Aluminum alloy containing strontium and rare earth and method for manufacturing the same

Abstract

The application discloses an aluminum alloy containing strontium and rare earth and a preparation method thereof, and the aluminum alloy is prepared by mixing and smelting the following components in percentage by mass: Mg 4-5%, Mn 0.6-0.7%, Ni 0.3-0.4%, Si 0.2-0.3%, Zn 0.08-0.10%, Cu 0.05-0.07%, Ti 0.03-0.04%, Nb 0.03-0.04%, Zr 0.02-0.03%, Sc 0.02-0.03%, and the balance of Al and other inevitable impurities; the intermediate alloy powder and aluminum-coated graphene are added into the molten liquid, stirred and mixed uniformly, and ultrasonic treated to obtain an alloy liquid; the alloy liquid is refined and deslagged, and then subjected to low-pressure casting, hot rolling, cold rolling and surface treatment by using graphite powder to obtain the aluminum alloy; and the aluminum alloy is subjected to heat treatment under the condition of an alternating magnetic field, thereby obtaining the aluminum alloy. The aluminum alloy has excellent comprehensive performance and can meet the processing requirements of automobile load-bearing parts.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy material preparation technology, specifically relating to an aluminum alloy containing strontium and rare earth elements and its preparation method. Background Technology

[0002] With increasing environmental and energy pressures and the rapid development of the automotive industry, lightweighting has become a key research focus in automobile manufacturing. Lightweighting helps reduce energy consumption and environmental pollution, aligning with current energy conservation and environmental protection requirements.

[0003] Currently, replacing ferrous metals with aluminum alloys is the main approach to automotive lightweighting. With the lightweighting of non-load-bearing components approaching its limit, lightweighting of load-bearing components such as chassis and wheels has become the focus of current research.

[0004] Taking wheel hubs as an example, aluminum alloys offer advantages such as reduced non-load-bearing weight, improved grip, enhanced acceleration and braking, increased rigidity, reduced tire or wheel tilt during cornering, and improved cooling of the braking system. However, aluminum alloys also have disadvantages, including high brittleness, susceptibility to cracking, low surface hardness leading to easy wear, and lower strength compared to steel. Therefore, optimizing the performance of aluminum alloys is essential to meet the demands of heavy-duty automotive components.

[0005] Patent CN105695813B discloses a special aluminum alloy ingot for automobile wheels and its preparation method. During the casting process, Ti, Eu, and La are added, along with the synergistic effect of other elements such as Si, Mn, Cr, Mg, B, and Sr. This modifies and refines the microstructure of the aluminum alloy, resulting in smaller and more uniform grain sizes across different parts of the microstructure. When this aluminum alloy ingot is used to cast aluminum alloy wheels, the resulting wheels exhibit significantly improved tensile strength, yield strength, and elongation compared to traditional aluminum alloy wheel materials, greatly enhancing their mechanical properties. However, mechanical performance tests show that the yield strength and elongation of the resulting aluminum alloy wheels are only average, still failing to meet the requirements for heavy-duty automotive components.

[0006] Patent CN110195175B discloses a corrosion-resistant die-cast aluminum alloy for automobiles and its preparation method. It incorporates strontium and rare earth elements and is prepared through processes including melting, refining, settling, die casting, solution quenching, and aging. The aluminum alloy of this invention exhibits significantly improved corrosion resistance. However, the tensile strength of the aluminum alloy obtained by this patented technology is very average, making it difficult to meet the long-term service requirements of load-bearing automotive components.

[0007] Therefore, it is very important to obtain aluminum alloys with excellent overall performance that are suitable for load-bearing automotive components. Summary of the Invention

[0008] In view of the shortcomings of the existing technology, the purpose of this invention is to provide an aluminum alloy containing strontium and rare earth elements and a method for preparing the same.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing an aluminum alloy containing strontium and rare earth elements, the specific steps of which are as follows:

[0011] S1. Preparation of intermediate alloy powder containing strontium and rare earth: High-purity aluminum powder, high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, high-purity europium powder and high-purity boron powder are mixed and ball-milled to obtain mixed powder, cold-pressed into a compact, sintered to obtain intermediate alloy, crushed and sieved to obtain intermediate alloy powder.

[0012] S2. Using graphene and nano-aluminum powder as raw materials, aluminum-coated graphene is prepared;

[0013] S3. The following components are mixed and smelted in the indicated mass percentages to obtain a molten liquid: Mg 4-5%, Mn 0.6-0.7%, Ni 0.3-0.4%, Si 0.2-0.3%, Zn 0.08-0.10%, Cu 0.05-0.07%, Ti 0.03-0.04%, Nb 0.03-0.04%, Zr 0.02-0.03%, Sc 0.02-0.03%, with the balance being Al and other unavoidable impurities;

[0014] S4. Add intermediate alloy powder and aluminum-coated graphene to the molten metal, stir and mix, ultrasonically treat to obtain alloy liquid, refine and remove slag, low-pressure casting, hot rolling, cold rolling to obtain plate.

[0015] S5. The surface of the plate is treated with graphite powder, and then heat-treated under an alternating magnetic field to obtain the aluminum alloy.

[0016] Preferably, in step S1, the mass percentage of high-purity aluminum powder in the mixed powder is 85-90%, the molar ratio of high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, and high-purity europium powder is 10:1.5-2:0.8-1:0.8-1, and the ratio of the total molar amount of high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, and high-purity europium powder to the molar amount of high-purity boron powder is 1:6. The mass content of high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, and high-purity europium powder is 99.9% or higher, and the mass content of high-purity aluminum powder and high-purity boron powder is 99.99% or higher.

[0017] Preferably, in step S1, the average particle size of the high-purity aluminum powder, high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, high-purity europium powder, and high-purity boron powder is less than 10 μm.

[0018] Preferably, in step S1, 11mm diameter zirconia balls are used for ball milling, the ball-to-material ratio (mass) is 6-8:1, the ball milling speed is 50-70 r / min, and the ball milling time is 8-10 hours.

[0019] Preferably, in step S1, the blank is cold-pressed into a cylindrical shape with a diameter of 30 mm and a height of 40 mm, and the density is 70%.

[0020] Preferably, in step S1, the sintering conditions are as follows: heating at 30-40℃ / min to 500-600℃ and holding for 2-3 hours; heating at 5-10℃ / min to 850-900℃ and holding for 1-2 hours; cooling in the furnace to 750-800℃ and holding for 10-20 minutes; applying an axial pressure of 40-50MPa to the compact 20 seconds before the end of the holding period; and then allowing it to cool naturally to room temperature.

[0021] Preferably, in step S1, the particle size of the intermediate alloy powder is less than 10 μm.

[0022] Preferably, the specific method of step S2 is as follows: under argon protection, the nano-aluminum powder is subjected to low-temperature plasma treatment, then poured into an aqueous solution of dodecyltrimethylammonium bromide, subjected to ultrasonic oscillation treatment, centrifuged to collect the precipitate, washed with water, and dried to obtain pretreated nano-aluminum; then, under argon protection, the pretreated nano-aluminum and graphene are added to anhydrous ethanol, heated to reflux, kept at reflux for 8-10 hours, centrifuged to collect the precipitate, washed with water, dried, and vacuum sintered to obtain the aluminum-coated graphene.

[0023] More preferably, the particle size of the nano-aluminum powder is less than 20 μm.

[0024] More preferably, the mass ratio of nano-aluminum powder, graphene, and anhydrous ethanol is 1:8-10:50-60; the amount of dodecyltrimethylammonium bromide aqueous solution is 8-10 times the mass of nano-aluminum powder, and the concentration of dodecyltrimethylammonium bromide aqueous solution is 0.3-0.5 g / mL.

[0025] Further preferred, the ultrasonic oscillation treatment process conditions are: power 18-20kW, frequency 20-25kHz, and time 8-10 minutes.

[0026] Further preferred low-temperature plasma treatment conditions are: argon as the protective gas, gas flow rate of 80-100 mL / min, power of 40-50 W, and treatment time of 3-4 minutes.

[0027] Further preferred vacuum sintering conditions are: vacuum degree ≤ 10 -2 Pa, sintering temperature 570~600℃, sintering time 5~7 hours.

[0028] Preferably, in step S3, a resistance furnace is used for melting, with a melting temperature of 750-770°C and a melting time of 50-60 minutes.

[0029] Preferably, in step S4, the mass ratio of intermediate alloy powder, aluminum-coated graphene, and melt is 0.2-0.3:0.08-0.1:100.

[0030] Preferably, in step S4, the ultrasonic treatment conditions are: power 18-20kW, frequency 20-25kHz, and time 5-8 minutes.

[0031] Preferably, in step S4, the refining agent used during refining is sodium chloride, and its dosage is 0.3% of the mass of the alloy liquid; the refining conditions are: refining temperature of 720-730℃, refining time of 10-12 minutes, and standing for 20-30 minutes.

[0032] Preferably, in step S4, the low-pressure casting conditions are as follows:

[0033] (A) Lifting stage: Lifting pressure 0.025~0.027MPa, lifting speed 2~2.5kPa / s;

[0034] (B) Filling stage: Filling pressure 0.06~0.07MPa, filling speed 1.2~1.5kPa / s, until the cavity is completely filled;

[0035] (C) Crystallization pressurization stage: pressurize to 0.8-0.9 MPa at a pressurization rate of 4-5 kPa / s;

[0036] (D) Crystallization holding pressure stage: Hold pressure for 25–35 s under conditions (C);

[0037] (E) Secondary pressurization stage: pressurize to 1.1-1.2 MPa at a pressurization rate of 0.6-0.8 kPa / s;

[0038] (F) Pressure holding stage: Hold pressure for 15–25 seconds under conditions (E);

[0039] (G) Release the pressure, open the mold and take out the casting.

[0040] Preferably, in step S4, the initial temperature of hot rolling is 520-550°C, the final rolling temperature is 260-280°C, and air cooling is performed after hot rolling.

[0041] Preferably, in step S4, a cold-rolled sheet with a thickness of 5-10 mm is obtained by multiple cold rolling passes.

[0042] Preferably, in step S5, the specific method for surface treatment of the plate using graphite powder is as follows: two oxygen-free copper plates are respectively covered with the plate, with the sides of the plates facing each other to form two electrodes; an alternating electric field with an alternating frequency of 0.5 to 0.8 MHz and an alternating current of 8 to 10 A is provided between the two electrodes; high-purity graphite powder (mass content of 99.9% or more) with a particle size of less than 10 μm is atomized with high-pressure airflow and sprayed between the two electrodes; after spraying, the plate can be removed; the amount of graphite powder used per square meter of plate is 10 to 15 g.

[0043] Further preferred high-pressure gas atomization conditions are: high-pressure gas nozzle pressure 8-10 MPa, and outlet velocity 20-22 m / s.

[0044] Preferably, in step S5, the alternating magnetic field processing conditions are: frequency 200-300kHz, magnetic field strength 1200-1300mT.

[0045] Preferably, in step S5, the heat treatment conditions are as follows: heat up to 350-380°C at 25-30°C / min and hold for 2-3 hours; heat up to 550-570°C at 5-7°C / min and hold for 3-4 hours; cool down to 420-450°C at 12-15°C / min and hold for 1-2 hours, then allow to cool naturally to room temperature.

[0046] Secondly, this invention claims protection for an aluminum alloy containing strontium and rare earth elements, obtained by the aforementioned preparation method.

[0047] Thirdly, the present invention provides the application of the aforementioned strontium- and rare earth-containing aluminum alloys in the processing of automotive load-bearing components.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] This invention provides an aluminum alloy containing strontium and rare earth elements and its preparation method. The alloy is prepared by mixing and melting the following components in the indicated mass percentages: Mg 4-5%, Mn 0.6-0.7%, Ni 0.3-0.4%, Si 0.2-0.3%, Zn 0.08-0.10%, Cu 0.05-0.07%, Ti 0.03-0.04%, Nb 0.03-0.04%, Zr 0.02-0.03%, Sc 0.02-0.03%, with the balance being Al and other unavoidable impurities. Intermediate alloy powder and aluminum-coated graphene are added to the melt, stirred and mixed, and ultrasonically treated to obtain an alloy liquid. This liquid is then refined to remove slag, low-pressure cast, hot-rolled, and cold-rolled to obtain a sheet metal. The sheet metal is then surface-treated with graphite powder and heat-treated under an alternating magnetic field to obtain the aluminum alloy. The aluminum alloy obtained by this invention exhibits excellent comprehensive properties and can meet the processing requirements of automotive load-bearing components.

[0050] This invention involves ball milling a mixture of high-purity aluminum powder, high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, high-purity europium powder, and high-purity boron powder to obtain a mixed powder. This powder is then cold-pressed into a compact, sintered, and pulverized and sieved to obtain a master alloy powder. This invention introduces strontium and rare earth elements into the master alloy powder, reducing losses and facilitating better mixing with other components, thereby improving the properties of the aluminum alloy.

[0051] This invention further utilizes graphene and nano-aluminum powder as raw materials to prepare aluminum-coated graphene. Aluminum-coated graphene exhibits good dispersibility in the system, promoting further improvement in the properties of aluminum alloys.

[0052] After obtaining the sheet material, this invention further treats the surface of the sheet material with graphite powder. Under the action of an electric current, the graphite powder explodes and decomposes into graphene. Simultaneously, under the instantaneous high temperature and pressure conditions of the explosion, the aluminum alloy on the surface of the sheet material composites with the graphene, thereby optimizing and improving the performance of the sheet material. Next, heat treatment is performed under alternating magnetic field conditions to further optimize the microstructure of the sheet material, which is beneficial to further improving the performance of the aluminum alloy. Detailed Implementation

[0053] 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 a part of the embodiments of the present invention, and not all of the 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.

[0054] Unless otherwise specified, all products in this invention were purchased through market channels.

[0055] Example 1

[0056] A method for preparing an aluminum alloy containing strontium and rare earth elements, comprising the following specific steps:

[0057] S1. Preparation of intermediate alloy powder containing strontium and rare earth: High-purity aluminum powder, high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, high-purity europium powder and high-purity boron powder are mixed and ball-milled to obtain mixed powder, cold-pressed into a compact, sintered to obtain intermediate alloy, crushed and sieved to obtain intermediate alloy powder.

[0058] S2. Using graphene and nano-aluminum powder as raw materials, aluminum-coated graphene is prepared;

[0059] S3. The following components are mixed and smelted in the following mass percentages to obtain a melt: Mg 4%, Mn 0.6%, Ni 0.3%, Si 0.2%, Zn 0.08%, Cu 0.05%, Ti 0.03%, Nb 0.03%, Zr 0.02%, Sc 0.02%, with the balance being Al and other unavoidable impurities;

[0060] S4. Add intermediate alloy powder and aluminum-coated graphene to the molten metal, stir and mix, ultrasonically treat to obtain alloy liquid, refine and remove slag, low-pressure casting, hot rolling, cold rolling to obtain plate.

[0061] S5. The surface of the plate is treated with graphite powder, and then heat-treated under an alternating magnetic field to obtain the aluminum alloy.

[0062] In step S1, the mass percentage of high-purity aluminum powder in the mixed powder is 85%, and the molar ratio of high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, and high-purity europium powder is 10:1.5:0.8:0.8. The ratio of the total molar amount of high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, and high-purity europium powder to the molar amount of high-purity boron powder is 1:6. The mass content of high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, and high-purity europium powder is above 99.9%, and the mass content of high-purity aluminum powder and high-purity boron powder is above 99.99%.

[0063] In step S1, the average particle size of the high-purity aluminum powder, high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, high-purity europium powder, and high-purity boron powder is less than 10 μm.

[0064] In step S1, 11mm diameter zirconia balls are used for ball milling, the ball-to-material ratio (mass) is 6:1, the ball milling speed is 50r / min, and the ball milling time is 8 hours.

[0065] In step S1, the blank is cold-pressed into a cylindrical blank with a diameter of 30 mm and a height of 40 mm, and the density is 70%.

[0066] In step S1, the sintering conditions are as follows: heat up to 500℃ at 30℃ / min and hold for 2 hours; heat up to 850℃ at 5℃ / min and hold for 1 hour; cool down to 750℃ in the furnace and hold for 10 minutes; apply an axial pressure of 40MPa to the compact 20 seconds before the end of the holding period, and then allow it to cool naturally to room temperature.

[0067] In step S1, the particle size of the intermediate alloy powder is less than 10 μm.

[0068] The specific method of step S2 is as follows: under argon protection, the nano-aluminum powder is subjected to low-temperature plasma treatment, then poured into an aqueous solution of dodecyltrimethylammonium bromide, subjected to ultrasonic oscillation treatment, centrifuged to collect the precipitate, washed with water, and dried to obtain pretreated nano-aluminum; then, under argon protection, the pretreated nano-aluminum and graphene are added to anhydrous ethanol, heated to reflux, kept at reflux for 8 hours, centrifuged to collect the precipitate, washed with water, dried, and vacuum sintered to obtain the aluminum-coated graphene.

[0069] The particle size of the nano-aluminum powder is less than 20 μm.

[0070] The mass ratio of nano-aluminum powder, graphene, and anhydrous ethanol is 1:8:50; the amount of dodecyltrimethylammonium bromide aqueous solution used is 8 times the mass of nano-aluminum powder, and the concentration of dodecyltrimethylammonium bromide aqueous solution is 0.3 g / mL.

[0071] The ultrasonic oscillation treatment process conditions are: power 18kW, frequency 20kHz, and time 8 minutes.

[0072] The low-temperature plasma treatment conditions are as follows: argon as the protective gas, gas flow rate of 80 mL / min, power of 40 W, and treatment time of 3 minutes.

[0073] Vacuum sintering conditions are: vacuum degree ≤ 10 -2 Pa, sintering temperature 570℃, sintering time 5 hours.

[0074] In step S3, a resistance furnace is used for melting, with a melting temperature of 750°C and a melting time of 50 minutes.

[0075] In step S4, the mass ratio of intermediate alloy powder, aluminum-coated graphene, and melt is 0.2:0.08:100.

[0076] In step S4, the ultrasonic treatment conditions are: power 18kW, frequency 20kHz, and time 5 minutes.

[0077] In step S4, the refining agent used during refining is sodium chloride, and its dosage is 0.3% of the mass of the alloy liquid; the refining conditions are: refining temperature of 720℃, refining time of 10 minutes, and standing for 20 minutes.

[0078] In step S4, the low-pressure casting conditions are as follows:

[0079] (A) Lifting stage: Lifting pressure 0.025MPa, lifting rate 2kPa / s;

[0080] (B) Filling stage: Filling pressure 0.06MPa, filling speed 1.2kPa / s, until the cavity is completely filled;

[0081] (C) Crystallization pressurization stage: pressurize to 0.8 MPa at a pressurization rate of 4 kPa / s;

[0082] (D) Crystallization holding pressure stage: Hold pressure for 25 seconds under condition (C);

[0083] (E) Secondary pressurization stage: pressurize to 1.1 MPa at a pressurization rate of 0.6 kPa / s;

[0084] (F) Pressure holding stage: Hold pressure for 15 seconds under condition (E);

[0085] (G) Release the pressure, open the mold and take out the casting.

[0086] In step S4, the initial temperature of hot rolling is 520℃, the final rolling temperature is 260℃, and air cooling is performed after hot rolling is completed.

[0087] In step S4, a cold-rolled sheet with a thickness of 10mm is obtained through multiple cold rolling passes.

[0088] In step S5, the specific method for surface treatment of the board using graphite powder is as follows: the board is covered on the surface of two oxygen-free copper plates respectively, with the sides of the board facing each other to form two electrodes; an alternating electric field with an alternating frequency of 0.5MHz and an alternating current of 8A is provided between the two electrodes; high-purity graphite powder (mass content above 99.9%) with a particle size of less than 10μm is atomized with high-pressure airflow and sprayed between the two electrodes. After spraying, the board can be removed; the amount of graphite powder used per square meter of board is 10g.

[0089] The high-pressure gas atomization conditions are: high-pressure gas nozzle pressure 8MPa, outlet velocity 20m / s.

[0090] In step S5, the alternating magnetic field processing conditions are: frequency 200kHz, magnetic field strength 1200mT.

[0091] In step S5, the heat treatment conditions are as follows: heat up to 350℃ at 25℃ / min and hold for 2 hours; heat up to 550℃ at 5℃ / min and hold for 3 hours; cool down to 420℃ at 12℃ / min and hold for 1 hour, then allow to cool naturally to room temperature.

[0092] Example 2

[0093] A method for preparing an aluminum alloy containing strontium and rare earth elements, comprising the following specific steps:

[0094] S1. Preparation of intermediate alloy powder containing strontium and rare earth: High-purity aluminum powder, high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, high-purity europium powder and high-purity boron powder are mixed and ball-milled to obtain mixed powder, cold-pressed into a compact, sintered to obtain intermediate alloy, crushed and sieved to obtain intermediate alloy powder.

[0095] S2. Using graphene and nano-aluminum powder as raw materials, aluminum-coated graphene is prepared;

[0096] S3. The following components are mixed and smelted in the following mass percentages to obtain a melt: Mg 5%, Mn 0.7%, Ni 0.4%, Si 0.3%, Zn 0.10%, Cu 0.07%, Ti 0.04%, Nb 0.04%, Zr 0.03%, Sc 0.03%, with the balance being Al and other unavoidable impurities;

[0097] S4. Add intermediate alloy powder and aluminum-coated graphene to the molten metal, stir and mix, ultrasonically treat to obtain alloy liquid, refine and remove slag, low-pressure casting, hot rolling, cold rolling to obtain plate.

[0098] S5. The surface of the plate is treated with graphite powder, and then heat-treated under an alternating magnetic field to obtain the aluminum alloy.

[0099] In step S1, the mass percentage of high-purity aluminum powder in the mixed powder is 90%, and the molar ratio of high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, and high-purity europium powder is 10:2:1:1. The ratio of the total molar amount of high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, and high-purity europium powder to the molar amount of high-purity boron powder is 1:6. The mass content of high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, and high-purity europium powder is above 99.9%, and the mass content of high-purity aluminum powder and high-purity boron powder is above 99.99%.

[0100] In step S1, the average particle size of the high-purity aluminum powder, high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, high-purity europium powder, and high-purity boron powder is less than 10 μm.

[0101] In step S1, 11mm diameter zirconia balls are used for ball milling, the ball-to-material ratio (mass) is 8:1, the ball milling speed is 70r / min, and the ball milling time is 10 hours.

[0102] In step S1, the blank is cold-pressed into a cylindrical blank with a diameter of 30 mm and a height of 40 mm, and the density is 70%.

[0103] In step S1, the sintering conditions are as follows: heat up to 600℃ at 40℃ / min and hold for 3 hours; heat up to 900℃ at 10℃ / min and hold for 2 hours; cool down to 800℃ in the furnace and hold for 20 minutes; apply an axial pressure of 50MPa to the compact 20 seconds before the end of the holding period, and then allow it to cool naturally to room temperature.

[0104] In step S1, the particle size of the intermediate alloy powder is less than 10 μm.

[0105] The specific method of step S2 is as follows: under argon protection, the nano-aluminum powder is subjected to low-temperature plasma treatment, then poured into an aqueous solution of dodecyltrimethylammonium bromide, subjected to ultrasonic oscillation treatment, centrifuged to collect the precipitate, washed with water, and dried to obtain pretreated nano-aluminum; then, under argon protection, the pretreated nano-aluminum and graphene are added to anhydrous ethanol, heated to reflux, kept at reflux for 10 hours, centrifuged to collect the precipitate, washed with water, dried, and vacuum sintered to obtain the aluminum-coated graphene.

[0106] The particle size of the nano-aluminum powder is less than 20 μm.

[0107] The mass ratio of nano-aluminum powder, graphene, and anhydrous ethanol is 1:10:60; the amount of dodecyltrimethylammonium bromide aqueous solution used is 10 times the mass of nano-aluminum powder, and the concentration of dodecyltrimethylammonium bromide aqueous solution is 0.5 g / mL.

[0108] The process conditions for ultrasonic oscillation treatment are: power 20kW, frequency 25kHz, and time 10 minutes.

[0109] The low-temperature plasma treatment conditions were as follows: argon as the protective gas, gas flow rate of 100 mL / min, power of 50 W, and treatment time of 4 minutes.

[0110] Vacuum sintering conditions are: vacuum degree ≤ 10 -2 Pa, sintering temperature 600℃, sintering time 7 hours.

[0111] In step S3, a resistance furnace is used for melting, with a melting temperature of 770°C and a melting time of 60 minutes.

[0112] In step S4, the mass ratio of intermediate alloy powder, aluminum-coated graphene, and melt is 0.3:0.1:100.

[0113] In step S4, the ultrasonic treatment conditions are: power 20kW, frequency 25kHz, and time 8 minutes.

[0114] In step S4, the refining agent used during refining is sodium chloride, and its dosage is 0.3% of the mass of the alloy liquid; the refining conditions are: refining temperature of 730℃, refining time of 12 minutes, and standing for 30 minutes.

[0115] In step S4, the low-pressure casting conditions are as follows:

[0116] (A) Lifting stage: Lifting pressure 0.027MPa, lifting rate 2.5kPa / s;

[0117] (B) Filling stage: Filling pressure 0.07MPa, filling speed 1.5kPa / s, until the cavity is completely filled;

[0118] (C) Crystallization pressurization stage: pressurize to 0.9 MPa at a pressurization rate of 5 kPa / s;

[0119] (D) Crystallization and holding pressure stage: Hold pressure for 35 seconds under condition (C);

[0120] (E) Secondary pressurization stage: pressurize to 1.2 MPa at a pressurization rate of 0.8 kPa / s;

[0121] (F) Pressure holding stage: Hold pressure for 25 seconds under condition (E);

[0122] (G) Release the pressure, open the mold and take out the casting.

[0123] In step S4, the initial temperature of hot rolling is 550℃, the final rolling temperature is 280℃, and air cooling is performed after hot rolling is completed.

[0124] In step S4, a cold-rolled sheet with a thickness of 10mm is obtained through multiple cold rolling passes.

[0125] In step S5, the specific method for surface treatment of the board using graphite powder is as follows: the board is covered on the surface of two oxygen-free copper plates respectively, with the sides of the board facing each other to form two electrodes; an alternating electric field with an alternating frequency of 0.8MHz and an alternating current of 10A is provided between the two electrodes; high-purity graphite powder (mass content above 99.9%) with a particle size of less than 10μm is atomized with high-pressure airflow and sprayed between the two electrodes. After spraying, the board can be removed; the amount of graphite powder used per square meter of board is 15g.

[0126] The high-pressure gas atomization conditions are: high-pressure gas nozzle pressure 10MPa, outlet velocity 22m / s.

[0127] In step S5, the alternating magnetic field processing conditions are: frequency 300kHz, magnetic field strength 1300mT.

[0128] In step S5, the heat treatment conditions are as follows: heat up to 380℃ at 30℃ / min and hold for 3 hours; heat up to 570℃ at 7℃ / min and hold for 4 hours; cool down to 450℃ at 15℃ / min and hold for 2 hours, then allow to cool naturally to room temperature.

[0129] Example 3

[0130] A method for preparing an aluminum alloy containing strontium and rare earth elements, comprising the following specific steps:

[0131] S1. Preparation of intermediate alloy powder containing strontium and rare earth: High-purity aluminum powder, high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, high-purity europium powder and high-purity boron powder are mixed and ball-milled to obtain mixed powder, cold-pressed into a compact, sintered to obtain intermediate alloy, crushed and sieved to obtain intermediate alloy powder.

[0132] S2. Using graphene and nano-aluminum powder as raw materials, aluminum-coated graphene is prepared;

[0133] S3. The following components are mixed and smelted in the indicated mass percentages to obtain a molten liquid: Mg 4.5%, Mn 0.65%, Ni 0.35%, Si 0.25%, Zn 0.09%, Cu 0.06%, Ti 0.04%, Nb 0.03%, Zr 0.02%, Sc 0.02%, with the balance being Al and other unavoidable impurities;

[0134] S4. Add intermediate alloy powder and aluminum-coated graphene to the molten metal, stir and mix, ultrasonically treat to obtain alloy liquid, refine and remove slag, low-pressure casting, hot rolling, cold rolling to obtain plate.

[0135] S5. The surface of the plate is treated with graphite powder, and then heat-treated under an alternating magnetic field to obtain the aluminum alloy.

[0136] In step S1, the mass percentage of high-purity aluminum powder in the mixed powder is 88%, and the molar ratio of high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, and high-purity europium powder is 10:1.7:0.9:0.9. The ratio of the total molar amount of high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, and high-purity europium powder to the molar amount of high-purity boron powder is 1:6. The mass content of high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, and high-purity europium powder is above 99.9%, and the mass content of high-purity aluminum powder and high-purity boron powder is above 99.99%.

[0137] In step S1, the average particle size of the high-purity aluminum powder, high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, high-purity europium powder, and high-purity boron powder is less than 10 μm.

[0138] In step S1, 11mm diameter zirconia balls are used for ball milling, the ball-to-material ratio (mass) is 7:1, the ball milling speed is 60r / min, and the ball milling time is 9 hours.

[0139] In step S1, the blank is cold-pressed into a cylindrical blank with a diameter of 30 mm and a height of 40 mm, and the density is 70%.

[0140] In step S1, the sintering conditions are as follows: heat up to 550°C at 35°C / min and hold for 2.5 hours; heat up to 880°C at 8°C / min and hold for 1.5 hours; cool down to 780°C in the furnace and hold for 15 minutes; apply an axial pressure of 45MPa to the compact 20 seconds before the end of the holding period, and then allow it to cool naturally to room temperature.

[0141] In step S1, the particle size of the intermediate alloy powder is less than 10 μm.

[0142] The specific method of step S2 is as follows: under argon protection, the nano-aluminum powder is subjected to low-temperature plasma treatment, then poured into an aqueous solution of dodecyltrimethylammonium bromide, subjected to ultrasonic oscillation treatment, centrifuged to collect the precipitate, washed with water, and dried to obtain pretreated nano-aluminum; then, under argon protection, the pretreated nano-aluminum and graphene are added to anhydrous ethanol, heated to reflux, kept at reflux for 9 hours, centrifuged to collect the precipitate, washed with water, dried, and vacuum sintered to obtain the aluminum-coated graphene.

[0143] The particle size of the nano-aluminum powder is less than 20 μm.

[0144] The mass ratio of nano-aluminum powder, graphene, and anhydrous ethanol is 1:9:55; the amount of dodecyltrimethylammonium bromide aqueous solution used is 9 times the mass of nano-aluminum powder, and the concentration of dodecyltrimethylammonium bromide aqueous solution is 0.4 g / mL.

[0145] The ultrasonic oscillation treatment process conditions are: power 19kW, frequency 22kHz, and time 9 minutes.

[0146] The low-temperature plasma treatment conditions were as follows: argon as the protective gas, gas flow rate of 90 mL / min, power of 45 W, and treatment time of 4 minutes.

[0147] Vacuum sintering conditions are: vacuum degree ≤ 10 -2 Pa, sintering temperature 580℃, sintering time 6 hours.

[0148] In step S3, a resistance furnace is used for melting, with a melting temperature of 760°C and a melting time of 55 minutes.

[0149] In step S4, the mass ratio of intermediate alloy powder, aluminum-coated graphene, and melt is 0.2:0.09:100.

[0150] In step S4, the ultrasonic treatment conditions are: power 19kW, frequency 22kHz, and time 7 minutes.

[0151] In step S4, the refining agent used during refining is sodium chloride, and its dosage is 0.3% of the mass of the alloy liquid; the refining conditions are: refining temperature of 725℃, refining time of 11 minutes, and standing for 25 minutes.

[0152] In step S4, the low-pressure casting conditions are as follows:

[0153] (A) Lifting stage: Lifting pressure 0.026MPa, lifting rate 2.2kPa / s;

[0154] (B) Filling stage: Filling pressure 0.06MPa, filling speed 1.4kPa / s, until the cavity is completely filled;

[0155] (C) Crystallization pressurization stage: pressurize to 0.9 MPa at a pressurization rate of 4 kPa / s;

[0156] (D) Crystallization and holding pressure stage: Hold pressure for 30 seconds under condition (C);

[0157] (E) Secondary pressurization stage: pressurize to 1.1 MPa at a pressurization rate of 0.7 kPa / s;

[0158] (F) Pressure holding stage: Hold pressure for 20 seconds under condition (E);

[0159] (G) Release the pressure, open the mold and take out the casting.

[0160] In step S4, the initial temperature of hot rolling is 530℃, the final rolling temperature is 270℃, and air cooling is performed after hot rolling.

[0161] In step S4, a cold-rolled sheet with a thickness of 10mm is obtained through multiple cold rolling passes.

[0162] In step S5, the specific method for surface treatment of the board using graphite powder is as follows: the board is covered on the surface of two oxygen-free copper plates respectively, with the sides of the board facing each other to form two electrodes; an alternating electric field with an alternating frequency of 0.6MHz and an alternating current of 9A is provided between the two electrodes; high-purity graphite powder (mass content above 99.9%) with a particle size of less than 10μm is atomized with high-pressure airflow and sprayed between the two electrodes. After spraying, the board can be removed; the amount of graphite powder used per square meter of board is 12g.

[0163] The high-pressure gas atomization conditions are: high-pressure gas nozzle pressure 9MPa, outlet velocity 21m / s.

[0164] In step S5, the alternating magnetic field processing conditions are: frequency 300kHz, magnetic field strength 1250mT.

[0165] In step S5, the heat treatment conditions are as follows: heat up to 360°C at 27°C / min and hold for 2 hours; heat up to 560°C at 6°C / min and hold for 3 hours; cool down to 440°C at 14°C / min and hold for 1.5 hours, then allow to cool naturally to room temperature.

[0166] Comparative Example 1

[0167] A method for preparing an aluminum alloy containing strontium and rare earth elements, comprising the following specific steps:

[0168] S1. Preparation of mixed powder containing strontium and rare earth elements: High-purity aluminum powder, high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, high-purity europium powder, and high-purity boron powder are mixed and ball-milled to obtain mixed powder;

[0169] S2. Using graphene and nano-aluminum powder as raw materials, aluminum-coated graphene is prepared;

[0170] S3. The following components are mixed and smelted in the following mass percentages to obtain a melt: Mg 4%, Mn 0.6%, Ni 0.3%, Si 0.2%, Zn 0.08%, Cu 0.05%, Ti 0.03%, Nb 0.03%, Zr 0.02%, Sc 0.02%, with the balance being Al and other unavoidable impurities;

[0171] S4. Add the mixed powder and aluminum-coated graphene to the molten metal, stir and mix well, ultrasonically treat to obtain alloy liquid, refine and remove slag, low-pressure casting, hot rolling, cold rolling to obtain plate;

[0172] S5. The surface of the plate is treated with graphite powder, and then heat-treated under an alternating magnetic field to obtain the aluminum alloy.

[0173] In step S1, the mass percentage of high-purity aluminum powder in the mixed powder is 85%, and the molar ratio of high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, and high-purity europium powder is 10:1.5:0.8:0.8. The ratio of the total molar amount of high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, and high-purity europium powder to the molar amount of high-purity boron powder is 1:6. The mass content of high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, and high-purity europium powder is above 99.9%, and the mass content of high-purity aluminum powder and high-purity boron powder is above 99.99%.

[0174] In step S1, the average particle size of the high-purity aluminum powder, high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, high-purity europium powder, and high-purity boron powder is less than 10 μm.

[0175] In step S1, 11mm diameter zirconia balls are used for ball milling, the ball-to-material ratio (mass) is 6:1, the ball milling speed is 50r / min, and the ball milling time is 8 hours.

[0176] The specific method of step S2 is as follows: under argon protection, the nano-aluminum powder is subjected to low-temperature plasma treatment, then poured into an aqueous solution of dodecyltrimethylammonium bromide, subjected to ultrasonic oscillation treatment, centrifuged to collect the precipitate, washed with water, and dried to obtain pretreated nano-aluminum; then, under argon protection, the pretreated nano-aluminum and graphene are added to anhydrous ethanol, heated to reflux, kept at reflux for 8 hours, centrifuged to collect the precipitate, washed with water, dried, and vacuum sintered to obtain the aluminum-coated graphene.

[0177] The particle size of the nano-aluminum powder is less than 20 μm.

[0178] The mass ratio of nano-aluminum powder, graphene, and anhydrous ethanol is 1:8:50; the amount of dodecyltrimethylammonium bromide aqueous solution used is 8 times the mass of nano-aluminum powder, and the concentration of dodecyltrimethylammonium bromide aqueous solution is 0.3 g / mL.

[0179] The ultrasonic oscillation treatment process conditions are: power 18kW, frequency 20kHz, and time 8 minutes.

[0180] The low-temperature plasma treatment conditions are as follows: argon as the protective gas, gas flow rate of 80 mL / min, power of 40 W, and treatment time of 3 minutes.

[0181] Vacuum sintering conditions are: vacuum degree ≤ 10 -2 Pa, sintering temperature 570℃, sintering time 5 hours.

[0182] In step S3, a resistance furnace is used for melting, with a melting temperature of 750°C and a melting time of 50 minutes.

[0183] In step S4, the mass ratio of the mixed powder, aluminum-coated graphene, and melt is 0.2:0.08:100.

[0184] In step S4, the ultrasonic treatment conditions are: power 18kW, frequency 20kHz, and time 5 minutes.

[0185] In step S4, the refining agent used during refining is sodium chloride, and its dosage is 0.3% of the mass of the alloy liquid; the refining conditions are: refining temperature of 720℃, refining time of 10 minutes, and standing for 20 minutes.

[0186] In step S4, the low-pressure casting conditions are as follows:

[0187] (A) Lifting stage: Lifting pressure 0.025MPa, lifting rate 2kPa / s;

[0188] (B) Filling stage: Filling pressure 0.06MPa, filling speed 1.2kPa / s, until the cavity is completely filled;

[0189] (C) Crystallization pressurization stage: pressurize to 0.8 MPa at a pressurization rate of 4 kPa / s;

[0190] (D) Crystallization holding pressure stage: Hold pressure for 25 seconds under condition (C);

[0191] (E) Secondary pressurization stage: pressurize to 1.1 MPa at a pressurization rate of 0.6 kPa / s;

[0192] (F) Pressure holding stage: Hold pressure for 15 seconds under condition (E);

[0193] (G) Release the pressure, open the mold and take out the casting.

[0194] In step S4, the initial temperature of hot rolling is 520℃, the final rolling temperature is 260℃, and air cooling is performed after hot rolling is completed.

[0195] In step S4, a cold-rolled sheet with a thickness of 10mm is obtained through multiple cold rolling passes.

[0196] In step S5, the specific method for surface treatment of the board using graphite powder is as follows: the board is covered on the surface of two oxygen-free copper plates respectively, with the sides of the board facing each other to form two electrodes; an alternating electric field with an alternating frequency of 0.5MHz and an alternating current of 8A is provided between the two electrodes; high-purity graphite powder (mass content above 99.9%) with a particle size of less than 10μm is atomized with high-pressure airflow and sprayed between the two electrodes. After spraying, the board can be removed; the amount of graphite powder used per square meter of board is 10g.

[0197] The high-pressure gas atomization conditions are: high-pressure gas nozzle pressure 8MPa, outlet velocity 20m / s.

[0198] In step S5, the alternating magnetic field processing conditions are: frequency 200kHz, magnetic field strength 1200mT.

[0199] In step S5, the heat treatment conditions are as follows: heat up to 350℃ at 25℃ / min and hold for 2 hours; heat up to 550℃ at 5℃ / min and hold for 3 hours; cool down to 420℃ at 12℃ / min and hold for 1 hour, then allow to cool naturally to room temperature.

[0200] Comparative Example 2

[0201] Aluminum-coated graphene is omitted;

[0202] The rest is the same as in Example 1.

[0203] Comparative Example 3

[0204] Step S5 omits the surface treatment of the board using graphite powder;

[0205] The rest is the same as in Example 1.

[0206] Comparative Example 4

[0207] Step S5 omits the alternating magnetic field condition;

[0208] The rest is the same as in Example 1.

[0209] Test case

[0210] The aluminum alloys obtained in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests, including:

[0211] 1. Elongation and yield strength test: The test was conducted using an electronic universal testing machine (DM8000-B, Yangzhou Dongming Testing Instruments).

[0212] 2. Wear resistance: Refer to GB / T 12444-2006 "Metallic Materials Wear Test Methods - Test Ring-Block Sliding Wear Test" to test wear resistance (the test block is a cube with a side length of 10mm).

[0213] 3. Hardness: Refer to GB / T 231.1-2018 "Metallic materials - Brinell hardness test - Part 1: Test method" to test the hardness.

[0214] The test results are shown in Table 1.

[0215] Table 1. Performance test results of aluminum alloy materials

[0216] Elongation (%) Yield strength (MPa) <![CDATA[Volume wear (mm 3 )]]> Hardness (HB) Example 1 17.6 390 0.117 162 Example 2 17.6 392 0.115 163 Example 3 17.8 395 0.105 166 Comparative Example 1 16.5 375 0.189 148 Comparative Example 2 15.6 362 0.229 130 Comparative Example 3 16.4 380 0.204 124 Comparative Example 4 16.5 377 0.192 150

[0217] As shown in Table 1, the aluminum alloys obtained in Examples 1 to 3 have excellent mechanical properties, good wear resistance, and high hardness, making them suitable for processing automotive load-bearing components.

[0218] In Comparative Example 1, a mixed powder obtained by ball milling high-purity aluminum powder, high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, high-purity europium powder, and high-purity boron powder was directly added. In Comparative Example 2, aluminum-coated graphene was omitted. In Comparative Example 3, surface treatment of the plate was omitted. In Comparative Example 4, alternating magnetic field conditions were omitted. The mechanical properties of the resulting aluminum alloys were significantly worse, and the wear resistance and hardness were also significantly worse. This shows that the present invention improves the microstructure of aluminum alloys and promotes the improvement of aluminum alloy performance by adding strontium and rare earth elements in a specific way, adding aluminum-coated graphene, and performing specific post-treatment of the plate.

[0219] The present invention has been illustrated through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of individual raw materials in the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing an aluminum alloy containing strontium and rare earth elements, characterized in that, The specific steps are as follows: S1. Preparation of intermediate alloy powder containing strontium and rare earth elements: High-purity aluminum powder, high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, high-purity europium powder, and high-purity boron powder are mixed and ball-milled to obtain a mixed powder, which is then cold-pressed into a compact, sintered, and pulverized and sieved to obtain intermediate alloy powder; the mass percentage of high-purity aluminum powder in the mixed powder is 85-90%, the molar ratio of high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, and high-purity europium powder is 10:1.5-2:0.8-1:0.8-1, and the ratio of the total molar amount of high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, and high-purity europium powder to the molar amount of high-purity boron powder is 1:6; S2. Using graphene and nano-aluminum powder as raw materials, aluminum-coated graphene is prepared; S3. The following components are mixed and smelted in the indicated mass percentages to obtain a molten liquid: Mg 4-5%, Mn 0.6-0.7%, Ni 0.3-0.4%, Si 0.2-0.3%, Zn 0.08-0.10%, Cu 0.05-0.07%, Ti 0.03-0.04%, Nb 0.03-0.04%, Zr 0.02-0.03%, Sc 0.02-0.03%, with the balance being Al and other unavoidable impurities; S4. Add intermediate alloy powder and aluminum-coated graphene to the molten metal, stir and mix, ultrasonically treat to obtain alloy liquid, refine and remove slag, low-pressure casting, hot rolling, cold rolling to obtain plate. S5. The surface of the plate is treated with graphite powder and then heat-treated under an alternating magnetic field to obtain the aluminum alloy. The specific method of step S2 is as follows: Under argon protection, the nano-aluminum powder is subjected to low-temperature plasma treatment, then poured into an aqueous solution of dodecyltrimethylammonium bromide, subjected to ultrasonic oscillation treatment, centrifuged to collect the precipitate, washed with water, and dried to obtain pretreated nano-aluminum; then, under argon protection, the pretreated nano-aluminum and graphene are added to anhydrous ethanol, heated to reflux, kept at reflux for 8-10 hours, centrifuged to collect the precipitate, washed with water, dried, and vacuum sintered to obtain the aluminum-coated graphene. In step S4, the mass ratio of intermediate alloy powder, aluminum-coated graphene, and melt is 0.2–0.3:0.08–0.1:100; In step S5, the specific method for surface treatment of the plate using graphite powder is as follows: two oxygen-free copper plates are respectively covered with the plate, with the sides of the plates facing each other to form two electrodes; an alternating electric field with an alternating frequency of 0.5-0.8MHz and an alternating current of 8-10A is provided between the two electrodes; high-purity graphite powder with a particle size of less than 10μm is atomized with high-pressure gas flow and sprayed between the two electrodes; after spraying, the plate is removed; the amount of graphite powder used per square meter of plate is 10-15g; the alternating magnetic field treatment conditions are: frequency 200-300kHz, magnetic field strength 1200-1300mT.

2. The preparation method according to claim 1, characterized in that, In step S1, the mass content of high-purity strontium powder, high-purity cerium powder, high-purity neodymium powder, and high-purity europium powder is above 99.9%, and the mass content of high-purity aluminum powder and high-purity boron powder is above 99.99%.

3. The preparation method according to claim 1, characterized in that, In step S1, the sintering conditions are as follows: heat up to 500-600℃ at 30-40℃ / min and hold for 2-3 hours; heat up to 850-900℃ at 5-10℃ / min and hold for 1-2 hours; cool down to 750-800℃ in the furnace and hold for 10-20 minutes; apply an axial pressure of 40-50MPa to the compact 20 seconds before the end of the holding period, and then allow it to cool naturally to room temperature.

4. The preparation method according to claim 1, characterized in that, In step S3, a resistance furnace is used for melting, with a melting temperature of 750-770℃ and a melting time of 50-60 minutes.

5. The preparation method according to claim 1, characterized in that, In step S5, the heat treatment conditions are as follows: heat up to 350-380℃ at 25-30℃ / min and hold for 2-3 hours; heat up to 550-570℃ at 5-7℃ / min and hold for 3-4 hours; cool down to 420-450℃ at 12-15℃ / min and hold for 1-2 hours, then allow to cool naturally to room temperature.

6. An aluminum alloy containing strontium and rare earth elements, characterized in that, It is obtained by the preparation method described in any one of claims 1 to 5.

7. The application of the strontium- and rare earth-containing aluminum alloy of claim 6 in the processing of automotive load-bearing components.