A high-strength aluminum alloy and a method for manufacturing the same

Abstract

The application relates to the technical field of aluminum alloy materials, and discloses a high-strength aluminum alloy and a preparation method thereof, the method comprising preparation of non-spherical nano-aluminum oxide particles, sorting of the aluminum oxide particles, aluminum alloy smelting and casting, hot rolling and cold rolling processing, and solid solution and aging treatment; the non-spherical nano-aluminum oxide particles are obtained through wet grinding combined with pulse electromagnetic field screening, the interface bonding force between the non-spherical structure and the aluminum matrix is enhanced, and dislocation movement is hindered, so that the strength of the aluminum alloy is improved, the problem of weak interface bonding of traditional spherical particles is avoided, and the stability of the mechanical properties of the material is improved; the non-spherical nano-aluminum oxide particles are introduced as heterogeneous nucleation cores, and the aluminum-titanium-boron intermediate alloy is used in cooperation to refine the grain structure and inhibit grain growth, so that the microstructure of the aluminum alloy is more uniform and compact, the forming quality of the material in subsequent processing is ensured, and the risk of structural defects is reduced.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy materials technology, specifically to a high-strength aluminum alloy and its preparation method. Background Technology

[0002] Aluminum alloys are alloys based on aluminum with the addition of a certain amount of other alloying elements. They are one of the light metal materials. In addition to the general properties of aluminum, aluminum alloys also have some specific alloy properties due to the different types and amounts of alloying elements added. The specific strength of aluminum alloys is close to that of high alloy steel, the specific stiffness exceeds that of steel, and they have good casting performance and plastic processing performance, good electrical and thermal conductivity, good corrosion resistance and weldability.

[0003] Currently, due to the lack of effective control over the morphology of reinforcing particles during the traditional aluminum alloy preparation process, the problem of weak interfacial bonding between nanoparticles and the aluminum matrix cannot be solved during melting and casting. If conventional spherical reinforcing particles are used, the dislocation hindering effect may be poor, which may not guarantee the improvement of the strength of the aluminum alloy and result in insufficient stability of the material's mechanical properties.

[0004] Therefore, a high-strength aluminum alloy and its preparation method are proposed to solve the above problems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a high-strength aluminum alloy and its preparation method, solving the problem mentioned in the background art of poor dislocation formation inhibition effect, inability to guarantee strength improvement of aluminum alloy, and insufficient stability of material mechanical properties.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a high-strength aluminum alloy, comprising the following steps: Step 1: Preparation of non-spherical nano-alumina particles. The α-phase alumina raw material is placed in the grinding media and wet-milled using a planetary ball mill. The grinding media is zirconia balls, the ball-to-material mass ratio is 5-10:1, the grinding speed is 300-500 r / min, and the grinding time is 10-15 h, to obtain an alumina slurry with a particle size distribution of 20-50 nm. Step 2: Sorting of alumina particles. The alumina slurry is centrifuged at a speed of 8000-12000 r / min for 20-30 min. The upper suspension is collected and then a pulsed electromagnetic field with a frequency of 50-100 kHz and a field strength of 1-3 T is applied to the upper suspension for screening to remove spherical and smooth particles, resulting in non-spherical nano-alumina particles with a surface roughness Ra of 5-10 nm. Step 3: Aluminum alloy smelting and casting. Magnesium ingots, zinc ingots, copper ingots, and aluminum ingots are mixed according to the following mass fractions: Mg 2-4%, Zn 1-3%, Cu 0.5-1.5%, with the balance being aluminum. The mixture is placed in a resistance furnace and heated to 700-750℃ to melt into a molten material. Non-spherical nano-alumina particles are added at 0.5-2% of the total mass of the molten material, along with 0.1-0.3% of an aluminum-titanium-boron master alloy. The mixture is stirred at 200-400 r / min for 10-20 min under argon protection. Then, it is poured into a metal mold preheated to 200-300℃ and cooled to room temperature to obtain the cast aluminum alloy. Step 4: Hot rolling and cold rolling processing. The cast aluminum alloy is hot rolled at 400-450℃ with a hot rolling deformation of 50-70%. Then it is cold rolled with 3-5 cold rolling passes, with a single pass deformation of 10-20% and a total cold rolling deformation of 40-60%, to obtain cold rolled aluminum alloy sheet. Step 5: Solution treatment and aging treatment. The cold-rolled aluminum alloy sheet is heated to 480-520℃ and held for 1-3 hours for solution treatment. Then it is water quenched to room temperature and heated to 120-180℃ and held for 8-12 hours for aging treatment to obtain high-strength aluminum alloy.

[0007] Preferably, in step one, the dispersant used in wet grinding is ammonium polyacrylate, the mass of the dispersant is 0.5-1% of the mass of the α-phase alumina raw material, the grinding medium is deionized water, and the solid-liquid mass ratio is 1:3-5.

[0008] Preferably, in step two, the pulse width of the pulsed electromagnetic field is 10-50 μs, the pulse interval is 100-500 μs, the screening time is 30-60 min, and the temperature of the suspension is maintained at 10-20℃ during the screening process.

[0009] Preferably, in step three, 0.05-0.15% of strontium is added during the smelting process. The strontium is added in the form of an aluminum-strontium master alloy, and the mass fraction of strontium in the aluminum-strontium master alloy is 10-15%.

[0010] Preferably, in step three, the stirring adopts a double-layer turbine stirring paddle with a blade diameter of 33.3%-50% of the inner diameter of the melt container. During the stirring process, ultrasonic vibration is applied simultaneously with an ultrasonic frequency of 20-40kHz and a power of 500-1000W.

[0011] Preferably, in step four, the cast aluminum alloy is homogenized before hot rolling at a temperature of 450-500℃ and a holding time of 12-24h. After homogenization, it is cooled in the furnace to 400-450℃ and then directly enters the hot rolling process.

[0012] Preferably, in step four, emulsion cooling is used during cold rolling, with an emulsion flow rate of 10-20 L / min and an emulsion temperature of 20-30°C. After cold rolling, the aluminum alloy sheet is subjected to stress-relief annealing at a temperature of 200-250°C and a holding time of 1-2 hours.

[0013] Preferably, in step five, the solution treatment is performed using a salt bath with a salt bath composition of 50-60 wt% potassium nitrate and 40-50 wt% sodium nitrite, and the heating rate is controlled at 5-10 °C / min.

[0014] Preferably, in step five, after aging treatment, micro-arc oxidation treatment is performed on the surface of the aluminum alloy sheet. The micro-arc oxidation electrolyte is a silicate system, the voltage is 300-500V, the frequency is 50-100Hz, the treatment time is 10-30min, and the thickness of the micro-arc oxidation film is 5-15μm.

[0015] A high-strength aluminum alloy, wherein the chemical composition of the high-strength aluminum alloy, by mass fraction, is: magnesium 2-4%, zinc 1-3%, copper 0.5-1.5%, silicon ≤0.2%, iron ≤0.3%, titanium 0.05-0.15%, boron 0.01-0.05%, strontium 0.05-0.15%, oxygen ≤0.1%, with the balance being aluminum and unavoidable impurities; The high-strength aluminum alloy has a metallographic structure in which non-spherical alumina particles with a size of 20-50 nm are distributed at the grain boundaries, the grain size is 5-15 μm, and the intragranular dislocation density is 1×10⁻⁶. 14 -5×10 14 m -2 The second phase particles have a size of 50-200 nm and a volume fraction of 5-10%.

[0016] Compared with the prior art, the present invention provides a high-strength aluminum alloy and its preparation method, which has the following beneficial effects: 1. In this invention, non-spherical nano-alumina particles are obtained by wet grinding combined with pulsed electromagnetic field screening. The non-spherical structure enhances the interfacial bonding force with the aluminum matrix and hinders dislocation movement, thereby ensuring the strength improvement of the aluminum alloy. At the same time, it avoids the problem of weak interfacial bonding of traditional spherical particles and improves the stability of the material's mechanical properties.

[0017] 2. In this invention, by introducing non-spherical nano-alumina particles as heterogeneous nucleation cores, and in conjunction with the synergistic effect of aluminum-titanium-boron intermediate alloys, the grain structure is refined, grain growth is inhibited, and the microstructure of the aluminum alloy becomes more uniform and dense, ensuring the forming quality of the material in subsequent processing and reducing the risk of structural defects.

[0018] 3. In this invention, a ceramic film layer is constructed on the material surface through micro-arc oxidation treatment, which seals the surface micropores and blocks the intrusion of corrosive media. At the same time, it forms a strong metallurgical bond with the substrate, so that the aluminum alloy has both excellent wear resistance and corrosion resistance, ensuring the long-term service reliability of the material in complex environments. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1: A method for preparing a high-strength aluminum alloy, comprising the following steps: Step 1: Preparation of non-spherical nano-alumina particles. The α-phase alumina raw material was placed in the grinding media and wet-milled using a planetary ball mill. The grinding media was zirconia balls, the ball-to-material mass ratio was 5:1, the grinding speed was 300 r / min, and the grinding time was 10 h, resulting in an alumina slurry with a particle size distribution of 20 nm. Step 2: Sorting of alumina particles. The alumina slurry is centrifuged at a speed of 8000 r / min for 20 min. The upper suspension is collected and then a pulsed electromagnetic field with a frequency of 50 kHz and a field strength of 1 T is applied to the upper suspension for screening to remove spherical and smooth particles, resulting in non-spherical nano-alumina particles with a surface roughness Ra of 5 nm. Step 3: Aluminum alloy smelting and casting. Magnesium ingots, zinc ingots, copper ingots, and aluminum ingots are mixed according to the mass fractions of Mg 2%, Zn 1%, Cu 0.5%, with the balance being aluminum. The mixture is placed in an electric resistance furnace and heated to 700℃ to melt into a melt. Non-spherical nano-alumina particles are added at 0.5% of the total mass of the melt, along with 0.1% of the total mass of the melt. The mixture is stirred at 200 r / min for 10 min under argon protection, and then poured into a metal mold preheated to 200℃. After cooling to room temperature, the as-cast aluminum alloy is obtained. Step 4: Hot rolling and cold rolling processing. The cast aluminum alloy is hot rolled at 400℃ with a hot rolling deformation of 50%. Then it is cold rolled in 3 passes with a single pass deformation of 10% and a total cold rolling deformation of 40% to obtain cold rolled aluminum alloy sheet. Step 5: Solution treatment and aging treatment. The cold-rolled aluminum alloy sheet is heated to 480℃ and held for 1 hour for solution treatment, then water-quenched to room temperature, and then heated to 120℃ and held for 8 hours for aging treatment to obtain high-strength aluminum alloy.

[0021] In step one, the dispersant used in wet grinding is ammonium polyacrylate, the mass of which is 0.5% of the mass of the α-phase alumina raw material, the grinding medium is deionized water, and the solid-liquid mass ratio is 1:3.

[0022] In step two, the pulse width of the pulsed electromagnetic field is 10 μs, the pulse interval is 100 μs, the screening time is 30 min, and the temperature of the suspension is maintained at 10℃ during the screening process.

[0023] In step three, 0.05% of the total mass of the melt is added during the smelting process. The strontium is added in the form of an aluminum-strontium master alloy, in which the mass fraction of strontium is 10%.

[0024] In step three, a double-layer turbine impeller is used for stirring. The impeller diameter is 33.3% of the inner diameter of the melt container. Ultrasonic oscillation is applied simultaneously during the stirring process. The ultrasonic frequency is 20kHz and the power is 500W.

[0025] In step four, the cast aluminum alloy is homogenized before hot rolling. The homogenization temperature is 450℃ and the holding time is 12h. After homogenization, it is cooled to 400℃ in the furnace and then directly enters the hot rolling process.

[0026] In step four, emulsion cooling is used during the cold rolling process. The emulsion flow rate is 10L / min and the emulsion temperature is 20℃. After cold rolling, the aluminum alloy sheet is subjected to stress-relief annealing at a temperature of 200℃ and a holding time of 1h.

[0027] In step five, the solution treatment is carried out by heating in a salt bath. The salt bath consists of a mixed salt of 50 wt% potassium nitrate and 40 wt% sodium nitrite, and the heating rate is controlled at 5 °C / min.

[0028] In step five, after aging treatment, micro-arc oxidation treatment is performed on the surface of the aluminum alloy sheet. The micro-arc oxidation electrolyte is a silicate system, the voltage is 300V, the frequency is 50Hz, the treatment time is 10min, and the thickness of the micro-arc oxidation film is 5μm.

[0029] A high-strength aluminum alloy, the chemical composition of which, by mass fraction, is: magnesium 2%, zinc 1%, copper 0.5%, silicon ≤0.2%, iron ≤0.3%, titanium 0.05%, boron 0.01%, strontium 0.05%, oxygen ≤0.1%, with the balance being aluminum and unavoidable impurities; The microstructure of the high-strength aluminum alloy contains non-spherical alumina particles with a size of 20 nm distributed at the grain boundaries, a grain size of 5 μm, and an intragranular dislocation density of 1 × 10⁻⁶. 14 m -2 The second phase particles have a size of 50 nm and a volume fraction of 5%.

[0030] Example 2: A method for preparing a high-strength aluminum alloy, comprising the following steps: Step 1: Preparation of non-spherical nano-alumina particles. The α-phase alumina raw material was placed in the grinding media and wet-milled using a planetary ball mill. The grinding media was zirconia balls, the ball-to-material mass ratio was 7:1, the grinding speed was 400 r / min, and the grinding time was 13 h, resulting in an alumina slurry with a particle size distribution of 35 nm. Step 2: Sorting of alumina particles. The alumina slurry is centrifuged at a speed of 10,000 r / min for 25 min. The upper suspension is collected and then a pulsed electromagnetic field with a frequency of 75 kHz and a field strength of 2 T is applied to the upper suspension for screening to remove spherical and smooth particles, resulting in non-spherical nano-alumina particles with a surface roughness Ra of 7 nm. Step 3: Aluminum alloy smelting and casting. Magnesium ingots, zinc ingots, copper ingots, and aluminum ingots are mixed according to the mass fractions of Mg 3%, Zn 2%, Cu 1.0%, with the balance being aluminum. The mixture is placed in an electric resistance furnace and heated to 725°C to melt into a melt. Non-spherical nano-alumina particles are added at 1.2% of the total mass of the melt, along with 0.2% of the total mass of the melt. The mixture is stirred at 300 r / min for 15 min under argon protection, and then poured into a metal mold preheated to 250°C. After cooling to room temperature, the as-cast aluminum alloy is obtained. Step 4: Hot rolling and cold rolling processing. The cast aluminum alloy is hot rolled at 425℃ with a hot rolling deformation of 60%. Then it is cold rolled in 4 passes with a single pass deformation of 15% and a total cold rolling deformation of 50% to obtain cold rolled aluminum alloy sheet. Step 5: Solution treatment and aging treatment. The cold-rolled aluminum alloy sheet is heated to 500℃ and held for 2 hours for solution treatment, then water-quenched to room temperature, and then heated to 150℃ and held for 10 hours for aging treatment to obtain high-strength aluminum alloy.

[0031] In step one, the dispersant used in wet grinding is ammonium polyacrylate, the mass of which is 0.75% of the mass of the α-phase alumina raw material, the grinding medium is deionized water, and the solid-liquid mass ratio is 1:4.

[0032] In step two, the pulse width of the pulsed electromagnetic field is 30 μs, the pulse interval is 300 μs, the screening time is 45 min, and the temperature of the suspension is maintained at 15℃ during the screening process.

[0033] In step three, 0.10% of the total mass of the melt is added during the smelting process. The strontium is added in the form of an aluminum-strontium master alloy, in which the mass fraction of strontium is 13%.

[0034] In step three, a double-layer turbine impeller is used for stirring. The impeller diameter is 41% of the inner diameter of the melt container. Ultrasonic oscillation is applied synchronously during the stirring process. The ultrasonic frequency is 30kHz and the power is 750W.

[0035] In step four, the cast aluminum alloy is homogenized before hot rolling. The homogenization temperature is 475℃ and the holding time is 18h. After homogenization, it is cooled to 425℃ in the furnace and then directly enters the hot rolling process.

[0036] In step four, emulsion cooling is used during the cold rolling process. The emulsion flow rate is 15L / min and the emulsion temperature is 25℃. After cold rolling, the aluminum alloy sheet is subjected to stress-relief annealing at a temperature of 225℃ and a holding time of 1.5h.

[0037] In step five, the solution treatment is carried out by heating in a salt bath. The salt bath consists of a mixed salt of 55 wt% potassium nitrate and 45 wt% sodium nitrite, and the heating rate is controlled at 7 °C / min.

[0038] In step five, after aging treatment, micro-arc oxidation treatment is performed on the surface of the aluminum alloy sheet. The micro-arc oxidation electrolyte is a silicate system, the voltage is 400V, the frequency is 75Hz, the treatment time is 20min, and the thickness of the micro-arc oxidation film is 10μm.

[0039] A high-strength aluminum alloy, the chemical composition of which, by mass fraction, is: magnesium 3%, zinc 2%, copper 1.0%, silicon ≤0.2%, iron ≤0.3%, titanium 0.10%, boron 0.03%, strontium 0.10%, oxygen ≤0.1%, with the balance being aluminum and unavoidable impurities; The microstructure of the high-strength aluminum alloy contains non-spherical alumina particles with a size of 35 nm distributed at the grain boundaries, a grain size of 10 μm, and an intragranular dislocation density of 3 × 10⁻⁶. 14 m -2 The second phase particles have a size of 125 nm and a volume fraction of 7%.

[0040] Example 3: A method for preparing a high-strength aluminum alloy, comprising the following steps: Step 1: Preparation of non-spherical nano-alumina particles. The α-phase alumina raw material was placed in the grinding media and wet-milled using a planetary ball mill. The grinding media was zirconia balls with a ball-to-material mass ratio of 10:1. The grinding speed was 500 r / min and the grinding time was 15 h to obtain an alumina slurry with a particle size distribution of 50 nm. Step 2: Sorting of alumina particles. The alumina slurry is centrifuged at a speed of 12000 r / min for 30 min. The upper suspension is collected and then a pulsed electromagnetic field with a frequency of 100 kHz and a field strength of 3 T is applied to the upper suspension for screening to remove spherical and smooth particles, resulting in non-spherical nano-alumina particles with a surface roughness Ra of 10 nm. Step 3: Aluminum alloy smelting and casting. Magnesium ingots, zinc ingots, copper ingots, and aluminum ingots are mixed according to the mass fractions of Mg 4%, Zn 3%, Cu 1.5%, with the balance being aluminum. The mixture is placed in an electric resistance furnace and heated to 750°C to melt into a melt. Non-spherical nano-alumina particles are added at 2% of the total mass of the melt, along with 0.3% of the total mass of the melt. The mixture is stirred at 400 r / min for 20 min under argon protection, and then poured into a metal mold preheated to 300°C. After cooling to room temperature, the as-cast aluminum alloy is obtained. Step 4: Hot rolling and cold rolling processing. The cast aluminum alloy is hot rolled at 450℃ with a hot rolling deformation of 70%. Then it is cold rolled in 5 passes with a single pass deformation of 20% and a total cold rolling deformation of 60% to obtain cold rolled aluminum alloy sheet. Step 5: Solution treatment and aging treatment. The cold-rolled aluminum alloy sheet is heated to 520℃ and held for 3 hours for solution treatment, then water-quenched to room temperature, and then heated to 180℃ and held for 12 hours for aging treatment to obtain high-strength aluminum alloy.

[0041] In step one, the dispersant used in wet grinding is ammonium polyacrylate, the mass of which is 1% of the mass of the α-phase alumina raw material, the grinding medium is deionized water, and the solid-liquid mass ratio is 1:5.

[0042] In step two, the pulse width of the pulsed electromagnetic field is 50 μs, the pulse interval is 500 μs, the screening time is 60 min, and the suspension temperature is maintained at 20℃ during the screening process.

[0043] In step three, 0.15% of the total mass of the melt is added during the smelting process. The strontium is added in the form of an aluminum-strontium master alloy, in which the mass fraction of strontium is 15%.

[0044] In step three, a double-layer turbine impeller is used for stirring. The impeller diameter is 50% of the inner diameter of the melt container. During the stirring process, ultrasonic vibration is applied simultaneously. The ultrasonic frequency is 40kHz and the power is 1000W.

[0045] In step four, the cast aluminum alloy is homogenized before hot rolling. The homogenization temperature is 500℃ and the holding time is 24h. After homogenization, it is cooled to 450℃ in the furnace and then directly enters the hot rolling process.

[0046] In step four, emulsion cooling is used during the cold rolling process. The emulsion flow rate is 20L / min and the emulsion temperature is 30℃. After cold rolling, the aluminum alloy sheet is subjected to stress-relief annealing at a temperature of 250℃ and a holding time of 1-2 hours.

[0047] In step five, the solution treatment is carried out by heating in a salt bath. The salt bath consists of a mixed salt of 60 wt% potassium nitrate and 50 wt% sodium nitrite, and the heating rate is controlled at 10 °C / min.

[0048] In step five, after aging treatment, micro-arc oxidation treatment is performed on the surface of the aluminum alloy sheet. The micro-arc oxidation electrolyte is a silicate system, the voltage is 500V, the frequency is 100Hz, the treatment time is 30min, and the thickness of the micro-arc oxidation film is 15μm.

[0049] A high-strength aluminum alloy, the chemical composition of which, by mass fraction, is: magnesium 4%, zinc 3%, copper 1.5%, silicon ≤0.2%, iron ≤0.3%, titanium 0.15%, boron 0.05%, strontium 0.15%, oxygen ≤0.1%, with the balance being aluminum and unavoidable impurities; The microstructure of the high-strength aluminum alloy contains non-spherical alumina particles with a size of 50 nm distributed at the grain boundaries, a grain size of 15 μm, and an intragranular dislocation density of 5 × 10⁻⁶. 14 m -2 The second phase particles have a size of 200 nm and a volume fraction of 10%.

[0050] Comparative Example 1 differs from Example 1 in that: in step one, this comparative example did not use wet grinding to prepare non-spherical nano-alumina particles, but instead directly used commercially available spherical alumina powder.

[0051] Comparative Example 2 differs from Example 1 in that: in step two, no pulsed electromagnetic field was applied to screen non-spherical particles in this comparative example; the upper suspension was collected directly by centrifugation and used directly.

[0052] Comparative Example 3 differs from Example 1 in that: in step three, non-spherical nano-alumina particles were not added in this comparative example; only an aluminum-titanium-boron master alloy was added for melting and casting.

[0053] Comparative Example 4 differs from Example 1 in that: in step five, micro-arc oxidation was not performed in this comparative example; instead, samples were directly taken for testing after solid solution and aging treatment were completed.

[0054] The high-strength aluminum alloys prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests. The test items and test methods are as follows: Tensile strength was tested using a universal testing machine, and the tensile strength was recorded. The yield strength test is conducted using the same method as the tensile strength test, and the specified plastic elongation strength is recorded. The elongation test is conducted using the same method as the tensile strength test, and the elongation after fracture is recorded. Hardness testing was conducted using a Brinell hardness tester with a load of 187.5 kgf and a holding time of 30 seconds. Intergranular corrosion was tested using a sulfuric acid-copper sulfate solution immersion method, and the corrosion weight loss rate was calculated.

[0055] The test data of the high-strength aluminum alloys prepared in Examples 1-3 and Comparative Examples 1-4 are recorded in the table below:

[0056] By comparing and analyzing the data in the table, it can be seen that the high-strength aluminum alloys prepared by the processes in Examples 1-3 have significantly better performance than those prepared by the processes in Comparative Examples 1-4. This indicates that in this invention, non-spherical nano-alumina particles are obtained by wet grinding combined with pulsed electromagnetic field screening. The non-spherical structure enhances the interfacial bonding force with the aluminum matrix and hinders dislocation movement, thereby ensuring the strength improvement of the aluminum alloy. At the same time, it avoids the problem of weak interfacial bonding of traditional spherical particles and improves the stability of the material's mechanical properties. By introducing non-spherical nano-alumina particles as heterogeneous nucleation cores, combined with the synergistic effect of aluminum-titanium-boron intermediate alloys, the grain structure is refined and grain growth is inhibited, making the microstructure of the aluminum alloy more uniform and dense, ensuring the forming quality of the material in subsequent processing and reducing the risk of structural defects. By constructing a ceramic film layer on the material surface through micro-arc oxidation treatment, the surface micropores are sealed and the intrusion of corrosive media is blocked. At the same time, a strong metallurgical bond is formed with the matrix, giving the aluminum alloy both excellent wear resistance and corrosion resistance, ensuring the long-term service reliability of the material in complex environments.

[0057] By comparing and analyzing the relevant data in the table, it can be seen that the high-strength aluminum alloy prepared by this invention has high tensile strength, high yield strength, good plasticity and excellent corrosion resistance.

[0058] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0059] 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 preparing a high-strength aluminum alloy, characterized in that: Includes the following steps: Step 1: Preparation of non-spherical nano-alumina particles. The α-phase alumina raw material is placed in the grinding media and wet-milled using a planetary ball mill. The grinding media is zirconia balls, the ball-to-material mass ratio is 5-10:1, the grinding speed is 300-500 r / min, and the grinding time is 10-15 h, to obtain an alumina slurry with a particle size distribution of 20-50 nm. Step 2: Sorting of alumina particles. The alumina slurry is centrifuged at a speed of 8000-12000 r / min for 20-30 min. The upper suspension is collected and then a pulsed electromagnetic field with a frequency of 50-100 kHz and a field strength of 1-3 T is applied to the upper suspension for screening to remove spherical and smooth particles, resulting in non-spherical nano-alumina particles with a surface roughness Ra of 5-10 nm. Step 3: Aluminum alloy smelting and casting. Magnesium ingots, zinc ingots, copper ingots, and aluminum ingots are mixed according to the mass fractions of Mg 2-4%, Zn 1-3%, Cu 0.5-1.5%, with the balance being aluminum. The mixture is placed in a resistance furnace and heated to 700-750℃ to melt into a molten material. Non-spherical nano-alumina particles are added at 0.5-2% of the total mass of the molten material, along with 0.1-0.3% of an aluminum-titanium-boron master alloy. The mixture is stirred at 200-400 r / min for 10-20 min under argon protection. Then, it is poured into a metal mold preheated to 200-300℃ and cooled to room temperature to obtain the cast aluminum alloy. Step 4: Hot rolling and cold rolling processing. The cast aluminum alloy is hot rolled at 400-450℃ with a hot rolling deformation of 50-70%. Then it is cold rolled with 3-5 cold rolling passes, with a single pass deformation of 10-20% and a total cold rolling deformation of 40-60%, to obtain cold rolled aluminum alloy sheet. Step 5: Solution treatment and aging treatment. The cold-rolled aluminum alloy sheet is heated to 480-520℃ and held for 1-3 hours for solution treatment. Then it is water quenched to room temperature and heated to 120-180℃ and held for 8-12 hours for aging treatment to obtain high-strength aluminum alloy.

2. The method for preparing a high-strength aluminum alloy according to claim 1, characterized in that: In step one, the dispersant used in wet grinding is ammonium polyacrylate, the mass of which is 0.5-1% of the mass of the α-phase alumina raw material, the grinding medium is deionized water, and the solid-liquid mass ratio is 1:3-5.

3. The method for preparing a high-strength aluminum alloy according to claim 1, characterized in that: In step two, the pulse width of the pulsed electromagnetic field is 10-50 μs, the pulse interval is 100-500 μs, the screening time is 30-60 min, and the temperature of the suspension is maintained at 10-20℃ during the screening process.

4. The method for preparing a high-strength aluminum alloy according to claim 1, characterized in that: In step three, 0.05-0.15% of strontium is added during the smelting process. The strontium is added in the form of an aluminum-strontium master alloy, and the mass fraction of strontium in the aluminum-strontium master alloy is 10-15%.

5. The method for preparing a high-strength aluminum alloy according to claim 1, characterized in that: In step three, a double-layer turbine impeller is used for stirring. The impeller diameter is 33.3%-50% of the inner diameter of the melt container. During the stirring process, ultrasonic vibration is applied simultaneously. The ultrasonic frequency is 20-40kHz and the power is 500-1000W.

6. The method for preparing a high-strength aluminum alloy according to claim 1, characterized in that: In step four, the cast aluminum alloy is homogenized before hot rolling. The homogenization temperature is 450-500℃ and the holding time is 12-24h. After homogenization, it is cooled in the furnace to 400-450℃ and then directly enters the hot rolling process.

7. The method for preparing a high-strength aluminum alloy according to claim 1, characterized in that: In step four, emulsion cooling is used during cold rolling. The emulsion flow rate is 10-20 L / min and the emulsion temperature is 20-30℃. After cold rolling, the aluminum alloy sheet is subjected to stress-relief annealing at a temperature of 200-250℃ and a holding time of 1-2 hours.

8. The method for preparing a high-strength aluminum alloy according to claim 1, characterized in that: In step five, the solid solution treatment is carried out by salt bath heating. The salt bath composition is a mixed salt of 50-60 wt% potassium nitrate and 40-50 wt% sodium nitrite, and the heating rate is controlled at 5-10℃ / min.

9. The method for preparing a high-strength aluminum alloy according to claim 1, characterized in that: In step five, after aging treatment, micro-arc oxidation treatment is performed on the surface of the aluminum alloy sheet. The micro-arc oxidation electrolyte is a silicate system, the voltage is 300-500V, the frequency is 50-100Hz, the treatment time is 10-30min, and the thickness of the micro-arc oxidation film is 5-15μm.

10. A high-strength aluminum alloy, prepared by the method for preparing a high-strength aluminum alloy according to any one of claims 1-9, characterized in that: The chemical composition of the high-strength aluminum alloy, by mass fraction, is: magnesium 2-4%, zinc 1-3%, copper 0.5-1.5%, silicon ≤0.2%, iron ≤0.3%, titanium 0.05-0.15%, boron 0.01-0.05%, strontium 0.05-0.15%, oxygen ≤0.1%, with the balance being aluminum and unavoidable impurities; The high-strength aluminum alloy has a microstructure in which non-spherical alumina particles with a size of 20-50 nm are distributed at the grain boundaries, the grain size is 5-15 μm, and the intragranular dislocation density is 1×10⁻⁶. 14 -5×10 14 m -2 The second phase particles have a size of 50-200 nm and a volume fraction of 5-10%.

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