted at the heat treatment temperature, and in the heat preservation process, a pressurizing device is used for continuously applying pressure perpendicular to the rolling direction to the aluminum alloy plate; and the aluminum alloy plate is taken out and air-cooled to the room temperature. By means of the method, an equiaxed crystal structure can be rapidly obtained at the low temperature and within the short heat preservation time, anisotropy of the alloy structure is eliminated, and growth of the alloy grain size and the size of compounds in the alloy can be effectively slowed down.

Description

Technical Field

[0001] The present invention relates to the technical field of nonferrous metal materials and heat treatment thereof, and more specifically to a pressure heat treatment method for rapidly obtaining an equiaxed crystal structure of an aluminum alloy. Background Art

[0002] With the rapid development of transportation, aerospace, building decoration, electronic appliances and other fields, the application of aluminum alloy has also been rapidly developed due to its own advantages such as low density, high mechanical properties, good corrosion resistance and machining performance. Aluminum alloy rolled plates have obtained good comprehensive performance due to the elimination of a large number of internal defects during the preparation process. They are most widely used in the fields of aerospace and automobile manufacturing. Their application can greatly reduce the weight and fuel consumption of aircraft and automobiles.

[0003] However, during the rolling process of aluminum alloy rolled plates, the structure along the rolling direction will be elongated to form a strip-shaped structure with long grains, while the structure perpendicular to the rolling direction is an equiaxed crystal structure. The microstructure of aluminum alloy rolled plates shows anisotropy, which will also bring about anisotropy of alloy properties, which is very unfavorable for the application of alloys. At present, in order to solve the anisotropy of the microstructure and mechanical properties of aluminum alloy rolled plates, the aluminum alloy plates are often recrystallized by recrystallization annealing to form a large number of fine equiaxed recrystallized grains. These fine recrystallized grains will grow during the insulation process, but still maintain an equiaxed shape. In order to make the structure of aluminum alloy plates more uniform, it is often necessary to keep the alloy at a higher temperature (above the recrystallization temperature) for a period of time, which will inevitably increase the grain size of the alloy and the size of the compounds in the alloy, and ultimately cause the reduction of alloy properties. For example, after the 5052 aluminum alloy rolled plate was kept at 400°C for 1 hour, the microstructure along the rolling direction was basically transformed into a uniform and equiaxed structure. After the 5A06 aluminum alloy was kept at 390°C for 2 hours, the microstructure along the rolling direction of the alloy was basically transformed into an equiaxed crystal structure. However, as the temperature increases and the holding time increases, the microstructure of the alloy gradually coarsens.

[0004] It can be seen that in order to transform the structure of aluminum alloy rolled plate along the rolling direction into equiaxed crystal structure, it is necessary to perform recrystallization annealing at a higher temperature or for a longer time. The current recrystallization annealing treatment method increases economic and time costs, so it is urgent to develop a method that can quickly transform the structure of aluminum alloy rolled plate along the rolling direction into equiaxed crystal structure at a lower temperature to reduce costs and avoid the negative effects of reduced mechanical properties caused by grain growth and compound size growth during annealing of aluminum alloy. Summary of the invention

[0005] To this end, the technical problem to be solved by the present invention is to provide a pressurized heat treatment method for quickly making aluminum alloys obtain equiaxed crystal structures. This method can quickly make rolled aluminum alloy plates obtain equiaxed crystal structures that are finer than conventional recrystallization annealing while lowering the heat treatment temperature and reducing the heat treatment time.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: A pressurized heat treatment method for rapidly obtaining an equiaxed grain structure of an aluminum alloy comprises the following steps: Step A: heating the heat treatment furnace to a heat treatment temperature; Step B: placing the rolled aluminum alloy plate in a heat treatment furnace and keeping it warm at the heat treatment temperature, and using a pressurizing device to continuously apply pressure perpendicular to the rolling direction to the plate surface of the aluminum alloy plate during the heat preservation process; if the pressurizing device applies pressure to the aluminum alloy plate in other directions during the recrystallization annealing process, it is not conducive to obtaining an equiaxed crystal structure; Step C: Take out the aluminum alloy plate and allow it to air cool to room temperature.

[0007] After deformation such as rolling, a large amount of strain energy will be generated inside the alloy, which puts the alloy in an unstable high-energy state. This strain energy not only affects the stability of the alloy, but also acts as a driving force to promote the recrystallization process of the alloy. In this process, the presence of strain energy will cause the grain boundary to bow to one side, forming the so-called "grain boundary bowing" phenomenon. The bowed position provides a growth point for the recrystallization nucleus, thereby forming recrystallized grains. This recrystallization mechanism is called the strain-induced grain boundary migration mechanism, or more specifically, the grain boundary bowing nucleation mechanism.

[0008] In the general heat treatment (recrystallization annealing) process, strain energy will be gradually released, and the recrystallization caused by the strain-induced grain boundary migration mechanism will gradually decrease. However, if the recrystallization annealing time is too long, the existing grains will grow excessively, resulting in poor structural uniformity and mechanical properties of the alloy. During heat treatment, the use of a pressure device to apply a force perpendicular to the rolling direction to the surface of the aluminum alloy plate can keep the alloy at a high strain energy during recrystallization treatment, slow down the release of strain energy, and keep the alloy in a high-energy state, thereby promoting the recrystallization process of the alloy, reducing the holding time required for recrystallization annealing, preventing excessive growth of the crystal nucleus, and transforming the strip-shaped structure along the rolling direction of the aluminum alloy into a uniform and fine equiaxed crystal structure under lower temperature and shorter time conditions.

[0009] In the above-mentioned pressurized heat treatment method for quickly making aluminum alloy obtain equiaxed crystal structure, in step B: the pressurizing device includes a load-bearing component, a hydraulic component and a clamping component; the load-bearing component is in surface contact with the aluminum alloy plate and supports the aluminum alloy plate, and then the hydraulic component drives the clamping component to be in surface contact with the aluminum alloy plate and apply pressure to the plate surface of the aluminum alloy plate.

[0010] In the above-mentioned pressurized heat treatment method for quickly making the aluminum alloy obtain an equiaxed crystal structure, in step B, the load-bearing component and the pressing component are both arranged in a heat treatment furnace, the plate surface of the aluminum alloy plate facing the load-bearing component is completely in contact with the surface of the load-bearing component, and the plate surface of the aluminum alloy plate facing the pressing component is completely in contact with the surface of the pressing component; the positions of the load-bearing component and the pressing component correspond.

[0011] In the above-mentioned pressurized heat treatment method for quickly obtaining an equiaxed crystal structure of an aluminum alloy, during the heat preservation process of step B, the change in the pressure applied by the pressing component to the aluminum alloy plate is less than or equal to 0.5 MPa / 10min. The pressure applied by the pressing component to the aluminum alloy plate should be kept as stable as possible to control the deformation of the aluminum alloy plate during processing, so that the strain energy inside the aluminum alloy remains stable during the recrystallization annealing process; changes in strain energy will change the growth rate and morphology of the grains. Therefore, maintaining the stability of the pressure applied by the pressing component to the aluminum alloy plate during the heat preservation process is conducive to the grains inside the aluminum alloy to grow at a relatively uniform rate and form an equiaxed crystal structure, which in turn helps to maintain the uniformity of the alloy microstructure and improve the mechanical properties of the alloy.

[0012] In the above-mentioned pressurized heat treatment method for rapidly obtaining an equiaxed crystal structure of an aluminum alloy, in step B, within 2 seconds after the aluminum alloy plate contacts the load-bearing component, the pressing component presses the aluminum alloy plate under the drive of the hydraulic component. After the aluminum alloy plate is placed on the surface of the load-bearing component, the pressing component should press the aluminum alloy plate as quickly as possible to reduce the time of the non-pressure heat treatment of the aluminum alloy plate, prevent the aluminum alloy from being heated to the recrystallization annealing temperature and undergoing recrystallization annealing in a non-pressure state, and then changing to a pressurized state during the recrystallization annealing process, causing grain growth defects, and further leading to a decrease in the uniformity of the alloy structure.

[0013] In the above-mentioned pressurized heat treatment method for quickly obtaining an equiaxed crystal structure of an aluminum alloy, in step A, the heat treatment temperature is 330-400°C; if the heat treatment temperature is too high, the alloy grain size and compound size will grow excessively, which is not conducive to the improvement of the mechanical properties of the alloy; if the heat treatment temperature is too low, it will take a longer time for the alloy to obtain an ideal equiaxed crystal structure, which will cost more time.

[0014] In step B, the holding time is 20 to 100 minutes, and the pressure device applies a pressure greater than 0 and less than or equal to 20MPa to the aluminum alloy plate. If the holding time is too short, it is not conducive to the formation of equiaxed crystal structure; although the equiaxed crystal structure can be obtained if the time is too long, it will cost more time and will also increase the size of the alloy grains and the size of the compound, which is also not conducive to the improvement of the mechanical properties of the alloy. If the pressure applied to the aluminum alloy plate is too low, the efficiency of obtaining the equiaxed crystal structure will be reduced, or the aluminum alloy needs to be heat treated at a higher temperature for a longer time to obtain the equiaxed crystal structure; and if the pressure is too high, although it helps to quickly obtain the equiaxed crystal structure, it may cause the alloy to deform.

[0015] In the above-mentioned pressurized heat treatment method for rapidly obtaining an equiaxed crystal structure in an aluminum alloy, in step B, the temperature fluctuation range in the heat treatment furnace is less than or equal to ±1° C. The temperature is kept relatively stable during the heat treatment process, which is beneficial to controlling the size uniformity of the equiaxed crystal structure and improving the overall quality and reliability of the aluminum alloy.

[0016] In the above-mentioned pressurized heat treatment method for quickly obtaining an equiaxed grain structure of an aluminum alloy, in step A, the heat treatment temperature is 350° C.; in step B, the holding time is 60 minutes, and the pressurizing device applies a pressure of 15 MPa to the aluminum alloy plate.

[0017] The above-mentioned pressurized heat treatment method for quickly obtaining an equiaxed crystal structure of an aluminum alloy, the aluminum alloy plate is made of 5182 aluminum alloy by cold rolling, and the reduction rate during cold rolling is 31% to 34%; the chemical composition of the 5182 aluminum alloy is 4.0wt.% to 5.0wt.% magnesium, 0.2wt.% to 0.4wt.% manganese, 0.1wt.% to 0.15wt.% silicon, 0.15wt.% to 0.25wt.% iron, 0.02wt.% to 0.06wt.% copper and 0.01wt.% to 0.03wt.% chromium, and the balance is aluminum. The cold rolling reduction rate is determined according to actual needs and the deformation capacity of 5182 aluminum alloy. When the rolling reduction rate of the alloy is large, its mechanical properties will become relatively good due to the reduction or elimination of defects; however, if the alloy cold rolling reduction rate (deformation) is too large, the alloy may crack, causing the product to fail. At the same time, a higher reduction rate also places higher requirements on rolling equipment. For the 5182 aluminum alloy with the above-mentioned element composition, an excessively large reduction rate during cold rolling will aggravate the formation of banded structure, and greater pressure, higher heat treatment temperature, and longer heat treatment time are required during heat treatment to obtain equiaxed crystal structure in the alloy.

[0018] The above-mentioned pressurized heat treatment method for quickly obtaining an equiaxed crystal structure of the aluminum alloy has a reduction rate of 33% during cold rolling. The chemical composition of the 5182 aluminum alloy is 4.6wt.% magnesium, 0.35wt.% manganese, 0.11wt.% silicon, 0.21wt.% iron, 0.04wt.% copper and 0.01wt.% chromium, and the balance is aluminum.

[0019] The technical solution of the present invention achieves the following beneficial technical effects: 1. A pressurized heat treatment method proposed in the present invention can quickly transform the banded structure of the 5182 aluminum alloy along the rolling direction into an equiaxed crystal structure by keeping the heat treatment temperature at 330-400°C for 20-100 minutes and applying a pressure greater than 0 and less than or equal to 20MPa to the 5182 aluminum alloy during the heat treatment process, thereby eliminating the anisotropy of the structure of the rolled aluminum alloy plate. Compared with conventional recrystallization annealing, the pressurized heat treatment method proposed in the present invention can shorten the time required for the banded structure to transform into an equiaxed crystal structure to 40 minutes at most, and the required temperature can be as low as 330°C, thereby preventing the aluminum alloy microstructure from coarsening due to excessively high temperature or excessively long heat preservation time during recrystallization annealing, so that fine equiaxed crystal structures are formed in the 5182 aluminum alloy rolled plate along the rolling direction.

[0020] 2. When using the pressurized heat treatment method provided in the present invention, an aluminum alloy sheet with a cold rolling reduction rate of 30% to 40% is used as a raw material. On the basis of the appropriate shape and size of the strip-shaped structure in the aluminum alloy sheet, a pressure perpendicular to the rolling direction is continuously applied to the plate surface of the aluminum alloy sheet. This pressure can slow down the release of strain energy, so that the aluminum alloy always maintains a high strain energy during the recrystallization annealing (heat treatment) process, promotes the rapid formation of new grain boundaries (i.e., the formation of new grains) inside the aluminum alloy, and reduces the time required for heat treatment; at the same time, during the heat treatment process, the alloy temperature and the internal strain energy remain stable, so that the heat treatment (recrystallization annealing) The new grains formed in the annealing process grow at a relatively uniform rate and form an equiaxed crystal structure with uniform size, which reduces grain distortion. The banded structure in the alloy can be fully transformed into a fine and uniform equiaxed crystal structure under the heat treatment conditions of 330-400℃, 20-100min of holding time and a pressure greater than 0 and less than or equal to 20MPa applied by a pressure device to the aluminum alloy plate. The problem of excessive grain growth in the alloy caused by excessively high heat treatment temperature or long time is avoided, and the anisotropy of the alloy structure is eliminated, thereby making the alloy structure more uniform, which will be beneficial to the improvement of the mechanical properties of the alloy.

[0021] 3. The pressurized heat treatment method proposed by the present invention is simple, has good process stability and high process controllability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Microstructure photograph of 5182 aluminum alloy along the rolling direction prepared in Example 5 of the present invention; Figure 2 Microstructure photograph of 5182 aluminum alloy along the rolling direction prepared in Example 8 of the present invention; Figure 3 Microstructure photograph of 5182 aluminum alloy prepared in comparative example 10 of the present invention along the rolling direction. DETAILED DESCRIPTION

[0023] Example 1 The 5182 aluminum alloy used in this embodiment has a composition of 4.6wt.% Mg, 0.35wt.% Mn, 0.11wt.% Si, 0.21wt.% Fe, 0.04wt.% Cu, 0.01wt.% Cr, and the remainder is Al. The 5182 aluminum alloy is cold-rolled into an aluminum alloy sheet. During the cold rolling, the 5182 aluminum alloy with a thickness of about 6mm is rolled on a cold rolling mill into an aluminum alloy sheet with a thickness of about 4mm (according to actual measurement, the reduction rate during cold rolling in this embodiment is 31.6%). After the cold rolling is completed, the aluminum alloy sheet is wire-cut into a block of 10mm×10mm×4mm, that is, an aluminum alloy sample is obtained.

[0024] The heat treatment furnace used in this embodiment is provided with a pressurizing device inside, which includes a hydraulic component, a first heat-resistant stainless steel rod as a bearing component, and a second heat-resistant stainless steel rod as a pressing component. Among them, the lower surface of the first heat-resistant stainless steel rod is in contact with the experimental table, and the upper surface is flush with the lower surface of the furnace of the heat treatment furnace; the second heat-resistant stainless steel rod is installed at the position corresponding to the first heat-resistant stainless steel rod on the upper surface of the furnace, and the hydraulic device is connected to the second heat-resistant stainless steel rod. During the heat treatment process, one plate surface of the aluminum alloy sample faces the first heat-resistant stainless steel rod and is placed on the upper surface of the first heat-resistant stainless steel rod (that is, the aluminum alloy plate is carried by the first heat-resistant stainless steel rod, and the first heat-resistant stainless steel rod and the aluminum alloy plate form a surface contact), the hydraulic device drives the second heat-resistant stainless steel rod to contact the aluminum alloy sample (that is, the second heat-resistant stainless steel rod and the aluminum alloy sample form a surface contact), and applies pressure perpendicular to the rolling direction to the aluminum alloy sample according to the set pressure value, and during the entire heat treatment process, the change in the pressure applied by the second heat-resistant stainless steel rod to the aluminum alloy sample is less than or equal to 0.5 MPa / 10min.

[0025] In this embodiment, the diameter of the first heat-resistant stainless steel rod as the bearing component and the second heat-resistant stainless steel rod as the pressing component are both 20 mm, and the area of ​​the circular surface of the two in contact with the aluminum alloy is larger than the area of ​​the aluminum alloy sample plate (10 mm × 10 mm). In some other embodiments, the bearing component and the pressing component can also be other shapes, as long as the size of the two can "cover" the aluminum alloy plate in contact (that is, the side of the aluminum alloy plate facing the bearing component is completely in contact with the surface of the bearing component, and the side of the aluminum alloy plate facing the pressing component is completely in contact with the surface of the pressing component).

[0026] In this embodiment, the process of quickly obtaining an equiaxed grain structure of 5182 aluminum alloy by a pressurized heat treatment method comprises the following steps: (1) Preheating of heat treatment furnace: Power on the heat treatment furnace and control the temperature to 330°C using the PID program.

[0027] (2) Heat treatment process: Open the heat treatment furnace door, quickly place the 5182 aluminum alloy sample on the upper surface of the first heat-resistant stainless steel rod configured in the middle of the bottom of the heat treatment furnace, quickly (within 2 seconds) contact the second heat-resistant stainless steel rod with the upper surface of the aluminum alloy sample, and apply a pressure of 5MPa, and quickly close the heat treatment furnace door, with the pressure direction perpendicular to the rolling direction of the aluminum alloy. During the heat treatment process, the temperature in the heat treatment furnace cavity remains stable, with a maximum fluctuation of no more than ±1°C.

[0028] (3) When the holding time reaches 80 minutes, open the furnace door, use crucible tongs to take out the sample and place it on the refractory bricks prepared in advance to cool to room temperature.

[0029] The surface of the 5182 aluminum alloy sample along the rolling direction was polished in sequence with 400#, 800#, 1200#, 1500#, and 2000#. After polishing, it was polished to a mirror surface with almost no scratches on a metallographic polishing machine, and then corroded with Kohler reagent (190 ml of distilled water, 5 ml of nitric acid, 3 ml of hydrochloric acid, and 2 ml of hydrofluoric acid). After that, the microstructure of the alloy along the rolling direction was observed with an optical metallographic microscope to determine whether an equiaxed grain structure was obtained.

[0030] The grain morphology of the aluminum alloy prepared in Example 1 along the rolling direction is shown in Table 1.

[0031] Example 2 The composition, heat treatment furnace and pressurizing device of the 5182 aluminum alloy used in this embodiment are the same as those in Example 1, except that the cold rolling reduction rate of the 5182 aluminum alloy used in this embodiment is 32.1%.

[0032] In this embodiment, the process of quickly obtaining an equiaxed grain structure of 5182 aluminum alloy by a pressurized heat treatment method comprises the following steps: (1) Preheating of heat treatment furnace: Power on the heat treatment furnace and control the temperature to 330°C using the PID program.

[0033] (2) Heat treatment process: Open the heat treatment furnace door, quickly place the 5182 aluminum alloy sample on the upper surface of the first heat-resistant stainless steel rod configured in the middle of the bottom of the heat treatment furnace, quickly (within 2 seconds) contact the second heat-resistant stainless steel rod with the upper surface of the aluminum alloy sample, and apply a pressure of 10MPa, and quickly close the heat treatment furnace door, with the pressure direction perpendicular to the rolling direction of the aluminum alloy. During the heat treatment process, the temperature in the heat treatment furnace cavity remains stable, with a maximum fluctuation of no more than ±1°C.

[0034] (3) When the holding time reaches 60 minutes, open the furnace door, use crucible tongs to take out the sample and place it on the refractory bricks prepared in advance to cool to room temperature.

[0035] The microstructure of the alloy along the rolling direction is observed by an optical metallographic microscope to determine whether an equiaxed crystal structure is obtained. The observation method is the same as that of Example 1.

[0036] The grain morphology of the aluminum alloy prepared in Example 2 along the rolling direction is shown in Table 1.

[0037] Example 3 The composition of the 5182 aluminum alloy, the heat treatment furnace and the pressurizing device used in this embodiment are the same as those in Example 1, except that the cold rolling reduction rate of the 5182 aluminum alloy used in this embodiment is 32.5%.

[0038] In this embodiment, the process of quickly obtaining an equiaxed grain structure of 5182 aluminum alloy by a pressurized heat treatment method comprises the following steps: (1) Preheating of heat treatment furnace: Power on the heat treatment furnace and control the temperature to 330°C using the PID program.

[0039] (2) Heat treatment process: Open the heat treatment furnace door, quickly place the 5182 aluminum alloy sample on the upper surface of the first heat-resistant stainless steel rod configured in the middle of the bottom of the heat treatment furnace, quickly (within 2 seconds) contact the second heat-resistant stainless steel rod with the upper surface of the aluminum alloy sample, and apply a pressure of 10MPa, and quickly close the heat treatment furnace door, with the pressure direction perpendicular to the rolling direction of the aluminum alloy. During the heat treatment process, the temperature in the heat treatment furnace cavity remains stable, with a maximum fluctuation of no more than ±1°C.

[0040] (3) When the holding time reaches 80 minutes, open the furnace door, use crucible tongs to take out the sample and place it on the refractory bricks prepared in advance to cool to room temperature.

[0041] The microstructure of the alloy along the rolling direction is observed by an optical metallographic microscope to determine whether an equiaxed crystal structure is obtained. The observation method is the same as that of Example 1.

[0042] The grain morphology of the aluminum alloy prepared in Example 3 along the rolling direction is shown in Table 1.

[0043] Example 4 The composition of the 5182 aluminum alloy, the heat treatment furnace and the pressurizing device used in this embodiment are the same as those in Example 1, except that the cold rolling reduction rate of the 5182 aluminum alloy used in this embodiment is 33.1%.

[0044] In this embodiment, the process of quickly obtaining an equiaxed grain structure of 5182 aluminum alloy by a pressurized heat treatment method comprises the following steps: (1) Preheating of heat treatment furnace: Power on the heat treatment furnace and control the temperature to 330°C using the PID program.

[0045] (2) Heat treatment process: Open the heat treatment furnace door, quickly place the 5182 aluminum alloy sample on the upper surface of the first heat-resistant stainless steel rod configured in the middle of the bottom of the heat treatment furnace, quickly (within 2 seconds) contact the second heat-resistant stainless steel rod with the upper surface of the aluminum alloy sample, and apply a pressure of 20MPa, and quickly close the heat treatment furnace door, with the pressure direction perpendicular to the rolling direction of the aluminum alloy. During the heat treatment process, the temperature in the heat treatment furnace cavity remains stable, with a maximum fluctuation of no more than ±1°C.

[0046] (3) When the holding time reaches 60 minutes, open the furnace door, use crucible tongs to take out the sample and place it on the refractory bricks prepared in advance to cool to room temperature.

[0047] The microstructure of the alloy along the rolling direction is observed by an optical metallographic microscope to determine whether an equiaxed crystal structure is obtained. The observation method is the same as that of Example 1.

[0048] The grain morphology of the aluminum alloy prepared in Example 4 along the rolling direction is shown in Table 1.

[0049] Example 5 The composition of the 5182 aluminum alloy, the heat treatment furnace and the pressurizing device used in this embodiment are the same as those in Example 1, except that the cold rolling reduction rate of the 5182 aluminum alloy used in this embodiment is 32.8%.

[0050] In this embodiment, the process of quickly obtaining an equiaxed grain structure of 5182 aluminum alloy by a pressurized heat treatment method comprises the following steps: (1) Preheating of heat treatment furnace: Power on the heat treatment furnace and control the temperature to 350°C using the PID program.

[0051] (2) Heat treatment process: Open the heat treatment furnace door, quickly place the 5182 aluminum alloy sample on the upper surface of the first heat-resistant stainless steel rod configured in the middle of the bottom of the heat treatment furnace, quickly (within 2 seconds) contact the second heat-resistant stainless steel rod with the upper surface of the aluminum alloy sample, and apply a pressure of 5MPa, and quickly close the heat treatment furnace door, with the pressure direction perpendicular to the rolling direction of the aluminum alloy. During the heat treatment process, the temperature in the heat treatment furnace cavity remains stable, with a maximum fluctuation of no more than ±1°C.

[0052] (3) When the holding time reaches 60 minutes, open the furnace door, use crucible tongs to take out the sample and place it on the refractory bricks prepared in advance to cool to room temperature.

[0053] The microstructure of the alloy along the rolling direction is observed by an optical metallographic microscope to determine whether an equiaxed crystal structure is obtained. The observation method is the same as that of Example 1.

[0054] The grain morphology of the aluminum alloy prepared in Example 5 along the rolling direction is shown in Table 1.

[0055] Example 6 The composition of the 5182 aluminum alloy, the heat treatment furnace and the pressurizing device used in this embodiment are the same as those in Example 1, except that the cold rolling reduction rate of the 5182 aluminum alloy used in this embodiment is 33.4%.

[0056] In this embodiment, the process of quickly obtaining an equiaxed grain structure of 5182 aluminum alloy by a pressurized heat treatment method comprises the following steps: (1) Preheating of heat treatment furnace: Power on the heat treatment furnace and control the temperature to 350°C using the PID program.

[0057] (2) Heat treatment process: Open the heat treatment furnace door, quickly place the 5182 aluminum alloy sample on the upper surface of the first heat-resistant stainless steel rod configured in the middle of the bottom of the heat treatment furnace, quickly (within 2 seconds) contact the second heat-resistant stainless steel rod with the upper surface of the aluminum alloy sample, and apply a pressure of 10MPa, and quickly close the heat treatment furnace door, with the pressure direction perpendicular to the rolling direction of the aluminum alloy. During the heat treatment process, the temperature in the heat treatment furnace cavity remains stable, with a maximum fluctuation of no more than ±1°C.

[0058] (3) When the holding time reaches 60 minutes, open the furnace door, use crucible tongs to take out the sample and place it on the refractory bricks prepared in advance to cool to room temperature.

[0059] The microstructure of the alloy along the rolling direction is observed by an optical metallographic microscope to determine whether an equiaxed crystal structure is obtained. The observation method is the same as that of Example 1.

[0060] The grain morphology of the aluminum alloy prepared in Example 6 along the rolling direction is shown in Table 1.

[0061] Example 7 The composition of the 5182 aluminum alloy, the heat treatment furnace and the pressurizing device used in this embodiment are the same as those in Example 1, except that the cold rolling reduction rate of the 5182 aluminum alloy used in this embodiment is 32.5%.

[0062] In this embodiment, the process of quickly obtaining an equiaxed grain structure of 5182 aluminum alloy by a pressurized heat treatment method comprises the following steps: (1) Preheating of heat treatment furnace: Power on the heat treatment furnace and control the temperature to 350°C using the PID program.

[0063] (2) Heat treatment process: Open the heat treatment furnace door, quickly place the 5182 aluminum alloy sample on the upper surface of the first heat-resistant stainless steel rod configured in the middle of the bottom of the heat treatment furnace, quickly (within 2 seconds) contact the second heat-resistant stainless steel rod with the upper surface of the aluminum alloy sample, and apply a pressure of 10MPa, and quickly close the heat treatment furnace door, with the pressure direction perpendicular to the rolling direction of the aluminum alloy. During the heat treatment process, the temperature in the heat treatment furnace cavity remains stable, with a maximum fluctuation of no more than ±1°C.

[0064] (3) When the holding time reaches 80 minutes, open the furnace door, use crucible tongs to take out the sample and place it on the refractory bricks prepared in advance to cool to room temperature.

[0065] The microstructure of the alloy along the rolling direction is observed by an optical metallographic microscope to determine whether an equiaxed crystal structure is obtained. The observation method is the same as that of Example 1.

[0066] The grain morphology of the aluminum alloy prepared in Example 7 along the rolling direction is shown in Table 1.

[0067] Example 8 The composition, heat treatment furnace and pressurizing device of the 5182 aluminum alloy used in this embodiment are the same as those in Example 1, except that the cold rolling reduction rate of the 5182 aluminum alloy used in this embodiment is 33.8%.

[0068] In this embodiment, the process of quickly obtaining an equiaxed grain structure of 5182 aluminum alloy by a pressurized heat treatment method comprises the following steps: (1) Preheating of heat treatment furnace: Power on the heat treatment furnace and control the temperature to 350°C using the PID program.

[0069] (2) Heat treatment process: Open the heat treatment furnace door, quickly place the 5182 aluminum alloy sample on the upper surface of the first heat-resistant stainless steel rod configured in the middle of the bottom of the heat treatment furnace, quickly (within 2 seconds) contact the second heat-resistant stainless steel rod with the upper surface of the aluminum alloy sample, and apply a pressure of 15MPa, and quickly close the heat treatment furnace door, with the pressure direction perpendicular to the rolling direction of the aluminum alloy. During the heat treatment process, the temperature in the heat treatment furnace cavity remains stable, with a maximum fluctuation of no more than ±1°C.

[0070] (3) When the holding time reaches 60 minutes, open the furnace door, use crucible tongs to take out the sample and place it on the refractory bricks prepared in advance to cool to room temperature.

[0071] The microstructure of the alloy along the rolling direction is observed by an optical metallographic microscope to determine whether an equiaxed crystal structure is obtained. The observation method is the same as that of Example 1.

[0072] The grain morphology of the aluminum alloy prepared in Example 8 along the rolling direction is shown in Table 1.

[0073] Example 9 The composition, heat treatment furnace and pressurizing device of the 5182 aluminum alloy used in this embodiment are the same as those in Example 1, except that the cold rolling reduction rate of the 5182 aluminum alloy used in this embodiment is 32.6%.

[0074] In this embodiment, the process of quickly obtaining an equiaxed grain structure of 5182 aluminum alloy by a pressurized heat treatment method comprises the following steps: (1) Preheating of heat treatment furnace: Power on the heat treatment furnace and control the temperature to 370°C using the PID program.

[0075] (2) Heat treatment process: Open the heat treatment furnace door, quickly place the 5182 aluminum alloy sample on the upper surface of the first heat-resistant stainless steel rod configured in the middle of the bottom of the heat treatment furnace, quickly (within 2 seconds) contact the second heat-resistant stainless steel rod with the upper surface of the aluminum alloy sample, and apply a pressure of 5MPa, and quickly close the heat treatment furnace door, with the pressure direction perpendicular to the rolling direction of the aluminum alloy. During the heat treatment process, the temperature in the heat treatment furnace cavity remains stable, with a maximum fluctuation of no more than ±1°C.

[0076] (3) When the holding time reaches 60 minutes, open the furnace door, use crucible tongs to take out the sample and place it on the refractory bricks prepared in advance to cool to room temperature.

[0077] The microstructure of the alloy along the rolling direction is observed by an optical metallographic microscope to determine whether an equiaxed crystal structure is obtained. The observation method is the same as that of Example 1.

[0078] The grain morphology of the aluminum alloy prepared in Example 9 along the rolling direction is shown in Table 1.

[0079] Example 10 The composition of the 5182 aluminum alloy, the heat treatment furnace and the pressurizing device used in this embodiment are the same as those in Example 1, except that the cold rolling reduction rate of the 5182 aluminum alloy used in this embodiment is 32.7%.

[0080] In this embodiment, the process of quickly obtaining an equiaxed grain structure of 5182 aluminum alloy by a pressurized heat treatment method comprises the following steps: (1) Preheating of heat treatment furnace: Power on the heat treatment furnace and control the temperature to 370°C using the PID program.

[0081] (2) Heat treatment process: Open the heat treatment furnace door, quickly place the 5182 aluminum alloy sample on the upper surface of the first heat-resistant stainless steel rod configured in the middle of the bottom of the heat treatment furnace, quickly (within 2 seconds) contact the second heat-resistant stainless steel rod with the upper surface of the aluminum alloy sample, and apply a pressure of 10MPa, and quickly close the heat treatment furnace door, with the pressure direction perpendicular to the rolling direction of the aluminum alloy. During the heat treatment process, the temperature in the heat treatment furnace cavity remains stable, with a maximum fluctuation of no more than ±1°C.

[0082] (3) When the holding time reaches 60 minutes, open the furnace door, use crucible tongs to take out the sample and place it on the refractory bricks prepared in advance to cool to room temperature.

[0083] The microstructure of the alloy along the rolling direction is observed by an optical metallographic microscope to determine whether an equiaxed crystal structure is obtained. The observation method is the same as that of Example 1.

[0084] The grain morphology of the aluminum alloy prepared in Example 10 along the rolling direction is shown in Table 1.

[0085] Embodiment 11 The composition of the 5182 aluminum alloy, the heat treatment furnace and the pressurizing device used in this embodiment are the same as those in Example 1, except that the cold rolling reduction rate of the 5182 aluminum alloy used in this embodiment is 33.5%.

[0086] In this embodiment, the process of quickly obtaining an equiaxed grain structure of 5182 aluminum alloy by a pressurized heat treatment method comprises the following steps: (1) Preheating of heat treatment furnace: Power on the heat treatment furnace and control the temperature to 370°C using the PID program.

[0087] (2) Heat treatment process: Open the heat treatment furnace door, quickly place the 5182 aluminum alloy sample on the upper surface of the first heat-resistant stainless steel rod configured in the middle of the bottom of the heat treatment furnace, quickly (within 2 seconds) contact the second heat-resistant stainless steel rod with the upper surface of the aluminum alloy sample, and apply a pressure of 15MPa, and quickly close the heat treatment furnace door, with the pressure direction perpendicular to the rolling direction of the aluminum alloy. During the heat treatment process, the temperature in the heat treatment furnace cavity remains stable, with a maximum fluctuation of no more than ±1°C.

[0088] (3) When the holding time reaches 40 minutes, open the furnace door, use crucible tongs to take out the sample and place it on the refractory bricks prepared in advance to cool to room temperature.

[0089] The microstructure of the alloy along the rolling direction is observed by an optical metallographic microscope to determine whether an equiaxed crystal structure is obtained. The observation method is the same as that of Example 1.

[0090] The grain morphology of the aluminum alloy prepared in Example 11 along the rolling direction is shown in Table 1.

[0091] Example 12 The composition, heat treatment furnace and pressurizing device of the 5182 aluminum alloy used in this embodiment are the same as those in Example 1, except that the cold rolling reduction rate of the 5182 aluminum alloy used in this embodiment is 33.6%.

[0092] In this embodiment, the process of quickly obtaining an equiaxed grain structure of 5182 aluminum alloy by a pressurized heat treatment method comprises the following steps: (1) Preheating of heat treatment furnace: Power on the heat treatment furnace and control the temperature to 370°C using the PID program.

[0093] (2) Heat treatment process: Open the heat treatment furnace door, quickly place the 5182 aluminum alloy sample on the upper surface of the first heat-resistant stainless steel rod configured in the middle of the bottom of the heat treatment furnace, quickly (within 2 seconds) contact the second heat-resistant stainless steel rod with the upper surface of the aluminum alloy sample, and apply a pressure of 20MPa, and quickly close the heat treatment furnace door, with the pressure direction perpendicular to the rolling direction of the aluminum alloy. During the heat treatment process, the temperature in the heat treatment furnace cavity remains stable, with a maximum fluctuation of no more than ±1°C.

[0094] (3) When the holding time reaches 40 minutes, open the furnace door, use crucible tongs to take out the sample and place it on the refractory bricks prepared in advance to cool to room temperature.

[0095] The microstructure of the alloy along the rolling direction is observed by an optical metallographic microscope to determine whether an equiaxed crystal structure is obtained. The observation method is the same as that of Example 1.

[0096] The grain morphology of the aluminum alloy prepared in Example 12 along the rolling direction is shown in Table 1.

[0097] Comparative Example 1 The composition of the 5182 aluminum alloy used in this comparative example is the same as that of Example 1, except that the cold rolling reduction rate of the 5182 aluminum alloy used in this comparative example is 33.4%.

[0098] In this comparative example, the process of quickly obtaining an equiaxed grain structure of 5182 aluminum alloy by a pressurized heat treatment method comprises the following steps: (1) Preheating of heat treatment furnace: Power on the heat treatment furnace and control the temperature to 350°C using the PID program.

[0099] (2) Heat treatment process: Open the door of the heat treatment furnace, quickly place the 5182 aluminum alloy sample on the upper surface of the first heat-resistant stainless steel rod arranged in the middle position of the bottom of the heat treatment furnace, and quickly close the door of the heat treatment furnace.

[0100] (3) When the holding time reaches 60 minutes, open the furnace door, use crucible tongs to take out the sample and place it on the refractory bricks prepared in advance to cool to room temperature.

[0101] The microstructure of the alloy along the rolling direction is observed by an optical metallographic microscope to determine whether an equiaxed crystal structure is obtained. The observation method is the same as that of Example 1.

[0102] The grain morphology of the aluminum alloy prepared in Comparative Example 1 along the rolling direction is shown in Table 1.

[0103] Comparative Example 2 The composition of the 5182 aluminum alloy used in this comparative example is the same as that of Example 1, except that the cold rolling reduction rate of the 5182 aluminum alloy used in this comparative example is 33.6%.

[0104] In this comparative example, the process of quickly obtaining an equiaxed grain structure of 5182 aluminum alloy by a pressurized heat treatment method comprises the following steps: (1) Preheating of heat treatment furnace: Power on the heat treatment furnace and control the temperature to 370°C using the PID program.

[0105] (2) Heat treatment process: Open the door of the heat treatment furnace, quickly place the 5182 aluminum alloy sample on the upper surface of the first heat-resistant stainless steel rod arranged in the middle position of the bottom of the heat treatment furnace, and quickly close the door of the heat treatment furnace.

[0106] (3) When the holding time reaches 80 minutes, open the furnace door, use crucible tongs to take out the sample and place it on the refractory bricks prepared in advance to cool to room temperature.

[0107] The microstructure of the alloy along the rolling direction is observed by an optical metallographic microscope to determine whether an equiaxed crystal structure is obtained. The observation method is the same as that of Example 1.

[0108] The grain morphology of the aluminum alloy prepared in Comparative Example 2 along the rolling direction is shown in Table 1.

[0109] Comparative Example 3 The composition of the 5182 aluminum alloy used in this comparative example is the same as that in Example 1, except that the cold rolling reduction rate of the 5182 aluminum alloy used in this comparative example is 33.2%.

[0110] In this comparative example, the process of quickly obtaining an equiaxed grain structure of 5182 aluminum alloy by a pressurized heat treatment method comprises the following steps: (1) Preheating of the heat treatment furnace: Turn on the power of the heat treatment furnace and control the temperature to 400°C using the PID program.

[0111] (2) Heat treatment process: Open the door of the heat treatment furnace, quickly place the 5182 aluminum alloy sample on the upper surface of the first heat-resistant stainless steel rod arranged in the middle position of the bottom of the heat treatment furnace, and quickly close the door of the heat treatment furnace.

[0112] (3) When the holding time reaches 100 min, open the furnace door, use crucible tongs to take out the sample and place it on the refractory bricks prepared in advance to cool to room temperature.

[0113] The microstructure of the alloy along the rolling direction is observed by an optical metallographic microscope to determine whether an equiaxed crystal structure is obtained. The observation method is the same as that of Example 1.

[0114] The grain morphology of the aluminum alloy prepared in Comparative Example 3 along the rolling direction is shown in Table 1.

[0115] Table 1 Grain morphology of 5182 aluminum alloy along the rolling direction after different pressurized heat treatments During the processing of rolled aluminum alloy plates, due to the rolling force, the grains will be elongated along the rolling direction, forming obvious banded structures. The morphology and properties of these banded structures are completely different from those of the structures perpendicular to the rolling direction, resulting in anisotropy in the microstructure and properties of the alloy, which limits the application range of the alloy to a certain extent. However, although the traditional recrystallization annealing method can improve the microstructure of the alloy to a certain extent, it usually requires a higher processing temperature and a longer annealing time. This will not only increase energy consumption, but may also cause excessive growth of the alloy grain size and compound size, making it difficult to form a uniform and fine equiaxed crystal structure in the alloy, thereby reducing the mechanical properties of the alloy.

[0116] However, most of the aluminum alloys prepared by the methods provided in Examples 1 to 20 contain equiaxed crystal structures. As can be seen from Table 1, with the increase of the pressure applied during the heat treatment process (comparison between Example 1 and Example 3), or the extension of the holding time (comparison between Example 2 and Example 3), or the increase of the holding temperature (comparison between Example 5 and Example 9), it is beneficial to transform the structure of the 5182 aluminum alloy along the rolling direction into an equiaxed crystal structure. Compared with Comparative Example 1 without applying pressure, Example 6, which applied a pressure of 10Mpa, can promote the transformation of the long strip grains in the alloy into equiaxed grains under the same heat treatment temperature and time conditions after applying pressure; and, from the comparison between Example 4 and Comparative Example 2, it can be seen that applying pressure can enable the alloy to quickly obtain an equiaxed crystal structure at a lower temperature and a shorter holding time, which can effectively avoid the growth of the alloy grain size and the size of the compounds in the alloy at a higher temperature and a longer holding time.

[0117] like Figure 1 This is a microstructure photograph of the 5182 aluminum alloy along the rolling direction obtained in Example 5 of the present invention. Figure 2 This is a microstructure photograph of the 5182 aluminum alloy along the rolling direction obtained in Example 8 of the present invention. Figure 3This is a microstructure photo of the 5182 aluminum alloy obtained in comparative example 10 of the present invention along the rolling direction. The vertical direction in the figure is the rolling direction, and the dark spots in the figure are compounds in the alloy. Figure 1 and Figure 2 By comparison, under the same temperature (350°C) and heat treatment time (60 min), when the applied pressure is low, the banded structure of the alloy along the rolling direction cannot be transformed into an equiaxed structure, such as Figure 1 As shown in the figure, the arrangement of compounds in the aluminum alloy clearly shows a tendency to be distributed in a strip-like manner along the rolling direction, indicating that the strip-like structure in the alloy has not been fully transformed into an equiaxed crystal structure; when the applied pressure increases, the alloy can obtain an equiaxed crystal structure along the rolling direction, such as Figure 2 As shown, the distribution state of the compounds in the alloy is Figure 1 The structure of the alloy is more uniform, indicating that the process of recrystallization of the banded structure into equiaxed structure in the alloy is relatively complete. Increasing the heat treatment temperature (370℃) can also make the alloy transform from banded structure to equiaxed structure within 60 minutes under relatively small pressure, but higher temperature will increase the grain size and compound size of the alloy, which is not conducive to the improvement of the mechanical properties of the alloy.

[0118] In the above embodiment, 5182 aluminum alloy rolled plate is used as the material for pressurized heat treatment. The pressurized heat treatment method is also applicable to other grades of rolled aluminum alloy plates, other metal rolled plates or extruded profiles, etc. The technicians can also adjust the pressurized pressure, insulation temperature, insulation time and other parameters according to actual needs.

[0119] In the above embodiments, the 5182 aluminum alloy is cold rolled only once. In some other embodiments, the 5182 aluminum alloy may be cold rolled twice, as long as the final cold rolling reduction ratio is within the range of 31% to 34%.

[0120] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A pressurized heat treatment method for rapidly obtaining an equiaxed grain structure in an aluminum alloy, characterized in that: The steps include: Step A: heating the heat treatment furnace to a heat treatment temperature of 330-400°C; Step B: placing the rolled aluminum alloy plate in a heat treatment furnace, and keeping it warm at the heat treatment temperature. During the heat preservation process, a pressure device is used to continuously apply a pressure perpendicular to the rolling direction to the plate surface of the aluminum alloy plate; the heat preservation time is 20 to 100 minutes. During the heat preservation process, the pressure device applies a pressure greater than 0 and less than or equal to 20 MPa to the aluminum alloy plate; Step C: Take out the aluminum alloy plate and allow it to air cool to room temperature.

2. The pressurized heat treatment method for rapidly obtaining an equiaxed grain structure of an aluminum alloy according to claim 1, characterized in that: In step B: the pressurizing device includes a bearing component, a hydraulic component and a clamping component. The bearing component makes surface contact with the aluminum alloy plate and bears the aluminum alloy plate, and then the hydraulic component drives the clamping component to make surface contact with the aluminum alloy plate and apply pressure to the plate surface of the aluminum alloy plate.

3. The pressurized heat treatment method for rapidly obtaining an equiaxed grain structure of an aluminum alloy according to claim 2, characterized in that: In step B, the bearing component and the clamping component are both arranged in a heat treatment furnace, the plate surface of the aluminum alloy plate facing the bearing component is completely in contact with the surface of the bearing component, and the plate surface of the aluminum alloy plate facing the clamping component is completely in contact with the surface of the clamping component; the positions of the bearing component and the clamping component correspond.

4. The pressurized heat treatment method for rapidly obtaining an equiaxed grain structure of an aluminum alloy according to claim 3, characterized in that: During the heat preservation process of step B, the change in the pressure applied by the pressing component to the aluminum alloy plate is less than or equal to 0.5 MPa / 10min.

5. The pressurized heat treatment method for rapidly obtaining an equiaxed grain structure of an aluminum alloy according to claim 3, characterized in that: In step B, within 2 seconds after the aluminum alloy plate contacts the bearing component, the pressing component presses the aluminum alloy plate under the drive of the hydraulic component.

6. The pressurized heat treatment method for rapidly obtaining an equiaxed grain structure of an aluminum alloy according to claim 1, characterized in that: In step A, the heat treatment temperature is 330-370°C; In step B, the heat preservation time is 40 to 60 minutes, and the pressure device applies a pressure of 5 to 20 MPa to the aluminum alloy plate.

7. The pressurized heat treatment method for rapidly obtaining an equiaxed grain structure of an aluminum alloy according to claim 6, characterized in that: In step B, the temperature fluctuation range in the heat treatment furnace is less than or equal to ±1°C.

8. The pressurized heat treatment method for rapidly obtaining an equiaxed grain structure of an aluminum alloy according to claim 6, characterized in that: In step A, the heat treatment temperature is 350° C.; in step B, the holding time is 60 min, and the pressurizing device applies a pressure of 15 MPa to the aluminum alloy plate.

9. The pressurized heat treatment method for rapidly obtaining an equiaxed grain structure of an aluminum alloy according to any one of claims 1 to 8, characterized in that: The aluminum alloy plate is made of 5182 aluminum alloy by cold rolling, and the reduction rate during cold rolling is 31% to 34%; the chemical composition of 5182 aluminum alloy is 4.0wt.% to 5.0wt.% magnesium, 0.2wt.% to 0.4wt.% manganese, 0.1wt.% to 0.15wt.% silicon, 0.15wt.% to 0.25wt.% iron, 0.02wt.% to 0.06wt.% copper and 0.01wt.% to 0.03wt.% chromium, and the balance is aluminum.

10. The pressurized heat treatment method for rapidly obtaining an equiaxed grain structure of an aluminum alloy according to claim 9, characterized in that: The reduction rate during cold rolling is 33%. The chemical composition of the 5182 aluminum alloy is 4.6wt.% magnesium, 0.35wt.% manganese, 0.11wt.% silicon, 0.21wt.% iron, 0.04wt.% copper and 0.01wt.% chromium, with the balance being aluminum.

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