High-elongation heat-treatment-free die-cast aluminum alloy and preparation method and structural parts thereof

Abstract

The present invention provides a high elongation heat-treatment-free die-cast aluminum alloy, containing 6.5-9% Si by mass, 0.01-0.3% Fe by mass, 0.01-0.2% Cu by mass, 0-0.25% Mn by mass, 0.01-0.15% Mg by mass, 0.01-0.2% Zn by mass, 0-0.01% B by mass, 0-0.05% Sr by mass, and 0.01-0.1% Ti by mass. The present invention also provides a method for preparing a high elongation heat-treatment-free die-cast aluminum alloy, and a structural part. The high elongation heat-treatment-free die-cast aluminum alloy of the present invention has a tensile strength greater than 260 MPa, a yield strength greater than 120 MPa, and an elongation greater than 16%.

Description

Technical Field

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

[0002] With the increasing demand for energy conservation and emission reduction in the automotive industry, the penetration of aluminum alloy vacuum die-castings in key automotive structural parts continues to increase due to their advantages such as integration, lightweighting, and excellent strength and toughness. For vehicle manufacturers, aluminum alloy die-castings for automotive structural parts differ from traditional aluminum alloy die-castings. The joining processes during manufacturing and the overall vehicle performance during service place high demands on the comprehensive mechanical properties, especially the plasticity, of the as-cast aluminum alloy die-castings. Current Al-Si and Al-Mg aluminum alloys generally have only moderate strength and plasticity, which are difficult to meet the requirements of automotive structural parts, especially large ones. Other industries such as aerospace, high-speed rail, shipbuilding, mobile devices, household appliances, chemicals, daily necessities, and construction also commonly require aluminum alloy die-castings, and they also have high requirements for comprehensive mechanical properties. Therefore, there is an urgent need to develop a high-elongation, heat-treatment-free die-cast aluminum alloy with excellent demolding properties, tensile strength, yield strength, and elongation. Summary of the Invention

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

[0004] The present invention provides a high-elongation heat-treatment-free die-casting aluminum alloy, which contains Al, 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, and 0.01-0.1% by mass of Ti.

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

[0006] The Al source is subjected to a first heating treatment to obtain aluminum liquid;

[0007] adding a Si source, an Fe source, a Cu source, a Mn source, a Mg source, a Zn source, a B source, a Sr source, and a Ti source to the aluminum liquid, and performing a second heating treatment to obtain an alloy liquid;

[0008] The alloy liquid is subjected to refining, slagging, and die-casting to obtain aluminum alloy parts; and

[0009] The aluminum alloy component is quenched to obtain a high-elongation heat-treatment-free die-cast aluminum alloy component, wherein the high-elongation heat-treatment-free die-cast aluminum alloy contains Al, and further contains 6.5-9% Si by mass, 0.01-0.3% Fe by mass, 0.01-0.2% Cu by mass, 0-0.25% Mn by mass, 0.01-0.15% Mg by mass, 0.01-0.2% Zn by mass, 0-0.01% B by mass, 0-0.05% Sr by mass, and 0.01-0.1% Ti by mass.

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

[0011] In the technical solution of the present invention, the high elongation heat-treatment-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, 0-0.25% Mn by mass, 0.01-0.15% Mg by mass, 0.01-0.2% Zn by mass, 0-0.01% B by mass, 0-0.05% Sr by mass, and 0.01-0.1% Ti by mass. The composite addition of Si, Fe, Cu, Mn, Mg, Zn, B, Sr, and Ti within the above content ranges influences and interacts with each other, which can make the tensile strength of the heat-treatment-free aluminum alloy greater than 260MPa, the yield strength greater than 120MPa, and the elongation greater than 16%. Specifically:

[0012] (1) Si can improve the process flow properties of aluminum alloys, but when the content is too high, it will reduce the elongation. 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;

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

[0014] (3) Cu can react with Al, Fe, Si, Mg, Zn, etc. to form second phases such as CuAl2, AlFeSiCu, AlCuMgSi, Al2CuZn, (CuMg)Al2, etc. to improve the tensile strength and yield strength. It can also promote the precipitation of second phases such as Mg2Si, Mg2Zn, Mg2SiZn, etc., and increase the volume fraction and dispersion of the precipitated phase. 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, 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 of the precipitated phases. The composite addition of Zn and Mg can form a strengthening phase Mg / Zn2, which significantly improves 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 form second phases such as Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu, and AlFeSiB to 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, Al 12 CuMn2, α-Al(FeMn)Si, τ(Cu2Mn3Al 20) and other second phases to improve the tensile strength and yield strength; Mn can significantly refine the grain size by lattice distortion produced by solid solution in the matrix and MnAl6 dispersed particles produced by reaction with Al to improve the elongation, and MnAl6 can also dissolve Fe to form α-(Fe,Mn)Al6 phase to reduce the Fe content and reduce Fe damage; Mn forms spherical particles or Chinese character-shaped AlFeMnSi compound phases with Al, Fe, Mn and Si, which can avoid the formation of long needle-shaped Fe phase to reduce Fe damage, and can also improve the tensile strength and yield strength of aluminum alloy while improving the demoulding property of aluminum alloy; Mn can also transform the coarse needle-shaped β-AlFeSi phase into small granular α-Al(FeMn)Si phase dispersed particles, improve the Fe morphology to eliminate Fe damage, specifically, Mn can replace part of the Fe in the coarse needle-shaped β-AlFeSi phase, produce The formation and growth shape of the β phase are improved, thereby reducing the Fe damage. Mn can also promote the transformation of the needle-shaped β-Al(FeMn)Si phase into a small granular α-Al(FeMn)Si dispersed 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 serve as non-uniform nucleation sites for the β' phase during the aging process, inducing its nucleation, thereby accelerating the precipitation of the β' phase. Mn can also react with impurities in the aluminum alloy liquid to form Al-Mn-X phases (X is an impurity element, including transition metal elements, etc.), thereby purifying 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.

[0018] (7) Sr preferentially combines with Fe to form dispersion strengthening, reducing the solid solubility of Fe to improve the yield strength and tensile strength; Sr can change the behavior of the intermetallic compound phase in crystallography and can be used as a modifier to refine the grains and the second phase by modifying the aluminum alloy through the heterogeneous nucleation theory or the twin valley 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 die during the die casting process; Sr can transform the coarse needle-shaped β-AlFeSi and β-AlFeMnSi phases in the ingot into small granular Chinese character-shaped α-AlFeSi and α-Al(FeMn)Si phases, reducing the homogenization time of the ingot and improving the yield strength, tensile strength and elongation;

[0019] (8) The TiAl2 phase generated by the reaction of Ti and Al acts as a non-spontaneous core during crystallization, which can refine the grains, second phases and precipitated phases to improve the tensile strength, yield strength and elongation of the aluminum alloy;

[0020] (9) B can undergo boronization reaction with transition metal elements (including Fe and other transition metal elements) to generate compounds such as boron-iron 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 also preventing the formation of the iron-rich phase in the aluminum alloy liquid; B can inhibit the segregation of Ti3Al, so the effect is better when Ti and B are used together; B can also refine the grains and the second phase to improve the elongation of the aluminum alloy.

[0021] The combined effect 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 effect of Mn, B, Ti, and Sr within the above content range can refine the grains, second phase, and precipitated 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 of the precipitated phase, and further improve the tensile strength, yield strength, and elongation of the aluminum alloy; the combined effect of Fe, Sr, and Mn within the above content range can improve the demolding performance of the aluminum alloy.

[0022] The Fe content of the present invention is relatively low (0.01-0.3wt%), and during the die-casting process, the temperature cooling rate is relatively high (can be 10-60K / s), so that the Fe basically forms a small, short rod-shaped or block-shaped Al-Fe phase or Al-Fe-Si phase. As a result, the Fe content within this content range has little effect on the elongation of the aluminum alloy. As the Fe content decreases, the elongation gradually increases, and in this case, there is no need to increase the addition of Mn or add more Mn to reduce the effect of Fe on the elongation of the aluminum alloy. The Mn content of the present invention is set to 0-0.25% by mass, and Mn is used to further improve the demolding performance of the aluminum alloy. Sr can also change the morphology of the eutectic silicon phase through its metamorphic effect, thereby reducing the tendency of die sticking during the die-casting process.

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

[0024] Heat-treatment-free aluminum alloys undergo natural aging during storage and transportation after die-casting, meaning their strength increases with extended storage time. This natural aging is attributed to the aggregation of solute atoms in the aluminum alloy, known as solute atom clusters. Solute atom clusters are disordered aggregations of solute atoms within the aluminum matrix, measuring several nanometers in size and typically consisting of a few to dozens of randomly distributed atoms with no clear crystal structure.

[0025] The change in the strength of heat-treatment-free aluminum alloys is mainly related to the size and volume fraction of solute atom clusters. During the natural aging process, the formation and growth of clusters are closely related to the change in the concentration of supersaturated quenching vacancies. Vacancies are thermal defects, and their concentration has an exponential function relationship with temperature. The present invention performs a low-temperature quenching treatment on aluminum alloy parts after the die-casting treatment to produce supersaturated vacancies to improve the mechanical properties of heat-treatment-free aluminum alloys. 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, thereby producing 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, and refine the α-Al phase and eutectic Si phase structure to improve the yield strength, tensile strength and elongation of the heat-treatment-free aluminum alloy.

[0026] The addition of Cu, Mn, Mg, Zn, Ti, Sr, Fe, and B can also regulate the clustering behavior of solute atoms in aluminum alloys, such as by adjusting vacancies to influence the formation of existing clusters and new clusters. When Mg (0.01-0.15 wt%) and Cu (0.01-0.2 wt%) are added to the aluminum melt of the present invention within a certain content range, the Mg atoms activate the diffusion of vacancies and promote the formation of Mg-Si and Cu-Mg clusters, significantly strengthening the clusters. The atomic radii of Mn and Sr are much larger than that of Al. Mn and Sr atoms within this content range create lattice distortion within the aluminum matrix. This, combined with the pinning of vacancies and Mg-Si and Cu-Mg clusters in the heat-treatment-free aluminum alloy, promotes cluster growth and further enhances the natural aging effect, thereby improving the yield strength, tensile strength, and elongation of the heat-treatment-free aluminum alloy.

[0027] 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-treatment-free aluminum alloy with excellent demolding performance, tensile strength, yield strength, and elongation is obtained. DETAILED DESCRIPTION

[0028] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

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

[0030] In one embodiment, the high elongation heat-treatment-free die-cast 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, 0.05-0.2% Zn by mass, 0.005-0.01% B by mass, 0.005-0.05% Sr by mass, 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 the prior art of aluminum alloys, it is generally believed that when the mass ratio of Mn to Fe is less than 0.6:1 or 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. The present invention sets the mass ratio of Mn to Fe to 0-0.8:1, preferably to 0-0.6:1, and more preferably to 0-0.5:1, and instead obtains a heat-treatment-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 will essentially form a small, short rod-shaped or block-shaped Al-Fe phase or Al-Fe-Si phase, making Fe have little effect on the elongation of the aluminum alloy. Furthermore, as the Fe content decreases, the elongation gradually increases, eliminating the need to add Mn, or adding more Mn, to reduce the effect of Fe on the elongation of the aluminum alloy. Furthermore, the lattice constant of Mn is much greater than that of the Al matrix. Mn dissolved in the Al matrix can cause discontinuity in the Al matrix's internal structure, leading to a sudden increase in the dislocation cutting radius and reduced elongation. Therefore, the present invention achieves better tensile strength, yield strength, and elongation by setting the Fe content to 0.01-0.3%, the Mn content to 0-0.25%, and the Mn to Fe mass ratio to 0-0.8:1.

[0033] Taking into account the demoulding 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 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 percentages of Mn and Fe to 0.25-0.5%. The combination of the four achieves better demoulding performance, tensile strength, yield strength, and elongation.

[0034] The mass percentage content of Si may 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 may 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 may 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 be specifically 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 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 be 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%, or 0.15%. The mass percentage content of Zn can be 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 mass percentage content of B 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 may 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 may 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, 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.

[0036] In the technical solution of the present invention, the high elongation heat-treatment-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, 0-0.25% Mn by mass, 0.01-0.15% Mg by mass, 0.01-0.2% Zn by mass, 0-0.01% B by mass, 0-0.05% Sr by mass, and 0.01-0.1% Ti by mass. The composite addition of Si, Fe, Cu, Mn, Mg, Zn, B, Sr, and Ti within the above content ranges influences and interacts with each other, which can make the tensile strength of the heat-treatment-free aluminum alloy greater than 260MPa, the yield strength greater than 120MPa, and the elongation greater than 16%. Specifically:

[0037] (1) Si can improve the process flow properties of aluminum alloys, but when the content is too high, it will reduce the elongation. 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;

[0038] (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 tensile strength and yield strength. Among them, when Mg is solid-dissolved in CuAl2 phase and AlFeSi phase, (CuMg)Al2 phase and AlFeSiMg phase are formed;

[0039] (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 of the precipitated phase. 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, 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 of the precipitated phases. The composite addition of Zn and Mg can form a strengthening phase Mg / Zn2, which significantly improves 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 form second phases such as Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu, and AlFeSiB to 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, Al 12 CuMn2, α-Al(FeMn)Si, τ(Cu2Mn3Al 20) and other second phases to improve the tensile strength and yield strength; Mn can significantly refine the grain size by lattice distortion produced by solid solution in the matrix and MnAl6 dispersed particles produced by reaction with Al to improve the elongation, and MnAl6 can also dissolve Fe to form α-(Fe,Mn)Al6 phase to reduce the Fe content and reduce Fe damage; Mn forms spherical particles or Chinese character-shaped AlFeMnSi compound phases with Al, Fe, Mn and Si, which can avoid the formation of long needle-shaped Fe phase to reduce Fe damage, and can also improve the tensile strength and yield strength of aluminum alloy while improving the demoulding property of aluminum alloy; Mn can also transform the coarse needle-shaped β-AlFeSi phase into small granular α-Al(FeMn)Si phase dispersed particles, improve the Fe morphology to eliminate Fe damage, specifically, Mn can replace part of the Fe in the coarse needle-shaped β-AlFeSi phase, produce The formation and growth shape of the β phase are improved, thereby reducing the Fe damage. Mn can also promote the transformation of the needle-shaped β-Al(FeMn)Si phase into a small granular α-Al(FeMn)Si dispersed 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 serve as non-uniform nucleation sites for the β' phase during the aging process, inducing its nucleation, thereby accelerating the precipitation of the β' phase. Mn can also react with impurities in the aluminum alloy liquid to form Al-Mn-X phases (X is an impurity element, including transition metal elements, etc.), thereby purifying 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.

[0043] (7) Sr preferentially combines with Fe to form dispersion strengthening, reducing the solid solubility of Fe to improve the yield strength and tensile strength; Sr can change the behavior of the intermetallic compound phase in crystallography and can be used as a modifier to refine the grains and the second phase by modifying the aluminum alloy through the heterogeneous nucleation theory or the twin valley 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 die during the die casting process; Sr can transform the coarse needle-shaped β-AlFeSi and β-AlFeMnSi phases in the ingot into small granular Chinese character-shaped α-AlFeSi and α-Al(FeMn)Si phases, reducing the homogenization time of the ingot and improving the yield strength, tensile strength and elongation;

[0044] (8) The TiAl2 phase generated by the reaction of Ti and Al acts as a non-spontaneous core during crystallization, which can refine the grains, second phases and precipitated phases to improve the tensile strength, yield strength and elongation of the aluminum alloy;

[0045] (9) B can undergo boronization reaction with transition metal elements (including Fe and other transition metal elements) to generate compounds such as boron-iron 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 also preventing the formation of the iron-rich phase in the aluminum alloy liquid; B can inhibit the segregation of Ti3Al, so the effect is better when Ti and B are used together; B can also refine the grains and the second phase to improve the elongation of the aluminum alloy.

[0046] The combined effect 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 effect of Mn, B, Ti, and Sr within the above content range can refine the grains, second phase, and precipitated 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 of the precipitated phase, and further improve the tensile strength, yield strength, and elongation of the aluminum alloy; the combined effect of Fe, Sr, and Mn within the above content range can improve the demolding performance of the aluminum alloy.

[0047] The Fe content of the present invention is relatively low (0.01-0.3wt%), and during the die-casting process, the temperature cooling rate is relatively high (can be 10-60K / s), so that the Fe basically forms a small, short rod-shaped or block-shaped Al-Fe phase or Al-Fe-Si phase. As a result, the Fe content within this content range has little effect on the elongation of the aluminum alloy. As the Fe content decreases, the elongation gradually increases, and in this case, there is no need to increase the addition of Mn or add more Mn to reduce the effect of Fe on the elongation of the aluminum alloy. The Mn content of the present invention is set to 0-0.25% by mass, and Mn is used to further improve the demolding performance of the aluminum alloy. Sr can also change the morphology of the eutectic silicon phase through its metamorphic effect, thereby reducing the tendency of die sticking during the die-casting process.

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

[0049] Heat-treatment-free aluminum alloys undergo natural aging during storage and transportation after die-casting, meaning their strength increases with extended storage time. This natural aging is attributed to the aggregation of solute atoms in the aluminum alloy, known as solute atom clusters. Solute atom clusters are disordered aggregations of solute atoms within the aluminum matrix, measuring several nanometers in size and typically consisting of a few to dozens of randomly distributed atoms with no clear crystal structure.

[0050] The change in the strength of heat-treatment-free aluminum alloys is mainly related to the size and volume fraction of solute atom clusters. During the natural aging process, the formation and growth of clusters are closely related to the change in the concentration of supersaturated quenching vacancies. Vacancies are thermal defects, and their concentration has an exponential function relationship with temperature. The present invention performs a low-temperature quenching treatment on aluminum alloy parts after the die-casting treatment to produce supersaturated vacancies to improve the mechanical properties of heat-treatment-free aluminum alloys. 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, thereby producing 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, and refine the α-Al phase and eutectic Si phase structure to improve the yield strength, tensile strength and elongation of the heat-treatment-free aluminum alloy.

[0051] The addition of Cu, Mn, Mg, Zn, Ti, Sr, Fe, and B can also regulate the clustering behavior of solute atoms in aluminum alloys, such as by adjusting vacancies to influence the formation of existing clusters and new clusters. When Mg (0.01-0.15 wt%) and Cu (0.01-0.2 wt%) are added to the aluminum melt of the present invention within a certain content range, the Mg atoms activate the diffusion of vacancies and promote the formation of Mg-Si and Cu-Mg clusters, significantly strengthening the clusters. The atomic radii of Mn and Sr are much larger than that of Al. Mn and Sr atoms within this content range create lattice distortion within the aluminum matrix. This, combined with the pinning of vacancies and Mg-Si and Cu-Mg clusters in the heat-treatment-free aluminum alloy, promotes cluster growth and further enhances the natural aging effect, thereby improving the yield strength, tensile strength, and elongation of the heat-treatment-free aluminum alloy.

[0052] 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-treatment-free aluminum alloy with excellent demolding performance, tensile strength, yield strength, and elongation is obtained.

[0053] The high elongation heat-treatment-free die-cast aluminum alloy further contains 0-0.06% by mass of Ca, specifically 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, or 0.06%. The high elongation heat-treatment-free die-cast aluminum alloy further contains 0-0.1% by mass of Sn, 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 heat-treatment-free die-cast aluminum alloy further contains 0-0.2% by weight of RE, 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 comprises La, Y, and Sm, with a ratio of 0.01-0.03:0.02-0.05:1. In another embodiment, RE comprises Pr, Er, and Nd, with a ratio of 0.02-0.05:0.03-0.08:1. In yet another embodiment, RE comprises Sm, Y, and Gd, with a ratio of 0.06-0.08:0.1-0.2:1. The combined addition of multiple rare earth elements achieves a superior refinement 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 the present invention, the high elongation heat-treatment-free die-cast aluminum alloy may also contain 0-0.06% by mass of Ca, 0-0.1% by mass of Sn, and 0-0.2% by mass of RE. Ca can improve the β-Fe phase to reduce the damage of Fe, and can also react with Al, Cu, Zn, and Si to generate Al4Ca, Al2Ca3, AlCa2, AlCaCu, CaZn, CaAlZn, Al2CaSi2 and other second phases to improve the tensile strength and yield strength. Ca can also refine the eutectic structure, improve the β-Fe phase, and also has a metamorphic effect on the aluminum alloy; Sn can react with Al, Mg, Sc and other to generate Al9Sn7, Al6Sn5, Al5Sn2, Al3Sn4, Mg2Sn, Mg2ScSn and other second phases to improve the tensile strength and yield strength; Sn can promote the formation of Mg2Si, Mg2Zn , Mg2SiZn, Al2Cu and other second phases to reduce the solid solubility of the above elements in the aluminum matrix; RE is consistent with the distribution area of Fe phase, and can form rare earth active film on the surface of iron-containing phase or combine with Al, Fe, Ti and other atoms to form rare earth compounds such as AlFeRE, to prevent the formation of hard and brittle β-AlFeSi phase on the grain boundary, effectively reduce the solid solution of harmful elements in the aluminum matrix, to improve the tensile strength and yield strength, RE can transform the elongated β-Fe phase into the spherical α-Fe phase, and metamorphose the elemental Si. RE can also promote the precipitation of dispersed phases such as CuAl2, (CuMg)Al2, etc., to further improve the tensile strength and yield strength. RE is a surface-active element with a radius larger than that of Al. It cannot enter the α-Al lattice, but it can segregate at grain boundaries or adsorb at the solid-liquid interface, causing partial undercooling and increasing the chance of dendrite melting. This refines grains, secondary phases, and precipitates (e.g., Al3Fe, Al3ScZr, AlSiMo, and Mg2Si phases), further improving the tensile strength, yield strength, and elongation of aluminum alloys. The combination of Ca and RE significantly refines grains and secondary phases, thereby enhancing tensile strength, yield strength, and elongation. When added within a certain range of RE (0-0.2wt%) and Zr (0.01-0.2wt%), with a mass ratio of RE to Zr of 0.1-1:1, this highly distorted coherent solid solution element promotes the formation of high-density Mg-Si and Cu-Mg clusters. It also significantly inhibits the diffusion of atoms within these clusters, enhancing cluster stability and ultimately improving yield strength, tensile strength, and elongation.

[0057] The high elongation heat-treatment-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-treatment-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-treatment-free die-cast aluminum alloy further contains Bi in an amount of 0-0.2% 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-treatment-free die-cast aluminum alloy further contains Cd in an amount of 0-0.1% 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-treatment-free die-cast aluminum alloy also contains 0-0.2% Cr in a mass percentage content, 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-treatment-free die-cast aluminum alloy further 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-treatment-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-treatment-free die-cast aluminum alloy further contains 0-0.3% by mass of V, 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 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 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, more preferably 0.2-0.5:1, specifically 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 :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 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 basically form small, short rods or block-shaped Al-Fe phase or Al-Fe-Si phase. RE can also round small, short rods or block-shaped Al-Fe phase or Al-Fe-Si phase 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, more preferably 0.2-0.5:1, and specifically 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 .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 : 1, 0.5:1, 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 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 basically form small short rods or block-shaped Al-Fe phase or Al-Fe-Si phase. The combination of RE and Zr can also significantly round the small short rods or block-shaped Al-Fe phase or Al-Fe-Si phase to improve the elongation.

[0061] When RE, Ti, and B are combined, TiB2 is not easy to coagulate and precipitate, which ensures the effective amount of TiB2 and prolongs the effective action time of Ti and B. This is because RE improves the wettability of aluminum liquid to boride; Ti can also assist B, Mn, Cr, and RE to further refine the grains and the second phase; B can react with Al, Si, and Fe to form AlFeSiB second phase to improve tensile strength and yield strength; B can also be combined with Mn, Cr, and RE to prevent the formation of iron-rich phase.

[0062] The combined effect of Mn, Cr and RE can effectively improve the Fe morphology, reduce the Fe content and refine the grain size, thereby obtaining an aluminum alloy with better tensile strength, yield strength and elongation. Specifically, Mn can significantly refine the recrystallized grains and the second phase, effectively transforming the coarse needle-shaped or flaky β-AlFeSi phase into small granular α-Al(FeMn)Si dispersed particles to improve the Fe morphology, and can also react with Fe to form α-(Fe,Mn)Al6 phase to reduce the Fe content. Obviously, Mn can reduce the Fe content, improve the Fe morphology, and refine 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 (CrFe)Al7 and (CrMn)Al 12 RE reduces the Fe content by forming dispersed phases such as AlCrSi and Mg(SiCr), increasing the precipitation volume fraction and uniformity of these dispersed phases and improving the alloy's mechanical properties. 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 the hard, brittle β-AlFeSi phase at grain boundaries. Furthermore, Mn significantly refines grain size, while Cr hinders grain growth, refining grains and secondary phases. RE also refines grains. The combined addition of Mn, Cr, and RE effectively improves Fe morphology. When added together, Mn and Cr form a dispersed α-Al(FeMnCr)Si phase with Fe and Si. This α-Al(FeMnCr)Si phase has a high bulk density and strong thermal stability. With extended stabilization time, these phases partially sink to the bottom and partially pin grain boundaries, effectively refining and controlling grain size. Furthermore, Mn, Cr, and RE react with trace impurities in the aluminum alloy liquid to form Al-Cr-X, Al-Mn-X, and Al-RE-X (where X is an impurity element) phases. These phases serve as grain nucleation sites, increasing the nucleation rate, refining the grains, and purifying the aluminum alloy, thereby 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 Fe morphology, reduces Fe content, and refines grains, resulting in an aluminum alloy with excellent overall properties.

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

[0065] In one embodiment, the high-elongation heat-treatment-free die-cast aluminum alloy further contains Te in an amount of 0-0.1% by weight, 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, they form fine, petal-shaped primary crystals, thereby increasing the tensile strength and elongation of the aluminum alloy.

[0066] In the technical solution of the present invention, the high elongation heat-treatment-free die-cast aluminum alloy further contains 0-0.2% Co by mass, 0-0.05% Be by mass, 0-0.2% Bi by mass, 0-0.1% Cd by mass, 0-0.2% Cr by mass, 0-0.2% Zr by mass, and 0-0.2% Sb by mass. Co can promote the formation of Fe ball phase, generate small-grained Al3(Fe,Co) phase that can improve the mechanical properties of the aluminum alloy, and can also transform coarse needle-shaped and flake-shaped Al3Fe phase into α-Al 15(Fe, Co) 3 Si 2 (its shape can be granular, small flower-shaped or small strips), and has a refining effect on the Al 3 Fe phase, further improving the tensile strength, yield strength, and elongation of the aluminum alloy; adding Ce and Co at the same time can not only improve the thermal stability of the aluminum alloy, but also promote <001> and <111> Be can react with Al, Fe, Si, etc. to form second phases such as Be-Fe(Al8Fe2SiBe)2 to improve the tensile strength and yield strength. Be can transform the eutectic Si phase from a lamellar phase to a fine phase to refine the Si phase, thereby reducing or eliminating the adverse effects of Si on the performance of the aluminum alloy. Be can transform the plate-like β intermediate phase into a relatively harmless Chinese character-shaped Be-Fe(Al8Fe2SiBe) phase and prevent the formation of needle-like β-Fe phase, thereby reducing or eliminating the adverse effects of Fe on the performance of the aluminum alloy. It can also promote the formation and precipitation of Mg2Si, Mg2Zn, Mg2SiZn, Al2Cu and other phases 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 to prevent the impurity elements from growing, and can be segregated on the grain boundary or adsorbed on the solid-liquid interface to form a partial supercooling, which increases the chance of dendrite melting and thus refines the grains. Among them, the refining effect of Be decreases with the increase of Be content. Increase; Bi can react with Mg and Cd to form second phases such as Mg3Bi2 and Mg3(BiCd)2 to improve 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 the tensile strength and yield strength and reduce the Fe content, Cd will form a large number of Cd-vacancy clusters in the aging stage, promote and accelerate the precipitation of CuAl2 phase, and reduce the solid solubility of the above elements in the aluminum matrix; Cr can transform the needle-shaped β-Fe phase into α-Fe phase to improve the Fe morphology to 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 12Intermetallic compounds such as Cr can hinder the nucleation and growth process of recrystallization, and can improve the yield strength, tensile strength, and elongation of aluminum alloys. Various chromium-containing fine compounds formed by Cr in aluminum alloys can be dissolved in the α phase again during the solid solution stage, and various Cr-containing phases such as α-AlCrSi dispersed phases are dispersed and precipitated during the natural aging stage. These Cr-containing phases can serve as the core of the heterogeneous nucleation of β" and θ" phases, accelerate the formation of β" and θ" phases, and thus improve the yield strength and tensile strength of aluminum alloys. At the same time, the Cr-containing phase in the matrix The dispersed precipitation of Cr will inevitably have a certain delay effect on the formation of θ' phase precipitated at the grain boundary. Mn and Cr can also 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. Pinning the grain boundary can effectively control the grain growth process and thus control the grain size. When Cr and Mo are added in combination, Cr-rich and Mo-rich multi-phases can be generated, which significantly improves the tensile strength of the aluminum alloy. V can react with Al to generate VAl 11 Refractory compounds such as V can refine the grains during the casting process. V can also refine the recrystallization structure and increase the recrystallization temperature to improve the tensile strength, yield strength and elongation of the aluminum alloy. During the die-casting process, the temperature cooling rate is relatively large. The non-steady-state phase Al3V obtained by the rapid cooling method will form a large number of fine and dispersed ellipsoidal Al(VCrTi)Si phases with Cr, Si and Ti in the aluminum alloy, which can prevent dislocation movement and recrystallization nucleation and growth, and significantly improve 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 to improve the tensile strength and yield strength. The addition of B can transform Zr from a solid solution state to a precipitation state, and it exists in the form of small 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 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 and can significantly improve the tensile strength, yield strength and elongation of aluminum alloys. Co can react with Al, Fe, Si, etc. to form Al 15(Fe, Co) 3 Si2, Al3 (Fe, Co) and other second phases, Be can react with Al, Fe, Si and other to form Be-Fe (Al8Fe2SiBe) 2 and other second phases, Al, Mg, Bi, Sn, Si, Cr, V, Cd and Sb can react with each other to form Mg3 (SbCd) 2, Mg2 (SnCd), Mg3 (BiCd) 2, AlCrSi, Al (VCrTi) Si, Mg2 (SiCr), Mg3Bi2, Mg2Sn, Mg3Sb2 and other second phases to improve the tensile strength and yield strength; Mn and Cr are added together to improve the tensile strength. Tensile strength and yield strength, control grain structure and delay dynamic recrystallization, and can also transform coarse AlFeSi phase into granular Al(MnCrFe)Si phase, thereby reducing the harm of impurity element Fe; Zr, Cd, and Be can promote the precipitation of precipitate phase; Co, Be, Cr, V, and Zr can also refine grains and precipitate phases; the combination of Be and Sc can also improve the morphology of needle-shaped Fe-containing phases, increase 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. In this way, Co, Be, Bi, Cd, Cr, V, Zr, Sn, and Sb interact with each other to promote the precipitation of precipitate phase, and then refine grains and precipitate phases to improve tensile strength, yield strength and elongation.

[0068] The high elongation heat-treatment-free die-cast aluminum alloy further contains 0-0.1% by mass of Ag, 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-treatment-free die-cast aluminum alloy further contains 0-0.2% by mass of Nb, 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-treatment-free die-cast aluminum alloy also contains 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 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 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, specifically 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 the present invention, the high-elongation, heat-treatment-free die-cast aluminum alloy further contains 0-0.1% by mass of Ag, 0-0.2% by mass of Nb, and 0-0.2% by mass of In. Ag promotes the precipitation of secondary phases (such as Al2Cu, Mg2Si, Mg3Sb2, and Mg3Bi2), refines the precipitated phases, and increases their density, enhancing the precipitation strengthening effect of the aluminum alloy, thereby improving the tensile strength, yield strength, and elongation of the aluminum alloy. In reacts with Al and Cu to form secondary phases such as AlIn and CuIn, thereby increasing tensile strength and yield strength. In also refines the grain size, thereby improving the elongation of the aluminum alloy. Nb reacts with Al and B to form high-temperature strengthening metallic compounds such as AlNb3, AlNb, Al3Nb, and NbB2. Some Nb can be dispersed at the matrix grain boundaries, significantly improving the yield strength and tensile strength of aluminum alloys. Nb can refine grains and secondary phases, 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 its interaction with Al, NbB2 is more likely to be a potential heterogeneous nucleation site than TiB2. The interaction of Ag, In, and Nb significantly promotes the precipitation of secondary phases and refines 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 the second phase and refine the precipitated phase, and Nb and In can also refine the grains and the second phase, thereby achieving the purpose of improving the tensile strength, yield strength and elongation of the aluminum alloy at the same time.

[0071] The high elongation heat-treatment-free die-cast aluminum alloy further contains 0-0.2% by mass of Mo, 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-treatment-free die-cast aluminum alloy further contains 0-0.1% by mass of Ge, 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 specifically 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 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 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 the present invention, the high-elongation, heat-treatment-free die-cast aluminum alloy further contains 0-0.2% by weight of Mo and 0-0.1% by weight of Ge. Mo can react with Al, Si, Fe, etc. to form secondary phases such as AlMo, AlSiMo, and AlSiFeMo, which are dispersed at the grain boundaries of the aluminum matrix. Mo also refines grain size and improves the morphology of Fe-containing intermetallic compounds, further enhancing the tensile strength, yield strength, and elongation of the aluminum alloy. Ge can react with Al and Si to generate Al9Ge7, Al6Ge5, Al5Ge2, Al3Ge4, SiGe and other secondary phases; Ge can easily capture the quenching vacancies in the α-Al matrix and form "Ge-vacancy pairs", "retaining" the quenching vacancies in the α-Al matrix, promoting the kinetics of artificial aging precipitation and improving the precipitation strengthening effect; Ge will not only replace some Si and Cu atoms in the metastable precipitate phase, but also refine the precipitate phase and increase the density of the precipitate phase, significantly improving the precipitation strengthening effect of the aluminum alloy; during the low-temperature quenching and holding process, the aluminum alloy matrix shrinks, plastically deforms, and generates internal stress; Ge can reduce the solubility of elements in aluminum, increase By adding nucleation points of clusters, during the process of rising to room temperature after the low-temperature quenching and holding treatment, these nucleation points combine with the "Ge-vacancy pairs" formed by quenching vacancies under the action of internal stress, rapidly increasing the volume fraction of Cu-Mg clusters, Mg-Si clusters, and Mg-Si-Cu clusters, thereby improving 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 of the Cu-Mg clusters, Mg-Si clusters, and Mg-Si-Cu clusters, thereby increasing the resistance of dislocations to cutting through these clusters; when the RE element is added, the combination of Ge and RE can 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 treatment-free aluminum alloy contains 6.5-9% Si by mass, 0.01-0.3% Fe by mass, 0.01-0.2% Cu by mass, 0-0.25% Mn by mass, 0.01-0.15% Mg by mass, 0.01-0.2% Zn 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.

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

[0076] In another embodiment of the present invention, the heat treatment-free aluminum alloy contains 6.5-9% Si by mass, 0.01-0.3% Fe by mass, 0.01-0.2% Cu by mass, 0-0.25% Mn by mass, 0.01-0.15% Mg by mass, 0.01-0.2% Zn 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.

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

[0078] Heating an Al source (preferably primary aluminum, such as electrolytic aluminum) at a temperature of 750-830°C to produce molten aluminum;

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

[0080] The alloy liquid is subjected to refining, slagging, and die-casting to obtain aluminum alloy parts; and

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

[0082] Si, Fe, Cu, Mn, Mg, Zn, B, Sr, and Ti sources can be added as single elements or alloys. Besides primary aluminum, the Al source can also be recycled aluminum. When recycled aluminum is used, the composition and content of the molten aluminum alloy must be tested, and the element content added to the recycled aluminum molten alloy is calculated based on the test results to obtain the high-elongation, heat-treatment-free die-cast aluminum alloy of the present invention.

[0083] Ice water or liquid nitrogen can be used for low-temperature quenching. The temperature of the low-temperature quenching is -200 to 0°C, specifically -200°C, -150°C, -100°C, -50°C, -10°C, or 0°C. The time of the low-temperature quenching is 0.1 to 10 hours, specifically 0.1 hour, 0.5 hour, 1 hour, 5 hours, or 10 hours. It is understood that ice / ice water can be added and liquid nitrogen can be replenished in time to maintain the temperature of the low-temperature quenching no greater than 0°C, retain as many vacancies as possible, and ensure the generation of supersaturated vacancies.

[0084] The alloy liquid is subjected to a refining treatment at a temperature of 710°C to 735°C for 10 to 30 minutes, wherein the mass ratio of the refining agent to the alloy liquid is 0.01 to 0.05:1, and the refining agent comprises a metal salt and hexachloroethane at a mass ratio of 0.5 to 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 to 1.5:0.5 to 1.5.

[0085] The molten alloy is die-casted at a temperature of 660-700°C, with the die-casting machine operating at a speed of 0.23-2.5 m / s. It is understood that the die-casting process of the present invention is a conventional die-casting process, but vacuum die-casting can also be used to die-cast the molten alloy. The strength (e.g., yield strength and tensile strength) and elongation of the aluminum alloy after vacuum die-casting are higher than those of the aluminum alloy 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-treatment-free die-cast aluminum alloy 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, a In source, a Zr source, a Mo source, a Cr source, a Ge source, a V source, and a RE source to the aluminum liquid. The Ca source, the Co source, the Cd source, the Be source, the Bi source, the Nb source, the Sn source, the Sb source, the Ag source, the In source, the Zr source, the Mo source, the Cr source, the Ge source, the V source, and the RE source can be added in the form of a simple substance or an alloy. The total mass percentage content of at least one element selected from Ca, Co, Cd, Be, Bi, Nb, Sn, Sb, Ag, In, Zr, Mo, Cr, Ge, V, and RE is no more than 0.6%, preferably no more than 0.5%, and specifically can be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or 0.6%. The content of individual impurities in the heat treatment-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 the present invention, the high elongation heat-treatment-free die-cast aluminum alloy prepared by the preparation method contains 6.5-9% Si by mass, 0.01-0.3% Fe by mass, 0.01-0.2% Cu by mass, 0-0.25% Mn by mass, 0.01-0.15% Mg by mass, 0.01-0.2% Zn by mass, 0-0.01% B by mass, 0-0.05% Sr by mass, and 0.01-0.1% Ti by mass. The composite addition of Si, Fe, Cu, Mn, Mg, Zn, B, Sr, and Ti within the above content ranges influences and interacts with each other, which can make the tensile strength of the heat-treatment-free aluminum alloy greater than 260MPa, the yield strength greater than 120MPa, and the elongation greater than 16%. Specifically:

[0088] (1) Si can improve the process flow properties of aluminum alloys, but when the content is too high, it will reduce the elongation. 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;

[0089] (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 tensile strength and yield strength. Among them, when Mg is solid-dissolved in CuAl2 phase and AlFeSi phase, (CuMg)Al2 phase and AlFeSiMg phase are formed;

[0090] (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 of the precipitated phase. 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, 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 of the precipitated phases. The composite addition of Zn and Mg can form a strengthening phase Mg / Zn2, which significantly improves 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 form second phases such as Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu, and AlFeSiB to 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, Al 12 CuMn2, α-Al(FeMn)Si, τ(Cu2Mn3Al 20) and other second phases to improve the tensile strength and yield strength; Mn can significantly refine the grain size by dissolving in the matrix to produce lattice distortion and reacting with Al to produce MnAl6 dispersed particles to improve elongation, and MnAl6 can also dissolve Fe to form α-(Fe,Mn)Al6 phase to reduce the Fe content and reduce Fe damage; Mn forms spherical particles or Chinese character-shaped AlFeMnSi compound phases with Al, Fe, Mn and Si, which can avoid the formation of long needle-shaped Fe phase to reduce Fe damage, and can also improve the tensile strength and yield strength of aluminum alloys while improving the demoulding properties of aluminum alloys; Mn can also transform coarse needle-shaped β-AlFeSi phases into small granular α-Al(FeMn)Si phase dispersed particles, improve Fe morphology to eliminate Fe damage, 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 phase improves the formation and growth shape of the β phase, thereby reducing Fe damage. Mn can also promote the transformation of the needle-shaped β-Al(FeMn)Si phase into small granular α-Al(FeMn)Si dispersed phase. The 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 serve as heterogeneous nucleation sites for the β' phase during natural aging, inducing its nucleation, thereby accelerating the precipitation of the β' phase. Mn can also react with impurities in the aluminum alloy liquid to form Al-Mn-X phases (X is an impurity element, including transition metal elements, etc.), thereby purifying 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.

[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 grains and second phases by modifying 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 die sticking during die casting; Sr can transform the coarse needle-shaped β-AlFeSi and β-AlFeMnSi phases in the ingot into small granular Chinese character-shaped α-AlFeSi and α-Al(FeMn)Si phases, reducing the homogenization time of the ingot, and improving the yield strength, tensile strength and elongation of the aluminum alloy;

[0095] (8) The TiAl2 phase generated by the reaction of Ti and Al acts as a non-spontaneous core during crystallization, which can refine the grains, second phases and precipitated phases to improve the tensile strength, yield strength and elongation of the aluminum alloy;

[0096] (9) B can undergo boronization reaction with transition metal elements (including Fe and other transition metal elements) to generate compounds such as boron-iron 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 also preventing the formation of the iron-rich phase in the aluminum alloy liquid; B can inhibit the segregation of Ti3Al, so the effect is better when Ti and B are used together; B can also refine the grains and the second phase to improve the elongation of the aluminum alloy.

[0097] The combined effect 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 effect of Mn, B, Ti, and Sr within the above content range can refine the grains, second phase, and precipitated 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 of the precipitated phase, and further improve the tensile strength, yield strength, and elongation of the aluminum alloy; the combined effect of Fe, Sr, and Mn within the above content range can improve the demolding performance of the aluminum alloy.

[0098] The Fe content of the present invention is relatively low (0.01-0.3wt%), and during the die-casting process, the temperature cooling rate is relatively high (can be 10-60K / s), so that the Fe basically forms a small, short rod-shaped or block-shaped Al-Fe phase or Al-Fe-Si phase. As a result, the Fe content within this content range has little effect on the elongation of the aluminum alloy. As the Fe content decreases, the elongation gradually increases, and in this case, there is no need to increase the addition of Mn or add more Mn to reduce the effect of Fe on the elongation of the aluminum alloy. The Mn content of the present invention is set to 0-0.25% by mass, and Mn is used to further improve the demolding performance of the aluminum alloy. Sr can also change the morphology of the eutectic silicon phase through its metamorphic effect, thereby reducing the tendency of die sticking during the die-casting process.

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

[0100] Heat-treatment-free aluminum alloys undergo natural aging during storage and transportation after die-casting, meaning their strength increases with extended storage time. This natural aging is attributed to the aggregation of solute atoms in the aluminum alloy, known as solute atom clusters. Solute atom clusters are disordered aggregations of solute atoms within the aluminum matrix, measuring several nanometers in size and typically consisting of a few to dozens of randomly distributed atoms with no clear crystal structure.

[0101] The change in the strength of heat-treatment-free aluminum alloys is mainly related to the size and volume fraction of solute atom clusters. During the natural aging process, the formation and growth of clusters are closely related to the change in the concentration of supersaturated quenching vacancies. Vacancies are thermal defects, and their concentration has an exponential function relationship with temperature. The present invention performs a low-temperature quenching treatment on aluminum alloy parts after the die-casting treatment to produce supersaturated vacancies to improve the mechanical properties of heat-treatment-free aluminum alloys. 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, thereby producing 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, and refine the α-Al phase and eutectic Si phase structure to improve the yield strength, tensile strength and elongation of the heat-treatment-free aluminum alloy.

[0102] The addition of Cu, Mn, Mg, Zn, Ti, Sr, Fe, and B can also regulate the clustering behavior of solute atoms in aluminum alloys, such as by adjusting vacancies to influence the formation of existing clusters and new clusters. When Mg (0.01-0.15 wt%) and Cu (0.01-0.2 wt%) are added to the aluminum melt of the present invention within a certain content range, the Mg atoms activate the diffusion of vacancies and promote the formation of Mg-Si and Cu-Mg clusters, significantly strengthening the clusters. The atomic radii of Mn and Sr are much larger than that of Al. Mn and Sr atoms within this content range create lattice distortion within the aluminum matrix. This, combined with the pinning of vacancies and Mg-Si and Cu-Mg clusters in the heat-treatment-free aluminum alloy, promotes cluster growth and further enhances the natural aging effect, thereby improving the yield strength, tensile strength, and elongation of the heat-treatment-free aluminum alloy.

[0103] 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-treatment-free aluminum alloy with excellent demolding performance, tensile strength, yield strength, and elongation is obtained.

[0104] The present invention also provides a structural component, at least partially made of a high-elongation, heat-treatment-free die-cast aluminum alloy or a high-elongation, heat-treatment-free die-cast aluminum alloy produced by this method. The structural component can be applied to new energy vehicles, including automotive components such as the vehicle body, rear wheel arch inner panel, rear longitudinal beam, floor panel connecting plate, rear floor panel, beam inner reinforcement plate, hood, fender, door, rear compartment, and roof. The structural component of the present invention may also be used in other fields, such as aerospace, high-speed rail, shipbuilding, mobile devices, household appliances, the chemical industry, daily necessities, and construction.

[0105] Examples and Comparative Examples

[0106] The components and contents of the aluminum alloys of Examples 1 to 5 and Comparative Examples 1 to 2 are shown in Table 1, and the performance test results are shown in Table 2.

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

[0108] To simplify the description, the contents of trace elements such as impurities in the comparative examples and examples are not shown.

[0109] A domestically produced CSS-44100 electronic universal tensile tester was used for processing and tensile testing according to the "Method for Tensile Testing of Metal Materials at Room Temperature" (GB / T228-2002) and the "Method for Tensile Testing of Metal Materials at High Temperature" (GB4338-2006-T). The processed specimens were polished using 800# and 1500# water-abrasive sandpaper, respectively. The tensile force of the tensile tester was 2kN, and the tensile speed was 2mm / min. Three specimens were tested under the same conditions, and the average value was calculated.

[0110] Table 2 Performance test results of aluminum alloys of Examples 1 to 5 and Comparative Examples 1 to 2

[0111]

[0112] The tensile strength, yield strength, and elongation of the high-elongation, heat-treatment-free die-cast aluminum alloys of Examples 1 to 5 are significantly greater than those of the high-elongation, heat-treatment-free die-cast aluminum alloys of Comparative Examples 1 and 2. This indicates that the high-elongation, heat-treatment-free die-cast aluminum alloys of the present invention exhibit superior properties. Specifically, the Fe content of Examples 1 to 5 is lower than that of Comparative Examples 1 and 2, and the Mn / Fe mass ratio of Examples 1 to 5 is lower than that of Comparative Examples 1 and 2.

[0113] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformation made by using the contents of the present invention specification 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-cast aluminum alloy, characterized in that: The high elongation heat-treatment-free die-cast aluminum alloy further 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% Zn 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-treatment-free die-cast aluminum alloy is subjected to die-casting treatment. During the die-casting process, the temperature cooling rate is 10-60K / s.

2. The high elongation heat-treatment-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%.

3. The high elongation heat-treatment-free die-cast aluminum alloy according to claim 1, characterized in that: The high elongation heat-treatment-free die-cast 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, 0.05-0.2% Zn by mass, 0.005-0.01% B by mass, 0.005-0.05% Sr by mass, and 0.05-0.1% Ti by mass.

4. The high elongation heat-treatment-free die-cast aluminum alloy according to any one of claims 1 to 3, 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; The high elongation heat treatment-free die-casting aluminum alloy further contains Bi in an amount of 0-0.2% by mass; 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-cast 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 Zr; 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 a mass percentage content of 0-0.1%; The high elongation heat treatment-free die-casting aluminum alloy further contains 0-0.3% by mass of V; The high elongation heat-treatment-free die-cast aluminum alloy further contains RE in an amount of 0-0.2% by mass, wherein RE is at least one of La, Ce, Pr, Nd, Er, Sm, Y, Gd, and Sc.

5. The high elongation heat-treatment-free die-cast aluminum alloy according to claim 4, characterized in that: Meet at least one of the following conditions: When the high elongation heat treatment-free die-cast 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-cast 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 RE and Zr, the mass ratio of RE to Zr is 0.1-1:1; 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 high elongation 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; When the high elongation heat treatment-free die-casting aluminum alloy further contains Ca, Sn and RE, the mass ratio of Ca, Sn and RE is 0.05-10:0.01-10:1; When the high elongation heat-treatment-free die-cast aluminum alloy further contains RE, the mass ratio of (Mn+RE) to Fe is 0.01-0.8:1; When the high elongation heat treatment-free die-casting aluminum alloy further contains RE and Zr, the mass ratio of (Mn+RE+Zr) to Fe is 0.01-0.8:

1.

6. The high elongation heat-treatment-free die-cast aluminum alloy according to claim 4, characterized in that: Meet at least one of the following conditions: The high elongation heat-treatment-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% Zn 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 treatment-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% Zn by mass, 0.01-0.1% Ti by mass, 0.01-0.1% Zr by mass, and 0.01-0.1% Zr by mass. Mo with a mass percentage of 0.01-0.1%, Ge with a mass percentage of 0.01-0.1%, Cr with a mass percentage of 0.01-0.1%, V with a mass percentage of 0.05-0.2%, La with a mass percentage of 0.01-0.03%, Ce with a mass percentage of 0.01-0.02%, Sm with a mass percentage of 0.01-0.05%, Y with a mass percentage of 0.01-0.05%, and Gd with a mass percentage of 0.01-0.05%; The high elongation heat-treatment-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% Zn 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.

7. A method for preparing a high-elongation heat-treatment-free die-cast aluminum alloy, comprising the following steps: The Al source is subjected to a first heating treatment to obtain aluminum liquid; adding a Si source, an Fe source, a Cu source, a Mn source, a Mg source, a Zn source, a B source, a Sr source, and a Ti source to the aluminum liquid, and performing a second heating treatment to obtain an alloy liquid; The alloy liquid is subjected to refining, slagging, and die-casting 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, and 0.01-0.15% Mg by mass. The composition comprises 0.01-0.2% Zn, 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, the temperature of the low-temperature quenching treatment is -150~0°C, and the time is 0.1~10h.

8. The method for preparing a high elongation heat-treatment-free die-cast aluminum alloy according to claim 7, 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 Zr source, a Mo source, a Cr source, a Ge source, a V source, and a RE source to the aluminum liquid.

9. 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 according to any one of claims 1 to 6 or the high-elongation heat-treatment-free die-cast aluminum alloy prepared by the preparation method according to any one of claims 7 to 8.

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