A ceramic particle-reinforced 7xxx-series aluminum-based composite sheet and a method of making the same

Abstract

This invention provides a ceramic particle-reinforced 7xxx series aluminum-based composite thin plate and its preparation method. The preparation method of this invention includes the following steps: (1) melting 7xxx series aluminum alloy, adding ceramic particle intermediate alloy to obtain a melt, and immediately stirring, adjusting the temperature of the melt during the stirring process; (2) starting casting, the melt flows through the tundish and enters the casting and rolling area for casting and rolling to obtain an aluminum-based composite slab; (3) subjecting the aluminum-based composite slab to asynchronous rolling, initial solution treatment, cold rolling, and solution aging treatment in sequence to finally obtain a ceramic particle-reinforced 7xxx series aluminum-based composite thin plate; 7xxx aluminum alloys include, but are not limited to, 7075 aluminum alloy and 7050 aluminum alloy. This invention realizes a short-process and efficient preparation of high-strength cast-rolled 7xxx series aluminum-based composite ceramics, solving the problems of difficult dispersion of ceramic particles, long process flow, high preparation cost, and difficulty in controlling metallurgical defects such as pores in the prior art.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy sheet preparation technology, specifically to a ceramic particle reinforced 7xxx series aluminum-based composite thin plate and its preparation method. Background Technology

[0002] Lightweight materials are a core pathway to improving the carrying efficiency and endurance of high-end equipment. 7xxx series high-strength aluminum alloy sheets, as important lightweight materials, are widely used in components such as aircraft and rocket skins, liquid oxygen tanks, and high-speed train car frames. However, with the in-depth implementation of major projects in my country, such as manned lunar landings, large passenger aircraft, and maglev trains, the requirements for material performance are becoming increasingly stringent. Traditional 7xxx aluminum alloys face bottlenecks such as limited strength improvement, low modulus, and poor thermal stability. 7xxx series aluminum-based composite materials, by introducing ceramic particles such as TiC and TiB2, can increase the elastic modulus to 80-100 GPa and the specific strength by 30%-50%, while also possessing high-temperature resistance and other properties, balancing lightweighting and service reliability. They have become strategic new materials in aerospace and other fields. Therefore, developing ceramic particle-reinforced 7xxx series aluminum-based composite material preparation technology is of great significance to the development of advanced materials in aerospace and other fields.

[0003] Currently, aluminum-based composite materials are mainly prepared through casting (such as stir casting) and additive manufacturing (such as powder metallurgy sintering and selective laser melting). While additive manufacturing is suitable for precision and complex parts, the products have high porosity, rapid thermal stress accumulation, and extremely high production costs, making it unsuitable for large-scale production of sheet materials. While the production cost of aluminum-based composite materials based on traditional casting processes has been reduced, the preparation of sheet materials still requires complex subsequent processing steps such as homogenization, hot rolling, intermediate annealing, and cold rolling. This results in large investments in production line equipment, high wear and tear, and a tendency to produce metallurgical defects such as shrinkage porosity, large and uneven dendritic structures, and thermal cracking. Therefore, developing a short-process, low-cost method for preparing aluminum-based composite thin plates that can achieve uniform dispersion of nanoparticles and control porosity defects has significant industrial application value. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a ceramic particle-reinforced 7xxx series aluminum-based composite thin plate and its preparation method. Through a fully coupled process of "mechanical stirring + ultrasonic treatment in the tundish + electromagnetic oscillation in the casting and rolling zone," the nanoparticles are dispersed and distributed. Combined with a short-process deformation heat treatment, this invention solves the problems of difficult dispersion of nano-ceramic particles, long process flow, high preparation cost, and difficulty in controlling metallurgical defects such as porosity in existing technologies.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: The first objective of this invention is to provide a method for preparing ceramic particle-reinforced 7xxx series aluminum-based composite thin plates, comprising the following steps: (1) Melt 7xxx series aluminum alloy, add ceramic particle intermediate alloy to obtain melt and stir immediately, and adjust the temperature of the melt during stirring; (2) The casting process begins. After the melt flows through the tundish, it enters the casting and rolling area to be cast and rolled to obtain an aluminum-based composite slab. (3) The aluminum-based composite slab is subjected to asynchronous rolling, initial solution treatment, cold rolling, and solution aging treatment in sequence to finally obtain ceramic particle reinforced 7xxx series aluminum-based composite thin plate.

[0006] Furthermore, the 7xxx series aluminum alloys include, but are not limited to, 7075 aluminum alloy and 7050 aluminum alloy.

[0007] The beneficial effects of this invention are: (1) Low-cost, short-process, large-scale preparation: Compared with the complex process of preparing aluminum-based composite thin plates based on traditional casting methods (such as melting, casting, sawing, homogenization, hot rolling, intermediate annealing, cold rolling and solution aging treatment), the preparation method of the present invention, "composite casting and rolling → deformation heat treatment", shortens the process flow (cycle) by about 60% and reduces energy consumption by more than 40%. At the same time, it avoids the complex operations of powder metallurgy such as encapsulation, hot pressing and sintering, and is suitable for large-scale production.

[0008] (2) Excellent effects of nanoparticle dispersion and metallurgical defect control: Mechanical stirring, ultrasonic and electromagnetic oscillation are applied in the smelting, tundish and casting and rolling zones respectively. Through multi-level treatment, the nanoparticles are dispersed in the matrix. Sub-rapid solidification of casting and rolling inhibits the interfacial reaction between aluminum matrix and ceramic particles, reduces the generation of harmful phases and improves the interfacial bonding strength. Semi-solid deformation of casting and rolling + electromagnetic oscillation eliminates pore defects. The composite grain refinement effect of ceramic particles and electromagnetic oscillation significantly reduces the solute segregation of cast and rolled 7xxx series aluminum alloys with high alloying and wide solidification range.

[0009] Based on the above technical solution, the present invention can be further improved as follows.

[0010] Furthermore, when the ceramic particle intermediate alloy is added in step (1), the temperature of the melt is 710℃-720℃; when the melt is poured in step (2), the temperature of the melt is 690℃-700℃.

[0011] The beneficial effects of adopting the above-mentioned further scheme are: within this temperature range, the tendency of ceramic particles to agglomerate is low, and the degree of macroscopic solute segregation is low, which is conducive to the preparation of high-quality cast and rolled slabs.

[0012] Furthermore, the particle size of the ceramic intermediate alloy in step (1) is 50 nm-200 nm, and the ceramic intermediate alloy includes ceramic particles and Al; the ceramic particles are at least one of TiC and TiB2. The mass ratio of the ceramic particles to the Al is 3:7; the ceramic particles account for 0.5%-3% of the mass fraction of the melt.

[0013] Furthermore, the mechanical stirring speed in step (1) is 60 rpm-100 rpm.

[0014] Furthermore, when the melt flows through the intermediate ladle in step (2), it is also subjected to ultrasonic treatment. The power of the ultrasonic treatment is 1000 W-1500 W, the frequency is 15 kHz-25 kHz, and the amplitude is 20 μm-50 μm.

[0015] Furthermore, the probe of the ultrasonic generator used in the ultrasonic process is fixed 20mm-30mm below the melt in the intermediate jar.

[0016] The beneficial effects of adopting the above-mentioned further scheme are: ultrasonic cavitation effect breaks up particle agglomeration, acoustic flow effect enhances melt convection, and promotes uniform particle distribution.

[0017] Furthermore, an electromagnetic oscillation field is applied in the casting and rolling area described in step (2), wherein the frequency of the pulse current of the electromagnetic oscillation field is 15 Hz-20 Hz, the peak current is 300 A-400 A, the duty cycle is 15%-20%, and the static magnetic field strength is 35 mT-40 mT.

[0018] The beneficial effects of adopting the above-mentioned further scheme are: the Lorentz force generated by the electromagnetic field can refine the solidification structure, suppress solute segregation, and further disperse the particles in the melt in the casting and rolling zone through electromagnetic stirring.

[0019] Furthermore, the casting and rolling area is the area surrounded by the upper and lower casting rolls and the casting nozzle.

[0020] Furthermore, the casting and rolling speed in step (2) is 0.8 m / min-1.2 m / min, the constant roll gap height is 6 mm-7 mm, and the casting and rolling force is 700 kN-900 kN.

[0021] Further, the asynchronous rolling in step (3) specifically involves: holding the aluminum-based composite slab at 450℃-470℃ for 1 hour and then asynchronously hot rolling it to a thickness of 2 mm-3.5 mm, with an asynchronous ratio of 1.2-1.3 between the upper and lower rolls and a hot rolling deformation of 55%-75%.

[0022] The beneficial effects of adopting the above-mentioned further scheme are: the shear deformation introduced by asynchronous rolling helps to break up the solidified structure and promote the dissolution of crystalline phases.

[0023] Furthermore, the initial solution treatment in step (3) specifically involves: maintaining the temperature at 470℃-480℃ for 1-2 hours, followed by air cooling.

[0024] The beneficial effect of adopting the above-mentioned further scheme is that it helps to quickly dissolve the broken crystalline phase.

[0025] Furthermore, cold rolling is used to obtain cold-rolled sheets with a thickness of 1.2-1.5 mm, which introduces work hardening and further breaks down the crystalline phase.

[0026] Furthermore, the solution aging treatment in step (3) specifically involves holding at 470 ℃ for 0.5 h-2 h, quenching, and holding at 120 ℃ for 24 h.

[0027] Furthermore, the final thickness of the ceramic particle-reinforced 7xxx series aluminum-based composite sheet is 1.2 mm-1.5 mm.

[0028] The second objective of this invention is to provide a ceramic particle-reinforced 7xxx series aluminum-based composite sheet.

[0029] The beneficial effects of the present invention are: the 7xxx series aluminum-based composite thin plate prepared by the preparation method of the present invention has a yield strength of not less than 500 MPa, a tensile strength of not less than 550 MPa, an elongation of not less than 10%, and an elastic modulus of not less than 75 GPa. Attached Figure Description

[0030] Figure 1 These are schematic diagrams illustrating the preparation process of 7xxx series aluminum-based composite slabs in Examples 1-5 and Comparative Examples 1-2 of the present invention. Figure 2 This is a crystalline phase distribution diagram of the 7xxx series aluminum-based composite thin plate in Example 1 of the present invention; Figure 3 This is a ceramic particle distribution diagram of the 7xxx series aluminum-based composite thin plate in Embodiment 1 of the present invention; Figure 4 This is a grain distribution diagram of the 7xxx series aluminum-based composite thin plate in Embodiment 1 of the present invention; Figure 5 This is a grain distribution diagram of the 7xxx series aluminum-based composite thin plate in Comparative Example 2 of the present invention; Figure 6 This is a grain distribution diagram of the second phase (crystalline phase and ceramic particles) of the 7xxx series aluminum-based composite thin plate in Comparative Example 1 of the present invention; Figure 7 This is the microstructure of the 7xxx series aluminum-based composite ingot in Comparative Example 3 of the present invention.

[0031] The attached diagram lists the components represented by each number as follows: 1. Mechanical stirring device; 2. Ultrasonic generating device; 3. Pulse current device; 4. Magnetic field generating device; 5. Resistance furnace; 6. Sprue; 7. Tundish; 8. Casting nozzle; 9. Casting and rolling zone; 10. Water-cooled casting and rolling rolls; 11. Aluminum-based composite slab. Detailed Implementation

[0032] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0033] The specific processes of Embodiments 1-5 and Comparative Examples 1 and 2 of this invention are as follows: Figure 1 As shown.

[0034] Example 1: (1) 7075 aluminum alloy raw material (Al-5.5Zn-2.3Mg-1.3Cu-0.2Cr-0.3Mn-0.3Si, wt%) was completely melted in resistance furnace 5. When the furnace temperature stabilized at 715℃, TiC ceramic particles were added as intermediate alloy to obtain the melt. The total mass fraction of TiC was 1% of the melt mass. Then, the melt was immediately mechanically stirred using mechanical stirring device 1 (graphite rod) at a stirring speed of 80 rpm. During the stirring process, the melt temperature was continuously adjusted. When the melt temperature dropped to 690℃, casting began. (2) The melt enters the tundish 7, the nozzle 8 and the casting and rolling zone 9 between the upper and lower rolls in sequence through the gating 6. While the melt passes through the tundish 7, the ultrasonic generator 2 is turned on and the ultrasonic generator probe is fixed 20-30 mm below the melt surface in the tundish to perform ultrasonic treatment on the melt at 1200 W, 20 kHz and 30 μm amplitude. When the melt passes through the casting and rolling zone, the pulse current device 3 and the magnetic field generator 4 are turned on to perform electromagnetic oscillation treatment. The pulse current frequency is 18 Hz, the peak current is 350A, the duty cycle is 15% and the static magnetic field strength is 35mT. The casting and rolling parameters are set as follows: casting and rolling speed 0.9 m / min, roll gap height between the upper and lower water-cooled casting and rolling rolls 10 7 mm, and casting and rolling force 800 kN to obtain the cast and rolled TiC / 7075 aluminum-based composite slab 11. (3) Short-process deformation heat treatment for cast and rolled TiC / 7075 aluminum-based composite slab 11: TiC / 7075 aluminum-based composite slab is held at 470℃ for 1 h and then asynchronously rolled (asynchronous ratio 1.28) to a thickness of 3.0 mm with a deformation of 62.5%. The hot-rolled slab is obtained by rolling three times. The hot-rolled slab is subjected to initial solution treatment, held at 475℃ for 2 h, air-cooled to room temperature and then cold-rolled to a thickness of 1.5 mm to obtain a cold-rolled plate. Finally, the cold-rolled plate is subjected to solution aging treatment, held at 475℃ for 1 h, quenched to room temperature, and held at 120℃ for 24 h to finally obtain a 1wt% TiC / 7075 aluminum-based composite thin plate.

[0035] Example 2: The only difference between this embodiment and embodiment 1 is that the mass fraction of TiC added in step (1) is 1.5% of the melt mass, and in step (3) the TiC / 7075 aluminum-based composite slab is asynchronously hot-rolled to a thickness of 2.5 mm and cold-rolled to a thickness of 1.2 mm. The remaining steps and conditions are the same as in embodiment 1.

[0036] Example 3: The only difference between this embodiment and embodiment 1 is that the mass fraction of TiC added in step (1) is 2.5% of the melt mass, the ultrasonic power in step (2) is 1500 W, the static magnetic field strength is 40 mT, the casting speed is 1 m / min, the casting force is 900 kN, and in step (3) the TiC / 7075 aluminum-based composite slab is asynchronously hot-rolled to a thickness of 2.5 mm and cold-rolled to a thickness of 1.2 mm. The remaining steps and conditions are the same as in embodiment 1.

[0037] Example 4: The only difference between this embodiment and Embodiment 1 is that the aluminum alloy raw material used in step (1) of this embodiment is 7050 aluminum alloy raw material (Al-6.0Zn-2.3Mg-2.2Cu-0.12Zr, wt%), and the casting speed during casting and rolling in step (2) is 0.8 m / min, and the roll gap height is 6.5 mm. All other steps and conditions are the same as in Embodiment 1.

[0038] Example 5: Compared with Example 1, the only difference in this embodiment is that the ceramic particle intermediate alloy used in step (1) of this embodiment is TiB2 ceramic particle intermediate alloy, and the mass fraction of TiB2 is 1% of the melt mass. The remaining steps and conditions are the same as in Example 1.

[0039] Example 6: The only difference between this embodiment and Example 1 is that the ceramic particles in the added ceramic particle intermediate alloy are TiB2 and TiC; the addition amounts of TiB2 and TiC are 0.5wt% and 1.0wt% of the melt mass, respectively. All other steps and conditions are the same as in Example 1.

[0040] Comparative Example 1: Compared with Example 1, the only difference in this comparative example is that step (2) does not involve ultrasonic treatment and electromagnetic oscillation treatment, while the other steps and conditions are the same as in Example 1.

[0041] Comparative Example 2: The only difference between this comparative example and Example 1 is that no ceramic particle intermediate alloy was added in step (1), while the other steps and conditions are the same as in Example 1.

[0042] Comparative Example 3: (1) 7075 aluminum alloy raw material (Al-5.5Zn-2.3Mg-1.3Cu-0.2Cr-0.3Mn-0.3Si, wt%) was completely melted in resistance furnace 5. When the furnace temperature stabilized at 715℃, TiC ceramic particles were added as intermediate alloy to obtain the melt. The total mass fraction of TiC was 1% of the melt mass. Then, the melt was immediately mechanically stirred using mechanical stirring device 1 (graphite rod) at a stirring speed of 80 rpm. During the stirring process, the melt temperature was continuously adjusted. When the melt temperature dropped to 690℃, casting began. (2) Pour the melt into a stainless steel mold preheated to 250 °C and let it solidify slowly to complete the preparation of TiC / 7075 aluminum-based composite ingot. The ingot size and thickness are 20 mm.

[0043] (3) The TiC / 7075 aluminum-based composite ingot is subjected to conventional rolling-heat treatment: the ingot is homogenized (held at 470℃ for 24 h, and air-cooled to room temperature), and the homogenized material is milled; after holding at 420℃ for 1 h, it is hot rolled and rolled to a thickness of 4.0 mm in 6 passes; the hot-rolled slab is subjected to intermediate annealing (held at 400℃ for 1 h), air-cooled to room temperature, and then cold-rolled to a thickness of 1.5 mm; finally, the cold-rolled plate is subjected to solution aging treatment (held at 475℃ for 1 h, quenched to room temperature, and held at 120℃ for 24 h), and finally TiC / 7075 aluminum-based composite thin plate is obtained.

[0044] Performance testing: 1. Microstructure The crystalline phase distribution of the composite thin plates obtained in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 was examined using a field emission scanning electron microscope (ZEISS Gemini 300). The ceramic particle distribution was examined using a field emission transmission electron microscope (JEM-2100), and the grain structure distribution was examined using an optical microscope (OLYMPUS BX53M). Figures 2-7 As shown: The microstructure of the composite thin plate obtained in Example 1 shows that TiC particles are dispersed without agglomeration, the grains are fine and uniform, the crystalline phase is relatively uniformly distributed, and there is no macroscopic segregation. The microstructure of the thin plate obtained in Comparative Example 1 shows that there is a large amount of ceramic particle aggregation, and the grain and undissolved crystalline phase are unevenly distributed. The microstructure of the thin plate obtained in Comparative Example 2 shows that the grain distribution varies greatly in different regions, and there are areas with large aggregations of undissolved crystalline phase. The microstructure of the aluminum-based composite ingot obtained in Comparative Example 3 shows obvious shrinkage cavities and low solidification density.

[0045] 2. Room temperature mechanical property testing along the rolling direction The room temperature mechanical properties of the obtained composite sheet along the rolling direction were tested using a 100 kN electronic universal testing machine (SHIMADZU AGX), and the results are shown in Table 1.

[0046] Table 1 From Table 1, we can obtain: This invention utilizes a coupled casting and rolling process—combining mechanical stirring in the melting furnace, ultrasonic treatment in the tundish, and electromagnetic oscillation in the casting and rolling zone—to effectively control the dispersion and solute segregation of nanoparticles in cast-rolled aluminum-based composite slabs. Combined with a short-process deformation heat treatment, it efficiently prepares high-strength, high-toughness, and high-modulus 7xxx series aluminum-based composite thin plates. The resulting composite thin plates exhibit a yield strength of not less than 500 MPa, a tensile strength of not less than 550 MPa, an elongation of not less than 10%, and an elastic modulus of not less than 75 GPa.

[0047] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a ceramic particle-reinforced 7xxx series aluminum-based composite thin plate, characterized in that, Includes the following steps: (1) Melt 7xxx series aluminum alloy, add ceramic particle intermediate alloy to obtain melt and stir immediately, and adjust the temperature of the melt during stirring; (2) The casting process begins. After the melt flows through the tundish, it enters the casting and rolling area to be cast and rolled to obtain an aluminum-based composite slab. (3) The aluminum-based composite slab is subjected to asynchronous rolling, initial solution treatment, cold rolling, and solution aging treatment in sequence to finally obtain ceramic particle reinforced 7xxx series aluminum-based composite thin plate.

2. The method for preparing a ceramic particle-reinforced 7xxx series aluminum-based composite thin plate according to claim 1, characterized in that, When the ceramic particle intermediate alloy is added in step (1), the temperature of the melt is 710℃-720℃; when the melt is poured in step (2), the temperature of the melt is 690℃-700℃.

3. The method for preparing a ceramic particle-reinforced 7xxx series aluminum-based composite thin plate according to claim 2, characterized in that, The ceramic intermediate alloy in step (1) has a particle size of 50 nm-200 nm, and the ceramic intermediate alloy includes ceramic particles and Al; the ceramic particles are at least one of TiC and TiB2. The mass ratio of the ceramic particles to the Al is 3:7; the ceramic particles account for 0.5%-3% of the mass fraction of the melt.

4. The method for preparing a ceramic particle-reinforced 7xxx series aluminum-based composite thin plate according to claim 1, characterized in that, When the melt flows through the intermediate ladle in step (2), it is subjected to ultrasonic treatment. The power of the ultrasonic treatment is 1000 W-1500 W, the frequency is 15 kHz-25 kHz, and the amplitude is 20 μm-50 μm.

5. The method for preparing a ceramic particle-reinforced 7xxx series aluminum-based composite thin plate according to claim 1, characterized in that, An electromagnetic oscillation field is applied in the casting and rolling area described in step (2), wherein the frequency of the pulse current of the electromagnetic oscillation field is 15Hz-20Hz, the peak current is 300A-400A, the duty cycle is 15%-20%, and the static magnetic field strength is 35mT-40mT.

6. The method for preparing a ceramic particle-reinforced 7xxx series aluminum-based composite thin plate according to claim 1, characterized in that, The casting and rolling speed in step (2) is 0.8 m / min-1.2 m / min, the constant roll gap height is 6 mm-7 mm, and the casting and rolling force is 700 kN-900 kN.

7. The method for preparing a ceramic particle-reinforced 7xxx series aluminum-based composite thin plate according to claim 1, characterized in that, The asynchronous rolling in step (3) specifically involves: holding the aluminum-based composite slab at 450℃-470℃ for 1 hour and then asynchronously hot rolling it to a thickness of 2 mm-3.5 mm, with an asynchronous ratio of 1.2-1.3 between the upper and lower rolls and a hot rolling deformation of 55%-75%.

8. The method for preparing a ceramic particle-reinforced 7xxx series aluminum-based composite thin plate according to claim 1, characterized in that, The initial solution treatment in step (3) specifically involves keeping the solution at 470℃-480℃ for 1-2 hours, followed by air cooling.

9. The method for preparing a ceramic particle-reinforced 7xxx series aluminum-based composite thin plate according to claim 1, characterized in that, The solution aging treatment in step (3) specifically involves holding at 470 ℃ for 0.5-2 h, quenching, and holding at 120 ℃ for 24 h.

10. A ceramic particle-reinforced 7xxx series aluminum-based composite thin plate, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

Images