An ultra-high-strength low-density Al-Mg-Zn-Sc-Zr-based alloy and a preparation method thereof

Abstract

This invention provides an ultra-high strength, low density Al-Mg-Zn-Sc-Zr-based alloy and its preparation method, belonging to the field of aluminum alloy material technology. The ultra-high strength, low density Al-Mg-Zn-Sc-Zr-based alloy provided by this invention, by mass fraction, has the following chemical composition: Mg 3.0~8.0%, Zn 1.0~5.0%, Cu 0.4~1.0%, Mn 0.1~0.8%, Ag 0.05~0.3%, Sc 0.01%~0.3%, Zr 0.05~0.3%, with the balance being Al. This invention achieves this by precisely controlling the elemental ratios of Mg, Zn, Cu, and Ag, resulting in an alloy that maintains its low density while exhibiting a strong age-hardening effect. Simultaneously, the reasonable addition of trace elements such as Mn, Sc, and Zr enables the alloy to possess a dispersion strengthening effect. Combined with heat treatment and hot deformation processes, this further improves the strength and ductility of the aluminum alloy.

Description

Technical Field This invention relates to the field of aluminum alloy materials technology, and in particular to an ultra-high strength, low density Al-Mg-Zn-Sc-Zr based alloy and its preparation method. Background Technology To reduce energy consumption, minimize environmental pollution, and improve the performance of vehicles, lightweight development has become an inevitable trend. Al-Mg alloys (5xxx series) possess advantages such as high specific strength, good formability, good weldability, impact resistance, and corrosion resistance, making them a crucial means of achieving lightweight vehicles. They are widely used in automobiles, aerospace, shipbuilding, and special vehicles. With the rapid development of these fields, there is a significant demand for lightweight, high-performance new aluminum alloys. While traditional Al-Mg alloys have low density, they are medium-strength aluminum alloys and cannot be age-strengthened. Therefore, it is difficult to significantly improve their overall performance. For example, the H131 state AA5059 alloy, widely used in armor materials, has a yield strength of only ~296 MPa, a tensile strength of only ~393 MPa, and an elongation of only ~7%. Therefore, exploring how to significantly enhance the strength of Al-Mg alloys while maintaining their inherent low density is of great significance for expanding their engineering applications in harsh and complex service conditions. Currently, the main approach to improving the overall performance of Al-Mg alloys is microalloying, such as adding Zn to induce the precipitation of T-Mg. 32 (Al,Zn) 49 The addition of Zn or η-MgZn2 phases produces an age-hardening effect. Furthermore, alloying elements such as Mn, Cr, Ti, Sc, Er, and Re are added to induce the precipitation of fine, dispersed second-phase particles within the alloy, resulting in dispersion strengthening and improved recrystallization resistance. However, the complex addition of multiple elements significantly complicates the phase equilibrium behavior of the alloy system, making it difficult to achieve a simultaneous and synergistic improvement in strength and plasticity. Simultaneously, excessive introduction of Zn and other high-density alloying elements leads to an increase in alloy density, weakening the lightweight advantage of Al-Mg alloys. Therefore, a reasonable balance must be struck between the levels of alloying elements added, and the composition range and element ratios must be meticulously designed. In addition, an unreasonable process design can easily lead to unstable control of microstructure precipitation behavior, failing to obtain the desired ideal second-phase precipitation characteristics. This invention involves adding 1-5% Zn to a high-magnesium-content Al-Mg alloy, along with the composite addition of various microalloying elements. Through appropriate heat treatment and hot working processes, the interaction between elements forms multiple types of precipitate strengthening phases. By comprehensively utilizing mechanisms such as dispersion strengthening, grain refinement strengthening, solid solution strengthening, and age hardening, the alloy is strengthened. This allows the alloy to maintain its low-density characteristics while increasing its strength to the 7xxx level, and simultaneously maintaining high plasticity. It is expected to replace traditional high-density 7xxx series alloys and promote the industrial application of new Al-Mg series alloys in fields such as aircraft, ships, and armored vehicles. Summary of the Invention

[0001] The purpose of this invention is to provide an ultra-high strength, low density Al-Mg-Zn-Sc-Zr based alloy and its preparation method. The aluminum alloy provided by this invention has low density, high strength, and low production cost, which can meet the application requirements of various fields for lightweight and high-performance materials. To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides an ultra-high strength, low density Al-Mg-Zn-Sc-Zr based alloy. The chemical composition of the aluminum alloy, by mass fraction, is: Mg 3.0~8.0%, Zn 1.0~5.0%, Cu 0.4~1.0%, Mn 0.1~0.8%, Ag 0.05~0.3%, Sc 0.01%~0.3%, Zr 0.05~0.3%, with the balance being Al. Preferably, the chemical composition of the ultra-high strength low density Al-Mg-Zn-Sc-Zr based alloy, by mass fraction, is: Mg 4.5~7.5%, Zn 3.0~5.0%, Cu 0.4~0.5%, Mn 0.1~0.5%, Ag 0.05~0.2%, Sc 0.01%~0.2%, Zr 0.05~0.2%, with the balance being Al. This invention designs an ultra-high strength, low density Al-Mg-Zn-Sc-Zr based alloy. Adding Zn, Cu, and Ag to the Al-Mg alloy imparts age-hardening capability. By controlling the mass ratio of Mg, Zn, Cu, and Ag in the alloy, age-hardening (T-Mg) is promoted. 32 (Al,Zn,Cu,Ag) 49The process promotes the dispersed precipitation of the Zn-Mg-(Cu) phase and its metastable phase, and inhibits the formation of the β-Al3Mg2 phase. Firstly, sufficient Mg solute atoms are ensured to participate in aging precipitation. Secondly, the Zn content is controlled to form a dense precipitation-strengthening T phase, and the T phase on the grain boundaries exhibits a fine, discontinuous distribution. Simultaneously, the Cu content is controlled to enhance the aging response and improve precipitation strengthening. Adding Mn promotes the intragranular precipitation of the Al6Mn phase, optimizes the morphology of the grain boundary T phase, reduces the adverse effects of impurities such as Fe and Si in the alloy, and increases the recrystallization temperature, inhibiting grain growth. The added Cu increases the number density of Zn-Mg-(Cu) clusters, which is beneficial for the formation of GP zones. GP zones can serve as effective nucleation sites for subsequent strengthening phases, promoting their transformation to the T' phase, thereby improving the alloy's rapid aging response. Similar to Cu, Ag effectively captures quenching vacancies and forms vacancy aggregates, promoting the nucleation of precipitates during aging, accelerating and strengthening the age hardening effect, and ultimately forming a uniformly dispersed Cu and Ag-containing precipitated strengthening T phase, achieving a simultaneous improvement in alloy strength and plasticity. The added trace elements Sc and Zr help to obtain dispersed Al3(Sc,Zr) phase particles in the matrix, playing a role in dispersion strengthening while refining grains, inhibiting recovery recrystallization, and further improving alloy strength. This invention also provides a method for preparing the ultra-high strength, low density Al-Mg-Zn-Sc-Zr based alloy described in the above technical solution, comprising the following steps: 1) Raw material smelting: The raw materials are prepared according to the designed composition ratio, smelted, and cast to obtain alloy ingots; 2) Homogenization: The alloy ingot obtained in step 1) is subjected to homogenization heat treatment, which involves heating it from room temperature to 450°C to 490°C at a rate of 30°C / h to 80°C / h, and holding it at that temperature for 8h to 36h. 3) Hot deformation: The homogenized alloy ingot obtained in step 2) is subjected to hot deformation treatment, including rolling, extrusion or forging; 4) Solution treatment: The alloy deformed in step 3) is subjected to solution treatment; 5) Aging treatment: The alloy after solution treatment in step 4) is subjected to aging treatment. Preferably, in step 3), the hot rolling temperature is 350~450℃ and the deformation is 70%~90%. Preferably, in step 4), the solution temperature is 430~480℃, the heat preservation time is 1~4h, and the solution is immediately quenched to room temperature after the heat preservation is completed. Preferably, in step 5), the aging process is a single-stage or double-stage aging process. The temperature for single-stage aging is 120~180℃, and the holding time is 8~48h. For double-stage aging, the first stage aging temperature is 70~100℃, and the first stage aging time is 18~36h. The second stage aging temperature is 120~160℃, and the second stage aging time is 12~48h. In the above technical solution, the homogenization treatment in step 2) can dissolve the non-equilibrium phase, eliminate dendritic segregation in the ingot, improve the hot deformation capability of the alloy, and improve the uniformity of the alloy's chemical composition and microstructure. In the above technical solution, the deformation treatment in step 3) can extend the alloy grains along the deformation direction, break down and refine the coarse and insoluble particles, and distribute the second phase evenly in the matrix, introducing a large number of dislocations, which is beneficial to improving the strength of the alloy. In the above technical solution, the solution treatment in step 4) increases the solid solubility of alloying elements by holding the solution at high temperature, and the precipitated phase is fully dissolved in the matrix, which is conducive to the uniform dispersion of the second phase during the subsequent aging process. The alloy undergoes recovery recrystallization, and the grains become fine equiaxed crystals. In the above technical solution, T-Mg precipitates in the alloy obtained by the aging treatment in step 5). 32 (Al, Zn, Cu, Ag) 49 The strengthening phase significantly improves the mechanical properties of the alloy. The beneficial effects of this invention are: Based on the intrinsic low density of Al-Mg alloys, this invention utilizes the aging strengthening effect of the alloy by precisely controlling the ratio of Mg, Zn, Cu, and Ag elements. At the same time, the reasonable addition of trace elements such as Mn, Sc, and Zr enables the alloy to have a dispersion strengthening effect. Combined with heat treatment and hot deformation processes, the strength and toughness of the aluminum alloy are further improved, thereby obtaining an ultra-high strength low density Al-Mg-Zn-Sc-Zr based alloy. (1) By precisely controlling the content and mass ratio of the main elements Mg and Zn, a large number of finely dispersed T phases are precipitated. By controlling the strengthening elements Cu and Ag, clusters are formed, precipitation kinetics are reduced, precipitation efficiency is improved, and the aging precipitation strengthening response is enhanced. By controlling the addition of trace elements such as Mn, Sc, and Zr, Al6Mn and Al3(Sc,Zr) dispersed phases are formed, which refine the grains and play a role in dispersion strengthening. Under the synergy of the above mechanisms, the aluminum alloy provided by this invention can achieve a tensile strength of over 600 MPa and a yield strength of over 550 MPa, while maintaining good elongation (≥8%) and density of 2.61~2.70 g / cm³. 3 . (2) By using a two-stage aging process, a uniformly dispersed precursor is first formed during the low-temperature pre-aging process as a nucleation site, which promotes the nucleation and growth of the precipitate phase during the subsequent high-temperature aging process, thereby improving the strength and plasticity of the alloy. (3) The Al-Mg-Zn-Sc-Zr based alloy prepared by this invention has superior performance and is expected to replace the traditional high-density 7xxx series alloys. The process is relatively simple and practical, and it can be applied to aircraft, ships and armored vehicles, promoting the development of lightweighting and having important social and economic benefits. Attached Figure Description Figure 1 Here is a SEM image of the aluminum alloy ingot in Example 1; Figure 2 This is a SEM image of the homogenized aluminum alloy ingot from Example 1. Figure 3 This is a SEM image of the ultra-high strength, low density Al-Mg-Zn-Sc-Zr based alloy obtained after aging in Example 1. Figure 4 Quasi-static tensile stress-strain curve of the ultra-high strength low density Al-Mg-Zn-Sc-Zr based alloy prepared in Example 1; Figure 5 The quasi-static tensile stress-strain curve of the ultra-high strength low density Al-Mg-Zn-Sc-Zr based alloy prepared in Example 2; Figure 6 Here is a SEM image of the aluminum alloy ingot in Example 3; Figure 7 This is a SEM image of the homogenized aluminum alloy ingot in Example 3; Figure 8 This is a SEM image of the ultra-high strength, low density Al-Mg-Zn-Sc-Zr based alloy obtained after aging in Example 3; Figure 9 The quasi-static tensile stress-strain curve of the ultra-high strength low density Al-Mg-Zn-Sc-Zr based alloy prepared in Example 3; Figure 10 The quasi-static tensile stress-strain curves of the Al-Mg-Zn alloy in Comparative Example 1 are shown. Figure 11 The quasi-static tensile stress-strain curves of the Al-Mg-Zn alloy in Comparative Example 2 are shown. Detailed Implementation The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Unless otherwise specified in the following examples, the conditions shall be performed under conventional conditions or conditions recommended by the manufacturer. There are no special restrictions on the source of any raw materials used in this invention. They may be obtained from commercial sources or prepared by conventional methods known to those skilled in the art. Unless otherwise specified, the reagents or instruments used are all conventional products that can be purchased commercially. In the following examples, Al and Ag are added in pure metal form, and other components are added in the form of aluminum-based master alloys. Example 1 An ultra-high strength, low density Al-Mg-Zn-Sc-Zr based alloy is made of the following elements in the following mass percentages and proportions: Mg: 5.5%, Zn: 4.6%, Cu: 0.5%, Mn: 0.1%, Sc: 0.1%, Zr: 0.15%, with the balance being Al. The preparation method is as follows: Aluminum alloy ingots are obtained by melting and casting alloy raw materials. Their as-cast microstructure is as follows: Figure 1 The aluminum alloy ingot was homogenized by heating it from room temperature to 475℃ at a rate of 50℃ / h and holding it at that temperature for 12 hours. Its metallographic structure is as follows: Figure 2 The homogenized aluminum alloy ingot was hot-rolled at 420℃ with a total deformation of 75% to obtain an aluminum alloy sheet. The obtained aluminum alloy sheet was solution-treated at 475℃ for 1 hour, and the sample was immediately water-quenched to room temperature. The solution-treated aluminum alloy sheet was subjected to a two-stage aging treatment: the first stage aging temperature was 90℃ and the holding time was 24 hours, and the second stage aging temperature was 130℃ and the holding time was 24 hours. The sample was then water-quenched to obtain an ultra-high strength low density aluminum alloy material. The metallographic structure of ultra-high strength, low density aluminum alloy observed using scanning electron microscopy, such as... Figure 3 As shown in the figure, the second phase inside the alloy grains is evenly distributed and small in size, with a high precipitation density. At the same time, the fibrous structure from the hot deformation process is retained, and the grains are refined. According to GB / T 1423-1996 "Test Methods for Density of Precious Metals and Their Alloys", a sample was taken from the aged plate for density testing, and the density was measured to be 2.70 g / cm³. 3 . According to GB / T 228.1-2010 "Metallic materials, tensile testing—Part 1: Test at room temperature," samples were taken from aging-treated plates for tensile testing, and the quasi-static stress-strain curves were obtained as follows: Figure 4 As shown in the figure, the alloy has a yield strength of 604 MPa, a tensile strength of 647 MPa, and an elongation of 10.0%. Example 2 An ultra-high strength, low density Al-Mg-Zn-Sc-Zr based alloy is made of the following elements in the following mass percentages and proportions: Mg: 5.5%, Zn: 4.6%, Cu: 0.5%, Mn: 0.1%, Sc: 0.1%, Zr: 0.15%, with the balance being Al. The preparation method is as follows: Aluminum alloy ingots were obtained by melting and casting alloy raw materials. The aluminum alloy ingots were then heated from room temperature to 475℃ at a rate of 80℃ / h and held for 12h for homogenization treatment. The homogenized aluminum alloy ingots were then hot-rolled at 420℃ with a total deformation of 75% to obtain aluminum alloy sheets. The obtained aluminum alloy sheets were then solution-treated at 475℃ for 1h, and the samples were immediately water-quenched to room temperature after removal. The solution-treated aluminum alloy sheets were then subjected to single-stage aging treatment at a temperature of 150℃ for 12h. After removal, the samples were water-quenched to obtain ultra-high strength low density aluminum alloy materials. According to GB / T 1423-1996 "Test Methods for Density of Precious Metals and Their Alloys", a sample was taken from the aged plate for density testing, and the density was measured to be 2.70 g / cm³. 3 . According to GB / T 228.1-2010 "Metallic materials, tensile testing—Part 1: Test at room temperature," samples were taken from aging-treated plates for tensile testing, and the quasi-static stress-strain curves were obtained as follows: Figure 5 As shown in the figure, the alloy has a yield strength of 585 MPa, a tensile strength of 608 MPa, and an elongation of 8.4%. Example 3 An ultra-high strength, low density Al-Mg-Zn-Sc-Zr based alloy is made of the following elements in the following mass percentages and their proportions: Mg: 6.0%, Zn: 3.0%, Cu: 0.5%, Mn: 0.4%, Ag: 0.15%, Sc: 0.15%, Zr: 0.2%, with the balance being Al. The preparation method is as follows: Aluminum alloy ingots are obtained by melting and casting alloy raw materials. Their as-cast microstructure is as follows: Figure 6 The aluminum alloy ingot was homogenized by heating it from room temperature to 475℃ at a rate of 80℃ / h and holding it at that temperature for 12 hours. Its metallographic structure is as follows: Figure 7 The homogenized aluminum alloy ingot was hot-rolled at 420℃ with a total deformation of 75% to obtain an aluminum alloy sheet. The obtained aluminum alloy sheet was solution-treated at 480℃ for 1 hour, and the sample was immediately water-quenched to room temperature. The solution-treated aluminum alloy sheet was subjected to a two-stage aging treatment: the first stage aging temperature was 90℃ and the holding time was 24 hours, and the second stage aging temperature was 130℃ and the holding time was 48 hours. The sample was then water-quenched to obtain an ultra-high strength low density aluminum alloy material. The metallographic structure of ultra-high strength, low density aluminum alloy observed using scanning electron microscopy, such as... Figure 8 As shown in the figure, the second phase inside the alloy grains is evenly distributed and small in size, with a high precipitation density. At the same time, it retains some of the fibrous structure from the hot deformation process, thus refining the grains. According to GB / T 1423-1996 "Test Methods for Density of Precious Metals and Their Alloys", a sample was taken from the aged plate for density testing, and the density was measured to be 2.68 g / cm³. 3 . According to GB / T 228.1-2010 "Metallic materials, tensile testing—Part 1: Test at room temperature," samples were taken from aging-treated plates for tensile testing, and the quasi-static stress-strain curves were obtained as follows: Figure 9 As shown in the figure, the alloy has a yield strength of 569 MPa, a tensile strength of 629 MPa, and an elongation of 10.5%. Example 4 An ultra-high strength, low density Al-Mg-Zn-Sc-Zr based alloy is made of the following elements in the following mass percentages and proportions: Mg: 8.0%, Zn: 2.0%, Cu: 1.0%, Mn: 0.8%, Sc: 0.3%, Zr: 0.2%, with the balance being Al. The preparation method is as follows: Aluminum alloy ingots were obtained by melting and casting alloy raw materials. The aluminum alloy ingots were homogenized by holding them at 465℃ for 36 hours. The homogenized aluminum alloy ingots were hot-rolled at 400℃ with a total deformation of 80% to obtain aluminum alloy sheets. The obtained aluminum alloy sheets were solution-treated by holding them at 465℃ for 4 hours. After the samples were removed, they were immediately water-quenched to room temperature. The solution-treated aluminum alloy sheets were subjected to a two-stage aging treatment. The first stage aging temperature was 80℃ and the holding time was 24 hours. The second stage aging temperature was 120℃ and the holding time was 24 hours. After the samples were removed, they were air-cooled to obtain ultra-high strength low density aluminum alloy materials. According to GB / T 1423-1996 "Test Methods for Density of Precious Metals and Their Alloys", a sample was taken from the aged plate for density testing, and the density was measured to be 2.65 g / cm³. 3 . According to GB / T 228.1-2010 "Metallic materials - Tensile testing - Part 1: Test method at room temperature", samples were taken from the aged plate for tensile testing, and the yield strength of the alloy was 575 MPa, the tensile strength was 632 MPa, and the elongation was 9.3%. Example 5 An ultra-high strength, low density Al-Mg-Zn-Sc-Zr based alloy is made from the following elements in the following mass percentages and their proportions: Mg: 7.5%, Zn: 5.0%, Cu: 0.4%, Mn: 0.2%, Sc: 0.1%, Zr: 0.3%, with the balance being Al. The preparation method is as follows: Aluminum alloy ingots were obtained by melting and casting alloy raw materials. The aluminum alloy ingots were then heated from room temperature to 480℃ at a rate of 70℃ / h and held for 20h for homogenization treatment. The homogenized aluminum alloy ingots were then hot-rolled at 450℃ with a total deformation of 85% to obtain aluminum alloy sheets. The obtained aluminum alloy sheets were then solution-treated at 480℃ for 2h. After the samples were removed, they were immediately water-quenched to room temperature. The solution-treated aluminum alloy sheets were then subjected to a two-stage aging treatment: the first stage aging temperature was 100℃ and the holding time was 18h, and the second stage aging temperature was 140℃ and the holding time was 24h. After the samples were removed, they were air-cooled to obtain ultra-high strength low density aluminum alloy materials. According to GB / T 1423-1996 "Test Methods for Density of Precious Metals and Their Alloys", a sample was taken from the aged plate for density testing, and the density was measured to be 2.68 g / cm³. 3 . According to GB / T 228.1-2010 "Metallic materials - Tensile testing - Part 1: Test at room temperature", samples were taken from the aged plate for tensile testing, and the yield strength of the alloy was 595 MPa, the tensile strength was 641 MPa, and the elongation was 8.9%. Comparative Example 1 An Al-Mg-Zn alloy is made of the following elements in the following mass percentages and proportions: Mg: 5.5%, Zn: 2.5%, Cu: 0.5%, Mn: 0.8%, Ag: 0.3%, Cr: 0.1%, Si: 0.15%, Zr: 0.28%, with the balance being Al. The preparation method is as follows: Aluminum alloy ingots were obtained by melting and casting alloy raw materials. The aluminum alloy ingots were then heated from room temperature to 475℃ at a rate of 80℃ / h and held for 12h for homogenization treatment. The homogenized aluminum alloy ingots were then hot-rolled at 420℃ with a total deformation of 75% to obtain aluminum alloy sheets. The obtained aluminum alloy sheets were then solution-treated at 475℃ for 1h. After the samples were removed, they were immediately water-quenched to room temperature. The solution-treated aluminum alloy sheets were then subjected to a two-stage aging treatment: the first stage aging temperature was 90℃ and the holding time was 24h, and the second stage aging temperature was 130℃ and the holding time was 48h. After the samples were removed, they were water-quenched to obtain aluminum alloy materials. According to GB / T 1423-1996 "Test Methods for Density of Precious Metals and Their Alloys", a sample was taken from the aged plate for density testing, and the density was measured to be 2.68 g / cm³.3 . According to GB / T 228.1-2010 "Metallic materials, tensile testing—Part 1: Test at room temperature," samples were taken from aging-treated plates for tensile testing, and the quasi-static stress-strain curves were obtained as follows: Figure 10 As shown in the figure, the alloy has a yield strength of 395 MPa, a tensile strength of 496 MPa, and an elongation of 11.5%. Comparative Example 2 An Al-Mg-Zn alloy is made from the following elements in the following mass percentages and proportions: Mg: 7.0%, Zn: 2.0%, Zr: 0.15%, with the balance being Al. The preparation method is as follows: Aluminum alloy ingots were obtained by melting and casting alloy raw materials. The aluminum alloy ingots were then heated from room temperature to 475℃ at a rate of 80℃ / h and held for 12h for homogenization treatment. The homogenized aluminum alloy ingots were then hot-rolled at 420℃ with a total deformation of 75% to obtain aluminum alloy sheets. The obtained aluminum alloy sheets were then solution-treated at 475℃ for 1h, and the samples were immediately water-quenched to room temperature after removal. The solution-treated aluminum alloy sheets were then subjected to single-stage aging treatment at a temperature of 180℃ for 36h. The samples were then water-quenched to obtain aluminum alloy materials. According to GB / T 1423-1996 "Test Methods for Density of Precious Metals and Their Alloys", a sample was taken from the aged plate for density testing, and the density was measured to be 2.63 g / cm³. 3 . According to GB / T 228.1-2010 "Metallic materials, tensile testing—Part 1: Test at room temperature," samples were taken from aging-treated plates for tensile testing, and the quasi-static stress-strain curves were obtained as follows: Figure 11 As shown in the figure, the alloy has a yield strength of 215 MPa, a tensile strength of 468 MPa, and an elongation of 16.0%. Comparative Example 3 An AA7075 aluminum alloy is made of the following elements and their proportions by mass percentage: Mg: 2.25%, Zn: 6.0%, Cu: 1.51%, Cr: 0.24%, Fe: 0.25%, Mn: 0.07%, Si: 0.07%, Ti: 0.02%, with the balance being Al. The preparation method is as follows: Aluminum alloy ingots were obtained by melting and casting alloy raw materials. The aluminum alloy ingots were then heated from room temperature to 465℃ at a rate of 80℃ / h and held for 24h for homogenization treatment. The homogenized aluminum alloy ingots were then hot-rolled at 420℃ with a total deformation of 75% to obtain aluminum alloy sheets. The obtained aluminum alloy sheets were then solution-treated at 470℃ for 1h, and the samples were immediately water-quenched to room temperature. The solution-treated aluminum alloy sheets were then subjected to single-stage aging treatment at 120℃ for 24h, and the samples were water-quenched to obtain aluminum alloy materials. According to GB / T 1423-1996 "Test Methods for Density of Precious Metals and Their Alloys", a sample was taken from the aged plate for density testing, and the density was measured to be 2.80 g / cm³. 3 . According to GB / T 228.1-2010 "Metallic materials - Tensile testing - Part 1: Test method at room temperature", samples were taken from the aged plate for tensile testing, and the yield strength of the quasi-alloy was 520 MPa, the tensile strength was 565 MPa, and the elongation was 7.6%. Comparative Example 4 An Al-Zn-Mg aluminum alloy containing Sc and Zr is made of the following elements in the following mass percentages and proportions: Mg: 2.20%, Zn: 6.50%, Cu: 0.20%, Mn: 0.40%, Sc: 0.30%, Zr: 0.06%, Fe: 0.16%, Si: 0.10%, Ti: 0.06%, with the balance being Al. The preparation method is as follows: Aluminum alloy ingots were obtained by melting and casting alloy raw materials. The aluminum alloy ingots were homogenized by holding them at 465℃ for 12 hours. The homogenized aluminum alloy ingots were then hot-extruded after holding them at 520℃ for 4 hours to obtain aluminum alloy profiles. The resulting aluminum alloy sheets were solution-treated by holding them at 480℃ for 1 hour. After removing the samples, they were immediately water-quenched to room temperature. The solution-treated aluminum alloy sheets were then subjected to single-stage aging treatment at 120℃ for 24 hours. After removing the samples, they were air-cooled to obtain aluminum alloy materials. According to GB / T 1423-1996 "Test Methods for Density of Precious Metals and Their Alloys", a sample was taken from the aged profile for density testing, and the density was measured to be 2.80 g / cm³. 3 . According to GB / T 228.1-2010 "Metallic materials - Tensile testing - Part 1: Test at room temperature", samples were taken from the aged plate for tensile testing, and the yield strength of the alloy was 537 MPa, the tensile strength was 575 MPa, and the elongation was 6.5%. The performance results of the aluminum alloys obtained in specific embodiments 1-5 and comparative examples 1-4 are shown in Table 1. Table 1. Properties of aluminum alloy materials in the examples and comparative examples serial number Tensile strength (MPa) Yield strength (MPa) Elongation (%) <![CDATA[Density (g / cm 3 )]]> Example 1 647 604 10.0 2.70 Example 2 608 585 8.4 2.70 Example 3 629 569 10.5 2.68 Example 4 632 575 9.3 2.65 Example 5 641 595 8.9 2.68 Comparative Example 1 496 395 11.5 2.68 Comparative Example 2 468 215 16.0 2.63 Comparative Example 3 565 520 7.6 2.80 Comparative Example 4 575 537 6.5 2.80 As can be seen from the above examples and comparative examples, the ultra-high strength, low density Al-Mg-Zn-Sc-Zr based alloy prepared by this invention has excellent comprehensive properties. Compared with the comparative alloy, it has lower density, higher yield strength and tensile strength, while maintaining good elongation. This indicates that the present invention, through the interaction of alloy components and the synergistic effect of the process, enables the alloy of the examples to have better room temperature mechanical properties than the alloy of the comparative example, achieving the effect of traditional ultra-high strength AA7075 aluminum alloy (Al-Zn-Mg-Cu system). The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-strength, low-density Al-Mg-Zn-Sc-Zr based alloy, characterized in that, The chemical composition of the aluminum alloy, by mass fraction, is: Mg 3.0~8.0%, Zn 1.0~5.0%, Cu 0.4~1.0%, Mn 0.1~0.8%, Ag 0.05~0.3%, Sc 0.01%~0.3%, Zr 0.05~0.3%, with the balance being Al.

2. The ultra-high strength, low density Al-Mg-Zn-Sc-Zr based alloy according to claim 1, characterized in that, The chemical composition of the ultra-high strength low density Al-Mg alloy, by mass fraction, is as follows: Mg 4.5~7.5%, Zn 3.0~5.0%, Cu 0.4~0.5%, Mn 0.1~0.5%, Ag 0.05~0.2%, Sc 0.01%~0.2%, Zr 0.05~0.2%, with the balance being Al.

3. The method for preparing the ultra-high strength, low density Al-Mg-Zn-Sc-Zr based alloy according to any one of claims 1 to 2, characterized in that, The process includes the following steps: 1) Raw material smelting: The raw materials are prepared according to the designed composition ratio, smelted, and cast to obtain alloy ingots; 2) Homogenization: The alloy ingot obtained in step 1) is subjected to homogenization heat treatment, which involves heating it from room temperature to 450°C to 490°C at a rate of 30°C / h to 80°C / h, and holding it at that temperature for 8h to 36h. 3) Hot deformation: The homogenized alloy ingot obtained in step 2) is subjected to hot deformation treatment, including rolling, extrusion or forging; 4) Solution treatment: The alloy deformed in step 3) is subjected to solution treatment; 5) Aging treatment: The alloy after solution treatment in step 4) is subjected to aging treatment.

4. The preparation method according to claim 3, characterized in that, In step 3), the hot rolling process temperature is 350~450℃, and the deformation is 70%~90%.

5. The preparation method according to claim 3, characterized in that, In step 4), the solution temperature is 430~480℃, the holding time is 1~4h, and the solution is immediately quenched to room temperature after the holding time is completed.

6. The preparation method according to claim 3, characterized in that, In step 5), the aging process can be single-stage or double-stage. The temperature for single-stage aging is 120~180℃, and the holding time is 8~48h. For double-stage aging, the first stage aging temperature is 70~100℃, and the first stage aging time is 18~36h. The second stage aging temperature is 120~160℃, and the second stage aging time is 12~48h.

7. The ultra-high strength, low density Al-Mg-Zn-Sc-Zr based alloy according to claims 1-10, characterized in that, The aluminum alloy material has a tensile strength ≥600MPa, a yield strength ≥550MPa, an elongation ≥8%, and a density of 2.61~2.70g / cm³. 3 .

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