V-microalloyed ultra-high-strength al-mg-si-cu alloy and preparation method therefor
Patent Information
- Application Number
- PCT/CN2026/086320
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-03-26
- Filing Date
- 2026-03-26
- Publication Date
- 2026-10-01
Smart Images
Figure CN2026086320_01102026_PF_FP_ABST
Abstract
Description
A V-microalloyed ultra-high strength Al-Mg-Si-Cu alloy and its preparation method Technical Field
[0001] This invention belongs to the field of aluminum alloy technology, specifically relating to a V microalloyed ultra-high strength Al-Mg-Si-Cu alloy and its preparation method. Background Technology
[0002] Aluminum alloy sheets used in automotive bodies must possess high mechanical properties while also exhibiting good formability, weldability, and corrosion resistance. Currently, 6xxx series aluminum alloys are widely used in automotive outer panels due to their moderate strength, excellent plasticity, corrosion resistance, and surface quality. However, with the increasing emphasis on lightweighting and safety in automobiles, new requirements are being placed on the mechanical properties of 6xxx series aluminum alloys.
[0003] As a typical heat-treatable aluminum alloy, 6xxx series aluminum alloys primarily improve their strength through aging precipitation. Currently, the commonly used alloying approach involves increasing the content of Mg and Si elements and optimizing their ratio to promote the nucleation and precipitation of the main strengthening phase (Mg-Si phase), thereby enhancing precipitation strengthening. Alternatively, introducing some Cu and Zn elements can promote Mg-Si phase precipitation while simultaneously introducing new strengthening phases (Mg-Si-Cu and Mg-Zn phases), thus improving alloy strength. However, the relatively low solid solubility of the Mg-Si phase in the Al matrix somewhat limits its precipitation strengthening effect.
[0004] Chinese Patent Application 1 (Publication No. CN110760723A) discloses an aluminum-magnesium-silicon erbium-zirconium alloy and a preparation process for improving its high-temperature mechanical properties. The alloy composition is: Mg: 0.8-1.2%, Si: 0.7-1.3%, Mn: 0.4-0.9%, Cu: 0.05-0.2%, Er: 0.01-0.4%, Zr: 0.01-0.4%, with the balance being Al. This Er and Zr composite microalloyed Al-Mg-Si alloy adds rare earth elements Er and Zr to the aluminum alloy in a microalloying manner, resulting in a significant improvement in both room temperature and high-temperature mechanical properties, as well as a significant increase in room temperature tensile strength and elongation.
[0005] Chinese Patent Application 2 (Publication No. CN115323203A) discloses a Cu and Sn composite microalloyed material of Al-Mg-Si alloy for automotive bodies, its preparation process, and its application. The alloy comprises the following elements by mass percentage: Mg: 0.5–1.5 wt%, Si: 1.0–2.0 wt%, Cu: 0.4–1.0 wt%, Sn: 0.1–0.5 wt%, Mn ≤ 0.05 wt%, Fe ≤ 0.10 wt%, with the balance being Al. This patent application, by compositely adding Cu and Sn elements, inhibits the formation of clusters in the alloy during the natural aging stage and promotes the formation of clusters that can directly transform into the β″ phase. This enhances the age-hardening effect of the Al-Mg-Si alloy, improves the baking hardness of the alloy, and solves the problem of insufficient baking hardening of Al-Mg-Si alloys used in automotive body panels after room temperature storage.
[0006] Chinese Patent Application No. 3 (Publication No. CN106480343A) discloses a novel Al-Mg-Si alloy material with high strength and resistance to seawater corrosion and its preparation method. The alloy material contains the following elements in the following mass percentages: Mg: 1.8-3.6 wt.%; Si: 1.6-3.3 wt.%; Mn: 0.45-0.65 wt.%; Cr: 0.25-0.35 wt.%; Zr: 0.15-0.3 wt.%; Ti: 0.2-0.3 wt.%; Ag: 0.2-0.5 wt.%; other impurities are individually ≤0.03 wt.% and the total is ≤0.1 wt.%, with the balance being aluminum. This patent application addresses the challenges of appropriately controlling the content of Mg and Si in the alloy and the Mg / Si ratio, and adding trace elements such as Mn, Cr, and Zr to alter the structure of harmful phases like iron, eliminate adverse effects, increase the recrystallization temperature and corrosion potential of the alloy, refine grains, and enhance the alloy's strength and ductility. Furthermore, the addition of Ag effectively enhances the heat treatment strengthening effect, increases the density of strengthening phase precipitation during aging, improves the alloy's mechanical properties, alters the atomic percentage of strengthening phase elements, reduces the potential difference between the precipitated phase and the matrix, and improves the alloy's corrosion resistance.
[0007] However, the yield strength of the Al-Mg-Si-Cu alloys in the aforementioned patent applications is 265–362 MPa, the tensile strength is 340–394 MPa, and the elongation is 10%–11.4%. However, the high prices of elements such as Er and Zr used in these Al-Mg-Si-Cu alloys limit their commercial application and make it difficult to meet the lightweight design requirements in the transportation sector. Summary of the Invention
[0008] To obtain aluminum alloys with higher strength and lower cost, the present invention aims to provide a V-microalloyed ultra-high strength Al-Mg-Si-Cu alloy and its preparation method. This invention achieves a higher strength aluminum alloy with excellent plasticity without adding costly Er and Zr-based elements. The obtained aluminum alloy has a yield strength ≥370MPa, tensile strength ≥420MPa, and elongation ≥14%, meeting the lightweight design and safety requirements of future transportation applications.
[0009] The first aspect of the present invention provides a V-microalloyed Al-Mg-Si-Cu alloy, wherein the chemical composition of the V-microalloyed Al-Mg-Si-Cu alloy, by mass percentage, is as follows: Mg: 1.20-2.00 wt.%, Si: 1.00-1.50 wt.%, Cu: 0.5-1.5 wt.%, Zn: 0.10-0.50 wt.%, Mn: 0.20-0.40 wt.%, V: 0.05-0.40 wt.%, Fe ≤ 0.20 wt.%, and the balance includes Al and unavoidable impurities; wherein 1.08 ≤ Mg / Si ≤ 1.70, preferably 1.10-1.34, and the element symbols are substituted with the corresponding mass percentage content of each element.
[0010] Preferably, the balance is Al and unavoidable impurities.
[0011] Preferably, the Al-Mg-Si-Cu alloy has a yield strength ≥370MPa, a tensile strength ≥420MPa, and an elongation ≥14%.
[0012] Preferably, the microstructure of the V-microalloyed Al-Mg-Si-Cu alloy consists of fine equiaxed crystals with a grain size of 14.0–18.0 μm, more preferably 15.2–16.4 μm; and the microstructure contains uniformly distributed nano-precipitated phases and dispersed phases, wherein the dispersed phase is an AlMgV phase with a density of 1.50 × 10⁻⁶. 12 ~2.70×10 12 / m 2 The preferred value is 1.79×10. 12 ~2.63×10 12 / m 2 The average size is 350–500 nm; the nano-precipitated phases are β″ and Q′ phases with a density of 5.50 × 10⁻⁶. 14 ~7.50×10 14 / m 2 Preferred value: 6.09×10 14 ~7.37×10 14 / m 2 The average length is 10.0–15.0 nm, preferably 11.7–14.5 nm.
[0013] The compositional design principle of the V-microalloyed ultra-high strength Al-Mg-Si-Cu alloy of this invention is as follows:
[0014] Mg: In this invention, the content of Mg and Si elements not only determines the content of the β-Mg2Si phase in 6xxx series aluminum alloys, but also the strengthening effect of the main strengthening phase β″ and its metastable phase. However, when the β″ phase content is too high, it is difficult for it to completely dissolve back into the matrix after high-temperature solution treatment. Therefore, it is necessary to control the total content of the above two elements. In addition, in Al-Mg-Si-Cu alloys, increasing the Mg / Si ratio of the alloy can accelerate the aging response rate of the alloy. This is because excess Mg can reduce the solid solubility of the β″ phase in the Al matrix, making it easier for the supersaturated solid solution to precipitate the strengthening phase during aging. Therefore, in this invention, the Mg content is controlled at 1.20 to 2.00 wt.%, and 1.08 ≤ Mg / Si ratio ≤ 1.70, preferably 1.10 to 1.34.
[0015] Si: Adding Si can form effective reinforcing phases such as Mg-Si and Mg-Si-Cu with Mg and Cu. However, the relatively high Mg content reduces the solid solubility of Si in the Al matrix. Furthermore, excess Si can also combine with Fe to form α-AlFeSi, β-AlFeSi, and Al... 15 Iron-rich intermetallic compounds of the (Fe,Mn)3Si2 phase reduce the material's deformability. Therefore, in this invention, the Si content is controlled at 1.00–1.50 wt.%.
[0016] Cu: In the system of this invention, under the premise of excess Mg content, the addition of some Cu can change the aging precipitation sequence of the β″ phase during aging, introduce a new strengthening phase -Q′ phase and its metastable phase, forming a two-phase strengthening effect, thereby improving the peak aging intensity of the alloy; in addition, the addition of Cu can also improve the aging response rate of the alloy and shorten the time required for peak aging treatment. Therefore, the Cu content is set to 0.5~1.5 wt.%.
[0017] Zn: Generally, Zn does not directly participate in the precipitation process of β″ and Q′ phases in 6xxx series aluminum alloys. Adding a small amount of Zn to 6xxx series aluminum alloys can improve the stability of Mg-Si clusters during aging or pre-aging treatment, and enhance aging response behavior and mechanical properties. Therefore, the Zn content in this invention is controlled at 0.10–0.50 wt.%.
[0018] Mn: As a commonly used trace element in aluminum alloys, adding a small amount of Mn can improve the morphology of the Fe-rich phase, transforming it from lath-like to spherical, thus improving the alloy's plasticity. Therefore, in this invention, the Mn content is controlled at 0.20–0.40 wt.%.
[0019] V: Adding trace amounts of V to Al-Mg alloys, under conditions of a high Mg / Si ratio (controlled at 1.08 ≤ Mg / Si ≤ 1.70), can generate a new dispersed strengthening phase – AlMgV phase, with the density of the dispersed strengthening phase controlled at 1.50 × 10⁻⁶. 12 ~2.70×10 12 / m 2 The preferred value is 1.79×10. 12 ~2.63×10 12 / m 2 The average size is controlled between 350 and 500 nm. This AlMgV phase can effectively pin grain boundaries during hot rolling, preventing grain growth and coarsening. While refining the grain size, it also improves the strength of the sheet through a combination of dispersion strengthening and precipitation strengthening. Therefore, the V content is controlled between 0.05 and 0.40 wt.% in this invention.
[0020] Fe: Fe is a common impurity element in aluminum alloys. Its solid solubility in the Al matrix is very low, and it readily forms coarse intermetallic compounds with Si, increasing the heat treatment pressure of the alloy and reducing the plasticity of the sheet. Therefore, strict control is required. Thus, this invention controls the Fe content to ≤0.20 wt.%.
[0021] This invention optimizes the content of Mg, Si, and Cu elements through rational design, and increases the Mg / Si ratio of the alloy to 1.08–1.70 (e.g., 1.10–1.34), thereby enhancing the nucleation driving force of the strengthening phase (β″ phase and its metastable phase) and promoting its precipitation. Furthermore, by adding trace amounts of V, an Al-Mg-V dispersed phase is formed in the matrix after homogenization treatment. On one hand, this phase pins grain boundary movement during hot working, inhibiting grain growth and coarsening, refining the alloy grain size, and controlling the microstructure to be fine equiaxed crystals with a grain size of 14.0–18.0 μm, preferably 15.2–16.4 μm. On the other hand, a combination of dispersed strengthening phase and precipitation strengthening is employed, and the dispersed phase density is controlled at 1.50 × 10⁻⁶. 12 ~2.70×10 12 / m 2The average size is controlled within 350–500 nm, improving the alloy strength and breaking through the existing strength range of Al-Mg-Si-Cu alloys. The resulting alloy in the peak aging state has a yield strength ≥370 MPa, tensile strength ≥420 MPa, and elongation ≥14%, which is superior to the Al-Mg-Si-Cu aluminum alloy plates reported previously (whose yield strength ranges from 265 to 362 MPa, tensile strength from 340 to 397 MPa, and elongation from 10% to 11.4%).
[0022] A second aspect of the present invention provides a method for preparing a V-microalloyed ultra-high strength Al-Mg-Si-Cu alloy, the method comprising the following steps performed sequentially:
[0023] 1) Smelting and casting:
[0024] Ingots are obtained through smelting and casting;
[0025] 2) Homogenization heat treatment:
[0026] The ingot is subjected to homogenization heat treatment to obtain a homogenized ingot. The homogenization heat treatment temperature is 545-560℃, the holding time of the homogenization heat treatment is 15-24h, preferably 16-24h, and the heating rate and cooling rate of the homogenization heat treatment are 0.50-1.00℃ / min.
[0027] 3) Hot rolling + cold rolling:
[0028] The homogenized ingot is hot-rolled and cold-rolled to obtain a cold-rolled sheet, wherein the total deformation of the hot rolling is 85-90% and the hot rolling temperature is 545-560℃.
[0029] 4) Solution treatment + quenching:
[0030] The cold-rolled sheet is subjected to solution treatment and quenching in sequence to obtain the solution-treated and quenched sheet. The solution treatment temperature is 555-573℃, preferably 555-570℃, the solution treatment time is 0.5-1.5h, and the quenching method is water quenching.
[0031] 5) Pre-aging treatment:
[0032] The plate after solution treatment and quenching is subjected to aging treatment to obtain V micro-alloyed Al-Mg-Si-Cu alloy, wherein the temperature of the pre-aging treatment is 150-185℃ and the holding time of the pre-aging treatment is 4-24h, preferably 10-24h.
[0033] Preferably, in step 1), the following raw materials are smelted and cast: high-purity aluminum, pure magnesium, pure zinc, Al-Si master alloy, Al-Cu master alloy, Al-Mn master alloy, Al-V master alloy, and Al-Fe master alloy are used as raw materials.
[0034] First, high-purity aluminum is completely melted and heated to 760–780°C. Al-V and Al-Fe master alloys are added, and after the master alloys are completely melted, a first melt is obtained. Then, the first melt is cooled to 740–760°C, and Al-Cu and Al-Mn master alloys are added. After they are fully melted, a second melt is obtained. The second melt is cooled to 730–740°C, and pure magnesium and pure zinc are added. The mixture is held at this temperature for 10–15 minutes to obtain a third melt. Then, a refining agent is added to the third melt. After the refining agent reacts fully with the third melt, a slag-removing agent is added, and the mixture is held at 720–740°C for 10–15 minutes. Finally, a refining agent is added, and the mixture is held at this temperature for 2–5 minutes before casting to obtain an ingot.
[0035] The slag remover is a sodium-free slag remover, and its addition amount is 0.30 to 0.40 wt.% of the mass of the third melt;
[0036] The refining agent is Al-5Ti-1B refining agent, and its addition amount is 0.05 to 0.1 wt.% of the mass of the third melt.
[0037] Preferably, in step 1), the casting temperature is 720–740°C.
[0038] Preferably, in step 3), the deformation of the cold rolling is ≥65%, and the temperature of the cold rolling is room temperature.
[0039] In the process design of V microalloying of Al-Mg-Si-Cu alloys, this invention:
[0040] The homogenization heat treatment temperature is set at 545–560℃, and the holding time is 15–24 h, preferably 16–24 h; the heating / cooling rate is 0.50–1.00℃ / min. This invention ensures the dispersed precipitation of the submicron AlMgV phase by controlling the homogenization heat treatment temperature and cooling rate. This effectively suppresses recrystallization during subsequent hot deformation, refines the grains, and improves the material's plasticity.
[0041] The solution treatment temperature is set at 555–573℃, preferably 555–570℃, and the solution treatment time is 0.5–1.5 h. During the solution treatment process, the use of high temperature and long holding time can ensure that effective strengthening elements such as Mg, Si, Cu and Zn are fully dissolved back into the matrix, promote the synergistic precipitation of various nano-precipitates, and improve the alloy strength.
[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0043] In terms of chemical composition design, this invention controls the Mg / Si ratio of the alloy to be between 1.08 and 1.70 by adjusting the contents of Mg, Si, and Cu elements. Under this high Mg / Si ratio condition, a new AlMgV phase is introduced as a dispersed phase by adding trace amounts of V element, and the density of the dispersed phase is controlled at 1.50 × 10⁻⁶. 12 ~2.70×10 12 / m 2 With an average size of 350–500 nm, the AlMgV phase achieves synergistic regulation of submicron dispersed phases and nano-reinforcing phases, improving the mechanical properties of the material. Simultaneously, the AlMgV phase inhibits grain boundary movement during hot deformation, reduces grain growth and coarsening rates, and refines grain size. While ensuring the plasticity of the aluminum alloy, it breaks through the strength limitations of 6xxx series aluminum alloys, obtaining a new 6xxx series aluminum alloy with higher strength. At peak aging, the alloy exhibits a yield strength ≥370 MPa, tensile strength ≥420 MPa, and elongation ≥14%. In contrast, the yield strength of existing high-strength Al-Mg-Si-Cu aluminum alloy sheets is only 265–362 MPa, the tensile strength is only 340–394 MPa, and the elongation is only 10%–11.4%.
[0044] Based on chemical composition design, this invention optimizes homogenization heat treatment, rolling process, and solution-quenching-aging treatment process. By controlling the composition and distribution of submicron dispersed phase and nano-reinforcing phase, the produced sheet material has good surface quality and fine grain size, achieving an excellent match between high strength and excellent plasticity. This invention has guiding significance for the development, processing and application of ultra-high strength 6xxx series aluminum alloy automotive body outer panels. Attached Figure Description
[0045] Figure 1 is a microstructure image of the V-microalloyed Al-Mg-Si-Cu alloy in Example 6 of the present invention;
[0046] Figure 2 is a grain morphology diagram of the V-microalloyed Al-Mg-Si-Cu alloy in Example 6 of the present invention;
[0047] Figure 3 is a microscopic morphology diagram of a typical dispersed phase in the homogenized state of the V-microalloyed Al-Mg-Si-Cu alloy in Example 6 of the present invention.
[0048] Figure 4 shows the microstructure of a typical strengthening phase in the aged state of the V-microalloyed Al-Mg-Si-Cu alloy in Example 6 of this invention.
[0049] Figure 5 is a microstructure image of the aluminum alloy material obtained in Comparative Example 1 of the present invention;
[0050] Figure 6 is a grain size distribution diagram of the aluminum alloy material obtained in Comparative Example 1 of the present invention;
[0051] Figure 7 is a comparison of the yield strength and elongation of the V-microalloyed Al-Mg-Si-Cu alloys obtained in Examples 1-8 of this invention with the high-strength Al-Mg-Si-Cu aluminum alloys reported in patents (CN110760723A, CN115323203A and CN106480343A). Detailed Implementation
[0052] The present invention will be further described below with reference to the embodiments and accompanying drawings. It should be understood that the following embodiments are only used to describe specific implementations of the present invention and do not constitute any limitation on the scope of protection of the present invention. Embodiments 1-8 and Comparative Examples 1-3
[0053] 1) Smelting and casting:
[0054] Ingots are obtained through smelting and casting;
[0055] 2) Homogenization heat treatment:
[0056] The ingot is subjected to homogenization heat treatment to obtain a homogenized ingot.
[0057] 3) Hot rolling + cold rolling:
[0058] The homogenized ingot is hot-rolled and cold-rolled to obtain a cold-rolled sheet.
[0059] 4) Solution treatment + quenching:
[0060] The cold-rolled sheet is subjected to solution treatment and water quenching to obtain a solution-treated and quenched sheet.
[0061] 5) Pre-aging treatment
[0062] The plate material after solution treatment and quenching is pre-aged to obtain a V-microalloyed Al-Mg-Si-Cu alloy.
[0063] The methods for testing microstructure and performance parameters are as follows:
[0064] The yield strength, tensile strength and elongation after fracture of aluminum alloys were determined by room temperature tensile testing method, with reference to GB / T 228.1-2021.
[0065] Grain size of aluminum alloys was determined using EBSD.
[0066] The composition of uniformly distributed nano-precipitates and dispersed phases in the matrix of aluminum alloy was analyzed using FESEM, TEM and STEM.
[0067] Based on statistical analysis of TEM images, the bulk density and average size of dispersed phases and nano-precipitates in the aluminum alloy matrix were obtained.
[0068] Table 1 shows the chemical composition of the aluminum alloys in Examples 1-8 and Comparative Examples 1-3 of this invention.
[0069] Table 2 shows the process parameters of the aluminum alloys in Examples 1-8 and Comparative Examples 1-3 of the present invention. Furthermore, in Examples 1-8 and Comparative Examples 1-3: In step 1), high-purity aluminum, pure magnesium, pure zinc, Al-Si master alloy, Al-Cu master alloy, Al-Mn master alloy, Al-V master alloy, and Al-Fe master alloy were used as raw materials for smelting and casting; first, the high-purity aluminum was completely melted and heated to 760°C, and Al-V and Al-Fe master alloys were added. After the master alloys were completely melted, a first melt was obtained; then, the first melt was cooled to 740°C, and Al-Cu and Al-Mn master alloys were added. After they were fully melted, the second melt was obtained. The second melt is cooled to 730°C, pure magnesium and pure zinc are added, and the mixture is held at this temperature for 15 minutes to obtain the third melt. A refining agent is then added to the third melt. After the refining agent has fully reacted with the third melt, a slag remover is added, and the mixture is held at 720°C for 15 minutes. Finally, a refining agent is added, and the mixture is held at this temperature for 2 minutes before casting (740°C) to obtain an ingot. The slag remover is a sodium-free slag remover, and its addition amount is 0.30 wt.% of the mass of the third melt. The refining agent is an Al-5Ti-1B refining agent, and its addition amount is 0.1 wt.% of the mass of the third melt. In step 3), the deformation amount of the cold rolling is 65%, and the cold rolling temperature is room temperature.
[0070] Table 3 shows the performance parameters of the aluminum alloys in Examples 1-8 and Comparative Examples 1-3 of the present invention.
[0071] Figure 1 is a microstructure image of the Al-Mg-Si-Cu alloy of Example 6 of the present invention, and Figure 2 is a grain size distribution diagram of the Al-Mg-Si-Cu alloy of Example 6 of the present invention. As can be seen from the images, the grain size of the Al-Mg-Si-Cu alloy material is small, with an average size of 15.3 μm.
[0072] Figure 3 shows the microstructure of typical dispersed phases in the homogenized Al-Mg-Si-Cu alloy ingot obtained in Example 6 of this invention. Figure 4 shows the microstructure of typical strengthening phases in the peak-aged state of the Al-Mg-Si-Cu alloy obtained in Example 6 of this invention. As can be seen from the images, a large number of submicron dispersed phases (AlMgV phase) and high-density nano-strengthening phases (β″ phase and Q′ phase) precipitate in the Al-Mg-Si-Cu alloy matrix, which improves the mechanical properties of the plate. Compared with the high-strength 6xxx series aluminum alloy plates reported in the patent, the mechanical properties of the material are greatly improved.
[0073] Figures 5 and 6 are microstructure images and grain size distribution diagrams of the aluminum alloy material obtained in Comparative Example 1 of the present invention, respectively. By comparing with Figures 1 and 2, it is found that the grain size in Comparative Example 1 is significantly coarser than that in Example 6 due to the lower density of the dispersed phase, and its average size has increased from 15.3 μm to 24.1 μm.
[0074] Figure 7 is a comparison of the yield strength and elongation of the Al-Mg-Si-Cu alloy materials obtained in Examples 1-8 of this invention with the high-strength Al-Mg-Si-Cu aluminum alloys reported in patents (CN110760723A, CN115323203A and CN106480343A). The comparison shows that the V-microalloyed high-strength Al-Mg-Si-Cu alloy described in this invention has higher strength and better plasticity.
[0075] As shown in Table 3, the Al-Mg-Si-Cu alloy designed in this invention, after solution treatment, quenching, and aging, exhibits a yield strength of 370–385 MPa, a tensile strength of 425–440 MPa, and an elongation of 14.5%–17%. Overall, the Al-Mg-Si-Cu alloy achieves a yield strength ≥370 MPa, a tensile strength ≥420 MPa, and an elongation ≥14%, which is superior to existing Al-Mg-Si-Cu aluminum alloy sheets. This invention develops a novel V-microalloyed ultra-high-strength Al-Mg-Si-Cu alloy and its preparation method, addressing the need for ultra-high-strength 6xxx series aluminum alloy sheets in the lightweight design requirements of the transportation sector.
[0076] In Comparative Example 1, no V element was added to the aluminum alloy, resulting in a larger grain size in the final microstructure and almost no dispersed phase in the aluminum alloy matrix. Therefore, the strength of the peak-aged state of this aluminum alloy was relatively low.
[0077] In Comparative Example 2, no V element was added to the aluminum alloy, and the Mg / Si ratio was relatively low, only 0.88. This resulted in a larger grain size, no dispersed phase precipitation, and a lower density of nano-precipitates. Ultimately, the strength and plasticity of the aluminum alloy in Comparative Example 2 were significantly lower than those in the Example.
[0078] In Comparative Example 3, V was added to the aluminum alloy, but the Mg / Si ratio was low (0.91). The nucleation and growth process of the nano-precipitates reduced the excess Mg content in the aluminum alloy matrix, limiting the formation of the AlMgV dispersed phase and weakening the grain refinement effect and the promoting effect on the nano-precipitates. Ultimately, the density of both the dispersed and precipitated phases in this aluminum alloy decreased to 0.83 × 10⁻⁶. 12 / m 2 and 5.59×10 12 / m 2The strength and plasticity of the resulting aluminum alloy sheet were lower than those of the example.
[0079] This invention, through the rational design and control of the content of Mg, Si, and Cu elements, and the addition of trace amounts of V element, combined with homogenization treatment and solution-quenching-aging treatment, introduces high-density precipitation strengthening phases (β″ and Q′ phases) and submicron dispersed phases—AlMgV phase—into the Al matrix. By employing a combination of dispersion strengthening and precipitation strengthening, the strength limitations of Al-Mg-Si-Cu alloys are overcome. Simultaneously, the AlMgV dispersed phase effectively inhibits grain boundary movement during hot deformation, reduces grain growth and coarsening rates, effectively refines the grain size of the sheet, and improves the alloy's plasticity. The Al-Mg-Si-Cu alloy sheet obtained by this invention possesses both ultra-high strength and excellent plasticity, as well as the advantage of low alloy cost. This addresses the need for ultra-high strength 6xxx series aluminum alloy sheets in the lightweight design requirements of the transportation sector, providing a new solution for the design and development of ultra-high strength aluminum alloys.
[0080] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A V-microalloyed Al-Mg-Si-Cu alloy, characterized in that, The chemical composition of the V-microalloyed Al-Mg-Si-Cu alloy, by mass percentage, is as follows: Mg: 1.20–2.00 wt.%, Si: 1.00–1.50 wt.%, Cu: 0.5–1.5 wt.%, Zn: 0.10–0.50 wt.%, Mn: 0.20–0.40 wt.%, V: 0.05–0.40 wt.%, Fe ≤ 0.20 wt.%, with the balance including Al and unavoidable impurities, wherein 1.08 ≤ Mg / Si ≤ 1.70, preferably 1.10–1.34, where the element symbols are replaced with the corresponding mass percentage content of each element.
2. The V-microalloyed Al-Mg-Si-Cu alloy according to claim 1, characterized in that, The balance consists of Al and unavoidable impurities.
3. The V-microalloyed Al-Mg-Si-Cu alloy according to claim 1 or 2, characterized in that, The microstructure of the Al-Mg-Si-Cu alloy microalloyed with V is composed of fine equiaxed crystals with a grain size of 14.0–18.0 μm, preferably 15.2–16.4 μm; and the microstructure contains uniformly distributed nano-precipitated phases and dispersed phases, wherein the dispersed phase is an AlMgV phase with a density of 1.50 × 10⁻⁶. 12 ~2.70×10 12 / m 2 The preferred value is 1.79×10. 12 ~2.63×10 12 / m 2 The average size is 350–500 nm; the nano-precipitated phases are β″ and Q′ phases with a density of 5.50 × 10⁻⁶. 14 ~7.50×10 14 / m 2 Preferred value: 6.09×10 14 ~7.37×10 14 / m 2 The average length is 10.0–15.0 nm, preferably 11.7–14.5 nm.
4. The V-microalloyed Al-Mg-Si-Cu alloy according to claim 1, 2, or 3, characterized in that, The V-microalloyed Al-Mg-Si-Cu alloy has a yield strength ≥370MPa, a tensile strength ≥420MPa, and an elongation ≥14.0%.
5. The method for preparing the V-microalloyed Al-Mg-Si-Cu alloy according to any one of claims 1 to 4, characterized in that, The preparation method includes the following steps performed sequentially: 1) Smelting and casting: Ingots are obtained through smelting and casting; 2) Homogenization heat treatment: The ingot is subjected to homogenization heat treatment to obtain a homogenized ingot. The homogenization heat treatment temperature is 545-560℃, the holding time of the homogenization heat treatment is 15-24h, preferably 16-24h, and the heating rate and cooling rate of the homogenization heat treatment are 0.50-1.00℃ / min. 3) Hot rolling + cold rolling: The homogenized ingot is hot-rolled and cold-rolled to obtain a cold-rolled sheet, wherein the total deformation of the hot rolling is 85% to 90% and the hot rolling temperature is 545 to 560°C. 4) Solution treatment + quenching: The cold-rolled sheet is subjected to solution treatment and quenching in sequence to obtain the solution-treated and quenched sheet. The solution treatment temperature is 555-573℃, preferably 555-570℃, the solution treatment time is 0.5-1.5h, and the quenching method is water quenching. 5) Pre-aging treatment: The plate after solution treatment and quenching is subjected to pre-aging treatment to obtain V micro-alloyed Al-Mg-Si-Cu alloy, wherein the temperature of the pre-aging treatment is 150-185℃ and the holding time of the pre-aging treatment is 4-24h, preferably 10-24h.
6. The preparation method according to claim 5, characterized in that, In step 1), the following raw materials are smelted and cast: high-purity aluminum, pure magnesium, pure zinc, Al-Si master alloy, Al-Cu master alloy, Al-Mn master alloy, Al-V master alloy, and Al-Fe master alloy are used as raw materials. First, high-purity aluminum is completely melted and heated to 760–780°C. Al-V and Al-Fe master alloys are added, and after the master alloys are completely melted, a first melt is obtained. Then, the first melt is cooled to 740–760°C, and Al-Cu and Al-Mn master alloys are added. After they are fully melted, a second melt is obtained. The second melt is cooled to 730–740°C, and pure magnesium and pure zinc are added. The mixture is held at this temperature for 10–15 minutes to obtain a third melt. Then, a refining agent is added to the third melt. After the refining agent reacts fully with the third melt, a slag-removing agent is added, and the mixture is held at 720–740°C for 10–15 minutes. Finally, a refining agent is added, and the mixture is held at this temperature for 2–5 minutes before casting to obtain an ingot. The slag remover is a sodium-free slag remover, and its addition amount is 0.30 to 0.40 wt.% of the mass of the third melt; The refining agent is Al-5Ti-1B refining agent, and its addition amount is 0.05 to 0.1 wt.% of the mass of the third melt.
7. The preparation method according to claim 5, characterized in that, In step 1), the casting temperature is 720–740°C.
8. The preparation method according to claim 5, characterized in that, In step 3), the cold rolling deformation is ≥65%, and the cold rolling deformation temperature is room temperature.