High-strength heat-treatment-free die-cast aluminum alloy, its preparation method, and structural component

Abstract

The present invention provides a high-strength heat-treatment-free die-casting aluminum alloy containing Si with a mass percentage content of 8-10.5%, Fe with a mass percentage content of 0.2-0.8%, Cu with a mass percentage content of 0.3-0.8%, Mn with a mass percentage content of 0.2-0.8%, Mg with a mass percentage content of 0.2-0.6%, Zn with a mass percentage content of 0.1-0.5%, B with a mass percentage content of 0-0.01%, Sr with a mass percentage content of 0-0.05%, Ge with a mass percentage content of 0-0.1%, and Ti with a mass percentage content of 0.01-0.25%. The present invention also provides a preparation method and a structural member of the high-strength heat-treatment-free die-casting aluminum alloy. The high-strength heat-treatment-free die-casting aluminum alloy of the present invention has a tensile strength greater than 280 MPa, a yield strength greater than 140 MPa, and an elongation greater than 10%.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and in particular to a high-strength heat-treatment-free die-cast aluminum alloy, a preparation method of the high-strength heat-treatment-free die-cast aluminum alloy, and a structural member. Background Art

[0002] With the rapid development of new energy vehicles, automotive structural components are rapidly developing towards integrated, lightweight, and high-efficiency design and manufacturing. Automotive die-cast structural components are closely related to the safety of vehicles. In an automobile body, many die-cast structural components are installed at the nodes of the body structure and connected to other components to form a high-strength frame that resists deformation. Such die-cast structural components usually have characteristics such as large size, thin walls, and complex structures. Since the safety and reliability of the vehicle need to be ensured during driving, the vehicle has relatively high requirements for the mechanical properties (such as tensile strength and yield strength) of die-cast structural components. However, currently, the heat-treatment-free die-cast aluminum alloys generally only have medium strength and are difficult to meet the safety requirements of automotive die-cast structural components. In other fields, such as aerospace, high-speed rail, electric bicycles, ships, mobile devices, household appliances, chemical industry, daily necessities, construction, etc., heat-treatment-free aluminum alloy die-cast structural components are usually also required, and the requirements for the mechanical properties of heat-treatment-free aluminum alloy die-castings are also relatively high. Therefore, there is an urgent need to develop a high-strength heat-treatment-free die-cast aluminum alloy with high tensile strength and yield strength. Summary of the Invention

[0003] Aiming at the above-mentioned defects of the prior art, the present invention provides a high-strength heat-treatment-free die-cast aluminum alloy, aiming to provide a high-strength heat-treatment-free die-cast aluminum alloy with excellent tensile strength and yield strength.

[0004] The present invention provides a high-strength heat-treatment-free die-cast aluminum alloy, which contains Al, and also contains Si with a mass percentage content of 8-10.5%, Fe with a mass percentage content of 0.2-0.8%, Cu with a mass percentage content of 0.3-0.8%, Mn with a mass percentage content of 0.2-0.8%, Mg with a mass percentage content of 0.2-0.6%, Zn with a mass percentage content of 0.1-0.5%, B with a mass percentage content of 0-0.01%, Sr with a mass percentage content of 0-0.05%, Ge with a mass percentage content of 0-0.1%, and Ti with a mass percentage content of 0.01-0.25%.

[0005] The present invention also provides a preparation method of a high-strength heat-treatment-free die-cast aluminum alloy, including the following steps:

[0006] Perform a first heat treatment on the Al source to obtain molten aluminum;

[0007] Add Si source, Fe source, Cu source, Mn source, Mg source, Zn source, B source, Sr source, Ge source, and Ti source to the aluminum liquid, and perform a second heat treatment to obtain an alloy liquid; and

[0008] Perform refining treatment, slag skimming treatment, and die-casting treatment on the alloy liquid to obtain aluminum alloy components; and

[0009] Perform low-temperature quenching treatment on the aluminum alloy components to obtain a high-strength heat-treatment-free die-cast aluminum alloy. The high-strength heat-treatment-free die-cast aluminum alloy contains Al, and also contains Si with a mass percentage content of 8-10.5%, Fe with a mass percentage content of 0.2-0.8%, Cu with a mass percentage content of 0.3-0.8%, Mn with a mass percentage content of 0.2-0.8%, Mg with a mass percentage content of 0.2-0.6%, Zn with a mass percentage content of 0.1-0.5%, B with a mass percentage content of 0-0.01%, Sr with a mass percentage content of 0-0.05%, Ge with a mass percentage content of 0-0.1%, and Ti with a mass percentage content of 0.01-0.25%.

[0010] The present invention also provides a structural member, at least part of the material of which is the above-mentioned high-strength heat-treatment-free die-cast aluminum alloy or the high-strength heat-treatment-free die-cast aluminum alloy prepared by the preparation method.

[0011] In the technical solution of the present invention, the high-strength heat-treatment-free die-cast aluminum alloy contains Si with a mass percentage content of 8-10.5%, Fe with a mass percentage content of 0.2-0.8%, Cu with a mass percentage content of 0.3-0.8%, Mn with a mass percentage content of 0.2-0.8%, Mg with a mass percentage content of 0.2-0.6%, Zn with a mass percentage content of 0.1-0.5%, B with a mass percentage content of 0-0.01%, Sr with a mass percentage content of 0-0.05%, Ge with a mass percentage content of 0-0.1%, and Ti with a mass percentage content of 0.01-0.25%. The composite addition of Si, Fe, Cu, Mn, Mg, Zn, B, Sr, Ge, and Ti within the above content ranges influences and interacts with each other, so that the tensile strength of the heat-treatment-free aluminum alloy is greater than 280 MPa, the yield strength is greater than 140 MPa, and the elongation is greater than 10%. Specifically:

[0012] (1) Si can improve the tensile strength, yield strength, and process flowability of aluminum alloys. However, when its content is too high, the elongation rate will decrease. Si can react with Al, Fe, Mg, Cu, B, etc. to form second phases such as Mg2Si, AlFeSi, AlFeSiCu, AlFeMgSi, AlCuMgSi, AlFeSiB, etc., to further improve the tensile strength and yield strength of aluminum alloys;

[0013] (2) Mg can react with Al, Fe, Si, Cu, Zn, etc. to form second phases such as AlFeMgSi, (CuMg)Al2, AlCuMgSi, Mg2Si, Mg2Zn, Mg2SiZn, etc., to improve the tensile strength and yield strength of aluminum alloys. Among them, when Mg is dissolved in the CuAl2 phase and the AlFeSi phase, (CuMg)Al2 phase and AlFeSiMg phase are formed;

[0014] (3) Cu can react with Al, Fe, Si, Mg, Zn, etc. to form second phases such as CuAl2, AlFeSiCu, AlCuMgSi, Al2CuZn, (CuMg)Al2, etc., to improve the tensile strength and yield strength of aluminum alloys. It can also promote the precipitation of second phases such as Mg2Si, Mg2Zn, Mg2SiZn, etc., and increase the volume fraction and dispersion degree of the precipitated phases. Subsequent natural aging or heat treatment during vehicle painting baking can further improve the aging strengthening effect of Cu and Mg;

[0015] (4) Zn can react with Al, Mg, Cu, and Si, etc. to form second phases such as MgZn2, Mg2SiZn, Al2CuZn, etc., to improve the tensile strength and yield strength of aluminum alloys. Zn can eliminate elemental Si to reduce the influence of Si on the properties of aluminum alloys. It can also promote the precipitation of second phases such as Mg2Si, Mg2Zn, Mg2SiZn, Al2Cu, Al2CuMg, etc., and increase the volume fraction and dispersion degree of the precipitated phases. The combined addition of Zn and Mg can form the strengthening phase Mg / Zn2, significantly improving the tensile strength and yield strength of aluminum alloys. In addition, the addition of Zn increases the lattice distortion energy of the matrix, which will promote the migration of Mg, Cu, and Si atoms from the matrix to form more Cu-Mg-Zn clusters and Mg-Si-Zn clusters, improving the cluster strengthening effect;

[0016] (5) Fe can improve the tensile strength and yield strength of aluminum alloys, can improve the demolding performance, and can also react with Al, Si, Mg, Cu, B to form second phases such as Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu, AlFeSiB, etc., to further improve the tensile strength and yield strength of aluminum alloys;

[0017] (6) Mn can react with Al, Fe, Si, and Cu to form second phases such as MnAl2, MnAl6, α-(Fe,Mn)Al6, A1 12 CuMn2, α-Al(FeMn)Si, τ(Cu2Mn3Al 20 ) etc., to improve the tensile strength and yield strength of aluminum alloys; Mn can significantly refine the grain size through lattice distortion generated by solid solution in the matrix and dispersed particles of MnAl6 produced by reacting with Al, so as to improve the elongation rate. Moreover, MnAl6 can also dissolve Fe to form the α-(Fe,Mn)Al6 phase, reducing the Fe content and minimizing the harm of Fe; Mn reacts with Al, Fe, Mn, and Si to form spherical or Chinese character-shaped AlFeMnSi compound phases, which can avoid the formation of long needle-shaped Fe phases to reduce the harm of Fe, and can also improve the tensile strength and yield strength of aluminum alloys when improving the demoulding property of aluminum alloys; Mn can also transform the coarse needle-shaped β-AlFeSi phase into small particle-shaped α-Al(FeMn)Si phase dispersed particles, improving the Fe morphology to eliminate the harm of Fe. Specifically, Mn can replace part of the Fe in the coarse needle-shaped β-AlFeSi phase to form small particle-shaped dispersed β-Al(FeMn)Si phases, and the formation and growth shape of the β phase are improved, thus reducing the harm of Fe; Mn can also promote the transformation of the needle-shaped β-Al(FeMn)Si phase into small particle-shaped α-Al(FeMn)Si dispersed phases. The formed α-Al(FeMn)Si phase dispersed particles are distributed in the aluminum matrix and strongly pin the sub-boundaries of aluminum alloys. This is mainly because the α-phase dispersed particles containing Mn in aluminum alloys can serve as non-uniform nucleation sites during the aging process of the β′ phase to induce its nucleation, thereby accelerating the precipitation of the β′ phase; Mn can also react with impurity phases in the aluminum alloy liquid to form Al-Mn-X phases (X is an impurity element, including but not limited to transition metal elements). In this way, the aluminum alloy liquid can be purified, and these phases can be used as grain nucleation points to increase the nucleation rate and refine the grains, so as to improve the tensile strength, yield strength, elongation rate, and fluidity of aluminum alloys;

[0018] (7) Sr preferentially combines with Fe to form dispersion strengthening, reducing the solid solubility of Fe, to improve the yield strength and tensile strength of aluminum alloys; Sr can change the behavior of intermetallic compound phases crystallographically and can be used as a modifier to refine grains and second phases in aluminum alloys through the heterogeneous nucleation theory or twin trough mechanism. For example, Sr can change the morphology of eutectic silicon phases through modification to improve the elongation rate of aluminum alloys and reduce the tendency of sticking to the mold during die casting; Sr can transform the coarse needle-shaped β-AlFeSi and β-AlFeMnSi phases in the ingot into small particle-shaped Chinese character-shaped α-AlFeSi and α-Al(FeMn)Si phases, reducing the homogenization time of the ingot, and can improve the yield strength, tensile strength, and elongation rate of aluminum alloys;

[0019] The TiAl2 phase formed by the reaction of Ti and Al can, as a non-spontaneous core during crystallization, refine grains, secondary phases, and precipitation phases to improve the tensile strength, yield strength, and elongation of aluminum alloys.

[0020] (9)B can react with transition metal elements (including transition metal elements such as Fe) to form compounds such as ferroboron compounds that can be separated from the aluminum alloy liquid to purify the aluminum alloy liquid; B is easily adsorbed on the surface of the iron-rich phase to inhibit the growth of the iron-rich phase, playing a role in controlling the size of the iron-rich phase, and can also prevent the formation of the iron-rich phase in the aluminum alloy liquid; B can inhibit the segregation of Ti3Al. Therefore, the effect is better when Ti and B are used together; B can also refine grains and secondary phases to improve the elongation of aluminum alloys.

[0021] (10)Ge is prone to capturing quenching vacancies in the α-Al matrix and forming "Ge-vacancy pairs" to "retain" the quenching vacancies in the α-Al matrix; during the low-temperature quenching and holding process, the aluminum alloy matrix shrinks, undergoes plastic deformation, and generates internal stress; Ge can reduce the solubility of elements in aluminum and increase the nucleation points of clusters. During the process of rising to room temperature after the low-temperature quenching and holding treatment, these nucleation points combine with the "Ge-vacancy pairs" formed by quenching vacancies under the action of internal stress to rapidly increase the volume fractions of Cu-Mg-Zn clusters, Mg-Si-Zn clusters, and Mg-Si-Cu-Zn clusters to improve the yield strength, tensile strength, and elongation of the heat-treatable aluminum alloy; in addition, Ge elements can also replace Si and Cu atoms in Cu-Mg-Zn clusters, Mg-Si-Zn clusters, and Mg-Si-Cu-Zn clusters to increase the resistance of dislocations to cut through these clusters; when RE elements are added, the combination of Ge and RE can further refine the size of the clusters and increase the volume fraction of the clusters.

[0022] The combined action of Si, Cu, Mn, Mg, Zn, Ti, Sr, Ge, and Fe within the above content ranges can significantly improve the tensile strength and yield strength of aluminum alloys; the combined action of Mn, B, Ti, Ge, and Sr within the above content ranges can refine grains, secondary phases, and precipitation phases to improve the elongation of aluminum alloys; the combined action of Cu, Ge, and Zn within the above content ranges can promote the precipitation of secondary phases, increase the volume fraction and dispersion degree of precipitation phases, and further improve the tensile strength, yield strength, and elongation of aluminum alloys; the combined action of Fe, Sr, and Mn within the above content ranges can improve the demolding performance of aluminum alloys.

[0023] During the die-casting process, when the temperature cooling rate is relatively large (which can be 10 - 60 K / S) and the mass percentage of Fe is 0.2 - 0.4%, Fe will basically form fine short rod-shaped or square-shaped Al-Fe phase or Al-Fe-Si phase. Thus, Fe within this content range has little impact on the elongation rate of the aluminum alloy, and there is no need to add a large amount of Mn to reduce the influence of Fe on the elongation rate of the aluminum alloy. At this time, the mass percentage content of Mn can be 0.2 - 0.4%; when the mass percentage of Fe is 0.4 - 0.8% and the mass percentage content of Mn is 0.4 - 0.8%, some Fe will also form fine short rod-shaped or square-shaped Al-Fe phase or Al-Fe-Si phase, and Mn can also reduce the influence of Fe on the elongation rate of the aluminum alloy.

[0024] Since the mechanical properties of the heat-treatment-free die-cast aluminum alloy cannot be improved by age heat treatment, most of the solute atoms in the heat-treatment-free die-cast aluminum alloy of the present invention usually exist in the aluminum matrix in a solid-solution form. In addition to fine-grain strengthening, the strength increment of the heat-treatment-free die-cast aluminum alloy mainly comes from the pinning of dislocations by the lattice volume mismatch and elastic misfit caused by solid-solution atoms, that is, solid-solution strengthening.

[0025] During the storage and transportation processes after die-casting treatment of the heat-treatment-free die-cast aluminum alloy, natural aging will occur, that is, as the placement time prolongs, the strength increases. This natural aging is attributed to the aggregation effect of solute atoms in the aluminum alloy, that is, solute atom clusters. Solute atom clusters are the disordered aggregation of solute atoms in the aluminum matrix, with a size of several nanometers, usually composed of several to dozens of atoms with no definite crystal structure and disordered distribution.

[0026] The change in the strength of the heat-treatment-free die-cast aluminum alloy is mainly related to the size and volume fraction of solute atom clusters. During natural aging, the formation and growth of clusters are closely related to the change in the concentration of supersaturated quenched vacancies. And vacancies belong to thermal defects, and their concentration has an exponential function relationship with temperature. In the present invention, after die-casting treatment, the aluminum alloy parts are subjected to low-temperature quenching treatment to generate supersaturated vacancies to improve the mechanical properties of the heat-treatment-free die-cast aluminum alloy. Specifically, during the die-casting process, the equilibrium vacancy concentration is relatively large; during the subsequent quenching process, some vacancies at high temperature are retained, thus generating supersaturated vacancies; moreover, the low-temperature quenching treatment can also cause the aluminum alloy to shrink, generate plastic deformation, and reduce the solubility of elements in aluminum, increase the nucleation points of clusters, refine the α-Al phase and eutectic Si phase structures, so as to improve the yield strength, tensile strength and elongation rate of the aluminum alloy.

[0027] The addition of Cu, Mn, Mg, Zn, Ti, Sr, Fe, and B can also regulate the behavior of solute atom clusters in aluminum alloys. For example, the formation of original clusters can be affected by adjusting vacancies, and new clusters can be formed. After adding elements of Mg (0.2 - 0.6 wt%) and Cu (0.3 - 0.8 wt%) within a certain content range to the aluminum melt of the present invention, Mg atoms activate the diffusion of vacancies and promote the formation of Cu - Mg - Zn clusters, Mg - Si - Zn clusters, and Mg - Si - Cu - Zn clusters, significantly strengthening the clusters. The atomic radii of Mn and Sr are much larger than that of Al. The atoms of Mn and Sr within the above - mentioned content range form lattice distortions in the aluminum matrix. Coupled with the pinned vacancies, Mg - Si clusters, Cu - Mg clusters, and Mg - Si - Cu clusters added in the heat - treatable die - casting aluminum alloy, and promoting the growth of clusters, it further promotes the natural aging effect and improves the yield strength, tensile strength, and elongation rate of the heat - treatable die - casting aluminum alloy.

[0028] In summary, under the combined action of Si, Cu, Mn, Mg, Zn, Ti, Sr, Fe, Ge, and B within the above - mentioned content range, a heat - treatable aluminum alloy with excellent demolding performance, tensile strength, yield strength, and elongation rate is obtained. Detailed implementation manners

[0029] 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, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] An embodiment of the present invention provides a high - strength heat - treatable die - casting aluminum alloy, which contains Si with a mass percentage content of 8 - 10.5%, Fe with a mass percentage content of 0.2 - 0.8%, Cu with a mass percentage content of 0.3 - 0.8%, Mn with a mass percentage content of 0.2 - 0.8%, Mg with a mass percentage content of 0.2 - 0.6%, Zn with a mass percentage content of 0.1 - 0.5%, B with a mass percentage content of 0 - 0.01%, Sr with a mass percentage content of 0 - 0.05%, Ge with a mass percentage content of 0 - 0.1%, Ti with a mass percentage content of 0.01 - 0.25%, and Al and inevitable impurities.

[0031] In one embodiment, the high-strength heat-treatment-free die-casting aluminum alloy contains Si with a mass percentage content of 9-10%, Fe with a mass percentage content of 0.2-0.5%, Cu with a mass percentage content of 0.5-0.7%, Mn with a mass percentage content of 0.5-0.7%, Mg with a mass percentage content of 0.4-0.5%, Zn with a mass percentage content of 0.3-0.4%, B with a mass percentage content of 0.001-0.01%, Sr with a mass percentage content of 0.01-0.04%, Ge with a mass percentage content of 0.01-0.1%, and Ti with a mass percentage content of 0.05-0.3%.

[0032] The mass ratio of Cu to Mg is 1.5-4, preferably 2-3:1, and specifically can be 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, 3.1:1, 3.2:1, 3.3:1, 3.4:1, 3.5:1, 3.6:1, 3.7:1, 3.8:1, 3.9:1, or 4:1. When elements of Mg (0.2-0.6 wt%) and Cu (0.3-0.8 wt%) within a certain content range are added to the aluminum melt of the present invention and the mass ratio of Cu to Mg is 1.5-4, Mg atoms activate the diffusion of vacancies, significantly promote the formation of Mg-Si clusters, Cu-Mg clusters, and Mg-Si-Cu clusters, significantly strengthen the clusters, and greatly improve the yield strength, tensile strength, and elongation rate of the aluminum alloy.

[0033] The mass ratio of Mg to Ge is 2 - 40:1, preferably 15 - 25:1, and specifically can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 25:1, 30:1, 35:1, or 40:1. The mass ratio of Ti to B is 1 - 50:1, preferably 10 - 30:1, and further preferably 15 - 20:1, and specifically can be 1:1, 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, or 50:1. The mass ratio of Mn to Fe is 0.5 - 3:1, can be 0.5 - 0.6:1, 0.6 - 1:1, or 1 - 3:1, and specifically can be 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, or 3:1.

[0034] In the prior art in the field of aluminum alloys, the Mn content can be set according to the Fe content and the mass ratio of Mn to Fe. Generally, it is considered that when the mass ratio of Mn to Fe is less than 0.6:1 and greater than 1:1, the tensile strength, yield strength and elongation rate of the aluminum alloy will be reduced. Therefore, in order to obtain better tensile strength, yield strength and elongation rate, the mass ratio of Mn to Fe is usually set to 0.6-1:1. In the present invention, the mass ratio of Mn to Fe is set to 0.5-3:1 (preferably 0.5-0.6:1, more preferably 0.5-0.59:1). In this range, a heat-treatment-free aluminum alloy with good tensile strength, yield strength and elongation rate can be obtained, wherein the tensile strength is greater than 280 MPa, the yield strength is greater than 140 MPa, and the elongation rate is greater than 10%. This is because, during the die-casting process, the temperature cooling rate is relatively large. When the Fe content (0.2-0.4 wt%) is relatively small, Fe basically forms fine short rod-shaped or square-shaped Al-Fe phases or Al-Fe-Si phases, so that Fe has little influence on the elongation rate of the aluminum alloy, and there is no need to add a large amount of Mn to reduce the influence of Fe on the elongation rate of the aluminum alloy; moreover, the lattice constant of Mn is much larger than that of the Al matrix, and the Mn dissolved in the Al matrix will cause the internal structure of the Al matrix to be discontinuous, resulting in a sudden change in the dislocation cutting radius and a reduction in the elongation rate. Therefore, in the present invention, when the Fe content is set to 0.2-0.4%, the Mn content is set to 0.2-0.4%, and the mass ratio of Mn to Fe is set to 0.5-1:1, especially 0.5-0.6:1, better tensile strength, yield strength and elongation rate are obtained instead; when the mass percentage of Fe is 0.4-0.8%, the mass percentage content of Mn is 0.4-0.8%, and the mass ratio of Mn to Fe is 1-3:1, during the die-casting process, the temperature cooling rate is relatively large, and some Fe will also form fine short rod-shaped or square-shaped Al-Fe phases or Al-Fe-Si phases, and Mn can also reduce the influence of Fe on the elongation rate of the aluminum alloy.

[0035] Considering the demolding performance, the present invention also sets the sum of the mass percentage contents of Mn and Fe to 0.6-1.5%, preferably 0.6-1%, and specifically can be 0.6%, 0.62%, 0.64%, 0.66%, 0.68%, 0.7%, 0.72%, 0.74%, 0.76%, 0.78%, 0.8%, 0.82%, 0.84%, 0.86%, 0.88%, 0.9%, 0.92%, 0.94%, 0.96%, 0.98%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%. The present invention combines the Fe content set to 0.2-0.8%, the Mn content set to 0.2-0.8%, the mass ratio of Mn to Fe set to 0.5-3:1, and the sum of the mass percentage contents of Mn and Fe set to 0.6-1.5%, and obtains better demolding performance, tensile strength, yield strength, and elongation rate.

[0036] The mass percentage content of Si can be 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%, or 10.5%. The mass percentage content of Fe can be 0.2%, 0.22%, 0.24%, 0.26%, 0.28%, 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, 0.4%, 0.42%, 0.44%, 0.46%, 0.48%, 0.5%, 0.52%, 0.54%, 0.56%, 0.58%, 0.6%, 0.62%, 0.64%, 0.66%, 0.68%, 0.7%, 0.72%, 0.74%, 0.76%, 0.78%, or 0.8%. The mass percentage content of Cu can specifically be 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, 0.4%, 0.42%, 0.44%, 0.46%, 0.48%, 0.5%, 0.52%, 0.54%, 0.56%, 0.58%, 0.6%, 0.62%, 0.64%, 0.66%, 0.68%, 0.7%, 0.72%, 0.74%, 0.76%, 0.78%, or 0.8%. The mass percentage content of Mn can specifically be 0.2%, 0.22%, 0.24%, 0.26%, 0.28%, 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, 0.4%, 0.42%, 0.44%, 0.46%, 0.48%, 0.5%, 0.52%, 0.54%, 0.56%, 0.58%, 0.6%, 0.62%, 0.64%, 0.66%, 0.68%, 0.7%, 0.72%, 0.74%, 0.76%, 0.78%, or 0.8%. The mass percentage content of Mg can specifically be 0.2%, 0.22%, 0.24%, 0.26%, 0.28%, 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, 0.4%, 0.42%, 0.44%, 0.46%, 0.48%, 0.5%, 0.52%, 0.54%, 0.56%, 0.58%, or 0.6%. The mass percentage content of Zn can specifically be 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.26%, 0.28%, 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, 0.4%, 0.42%, 0.44%, 0.46%, 0.48%, or 0.5%.The mass percentage content of Ti can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, or 0.25%. The mass percentage content of B is 0 - 0.01%, specifically it can be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, or 0.01%. The mass percentage content of Sr can be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, or 0.05%. The mass percentage content of Ge 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%.

[0037] In the technical solution of the present invention, the high-strength heat-treatment-free die-cast aluminum alloy contains Si with a mass percentage content of 8 - 10.5%, Fe with a mass percentage content of 0.2 - 0.8%, Cu with a mass percentage content of 0.3 - 0.8%, Mn with a mass percentage content of 0.2 - 0.8%, Mg with a mass percentage content of 0.2 - 0.6%, Zn with a mass percentage content of 0.1 - 0.5%, B with a mass percentage content of 0 - 0.01%, Sr with a mass percentage content of 0 - 0.05%, Ge with a mass percentage content of 0 - 0.1%, and Ti with a mass percentage content of 0.01 - 0.25%. With the combined addition of Si, Fe, Cu, Mn, Mg, Zn, B, Sr, Ge, and Ti within the above content ranges, interacting with each other, the tensile strength of the heat-treatment-free aluminum alloy can be greater than 280 MPa, the yield strength can be greater than 140 MPa, and the elongation can be greater than 10%. Specifically:

[0038] (1) Si can improve the tensile strength, yield strength, and process fluidity of the aluminum alloy, but when the content is too high, it will reduce the elongation. Si can react with Al, Fe, Mg, Cu, B, etc. to form secondary phases such as Mg2Si, AlFeSi, AlFeSiCu, AlFeMgSi, AlCuMgSi, AlFeSiB, etc., to further improve the tensile strength and yield strength of the aluminum alloy;

[0039] (2) Mg can react with Al, Fe, Si, Cu, Zn, etc. to form secondary phases such as AlFeMgSi, (CuMg)Al2, AlCuMgSi, Mg2Si, Mg2Zn, Mg2SiZn, etc., to improve the tensile strength and yield strength of aluminum alloys. Among them, when Mg is dissolved in the CuAl2 phase and the AlFeSi phase, (CuMg)Al2 phase and AlFeSiMg phase are formed;

[0040] (3) Cu can react with Al, Fe, Si, Mg, Zn, etc. to form secondary phases such as CuAl2, AlFeSiCu, AlCuMgSi, Al2CuZn, (CuMg)Al2, etc., to improve the tensile strength and yield strength of aluminum alloys. It can also promote the precipitation of secondary phases such as Mg2Si, Mg2Zn, Mg2SiZn, etc., and improve the volume fraction and dispersion degree of the precipitated phases. Subsequent natural aging or heat treatment during vehicle painting baking can further improve the age hardening effect of Cu and Mg;

[0041] (4) Zn can react with Al, Mg, Cu, and Si, etc. to form secondary phases such as MgZn2, Mg2SiZn, Al2CuZn, etc., to improve the tensile strength and yield strength of aluminum alloys. Zn can eliminate elemental Si to reduce the influence of Si on the properties of aluminum alloys. It can also promote the precipitation of secondary phases such as Mg2Si, Mg2Zn, Mg2SiZn, Al2Cu, Al2CuMg, etc., and improve the volume fraction and dispersion degree of the precipitated phases; The combined addition of Zn and Mg can form the strengthening phase Mg / Zn2, significantly improving the tensile strength and yield strength of aluminum alloys; Zn increases the lattice distortion energy of the matrix, which will promote the migration of Mg, Cu, and Si atoms from the matrix to form more Cu-Mg-Zn clusters and Mg-Si-Zn clusters, improving the cluster strengthening effect;

[0042] (5) Fe can improve the tensile strength and yield strength of aluminum alloys, can improve the demolding performance, and can also react with Al, Si, Mg, Cu, B to form secondary phases such as Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu, AlFeSiB, etc., further improving the tensile strength and yield strength of aluminum alloys;

[0043] (6) Mn can react with Al, Fe, Si, Cu to form MnAl2, MnAl6, α-(Fe,Mn)Al6, A1 12 CuMn2, α-Al(FeMn)Si, τ(Cu2Mn3Al 20) The second phases such as

[0044] (7) Sr preferentially combines with Fe to form dispersion strengthening, reducing the solid solubility of Fe, so as to improve the yield strength and tensile strength of aluminum alloy; Sr can change the behavior of intermetallic compound phases crystallographically and can be used as a modifier to refine grains and the second phase in aluminum alloy through the heterogeneous nucleation theory or the twin trough mechanism. For example, Sr can change the morphology of eutectic silicon phase through modification to improve the elongation rate of aluminum alloy and reduce the tendency of sticking to the mold during die-casting; Sr can change the coarse needle-shaped β-AlFeSi and β-AlFeMnSi phases in the ingot into small granular Chinese character-shaped α-AlFeSi and α-Al(FeMn)Si phases, reducing the homogenization time of the ingot and improving the yield strength, tensile strength and elongation rate of aluminum alloy;

[0045] (8) The TiAl2 phase formed by the reaction of Ti with Al can be used as a non-spontaneous core during crystallization to refine grains, the second phase and precipitation phases, so as to improve the tensile strength, yield strength and elongation rate of aluminum alloy;

[0046] (9) B can undergo a boriding reaction with transition metal elements (including transition metal elements such as Fe), generating compounds such as ferroboron compounds that can be separated from the aluminum alloy liquid to purify the aluminum alloy liquid; B is easily adsorbed on the surface of the iron-rich phase, inhibiting the growth of the iron-rich phase, playing a role in controlling the size of the iron-rich phase, and can also prevent the formation of the iron-rich phase in the aluminum alloy liquid; B can inhibit the segregation of Ti3Al. Therefore, the effect is better when Ti and B are used together; B can also refine grains and the second phase to improve the elongation of the aluminum alloy.

[0047] (10) Ge is easy to capture the quenching vacancies in the α-Al matrix and form "Ge-vacancy pairs", "retaining" the quenching vacancies in the α-Al matrix, promoting the artificial aging precipitation kinetics and enhancing the precipitation strengthening effect; Ge not only replaces some Si and Cu atoms in the metastable precipitation phase, but also refines the precipitation phase and increases the precipitation phase density, significantly enhancing the precipitation strengthening effect of the aluminum alloy; during the low-temperature quenching and holding process, the aluminum alloy matrix shrinks, undergoes plastic deformation, and generates internal stress; Ge can reduce the solubility of elements in aluminum, increase the nucleation points of clusters. During the process of rising to room temperature after the low-temperature quenching and holding treatment, these nucleation points combine with the "Ge-vacancy pairs" formed by quenching vacancies under the action of internal stress, rapidly increasing the volume fractions of Cu-Mg clusters, Mg-Si clusters, and Mg-Si-Cu clusters to improve the yield strength, tensile strength, and elongation of the heat-treatable aluminum alloy; in addition, Ge elements can also replace Si and Cu atoms in Cu-Mg clusters, Mg-Si clusters, and Mg-Si-Cu clusters, increasing the resistance of dislocations to cut through these clusters; when adding RE elements, Ge and RE cooperate to further refine the cluster size and increase the volume fraction of clusters.

[0048] The combined action of Si, Cu, Mn, Mg, Zn, Ti, Sr, Ge, and Fe within the above content ranges can significantly improve the tensile strength and yield strength of the aluminum alloy; the combined action of Mn, B, Ti, Ge, and Sr within the above content ranges can refine grains, the second phase, and the precipitation phase to improve the elongation of the aluminum alloy; the combined action of Cu, Ge, and Zn within the above content ranges can promote the precipitation of the second phase, increase the volume fraction and dispersion degree of the precipitation phase, and further improve the tensile strength, yield strength, and elongation of the aluminum alloy; the combined action of Fe, Sr, and Mn within the above content ranges can improve the demolding performance of the aluminum alloy.

[0049] Since the mechanical properties of the heat-treatable die-cast aluminum alloy cannot be improved by age heat treatment, most of the solute atoms in the heat-treatable die-cast aluminum alloy of the present invention usually exist in the aluminum matrix in a solid solution form. In addition to fine grain strengthening, the strength increment of the heat-treatable die-cast aluminum alloy mainly comes from the pinning of dislocations by the lattice volume mismatch and elastic mismatch caused by solid solution atoms, that is, solid solution strengthening.

[0050] During the storage and transportation processes after die-casting treatment, natural aging occurs in the heat-treatable die-cast aluminum alloy, that is, the strength increases as the placement time prolongs. This natural aging is attributed to the aggregation effect of solute atoms in the aluminum alloy, namely solute atom clusters. Solute atom clusters are the disordered aggregation of solute atoms in the aluminum matrix, with a size of several nanometers, usually composed of several to dozens of atoms with no definite crystal structure and disordered distribution.

[0051] The change in the strength of the heat-treatable die-cast aluminum alloy is mainly related to the size and volume fraction of solute atom clusters. During natural aging, the formation and growth of clusters are closely related to the change in the concentration of supersaturated quenched vacancies. And vacancies belong to thermal defects, and their concentration has an exponential function relationship with temperature. In the present invention, after die-casting treatment, the aluminum alloy parts are subjected to low-temperature quenching treatment to generate supersaturated vacancies, so as to improve the mechanical properties of the heat-treatable die-cast aluminum alloy. Specifically, during the die-casting treatment process, the equilibrium vacancy concentration is relatively large; during the subsequent quenching treatment process, some vacancies at high temperature are retained, thus generating supersaturated vacancies; moreover, the low-temperature quenching treatment can also cause the aluminum alloy to shrink, generate plastic deformation, and reduce the solubility of elements in aluminum, increase the nucleation points of clusters, refine the α-Al phase and eutectic Si phase structures, so as to improve the yield strength, tensile strength and elongation rate of the aluminum alloy.

[0052] The addition of Cu, Mn, Mg, Zn, Ti, Sr, Fe and B can also regulate the behavior of solute atom clusters in the aluminum alloy, such as affecting the formation of the original clusters and forming new clusters by regulating vacancies. After adding elements of Mg (0.2-0.6wt%) and Cu (0.3-0.8wt%) within a certain content range to the aluminum liquid of the present invention, Mg atoms activate the diffusion of vacancies and promote the formation of Mg-Si clusters, Cu-Mg clusters, and Mg-Si-Cu clusters, significantly strengthening the clusters. The atomic radii of Mn and Sr are much larger than that of Al. The atoms of Mn and Sr within the above content range form lattice distortion in the aluminum matrix. Coupled with the pinned vacancies and Mg-Si clusters, Cu-Mg clusters, and Mg-Si-Cu clusters added in the heat-treatable die-cast aluminum alloy, and promoting the growth of clusters, further promoting the natural aging effect, so as to improve the yield strength, tensile strength and elongation rate of the heat-treatable die-cast aluminum alloy.

[0053] In summary, under the combined action of Si, Cu, Mn, Mg, Zn, Ti, Sr, Fe, Ge and B within the above content range, a heat-treatable aluminum alloy with excellent demolding performance, tensile strength, yield strength and elongation rate is obtained.

[0054] The high-strength heat-treatment-free die-casting aluminum alloy further contains Ca with a mass percentage content of 0-0.06%, specifically, it can be 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, or 0.06%. The high-strength heat-treatment-free die-casting aluminum alloy further contains Sn with a mass percentage content of 0-0.1%, specifically, it 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%. The high-strength heat-treatment-free die-casting aluminum alloy further contains RE with a mass percentage content of 0-0.2%, specifically, it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%. RE is at least one of La, Ce, Pr, Nd, Er, Sm, Y, Gd, and Sc. The high-strength heat-treatment-free die-casting aluminum alloy further contains Zr with a mass percentage content of 0-0.2%, specifically, it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%.

[0055] In one embodiment, RE is La, Y, and Sm, and the ratio of the three is 0.01-0.03:0.02-0.05:1. In another embodiment, RE is Pr, Er, and Nd, and the ratio of the three is 0.02-0.05:0.03-0.08:1. In yet another embodiment, RE is Sm, Y, and Gd, and the ratio of the three is 0.06-0.08:0.1-0.2:1. Adding multiple rare earth elements in combination has a better refinement effect.

[0056] The mass ratio of Ca, Sn and RE is 0.05-10:0.01-10:1, preferably 0.01-10:0.05-5:1. Specifically, it can be 0.05:0.01:1, 0.05:0.05:1, 0.05:0.1:1, 0.05:0.5:1, 0.05:1:1, 0.05:5:1, 0.05:10:1, 0.1:0.01:1, 0.1:0.05:1, 0.1:0.1:1, 0.1:0.5:1, 0.1:1:1, 0.1:5:1, 0.1:10:1, 0.5:0.01:1, 0.5:0.05:1, 0.5:0.1:1, 0.5:0.5:1, 0.5:1:1, 0.5:5:1, 0.5:10:1, 1:0.01:1, 1:0.05:1, 1:0.1:1, 1:0.5:1, 1:1:1, 1:5:1, or 1:10:1.

[0057] The mass ratio of Er and Zr can be 0.5-5:1, preferably 1-3:1. Specifically, it can be 0.5:1, 1:1, 2:1, 3:1, 4:1, or 5:1. The mass ratio of RE and Zr is 0.1-1:1, preferably 0.5-1:1. Specifically, it can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, or 1:1.

[0058] In the technical solution of the present invention, the high-strength heat-treatment-free die-casting aluminum alloy may further contain Ca with a mass percentage content of 0-0.06%, Sn with a mass percentage content of 0-0.1%, and RE with a mass percentage content of 0-0.2%. Ca can improve the β-Fe phase to reduce the harm of Fe, and can also react with Al, Cu, Zn, and Si to form second phases such as Al4Ca, Al2Ca3, AlCa2, AlCaCu, CaZn, CaAlZn, and Al2CaSi2 to improve the tensile strength and yield strength of the aluminum alloy. Ca can also refine the eutectic structure, improve the β-Fe phase, and has a modification effect on the aluminum alloy; Sn can react with Al, Mg, Sc, etc. to form second phases such as Al9Sn7, Al6Sn5, Al5Sn2, Al3Sn4, Mg2Sn, and Mg2ScSn to improve the tensile strength and yield strength of the aluminum alloy; Sn can promote the precipitation of second phases such as Mg2Si, Mg2Zn, Mg2SiZn, and Al2Cu to reduce the solid solubility of the above elements in the aluminum matrix; RE is distributed in the same region as the Fe phase, can form a rare-earth active film on the surface of the iron-containing phase or combine with atoms such as Al, Fe, and Ti to form rare-earth compounds such as AlFeRE, prevent the formation of brittle β-AlFeSi phase at the grain boundary, effectively reduce the solid solution of harmful elements in the aluminum matrix, and improve the tensile strength and yield strength of the aluminum alloy. RE can transform the long strip-shaped β-Fe phase into a spherical ɑ-Fe phase and modify the elemental Si. RE can also promote the precipitation of dispersed phases such as CuAl2 and (CuMg)Al2 to further improve the tensile strength and yield strength of the aluminum alloy. RE is a surface-active element with a radius larger than that of Al, cannot enter the α-Al lattice, but can segregate at the grain boundary or adsorb on the solid-liquid interface to form subcooling, increasing the chance of dendrite fusing, thereby refining the grains, second phases, and precipitation phases (for example, it can refine Al3Fe, Al3ScZr, AlSiMo, and Mg2Si phases), and further improving the tensile strength, yield strength, and elongation of the aluminum alloy. The combination of Ca and RE can significantly refine the grains and second phases, thereby improving the tensile strength, yield strength, and elongation. After adding a certain content range of RE (0-0.2wt%) and Zr (0.01-0.2wt%), and when the mass ratio of RE to Zr is 0.1-1:1, the high-distortion coherent solid solution elements can promote the formation of atomic clusters such as high-density Mg-Si clusters and Cu-Mg clusters, and significantly inhibit the diffusion of atoms in the atomic clusters, improving the stability of the atomic clusters, and improving the yield strength, tensile strength, and elongation of the aluminum alloy.

[0059] The high-strength heat-treatment-free die-casting aluminum alloy also contains Co with a mass percentage content of 0 - 0.2%, specifically it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%. The high-strength heat-treatment-free die-casting aluminum alloy also contains Be with a mass percentage content of 0 - 0.05%, specifically it can be 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, or 0.05%. The high-strength heat-treatment-free die-casting aluminum alloy also contains Bi with a mass percentage content of 0 - 0.2%, specifically it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%. The high-strength heat-treatment-free die-casting aluminum alloy also contains Cd with a mass percentage content of 0 - 0.1%, specifically it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. The high-strength heat-treatment-free die-casting aluminum alloy also contains Cr with a mass percentage content of 0 - 0.2%, specifically it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%. The high-strength heat-treatment-free die-casting aluminum alloy also contains Sb with a mass percentage content of 0 - 0.2%, specifically it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%.The high-strength heat-treatment-free die-casting aluminum alloy further contains V with a mass percentage content of 0-0.3%, specifically, it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, or 0.3%.

[0060] The mass ratio of Mg to Sb is 1-20:1, preferably 5-15:1, and further preferably 5-10:1. Specifically, it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, or 20:1.

[0061] The mass ratio of (Mn + RE) to Fe is 0.5-3:1 (that is, the ratio of the sum of the mass percentage contents of Mn + RE to the mass percentage content of Fe), preferably 0.5-1:1. Specifically, it can be 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, or 3:1. During the die-casting process, the temperature cooling rate is relatively large. When the mass percentage of Fe is 0.2-0.4%, Fe basically forms fine short rod-shaped or square-shaped Al-Fe phase or Al-Fe-Si phase. In this way, Fe within this content range has little impact on the elongation rate of the aluminum alloy, and there is no need to add a large amount of Mn to reduce the impact of Fe on the elongation rate of the aluminum alloy. RE can also round the fine short rod-shaped or square-shaped Al-Fe phase or Al-Fe-Si phase to improve the elongation rate. At this time, the mass percentage content of Mn can be 0.2-0.4%, and the mass ratio of (Mn + RE) to Fe is 0.5-1:1; when the mass percentage of Fe is 0.4-0.8%, the mass percentage content of Mn is 0.4-0.8%, and the mass ratio of (Mn + RE) to Fe is 1-3:1, part of Fe will also form fine short rod-shaped or square-shaped Al-Fe phase or Al-Fe-Si phase. Mn can also reduce the impact of Fe on the elongation rate of the aluminum alloy, and RE can also round the fine short rod-shaped or square-shaped Al-Fe phase or Al-Fe-Si phase to improve the elongation rate.

[0062] The mass ratio of (Mn + RE + Zr) to Fe is 0.5 - 3:1 (i.e., the ratio of the sum of the mass percentage contents of Mn, RE, and Zr to the mass percentage content of Fe), preferably 0.5 - 1:1, specifically it can be 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, or 3:1. During the die-casting process, the temperature cooling rate is relatively large. When the mass percentage of Fe is 0.2 - 0.4%, Fe basically forms fine short rod-shaped or block-shaped Al-Fe phase or Al-Fe-Si phase. In this case, Fe within this content range has little effect on the elongation of the aluminum alloy, and there is no need to add a large amount of Mn to reduce the influence of Fe on the elongation of the aluminum alloy. RE can also round the fine short rod-shaped or block-shaped Al-Fe phase or Al-Fe-Si phase to improve the elongation. At this time, the mass percentage content of Mn can be 0.2 - 0.4%, and the mass ratio of (Mn + RE + Zr) to Fe is 0.5 - 1:1; when the mass percentage of Fe is 0.4 - 0.8%, the mass percentage content of Mn is 0.4 - 0.8%, and the mass ratio of (Mn + RE + Zr) to Fe is 1 - 3:1, some Fe will also form fine short rod-shaped or block-shaped Al-Fe phase or Al-Fe-Si phase. Mn can also reduce the influence of Fe on the elongation of the aluminum alloy, and the combination of RE and Zr can also round the fine short rod-shaped or block-shaped Al-Fe phase or Al-Fe-Si phase to improve the elongation.

[0063] When RE, Ti, and B are combined, TiB2 is not easily agglomerated and precipitated, ensuring the number of effective TiB2, and prolonging the effective action time of Ti and B. This is because RE improves the wettability of the aluminum liquid to the boride; Ti can also assist B, Mn, Cr, and RE to further refine the grains and the second phase; B can react with Al, Si, and Fe to form the AlFeSiB second phase to improve the tensile strength and yield strength of the aluminum alloy; B can also cooperate with Mn, Cr, and RE to prevent the formation of the iron-rich phase.

[0064] The combined action of Mn, Cr, and RE can effectively improve the morphology of Fe, reduce the Fe content, and refine and control the grain size, resulting in an aluminum alloy with better tensile strength, yield strength, and elongation. Specifically, Mn can significantly refine the recrystallized grains and the second phase, effectively transform the coarse needle-like or flaky β-AlFeSi phase into small granular α-Al(FeMn)Si dispersed particles to improve the Fe morphology, and can also react with Fe to form the α-(Fe,Mn)Al6 phase to reduce the Fe content. Obviously, Mn can play the roles of reducing the Fe content, improving the Fe morphology, and refining the grains and the second phase. Cr can effectively transform the needle-like β-Fe phase into the α-Fe phase to improve the Fe morphology, and can also react with Fe to form dispersed phases such as (CrFe)Al7 and (CrMn)Al 12 and other dispersed phases to reduce the Fe content. In addition, dispersed phases such as AlCrSi and Mg2(SiCr) are also formed, and the precipitation volume fraction and uniform distribution of the dispersed phases are increased, enhancing the mechanical properties of the alloy. The distribution region of RE is consistent with that of the Fe phase, and it can form a rare earth active film on the surface of the Fe phase, preventing the formation of brittle β-AlFeSi phase at the grain boundaries. In addition, Mn can also significantly refine the grain size, Cr can hinder the growth of grains, refine the grains and the second phase, and RE can also refine the grains. When Mn, Cr, and RE are added together, the Fe morphology can be effectively improved; when Mn and Cr are added together, they can form the dispersed α-Al(FeMnCr)Si phase with Fe and Si. The α-Al(FeMnCr)Si phase has a high bulk density and strong thermal stability. As the standing time prolongs, some of these phases sink to the bottom and some pin the grain boundaries, effectively refining and controlling the grain size. In addition, Mn, Cr, and RE can also react with trace impurities in the aluminum alloy liquid to generate phases such as Al-Cr-X, Al-Mn-X, and Al-RE-X (X is an impurity element). These phases can serve as grain nucleation sites to increase the nucleation rate, refine the grains, purify the aluminum alloy, and improve the tensile strength, yield strength, fluidity, and elongation of the aluminum alloy. In summary, the Mn, Cr, and RE within the above content ranges interact synergistically to refine the grains while improving the Fe morphology and reducing the Fe content, obtaining an aluminum alloy with excellent comprehensive properties.

[0065] The mass ratio of Cr to V is 0.1 - 10:1, preferably 0.5 - 10:1, and specifically can be 0.1:1, 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1. The mass ratio of Bi, Cd, and Mg is 0.01 - 1:0.01 - 0.5:1, preferably 0.05 - 1:0.05 - 0.1:1, and specifically can be 0.01:0.01:1, 0.01:0.05:1, 0.01:0.1:1, 0.01:0.5:1, 0.05:0.01:1, 0.05:0.05:1, 0.05:0.1:1, 0.05:0.5:1, 0.1:0.01:1, 0.1:0.05:1, 0.1:0.1:1, 0.1:0.5:1, 0.5:0.01:1, 0.5:0.05:1, 0.5:0.1:1, 0.5:0.5:1, 1:0.01:1, 1:0.05:1, 1:0.1:1, or 1:0.5:1. The mass ratio of Co, Be, and Fe is 0.01 - 1:0.01 - 0.25:1, preferably 0.05 - 0.5:0.05 - 0.1:1, and specifically can be 0.01:0.01:1, 0.01:0.05:1, 0.01:0.1:1, 0.01:0.2:1, 0.01:0.25:1, 0.05:0.01:1, 0.05:0.05:1, 0.05:0.1:1, 0.05:0.2:1, 0.05:0.25:1, 0.1:0.01:1, 0.1:0.05:1, 0.1:0.1:1, 0.1:0.2:1, 0.1:0.25:1, 0.5:0.01:1, 0.5:0.05:1, 0.5:0.1:1, 0.5:0.2:1, 0.5:0.25:1, 1:0.01:1, 1:0.05:1, 1:0.1:1, 1:0.2:1, or 1:0.25:1.

[0066] In one embodiment, the high-strength heat-treatment-free die-cast aluminum alloy further contains Te with a mass percentage content of 0 - 0.1%, and specifically 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%. When Sb and Te are compounded and added, fine petal-shaped primary crystals can be formed to improve the tensile strength and elongation rate of the aluminum alloy.

[0067] In the technical solution of the present invention, the high-strength heat-treatment-free die-casting aluminum alloy further contains Co with a mass percentage content of 0-0.2%, Be with a mass percentage content of 0-0.05%, Bi with a mass percentage content of 0-0.2%, Cd with a mass percentage content of 0-0.1%, Cr with a mass percentage content of 0-0.2%, Zr with a mass percentage content of 0-0.2%, and Sb with a mass percentage content of 0-0.2%. Co can promote the formation of the Fe spherical phase, generate the small-particle-size Al3(Fe,Co) phase that can improve the mechanical properties of the aluminum alloy, and can also transform the coarse needle-shaped and flaky Al3Fe phase into α-Al 15(Fe,Co)3Si2 (which can be in the shape of granules, small flower-like shapes or fine strips), and has a refining effect on the Al3Fe phase, further improving the tensile strength, yield strength, and elongation rate of the aluminum alloy; at the same time, adding Ce and Co can not only improve the thermal stability of the aluminum alloy, but also promote the formation of <001> and <111> orientations to improve the tensile strength and yield strength of the aluminum alloy; Be can react with Al, Fe, Si, etc. to form second phases such as Be-Fe(Al8Fe2SiBe)2, to improve the tensile strength and yield strength of the aluminum alloy. Be can change the eutectic Si phase from a flake phase to a fine phase to refine the Si phase, to reduce or eliminate the adverse effects of Si on the performance of the aluminum alloy. Be can transform the plate-like β intermediate phase into a relatively harmless Chinese character-shaped Be-Fe(Al8Fe2SiBe) phase and prevent the formation of needle-like β-Fe phase, to reduce or eliminate the adverse effects of Fe on the performance of the aluminum alloy, and can also promote the formation and precipitation of phases such as Mg2Si, Mg2Zn, Mg2SiZn, Al2Cu, etc., to reduce the solid solubility of the above elements in the aluminum matrix. Be can also form an active film on the surface of impurity element phases such as Fe, prevent the growth of impurity elements, and can segregate at grain boundaries or adsorb on the solid-liquid interface to form differential supercooling, promoting an increase in the chance of dendrite fusing, thereby refining the grains. Among them, the refining effect of Be increases with the increase of Be content; Bi can react with Mg and Cd, etc. to form second phases such as Mg3Bi2, Mg3(BiCd)2, etc., to improve the tensile strength and yield strength of the aluminum alloy; Cd can refine α-Al, and react with Al, RE, Cu, Mg, Si, Fe, Sb, Bi, etc. in the melt to form strengthening phases such as REAl2Cd3, Al3Cd, Al2Cd3, (CuCd)Al2, Mg2(SiCdREFe), Mg3(SbCd)2, Mg3(BiCd)2, etc., to improve the tensile strength and yield strength of the aluminum alloy and reduce the Fe content. Cd will form a large number of Cd-vacancy clusters during the aging stage, promoting and accelerating the precipitation of the CuAl2 phase, to reduce the solid solubility of the above elements in the aluminum matrix; Cr can transform the needle-like β-Fe phase into the α-Fe phase to improve the morphology of Fe to eliminate the harmful effects of Fe, and can also easily form a dispersion phase with Fe, to reduce the Fe content and reduce the harmful effects of Fe. (CrFe)Al7 and (CrMn)Al formed by Cr in the aluminum alloy liquid 12Intermetallic compounds such as can hinder the nucleation and growth process of recrystallization, improve the yield strength, tensile strength, and elongation rate of aluminum alloys. During the solution stage, various chromium-containing fine compounds formed by Cr in aluminum alloys can dissolve in the α-phase again. During the natural aging stage, various Cr-containing phases precipitate dispersedly, such as α-AlCrSi dispersed phase, etc. These Cr-containing phases can serve as the cores for the heterogeneous nucleation of β" and θ" phases, accelerate the formation of β" and θ" phases, and improve the yield strength and tensile strength of aluminum alloys. At the same time, the dispersed precipitation of Cr-containing phases in the matrix will inevitably have a certain delaying effect on the formation of θ′ phases precipitated at the grain boundaries. Mn and Cr can also form dispersed α-Al(FeMnCr)Si phases with Fe and Si. The α-Al(FeMnCr)Si phase has a high bulk density and strong thermal stability, and pinning the grain boundaries can effectively control the grain growth process, thereby controlling the grain size. When Cr and Mo are added in combination, multi-element phases rich in Cr and Mo can be generated, significantly improving the tensile strength of aluminum alloys. V can react with Al to form refractory compounds such as VAl 11 etc., which play a role in refining grains during the melting and casting process. V can also refine the recrystallized structure and increase the recrystallization temperature to improve the tensile strength, yield strength, and elongation rate of aluminum alloys. During the die-casting process, the temperature cooling rate is relatively large. The metastable phase Al3V obtained by the rapid cooling method will form a large number of fine and dispersed ellipsoidal Al(VCrTi)Si phases with Cr, Si, and Ti in the aluminum alloy, which can prevent dislocation movement and the nucleation and growth of recrystallization, significantly improving the tensile strength and yield strength of aluminum alloys. Zr can react with Al, RE, etc. to form second phases such as Al3ScZr and (Zr,RE)Al3 to improve the tensile strength and yield strength of aluminum alloys. Zr can also promote the precipitation of phases such as Mg2Sn, Mg2Si, Mg3Sb2, and CuAl2 to reduce the solid solubility of the above elements in the aluminum matrix. Zr can also refine grains and further improve the elongation rate of aluminum alloys. The addition of B can transform Zr from the solid solution state to the precipitation state, existing in the form of fine plate-like second-phase particles inside and at the grain boundaries, reducing lattice distortion, improving the orderliness of the aluminum matrix, and enhancing the tensile strength and yield strength of aluminum alloys. The combined action of Er and Zr can promote the precipitation of β″ phase and make the β″ phase finer and more dispersed. The synergistic effect of Er and Zr can significantly inhibit the recrystallization of Al-Fe alloys.

[0068] The mutual cooperation and interaction of Co, Be, Bi, Cd, Cr, V, Zr, Sn, and Sb can significantly improve the tensile strength, yield strength, and elongation rate of aluminum alloys. Co can react with Al, Fe, Si, etc. to form Al 15Second phases such as (Fe,Co)3Si2 and Al3(Fe,Co) etc. Be can react with Al, Fe, Si, etc. to form second phases such as Be-Fe(Al8Fe2SiBe)2 etc. Al, Mg, Bi, Sn, Si, Cr, V, Cd and Sb can react with each other to form second phases such as Mg3(SbCd)2, Mg2(SnCd), Mg3(BiCd)2, AlCrSi, Al(VCrTi)Si, Mg2(SiCr), Mg3Bi2, Mg2Sn, Mg3Sb2 etc., so as to improve the tensile strength and yield strength of the aluminum alloy; the compound addition of Mn and Cr can improve the tensile strength and yield strength of the aluminum alloy, control the grain structure and postpone dynamic recrystallization, and can also transform the coarse AlFeSi phase into granular Al(MnCrFe)Si phase, thereby reducing the harm of impurity element Fe; Zr, Cd, Be can promote the precipitation of the precipitation phase; Co, Be, Cr, V, Zr can also refine the grains and precipitation phase; the combination of Be and Sc can also improve the morphology of acicular Fe-containing phase, and improve the yield strength, tensile strength and elongation of the aluminum alloy; the combination of Er and Zr can promote the precipitation of β″ phase and make the β″ phase finer and more dispersed, and the synergistic effect of Zr and Er can significantly inhibit the recrystallization of Al-0.4Fe alloy. Thus, Co, Be, Bi, Cd, Cr, V, Zr, Sn, and Sb cooperate and interact with each other. After promoting the precipitation of the precipitation phase, the grains and precipitation phase are refined to improve the tensile strength, yield strength and elongation of the aluminum alloy.

[0069] The high-strength heat-treatment-free die-cast aluminum alloy also contains Ag with a mass percentage content of 0-0.1%, specifically it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09% or 0.1%. The high-strength heat-treatment-free die-cast aluminum alloy also contains Nb with a mass percentage content of 0-0.2%, specifically it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19% or 0.2%. The high-strength heat-treatment-free die-cast aluminum alloy also contains In with a mass percentage content of 0-0.2%, specifically it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19% or 0.2%.

[0070] The mass ratio of Mg to Ag is 2 - 40:1, preferably 10 - 20:1, and specifically can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 25:1, 30:1, 35:1, or 40:1. The mass ratio of Mg and Nb is 1 - 20:1, preferably 1 - 10:1, and specifically can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, or 20:1. The mass ratio of Cu to In is 2 - 20:1, preferably 10 - 15:1, and specifically can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, or 20:1.

[0071] In the technical solution of the present invention, the high-strength heat-treatment-free die-cast aluminum alloy further contains Ag with a mass percentage content of 0 - 0.1%, Nb with a mass percentage content of 0 - 0.2%, and In with a mass percentage content of 0 - 0.2%. Ag can promote the precipitation of the second phase (such as Al2Cu, Mg2Si, Mg3Sb2, and Mg3Bi2, etc.), refine the precipitated phase and increase the density of the precipitated phase, enhance the precipitation strengthening effect of the aluminum alloy, thereby improving the tensile strength, yield strength, and elongation of the aluminum alloy. In can react with Al and Cu to form second phases such as AlIn and CuIn, etc., to improve the tensile strength and yield strength of the aluminum alloy; In can also refine the grains to improve the elongation of the aluminum alloy. Nb can react with Al and B to form high-temperature strengthening metal compounds such as AlNb3, AlNb, Al3Nb, NbB2, etc. Part of Nb can be distributed in the matrix grain boundaries in a dispersed phase, which can significantly improve the yield strength and tensile strength of the aluminum alloy. Nb can refine the grains and the second phase to improve the elongation of the aluminum alloy. The lattice mismatch constant between NbB2 and Al (30.6%) is smaller than the lattice mismatch constant between TiB2 and Al (34.0%). Only considering the mutual combination with Al, NbB2 is more likely to become a potential heterogeneous nucleation site than TiB2. The cooperation of Ag, In, and Nb can significantly promote the precipitation of the second phase and refine the grains and the precipitated phase. Specifically, In can react with Al and Cu to form second phases such as AlIn and CuIn; Nb, Ti, and Al can form second phases such as TiAl-Nb; Ag can promote the precipitation of the second phase and refine the precipitated phase. Nb and In can also refine the grains and the second phase, thus achieving the purpose of improving the tensile strength, yield strength, and elongation of the aluminum alloy at the same time.

[0072] The high-strength heat-treatment-free die-casting aluminum alloy also contains Mo with a mass percentage content of 0 - 0.2%, specifically it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%.

[0073] The mass ratio of Fe to Mo is 1 - 20:1, preferably 1 - 10:1, specifically it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, or 20:1.

[0074] In the technical solution of the present invention, the high-strength heat-treatment-free die-casting aluminum alloy also contains Moe with a mass percentage content of 0 - 0.2%. Mo can also react with Al, Si, Fe, etc. to generate second phases such as AlMo, AlSiMo, AlSiFeMo, etc., which are distributed in the form of dispersed phases at the grain boundaries of the aluminum matrix; Mo can also refine the grains and improve the morphology of Fe-containing intermetallic compounds, further improving the tensile strength, yield strength and elongation of the aluminum alloy. Ge can react with Al and Si, etc. to generate second phases such as Al9Ge7, Al6Ge5, Al5Ge2, Al3Ge4, SiGe.

[0075] In an embodiment of the present invention, the high-strength heat-treatment-free die-casting aluminum alloy contains Si with a mass percentage content of 8 - 10.5%, Fe with a mass percentage content of 0.2 - 0.8%, Cu with a mass percentage content of 0.3 - 0.8%, Mn with a mass percentage content of 0.2 - 0.8%, Mg with a mass percentage content of 0.2 - 0.6%, Zn with a mass percentage content of 0.1 - 0.5%, B with a mass percentage content of 0 - 0.01%, Sr with a mass percentage content of 0 - 0.05%, Ge with a mass percentage content of 0 - 0.1%, Ti with a mass percentage content of 0.01 - 0.25%, Ca with a mass percentage content of 0.01 - 0.05%, Sn with a mass percentage content of 0.01 - 0.1%, Co with a mass percentage content of 0.01 - 0.1%, Be with a mass percentage content of 0.01 - 0.05%, and Sb with a mass percentage content of 0.01 - 0.1%.

[0076] In another embodiment of the present invention, the high-strength heat-treatment-free die-casting aluminum alloy contains Si with a mass percentage content of 8-10.5%, Fe with a mass percentage content of 0.2-0.8%, Cu with a mass percentage content of 0.3-0.8%, Mn with a mass percentage content of 0.2-0.8%, Mg with a mass percentage content of 0.2-0.6%, Zn with a mass percentage content of 0.1-0.5%, B with a mass percentage content of 0-0.01%, Sr with a mass percentage content of 0-0.05%, Ge with a mass percentage content of 0-0.1%, Ti with a mass percentage content of 0.01-0.25%, Zr with a mass percentage content of 0.01-0.1%, Mo with a mass percentage content of 0.01-0.1%, Cr with a mass percentage content of 0.01-0.1%, V with a mass percentage content of 0.05-0.2%, La with a mass percentage content of 0.01-0.03%, Ce with a mass percentage content of 0.01-0.02%, Sm with a mass percentage content of 0.01-0.05%, Y with a mass percentage content of 0.01-0.05%, and Gd with a mass percentage content of 0.01-0.05%.

[0077] In yet another embodiment of the present invention, the high-strength heat-treatment-free die-casting aluminum alloy contains Si with a mass percentage content of 8-10.5%, Fe with a mass percentage content of 0.2-0.8%, Cu with a mass percentage content of 0.3-0.8%, Mn with a mass percentage content of 0.2-0.8%, Mg with a mass percentage content of 0.2-0.6%, Zn with a mass percentage content of 0.1-0.5%, B with a mass percentage content of 0-0.01%, Sr with a mass percentage content of 0-0.05%, Ge with a mass percentage content of 0-0.1%, Ti with a mass percentage content of 0.01-0.25%, Nb with a mass percentage content of 0.01-0.1%, Cd with a mass percentage content of 0.01-0.1%, Bi with a mass percentage content of 0.01-0.1%, Ag with a mass percentage content of 0.01-0.05%, and In with a mass percentage content of 0.01-0.1%.

[0078] The present invention also provides a method for preparing a high-strength heat-treatment-free die-casting aluminum alloy, comprising the following steps:

[0079] Perform a first heat treatment on the Al source (preferably pure aluminum, specifically electrolytic aluminum), heat it to 750-830 °C to obtain molten aluminum;

[0080] Add Si source, Fe source, Cu source, Mn source, Mg source, Zn source, B source, Sr source, Ge source, and Ti source to the molten aluminum, and perform a second heat treatment to obtain an alloy liquid; and

[0081] The alloy liquid is subjected to refining treatment, slag skimming treatment, and die-casting treatment to obtain aluminum alloy parts; and

[0082] The aluminum alloy parts are subjected to cryogenic quenching treatment to obtain a high-strength heat-treatment-free die-casting aluminum alloy. The high-strength heat-treatment-free die-casting aluminum alloy contains Al, and also contains Si with a mass percentage content of 8-10.5%, Fe with a mass percentage content of 0.2-0.8%, Cu with a mass percentage content of 0.3-0.8%, Mn with a mass percentage content of 0.2-0.8%, Mg with a mass percentage content of 0.2-0.6%, Zn with a mass percentage content of 0.1-0.5%, B with a mass percentage content of 0-0.01%, Sr with a mass percentage content of 0-0.05%, Ge with a mass percentage content of 0-0.1%, and Ti with a mass percentage content of 0.01-0.25%.

[0083] The Si source, Fe source, Cu source, Mn source, Mg source, Zn source, B source, Sr source, Ge source, and Ti source can be added in the form of elements or alloys. Except for primary aluminum, the Al source can also be recycled aluminum. When using recycled aluminum, it is necessary to detect the composition and content of the molten recycled aluminum liquid, and then calculate the element content added to the recycled aluminum liquid according to the detection results to obtain the heat-treatment-free aluminum alloy of the present invention.

[0084] Ice water or liquid nitrogen can be used for cryogenic quenching treatment. The temperature of the cryogenic quenching treatment is -200~0°C, specifically -200°C, -150°C, -100°C, -50°C, -10°C, or 0°C. The time of the cryogenic quenching treatment is 0.1~10h, specifically 0.1h, 0.5h, 1h, 5h, or 10h. It can be understood that ice / ice water can be added in time and liquid nitrogen can be replenished in time to maintain the temperature of the cryogenic quenching treatment not greater than 0°C, retain as many vacancies as possible, and ensure the generation of supersaturated vacancies.

[0085] The alloy liquid is refined at a temperature of 710~735ºC for 10~30min. Among them, the mass ratio of the refining agent to the alloy liquid is 0.01~0.05:1. The refining agent includes a metal salt and hexachloroethane with a mass ratio of 0.5~1.5:1. The metal salt is at least one of aluminum fluoride, sodium fluoride, sodium nitrate, aluminum nitrate, manganese chloride, zinc chloride, and sodium chloride. In one embodiment, the mass ratio of the fluoride salt, nitrate salt, and chloride salt is 1:0.5~1.5:0.5~1.5.

[0086] The alloy liquid is subjected to die-casting treatment at a temperature of 660 - 700 °C, wherein the die-casting speed of the die-casting machine is 0.23 - 2.5 m / s. It can be understood that the die-casting treatment of the present invention is an ordinary die-casting treatment, and vacuum die-casting can also be used to perform die-casting treatment on the alloy liquid. The strength (such as yield strength and tensile strength) and elongation of the aluminum alloy after vacuum die-casting treatment will be higher than those of the aluminum alloy after ordinary die-casting treatment.

[0087] The preparation method of the high-strength heat-treatment-free die-casting aluminum alloy further includes the step of adding at least one of Ca source, Co source, Cd source, Be source, Bi source, Nb source, Sn source, Sb source, Ag source, In source, Zr source, Mo source, Cr source, V source, and RE source to the aluminum liquid. Among them, the Ca source, Co source, Cd source, Be source, Bi source, Nb source, Sn source, Sb source, Ag source, In source, Zr source, Mo source, Cr source, V source, and RE source can be added in the form of single substances or alloys. The total mass percentage content of the elements selected from at least one of Ca, Co, Cd, Be, Bi, Nb, Sn, Sb, Ag, In, Zr, Mo, Cr, V, and RE is not more than 0.6%, preferably not more than 0.5%, and specifically can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or 0.6%. The content of a single impurity in the high-strength heat-treatment-free die-casting aluminum alloy does not exceed 0.05%, and the total impurity content does not exceed 0.15%.

[0088] In the technical solution of the present invention, the high-strength heat-treatment-free die-casting aluminum alloy prepared by the preparation method contains Si with a mass percentage content of 8 - 10.5%, Fe with a mass percentage content of 0.2 - 0.8%, Cu with a mass percentage content of 0.3 - 0.8%, Mn with a mass percentage content of 0.2 - 0.8%, Mg with a mass percentage content of 0.2 - 0.6%, Zn with a mass percentage content of 0.1 - 0.5%, B with a mass percentage content of 0 - 0.01%, Sr with a mass percentage content of 0 - 0.05%, Ge with a mass percentage content of 0 - 0.1%, and Ti with a mass percentage content of 0.01 - 0.25%. The combined addition of Si, Fe, Cu, Mn, Mg, Zn, B, Sr, Ge, and Ti within the above content ranges interact with each other, which can make the tensile strength of the heat-treatment-free aluminum alloy greater than 280 MPa, the yield strength greater than 140 MPa, and the elongation greater than 10%. Specifically:

[0089] (1) Si can improve the tensile strength, yield strength, and process flowability of aluminum alloys. However, when its content is too high, it will reduce the elongation. Si can react with Al, Fe, Mg, Cu, B, etc. to form secondary phases such as Mg2Si, AlFeSi, AlFeSiCu, AlFeMgSi, AlCuMgSi, AlFeSiB, etc., to further improve the tensile strength and yield strength of aluminum alloys.

[0090] (2) Mg can react with Al, Fe, Si, Cu, Zn, etc. to form secondary phases such as AlFeMgSi, (CuMg)Al2, AlCuMgSi, Mg2Si, Mg2Zn, Mg2SiZn, etc., to improve the tensile strength and yield strength of aluminum alloys. Among them, when Mg is dissolved in the CuAl2 phase and the AlFeSi phase, it forms the (CuMg)Al2 phase and the AlFeSiMg phase.

[0091] (3) Cu can react with Al, Fe, Si, Mg, Zn, etc. to form secondary phases such as CuAl2, AlFeSiCu, AlCuMgSi, Al2CuZn, (CuMg)Al2, etc., to improve the tensile strength and yield strength of aluminum alloys. It can also promote the precipitation of secondary phases such as Mg2Si, Mg2Zn, Mg2SiZn, etc., and increase the volume fraction and dispersion degree of the precipitated phases. Subsequent natural aging or heat treatment during vehicle painting baking can further improve the age hardening effect of Cu and Mg.

[0092] (4) Zn can react with Al, Mg, Cu, and Si, etc. to form secondary phases such as MgZn2, Mg2SiZn, Al2CuZn, etc., to improve the tensile strength and yield strength of aluminum alloys. Zn can eliminate elemental Si to reduce the influence of Si on the properties of aluminum alloys. It can also promote the precipitation of secondary phases such as Mg2Si, Mg2Zn, Mg2SiZn, Al2Cu, Al2CuMg, etc., and increase the volume fraction and dispersion degree of the precipitated phases. The combined addition of Zn and Mg can form the strengthening phase Mg / Zn2, significantly improving the tensile strength and yield strength of aluminum alloys. Zn increases the lattice distortion energy of the matrix, which will promote the migration of Mg, Cu, and Si atoms from the matrix to form more Cu-Mg-Zn clusters and Mg-Si-Zn clusters, improving the cluster strengthening effect.

[0093] (5) Fe can improve the tensile strength and yield strength of aluminum alloys, can improve the demolding performance, and can also react with Al, Si, Mg, Cu, B to form secondary phases such as Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu, AlFeSiB, etc., to further improve the tensile strength and yield strength of aluminum alloys.

[0094] (6) Mn can react with Al, Fe, Si, and Cu to form second phases such as MnAl2, MnAl6, α-(Fe,Mn)Al6, A1 12 CuMn2, α-Al(FeMn)Si, τ(Cu2Mn3Al 20 ) etc., to improve the tensile strength and yield strength of aluminum alloys; Mn can significantly refine the grain size through lattice distortion generated by solid solution in the matrix and MnAl6 dispersed particles produced by reacting with Al, so as to improve the elongation rate. Moreover, MnAl6 can also dissolve Fe to form the α-(Fe,Mn)Al6 phase, reducing the Fe content and minimizing the harm of Fe; Mn reacts with Al, Fe, Mn, and Si to form spherical or Chinese character-shaped AlFeMnSi compound phases, which can avoid the formation of long needle-shaped Fe phases to reduce the harm of Fe, and can also improve the tensile strength and yield strength of aluminum alloys when improving the demoulding property of aluminum alloys; Mn can also transform the coarse needle-shaped β-AlFeSi phase into small granular α-Al(FeMn)Si phase dispersed particles, improving the Fe morphology to eliminate the harm of Fe. Specifically, Mn can replace part of Fe in the coarse needle-shaped β-AlFeSi phase to form small granular dispersed β-Al(FeMn)Si phase, and the formation and growth shape of the β phase are improved, thereby reducing the harm of Fe; Mn can also promote the transformation of the needle-shaped β-Al(FeMn)Si phase into small granular α-Al(FeMn)Si dispersed phase. The formed α-Al(FeMn)Si phase dispersed particles are distributed in the aluminum matrix and strongly pin at the subgrain boundaries of aluminum alloys. This is mainly because the α-phase dispersed particles containing Mn in aluminum alloys can serve as non-uniform nucleation sites during the aging process of the β′ phase to induce its nucleation, thus accelerating the precipitation of the β′ phase; Mn can also react with impurity phases in the aluminum alloy liquid to form Al-Mn-X phases (X is an impurity element, including but not limited to transition metal elements). In this way, the aluminum alloy liquid can be purified, and these phases can serve as grain nucleation points to increase the nucleation rate and refine the grains, improving the tensile strength, yield strength, elongation rate, and fluidity of aluminum alloys;

[0095] (7) Sr preferentially combines with Fe to form dispersion strengthening, reducing the solid solubility of Fe, to improve the yield strength and tensile strength of aluminum alloys; Sr can change the behavior of intermetallic compound phases crystallographically and can be used as a modifier to refine grains and second phases in aluminum alloys through the heterogeneous nucleation theory or twin valley mechanism. For example, Sr can change the morphology of eutectic silicon phase through modification to improve the elongation rate of aluminum alloys and reduce the tendency of sticking to the mold during die-casting; Sr can transform the coarse needle-shaped β-AlFeSi and β-AlFeMnSi phases in the ingot into small granular Chinese character-shaped α-AlFeSi and α-Al(FeMn)Si phases, reducing the homogenization time of the ingot and improving the yield strength, tensile strength, and elongation rate of aluminum alloys;

[0096] The TiAl2 phase formed by the reaction of Ti and Al can, as a non-spontaneous nucleus during crystallization, refine grains, secondary phases and precipitation phases to improve the tensile strength, yield strength and elongation of aluminum alloys;

[0097] (9)B can react with transition metal elements (including transition metal elements such as Fe) to form compounds such as ferroboron compounds that can be separated from the aluminum alloy liquid to purify the aluminum alloy liquid; B is easily adsorbed on the surface of the iron-rich phase to inhibit the growth of the iron-rich phase, playing a role in controlling the size of the iron-rich phase, and can also prevent the formation of the iron-rich phase in the aluminum alloy liquid; B can inhibit the segregation of Ti3Al. Therefore, the effect is better when Ti and B are used together; B can also refine grains and secondary phases to improve the elongation of aluminum alloys;

[0098] (10)Ge is easy to capture quenching vacancies in the α-Al matrix and form "Ge-vacancy pairs", "retaining" the quenching vacancies in the α-Al matrix, promoting artificial aging precipitation kinetics and enhancing the precipitation strengthening effect; Ge not only replaces some Si and Cu atoms in the metastable precipitation phase, but also refines the precipitation phase and increases the precipitation phase density, significantly enhancing the precipitation strengthening effect of aluminum alloys; during the low-temperature quenching and holding process, the aluminum alloy matrix shrinks, undergoes plastic deformation, and generates internal stress; Ge can reduce the solubility of elements in aluminum and increase the nucleation points of clusters. During the process of rising to room temperature after the low-temperature quenching and holding treatment, these nucleation points combine with the "Ge-vacancy pairs" formed by quenching vacancies under the action of internal stress to rapidly increase the volume fraction of Cu-Mg clusters, Mg-Si clusters, and Mg-Si-Cu clusters to improve the yield strength, tensile strength and elongation of aluminum alloys; in addition, Ge elements can also replace Si and Cu atoms in Cu-Mg clusters, Mg-Si clusters, and Mg-Si-Cu clusters to increase the resistance of dislocations to cut through these clusters. When adding RE elements, the combination of Ge and RE can further refine the size of the clusters and increase the volume fraction of the clusters.

[0099] The combined action of Si, Cu, Mn, Mg, Zn, Ti, Sr, Ge, and Fe within the above content ranges can significantly improve the tensile strength and yield strength of aluminum alloys; the combined action of Mn, B, Ti, Ge, and Sr within the above content ranges can refine grains, secondary phases and precipitation phases to improve the elongation of aluminum alloys; the combined action of Cu, Ge, and Zn within the above content ranges can promote the precipitation of secondary phases, increase the volume fraction and dispersion degree of precipitation phases, and further improve the tensile strength, yield strength, and elongation of aluminum alloys; the combined action of Fe, Sr, and Mn within the above content ranges can improve the demolding performance of aluminum alloys.

[0100] Since the mechanical properties of the heat - treatable - free die - casting aluminum alloy cannot be improved by age heat treatment, most of the solute atoms in the heat - treatable - free die - casting aluminum alloy of the present invention usually exist in a solid - solution form in the aluminum matrix. In addition to fine - grain strengthening, the strength increment of the heat - treatable - free die - casting aluminum alloy mainly comes from the pinning of dislocations by the lattice volume mismatch and elastic mismatch caused by solid - solution atoms, that is, solid - solution strengthening.

[0101] During the storage and transportation of the heat - treatable - free die - casting aluminum alloy after die - casting treatment, natural aging will occur, that is, the strength increases with the extension of the placement time. This natural aging is attributed to the aggregation effect of solute atoms in the aluminum alloy, that is, solute atom clusters. Solute atom clusters are the disordered aggregation of solute atoms in the aluminum matrix, with a size of several nanometers, usually composed of several to dozens of atoms with no definite crystal structure and disordered distribution.

[0102] The change in the strength of the heat - treatable - free die - casting aluminum alloy is mainly related to the size and volume fraction of solute atom clusters. During natural aging, the formation and growth of clusters are closely related to the change in the concentration of supersaturated quenched vacancies. And vacancies belong to thermal defects, and their concentration has an exponential function relationship with temperature. In the present invention, after die - casting treatment, the aluminum alloy parts are subjected to low - temperature quenching treatment to generate supersaturated vacancies to improve the mechanical properties of the heat - treatable - free die - casting aluminum alloy. Specifically, during the die - casting process, the equilibrium vacancy concentration is relatively large; during the subsequent quenching process, some vacancies at high temperatures are retained, thus generating supersaturated vacancies; moreover, the low - temperature quenching treatment can also cause the aluminum alloy to shrink, generate plastic deformation, and reduce the solubility of elements in aluminum, increase the nucleation points of clusters, refine the α - Al phase and eutectic Si phase structures, so as to improve the yield strength, tensile strength and elongation of the aluminum alloy.

[0103] The addition of Cu, Mn, Mg, Zn, Ti, Sr, Fe and B can also regulate the behavior of solute atom clusters in the aluminum alloy, such as affecting the formation of the original clusters and forming new clusters by adjusting vacancies. After adding elements of Mg (0.2 - 0.6 wt%) and Cu (0.3 - 0.8 wt%) within a certain content range to the aluminum liquid of the present invention, Mg atoms activate the diffusion of vacancies and promote the formation of Mg - Si clusters, Cu - Mg clusters, and Mg - Si - Cu clusters, significantly strengthening the clusters. The atomic radii of Mn and Sr are much larger than that of Al. The atoms of Mn and Sr within the above - mentioned content range form lattice distortions in the aluminum matrix. Coupled with the pinned vacancies, Mg - Si clusters, Cu - Mg clusters, and Mg - Si - Cu clusters added to the heat - treatable - free die - casting aluminum alloy, and promoting the growth of clusters, further promoting the natural aging effect, so as to improve the yield strength, tensile strength and elongation of the heat - treatable - free die - casting aluminum alloy.

[0104] In summary, under the combined action of Si, Cu, Mn, Mg, Zn, Ti, Sr, Fe, Ge, and B within the above content ranges, a heat-treatment-free aluminum alloy with excellent demolding performance, tensile strength, yield strength, and elongation is obtained.

[0105] The present invention also provides a structural member, at least part of which is made of the high-strength heat-treatment-free die-cast aluminum alloy or the high-strength heat-treatment-free die-cast aluminum alloy prepared by the preparation method. This structural member can be applied to new energy vehicles and is an automotive structural member, such as the entire vehicle body, inner panel of the rear wheel housing, rear longitudinal beam, floor connecting plate, rear floor, inner reinforcing plate of the beam, engine hood, fender, door, rear compartment, and roof, etc. Of course, the structural member of the present invention can also be used in other aspects, such as in the fields of aerospace, high-speed rail, ships, mobile devices, household appliances, chemical industry, daily necessities, construction, etc.

[0106] Examples and Comparative Examples

[0107] For the components and contents of the aluminum alloys in the examples and comparative examples, please refer to Table 1, and for the performance test results, please refer to Table 2.

[0108] Table 1 Components and Contents of Aluminum Alloys in Examples 1 to 5 and Comparative Examples 1 to 2

[0109]

[0110] For simplicity of expression, the contents of trace elements such as impurities in the comparative examples and examples are not shown.

[0111] Using a domestic CSS-44100 type electronic universal tensile testing machine, processing and tensile testing were carried out in accordance with the provisions of the room temperature tensile test method for metallic materials (GB / T 228-2002) and the high temperature tensile test method for metallic materials (GB 4338-2006-T). Among them, the processed specimens were polished with 800# and 1500# water sandpaper respectively. The tensile force of the tensile testing machine was 2 kN, the tensile speed was 2 mm / min, and three specimens were tested under the same conditions, and the average value was taken.

[0112] Table 2 Performance Test Results of Aluminum Alloys in Examples 1 to 5 and Comparative Examples 1 to 2

[0113]

[0114] The tensile strength, yield strength, and elongation of the high-strength heat-treatment-free die-cast aluminum alloys in Examples 1 to 5 are significantly greater than those of the high-strength heat-treatment-free die-cast aluminum alloys in Comparative Examples 1 to 2. It shows that the high-strength heat-treatment-free die-cast aluminum alloy of the present invention has better performance in all aspects.

[0115] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made by using the content of the specification of the present invention under the inventive concept of the present invention, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A high-strength heat-treatment-free die-casting aluminum alloy contains Al, characterized in that, The high-strength heat-treatment-free die-cast aluminum alloy also contains Si with a mass percentage content of 8-10.5%, Fe with a mass percentage content of 0.2-0.8%, Cu with a mass percentage content of 0.3-0.8%, Mn with a mass percentage content of 0.2-0.8%, Mg with a mass percentage content of 0.2-0.6%, Zn with a mass percentage content of 0.1-0.5%, B with a mass percentage content of 0-0.01%, Sr with a mass percentage content of 0-0.05%, Ge with a mass percentage content of 0-0.1%, and Ti with a mass percentage content of 0.01-0.25%. Among them, the high-strength heat-treatment-free die-cast aluminum alloy is subjected to die-casting treatment and cryogenic quenching treatment. After the die-casting treatment, aluminum alloy parts are obtained, and then the aluminum alloy parts are subjected to cryogenic quenching treatment to obtain the high-strength heat-treatment-free die-cast aluminum alloy. During the die-casting treatment, the temperature cooling rate is 10-60 K / s, the temperature of the cryogenic quenching treatment is -150 to 0 °C, and the time is 0.1-10 h.

2. The high-strength heat-treatment-free die-casting aluminum alloy according to claim 1, wherein, The high-strength heat-treatment-free die-cast aluminum alloy contains Si with a mass percentage content of 9-10%, Fe with a mass percentage content of 0.2-0.5%, Cu with a mass percentage content of 0.5-0.7%, Mn with a mass percentage content of 0.5-0.7%, Mg with a mass percentage content of 0.4-0.5%, Zn with a mass percentage content of 0.3-0.4%, B with a mass percentage content of 0.001-0.01%, Sr with a mass percentage content of 0.01-0.04%, Ge with a mass percentage content of 0.01-0.05%, and Ti with a mass percentage content of 0.05-0.25%.

3. The high-strength heat-treatment-free die-casting aluminum alloy according to claim 1, wherein At least one of the following conditions is satisfied: The mass ratio of Cu to Mg is 1.5-4:1; The mass ratio of Mg to Ge is 2-40:1; The mass ratio of Mn to Fe is 0.5-3:1; The sum of the mass percentage contents of Mn and Fe is 0.6-1.5%.

4. The high-strength heat-treatment-free die-casting aluminum alloy according to any one of claims 1 to 3, characterized in that, At least one of the following conditions is satisfied: The high-strength heat-treatment-free die-cast aluminum alloy also contains Ca with a mass percentage content of 0-0.06%; The high-strength heat-treatment-free die-cast aluminum alloy also contains Co with a mass percentage content of 0-0.2%; The high-strength heat-treatment-free die-cast aluminum alloy also contains Be with a mass percentage content of 0-0.05%; The high-strength heat-treatment-free die-cast aluminum alloy also contains Nb with a mass percentage content of 0-0.2%; The high-strength heat-treatment-free die-cast aluminum alloy also contains Sn with a mass percentage content of 0-0.1%; The high-strength heat-treatment-free die-cast aluminum alloy also contains Sb with a mass percentage content of 0-0.2%; The high-strength heat-treatment-free die-cast aluminum alloy also contains Ag with a mass percentage content of 0-0.1%; The high-strength heat-treatment-free die-cast aluminum alloy also contains In with a mass percentage content of 0-0.2%; The high-strength heat-treatment-free die-cast aluminum alloy also contains Mo with a mass percentage content of 0-0.2%; The high-strength heat-treatment-free die-casting aluminum alloy also contains Cd with a mass percentage content of 0-0.1%; The high-strength heat-treatment-free die-casting aluminum alloy also contains Cr with a mass percentage content of 0-0.2%; The high-strength heat-treatment-free die-casting aluminum alloy also contains V with a mass percentage content of 0-0.3%; The high-strength heat-treatment-free die-casting aluminum alloy also contains Zr with a mass percentage content of 0-0.2%; The high-strength heat-treatment-free die-casting aluminum alloy also contains Bi with a mass percentage content of 0-0.2%; The high-strength heat-treatment-free die-casting aluminum alloy also contains RE with a mass percentage content of 0-0.2%, where RE is at least one of La, Ce, Pr, Nd, Er, Sm, Y, Gd, and Sc.

5. The high-strength heat-treatment-free die-casting aluminum alloy according to claim 4, wherein Meet at least one of the following conditions: When the high-strength heat-treatment-free die-casting aluminum alloy also contains Sb, the mass ratio of Mg to Sb is 1-20:1; When the high-strength heat-treatment-free die-casting aluminum alloy also contains Nb, the mass ratio of Mg to Nb is 1-20:1; When the high-strength heat-treatment-free die-casting aluminum alloy also contains Ag, the mass ratio of Mg to Ag is 2-40:1; When the high-strength heat-treatment-free die-casting aluminum alloy also contains In, the mass ratio of Cu to In is 2-20:1; When the high-strength heat-treatment-free die-casting aluminum alloy also contains Mo, the mass ratio of Fe to Mo is 1-20:1; When the high-strength heat-treatment-free die-casting aluminum alloy also contains Co and Be, the mass ratio of Co, Be, and Fe is 0.01-1:0.01-0.25:1; When the high-strength heat-treatment-free die-casting aluminum alloy also contains Ca, Sn, and RE, the mass ratio of Ca, Sn, and RE is 0.05-10:0.01-10:1; When the high-strength heat-treatment-free die-casting aluminum alloy also contains Cr and V, the mass ratio of Cr to V is 0.1-10:1; When the high-strength heat-treatment-free die-casting aluminum alloy also contains Bi and Cd, the mass ratio of Bi, Cd, and Mg is 0.01-1:0.01-0.5:1; When the high-strength heat-treatment-free die-casting aluminum alloy also contains RE, the mass ratio of (Mn + RE) to Fe is 0.5~3:1; When the high-strength heat-treatment-free die-casting aluminum alloy also contains Zr and RE, the mass ratio of RE to Zr is 0.1~1:1, and the mass ratio of (Mn + RE + Zr) to Fe is 0.5~3:

1.

6. The high-strength heat-treatment-free die-cast aluminum alloy according to claim 4, wherein Meet at least one of the following conditions: The high-strength heat-treatment-free die-casting aluminum alloy contains Si with a mass percentage content of 8-10.5%, Fe with a mass percentage content of 0.2-0.8%, Cu with a mass percentage content of 0.3-0.8%, Mn with a mass percentage content of 0.2-0.8%, Mg with a mass percentage content of 0.2-0.6%, Zn with a mass percentage content of 0.1-0.5%, B with a mass percentage content of 0-0.01%, Sr with a mass percentage content of 0-0.05%, Ge with a mass percentage content of 0.01-0.1%, Ti with a mass percentage content of 0.01-0.25%, Ca with a mass percentage content of 0.01-0.1%, Sn with a mass percentage content of 0.01-0.1%, Co with a mass percentage content of 0.01-0.1%, Be with a mass percentage content of 0.01-0.05%, and Sb with a mass percentage content of 0.01-0.1%. The high-strength heat-treatment-free die-casting aluminum alloy contains Si with a mass percentage content of 8-10.5%, Fe with a mass percentage content of 0.2-0.8%, Cu with a mass percentage content of 0.3-0.8%, Mn with a mass percentage content of 0.2-0.8%, Mg with a mass percentage content of 0.2-0.6%, Zn with a mass percentage content of 0.1-0.5%, B with a mass percentage content of 0-0.01%, Sr with a mass percentage content of 0-0.05%, Ge with a mass percentage content of 0.01-0.1%, Ti with a mass percentage content of 0.01-0.25%, Zr with a mass percentage content of 0.01-0.1%, Mo with a mass percentage content of 0.01-0.1%, Cr with a mass percentage content of 0.01-0.1%, V with a mass percentage content of 0.05-0.2%, La with a mass percentage content of 0.01-0.03%, Ce with a mass percentage content of 0.01-0.02%, Sm with a mass percentage content of 0.01-0.05%, Y with a mass percentage content of 0.01-0.05%, and Gd with a mass percentage content of 0.01-0.05%. The high-strength heat-treatment-free die-casting aluminum alloy contains Si with a mass percentage content of 8-10.5%, Fe with a mass percentage content of 0.2-0.8%, Cu with a mass percentage content of 0.3-0.8%, Mn with a mass percentage content of 0.2-0.8%, Mg with a mass percentage content of 0.2-0.6%, Zn with a mass percentage content of 0.1-0.5%, B with a mass percentage content of 0-0.01%, Sr with a mass percentage content of 0-0.05%, Ge with a mass percentage content of 0.01-0.1%, Ti with a mass percentage content of 0.01-0.25%, Nb with a mass percentage content of 0.01-0.1%, Cd with a mass percentage content of 0.01-0.1%, Bi with a mass percentage content of 0.01-0.1%, Ag with a mass percentage content of 0.01-0.05%, and In with a mass percentage content of 0.01-0.1%.

7. A preparation method of a high-strength heat-treatment-free die-casting aluminum alloy, comprising the following steps: Performing a first heat treatment on an Al source to obtain molten aluminum; Adding an Si source, an Fe source, a Cu source, a Mn source, a Mg source, a Zn source, a B source, an Sr source, a Ge source, and a Ti source to the molten aluminum, and performing a second heat treatment to obtain an alloy liquid; And Performing a refining treatment, a slag skimming treatment, and a die-casting treatment on the alloy liquid to obtain aluminum alloy parts. During the die-casting treatment, the temperature cooling rate is 10-60 K / s; and Performing a cryogenic quenching treatment on the aluminum alloy parts to obtain a high-strength heat-treatment-free die-casting aluminum alloy. The high-strength heat-treatment-free die-casting aluminum alloy contains Al and also contains Si with a mass percentage content of 8-10.5%, Fe with a mass percentage content of 0.2-0.8%, Cu with a mass percentage content of 0.3-0.8%, Mn with a mass percentage content of 0.2-0.8%, Mg with a mass percentage content of 0.2-0.6%, Zn with a mass percentage content of 0.1-0.5%, B with a mass percentage content of 0-0.01%, Sr with a mass percentage content of 0-0.05%, Ge with a mass percentage content of 0-0.1%, and Ti with a mass percentage content of 0.01-0.25%. Among them, the temperature of the cryogenic quenching treatment is -150 to 0 °C, and the time is 0.1 to 10 h.

8. The preparation method of the high-strength heat-treatment-free die-casting aluminum alloy according to claim 7, characterized in that, It further includes the step of adding at least one of a Ca source, a Co source, a Be source, a Nb source, a Sn source, an Sb source, an Ag source, an In source, a Mo source, a Cd source, a Cr source, a V source, a Zr source, a Bi source, and a RE source into the molten aluminum. Among them, in the high-strength heat-treatment-free die-cast aluminum alloy, the mass percentage content of Ca is 0.001-0.06%, the mass percentage content of Co is 0.01-0.2%, the mass percentage content of Be is 0.001-0.05%, the mass percentage content of Nb is 0.01-0.2%, the mass percentage content of Sn is 0.001-0.1%, the mass percentage content of Sb is 0.01-0.2%, the mass percentage content of Ag is 0.01-0.1%, the mass percentage content of In is 0.01-0.2%, the mass percentage content of Mo is 0.01-0.2%, the mass percentage content of Cd is 0.01-0.1%, the mass percentage content of Cr is 0.01-0.2%, the mass percentage content of V is 0.01-0.3%, the mass percentage content of Zr is 0.01-0.2%, the mass percentage content of Bi is 0.01-0.2%, and the mass percentage content of RE is 0.01-0.2%.

9. A structural member, characterized in that, At least part of the structural member is made of the high-strength heat-treatment-free die-cast aluminum alloy according to any one of claims 1 to 6 or the high-strength heat-treatment-free die-cast aluminum alloy prepared by the preparation method according to any one of claims 7 to 8.

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