An ultra-high-strength aluminum alloy material, a preparation method and application thereof

Abstract

The application discloses an ultrahigh-strength aluminum alloy material and a preparation method and application thereof. The ultrahigh-strength aluminum alloy material comprises alloy raw materials with the following mass percentages: Zn: 9.1-14.5%, Mg: 2.3-4.5%, Cu: 1.1-3.1%, Sc: 0.4-0.7%, Zr: 0.1-0.3%, Ti: 0.1-0.3%, Mn: 0.1-0.8%, Be: 0.05-0.5%, Fe: less than or equal to 0.4%, Si: less than or equal to 0.2%, and Al is the balance. The alloy raw materials are smelted, refined and cast into ingots; the ingots are sequentially subjected to first aging treatment, multi-stage homogenization heat treatment, hot deformation treatment, solid solution treatment and second aging treatment, and the ultrahigh-strength aluminum alloy material is obtained. The first aging treatment introduces dispersedly distributed nanoscale Al3(Sc x ,Zr 1‑x ) secondary aging phases in the aluminum alloy material, and the secondary aging phases and MgZn2 main aging phases generated by the second aging treatment produce a significant synergistic strengthening effect, and the alloy performance is greatly improved, and the maximum tensile strength is more than 850 MPa.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy technology, and in particular to an ultra-high strength aluminum alloy material, its preparation method, and its application. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Al-Zn-Mg-Cu aluminum alloys possess advantages such as low density, high strength, and ease of processing, making them crucial structural materials for aircraft, rockets, rail transportation, and weaponry. Currently, the tensile strength of Al-Zn-Mg-Cu aluminum alloys is generally between 500-700 MPa. Under certain service conditions with high performance requirements for structural components, traditional metal materials such as steel can still be used.

[0004] Patent CN100415918C discloses a high-Zn-content, ultra-high-strength, high-toughness, and high-damage-tolerance aluminum alloy material and its preparation method. The alloy composition is: Zn: 9–10 wt%, Mg: 2.0–2.5%, Cu: 1.2–1.7%, Zr: 0.2–0.5%, with the remainder being Al. After melting, the alloy is rapidly sprayed and solidified using an inert gas as the atomizing gas, achieving a tensile strength exceeding 750 MPa. While rapid solidification using spraying can yield higher-strength aluminum alloy materials, the process is complex, costly, and makes it difficult to manufacture large-size materials.

[0005] Patent CN114990396B discloses an ultra-high strength 7000 series aluminum alloy material, its preparation method, and its applications. The alloying elements include Al, Zn, Mg, Cu, Zr, Er, Si, and Fe, with Zn content ranging from 6.8% to 11%, Mg content from 1.8% to 3.0%, Cu content from 1.2% to 2.8%, Er content from 0.1% to 0.5%, Zr content from 0.1% to 0.15%, and Si and Fe as impurity elements. The process involves casting the melt into a billet, followed by homogenization, extrusion, rolling, solution treatment, and aging. The resulting aluminum alloy material achieves a tensile strength of up to 773 MPa. Therefore, how to prepare ultra-high strength aluminum alloy materials with tensile strengths exceeding 800 MPa is currently one of the urgent problems to be solved. Summary of the Invention

[0006] In view of this, the present invention provides an ultra-high strength aluminum alloy material, its preparation method and application, wherein the tensile strength of the prepared ultra-high strength aluminum alloy material can reach more than 800 MPa.

[0007] In a first aspect, the present invention provides a method for preparing an ultra-high strength aluminum alloy material, wherein the ultra-high strength aluminum alloy material comprises the following alloy raw materials by mass percentage:

[0008] Zn: 9.1–14.5%, Mg: 2.3–4.5%, Cu: 1.1–3.1%, Sc: 0.4–0.7%; Zr: 0.1–0.3%, Ti: 0.1–0.3%, Mn: 0.1–0.8%, Be: 0.05–0.5%, Fe≤0.4%, Si≤0.2%, Al balance;

[0009] The alloy raw materials are melted, refined and cast into ingots; the ingots are then subjected to a first aging treatment, a multi-stage homogenization heat treatment, a hot deformation treatment, a solution treatment and a second aging treatment in sequence.

[0010] Preferably, in the alloy raw materials, Zn / Mg = 2-4, Mg / Cu = 1.1-2.3, and (Mn+Be) / Fe ≥ 1.0.

[0011] Preferably, the alloy raw material is smelted at a temperature of 750–850°C, refined at a temperature of 740–750°C, and cast at a temperature of 700–730°C; further, the casting mold is a water-cooled copper mold.

[0012] Preferably, the temperature of the first aging treatment is 250–370°C, and the holding time is 20–40 h.

[0013] Preferably, the temperature of the multi-stage homogenization heat treatment is 400-480℃; more preferably, the steps of the multi-stage homogenization heat treatment are: holding at 400-410℃ for 2-4 hours, holding at 425-435℃ for 2-4 hours, holding at 445-460℃ for 2-4 hours, and holding at 470-480℃ for 18-24 hours.

[0014] Preferably, the hot deformation treatment method is selected from one of hot extrusion, equal diameter angular extrusion, hot forging and hot rolling, and the temperature of the hot deformation treatment is 380-520℃.

[0015] Preferably, the solution treatment temperature is 450–490°C, and the holding time is 0.5–2 h.

[0016] Preferably, the temperature of the second aging treatment is 110-130℃, and the holding time is 20-30h.

[0017] Secondly, the present invention provides an ultra-high strength aluminum alloy material obtained by the above preparation method; the tensile strength of the ultra-high strength aluminum alloy material is above 800 MPa.

[0018] Thirdly, this invention provides applications of the aforementioned ultra-high strength aluminum alloy materials in the fields of aerospace, nuclear industry, automobiles, or petroleum equipment.

[0019] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0020] (1) This invention provides an ultra-high strength Al-Zn-Mg-Cu aluminum alloy material with high Zn and Sc content and a tensile strength of over 800 MPa. The material incorporates dispersed nano-sized Al3(Sc) particles through a first aging treatment. x ,Zr 1-x The secondary aging phase, together with the MgZn2 main aging phase generated by the second aging treatment, produces a significant synergistic strengthening effect, greatly improving the alloy properties, with the tensile strength exceeding 850 MPa.

[0021] (2) This invention performs an aging treatment before the multi-stage homogenization heat treatment, effectively solving the main aging problem of MgZn2 and Al3(Sc) x ,Zr 1-x The contradiction between the secondary aging phases within the heat treatment temperature range ultimately resulted in the simultaneous retention of MgZn2 and Al3(Sc) phases in the aluminum alloy matrix. x ,Zr 1-x Two nano-aging strengthening phases significantly improve the mechanical strength of Al-Zn-Mg-Cu aluminum alloy materials. Attached Figure Description

[0022] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation thereof. Obviously, those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0023] Figure 1 This is the tensile curve of the ultra-high strength aluminum alloy material of Embodiment 1 of the present invention;

[0024] Figure 2 This is a cast metallographic diagram of the ultra-high strength aluminum alloy material of Embodiment 1 of the present invention;

[0025] Figure 3 This is a metallographic diagram of the as-cast aluminum alloy material of Comparative Example 2 of the present invention. Detailed Implementation

[0026] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0027] As described in the background section, the tensile strength of aluminum alloy materials in the prior art is generally below 800 MPa. Therefore, this invention provides a method for preparing an ultra-high strength aluminum alloy material, wherein the ultra-high strength aluminum alloy material is composed of the following alloy raw materials by mass percentage:

[0028] Zn: 9.1–14.5%, Mg: 2.3–4.5%, Cu: 1.1–3.1%, Sc: 0.4–0.7%; Zr: 0.1–0.3%, Ti: 0.1–0.3%, Mn: 0.1–0.8%, Be: 0.05–0.5%, Fe≤0.4%, Si≤0.2%, Al balance;

[0029] The alloy raw materials are melted, refined and cast to obtain an ingot; the ingot is then subjected to a first aging treatment, a multi-stage homogenization heat treatment, a hot deformation treatment, a solution treatment and a second aging treatment in sequence.

[0030] In existing technologies, Sc is mainly used as a grain refiner in aluminum alloys, with an addition amount typically ranging from 0.05% to 0.2%. This invention significantly increases the Sc content to 0.4%-0.7%, allowing Sc to exist as a supersaturated solid solution in the Al matrix. Combined with Zr and subsequent heat treatment processes, this effectively disperses and precipitates Al3(Sc) within the Al alloy matrix. x ,Zr 1-x Nano-reinforced phase.

[0031] During the aging precipitation process, Sc forms an L12-type Al3Sc nanophase coherent with the Al matrix, with a lattice constant a = 0.410 nm at room temperature. This phase exhibits a lattice mismatch of only 1.5% with the Al matrix (a = 0.405 nm) at room temperature, significantly reinforcing the Al matrix. While the homogenization and solution temperatures of the MgZn2 phase are both above 450℃, Al3Sc rapidly coarsens above 400℃, losing its coherent relationship with the Al matrix and thus its strengthening effect. Therefore, there is a significant contradiction in the heat treatment temperature ranges of the MgZn2 and Al3Sc phases. To address this issue, this invention adds a certain amount of Zr to the alloy. Through the combined addition of Zr and Sc, an L12-type core-shell structure of Al3(Sc) coherent with the Al matrix can be formed. x ,Zr 1-x The Zr phase also exhibits a coherent relationship with the Al matrix. Zr has a very low diffusion coefficient at high temperatures; in the temperature range of 400℃ to 550℃, the diffusion coefficient D... Sc / D Zr≈1800~190. In other words, in the temperature range of 400℃~550℃, the diffusion coefficient of Zr is only about 1 / 200~1 / 2000 of that of Sc. Therefore, the core-shell structure Al3(Sc) with a Zr outer shell... x ,Zr 1-x The MgZn2 phase has extremely high thermal stability and will not undergo significant coarsening even after long-term heat treatment at 450℃, thus resolving the obvious contradiction between the heat treatment temperature ranges of the MgZn2 and Al3Sc phases.

[0032] The alloy raw material of this invention incorporates Mn and Be elements, which have a strong modifying effect on Fe, effectively preventing the formation of long needle-like AlFe and AlFeSi phases. Currently, in ultra-high strength aluminum alloys such as 7055, the Fe content is strictly controlled below 0.1%. For example, patent CN100415918C explicitly requires an Fe content ≤0.05wt%; patent CN115418514B also explicitly requires an Fe content ≤0.08wt%. This strict requirement for Fe content not only necessitates the use of a certain amount of expensive high-purity aluminum (99.99wt%), resulting in high raw material costs, but also leads to a sharp increase in smelting difficulty and cost once the Fe content is reduced to a certain level. This invention, by introducing Mn and Be elements into the alloy, can synergistically improve the Fe-rich phase. Adding Mn can transform the long needle-like Fe-rich phase into dense, spherical Al phases. 15 The (Fe,Mn)3Si2 phase effectively improves the tensile strength and elongation of the alloy. The addition of Be alters the solidification sequence of the iron-rich phase; the harmful Fe-rich eutectic phase generated by the original eutectic reaction is replaced by a peritectic reaction forming the Be-Fe phase, resulting in the Chinese character-shaped Al8Fe2BeSi phase, which effectively inhibits crack initiation and propagation during alloy stress. Therefore, this invention effectively avoids the formation of long, needle-like Fe-containing phases in the alloy and significantly increases the allowable Fe content to 0.4%. Even with a high Fe content, the alloy still maintains very high tensile strength, while also significantly reducing the cost of smelting raw materials, process difficulty, and overall process cost.

[0033] In the alloy raw materials of the present invention, the formation boundary of the precipitated phase is reasonably determined according to the phase diagram, and the appropriate proportions of each element are determined as follows: Zn / Mg = 2~4, Mg / Cu = 1.1~2.3, (Mn+Be) / Fe ≥ 1.0.

[0034] The aluminum alloy material casting process of this invention adopts the most conventional metal mold gravity casting method, which is simple and easy to operate. Specifically, the alloy raw material is melted at 750-850°C, and then degassed and refined by pressing hexachloroethane into a bell jar or introducing argon gas. The refining temperature is 740-750°C. After slag removal and refining, the mixture is allowed to stand for more than 30 minutes, and then cooled to 700-730°C for casting. To improve the solidification rate of the alloy, the casting mold of this invention is preferably a water-cooled copper mold, which can fix Sc in the Al matrix as a supersaturated solid solution through rapid cooling casting, thereby preparing for the first aging precipitation in the next step.

[0035] To prevent the natural aging of Sc, this invention requires a first aging treatment as soon as possible after casting. The temperature for the first aging treatment is 250–370℃, and the holding time is 20–40 hours. During the first aging treatment, the relatively low temperature and long treatment time ensure the aging precipitation of the Al3Sc phase while also ensuring sufficient diffusion of Zr. Ultimately, this results in the formation of a large number of diffusely distributed L12-type core-shell Al3(Sc) phases coherent with the Al matrix. x ,Zr 1-x The phase exhibits significant high-temperature thermal stability at high temperatures.

[0036] The alloy is then subjected to a multi-stage homogenization heat treatment at a temperature of 400–480℃. The specific steps are: holding at 400–410℃ for 2–4 hours, at 425–435℃ for 2–4 hours, at 445–460℃ for 2–4 hours, and at 470–480℃ for 18–24 hours; preferably: holding at 400℃ for 3 hours, at 430℃ for 3 hours, at 450℃ for 3 hours, and at 480℃ for 20 hours. During this multi-stage homogenization heat treatment of the MgZn2 phase within the 400–480℃ range, the low diffusivity of Zr at high temperatures allows Al3(Sc) to be homogenized during the process. x ,Zr 1-x The Al3(Sc) phase remains stable, does not coarsen, and maintains a certain coherent relationship with the Al matrix, thus preserving its strengthening effect on the alloy properties. Furthermore, Al3(Sc) x ,Zr 1-x The phase can also significantly increase the recrystallization temperature of the alloy and maintain the stability of the grain structure during subsequent hot deformation.

[0037] The present invention does not impose any special limitation on the method of hot deformation treatment, and can be selected from any one of the commonly used methods in the art, such as hot extrusion, equal diameter angular extrusion, hot forging and hot rolling, and the temperature of hot deformation treatment is 380 to 520°C.

[0038] This invention does not impose special limitations on the solution treatment process; commonly used solution treatment methods in the art can be employed. The preferred solution treatment temperature is 450–490°C, and the preferred holding time is 0.5–2 hours.

[0039] This invention involves a second aging treatment after solution treatment at a temperature of 110–130°C for 20–30 hours. This second aging treatment generates a large amount of dispersed MgZn2 main aging phase in the Al matrix. This phase interacts with Al3(Sc) x ,Zr 1-x The secondary aging phases work together to synergistically strengthen the Al matrix, significantly improving the strength of the Al alloy.

[0040] This invention yields an ultra-high strength aluminum alloy material with a tensile strength exceeding 800 MPa through the above-described preparation method. The ultra-high strength aluminum alloy material contains nano-sized Al3(Sc) x ,Zr 1-x The secondary aging phase is dispersed and has a significant synergistic effect with the main aging phase of MgZn2, which greatly improves the alloy properties, with the tensile strength exceeding 850MPa.

[0041] The ultra-high strength aluminum alloy material prepared by this invention has excellent tensile strength, and therefore can be widely used in aerospace, nuclear industry, automotive and petroleum equipment and other fields.

[0042] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0043] Example 1

[0044] This embodiment provides an ultra-high strength aluminum alloy material composed of the following raw material mass ratios: Zn: 14.5%, Mg: 4.2%, Cu: 3.1%, Sc: 0.7%, Zr: 0.3%, Ti: 0.3%, Mn: 0.7%, Be: 0.1%, with Al as the balance; Fe and Si are unavoidable impurities.

[0045] (1) Weigh out A00 standard aluminum (purity: 99.7%), pure Zn (purity: 99.9%), pure Mg (purity: 99.9%), pure Cu (purity: 99.9%), and Al-2%Sc, Al-5%Zr, Al-5%Ti, Al-5%Zr, Al-10%Mn, and Al-3%Be master alloys according to the mass ratio;

[0046] (2) The copper mold is formed by smelting, refining, and water-cooling gravity casting.

[0047] (3) The first aging treatment was carried out at 350℃ for 20 hours, followed by multi-stage homogenization treatment, specifically: first, the temperature was kept at 400℃ for 3 hours, then the temperature was raised to 430℃ and kept for 3 hours, then the temperature was raised to 450℃ and kept for 3 hours, and finally the temperature was kept at 480℃ for 20 hours.

[0048] (4) The hot deformation treatment adopts the hot extrusion process with an extrusion temperature of 520℃; solution treatment at 490℃ for 2 hours, and then a second aging treatment at 110℃ for 30 hours.

[0049] Figure 1 The tensile curve of the ultra-high strength aluminum alloy material prepared in this embodiment shows that the tensile strength reaches 853 MPa.

[0050] Example 2

[0051] This embodiment provides an ultra-high strength aluminum alloy material composed of the following raw material mass ratios: Zn: 12.1%, Mg: 3.3%, Cu: 2.1%, Sc: 0.5%, Zr: 0.2%, Ti: 0.2%, Mn: 0.5%, Be: 0.3%, Al as the balance, and Fe and Si as unavoidable impurities.

[0052] The preparation process in this embodiment is the same as that in Example 1.

[0053] Example 3

[0054] This embodiment provides an ultra-high strength aluminum alloy material composed of the following raw material mass ratios: Zn: 9.1%, Mg: 2.3%, Cu: 1.1%, Sc: 0.4%, Zr: 0.1%, Ti: 0.1%, Mn: 0.1%, Be: 0.3%; Al is the balance, and Fe and Si are unavoidable impurities.

[0055] The preparation process in this embodiment is the same as that in Example 1.

[0056] Comparative Example 1

[0057] Unlike Example 1, the amount of Sc added in Comparative Example 1 was 0.2%.

[0058] Comparative Example 2

[0059] Unlike Example 1, Comparative Example 2 does not include Mn and Be.

[0060] Comparative Example 3

[0061] Unlike Example 1, Comparative Example 3 did not undergo a first aging treatment.

[0062] Test case

[0063] The aluminum alloy materials prepared in Examples 1-3 and Comparative Examples 1-3 were sampled and subjected to tensile property tests according to GB / T228.1-2010 standard. The test properties are shown in Table 1.

[0064] Table 1. Mechanical property determination of aluminum alloys in examples and comparative examples.

[0065]

[0066] As shown in Table 1, with the increase of the main aging phase elements Zn and Mg, and the secondary aging phase elements Sc and Zr in the alloy, the tensile strength of the alloy significantly increased from 807 MPa to 853 MPa. In Comparative Example 1, due to the significant reduction in the Sc content compared to Example 1, it was difficult to generate sufficient Al3(Sc) in the Al matrix. x ,Zr 1-x It is a coherent phase, therefore its tensile strength is significantly lower than that of Example 1.

[0067] Comparative Example 2, without the addition of Mn and Be elements that can modify Fe and Si, exhibited significantly lower tensile strength than Example 1. Since small amounts of Fe and Si impurities are inevitably introduced during alloy preparation, both in the smelting raw materials and the tools used, the addition of Mn and Be elements in Example 1 effectively modified these impurities, preventing the formation of harmful acicular phases (such as...) in the Al matrix. Figure 2 As shown). In Comparative Example 2, since no modification treatment was performed on the Fe and Si impurities, a certain amount of long needle-like phases (such as...) were generated. Figure 3 As shown in the figure, this phase will cut the Al matrix and significantly impair the performance of the alloy. Therefore, the tensile strength of Comparative Example 2 is less than that of Example 1.

[0068] In Comparative Example 3, the first aging treatment was not performed in a timely manner. Although Al3(Sc) still exists in the matrix... x ,Zr 1-x These phases are formed after the Al3Sc phase has already coarsened, with Zr elements diffusing into the vicinity of the Al3Sc phase. They are significantly coarsened Al3(Sc) phases. x ,Zr 1-x The phase has no strengthening effect on the alloy and cannot form a synergistic strengthening effect with the MgZn2 main aging phase, resulting in the tensile strength of Comparative Example 3 being significantly lower than that of Example 1.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an ultra-high strength aluminum alloy material, characterized in that, The ultra-high strength aluminum alloy material comprises the following alloy raw materials by mass percentage: Zn: 9.1~14.5%, Mg: 2.3~4.5%, Cu: 1.1~3.1%, Sc: 0.4~0.7%; Zr: 0.1~0.3%, Ti: 0.1~0.3%, Mn: 0.1~0.8%, Be: 0.05~0.5%, Fe≤0.4%, Si≤0.2%, Al is the balance; The alloy raw materials are melted, refined and cast into ingots; the ingots are then subjected to a first aging treatment, a multi-stage homogenization heat treatment, a hot deformation treatment, a solution treatment and a second aging treatment in sequence. In the alloy raw materials, Zn / Mg = 2~4, Mg / Cu = 1.1~2.3, and (Mn+Be) / Fe ≥ 1.0; The ultra-high strength aluminum alloy material simultaneously retains MgZn2 and Al3(Sc) x ,Zr 1-x Two nano-aging-enhancing phases; The temperature for the first aging treatment is 250~370℃, and the holding time is 20~40h; The second aging treatment is performed at a temperature of 110~130℃ for 20-30 hours.

2. The preparation method according to claim 1, characterized in that, The alloy raw material is smelted at a temperature of 750~850℃, refined at a temperature of 740~750℃, and cast at a temperature of 700~730℃; the casting mold is a water-cooled copper mold.

3. The preparation method according to claim 1, characterized in that, The temperature of the multi-stage homogenization heat treatment is 400~480℃.

4. The preparation method according to claim 1, characterized in that, The steps of the multi-stage homogenization heat treatment are as follows: heat treatment at 400~410℃ for 2~4 hours, heat treatment at 425~435℃ for 2~4 hours, heat treatment at 445~460℃ for 2~4 hours, and heat treatment at 470~480℃ for 18~24 hours.

5. The preparation method according to claim 1, characterized in that, The hot deformation treatment method is selected from one of hot extrusion, equal diameter angular extrusion, hot forging and hot rolling, and the temperature of the hot deformation treatment is 380~520℃.

6. The preparation method according to claim 1, characterized in that, The solution treatment temperature is 450~490℃, and the holding time is 0.5~2h.

7. An ultra-high strength aluminum alloy material prepared by the preparation method according to any one of claims 1-6, characterized in that, The tensile strength of the ultra-high strength aluminum alloy material is above 800 MPa.

8. The application of the ultra-high strength aluminum alloy material as described in claim 7 in the fields of aerospace, nuclear industry, automobile or petroleum equipment.

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