A copper-free ultra-high-strength aluminum alloy and a preparation method thereof

Abstract

The application discloses a copper-free ultra-high-strength aluminum alloy and a preparation method thereof, and belongs to the field of aluminum alloy design and processing. The alloy composition is as follows: Zn is 8.00%-12.00%, Mg is 2.00%-3.00%, Zr is 0.05%-0.15%, Cr is <0.15%, Ti is <0.10%, Cu is <0.15%, the total amount of impurity elements such as Fe and Si is <0.05%, and the balance is Al. The preparation and processing technology comprises the following steps: alloy batching and smelting, homogenization treatment, hot extrusion or hot rolling, solid solution treatment and aging treatment, so that the aluminum alloy has the following properties: tensile strength UTS >700MPa, elongation after fracture δ >8%, EA-grade anti-exfoliation corrosion, and excellent surface smoothness. The alloy has high zinc and magnesium, low copper, and by strictly controlling micro-alloying elements and impurity elements, the alloy has extremely high strength, almost no micron-sized second phase, and can maintain surface smoothness, good oxidation coloring effect and corrosion resistance. The application has the advantages of simple process, low cost, suitability for large-scale industrial production, and the ability to meet the demand for high-performance aluminum alloys in the fields of consumer electronics, transportation, aerospace and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of aluminum alloy design and processing, and particularly relates to a novel ultra-high-strength aluminum alloy without copper element and a preparation method thereof, which meets the demand of high surface processing and treatment performance of high-strength aluminum alloy in the fields of consumer electronics and transportation. BACKGROUND

[0002] Aluminum alloy has the advantages of high specific strength, corrosion resistance, easy processing and unique metallic luster, and is widely used in the fields of consumer electronics, transportation, aerospace, etc. Among them, the high-performance aluminum alloy is rapidly growing in the fields of the shell, frame and heat sink of portable consumer electronic products. The commonly used 6061 and 6063 series aluminum alloys have excellent corrosion resistance and oxidation coloring effect, but have the problems of low strength (<300 MPa) and insufficient precision machining capability. With the large-scale and light-thin of consumer electronic products, the development and application of high-strength Al-Zn-Mg-(Cu) (7xxx series) aluminum alloy products have gradually attracted attention. For example, the 7003 and 7N01 aluminum alloys have a tensile strength of 300-400 MPa, and have good surface processing, oxidation coloring effect and corrosion resistance. However, compared with stainless steel (tensile strength of 600-800 MPa), the strength level of the 7003 and 7N01 aluminum alloys still has a large gap. Therefore, it is a major demand to develop an ultra-high-strength aluminum alloy with surface finishing capability, anodic oxidation surface treatment capability and corrosion resistance equivalent to the existing 7003 and 7N01 alloys, and with a greatly improved strength that can reach the level of stainless steel, so as to realize the light weight of consumer electronic products and high-end transportation equipment.

[0003] Component optimization design is a very important means to realize the performance improvement of aluminum alloy. The content of Zn in 7003, 7N01 and other aluminum alloys is in the range of 4.0% to 6.5%, the content of Mg is in the range of 0.5% to 2.0%, and the content of Cu is less than 0.2%. By further increasing the total content of main elements such as Zn and Mg, and adding appropriate micro-alloying elements, the density of intracrystalline precipitated phase is increased, and the grain size is refined, so that the strength of Al-Zn-Mg-(Cu) series aluminum alloy can be improved. However, when the content of main elements exceeds the maximum solid solubility of the elements in the alloy, or the matching between the main elements is unreasonable, one of the elements will be "excessive", and a large number of micron-sized coarse second phases will be produced, which cannot be eliminated by homogenization and solid solution heat treatment, and the toughness, product surface processing and corrosion resistance of the alloy will be significantly deteriorated, thereby damaging the comprehensive performance of the alloy and the use performance of the product / equipment. Therefore, reasonable matching of the main elements of complex alloy, addition of appropriate micro-alloying elements, and inhibition or elimination of the formation of micron-sized coarse second phases are a major challenge in the design of complex component high-performance aluminum alloy for a long time. On the other hand, the optimization of solid solution and aging treatment parameters of complex component strengthening type alloy is the key to eliminate coarse primary phase, obtain high-density, fine and uniform distribution of precipitated phase, improve the comprehensive performance of the alloy, and improve the smoothness of the processed product, the surface treatment ability of anodic oxidation and the corrosion resistance.

[0004] However, high-strength aluminum alloys represented by Al-Zn-Mg-(Cu) series have problems such as complex composition, long preparation process, various target properties, and difficulty in constructing the intrinsic relationship between composition, process, organization and performance. Using the traditional "experience + trial and error" strategy, it is inefficient to search for possible composition and process schemes in a large composition and process space to develop new high-performance aluminum alloys. With the development of new paradigm of data-driven research, it is possible to break through the above difficulties by using machine learning combined with theoretical calculation method. SUMMARY

[0005] The present application aims at the fact that the strength, surface smoothness, oxidation coloring effect, corrosion resistance and other properties of the existing industrialized Al-Zn-Mg-(Cu) alloy cannot meet the demand of consumer electronics and high-end transportation equipment field for aluminum alloy materials at the same time, and a new type of copper-free ultra-high strength aluminum alloy Al-Zn-Mg-Zr-(Cr)-(Ti) is developed, which is characterized in that the mass fraction (wt%) of new alloy elements is as follows: Zn is 8.00% to 12.00%, Mg is 2.00% to 3.00%, Zr is 0.05% to 0.15%, Cr is <0.15%, Ti is <0.10%, Cu is <0.15%, the total of impurity elements such as Fe and Si is <0.05%, and the balance is Al.

[0006] Compared with the 7003 and 7N01 alloys, the Zn element content of the copper-free ultra-high strength aluminum alloy is significantly increased from 4.40% to 6.50% to 8.00% to 12.00%; the Mg content is greatly increased from 0.50% to 2.00% to 2.00% to 3.00%, which is helpful to increase the strength of the alloy. The micro-alloying elements Zr, Cr, Ti and impurity elements Fe, Si are more strictly controlled, so that the micron-sized second phase is almost completely absent in the alloy.

[0007] Further preferred component mass fractions (wt%) of the alloy elements are: Zn is 9.00% to 11.00%, Mg is 2.40% to 2.80%, Zr is 0.08% to 0.13%, Cr is <0.10%, Ti is <0.07%, Cu is <0.10%, the total of impurity elements such as Fe and Si is <0.05%, and the balance is Al.

[0008] In order to match the characteristics of the above-mentioned aluminum alloy composition, the present application provides a preparation process, which comprises the following steps:

[0009] 1) Using high-purity aluminum, industrial pure zinc, industrial pure magnesium, aluminum-chromium intermediate alloy, aluminum-zirconium intermediate alloy, and aluminum-titanium intermediate alloy as raw materials, wherein the purity of the high-purity aluminum is ≥99.95wt%, the purity of the industrial pure zinc is ≥99.99wt%, the purity of the industrial pure magnesium is ≥99.99wt%, the chromium content in the aluminum-chromium intermediate alloy is ≥5wt%, the zirconium content in the aluminum-zirconium intermediate alloy is ≥5wt%, and the titanium content in the aluminum-titanium intermediate alloy is ≥10wt%;

[0010] 2) The alloy raw materials are weighed according to the alloy composition, and after melting and melt purification, mold casting or semi-continuous casting is performed, and the melting temperature is controlled at 700-800℃;

[0011] 3) The cast ingot obtained in step 2) is subjected to homogenization treatment: first heated to 380-420℃, and then heated to 460-475℃, and then cooled to room temperature in the air after 10-30h of heat preservation;

[0012] 4) The cast ingot after the homogenization treatment in step 3) is subjected to hot extrusion or hot rolling processing: the heating temperature of the aluminum alloy cast ingot is 380-420℃, and the heating time is 2-4h; the extrusion ratio is 7-50 during extrusion, and the total deformation amount of hot rolling is 50% to 90% during hot rolling;

[0013] 5) The billet after the hot processing in step 4) is subjected to three-stage solid solution treatment: first heated to 430-450℃, and then heated to 465-475℃, and then heated to 475-485℃, and then quenched in room temperature water after 0.5h of heat preservation;

[0014] 6) Perform single-stage aging treatment on the billet after solution treatment in step 5): heat the billet to 110-130℃ and hold for 15-30 hours to obtain the final state aluminum material.

[0015] Furthermore, the microstructure characteristics of the final state aluminum material are as follows: smooth surface, volume fraction of micron-sized second phase less than 0.001%, grain size of 6–15 μm, and the presence of nanoscale dispersed phases rich in Zr and other elements, with a size range of 20–300 nm, as shown in the attached figure. Figure 2 As shown, the matrix also contains nanoscale precipitates such as η' and GP regions with a volume fraction greater than 8%, ranging in size from 2 to 10 nm, as shown in the attached figure. Figure 3 As shown.

[0016] Furthermore, the final performance characteristics of the aluminum material are as follows: tensile strength UTS>700MPa, elongation after fracture δ>8%, and exfoliation corrosion resistance grade EA, which significantly improves strength while maintaining excellent corrosion resistance.

[0017] The principle of this invention is:

[0018] 1. From a compositional perspective, the difference between this invention and existing technologies lies in the significant increase in Zn and Mg content. The increased Zn and Mg content serves two purposes: Zn and Mg have high solid solubility in the aluminum matrix, and increasing their content can increase the volume fraction of precipitated phases such as the η' phase and GP zone in the alloy without generating a micron-sized second phase. The volume fraction of precipitated phases in 7003 and 7N01 alloys is around 4%, while the volume fraction in the alloy of this invention is around 8%, resulting in a stronger age-hardening effect and significantly improving alloy strength. The alloy also contains Zr, Cr, and Ti, which, while ensuring the absence of a micron-sized second phase, form Al3Zr and Al... 18 Nanoscale dispersed phases such as (Cr,Ti)2Mg3 play a role in dispersion strengthening, grain refinement, and corrosion propagation inhibition, thereby improving the mechanical properties and corrosion resistance of the alloy.

[0019] 2. From the perspective of manufacturing process, the present invention adopts a three-stage solution treatment system. Compared with the single-stage solution treatment system, the three-stage solution treatment system can make the temperature exceed the multiphase eutectic temperature without producing overburnt structure, improve the solubility of residual soluble second phase, and at the same time ensure a low degree of recrystallization, increase the supersaturation of the solid solution after quenching, improve the age hardening effect of the alloy, and thus improve the mechanical properties and corrosion resistance of the alloy.

[0020] The application collects and discloses the aluminum alloy composition-process-performance data reported, adopts a machine learning strategy combined with thermodynamic calculation, realizes rapid design of alloy composition and synchronous prediction of organization-performance, efficiently screens out a composition design and a preparation process scheme after aging treatment without micron-sized coarse second phase organization, and greatly improves mechanical properties, and meets new aluminum alloys of consumer electronic products and other high-end manufacturing harsh requirements.

[0021] Compared with the general Al-Zn-Mg-Cu alloy, due to the presence of Cu in the Al-Zn-Mg-Cu alloy, the surface after anodic oxidation presents red and other mixed colors, which affects the surface quality, in order to overcome this problem, the application replaces Cu in the Al-Zn-Mg-Cu alloy by greatly increasing Zn-Mg in the Al-Zn-Mg-(Cu) alloy, which can also improve the mechanical properties and corrosion resistance of the alloy, and the residual Cu in the application is an unavoidable impurity brought in by the return material in the smelting process, which will not affect the performance of the Al-Zn-Mg-(Cu) alloy itself.

[0022] The new type of aluminum alloy almost completely does not have micron-sized second phases after solid solution-aging treatment, which greatly reduces the sites of pitting and cavitation, as shown in the accompanying drawings. Figure 1 The alloy is produced by using conventional aluminum alloy process, has low cost and can be mass produced, the ultimate product has a tensile strength UTS>700MPa, an elongation δ>8% and an exfoliation corrosion resistance of EA grade. While the strength of the alloy is significantly improved, the excellent surface finish, oxidation coloring effect and excellent corrosion resistance are also considered.

[0023] Compared with the existing Al-Zn-Mg-(Cu) aluminum alloy, the application has the following advantages:

[0024] (1) The copper-free ultra-high strength aluminum alloy prepared by the application has a tensile strength UTS>700MPa, which is more than twice the strength of 7003 and 7N01 aluminum alloys, reaching the level of stainless steel. Ultra-high strength is of great significance for the lightweight of consumer electronic products and high-end transportation equipment.

[0025] (2) The copper-free ultra-high strength aluminum alloy prepared by the application strictly controls the micro-alloying elements and impurity elements, so that there is almost no micron-sized second phase in the alloy, ensuring the smooth surface, excellent oxidation coloring effect and corrosion resistance, which is equivalent to the level of 7003 and 7N01 aluminum alloys.

[0026] (3) The application adopts conventional casting (die casting or semi-continuous casting) → homogenization → hot extrusion or hot rolling → solid solution treatment → aging treatment, which is suitable for mass industrial production and is conducive to low-cost production. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The micron-level second phase distribution of the copper-free ultra-high-strength Al-Zn-Mg-(Cu) series aluminum alloy,

[0028] Figure 2 The nanometer-level dispersed phase distribution of the copper-free ultra-high-strength Al-Zn-Mg-(Cu) series aluminum alloy,

[0029] Figure 3 The nanometer-level precipitated phase distribution of the copper-free ultra-high-strength Al-Zn-Mg-(Cu) series aluminum alloy. DETAILED DESCRIPTION

[0030] In order to more clearly show the technical solutions and advantages of the new alloy of the present application, the present application will be further described in detail below in combination with embodiments.

[0031] Embodiment 1: The present embodiment provides a copper-free ultra-high-strength aluminum alloy and a preparation method thereof. The invented Al-Zn-Mg-(Cu) series aluminum alloy has the following components (wt%): Zn is 10.04%, Mg is 2.47%, Zr is 0.09%, Cr is 0.10%, Ti is 0.064%, Cu is 0.06%, Fe is 0.01%, Si is 0.017%, and the balance is Al.

[0032] 1) Using high-purity aluminum, industrial pure zinc, industrial pure magnesium, aluminum-chromium intermediate alloy, aluminum-zirconium intermediate alloy, and aluminum-titanium intermediate alloy as raw materials: the purity of the high-purity aluminum is ≥99.95wt%, the purity of the industrial pure zinc is ≥99.99wt%, the purity of the industrial pure magnesium is ≥99.99wt%, the chromium content in the aluminum-chromium intermediate alloy is ≥5wt%, the zirconium content in the aluminum-zirconium intermediate alloy is ≥5wt%, and the titanium content in the aluminum-titanium intermediate alloy is ≥10wt%;

[0033] 2) The alloy raw materials are weighed according to the alloy components, and after melting and melt purification, mold casting is performed, the melting temperature is controlled at 711-742℃, and N2 refining is used for melt purification;

[0034] 3) The cast ingot obtained in step 2) is subjected to homogenization treatment: first heated to 400℃, held for 23h, then heated to 470℃, held for 24h, and then taken out of the furnace and air-cooled to room temperature;

[0035] 4) The cast ingot after homogenization treatment in step 3) is subjected to hot extrusion: during extrusion, the aluminum alloy temperature is 395-415℃, the heating time is 2h; the temperature of the extrusion cylinder, die, and pad is 415-425℃, the heating time is 12h, and the extrusion ratio is 9;

[0036] 5) The billet after hot extrusion in step 4) is subjected to three-stage solid solution treatment: first, heating to 450℃, holding for 1h; then, heating to 470℃, holding for 1h; finally, heating to 480℃, holding for 1.5h, and then quenching in room temperature water;

[0037] 6) The billet after solid solution treatment in step 5) is subjected to aging treatment: heating the billet to 120℃, holding for 24h, to obtain the final aluminum material.

[0038] The microstructure characteristics of the final aluminum material are as follows: smooth surface, volume fraction of micron-sized second phase less than 0.001%; grain size 6.9±10.0μm; Al3Zr and Al 18 (Cr,Ti)2Mg3 nanoscale dispersed phase with size range of 20-300nm; and η' and GP zone nanoscale precipitates with volume fraction of about 8.8% and size range of 2-10nm in the matrix.

[0039] The final properties of the final aluminum material are: tensile strength UTS=765±3MPa, yield strength σ 0.2 =745±3MPa, elongation at break δ=8.4±0.9%, and exfoliation corrosion resistance rating EA.

[0040] Embodiment 2: The embodiment provides a copper-free ultra-high strength aluminum alloy and a preparation method thereof. The Al-Zn-Mg-(Cu) aluminum alloy has the following components (wt%): Zn 9.45%, Mg 2.76%, Zr 0.12%, Cr 0.002%, Ti 0.055%, Cu 0.01%, Fe 0.01%, Si 0.014%, and the balance being Al.

[0041] 1) Using high-purity aluminum, industrial pure zinc, industrial pure magnesium, aluminum-chromium intermediate alloy, aluminum-zirconium intermediate alloy, and aluminum-titanium intermediate alloy as raw materials: the purity of the high-purity aluminum is ≥99.95wt%, the purity of the industrial pure zinc is ≥99.99wt%, the purity of the industrial pure magnesium is ≥99.99wt%, the chromium content in the aluminum-chromium intermediate alloy is ≥5wt%, the zirconium content in the aluminum-zirconium intermediate alloy is ≥5wt%, and the titanium content in the aluminum-titanium intermediate alloy is ≥10wt%;

[0042] 2) The alloy raw materials are weighed according to the alloy components, and after melting and melt purification, the ingot is cast, the melting temperature is controlled at 708-738℃, and the melt purification is performed by N2 refining;

[0043] 3) The ingot obtained in step 2) is subjected to homogenization treatment: first, heating to 400℃, holding for 22h, then heating to 472℃, holding for 24h, and then air cooling to room temperature after discharging;

[0044] 4) homogenizing the ingot after step 3) : during the extrusion, the temperature of the aluminum alloy is 405-420℃, and the heating time is 2h; the temperature of the extrusion cylinder, die and pad is 415-430℃, and the heating time is 12h, and the extrusion ratio is 9;

[0045] 5) solid solution treatment of the billet after step 4) : first, the temperature is raised to 450℃, and the holding time is 1h; then, the temperature is raised to 470℃, and the holding time is 1h; finally, the temperature is raised to 480℃, and the holding time is 1.5h, and then the billet is quenched in room temperature water;

[0046] 6) aging treatment of the billet after step 5) : the temperature of the billet is raised to 125℃, and the holding time is 23h, and then the final aluminum material is obtained.

[0047] The microstructure characteristics of the final aluminum material are as follows: the surface is smooth, the volume fraction of micron-sized second phase is less than 0.001%, the grain size is 6.8±9.3μm, there is Al3(Zr,Ti) nanoscale dispersion phase in the alloy, the size range is 20-50nm, and there are also η' and GP zone nanoscale precipitates in the matrix, the size range is 2-10nm.

[0048] The final properties of the final aluminum material are as follows: the tensile strength UTS = 749±10MPa, the yield strength σ 0.2 = 747±12MPa, the elongation δ = 8.0±0.4%, and the corrosion resistance is EA grade.

[0049] Example 3: The present embodiment provides a copper-free ultra-high strength aluminum alloy and a preparation method thereof. The composition of the Al-Zn-Mg-(Cu) aluminum alloy is as follows (wt%): Zn is 10.90%, Mg is 2.42%, Zr is 0.12%, Cr is 0.061%, Ti is 0.053%, Cu is 0.04%, Fe is 0.01%, Si is 0.011%, and the balance is Al.

[0050] 1) high-purity aluminum, industrial pure zinc, industrial pure magnesium, aluminum-chromium intermediate alloy, aluminum-zirconium intermediate alloy, and aluminum-titanium intermediate alloy are used as raw materials: the purity of high-purity aluminum is ≥99.95wt%, the purity of industrial pure zinc is ≥99.99wt%, the purity of industrial pure magnesium is ≥99.99wt%, the chromium content in the aluminum-chromium intermediate alloy is ≥5wt%, the zirconium content in the aluminum-zirconium intermediate alloy is ≥5wt%, and the titanium content in the aluminum-titanium intermediate alloy is ≥10wt%;

[0051] 2) the alloy raw materials are weighed according to the alloy composition, and after melting and melt purification, semi-continuous casting is carried out, and the melting temperature is controlled at 704-740℃;

[0052] 3) homogenization treatment of the ingot obtained in step 2): first heating to 410°C, holding for 20h, then heating to 473°C, holding for 26h, and then air cooling to room temperature;

[0053] 4) hot rolling treatment of the ingot after the homogenization treatment in step 3): the temperature of the aluminum alloy during hot rolling is 380-410°C, and the deformation amount is 90%;

[0054] 5) three-stage solid solution treatment of the billet after the hot extrusion treatment in step 4): first heating to 440°C, holding for 1h, then heating to 466°C, holding for 1h, and finally heating to 478°C, holding for 1.5h, and then quenching in room temperature water;

[0055] 6) aging treatment of the billet after the solid solution treatment in step 5): heating the billet to 120°C, holding for 24h, and obtaining the final aluminum material.

[0056] The microstructure characteristics of the final aluminum material are: smooth surface, volume fraction of micron-sized second phase less than 0.001%, grain size 8.5±6.6μm, and Al3Zr and Al 18 (Cr,Ti)2Mg3 nanoscale dispersed phase with size range of 20-300nm, and η' and GP zone nanoscale precipitates with size range of 2-10nm with volume fraction of 8.9% in the matrix.

[0057] The final properties of the final aluminum material are: tensile strength UTS=708±7MPa, yield strength σ 0.2 =686±10MPa, elongation δ=8.7±0.1%, and exfoliation corrosion resistance EA level.

Claims

1. A copper-free ultra-high strength aluminum alloy, characterized by comprising, in mass %, wt% of alloying elements: Zn 8.00%~12.00%, Mg 2.00%~3.00%, Zr 0.05%~0.15%, Cr <0.15%, Ti <0.10%, Cu <0.15%, total of Fe, Si impurities <0.05%, balance Al; The copper-free ultra-high-strength aluminum alloy is prepared by die casting or semi-continuous casting, homogenization, hot extrusion or hot rolling, solid solution treatment and aging treatment. The specific steps are as follows: 1) using high-purity aluminum, industrial pure zinc, industrial pure magnesium, aluminum-chromium intermediate alloy, aluminum-zirconium intermediate alloy and aluminum-titanium intermediate alloy as raw materials, wherein the purity of high-purity aluminum is ≥99.95wt%, the purity of industrial pure zinc is ≥99.99wt%, the purity of industrial pure magnesium is ≥99.99wt%, the chromium content in the aluminum-chromium intermediate alloy is ≥5wt%, the zirconium content in the aluminum-zirconium intermediate alloy is ≥5wt%, and the titanium content in the aluminum-titanium intermediate alloy is ≥10wt%; 2) weighing the alloy raw materials according to the alloy composition, after melting and melt purification, die casting or semi-continuous casting is carried out, and the melting temperature is controlled at 700~800℃; 3) homogenizing the ingot obtained in step 2): first heating to 380~420℃, holding for 10~30h, then heating to 460~475℃, holding for 10~30h, and then air cooling to room temperature after discharging; 4) hot extrusion or hot rolling of the ingot after homogenization in step 3): the heating temperature of the aluminum alloy ingot is 380~420℃, and the heating time is 2~4h; the extrusion ratio is 7~50 during extrusion, and the total deformation of hot rolling is 50%~90%; 5) three-stage solid solution treatment of the billet after hot working in step 4): first heating to 430~450℃, holding for 1h; then heating to 465~475℃, holding for 1h; finally heating to 475~485℃, holding for 1.5h, and then quenching in room temperature water; 6) single-stage aging treatment of the billet after solid solution treatment in step 5): heating the billet to 110~130℃, holding for 15~30h, and obtaining the final aluminum material; 2. The copper-free ultra-high strength aluminum alloy of claim 1, wherein, The copper-free ultra-high-strength aluminum alloy has a tensile strength UTS>700MPa, an elongation δ>8% after fracture, and an EA-grade exfoliation corrosion resistance.

3. The process for preparing a copper-free ultra-high strength aluminum alloy according to claim 1 or 2, characterized in that Preferably, the wt% of alloying elements are as follows: Zn 9.00%~11.00%, Mg 2.40%~2.80%, Zr 0.08%~0.13%, Cr <0.10%, Ti <0.07%, Cu <0.10%, total of Fe, Si impurities <0.05%, balance Al. The specific steps are as follows: 1) using high-purity aluminum, industrial pure zinc, industrial pure magnesium, aluminum-chromium intermediate alloy, aluminum-zirconium intermediate alloy and aluminum-titanium intermediate alloy as raw materials, wherein the purity of high-purity aluminum is ≥99.95wt%, the purity of industrial pure zinc is ≥99.99wt%, the purity of industrial pure magnesium is ≥99.99wt%, the chromium content in the aluminum-chromium intermediate alloy is ≥5wt%, the zirconium content in the aluminum-zirconium intermediate alloy is ≥5wt%, and the titanium content in the aluminum-titanium intermediate alloy is ≥10wt%; 2) Weigh the alloy raw materials according to the alloy composition, melt, purify the melt, and then conduct mold casting or semi-continuous casting, with the melting temperature controlled at 700-800℃; 3) Homogenize the ingot obtained in step 2): first heat to 380-420℃, keep for 10-30h, then heat to 460-475℃, keep for 10-30h, and then air cool to room temperature after discharging; 4) Hot extrusion or hot rolling of the ingot after homogenization in step 3): the heating temperature of the aluminum alloy ingot is 380-420℃, and the heating time is 2-4h; the extrusion ratio is 7-50 during extrusion, and the total deformation of hot rolling is 50%-90%; 5) Three-stage solid solution treatment of the billet after hot working in step 4): first heat to 430-450℃, keep for 1h; then heat to 465-475℃, keep for 1h; finally heat to 475-485℃, keep for 1.5h, and then quench in room temperature water; 6) Single-stage aging treatment of the billet after solid solution treatment in step 5): heat the billet to 110-130℃, keep for 15-30h, and obtain the final aluminum material.

4. The process for making a copper-free ultra-high strength aluminum alloy of claim 3, wherein, The microstructure of the final aluminum material is characterized by a smooth surface after polishing, no defects, black spots and high and low undulations; the volume fraction of micron-sized second phase is less than 0.001%; the grain size is 6-15μm; there is a nanometer-sized dispersed phase of Zr-rich elements in the alloy, with a size range of 20-300nm; and there are η' and GP zone nanometer-sized precipitates in the matrix, with a volume fraction of more than 8% and a size range of 2-10nm.

5. The process for making a copper-free ultra-high strength aluminum alloy of claim 4, wherein, The final aluminum material has an alloy tensile strength UTS>700MPa, an elongation after fracture δ>8%, and an EA level of exfoliation corrosion resistance.

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