Corrosion-resistant aluminum alloy profile for automobiles and method for manufacturing the same

Abstract

The application belongs to the technical field of aluminum alloy profiles, and discloses a kind of corrosion-resistant aluminum alloy profiles for automobile and preparation method thereof, including aluminum alloy matrix, composite reinforcing phase and corrosion-resistant coating, the mass ratio of aluminum alloy matrix, composite reinforcing phase and corrosion-resistant coating is 70:15:15, composite reinforcing phase includes nano Al2O3 particle and SiC particle, corrosion-resistant coating is polyamide-imide-based composite coating, aluminum alloy matrix is additionally added with rare earth elements Ce and La with mass fraction of 0.5%-1.2%, for refining grain, improving passivation film stability, by introducing nano Al2O3 and SiC composite reinforcing phase in aluminum alloy matrix, and combining the micro-alloying effect of rare earth elements Ce and La, grain is refined from conventional 50-100 μm to 10-20 μm, grain refinement makes strength improve, plays the purification effect of degassing and deslagging, hydrogen content in melt is reduced, air hole and loose defect in ingot is reduced, and the density of material is improved.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy profile technology, specifically a corrosion-resistant aluminum alloy profile for automobiles and its preparation method. Background Technology

[0002] Aluminum alloys are widely used in the automotive manufacturing industry due to their lightweight, high strength, and good processing performance, especially in body structural components, chassis systems, and battery pack housings. The proportion of aluminum alloy profiles in automotive materials is constantly increasing. With the rapid development of new energy vehicles, higher requirements are placed on the comprehensive performance of aluminum alloy profiles. Compared with traditional fuel vehicles, the power battery packs, electric drive systems, and chassis structural components of new energy vehicles are particularly sensitive to the corrosion resistance of materials. On the one hand, the battery pack housings of new energy vehicles are usually installed at the bottom of the vehicle and are exposed to harsh environments such as moisture, mud, and de-icing agents for a long time. Once corrosion and perforation occur, it will directly threaten the sealing and safety of the battery system. In addition, the application of aluminum alloy profiles in key safety components such as body frames, anti-collision beams, and energy-absorbing boxes also places higher demands on the strength, toughness, and fatigue life of the materials. For new energy vehicles, corrosion problems not only affect the appearance quality and resale value of the vehicle, but may also cause major safety hazards such as water ingress into the battery pack and electrical short circuits.

[0003] However, the existing corrosion-resistant aluminum alloy profile for automobiles and its preparation method are not perfect and still have certain shortcomings: Currently, most aluminum alloy profiles used in automobiles employ a single aluminum alloy substrate, with surface protection achieved through anodizing or simple spraying. The anodized layer has limited thickness, making it prone to wear and peeling during use. Ordinary organic coatings exhibit poor adhesion and insufficient weather resistance. In automotive assembly lines, the oxide layer is easily scratched and worn during conveying, cutting, and drilling operations, resulting in protective defects even before assembly. Ordinary organic coatings typically show significant aging and peeling within three years in the environment, while the design life of automobiles is usually ten years, indicating a severe mismatch between the protection period and the design life. After the oxide film and coating on a single aluminum alloy substrate are damaged, corrosive media directly contact the substrate, rapidly developing pitting corrosion into stress corrosion cracking. Corrosion reduces the profile cross-section and load-bearing capacity, posing safety hazards under vehicle collisions and fatigue loads. Damaged anodized layers cannot be locally repaired, requiring complete rework. Self-piercing riveting is widely used in automobile manufacturing, a process that can locally damage the anodized layer. Therefore, a corrosion-resistant aluminum alloy profile for automobiles and its preparation method are designed. Summary of the Invention

[0004] The purpose of this invention is to provide a corrosion-resistant aluminum alloy profile for automobiles and its preparation method, in order to solve the problems mentioned in the background art, such as the direct contact of corrosive media with the substrate after the oxide film and coating are damaged, the rapid development of pitting corrosion into stress corrosion cracking, the reduction of profile cross-section and load-bearing capacity due to corrosion, the safety hazards under automobile collision and fatigue load, and the inability to locally repair the damaged anodized layer.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a corrosion-resistant aluminum alloy profile for automobiles, comprising an aluminum alloy matrix, a composite reinforcing phase, and a corrosion-resistant coating, wherein the mass ratio of the aluminum alloy matrix, the composite reinforcing phase, and the corrosion-resistant coating is 70:15:15, the composite reinforcing phase comprises nano-Al2O3 particles and SiC particles, and the corrosion-resistant coating is a polyamide-imide composite coating.

[0006] Preferably, the aluminum alloy matrix also contains 0.5%-1.2% rare earth elements Ce and La by mass fraction to refine the grains and improve the stability of the passivation film. The mass ratio of nano-Al2O3 particles to SiC particles in the composite reinforcing phase is 3:1, and the two are uniformly dispersed in the aluminum matrix by high-energy ball milling.

[0007] Preferably, the corrosion-resistant coating is a composite coating of polyamide-imide and polytetrafluoroethylene with a mass ratio of 80:20. The coating contains 5% by mass of nano-TiO2 filler to enhance the coating's weather resistance and resistance to ultraviolet aging.

[0008] Preferably, after melting the aluminum alloy matrix material, composite reinforcing phase particles are added, and after ultrasonic dispersion and mechanical stirring, semi-solid extrusion molding is used to form a profile blank. The profile blank is then subjected to solution treatment at a temperature of 540°C for 3 hours.

[0009] Preferably, after the solution treatment, the material is further subjected to water quenching at a temperature of 170°C for 6 hours. A corrosion-resistant coating with a thickness of 20 μm is then applied to the surface of the profile by electrostatic spraying. After spraying, the material is placed in an oven for curing at a temperature of 200°C for 30 minutes.

[0010] Preferably, the solution treatment is carried out in a protective atmosphere, namely nitrogen or argon, to prevent surface oxidation.

[0011] Preferably, after the water quenching treatment, a surface pretreatment is performed by spraying a silane coupling agent solution onto the profile surface. The silane coupling agent solution has a mass fraction of 1%, the treatment time is 5-10 minutes, and the resulting transition layer is 2 μm.

[0012] Preferably, the surface pretreatment includes degreasing, pickling, washing and drying, the surface roughness is controlled at Ra 1.6 μm, and in the surface pretreatment, the pickling solution is a 15% nitric acid solution by mass, and the pickling time is 4 minutes.

[0013] Preferably, the profile after the sealing treatment is trimmed, deburred and dimensionally finished. The corrosion resistance of the aluminum alloy profile is tested by neutral salt spray test, the tensile strength is tested by universal testing machine, and the cross-sectional structure of the coating and the coating are observed by scanning electron microscope.

[0014] A method for preparing corrosion-resistant aluminum alloy profiles for automobiles includes the following steps: S1: Raw material pretreatment: The aluminum alloy matrix material is placed in a melting furnace and heated to 740°C until completely melted. After mixing nano-Al2O3 particles and SiC particles in a certain proportion, rare earth elements Ce and La with a mass fraction of 0.5%-1.2% are added. The mixture is pre-dispersed for 5 hours by high-energy ball milling at a speed of 350 rpm to obtain a uniformly dispersed composite reinforcing phase premix. S2: Melt treatment: Add the composite reinforcing phase premix to the aluminum alloy melt, and perform ultrasonic dispersion treatment for 20 minutes, followed by mechanical stirring for 20 minutes; S3: Semi-solid extrusion molding: The melt temperature is reduced to the semi-solid temperature range of 590°C, held for 15 minutes, and then extruded using a semi-solid extruder at an extrusion speed of 1m / s to form a profile blank. S4: Solution treatment, quenching treatment, aging treatment and surface pretreatment: Quickly transfer the solution-treated profile to the quenching tank for water quenching treatment. The quenching transfer time shall not exceed 15 seconds. Place the quenched profile in the aging furnace for heat preservation. S5: Transition layer treatment: The profile surface is sprayed with a silane coupling agent solution; S6: Post-processing and performance testing: After the sealing treatment, the profiles are trimmed, and the finished products are tested for corrosion resistance, mechanical properties and microstructure. After passing the tests, they are packaged and put into storage.

[0015] The beneficial effects of this invention are as follows: 1. This invention introduces nano-sized Al2O3 and SiC composite reinforcing phases into an aluminum alloy matrix, and combines this with the microalloying effect of rare earth elements Ce and La. During alloy solidification, these nanoparticles provide numerous nucleation sites for α-Al grains, refining the grain size from the conventional 50-100 μm to 10-20 μm. μm grain refinement enhances strength. Simultaneously, the fine equiaxed grain structure eliminates the anisotropy caused by coarse columnar grains, improving the material's toughness and fatigue resistance. Al2O3 particles exhibit good wettability with the aluminum matrix, resulting in high interfacial bonding strength, which is beneficial for load transfer. SiC particles have higher hardness and stronger wear resistance. Furthermore, their thermal expansion coefficient differs significantly from that of the aluminum matrix, introducing beneficial residual compressive stress at the interface and inhibiting crack initiation. Rare earth elements Ce and La possess extremely high chemical reactivity, combining with hydrogen, oxygen, and sulfur impurities in the melt to form stable rare earth compounds, playing a purifying role in degassing and slag removal. The reduced hydrogen content in the melt decreases porosity and looseness defects in the ingot, improving the material's density.

[0016] 2. In the heat treatment process of this invention, the presence of rare earth elements keeps the grains fine, avoiding grain coarsening during high-temperature solution treatment, and ensuring that the material retains a fine-grained structure in the final aged state. Rare earth elements Ce and La form a dense rare earth oxide film on the aluminum alloy surface, which, combined with the natural oxide film of aluminum, forms a double-layer passivation film structure. A composite coating of polyamide-imide and polytetrafluoroethylene is used, and nano-TiO2 filler is added to form a surface protective layer with excellent adhesion, weather resistance and chemical corrosion resistance. Under the action of electrostatic force, it is adsorbed onto the grounded aluminum alloy profile surface. After impregnation with a fluorinated silane coupling agent solution, the molecules penetrate into the micropores and microcracks on the coating surface. After drying and curing, the alkoxy groups in the molecules hydrolyze and condense to form a Si-O-Si network, filling the micropore defects. Fluorinated alkyl chains are oriented on the surface to form a low surface energy hydrophobic layer. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 This is a production flow diagram of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Please see Figure 1 This invention provides a technical solution for corrosion-resistant aluminum alloy profiles for automobiles and a method for preparing the same: The material comprises an aluminum alloy substrate, a composite reinforcing phase, and a corrosion-resistant coating. The mass ratio of the aluminum alloy substrate, the composite reinforcing phase, and the corrosion-resistant coating is 70:15:15. The composite reinforcing phase includes nano-Al2O3 particles and SiC particles. The corrosion-resistant coating is a polyamide-imide-based composite coating. The aluminum alloy substrate also contains 0.5%-1.2% by mass of rare earth elements Ce and La to refine the grains and improve the stability of the passivation film. The mass ratio of nano-Al2O3 particles to SiC particles in the composite reinforcing phase is 3:1. Both are uniformly dispersed in the aluminum substrate by high-energy ball milling. The corrosion-resistant coating is a polyamide-imide and polytetrafluoroethylene composite coating with a mass ratio of 80:20. The coating contains 5% by mass of nano-TiO2 filler to enhance the coating's weather resistance and resistance to ultraviolet aging.

[0020] The process involves melting the aluminum alloy matrix material, adding composite reinforcing phase particles, ultrasonically dispersing and mechanically stirring, and then semi-solid extrusion molding to form a profile blank. The profile blank undergoes solution treatment at 540°C for 3 hours, followed by water quenching at 170°C for 6 hours. A corrosion-resistant coating with a thickness of 20μm is then applied to the profile surface using electrostatic spraying. After spraying, the surface is placed in an oven for curing at 200°C for 30 minutes. The solution treatment is carried out in a protective atmosphere, such as nitrogen or argon, to prevent surface oxidation.

[0021] During use, after water quenching, surface pretreatment is carried out. A silane coupling agent solution is sprayed onto the profile surface. The mass fraction of the silane coupling agent solution is 1%, and the treatment time is 5-10 minutes. The resulting transition layer is 2μm. The surface pretreatment includes degreasing, pickling, water washing, and drying. The surface roughness is controlled at Ra 1.6μm. In the surface pretreatment, the pickling solution is a 15% nitric acid solution, and the pickling time is 4 minutes. After the sealing treatment, the profile is trimmed, deburred, and dimensionally finished. The corrosion resistance of the aluminum alloy profile is tested using a neutral salt spray test. The tensile strength is tested using a universal testing machine. The cross-sectional structure of the coating and the coating itself are observed using a scanning electron microscope.

[0022] A method for preparing corrosion-resistant aluminum alloy profiles for automobiles includes the following steps: S1: Raw material pretreatment: The aluminum alloy matrix material is placed in a melting furnace and heated to 740°C until completely melted. After mixing nano-Al2O3 particles and SiC particles in a certain proportion, rare earth elements Ce and La with a mass fraction of 0.5%-1.2% are added. The mixture is pre-dispersed for 5 hours by high-energy ball milling at a speed of 350 rpm to obtain a uniformly dispersed composite reinforcing phase premix. S2: Melt treatment: Add the composite reinforcing phase premix to the aluminum alloy melt, and perform ultrasonic dispersion treatment for 20 minutes, followed by mechanical stirring for 20 minutes; S3: Semi-solid extrusion molding: The melt temperature is reduced to the semi-solid temperature range of 590°C, held for 15 minutes, and then extruded using a semi-solid extruder at an extrusion speed of 1m / s to form a profile blank. S4: Solution treatment, quenching treatment, aging treatment and surface pretreatment: Quickly transfer the solution-treated profile to the quenching tank for water quenching treatment. The quenching transfer time shall not exceed 15 seconds. Place the quenched profile in the aging furnace for heat preservation. S5: Transition layer treatment: The profile surface is sprayed with a silane coupling agent solution; S6: Post-processing and performance testing: After the sealing treatment, the profiles are trimmed, and the finished products are tested for corrosion resistance, mechanical properties and microstructure. After passing the tests, they are packaged and put into storage.

[0023] Aluminum alloys are widely used in the automotive manufacturing industry due to their lightweight, high strength, and good machinability, especially in body structural components, chassis systems, and battery pack housings. The proportion of aluminum alloy profiles in automotive materials is constantly increasing. With the rapid development of new energy vehicles, higher requirements are being placed on the comprehensive performance of aluminum alloy profiles. Compared with traditional fuel vehicles, the power battery packs, electric drive systems, and chassis structural components of new energy vehicles are particularly sensitive to the corrosion resistance of materials. On the one hand, the battery pack housings of new energy vehicles are usually installed at the bottom of the vehicle and are exposed to harsh environments such as moisture, mud, and de-icing agents for extended periods. Once corrosion occurs... Holes directly threaten the sealing and safety of the battery system. Furthermore, the application of aluminum alloy profiles in key safety components such as vehicle frames, crash beams, and energy-absorbing boxes places higher demands on the material's strength, toughness, and fatigue life. For new energy vehicles, corrosion not only affects the vehicle's appearance and resale value but can also lead to significant safety hazards such as water ingress into the battery pack and electrical short circuits. However, existing corrosion-resistant automotive aluminum alloy profiles and their preparation methods are not perfect and still have certain shortcomings: Currently, automotive aluminum alloy profiles mostly use a single aluminum alloy matrix, with surface protection achieved through anodizing or simple spraying. Due to the limited thickness of the oxide layer, aluminum alloy profiles are prone to wear and peeling during use. Ordinary organic coatings have poor adhesion and insufficient weather resistance. In automotive assembly lines, the oxide layer is easily scratched and worn during conveying, cutting, and drilling operations, resulting in protective defects even before assembly. Ordinary organic coatings typically show significant aging and peeling within three years in the environment, while the design life of automobiles is usually ten years. This mismatch between the protection period and the design life is serious. After the oxide film and coating are damaged, corrosive media come into direct contact with the substrate, and pitting corrosion rapidly develops into stress corrosion cracking. Corrosion leads to a reduction in the cross-section of the profile and its load-bearing capacity. The decline in corrosion resistance poses safety hazards under automotive collisions and fatigue loads. Damage to the anodized layer cannot be locally repaired, requiring complete rework. Self-piercing riveting is widely used in automotive manufacturing, a process that can locally damage the anodized layer. Therefore, a corrosion-resistant aluminum alloy profile for automobiles and its preparation method are designed. The profile comprises an aluminum alloy matrix, a composite reinforcing phase, and a corrosion-resistant coating, with a mass ratio of 70:15:15. The composite reinforcing phase includes nano-Al2O3 particles and SiC particles, and the corrosion-resistant coating is a polyamide-imide composite coating. The aluminum alloy matrix also contains 0.5%-1% of [unspecified ingredient].2% rare earth elements Ce and La are used to refine grains and improve the stability of the passivation film. The mass ratio of nano-Al2O3 particles to SiC particles in the composite reinforcing phase is 3:1. They are uniformly dispersed in the aluminum matrix by high-energy ball milling. The corrosion-resistant coating is a composite coating of polyamide-imide and polytetrafluoroethylene with a mass ratio of 80:20. 5% nano-TiO2 filler is added to the coating to enhance its weather resistance and UV aging resistance. After melting the aluminum alloy matrix material, the composite reinforcing phase particles are added. After ultrasonic dispersion and mechanical stirring, the material is semi-solid extruded to form a profile billet. The profile billet is then solution treated at 540°C for 3 hours. After solution treatment, the material undergoes water quenching at 170°C for 6 hours. A 20μm thick corrosion-resistant coating is then applied to the profile surface using electrostatic spraying. Following spraying, the material is cured in an oven at 200°C for 30 minutes. Solution treatment is performed under a protective atmosphere (nitrogen or argon) to prevent surface oxidation. After water quenching, surface pretreatment is carried out by spraying a 1% silane coupling agent solution onto the profile surface for 5-10 minutes, forming a 2μm transition layer. Surface pretreatment includes degreasing, pickling, washing, and drying, with the surface roughness controlled within Ra. The surface pretreatment process involved a 1.6 μm thick aluminum alloy profile. The pickling solution was a 15% (w / w) nitric acid solution, and the pickling time was 4 minutes. After sealing, the profile underwent trimming, deburring, and dimensional finishing. The corrosion resistance of the aluminum alloy profile was tested using a neutral salt spray test. Tensile strength was tested using a universal testing machine. The cross-sectional structure and appearance of the coating were observed using a scanning electron microscope.

[0024] 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 corrosion-resistant aluminum alloy profile for automobiles, characterized in that: The material comprises an aluminum alloy substrate, a composite reinforcing phase, and a corrosion-resistant coating, wherein the mass ratio of the aluminum alloy substrate, the composite reinforcing phase, and the corrosion-resistant coating is 70:15:15, the composite reinforcing phase comprises nano-Al2O3 particles and SiC particles, and the corrosion-resistant coating is a polyamide-imide composite coating.

2. The corrosion-resistant aluminum alloy profile for automobiles according to claim 1, characterized in that: The aluminum alloy matrix also contains 0.5%-1.2% rare earth elements Ce and La by mass fraction to refine the grains and improve the stability of the passivation film. The composite reinforcing phase has a mass ratio of nano-Al2O3 particles to SiC particles of 3:1, and the two are uniformly dispersed in the aluminum matrix by high-energy ball milling.

3. The corrosion-resistant aluminum alloy profile for automobiles according to claim 1, characterized in that: The corrosion-resistant coating is a composite coating of polyamide-imide and polytetrafluoroethylene with a mass ratio of 80:

20. The coating contains 5% by mass of nano-TiO2 filler to enhance its weather resistance and UV aging resistance.

4. The corrosion-resistant aluminum alloy profile for automobiles according to claim 3, characterized in that: After melting the aluminum alloy matrix material, composite reinforcing phase particles are added. After ultrasonic dispersion and mechanical stirring, the material is semi-solid extrusion molding to form a profile blank. The profile blank is then subjected to solution treatment at a temperature of 540°C for 3 hours.

5. The corrosion-resistant aluminum alloy profile for automobiles according to claim 4, characterized in that: After solution treatment, the material is further subjected to water quenching at 170°C for 6 hours. A corrosion-resistant coating with a thickness of 20 μm is then applied to the surface of the profile using electrostatic spraying. After spraying, the material is placed in an oven for curing at 200°C for 30 minutes.

6. The corrosion-resistant aluminum alloy profile for automobiles according to claim 5, characterized in that: The solution treatment is carried out in a protective atmosphere, namely nitrogen or argon, to prevent surface oxidation.

7. The corrosion-resistant aluminum alloy profile for automobiles according to claim 5, characterized in that: After the water quenching treatment, surface pretreatment is carried out by spraying a silane coupling agent solution onto the profile surface. The silane coupling agent solution has a mass fraction of 1% and the treatment time is 5-10 minutes, forming a transition layer of 2μm.

8. The corrosion-resistant aluminum alloy profile for automobiles according to claim 7, characterized in that: The surface pretreatment includes degreasing, pickling, water washing and drying. The surface roughness is controlled at Ra 1.6 μm. In the surface pretreatment, the pickling solution is a 15% nitric acid solution and the pickling time is 4 minutes.

9. The corrosion-resistant aluminum alloy profile for automobiles according to claim 7, characterized in that: The profiles after the sealing treatment are trimmed, deburred and dimensionally finished. The corrosion resistance of the aluminum alloy profiles is tested by neutral salt spray test, the tensile strength is tested by universal testing machine, and the cross-sectional structure and coating are observed by scanning electron microscope.

10. A method for preparing a corrosion-resistant aluminum alloy profile for automobiles, the method being applicable to the corrosion-resistant aluminum alloy profile for automobiles described in claims 1-9 above, characterized in that... Includes the following steps: S1: Raw material pretreatment: The aluminum alloy matrix material is placed in a melting furnace and heated to 740°C until completely melted. After mixing nano-Al2O3 particles and SiC particles in a certain proportion, rare earth elements Ce and La with a mass fraction of 0.5%-1.2% are added. The mixture is pre-dispersed for 5 hours by high-energy ball milling at a speed of 350 rpm to obtain a uniformly dispersed composite reinforcing phase premix. S2: Melt treatment: Add the composite reinforcing phase premix to the aluminum alloy melt, and perform ultrasonic dispersion treatment for 20 minutes, followed by mechanical stirring for 20 minutes; S3: Semi-solid extrusion molding: The melt temperature is reduced to the semi-solid temperature range of 590°C, held for 15 minutes, and then extruded using a semi-solid extruder at an extrusion speed of 1m / s to form a profile blank. S4: Solution treatment, quenching treatment, aging treatment and surface pretreatment: Quickly transfer the solution-treated profile to the quenching tank for water quenching treatment. The quenching transfer time shall not exceed 15 seconds. Place the quenched profile in the aging furnace for heat preservation. S5: Transition layer treatment: The profile surface is sprayed with a silane coupling agent solution; S6: Post-processing and performance testing: After the sealing treatment, the profiles are trimmed, and the finished products are tested for corrosion resistance, mechanical properties and microstructure. After passing the tests, they are packaged and put into storage.

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