High-toughness corrosion-resistant aluminum alloy for multi-cavity automobile profile and preparation method of high-toughness corrosion-resistant aluminum alloy

Abstract

According to the high-strength-toughness corrosion-resistant aluminum alloy for the multi-cavity automobile profile and the preparation method of the high-strength-toughness corrosion-resistant aluminum alloy, recrystallization and grain growth can be effectively inhibited by optimizing chemical components of the high-strength-toughness corrosion-resistant aluminum alloy, homogenization treatment and two-stage aging treatment are combined, high dispersion and uniform precipitation of a strengthening phase are promoted, and the corrosion resistance of the high-strength-toughness corrosion-resistant aluminum alloy is improved. The precipitation strengthening effect is maximized, so that the prepared alloy has high strength and high toughness; besides, an Al-3Ti-C intermediate alloy is added as an alterant and is combined with rare earth elements, so that the alloy structure is more uniform, lattice defects and introduction of impurity elements can be reduced, and then excellent corrosion resistance is obtained; and electromagnetic stirring, ultrasonic treatment, homogenization treatment and two-stage aging treatment are combined, so that a precipitated phase is further promoted to be moderately coarsened and tends to be stable, the potential difference between the grain boundary and the intracrystalline is remarkably reduced, the intergranular corrosion and exfoliation corrosion capacities of the aluminum alloy are remarkably improved, meanwhile, part of internal stress is released, and the dimensional stability is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum alloy preparation, in particular to a high-strength and high-toughness corrosion-resistant aluminum alloy for multi-cavity automobile profiles and a preparation method thereof. BACKGROUND

[0002] Aluminum alloy has become one of the key materials for automobile lightweighting due to its excellent specific strength, good formability, corrosion resistance and recyclability. In particular, in multi-cavity thin-walled profiles such as battery pack shell frames, door impact beams, front and rear energy absorption boxes, auxiliary frames and other structural parts, the material is required to have high strength, high toughness and good corrosion resistance after extrusion forming.

[0003] At present, the commonly used 6-series aluminum alloy, especially 6061 aluminum alloy, has high strength in the conventional T6 peak aging state, but its toughness and plasticity are often insufficient, which is difficult to meet the comprehensive performance requirements of multi-cavity thin-walled profiles in terms of crash energy absorption and structural integrity. The traditional 6061 aluminum alloy mainly optimizes the performance by adjusting the main alloying elements (such as Si, Mg, Cu), but it is difficult to significantly improve the toughness while maintaining high strength by simply relying on element adjustment.

[0004] Although attempts have been made in the prior art to improve performance by adding trace elements or adjusting the process, there are often problems such as complex process, high cost or limited effect. For example, the addition of rare earth elements can improve corrosion resistance, but the synergistic mechanism of nucleation, grain refinement and inhibition of recrystallization in aluminum alloy is not clear.

[0005] Therefore, it is urgent to develop a new type of high-strength and high-toughness corrosion-resistant aluminum alloy and its preparation method to overcome the above-mentioned defects of the prior art and meet the comprehensive requirements of material strength, toughness and corrosion resistance for multi-cavity automobile profiles. SUMMARY

[0006] Therefore, in order to solve one of the above technical problems, the present application provides a high-strength and high-toughness corrosion-resistant aluminum alloy for multi-cavity automobile profiles and a preparation method thereof, and the specific technical solutions are as follows: A high-strength and high-toughness corrosion-resistant aluminum alloy for multi-cavity automobile profiles, the high-strength and high-toughness corrosion-resistant aluminum alloy comprises the following chemical components by mass percentage: Si 0.45-0.6%, Mg 0.80-0.95%, Cu 0.15-0.3%, Mn 0.10-0.2%, Cr 0.05-0.15%, La 0.10-0.2%, Fe≤0.2%, individual impurity content≤0.05%, total impurity content≤0.15%, and the balance is Al.

[0007] Further, the high-toughness corrosion-resistant aluminum alloy further comprises TiC particles, which are introduced by Al-3Ti-C intermediate alloy, and the content of the Al-3Ti-C intermediate alloy accounts for 0.05%-0.1% of the total mass of the aluminum alloy melt.

[0008] In addition, the application further provides a preparation method of the high-toughness corrosion-resistant aluminum alloy for multi-cavity automobile profiles, which comprises the following steps: (1) selecting copper plate, elemental silicon, Al-10La intermediate alloy, manganese additive, chromium additive, aluminum ingot with a purity of 99.8%, and magnesium ingot with a purity of 99.9% as raw materials; (2) performing melting treatment on the raw materials in step (1) to obtain an aluminum alloy melt; (3) adding Al-3Ti-C intermediate alloy to the aluminum alloy melt and performing electromagnetic stirring; (4) performing refining treatment on the aluminum alloy melt after step (3), and performing spectral analysis on the rapidly sampled melt to finely adjust the composition so that the composition is accurately controlled within the target range, and then performing slagging and standing treatment; (5) performing ultrasonic treatment on the aluminum alloy melt after step (4); (6) performing degassing and filtering treatment on the aluminum alloy melt after step (5); (7) performing casting on the aluminum alloy melt after step (6) to obtain an aluminum alloy ingot; (8) performing homogenization treatment on the aluminum alloy ingot and air cooling to room temperature; (9) extruding the homogenization-treated aluminum alloy ingot to obtain an aluminum alloy profile; (10) performing solid solution treatment on the aluminum alloy profile; (11) performing two-stage aging treatment on the aluminum alloy profile after the solid solution treatment to obtain a high-toughness corrosion-resistant aluminum alloy for multi-cavity automobile profiles.

[0009] Further, in step (1), the elemental silicon needs to be pre-crushed into particles with a particle size of 1mm-5mm and pre-heated at 150°C-250°C for 2h-4h to remove adsorbed water and improve its dissolution efficiency in the melt.

[0010] Further, in step (2), the pure aluminum ingot is added to the melting furnace, heated to 740°C-760°C to completely melt, then the pre-heated elemental silicon is slowly added to the aluminum liquid under stirring at 200rpm-400rpm, after complete dissolution, the Al-10La intermediate alloy, copper plate, manganese additive and chromium additive are sequentially added, and after complete dissolution, the pure magnesium ingot is pressed into the aluminum alloy melt below the liquid surface for melting.

[0011] Further, in step (3), the Al-3Ti-C intermediate alloy contains 1% to 5% of titanium and 1% to 5% of carbon, with the balance being aluminum.

[0012] Further, in step (5), the power of the sonication is 160 W to 180 W, and the sonication time is 10 min to 15 min.

[0013] Further, in step (6), the melt temperature is reduced to 700°C to 710°C, and primary degassing is performed through a degassing box and a double-layered foam ceramic filter plate, with the rotation speed of the degassing box being 200 r / min to 300 r / min, the argon flow rate being 4 m 3 / h to 5 m 3 / h, and the filtration being performed using a double-layered foam ceramic filter plate with a porosity of 40 ppi + 60 ppi.

[0014] Further, in step (7), the aluminum alloy melt is introduced into a crystallizer, a low-frequency electromagnetic field surrounding the crystallizer is turned on, the frequency is 3 Hz to 10 Hz, the current intensity is 50 A to 150 A, a semi-continuous casting process is used, the casting temperature is 710°C to 740°C, the casting speed is 90 mm / min to 120 mm / min, and the cooling water pressure is 0.1 MPa to 0.2 MPa.

[0015] Further, in step (8), the homogenization treatment is as follows: First stage: heating to 300°C to 320°C at a rate of ≤30°C / h, and holding for 1 h to 3 h; Second stage: heating to 470°C to 500°C at a rate of 40°C / h to 60°C / h, and holding for 6 h to 10 h; Third stage: heating to 550°C to 570°C at a rate of 20°C / h to 30°C / h, and holding for 8 h to 10 h.

[0016] Compared with the prior art, the present application has the following beneficial effects: 1. The present application optimizes the chemical composition of the high-strength and high-toughness corrosion-resistant aluminum alloy, effectively inhibits recrystallization and grain growth, combines homogenization treatment and double-stage aging treatment, promotes the highly dispersed and uniform precipitation of strengthening phases, maximizes the precipitation strengthening effect, and makes the alloy prepared by the present application have high strength and high toughness; in addition, the Al-3Ti-C intermediate alloy is added as a modifier, combined with rare earth elements, the alloy structure is more uniform, the introduction of lattice defects and impurity elements is reduced, and excellent corrosion resistance is obtained.

[0017] 2. The application can ensure the initial dispersion of TiC particles through electromagnetic stirring and ultrasonic treatment, and under the cavitation effect of ultrasonic treatment, the Al3Ti phase clusters are broken, the TiC particles are uniformly dispersed, and the micro pores and inclusions in the melt are effectively removed, thereby significantly improving the uniformity and purity of the aluminum alloy melt. In combination with subsequent homogenization treatment and two-stage aging treatment, the diffusion and uniform distribution of elements such as Mn and Cr are effectively promoted, the uniform fiber structure and dispersed phase are formed during extrusion, the grain growth is inhibited, and the mechanical properties of the aluminum alloy are effectively improved. On the basis of ensuring the mechanical properties of the aluminum alloy, through two-stage aging, the precipitated phase is moderately coarsened and tends to be stable, the potential difference between the grain boundary and the grain is significantly reduced, the intergranular corrosion and exfoliation corrosion resistance of the aluminum alloy is significantly improved, and part of the internal stress is released, thereby improving the dimensional stability. BRIEF DESCRIPTION OF DRAWINGS

[0018] The application can be further understood from the following description made with reference to the drawings. The components in the drawings are not necessarily drawn to scale, but emphasis is instead placed on illustrating the principles of the embodiments. In different views, the same reference numerals designate corresponding parts.

[0019] Figure 1 is a schematic diagram of the microstructure of the aluminum alloy in embodiment 1 of the application. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the application more clear and understandable, the application will be further described in detail below in combination with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and do not limit the protection scope of the application.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0022] The high-strength and high-toughness corrosion-resistant aluminum alloy for a multi-cavity automobile profile in an embodiment of the application includes the following mass percentages of chemical components: Si 0.45-0.6%, Mg 0.80-0.95%, Cu 0.15-0.3%, Mn 0.10-0.2%, Cr 0.05-0.15%, La 0.10-0.2%, Fe≤0.2%, individual mass content of impurities≤0.05%, total mass content of impurities≤0.15%, and the balance being Al.

[0023] The present application realizes significant improvement of strength by precisely controlling the chemical composition of the aluminum alloy, ensuring sufficient Mg2Si strengthening phase, and forming S'(Al2CuMg) phase by solid solution strengthening of Cu, while avoiding sharp decline of plasticity, toughness and corrosion resistance caused by excess Si or excessive Cu content; adding an appropriate amount of rare earth La element, the La element can react with impurities such as hydrogen and oxygen, and deeply purify the melt; the La element is enriched in the grain boundary, which can refine the as-cast structure and improve the recrystallization temperature, and inhibit grain coarsening in subsequent hot working, laying the foundation for obtaining fine-grained structure, thereby synchronously improving the strength and toughness. Adding Mn element can form dispersed Mn / Cr-containing intermetallic compounds, which can effectively pin dislocations and grain boundaries, inhibit recrystallization behavior during extrusion, obtain subgrain structure, and further improve strength and stress corrosion cracking resistance; by adding Al-3Ti-C intermediate alloy to introduce trace TiC particles, TiC acts as a heterogeneous nucleation core to greatly refine α-Al grains during casting and solidification; at the same time, these high-hardness and high-thermal-stability nano / submicron particles are dispersed in the matrix during subsequent processing, which can effectively hinder dislocation movement, and produce significant grain refinement and second phase strengthening effects.

[0024] Specifically, the rare earth element La can effectively improve the corrosion resistance, toughness and strength of the aluminum alloy, and using La instead of part of the main elements can improve the extrudability. The La element will be enriched on the surface of the Mg2Si particles, delaying the corrosion of the Mg2Si particles; at the same time, the La element changes the morphology of the Si particles from continuous distribution of flaky to discontinuous short rod shape, hindering the corrosion expansion along the grain boundary. The La element also enriches at the grain boundary, hindering the migration of the grain boundary, thereby effectively inhibiting the recrystallization process and the growth of the grains at high temperature, improving the yield strength and tensile strength. The fine grains mean more grain boundaries, which can effectively hinder the crack propagation, change the crack propagation path, and consume more energy, thereby improving the fracture toughness of the material.

[0025] The addition of Mn can change the morphology and distribution of impurity phases (such as iron-rich phases) in the alloy, making them change from coarse needles to finer particles, which reduces stress concentration points and indirectly makes the Mg2Si precipitation strengthening phase more effective, thereby improving the overall strength and toughness of the material.

[0026] The addition of Cr forms dispersed chromium carbide particles, effectively inhibiting recrystallization, refining grains, and producing significant grain refinement effects. Stable chromium carbide particles can hinder dislocation movement and grain boundary sliding, effectively improving the room temperature strength of the alloy, and significantly enhancing its high temperature stability and softening resistance, and also having a positive effect on toughness.

[0027] The TiC particles have a face-centered cubic structure, and the lattice constant is very close to that of aluminum, and the interface energy is low. This enables it to be an efficient heterogeneous nucleation core for aluminum grains. In the early stage of melt solidification, aluminum atoms are more likely to adhere to the surface of the TiC particles and arrange in order, and begin to crystallize, thereby greatly increasing the nucleation rate. The dispersed fine TiC particles not only promote nucleation, but also pin at the grain boundaries in the late solidification, hindering the migration of the grain boundaries, thereby inhibiting the growth of the grains. The fine grains make the subsequent heat treatment, the dissolution and precipitation of the strengthening phase (such as Mg2Si) more dispersed and uniform, thereby improving the strength and toughness of the aluminum alloy.

[0028] The double-stage aging can make the eutectic Si in the microstructure of the alloy spherical and dispersed. The eutectic Si spheroidization can effectively reduce the fragmentation ability to the matrix and reduce the stress concentration. At the same time, after the double-stage aging, the equiaxed grains are more refined, the strengthening phase is more, and the precipitation is more uniform, and the dispersion degree is correspondingly increased. The dispersed strengthening phase is uniformly distributed in the alloy matrix, which hinders the pinning of dislocation sliding, thereby effectively improving the tensile strength and plasticity of the alloy.

[0029] In one embodiment, the high-strength and high-toughness corrosion-resistant aluminum alloy further comprises TiC particles, the TiC particles are introduced by Al-3Ti-C intermediate alloy, and the content of the Al-3Ti-C intermediate alloy accounts for 0.05% to 0.1% of the total mass of the aluminum alloy melt.

[0030] In addition, the application also provides a preparation method of a high-strength and high-toughness corrosion-resistant aluminum alloy for a multi-cavity automobile profile, and the preparation method comprises the following steps: (1) copper plate, elemental silicon, Al-10La intermediate alloy, manganese additive, chromium additive, and aluminum ingot with a purity of 99.8% and magnesium ingot with a purity of 99.9% are selected as raw materials; (2) the raw materials in step (1) are subjected to melting treatment to obtain an aluminum alloy melt; (3) Al-3Ti-C intermediate alloy is added to the aluminum alloy melt, and electromagnetic stirring is performed; (4) the aluminum alloy melt after step (3) is subjected to refining treatment, and rapid sampling is performed for spectral analysis, the composition is finely adjusted, the composition is accurately controlled within the target range, and the slag is removed, and the aluminum alloy melt is subjected to static treatment; (5) the aluminum alloy melt after step (4) is subjected to ultrasonic treatment; (6) the aluminum alloy melt after step (5) is subjected to degassing and filtering treatment; (7) the aluminum alloy melt after step (6) is subjected to casting to obtain an aluminum alloy ingot; (8) the aluminum alloy ingot is subjected to homogenization treatment, and air cooling is performed to room temperature; (9) the aluminum alloy ingot subjected to homogenization treatment is extruded to form an aluminum alloy profile. (10) solid solution treatment of the aluminum alloy profile; (11) double-stage aging treatment of the aluminum alloy profile after the solid solution treatment, to obtain a high-strength and high-toughness corrosion-resistant aluminum alloy for multi-cavity automobile profiles.

[0031] In one of the embodiments, in step (1), the elemental silicon is pre-crushed into particles with a particle size of 1 mm to 5 mm, and pre-heated at 150°C to 250°C for 2 h to 4 h to remove adsorbed moisture and improve the dissolution efficiency in the melt.

[0032] In one of the embodiments, in step (2), the pure aluminum ingot is added into the smelting furnace, heated to 740°C to 760°C to completely melt it, then the pre-heated elemental silicon is slowly added into the aluminum liquid under stirring at 200 rpm to 400 rpm, after complete dissolution, the Al-10La intermediate alloy, copper plate, manganese additive and chromium additive are sequentially added, after complete dissolution, the pure magnesium ingot is melted by pressing it into the aluminum alloy melt below the liquid surface with a bell cover. By optimizing the sequence of adding materials, the oxidation loss of elements can be reduced, and the composition ratio of elements can be ensured.

[0033] In one of the embodiments, in step (3), in the Al-3Ti-C intermediate alloy, the titanium content is 1% to 5%, the carbon content is 1% to 5%, and the balance is aluminum.

[0034] In one of the embodiments, in step (5), the power of ultrasonic treatment is 160 W to 180 W, and the vibration time is 10 min to 15 min. The introduction of ultrasonic treatment can promote the uniform dispersion of TiC and Al3Ti nucleation particles, break up the aggregated Al3Ti phase, further uniform the composition, eliminate the gas enrichment area and promote the floating of fine scum.

[0035] In one of the embodiments, in step (6), the melt temperature is reduced to 700°C to 710°C, primary degassing is carried out through a degassing box, and a double-layer foam ceramic filter plate is used, the rotation speed of the degassing box is 200 r / min to 300 r / min, the argon flow rate is 4 m 3 / h to 5 m 3 / h, and the filtration uses a double-layer foam ceramic filter plate with a porosity of 40 ppi + 60 ppi.

[0036] In one of the embodiments, in step (7), the aluminum alloy melt is introduced into the crystallizer, the low-frequency electromagnetic field surrounding the crystallizer is turned on, the frequency is 3 Hz to 10 Hz, the current intensity is 50 A to 150 A, the semi-continuous casting process is used, the casting temperature is 710°C to 740°C, the casting speed is 90 mm / min to 120 mm / min, and the cooling water pressure is 0.1 MPa to 0.2 MPa.

[0037] In one embodiment, the homogenization treatment in step (8) is: First stage: heating at a rate of ≤30℃ / h to 300℃~320℃, holding for 1h~3h; the first stage makes the low-melting eutectic phase partially re-dissolve; Second stage: heating at a rate of 40℃ / h~60℃ / h to 470℃~500℃, holding for 6h~10h; the second stage fully dissolves the main Mg2Si strengthening phase; Third stage: heating at a rate of 20℃ / h~30℃ / h to 550℃~570℃, holding for 8h~10h. The third stage can effectively promote the surface micro-alloying of the aluminum alloy ingot, maximally eliminate the dendritic segregation, and significantly refine the as-cast grains.

[0038] In one embodiment, the extrusion temperature in step (9) is 460℃~480℃, the die temperature is 460℃~480℃, the extrusion cylinder temperature is 400℃~420℃, and the extrusion speed is 1.5mm / s~2.5mm / s.

[0039] In one embodiment, the solid solution treatment in step (10) is at a temperature of 520℃~540℃ for 40min~60min, followed by immediate water quenching.

[0040] In one embodiment, the two-stage aging treatment in step (11) includes: first stage: 160℃~180℃ for 1h~3h; second stage: 190℃~210℃ for 1h~2h. Through the two-stage aging, the first stage can form a large number of fine GP zones or β'' phases, ensuring the basic strength, and the second stage can promote the partial coarsening of the strengthening phase and tend to be stable, significantly improve the corrosion resistance, especially the intergranular corrosion resistance, while retaining sufficient strength and toughness.

[0041] The above scheme can obtain a high-strength and high-toughness corrosion-resistant aluminum alloy for multi-cavity automotive profiles through optimization of the composition and process, which has excellent mechanical properties and significantly improved corrosion resistance.

[0042] The embodiments of the present application will be described in detail below with reference to specific examples.

[0043] Example 1: The high-strength and high-toughness corrosion-resistant aluminum alloy in this embodiment includes the following chemical components by mass percentage: Si 0.55%, Mg 0.85%, Cu 0.22%, Mn 0.13%, Cr 0.12%, La 0.14%, Fe 0.1%, individual impurity content ≤0.05%, total impurity content ≤0.15%, and the balance being Al; The high-strength, tough, and corrosion-resistant aluminum alloy also includes TiC particles, which are introduced by an Al-3Ti-C master alloy. The content of the Al-3Ti-C master alloy accounts for 0.08% of the total mass of the aluminum alloy melt. In the Al-3Ti-C master alloy, the titanium content is 3%, the carbon content is 1%, and the balance is aluminum. Elemental silicon needs to be crushed into particles with a diameter of 2 mm and preheated at 150°C for 4 hours. A method for preparing a high-strength, high-toughness, and corrosion-resistant aluminum alloy for multi-cavity automotive profiles, the method comprising the following steps: (1) Copper plates, elemental silicon, Al-10La master alloy, manganese additives, chromium additives, aluminum ingots with a purity of 99.8%, and magnesium ingots with a purity of 99.9% were selected as raw materials. (2) Add pure aluminum ingots to the melting furnace and heat it to 760°C to melt it completely. Then, add preheated elemental silicon slowly to the aluminum liquid under stirring at 300 rpm. After it is completely dissolved, add Al-10La master alloy, copper plate, manganese additive and chromium additive in sequence. After it is completely dissolved, press pure magnesium ingots into the aluminum alloy melt below the surface of the liquid using a bell jar to melt it and obtain aluminum alloy melt. (3) Add Al-3Ti-C master alloy to the aluminum alloy melt and stir electromagnetically for 20 min; (4) The aluminum alloy melt after step (3) is refined and sampled quickly for spectral analysis. The composition is finely adjusted so that the composition is precisely controlled within the target range. Then the slag is removed and the mixture is allowed to stand. (5) The aluminum alloy melt after step (4) is subjected to ultrasonic treatment at a power of 180W for 10 minutes; (6) The melt temperature is reduced to 700℃, and primary degassing is performed through a degassing box and a double-layer foam ceramic filter plate is applied. The degassing box rotates at 200 r / min and the argon flow rate is 4 m³ / min. 3 / h, the filtration uses a double-layer foam ceramic filter plate with a porosity of 40ppi+60ppi; (7) The aluminum alloy melt is introduced into the crystallizer, and the low-frequency electromagnetic field surrounding the crystallizer is turned on. The frequency is 5 Hz, the current intensity is 60 A, the semi-continuous casting process is adopted, the casting temperature is 730℃, the casting speed is 90mm / min, the cooling water pressure is 0.2MPa, and the aluminum alloy ingot is obtained. (8) The aluminum alloy ingot is subjected to homogenization treatment, and the homogenization treatment includes the following stages: first stage: heating to 300°C at a rate of 25°C / h and holding for 3h; second stage: heating to 500°C at a rate of 40°C / h and holding for 6h; third stage: heating to 550°C at a rate of 20°C / h~30°C / h and holding for 8h, and then air-cooling to room temperature. (9) The homogenized aluminum alloy ingot is extruded and formed at a temperature of 480°C, a die temperature of 480°C, an extrusion cylinder temperature of 420°C, and an extrusion speed of 2.5 mm / s to obtain an aluminum alloy profile. (10) The aluminum alloy profile is solution treated at 520°C for 40 minutes, and then immediately water-quenched. (11) The aluminum alloy profile after solution treatment is subjected to a two-stage aging treatment, which includes: the first stage: 180℃ for 2 hours; the second stage: 200℃ for 2 hours; to obtain a high-strength, tough and corrosion-resistant aluminum alloy for multi-cavity automotive profiles.

[0044] Example 2: The high-strength, tough, and corrosion-resistant aluminum alloy described in this embodiment comprises the following chemical composition by mass percentage: Si 0.58%, Mg 0.87%, Cu 0.25%, Mn 0.11%, Cr 0.13%, La 0.16%, Fe 0.1%, with individual impurity content ≤0.05%, total impurity content ≤0.15%, and the balance being Al; The high-strength, tough, and corrosion-resistant aluminum alloy also includes TiC particles, which are introduced by an Al-3Ti-C master alloy. The content of the Al-3Ti-C master alloy accounts for 0.1% of the total mass of the aluminum alloy melt. The Al-3Ti-C master alloy contains 3% titanium, 1% carbon, and the balance is aluminum. Elemental silicon needs to be crushed into particles with a diameter of 2 mm and preheated at 200°C for 3 hours. A method for preparing a high-strength, high-toughness, and corrosion-resistant aluminum alloy for multi-cavity automotive profiles, the method comprising the following steps: (1) Copper plates, elemental silicon, Al-10La master alloy, manganese additives, chromium additives, aluminum ingots with a purity of 99.8%, and magnesium ingots with a purity of 99.9% were selected as raw materials. (2) Add pure aluminum ingots to the melting furnace and heat it to 760°C to melt it completely. Then, add preheated elemental silicon slowly to the aluminum liquid under stirring at 300 rpm. After it is completely dissolved, add Al-10La master alloy, copper plate, manganese additive and chromium additive in sequence. After it is completely dissolved, press pure magnesium ingots into the aluminum alloy melt below the surface of the liquid using a bell jar to melt it and obtain aluminum alloy melt. (3) Add Al-3Ti-C master alloy to the aluminum alloy melt and stir electromagnetically for 20 min; (4) The aluminum alloy melt after step (3) is refined and sampled quickly for spectral analysis. The composition is finely adjusted so that the composition is precisely controlled within the target range. Then the slag is removed and the mixture is allowed to stand. (5) the aluminum alloy melt after step (4) is subjected to ultrasonic treatment at a power of 160 W for 15 min; (6) the melt temperature is lowered to 705℃, primary degassing is performed through a degassing box and a double-layer foam ceramic filter plate, the rotation speed of the degassing box is 300 r / min, the argon flow rate is 5 m 3 / h, and the filtration uses a double-layer foam ceramic filter plate with a porosity of 40 ppi+60 ppi; (7) the aluminum alloy melt is introduced into a crystallizer, a low-frequency electromagnetic field surrounding the crystallizer is turned on, the frequency is 5 Hz, the current intensity is 60 A, a semi-continuous casting process is adopted, the casting temperature is 740℃, the casting speed is 90 mm / min, the cooling water pressure is 0.2 MPa, and an aluminum alloy ingot is obtained; (8) the aluminum alloy ingot is subjected to homogenization treatment, and the homogenization treatment comprises a first stage: heating to 300℃ at a rate of 20℃ / h and keeping for 3 h; a second stage: heating to 500℃ at a rate of 60℃ / h and keeping for 8 h; and a third stage: heating to 560℃ at a rate of 20℃ / h and keeping for 8 h, and air cooling to room temperature; (9) the homogenization-treated aluminum alloy ingot is extruded, and the extrusion temperature is 480℃, the die temperature is 480℃, the extrusion cylinder temperature is 420℃, and the extrusion speed is 2.5 mm / s, and an aluminum alloy profile is obtained; (10) the aluminum alloy profile is subjected to solid solution treatment at a temperature of 525℃ for 50 min, and then immediately water-quenched; (11) the aluminum alloy profile after the solid solution treatment is subjected to two-stage aging treatment, and the two-stage aging treatment comprises: a first stage: keeping at 180℃ for 2 h; and a second stage: keeping at 210℃ for 1 h; and a high-strength and high-toughness corrosion-resistant aluminum alloy for multi-cavity automobile profiles is obtained.

[0045] Example 3: The high-strength and high-toughness corrosion-resistant aluminum alloy in this example comprises the following chemical components by mass percentage: Si 0.58%, Mg 0.88%, Cu 0.24%, Mn 0.15%, Cr 0.13%, La 0.15%, Fe 0.1%, individual impurity content ≤0.05%, total impurity content ≤0.15%, and the balance is Al; The high-strength and high-toughness corrosion-resistant aluminum alloy further comprises TiC particles, which are introduced in the form of Al-3Ti-C intermediate alloy, and the content of the Al-3Ti-C intermediate alloy accounts for 0.08% of the total mass of the aluminum alloy melt; in the Al-3Ti-C intermediate alloy, the titanium content is 3%, the carbon content is 1%, and the balance is aluminum; The elemental silicon needs to be pre-crushed to a particle size of 2 mm and pre-heated at 200℃ for 3 h; A method for preparing a high-toughness corrosion-resistant aluminum alloy for multi-cavity automobile profiles, the method comprising the following steps: (1) selecting copper plate, elemental silicon, Al-10La intermediate alloy, manganese additive, chromium additive, and aluminum ingots with a purity of 99.8% and magnesium ingots with a purity of 99.9% as raw materials; (2) adding the pure aluminum ingots into a smelting furnace, heating to 760°C to completely melt them, then slowly adding the preheated elemental silicon into the aluminum liquid under stirring at 300 rpm, after complete dissolution, sequentially adding the Al-10La intermediate alloy, copper plate, manganese additive, and chromium additive, after complete dissolution, melting the pure magnesium ingots below the surface of the aluminum alloy melt by bell jar pressing, to obtain an aluminum alloy melt; (3) adding Al-3Ti-C intermediate alloy into the aluminum alloy melt, and electromagnetic stirring for 20 min; (4) refining the aluminum alloy melt after step (3), and quickly sampling for spectral analysis to finely adjust the composition so that the composition is accurately controlled within the target range, then skimming the slag, and standing for treatment; (5) ultrasonic treating the aluminum alloy melt after step (4) for 12 min at a power of 170 W; (6) reducing the melt temperature to 710°C, performing primary degassing through a degassing box and double-layer foam ceramic filter plates, the rotation speed of the degassing box is 300 r / min, the argon flow rate is 5 m 3 / h, and the double-layer foam ceramic filter plates have a porosity of 40 ppi+60 ppi; (7) introducing the aluminum alloy melt into a crystallizer, starting a low-frequency electromagnetic field surrounding the crystallizer, the frequency is 6 Hz and the current intensity is 60 A, using a semi-continuous casting process, the casting temperature is 720°C, the casting speed is 90 mm / min, the cooling water pressure is 0.2 MPa, to obtain an aluminum alloy ingot; (8) homogenizing the aluminum alloy ingot, and the homogenization process comprises a first stage of heating to 320°C at a rate of 20°C / h and holding for 2 h, a second stage of heating to 500°C at a rate of 50°C / h and holding for 6 h, and a third stage of heating to 570°C at a rate of 30°C / h and holding for 8 h, and air cooling to room temperature; (9) extruding the homogenized aluminum alloy ingot, and the extrusion temperature is 480°C, the die temperature is 480°C, the extrusion cylinder temperature is 410°C, and the extrusion speed is 2.5 mm / s, to obtain an aluminum alloy profile; (10) solid solution treating the aluminum alloy profile at a temperature of 540°C for 60 min, and then immediately water quenching; (11) the solution treated aluminum alloy profile is subjected to two-stage aging treatment, and the two-stage aging treatment comprises: first stage: 180℃ for 13h; second stage: 200℃ for 1h; and a high-strength and high-toughness corrosion-resistant aluminum alloy for multi-cavity automobile profiles is obtained.

[0046] Comparative Example 1 Comparative Example 1 is different from Example 3 in that the chemical composition and the component ratio of the high-strength and high-toughness corrosion-resistant aluminum alloy in Comparative Example 1 are different, and the others are the same as those in Example 3. The aluminum alloy in Comparative Example 1 comprises the following chemical components in mass percentage: Si 0.78%, Mg 1.52%, Cu 0.56%, Mn 0.07%, Cr 0.02%, La 0.03%, Fe 0.1%, ≤0.05% for single mass content of impurities, ≤0.15% for total amount of impurities, and the balance of Al.

[0047] Comparative Example 2 Comparative Example 2 is different from Example 3 in that the aluminum alloy in Comparative Example 2 does not add La element, and the others are the same as those in Example 3.

[0048] Comparative Example 3 Comparative Example 3 is different from Example 3 in that the Al-3Ti-C intermediate alloy is not added in Comparative Example 3, and the others are the same as those in Example 3.

[0049] Comparative Example 4 Comparative Example 4 is different from Example 3 in that the homogenization treatment process in Comparative Example 4 is different, and the others are the same as those in Example 3. The homogenization treatment process in Comparative Example 4 is: temperature is 550℃, and the holding time is 10h.

[0050] Comparative Example 5 Comparative Example 5 is different from Example 3 in that the single-stage aging treatment is used in Comparative Example 5, and the temperature is 160℃, and the holding time is 16h.

[0051] I. The aluminum alloy samples prepared in Example 3 and the aluminum alloy samples prepared in Comparative Examples 1-5 are subjected to mechanical property tests, and the results are shown in Table 1 below.

[0052] Table 1: Mechanical property test results

[0053] From the data analysis of Table 1, it can be seen that after optimization of the composition and process, the aluminum alloy as a whole can obtain excellent mechanical properties, and the performance is better than the performance requirement, realizing the requirements of high strength and high toughness. Compared with Example 3, the composition ratio in Comparative Example 1 is different, resulting in the formation of excessive coarse Mg2Si phase and Cu-containing phase, and further affecting the performance of the aluminum alloy; in Comparative Example 2, La is not added, the effect of refining grains and inhibiting recrystallization is weakened, resulting in relatively coarse grains and decreased uniformity of the structure; in Comparative Example 3, Al-3Ti-C intermediate alloy is not added, lacking the heterogeneous nucleation effect of TiC particles, the as-cast grains are coarsened, and the effect of fine-grain strengthening is weakened in subsequent processing; in Comparative Example 4, single-stage homogenization treatment is used, although the main strengthening phase can be dissolved, but it cannot effectively eliminate the dendritic segregation and promote the full spheroidization and diffusion of the insoluble phase. This leads to uneven distribution of the strengthening phase in subsequent extrusion and aging, and further affects the mechanical properties; in Comparative Example 5, the aging treatment process is different, although it has better strength, but the size of the precipitated phase is small and the distribution is dense, resulting in poorer plasticity than Example 3, while the present application significantly improves the toughness of the material by moderately coarsening and stabilizing the precipitated phase at the cost of small strength, achieving the balance of strength and toughness.

[0054] II. The aluminum alloy samples prepared in Example 3 and the aluminum alloy samples prepared in Comparative Examples 1-5 were subjected to corrosion resistance performance test, and the results are shown in Table 2.

[0055] Table 2: Corrosion performance test results

[0056] From the data analysis of Table 2, it can be seen that after optimization of the composition and process, the corrosion weight loss and corrosion depth of the aluminum alloy prepared by the present application are at a relatively low level, and the intergranular corrosion resistance is excellent. Compared with Example 3, the composition of Comparative Example 1 is significantly different, resulting in the formation of continuous network-shaped Cu-rich phase at the grain boundary, which forms a strong galvanic corrosion pair with the matrix and becomes a preferential corrosion channel, resulting in poorer corrosion performance than Example 3; in Comparative Example 2, La element is not added, lacking the optimization effect of La on grain boundaries and impurity phases, there are continuous sheet-shaped Si phases and impurity enrichment at the grain boundaries, corrosion easily expands along the grain boundaries, and the corrosion resistance decreases significantly; in Comparative Example 3, Al-3Ti-C intermediate alloy is not added, the grains are relatively coarse, and the uniformity of the structure is slightly poor, resulting in increased local corrosion sensitivity and poorer corrosion resistance than Example 3; in Comparative Example 4, the homogenization treatment process is different, resulting in insufficient uniformity of the structure and composition segregation, leading to uneven microelectrochemistry and poorer corrosion resistance than Example 3; in Comparative Example 5, the aging treatment process is different, after single-stage peak aging, the precipitated phase at the grain boundary is continuous and small, and there is a significant potential difference with the intracrystalline, which easily induces serious intergranular corrosion, indicating that the aging treatment of the present application is beneficial to the regulation of the size and distribution of the precipitated phase, and can significantly improve the corrosion resistance.

[0057] In addition, Figure 1 The microstructure of the aluminum alloy of the embodiment 1 is shown in the following figure: Figure 1 As can be seen from the figure, the aluminum alloy of the present application has small grain size and high overall uniformity.

[0058] The technical features of the above-mentioned embodiments can be combined arbitrarily, and in order to make the description simple, all possible combinations of the technical features in the above-mentioned embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0059] The above-mentioned embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A high-strength, high-toughness, and corrosion-resistant aluminum alloy for multi-cavity automotive profiles, characterized in that, The high-strength, tough, and corrosion-resistant aluminum alloy comprises the following chemical composition by mass percentage: Si 0.45~0.6%, Mg 0.80~0.95%, Cu 0.15~0.3%, Mn 0.10~0.2%, Cr 0.05~0.15%, La 0.10~0.2%, Fe ≤0.2%, individual impurity mass content ≤0.05%, total impurity content ≤0.15%, and the balance being Al.

2. The high-strength, high-toughness, and corrosion-resistant aluminum alloy according to claim 1, characterized in that, The high-strength, tough, and corrosion-resistant aluminum alloy also includes TiC particles, which are introduced by an Al-3Ti-C master alloy, and the content of the Al-3Ti-C master alloy accounts for 0.05% to 0.1% of the total mass of the aluminum alloy melt.

3. A method for preparing a high-strength, high-toughness, and corrosion-resistant aluminum alloy for multi-cavity automotive profiles, characterized in that, The preparation method is used to prepare the high-strength, high-toughness, and corrosion-resistant aluminum alloy for multi-cavity automotive profiles as described in claim 1 or 2, and the preparation method includes the following steps: (1) Copper plates, elemental silicon, Al-10La master alloy, manganese additives, chromium additives, aluminum ingots with a purity of 99.8%, and magnesium ingots with a purity of 99.9% were selected as raw materials. (2) The raw materials in step (1) are smelted to obtain aluminum alloy melt; (3) Add Al-3Ti-C master alloy to the aluminum alloy melt and stir electromagnetically; (4) The aluminum alloy melt after step (3) is refined and sampled quickly for spectral analysis. The composition is finely adjusted so that the composition is precisely controlled within the target range. Then the slag is removed and the mixture is allowed to stand. (5) The aluminum alloy melt after step (4) is subjected to ultrasonic treatment; (6) Degas and filter the aluminum alloy melt after step (5); (7) Cast the aluminum alloy melt after step (6) to obtain an aluminum alloy ingot; (8) The aluminum alloy ingot is homogenized and then air-cooled to room temperature; (9) The homogenized aluminum alloy ingot is extruded to obtain aluminum alloy profiles; (10) The aluminum alloy profile is subjected to solution treatment; (11) The aluminum alloy profile after solution treatment is subjected to two-stage aging treatment to obtain a high-strength, high-toughness, and corrosion-resistant aluminum alloy for multi-cavity automotive profiles.

4. The preparation method according to claim 3, characterized in that, In step (1), elemental silicon needs to be crushed to particles with a particle size of 1 mm to 5 mm and preheated at 150°C to 250°C for 2 to 4 hours to remove adsorbed moisture and improve its dissolution efficiency in the melt.

5. The preparation method according to claim 3, characterized in that, In step (2), pure aluminum ingots are added to a melting furnace and heated to 740℃~760℃ to completely melt them. Then, preheated elemental silicon is slowly added to the molten aluminum under stirring at 200rpm~400rpm. After it is completely dissolved, Al-10La master alloy, copper plate, manganese additive and chromium additive are added in sequence. After it is completely dissolved, pure magnesium ingots are pressed into the molten aluminum alloy below the surface of the molten aluminum alloy using a bell jar to melt them.

6. The preparation method according to claim 3, characterized in that, In step (3), the Al-3Ti-C master alloy contains 1% to 5% titanium, 1% to 5% carbon, and the balance is aluminum.

7. The preparation method according to claim 3, characterized in that, In step (5), the power of the acoustic treatment is 160W~180W, and the vibration time is 10min~15min.

8. The preparation method according to claim 3, characterized in that, In step (6), the melt temperature is reduced to 700℃~710℃, and primary degassing is performed through a degassing box and a double-layer foam ceramic filter plate is applied. The degassing box rotates at a speed of 200r / min~300r / min, and the argon flow rate is 4m³ / min. 3 / h~5m 3 / h, the filtration uses a double-layer foam ceramic filter plate with a porosity of 40ppi+60ppi.

9. The preparation method according to claim 3, characterized in that, In step (7), the aluminum alloy melt is introduced into the crystallizer, and a low-frequency electromagnetic field surrounding the crystallizer is turned on. The frequency is 3Hz~10Hz, the current intensity is 50A~150A, a semi-continuous casting process is adopted, the casting temperature is 710℃~740℃, the casting speed is 90mm / min~120mm / min, and the cooling water pressure is 0.1MPa~0.2MPa.

10. The preparation method according to claim 3, characterized in that, In step (8), the homogenization process is as follows: First stage: Heat to 300℃~320℃ at a rate of ≤30℃ / h, and hold for 1h~3h; Second stage: Increase the temperature to 470℃~500℃ at a rate of 40℃ / h~60℃ / h, and hold for 6h~10h; The third stage: Increase the temperature to 550℃~570℃ at a rate of 20℃ / h~30℃ / h, and hold for 8h~10h.

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