Ultrahigh-strength Al-Zn-Mg-Cu series aluminum alloy, preparation method thereof and aluminum alloy structural member

Abstract

The invention provides an ultrahigh-strength Al-Zn-Mg-Cu series aluminum alloy, a preparation method of the ultrahigh-strength Al-Zn-Mg-Cu series aluminum alloy and an aluminum alloy structural part. The ultrahigh-strength Al-Zn-Mg-Cu series aluminum alloy is prepared from the following components in percentage by mass: 7 to 12 weight percent of Zn, 1 to 3.5 weight percent of Mg, 0.5 to 2.5 weight percent of Cu, 0.001 to 0.2 weight percent of Si, 0 to 0.4 weight percent of Fe, 0 to 0.6 weight percent of Mn, 0 to 0.2 weight percent of Ti, 0 to 0.3 weight percent of Cr, 0 to 0.5 weight percent of Zr, 0 to 0.2 weight percent of V, 0 to 0.1 weight percent of Be, 0 to 0.5 weight percent of RE, 0 to 0.5 weight percent of Ag, 0 to 0.1 weight percent of Sr, 0 to 0.2 weight percent of B, 0 to 0.1 weight percent of Sn, Al and inevitable impurities.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy technology, and in particular to an ultra-high strength Al-Zn-Mg-Cu aluminum alloy, a method for preparing the ultra-high strength Al-Zn-Mg-Cu aluminum alloy, and aluminum alloy structural components. Background Technology

[0002] Ultra-high strength Al-Zn-Mg-Cu aluminum alloys are widely used in transportation, aerospace, military equipment and weaponry, sporting goods and high-performance consumer products, molds, fixtures and mechanical equipment due to their excellent comprehensive properties. However, the high Zn content in ultra-high strength Al-Zn-Mg-Cu aluminum alloys can lead to micro-cracks during the casting process. Furthermore, Al-Zn-Mg-Cu aluminum alloys have poor casting properties, generally requiring deformation processing to produce simple structural parts, and cannot be used to produce complex structures, severely limiting their applications. Summary of the Invention

[0003] To address the aforementioned deficiencies in the prior art, this invention provides an ultra-high strength Al-Zn-Mg-Cu aluminum alloy, aiming to reduce microcracks in the ultra-high strength Al-Zn-Mg-Cu aluminum alloy.

[0004] This invention provides an ultra-high strength Al-Zn-Mg-Cu aluminum alloy containing 7-12% Zn, 1-3.5% Mg, 0.5-2.5% Cu, 0.001-0.2% Si, 0-0.4% Fe, 0-0.6% Mn, 0-0.2% Ti, 0-0.3% Cr, 0-0.5% Zr, 0-0.2% V, 0-0.1% Be, 0-0.5% RE, 0-0.5% Ag, 0-0.1% Sr, 0-0.2% B, 0-0.1% Sn, Al, and unavoidable impurities.

[0005] Furthermore, the ultra-high strength Al-Zn-Mg-Cu aluminum alloy contains 7-12% Zn, 1-3.5% Mg, 0.5-2.5% Cu, 0.001-0.2% Si, 0.001-0.4% Fe, 0.001-0.6% Mn, 0.001-0.2% Ti, and 0.001% Mn. -0.3% Cr, 0.001-0.5% Zr, 0.001-0.2% V, 0.001-0.1% Be, 0.001-0.5% RE, 0.001-0.5% Ag, 0.001-0.6% Sr, 0.001-0.2% B, and 0.001-0.1% Sn.

[0006] Furthermore, at least one of the following conditions must be met: The mass ratio of Zn to Mg is greater than 2; The sum of the mass percentages of Si and Fe is less than 0.5%; The sum of the mass percentages of V and Ti is less than 0.4%; The atomic percentages of Zr and RE are 1-1.2:1.

[0007] Furthermore, the ultra-high strength Al-Zn-Mg-Cu aluminum alloy also contains at least one of In, Nb, Bi, Ge, Mo, Ni, Te, Co, Sb, Cd, and Ca, with the following mass percentage content: In 0-0.2%, Nb 0-0.5%, Bi 0-0.2%, Ge 0-0.5%, Mo 0-0.5%, Ni 0-0.5%, Te 0-0.5%, Co 0-0.5%, Sb 0-0.2%, Cd 0-0.3%, and Ca 0-0.05%.

[0008] This application also provides a method for preparing ultra-high strength Al-Zn-Mg-Cu aluminum alloy, comprising the following steps: The Al source is subjected to a first heating treatment to obtain molten aluminum. Add Zn source, Mg source, Cu source, Si source, Fe source, Mn source, Ti source, Cr source, Zr source, V source, Be source, RE source, Ag source, B source, Sn source, and Sr source to the aluminum liquid, and perform a second heat treatment to obtain an alloy liquid; The alloy liquid is refined, slag removed, and formed to obtain an ultra-high strength Al-Zn-Mg-Cu aluminum alloy. This ultra-high strength Al-Zn-Mg-Cu aluminum alloy contains 7-12% Zn, 1-3.5% Mg, 0.5-2.5% Cu, 0.001-0.2% Si, 0-0.4% Fe, 0-0.6% Mn, and [other components are missing from the original text]. The content is 0-0.2% Ti, 0-0.3% Cr, 0-0.5% Zr, 0-0.2% V, 0-0.1% Be, 0-0.5% RE, 0-0.5% Ag, 0-0.1% Sr, 0-0.2% B, 0-0.1% Sn, and Al and unavoidable impurities.

[0009] Furthermore, the molding process includes the following steps: The molten alloy is pushed into a mold and subjected to low-pressure filling casting. Once the molten alloy enters the semi-solid solidification zone, it forms a semi-solid aluminum alloy part. The semi-solid aluminum alloy part is then subjected to in-situ first-stage forging in the mold. The deformation of the semi-solid aluminum alloy part during the in-situ first-stage forging process is 10-70%.

[0010] Furthermore, the molding process also includes the following steps: After in-situ primary forging, in-situ secondary forging deformation is performed to obtain aluminum alloy parts.

[0011] Furthermore, the molding process also includes the following steps: Ultra-high strength Al-Zn-Mg-Cu aluminum alloys are obtained by heat treatment of aluminum alloy parts after in-situ primary forging or in-situ secondary forging deformation.

[0012] Furthermore, the heat treatment includes aging treatment, wherein the aging treatment is performed at a temperature of 100-130°C for a time of 20-50 hours; or The heat treatment includes solution treatment and aging treatment. In the solution treatment, the temperature is 440-475°C and the time is 1-20 hours. In the aging treatment, the temperature is 100-130°C and the time is 18-40 hours. The heat treatment is a bipolar aging process. The first stage of aging is performed at a temperature of 100-120°C for 2-20 hours, and the second stage of aging is performed at a temperature of 150-180°C for 2-20 hours.

[0013] The present invention also provides an aluminum alloy structural component, wherein at least a portion of the material of the aluminum alloy structural component is the above-mentioned ultra-high strength Al-Zn-Mg-Cu series aluminum alloy or the ultra-high strength Al-Zn-Mg-Cu series aluminum alloy prepared by the preparation method described above.

[0014] In the technical solution of this invention, the ultra-high strength Al-Zn-Mg-Cu aluminum alloy contains 7-12% Zn, 1-3.5% Mg, 0.5-2.5% Cu, 0.001-0.2% Si, 0-0.4% Fe, 0-0.6% Mn, 0-0.2% Ti, and [other components] by mass percentage. The alloy contains 0-0.3% Cr, 0-0.5% Zr, 0-0.2% V, 0-0.1% Be, 0-0.5% RE, 0-0.5% Ag, 0-0.1% Sr, 0-0.2% B, 0-0.1% Sn, and Al, as well as unavoidable impurities. The combined addition of Zn, Mg, Cu, Si, Fe, Mn, Ti, Cr, Zr, V, Be, RE, Ag, Sr, B, and Sn within the above content ranges interacts and influences each other, ensuring excellent mechanical properties while maintaining good formability in the ultra-high strength Al-Zn-Mg-Cu aluminum alloy. Detailed Implementation

[0015] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0016] One embodiment of the present invention provides an ultra-high strength Al-Zn-Mg-Cu aluminum alloy, which contains 7-12% Zn, 1-3.5% Mg, 0.5-2.5% Cu, 0.001-0.2% Si, 0-0.4% Fe, 0-0.6% Mn, 0-0.2% Ti, and [other components] by mass percentage. The content of Cr is 0-0.3%, Zr is 0-0.5%, V is 0-0.2%, Be is 0-0.1%, RE is 0-0.5%, Ag is 0-0.5%, Sr is 0-0.1%, B is 0-0.2%, Sn is 0-0.1%, and Al and unavoidable impurities.

[0017] The specific percentage of Zn content by mass can be 7%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9%, 8%, 8.1%, 8.2%, 8.3%, 8.4%, 8.5%, 8.6%, 8.7%, 8.8%, 8.9%, 9%, 9.1%, 9.2%, 9.3%, 9.4%, 9.5%, 9.6%, 9.7%, 9.8%, 9.9%, 10%, 10.1%, 10.2%, 10.3%, 10.4%, 10.5%, 10.6%, 10.7%, 10.8%, 10.9%, 11%, 11.1%, 11.2%, 11.3%, 11.4%, 11.5%, 11.6%, 11.7%, 11.8%, 11.9%, or 12%.

[0018] The specific percentage content of Mg by mass can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, or 3.5%.

[0019] The specific percentage content of Cu by mass can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, or 2.5%.

[0020] The specific percentage content of Si by mass can be 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, or 0.2%.

[0021] The specific percentage content of Fe by mass can be 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, or 0.4%.

[0022] The specific percentage content of Mn by mass can be 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, or 0.6%.

[0023] The specific percentage content of Ti by mass can be 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, or 0.2%.

[0024] The specific percentage content of Cr by mass can be 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, or 0.3%.

[0025] The specific percentage content of Zr by mass can be 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%.

[0026] The specific percentage content of V by mass can be 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, or 0.2%.

[0027] The specific percentage content of Be by mass can be 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%.

[0028] The specific percentage content of RE by mass can be 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%.

[0029] The specific percentage content of Ag by mass can be 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%.

[0030] The specific percentage content of Sr by mass can be 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%.

[0031] The specific percentage content of B by mass can be 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, or 0.2%.

[0032] The specific percentage content of Sn by mass can be 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%.

[0033] In one embodiment, the ultra-high strength Al-Zn-Mg-Cu aluminum alloy contains 7-12% Zn, 1-3.5% Mg, 0.5-2.5% Cu, 0.001-0.2% Si, 0.001-0.4% Fe, 0.001-0.6% Mn, 0.001-0.2% Ti, and 0.00% Fe. 1-0.3% Cr, 0.001-0.5% Zr, 0.001-0.2% V, 0.001-0.1% Be, 0.001-0.5% RE, 0.001-0.5% Ag, 0.001-0.6% Sr, 0.001-0.2% B, and 0.001-0.1% Sn.

[0034] The mass ratio of Zn to Mg is greater than 2, but not greater than 12, specifically 2.1, 2.2, 2.3, 2.4, 2.5, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, to facilitate the formation of the η′(MgZn2) phase and the T′(AlMgZnCu) phase, and to prevent the coarsening of the η(MgZn2) phase to improve the strength of the aluminum alloy.

[0035] The sum of the mass percentages of Si and Fe is less than 0.5%, specifically less than 0.45%, 0.4%, 0.35%, 0.3%, 0.25%, 0.2%, 0.15%, 0.1%, 0.05%, 0.01%, and 0.002%. In the casting-forging integrated process, the alloy solution needs to be slowly and under high pressure to enter the mold cavity; fluidity of the alloy solution is not required. Therefore, the sum of the mass percentages of Si and Fe can be set to less than 0.5% to reduce the adverse effects of Si and Fe on the elongation of the aluminum alloy, thereby reducing the likelihood of cracks during deformation and resulting in thin-walled and medium-thick aluminum alloy structural parts.

[0036] The sum of the mass percentages of V and Ti is less than 0.4%, such as less than 0.3% or less than 0.2%, specifically less than 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, or 0.39%. When V and Ti are combined, their individual contents can be reduced; however, if the combined content exceeds 0.4%, a coarse second phase will form, leading to a decrease in the alloy's mechanical properties.

[0037] The sum of the mass percentages of RE and Zr is less than 1%, such as 0.95%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, 0.05%, 0.01%, or 0.002%. When RE and Zr are used together, they can effectively refine the grains, second phase, and precipitated phases to improve the strength and elongation of aluminum alloys; the core-shell structure formed by the two, such as the Li2 second phase, can significantly improve the thermal stability of aluminum alloys.

[0038] The atomic percentage of Zr and RE is 1-1.2:1, specifically 1:1, 1.1:1, or 1.2:1. At this atomic percentage, it is beneficial to form the Al3(ZrRE) phase to refine the grains, the second phase, and the precipitated phases, increasing the recrystallization temperature and further improving the tensile strength and elongation of the aluminum alloy. It also ensures sufficient Al3(ZrRE) phase to promote nucleation and increase the solid fraction during subsequent in-situ primary and secondary forging processes. Combined with the cooling steps, this increases the deformation amount in the in-situ primary and secondary forging processes, further enhancing the strength and elongation of the aluminum alloy.

[0039] The sum of the mass percentages of Mn, Cr, Zr, and RE is less than 1.5%, such as less than 1% or less than 0.5%, specifically less than 1.4%, 1.3%, 1.2%, 1.1%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, or 0.1%. Mn, Cr, Zr, and RE react with each other to form Al. 12 The (Mn,Cr) and Al3(RE,Zr) second phases can significantly improve the strength of aluminum alloys.

[0040] In the technical solution of this invention, the ultra-high strength Al-Zn-Mg-Cu aluminum alloy contains 7-12% Zn by mass, 1-3.5% Mg by mass, 0.5-2.5% Cu by mass, 0.001-0.2% Si by mass, 0-0.4% Fe by mass, 0-0.6% Mn by mass, 0-0.2% Ti by mass, and [other components not specified in the original text]. The alloy contains 0-0.3% Cr, 0-0.5% Zr, 0-0.2% V, 0-0.1% Be, 0-0.5% RE, 0-0.5% Ag, 0-0.1% Sr, 0-0.2% B, 0-0.1% Sn, and Al, as well as unavoidable impurities. The combined addition of Zn, Mg, Cu, Si, Fe, Mn, Ti, Cr, Zr, V, Be, RE, Ag, Sr, B, and Sn within the above content range interacts and influences each other, ensuring that the ultra-high strength Al-Zn-Mg-Cu aluminum alloy possesses excellent mechanical properties (such as strength and elongation) while maintaining good formability. Specifically: By setting the Zn mass percentage content to 7-12%, the Mg mass percentage content to 1-3.5%, and the Cu mass percentage content to 0.5-2.5%, Mg can react with Zn to form η′(MgZn2) phase, T'(AlMgZnCu) phase, and S'(Al2CuMg) phase, thereby improving the strength of the aluminum alloy and shortening the peak aging time of the alloy. Mg, Zn, Al, Fe, Cu, Mn, and Si can also react with each other to form AlFeMgSi, AlCuMgSi, AlFeSiCu, Al2CuZn, and Al... 12 CuMn2, Mg2Si, Mg2SiZn, τ (Cu2Mn3Al 20Cu can enhance the tensile strength of aluminum alloys by forming second phases such as MgZn2, T'(AlMgZnCu), S'(Al2CuMg), and β''(Mg2Si). Setting the Si mass percentage content to 0.001-0.2% improves the processing fluidity of aluminum alloys. Setting the Fe mass percentage content to 0-0.4% improves demolding performance and allows Fe to react with Al, Si, Cu, Ni, Mg, and Mn to form second phases such as Al3Fe, AlFeSi, AlFeSiCu, AlFeMgSiNi, AlFeSiNi, FeNiAl9, AlFeMgSi, Al6(Fe,Mn), and α-Al(FeMn)Si, thus enhancing the tensile strength of aluminum alloys. Setting the Mn mass percentage content to 0-0.6% allows Mn to react with Al, Fe, Si, and Cu to form MnAl2, MnAl6, and Al2Si phases, further improving the strength of aluminum alloys. 12 CuMn2, Al3(Fe,Mn), Al6(Fe,Mn), Al 12 (Fe,Mn)3Si, α-Al(FeMn)Si, τ(Cu2Mn3Al 20 The formation of α-Al(FeMn)Si, a second phase, enhances the tensile strength of aluminum alloys. It inhibits the coarsening of grain boundary phases η(MgZn2), T(AlMgZnCu), S(Al2CuMg), and β(Mg2Si), and reduces the content of Fe impurities. Mn significantly refines grain size through lattice distortion caused by solid solution in the matrix and the dispersed MnAl6 particles produced by its reaction with Al, hindering dislocation and grain boundary migration, thereby increasing the recrystallization temperature and effectively preventing grain growth to improve elongation. Furthermore, the addition of manganese and chromium significantly improves the alloy's resistance to stress corrosion. Setting the Ti mass percentage content to 0-0.2% allows the TiAl3 phase, formed by the reaction of Ti with Al, to act as a non-spontaneous nucleus during crystallization, refining grains, second phases, and precipitates to improve the tensile strength and elongation of aluminum alloys and reduce ingot cracking tendency. Mg also disrupts the original oxide film between Ti and the aluminum matrix, promoting the formation of Al from Ti and the aluminum alloy. 18The Ti₂Mg₃ ternary phase is used to improve the strength of aluminum alloys. Furthermore, Ti can increase the recrystallization temperature of the alloy. Setting the Cr mass percentage content to 0-0.3% allows Cr to transform the acicular β-Fe phase into the α-Fe phase, improving the Fe morphology and eliminating the harmful effects of Fe. Cr can also easily form dispersed phases with Fe, reducing the Fe content and mitigating its harmful effects. Cr can also inhibit the nucleation and growth process of recrystallization, thus improving the tensile strength and elongation of aluminum alloys. The various chromium-containing fine compounds formed by Cr in aluminum alloys can be further enhanced during the solid solution stage. Dissolving in the α phase, various Cr-containing phases, such as α-AlCrSi dispersed phase, are dispersed and precipitated during the natural aging stage. These Cr-containing phases can serve as nuclei for the heterogeneous nucleation of η′, T′, S′, and β" phases, accelerating their formation and thus improving the tensile strength of aluminum alloys. The addition of Cr can also generate dispersed particles, such as Al7Cr phase, during ingot homogenization annealing, hindering the migration of dislocations and grain boundaries, thereby increasing the recrystallization temperature, effectively preventing grain growth, and refining the grains. In addition, adding chromium can improve the stress corrosion resistance of the alloy. If manganese and chromium are added at the same time, the effect of reducing stress corrosion tendency is even better. Setting the mass percentage content of Zr to 0-0.5% can improve the tensile strength of aluminum alloys. Zr can also promote the precipitation of second phases such as η′(MgZn2), T′(AlMgZnCu), S'(Al2CuMg), β''(Mg2Si), Al2CuZn, and AlCuMgSi, thereby reducing the solid solubility of the above elements in the aluminum matrix. Zr can also refine the grains, second phases and precipitated phases, further improving the elongation of aluminum alloys. Trace amounts of Zr form L12-type Al3Zr dispersed phases coherent with the matrix, inhibiting the recrystallization of the alloy, thereby improving the mechanical properties and corrosion resistance of the alloy. However, Zr segregation leads to uneven distribution of Al3Zr dispersed phases in the alloy, and recrystallization is prone to occur in Zr-depleted areas. Adding trace amounts of Ti can alter the precipitation and function of the L12 type Al3Zr dispersed phase, allowing Ti to enter the L12 type Al3Zr dispersed phase and form an L12 type Al3(Zr,Ti) dispersed phase. Setting the mass percentage of V to 0-0.2% allows V to react with Al to form VAl. 11Refractory compounds such as vanadium (V) play a role in refining grains during the casting process. V can also refine the recrystallization structure and increase the recrystallization temperature, thereby improving the tensile strength and elongation of aluminum alloys. Setting the mass percentage content of vanadium (Be) to 0-0.1% allows Be to improve the tensile strength of aluminum alloys. It can also transform the plate-like β-intermediate phase into the relatively harmless Chinese character-shaped Be-Fe (Al8Fe2SiBe) phase and prevent the formation of acicular β-Fe phase, thus reducing or eliminating the adverse effects of Fe on the properties of aluminum alloys. Be can also promote the formation and precipitation of η′ (MgZn2) phase, T′ (AlMgZnCu), S' (Al2CuMg), β'' (Mg2Si), Mg2SiZn, and other phases, reducing the solid solubility of these elements in the aluminum matrix. Be can also form an active film on the surface of impurity element phases such as Fe, preventing the growth of impurity elements. Furthermore, Be can segregate at grain boundaries or adsorb at the solid-liquid interface, forming supercooling and increasing the chance of dendrite melting, thereby refining the grains. Setting the mass percentage content of vanadium (RE) to 0-0.5%... Rare earth elements (REs) can refine the alloy microstructure to improve the mechanical properties of aluminum alloys. They can also form rare earth active films on the Fe-containing surface or combine with Al, Fe, Ti, and other atoms to form rare earth compounds, effectively reducing the solid solution of harmful elements in the aluminum matrix. REs can also transform elongated β-Fe phases into spherical α-Fe phases and modify elemental Si. Furthermore, REs can promote the dispersion of phases such as η′(MgZn2), T′(AlMgZnCu), S′(Al2CuMg), β′′(Mg2Si), and Al3F. The precipitation of Mg2SiZn and other elements improves the tensile strength and elongation of aluminum alloys. Refined iron (RE) can also refine grains, second phases, and precipitated phases (e.g., it can refine η′(MgZn2) phase, T′(AlMgZnCu), S′(Al2CuMg), β′′(Mg2Si) phase), etc., further improving the tensile strength and elongation of aluminum alloys. Furthermore, the composite addition of trace amounts of Cr and RE to the alloy forms an L12-type (Al,Cr)3(Zr, Mg2Si) alloy with a small amount of Cr, coherent with the matrix. (RE) Fine dispersed phases can significantly inhibit alloy recrystallization, improve the alloy's strength and stress corrosion resistance; setting the Ag mass percentage content to 0-0.5% can accelerate the age hardening effect and improve the age hardening level of the alloy. Ag will form η′(Mg(ZnAg)2) phase, T′(AlMgZnCuAg), S'(Al2CuMgAg), β''(Mg2SiAg) and other phases in the alloy. The formation of these phases will inhibit the precipitation of coarse grain boundary Al2CuMg, Mg2Si, η(MgZn2), T(AlMgZnCu) phases, and change the age precipitation process of strengthening phases. Ag can also increase the stability temperature range of the GP zone, which can significantly improve plasticity and strength; setting the Sr mass percentage content to 0-0.5% can also improve the stability temperature range of the GP zone, significantly improving plasticity and strength.Sr (1%) has the functions of refining grains and inhibiting recrystallization growth, which can improve the strength and elongation of aluminum alloys. Sr can also hinder the diffusion of Fe atoms, resulting in compositional supercooling, which causes the morphology of the Al3Fe phase to change from needle-like to flower-like, thus eliminating the influence of Fe impurities on the alloy. Setting the mass percentage of boron (B) to 0-0.2% allows B to undergo borylation reactions with transition metal elements (including Fe) to generate compounds such as ferroboron compounds that can be separated from the molten aluminum alloy, thereby purifying the molten aluminum alloy. B is easily adsorbed on the surface of the iron-rich phase, inhibiting its growth and controlling its size. In addition to its physical properties, boron (B) can prevent the formation of iron-rich phases in molten aluminum alloys. It can also inhibit the segregation of Ti3Al, thus the combined use of Ti and B yields better results. B can also refine grains, second phases, and precipitates, thereby improving the elongation of aluminum alloys. Setting the mass percentage content of Sn to 0-0.1% allows Sn to refine grains, second phases, and precipitates, improving the tensile strength and elongation of aluminum alloys. Sn can also react with Mg to form the Mg2Sn phase, further enhancing the strength of aluminum alloys. Furthermore, the presence of Sn binds free vacancies after quenching, thus slowing the diffusion of other solid solution atoms and the growth of precipitates in the matrix. The fine, dispersed second phase particles also contribute to higher peak hardness.

[0041] In summary, the tensile strength of aluminum alloys can be significantly improved by increasing the content of Zn, Mg, Cu, Si, Fe, Ag, and Mn as described above, with η′(MgZn2) phase, T′(AlMgZnCu), and S'(Al2CuMg) being the main strengthening phases. The content of Si and Fe can improve the fluidity and mold release properties of aluminum alloys. The content of Mn, Ti, V, Cr, Sr, RE, B, Be, Sn, and Ag can refine the grains, second phases (especially η′(MgZn2) and T′(AlMgZnCu) phases), and precipitated phases, thereby improving the tensile strength and elongation of aluminum alloys. Zr, RE, and Be can also promote the precipitation of second phases (such as η′(MgZn2) phase, T′(AlMgZnCu), S'(Al2CuMg), Mg2SiZn, and β''(Mg2SiMg2Si) phase), further improving the tensile strength and elongation of aluminum alloys. This yields ultra-high strength Al-Zn-Mg-Cu aluminum alloys with excellent mechanical and formability properties.

[0042] The ultra-high strength Al-Zn-Mg-Cu aluminum alloy also contains 0-0.2% In by mass, specifically 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, or 0.2%. In can improve the mechanical properties of aluminum alloys. In can react with other elements to form second phases, thereby improving the mechanical properties of aluminum alloys. Specifically, In can react with Al and Cu to form second phases such as AlIn and CuIn. In addition, In can refine the grains, thereby improving the elongation of aluminum alloys.

[0043] The ultra-high strength Al-Zn-Mg-Cu aluminum alloy also contains 0-0.5% Nb by mass, specifically 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%. Nb can improve the mechanical properties of the aluminum alloy. Nb can react with other elements to form a second phase, thereby improving the mechanical properties of the aluminum alloy. Specifically, Nb can react with Ti and Al to form the TiAl-Nb phase. In addition, Nb can refine the grain size, thereby increasing the elongation of the aluminum alloy.

[0044] The ultra-high strength Al-Zn-Mg-Cu aluminum alloy also contains 0-0.2% Bi by mass, specifically 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, or 0.2%. Bi can improve the mechanical properties of aluminum alloys. Bi can react with other elements to form second phases, thereby improving the mechanical properties of aluminum alloys. Specifically, Bi can react with Mg and Cd to form second phases such as Mg3Bi2 and Mg3(BiCd)2.

[0045] The ultra-high strength Al-Zn-Mg-Cu aluminum alloy also contains 0-0.5% Ge by mass, specifically 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%. Ge can improve the mechanical properties of aluminum alloys. Ge can react with other elements to improve the mechanical properties of aluminum alloys. Specifically, Ge can react with Al and Si to form second phases such as Al9Ge7, Al6Ge5, Al5Ge2, Al3Ge4, and SiGe. Ge can also promote the precipitation of second phases such as η′(MgZn2) phase, T′(AlMgZnCu), S'(Al2CuMg), β''(Mg2Si), and Mg2SiZn, refining the precipitated phases and reducing the solid solubility of the above elements in the aluminum matrix. Ge can also replace some of the Si, Zn, Mg, and Cu atoms in the metastable precipitated phases. The precipitated X-Ge phase (X is Si, Zn, Mg, or Cu) provides nucleation sites for phases such as η'(MgZn2) phase, T'(AlMgZnCu), S'(Al2CuMg), and β''-Mg2Si, increasing their density and further improving the mechanical properties of aluminum alloys.

[0046] The ultra-high strength Al-Zn-Mg-Cu aluminum alloy also contains 0-0.5% Mo by mass, specifically 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%. Mo can improve the mechanical properties of aluminum alloys. Mo can react with other elements to improve the mechanical properties of aluminum alloys. Specifically, Mo can react with Al, Si, Fe, etc., to form second phases such as AlMo, AlSiMo, and AlSiFeMo, which are dispersed phases distributed at the grain boundaries of the aluminum matrix. In addition, Mo can refine the grains and improve the morphology of Fe-containing intermetallic compounds, further improving the mechanical properties of aluminum alloys.

[0047] The ultra-high strength Al-Zn-Mg-Cu aluminum alloy also contains 0-0.5% Ni by mass, specifically 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%. Ni can refine the grains, improve the tensile strength of the aluminum alloy, and promote the precipitation of the second phase, increasing the volume fraction and dispersion of the precipitated phase.

[0048] The ultra-high strength Al-Zn-Mg-Cu aluminum alloy also contains 0-0.5% Te by mass, specifically 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%. Te can improve the mechanical properties of aluminum alloys. Te can narrow the solidification temperature range of aluminum alloys, form fine petal-like rather than dendritic primary crystals, reduce or eliminate micro shrinkage porosity, thereby improving the mechanical properties of aluminum alloys.

[0049] The ultra-high strength Al-Zn-Mg-Cu aluminum alloy also contains 0-0.5% Co by mass, specifically 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%. Co can refine the grains to improve the mechanical properties of the aluminum alloy, and can also react with other elements to form a second phase, further improving the mechanical properties of the aluminum alloy. Specifically, Co can react with Al, Fe, Si, etc., to form Al 15 Secondary phases include (Fe,Co)3Si2 and Al3(Fe,Co). Furthermore, Co has a refining effect on the Al3Fe phase, transforming coarse needle-like and plate-like β-Al3Fe phases into small flower-like and fine strip-like α-Al3Fe phases. 15 The (Fe,Co)3Si2 phase can also promote α-Al 15 The precipitation of the (Fe,Co)3Si2 phase further improves the mechanical properties of aluminum alloys. The combined addition of Ni and Co can effectively modify Fe and transform free Fe into the second phase. The combined addition of Co, Ni and Be can rapidly reduce their solid solubility in the alloy and increase the volume fraction of the second phase, thereby improving the mechanical properties of aluminum alloys.

[0050] The ultra-high strength Al-Zn-Mg-Cu aluminum alloy also contains 0-0.2% Sb by mass, specifically 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, or 0.2%. Sb can refine grains, the second phase, and precipitated phases, thereby improving the tensile strength and elongation of the aluminum alloy. Sn can also improve the morphology of Si precipitation, further enhancing the mechanical properties of the aluminum alloy.

[0051] The ultra-high strength Al-Zn-Mg-Cu aluminum alloy also contains 0-0.3% Cd by mass, specifically 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, or 0.3%. Cd can refine α-Al, and Cd will form a large number of Cd-vacancy clusters, promoting and accelerating the precipitation of η′(MgZn2) phase, T′(AlMgZnCu), S'(Al2CuMg), β''(Mg2Si), Mg2SiZn and other phases, thereby reducing the impact of high Cu content on the elongation of the aluminum alloy.

[0052] The ultra-high strength Al-Zn-Mg-Cu aluminum alloy also contains 0-0.05% Ca by mass, specifically 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, or 0.05%. Ca can improve the β-Fe phase to reduce Fe toxicity, and can also react with Al, Cu, Zn, and Si to form second phases such as Al4Ca, Al2Ca3, AlCa2, AlCaCu, CaZn, CaAlZn, and Al2CaSi2, thereby improving the tensile strength of the aluminum alloy. Ca can also refine the eutectic structure, improve the β-Fe phase, and has a modifying effect on Al-Zn-Mg-Cu alloys, refining the Si phase. Sn can react with Al, Mg, Sc, etc., to form Al9Sn7, Al6Sn5, and Al5 Secondary phases such as Sn2, Al3Sn4, Mg2Sn, and Mg2ScSn enhance the tensile strength of aluminum alloys. Sn promotes the precipitation of secondary phases such as η′(MgZn2), T′(AlMgZnCu), S'(Al2CuMg), β''(Mg2Si), and Mg2SiZn, thereby reducing the solid solubility of these elements in the aluminum matrix. Ca and Sn can also significantly reduce the surface tension of molten aluminum alloys, minimizing or even eliminating the influence of surface tension on the oxide film, thus improving the fluidity of the aluminum alloy. The combination of Ca and RE phases can significantly refine the grains and secondary phases, thereby improving tensile strength, fluidity, and elongation.

[0053] This invention also provides a method for preparing ultra-high strength Al-Zn-Mg-Cu aluminum alloy, comprising the following steps: Aluminum liquid is obtained by heating an Al source at a temperature of 750-830°C; At a temperature of 720-780°C, Zn source, Mg source, Cu source, Si source, Fe source, Mn source, Ti source, Cr source, Zr source, V source, Be source, RE source, Ag source, B source, Sn source, and Sr source are added to the aluminum liquid to obtain an alloy liquid; The alloy liquid is refined, slag removed, and formed to obtain an ultra-high strength Al-Zn-Mg-Cu aluminum alloy. This ultra-high strength Al-Zn-Mg-Cu aluminum alloy contains 7-12% Zn, 1-3.5% Mg, 0.5-2.5% Cu, 0.001-0.2% Si, 0-0.4% Fe, 0-0.6% Mn, and [other components are missing from the original text]. The content is 0-0.2% Ti, 0-0.3% Cr, 0-0.5% Zr, 0-0.2% V, 0-0.1% Be, 0-0.5% RE, 0-0.5% Ag, 0-0.1% Sr, 0-0.2% B, 0-0.1% Sn, and Al and unavoidable impurities.

[0054] Zn source, Mg source, Cu source, Si source, Fe source, Mn source, Ti source, Cr source, Zr source, V source, Be source, RE source, Ag source, B source, Sn source, and Sr source can be added in the form of elements or alloys.

[0055] At least one of the following sources can be added to the molten aluminum: In, Nb, Bi, Ge, Mo, Ni, Te, Co, Sb, Cd, and Ca. These raw materials can also be added in elemental form or as intermediate alloys.

[0056] The degassing process involves adjusting the temperature of the molten alloy to 650-780℃ and introducing an inert gas such as argon into the molten alloy using a degassing machine. Specific degassing temperatures can be 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, or 780℃. The degassing time is 10-30 minutes, specifically 10 minutes, 15 minutes, 20 minutes, 25 minutes, or 30 minutes.

[0057] The refining process involves introducing inert gases such as argon into the molten alloy using a degasser. A refining agent can be added simultaneously. The vortex formed by the degasser's rotating disc in the molten alloy allows the refining agent to be evenly mixed into the alloy. The refining agent refines the alloy microstructure, thereby improving the tensile strength and elongation of the aluminum alloy. It has the advantages of good dispersibility and low cost. The refining time is 10-30 minutes, specifically 10, 15, 20, 25, or 30 minutes. The refining temperature is 650-780℃, specifically 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, or 780℃. The refining agent contains: 5-10 parts potassium fluoroaluminate, 6-20 parts AlTi5B1 metal powder, 8-25 parts potassium titanate whisker powder, 20-40 parts sodium chloride + potassium chloride, 5-10 parts potassium nitrate, 5-10 parts potassium carbonate, and 0.5-3 parts potassium silicate.

[0058] The parting surface of the mold can undergo surface treatment to form a boron carbide layer. This layer not only improves demolding performance but also enhances the mold's wear resistance and protects against corrosion from acids, alkalis, salts, and other chemicals, as well as thermal erosion of the aluminum alloy, thus extending the mold's service life. The thickness of the boron carbide layer can range from 1 to 10 mm, specifically 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, or 10 mm. The surface treatment can involve mixing a boron-containing gas (such as BCl3) with a carbon-containing gas (such as CH4) to obtain a mixed gas. This mixed gas is then introduced into the cavity, and through chemical vapor deposition (CVD), the boron-containing and carbon-containing gases react chemically and deposit onto the parting surface to form the boron carbide layer. The CVD temperature is 900-1200°C, the deposition pressure is 200-500 Pa, and the carrier gas flow rate is 100-200 sccm. The boron carbide layer can increase the hardness of mold steel to 3000-4000 Hv; the boron carbide layer can reduce the affinity of the mixed melt to the mold surface, improve the demolding performance of aluminum alloy, and greatly increase the elongation of aluminum alloy; the boron carbide layer can resist the corrosion of chemicals such as acids, alkalis, and salts, and can improve the corrosion resistance of aluminum alloy; the boron carbide layer can maintain good physical and chemical properties at high temperature, and can improve the thermal stability of aluminum alloy; the boron carbide layer has an extremely low coefficient of friction, which can improve the surface smoothness of aluminum alloy and significantly reduce the wear and energy consumption of aluminum alloy products caused by mechanical friction; the boron carbide layer also has high heat transfer properties. During the instant of aluminum alloy forming, the boron carbide layer can quickly conduct away heat, increasing the heat transfer rate of the mold by 2-4 times that of ordinary molds, allowing the aluminum alloy to cool down faster.

[0059] The forming process includes the following steps: Molten alloy is poured into a mold and subjected to low-pressure filling casting. Once the molten alloy enters the semi-solid solidification zone, semi-solid aluminum alloy parts are formed. These semi-solid aluminum alloy parts are then subjected to in-situ primary forging within the mold to obtain the final aluminum alloy parts. The deformation amount of the semi-solid aluminum alloy parts during the in-situ primary forging process is 10-70%. Further in-situ secondary forging deformation of the aluminum alloy parts after primary forging can be performed to obtain the final aluminum alloy parts. The deformation amount of the semi-solid aluminum alloy parts during the in-situ secondary forging process is 5-80%. Finally, the aluminum alloy parts after either primary or secondary forging can be heat-treated to obtain ultra-high strength Al-Zn-Mg-Cu aluminum alloys.

[0060] It is understandable that the above forming process steps can be selected according to needs, and this application does not impose any restrictions on this. For example, aluminum alloy parts can be obtained after only performing in-situ primary forging. The aluminum alloy parts after in-situ primary forging can also be heat-treated. Alternatively, in-situ primary forging and in-situ secondary forging deformation can be performed sequentially. Furthermore, heat treatment can be performed after in-situ primary forging and in-situ secondary forging deformation.

[0061] In low-pressure filling casting, the filling speed (i.e., the moving speed of the punch) is 0.1-1.2 m / s, the filling time (i.e., the time required for the molten alloy to completely fill the mold) is 2-20 s, the casting pressure is 0.1-40 MPa, the holding time is 2-10 s (i.e., the time to maintain the molten alloy under a certain pressure after it has completely filled the mold), the mold temperature is 180-300 ℃, and the alloy casting temperature (i.e., the temperature when the molten alloy is filled into the mold) is 650-720 ℃.

[0062] A filling speed of 0.1-1.2 m / s increases the fluidity of the molten alloy, facilitating its full filling of the cavity. At this speed, the pressure applied by the punch to the molten alloy is also relatively low (specific pressure approximately 50-200 MPa), preventing casting defects such as porosity, shrinkage cavities, and looseness in the aluminum alloy product. It also avoids splashing and turbulence caused by excessively fast filling speeds, which can lead to casting defects such as oxide inclusions and air entrapment. Specific filling speeds can be 0.1 m / s, 0.2 m / s, 0.3 m / s, 0.4 m / s, 0.5 m / s, 0.6 m / s, 0.7 m / s, 0.8 m / s, 0.9 m / s, 1 m / s, 1.05 m / s, 1.1 m / s, 1.15 m / s, or 1.2 m / s. Specific filling times can be 2 s, 5 s, 10 s, 15 s, or 20 s.

[0063] Under casting pressures ranging from 0.1 to 40 MPa, the molten alloy is relatively stable and can solidify in a directional sequence. The precipitated phases within the semi-solid aluminum alloy parts are perpendicular to the basal surface of the aluminum alloy matrix. When the molten alloy solidifies stably, there are fewer pores, looseness, and cracks in the semi-solid aluminum alloy parts. Specific casting pressures can be 0.1 MPa, 0.5 MPa, 1 MPa, 5 MPa, 10 MPa, 15 MPa, 20 MPa, 25 MPa, 30 MPa, 35 MPa, or 40 MPa.

[0064] Semi-solid aluminum alloy parts can be formed within a holding time of 2-10 seconds and a casting pressure of 0.1-40 MPa. Moreover, the solidification range of ultra-high strength Al-Zn-Mg-Cu aluminum alloys is very large, which easily leads to casting defects such as low density and a large number of inclusions, as well as hot and cold cracking problems. Within the low casting pressure range of 0.1-40 MPa, the above-mentioned casting defects can be solved, as well as the porosity problem of high pressure casting.

[0065] As the holding time and casting pressure increase, the casting structure inside the semi-solid aluminum alloy parts gradually becomes uniform and dense. If the holding time exceeds 10 seconds or the casting pressure is too high, the liquid phase inside the mold will completely solidify, and the semi-solid aluminum alloy parts cannot be formed. The holding time can be 2s, 3s, 4s, 5s, 6s, 7s, 8s, 9s, or 10s.

[0066] The low-pressure filling casting process of this invention requires lower casting and mold preheating temperatures, which not only reduces thermal shock corrosion to the mold but also saves energy. The mold temperature can specifically be 180°C, 200°C, or 250°C. The alloy casting temperature can specifically be 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, or 720°C.

[0067] In semi-solid aluminum alloy parts, the solid-liquid ratio, or solid phase fraction, is 20-90%, specifically 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90%. At this solid-liquid ratio, there are fewer casting defects in semi-solid aluminum alloy parts, and the precipitated phases within them solidify almost entirely vertically.

[0068] In the in-situ primary forging process, the forging temperature (i.e., the temperature of the semi-solid aluminum alloy parts in the mold) is 520-640℃, the forging specific pressure is 40-300MPa, the forging start time (i.e., the time interval between the formation of the semi-solid aluminum alloy parts and the in-situ primary forging process) is 2-20s, the holding time is 2-20s, and the deformation is 10-70%. After this in-situ primary forging process, the semi-solid aluminum alloy parts are transformed into solid parts.

[0069] Setting the forging temperature to 520-640℃ ensures the alloy remains in a semi-solid state. Specific forging temperatures can be 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, or 640℃. Specific forging pressures can be 40MPa, 50MPa, 60MPa, 70MPa, 80MPa, 90MPa, 100MPa, 120MPa, 140MPa, 160MPa, 180MPa, 200MPa, 220MPa, 240MPa, 260MPa, 280MPa, or 300MPa. The specific forging start time can be 2s, 3s, 4s, 5s, 6s, 7s, 8s, 9s, 10s, 11s, 12s, 13s, 14s, 15s, 16s, 17s, 18s, 19s, or 20s. The specific pressure holding time can be 2s, 3s, 4s, 5s, 6s, 7s, 8s, 9s, 10s, 11s, 12s, 13s, 14s, 15s, 16s, 17s, 18s, 19s, or 20s.

[0070] With a deformation amount of 10-70%, semi-solid aluminum alloy parts can be transformed into solid aluminum alloy parts after in-situ primary forging. As the deformation amount increases, the volume fraction of Al2CuMg precipitates in the solid aluminum alloy parts gradually increases, while the volume fraction of Al2Cu phase gradually decreases, thereby improving the mechanical properties of the aluminum alloy (including tensile strength and elongation). The preferred deformation amount is 20-60%, with the precipitates being essentially perpendicular to the basal plane, significantly improving the alloy's mechanical properties (including tensile strength and elongation). Specific deformation amounts can be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, or 70%.

[0071] In this in-situ primary forging process, the semi-solid aluminum alloy parts are not cooled, removed from the mold, and then placed in the forging device for reheating to the forging temperature. Instead, the semi-solid aluminum alloy parts are directly subjected to in-situ primary forging in the original mold without the need for cooling and reheating. This allows the solid-liquid mixed phases present in the semi-solid aluminum alloy parts to deform and solidify uniformly in the in-situ primary forging process on the basis of low-pressure filling casting (without cooling to room temperature before reheating and forging, the deformation during cooling and heating is uncontrollable and it is difficult to maintain the semi-solid state). This further eliminates casting defects in the semi-solid aluminum alloy parts, significantly refines the coarse grains and the second-phase as-cast structure, refines the size of the precipitates, and introduces a large number of nano-sized precipitates inside the grains. The volume fraction of the precipitates gradually increases, thereby improving the mechanical properties of the alloy.

[0072] To improve the smooth transition between low-pressure filling casting and in-situ primary forging, a first cooling process is performed during low-pressure filling casting. This ensures that semi-solid aluminum alloy parts with a temperature of 520-640℃ are obtained immediately after pressure holding, allowing for faster entry into the in-situ primary forging process. Alternatively, if the first cooling process during low-pressure filling casting does not result in a semi-solid aluminum alloy part with a solid content of 20-90% after pressure holding (e.g., the solid content is below 20%), a semi-solid aluminum alloy part with a temperature of 520-640℃ (solid content of 20-90%) can be obtained by undergoing a forging start-up time. Alternatively, a second cooling process during the forging start-up time and in-situ primary forging can also achieve a semi-solid aluminum alloy part with a temperature of 520-640℃ (solid content of 20-90%). A circulating oil circuit, such as a 3D contour cooling circuit, can be configured for cooling and temperature control.

[0073] In low-pressure filling casting, the cooling rate for the first cooling process is 1-50℃ / s, specifically 1℃ / s, 5℃ / s, 10℃ / s, 15℃ / s, 20℃ / s, 25℃ / s, 30℃ / s, 35℃ / s, 40℃ / s, 45℃ / s, or 50℃ / s. In in-situ primary forging, the cooling rate for the second cooling process is 5-60℃ / s, specifically 5℃ / s, 10℃ / s, 15℃ / s, 20℃ / s, 25℃ / s, 30℃ / s, 35℃ / s, 40℃ / s, 45℃ / s, 50℃ / s, 55℃ / s, or 60℃ / s.

[0074] In the in-situ secondary forging deformation treatment, the forging temperature is 350-460℃, the forging pressure is 50-500MPa, the holding time is 0-10s, and the deformation is 10-70%.

[0075] The forging temperature can be 350℃, 400℃, 450℃, or 460℃. Temperatures below 350℃ can cause aluminum alloy parts to break easily, while temperatures above 460℃ can easily lead to complete recrystallization, resulting in excessively large grain size and precipitated phase size, which is also not conducive to the formation of twins and causes a reduction in mechanical properties.

[0076] The forging specific pressure can be 50 MPa, 60 MPa, 70 MPa, 80 MPa, 90 MPa, 100 MPa, 120 MPa, 140 MPa, 160 MPa, 180 MPa, 200 MPa, 220 MPa, 240 MPa, 260 MPa, 280 MPa, 300 MPa, 320 MPa, 340 MPa, 360 MPa, 380 MPa, 400 MPa, 420 MPa, 440 MPa, 460 MPa, 480 MPa, or 500 MPa. The forging specific pressure in the in-situ secondary forging deformation treatment is preferably greater than that in the in-situ primary forging treatment to further promote the refinement of the precipitated phase size. In one embodiment, the forging specific pressure of the in-situ secondary forging deformation treatment is 0.072-16 times that of the in-situ primary forging treatment, specifically 0.072 times, 0.1 times, 0.5 times, 1 time, 5 times, or 8 times. This first-stage in-situ forging treatment can effectively eliminate casting defects in semi-solid aluminum alloy parts and initially refine the grains and second-phase as-cast structure, resulting in a large number of nanoscale precipitates within the grains. The second-stage in-situ forging deformation treatment further refines these precipitates, thereby obtaining an aluminum alloy with excellent mechanical properties.

[0077] The holding time can be 0s, 1s, 2s, 3s, 4s, 5s, 6s, 7s, 8s, 9s, or 10s. For example, after in-situ primary forging, when the parameter requirements of in-situ secondary forging deformation are met, the pressure can be held for a certain period of time (e.g., 2s). For example, when the parameters reach the in-situ secondary forging deformation, the in-situ secondary forging deformation can be stopped immediately, and subsequent heat treatment can be carried out; this holding time can be 0s. For example, when the parameters reach the in-situ secondary forging deformation, the pressure can be held for 5s before subsequent heat treatment.

[0078] The deformation amount can be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, or 70%.

[0079] In in-situ primary forging and in-situ secondary forging deformation processes, when the deformation amount is large, Ag can be dissolved in the main strengthening phase to form more dispersed and finer precipitates (such as η′(Mg(ZnAg)2) phase, T′(AlMgZnCuAg), S'(Al2CuMgAg), β''(Mg2SiAg) phase, etc.), which can significantly improve the strength of aluminum alloys. This allows the Ag content of this application to reach 0.5%.

[0080] In the in-situ primary forging process, the molten aluminum alloy gradually transforms into a semi-solid state, and the nucleus content increases accordingly. A higher nucleus content results in a higher solid fraction. The Al3(RE,Zr) phase formed by Zr reacting with Al and RE is conducive to nucleus formation. In this application, the Zr and RE content can reach 0.5% to ensure sufficient Al3(RE,Zr) phase presence, thereby increasing the solid fraction. The relatively high cooling rates of the in-situ primary forging and secondary forging deformation processes prevent Al3(RE,Zr) phase coarsening, avoiding adverse effects on the strength and elongation of the aluminum alloy when the Zr and RE content is high. Moreover, the in-situ primary forging process and the in-situ secondary forging deformation process of this application are performed in "in-situ" (which can be understood as the two forging processes being carried out in the same location without being moved to other locations). Compared with the non-"in-situ" forming technology in the prior art (which requires reheating and homogenization after casting), the grains are less likely to grow. Combined with a larger cooling rate and a higher solid fraction, the in-situ primary forging process and the in-situ secondary forging deformation process of this application can have a larger deformation amount.

[0081] Preferably, the content of Zr and RE is 0.1-0.5%.

[0082] Understandably, the mold is an integrated casting and forging mold. The punch, driven by a feed rod, pushes the mixture into the mold cavity for casting and forging. During low-pressure filling casting, the filling speed and time can be adjusted by regulating the punch speed. The downward pressure of the punch during filling generates filling injection force, and the stroke of the punch after filling generates boosting pressure. These filling injection force and boosting pressure can be used to regulate the casting pressure during the casting process. In subsequent in-situ primary forging and in-situ secondary forging deformation processes, the forging pressure can also be adjusted by regulating the punch stroke.

[0083] To improve the smoothness of the connection between the in-situ primary forging process and the in-situ secondary forging deformation process, a second cooling process was carried out during the in-situ primary forging process. This process ensures that solid aluminum alloy parts with a temperature of 350-460℃ are obtained as soon as possible after the pressure holding is completed, so that they can enter the in-situ secondary forging deformation process as soon as possible.

[0084] The high dislocation density generated by the pre-formed twins through in-situ secondary forging pre-deformation treatment provides more diffusion pathways for the dissolution of Mg, Cu, Zn, Si, Fe, Ag, and Mn solute atoms in the aluminum matrix, promotes the nucleation of precipitates, accelerates the formation of precipitates, enhances the hardening response of the alloy, and further refines the grain size.

[0085] A third cooling treatment was performed during the in-situ secondary forging deformation process to facilitate the formation of twins. The cooling rate for this third cooling treatment in the in-situ secondary forging deformation process was 20-60℃ / s, specifically 20℃ / s, 25℃ / s, 30℃ / s, 35℃ / s, 40℃ / s, 45℃ / s, 50℃ / s, 55℃ / s, or 60℃ / s. Cooling treatment was performed during the low-pressure filled casting, in-situ primary forging, and in-situ secondary forging deformation processes. After these cooling treatments, the precipitation of phases such as η′(MgZn2), T′(AlMgZnCu), S'(Al2CuMg), β''(Mg2Si), Mg2SiZn, and AlCuMgSi was promoted, and their sizes were gradually refined, improving the tensile strength and elongation of the aluminum alloy.

[0086] In one embodiment, the heat treatment is an aging treatment at a temperature of 100-130°C, specifically 100°C, 110°C, 120°C, or 130°C, for a time of 20-50 hours, specifically 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours, or 50 hours. During the aging treatment, the precipitated phases gradually grow, resulting in an aluminum alloy product with excellent comprehensive properties (including tensile strength and elongation).

[0087] In another embodiment, the heat treatment comprises solution treatment and aging treatment. In the solution treatment, the temperature is 440-475°C, specifically 440°C, 450°C, 460°C, 470°C, or 475°C, and the time is 1-20 hours, specifically 1 hour, 5 hours, 10 hours, 15 hours, or 20 hours. In the aging treatment, the temperature is 100-130°C, specifically 100°C, 110°C, 120°C, or 130°C, and the time is 18-40 hours, specifically 18 hours, 20 hours, 25 hours, 30 hours, 35 hours, or 40 hours. Solution treatment promotes uniform diffusion of solute atoms, dissolves coarse second phases (such as η(MgZn2), T(AlMgZnCu), Al2CuAg, (CuMg)Al2, Mg2Si, and AlFeSi phases), and increases the solid solubility of alloying elements in the aluminum matrix, creating conditions for subsequent aging treatment. During aging treatment, the precipitated phases gradually grow, resulting in aluminum alloy products with excellent comprehensive properties (including tensile strength and elongation).

[0088] In another embodiment, the heat treatment is a bipolar aging treatment. The temperature of the first-stage aging treatment is 100-120°C, specifically 100°C, 105°C, 110°C, 115°C, or 120°C, and the time is 2-20 hours, specifically 2 hours, 5 hours, 10 hours, or 20 hours. The temperature of the second-stage aging treatment is 150-180°C, specifically 150°C, 160°C, 170°C, or 180°C, and the time is 2-20 hours, specifically 2 hours, 5 hours, 10 hours, 15 hours, or 20 hours. During the first-stage aging process, the diffusion rate of solute atoms (such as Zn, Mg, Cu, Si, etc.) is low, which can form extremely fine and dense GP regions in the aluminum matrix and suppress the formation of coarse η(MgZn2) phase, T(AlMgZnCu), S(Al2CuMg), β(Mg2Si) phase, and establish a high-density fine core for the second-stage aging. During the second-stage aging treatment, the coherent strengthening phase can rapidly grow to a suitable size, transforming the GP zone into more stable and stronger precipitated phases (such as η′(MgZn2) phase, T′(AlMgZnCu), S'(Al2CuMg), β''(Mg2Si) phase, etc.), thereby significantly improving the strength of the aluminum alloy. Moreover, based on the high-density fine nuclei formed during the first-stage aging treatment, the precipitated phases in the second-stage aging treatment precipitate more uniformly, reducing the content of coarse precipitated phases, thereby significantly improving the elongation of the aluminum alloy. Since the temperature of the second-stage aging treatment is higher than that of the first-stage aging treatment, residual stress can be eliminated, thereby improving the stability of the aluminum alloy, making the aluminum alloy of the present invention suitable for manufacturing large thin-walled structural parts.

[0089] In this invention, an alloy liquid containing Zn, Mg, Cu, Si, Fe, Mn, Ti, Cr, Zr, V, Be, RE, Ag, Sr, B, and Sn elements is refined, degassed, and formed to obtain an ultra-high strength Al-Zn-Mg-Cu aluminum alloy. The composite addition of Zn, Mg, Cu, Si, Fe, Mn, Ti, Cr, Zr, V, Be, RE, Ag, Sr, B, and Sn within the above-mentioned content range interacts and influences each other, resulting in superior mechanical properties for the ultra-high strength Al-Zn-Mg-Cu aluminum alloy. The alloy liquid may further contain at least one source selected from In, Nb, Bi, Ge, Mo, Ni, Te, Co, Sb, Cd, and Ca.

[0090] During the forming process, the molten alloy is pushed into the mold by a punch for low-pressure filling casting. Once the molten alloy enters the semi-solid solidification zone, the semi-solid aluminum alloy part undergoes in-situ first-stage forging and second-stage forging deformation processes with large deformation amounts within the mold, resulting in the aluminum alloy part. The part is then heat-treated to obtain the final aluminum alloy product. This aluminum alloy product possesses not only the structural complexity of cast products but also the high strength and toughness of deformed products. By eliminating the need to remove the semi-solid aluminum alloy part from the low-pressure filling casting mold and place it into the subsequent multi-stage forging mold, the aluminum alloy preparation method of this invention offers advantages such as fewer process steps, shorter production cycle, higher production efficiency, and lower cost. During the low-pressure filling casting process, casting defects within the aluminum alloy part are minimal. During the in-situ primary forging process with large deformation, casting defects inside the semi-solid aluminum alloy parts are further eliminated, and the coarse grains and second-phase as-cast structure are significantly refined. A large number of nanoscale precipitates appear within the grains, their size is refined, and their volume fraction is increased, thus improving the mechanical properties of the alloy (including tensile strength and elongation). During the in-situ secondary forging pre-deformation process, the grain size can be further refined. Furthermore, the high dislocation density generated by pre-formed twins provides more diffusion pathways for the dissolution of Mg, Cu, Zn, Si, Fe, Ag, and Mn solute atoms in the aluminum matrix during subsequent heat treatment. This promotes the nucleation of precipitates, enhances the alloy's hardening response, accelerates precipitate formation, and further increases the volume fraction of precipitates, thereby improving the alloy's mechanical properties.

[0091] This invention also provides an aluminum alloy structural component, at least a portion of which is made of the aforementioned ultra-high strength Al-Zn-Mg-Cu aluminum alloy or an ultra-high strength Al-Zn-Mg-Cu aluminum alloy prepared by the same method. The aluminum alloy structural component possesses excellent mechanical properties and elongation, and can be applied in aerospace, automotive and transportation, military and weaponry, mold and machinery manufacturing, and special high-temperature structural components. Since this aluminum alloy structural component adopts all the technical solutions of all embodiments of the aforementioned ultra-high strength Al-Zn-Mg-Cu aluminum alloy, it possesses at least all the beneficial effects brought about by the technical solutions of the aforementioned embodiments, which will not be elaborated upon here.

[0092] For aluminum alloy structural components, the mechanical properties decrease sharply with increasing thickness. However, the aluminum alloy of this invention, when using an integrated casting and forging process, maintains good mechanical properties even when its thickness is greater than 3mm and further greater than 5mm. Furthermore, when using die casting and vacuum die casting processes, the aluminum alloy of this invention maintains good mechanical properties even when its thickness is greater than 2mm.

[0093] Example Please refer to Table 1 for the composition and content of the aluminum alloys in Examples 1 to 10, and Table 2 for the performance test results.

[0094] Table 1. Composition and content of aluminum alloys in Examples 1 to 10 For the sake of simplicity, the content of trace elements such as impurities in the examples is not shown.

[0095] When preparing the aluminum alloys of Examples 1 to 11, the preparation methods of these aluminum alloys differ in the types and contents of elements, as well as in the forming process. Other steps, such as Al source heating temperature, refining process, and degassing process, can be the same.

[0096] In preparing the Al-Zn-Mg-Cu cast-forged integrated aluminum alloy of Example 1, the forming process included low-pressure filling casting, in-situ primary forging, in-situ secondary forging deformation, and aging treatment. In the low-pressure filling casting, the filling speed was 0.1 m / s, the filling time was 20 s, the casting pressure was 0.2 MPa, the holding time was 2 s, the mold temperature was 200℃, the alloy casting temperature was 660℃, and the cooling rate was 5℃ / s. In the in-situ primary forging, the forging temperature was 600℃, the forging specific pressure was 60 MPa, the forging start time was 2 s, the holding time was 10 s, the cooling rate was 25℃ / s, and the deformation was 10%. In the in-situ secondary forging deformation, the forging temperature was 350℃, the forging specific pressure was 110 MPa, the holding time was 2 s, the cooling rate was 50℃ / s, and the deformation was 40%. During the aging process, the temperature was 100℃ and the time was 30 hours.

[0097] In preparing the Al-Zn-Mg-Cu cast-forged integrated aluminum alloy of Example 2, the forming process included low-pressure filling casting, in-situ primary forging, in-situ secondary forging deformation, solution treatment, and aging treatment. In the low-pressure filling casting, the filling speed was 0.2 m / s, the filling time was 15 s, the casting pressure was 0.5 MPa, the holding time was 2 s, the mold temperature was 200℃, the alloy casting temperature was 660℃, and the cooling rate was 5℃ / s. In the in-situ primary forging, the forging temperature was 610℃, the forging specific pressure was 300 MPa, the forging start time was 2 s, the holding time was 10 s, the cooling rate was 20℃ / s, and the deformation was 60%. In the in-situ secondary forging deformation, the forging temperature was 410℃, the forging specific pressure was 120 MPa, the holding time was 5 s, the cooling rate was 30℃ / s, and the deformation was 30%. In the solution treatment, the temperature was 450℃ and the time was 2 hours. In the aging treatment, the temperature was 130℃ and the time was 20 hours.

[0098] In preparing the Al-Zn-Mg-Cu cast-forged integrated aluminum alloy of Example 3, the forming process included low-pressure filling casting, in-situ primary forging, in-situ secondary forging deformation, solution treatment, and aging treatment. In the low-pressure filling casting, the filling speed was 0.6 m / s, the filling time was 10 s, the casting pressure was 40 MPa, the holding time was 2 s, the mold temperature was 250℃, the alloy casting temperature was 720℃, and the cooling rate was 10℃ / s. In the in-situ primary forging, the forging temperature was 600℃, the forging specific pressure was 300 MPa, the forging start time was 2 s, the holding time was 3 s, the cooling rate was 50℃ / s, and the deformation was 40%. In the in-situ secondary forging deformation, the forging temperature was 450℃, the forging specific pressure was 80 MPa, the holding time was 1 s, the cooling rate was 20℃ / s, and the deformation was 50%. In the solution treatment, the temperature was 460℃ and the time was 9 hours. In the aging treatment, the temperature was 100℃ and the time was 18 hours.

[0099] In preparing the Al-Zn-Mg-Cu cast-forged integrated aluminum alloy of Example 4, the forming process included low-pressure filling casting, in-situ primary forging, in-situ secondary forging deformation, and bipolar aging. In the low-pressure filling casting, the filling speed was 0.5 m / s, the filling time was 12 s, the casting pressure was 35 MPa, the holding time was 3 s, the mold temperature was 210℃, the alloy casting temperature was 660℃, and the cooling rate was 10℃ / s. In the in-situ primary forging, the forging temperature was 550℃, the forging specific pressure was 280 MPa, the forging start time was 2 s, the holding time was 2.5 s, the cooling rate was 40℃ / s, and the deformation was 30%. In the in-situ secondary forging deformation, the forging temperature was 450℃, the forging specific pressure was 120 MPa, the holding time was 1 s, the cooling rate was 30℃ / s, and the deformation was 10%. In the first stage of aging treatment, the temperature is 110℃ and the time is 13 hours. In the second stage of aging treatment, the temperature is 160℃ and the time is 14 hours.

[0100] In preparing the Al-Zn-Mg-Cu cast-forged integrated aluminum alloy of Example 5, the forming process included low-pressure filling casting, in-situ primary forging, in-situ secondary forging deformation, solution treatment, and aging treatment. In the low-pressure filling casting, the filling speed was 1.1 m / s, the filling time was 3 s, the casting pressure was 3 MPa, the holding time was 2 s, the mold temperature was 250℃, the alloy casting temperature was 720℃, and the cooling rate was 40℃ / s. In the in-situ primary forging, the forging temperature was 540℃, the forging specific pressure was 120 MPa, the forging start time was 2 s, the holding time was 5 s, the cooling rate was 40℃ / s, and the deformation was 30%. In the in-situ secondary forging deformation, the forging temperature was 440℃, the forging specific pressure was 150 MPa, the holding time was 1 s, the cooling rate was 20℃ / s, and the deformation was 30%. In the solution treatment, the temperature was 450℃ and the time was 1 hour. In the aging treatment, the temperature was 120℃ and the time was 25 hours.

[0101] In preparing the Al-Zn-Mg-Cu cast-forged integrated aluminum alloy of Example 6, the forming process included low-pressure filling casting, in-situ primary forging, in-situ secondary forging deformation, solution treatment, and aging treatment. In the low-pressure filling casting, the filling speed was 1.1 m / s, the filling time was 3 s, the casting pressure was 5 MPa, the holding time was 2 s, the mold temperature was 180℃, the alloy casting temperature was 710℃, and the cooling rate was 30℃ / s. In the in-situ primary forging, the forging temperature was 610℃, the forging specific pressure was 140 MPa, the forging start time was 2 s, the holding time was 10 s, the cooling rate was 20℃ / s, and the deformation was 25%. In the in-situ secondary forging deformation, the forging temperature was 410℃, the forging specific pressure was 160 MPa, the holding time was 1 s, the cooling rate was 20℃ / s, and the deformation was 60%. In the solution treatment, the temperature was 450℃ and the time was 1 hour. In the aging treatment, the temperature was 110℃ and the time was 25 hours.

[0102] In preparing the Al-Zn-Mg-Cu cast-forged integrated aluminum alloy of Example 7, the forming process included low-pressure filling casting, in-situ primary forging, in-situ secondary forging deformation, and two-stage aging treatment. In the low-pressure filling casting, the filling speed was 1 m / s, the filling time was 5 s, the casting pressure was 15 MPa, the holding time was 2 s, the mold temperature was 200℃, the alloy casting temperature was 710℃, and the cooling rate was 5℃ / s. In the in-situ primary forging, the forging temperature was 600℃, the forging specific pressure was 80 MPa, the forging start time was 2 s, the holding time was 4 s, the cooling rate was 50℃ / s, and the deformation was 10%. In the in-situ secondary forging deformation, the forging temperature was 400℃, the forging specific pressure was 500 MPa, the holding time was 5 s, the cooling rate was 60℃ / s, and the deformation was 70%. In the first stage of aging treatment, the temperature is 100℃ and the time is 13 hours. In the second stage of aging treatment, the temperature is 170℃ and the time is 6 hours.

[0103] In preparing the Al-Zn-Mg-Cu cast-forged integrated aluminum alloy of Example 8, the forming process included low-pressure filling casting, in-situ primary forging, in-situ secondary forging pre-deformation, solution treatment, and aging treatment. In the low-pressure filling casting, the filling speed was 0.8 m / s, the filling time was 10 s, the casting pressure was 20 MPa, the holding time was 5 s, the mold temperature was 200℃, the alloy casting temperature was 700℃, and the temperature cooling rate was 10℃ / s. In the in-situ primary forging, the forging temperature was 550℃, the forging specific pressure was 60 MPa, the forging start time was 2 s, the holding time was 2 s, the temperature cooling rate was 50℃ / s, and the deformation was 10%. In the in-situ secondary forging pre-deformation, the forging temperature was 450℃, the forging specific pressure was 120 MPa, the holding time was 10 s, the temperature cooling rate was 30℃ / s, and the deformation was 20%. In the solution treatment, the temperature was 475℃ and the time was 2 hours. In the aging treatment, the temperature was 100℃ and the time was 40 hours.

[0104] In preparing the Al-Zn-Mg-Cu cast-forged integrated aluminum alloy of Example 9, the forming process included low-pressure filling casting, in-situ primary forging, in-situ secondary forging pre-deformation, and two-stage aging treatment. In the low-pressure filling casting, the filling speed was 1 m / s, the filling time was 5 s, the casting pressure was 10 MPa, the holding time was 2 s, the mold temperature was 210℃, the alloy casting temperature was 700℃, and the cooling rate was 10℃ / s. In the in-situ primary forging, the forging temperature was 600℃, the forging specific pressure was 60 MPa, the forging start time was 2 s, the holding time was 5 s, the cooling rate was 40℃ / s, and the deformation was 10%. In the in-situ secondary forging pre-deformation, the forging temperature was 400℃, the forging specific pressure was 250 MPa, the holding time was 10 s, the cooling rate was 30℃ / s, and the deformation was 50%. In the first stage of aging treatment, the temperature is 110℃ and the time is 10 hours. In the second stage of aging treatment, the temperature is 160℃ and the time is 8 hours.

[0105] In preparing the Al-Zn-Mg-Cu cast-forged integrated aluminum alloy of Example 10, the forming process included low-pressure filling casting, in-situ primary forging, solution treatment, and aging treatment. In the low-pressure filling casting, the filling speed was 0.1 m / s, the filling time was 20 s, the casting pressure was 0.2 MPa, the holding time was 2 s, the mold temperature was 200℃, the alloy casting temperature was 690℃, and the cooling rate was 5℃ / s. In the in-situ primary forging, the forging temperature was 580℃, the forging specific pressure was 60 MPa, the forging start time was 2 s, the holding time was 6 s, the cooling rate was 50℃ / s, and the deformation was 10%. In the solution treatment, the temperature was 460℃ and the time was 20 h. In the aging treatment, the temperature was 110℃ and the time was 20 h.

[0106] Table 2 Performance test results of aluminum alloys in Examples 1 to 10 Referring to Table 2, the ultra-high strength Al-Zn-Mg-Cu aluminum alloys of Examples 1 to 10 exhibit excellent tensile strength and elongation. Specifically, the ultra-high strength Al-Zn-Mg-Cu cast-forged aluminum alloys of Examples 1 to 10 have a tensile strength of not less than 410 MPa and an elongation of not less than 7.5%. In summary, the ultra-high strength Al-Zn-Mg-Cu cast-forged aluminum alloy of the present invention has a tensile strength of not less than 410 MPa and an elongation of not less than 7.5%.

[0107] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the content of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. An ultra-high strength Al-Zn-Mg-Cu aluminum alloy, characterized in that, The ultra-high strength Al-Zn-Mg-Cu aluminum alloy contains 7-12% Zn, 1-3.5% Mg, 0.5-2.5% Cu, 0.001-0.2% Si, 0-0.4% Fe, 0-0.6% Mn, 0-0.2% Ti, 0-0.3% Cr, 0-0.5% Zr, 0-0.2% V, 0-0.1% Be, 0-0.5% RE, 0-0.5% Ag, 0-0.1% Sr, 0-0.2% B, 0-0.1% Sn, and Al, as well as unavoidable impurities.

2. The ultra-high strength Al-Zn-Mg-Cu aluminum alloy according to claim 1, characterized in that, The ultra-high strength Al-Zn-Mg-Cu aluminum alloy contains 7-12% Zn, 1-3.5% Mg, 0.5-2.5% Cu, 0.001-0.2% Si, 0.001-0.4% Fe, 0.001-0.6% Mn, 0.001-0.2% Ti, and 0.001-0.6% Fe. 3% Cr, 0.001-0.5% Zr, 0.001-0.2% V, 0.001-0.1% Be, 0.001-0.5% RE, 0.001-0.5% Ag, 0.001-0.6% Sr, 0.001-0.2% B, and 0.001-0.1% Sn.

3. The ultra-high strength Al-Zn-Mg-Cu aluminum alloy according to claim 1, characterized in that, At least one of the following conditions must be met: The mass ratio of Zn to Mg is greater than 2; The sum of the mass percentages of Si and Fe is less than 0.5%; The sum of the mass percentages of V and Ti is less than 0.4%; The atomic percentages of Zr and RE are 1-1.2:

1.

4. The ultra-high strength Al-Zn-Mg-Cu aluminum alloy according to claim 1, characterized in that, The ultra-high strength Al-Zn-Mg-Cu aluminum alloy also contains at least one of In, Nb, Bi, Ge, Mo, Ni, Te, Co, Sb, Cd, and Ca, with In having a mass percentage content of 0-0.2%, Nb 0-0.5%, Bi 0-0.2%, Ge 0-0.5%, Mo 0-0.5%, Ni 0-0.5%, Te 0-0.5%, Co 0-0.5%, Sb 0-0.2%, Cd 0-0.3%, and Ca 0-0.05%.

5. A method for preparing an ultra-high strength Al-Zn-Mg-Cu aluminum alloy, comprising the following steps: The Al source is subjected to a first heating treatment to obtain molten aluminum. Add Zn source, Mg source, Cu source, Si source, Fe source, Mn source, Ti source, Cr source, Zr source, V source, Be source, RE source, Ag source, B source, Sn source, and Sr source to the aluminum liquid, and perform a second heat treatment to obtain an alloy liquid; The alloy liquid is refined, slag removed, and formed to obtain an ultra-high strength Al-Zn-Mg-Cu aluminum alloy. This ultra-high strength Al-Zn-Mg-Cu aluminum alloy contains 7-12% Zn, 1-3.5% Mg, 0.5-2.5% Cu, 0.001-0.2% Si, 0-0.4% Fe, 0-0.6% Mn, and [other components are missing from the original text]. The content is 0-0.2% Ti, 0-0.3% Cr, 0-0.5% Zr, 0-0.2% V, 0-0.1% Be, 0-0.5% RE, 0-0.5% Ag, 0-0.1% Sr, 0-0.2% B, 0-0.1% Sn, and Al and unavoidable impurities.

6. The method for preparing ultra-high strength Al-Zn-Mg-Cu aluminum alloy according to claim 5, characterized in that, The molding process includes the following steps: The molten alloy is pushed into a mold and subjected to low-pressure filling casting. Once the molten alloy enters the semi-solid solidification zone, it forms a semi-solid aluminum alloy part. The semi-solid aluminum alloy part is then subjected to in-situ first-stage forging in the mold. The deformation of the semi-solid aluminum alloy part during the in-situ first-stage forging process is 10-70%.

7. The method for preparing ultra-high strength Al-Zn-Mg-Cu aluminum alloy according to claim 6, characterized in that, The molding process also includes the following steps: After in-situ primary forging, in-situ secondary forging deformation is performed to obtain aluminum alloy parts.

8. The method for preparing ultra-high strength Al-Zn-Mg-Cu aluminum alloy according to claim 6 or 7, characterized in that, The molding process also includes the following steps: Ultra-high strength Al-Zn-Mg-Cu aluminum alloys are obtained by heat treatment of aluminum alloy parts after in-situ primary forging or in-situ secondary forging deformation.

9. The method for preparing ultra-high strength Al-Zn-Mg-Cu aluminum alloy according to claim 8, characterized in that, The heat treatment includes aging treatment, wherein the aging treatment is performed at a temperature of 100-130°C for a time of 20-50 hours; or The heat treatment includes solution treatment and aging treatment. In the solution treatment, the temperature is 440-475°C and the time is 1-20 hours. In the aging treatment, the temperature is 100-130°C and the time is 18-40 hours. The heat treatment is a bipolar aging process. The first stage of aging is performed at a temperature of 100-120°C for 2-20 hours, and the second stage of aging is performed at a temperature of 150-180°C for 2-20 hours.

10. An aluminum alloy structural component, characterized in that, At least a portion of the aluminum alloy structural component is made of the ultra-high strength Al-Zn-Mg-Cu aluminum alloy as described in any one of claims 1 to 4 or the ultra-high strength Al-Zn-Mg-Cu aluminum alloy prepared by the preparation method as described in any one of claims 5 to 9.

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