Aluminum alloy extruded profile and preparation method thereof

Abstract

The invention discloses an aluminum alloy extruded profile and a preparation method thereof, and belongs to the field of metal material processing. The preparation method comprises the following steps that an aluminum alloy round cast ingot is pretreated; under the protective atmosphere, the aluminum alloy round cast ingot treated in the step S100 is subjected to programmed heating to the extrusion temperature; before extrusion, a mold and an ingot containing barrel are preheated; extruding when the temperature of the aluminum alloy round cast ingot reaches a target temperature; after the profile is extruded out of the die orifice, step quenching treatment is carried out; after quenching is completed, stretching and straightening are conducted; and aging treatment is conducted on the stretched profile, and the target aluminum alloy extrusion profile is obtained. According to the method, the Mg / Si mass ratio is accurately controlled, a [Zr] eq (zirconium equivalent) quantitative model is introduced, and key processes are optimized cooperatively, so that the aluminum alloy extruded profile which is better balanced in key performance such as strength, toughness, residual stress and dimensional stability is obtained.

Description

Technical Field

[0001] This invention relates to the field of metal material processing technology, specifically to an aluminum alloy extruded profile and its preparation method. Background Technology

[0002] With the increasing demand for lightweighting in high-end manufacturing sectors such as aerospace and new energy vehicles, the market has placed higher requirements on the comprehensive performance of aluminum alloy extruded profiles, demanding high strength along with excellent toughness, low residual stress, good corrosion resistance, and high dimensional stability. However, existing extrusion-heat treatment processes based on conventional 6000 series aluminum alloys face significant bottlenecks in achieving the synergistic optimization of these properties.

[0003] Traditional alloy composition design focuses too much on adjusting magnesium and silicon content to form the Mg2Si strengthening phase, while neglecting active control over grain refinement and recrystallization behavior. Elements such as chromium and manganese added to suppress recrystallization tend to form coarse, brittle intermetallic compounds. These phases are difficult to homogenize during subsequent processing, not only impairing the material's toughness and fatigue properties but also having limited effectiveness in inhibiting grain growth.

[0004] In the production process, parameters are often optimized in isolation at each stage, lacking overall process coordination. For example, the ingot homogenization treatment and subsequent heating regime fail to precisely match the precipitation behavior of microalloying elements, making it impossible to pre-create the ideal dispersed phase distribution before extrusion to effectively suppress dynamic recrystallization. Furthermore, the commonly used direct water cooling or forced air cooling quenching methods easily lead to uneven cooling of different parts of complex cross-section profiles, introducing high residual stress and torsional deformation, severely affecting dimensional accuracy. Simultaneously, the subsequent aging heat treatment regime fails to fully respond to the material's microstructure determined by the preceding extrusion and quenching processes, resulting in imprecise control of the size and distribution of strengthening precipitates, making it difficult to achieve an optimal balance of strength, toughness, and other properties. Summary of the Invention

[0005] The purpose of this invention is to provide an aluminum alloy extruded profile and its preparation method. Through synergistic optimization of composition and key processes, an aluminum alloy extruded profile with a better balance in key properties such as strength, toughness, residual stress, and dimensional stability is obtained, thereby solving the problem of insufficient comprehensive performance of existing products.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for preparing an aluminum alloy extruded profile includes the following steps:

[0008] S100. Pre-treatment of aluminum alloy round ingots;

[0009] S200. Under a protective atmosphere, the aluminum alloy round ingot processed in step S100 is heated to the extrusion temperature.

[0010] S300: Before extrusion, preheat the mold and ingot container; extrusion is carried out when the aluminum alloy round ingot reaches the target temperature.

[0011] S400 profiles are extruded through the die and then subjected to graded quenching.

[0012] S500. After quenching, perform tensile straightening.

[0013] S600. The stretched profile is subjected to aging treatment to obtain the target aluminum alloy extruded profile.

[0014] This invention precisely combines the pretreatment for inducing the precipitation of nano-phases in microalloys, protective multi-stage programmed heating, and hot extrusion based on the nano-phase pinning effect in terms of sequence and parameters. This ensures that the microstructure evolution from ingot to profile remains under control, resulting in a unique non-recrystallized fine-grained fibrous structure. Simultaneously, a staged quenching strategy is employed. Through a cooling path design of slow cooling followed by rapid cooling, the inherent contradiction between fixing the supersaturated solid solution and minimizing quenching stress is cleverly balanced at the physical level, laying the foundation for obtaining low-stress, high-precision products. Furthermore, the synergistic effect of tensile straightening and multi-stage aging with aging windows and mechanical states not only corrects the macroscopic shape but also achieves an optimal balance of strength, toughness, and corrosion resistance by precisely controlling the precipitation sequence.

[0015] First, through S100 pretreatment, after homogenization, controlled cooling and medium-temperature holding induce the pre-precipitation of microalloying elements in the form of nanoscale precipitates, pre-forming crucial grain refinement and recrystallization inhibition particles for subsequent deformation. Next, S200 undergoes multi-stage programmed heating under a protective atmosphere to achieve full and uniform solid solution of alloying elements, while precisely managing thermal stress, preparing ingots with consistent microstructures for extrusion. During S300 extrusion, these pre-formed nanophases act as pinning agents, effectively inhibiting dynamic recrystallization and promoting the formation of a fibrous deformation structure with high dislocation density, thus laying the foundation for the material's high strength.

[0016] Subsequently, S400 employs a staged quenching strategy of slow cooling followed by rapid cooling, balancing the contradiction between fixing the supersaturated solid solution and minimizing quenching stress. This significantly reduces residual stress and distortion tendency in the profile while preserving its strengthening potential. After quenching, S500 directly eliminates internal stress and corrects geometry through precise tensile deformation, ensuring high levels of straightness and dimensional accuracy in the profile. Finally, S600 uses a multi-stage aging regime to precisely control the precipitation sequence of the strengthening phases, ensuring they are uniform, fine, and dispersed. This allows the material to achieve peak strength while simultaneously achieving an optimal balance of toughness, corrosion resistance, and other comprehensive properties.

[0017] The aluminum alloy round ingot of the present invention is prepared by the following method:

[0018] Step 1: Raw material preparation and precise ingredient proportioning

[0019] Raw materials: intermediate alloys of high-purity aluminum ingots (≥99.85%), high-purity magnesium ingots, high-purity aluminum-silicon (Al-Si), aluminum-iron (Al-Fe), aluminum-manganese (Al-Mn), aluminum-zirconium (Al-Zr), aluminum-titanium (Al-Ti), aluminum-scandium (Al-Sc), and aluminum-vanadium (Al-V).

[0020] The batching calculation was performed according to the final composition range (Mg: 0.60~0.85%, Si: 0.45~0.70%, Mg / Si ratio: 1.15~1.25, Fe: 0.08~0.15%, Mn: 0.05~0.20%, Zr: 0.05~0.15%, Ti: 0.01~0.05%, Cr: 0.01~0.05%, Sc: 0.01~0.05%, V: 0.01~0.08%), where Sc and V were added at the upper limit to compensate for possible burn-off.

[0021] Step 2: To reduce element loss due to burning and promote the dissolution of refractory elements, staged melting and sequential addition are employed.

[0022] Matrix melting: Add aluminum ingots and aluminum-silicon master alloys to the melting furnace and heat to 740~760℃ to completely melt them.

[0023] Adding refractory elements and iron and manganese: After the melt becomes clear, add aluminum-zirconium (Al-Zr) and aluminum-vanadium (Al-V) master alloys in sequence, and stir thoroughly at 750~760℃ to promote the dissolution of refractory elements. Subsequently, add aluminum-iron (Al-Fe) and aluminum-manganese (Al-Mn) master alloys, and stir thoroughly. After each addition of raw materials, stir thoroughly for at least 5 minutes.

[0024] Add titanium and chromium: Next, add aluminum-titanium (Al-Ti) and aluminum-chromium (Al-Cr) master alloys and continue stirring thoroughly. Iron (Fe), manganese (Mn), and chromium (Cr) are added together at this stage to create a uniform melt environment for the subsequent formation of fine Al(Fe,Mn,Cr)Si impurity control phases.

[0025] Add scandium: Reduce the melt temperature to 720~730℃, add aluminum-scandium (Al-Sc) master alloy and stir thoroughly to reduce the high-temperature oxidation loss of Sc.

[0026] Finally, add magnesium: Add high-purity magnesium ingots at around 720℃, stir quickly, and then remove the slag.

[0027] Step 3: Stabilize the melt temperature at 730~740℃, and refine it by introducing high-purity argon gas through a rotary jet for 20~30 minutes, so as to stabilize the hydrogen content of the melt at ≤0.08ml / 100gAl.

[0028] Step 4: After refining, add aluminum-titanium-carbon (Al-5Ti-0.2C) grain refiner wire. The amount added should be 0.01%-0.02% to introduce additional Ti content, so as to compensate for the consumption of Ti in the intermediate alloy and achieve effective refinement.

[0029] Let it stand for 10-15 minutes, maintaining the temperature at 715-725℃, to allow the refining agent to disperse and distribute, while allowing the residual slag to float fully.

[0030] Step 5: Use hot-top horizontal DC semi-continuous casting. Control the casting temperature at 720~730℃, and for Φ200mm ingots, the casting rate is 50~80mm / min.

[0031] In addition, after every 8 to 12 ingots are extruded during the extrusion process, the mold surface is cleaned with laser to remove adhering aluminum. The entire process does not require machine downtime, ensuring continuous production and stable profile surface quality.

[0032] Furthermore, the aluminum alloy round ingot comprises the following components by weight percentage:

[0033] Mg: 0.60~0.85%, Si: 0.45~0.70%, Fe: 0.08~0.15%, Mn: 0.05~0.20%, Zr: 0.05-0.15%, Ti: 0.01~0.05%, Cr: 0.01~0.05%, Sc: 0.01%~0.05%, balance being Al and unavoidable impurities;

[0034] The mass ratio of Mg to Si is 1.15 to 1.25.

[0035] The mass percentages of Zr, Ti, and Sc conform to the formula [Zr]eq=[Zr]+1.5[Ti]+6[Sc], where the value of [Zr]eq ranges from 0.16% to 0.41%.

[0036] This invention limits the mass ratio of Mg to Si to 1.15~1.25, ensuring the formation of the maximum quantity of β”-Mg2Si strengthening phase precursors with ideal stoichiometry during aging, thereby achieving optimal aging strengthening response and avoiding the adverse effects of excess Si or Mg on conductivity, corrosion resistance, and formability. For the unavoidable impurity iron (Fe), the synergistic effect of manganese (Mn) and chromium (Cr) transforms it into fine, dispersed Al(Fe,Mn,Cr)Si type particles. This transformation effectively passivates the harmful coarse needle-like β-Fe phase, not only reducing damage to toughness but also contributing additional dispersion strengthening effects.

[0037] This invention discovers that Zr, Ti, and Sc elements have a significant synergistic effect on inhibiting recrystallization and refining grain size. To accurately quantify and control this composite effect, this invention defines the zirconium equivalent ([Zr]eq) to uniformly quantify the synergistic effect of the three microalloying elements: zirconium (Zr), titanium (Ti), and scandium (Sc). The calculation formula is [Zr]eq = [Zr] + 1.5[Ti] + 6[Sc], where [Zr], [Ti], and [Sc] are the mass percentages of Zr, Ti, and Sc in the aluminum alloy, respectively. Zr and Ti form the basis, creating the highly thermally stable Al3(Zr,Ti) nanophase, which acts as a framework to inhibit recrystallization. Sc, on the other hand, acts as a highly efficient reinforcing agent, forming a more stable Al3Sc or Al3(Sc,Zr) phase with extremely strong pinning ability. In the above calculation formula, the coefficients 1.5 and 6 represent the efficiency equivalents of Ti and Sc relative to Zr in forming stable nanophases, respectively. By controlling [Zr]eq within a preferred range of 0.16~0.41%, this invention ensures that the alloy can form a nano-dispersed phase distribution with optimal density and size within a wide range of compositional design, thereby obtaining a stable and excellent non-recrystallized fine-grained structure.

[0038] To optimize the formation of the Al3(Zr,Ti) core composite phase, this invention preferably controls the mass ratio of Zr to Ti to be 3~5:1. This ratio works synergistically with the aforementioned [Zr]eq range to ensure the extreme stability of the alloy's microstructure during hot working.

[0039] This invention achieves a high level of synergy between strength, toughness and thermal stability. While obtaining high strength, the alloy maintains excellent plasticity, fatigue resistance and high-temperature structural stability.

[0040] Furthermore, the aluminum alloy also includes V; by mass percentage, V: 0.01%~0.08%, and the total amount of V and Sc ≤0.12%.

[0041] Vanadium (V), as a partial substitute or complement to scandium (Sc), can form fine dispersed phases such as AlSiV, providing an additional strengthening pathway.

[0042] Furthermore, in S100, the pretreatment includes the following: treating at 455~475℃ for 10~14 hours; cooling the ingot to 180~220℃ at a rate of 90~120℃ / h; and holding the cooled ingot at 300~350℃ for 1~3 hours.

[0043] This invention first involves prolonged holding at 455–475°C to thoroughly dissolve the coarse non-equilibrium eutectic phase in the as-cast microstructure, allowing elements such as Mg, Si, and Zr to diffuse fully and achieve macroscopic composition homogenization. Subsequently, cooling is performed at a specific rate of 90–120°C / h to induce the precipitation of supersaturated microalloying elements (especially Zr and Sc) as fine, dispersed nanoscale Al3(Zr,Sc) phases, avoiding the formation of coarse, ineffective phases under slow cooling. Finally, holding at 300–350°C further ensures a more uniform distribution and dimensional stability of these newly formed nanophases, and eliminates some cooling stress.

[0044] Furthermore, in the S200, the programmed temperature rise includes the following:

[0045] The ingot is heated to 360-375℃ at a rate of 140-170℃ / h and held at that temperature for 1-1.5 hours.

[0046] Slowly heat to 485-495℃ at a rate of 40-55℃ / h and hold for 1.5-2.5 hours.

[0047] The first stage involves rapidly heating the ingot to 360-375℃ at a relatively fast rate (140-170℃ / h) and holding it at that temperature. The main purpose is to quickly achieve uniform temperature between the core and surface of the ingot, while also allowing some low-temperature unstable phases to initially dissolve, thus reducing the burden on the subsequent high-temperature stages. The second stage uses a slow heating rate (40-55℃ / h) to a higher solution temperature (485-495℃) and holds it at that temperature for an extended period. Its core purpose is to ensure that, under strict control of thermal stress, the main strengthening elements such as Mg and Si dissolve to the maximum extent in the aluminum matrix, forming a supersaturated solid solution, while also allowing the nanophases formed during pretreatment to undergo moderate re-dissolution and size optimization.

[0048] Furthermore, in S300, the mold is preheated to 435~455℃, the ingot container is heated to 390~410℃, and extrusion is carried out when the ingot temperature reaches 490~510℃, with the extrusion speed controlled at 2.0~3.0m / min.

[0049] Preheating the mold to 435~455℃ (slightly lower than the ingot temperature) reduces the rapid cooling of the ingot surface upon contact with the mold, ensuring uniform metal flow and preventing surface cracks. Setting the ingot container temperature (390~410℃) balances the conflict between reducing heat loss and preventing premature softening of the ingot. When the ingot temperature reaches 490~510℃, extrusion is performed at a moderate speed of 2.0~3.0 m / min. During plastic deformation, the metal softens sufficiently at high temperatures to reduce extrusion pressure. Simultaneously, the pinning of the microalloyed nanophases and a suitable strain rate effectively suppress the overall occurrence of dynamic recrystallization, promoting the formation of a slender, fibrous deformable structure rich in dislocations.

[0050] Furthermore, in S400, the graded quenching process includes the following:

[0051] After demolding, air cool within 3 seconds to 450~480℃; cool with water spray within 30~60 seconds to below 200℃; and allow to cool naturally to below 60℃.

[0052] Immediately after demolding, the profile undergoes air cooling, reducing the surface temperature from the high exit temperature to 450-480°C within 3 seconds. This relatively gentle initial cooling stage allows for a certain temperature equilibrium between the inside and outside of the profile cross-section, significantly reducing the thermal shock during subsequent rapid cooling. Subsequently, water spray cooling is applied, completing the bulk phase transformation from high to low temperature (below 200°C) within 30-60 seconds. This rapid cooling stage aims to fix the supersaturated solid solution formed during extrusion, preventing premature precipitation of strengthening elements and loss of strengthening potential. The final natural cooling to below 60°C is a stress relaxation and homogenization process.

[0053] Furthermore, in S500, after quenching, tensile straightening is performed, with the tensile amount controlled at 1~2%.

[0054] After quenching, the profile contains macroscopic residual stress and microscopic lattice distortion. While the material still retains some plasticity, applying a small, but exceeding-yield-strength, permanent tensile deformation can force a uniform, micro-plastic flow across the entire cross-section. This process effectively counteracts and redistributes the internal stress generated during quenching and corrects bending and torsional deformations in the profile. Strictly controlling the tensile amount to a low level of 1-2% is crucial to eliminate stress and correct shape while avoiding the introduction of new work hardening or damage to the material's elongation properties due to excessive plastic deformation.

[0055] Furthermore, in S600, timeliness processing includes the following:

[0056] Place the profile at 25-35℃ for 8-24 hours; keep it at 125-135℃ for 2-4 hours; slowly raise the temperature to 170-180℃ at a rate of 12-18℃ / h and keep it at that temperature for 5-8 hours.

[0057] First, the mixture is placed at 25-35℃ for 8-24 hours. Utilizing the high concentration of vacancies retained after quenching, solute atoms spontaneously aggregate to form high-density GP regions (atomic clusters), providing ample nucleation sites for subsequent precipitates. Next, a first artificial aging process is performed at 125-135℃ to stabilize the GP regions and initially transform them into a more ordered intermediate phase (such as the β″-phase precursor). Temperature control during this stage prevents excessive precipitation. Subsequently, the temperature is increased at an extremely slow rate (12-18℃ / h) to the peak aging temperature of 170-180℃. This slow heating allows the formed precipitate nuclei to grow gradually and uniformly, preventing some nuclei from dissolving and others from coarsening due to excessively rapid heating. Finally, the mixture is held at the peak temperature for an extended period to allow the strengthening phase (mainly β″-Mg2Si) to reach the desired size and volume fraction.

[0058] An aluminum alloy extruded profile prepared by the method described above.

[0059] Compared with the prior art, the beneficial effects of the present invention are:

[0060] This invention, by precisely controlling the Mg / Si mass ratio and introducing a [Zr]eq (zirconium equivalent) quantification model, enables aluminum alloys to achieve high strength (RP0.2 can reach over 340 MPa) while maintaining excellent plasticity (elongation up to 13%) and impact toughness (up to 45 J / cm). 2 This process achieves a high level of synergy between strength and toughness. The combination of this compositional system with subsequent integrated processes promotes the formation of fine-grained, non-recrystallized microstructures and uniform nano-precipitates, laying a solid foundation for the microstructural stability of the alloy.

[0061] The unique graded quenching and tensile straightening process of this invention can significantly reduce the residual stress of the profile (which can be controlled at around -65MPa) and greatly improve its dimensional accuracy (straightness can reach 0.8mm / m). This significantly optimized low internal stress state, combined with a highly stable microstructure, contributes to the improvement of the material's overall performance, giving it superior fatigue resistance and long-term service reliability. It is particularly suitable for dynamic load-bearing components with extremely demanding requirements for lightweighting, durability, and dimensional stability. Detailed Implementation

[0062] The present invention will now be further described.

[0063] Example 1

[0064] By mass percentage, aluminum alloy round ingots comprise the following components:

[0065] Mg: 0.72%, Si: 0.6%, Fe: 0.12%, Mn: 0.15%, Zr: 0.1%, Ti: 0.02%, Cr: 0.03%, Sc: 0.02%, balance being Al and unavoidable impurities;

[0066] The mass ratio of Mg to Si is 1.2:1; the mass ratio of Zr to Ti is 5:1.

[0067] The mass percentages of Zr, Ti, and Sc conform to the formula [Zr]eq=[Zr]+1.5[Ti]+6[Sc], and the value of [Zr]eq is 0.25%.

[0068] A method for preparing an aluminum alloy extruded profile includes the following steps:

[0069] S100. Treat the aluminum alloy round ingot at 465℃ for 12 hours; cool the ingot to 200℃ at a rate of 105℃ / h; hold the cooled ingot at 330℃ for 2 hours.

[0070] S200. Under nitrogen atmosphere, the aluminum alloy round ingot processed in step S100 is heated to the extrusion temperature.

[0071] The program's warm-up process includes the following:

[0072] The ingot is heated to 368°C at a rate of 155°C / h and held at that temperature for 1.2 hours.

[0073] Slowly heat to 490℃ at a rate of 48℃ / h and hold for 2 hours.

[0074] S300: Before extrusion, the die is preheated to 445℃ and the ingot container is heated to 400℃. When the ingot temperature reaches 500℃, extrusion is carried out, and the extrusion speed is controlled at 2.5m / min.

[0075] S400 profiles are extruded through the die and then subjected to graded quenching.

[0076] The graded quenching process includes the following:

[0077] After demolding, air cool to 465°C within 3 seconds; cool to below 200°C within 45 seconds using water spray cooling; and allow to cool naturally to below 60°C.

[0078] S500: After quenching, perform tensile straightening, with the tensile amount controlled at 1.5%.

[0079] S600. The stretched profile is subjected to aging treatment to obtain the target aluminum alloy extruded profile.

[0080] Timeliness processing includes the following:

[0081] The profile was placed at 30℃ for 16 hours; kept at 130℃ for 3 hours; and slowly heated to 175℃ at a rate of 15℃ / h and kept at that temperature for 6.5 hours.

[0082] Example 2

[0083] By mass percentage, aluminum alloy round ingots comprise the following components:

[0084] Mg: 0.6%, Si: 0.48%, Fe: 0.08%, Mn: 0.05%, Zr: 0.05%, Ti: 0.01%, Cr: 0.01%, Sc: 0.05%, balance being Al and unavoidable impurities;

[0085] The mass ratio of Mg to Si is 1.25:1; the mass ratio of Zr to Ti is 5:1.

[0086] The mass percentages of Zr, Ti, and Sc conform to the formula [Zr]eq=[Zr]+1.5[Ti]+6[Sc], and the value of [Zr]eq is 0.365.

[0087] A method for preparing an aluminum alloy extruded profile includes the following steps:

[0088] S100: Treat aluminum alloy round ingots at 455~475℃ for 10~14 hours; cool the ingots to 180~220℃ at a rate of 90~120℃ / h; hold the cooled ingots at 300~350℃ for 1~3 hours.

[0089] S200. Under nitrogen atmosphere, the aluminum alloy round ingot processed in step S100 is heated to the extrusion temperature.

[0090] The program's warm-up process includes the following:

[0091] The ingot is heated to 360-375℃ at a rate of 140-170℃ / h and held at that temperature for 1-1.5 hours.

[0092] Slowly heat to 485-495℃ at a rate of 40-55℃ / h and hold for 1.5-2.5 hours.

[0093] S300: Before extrusion, the die is preheated to 435~455℃ and the ingot container is heated to 390~410℃. When the ingot temperature reaches 490~510℃, extrusion is carried out, and the extrusion speed is controlled at 2.0~3.0m / min.

[0094] S400 profiles are extruded through the die and then subjected to graded quenching.

[0095] The graded quenching process includes the following:

[0096] After demolding, air cool within 3 seconds to 450~480℃; cool with water spray within 30~60 seconds to below 200℃; and allow to cool naturally to below 60℃.

[0097] S500: After quenching, perform tensile straightening, with the tensile amount controlled at 1.5%.

[0098] S600. The stretched profile is subjected to aging treatment to obtain the target aluminum alloy extruded profile.

[0099] Timeliness processing includes the following:

[0100] Place the profile at 25-35℃ for 8-24 hours; keep it at 125-135℃ for 2-4 hours; slowly raise the temperature to 170-180℃ at a rate of 12-18℃ / h and keep it at that temperature for 5-8 hours.

[0101] Example 3

[0102] By mass percentage, aluminum alloy round ingots comprise the following components:

[0103] Mg: 0.85%, Si: 0.70%, Fe: 0.15%, Mn: 0.20%, Zr: 0.15%, Ti: 0.05%, Cr: 0.05%, Sc: 0.03%, balance Al and unavoidable impurities;

[0104] The mass ratio of Mg to Si is 1.21:1; the mass ratio of Zr to Ti is 3:1.

[0105] The mass percentages of Zr, Ti, and Sc conform to the formula [Zr]eq=[Zr]+1.5[Ti]+6[Sc], and the value of [Zr]eq is 0.405%.

[0106] A method for preparing an aluminum alloy extruded profile includes the following steps:

[0107] S100. Treat the aluminum alloy round ingot at 455℃ for 10 hours; cool the ingot to 180℃ at a rate of 90℃ / h; hold the cooled ingot at 300℃ for 1 hour.

[0108] S200. Under nitrogen atmosphere, the aluminum alloy round ingot processed in step S100 is heated to the extrusion temperature.

[0109] The program's warm-up process includes the following:

[0110] The ingot is heated to 360°C at a rate of 140°C / h and held at that temperature for 1 hour.

[0111] Slowly heat to 485℃ at a rate of 40℃ / h and hold for 1.5 hours.

[0112] S300: Before extrusion, the die is preheated to 435°C and the ingot container is heated to 390°C. When the ingot temperature reaches 490°C, extrusion is carried out, and the extrusion speed is controlled at 2.0 m / min.

[0113] S400 profiles are extruded through the die and then subjected to graded quenching.

[0114] The graded quenching process includes the following:

[0115] After demolding, air cool to 450°C within 3 seconds; cool to below 200°C within 30 seconds using water spray cooling; and allow to cool naturally to below 60°C.

[0116] S500: After quenching, perform tensile straightening, with the tensile amount controlled at 1%.

[0117] S600. The stretched profile is subjected to aging treatment to obtain the target aluminum alloy extruded profile.

[0118] Timeliness processing includes the following:

[0119] The profile was placed at 25℃ for 8 hours; kept at 125℃ for 2 hours; and slowly heated to 170℃ at a rate of 12℃ / h, and kept at that temperature for 5 hours.

[0120] Example 4

[0121] By mass percentage, aluminum alloy round ingots comprise the following components:

[0122] Mg: 0.69%, Si: 0.6%, Fe: 0.12%, Mn: 0.15%, Zr: 0.08%, Ti: 0.02%, Cr: 0.03%, Sc: 0.01%, balance being Al and unavoidable impurities;

[0123] The mass ratio of Mg to Si is 1.15:1; the mass ratio of Zr to Ti is 4:1.

[0124] The mass percentages of Zr, Ti, and Sc conform to the formula [Zr]eq=[Zr]+1.5[Ti]+6[Sc], and the value of [Zr]eq is 0.17%.

[0125] V: 0.05%, and the total amount of V and Sc is 0.10%.

[0126] A method for preparing an aluminum alloy extruded profile includes the following steps:

[0127] S100: Treat aluminum alloy round ingots at 470℃ for 13 hours; cool the ingots to 210℃ at a rate of 100℃ / h; hold the cooled ingots at 330℃ for 2.5 hours.

[0128] S200. Under nitrogen atmosphere, the aluminum alloy round ingot processed in step S100 is heated to the extrusion temperature.

[0129] The program's warm-up process includes the following:

[0130] The ingot is heated to 370℃ at a rate of 150℃ / h and held at that temperature for 1.3 hours.

[0131] Slowly heat to 488℃ at a rate of 50℃ / h and hold at that temperature for 2.2 hours.

[0132] S300: Before extrusion, the die is preheated to 440℃ and the ingot container is heated to 395℃. When the ingot temperature reaches 505℃, extrusion is carried out, and the extrusion speed is controlled at 2.8m / min.

[0133] S400 profiles are extruded through the die and then subjected to graded quenching.

[0134] The graded quenching process includes the following:

[0135] After demolding, air cool to 460°C within 3 seconds; cool to below 200°C within 35 seconds using water spray cooling; and allow to cool naturally to below 60°C.

[0136] S500: After quenching, perform tensile straightening, with the tensile amount controlled at 1.8%.

[0137] S600. The stretched profile is subjected to aging treatment to obtain the target aluminum alloy extruded profile.

[0138] Timeliness processing includes the following:

[0139] The profile was placed at 30℃ for 20 hours; kept at 128℃ for 3.5 hours; and slowly heated to 172℃ at a rate of 16℃ / h and kept there for 7 hours.

[0140] Example 5

[0141] The aluminum alloy round ingot also includes V: 0.01% by mass percentage; other components and preparation methods are the same as in Example 1.

[0142] Example 6

[0143] The aluminum alloy round ingot also includes V: 0.08% by mass percentage; other components and preparation methods are the same as in Example 1.

[0144] Comparative Example 1

[0145] By mass percentage, aluminum alloy round ingots comprise the following components:

[0146] Mg: 0.72%, Si: 0.6%, Fe: 0.12%, Mn: 0.15%, Zr: 0.05%, Ti: 0.01%, Cr: 0.03%, Sc: 0.01%, balance being Al and unavoidable impurities;

[0147] The mass ratio of Mg to Si is 1.2:1; the mass ratio of Zr to Ti is 5:1.

[0148] The mass percentages of Zr, Ti, and Sc conform to the formula [Zr]eq=[Zr]+1.5[Ti]+6[Sc], and the value of [Zr]eq is 0.125%.

[0149] The preparation method is the same as in Example 1.

[0150] Comparative Example 2

[0151] By mass percentage, aluminum alloy round ingots comprise the following components:

[0152] Mg: 0.72%, Si: 0.6%, Fe: 0.12%, Mn: 0.15%, Zr: 0.12%, Ti: 0.04%, Cr: 0.03%, Sc: 0.05%, balance Al and unavoidable impurities;

[0153] The mass ratio of Mg to Si is 1.2:1; the mass ratio of Zr to Ti is 3:1.

[0154] The mass percentages of Zr, Ti, and Sc conform to the formula [Zr]eq=[Zr]+1.5[Ti]+6[Sc], and the value of [Zr]eq is 0.48%.

[0155] The preparation method is the same as in Example 1.

[0156] Comparative Example 3

[0157] By mass percentage, aluminum alloy round ingots comprise the following components:

[0158] Mg: 0.72%, Si: 0.6%, Fe: 0.12%, Mn: 0.15%, Zr: 0.1%, Ti: 0.04%, Cr: 0.03%, Sc: 0.01%, balance being Al and unavoidable impurities;

[0159] The mass ratio of Mg to Si is 1.2:1; the mass ratio of Zr to Ti is 2.5:1.

[0160] The mass percentages of Zr, Ti, and Sc conform to the formula [Zr]eq = [Zr] + 1.5[Ti] + 6[Sc], and the value of [Zr]eq is 0.22%. The preparation method is the same as in Example 1.

[0161] Comparative Example 4

[0162] By mass percentage, aluminum alloy round ingots comprise the following components:

[0163] Mg: 0.72%, Si: 0.6%, Fe: 0.12%, Mn: 0.15%, Zr: 0.12%, Ti: 0.02%, Cr: 0.03%, Sc: 0.02%, balance being Al and unavoidable impurities;

[0164] The mass ratio of Mg to Si is 1.2:1; the mass ratio of Zr to Ti is 6:1.

[0165] The mass percentages of Zr, Ti, and Sc conform to the formula [Zr]eq=[Zr]+1.5[Ti]+6[Sc], and the value of [Zr]eq is 0.27%.

[0166] The preparation method is the same as in Example 1.

[0167] Comparative Example 5

[0168] By mass percentage, aluminum alloy round ingots comprise the following components:

[0169] Mg: 0.72%, Si: 0.48%, Fe: 0.12%, Mn: 0.15%, Zr: 0.1%, Ti: 0.02%, Cr: 0.03%, Sc: 0.02%, balance being Al and unavoidable impurities;

[0170] The mass ratio of Mg to Si is 1.5:1; the mass ratio of Zr to Ti is 5:1.

[0171] The mass percentages of Zr, Ti, and Sc conform to the formula [Zr]eq=[Zr]+1.5[Ti]+6[Sc], and the value of [Zr]eq is 0.25%.

[0172] The preparation method is the same as in Example 1.

[0173] Comparative Example 6

[0174] By mass percentage, aluminum alloy round ingots comprise the following components:

[0175] Mg: 0.72%, Si: 0.7%, Fe: 0.12%, Mn: 0.15%, Zr: 0.1%, Ti: 0.02%, Cr: 0.03%, Sc: 0.02%, balance being Al and unavoidable impurities;

[0176] The mass ratio of Mg to Si is 1.03:1; the mass ratio of Zr to Ti is 5:1.

[0177] The mass percentages of Zr, Ti, and Sc conform to the formula [Zr]eq=[Zr]+1.5[Ti]+6[Sc], and the value of [Zr]eq is 0.25%.

[0178] The preparation method is the same as in Example 1.

[0179] Comparative Example 7

[0180] The composition of the aluminum alloy round ingot is the same as that in Example 1.

[0181] A method for preparing an aluminum alloy extruded profile includes the following steps:

[0182] S1. Preparation: Preheating the mold and ingot container in advance, and selecting the aluminum alloy round ingot;

[0183] S2. Heating process control: Add an isothermal stage, control the heating rate and control the furnace temperature of the profile. Before reaching the solution temperature, isothermal treatment is carried out at 500℃. The heating rate in the low temperature stage is controlled at 180℃ / h, the heating rate in the high temperature stage is controlled at 50℃ / h, and the furnace temperature of the profile is ≤130℃.

[0184] S3. Melting: The selected qualified aluminum alloy round ingots are placed into a heating furnace for melting. The temperature of the heating furnace is set at 380℃. When the aluminum rods are put into the machine, the temperature is controlled according to the wall thickness. If T≥1.4mm, the temperature is controlled at 500℃; if T<1.4mm, the temperature is controlled at 480℃.

[0185] S4. Extrusion: When the temperature of the ingot container reaches 380℃, the temperature of the mold reaches 440℃, and the temperature of the aluminum alloy ingot reaches 400-540℃, quickly load the mold onto the machine for extrusion to prevent the mold from cooling down. The temperature of the aluminum alloy ingot must be ≤540℃ to avoid mold blockage. During the extrusion process, the temperature is measured once every 15 ingots with a handheld thermometer in order to keep track of the ingot temperature changes and maintain the normal extrusion temperature.

[0186] S5. Venting: For each aluminum alloy ingot extruded, during the initial upsetting stage, when the pressure reaches 130 kg / cm³, venting is performed. 2 When the pressure is released, the pressure is then raised again for normal extrusion. The outlet temperature is controlled at ≥500℃. After extrusion, the material is discharged and the extruded aluminum alloy profile is taken out and directly water-cooled. The temperature is controlled to drop below 220℃ in 2.5 minutes.

[0187] S6. Mounting and clamping: For bracket profiles, use a vertical placement method with the solid and heavy parts of the profile facing down. For swaying profiles, use a flat placement method with the flat side facing down. Use iron bars to firmly bind the profiles to the quenching fixtures. Suspended parts should be leveled and supported.

[0188] S7. Quenching and Cooling Process Control: Take out the extruded aluminum alloy profile and directly water cool it. The water temperature is controlled at ≥65℃, and the temperature is reduced to below 220℃ in 2.5 minutes.

[0189] Comparative Example 8

[0190] The composition of the aluminum alloy round ingot is the same as that in Example 1.

[0191] A method for preparing aluminum alloy extruded profiles, wherein in step S100, the high-temperature homogenization, controlled cooling and medium-temperature heat preservation steps are omitted, and only the aluminum alloy round ingot is heated to 330°C and held for 2 hours.

[0192] The other steps are the same as in Example 1.

[0193] Comparative Example 9

[0194] The composition of the aluminum alloy round ingot is the same as that in Example 1.

[0195] A method for preparing aluminum alloy extruded profiles, S200: Under nitrogen atmosphere, the aluminum alloy round ingot treated in step S100 is...

[0196] The ingot is heated to 490℃ at a rate of 100℃ / h and held at that temperature for 3.2 hours.

[0197] The other steps are the same as in Example 1.

[0198] Comparative Example 10

[0199] The composition of the aluminum alloy round ingot is the same as that in Example 1.

[0200] A method for preparing aluminum alloy extruded profiles, wherein the S400 profile is extruded through a die and then naturally cooled to 60°C;

[0201] The other steps are the same as in Example 1.

[0202] Comparative Example 11

[0203] The composition of the aluminum alloy round ingot is the same as that in Example 1.

[0204] Step S500 is omitted in the preparation method, and the other steps are the same as in Example 1.

[0205] Comparative Example 12

[0206] The composition of the aluminum alloy round ingot is the same as that in Example 1.

[0207] S600. The stretched profile is slowly heated to 175°C at a rate of 15°C / h and held at that temperature for 25.5 hours to obtain the target aluminum alloy extruded profile.

[0208] The other steps are the same as in Example 1.

[0209] The performance of the aluminum alloy extruded profiles prepared by the methods in Examples 1-6 was measured, and the measurement results are shown in Table 1.

[0210] The performance testing method is as follows:

[0211] Tensile strength (Rm) and specified non-proportional elongation strength (RP0.2): Tested according to GB / T228.1 Metallic materials, tensile testing at room temperature. Samples are taken longitudinally from the profile and processed into standard proportional specimens (round or rectangular bar specimens with L0=5d). The test is conducted on a universal testing machine, and an extensometer is required to accurately measure the deformation. RP0.2 is obtained using the stress-strain curve graphical method. The test rate is performed according to the standard specifications until the specimen breaks.

[0212] The elongation after fracture (A) was performed simultaneously with the tensile test described above. After the specimen broke, the broken parts were tightly joined together, and the original gauge length (L0) and the gauge length after fracture (Lu) were measured using vernier calipers. The result was calculated using the formula A=[(Lu-L0) / L0]×100%.

[0213] Impact toughness (KU2 or KV2) is determined according to GB / T229, Charpy impact test method for metallic materials. Samples are taken from the profile and machined into standard Charpy V-notch specimens (10mm × 10mm × 55mm). The notch axis should be perpendicular to the extrusion direction. The test is conducted on a pendulum impact testing machine at room temperature (23±5℃), and the impact energy absorbed at fracture is recorded in joules (J).

[0214] Residual stress (σres) was determined using the borehole strain method (blind hole method) according to GB / T31310 or ASTM E837 standards. A special strain rosette was attached to the flat surface of the profile. A shallow hole with a small diameter (approximately 1.8 mm) was drilled in the center of the strain rosette using a high-precision drilling device. The magnitude and direction of the principal stress at the drilled hole were calculated by observing the change in resistance of the strain rosette before and after drilling.

[0215] Straightness: Place the profile of the specified length (full length) freely on the primary inspection plate. Measure using a high-precision laser tracker, laser collimator, or feeler gauge. Measure the maximum gap between the profile surface and the reference straight line (or plane) along the length direction. This gap value is the straightness deviation, usually expressed in millimeters per meter (mm / m) or the absolute deviation (mm) over the total length.

[0216] Table 1. Performance of aluminum alloy extruded profiles prepared by the methods in Examples 1-6

[0217]

[0218] As shown in Table 1, Example 1 represents the optimal performance balance achieved through the synergistic effect of multi-scale strengthening mechanisms. A precise Mg / Si ratio and optimized [Zr]eq jointly ensured the efficient formation and ideal distribution of the β″-Mg2Si phase and the Al3(Zr,Sc,Ti) nano-L12 phase, while staged quenching and multi-stage aging processes precisely fixed and controlled these strengthening phases. The result is a material that simultaneously possesses high load-bearing capacity (RP0.2 up to 340 MPa) and high fracture resistance (elongation 13.0%), while maintaining low residual stress and high dimensional accuracy.

[0219] Example 3 reveals the inherent trade-off in material properties when composition and process parameters approach the theoretical upper limit. The extremely high nanophase density brings peak strength (RP0.2 reaches 355 MPa), but also severely hinders dislocation movement, leading to a decrease in plasticity. At the same time, the higher eigenvalue of phase transformation stress makes residual stress control more difficult, and some stress is released in the form of macroscopic deformation (straightness 1.5 mm / m).

[0220] Examples 4 to 6 introduce vanadium (V) as an additional precipitation strengthening element. Its addition allows RP0.2 to achieve a linear and controllable gain from 343 MPa to 350 MPa, while plasticity and impact toughness only undergo expected minor adjustments. This demonstrates that the composition system of the present invention has the flexibility to fine-tune performance for specific applications while maintaining the core performance framework.

[0221] The performance of the aluminum alloy extruded profiles prepared by the methods of Examples 1 and Comparative Examples 1-12 is shown in Table 2.

[0222] Table 2. Performance of aluminum alloy extruded profiles prepared by the methods of Examples 1 and Comparative Examples 1-12

[0223]

[0224] As shown in Table 2, Comparative Example 1 ([Zr]eq=0.125%) suffers from insufficient number density of nanoscale L12 precipitates, leading to a significant weakening of its ability to suppress dynamic recrystallization and dislocation pinning strength. This is macroscopically manifested as a simultaneous decrease in RP0.2 (285 MPa) and impact toughness (30 J / cm²). Comparative Example 2 ([Zr]eq=0.48%), on the other hand, has an excessively high Sc content, resulting in the formation of coarse primary Al3Sc intermetallic compounds during solidification. These brittle phases become stress concentration points and crack initiations during subsequent deformation, causing the material to maintain RP0.2 at 350 MPa while its plasticity (elongation 7.0%) and toughness deteriorate. This demonstrates that the upper limit of [Zr]eq plays a decisive role in avoiding brittle phases and ensuring strength and toughness.

[0225] In Comparative Example 3, the slightly lower Zr / Ti ratio (2.5:1) did not cause a significant decrease in strength, but its core harm lies in disrupting the uniformity of composition and size of the Al3(Zr,Ti) nanophase. Deviating from the optimal ratio reduces the synergistic efficiency of Zr and Ti atoms in forming the Al3(Zr,Ti) composite nanophase. An ideal ratio favors the formation of a coherent strengthening phase with uniform composition and concentrated size distribution; while a lower ratio may tend to form Ti-rich or compositionally heterogeneous precipitates. The decreased uniformity of these phases' distribution in the matrix leads to differences in their pinning effects on dislocations and grain boundaries in the microscopic region, resulting in macroscopically reduced volatility and repeatability of mechanical properties (especially toughness and yield strength).

[0226] Comparative Example 4, with a Zr / Ti mass ratio increased to 6:1, showed a tensile strength of 355 MPa, an RP0.2 of 330 MPa, and an elongation of 11.0%, exhibiting a slight difference from the optimal Example 1. An excessively high Zr / Ti ratio may alter the occupancy and ordering process of the core atoms in the Al3(Zr,Ti) composite phase, slightly affecting the lattice coherence between this phase and the aluminum matrix, thus slightly weakening its pinning strengthening effect. A mismatch in the ratio may also cause a small amount of Zr-rich and Ti-rich phases to nucleate and grow separately during subsequent heat treatment, rather than forming a completely uniform single composite phase. This subtle change in the nanophase microstructure systematically impairs the overall performance matching of the material, particularly preventing the optimal synergistic optimization of strength and plasticity.

[0227] Comparative Examples 5 and 6 visually demonstrate the dominant influence of the Mg / Si stoichiometric ratio on the aging strengthening potential. Deviating from the optimal ratio directly reduces the driving force for the formation of the β″ phase and the precipitation efficiency, resulting in a significant loss of basic strength (RP0.2).

[0228] The parameter window of the prior art in Comparative Example 7 is broad and lacks precise coordination for the specific components of this invention (especially high Sc and Zr content), resulting in coarse control of microstructure and stress. The ultra-high residual stress (-180MPa) and the deterioration straightness (2.5mm / m) constitute the most compelling contrast, due to the lack of microstructure pre-treatment for microalloying elements and the single, intense water-cooling quenching process, which fails to achieve coordinated control of microstructure properties and internal stress.

[0229] Comparative Example 8 (simplified homogenization) and Comparative Example 9 (simplified solid solution) respectively disrupted the kinetic conditions of the pre-set nano-precipitated phase and the homogeneity of the solid solution, resulting in final tissue instability and uneven performance.

[0230] Comparative Example 10 (without quenching) suffered a complete loss of solid solution strengthening and age hardening potential due to the decomposition of the supersaturated solid solution into a coarse equilibrium phase, resulting in a collapse in strength (RP 0.2275 MPa). Comparative Example 11 (without straightening) suffered an unacceptable shape distortion (straightness 2.2 mm / m) because the quenching stress was not mechanically eliminated.

[0231] Comparative Example 12, subjected to single-stage long-term aging (175°C for 25.5 hours), exhibited tensile strength (370 MPa) and specified non-proportional elongation strength (345 MPa) slightly higher than that of the optimal Example 1, but its elongation (8.0%) and impact toughness (28 J / cm²) showed a precipitous drop. The prolonged single-temperature aging caused excessive coarsening of the main strengthening phase β″-Mg₂Si and the possible Al₃(Zr,Sc,Ti) phase. The precipitates grew from initially high-density nanoscale to coarse phases with excessively large sizes and spacing. While these coarse precipitates still contribute to strength, they severely hinder dislocation movement and become pathways for microcrack nucleation and propagation, leading to severe material embrittlement.

[0232] This invention, through the systematic synergy of the above-mentioned components and processes, successfully prepared high-performance aluminum alloy profiles, achieving a synergistic improvement in high strength (RP 0.2340 MPa), high plasticity (elongation 13%), low residual stress, and high straightness, thus improving the long-standing performance imbalance problem of high-end aluminum alloy profiles.

Claims

1. A method for preparing an aluminum alloy extruded profile, characterized in that, Includes the following steps: S100. Pretreatment of aluminum alloy round ingots; S200. Under a protective atmosphere, the aluminum alloy round ingot processed in step S100 is heated to the extrusion temperature. S300: Before extrusion, preheat the mold and ingot container; extrusion is carried out when the aluminum alloy round ingot reaches the target temperature. S400 profiles are extruded through the die and then subjected to graded quenching. S500. After quenching, perform tensile straightening. S600. The stretched profile is subjected to aging treatment to obtain the target aluminum alloy extruded profile.

2. The preparation method according to claim 1, characterized in that, The aluminum alloy round ingot, by mass percentage, comprises the following components: Mg: 0.60~0.85%, Si: 0.45~0.70%, Fe: 0.08~0.15%, Mn: 0.05~0.20%, Zr: 0.05-0.15%, Ti: 0.01~0.05%, Cr: 0.01~0.05%, Sc: 0.01~0.05%, with the balance being Al and unavoidable impurities; The mass ratio of Mg to Si is 1.15 to 1.

25. The mass percentages of Zr, Ti, and Sc conform to the formula [Zr]eq=[Zr]+1.5[Ti]+6[Sc], where the value of [Zr]eq ranges from 0.16% to 0.41%.

3. The preparation method according to claim 1, characterized in that, The aluminum alloy also includes V; by mass percentage, V: 0.01%~0.08%, and the total amount of V and Sc ≤0.12%.

4. The preparation method according to claim 1, characterized in that, In S100, the pretreatment includes the following: treating at 455~475℃ for 10~14 hours; cooling the ingot to 180~220℃ at a rate of 90~120℃ / h; and holding the cooled ingot at 300~350℃ for 1~3 hours.

5. The preparation method according to claim 1, characterized in that, In the S200, the programmed temperature rise includes the following: The ingot is heated to 360-375℃ at a rate of 140-170℃ / h and held at that temperature for 1-1.5 hours. Slowly heat to 485-495℃ at a rate of 40-55℃ / h and hold for 1.5-2.5 hours.

6. The preparation method according to claim 1, characterized in that, In S300, the mold is preheated to 435~455℃, the ingot container is heated to 390~410℃, and extrusion is carried out when the ingot temperature reaches 490~510℃. The extrusion speed is controlled at 2.0~3.0m / min.

7. The preparation method according to claim 1, characterized in that, In S400, the graded quenching process includes the following: After demolding, air cool within 3 seconds to 450~480℃; cool with water spray within 30~60 seconds to below 200℃; and allow to cool naturally to below 60℃.

8. The preparation method according to claim 1, characterized in that, In S500, after quenching, tensile straightening is performed, with the tensile amount controlled at 1~2%.

9. The preparation method according to claim 1, characterized in that, In S600, timeliness processing includes the following: Place the profile at 25-35℃ for 8-24 hours; keep it at 125-135℃ for 2-4 hours; slowly raise the temperature to 170-180℃ at a rate of 12-18℃ / h and keep it at that temperature for 5-8 hours.

10. An aluminum alloy extruded profile prepared by the preparation method according to any one of claims 1 to 9.

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