High-toughness Al-Mg-Si-Cu-Er-Zr alloy and extrusion preparation method thereof

Abstract

The application discloses a kind of high-strength high-toughness Al-Mg-Si-Cu-Er-Zr alloy and its extrusion preparation method, wherein alloy is by mass percentage, its chemical composition includes: Si 0.8-1.2%, Mg 0.6-1.0%, Cu 0.3-0.5%, Er 0.15-0.3%, Zr 0.1-0.2%, Ti 0.01-0.03%, remainder is Al and inevitable impurities;The application also provides the extrusion preparation method of above-mentioned alloy, including melting and casting and homogenization, low temperature predeformation, preheating before extrusion, ultrasonic assisted isothermal high-speed extrusion, on-line quenching and grading aging treatment steps.The profile prepared by the application completely eliminates coarse grain defect, and the tensile strength can reach more than 450MPa, the yield strength can reach more than 390MPa, the elongation is greater than or equal to 12%, and the performance of high strength, high toughness and high thermal conductivity is considered, which fully meets the performance requirements of new energy automobile battery tray, structural parts and other high-end components.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy material preparation technology, specifically relating to a high-strength and high-toughness Al-Mg-Si-Cu-Er-Zr alloy and its extrusion preparation method. Background Technology

[0002] 6xxx series Al-Mg-Si aluminum alloys have been widely used in construction, transportation, electronics, and other fields due to their moderate strength, excellent corrosion resistance, good weldability, and outstanding extrusion performance. Especially in recent years, with the rapid development of the new energy vehicle industry, 6-series aluminum alloy extruded profiles have become the preferred material for core components such as battery trays, vehicle body structural parts, and crash beams, thanks to their comprehensive performance advantages.

[0003] However, with the increasing demands for lightweighting, safety, and production efficiency in new energy vehicles, traditional 6-series aluminum alloys and their associated extrusion processes have gradually revealed numerous technical bottlenecks. Firstly, regarding extrusion efficiency, to ensure forming quality and mechanical properties, the extrusion speed of traditional 6-series aluminum alloys is typically controlled within a low range of 5-10 m / min, which is insufficient to meet the urgent needs of large-scale mass production for high efficiency and low cost, severely restricting the overall improvement of production efficiency in the industry. Secondly, under high-speed extrusion conditions, the profile generates heat during deformation due to friction and plastic deformation, causing a rapid increase in surface temperature. This easily leads to abnormal grain growth, forming a coarse-grained layer with a thickness of 100-300 μm. The presence of this coarse-grained layer significantly reduces the fatigue performance, corrosion resistance, and subsequent processing performance of the profile, becoming a key quality issue restricting the reliable application of high-performance profiles. Furthermore, in terms of strength-toughness matching, the tensile strength of traditional 6-series aluminum alloys (such as 6061 and 6063) typically only reaches 300-350 MPa, making it difficult to meet the high load-bearing capacity requirements of high-end structural components. While increasing the content of alloying elements can improve strength to some extent, it often leads to deterioration of extrusion molding performance and a decrease in elongation, making it difficult to achieve a good balance between high strength and high toughness.

[0004] Therefore, the aluminum extrusion industry urgently needs a new alloy composition design and matching extrusion process that can simultaneously achieve a significant improvement in extrusion efficiency, elimination of coarse grain defects, and synergistic optimization of strength and toughness to meet the needs of high-end manufacturing. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a high-strength and high-toughness Al-Mg-Si-Cu-Er-Zr alloy and its extrusion preparation method, thereby solving the technical problems of low extrusion speed, easy occurrence of coarse grain defects, and difficulty in achieving both strength and toughness in existing 6-series aluminum alloys.

[0006] The present invention achieves the above objectives using the following technical solution: A high-strength and high-toughness Al-Mg-Si-Cu-Er-Zr alloy, whose chemical composition by mass percentage includes: Si 0.8-1.2%, Mg 0.6-1.0%, Cu 0.3-0.5%, Er 0.15-0.3%, Zr 0.1-0.2%, Ti 0.01-0.03%, with the balance being Al and unavoidable impurities.

[0007] Preferably, the content of a single unavoidable impurity element is ≤0.05%, and the total impurity content is ≤0.15%.

[0008] This invention also provides a method for extruding a high-strength and high-toughness Al-Mg-Si-Cu-Er-Zr alloy, comprising the following steps: S1 Melting and Homogenization: The raw materials are prepared according to the chemical composition described in claim 1 or 2, and melted at 750-760℃. After melting, the materials are refined, and then an ingot is obtained at 720-730℃. The ingot is heated to 560-580℃ and held for 12-16 hours for homogenization to eliminate dendritic segregation in the as-cast state, followed by air cooling to room temperature; S2 Low-Temperature Pre-Deformation: The homogenized ingot is machined to remove the surface oxide scale, and then subjected to low-temperature pre-compression deformation. The deformation temperature is controlled at 250-300℃, the deformation amount is 10-15%, and the deformation rate is 0.1-0.5s. - ¹ This pre-deformation treatment can introduce a large number of deformation dislocations inside the ingot, providing nucleation sites for the subsequent Er and Zr element precipitates, promoting the uniform precipitation of nanoscale Al3(Er,Zr) composite precipitates, and refining the as-cast grains to improve the subsequent extrusion deformation capability; S3 Preheating before extrusion: Preheating the pre-deformed ingot and extrusion die to ensure temperature uniformity during extrusion, providing a basis for isothermal extrusion; S4 Ultrasonic-assisted isothermal high-speed extrusion: The preheated ingot is loaded into the extrusion cylinder, and during the extrusion process, ultrasonic vibration is applied to the extrusion die at a frequency of 20-30kHz and an output power of 500-800W. Ultrasonic vibration can effectively reduce the deformation resistance of the alloy. This process improves the flow properties of the metal and breaks down coarse grains during deformation, promoting dynamic recrystallization. Based on this, the extrusion speed is controlled at 15-20 m / min, and the outlet temperature of the profile is stabilized at 530-550℃ through a temperature-speed closed-loop control system, with temperature fluctuations controlled within ±5℃, achieving isothermal high-speed extrusion and avoiding grain growth caused by excessively high local temperatures. S5: Online quenching: The extruded profile immediately enters an online quenching device, using a water mist combined quenching method, with the water temperature controlled at 20-40℃. S6: Graded aging: After quenching, the profile immediately enters an aging furnace for graded aging treatment; finally, it is cooled to room temperature in the furnace to obtain the finished profile.

[0009] Preferably, in step S1, industrial pure aluminum, pure magnesium, pure silicon, Al-Cu master alloy, Al-Er master alloy, Al-Zr master alloy, and Al-Ti-B master alloy are used as raw materials for batching.

[0010] Preferably, in step S1, after smelting, a rotary powder spraying method is used for refining to remove gas and slag.

[0011] Preferably, in step S1, semi-continuous casting is performed at 720-730°C to obtain an ingot with a diameter of 152 mm.

[0012] Preferably, in step S3, the pre-deformed ingot is preheated to 480-500°C, and the extrusion die is preheated to 460-480°C.

[0013] Preferably, in step S4, axial ultrasonic vibration is applied to the extrusion die.

[0014] Preferably, in step S5, the quenching transfer time is ≤5s and the quenching cooling rate is ≥100℃ / s.

[0015] Preferably, in step S6, a graded aging treatment is performed: first, the temperature is kept at 110~130℃ for 1.5~2.5h for pre-aging to promote the uniform nucleation of the precipitated phase; then, the temperature is raised to 160~180℃ and kept for 3.5~4.5h to promote the growth and dispersion of the precipitated phase.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) Synergistic Innovation in Composition Design: Based on the Al-Mg-Si-Cu alloy, this invention synergistically adds trace amounts of Er and Zr elements, which can form nanoscale Al3(Er,Zr) composite precipitates, effectively pinning grain boundaries and increasing the recrystallization temperature of the alloy. Even under the high-temperature conditions of high-speed extrusion, it can effectively inhibit grain growth and eliminate defects in the surface coarse grain layer. At the same time, this composite precipitate can also play a role in dispersion strengthening, improving the strength of the alloy without compromising its toughness.

[0017] (2) Integrated process innovation: This invention integrates low-temperature pre-deformation, ultrasonic-assisted extrusion, and graded aging. Low-temperature pre-deformation provides nucleation sites for the precipitates, promoting the uniform precipitation of the composite precipitates. Ultrasonic-assisted extrusion effectively reduces deformation resistance and increases extrusion speed. Graded aging ensures the uniform dispersion of the precipitates, achieving synergistic optimization of strength and toughness.

[0018] (3) Comprehensive performance improvement: The profile prepared by this invention completely eliminates coarse grain defects, with tensile strength of over 450MPa, yield strength of over 390MPa, and elongation of ≥12%. It takes into account high strength, high toughness, and high thermal conductivity, and fully meets the performance requirements of high-end components such as battery trays and structural parts for new energy vehicles. Attached Figure Description

[0019] Figure 1 Metallographic image of the grain structure of the alloy product prepared in Example 1 of this invention.

[0020] Figure 2 Metallographic image of the grain structure of the conventional 6061 alloy prepared in Comparative Example 1. Detailed Implementation

[0021] Example 1 The high-strength, high-toughness Al-Mg-Si-Cu-Er-Zr alloy of this embodiment has the following chemical composition by weight percentage: Si: 1.0%, Mg: 0.8%, Cu: 0.4%, Er: 0.2%, Zr: 0.15%, Ti: 0.02%, B: 0.003%, with the balance being Al. Unavoidable impurities are present in individual components ≤0.05% and total impurities ≤0.15%. Its preparation method is as follows: (1) Melting and Homogenization: According to the above composition, industrial pure aluminum, pure magnesium, pure silicon, Al-50Cu master alloy, Al-10Er master alloy, Al-10Zr master alloy, and Al-5Ti-B master alloy were used as raw materials. The mixture was melted at 755℃, and after refining, degassing, and slag removal, it was semi-continuously cast at 725℃ to obtain an ingot with a diameter of 152mm. The ingot was then heated to 570℃, held for 14 hours, and air-cooled to room temperature.

[0022] (2) Pre-deformation treatment: The oxide scale on the surface of the ingot is removed by the car body, and then pre-compression deformation is carried out at 280℃ with a deformation amount of 12% and a deformation rate of 0.3s. - ¹.

[0023] (3) Preheating: Heat the ingot to 490°C for preheating, and heat the mold to 470°C for preheating.

[0024] (4) Extrusion: During the extrusion process, ultrasonic vibration is applied to the mold at a frequency of 25kHz and a power of 600W. The extrusion speed is controlled at 18m / min, and the profile outlet temperature is stabilized at 540℃ with a fluctuation of ±3℃.

[0025] (5) Online heat treatment: Water mist quenching is performed immediately after extrusion and demolding. The water temperature is 30℃, the transfer time is 3s, and the cooling rate is 120℃ / s.

[0026] (6) Grading aging: First, keep at 120℃ for 2 hours, then keep at 170℃ for 4 hours, and then cool with the furnace.

[0027] Example 2 The high-strength, high-toughness Al-Mg-Si-Cu-Er-Zr alloy of this embodiment has the following chemical composition by weight percentage: Si: 0.8%, Mg: 0.6%, Cu: 0.3%, Er: 0.15%, Zr: 0.1%, Ti: 0.01%, B: 0.001%, with the balance being Al. Unavoidable impurities are present in individual components ≤0.05% and total impurities ≤0.15%. Its preparation method is as follows: (1) Melting and Homogenization: According to the above composition, industrial pure aluminum, pure magnesium, pure silicon, Al-50Cu master alloy, Al-10Er master alloy, Al-10Zr master alloy, and Al-5Ti-B master alloy were used as raw materials. The mixture was melted at 755℃, and after refining, degassing, and slag removal, it was semi-continuously cast at 725℃ to obtain an ingot with a diameter of 152mm. The ingot was then heated to 560℃, held for 12 hours, and air-cooled to room temperature.

[0028] (2) Pre-deformation treatment: The oxide scale on the surface of the ingot is removed by the car body, and then pre-compression deformation is carried out at 250°C with a deformation amount of 10% and a deformation rate of 0.3s. - ¹.

[0029] (3) Preheating: Heat the ingot to 480°C for preheating, and heat the mold to 460°C for preheating.

[0030] (4) Extrusion: During the extrusion process, ultrasonic vibration is applied to the mold at a frequency of 20kHz and a power of 500W. The extrusion speed is controlled at 15m / min, and the profile outlet temperature is stabilized at 530℃ with a fluctuation of ±3℃.

[0031] (5) Online heat treatment: Water mist quenching is performed immediately after extrusion and demolding. The water temperature is 30℃, the transfer time is 3s, and the cooling rate is 120℃ / s.

[0032] (6) Graded aging: First, keep at 110℃ for 1.5h, then keep at 160℃ for 3.5h, and then cool with the furnace.

[0033] Example 3 The high-strength, high-toughness Al-Mg-Si-Cu-Er-Zr alloy of this embodiment has the following chemical composition by weight percentage: Si: 1.2%, Mg: 1.0%, Cu: 0.5%, Er: 0.3%, Zr: 0.2%, Ti: 0.03%, B: 0.005%, with the balance being Al. Unavoidable impurities are present in individual components ≤0.05% and total impurities ≤0.15%. Its preparation method is as follows: (1) Melting and Homogenization: According to the above composition, industrial pure aluminum, pure magnesium, pure silicon, Al-50Cu master alloy, Al-10Er master alloy, Al-10Zr master alloy, and Al-5Ti-B master alloy were used as raw materials. The mixture was melted at 755℃, and after refining, degassing, and slag removal, it was semi-continuously cast at 725℃ to obtain an ingot with a diameter of 152mm. The ingot was then heated to 580℃, held for 16 hours, and air-cooled to room temperature.

[0034] (2) Pre-deformation treatment: The oxide scale on the surface of the ingot is removed by the car body, and then pre-compression deformation is carried out at 300℃ with a deformation amount of 15% and a deformation rate of 0.3s. - ¹.

[0035] (3) Preheating: Heat the ingot to 500°C for preheating, and heat the mold to 480°C for preheating.

[0036] (4) Extrusion: During the extrusion process, ultrasonic vibration is applied to the mold at a frequency of 30kHz and a power of 800W. The extrusion speed is controlled at 20m / min, and the profile outlet temperature is stabilized at 550℃ with a fluctuation of ±3℃.

[0037] (5) Online heat treatment: Water mist quenching is performed immediately after extrusion and demolding. The water temperature is 30℃, the transfer time is 3s, and the cooling rate is 120℃ / s.

[0038] (6) Graded aging: First, keep at 130℃ for 2.5h, then keep at 180℃ for 4.5h, and then cool with the furnace.

[0039] Comparative Example 1 The comparative example uses traditional 6061 aluminum alloy, with the following composition by weight percentage: Si 0.6%, Mg 1.0%, Cu 0.25%, Cr 0.2%, and the balance Al. Traditional extrusion processes were employed: ingot preheating to 530℃, die preheating to 480℃, extrusion speed 8m / min, followed by T6 aging (170℃ for 8 hours).

[0040] like Figure 1 and Figure 2 The comparison shows that the alloy product prepared in Comparative Example 1 exhibits a typical recrystallized grain structure with an average grain size of approximately 60 μm, and some coarse grains reaching a size of 198.2 μm. The grain boundaries are clear and straight, indicating that relatively complete dynamic recrystallization occurred during the extrusion hot deformation process.

[0041] The alloy product prepared in Example 1 of this invention has significantly refined grains, with an average grain size of approximately 30 μm. The reason for this grain refinement is as follows: (1) The formation of Al3(Er,Zr) phase induces non-uniform nucleation, refines the cast grains, and provides a fine-grained starting structure for subsequent hot deformation; (2) A large number of dislocations are introduced before preheating to 490℃. These dislocations will recover and form subgrains during subsequent preheating and extrusion, increasing the nucleation points of Al3(Er,Zr) phase, making the dispersed phase distribution more dispersed, and further strengthening the inhibition of recrystallization; (3) Ultrasonic vibration reduces the friction of the mold-metal interface, reduces the non-uniformity of the shear deformation zone, inhibits local adiabatic heating, and avoids abnormal grain growth induced by local overheating.

[0042] Table 1 Performance test results of each embodiment and comparative example product

[0043] The performance test results in the table above show that the alloy products prepared in Examples 1-3 of this invention have completely eliminated coarse grain defects, with yield strength of over 390 MPa, tensile strength of over 450 MPa, and elongation of ≥12%. All these properties are far superior to those of alloy products prepared by traditional methods. They also take into account high strength, high toughness, and high thermal conductivity, and can fully meet the performance requirements of high-end components such as battery trays and structural parts for new energy vehicles.

Claims

1. A high-strength and high-toughness Al-Mg-Si-Cu-Er-Zr alloy, characterized in that, Its chemical composition by mass percentage includes: Si 0.8-1.2%, Mg 0.6-1.0%, Cu 0.3-0.5%, Er 0.15-0.3%, Zr 0.1-0.2%, Ti 0.01-0.03%, with the balance being Al and unavoidable impurities.

2. The alloy according to claim 1, characterized in that, The unavoidable impurities have an individual element content of ≤0.05% and a total impurity content of ≤0.15%.

3. A method for extruding a high-strength and high-toughness Al-Mg-Si-Cu-Er-Zr alloy, characterized in that, Includes the following steps: S1 Melting and Homogenization: The chemical composition according to claim 1 or 2 is used for batching, and melting is carried out at 750-760°C. After melting, refining is carried out, and then ingots are obtained at 720-730°C. The ingots are heated to 560-580°C and held for 12-16 hours for homogenization treatment, and then air-cooled to room temperature. S2 Low-Temperature Pre-Deformation Treatment: The homogenized ingot is machined to remove the surface oxide scale, followed by low-temperature pre-compression deformation. The deformation temperature is controlled at 250-300℃, the deformation amount is 10-15%, and the deformation rate is 0.1-0.5s. - ¹; S3 Preheating before extrusion: Preheat the pre-deformed ingot and extrusion die; S4 Ultrasonic Assisted Isothermal High-Speed ​​Extrusion: The preheated ingot is loaded into the extrusion cylinder. During the extrusion process, ultrasonic vibration is applied to the extrusion die. The vibration frequency is 20-30kHz, the output power is 500-800W, and the extrusion speed is controlled at 15-20m / min. Through the temperature-speed closed-loop control system, the outlet temperature of the profile is stabilized at 530-550℃, and the temperature fluctuation range is controlled within ±5℃. S5: Online quenching: The extruded profile immediately enters the online quenching device and adopts a water mist combined quenching method, with the water temperature controlled at 20-40℃. S6 graded aging: After quenching, the profile is immediately put into an aging furnace for graded aging treatment; finally, it is cooled to room temperature with the furnace to obtain the finished profile.

4. The preparation method according to claim 3, characterized in that, In step S1, industrial pure aluminum, pure magnesium, pure silicon, Al-Cu master alloy, Al-Er master alloy, Al-Zr master alloy, and Al-Ti-B master alloy are used as raw materials for batching.

5. The preparation method according to claim 3 or 4, characterized in that, In step S1, after smelting, a rotary powder spraying method is used for refining to remove gas and slag.

6. The preparation method according to claim 5, characterized in that, In step S1, semi-continuous casting is carried out at 720-730℃ to obtain an ingot with a diameter of 152mm.

7. The preparation method according to claim 3, characterized in that, In step S3, the pre-deformed ingot is heated to 480-500℃ for preheating, and the extrusion die is heated to 460-480℃ for preheating.

8. The preparation method according to claim 3, characterized in that, In step S4, axial ultrasonic vibration is applied to the extrusion die.

9. The preparation method according to claim 3, characterized in that, In step S5, the quenching transfer time is guaranteed to be ≤5s and the quenching cooling rate is ≥100℃ / s.

10. The preparation method according to claim 3, characterized in that, In step S6, the graded aging process is carried out: first, the temperature is kept at 110~130℃ for 1.5~2.5h for pre-aging; then the temperature is raised to 160~180℃ and kept for 3.5~4.5h.

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