Extrusion casting aluminum alloy material with high toughness and high corrosion resistance and preparation method of extrusion casting aluminum alloy material

Abstract

The invention discloses a high-toughness and high-corrosion-resistance extrusion casting aluminum alloy material which comprises the following components in percentage by weight: 6%-10% of Si, 0.4%-0.6% of Mg, 0.8%-1.4% of Cu, 0.08%-0.15% of Fe, 0.04%-0.12% of Ti, 0.015%-0.030% of Sr, 0.02%-0.15% of Cr, 0.02%-0.09% of Zr, less than or equal to 0.1% of impurities and the balance of Al, and the weight ratio of Ti to Zr is Ti + Zr < lt >. 0.18%, 0.1% lt; cr + Zr [lt]; and 0.2%. According to the aluminum alloy material, the strength and toughness are improved by reasonably proportioning Cu and Mg elements, the structure compactness is optimized by combining an extrusion casting process, an oxidation film is thickened by accurately adding low-content Cr and Zr elements, the strength and the corrosion resistance are synergistically improved, the blank in the aspect of optimizing the comprehensive performance of AlSiMg alloy in the prior art is filled up, and the aluminum alloy material is suitable for being used in the field of aluminum alloy production. And the harsh requirements on materials in the high-end manufacturing field are met.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy material technology, specifically relating to an extrusion-cast aluminum alloy material with high strength, toughness and high corrosion resistance, and a method for preparing the aluminum alloy material, focusing on the core requirement of synergistic optimization of high strength, toughness and high corrosion resistance. Background Technology

[0002] AlSiMg cast aluminum alloys, with their low density, excellent casting performance, and cost advantages, have become key candidate materials in high-end manufacturing fields such as lightweight automotive structural components and aerospace auxiliary components. As industry demands for component reliability and service life continue to rise, aluminum alloys with excellent single properties can no longer meet the requirements. The comprehensive performance of high strength and toughness combined with high corrosion resistance has become the core direction of material research and development, and a key breakthrough in promoting the lightweighting and long service life upgrade of high-end equipment.

[0003] In strengthening AlSiMg alloys, the industry commonly enhances strength and toughness by adding Cu and Mg. Cu and Mg form a strengthening phase after T6 heat treatment, hindering dislocation movement through a dispersion strengthening effect and significantly improving alloy strength. Simultaneously, a properly proportioned Cu and Mg composition optimizes the microstructure, avoiding toughness degradation caused by excessive amounts of a single element. However, this approach has inherent contradictions: the introduction of Cu and Mg disrupts the integrity of the passivation film on the alloy surface, leading to a decrease in corrosion potential and an increase in corrosion current density. This makes the alloy susceptible to pitting and intergranular corrosion under complex conditions such as humidity and salt content, severely impacting service reliability.

[0004] To address the limitations imposed by casting defects on strength and toughness, squeeze casting is widely used in the forming of AlSiMg alloys. This process, through high-pressure filling and solidification, effectively suppresses defects such as porosity and shrinkage cavities, increases alloy density, and refines grains, further optimizing strength and toughness. However, squeeze casting only improves microstructure density and cannot solve the problem of decreased corrosion resistance caused by Cu and Mg elements. Current technologies still struggle to achieve a synergistic optimization of "strength and toughness improvement" and "corrosion resistance assurance."

[0005] Current industry solutions for improving the corrosion resistance of AlSiMg alloys have significant shortcomings: Anodizing technology: Although it can form an oxide film on the surface, for AlSiMg alloys containing Cu and Si, the oxide film is prone to problems such as roughness, dullness and high porosity. Moreover, it cannot fundamentally solve the corrosion risks caused by Cu and Zn segregation in the substrate. The surface protection effect is limited and affects the appearance of the product.

[0006] Chemical composition optimization schemes: Some technologies improve corrosion resistance through microalloying. For example, patent CN115491552B discloses a corrosion-resistant cast aluminum alloy, its preparation method, and its application. By adding elements such as Cr, V, Zr, and Sc, the oxide film thickness is increased. However, elements such as Sc and V are expensive and difficult to apply industrially. Moreover, the mass fractions of Cr and Zr are both greater than 0.1%, which easily form coarse second phases such as Al3Zr and Al7Cr, which break the aluminum matrix and lead to a decrease in alloy elongation, conflicting with the strength and toughness requirements of the extrusion casting process. The synergistic ratio of Cr, Zr, Cu, and Mg is not clearly defined, making it impossible to balance the strengthening effect and corrosion resistance. There is a lack of design adapted to the extrusion casting process, and the coarse second phase is prone to segregation during high-pressure solidification, further aggravating the deterioration of toughness.

[0007] For example, patent CN105463269B attempts to improve performance by adding Si 7.0-15%, Mg 0.2-0.6%, Mn 0.2-1.0%, Zn 0-1.0%, Sr 0.02-0.1%, Fe 0.4-1.0%, Cu 0-0.5%, and rare earth elements (RE) or Ti, Zr, V combination elements (M 0.01-1.5%). However, the cost of rare earth elements is high, and the final elongation of the alloy is only about 3%, which cannot meet the application requirements of high strength and high toughness.

[0008] Therefore, the relevant defects of the existing technology are: 1. The alloy composition is complex, and the introduction of too many elements leads to an excess of the second phase, which in turn causes insufficient toughness; 2. The high price of some alloying elements leads to high production costs, making industrial-scale promotion difficult; 3. Excessive Zr (0.1~0.2%) and Cr (0.15~0.3%) content easily leads to the formation of Al3Zr, (Al,Si)3(Ti,Zr), and α-Al. 65 Cr 27 Coarse second phases such as Fe8 tend to concentrate and become too large in size under squeeze casting conditions, thus becoming stress concentration points, reducing the elongation of the alloy, and resulting in poor compatibility with the squeeze casting process. 4. The casting method used in the existing technology has too low a cooling rate, which easily leads to internal defects such as shrinkage cavities and porosity, making it difficult to meet the requirements of high strength and high toughness.

[0009] The above background information is provided only to aid in understanding the inventive concept and technical solution of this invention. It does not necessarily belong to the prior art of this invention. In the absence of clear evidence that the above information was disclosed before the filing date of this invention, the above background information should not be used to evaluate the novelty and inventiveness of this invention. Summary of the Invention

[0010] In view of this, in order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a high-strength, high-toughness, and high-corrosion-resistant extrusion-cast aluminum alloy material, which significantly improves the corrosion resistance of aluminum alloy under the extrusion casting process conditions, while ensuring the mechanical properties of the alloy (especially elongation), thus solving the problem that existing aluminum alloy materials cannot simultaneously achieve both strength and corrosion resistance.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: A high-strength, high-toughness, and high-corrosion-resistant extrusion-cast aluminum alloy material, by weight fraction, comprises the following components: Si: 6%~10%, Mg: 0.4~0.6%, Cu: 0.8~1.4%, Fe: 0.08~0.15%, Ti: 0.04~0.14%, Sr: 0.015~0.030%, Cr: 0.02~0.15%, Zr: 0.02~0.09%, impurity content not exceeding 0.1%, and the balance being Al, wherein the weight ratio is: Ti + Zr < 0.18%, 0.1%... <Cr+Zr<0.2%。

[0012] According to some preferred embodiments of the invention, the weight ratio of Cu / (Cr+Zr) in the aluminum alloy material is <10.

[0013] According to some preferred embodiments of the present invention, in the aluminum alloy material, the product of the weight percentages of Cu and Mg is 0.45 to 0.6.

[0014] According to some preferred embodiments of the present invention, the aluminum alloy material has a tensile strength ≥400MPa, a yield strength ≥320MPa, and an elongation ≥8%; the corrosion area of ​​the aluminum alloy material after salt spray corrosion test is 2.4%~2.7%, and the average corrosion depth is ≤37μm.

[0015] According to some preferred embodiments of the present invention, the as-cast microstructure of the aluminum alloy material includes one or more of the following: The maximum length of the generated Al3Zr phase does not exceed 20 μm, and any phase longer than 1 mm... 2 The area proportion of the Al3Zr phase in the region does not exceed 0.1%; The average grain size is 100~250μm, and the maximum grain size does not exceed 400μm; The area ratio of eutectic is 7%~18%; The area percentage of the generated Cu-containing phase is 1.2~1.8%; The size of the Fe-containing phase is less than 20 μm.

[0016] Preferably, the area ratio of the Al2Cu phase in the Cu-containing phase is 0.6~0.8%, and the area ratio of the Q phase is 0.6~1.0%.

[0017] Preferably, the Fe-containing phase includes βAl5FeSi and / or αAlCrFe.

[0018] According to some preferred embodiments of the present invention, the microstructure of the aluminum alloy material after extrusion casting and heat treatment includes one or more of the following: All Cu-containing phases were dissolved back into the matrix; The length of the Al3Zr phase and / or αAlCrFe phase is less than 20 μm; Eutectic Si transforms into round or short rod-shaped Si particles, with the size of a single Si particle ranging from 0.2 to 8 μm.

[0019] The present invention also provides a method for preparing aluminum alloy material according to the above description, comprising the following steps: preparing and smelting the aluminum alloy material according to its composition, and then casting the aluminum alloy material.

[0020] According to some preferred embodiments of the invention, the casting is extrusion casting.

[0021] In some embodiments of the present invention, the preparation method of high-strength, high-toughness, and high-corrosion-resistant extruded aluminum alloy materials specifically includes the following steps: 1) Material preparation According to the set chemical composition, weigh out industrial pure aluminum, Al-Si master alloy, pure magnesium, pure copper, Al-Fe master alloy, Al-Sr master alloy, Al-Cr master alloy, Al-Zr master alloy, slag remover, refining agent, etc., and dry them.

[0022] 2) Melting aluminum ingots Industrial pure aluminum ingots and pure copper, preheated to 200-250°C, are placed in a smelting furnace for melting at a temperature of 760-780°C until all the pure aluminum is melted.

[0023] 3) Smelting After cooling the melt from step 2) to 740~745℃, add Al-Si, Al-Fe, and Al-Cr master alloys to the melt. After the alloys have completely melted, cool the melt to 720~725℃, stir for 3~4 minutes, add pure magnesium and Al-Zr master alloys, stir for 3~4 minutes, let stand for 10~15 minutes, and then remove the slag from the surface of the melt.

[0024] Then, the temperature is lowered to 700-710℃ and allowed to stand for 20-30 minutes. After that, a sodium-free covering agent is evenly sprinkled on the surface of the melt. The aluminum refining agent is wrapped in pure aluminum foil and then stuffed into a graphite bell jar. The amount of refining agent is 0.4-0.5% of the mass of the melt. The bell jar is pressed deep into the molten aluminum and then moved horizontally to various parts of the furnace. The reaction time is 4-6 minutes. After the reaction is complete, the slag is skimmed off.

[0025] After slag removal, the melt temperature is lowered to 720~730℃ and protected with inert gas. 0.25% Al-Sr master alloy is added and pressed into the bottom of the melting furnace for melting. After melting, the mixture is stirred evenly and allowed to stand for 10~15 minutes before furnace composition analysis to detect the composition content of the alloy melt. After passing the test, the melt is degassed.

[0026] 4) Degassing Heat the melt in step 3) to 700~720℃, introduce argon gas for 20~30 minutes to degas it, let the melt stand for 10~20 minutes after degassing, and then cast the sample by extrusion casting.

[0027] Due to the adoption of the above technical solutions, compared with the prior art, the high-strength, high-toughness, and high-corrosion-resistant extrusion-cast aluminum alloy material of the present invention has the following beneficial effects: 1. Excellent corrosion resistance: The composite oxide film formed by Cr-Zr synergy, combined with the precise matching of composition with extrusion casting and heat treatment processes, reduces matrix defects by leveraging the high-pressure densification effect of extrusion casting, while ensuring complete redissolution of the Q phase and avoiding the precipitation of coarse Cr-Zr-containing second phases, significantly improving the continuity and density of the oxide film.

[0028] 2. Balanced strength and toughness: The aluminum alloy of this invention has a tensile strength ≥400MPa, a yield strength ≥320MPa, and an elongation ≥8%. Compared with existing aluminum alloys of the same type, the strength is increased by 15~20% and the toughness is increased by 20~30%, which can meet the stringent requirements of high-end fields for the strength and toughness of materials.

[0029] 3. Excellent machinability: Through Sr modification treatment and Ti grain refinement, the alloy has excellent casting and subsequent machinability, enabling the forming of complex-shaped parts, and is suitable for mass production.

[0030] 4. Controllable cost: The raw materials used are all industrial-grade conventional raw materials, and the preparation process is a mature smelting-casting-heat treatment process. No special equipment is required, the production cost is low, and it is easy to promote industrialization. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a grain size diagram of the aluminum alloy material in Embodiment 1 of the present invention after heat treatment; Figure 2This is an electron micrograph of the aluminum alloy material in Comparative Example 1 of the present invention after heat treatment. Figure 3 and Figure 4 All of these are electron micrographs of the aluminum alloy material in Comparative Example 2 of this invention after heat treatment. Figure 5 This is an electron microscope image of the aluminum alloy material in Embodiment 1 of the present invention after heat treatment; Figure 6 The images show the samples from Examples 1-4 and Comparative Examples 1-2 after being subjected to CCT4 standard salt spray corrosion. Detailed Implementation

[0033] To enable those skilled in the art to better understand the technical solutions of the present invention, 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 should fall within the scope of protection of the present invention.

[0034] The relevant terms used in this invention are explained as follows: Squeeze casting: A casting process in which liquid metal is forced into a mold cavity under high pressure and solidified under high pressure, which can significantly improve the density and uniformity of the material.

[0035] T6 heat treatment: a heat treatment process that first involves solution treatment (high-temperature holding to dissolve the strengthening phase), then rapid quenching (to retain the supersaturated solid solution), and finally artificial aging (to precipitate fine and dispersed strengthening phases).

[0036] Composite oxide film: A surface protective film formed by the synergistic action of Al2O3, Cr2O3 and ZrO2, which has both high stability and high adhesion, and can block the intrusion of corrosive media.

[0037] Q phase: refers to the Al5Cu2Mg8Si6 phase, which is an important strengthening phase in AlSiCuMg alloys. It needs to be completely dissolved back into the matrix through solid solution treatment to avoid affecting the corrosion resistance.

[0038] CCT4 Salt Spray Corrosion Test: A cyclic salt spray corrosion test method in Japanese standards, used to simulate harsh corrosive environments and evaluate the corrosion resistance of materials.

[0039] Precisely controlling the mass fractions of Cr and Zr elements in aluminum alloy materials can significantly reduce the corrosion rate by forming a dense composite oxide film on the alloy surface. At the same time, low contents of Cr and Zr can avoid the formation of coarse secondary phases and can synergistically act with the strengthening phases formed by Cu and Mg without affecting the strength and toughness of the alloy. Combining the densification advantages of the squeeze casting process, triple synergy of "microstructure strengthening + fine grain strengthening + oxide film protection" can be achieved. In addition, coarse secondary phases will damage the continuity of the oxide film, and the unredissolved Q phase during the heat treatment process will also lead to discontinuous oxide film, triggering the penetration of corrosive media. Therefore, the matching of heat treatment and composition is crucial, and it is necessary to ensure that all of the Q phase is redissolved into the matrix to avoid the formation of microcells between the residual Q phase and the aluminum matrix and accelerate the dissolution of Al.

[0040] Based on this, the present invention aims to provide an AlSiMg cast aluminum alloy material with excellent performance. By reasonably proportioning Cu and Mg elements to improve strength and toughness, combining the squeeze casting process to optimize tissue densification, and then precisely adding low contents of Cr and Zr elements to thicken the oxide film, the synergistic improvement of strength and toughness and corrosion resistance is achieved, filling the gap in the comprehensive performance optimization of AlSiMg alloys in the prior art and meeting the stringent requirements of the high-end manufacturing field for materials.

[0041] Based on the above purpose, for the high-strength, high-toughness and high-corrosion-resistant squeeze-cast aluminum alloy material of the present invention, by weight fraction, the aluminum alloy material comprises the following components: Si: 6% - 10%, Mg: 0.4 - 0.6%, Cu: 0.8 - 1.4%, Fe: 0.08 - 0.15%, Ti: 0.04 - 0.12%, Sr: 0.015 - 0.030%, Cr: 0.02 - 0.15%, Zr: 0.02 - 0. [09%], where the weight ratio: Ti + Zr < 0.18%, 0.1% < Cr + Zr < 0.2%, Cu / (Cr + Zr) < 10 (the thickness of the oxide film increases with the increase of Cu content), the product of the weight percentages of Cu and Mg elements is controlled within 0.45 - 0.6 (both elements are key elements for enhancing strength but will reduce the elongation, so it is controlled within a certain range), the content of other impurities (such as Pb, Ca, etc.) does not exceed 0.1%, and the balance is Al. The tensile strength of the aluminum alloy material is ≥ 400 MPa, the yield strength is ≥ 320 MPa, and the elongation is ≥ 8%; the corrosion area ratio of the aluminum alloy material after salt spray corrosion test is 2.4% - 2.7%, and the average corrosion depth is ≤ 37 μm.

[0042] The preparation method of the above high-strength, high-toughness and high-corrosion-resistant squeeze-cast aluminum alloy material comprises the following steps: 1) Prepare materials According to the set chemical composition, weigh out industrial pure aluminum, Al-20%Si master alloy, pure magnesium, pure copper, Al-20%Fe master alloy, Al-10%Sr master alloy, Al-10%Cr master alloy, Al-10%Zr master alloy, slag remover, refining agent, etc. according to the stoichiometric ratio, and dry them.

[0043] 2) Melting aluminum ingots Industrial pure aluminum ingots and pure copper, preheated to 200-250°C, are placed in a smelting furnace for melting at a temperature of 760-780°C until all the pure aluminum is melted.

[0044] 3) Smelting After cooling the melt from step 2) to 740~745℃, add Al-20%Si, Al-20%Fe, and Al-10%Cr master alloys to the melt. After the alloys have completely melted, cool the melt to 720~725℃ and stir manually for 3~4 minutes. Then add pure magnesium and Al-10%Zr master alloys and stir manually for 3~4 minutes. After standing for 10~15 minutes, remove the slag from the surface of the melt.

[0045] Then, the temperature is lowered to 700-710℃ and allowed to stand for 20-30 minutes. After that, a sodium-free covering agent is evenly sprinkled on the surface of the melt. The aluminum refining agent is wrapped in pure aluminum foil and then stuffed into the graphite bell jar. The amount of refining agent is 0.4-0.5% of the mass of the melt. The bell jar is pressed into the depth of the molten aluminum, about 10 cm from the bottom of the furnace, and then moved horizontally to various parts of the furnace. The reaction time is about 4-6 minutes. After the reaction is completed, the slag is skimmed off.

[0046] After slag removal, the melt temperature is lowered to 720~730℃ and protected with inert argon gas. Then, 0.25% by mass of Al-10%Sr master alloy is added and pressed into the bottom of the melting furnace for melting. After melting, the mixture is stirred evenly and allowed to stand for 10~15 minutes before furnace composition analysis to detect the composition content of the alloy melt. After passing the test, the melt is degassed.

[0047] 4) Degassing Heat the melt from step 3) to 700-720℃, introduce argon gas for 20-30 minutes to degas, let the melt stand for 10-20 minutes, and then cast the sample. The casting method is squeeze casting, and the preferred squeeze casting process parameters are shown in the table below: Table 1. Squeeze Casting Process Parameters like Figure 1 As shown, the as-cast microstructure of aluminum alloy materials after extrusion casting has the following characteristics: (1) The maximum length of the generated Al3Zr phase does not exceed 20 μm, and any region (the region is greater than 1 mm) 2The area ratio of the Al3Zr phase in the sample does not exceed 0.1%; (2) The average grain size is 100~250μm and the maximum grain size does not exceed 400μm; (3) The area ratio of the eutectic is 7%~18%; (4) The area ratio of the generated Cu-containing phase is 1.2~1.8%, of which the area ratio of Al2Cu phase is 0.6~0.8% and the area ratio of Q-Al5Cu2Mg8Si6 phase is 0.6~1.0%; (5) The size of the Fe phase in the cast alloy is less than 20 μm, wherein the Fe phase includes βAl5FeSi and αAlCrFe.

[0048] The above-described as-cast microstructure characteristics indicate that under these compositional ratios and casting process conditions, the generated Al3Zr phase is small in size and uniformly distributed, with small grain size, which helps to ensure the toughness of the alloy. The Cu-containing Al2Cu and Q phases are also small in size and easily dissolve. During the solid solution stage, the Cu phase dissolves more, which is beneficial for improving elongation and the precipitation of higher-density strengthening phases during subsequent aging.

[0049] The aluminum alloy material after extrusion casting is then subjected to heat treatment. The preferred heat treatment process steps and parameters are as follows: (1) Solution treatment stage The temperature is raised from room temperature to 535℃ and held for 3-6 hours at a rate of 3-6℃ / min. A one-stage heat treatment is adopted, and overheating is avoided through reasonable component matching, ensuring that all Cu-containing phases are dissolved back into the matrix and improving the dissolution efficiency.

[0050] (2) Quenching stage Solution treatment is completed by water quenching at room temperature, resulting in a solution-treated casting.

[0051] (3) Place before the expiration date The solid solution treated castings should be left at room temperature for ≤12 hours.

[0052] (4) Time-limited stage The quenched casting is heated to 170±5℃ and held for 6~10 hours at a heating rate of 3~6℃ / min.

[0053] (5) Cooling After the heat preservation is complete, remove the sample and air cool it to room temperature.

[0054] The microstructure of heat-treated aluminum alloy materials has the following characteristics: (1) All Cu-containing phases (mainly including Q-Al5Cu2Mg8Si6 and Al2Cu phases) were completely dissolved back into the matrix; (2) The lengths of both the Al3Zr phase and the αAlCrFe phase are less than 20 μm; (3) Eutectic Si transforms into round or short rod-shaped Si particles, with the size of a single Si particle being 0.2~8μm; (4) The grain size remains basically unchanged after heat treatment.

[0055] The microstructure characteristics after the heat treatment shown above indicate that under the heat treatment process conditions, all Cu-containing phases are dissolved back. On the one hand, this helps the strengthening phase to precipitate during the aging process and improves the strength of the alloy. On the other hand, the complete dissolution of the coarse Cu-containing phases helps to improve the toughness of the alloy.

[0056] Because two Cu-containing phases (Al2Cu phase and Q-AlSiCuMg phase) are generated, existing technologies often use a heat treatment process of holding at 500℃ for a period of time to dissolve the Al2Cu phase, followed by heating to around 530℃ to dissolve the Q phase. The Al2Cu dissolution temperature is around 500℃; higher temperatures would cause overheating. However, in this invention, with the Mg and Cu contents set in the above formula, the generated Al2Cu phase is smaller and of lower size. Under the above heat treatment regime, heating to around 500℃ completely dissolves the Al2Cu phase, eliminating the need for heat treatment. Even if the temperature is further increased to 535℃, overheating will not occur, resulting in high efficiency.

[0057] The above-mentioned squeeze casting and heat treatment processes are preferred parameters. In some embodiments, squeeze casting and heat treatment processes with other existing parameters may also be used.

[0058] Example 1 The high-strength, high-toughness, and high-corrosion-resistant extruded aluminum alloy material in this embodiment comprises the following components by weight fraction: Si: 7.1%, Mg: 0.45%, Cu: 1.21%, Fe: 0.10%, Ti: 0.09%, Sr: 0.025%, Cr: 0.05%, Zr: 0.08%.

[0059] The preparation method of the above-mentioned high-strength, high-toughness, and high-corrosion-resistant extrusion-cast aluminum alloy material includes the following steps: 1) Material preparation According to the set chemical composition, weigh out industrial pure aluminum, Al-20%Si master alloy, pure magnesium, pure copper, Al-20%Fe master alloy, Al-10%Sr master alloy, Al-10%Cr master alloy, Al-10%Zr master alloy, slag remover, refining agent, etc. according to the stoichiometric ratio, and dry them.

[0060] 2) Melting aluminum ingots Industrial pure aluminum ingots and pure copper, preheated to 200°C, are placed in a smelting furnace for melting at a temperature of 760-780°C until all the pure aluminum is melted.

[0061] 3) Smelting After cooling the melt from step 2) to 740°C, add Al-20%Si, Al-20%Fe, and Al-10%Cr master alloys to the melt. After the alloys have completely melted, cool the melt to 720°C, stir manually for 3 minutes, and add pure magnesium and Al-10%Zr master alloys. Stir manually for 3 minutes, let stand for 12 minutes, and then remove the slag from the surface of the melt.

[0062] Then, the temperature was lowered to 700-710℃ and allowed to stand for 20 minutes. After that, a sodium-free covering agent was evenly sprinkled on the surface of the melt. The aluminum refining agent was wrapped in pure aluminum foil and then stuffed into a graphite bell jar. The amount of refining agent was 0.5% of the mass of the melt. The bell jar was pressed into the depth of the molten aluminum, about 10 cm from the bottom of the furnace, and then moved horizontally to various parts of the furnace. The reaction time was about 5 minutes. After the reaction was completed, the slag was skimmed off.

[0063] After slag removal, the melt temperature is lowered to 725℃ and protected with inert argon gas. Then, 0.25% by mass of Al-10%Sr master alloy is added and pressed into the bottom of the melting furnace for melting. After melting, the mixture is stirred evenly and allowed to stand for 12 minutes before furnace composition analysis to detect the composition content of the alloy melt. After passing the test, the melt is degassed.

[0064] 4) Degassing Heat the melt in step 3) to 710°C, introduce argon gas for 20 minutes to degas it, let the melt stand for 20 minutes after degassing, and then cast the sample. The casting method is extrusion casting, and the extrusion casting process parameters are shown in Table 1.

[0065] The aluminum alloy material after extrusion casting is subjected to heat treatment: the furnace is heated at a rate of 180℃ / h to 535℃ and held for 6 hours, then water-quenched, and immediately aged after quenching, then heated to 170℃ and held for 6 hours, and mechanical property tests are performed.

[0066] Example 2 The high-strength, high-toughness, and high-corrosion-resistant extruded aluminum alloy material in this embodiment comprises the following components by weight fraction: Si: 6.85%, Mg: 0.49%, Cu: 1.20%, Fe: 0.11%, Ti: 0.09%, Sr: 0.023%, Cr: 0.07%, Zr: 0.06%, other impurities not exceeding 0.1%, and the balance being Al.

[0067] The preparation method, extrusion casting method, and heat treatment method of the aluminum alloy material in this embodiment are basically the same as those in Embodiment 1, and will not be repeated here.

[0068] Example 3 The high-strength, high-toughness, and high-corrosion-resistant extruded aluminum alloy material in this embodiment comprises the following components by weight fraction: Si: 7.18%, Mg: 0.50%, Cu: 1.19%, Fe: 0.10%, Ti: 0.10%, Sr: 0.024%, Cr: 0.06%, Zr: 0.07%, other impurities not exceeding 0.1%, and the balance being Al.

[0069] The preparation method, extrusion casting method, and heat treatment method of the aluminum alloy material in this embodiment are basically the same as those in Embodiment 1, and will not be repeated here.

[0070] Example 4 The high-strength, high-toughness, and high-corrosion-resistant extruded aluminum alloy material in this embodiment comprises the following components by weight fraction: Si: 6.89%, Mg: 0.47%, Cu: 1.22%, Fe: 0.10%, Ti: 0.09%, Sr: 0.025%, Cr: 0.08%, Zr: 0.05%, other impurities not exceeding 0.1%, and the balance being Al.

[0071] The preparation method, extrusion casting method, and heat treatment method of the aluminum alloy material in this embodiment are basically the same as those in Embodiment 1, and will not be repeated here.

[0072] Comparative Example 1 The aluminum alloy material in this comparative example, by weight fraction, comprises the following components: Si: 7.02%, Mg: 0.48%, Cu: 1.24%, Fe: 0.11%, Ti: 0.10%, Sr: 0.024%, with other impurities not exceeding 0.1%, and the balance being Al. That is, the aluminum alloy material in this comparative example does not contain Cr or Zr.

[0073] The remaining parameters, preparation methods, casting methods, and heat treatment methods are basically the same as in Example 1, and will not be repeated here.

[0074] Comparative Example 2 The aluminum alloy material in this comparative example, by weight fraction, comprises the following components: Si: 7.10%, Mg: 0.52%, Cu: 1.12%, Fe: 0.12%, Ti: 0.10%, Sr: 0.024%, Cr: 0.3%, Zr: 0.2%, with other impurities not exceeding 0.1%, and the balance being Al. That is, in the aluminum alloy material of this comparative example, Ti+Zr > 0.18%, and Cr+Zr > 0.2%.

[0075] The remaining parameters, preparation methods, casting methods, and heat treatment methods are basically the same as in Example 1, and will not be repeated here.

[0076] Comparative Example 3 The aluminum alloy material in this comparative example, by weight fraction, comprises the following components: Si: 7.32%, Mg: 0.46%, Cu: 1.17%, Fe: 0.10%, Ti: 0.14%, Sr: 0.024%, Cr: 0.06%, Zr: 0.09%, with other impurities not exceeding 0.1%, and the balance being Al. That is, in the aluminum alloy material of this comparative example, Ti + Zr > 0.18%.

[0077] The remaining parameters, preparation methods, casting methods, and heat treatment methods are basically the same as in Example 1, and will not be repeated here.

[0078] Comparative Example 4 The aluminum alloy material in this comparative example, by weight fraction, comprises the following components: Si: 7.41%, Mg: 0.6%, Cu: 1.4%, Fe: 0.11%, Ti: 0.10%, Sr: 0.023%, Cr: 0.08%, Zr: 0.08%, with other impurities not exceeding 0.1%, and the balance being Al. That is, the product of the weight percentages of Cu and Mg in the aluminum alloy material of this comparative example is greater than 0.6.

[0079] The remaining parameters, preparation methods, casting methods, and heat treatment methods are basically the same as in Example 1, and will not be repeated here.

[0080] Comparative Example 5 The aluminum alloy material in this comparative example, by weight fraction, comprises the following components: Si: 7.11%, Mg: 0.48%, Cu: 1.19%, Fe: 0.10%, Ti: 0.10%, Sr: 0.024%, Cr: 0.04%, Zr: 0.06%, with other impurities not exceeding 0.1%, and the balance being Al. That is, in the aluminum alloy material of this comparative example, Cu / (Cr+Zr) > 10.

[0081] The remaining parameters, preparation methods, casting methods, and heat treatment methods are basically the same as in Example 1, and will not be repeated here.

[0082] Table 2 Ingredients Testing and Results Analysis: Salt spray corrosion tests were conducted on the aluminum alloy materials obtained in the examples and comparative examples, and the results were obtained, including the following steps: (1) Take out a 50mm*25mm*3mm sample from the heat-treated casting. Grind the sample with 80 mesh, 180 mesh, 600 mesh, 1200 mesh and 2000 mesh sandpaper in sequence. After grinding, put the sample into the salt spray corrosion chamber for salt spray corrosion test (CCT4, Japanese standard).

[0083] (2) After corrosion is completed, the surface and longitudinal corrosion depth of the sample are observed and statistically analyzed to obtain the test results, such as... Figure 6 As shown in Table 3; (3) The heat-treated sample was subjected to mechanical property testing (GB / T 16865), and the test results are shown in Table 3.

[0084] Figure 2 The image shown is an electron microscope image of the aluminum alloy material of Comparative Example 1 after T6 heat treatment. After heat treatment, it contains only a portion of Fe phase and a small amount of Cu phase. The composition of the aluminum alloy material of Comparative Example 1, excluding Cr and Zr, is within the preferred range of the present invention. The Cu phase (Al2Cu, Q phase) dissolves very well. However, as can be seen from the data in Table 3 below, the corrosion area of ​​the aluminum alloy material of Comparative Example 1 is too large, the average corrosion depth is too deep, and the corrosion resistance is very poor. Figure 3 and Figure 4 All images are electron microscope photographs of the aluminum alloy material of Comparative Example 2 after heat treatment. As can be seen from the images, due to the excessive Cr and Zr content and the influence of pressure during the extrusion casting process, the concentrated distribution of Al3Zr phase (size greater than 30μm) and α-AlCrFe phase (size greater than 45μm) will seriously reduce the elongation of the alloy.

[0085] Figure 5 These are electron microscope images of the aluminum alloy material from Example 1 after heat treatment. They show a low Zr phase content, with a size below 15 μm, and virtually no AlCrFe phase observed. This indicates a reasonable composition range; the small size of the Al3Zr and AlCrFe phases will not significantly reduce the elongation.

[0086] Table 3. Mechanical properties and corrosion resistance data of the aluminum alloy materials in the examples and comparative examples after heat treatment. As can be seen from the data in Table 3, after heat treatment, the aluminum alloy materials of Examples 1-4 exhibit stable tensile strength above 400 MPa, yield strength ≥ 320 MPa, elongation of 8.0~8.4%, corrosion area ratio of 2.40~2.68%, and average corrosion depth of 35.78~36.78 μm. Compared with Comparative Example 1 (excluding Cr and Zr), the corrosion area is reduced by more than 77%, the average corrosion depth is reduced by more than 64%, and the elongation is basically the same. This indicates that the corrosion resistance of alloys with Cr, Zr, and Ti in this composition range is significantly improved, while the mechanical properties are basically not reduced. Compared with Comparative Example 2 (Ti+Zr>0.18%, Cr+Zr>0.2%), the elongation... The corrosion resistance increased by more than 135% while the corrosion resistance remained the same, indicating that Ti+Zr greater than 0.18% and Cr+Zr greater than 0.2% would lead to a significant decrease in elongation. Compared with Comparative Example 4 (the product of the weight percentages of Cu and Mg elements is greater than 0.6), the corrosion area decreased by more than 46%, the average corrosion depth decreased by more than 33%, and the elongation increased by more than 158%, indicating that the product of Cu and Mg content in the example was less than 0.6, which significantly improved both corrosion resistance and elongation. Compared with Comparative Example 5 (Cu / (Cr+Zr) > 10), the corrosion area decreased by more than 57% and the average corrosion depth decreased by more than 38%, indicating that Cu / (Cr+Zr) was less than 10, resulting in a significant improvement in corrosion resistance.

[0087] Figure 6 The images show samples from Examples 1-4 and Comparative Examples 1-2 after CCT4 standard salt spray corrosion. The black spots are the corrosion spots. The corrosion area of ​​the samples from Examples 1-4 is between 2.4% and 2.7%, with an average corrosion depth ≤37μm. Compared with Comparative Example 1 (corrosion area 11.67%, average corrosion depth 102.65μm), the corrosion resistance is significantly improved, and the corrosion resistance is comparable to that of Comparative Example 2 (high Cr / Zr content).

[0088] The existing patent CN115491552B, a corrosion-resistant cast aluminum alloy, its preparation method and application, has the following alloy composition: Si 5~9%, Cu 0.6~4.5%, Mg 0.3~1.2%, Zn 0.7~1.5%, Zr 0.1~0.2%, Mn 0.1~0.3%, Cr 0.15~0.3%, V 0.05~0.2%, Ag 0.05~0.2%, Sc 0.05~0.2%, Y 0.05~0.2%, Ga 0.05~0.2%, Sn 0.05~0.2%, with unavoidable impurity element content <0.15%, and the balance being Al. The patent has the following problems: the alloy composition is complex, and the introduction of too many elements leads to an excessive amount of second phase; some alloying elements (such as Sc and V) are expensive, increasing production costs and making them unsuitable for mass production; the contents of Zr (0.1~0.2%) and Cr (0.15~0.3%) are too high, which easily introduces coarse second phases, which will accumulate under squeeze casting conditions, resulting in a significant reduction in alloy elongation.

[0089] To achieve high strength in aluminum alloys, Mg and Cu elements must be added. However, adding excessive Cu and Mg elements during casting results in numerous pores. Both increased Cu and Mg levels and increased pores significantly reduce corrosion resistance. Therefore, Cr and Zr elements need to be added to improve corrosion resistance. However, the normal Cr, Zr, or other element content added in existing technologies is not suitable for extrusion casting because extrusion casting can cause the second phase formed by these elements to concentrate and become excessively large. The application scenario and effect of this invention are extrusion casting + high strength and toughness requirements + high corrosion resistance. This invention achieves good corrosion resistance and good mechanical properties while using low Cr and Zr content, realizing high strength, high corrosion resistance, and high toughness.

[0090] This invention successfully overcomes the core defects of existing technologies through a combination of precise composition design, extrusion casting, and synergistic optimization of heat treatment. It achieves a significant improvement in corrosion resistance without reducing the alloy's elongation and strength. This achieves synergistic optimization of "high strength and toughness + high corrosion resistance," while avoiding the use of expensive elements. The process is mature and controllable, suitable for industrial mass production. Specifically, the innovations of this invention mainly include the following: 1. Innovative Cr-Zr synergistic element design to construct a dense and stable composite oxide film: Breaking through the limitations of traditional single corrosion-resistant elements, by precisely controlling the content ratio of Cr and Zr, a composite oxide film composed of Al2O3, Cr2O3, and ZrO2 is synergistically formed on the alloy surface. This composite oxide film not only possesses the high chemical stability brought by Cr2O3, but also the high adhesion brought by the refined grains of ZrO2, effectively blocking the intrusion of corrosive media and significantly improving the corrosion resistance of the alloy, making it particularly suitable for harsh corrosive environments.

[0091] 2. Achieving synergistic optimization of high strength and toughness and high corrosion resistance: By precisely matching the Si-Mg-Cu multi-component strengthening system and the Cr-Zr corrosion-resistant system, while ensuring the full precipitation of the strengthening phase to improve strength, Ti-Sr is used to refine the grains and improve toughness, and the Cr-Zr composite oxide film ensures corrosion resistance, thus solving the technical pain point of existing aluminum alloys that "it is difficult to achieve both high strength and toughness and high corrosion resistance".

[0092] 3. Composition-process synergistic optimization to enhance material stability: Limiting the content of other impurities to no more than 0.1% to prevent impurity elements from damaging the continuity and integrity of the composite oxide film; at the same time, optimizing the content range of each main alloying element to ensure optimal synergistic effect between elements and avoid performance degradation or coarse second phase precipitation due to compositional imbalance; in addition, through the synergistic matching of composition with extrusion casting and heat treatment processes, leveraging the advantages of high-pressure densification and grain refinement of extrusion casting, matrix defects are reduced, further ensuring the continuity of the oxide film and improving the mass production stability and long-term service reliability of the alloy.

[0093] The above embodiments prepared by the method of the present invention are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

[0094] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A high-strength, high-toughness, and high-corrosion-resistant extruded aluminum alloy material, characterized in that, The aluminum alloy material, by weight fraction, comprises the following components: Si: 6%~10%, Mg: 0.4~0.6%, Cu: 0.8~1.4%, Fe: 0.08~0.15%, Ti: 0.04~0.14%, Sr: 0.015~0.030%, Cr: 0.02~0.15%, Zr: 0.02~0.09%, with impurities not exceeding 0.1%, and the balance being Al. The weight ratio is: Ti + Zr < 0.18%, 0.1%... <Cr+Zr<0.2%。 2. The aluminum alloy material according to claim 1, characterized in that, In the aluminum alloy material, the weight ratio Cu / (Cr+Zr) < 10.

3. The aluminum alloy material according to claim 1, characterized in that, In the aluminum alloy material, the product of the weight percentages of Cu and Mg is 0.45 to 0.

6.

4. The aluminum alloy material according to claim 1, characterized in that, The aluminum alloy material has a tensile strength ≥400MPa, a yield strength ≥320MPa, and an elongation ≥8%; the corrosion area of ​​the aluminum alloy material after salt spray corrosion test is 2.4%~2.7%, and the average corrosion depth is ≤37μm.

5. The aluminum alloy material according to claim 1, characterized in that, The as-cast microstructure of the aluminum alloy material includes one or more of the following: The maximum length of the generated Al3Zr phase does not exceed 20 μm, and any phase longer than 1 mm... 2 The area proportion of the Al3Zr phase in the region does not exceed 0.1%; The average grain size is 100~250μm, and the maximum grain size does not exceed 400μm; The area ratio of eutectic is 7%~18%; The area percentage of the generated Cu-containing phase is 1.2~1.8%; The size of the Fe-containing phase is less than 20 μm.

6. The aluminum alloy material according to claim 5, characterized in that, The area ratio of the Al2Cu phase in the Cu-containing phase is 0.6~0.8%, and the area ratio of the Q phase is 0.6~1.0%.

7. The aluminum alloy material according to claim 5, characterized in that, The Fe-containing phase includes βAl5FeSi and / or αAlCrFe.

8. The aluminum alloy material according to claim 1 or 5, characterized in that, The microstructure of the aluminum alloy material after extrusion casting and heat treatment includes one or more of the following: All Cu-containing phases were dissolved back into the matrix; The length of the Al3Zr phase and / or αAlCrFe phase is less than 20 μm; Eutectic Si transforms into round or short rod-shaped Si particles, with the size of a single Si particle ranging from 0.2 to 8 μm.

9. A method for preparing an aluminum alloy material according to any one of claims 1-8, characterized in that, The process includes the following steps: preparing and smelting the aluminum alloy material according to its composition, and then casting the aluminum alloy material.

10. The preparation method according to claim 9, characterized in that, The casting is a squeeze casting.

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