High-elongation heat-treatment-free die-cast aluminum alloy, method for manufacturing same, and structural member

Abstract

The application provides a high-elongation heat-treatment-free die-casting aluminum alloy and a preparation method and a structural member thereof, the aluminum alloy containing 6.5-9% of Si in terms of mass percentage, 0.01-0.3% of Fe in terms of mass percentage, 0.01-0.2% of Cu in terms of mass percentage, 0.001-0.25% of Mn in terms of mass percentage, 0.01-0.15% of Mg in terms of mass percentage, 0.01-0.2% of Zn in terms of mass percentage, 0-0.01% of B in terms of mass percentage, 0-0.05% of Sr in terms of mass percentage, 0.01-0.2% of RE in terms of mass percentage, and the balance of Al and impurities, and the mass ratio of Mn to Fe is 0.004-0.5:1, and the high-elongation heat-treatment-free die-casting aluminum alloy is subjected to die-casting treatment, and the temperature cooling rate during the die-casting treatment is 10-60 K / s.

Description

High elongation heat-free die-cast aluminum alloys, their preparation methods, and structural components Technical Field

[0001] This invention relates to the field of aluminum alloy technology, and more particularly to a high elongation-rate heat-free die-cast aluminum alloy, a method for preparing the high elongation-rate heat-free die-cast aluminum alloy, and structural components thereof. Background Technology

[0002] With the increasingly stringent requirements for energy conservation and emission reduction in the automotive industry, aluminum alloy vacuum die castings are seeing a continuous increase in their application penetration in key automotive structural components due to their advantages such as integration, lightweight, and high strength and toughness. For vehicle manufacturers, aluminum alloy die castings for automotive structural components differ from traditional aluminum alloy die castings. The joining processes during manufacturing and the overall vehicle performance during service place higher demands on the comprehensive mechanical properties, especially plasticity, of aluminum alloy die castings in the as-cast state. Currently, Al-Si and Al-Mg alloys generally only possess moderate strength and plasticity, which is insufficient to meet the needs of automotive structural components (especially large automotive structural components). Other fields, such as aerospace, high-speed rail, shipbuilding, mobile devices, home appliances, chemical industry, daily necessities, and construction, also typically require aluminum alloy die castings, and the requirements for their comprehensive mechanical properties are also high. Therefore, there is an urgent need to develop a high-elongation, heat-treatable die-cast aluminum alloy with excellent demolding performance, tensile strength, yield strength, and elongation. Summary of the Invention

[0003] In view of the above-mentioned deficiencies of the prior art, the present invention provides a high elongation-free die-cast aluminum alloy, which aims to improve the demolding performance, tensile strength, yield strength and elongation of the heat-free aluminum alloy.

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

[0005] This invention also provides a method for preparing a high elongation, heat-free die-cast aluminum alloy, comprising the following steps:

[0006] The Al source is subjected to a first heating treatment to obtain molten aluminum.

[0007] 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 heating treatment to obtain an alloy liquid;

[0008] The alloy liquid is refined, slag removed, and die-cast to obtain aluminum alloy parts; and

[0009] The aluminum alloy parts are subjected to low-temperature quenching to obtain a high-elongation, heat-free die-cast aluminum alloy. The high-elongation, heat-free die-cast aluminum alloy contains 6.5-9% Si, 0.01-0.3% Fe, 0.01-0.2% Cu, 0.001-0.25% Mn, 0.01-0.15% Mg, 0.01-0.2% Zn, 0-0.01% B, 0-0.05% Zr, 0.01-0.1% Ti, and the balance Al and impurities. The mass ratio of Mn to Fe is 0.004-0.5:1. During the die-casting process, the temperature cooling rate is 10-60 K / s.

[0010] The present invention also provides a structural component, at least a portion of which is made of the above-mentioned high elongation heat-free die-cast aluminum alloy or a high elongation heat-free die-cast aluminum alloy prepared by the above-mentioned preparation method.

[0011] In the technical solution of this invention, the high elongation-rate heat-free die-cast aluminum alloy contains 6.5-9% Si, 0.01-0.3% Fe, 0.01-0.2% Cu, 0-0.25% Mn, 0.01-0.15% Mg, 0.01-0.2% Zn, 0-0.01% B, 0-0.05% Sr, and 0.01-0.1% Ti by mass. The combined addition of Si, Fe, Cu, Mn, Mg, Zn, B, Sr, and Ti within the above content ranges interacts and influences each other, enabling the heat-free aluminum alloy to achieve a tensile strength greater than 260 MPa, a yield strength greater than 120 MPa, and an elongation greater than 16%. Specifically:

[0012] (1) Si can improve the process flow properties of aluminum alloys, but if the content is too high, it will reduce the elongation. Si can react with Al, Fe, Mg, Cu, B and other substances to generate second phases such as Mg2Si, AlFeSi, AlFeSiCu, AlFeMgSi, AlCuMgSi, AlFeSiB, which can improve tensile strength and yield strength.

[0013] (2) Mg can react with Al, Fe, Si, Cu, Zn and other elements to form second phases such as AlFeMgSi, (CuMg)Al2, AlCuMgSi, Mg2Si, Mg2Zn, and Mg2SiZn, which can improve tensile strength and yield strength. Among them, when Mg is dissolved in CuAl2 and AlFeSi phases, it forms (CuMg)Al2 and AlFeSiMg phases.

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

[0015] (4) Zn can react with Al, Mg, Cu and Si to form second phases such as MgZn2, Mg2SiZn and Al2CuZn, which can improve 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 and Al2CuMg, and increase the volume fraction and dispersion of precipitated phases. The combined addition of Zn and Mg can form the strengthening phase Mg / Zn2, which can significantly improve the tensile strength and yield strength of aluminum alloys.

[0016] (5) Fe can improve demolding performance. Fe can also react with Al, Si, Mg, Cu and B to generate second phases such as Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu and AlFeSiB, which can improve tensile strength and yield strength.

[0017] (6) Mn can react with Al, Fe, Si, and Cu to form MnAl2, MnAl6, α-(Fe,Mn)Al6, and Al. 12 CuMn2, α-Al(FeMn)Si, τ(Cu2Mn3Al 20Mn can improve tensile strength and yield strength by forming a second phase, such as α-Al(Fe,Mn)Al6. Mn can significantly refine grain size by causing lattice distortion in the matrix and producing MnAl6 dispersed particles through reaction with Al, thereby improving elongation. MnAl6 can also dissolve Fe to form α-(Fe,Mn)Al6, reducing Fe content and mitigating Fe hazard. Mn reacts with Al, Fe, Mn, and Si to form spherical or granular AlFeMnSi composite phases, which can prevent the formation of long needle-like Fe phases, thus reducing Fe hazard. This improves the mold release properties of aluminum alloys and also enhances their tensile strength and yield strength. Mn can also transform coarse needle-like β-AlFeSi phases into small granular α-Al(FeMn)Si dispersed particles, improving Fe morphology and eliminating Fe hazard. Specifically, Mn can replace some of the Fe in the coarse needle-like β-AlFeSi phase, generating… The formation of small-particle dispersed β-Al(FeMn)Si phase improves the formation and growth shape of the β phase, thereby reducing the harm caused by Fe. Mn can also promote the transformation of acicular β-Al(FeMn)Si phase into small-particle dispersed α-Al(FeMn)Si phase. The generated α-Al(FeMn)Si phase dispersed particles are distributed in the aluminum matrix and strongly pinned to the subgrain boundaries of the aluminum alloy. This is mainly because the Mn-containing α-phase dispersed particles in the aluminum alloy can act as non-uniform nucleation sites during the aging process of the β′ phase, thus inducing its nucleation and accelerating the precipitation of the β′ phase. Mn can also react with impurity phases in the aluminum alloy liquid to form Al-Mn-X phase (X is an impurity element, including transition metal elements, etc.), which can purify the aluminum alloy liquid. These phases can act as grain nucleation sites to increase the nucleation rate, refine the grains, and improve the tensile strength, yield strength, elongation and fluidity of the aluminum alloy.

[0018] (7) Sr preferentially combines with Fe to form dispersion strengthening, reducing the solid solubility of Fe, thereby improving yield strength and tensile strength; Sr can change the behavior of intermetallic compound phases in crystallography, and can be used as a modifier to refine the grains and second phase of aluminum alloys through heterogeneous nucleation theory or twin valley mechanism. For example, Sr can change the morphology of eutectic silicon phase through modification, thereby improving the elongation of aluminum alloys and reducing 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 improving yield strength, tensile strength and elongation;

[0019] (8) The TiAl2 phase generated by the reaction of Ti and Al, as a non-spontaneous nucleus during crystallization, can refine the grains, second phase and precipitated phase, thereby improving the tensile strength, yield strength and elongation of aluminum alloys;

[0020] (9) B can undergo borylation reaction with transition metal elements (including transition metal elements such as Fe) to generate compounds such as ferroboron compounds that can be separated from aluminum alloy liquid, thereby purifying the aluminum alloy liquid; B is easily adsorbed on the surface of iron-rich phase, inhibiting the growth of iron-rich phase and playing a role in controlling the size of iron-rich phase, and can also prevent the formation of iron-rich phase in 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 aluminum alloy.

[0021] The combined effects of Si, Cu, Mn, Mg, Zn, Ti, Sr, and Fe within the aforementioned content range can improve the tensile strength and yield strength of aluminum alloys; the combined effects of Mn, B, Ti, and Sr within the aforementioned content range can refine grains, the second phase, and precipitated phases, thereby improving the elongation of aluminum alloys; Cu and Zn within the aforementioned content range can promote the precipitation of the second phase, increasing the volume fraction and dispersion of the precipitated phase, further improving the tensile strength, yield strength, and elongation of aluminum alloys; the combined effects of Fe, Sr, and Mn within the aforementioned content range can improve the mold release properties of aluminum alloys.

[0022] The Fe content in this invention is relatively low (0.01-0.3 wt%). During the die-casting process, the temperature cooling rate is relatively high (10-60 K / s), causing Fe to form mostly fine, short rod-shaped or cubic Al-Fe or Al-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, so 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. This invention sets the Mn content to 0-0.25% by mass, which further improves the demolding performance of the aluminum alloy. Sr can also change the morphology of the eutectic silicon phase through modification to reduce the tendency of sticking during the die-casting process.

[0023] Since the mechanical properties of heat-free aluminum alloys cannot be improved by aging heat treatment, most of the solute atoms in the heat-free aluminum alloys of the present invention usually exist in the aluminum matrix in the form of solid solution. In addition to grain refinement, the strength increase of the heat-free aluminum alloy mainly comes from the pinning of dislocations by lattice volume mismatch and elastic mismatch caused by solid solution atoms, i.e., solid solution strengthening.

[0024] During storage and transportation after die casting, heat-free aluminum alloys undergo natural aging, meaning their strength increases with prolonged storage time. This natural aging is attributed to the aggregation effect of solute atoms in the aluminum alloy, forming solute atom clusters. These clusters are disordered aggregations of solute atoms within the aluminum matrix, typically ranging in size from a few nanometers and composed of several to dozens of randomly distributed atoms without a defined crystal structure.

[0025] The strength variation of heat-free aluminum alloys is mainly related to the size and volume fraction of solute atomic clusters. During natural aging, the formation and growth of clusters are closely linked to changes in the concentration of supersaturated quenching vacancies. Vacancies are thermal defects, and their concentration has an exponential relationship with temperature. This invention performs low-temperature quenching on aluminum alloy parts after die casting to generate supersaturated vacancies, thereby improving the mechanical properties of heat-free aluminum alloys. Specifically, during die casting, the equilibrium vacancy concentration is relatively high; during subsequent quenching, some vacancies at high temperatures are retained, resulting in supersaturated vacancies. Furthermore, the low-temperature quenching also causes the aluminum alloy to shrink, producing plastic deformation, reducing the solubility of elements in aluminum, increasing the nucleation sites of clusters, and refining the α-Al phase and eutectic Si phase structure, thereby improving the yield strength, tensile strength, and elongation of heat-free aluminum alloys.

[0026] The addition of Cu, Mn, Mg, Zn, Ti, Sr, Fe, and B can also regulate the behavior of solute atom clusters in aluminum alloys, such as by adjusting vacancies to influence the formation of existing clusters and the formation of new clusters. In the aluminum melt of this invention, the addition of Mg (0.01-0.15 wt%) and Cu (0.01-0.2 wt%) within a certain content range activates vacancy diffusion and promotes the formation of Mg-Si and Cu-Mg clusters, significantly strengthening the clusters. Mn and Sr have much larger atomic radii than Al. The Mn and Sr atoms within the aforementioned content range form lattice distortions in the aluminum matrix. Combined with the pinned vacancies and Mg-Si and Cu-Mg clusters added to the heat-free aluminum alloy, and the promotion of cluster growth, further enhance the natural aging effect, thereby improving the yield strength, tensile strength, and elongation of the heat-free aluminum alloy.

[0027] In summary, under the combined effect of Si, Cu, Mn, Mg, Zn, Ti, Sr, Fe and B within the above-mentioned content range, a heat-free aluminum alloy with excellent demolding performance, tensile strength, yield strength and elongation is obtained. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] One embodiment of the present invention provides a high elongation-rate heat-free die-cast aluminum alloy, which contains 6.5-9% by mass of Si, 0.01-0.3% by mass of Fe, 0.01-0.2% by mass of Cu, 0-0.25% by mass of Mn, 0.01-0.15% by mass of Mg, 0.01-0.2% by mass of Zn, 0-0.01% by mass of B, 0-0.05% by mass of Sr, 0.01-0.1% by mass of Ti, and Al and unavoidable impurities.

[0030] In one embodiment, the high elongation heat-free die-cast aluminum alloy contains 6.5-9% Si, 0.01-0.1% Fe, 0.05-0.1% Cu, 0.05-0.2% Mn, 0.05-0.1% Mg, 0.05-0.2% Zn, 0.005-0.01% B, 0.005-0.05% Sr, and 0.05-0.1% Ti by mass.

[0031] 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.

[0032] In existing technologies in the aluminum alloy field, it is generally believed that a Mn to Fe mass ratio less than 0.6:1 and greater than 1:1 will reduce the tensile strength, yield strength, and elongation of the aluminum alloy. Therefore, to obtain better tensile strength, yield strength, and elongation, the Mn to Fe mass ratio is usually set to 0.6-1:1. This invention sets the Mn to Fe mass ratio to 0-0.8:1, preferably 0-0.6:1, and even more preferably 0-0.5:1, resulting in a heat-free aluminum alloy with better tensile strength, yield strength, and elongation, 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, when the cooling rate is high and the Fe content is low, Fe generally forms fine, short rod-shaped or cubic Al-Fe or Al-Fe-Si phases, making its impact on the elongation of the aluminum alloy minimal. Furthermore, as the Fe content decreases, the elongation gradually increases, eliminating the need to add Mn or a large amount of Mn to reduce the influence of Fe on the elongation of the aluminum alloy. Moreover, the lattice constant of Mn is much greater than that of the Al matrix; Mn dissolved in the Al matrix causes discontinuities in the internal structure of the Al matrix, leading to abrupt changes in dislocation cutting radii and reducing elongation. Therefore, this invention achieves better tensile strength, yield strength, and elongation when the Fe content is set to 0.01-0.3%, the Mn content to 0-0.25%, and the mass ratio of Mn to Fe to 0-0.8:1.

[0033] Considering 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%, specifically 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%. The present invention sets the Fe content to 0.01-0.3%, the Mn content to 0-0.25%, the mass ratio of Mn to Fe to 0-0.8:1, and the sum of the mass percentage contents of Mn and Fe to 0.25-0.5%. By combining these four factors, better demolding performance, tensile strength, yield strength, and elongation are obtained.

[0034] 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 specific percentage content of Cu by mass 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 specific mass percentage content of Mn can be 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 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 specific mass percentage content of Mg 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%, or 0.15%. The specific percentage content of Zn by mass 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 percentage content of B by mass is 0-0.01%, specifically 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%.

[0035] The mass ratio of Ti to B is 1-50:1, preferably 10-30:1, and even more preferably 15-20:1. Specifically, it 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.

[0036] In the technical solution of this invention, the high elongation-rate heat-free die-cast aluminum alloy contains 6.5-9% Si, 0.01-0.3% Fe, 0.01-0.2% Cu, 0-0.25% Mn, 0.01-0.15% Mg, 0.01-0.2% Zn, 0-0.01% B, 0-0.05% Sr, and 0.01-0.1% Ti by mass. The combined addition of Si, Fe, Cu, Mn, Mg, Zn, B, Sr, and Ti within the above content ranges interacts and influences each other, enabling the heat-free aluminum alloy to achieve a tensile strength greater than 260 MPa, a yield strength greater than 120 MPa, and an elongation greater than 16%. Specifically:

[0037] (1) Si can improve the process flow properties of aluminum alloys, but if the content is too high, it will reduce the elongation. Si can react with Al, Fe, Mg, Cu, B and other substances to generate second phases such as Mg2Si, AlFeSi, AlFeSiCu, AlFeMgSi, AlCuMgSi, AlFeSiB, which can improve tensile strength and yield strength.

[0038] (2) Mg can react with Al, Fe, Si, Cu, Zn and other elements to form second phases such as AlFeMgSi, (CuMg)Al2, AlCuMgSi, Mg2Si, Mg2Zn, and Mg2SiZn, which can improve tensile strength and yield strength. Among them, when Mg is dissolved in CuAl2 and AlFeSi phases, it forms (CuMg)Al2 and AlFeSiMg phases.

[0039] (3) Cu can react with Al, Fe, Si, Mg, Zn and other substances to form second phases such as CuAl2, AlFeSiCu, AlCuMgSi, Al2CuZn, (CuMg)Al2, which can improve tensile strength and yield strength. It can also promote the precipitation of second phases such as Mg2Si, Mg2Zn, Mg2SiZn, and increase the volume fraction and dispersion of the precipitated phases. Subsequent natural aging or vehicle paint baking heat treatment can further improve the aging strengthening effect of Cu and Mg.

[0040] (4) Zn can react with Al, Mg, Cu and Si to form second phases such as MgZn2, Mg2SiZn and Al2CuZn, which can improve 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 and Al2CuMg, and increase the volume fraction and dispersion of precipitated phases. The combined addition of Zn and Mg can form the strengthening phase Mg / Zn2, which can significantly improve the tensile strength and yield strength of aluminum alloys.

[0041] (5) Fe can improve demolding performance. Fe can also react with Al, Si, Mg, Cu and B to generate second phases such as Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu and AlFeSiB, which can improve tensile strength and yield strength.

[0042] (6) Mn can react with Al, Fe, Si, and Cu to form MnAl2, MnAl6, α-(Fe,Mn)Al6, and Al. 12 CuMn2, α-Al(FeMn)Si, τ(Cu2Mn3Al 20Mn can improve tensile strength and yield strength by forming a second phase, such as α-Al(Fe,Mn)Al6. Mn can significantly refine grain size by causing lattice distortion in the matrix and producing MnAl6 dispersed particles through reaction with Al, thereby improving elongation. MnAl6 can also dissolve Fe to form α-(Fe,Mn)Al6, reducing Fe content and mitigating Fe hazard. Mn reacts with Al, Fe, Mn, and Si to form spherical or granular AlFeMnSi composite phases, which can prevent the formation of long needle-like Fe phases, thus reducing Fe hazard. This improves the mold release properties of aluminum alloys and also enhances their tensile strength and yield strength. Mn can also transform coarse needle-like β-AlFeSi phases into small granular α-Al(FeMn)Si dispersed particles, improving Fe morphology and eliminating Fe hazard. Specifically, Mn can replace some of the Fe in the coarse needle-like β-AlFeSi phase, generating… The formation of small-particle dispersed β-Al(FeMn)Si phase improves the formation and growth shape of the β phase, thereby reducing the harm caused by Fe. Mn can also promote the transformation of acicular β-Al(FeMn)Si phase into small-particle dispersed α-Al(FeMn)Si phase. The generated α-Al(FeMn)Si phase dispersed particles are distributed in the aluminum matrix and strongly pinned to the subgrain boundaries of the aluminum alloy. This is mainly because the Mn-containing α-phase dispersed particles in the aluminum alloy can act as non-uniform nucleation sites during the aging process of the β′ phase, thus inducing its nucleation and accelerating the precipitation of the β′ phase. Mn can also react with impurity phases in the aluminum alloy liquid to form Al-Mn-X phase (X is an impurity element, including transition metal elements, etc.), which can purify the aluminum alloy liquid. These phases can act as grain nucleation sites to increase the nucleation rate, refine the grains, and improve the tensile strength, yield strength, elongation and fluidity of the aluminum alloy.

[0043] (7) Sr preferentially combines with Fe to form dispersion strengthening, reducing the solid solubility of Fe, thereby improving yield strength and tensile strength; Sr can change the behavior of intermetallic compound phases in crystallography, and can be used as a modifier to refine the grains and second phase of aluminum alloys through heterogeneous nucleation theory or twin valley mechanism. For example, Sr can change the morphology of eutectic silicon phase through modification, thereby improving the elongation of aluminum alloys and reducing 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 improving yield strength, tensile strength and elongation;

[0044] (8) The TiAl2 phase generated by the reaction of Ti and Al, as a non-spontaneous nucleus during crystallization, can refine the grains, second phase and precipitated phase, thereby improving the tensile strength, yield strength and elongation of aluminum alloys;

[0045] (9) B can undergo borylation reaction with transition metal elements (including transition metal elements such as Fe) to generate compounds such as ferroboron compounds that can be separated from aluminum alloy liquid, thereby purifying the aluminum alloy liquid; B is easily adsorbed on the surface of iron-rich phase, inhibiting the growth of iron-rich phase and playing a role in controlling the size of iron-rich phase, and can also prevent the formation of iron-rich phase in 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 aluminum alloy.

[0046] The combined effects of Si, Cu, Mn, Mg, Zn, Ti, Sr, and Fe within the aforementioned content range can improve the tensile strength and yield strength of aluminum alloys; the combined effects of Mn, B, Ti, and Sr within the aforementioned content range can refine grains, the second phase, and precipitated phases, thereby improving the elongation of aluminum alloys; Cu and Zn within the aforementioned content range can promote the precipitation of the second phase, increasing the volume fraction and dispersion of the precipitated phase, further improving the tensile strength, yield strength, and elongation of aluminum alloys; the combined effects of Fe, Sr, and Mn within the aforementioned content range can improve the mold release properties of aluminum alloys.

[0047] The Fe content in this invention is relatively low (0.01-0.3 wt%). During the die-casting process, the temperature cooling rate is relatively high (10-60 K / s), causing Fe to form mostly fine, short rod-shaped or cubic Al-Fe or Al-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, so 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. This invention sets the Mn content to 0-0.25% by mass, which further improves the demolding performance of the aluminum alloy. Sr can also change the morphology of the eutectic silicon phase through modification to reduce the tendency of sticking during the die-casting process.

[0048] Since the mechanical properties of heat-free aluminum alloys cannot be improved by aging heat treatment, most of the solute atoms in the heat-free aluminum alloys of the present invention usually exist in the aluminum matrix in the form of solid solution. In addition to grain refinement, the strength increase of the heat-free aluminum alloy mainly comes from the pinning of dislocations by lattice volume mismatch and elastic mismatch caused by solid solution atoms, i.e., solid solution strengthening.

[0049] During storage and transportation after die casting, heat-free aluminum alloys undergo natural aging, meaning their strength increases with prolonged storage time. This natural aging is attributed to the aggregation effect of solute atoms in the aluminum alloy, forming solute atom clusters. These clusters are disordered aggregations of solute atoms within the aluminum matrix, typically ranging in size from a few nanometers and composed of several to dozens of randomly distributed atoms without a defined crystal structure.

[0050] The strength variation of heat-free aluminum alloys is mainly related to the size and volume fraction of solute atomic clusters. During natural aging, the formation and growth of clusters are closely linked to changes in the concentration of supersaturated quenching vacancies. Vacancies are thermal defects, and their concentration has an exponential relationship with temperature. This invention performs low-temperature quenching on aluminum alloy parts after die casting to generate supersaturated vacancies, thereby improving the mechanical properties of heat-free aluminum alloys. Specifically, during die casting, the equilibrium vacancy concentration is relatively high; during subsequent quenching, some vacancies at high temperatures are retained, resulting in supersaturated vacancies. Furthermore, the low-temperature quenching also causes the aluminum alloy to shrink, producing plastic deformation, reducing the solubility of elements in aluminum, increasing the nucleation sites of clusters, and refining the α-Al phase and eutectic Si phase structure, thereby improving the yield strength, tensile strength, and elongation of heat-free aluminum alloys.

[0051] The addition of Cu, Mn, Mg, Zn, Ti, Sr, Fe, and B can also regulate the behavior of solute atom clusters in aluminum alloys, such as by adjusting vacancies to influence the formation of existing clusters and the formation of new clusters. In the aluminum melt of this invention, the addition of Mg (0.01-0.15 wt%) and Cu (0.01-0.2 wt%) within a certain content range activates vacancy diffusion and promotes the formation of Mg-Si and Cu-Mg clusters, significantly strengthening the clusters. Mn and Sr have much larger atomic radii than Al. The Mn and Sr atoms within the aforementioned content range form lattice distortions in the aluminum matrix. Combined with the pinned vacancies and Mg-Si and Cu-Mg clusters added to the heat-free aluminum alloy, and the promotion of cluster growth, further enhance the natural aging effect, thereby improving the yield strength, tensile strength, and elongation of the heat-free aluminum alloy.

[0052] In summary, under the combined effect of Si, Cu, Mn, Mg, Zn, Ti, Sr, Fe and B within the above-mentioned content range, a heat-free aluminum alloy with excellent demolding performance, tensile strength, yield strength and elongation is obtained.

[0053] The high elongation, heat-free die-cast aluminum alloy further contains 0-0.06% Ca by mass, specifically 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, or 0.06%. The high elongation, heat-free die-cast aluminum alloy further contains 0-0.1% Sn by mass, specifically 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. The high elongation-rate heat-free die-cast aluminum alloy also contains 0-0.2% RE by mass, specifically 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%. RE is at least one of La, Ce, Pr, Nd, Er, Sm, Y, Gd, and Sc.

[0054] In one embodiment, RE consists of La, Y, and Sm, in a ratio of 0.01-0.03:0.02-0.05:1. In another embodiment, RE consists of Pr, Er, and Nd, in a ratio of 0.02-0.05:0.03-0.08:1. In yet another embodiment, RE consists of Sm, Y, and Gd, in a ratio of 0.06-0.08:0.1-0.2:1. Adding multiple rare earth elements in combination achieves a better refining effect.

[0055] 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.

[0056] In the technical solution of this invention, the high elongation heat-free die-cast aluminum alloy may also contain 0-0.06% Ca, 0-0.1% Sn, and 0-0.2% RE by mass percentage. Ca can improve the β-Fe phase to reduce the harm of Fe, and can also react with Al, Cu, Zn, and Si to form second phases such as Al4Ca, Al2Ca3, AlCa2, AlCaCu, CaZn, CaAlZn, and Al2CaSi2, thereby improving tensile strength and yield strength. Ca can also refine the eutectic structure, improve the β-Fe phase, and has a modifying effect on aluminum alloys. Sn can react with Al, Mg, Sc, etc., to form second phases such as Al9Sn7, Al6Sn5, Al5Sn2, Al3Sn4, Mg2Sn, and Mg2ScSn, thereby improving tensile strength and yield strength. Sn can promote the formation of Mg2Si and Mg2Zn. The precipitation of second phases such as Mg2SiZn and Al2Cu reduces the solid solubility of these elements in the aluminum matrix. The rare earth element (RE) is distributed in the same region as the Fe phase and can form a rare earth active film on the surface of the iron-containing phase or combine with Al, Fe, Ti and other atoms to form rare earth compounds such as AlFeRE. This prevents the formation of hard and brittle β-AlFeSi phase at the grain boundaries, effectively reducing the solid solubility of harmful elements in the aluminum matrix, thereby improving tensile strength and yield strength. RE can transform the long strip-shaped β-Fe phase into a spherical α-Fe phase and modify elemental Si. RE can also promote the precipitation of dispersed phases such as CuAl2 and (CuMg)Al2, further improving tensile strength and yield strength. Resin (RE) is a surface-active element with a radius larger than that of Al. It cannot enter the α-Al lattice but can segregate at grain boundaries or adsorb at the solid-liquid interface, forming supercooling. This increases the chance of dendrite melting, thereby refining the grains, second phase, and precipitated phases (e.g., refining Al3Fe, Al3ScZr, AlSiMo, and Mg2Si phases), further improving the tensile strength, yield strength, and elongation of aluminum alloys. The combination of Ca and RE can significantly refine the grains and second phase, thus improving tensile strength, yield strength, and elongation. When RE (0-0.2 wt%) and Zr (0.01-0.2 wt%) are added within a certain range, and the mass ratio of RE to Zr is 0.1-1:1, highly distorted coherent solid solution elements can promote the formation of high-density Mg-Si clusters, Cu-Mg clusters, and other atomic clusters, and significantly inhibit the diffusion of atoms within these clusters, improving their stability and thus increasing yield strength, tensile strength, and elongation.

[0057] The high elongation, heat-free die-cast aluminum alloy further contains 0-0.2% Co by mass, specifically 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, heat-free die-cast aluminum alloy further contains 0-0.05% Be by mass, specifically 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, or 0.05%. The high elongation, heat-free die-cast aluminum alloy further contains 0-0.2% Bi by mass, specifically 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, heat-free die-cast aluminum alloy further contains 0-0.1% Cd by mass, specifically 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. The high elongation, heat-free die-cast aluminum alloy also contains 0-0.2% Cr by mass, specifically 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, heat-free die-cast aluminum alloy also contains 0-0.2% Sb by mass, specifically 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 heat-free die-cast aluminum alloy also contains 0-0.2% Zr by mass, specifically 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, heat-free die-cast aluminum alloy also contains 0-0.3% V by mass, specifically 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%.

[0058] The mass ratio of Mg to Sb is 0.5-10:1, preferably 1-5:1, and specifically 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, 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, or 1:1.

[0059] 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, and more preferably 0.2-0.5:1. Specifically, it 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 die casting, when the cooling rate is high, the Fe content is low, and the mass ratio of (Mn+RE) to Fe is 0-0.8:1, Fe will generally form fine, short rod-shaped or cubic Al-Fe or Al-Fe-Si phases. RE can also round out these fine, short rod-shaped or cubic Al-Fe or Al-Fe-Si phases to improve elongation.

[0060] The mass ratio of (Mn+RE+Zr) to Fe is 0-0.8:1 (i.e., the ratio of the mass percentage content of Mn, RE, and Zr to the mass percentage content of Fe), preferably 0.1-0.6:1, and more preferably 0.2-0.5:1. Specifically, it 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... 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, 0.4 The possible ratios of Fe to Fe in the die-casting process are 5:1, 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 die-casting, when the cooling rate is high, the Fe content is low, and the mass ratio of (Mn+RE+Zr) to Fe is 0-0.8:1, Fe will generally form fine, short rod-shaped or cubic Al-Fe or Al-Fe-Si phases. The combination of RE and Zr can also significantly round out the fine, short rod-shaped or cubic Al-Fe or Al-Fe-Si phases, thereby improving elongation.

[0061] When RE, Ti, and B are combined, TiB2 is less likely to agglomerate and precipitate, ensuring the effective amount of TiB2 and prolonging the effective interaction time of Ti and B. This is because RE improves the wettability of aluminum liquid to borides. Ti can also assist B, Mn, Cr, and RE in further refining the grains and the second phase. B can react with Al, Si, and Fe to form the AlFeSiB second phase, thereby improving tensile strength and yield strength. B can also combine with Mn, Cr, and RE to prevent the formation of iron-rich phases.

[0062] The combined action of Mn, Cr, and RE effectively improves the morphology of Fe, reduces the Fe content, and refines and controls the grain size, resulting in aluminum alloys with better tensile strength, yield strength, and elongation. Specifically, Mn can significantly refine recrystallized grains and the second phase, effectively transforming coarse needle-like or plate-like β-AlFeSi phases into small granular α-Al(FeMn)Si dispersed particles to improve Fe morphology. It can also react with Fe to form α-(Fe,Mn)Al6 phase to reduce Fe content. Clearly, Mn can reduce Fe content, improve Fe morphology, and refine grains and the second phase. Cr can effectively transform needle-like β-Fe phases into α-Fe phases to improve Fe morphology, and can also react with Fe to form (CrFe)Al7 and (CrMn)Al6 phases. 12 Mn and Cr can reduce the Fe content by adding dispersed phases. Furthermore, they can form dispersed phases such as AlCrSi and Mg2(SiCr), increasing the precipitation volume fraction and uniformity of the dispersed phases, thus improving the mechanical properties of the alloy. Resin (RE) is distributed in the same region as the Fe phase, allowing for the formation of a rare earth active film on the Fe phase surface, preventing the formation of a hard and brittle β-AlFeSi phase at grain boundaries. Additionally, Mn can significantly refine grain size, Cr can hinder grain growth, refine grains and the second phase, and RE can also refine grains. The combined addition of Mn, Cr, and RE effectively improves the Fe morphology. 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 high bulk density and strong thermal stability. With prolonged standing time, some of these phases settle to the bottom, while others pin grain boundaries, effectively refining and controlling grain size. Furthermore, Mn, Cr, and RE can react with trace impurities in molten aluminum alloys to form Al-Cr-X, Al-Mn-X, and Al-RE-X phases (where X is the impurity element). These phases can act as nucleation sites, increasing the nucleation rate, refining the grains, purifying the aluminum alloy, and improving its tensile strength, yield strength, fluidity, and elongation. In summary, the synergistic effect of Mn, Cr, and RE within the aforementioned content ranges improves the Fe morphology, reduces the Fe content, and refines the grains, resulting in aluminum alloys with excellent overall performance.

[0063] The mass ratio of Cr to V is 0.1-10:1, preferably 0.5-10:1, and can specifically 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 is 0.5-5:1, preferably 1-3:1, and can specifically 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, more 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.

[0064] The mass ratio of Co, Be, and Fe is 0.1-10:0.01-5:1, preferably 0.5-10:0.05-5:1, and more preferably 1-5:1-3:1. Specifically, it 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, or 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.

[0065] In one embodiment, the high elongation heat-free die-cast aluminum alloy further contains 0-0.1% Te by mass, specifically 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. When Sb and Te are added together, fine petal-shaped primary crystals can be formed to improve the tensile strength and elongation of the aluminum alloy.

[0066] In the technical solution of this invention, the high elongation-rate heat-free die-cast aluminum alloy further contains 0-0.2% Co, 0-0.05% Be, 0-0.2% Bi, 0-0.1% Cd, 0-0.2% Cr, 0-0.2% Zr, and 0-0.2% Sb by mass. Co can promote the formation of Fe spherical phase, generating small-particle-size Al3(Fe,Co) phase that can improve the mechanical properties of aluminum alloy, and can also transform coarse needle-like and plate-like Al3Fe phase into α-Al. 15(Fe,Co)3Si2 (which can be granular, flower-like, or fine strip-like) has a refining effect on the Al3Fe phase, further improving the tensile strength, yield strength, and elongation of aluminum alloys. Simultaneously, the addition of Ce and Co not only improves the thermal stability of aluminum alloys but also promotes… <001> and <111> Be can enhance the tensile and yield strength of aluminum alloys by forming orientations. Be can react with Al, Fe, and Si to form second phases such as Be-Fe (Al8Fe2SiBe)2, thereby improving tensile and yield strength. Be can refine the Si phase by transforming the eutectic Si phase from a lamellar phase to a finer phase, thus reducing or eliminating the adverse effects of Si on the properties of aluminum alloys. Be can transform the plate-like β-intermediate phase into the relatively harmless Chinese character-shaped Be-Fe (Al8Fe2SiBe) phase and prevent the formation of the acicular β-Fe phase, thereby reducing or eliminating the adverse effects of Fe on the properties of aluminum alloys. It can also promote the formation and precipitation of phases such as Mg2Si, Mg2Zn, Mg2SiZn, and Al2Cu, reducing the solid solubility of these elements in the aluminum matrix. Be can also form an active film on the surface of impurity element phases such as Fe, preventing the growth of impurity elements. Furthermore, Be can segregate at grain boundaries or adsorb at the solid-liquid interface, forming supercooling and increasing the chance of dendrite melting, thus refining the grains. The refining effect of Be increases with increasing Be content. Bi can react with Mg and Cd to form second phases such as Mg3Bi2 and Mg3(BiCd)2, thereby improving 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, and Mg3(BiCd)2. To improve tensile strength and yield strength and reduce Fe content, Cd forms a large number of Cd-vacancy clusters during the aging stage, promoting and accelerating the precipitation of CuAl2 phase, thereby reducing 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, and can also easily form a dispersed phase with Fe to reduce the Fe content and reduce the harmful effects of Fe. Cr forms (CrFe)Al7 and (CrMn)Al in the aluminum alloy liquid. 12Intermetallic compounds can hinder the nucleation and growth process of recrystallization, thereby improving the yield strength, tensile strength, and elongation of aluminum alloys. Various fine chromium-containing compounds formed by Cr in aluminum alloys can redissolve in the α phase during the solid solution stage, and disperse into various Cr-containing phases, such as α-AlCrSi dispersed phases, during the natural aging stage. These Cr-containing phases can act as nuclei for the heterogeneous nucleation of β" and θ" phases, accelerating their formation and thus improving the yield strength and tensile strength of the aluminum alloy. Simultaneously, the Cr-containing phases in the matrix... The dispersed precipitation of Mn and Cr inevitably delays the formation of the θ′ phase precipitated at grain boundaries. Mn and Cr can also form dispersed α-Al(FeMnCr)Si phases with Fe and Si. The α-Al(FeMnCr)Si phase has high bulk density and strong thermal stability, and pinning grain boundaries can effectively control the grain growth process, thereby controlling the grain size. When Cr and Mo are added together, Cr-rich and Mo-rich multi-component phases can be generated, which significantly improves the tensile strength of aluminum alloys. V can react with Al to form VAl. 11 Refractory compounds such as Al3V and Zr can refine grains during the casting process. V can also refine the recrystallization structure and increase the recrystallization temperature, thereby improving the tensile strength, yield strength, and elongation of aluminum alloys. During die casting, the rapid cooling rate results in a high-temperature cooling rate, where the unstable Al3V phase reacts with Cr, Si, and Ti in the aluminum alloy to form numerous fine, dispersed ellipsoidal Al(VCrTi)Si phases. These phases inhibit dislocation movement and recrystallization nucleation and growth, significantly improving the tensile strength and yield strength of the aluminum alloy. Zr can react with Al, RE, etc., to form second phases such as Al3ScZr and (Zr,RE)Al3, further enhancing tensile strength and yield strength. In addition to improving tensile strength, Zr can also promote the precipitation of phases such as Mg2Sn, Mg2Si, Mg3Sb2 and CuAl2, thereby reducing the solid solubility of these elements in the aluminum matrix. Zr can also refine the grains and further improve the elongation of the aluminum alloy. The addition of boron can transform Zr from a solid solution state to a precipitated state, existing in the form of fine plate-like second phase particles inside the grains and at the grain boundaries, reducing lattice distortion, improving the orderliness of the aluminum matrix, and enhancing the tensile strength and yield strength of the aluminum alloy. The combined effect of Er and Zr can promote the precipitation of the β″ phase and make the β″ phase finer and more dispersed. The synergistic effect of Er and Zr can significantly inhibit the recrystallization of Al-Fe alloys.

[0067] Co, Be, Bi, Cd, Cr, V, Zr, Sn, and Sb interact with each other to significantly improve the tensile strength, yield strength, and elongation of aluminum alloys. Co can react with Al, Fe, Si, etc., to form Al. 15Secondary phases such as (Fe,Co)3Si2 and Al3(Fe,Co) can be formed. Be can react with Al, Fe, and Si to form secondary phases such as Be-Fe(Al8Fe2SiBe)2. Al, Mg, Bi, Sn, Si, Cr, V, Cd, and Sb can react with each other to form secondary phases such as Mg3(SbCd)2, Mg2(SnCd), Mg3(BiCd)2, AlCrSi, Al(VCrTi)Si, Mg2(SiCr), Mg3Bi2, Mg2Sn, and Mg3Sb2, thereby improving tensile strength and yield strength. The combined addition of Mn and Cr can improve tensile strength and yield strength. The coarse AlFeSi phase can be transformed into granular Al(MnCrFe)Si phase, thereby reducing the harmful effects of Fe impurity. Zr, Cd, and Be can promote the precipitation of precipitates. Co, Be, Cr, V, and Zr can refine grains and precipitates. The combination of Be and Sc can improve the morphology of acicular Fe-containing phases, increasing 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. 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 interact with each other to promote the precipitation of precipitates and then refine grains and precipitates, thereby improving tensile strength, yield strength, and elongation.

[0068] The high elongation, heat-free die-cast aluminum alloy further contains 0-0.1% Ag by mass, specifically 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. The high elongation, heat-free die-cast aluminum alloy further contains 0-0.2% Nb by mass, specifically 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%. High elongation, heat-free die-cast aluminum alloys also contain 0-0.2% In by mass, specifically 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%.

[0069] 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 to 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 can specifically 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.

[0070] In the technical solution of this invention, the high elongation heat-free die-cast aluminum alloy further contains 0-0.1% Ag, 0-0.2% Nb, and 0-0.2% In by mass percentage. Ag can promote the precipitation of second phases (such as Al2Cu, Mg2Si, Mg3Sb2, and Mg3Bi2), refine the precipitated phases, and increase the density of the precipitated phases, thereby improving the precipitation strengthening effect of the aluminum alloy and thus increasing the tensile strength, yield strength, and elongation of the aluminum alloy. In can react with Al and Cu to form second phases such as AlIn and CuIn, thereby improving tensile strength and yield strength; In can also refine the grains to increase the elongation of the aluminum alloy. Nb can react with Al and B to form high-temperature strengthening metallic compounds such as AlNb3, AlNb, Al3Nb, and NbB2. Some Nb can be dispersed as a phase at the matrix grain boundaries, significantly improving the yield strength and tensile strength of aluminum alloys. Nb can refine grains and the second phase, thereby increasing the elongation of aluminum alloys. The lattice mismatch constant between NbB2 and Al (30.6%) is smaller than that between TiB2 and Al (34.0%). Considering only the interaction with Al, NbB2 is a more potential heterogeneous nucleation site than TiB2. The synergistic effect of Ag, In, and Nb can significantly promote the precipitation of the second phase and refine the grains and precipitated phases. 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 second phases and refine the precipitated phases; Nb and In can also refine the grains and second phases, thus simultaneously improving the tensile strength, yield strength and elongation of aluminum alloys.

[0071] High elongation, heat-free die-cast aluminum alloys also contain 0-0.2% Mo by mass, specifically 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%. High elongation, heat-free die-cast aluminum alloys also contain 0-0.1% Ge by mass, specifically 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%.

[0072] The mass ratio of Fe to Mo is 0.1-3:1, preferably 0.5-2:1, and can specifically 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, and can specifically 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, and can specifically 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.

[0073] In the technical solution of this invention, the high elongation heat-free die-cast aluminum alloy further contains 0-0.2% Mo and 0-0.1% Ge by mass. Mo can also react with Al, Si, Fe, etc., to form second phases such as AlMo, AlSiMo, and AlSiFeMo, which are dispersed in the grain boundaries of the aluminum matrix. Mo can also refine the 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 to form second phases such as Al9Ge7, Al6Ge5, Al5Ge2, Al3Ge4, and SiGe. Ge readily captures quenching vacancies in the α-Al matrix, forming "Ge-vacancy pairs," thus "retaining" quenching vacancies in the α-Al matrix, promoting artificial aging precipitation kinetics and enhancing precipitation strengthening. Ge not only replaces some Si and Cu atoms in metastable precipitates but also refines the precipitates and increases their density, significantly improving the precipitation strengthening effect of aluminum alloys. During low-temperature quenching and holding, the aluminum alloy matrix shrinks, undergoes plastic deformation, and generates internal stress; Ge can reduce the solubility of elements in aluminum, increasing... During the process of raising the temperature to room temperature after low-temperature quenching and holding, the nucleation sites of the clusters combine with the "Ge-vacancy pairs" formed by the quenching vacancies under the action of internal stress, which rapidly increases the volume fraction of Cu-Mg clusters, Mg-Si clusters, and Mg-Si-Cu clusters, thereby improving the yield strength, tensile strength, and elongation of heat-free aluminum alloys. In addition, Ge can also replace Si and Cu atoms in Cu-Mg clusters, Mg-Si clusters, and Mg-Si-Cu clusters, increasing the resistance of dislocations cutting through these clusters. When RE is added, Ge and RE work together to further refine the size of the clusters and increase the volume fraction of the clusters.

[0074] In one embodiment of the present invention, the heat-free aluminum alloy contains 6.5-9% Si, 0.01-0.3% Fe, 0.01-0.2% Cu, 0-0.25% Mn, 0.01-0.15% Mg, 0.01-0.2% Zn, 0.01-0.1% Ti, 0.01-0.05% Ca, 0.01-0.1% Co, 0.01-0.05% Be, and 0.01-0.1% Sb by mass.

[0075] In another embodiment of the present invention, the heat-free aluminum alloy contains 6.5-9% Si, 0.01-0.3% Fe, 0.01-0.2% Cu, 0-0.25% Mn, 0.01-0.15% Mg, 0.01-0.2% Zn, 0.01-0.1% Ti, 0.01-0.1% Zr, and [other components are missing from the original text]. The content of Mo is 0.01-0.1%, the content of Ge is 0.01-0.1%, the content of Cr is 0.01-0.1%, the content of V is 0.05-0.2%, the content of La is 0.01-0.03%, the content of Ce is 0.01-0.02%, the content of Sm is 0.01-0.05%, the content of Y is 0.01-0.05%, and the content of Gd is 0.01-0.05%.

[0076] In another embodiment of the present invention, the heat-free aluminum alloy contains 6.5-9% Si, 0.01-0.3% Fe, 0.01-0.2% Cu, 0-0.25% Mn, 0.01-0.15% Mg, 0.01-0.2% Zn, 0.01-0.1% Ti, 0.001-0.01% B, 0.01-0.1% Nb, 0.01-0.1% Sn, 0.01-0.05% Ag, and 0.01-0.1% In by mass.

[0077] This invention also provides a method for preparing a high elongation, heat-free die-cast aluminum alloy, comprising the following steps:

[0078] Aluminum liquid is obtained by heating an Al source (preferably primary aluminum, such as electrolytic aluminum) at a temperature of 750-830°C;

[0079] At a temperature of 720-780°C, Si source, Fe source, Cu source, Mn source, Mg source, Zn source, B source, Sr source and Ti source are added to the aluminum liquid to obtain an alloy liquid;

[0080] The alloy liquid is refined, slag removed, and die-cast to obtain aluminum alloy parts; and

[0081] The aluminum alloy parts are subjected to low-temperature quenching to obtain a high elongation, heat-free die-cast aluminum alloy. The high elongation, heat-free die-cast aluminum alloy contains Al, and also contains 6.5-9% Si, 0.01-0.3% Fe, 0.01-0.2% Cu, 0-0.25% Mn, 0.01-0.15% Mg, 0.01-0.2% Zn, 0-0.01% B, 0-0.05% Sr, and 0.01-0.1% Ti.

[0082] The source aluminum can be Si, Fe, Cu, Mn, Mg, Zn, B, Sr, and Ti, either in elemental or alloy form. Besides primary aluminum, recycled aluminum can also be used as the Al source. When using recycled aluminum, the composition and content of the molten aluminum alloy need to be tested, and the element content to be added to the recycled aluminum liquid is calculated based on the test results to obtain the high elongation heat-free die-cast aluminum alloy of this invention.

[0083] Low-temperature quenching can be performed using ice water or liquid nitrogen. The temperature for the low-temperature quenching treatment is -200°C to 0°C, specifically -200°C, -150°C, -100°C, -50°C, -10°C, or 0°C. The duration of the low-temperature quenching treatment is 0.1 to 10 hours, specifically 0.1 hours, 0.5 hours, 1 hour, 5 hours, or 10 hours. It is understood that ice / ice water and liquid nitrogen can be added as needed to maintain the temperature of the low-temperature quenching treatment below 0°C, preserving as many vacancies as possible and ensuring the formation of supersaturated vacancies.

[0084] The alloy liquid is refined at a temperature of 710~735ºC for 10~30 min, wherein the mass ratio of refining agent to alloy liquid is 0.01~0.05:1, and the refining agent comprises a metal salt and hexachloroethane in a mass ratio of 0.5~1.5:1, wherein the metal salt is at least one selected from aluminum fluoride, sodium fluoride, sodium nitrate, aluminum nitrate, manganese chloride, zinc chloride, and sodium chloride. In one embodiment, the mass ratio of fluoride, nitrate, and chloride salt is 1:0.5~1.5:0.5~1.5.

[0085] The alloy molten material is die-cast at a temperature of 660-700ºC, wherein the die-casting speed of the die-casting machine is 0.23-2.5 m / s. It is understood that the die-casting process of this invention is a conventional die-casting process; vacuum die-casting can also be used to die-cast the alloy molten material. The strength (e.g., yield strength and tensile strength) and elongation of the aluminum alloy after vacuum die-casting will be higher than those after conventional die-casting. The cooling rate during the die-casting process 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.

[0086] The method for preparing the high elongation heat-free die-cast aluminum alloy further includes the step of adding at least one of the following sources to the molten aluminum: Ca, Co, Cd, Be, Bi, Nb, Sn, Sb, Ag, In, Zr, Mo, Cr, Ge, V, and RE. The Ca, Co, Cd, Be, Bi, Nb, Sn, Sb, Ag, In, Zr, Mo, Cr, Ge, V, and RE sources can be added in elemental or alloy form. The total mass percentage of 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 greater than 0.6%, preferably not greater than 0.5%, and can specifically be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or 0.6%. The content of a single impurity in the heat-free die-cast aluminum alloy does not exceed 0.05%, and the total impurity content does not exceed 0.15%.

[0087] In the technical solution of this invention, the high elongation heat-free die-cast aluminum alloy prepared by the aforementioned method contains 6.5-9% Si, 0.01-0.3% Fe, 0.01-0.2% Cu, 0-0.25% Mn, 0.01-0.15% Mg, 0.01-0.2% Zn, 0-0.01% B, 0-0.05% Sr, and 0.01-0.1% Ti by mass. The combined addition of Si, Fe, Cu, Mn, Mg, Zn, B, Sr, and Ti within the above content ranges interacts and influences each other, enabling the heat-free aluminum alloy to achieve a tensile strength greater than 260 MPa, a yield strength greater than 120 MPa, and an elongation greater than 16%. Specifically:

[0088] (1) Si can improve the process flow properties of aluminum alloys, but if the content is too high, it will reduce the elongation. Si can react with Al, Fe, Mg, Cu, B and other substances to generate second phases such as Mg2Si, AlFeSi, AlFeSiCu, AlFeMgSi, AlCuMgSi, AlFeSiB, which can improve tensile strength and yield strength.

[0089] (2) Mg can react with Al, Fe, Si, Cu, Zn and other elements to form second phases such as AlFeMgSi, (CuMg)Al2, AlCuMgSi, Mg2Si, Mg2Zn, and Mg2SiZn, which can improve tensile strength and yield strength. Among them, when Mg is dissolved in CuAl2 and AlFeSi phases, it forms (CuMg)Al2 and AlFeSiMg phases.

[0090] (3) Cu can react with Al, Fe, Si, Mg, Zn and other substances to form second phases such as CuAl2, AlFeSiCu, AlCuMgSi, Al2CuZn, (CuMg)Al2, which can improve tensile strength and yield strength. It can also promote the precipitation of second phases such as Mg2Si, Mg2Zn, Mg2SiZn, and increase the volume fraction and dispersion of the precipitated phases. Subsequent natural aging or vehicle paint baking heat treatment can further improve the aging strengthening effect of Cu and Mg.

[0091] (4) Zn can react with Al, Mg, Cu and Si to form second phases such as MgZn2, Mg2SiZn and Al2CuZn, which can improve 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 and Al2CuMg, and increase the volume fraction and dispersion of precipitated phases. The combined addition of Zn and Mg can form the strengthening phase Mg / Zn2, which can significantly improve the tensile strength and yield strength of aluminum alloys.

[0092] (5) Fe can improve demolding performance. Fe can also react with Al, Si, Mg, Cu and B to generate second phases such as Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu and AlFeSiB, which can improve tensile strength and yield strength.

[0093] (6) Mn can react with Al, Fe, Si, and Cu to form MnAl2, MnAl6, α-(Fe,Mn)Al6, and Al. 12 CuMn2, α-Al(FeMn)Si, τ(Cu2Mn3Al 20Mn can improve tensile strength and yield strength by forming a second phase, such as α-Al(Fe,Mn)Al6. Mn can significantly refine grain size by causing lattice distortion in the matrix through solid solution and by producing MnAl6 dispersed particles through reaction with Al, thereby improving elongation. MnAl6 can also dissolve Fe to form α-(Fe,Mn)Al6, reducing Fe content and mitigating Fe hazard. Mn reacts with Al, Fe, Mn, and Si to form spherical or granular AlFeMnSi composite phases, which can prevent the formation of long needle-like Fe phases, thus reducing Fe hazard. This improves the mold release properties of aluminum alloys and also enhances their tensile strength and yield strength. Mn can also transform coarse needle-like β-AlFeSi phases into small granular α-Al(FeMn)Si dispersed particles, improving Fe morphology and eliminating Fe hazard. Specifically, Mn can replace some of the Fe in the coarse needle-like β-AlFeSi phase, forming... The formation and growth shape of the β phase are improved by small-particle dispersed β-Al(FeMn)Si phase, thereby reducing the harm caused by Fe. Mn can also promote the transformation of the needle-like β-Al(FeMn)Si phase into small-particle dispersed α-Al(FeMn)Si phase. The generated α-Al(FeMn)Si phase dispersed particles are distributed in the aluminum matrix and strongly pinned to the subgrain boundaries of the aluminum alloy. This is mainly because the Mn-containing α-phase dispersed particles in the aluminum alloy can act as non-uniform nucleation sites for the β′ phase during natural aging, thus inducing its nucleation and accelerating the precipitation of the β′ phase. Mn can also react with impurity phases in the aluminum alloy liquid to form Al-Mn-X phase (X is an impurity element, including transition metal elements, etc.), which can purify the aluminum alloy liquid. These phases can act as grain nucleation sites to increase the nucleation rate, refine the grains, and improve the tensile strength, yield strength, elongation, and fluidity of the aluminum alloy.

[0094] (7) Sr preferentially combines with Fe to form dispersion strengthening, reducing the solid solubility of Fe, thereby improving the yield strength and tensile strength of aluminum alloys; Sr can change the behavior of intermetallic compound phases in crystallography, and can be used as a modifier to refine the grains and second phase of aluminum alloys through heterogeneous nucleation theory or twin valley mechanism. For example, Sr can change the morphology of eutectic silicon phase through modification, thereby improving the elongation of aluminum alloys and reducing 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 improving the yield strength, tensile strength and elongation of aluminum alloys;

[0095] (8) The TiAl2 phase generated by the reaction of Ti and Al, as a non-spontaneous nucleus during crystallization, can refine the grains, second phase and precipitated phase, thereby improving the tensile strength, yield strength and elongation of aluminum alloys;

[0096] (9) B can undergo borylation reaction with transition metal elements (including transition metal elements such as Fe) to generate compounds such as ferroboron compounds that can be separated from aluminum alloy liquid, thereby purifying the aluminum alloy liquid; B is easily adsorbed on the surface of iron-rich phase, inhibiting the growth of iron-rich phase and playing a role in controlling the size of iron-rich phase, and can also prevent the formation of iron-rich phase in 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 aluminum alloy.

[0097] The combined effects of Si, Cu, Mn, Mg, Zn, Ti, Sr, and Fe within the aforementioned content range can improve the tensile strength and yield strength of aluminum alloys; the combined effects of Mn, B, Ti, and Sr within the aforementioned content range can refine grains, the second phase, and precipitated phases, thereby improving the elongation of aluminum alloys; Cu and Zn within the aforementioned content range can promote the precipitation of the second phase, increasing the volume fraction and dispersion of the precipitated phase, further improving the tensile strength, yield strength, and elongation of aluminum alloys; the combined effects of Fe, Sr, and Mn within the aforementioned content range can improve the mold release properties of aluminum alloys.

[0098] The Fe content in this invention is relatively low (0.01-0.3 wt%). During the die-casting process, the temperature cooling rate is relatively high (10-60 K / s), causing Fe to form mostly fine, short rod-shaped or cubic Al-Fe or Al-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, so 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. This invention sets the Mn content to 0-0.25% by mass, which further improves the demolding performance of the aluminum alloy. Sr can also change the morphology of the eutectic silicon phase through modification to reduce the tendency of sticking during the die-casting process.

[0099] Since the mechanical properties of heat-free aluminum alloys cannot be improved by aging heat treatment, most of the solute atoms in the heat-free aluminum alloys of the present invention usually exist in the aluminum matrix in the form of solid solution. In addition to grain refinement, the strength increase of the heat-free aluminum alloy mainly comes from the pinning of dislocations by lattice volume mismatch and elastic mismatch caused by solid solution atoms, i.e., solid solution strengthening.

[0100] During storage and transportation after die casting, heat-free aluminum alloys undergo natural aging, meaning their strength increases with prolonged storage time. This natural aging is attributed to the aggregation effect of solute atoms in the aluminum alloy, forming solute atom clusters. These clusters are disordered aggregations of solute atoms within the aluminum matrix, typically ranging in size from a few nanometers and composed of several to dozens of randomly distributed atoms without a defined crystal structure.

[0101] The strength variation of heat-free aluminum alloys is mainly related to the size and volume fraction of solute atomic clusters. During natural aging, the formation and growth of clusters are closely linked to changes in the concentration of supersaturated quenching vacancies. Vacancies are thermal defects, and their concentration has an exponential relationship with temperature. This invention performs low-temperature quenching on aluminum alloy parts after die casting to generate supersaturated vacancies, thereby improving the mechanical properties of heat-free aluminum alloys. Specifically, during die casting, the equilibrium vacancy concentration is relatively high; during subsequent quenching, some vacancies at high temperatures are retained, resulting in supersaturated vacancies. Furthermore, the low-temperature quenching also causes the aluminum alloy to shrink, producing plastic deformation, reducing the solubility of elements in aluminum, increasing the nucleation sites of clusters, and refining the α-Al phase and eutectic Si phase structure, thereby improving the yield strength, tensile strength, and elongation of heat-free aluminum alloys.

[0102] The addition of Cu, Mn, Mg, Zn, Ti, Sr, Fe, and B can also regulate the behavior of solute atom clusters in aluminum alloys, such as by adjusting vacancies to influence the formation of existing clusters and the formation of new clusters. In the aluminum melt of this invention, the addition of Mg (0.01-0.15 wt%) and Cu (0.01-0.2 wt%) within a certain content range activates vacancy diffusion and promotes the formation of Mg-Si and Cu-Mg clusters, significantly strengthening the clusters. Mn and Sr have much larger atomic radii than Al. The Mn and Sr atoms within the aforementioned content range form lattice distortions in the aluminum matrix. Combined with the pinned vacancies and Mg-Si and Cu-Mg clusters added to the heat-free aluminum alloy, and the promotion of cluster growth, further enhance the natural aging effect, thereby improving the yield strength, tensile strength, and elongation of the heat-free aluminum alloy.

[0103] In summary, under the combined effect of Si, Cu, Mn, Mg, Zn, Ti, Sr, Fe and B within the above-mentioned content range, a heat-free aluminum alloy with excellent demolding performance, tensile strength, yield strength and elongation is obtained.

[0104] This invention also provides a structural component, at least a portion of which is made of a high-elongation, heat-treatable-free die-cast aluminum alloy or a high-elongation, heat-treatable-free die-cast aluminum alloy prepared by this method. The structural component can be applied to new energy vehicles as automotive structural parts, such as the entire vehicle body, rear wheel arch inner panel, rear longitudinal beam, floor connecting plate, rear floor plate, beam inner reinforcing plate, hood, mudguards, doors, rear cargo box, and roof. The structural component of this invention can also be used in other fields such as aerospace, high-speed rail, shipbuilding, mobile devices, home appliances, chemical industry, daily necessities, and construction.

[0105] Examples and Comparative Examples

[0106] Please refer to Table 1 for the composition and content of the aluminum alloys in Examples 1 to 5 and Comparative Examples 1 to 2, and please refer to Table 2 for the performance test results.

[0107] Table 1. Composition and content of aluminum alloys in Examples 1 to 5 and Comparative Examples 1 to 2

[0108]

[0109] For the sake of simplicity, the content of trace elements such as impurities in the comparative examples and embodiments is not shown.

[0110] A domestically produced CSS-44100 electronic universal tensile testing machine was used to process and test the specimens according to the specifications of the "Metallic Materials - Tensile Testing at Room Temperature" (GB / T228-2002) and the "Metallic Materials - Tensile Testing at High Temperature" (GB4338-2006-T). The processed specimens were polished using 800# and 1500# wet sandpaper. The tensile force of the machine was 2 kN, and the tensile speed was 2 mm / min. Three specimens were tested under the same conditions, and the average value was taken.

[0111] Table 2 shows the performance test results of the aluminum alloys in Examples 1 to 5 and Comparative Examples 1 to 2.

[0112]

[0113] The high elongation-rate, heat-treatable die-cast aluminum alloys of Examples 1 to 5 exhibit significantly higher tensile strength, yield strength, and elongation than those of the high elongation-rate, heat-treatable die-cast aluminum alloys of Comparative Examples 1 to 2. This indicates that the high elongation-rate, heat-treatable die-cast aluminum alloys of the present invention have superior properties. Furthermore, 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 lower than that in Comparative Examples 1 to 2.

[0114] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the content of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A high elongation, heat-free die-cast aluminum alloy, characterized in that, The high elongation heat-free die-cast aluminum alloy is composed of the following elements: 6.5-9% Si, 0.01-0.3% Fe, 0.01-0.2% Cu, 0-0.25% Mn, 0.01-0.15% Mg, 0.01-0.2% Zn, 0-0.01% B, 0-0.05% Sr, and [other elements are missing from the original text]. The high elongation-rate heat-free die-cast aluminum alloy contains 0.01-0.2% RE, 0.01-0.1% Ti by mass, and the balance Al and impurities. The mass ratio of Mn to Fe is 0-0.1:

1. The high elongation-rate heat-free die-cast aluminum alloy undergoes die-casting and low-temperature quenching. During the die-casting process, the temperature cooling rate is 10-60 K / s. The low-temperature quenching process is carried out at a temperature of -150~0°C for 0.1~10 h. RE is at least one of La, Ce, Pr, Nd, Er, Sm, Y, Gd, and Sc.

2. The high elongation, heat-free die-cast aluminum alloy according to claim 1, characterized in that, The mass ratio of Mn to Fe is 0.004-0.05:

1.

3. The high elongation, heat-free die-cast aluminum alloy according to claim 1, characterized in that, The mass ratio of Mn to Fe is 0.004-0.009:

1.

4. The high elongation, heat-free die-cast aluminum alloy according to claim 1, characterized in that, The sum of the mass percentages of Mn and Fe is 0.25-0.45%.

5. The high elongation, heat-free die-cast aluminum alloy according to claim 1, characterized in that, The mass ratio of (Mn+RE) to Fe is 0.01-0.3:

1.

6. The high elongation, heat-free die-cast aluminum alloy according to claim 1, characterized in that, The high elongation heat-free die-cast aluminum alloy contains 6.5-9% Si, 0.01-0.1% Fe, 0.05-0.1% Cu, 0.05-0.2% Mn, 0.05-0.1% Mg, 0.05-0.2% Zn, 0.005-0.01% B, 0.005-0.05% Sr, 0.01-0.1% Ti, and 0.01-0.2% RE.

7. The high elongation, heat-free die-cast aluminum alloy according to claim 1, characterized in that, The high elongation-rate, heat-treatable die-cast aluminum alloy further contains 0-0.06% Ca by mass; 0-0.1% Cd by mass; 0-0.05% Be by mass; 0-0.2% Bi by mass; 0-0.2% Nb by mass; and 0-0.1% Sn by mass. The die-cast aluminum alloy also contains 0-0.2% Sb by mass; the high elongation-rate, heat-free die-cast aluminum alloy also contains 0-0.1% Ag by mass; the high elongation-rate, heat-free die-cast aluminum alloy also contains 0-0.2% In by mass; the high elongation-rate, heat-free die-cast aluminum alloy also contains 0-0.2% Mo by mass; the high elongation-rate, heat-free die-cast aluminum alloy also contains 0-0.2% Cr by mass; the high elongation-rate, heat-free die-cast aluminum alloy also contains 0-0.1% Ge by mass; and the high elongation-rate, heat-free die-cast aluminum alloy also contains 0-0.3% V by mass.

8. The high elongation-rate, heat-treatable-free die-cast aluminum alloy according to claim 7, characterized in that, The high elongation-rate, heat-free die-cast aluminum alloy must meet at least one of the following conditions: when the high elongation-rate, heat-free die-cast aluminum alloy also contains Sb, the mass ratio of Mg to Sb is 0.5-10:1; when the high elongation-rate, heat-free die-cast aluminum alloy also contains Nb, the mass ratio of Mg to Nb is 0.2-15:1; when the high elongation-rate, heat-free die-cast aluminum alloy also contains Ag, the mass ratio of Mg to Ag is 1-20:1; when the high elongation-rate, heat-free die-cast aluminum alloy also contains In, the mass ratio of Cu to In is 0.1-5:

1. When the high elongation-rate die-cast aluminum alloy without heat treatment also contains Mo, the mass ratio of Fe to Mo is 0.1-3:1; when the high elongation-rate die-cast aluminum alloy without heat treatment also contains Ge, the mass ratio of Mg to Ge is 1-20:1; when the high elongation-rate die-cast aluminum alloy without heat treatment also contains Cr and V, the mass ratio of Cr to V is 0.1-10:1; when the high elongation-rate die-cast aluminum alloy without heat treatment also contains Bi and Cd, the mass ratio of Bi, Cd and Mg is 0.2-10:0.1-10:

1.

9. The high elongation-rate, heat-treatable-free die-cast aluminum alloy according to claim 7, characterized in that, The high elongation-rate, heat-free die-cast aluminum alloy contains, by mass percentage, 6.5-9% Si, 0.01-0.3% Fe, 0.01-0.2% Cu, 0.001-0.25% Mn, 0.01-0.15% Mg, 0.01-0.2% Zn, and 0.005-0.01% B, and by mass percentage, [the following is a partial list of unrelated elements]. The composition includes 0.005-0.05% Sr, 0.01-0.1% Ti, 0.01-0.1% Mo, 0.01-0.1% Ge, 0.01-0.1% Cr, 0.05-0.2% V, 0.01-0.03% La, 0.01-0.02% Ce, and 0.01-0.05% Sr. The high elongation, heat-free die-cast aluminum alloy contains 6.5-9% Si, 0.01-0.3% Fe, 0.01-0.2% Cu, 0.001-0.25% Mn, 0.01-0.15% Mg, and 0.0% Gd. 1-0.2% Zn, 0.01-0.2% RE, 0.01-0.1% Ti, 0.001-0.01% B, 0.005-0.05% Sr, 0.01-0.1% Nb, 0.01-0.1% Sn, 0.01-0.05% Ag, and 0.01-0.1% In.

10. A method for preparing a high elongation-rate, heat-treatable die-cast aluminum alloy as described in any one of claims 1-9, comprising the following steps: The Al source is subjected to a first heating treatment to obtain molten aluminum. Si, Fe, Cu, Mn, Mg, Zn, B, Sr, Ti, and RE sources are added to the molten aluminum, followed by a second heating treatment to obtain an alloy liquid. The alloy liquid is then refined, slag-removing, and die-cast to obtain aluminum alloy parts. Finally, the aluminum alloy parts are subjected to low-temperature quenching to obtain a high-elongation, heat-free die-cast aluminum alloy. This high-elongation, heat-free die-cast aluminum alloy contains 6.5-9% Si, 0.01-0.3% Fe, 0.01-0.2% Cu, and 0-0.25% Mn by mass. The mixture comprises 0.01-0.15% Mg, 0.01-0.2% Zn, 0-0.01% B, 0-0.05% Sr, 0.01-0.2% RE, 0.01-0.1% Ti, and the balance Al and impurities. The mass ratio of Mn to Fe is 0-0.1:

1. During the die casting process, the temperature cooling rate is 10-60 K / s, and the low-temperature quenching temperature is -150~0°C for 0.1~10 h. RE is at least one of La, Ce, Pr, Nd, Er, Sm, Y, Gd, and Sc.

11. A structural component, characterized in that, At least a portion of the structural component is made of a high elongation heat-free die-cast aluminum alloy as described in any one of claims 1-9 or a high elongation heat-free die-cast aluminum alloy prepared by the preparation method described in claim 10.

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