High-elongation heat-treatment-free die-casting aluminum alloy, preparation method thereof and structural part

Abstract

The invention provides a high-elongation heat-treatment-free die-casting aluminum alloy, a preparation method thereof and a structural part. The aluminum alloy comprises, by mass, 6.5%-9% of Si, 0.01%-0.3% of Fe, 0.01%-0.2% of Cu, 0.001%-0.25% of Mn, 0.01%-0.15% of Mg, 0.01%-0.2% of Zr, 0%-0.01% of B, 0%-0.05% of Sr, 0.01%-0.1% of Ti and the balance aluminum and inevitable impurities. The mass ratio of Mn to Fe is (0.004-0.5): 1, the high-elongation heat-treatment-free die-casting aluminum alloy is subjected to die-casting treatment, and in the die-casting treatment process, the temperature cooling rate is 10-60 K / s.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and particularly relates to a high elongation rate heat - treatment - free die - casting aluminum alloy, a preparation method of the high elongation rate heat - treatment - free die - casting aluminum alloy, and a structural part. Background Art

[0002] With the increasingly severe demand for energy conservation and emission reduction in the automotive industry, due to the advantages of integration, lightweight, good strength and toughness, etc., the application penetration rate of aluminum alloy vacuum die - castings in key automotive structural parts is continuously increasing. For vehicle manufacturers, aluminum alloy die - castings used in automotive structural parts are different from traditional aluminum alloy die - castings. The joining process during manufacturing and the overall vehicle performance during service have relatively high requirements for the comprehensive mechanical properties, especially plasticity, of aluminum alloy die - castings in the as - cast state. Currently, common Al - Si - based and Al - Mg - based aluminum alloys generally only have medium strength and plasticity, and it is difficult to meet the requirements of automotive structural parts (especially large - scale automotive structural parts). In other fields, such as aerospace, high - speed rail, ships, mobile devices, household appliances, chemical industry, daily necessities, construction, etc., aluminum alloy die - castings are usually also required, and the requirements for the comprehensive mechanical properties of aluminum alloy die - castings are also relatively high. Therefore, there is an urgent need to develop a high elongation rate heat - treatment - free die - casting aluminum alloy with better demolding performance, tensile strength, yield strength, and elongation rate. Summary of the Invention

[0003] Aiming at the above - mentioned defects of the prior art, the present invention provides a high elongation rate heat - treatment - free die - casting aluminum alloy, aiming to improve the demolding performance, tensile strength, yield strength, and elongation rate of heat - treatment - free aluminum alloys.

[0004] The present invention provides a high elongation rate heat - treatment - free die - casting aluminum alloy, which contains Si with a mass percentage content of 6.5 - 9%, Fe with a mass percentage content of 0.01 - 0.3%, Cu with a mass percentage content of 0.01 - 0.2%, Mn with a mass percentage content of 0.001 - 0.25%, Mg with a mass percentage content of 0.01 - 0.15%, Zr with a mass percentage content of 0.01 - 0.2%, B with a mass percentage content of 0 - 0.01%, Sr with a mass percentage content of 0 - 0.05%, Ti with a mass percentage content of 0.01 - 0.1%, and the balance Al and impurities. The mass ratio of Mn to Fe is 0.004 - 0.5:1. The high elongation rate heat - treatment - free die - casting aluminum alloy is subjected to die - casting treatment, and during the die - casting treatment process, the temperature cooling rate is 10 - 60 K / s.

[0005] The present invention also provides a preparation method of a high elongation rate heat - treatment - free die - casting aluminum alloy, including the following steps: Perform a first heat treatment on the Al source to obtain molten aluminum; Add Si source, Fe source, Cu source, Mn source, Mg source, Zr source, B source, Sr source, and Ti source to the aluminum liquid, and perform a second heat treatment to obtain an alloy liquid; Perform refining treatment, slag skimming treatment, and die-casting treatment on the alloy liquid to obtain aluminum alloy components; and Perform low-temperature quenching treatment on the aluminum alloy components to obtain a high elongation rate heat-treatable die-casting aluminum alloy. The high elongation rate heat-treatable die-casting aluminum alloy contains Si with a mass percentage content of 6.5-9%, Fe with a mass percentage content of 0.01-0.3%, Cu with a mass percentage content of 0.01-0.2%, Mn with a mass percentage content of 0.001-0.25%, Mg with a mass percentage content of 0.01-0.15%, Zn with a mass percentage content of 0.01-0.2%, B with a mass percentage content of 0-0.01%, Sr with a mass percentage content of 0-0.05%, Ti with a mass percentage content of 0.01-0.1%, and the balance Al and impurities. The mass ratio of Mn to Fe is 0.004-0.5:1. During the die-casting treatment process, the temperature cooling rate is 10-60 K / s.

[0006] The present invention also provides a structural member, at least part of the material of which is the above-mentioned high elongation rate heat-treatable die-casting aluminum alloy or the high elongation rate heat-treatable die-casting aluminum alloy prepared by the preparation method.

[0007] In the technical solution of the present invention, the high elongation rate heat-treatable die-casting aluminum alloy contains Si with a mass percentage content of 6.5-9%, Fe with a mass percentage content of 0.01-0.3%, Cu with a mass percentage content of 0.01-0.2%, Mn with a mass percentage content of 0-0.25%, Mg with a mass percentage content of 0.01-0.15%, Zn with a mass percentage content of 0.01-0.2%, B with a mass percentage content of 0-0.01%, Sr with a mass percentage content of 0-0.05%, and Ti with a mass percentage content of 0.01-0.1%. The combined addition of Si, Fe, Cu, Mn, Mg, Zn, B, Sr, and Ti within the above content ranges interacts with each other and can make the tensile strength of the heat-treatable aluminum alloy greater than 260 MPa, the yield strength greater than 120 MPa, and the elongation rate greater than 16%. Specifically: (1) Si can improve the process flowability of the aluminum alloy, but when the content is too high, it will reduce the elongation rate. Si can react with Al, Fe, Mg, Cu, B, etc. to form second phases such as Mg2Si, AlFeSi, AlFeSiCu, AlFeMgSi, AlCuMgSi, AlFeSiB, etc. to improve the tensile strength and yield strength; (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. Among them, when Mg is dissolved in the CuAl2 phase and the AlFeSi phase, (CuMg)Al2 phase and AlFeSiMg phase are formed; (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. 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 vehicle painting and baking heat treatment can further improve the age hardening effect of Cu and Mg; (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. Zn can eliminate elemental Si to reduce the influence of Si on the properties of aluminum alloy. 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 alloy; (5) Fe can improve the demolding performance. Fe can also react with Al, Si, Mg, Cu, B to form second phases such as Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu, AlFeSiB, etc., to improve the tensile strength and yield strength; (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 [etc.] are used to increase the tensile strength and yield strength; Mn can significantly refine the grain size through the lattice distortion generated by solid solution in the matrix and the MnAl6 dispersed particles formed by reacting with Al, so as to increase 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 increase the tensile strength and yield strength of the aluminum alloy when improving its demouldability; 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 the Fe in the coarse needle-shaped β-AlFeSi phase to form small granular dispersed β-Al(FeMn)Si phases, improving the formation and growth shape of the β phase, 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 phases. The formed α-Al(FeMn)Si phase dispersed particles are distributed in the aluminum matrix and strongly pin at the sub-grain boundaries of the aluminum alloy. This is mainly because the α-phase dispersed particles containing Mn in the aluminum alloy 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 the impurity phases in the aluminum alloy liquid to form Al-Mn-X phases (X is an impurity element, including transition metal elements, etc.), which can purify the aluminum alloy liquid. These phases can serve as grain nucleation points to increase the nucleation rate and refine the grains, thereby improving the tensile strength, yield strength, elongation rate, and fluidity of the aluminum alloy; (7) Sr preferentially combines with Fe to form dispersion strengthening, reducing the solid solubility of Fe, to increase the yield strength and tensile strength; Sr can change the behavior of intermetallic compound phases crystallographically and can be used as a modifier to refine the grains and second phases of the aluminum alloy through the heterogeneous nucleation theory or the twin trough mechanism. For example, Sr can change the morphology of the eutectic silicon phase through modification to increase the elongation rate of the aluminum alloy 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 increasing the yield strength, tensile strength, and elongation rate; (8) The TiAl2 phase formed by the reaction of Ti with Al, as a non-spontaneous core during crystallization, can refine the grains, second phases, and precipitation phases to increase the tensile strength, yield strength, and elongation rate of the aluminum alloy; (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.

[0008] The combined action of Si, Cu, Mn, Mg, Zn, Ti, Sr, and Fe within the above content range can improve the tensile strength and yield strength of the aluminum alloy; the combined action of Mn, B, Ti, and Sr within the above content range can refine grains, the second phase, and the precipitation phase to improve the elongation of the aluminum alloy; Cu and Zn within the above content range 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 range can improve the demolding performance of the aluminum alloy.

[0009] The mass percentage content of Fe in the present invention (0.01 - 0.3 wt%) is relatively small. During the die-casting process, the temperature cooling rate is relatively large (which can be 10 - 60 K / S), such that Fe basically forms fine short rod-shaped or square-shaped A1-Fe phases or A1-Fe-Si phases. Thus, Fe within this content range has little effect on the elongation of the aluminum alloy; as the Fe content decreases, the elongation gradually increases. At this time, there is no need to increase the addition of Mn or add a large amount of Mn to reduce the influence of Fe on the elongation of the aluminum alloy; the present invention sets the mass percentage content of Mn to 0 - 0.25%, and further improves the demolding performance of the aluminum alloy through Mn; Sr can also change the morphology of the eutectic silicon phase through modification to reduce the tendency of sticking to the mold during the die-casting process.

[0010] Since the mechanical properties of the heat-treatable aluminum alloy cannot be improved by age heat treatment, most of the solute atoms in the heat-treatable 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 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.

[0011] During the storage and transportation processes after die-casting treatment of the heat-treatable aluminum alloy, natural aging will occur, that is, as the storage time prolongs, the strength increases. This natural aging is attributed to the clustering 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 clear crystal structure and disordered distribution.

[0012] The change in the strength of the heat-treatable 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. 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 aluminum alloy. Specifically, during the die-casting treatment, the equilibrium vacancy concentration is relatively large; during the subsequent quenching treatment, 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 of the heat-treatable aluminum alloy.

[0013] 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 (0.01-0.15wt%) and Cu (0.01-0.2wt%) 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 Mg-Si clusters and Cu-Mg 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 distortions in the aluminum matrix. Coupled with the pinned vacancies, Mg-Si clusters and Cu-Mg clusters added in the heat-treatable 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 aluminum alloy.

[0014] In summary, under the combined action of Si, Cu, Mn, Mg, Zn, Ti, Sr, Fe and B within the above content range, a heat-treatable aluminum alloy with excellent demolding performance, tensile strength, yield strength and elongation is obtained. Detailed implementation mode

[0015] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, 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.

[0016] An embodiment of the present invention provides a high elongation heat - treatable die - casting aluminum alloy, which contains Si with a mass percentage content of 6.5 - 9%, Fe with a mass percentage content of 0.01 - 0.3%, Cu with a mass percentage content of 0.01 - 0.2%, Mn with a mass percentage content of 0 - 0.25%, Mg with a mass percentage content of 0.01 - 0.15%, Zn with a mass percentage content of 0.01 - 0.2%, B with a mass percentage content of 0 - 0.01%, Sr with a mass percentage content of 0 - 0.05%, Ti with a mass percentage content of 0.01 - 0.1%, and Al and inevitable impurities.

[0017] In one embodiment, the high elongation heat - treatable die - casting aluminum alloy contains Si with a mass percentage content of 6.5 - 9%, Fe with a mass percentage content of 0.01 - 0.1%, Cu with a mass percentage content of 0.05 - 0.1%, Mn with a mass percentage content of 0.05 - 0.2%, Mg with a mass percentage content of 0.05 - 0.1%, Zn with a mass percentage content of 0.05 - 0.2%, B with a mass percentage content of 0.005 - 0.01%, Sr with a mass percentage content of 0.005 - 0.05%, and Ti with a mass percentage content of 0.05 - 0.1%.

[0018] The mass ratio of Mn to Fe is 0 - 0.8:1, preferably 0 - 0.6:1. Specifically, it can be 0:1, 0.001:1, 0.002:1, 0.003:1, 0.004:1, 0.005:1, 0.006:1, 0.007:1, 0.008:1, 0.009:1, 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, or 0.8:1.

[0019] In the prior art in the field of aluminum alloys, it is generally believed 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 of the aluminum alloy will be reduced. Therefore, in order to obtain better tensile strength, yield strength and elongation, 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 0-0.8:1, preferably 0-0.6:1, and further preferably 0-0.5:1. Instead, a heat-treatment-free aluminum alloy with better tensile strength, yield strength and elongation is obtained, wherein the tensile strength is greater than 260 MPa, the yield strength is greater than 120 MPa, and the elongation is greater than 16%. This is because during the die-casting process, the temperature cooling rate is relatively large. When the Fe content is small, Fe basically forms fine short rod-shaped or square-shaped A1-Fe phases or A1-Fe-Si phases, so that the influence of Fe on the elongation of the aluminum alloy is not significant. Moreover, as the Fe content decreases, the elongation gradually increases, which means that there is no need to add Mn or add less Mn to reduce the influence of Fe on the elongation of the aluminum alloy; moreover, the lattice constant of Mn is much larger than that of the Al matrix, and Mn dissolved in the Al matrix will cause discontinuity in the internal structure of the Al matrix, resulting in a sudden change in the dislocation cutting radius and a decrease in elongation. Therefore, when the Fe content is set to 0.01-0.3%, the Mn content is set to 0-0.25%, and the mass ratio of Mn to Fe is set to 0-0.8:1 in the present invention, better tensile strength, yield strength and elongation are obtained instead.

[0020] Considering the demolding performance, the present invention also sets the sum of the mass percentage contents of Mn and Fe to 0.25-0.5%, preferably 0.3-0.4%, and specifically can be 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.3%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.4%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, or 0.5%. By combining the Fe content set to 0.01-0.3%, the Mn content set to 0-0.25%, the mass ratio of Mn to Fe set to 0-0.8:1, and the sum of the mass percentage contents of Mn and Fe set to 0.25-0.5% in the present invention, better demolding performance, tensile strength, yield strength, and elongation are obtained.

[0021] The mass percentage content of Si can be 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7%, 7.2%, 7.4%, 7.6%, 7.8%, 8%, 8.2%, 8.4%, 8.6%, 8.8%, or 9%. The mass percentage content of Fe 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%. The mass percentage content of Cu can specifically 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 mass percentage content of Mn can specifically be 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 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 Mg can specifically 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%, or 0.15%. The mass percentage content of Zn can specifically 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 mass percentage content of B is 0 - 0.01%, and can specifically 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 Ti can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%.

[0022] The mass ratio of Ti to B is 1 - 50:1, preferably 10 - 30:1, more 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.

[0023] In the technical solution of the present invention, the high elongation rate heat - treatable die - casting aluminum alloy contains Si with a mass percentage content of 6.5 - 9%, Fe with a mass percentage content of 0.01 - 0.3%, Cu with a mass percentage content of 0.01 - 0.2%, Mn with a mass percentage content of 0 - 0.25%, Mg with a mass percentage content of 0.01 - 0.15%, Zn with a mass percentage content of 0.01 - 0.2%, B with a mass percentage content of 0 - 0.01%, Sr with a mass percentage content of 0 - 0.05%, and Ti with a mass percentage content of 0.01 - 0.1%. The combined addition of Si, Fe, Cu, Mn, Mg, Zn, B, Sr, and Ti within the above content ranges interact with each other, which can make the tensile strength of the heat - treatable aluminum alloy greater than 260 MPa, the yield strength greater than 120 MPa, and the elongation rate greater than 16%. Specifically: (1) Si can improve the process flowability of the aluminum alloy, but when the content is too high, it will reduce the elongation rate. Si can react with Al, Fe, Mg, Cu, B, etc. to form second - phase substances such as Mg2Si, AlFeSi, AlFeSiCu, AlFeMgSi, AlCuMgSi, AlFeSiB, etc., to improve the tensile strength and yield strength; (2) Mg can react with Al, Fe, Si, Cu, Zn, etc. to form second - phase substances such as AlFeMgSi, (CuMg)Al2, AlCuMgSi, Mg2Si, Mg2Zn, Mg2SiZn, etc., to improve the tensile strength and yield strength. Among them, when Mg is dissolved in the CuAl2 phase and the AlFeSi phase, (CuMg)Al2 phase and AlFeSiMg phase are formed; (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. 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 and baking can further improve the age hardening effect of Cu and Mg; (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. 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; (5) Fe can improve the demolding performance. Fe can also react with Al, Si, Mg, Cu, B to form second phases such as Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu, AlFeSiB, etc., to improve the tensile strength and yield strength; (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 [description of second phases] are used to improve the tensile strength and yield strength; Mn can significantly refine the grain size through the lattice distortion generated by solid solution in the matrix and the dispersed MnAl6 particles formed by reacting with Al, so as to improve the elongation. 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 the aluminum alloy when improving the demoulding property of the aluminum alloy; Mn can also transform the coarse needle-shaped β-AlFeSi phase into small particulate 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 generate small particulate dispersed β-Al(FeMn)Si phases, 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 particulate α-Al(FeMn)Si dispersed phases. The generated α-Al(FeMn)Si phase dispersed particles are distributed in the aluminum matrix and strongly pin the sub-boundaries of the aluminum alloy. This is mainly because the α phase dispersed particles containing Mn in the aluminum alloy can serve as the heterogeneous 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 the impurity phases in the aluminum alloy liquid to form Al-Mn-X phases (X is an impurity element, including transition metal elements, etc.), which can purify the aluminum alloy liquid. These phases can serve as grain nucleation sites to increase the nucleation rate and refine the grains, thereby improving the tensile strength, yield strength, elongation, and fluidity of the aluminum alloy; (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; Sr can change the behavior of intermetallic compound phases crystallographically and can be used as a modifier to refine the grains and second phases of the aluminum alloy through the heterogeneous nucleation theory or the twin trough mechanism. For example, Sr can change the morphology of the eutectic silicon phase through modification to improve the elongation of the aluminum alloy 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 particulate 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; (8) The TiAl2 phase formed by the reaction of Ti with Al can be used as a non-spontaneous core during crystallization to refine the grains, second phases, and precipitation phases, so as to improve the tensile strength, yield strength, and elongation of the aluminum alloy; (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.

[0024] The combined action of Si, Cu, Mn, Mg, Zn, Ti, Sr, and Fe within the above content ranges can improve the tensile strength and yield strength of the aluminum alloy; the combined action of Mn, B, Ti, 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; Cu 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.

[0025] The mass percentage content of Fe in the present invention (0.01 - 0.3 wt%) is relatively small. During the die-casting process, the temperature cooling rate is relatively large (it can be 10 - 60 K / S), so that Fe basically forms fine short rod-shaped or square-shaped A1-Fe phases or A1-Fe-Si phases. Thus, Fe within this content range has little effect on the elongation of the aluminum alloy; as the Fe content decreases, the elongation gradually increases. At this time, there is no need to increase the addition of Mn or add a large amount of Mn to reduce the influence of Fe on the elongation of the aluminum alloy; the present invention sets the mass percentage content of Mn to 0 - 0.25% to further improve the demolding performance of the aluminum alloy through Mn; Sr can also change the morphology of the eutectic silicon phase through modification to reduce the tendency of sticking to the mold during the die-casting process.

[0026] Since the mechanical properties of the heat-treatable aluminum alloy cannot be improved by age heat treatment, most of the solute atoms in the heat-treatable 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 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.

[0027] During the storage and transportation processes after die-casting treatment of the heat-treatable aluminum alloy, natural aging will occur, that is, as the storage time prolongs, the strength increases. This natural aging is attributed to the clustering 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.

[0028] The change in the strength of the heat-treatable 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. 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 aluminum alloy. Specifically, during the die-casting treatment, the equilibrium vacancy concentration is relatively large; during the subsequent quenching treatment, some vacancies at high temperature are retained, thereby 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 heat-treatable aluminum alloy.

[0029] 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. For example, the formation of original clusters is affected by adjusting vacancies and new clusters are formed. After adding elements of Mg (0.01-0.15 wt%) and Cu (0.01-0.2 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 Mg-Si clusters and Cu-Mg 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, Mg-Si clusters and Cu-Mg clusters added to the heat-treatable 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 aluminum alloy.

[0030] In summary, under the combined action of Si, Cu, Mn, Mg, Zn, Ti, Sr, Fe and B within the above content range, a heat-treatable aluminum alloy with excellent demolding performance, tensile strength, yield strength and elongation is obtained.

[0031] The high elongation rate heat - treatable die - casting aluminum alloy also 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 elongation rate heat - treatable die - casting aluminum alloy also 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 elongation rate heat - treatable die - casting aluminum alloy also 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, Sc.

[0032] 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 refining effect.

[0033] 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.

[0034] In the technical solution of the present invention, the high elongation rate heat - treatable 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, Si to form second phases such as Al4Ca, Al2Ca3, AlCa2, AlCaCu, CaZn, CaAlZn, Al2CaSi2, etc., to improve the tensile strength and yield strength. 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, Mg2ScSn, etc., to improve the tensile strength and yield strength; Sn can promote the precipitation of second phases such as Mg2Si, Mg2Zn, Mg2SiZn, Al2Cu, etc., 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, 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. RE can transform the long - strip 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, (CuMg)Al2, etc., further improving the tensile strength and yield strength. 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, forming a component undercooling, increasing the chance of dendrite fusing, thereby refining the grains, second phases, and precipitation phases (for example, it can refine Al3Fe, Al3ScZr, AlSiMo, Mg2Si phases), further improving the tensile strength, yield strength, and elongation rate 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 rate. After adding a certain content range of RE (0 - 0.2 wt%) and Zr (0.01 - 0.2 wt%), 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, Cu - Mg clusters, etc., and significantly inhibit the diffusion of atoms in the atomic clusters to improve the stability of the atomic clusters, thereby improving the yield strength, tensile strength, and elongation rate.

[0035] The high elongation rate 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 elongation rate 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 elongation rate 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 elongation rate 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 elongation rate 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 elongation rate 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 elongation rate heat-treatment-free die-casting aluminum alloy also 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%.The high elongation rate heat-treatment-free die-casting aluminum alloy also 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%.

[0036] The mass ratio of Mg to Sb is 0.5-10:1, preferably 1-5:1, specifically, it can be 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 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 RE to 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.

[0037] The mass ratio of (Mn + RE) to Fe is 0 - 0.8:1 (i.e., the ratio of the mass percentage content of Mn + RE to the mass percentage content of Fe), preferably 0.1 - 0.6:1, more preferably 0.2 - 0.5:1, and specifically can be 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, 0.11:1, 0.12:1, 0.13:1, 0.14:1, 0.15:1, 0.16:1, 0.17:1, 0.18:1, 0.19:1, 0.2:1, 0.21:1, 0.22:1, 0.23:1, 0.24:1, 0.25:1, 0.26:1, 0.27:1, 0.28:1, 0.29:1, 0.3:1, 0.31:1, 0.32:1, 0.33:1, 0.34:1, 0.35:1, 0.36:1, 0.37:1, 0.38:1, 0.39:1, 0.4:1, 0.41:1, 0.42:1, 0.43:1, 0.44:1, 0.45:1, 0.46:1, 0.47:1, 0.48:1, 0.49:1, 0.5:1, 0.51:1, 0.52:1, 0.53:1, 0.54:1, 0.55:1, 0.56:1, 0.57:1, 0.58:1, 0.59:1, 0.6:1, 0.65:1, 0.7:1, 0.75:1, or 0.8:1. During the die-casting process, when the temperature cooling rate is relatively large, the Fe content is relatively small, and the mass ratio of (Mn + RE) to Fe is 0 - 0.8:1, Fe will basically form fine short rod-shaped or square-shaped Al-Fe phases or Al-Fe-Si phases, and RE can also round the fine short rod-shaped or square-shaped Al-Fe phases or Al-Fe-Si phases to improve the elongation rate.

[0038] The mass ratio of (Mn + RE + Zr) to Fe is 0 - 0.8:1 (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 0.1 - 0.6:1, more preferably 0.2 - 0.5:1, and specifically can be 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, 0.11:1, 0.12:1, 0.13:1, 0.14:1, 0.15:1, 0.16:1, 0.17:1, 0.18:1, 0.19:1, 0.2:1, 0.21:1, 0.22:1, 0.23:1, 0.24:1, 0.25:1, 0.26:1, 0.27:1, 0.28:1, 0.29:1, 0.3:1, 0.31:1, 0.32:1, 0.33:1, 0.34:1, 0.35:1, 0.36:1, 0.37:1, 0.38:1, 0.39:1, 0.4:1, 0.41:1, 0.42:1, 0.43:1, 0.44:1, 0.45:1, 0.46:1, 0.47:1, 0.48:1, 0.49:1, 0.5:1, 0.51:1, 0.52:1, 0.53:1, 0.54:1, 0.55:1, 0.56:1, 0.57:1, 0.58:1, 0.59:1, 0.6:1, 0.65:1, 0.7:1, 0.75:1, or 0.8:1. During the die-casting process, when the temperature cooling rate is relatively large, the Fe content is relatively small, and the mass ratio of (Mn + RE + Zr) to Fe is 0 - 0.8:1, Fe will basically form fine short rod-shaped or block-shaped Al-Fe phase or Al-Fe-Si phase. The combination of RE and Zr can also significantly round the fine short rod-shaped or block-shaped Al-Fe phase or Al-Fe-Si phase to improve the elongation rate.

[0039] 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 generate the AlFeSiB second phase to improve the tensile strength and yield strength; B can also cooperate with Mn, Cr, and RE to prevent the formation of the iron-rich phase.

[0040] The combined action of Mn, Cr, and RE can effectively improve the morphology of Fe, reduce the Fe content, refine and control the grain size, and obtain 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-shaped or plate-shaped 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-shaped 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 to prevent 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 a 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, resulting in an aluminum alloy with excellent comprehensive properties.

[0041] 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 Er to Zr can be 0.5 - 5:1, preferably 1 - 3:1, and specifically can be 0.5:1, 1:1, 2:1, 3:1, 4:1, or 5:1. The mass ratio of Bi, Cd, and Mg is 0.2 - 10:0.1 - 10:1, preferably 0.5 - 5:0.5 - 5:1, further preferably 1 - 3:1 - 2:1, and specifically can be 0.2:0.1:1, 0.2:0.5:1, 0.2:1:1, 0.2:5:1, 0.2:10:1, 0.5:0.1:1, 0.5:0.5:1, 0.5:1:1, 0.5:5:1, 0.5:10:1, 1:0.1:1, 1:0.5:1, 1:1:1, 1:5:1, 1:10:1, 5:0.1:1, 5:0.5:1, 5:1:1, 5:5:1, 5:10:1, 10:0.1:1, 10:0.5:1, 10:1:1, 10:5:1, or 10:10:1.

[0042] The mass ratio of Co, Be, and Fe is 0.1 - 10:0.01 - 5:1, preferably 0.5 - 10:0.05 - 5:1, further preferably 1 - 5:1 - 3:1, and specifically can be 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, 0.5:0.01:1, 0.5:0.05:1, 0.5:0.1:1, 0.5:0.5:1, 0.5:1:1, 0.5:5:1, 1:0.01:1, 1:0.05:1, 1:0.1:1, 1:0.5:1, 1:1:1, 1:5:1, 5:0.01:1, 5:0.05:1, 5:0.1:1, 5:0.5:1, 5:1:1, 5:5:1, 10:0.01:1, 10:0.05:1, 10:0.1:1, 10:0.5:1, 10:1:1, or 10:5:1.

[0043] In one embodiment, the high elongation rate non - heat - treated die - casting 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 added in combination, fine petal - shaped primary crystals can be formed to improve the tensile strength and elongation rate of the aluminum alloy.

[0044] In the technical solution of the present invention, the high elongation rate 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 Fe spherical phases, generate small-particle-size Al3(Fe,Co) phases that can improve the mechanical properties of the aluminum alloy, and can also transform the coarse needle-shaped and flaky Al3Fe phases 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 increase 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, etc., to increase the tensile strength and yield strength. Be can change the eutectic Si phase from a flaky 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-like 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 at the solid-liquid interface to form subcooling, increasing 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 increase the tensile strength and yield strength; 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 increase the tensile strength and yield strength 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 Fe morphology and eliminate the harmful effects of Fe. It can also easily form a dispersed 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 processes of recrystallization, improve the yield strength, tensile strength, and elongation rate of aluminum alloys. During the solution stage, various fine chromium-containing compounds formed by Cr in aluminum alloys can dissolve in the α-phase again, and various Cr-containing phases precipitate dispersively during the natural aging stage, such as α-AlCrSi dispersion phases, etc. These Cr-containing phases can serve as the cores for the heterogeneous nucleation of β" and θ" phases, accelerating the formation of β" and θ" phases to improve the yield strength and tensile strength of aluminum alloys. At the same time, the dispersive precipitation of Cr-containing phases in the matrix will inevitably have a certain delaying effect on the formation of θ′ phases precipitated at grain boundaries. Mn and Cr can also form dispersively distributed 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 formed, 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 dispersive 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. 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″ phases and make the β″ phases finer and more dispersed. The synergistic effect of Er and Zr can significantly inhibit the recrystallization of Al-Fe alloys.

[0045] 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. The mutual reactions of Al, Mg, Bi, Sn, Si, Cr, V, Cd and Sb can form second phases such as Mg3(SbCd)2, Mg2(SnCd), Mg3(BiCd)2, AlCrSi, Al(VCrTi)Si, Mg2(SiCr), Mg3Bi2, Mg2Sn, Mg3Sb2 etc. to improve the tensile strength and yield strength; the combined addition of Mn and Cr can improve the tensile strength, yield strength, control the grain structure and postpone the 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 precipitated phase; Co, Be, Cr, V, Zr can also refine the grains and precipitated phase; the combination of Be and Sc can also improve the morphology of acicular Fe-containing phase, improve the yield strength, tensile strength and elongation; 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 with each other and interact with each other. After promoting the precipitation of the precipitated phase, the grains and precipitated phase are refined to improve the tensile strength, yield strength and elongation.

[0046] The high elongation rate heat-treatable 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 elongation rate heat-treatable 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 elongation rate heat-treatable 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%.

[0047] The mass ratio of Mg to Ag is 1 - 20:1, preferably 5 - 15:1, more preferably 5 - 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 Mg and Nb is 0.2 - 15:1, preferably 1 - 10:1, and specifically can be 0.2:1, 0.5:1, 1:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, or 15:1. The mass ratio of Cu to In is 0.1 - 5:1, preferably 1 - 5:1, and specifically 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, 1:1, 2:1, 3:1, 4:1, or 5:1.

[0048] In the technical solution of the present invention, the high elongation rate non - heat - treated die - casting 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 rate of the aluminum alloy. In can react with Al and Cu to form second phases such as AlIn and CuIn, to improve the tensile strength and yield strength; In can also refine the grains, to improve the elongation rate 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 as a dispersed phase at the matrix grain boundaries, 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 rate of the aluminum alloy. The lattice mismatch constant between NbB2 and Al (30.6%) is less 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, and Nb and In can also refine the grains and the second phase, so as to achieve the purpose of improving the tensile strength, yield strength, and elongation rate of the aluminum alloy at the same time.

[0049] The high elongation rate heat - treatable 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%. The high elongation rate heat - treatable die - casting aluminum alloy also contains Ge 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%.

[0050] The mass ratio of Fe to Mo is 0.1 - 3:1, preferably 0.5 - 2:1, 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, 1:1, 0.11:1, 0.12:1, 0.13:1, 0.14:1, 0.15:1, 0.16:1, 0.17:1, 0.18:1, 0.19:1, 2:1, 0.21:1, 0.22:1, 0.23:1, 0.24:1, 0.25:1, 0.26:1, 0.27:1, 0.28:1, 0.29:1 or 3:1. The mass ratio of Mg to Ge is 1 - 20:1, preferably 5 - 10:1, specifically it can be 1:1, 5:1, 10:1, 15:1, or 20:1. The mass ratio of Ge to RE is 0.1 - 2:1, 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, 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, or 2:1.

[0051] In the technical solution of the present invention, the high elongation heat-treatment-free die-cast aluminum alloy further contains Mo with a mass percentage content of 0-0.2% and Ge with a mass percentage content of 0-0.1%. Mo can also react with Al, Si, Fe, etc. to form 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 grains, improve the morphology of Fe-containing intermetallic compounds, and further improve the tensile strength, yield strength and elongation of the aluminum alloy. Ge can react with Al and Si, etc. to form second phases such as Al9Ge7, Al6Ge5, Al5Ge2, Al3Ge4, SiGe, etc.; 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 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 heat preservation 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, and during the process of rising to room temperature after the low-temperature quenching and heat preservation 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, so as to improve the yield strength, tensile strength and elongation of the heat-treatment-free aluminum alloy; in addition, the Ge element can also replace the Si and Cu atoms in the 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 size of the clusters and increase the volume fraction of the clusters.

[0052] In an embodiment of the present invention, the heat-treatment-free aluminum alloy contains Si with a mass percentage content of 6.5-9%, Fe with a mass percentage content of 0.01-0.3%, Cu with a mass percentage content of 0.01-0.2%, Mn with a mass percentage content of 0-0.25%, Mg with a mass percentage content of 0.01-0.15%, Zn with a mass percentage content of 0.01-0.2%, Ti with a mass percentage content of 0.01-0.1%, Ca with a mass percentage content of 0.01-0.05%, 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%.

[0053] In another embodiment of the present invention, the heat-treatable aluminum alloy contains Si with a mass percentage content of 6.5-9%, Fe with a mass percentage content of 0.01-0.3%, Cu with a mass percentage content of 0.01-0.2%, Mn with a mass percentage content of 0-0.25%, Mg with a mass percentage content of 0.01-0.15%, Zn with a mass percentage content of 0.01-0.2%, Ti with a mass percentage content of 0.01-0.1%, Zr with a mass percentage content of 0.01-0.1%, Mo with a mass percentage content of 0.01-0.1%, Ge 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%.

[0054] In yet another embodiment of the present invention, the heat-treatable aluminum alloy contains Si with a mass percentage content of 6.5-9%, Fe with a mass percentage content of 0.01-0.3%, Cu with a mass percentage content of 0.01-0.2%, Mn with a mass percentage content of 0-0.25%, Mg with a mass percentage content of 0.01-0.15%, Zn with a mass percentage content of 0.01-0.2%, Ti with a mass percentage content of 0.01-0.1%, B with a mass percentage content of 0.001-0.01%, Nb with a mass percentage content of 0.01-0.1%, Sn 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%.

[0055] The present invention also provides a method for preparing a heat-treatable die-casting aluminum alloy with high elongation rate, comprising the following steps: At a temperature of 750-830 °C, heat the Al source (preferably primary aluminum, such as electrolytic aluminum) to obtain molten aluminum; At a temperature of 720-780 °C, add the Si source, Fe source, Cu source, Mn source, Mg source, Zn source, B source, Sr source, and Ti source to the molten aluminum to obtain an alloy liquid; Perform refining treatment, slag skimming treatment, and die-casting treatment on the alloy liquid to obtain aluminum alloy components; and The aluminum alloy parts are subjected to cryogenic quenching treatment to obtain a die-cast aluminum alloy with high elongation rate without heat treatment. The die-cast aluminum alloy with high elongation rate without heat treatment contains Al, and also contains Si with a mass percentage content of 6.5 - 9%, Fe with a mass percentage content of 0.01 - 0.3%, Cu with a mass percentage content of 0.01 - 0.2%, Mn with a mass percentage content of 0 - 0.25%, Mg with a mass percentage content of 0.01 - 0.15%, Zn with a mass percentage content of 0.01 - 0.2%, B with a mass percentage content of 0 - 0.01%, Sr with a mass percentage content of 0 - 0.05%, and Ti with a mass percentage content of 0.01 - 0.1%.

[0056] The Si source, Fe source, Cu source, Mn source, Mg source, Zn source, B source, Sr source, and Ti source can be added in the form of single substances or alloys. In addition to 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 aluminum alloy liquid, and then calculate the element content added to the recycled aluminum liquid according to the detection results to obtain the die-cast aluminum alloy with high elongation rate without heat treatment of the present invention.

[0057] 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 supplemented and liquid nitrogen can be supplemented 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.

[0058] 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.

[0059] 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. The cooling rate in the die-casting treatment can be 10 - 60 K / S, specifically 10 K / S, 15 K / S, 20 K / S, 25 K / S, 30 K / S, 35 K / S, 40 K / S, 45 K / S, 50 K / S, 55 K / S, or 60 K / S.

[0060] The preparation method of the high-elongation 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, Ge 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, Ge 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, Ge, V, and RE is not more than 0.6%, preferably not more than 0.5%, specifically 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or 0.6%. The content of a single impurity in the heat-treatment-free die-casting aluminum alloy does not exceed 0.05%, and the total impurity content does not exceed 0.15%.

[0061] In the technical solution of the present invention, the high-elongation heat-treatment-free die-casting aluminum alloy prepared by the preparation method contains Si with a mass percentage content of 6.5 - 9%, Fe with a mass percentage content of 0.01 - 0.3%, Cu with a mass percentage content of 0.01 - 0.2%, Mn with a mass percentage content of 0 - 0.25%, Mg with a mass percentage content of 0.01 - 0.15%, Zn with a mass percentage content of 0.01 - 0.2%, B with a mass percentage content of 0 - 0.01%, Sr with a mass percentage content of 0 - 0.05%, and Ti with a mass percentage content of 0.01 - 0.1%. With the combined addition of Si, Fe, Cu, Mn, Mg, Zn, B, Sr, 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 260 MPa, the yield strength can be greater than 120 MPa, and the elongation can be greater than 16%. Specifically: (1)Si can improve the process flowability of aluminum alloy, but 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 improve the tensile strength and yield strength; (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. Among them, when Mg is dissolved in the CuAl2 phase and the AlFeSi phase, (CuMg)Al2 phase and AlFeSiMg phase are formed; (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. 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 vehicle painting and baking heat treatment can further improve the aging strengthening effect of Cu and Mg; (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. Zn can eliminate elemental Si to reduce the influence of Si on the properties of aluminum alloy. 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 alloy; (5)Fe can improve the demolding performance. Fe can also react with Al, Si, Mg, Cu, B to form secondary phases such as Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu, AlFeSiB, etc., to improve the tensile strength and yield strength; (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 20The second phases such as (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 second phases in aluminum alloy through heterogeneous nucleation theory or 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 transform the coarse needle-like 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 can improve the yield strength, tensile strength and elongation rate of aluminum alloy; (8)The TiAl2 phase formed by the reaction of Ti and Al can be used as a non-spontaneous core during crystallization to refine grains, second phases and precipitation phases, so as to improve the tensile strength, yield strength and elongation rate of aluminum alloy; (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.

[0062] The combined action of Si, Cu, Mn, Mg, Zn, Ti, Sr, and Fe within the above content ranges can improve the tensile strength and yield strength of the aluminum alloy; the combined action of Mn, B, Ti, 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; Cu 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.

[0063] The mass percentage content of Fe in the present invention (0.01 - 0.3 wt%) is relatively small. During the die-casting process, the temperature cooling rate is relatively large (which can be 10 - 60 K / S), such that Fe basically forms fine short rod-shaped or square-shaped A1-Fe phase or A1-Fe-Si phase. Thus, Fe within this content range has little influence on the elongation of the aluminum alloy; as the Fe content decreases, the elongation gradually increases. At this time, there is no need to increase the addition of Mn or add a large amount of Mn to reduce the influence of Fe on the elongation of the aluminum alloy; the present invention sets the mass percentage content of Mn to 0 - 0.25%, and further improves the demolding performance of the aluminum alloy through Mn; Sr can also change the morphology of the eutectic silicon phase through modification to reduce the tendency of sticking to the mold during the die-casting process.

[0064] Since the mechanical properties of the heat-treatable aluminum alloy cannot be improved by age heat treatment, most of the solute atoms in the heat-treatable 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 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.

[0065] During the storage and transportation processes after die-casting treatment of the heat-treatable aluminum alloy, natural aging will occur, that is, as the storage time prolongs, the strength increases. This natural aging is attributed to the clustering 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 clear crystal structure and disordered distribution.

[0066] The change in the strength of the heat - treatable 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. Vacancies belong to thermal defects, and their concentration has an exponential function relationship with temperature. In the present invention, after die - casting treatment, low - temperature quenching treatment is carried out on aluminum alloy parts to generate supersaturated vacancies, so as to improve the mechanical properties of the heat - treatable 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, produce 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 heat - treatable aluminum alloy.

[0067] 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. For example, by adjusting vacancies, it affects the formation of original clusters and the formation of new clusters. After adding elements of Mg (0.01 - 0.15wt%) and Cu (0.01 - 0.2wt%) 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 Mg - Si clusters and Cu - Mg 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 and Cu - Mg clusters added in the heat - treatable aluminum alloy, and promoting the growth of clusters, it further promotes the natural aging effect, so as to improve the yield strength, tensile strength and elongation of the heat - treatable aluminum alloy.

[0068] In summary, under the combined action of Si, Cu, Mn, Mg, Zn, Ti, Sr, Fe and B within the above - mentioned content range, a heat - treatable aluminum alloy with excellent demolding performance, tensile strength, yield strength and elongation is obtained.

[0069] The present invention also provides a structural member, at least part of which is made of a high - elongation heat - treatable die - cast aluminum alloy or a high - elongation heat - treatable die - cast aluminum alloy prepared by this preparation method. The 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. The structural member of the present invention can also be used in other aspects such as aerospace, high - speed rail, ship, mobile device, household appliance, chemical industry, daily necessities, construction and other fields.

[0070] Examples and Comparative Examples For the components and contents of the aluminum alloys in Examples 1 to 5 and Comparative Examples 1 to 2, please refer to Table 1, and for the performance test results, please refer to Table 2.

[0071] Table 1 Components and Contents of the Aluminum Alloys in Examples 1 to 5 and Comparative Examples 1 to 2 For the sake of simplified expression, the contents of trace elements such as impurities in the comparative examples and examples are not shown.

[0072] A domestic CSS-44100 type electronic universal tensile testing machine was used, and 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.

[0073] Table 2 Performance Test Results of the Aluminum Alloys in Examples 1 to 5 and Comparative Examples 1 to 2 The tensile strength, yield strength, and elongation rate of the high elongation rate heat-treatment-free die-cast aluminum alloys in Examples 1 to 5 are significantly greater than those of the high elongation rate heat-treatment-free die-cast aluminum alloys in Comparative Examples 1 to 2. It shows that: the performance of the high elongation rate heat-treatment-free die-cast aluminum alloy of the present invention is better in all aspects. Among them, the Fe content in Examples 1 to 5 is lower than that in Comparative Examples 1 to 2, and the Mn / Fe mass ratio in Examples 1 to 5 is less than that in Comparative Examples 1 to 2.

[0074] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. 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 elongation heat-treatment-free die-casting aluminum alloy, characterized in that: The high elongation heat-free die-casting aluminum alloy contains 6.5-9% Si by mass, 0.01-0.3% Fe by mass, 0.01-0.2% Cu by mass, 0.001-0.25% Mn by mass, 0.01-0.15% Mg by mass, 0.01-0.2% Zr by mass, 0-0.01% B by mass, 0-0.05% Sr by mass, 0.01-0.1% Ti by mass, and the remainder Al and impurities, the mass ratio of Mn to Fe is 0.004-0.5:1, and the high elongation heat-free die-casting aluminum alloy is subjected to die-casting treatment, and during the die-casting treatment, the temperature cooling rate is 10-60K / s.

2. The high elongation heat-treatment-free die-casting aluminum alloy according to claim 1, characterized in that: The sum of the mass percentage contents of Mn and Fe is 0.25-0.45%.

3. The high elongation heat-treatment-free die-casting aluminum alloy according to claim 1, characterized in that: The mass ratio of Ti to B is 1-50:

1.

4. The high elongation heat-treatment-free die-casting aluminum alloy according to claim 1, characterized in that: The high elongation heat-free die-casting aluminum alloy contains 6.5-9% Si by mass, 0.01-0.1% Fe by mass, 0.05-0.1% Cu by mass, 0.05-0.2% Mn by mass, 0.05-0.1% Mg by mass, 0.01-0.2% Zr by mass, 0.005-0.01% B by mass, 0.005-0.05% Sr by mass, and 0.05-0.1% Ti by mass.

5. The high elongation heat-treatment-free die-casting aluminum alloy according to any one of claims 1 to 4, characterized in that: Meet at least one of the following conditions: The high elongation heat-treatment-free die-casting aluminum alloy further contains 0-0.06% by mass of Ca; The high elongation heat-treatment-free die-casting aluminum alloy further contains Co in a mass percentage content of 0-0.2%; The high elongation heat-treatment-free die-casting aluminum alloy further contains 0-0.1% by mass of Cd; The high elongation heat-treatment-free die-casting aluminum alloy further contains 0-0.05% Be by mass percentage; The high elongation heat-treatment-free die-casting aluminum alloy further contains 0-0.2% by mass of Bi; The high elongation heat-treatment-free die-casting aluminum alloy further contains 0-0.2% by mass of Nb; The high elongation heat-treatment-free die-casting aluminum alloy further contains Sn in a mass percentage content of 0-0.1%; The high elongation heat-treatment-free die-casting aluminum alloy further contains Sb in an amount of 0-0.2% by mass; The high elongation heat-treatment-free die-casting aluminum alloy further contains 0-0.1% by mass of Ag; The high elongation heat-treatment-free die-casting aluminum alloy further contains 0-0.2% by mass of In; The high elongation heat-treatment-free die-casting aluminum alloy further contains 0-0.2% by mass of Mo; The high elongation heat-treatment-free die-casting aluminum alloy further contains 0-0.2% by mass of Cr; The high elongation heat-treatment-free die-casting aluminum alloy further contains Ge in an amount of 0-0.1% by mass; The high elongation heat-treatment-free die-casting aluminum alloy further contains 0-0.3% by mass of V.

6. The high elongation heat-treatment-free die-casting aluminum alloy according to claim 5, characterized in that: Meet at least one of the following conditions: When the high elongation heat-treatment-free die-casting aluminum alloy further contains Sb, the mass ratio of Mg to Sb is 0.5-10:1; When the high elongation heat-treatment-free die-casting aluminum alloy further contains Nb, the mass ratio of Mg to Nb is 0.2-15:1; When the high elongation heat-treatment-free die-casting aluminum alloy further contains Ag, the mass ratio of Mg to Ag is 1-20:1; When the high elongation heat-treatment-free die-casting aluminum alloy further contains In, the mass ratio of Cu to In is 0.1-5:1; When the high elongation heat-treatment-free die-casting aluminum alloy further contains Mo, the mass ratio of Fe to Mo is 0.1-3:1; When the high elongation heat-treatment-free die-casting aluminum alloy further contains Ge, the mass ratio of Mg to Ge is 1-20:1; When the Al-Si series heat treatment-free die-casting aluminum alloy further contains Cr and V, the mass ratio of Cr to V is 0.1-10:1; When the high elongation heat-treatment-free die-casting aluminum alloy further contains Bi and Cd, the mass ratio of Bi, Cd and Mg is 0.2-10:0.1-10:1; When the high elongation heat-treatment-free die-casting aluminum alloy further contains Co and Be, the mass ratio of Co, Be and Fe is 0.1-10:0.01-5:

1.

7. The high elongation heat-treatment-free die-casting aluminum alloy according to claim 5, characterized in that: Meet at least one of the following conditions: The high elongation heat-free die-casting aluminum alloy contains 6.5-9% Si by mass, 0.01-0.3% Fe by mass, 0.01-0.2% Cu by mass, 0.001-0.25% Mn by mass, 0.01-0.15% Mg by mass, 0.01-0.2% Zr by mass, 0.01-0.1% Ti by mass, 0.01-0.05% Ca by mass, 0.01-0.1% Co by mass, 0.01-0.05% Be by mass, and 0.01-0.1% Sb by mass; The high elongation heat-free die-casting aluminum alloy contains 6.5-9% Si by mass, 0.01-0.3% Fe by mass, 0.01-0.2% Cu by mass, 0.001-0.25% Mn by mass, 0.01-0.15% Mg by mass, 0.01-0.2% Zr by mass, 0.01-0.1% Ti by mass, 0.01-0.1% Mo by mass, 0.01-0.1% Ge by mass, 0.01-0.1% Cr by mass, and 0.05-0.2% V by mass; The high elongation heat-free die-casting aluminum alloy contains 6.5-9% Si by mass, 0.01-0.3% Fe by mass, 0.01-0.2% Cu by mass, 0.001-0.25% Mn by mass, 0.01-0.15% Mg by mass, 0.01-0.2% Zr by mass, 0.01-0.1% Ti by mass, 0.001-0.01% B by mass, 0.01-0.1% Nb by mass, 0.01-0.1% Sn by mass, 0.01-0.05% Ag by mass, and 0.01-0.1% In by mass.

8. A method for preparing a high elongation heat-treatment-free die-casting aluminum alloy, comprising the following steps: The Al source is subjected to a first heating treatment to obtain aluminum liquid; Adding Si source, Fe source, Cu source, Mn source, Mg source, Zr source, B source, Sr source, and Ti source to the aluminum liquid, and performing a second heating treatment to obtain an alloy liquid; The alloy liquid is subjected to refining treatment, slag removal treatment, and die-casting treatment to obtain aluminum alloy parts; and The aluminum alloy parts are subjected to low temperature quenching treatment to obtain a high elongation heat-free die-cast aluminum alloy, wherein the high elongation heat-free die-cast aluminum alloy contains 6.5-9% Si by mass, 0.01-0.3% Fe by mass, 0.01-0.2% Cu by mass, 0.001-0.25% Mn by mass, 0.01-0.15% Mg by mass, 0.01-0.2% Zr by mass, 0-0.01% B by mass, 0-0.05% Sr by mass, 0.01-0.1% Ti by mass, and the remainder Al and impurities, the mass ratio of Mn to Fe is 0.004-0.5:1, and during the die-casting process, the temperature cooling rate is 10-60K / s.

9. The method for preparing a high elongation heat-treatment-free die-casting aluminum alloy according to claim 8, characterized in that: The method further includes adding at least one of a Ca source, a Co source, a Cd source, a Be source, a Bi source, a Nb source, a Sn source, a Sb source, an Ag source, an In source, a Mo source, a Cr source, a Ge source, and a V source to the aluminum liquid.

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

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