A high-strength heat-resistant Al-Zn-Mg-Cu-Zr-Ni aluminum alloy, a preparation method thereof and an aluminum alloy product

Abstract

This invention provides a high-strength, heat-resistant Al-Zn-Mg-Cu-Zr-Ni aluminum alloy, comprising, by mass percentage: Zn 7.0–8.0%, Mg 3.5–4.0%, Cu 1.0–1.5%, Zr 0.08–0.15%, Ni 0.08–0.15%, with Zn / Mg < 2.5, Cu / Mg > 0.3, Zr + Ni ≤ 0.2, and the balance being Al. This application also provides a method for preparing the aluminum alloy. By controlling the elemental ratio of the high-alloyed Al-Zn-Mg-Cu-Zr-Ni alloy, this invention transforms the strengthening phase, which is prone to coarsening at high temperatures, into a heat-resistant strengthening phase. Simultaneously, it uses low-cost Zr and Ni elements to replace elements such as Sc and Er, resulting in a high-strength, heat-resistant, and low-cost aluminum alloy.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy technology, and more particularly to a high-strength, heat-resistant Al-Zn-Mg-Cu-Zr-Ni aluminum alloy, its preparation method, and an aluminum alloy product. Background Technology

[0002] Aluminum alloys possess advantages such as high strength, low density, and excellent corrosion resistance, making them widely used in aerospace, rail transportation, and other industries. High-strength aluminum alloys for aerospace engines require heat exposure in high-temperature environments for a period of time. With the increasing carrying capacity of spacecraft, the required engine thrust is increasing, raising the engine service temperature to around 200℃. These engines need to maintain a tensile strength of over 400MPa after 20 hours of heat exposure at 200℃. Currently used 7075 and 7050 aluminum alloys, during 200℃ heat exposure, are prone to precipitated phase coarsening and growth or dissolving back into the matrix, leading to a sharp drop in mechanical properties and posing significant safety risks during service. Therefore, developing new high-strength, heat-resistant aluminum alloys is of great significance for developing the next generation of large aerospace vehicles.

[0003] Currently, the main method to improve the heat resistance of aluminum alloys is to introduce a heat-resistant second phase into the matrix. There are two ways to introduce the heat-resistant second phase: one is through alloying, adding elements with high melting points to form a heat-resistant phase with other elements in the matrix; the other is to directly add ceramic reinforcing particles with high thermal stability to conventional aluminum alloys to form aluminum matrix composites.

[0004] Specifically, for the first alloying method, there are two types of alloying elements added to the aluminum alloy. One type is high-melting-point elements such as Fe, Si, and Ni. These elements react with the aluminum matrix to form second phases such as Al7Cu2Fe, Al9FeNi, and Mg2Si, which play an important role in heat resistance. However, these second phases are formed during solidification and are distributed at the micrometer scale, so their improvement on room temperature mechanical properties is limited, only improving mechanical properties at high temperatures. The second type is rare earth elements such as Sc, Er, and Ce. These react with the aluminum matrix to form L12-type nano-Al3RE reinforcing phases. Al3RE has a good effect on improving the mechanical properties of aluminum alloys at both room temperature and high temperature, but the overall improvement effect is limited due to its relatively low solid solubility. At the same time, the addition of rare earth elements greatly increases the material cost.

[0005] Adding high thermal stability reinforcing particles to conventional aluminum alloys to form aluminum matrix composites is another effective means of addressing the temperature sensitivity of conventional aluminum alloys. Reinforcing particles used for strengthening include ceramic particles such as SiC, B4C, and Al2O3. However, the poor wettability between ceramic particles and metals leads to defects in ceramic particle-reinforced aluminum matrix composites, such as poor interfacial bonding and easy agglomeration of ceramic particles, resulting in poor reliability and repeatability of this material system. Furthermore, the addition of brittle, hard ceramic phases to particle-reinforced aluminum matrix composites leads to poor processing performance, further limiting their engineering applications.

[0006] Therefore, providing a high-strength, heat-resistant aluminum alloy remains a technical challenge. Summary of the Invention

[0007] The technical problem solved by this invention is to provide an Al-Zn-Mg-Cu-Zr-Ni aluminum alloy, which has the advantages of high strength and heat resistance.

[0008] In view of this, this application provides a high-strength and heat-resistant Al-Zn-Mg-Cu-Zr-Ni aluminum alloy, comprising, by mass percentage: Zn 7.0-8.0%, Mg 3.5-4.0%, Cu 1.0-1.5%, Zr 0.08-0.15%, Ni 0.08-0.15%, and Zn / Mg < 2.5, Cu / Mg > 0.3, Zr+Ni ≤ 0.2, with the balance being Al.

[0009] Preferably, the Zn content is 7.5-7.8%, the Mg content is 3.7-3.9%, and the Zn / Mg ratio is ≤2.3.

[0010] Preferably, the Cu content is 1.2-1.4%, and the Cu / Mg ratio is ≥0.35.

[0011] Preferably, the Zr content is 0.1-0.14%, the Ni content is 0.1-0.14%, and Zr+Ni≤0.18.

[0012] Preferably, the density of the aluminum alloy is 2.788–2.826 g / cm³. 3 .

[0013] This application also provides a method for preparing the aluminum alloy, comprising the following steps:

[0014] S1) The ingredients are prepared according to the composition ratio, and then smelted and cast in sequence to obtain aluminum alloy ingots;

[0015] S2) The aluminum alloy ingot is subjected to homogenization heat treatment;

[0016] S3) The aluminum alloy ingot obtained in step S2) is hot-processed. After processing, it is solution-treated at 400-500℃ for 1-3 hours, water-quenched, and then aged at 100-150℃ for 12-36 hours to obtain the aluminum alloy.

[0017] Preferably, step S1) specifically includes:

[0018] According to the ingredient ratio, high-purity Al is added to the medium-frequency induction furnace. After the aluminum ingot is completely melted, pure Zn, pure Cu, Al-5Zr master alloy and Al-10Ni master alloy are added. The temperature is maintained for 1 to 2 hours. The molten aluminum liquid is raised to 700 to 750°C. Pure Mg is added. The temperature is then stabilized at 700 to 750°C.

[0019] Then the refining process begins, which is carried out in three stages. The first stage uses argon gas for refining, the second stage uses argon gas and CCl4 for refining, and the third stage uses argon gas and C2Cl6 for refining. After refining, the slag is removed and the mixture is allowed to stand. Finally, the resulting molten aluminum is cooled to 670-690°C before casting begins.

[0020] Preferably, the homogenization heat treatment specifically includes:

[0021] The ingot is subjected to homogenization heat treatment at 400-450℃ for 8-12 hours, then heated to 460-480℃ in the furnace, held for 24-36 hours, and then cooled.

[0022] Preferably, the temperature window for the heat treatment is 400–450°C, and the strain rate is 0.001–0.01 s. -1 .

[0023] This application also provides an aluminum alloy article prepared from the high-strength and heat-resistant Al-Zn-Mg-Cu-Zr-Ni aluminum alloy or the Al-Zn-Mg-Cu-Zr-Ni aluminum alloy prepared by the preparation method described above.

[0024] This application provides a high-strength, heat-resistant Al-Zn-Mg-Cu-Zr-Ni aluminum alloy, comprising, by mass percentage: Zn 7.0–8.0%, Mg 3.5–4.0%, Cu 1.0–1.5%, Zr 0.08–0.15%, Ni The alloy composition is 0.08–0.15%, with Zn / Mg < 2.5, Cu / Mg > 0.3, Zr + Ni ≤ 0.2, and the balance being Al. This application provides an aluminum alloy with a low Zn / Mg alloying strategy, ensuring that all main alloying elements dissolve back into the matrix at the solution temperature and exist as a highly heat-resistant T phase during aging and thermal exposure. The Cu content is increased to allow the slower-diffusion-rate Cu to dissolve into the T′ and η′ phases, reducing their coarsening rate. Furthermore, low-cost Zr is used to replace more expensive rare earth elements, reducing the alloy's overall cost. Compared to alloying with high-melting-point elements such as Fe, Si, and Ni, this alloy can simultaneously improve mechanical properties at both room and high temperatures. Therefore, by controlling the proportions of elements in the aluminum alloy, this application transforms the easily coarsening strengthening phase at high temperatures into a heat-resistant strengthening phase. Simultaneously, low-cost Zr and Ni elements are used to replace elements such as Sc and Er, resulting in a high-strength, heat-resistant, and low-cost aluminum alloy. Attached Figure Description

[0025] Figure 1 This is the isothermal cross-section of the Al-Zn-Mg system of this invention at 470℃;

[0026] Figure 2 This is the isothermal cross-section of the Al-Zn-Mg system of this invention at 200℃;

[0027] Figure 3 The alloy phase diagram of Al-7.5Zn-3.7Mg-xCu of this invention is shown below;

[0028] Figure 4 Photograph of the as-cast microstructure of the aluminum alloy prepared in Example 1 of this invention;

[0029] Figure 5 The homogenized Al3Zr precipitate phase in the aluminum alloy prepared in Example 1 of this invention;

[0030] Figure 6 This is a photograph of the morphology of the precipitated phases in the aluminum alloy prepared in Example 1 of the present invention after aging. Detailed Implementation

[0031] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0032] In view of the demand for heat resistance in existing aluminum alloys, this invention provides an Al-Zn-Mg-Cu-Zr-Ni aluminum alloy. By controlling the elemental ratio of the highly alloyed Al-Zn-Mg-Cu alloy, the strengthening phase that easily coarsens at high temperatures is transformed into a heat-resistant strengthening phase. Simultaneously, low-cost Zr and Ni elements are used to replace elements such as Sc and Er, thus obtaining a high-strength, heat-resistant, and low-cost aluminum alloy. Specifically, this invention discloses a high-strength, heat-resistant Al-Zn-Mg-Cu-Zr-Ni aluminum alloy, comprising, by mass percentage: Zn 7.0–8.0%, Mg 3.5–4.0%, Cu 1.0–1.5%, Zr 0.08–0.15%, Ni 0.08–0.15%, with Zn / Mg < 2.5, Cu / Mg > 0.3, Zr + Ni ≤ 0.2, and the balance being Al.

[0033] In the high-strength, heat-resistant, and highly alloyed Al-Zn-Mg-Cu-Zr-Ni aluminum alloy provided in this application, Zn, Mg, and Cu are the main strengthening elements. After solution treatment and aging, they combine in the aluminum matrix to form strengthening phases η (Mg(Zn,Cu,Al)2) and T (Al2Mg3Zn3). The η and T phases have high solubility at high temperatures; at 475℃, the limiting solubility of the η phase in the Al matrix can reach 28%, decreasing to 4% at room temperature, exhibiting a strong age-strengthening effect. Furthermore, the Zn / Mg ratio affects the content of the η and T phases. This application designs a low Zn / Mg ratio to ensure that the main alloying elements are completely dissolved back into the matrix at the solution temperature, and mainly exist in the form of the highly heat-resistant T′ phase during aging and heat exposure. Figure 1 and Figure 2 The high-Cu design allows the slower-diffusion Cu element to dissolve into the T′ and η′ phases, reducing their coarsening rate. Simultaneously, the addition of Cu should avoid forming the sparingly soluble S phase (Al₂CuMg) during homogenization or solidification. Figure 3The Zn content is 7.0%–8.0%, specifically 7.5%–7.8%; for example, the Zn content in this application is 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9%, or 8.0%. The Mg content is 3.5%–4.0%, specifically 3.7%–3.9%; for example, the Mg content in this application is 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0%. The Cu content is 1.0%–1.5%, specifically 1.2%–1.4%; for example, the Cu content in this application is 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%. Furthermore, Zn / Mg < 2.5, specifically, Zn / Mg ≤ 2.3, more specifically, Zn / Mg = 2.0. Cu / Mg > 0.3 to suppress the formation of the S phase; specifically, Cu / Mg ≥ 0.35, more specifically, Cu / Mg = 0.38 or 0.4.

[0034] Zr and Ni are added as grain refiners to the Al-Zn-Mg-Cu alloy. During the alloy solidification process, Zr and Ni combine with Al to form primary phases Al3Zr and Al3Ni, increasing the number of nucleation sites and reducing the grain size in the as-cast state, thereby improving mechanical properties. Furthermore, nano-Al3Zr and Al3Ni are also formed during the homogenization stage, exhibiting high thermal stability and further improving mechanical and heat resistance properties. However, the amount of Zr and Ti added does not exceed their limiting solid solubility in aluminum to prevent the formation of coarse-grained second phases. The Zr content is 0.08–0.15%, specifically 0.1–0.14%; for example, the Zr content in this application is 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, or 0.14%. The Ni content is 0.08%–0.15%, specifically 0.1%–0.14%; for example, the Ni content in this application is 0.08%, 0.09%, 0.1%, 0.12%, 0.13%, 0.14%, or 0.15%. Zr+Ni ≤ 0.2% to avoid the formation of a large amount of primary coarse Al3Zr and Al3Ni, which are difficult to remove effectively during subsequent plastic deformation and heat treatment; specifically, Zr+Ni ≤ 0.18%.

[0035] The high-strength, heat-resistant Al-Zn-Mg-Cu-Zr-Ni aluminum alloy provided in this application has a density of 2.788–2.826 g / cm³. 3 .

[0036] This application also provides a method for preparing high-strength, heat-resistant Al-Zn-Mg-Cu-Zr-Ni aluminum alloy, comprising the following steps:

[0037] S1) The ingredients are prepared according to the composition ratio, and then smelted and cast in sequence to obtain aluminum alloy ingots;

[0038] S2) The aluminum alloy ingot is subjected to homogenization heat treatment;

[0039] S3) The aluminum alloy ingot obtained in step S2) is hot-processed. After processing, it is solution-treated at 400-500℃ for 1-3 hours, water-quenched, and then aged at 100-150℃ for 12-36 hours to obtain a high-strength heat-resistant aluminum alloy.

[0040] In the aluminum alloy preparation process, the materials are first batched according to the component ratio, and then melted and cast sequentially to obtain aluminum alloy ingots. To avoid the introduction of impurities from equipment and tools and the loss of alloying elements, the specific preparation process of the aluminum alloy ingots is as follows:

[0041] Tools and equipment that come into direct contact with raw materials are coated with ZnO. The raw materials are weighed and proportioned according to the alloy composition. The raw materials are then cleaned and dried. The elemental loss rates of Zn and Mg are calculated as 2.5% and 6%, respectively.

[0042] The prepared high-purity Al ingots are added to a medium-frequency induction furnace. After the aluminum ingots are completely melted, pure Zn, pure Cu, Al-5Zr, and Al-10Ni master alloys are added. The furnace is held at this temperature for 1–2 hours until all the newly added materials have melted. The temperature of the molten aluminum is then raised to 700–750°C, and pure Mg is added. The temperature is then stabilized at 700–750°C. Refining then begins, which is carried out in three stages: the first stage uses argon gas, the second stage uses argon gas and CCl4, and the third stage uses argon gas and C2Cl6. After refining, the slag is removed and the furnace is allowed to stand. After all the above steps are completed, the temperature of the molten aluminum is lowered to 670–690°C, and casting begins. The molten aluminum is poured into a preheated mold, and after cooling, ingots are obtained.

[0043] In the above process, the heat preservation time is specifically 1 hour, the aluminum liquid is specifically heated to 740°C, the temperature is specifically stabilized at 740°C, and the aluminum liquid temperature is specifically reduced to 690°C.

[0044] After the above casting process, the solidification structure of the aluminum alloy includes α(Al), T phase, and Fe-rich phase. Figure 4 ), where the T phase includes Al 32 (Mg, Zn) 49 There are three forms: Al6CuMg4 and Al2Mg3Zn3. These three T phases can be infinitely miscible to form the AlZnMgCu quaternary phase. This invention does not distinguish between them and generally refers to them as T phases.

[0045] This application then subjectes the aforementioned aluminum alloy ingot to homogenization heat treatment, specifically: homogenizing the ingot at 400–450°C for 8–12 hours, then raising the furnace temperature to 460–480°C, holding at that temperature for 24–36 hours, and then cooling; more specifically: homogenizing the ingot at 420°C for 10 hours, then raising the furnace temperature to 470°C, holding at that temperature for 24 hours, and then cooling. After homogenization heat treatment, a large amount of Al3Ni and Al3Zr precipitates are formed in the matrix, with precipitate sizes between 20 and 30 nm. Figure 5 ).

[0046] According to this invention, the homogenized heat-treated aluminum alloy ingot is then subjected to hot working. The hot working is a technique well-known to those skilled in the art, and can be hot rolling, hot forging, or hot extrusion. That is, this application does not impose any particular limitation on the specific hot working method; however, the temperature window for hot working is 400–450°C, and the strain rate is 0.001–0.01 s⁻¹. -1 More specifically, the temperature window is 420–440°C.

[0047] Finally, this application involves solution treatment and aging of the aluminum alloy ingot. Specifically, the aluminum alloy ingot is heated to 400–500°C and held for 1–3 hours for solution treatment, followed by water quenching and aging at 100–150°C for 12–36 hours. More specifically, the solution treatment temperature is 450–470°C for 2 hours, and the aging temperature is 120–140°C for 24 hours. After solution treatment, most of the primary phase formed during solidification dissolves back, leaving only the difficult-to-dissolve Fe-rich phase. After aging treatment, two nano-reinforcing phases precipitate in the matrix, namely the T′ phase and the η′ phase (…). Figure 6 ).

[0048] In aged aluminum alloys, the matrix mainly contains T′ and η′ phases. Since the T′ phase is spherical, its projection is approximately circular from any direction. However, the η′ phase is rod-shaped, appearing circular from the front and rod-shaped from the side. <110> Bright-field TEM images along the Al direction reveal a circular η′ phase on one half of the front and a rod-shaped η′ phase on the other half of the side. The proportion of η′ can be calculated from the morphology of the precipitated phases in the TEM images using the following formula:

[0049]

[0050] In the formula N total for <110> The total number of precipitates in the Al square TEM image, N edge-on The total number of rod-shaped precipitates in the figure is shown. In the aluminum alloy provided in this application, T′ phase strengthening is dominant, meaning the proportion of T′ phase exceeds 50%.

[0051] The aluminum alloy provided in this application can be prepared by the above-mentioned method, and can also be prepared by powder metallurgy, spray deposition and other methods.

[0052] Experimental results show that the aluminum alloy provided in this application has the following properties at room temperature: tensile strength greater than 600 MPa, yield strength greater than 560 MPa, and elongation greater than 6%; after heat exposure of 120℃ / 4h+160℃ / 4h+180℃ / 4h+200℃ / 20h, the tensile strength is greater than 400 MPa, the yield strength is greater than 340 MPa, and the elongation is greater than 10%.

[0053] To further understand the present invention, the high-strength heat-resistant Al-Zn-Mg-Cu-Zr-Ni aluminum alloy and its preparation method provided by the present invention will be described in detail below with reference to the embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0054] Example 1

[0055] (1) A high-strength heat-resistant aluminum alloy comprises, by weight percentage: Zn (7.5%), Mg (3.7%), Cu (1.4%), Zr (0.1%), Ni (0.1%), with the remainder being Al and unavoidable impurities; the density of the high-strength heat-resistant aluminum alloy is 2.810 g / cm³. 3 ;

[0056] (2) The raw materials are pure Al (99.99% wt%), pure Zn (99.9% wt%), pure Mg (99.9% wt%), Al-50Cu (wt%), Al-5Zr (wt%) and Al-10Ni (wt%) master alloys, and the element burn-off rates of Zn and Mg are calculated as 2.5% and 6% respectively;

[0057] According to the target composition of the alloy, the raw materials are weighed and proportioned, and the raw materials are cleaned and dried. The tools and equipment that come into direct contact with the raw materials are coated with ZnO.

[0058] The prepared high-purity Al ingots are added to a medium-frequency induction furnace. After the aluminum ingots have completely melted, pure Zn, pure Cu, Al-5Zr, and Al-10Ni master alloys are added. The furnace is held at this temperature for about 1 hour. After all the newly added materials have melted, the temperature of the molten aluminum is raised to 740℃, and high-purity Mg is added. The temperature is then stabilized at 740℃. Refining then begins, and is carried out in three stages: the first stage uses argon gas, the second stage uses argon and CCl4, and the third stage uses argon and C2Cl6. After refining, the slag is removed, the furnace is allowed to stand, and finally, the resulting molten aluminum is cooled to 670–690℃ before casting begins. Figure 4 As shown, Figure 4 These are photographs of the microstructure of an aluminum alloy in its as-cast state, by... Figure 4It can be seen that the solidification structure of aluminum alloys includes α(Al), T phase and Fe-rich phase;

[0059] (3) Pour the molten aluminum into a preheated mold at a preheating temperature of 200°C. The mold is an air-cooled steel mold with dimensions of 200×300×400mm. After cooling, the ingot is obtained.

[0060] (4) The ingot is homogenized and heat-treated at 420℃ for 10 hours, then heated to 470℃ in the furnace, held at that temperature for 24 hours, and then cooled in the furnace. Figure 5 As shown, Figure 5 Photographs of the precipitated phases in the aluminum alloy after homogenization heat treatment, such as Figure 5 It can be seen that after homogenization heat treatment, a large number of Al3Ni and Al3Zr precipitates are formed in the aluminum alloy matrix, and the size of the precipitates is between 20 and 30 nm.

[0061] (5) The homogenized ingot is processed into an 11mm thick plate, which is then milled into a smooth 10mm thick plate. The thick plate is hot-rolled at 420℃ and rolled into a 3mm thick plate through multiple passes. The plate is held at 420℃ for 3 minutes between passes, and the reduction between passes is controlled to keep the strain rate between 0.001 and 0.01 s. -1 between;

[0062] (6) The rolled sheet is heated to 470℃ in the furnace and held for 2 hours, then quenched in water. After quenching, it is aged at 120℃ for 24 hours to obtain the finished aluminum alloy product; Figure 6 As shown, Figure 6 These are photographs showing the morphology of the precipitated phases in aluminum alloys after aging, such as... Figure 6 It can be seen that two nano-reinforcing phases precipitated in the matrix, namely the T′ phase and the η′ phase;

[0063] (7) The above aluminum alloy finished products were subjected to mechanical property tests. At room temperature, the tensile strength was 634 MPa, the yield strength was 586 MPa, and the elongation was 6.3%. After being exposed to heat for 120℃ / 4h+160℃ / 4h+180℃ / 4h+200℃ / 20h, the tensile strength was 412 MPa, the yield strength was 346 MPa, and the elongation was 11.2%.

[0064] Example 2

[0065] (1) The weight percentage of a high-strength heat-resistant aluminum alloy is as follows: Zn (7.5%), Mg (3.5%), Cu (1.4%), Zr (0.1%), Ni (0.1%), with the remainder being Al and unavoidable impurities; the density of the high-strength heat-resistant aluminum alloy is 2.810 g / cm³. 3 ;

[0066] (3) The raw materials are pure Al (99.99% wt.%), pure Zn (99.9% wt.%), pure Mg (99.9% wt.%), Al-50Cu (wt.%), Al-5Zr (wt.%), and Al-10Ni (wt.%) master alloys. The elemental loss rates of Zn and Mg are calculated as 2.5% and 6%, respectively;

[0067] According to the target composition of the alloy, the raw materials are weighed and proportioned, and the raw materials are cleaned and dried. The tools and equipment that come into direct contact with the raw materials are coated with ZnO.

[0068] Raw materials, including pure aluminum, pure zinc, Al-50Cu master alloy, Al-5Zr, and Al-10Ni master alloy, were placed in an electric resistance furnace and heated to 740°C. After all materials melted, pure magnesium was added to the furnace, and the temperature was continued to rise. The melt temperature was then maintained at 740°C. A small amount of melt was then taken from the furnace, and its composition was measured after solidification and cooling.

[0069] Once the composition meets the requirements, refining begins. The refining process is carried out in three stages: the first stage uses argon gas, the second stage uses argon gas and CCl4, and the third stage uses argon gas and C2Cl6. After refining, the residue is removed and the mixture is left to stand.

[0070] After completing the above operations, the aluminum liquid is cooled to 690℃ and left to stand for 30 minutes. Then, the aluminum liquid is injected into the crystallizer through the flow channel and continuous casting begins. The crystallizer has a size of Φ320mm and the casting speed is 60mm / min.

[0071] (4) The ingot is homogenized and heat-treated at 420°C for 10 hours, then heated to 470°C in the furnace, and then held for 24 hours. After the treatment, it is cooled in the furnace.

[0072] (5) The homogenized ingot is processed into forging blocks of 100×100×100mm, and then subjected to a "three-upsetting and three-drawing" forging process at 420℃, with the upsetting and drawing rate maintained at 0.001~0.01s. -1 ;

[0073] (6) The forging block is heated to 470℃ and held for 2 hours in the furnace, then quenched in water, and after quenching, it is aged at 120℃ for 24 hours to obtain the finished aluminum alloy product.

[0074] (10) The above aluminum alloy finished products were subjected to mechanical property tests. At room temperature, the tensile strength was 607 MPa, the yield strength was 562 MPa, and the elongation was 7.1%. After being exposed to heat at 120℃ / 4h+160℃ / 4h+180℃ / 4h+200℃ / 20h, the tensile strength was 405 MPa, the yield strength was 353 MPa, and the elongation was 10.3%.

[0075] Comparative Example 1

[0076] (1) Typical 7xxxx series 7075 aluminum alloy is used, and the alloy composition is calculated by mass ratio as Al-5.7Zn-2.5Mg-1.7Cu-0.2Cr;

[0077] (2) The raw materials are pure Al (99.99% wt.%), pure Zn (99.9% wt.%), pure Mg (99.9% wt.%), Al-50Cu (wt.%), and Al-10Cr (wt.%) master alloys. The elemental loss rates of Zn and Mg are calculated as 2.5% and 6%, respectively;

[0078] According to the target composition of the alloy, the raw materials are weighed and proportioned, and the raw materials are cleaned and dried. The tools and equipment that come into direct contact with the raw materials are coated with ZnO.

[0079] Add the prepared high-purity Al ingots into the medium-frequency induction furnace. After the aluminum ingots have melted completely, add pure Zn, pure Cu and Al-10Cr master alloy. Hold the temperature for about 1 hour. After all the newly added materials have melted, raise the temperature of the aluminum liquid to 740℃, add high-purity Mg, and then stabilize the temperature at 740℃.

[0080] Then the refining process begins, which is carried out in three stages. The first stage uses argon gas for refining, the second stage uses argon gas and CCl4 for refining, and the third stage uses argon gas and C2Cl6 for refining. After refining, the slag is removed and the mixture is allowed to stand. Finally, the resulting molten aluminum is cooled to 670-690°C and casting begins.

[0081] (3) Pour the molten aluminum into a preheated mold at a preheating temperature of 200°C. The mold is an air-cooled steel mold with dimensions of 200×300×400mm. After cooling, the ingot is obtained.

[0082] (4) The ingot is homogenized at 420°C for 10 hours, then heated to 470°C in the furnace, and then held for 24 hours. After the furnace is finished, it is cooled.

[0083] (5) The homogenized ingot is processed into 11mm thick plates, which are then milled into smooth 10mm thick plates. The thick plates are hot rolled at 420℃ and rolled into 3mm thick plates through multiple passes. The plates are kept at 420℃ for 3 minutes between passes, and the reduction between passes is between 10-25%.

[0084] (6) The rolled sheet is heated to 470℃ in the furnace and held for 2 hours, and then quenched in water. After quenching, it is aged at 120℃ for 24 hours.

[0085] Comparative Example 2

[0086] (1) Typical 7xxxx series 7050 aluminum alloy is used, and the alloy composition is calculated by mass ratio as Al-6.5Zn-2.3Mg-2.3Cu-0.12Zr;

[0087] (2) The raw materials are pure Al (99.99% wt.%), pure Zn (99.9% wt.%), pure Mg (99.9% wt.%), Al-50Cu (wt.%), and Al-5Zr (wt.%) master alloys. The elemental burn-off rates of Zn and Mg are calculated as 2.5% and 6%, respectively;

[0088] According to the target composition of the alloy, the raw materials are weighed and proportioned, and the raw materials are cleaned and dried. The tools and equipment that come into direct contact with the raw materials are coated with ZnO.

[0089] The prepared high-purity Al ingots are added to the medium-frequency induction furnace. After the aluminum ingots are completely melted, pure Zn, pure Cu and Al-5Zr master alloy are added and the furnace is kept at the temperature for about 1 hour. After all the newly added materials have melted, the temperature of the aluminum liquid is raised to 740°C and high-purity Mg is added. The temperature is then stabilized at 740°C and refining is started. The refining is carried out in three stages: the first refining is done with argon, the second refining is done with argon and CCl4, and the third refining is done with argon and C2Cl6. After the refining is completed, the slag is removed and the furnace is allowed to stand. Finally, the temperature of the obtained aluminum liquid is lowered to 670-690°C and casting is started.

[0090] (3) Pour the molten aluminum into a preheated mold at a preheating temperature of 200°C. The mold is an air-cooled steel mold with dimensions of 200×300×400mm. After cooling, the ingot is obtained.

[0091] (4) The ingot is homogenized at 420°C for 10 hours, then heated to 470°C in the furnace, and then held for 24 hours. After the furnace is finished, it is cooled.

[0092] (5) The homogenized ingot is processed into 11mm thick plates, which are then milled into smooth 10mm thick plates. The thick plates are hot rolled at 420℃ and rolled into 3mm thick plates through multiple passes. The plates are kept at 420℃ for 3 minutes between passes, and the reduction between passes is between 10-25%.

[0093] (6) The rolled sheet is heated to 470℃ in the furnace and held for 2 hours, and then quenched in water. After quenching, it is aged at 120℃ for 24 hours.

[0094] The properties of the aluminum alloys prepared in Comparative Example 1 and Comparative Example 2 were tested, and the test results are shown in Table 1.

[0095] Table 1. Mechanical property data of aluminum alloys prepared by comparative examples and embodiments of the present invention.

[0096]

[0097] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0098] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-strength, heat-resistant Al-Zn-Mg-Cu-Zr-Ni aluminum alloy, comprising, by weight percentage: Zn 7.0–8.0%, Mg 3.5–4.0%, Cu 1.0–1.5%, Zr 0.08–0.15%, Ni 0.08–0.15%, and Zn / Mg < 2.5, Cu / Mg > 0.3, Zr + Ni ≤ 0.2, with the balance being Al.

2. The aluminum alloy according to claim 1, characterized in that, The Zn content is 7.5-7.8%, the Mg content is 3.7-3.9%, and the Zn / Mg ratio is ≤2.

3.

3. The aluminum alloy according to claim 1, characterized in that, The Cu content is 1.2-1.4%, and the Cu / Mg ratio is ≥0.

35.

4. The aluminum alloy according to claim 1, characterized in that, The Zr content is 0.1-0.14%, the Ni content is 0.1-0.14%, and Zr+Ni≤0.

18.

5. The aluminum alloy according to claim 1, characterized in that, The density of the aluminum alloy is 2.788–2.826 g / cm³. 3 .

6. A method for preparing the aluminum alloy according to claim 1, comprising the following steps: S1) The ingredients are prepared according to the proportions, and then melted and cast in sequence to obtain aluminum alloy ingots; S2) The aluminum alloy ingot is subjected to homogenization heat treatment; S3) The aluminum alloy ingot obtained in step S2) is hot-processed. After processing, it is solution-treated at 400-500℃ for 1-3 hours, water-quenched, and then aged at 100-150℃ for 12-36 hours to obtain the aluminum alloy.

7. The preparation method according to claim 6, characterized in that, Step S1) specifically refers to: According to the ingredient ratio, high-purity Al is added to the medium-frequency induction furnace. After the aluminum ingot is completely melted, pure Zn, pure Cu, Al-5Zr master alloy and Al-10Ni master alloy are added. The temperature is maintained for 1 to 2 hours. The molten aluminum liquid is raised to 700 to 750°C. Pure Mg is added. The temperature is then stabilized at 700 to 750°C. Then the refining process begins, which is carried out in three stages. The first stage uses argon gas for refining, the second stage uses argon gas and CCl4 for refining, and the third stage uses argon gas and C2Cl6 for refining. After refining, the slag is removed and the mixture is allowed to stand. Finally, the resulting molten aluminum is cooled to 670-690°C before casting begins.

8. The preparation method according to claim 6, characterized in that, The homogenization heat treatment specifically includes: The ingot is subjected to homogenization heat treatment at 400-450℃ for 8-12 hours, then heated to 460-480℃ in the furnace, held for 24-36 hours, and then cooled.

9. The preparation method according to claim 6, characterized in that, The temperature window for the heat treatment is 400–450°C, and the strain rate is 0.001–0.01 s⁻¹. -1 .

10. An aluminum alloy product, prepared from the high-strength, heat-resistant Al-Zn-Mg-Cu-Zr-Ni aluminum alloy according to any one of claims 1 to 5 or the Al-Zn-Mg-Cu-Zr-Ni aluminum alloy prepared by the preparation method according to any one of claims 6 to 9.

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