High flow non-heat treated die cast aluminum alloy and method of making, structural member

Abstract

The application provides a high-fluidity heat-treatment-free die-casting aluminum alloy containing 10-11.5% of Si in mass percentage, 0.01-0.6% of Fe in mass percentage, 0.2-0.8% of Cu in mass percentage, 0.01-1% of Mn in mass percentage, 0.1-0.5% of Mg in mass percentage, 0.2-1% of Zn in mass percentage, 0-0.01% of B in mass percentage, 0-0.05% of Sr in mass percentage, 0-0.2% of RE in mass percentage, 0-0.3% of Bi in mass percentage and 0.01-0.3% of Ti in mass percentage. The application also provides a preparation method and a structural member of the high-fluidity heat-treatment-free die-casting aluminum alloy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum alloy, in particular to a high-fluidity heat-treatment-free die-casting aluminum alloy, a preparation method of the high-fluidity heat-treatment-free die-casting aluminum alloy, and a structural member. BACKGROUND

[0002] Under the continuous driving of reducing fuel consumption and emission of fuel vehicles and increasing the endurance of electric vehicles, the automobile lightweight is the general trend. The density of aluminum is only 1 / 3 of that of steel, and the heat-treatment-free aluminum alloy becomes the first choice for automobile die-castings. The fluidity of the heat-treatment-free aluminum alloy in the as-cast state is required to be high for obtaining large and thin automobile die-castings. Of course, the heat-treatment-free aluminum alloy with high fluidity is also required in other fields, such as aerospace, high-speed rail, ship, mobile device, household appliance, chemical industry, daily necessities, building, etc.

[0003] However, the fluidity of the existing heat-treatment-free die-casting aluminum alloy is not high, for example, the fluidity of C611 aluminum alloy is about 1550 mm, which is greatly different from that of the commonly used ADC12 aluminum alloy (about 1936 mm), and it is difficult to meet the requirement of the fluidity of the heat-treatment-free aluminum alloy in the automobile field.

[0004] Therefore, it is urgent to develop a heat-treatment-free die-casting aluminum alloy with high fluidity. SUMMARY

[0005] In view of the above defects of the prior art, the present application provides a heat-treatment-free die-casting aluminum alloy with high fluidity.

[0006] The present application provides a heat-treatment-free die-casting aluminum alloy with high fluidity, which contains Al, and further contains Si with a mass percentage content of 10-11.5%, Fe with a mass percentage content of 0.01-0.6%, Cu with a mass percentage content of 0.2-0.8%, Mn with a mass percentage content of 0.01-1%, Mg with a mass percentage content of 0.1-0.5%, Zn with a mass percentage content of 0.2-1%, B with a mass percentage content of 0-0.01%, Sr with a mass percentage content of 0-0.05%, RE with a mass percentage content of 0-0.2%, Bi with a mass percentage content of 0-0.3%, and Ti with a mass percentage content of 0.01-0.3%.

[0007] The present application further provides a preparation method of the heat-treatment-free die-casting aluminum alloy with high fluidity, which comprises the following steps:

[0008] The Al source is subjected to a first heating treatment to obtain aluminum liquid;

[0009] adding Si source, Fe source, Cu source, Mn source, Mg source, Zn source, B source, Sr source, RE source, Bi source, and Ti source into the molten aluminum, and performing second heating treatment to obtain an alloy liquid;

[0010] performing refining treatment, skimming treatment, and die casting treatment on the alloy liquid to obtain an aluminum alloy part;

[0011] performing low-temperature quenching treatment on the aluminum alloy part to obtain a high-flowability heat-treatment-free die-cast aluminum alloy, wherein the high-flowability heat-treatment-free die-cast aluminum alloy contains Al, and further contains Si with a mass percentage of 10-11.5%, Fe with a mass percentage of 0.1-0.4%, Cu with a mass percentage of 0.4-0.6%, Mn with a mass percentage of 0.2-0.8%, Mg with a mass percentage of 0.2-0.4%, Zn with a mass percentage of 0.4-0.8%, B with a mass percentage of 0.005-0.01%, Sr with a mass percentage of 0.005-0.05%, RE with a mass percentage of 0.01-0.1%, Bi with a mass percentage of 0.01-0.1%, and Ti with a mass percentage of 0.05-0.15%.

[0012] The application further provides a structural member, at least a part of which is made of the high-elongation heat-treatment-free aluminum alloy or the high-elongation heat-treatment-free aluminum alloy prepared by the preparation method.

[0013] In the technical scheme, the high-flowability heat-treatment-free die-cast aluminum alloy contains Si with a mass percentage of 10-11.5%, Fe with a mass percentage of 0.01-0.6%, Cu with a mass percentage of 0.2-0.8%, Mn with a mass percentage of 0.01-1%, Mg with a mass percentage of 0.1-0.5%, Zn with a mass percentage of 0.2-1%, B with a mass percentage of 0-0.01%, Sr with a mass percentage of 0-0.05%, RE with a mass percentage of 0-0.2%, Bi with a mass percentage of 0-0.3%, and Ti with a mass percentage of 0.01-0.3%. The Si, Fe, Cu, Mn, Mg, Zn, B, Sr, RE, Bi, and Ti are added in the above content ranges, and interact with each other, so that the heat-treatment-free aluminum alloy has a tensile strength greater than 260 MPa, a yield strength greater than 120 MPa, an elongation greater than 10%, and a flowability better than that of C611 aluminum alloy and ADC12 aluminum alloy.

[0014] (1) When a trace amount of Si is added to the aluminum alloy, the flowability of the aluminum alloy sharply decreases, but as the Si content continues to increase, the flowability of the aluminum alloy starts to slowly increase when the Si content is greater than 6%, and the flowability of the aluminum alloy is better when the Si content is about 10-11.5%, and the aluminum alloy can also avoid being loose and hot cracking; Si can also react with Al, Fe, Mg, Cu, B, etc. to generate Mg2Si, AlFeSi, AlFeSiCu, AlFeMgSi, AlCuMgSi, AlFeSiB, etc. Second phase to improve the tensile strength and yield strength of the aluminum alloy;

[0015] (2) Mg can react with Al, Fe, Si, Cu, Zn, etc. to generate AlFeMgSi, (CuMg)Al2, AlCuMgSi, MgZnCu, Mg2Si, Mg2Zn, Mg2SiZn, etc. Second phase to improve the tensile strength and yield strength of the aluminum alloy, among them, Mg is dissolved in CuAl2 phase and AlFeSi phase to form (CuMg)Al2 phase and AlFeSiMg phase; When the Mg content is 0.1-0.5%, the grass-like eutectic Si appears in the aluminum alloy, which can improve the flowability of the aluminum alloy, and Mg can also hinder the growth of eutectic Si, reduce the length of grass-like eutectic Si in the aluminum alloy, hinder the growth of primary Al phase, and further improve the flowability of the aluminum alloy; In addition, Mg can significantly reduce the surface tension of molten aluminum alloy, which can reduce or even eliminate the influence of the surface tension of the aluminum alloy surface oxide film on the flowability of the aluminum alloy.

[0016] (3) Cu can react with Al, Fe, Si, Mg, Zn, etc. to generate CuAl2, AlFeSiCu, AlCuMgSi, Al2CuZn, MgZnCu, (CuMg)Al2, etc. Second phase to improve the tensile strength and yield strength of the aluminum alloy, and can also promote the precipitation of Mg2Si, Mg2Zn, Mg2SiZn, etc. Second phase, improve the volume fraction and dispersion degree of the precipitated phase, and the subsequent natural aging or vehicle painting baking paint heating treatment (referred to as T85 treatment) can further improve the aging strengthening effect of Cu and Mg; The MgZnCu eutectic structure precipitated in the aluminum alloy can refine the grains, reduce the solidification interval, reduce the dendritic coherence temperature, and reduce the dendritic growth rate, thereby improving the flowability of the aluminum alloy;

[0017] (4) Zn can react with Al, Mg, Cu and Si to form secondary phases MgZn2, Mg2SiZn, MgZnCu, Al2CuZn, etc. to improve the tensile strength and yield strength of the aluminum alloy, Zn can eliminate elemental Si to reduce the influence of Si on the performance of the aluminum alloy, and can also promote the precipitation of secondary phases Mg2Si, MgZn2, Mg2SiZn, Al2Cu, Al2CuMg, etc. to improve the volume fraction and dispersion degree of the precipitated phases; with the increase of the content of Zn, the shrinkage of the aluminum alloy decreases and the fluidity increases, because the thermal conductivity of Zn is significantly lower than that of Al, with the increase of the content of Zn, the liquidus region of the melt increases, thereby reducing the shrinkage of the aluminum alloy and improving the fluidity of the aluminum alloy; the combined addition of Zn and Mg can form MgZn strengthening phase, which can significantly improve the tensile strength and yield strength of the aluminum alloy, the shrinkage of MgZn phase is lower than that of Al, so MgZn phase can also improve the fluidity of the aluminum alloy; in addition, the addition of Zn increases the lattice distortion energy of the matrix, which promotes the migration of Mg, Cu and Si atoms from the matrix to form more Cu-Mg-Zn clusters, Mg-Si-Zn clusters, and improves the cluster strengthening effect;

[0018] (5) Fe can improve the tensile strength, yield strength and demolding performance of the aluminum alloy, and can also react with Al, Si, Mg, Cu and B to form secondary phases Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu, AlFeSiB, etc. to improve the tensile strength and yield strength of the aluminum alloy; with the increase of the content of Fe, the formation temperature of Fe-rich phase gradually increases, which promotes the transformation of the primary Fe-rich phase from ternary eutectic with Al-Si to binary eutectic with α-Al, the transformation of the primary Fe-rich phase promotes the increase of the content of needle-shaped iron phase, and at the same time leads to the coarsening of α-Al, increases the resistance and reduces the fluidity of the aluminum alloy, while the thermal conductivity of Fe is lower than that of Al, which can increase the fluidity of the aluminum alloy, the above factors comprehensively, Fe has little effect on the fluidity and shrinkage of the aluminum alloy as a whole;

[0019] (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) etc. second phase to improve the tensile strength and yield strength of the aluminum alloy; Mn can significantly refine the grain size by the lattice distortion produced by solid solution in the matrix and MnAl6 dispersed particles generated by the 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 the Fe hazard; Mn and Al, Fe, Mn and Si generate AlFeMnSi phase in spherical particle or Chinese character shape, which can avoid the formation of long needle-like Fe phase to reduce the Fe hazard, and can also improve the tensile strength and yield strength of the aluminum alloy when improving the mold release property of the aluminum alloy; Mn can also convert the coarse needle-like β-AlFeSi phase into small particle-like α-Al(FeMn)Si phase dispersed particles, improve the Fe morphology to eliminate the Fe hazard, specifically, Mn can replace part of Fe in the coarse needle-like β-AlFeSi phase to generate small particle-like dispersed β-Al(FeMn)Si phase, the generation and growth shape of the β phase are improved, thereby reducing the Fe hazard; Mn can also promote the conversion of needle-like β-Al(FeMn)Si phase to small particle-like α-Al(FeMn)Si dispersed phase, and the generated α-Al(FeMn)Si phase dispersed particles are distributed in the aluminum matrix and strongly pinned at the grain boundaries of the aluminum alloy, which is mainly because the Mn-containing α phase dispersed particles in the aluminum alloy can act as non-uniform nucleation sites during the natural aging process of the β' phase to induce nucleation, thereby accelerating the precipitation of the β' phase; Mn can also react with impurity phases in the aluminum alloy liquid to generate Al-Mn-X phases (X is an impurity element, including but not limited to transition metal elements), which can purify the aluminum alloy liquid to improve the flowability of the aluminum alloy, and these phases can act as grain nucleation sites to improve the nucleation rate, refine the grain size, and improve the tensile strength, yield strength, elongation and flowability of the aluminum alloy;

[0020] (7) Sr preferentially combines with Fe to form dispersion strengthening, reduces the solid solubility of Fe, and improves the yield strength and tensile strength of the aluminum alloy; Sr can change the behavior of intermetallic compound phases in crystallography, and can be used as a modifier to refine the grain size, Si phase and second phase by modifying the aluminum alloy through the heterogeneous nucleation theory or twin valley mechanism, such as Sr can change the morphology of eutectic silicon phase through modification to improve the elongation and flowability of the aluminum alloy and reduce the sticking tendency during the die casting process; Sr can convert the coarse needle-like β-AlFeSi and β-AlFeMnSi phases in the ingot into small particle-like Chinese character-shaped α-AlFeSi and α-Al(FeMn)Si phases, which reduces the homogenization time of the ingot and improves the yield strength, tensile strength and elongation of the aluminum alloy;

[0021] (8) TiAl2 phase generated by the reaction of Ti and Al as a non-spontaneous core during crystallization can refine the grain size, second phase and precipitated phase to improve the tensile strength, yield strength, flowability and elongation of the aluminum alloy;

[0022] (9) B can react with transition metal elements (including Fe and other transition metal elements) to form compounds such as boron-iron compounds that can be separated from the aluminum alloy liquid, to purify the aluminum alloy liquid and improve the fluidity of the aluminum alloy; B is easy to be adsorbed on the surface of the iron-rich phase, inhibiting the growth of the iron-rich phase, and playing a role in controlling the size of the iron-rich phase, and can also prevent the generation of the iron-rich phase in the aluminum alloy liquid; B can also refine the grains, Si phase and second phase, to improve the fluidity and elongation of the aluminum alloy; Ti and B can also convert the coarse dendrites in the aluminum alloy into fine equiaxed crystals when refining the grains and second phase, reducing the intersection between the dendrites, allowing more solid phase to precipitate before the aluminum alloy stops flowing, increasing the flow time, and thus improving the fluidity of the aluminum alloy; B can inhibit the segregation of Ti3Al, and therefore, the use of Ti and B together can significantly improve the fluidity of the aluminum alloy;

[0023] (10) Bi can react with Mg and Cd to form second phases such as Mg3Bi2 and Mg3(BiCd)2, to improve the tensile strength and yield strength of the aluminum alloy; Bi can also significantly reduce the surface tension of the molten aluminum alloy, and can reduce or even eliminate the influence of the surface tension of the aluminum alloy surface oxide film, to improve the fluidity of the aluminum alloy;

[0024] (11) RE can reduce the solidification interval of the aluminum alloy, to improve the fluidity of the aluminum alloy, and La and Ce can significantly reduce the solidification interval of the aluminum alloy, playing a role in heterogeneous nucleation, to refine the grains and improve the fluidity; A large amount of primary phase is precipitated during the solidification of the aluminum alloy, which can increase the liquidus temperature of the aluminum alloy melt, reduce the superheat of the aluminum alloy melt, and increase the viscosity of the aluminum alloy melt, thereby reducing the fluidity of the aluminum alloy; RE is a surface active element with a radius larger than that of Al, and cannot enter the α-Al lattice; during the solidification process of the aluminum alloy, RE gathers at the front of the solid-liquid interface, increases the composition undercooling at the front, intensifies the growth and crystallization of cellular dendrites, the growth of the dendrites is more developed, the secondary dendrites increase, and finally the secondary dendrite arm spacing of the aluminum alloy is reduced, thereby refining the grains, second phase and precipitated phase (such as Al3Fe, Al3ScZr, AlSiMo, Mg2Si phase), to improve the tensile strength, yield strength, fluidity and elongation of the aluminum alloy; RE has the same distribution area as the Fe phase, 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 AlFeRE and other rare earth compounds, 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 of the aluminum alloy; RE can convert long strip-shaped β-Fe phase into spherical ɑ-Fe phase, and modify and refine elemental Si; RE can also promote the precipitation of dispersed phases such as CuAl2, (CuMg)Al2, to further improve the tensile strength and yield strength of the aluminum alloy.

[0025] The Si, Fe, Cu, Mn, Mg, Zn, Sr, B, RE, Bi and Ti in the above content range have complex effects, which not only can make the heat treatment-free die casting aluminum alloy have better fluidity, but also have excellent demolding performance, tensile strength, yield strength and elongation. The Si, Mg, Cu, Zn, Mn, Sr, Ti, RE, Bi and B in the above content range can all improve the fluidity of the aluminum alloy. Among them, the Mg, Zn and Cu in the above content range can react with each other to form MgZnCu eutectic structure, and the precipitated MgZnCu eutectic structure can significantly improve the fluidity of the aluminum alloy; when Ti and B are used together, B can inhibit the segregation of Ti3Al, so that Ti and B can more effectively improve the fluidity of the aluminum alloy; the Mn, B, Ti, RE and Sr in the above content range have complex effects, which can refine the grains, second phases, Si phases and precipitates, so as to improve the elongation and fluidity of the aluminum alloy; Zn and Cu can both reduce the shrinkage of the aluminum alloy, so as to improve the fluidity of the aluminum alloy; RE can shorten the solidification interval of the aluminum alloy, and plays a heterogeneous nucleation role, so as to improve the fluidity of the aluminum alloy; Mg and Bi can also significantly reduce the surface tension of the molten aluminum alloy, can reduce or even eliminate the influence of the surface tension of the surface oxide film of the aluminum alloy, so as to improve the fluidity of the aluminum alloy; the Cu and Zn in the above content range can promote the precipitation of the second phase (such as MgZnCu), can improve the volume fraction and dispersion degree of the precipitated phase, and further improve the tensile strength, yield strength, fluidity and elongation of the aluminum alloy; the Fe, Sr and Mn in the above content range have complex effects, which can improve the demolding performance of the aluminum alloy.

[0026] During the die casting process, when the temperature cooling rate is large (may be 10-60K / S) and the mass percentage of Fe is 0.01-0.4%, preferably 0.01-0.15%, the Fe basically forms fine short rod-shaped or block-shaped Al-Fe phases or Al-Fe-Si phases, so that the Fe in the content range has little effect on the elongation, and more Mn does not need to be added to reduce the effect of Fe on the elongation of the aluminum alloy, and the mass percentage content of Mn may be 0.01-0.4%.

[0027] Since the mechanical properties of the heat treatment-free die casting aluminum alloy cannot be improved by aging heat treatment, most of the solute atoms of the heat treatment-free die casting aluminum alloy of the present application usually exist in the form of solid solution in the aluminum matrix, and in addition to fine grain strengthening, the strength increment of the heat treatment-free die casting aluminum alloy mainly comes from the pinning of dislocations caused by the lattice volume mismatch and elastic mismatch of solid solution atoms, that is, solid solution strengthening.

[0028] The natural aging of the heat-treatment-free die-casting aluminum alloy occurs during the storage and transportation after the die-casting process, i.e. the strength of the alloy increases with the extension of the storage time. The natural aging is attributed to the aggregation of solute atoms, i.e. solute atom clusters. The solute atom clusters are the disordered aggregation of solute atoms in the aluminum matrix, with the size of several nanometers, usually composed of several to tens of disordered distributed atoms without clear crystal structure.

[0029] The change of the strength of the heat-treatment-free die-casting aluminum alloy is mainly related to the size and volume fraction of the solute atom clusters. During the natural aging, the formation and growth of the clusters are closely related to the change of the supersaturated quenching vacancy concentration. The vacancy belongs to thermal defects, and its concentration has an exponential function relationship with the temperature. In the present application, the aluminum alloy parts are subjected to low-temperature quenching treatment after the die-casting process to produce supersaturated vacancies and improve the mechanical properties of the heat-treatment-free die-casting aluminum alloy. Specifically, during the die-casting process, the equilibrium vacancy concentration is large; during the subsequent quenching process, part of the vacancies at high temperature are retained, thereby producing supersaturated vacancies; and the low-temperature quenching treatment can also make the aluminum alloy shrink, produce plastic deformation, reduce the solubility of elements in aluminum, increase the nucleation points of clusters, refine the α-Al phase and eutectic Si phase structures, and improve the yield strength, tensile strength, flowability and elongation of the aluminum alloy.

[0030] The addition of Cu, Mn, Mg, Zn, Ti, Sr, Fe and B can also regulate the behavior of solute atom clusters in the aluminum alloy, such as affecting the formation of original clusters and forming new clusters by adjusting vacancies. After adding Mg (0.1-0.5wt%) and Cu (0.2-0.8wt%) elements in the aluminum liquid within a certain content range, the Mg atoms activate the diffusion of vacancies and promote the formation of Cu-Mg-Zn clusters, Mg-Si-Zn clusters and Mg-Si-Cu-Zn clusters, significantly strengthening the clusters. The atomic radii of Mn and Sr are much larger than that of Al, and the atoms of Mn and Sr within the above content range form lattice distortion in the aluminum matrix. In addition, the heat-treatment-free die-casting aluminum alloy is added with pinned vacancies and Mg-Si clusters, Cu-Mg clusters and Mg-Si-Cu clusters, and promotes the growth of clusters, further promotes the natural aging effect, and improves the yield strength, tensile strength and elongation of the heat-treatment-free die-casting aluminum alloy. In addition, RE and Bi can further promote the formation of Cu-Mg-Zn clusters, Mg-Si-Zn clusters and Mg-Si-Cu-Zn clusters, and significantly strengthen the clusters.

[0031] In summary, under the combined action of Si, Fe, Cu, Mn, Mg, Zn, Sr, B, RE, Bi and Ti within the above content range, a heat-treatment-free aluminum alloy with excellent flowability, demolding performance, tensile strength, yield strength and elongation is obtained. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0033] An embodiment of the present application provides a high-fluidity heat-treatment-free die-casting aluminum alloy, which contains Si in a mass percentage of 10-11.5%, Fe in a mass percentage of 0.01-0.6%, Cu in a mass percentage of 0.2-0.8%, Mn in a mass percentage of 0.01-1%, Mg in a mass percentage of 0.1-0.5%, Zn in a mass percentage of 0.2-1%, B in a mass percentage of 0-0.01%, Sr in a mass percentage of 0-0.05%, RE in a mass percentage of 0-0.2%, Bi in a mass percentage of 0-0.3%, Ti in a mass percentage of 0.01-0.3%, and Al and inevitable impurities.

[0034] In an embodiment, the high-fluidity heat-treatment-free die-casting aluminum alloy contains Si in a mass percentage of 10-11.5%, Fe in a mass percentage of 0.1-0.4%, Cu in a mass percentage of 0.4-0.6%, Mn in a mass percentage of 0.2-0.8%, Mg in a mass percentage of 0.2-0.4%, Zn in a mass percentage of 0.4-0.8%, B in a mass percentage of 0.005-0.01%, Sr in a mass percentage of 0.005-0.05%, RE in a mass percentage of 0.01-0.1%, Bi in a mass percentage of 0.01-0.1%, and Ti in a mass percentage of 0.05-0.15%.

[0035] The mass ratio of Ti to B is 1-50:1, preferably 10-30:1, 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] The mass ratio of Cu to Mg is 1.5-4, preferably 2-3:1, and can be 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, 3.1:1, 3.2:1, 3.3:1, 3.4:1, 3.5:1, 3.6:1, 3.7:1, 3.8:1, 3.9:1, or 4:1. When Mg (0.1-0.5wt%) and Cu (0.2-0.8wt%) elements are added in a certain content range in the molten aluminum of the application, and the mass ratio of Cu to Mg is 1.5-4, the Mg atoms activate the diffusion of vacancies, significantly promote the formation of Mg-Si clusters, Cu-Mg clusters, and Mg-Si-Cu clusters, significantly strengthen the clusters, and greatly improve the yield strength, tensile strength, and elongation of the aluminum alloy.

[0037] RE is at least one of La, Ce, Pr, Nd, Er, Sm, Y, Gd, and Sc. In one embodiment, RE is La, Ce, and Sm, and the ratio of the three is 0.01-0.03:0.02-0.05:1. In another embodiment, RE is Pr, Er, and Nd, and the ratio of the three is 0.02-0.05:0.03-0.08:1. In yet another embodiment, RE is Sm, Y, and Gd, and the ratio of the three is 0.06-0.08:0.1-0.2:1. The addition of multiple rare earth elements in combination has a better refining effect.

[0038] The mass ratio of Mn to Fe is 0.1-3:1. The mass ratio of Mn to Fe can be 0.1-0.6:1, or 0.6-3:1, and can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, or 3:1.

[0039] In the prior art in the field of aluminum alloy, the content of Mn can be set according to the content of Fe and the mass ratio of Mn to Fe, and it is generally believed that when the mass ratio of Mn to Fe is less than 0.6:1 and greater than 1:1, the tensile strength, yield strength, flowability and elongation of the aluminum alloy are reduced. Therefore, in order to obtain better tensile strength, yield strength, flowability and elongation, the mass ratio of Mn to Fe is usually set to 0.6-1:1. In the present application, the mass ratio of Mn to Fe is set to 0.1-3:1, and in this range, the heat treatment-free aluminum alloy with good tensile strength, yield strength, flowability and elongation can be obtained, wherein the tensile strength is greater than 260 MPa, the yield strength is greater than 120 MPa, the elongation is greater than 10%, and the flowability is better than that of C611 aluminum alloy and ADC12 aluminum alloy. This is because, during the die casting process, the temperature cooling rate is large, and when the content of Fe (0.01-0.4 wt%) is small, Fe basically forms fine short rod-shaped or block-shaped Al-Fe phase or Al-Fe-Si phase, so that Fe has little effect on the elongation and flowability of the aluminum alloy, and it is not necessary to add more Mn to reduce the effect of Fe on the flowability and elongation of the aluminum alloy. Moreover, the lattice constant of Mn is much larger than that of Al matrix, and the Mn dissolved in the Al matrix will cause the internal structure of the Al matrix to be discontinuous, resulting in a sudden change in dislocation cutting radius and reducing the elongation. Therefore, when the mass ratio of Mn to Fe is set to 0.1-0.6:1, the present application has achieved better tensile strength, yield strength, flowability and elongation; when the mass ratio of Mn to Fe is 0.6-3:1, Mn can form a second phase with various elements (such as Al, Si, Cu, etc.) to improve the tensile strength and yield strength of the aluminum alloy, and Al-Mn-X phase (X is an impurity element) can be formed when Mn removes impurity phases in the aluminum alloy liquid, so that the adverse effects caused by excessive Mn content can be avoided; when the mass ratio of Mn to Fe is greater than 0.6:1, especially greater than 1.2:1, the α-Al(MnFeX)Si phase (X can be Cr, RE, Co, Be, Sr, etc.) can still remain fine and dispersed, and there is no excessive Mn and Al to form coarse AlMn phase; in addition, electromagnetic stirring can accelerate the dissolution of Mn and other alloying elements, and on the other hand, more Mn and Fe can participate in the reaction to form more dispersed and fine α-Al(FeMn)Si phase, thereby improving the modification effect of Fe.

[0040] Further considering the demoulding performance, the present application also sets the sum of the mass percentage contents of Mn and Fe to be 0.25-1.2%, preferably 0.3-0.6%, and specifically can be 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1%, 1.1%, or 1.2%. The present application sets the Fe content to be 0.01-0.6%, the Mn content to be 0.01-1%, the mass ratio of Mn to Fe to be 0.1-3:1, and the sum of the mass percentage contents of Mn and Fe to be 0.25-1.2%, and the combination of the four achieves better demoulding performance, tensile strength, yield strength, flowability, and elongation.

[0041] The mass percent content of Si can be 10%, 10.1%, 10.2%, 10.3%, 10.4%, 10.5%, 10.6%, 10.7%, 10.8%, 10.9%, 11%, 11.1%, 11.2%, 11.3%, 11.4%, or 11.5%. The mass percent content of Fe can be 0.01%, 0.05%, 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%, 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%, 0.5%, 0.51%, 0.52%, 0.53%, 0.54%, 0.55%, 0.56%, 0.57%, 0.58%, 0.59%, or 0.6%. The mass percent content of Cu can specifically be 0.2%, 0.22%, 0.24%, 0.26%, 0.28%, 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, 0.4%, 0.42%, 0.44%, 0.46%, 0.48%, 0.5%, 0.52%, 0.54%, 0.56%, 0.58%, 0.6%, 0.62%, 0.64%, 0.66%, 0.68%, 0.7%, 0.72%, 0.74%, 0.76%, 0.78%, or 0.8%.The mass percent content of Mn can specifically be 0.01%, 0.05%, 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%, 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%, 0.5%, 0.51%, 0.52%, 0.53%, 0.54%, 0.55%, 0.56%, 0.57%, 0.58%, 0.59%, 0.6%, 0.62%, 0.64%, 0.66%, 0.68%, 0.7%, 0.72%, 0.74%, 0.76%, 0.78%, 0.8%, 0.82%, 0.84%, 0.86%, 0.88%, 0.9%, 0.92%, 0.94%, 0.96%, 0.98%, or 1%. The mass percent content of Mg can specifically be 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.26%, 0.28%, 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, 0.4%, 0.42%, 0.44%, 0.46%, 0.48%, or 0.5%. The mass percent content of Zn can specifically be 0.2%, 0.22%, 0.24%, 0.26%, 0.28%, 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, 0.4%, 0.42%, 0.44%, 0.46%, 0.48%, 0.5%, 0.52%, 0.54%, 0.56%, 0.58%, 0.6%, 0.62%, 0.64%, 0.66%, 0.68%, 0.7%, 0.72%, 0.74%, 0.76%, 0.78%, 0.8%, 0.82%, 0.84%, 0.86%, 0.88%, 0.9%, 0.92%, 0.94%, 0.96%, 0.98%, or 1%. The mass percent 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 percent 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 percent content of Ti can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, or 0.3%. The mass percent content of RE 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 mass percent content of Bi 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%.

[0042] The high-flowability heat-treatment-free die-casting aluminum alloy contains Si in a mass percentage of 10-11.5%, Fe in a mass percentage of 0.01-0.6%, Cu in a mass percentage of 0.2-0.8%, Mn in a mass percentage of 0.01-1%, Mg in a mass percentage of 0.1-0.5%, Zn in a mass percentage of 0.2-1%, B in a mass percentage of 0-0.01%, Sr in a mass percentage of 0-0.05%, RE in a mass percentage of 0-0.2%, Bi in a mass percentage of 0-0.3%, and Ti in a mass percentage of 0.01-0.3%. The Si, Fe, Cu, Mn, Mg, Zn, B, Sr, RE, Bi, and Ti in the above content ranges are added in combination, interact with each other, and can make the heat-treatment-free aluminum alloy have a tensile strength greater than 260 MPa, a yield strength greater than 120 MPa, an elongation greater than 10%, and a flowability better than that of C611 aluminum alloy and ADC12 aluminum alloy. Specifically:

[0043] (1) When a small amount of Si is added to the aluminum alloy, the flowability of the aluminum alloy sharply decreases, but as the Si content continues to increase, the flowability of the aluminum alloy slowly increases when the Si content is greater than 6%, and the flowability of the aluminum alloy is better when the Si content is about 10-11.5%, and the aluminum alloy can also avoid being loose and hot cracking; Si can also react with Al, Fe, Mg, Cu, B, etc. to form second phases such as Mg2Si, AlFeSi, AlFeSiCu, AlFeMgSi, AlCuMgSi, and AlFeSiB, to improve the tensile strength and yield strength of the aluminum alloy;

[0044] (2) Mg can react with Al, Fe, Si, Cu, Zn, etc. to form second phases such as AlFeMgSi, (CuMg)Al2, AlCuMgSi, MgZnCu, Mg2Si, Mg2Zn, and Mg2SiZn, to improve the tensile strength and yield strength of the aluminum alloy, wherein Mg is dissolved in the (CuMg)Al2 phase and the AlFeSi phase to form the (CuMg)Al2 phase and the AlFeSiMg phase; when the Mg content is 0.1-0.5%, the aluminum alloy contains and forms water grass-like eutectic Si, the eutectic Si phase can improve the flowability of the aluminum alloy, Mg can also hinder the growth of the eutectic Si, reduce the length of the water grass-like eutectic Si in the aluminum alloy, hinder the growth of the primary Al phase, refine the grains, and further improve the flowability of the aluminum alloy; in addition, Mg can significantly reduce the surface tension of the molten aluminum alloy, can reduce or even eliminate the influence of the surface tension of the surface oxide film of the aluminum alloy, and can improve the flowability of the aluminum alloy.

[0045] (3) Cu can react with Al, Fe, Si, Mg, Zn, etc. to form CuAl2, AlFeSiCu, AlCuMgSi, Al2CuZn, MgZnCu, (CuMg)Al2, etc. second phases to improve the tensile strength and yield strength of the aluminum alloy, and can also promote the precipitation of Mg2Si, Mg2Zn, Mg2SiZn, etc. second phases to improve the volume fraction and dispersion degree of the precipitated phases, and the subsequent natural aging or vehicle painting baking treatment (referred to as T85 treatment) can further improve the aging strengthening effect of Cu and Mg; the MgZnCu eutectic structure precipitated in the aluminum alloy can refine the grains, reduce the solidification interval, reduce the coherent temperature of the dendrites, and reduce the dendrite growth rate to improve the flowability of the aluminum alloy;

[0046] (4) Zn can react with Al, Mg, Cu and Si, etc. to form MgZn2, Mg2SiZn, MgZnCu, Al2CuZn, etc. second phases to improve the tensile strength and yield strength of the aluminum alloy, Zn can eliminate elemental Si to reduce the influence of Si on the performance of the aluminum alloy, and can also promote the precipitation of Mg2Si, MgZn2, Mg2SiZn, Al2Cu, Al2CuMg, etc. second phases to improve the volume fraction and dispersion degree of the precipitated phases; with the increase of the Zn content, the shrinkage of the aluminum alloy decreases and the flowability increases, because the thermal conductivity of Zn is significantly lower than that of Al, and with the increase of the Zn content, the liquid phase region of the melt increases, thereby reducing the shrinkage of the aluminum alloy and improving the flowability of the aluminum alloy; the combined addition of Zn and Mg can form MgZn strengthening phase to significantly improve the tensile strength and yield strength of the aluminum alloy, and the shrinkage of the MgZn phase is lower than that of Al, so the MgZn phase can also improve the flowability of the aluminum alloy; in addition, the addition of Zn increases the lattice distortion energy of the matrix, which promotes the migration of Mg, Cu, Si atoms from the matrix to form more Cu-Mg-Zn clusters, Mg-Si-Zn clusters, and improves the cluster strengthening effect;

[0047] (5) Fe can improve the tensile strength, yield strength and demolding performance of the aluminum alloy, and can also react with Al, Si, Mg, Cu, B to form Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu, AlFeSiB, etc. second phases to improve the tensile strength and yield strength of the aluminum alloy; with the increase of the Fe content, the formation temperature of the Fe-rich phase gradually increases, which promotes the primary Fe-rich phase to change from a ternary eutectic with Al-Si to a binary eutectic with α-Al, and the change of the primary Fe-rich phase promotes the increase of the content of needle-like iron phase, while leading to the coarsening of α-Al, increasing the resistance and reducing the flowability of the aluminum alloy, while the thermal conductivity of Fe is lower than that of Al, which can increase the flowability of the aluminum alloy, and the above factors comprehensively, Fe has little effect on the flowability and shrinkage of the aluminum alloy;

[0048] (6) Mn can react with Al, Fe, Si, Cu to form MnAl2, MnAl6, a-(Fe, Mn)Al6, A1 12 CuMn2, a-Al(FeMn)Si, τ(Cu2Mn3Al 20 ) and other second phases to improve the tensile strength and yield strength of the aluminum alloy; Mn can significantly refine the grain size by the lattice distortion produced by solid solution in the matrix and the MnAl6 dispersed particles generated by the reaction with Al to improve the elongation, and MnAl6 can also dissolve Fe to form a-(Fe, Mn)Al6 phase to reduce the Fe content and reduce the Fe hazard; Mn and Al, Fe, Mn and Si form AlFeMnSi phase in spherical particle or Chinese character shape, which can avoid the formation of long needle-like Fe phase to reduce the Fe hazard, and can also improve the tensile strength and yield strength of the aluminum alloy when improving the demolding property of the aluminum alloy; Mn can also convert the coarse needle-like β-AlFeSi phase into small particle-like α-Al(FeMn)Si phase dispersed particles, improve the Fe morphology to eliminate the Fe hazard, specifically, Mn can replace part of Fe in the coarse needle-like β-AlFeSi phase to form small particle-like dispersed β-Al(FeMn)Si phase, the generation and growth shape of the β phase are improved, thereby reducing the Fe hazard; Mn can also promote the conversion of needle-like β-Al(FeMn)Si phase to small particle-like α-Al(FeMn)Si dispersed phase, and the generated α-Al(FeMn)Si phase dispersed particles are distributed in the aluminum matrix and strongly pinned at the grain boundaries of the aluminum alloy, which is mainly because the Mn-containing α phase dispersed particles in the aluminum alloy can act as non-uniform nucleation sites during the natural aging process of the β' phase to induce nucleation, thereby accelerating the precipitation of the β' phase; Mn can also react with impurity phases in the aluminum alloy liquid to form Al-Mn-X phases (X is an impurity element, including but not limited to transition metal elements), which can purify the aluminum alloy liquid to improve the flowability of the aluminum alloy, these phases can act as grain nucleation sites to improve the nucleation rate, refine the grain size, and improve the tensile strength, yield strength, elongation and flowability of the aluminum alloy;

[0049] (7) Sr preferentially combines with Fe to form dispersion strengthening, reduce the solid solubility of Fe, and improve the yield strength and tensile strength of the aluminum alloy; Sr can change the behavior of intermetallic compound phases in crystallography, and can be used as a modifier to refine the grain size, Si phase and second phase by modifying the aluminum alloy through the heterogeneous nucleation theory or twin valley mechanism, such as Sr can change the morphology of the eutectic silicon phase by modification to improve the elongation and flowability of the aluminum alloy and reduce the sticking tendency during the die casting process; Sr can convert the coarse needle-like β-AlFeSi and β-AlFeMnSi phases in the ingot into small particle-like Chinese character-shaped α-AlFeSi and α-Al(FeMn)Si phases, which can reduce the homogenization time of the ingot and improve the yield strength, tensile strength and elongation of the aluminum alloy;

[0050] (8) TiAl2 phase generated by the reaction of Ti and Al, as a non-spontaneous core during crystallization, can refine the grains, second phase and precipitated phase, to improve the tensile strength, yield strength, flowability and elongation of the aluminum alloy;

[0051] (9) B can react with transition metal elements (including Fe and other transition metal elements) to generate compounds such as boron-iron compounds, which can be separated from the aluminum alloy liquid, to purify the aluminum alloy liquid and improve the flowability of the aluminum alloy; B is easy to be adsorbed on the surface of iron-rich phase, to inhibit the growth of the iron-rich phase, and to control the size of the iron-rich phase; B can also refine the grains, Si phase and second phase, to improve the flowability and elongation of the aluminum alloy; Ti and B can also convert the coarse dendrites in the aluminum alloy into fine equiaxed crystals, reduce the intersection between the dendrites, and make more solid phase precipitate before the aluminum alloy stops flowing, to increase the flow time and improve the flowability of the aluminum alloy; B can inhibit the segregation of Ti3Al, and therefore, the use of Ti and B together can significantly improve the flowability of the aluminum alloy;

[0052] (10) Bi can react with Mg and Cd to generate second phases such as Mg3Bi2 and Mg3(BiCd)2, to improve the tensile strength and yield strength of the aluminum alloy; Bi can also significantly reduce the surface tension of the molten aluminum alloy, to reduce or even eliminate the influence of the surface tension of the surface oxide film of the aluminum alloy, and to improve the flowability of the aluminum alloy;

[0053] (11) RE can reduce the solidification range of the aluminum alloy to improve the fluidity of the aluminum alloy, and La and Ce can significantly reduce the solidification range of the aluminum alloy, play the role of heterogeneous nucleation, refine the grains and improve the fluidity; a large amount of primary phase is precipitated during the solidification of the aluminum alloy, the primary phase can increase the liquidus temperature of the aluminum alloy melt, reduce the superheat of the aluminum alloy melt, increase the viscosity of the aluminum alloy melt, and reduce the fluidity of the aluminum alloy; RE is a surface active element, the radius is larger than the radius of Al, and cannot enter the α-Al lattice, in the solidification process of the aluminum alloy, RE gathers at the front of the solid-liquid interface, increases the composition undercooling at the front, intensifies the growth of cellular dendrite, the growth of the dendrite is more developed, the secondary dendrite increases, and finally the secondary dendrite arm spacing of the aluminum alloy is reduced, so that the grains, the second phase and the precipitated phase (such as, Al3Fe, Al3ScZr, AlSiMo, Mg2Si phase) are refined, the tensile strength, yield strength, fluidity and elongation of the aluminum alloy are improved; the distribution area of RE and Fe phase is consistent, a rare earth active film can be formed on the surface of the iron-containing phase or Al, Fe, Ti and other atoms are combined to form AlFeRE and other rare earth compounds, which can 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, and improve the tensile strength and yield strength of the aluminum alloy; RE can convert long strip-shaped β-Fe phase into spherical ɑ-Fe phase, and modify and refine elemental Si, and RE can also promote the precipitation of dispersed phases such as CuAl2, (CuMg)Al2, and further improve the tensile strength and yield strength of the aluminum alloy.

[0054] The Si, Fe, Cu, Mn, Mg, Zn, Sr, B, RE, Bi, and Ti in the above content range have a complex effect, which not only can make the heat treatment-free die-casting aluminum alloy have better fluidity, but also have excellent demolding performance, tensile strength, yield strength, and elongation. The Si, Mg, Cu, Zn, Mn, Sr, Ti, RE, Bi, and B in the above content range can all improve the fluidity of the aluminum alloy. Among them, the Mg, Zn, and Cu in the above content range can react with each other to form MgZnCu eutectic structures, and the precipitation of the MgZnCu eutectic structures can significantly improve the fluidity of the aluminum alloy; when Ti and B are used together, B can inhibit the segregation of Ti3Al, so that Ti and B can more effectively improve the fluidity of the aluminum alloy; the Mn, B, Ti, RE, and Sr in the above content range have a complex effect, which can refine the grains, second phases, Si phases, and precipitates, to improve the elongation and fluidity of the aluminum alloy; both Zn and Cu can reduce the shrinkage of the aluminum alloy, to improve the fluidity of the aluminum alloy; RE can shorten the solidification interval of the aluminum alloy, and has a heterogeneous nucleation effect, to improve the fluidity of the aluminum alloy; Mg and Bi can also significantly reduce the surface tension of the molten aluminum alloy, can reduce or even eliminate the influence of the surface tension of the surface oxide film of the aluminum alloy, to improve the fluidity of the aluminum alloy; the Cu and Zn in the above content range can promote the precipitation of the second phase (such as MgZnCu), can improve the volume fraction and dispersion degree of the precipitates, and further improve the tensile strength, yield strength, fluidity, and elongation of the aluminum alloy; the Fe, Sr, and Mn in the above content range have a complex effect, which can improve the demolding performance of the aluminum alloy.

[0055] The addition of Cu, Mn, Mg, Zn, Ti, Sr, Fe, and B can also regulate the solute atom cluster behavior in the aluminum alloy, such as affecting the formation of original clusters and forming new clusters by adjusting vacancies. After adding Mg (0.1-0.5wt%) and Cu (0.2-0.8wt%) in a certain content range in the molten aluminum of the present application, the diffusion of vacancies is activated by Mg atoms, and the formation of Cu-Mg-Zn clusters, Mg-Si-Zn clusters, and Mg-Si-Cu-Zn clusters is promoted, which significantly strengthens the clusters. The atomic radii of Mn and Sr are much larger than that of Al, and the atoms of Mn and Sr in the above content range form lattice distortion in the aluminum matrix, and in addition, the vacancies and Mg-Si clusters, Cu-Mg clusters, and Mg-Si-Cu clusters added in the heat treatment-free die-casting aluminum alloy are pinned, and the growth of the clusters is promoted, which further promotes the natural aging effect, and improves the yield strength, tensile strength, and elongation of the aluminum alloy. RE and Bi can also promote the formation of Cu-Mg-Zn clusters, Mg-Si-Zn clusters, and Mg-Si-Cu-Zn clusters, and significantly strengthen the clusters.

[0056] In summary, under the combined action of Si, Fe, Cu, Mn, Mg, Zn, Sr, B, RE, Bi, and Ti in the above content range, the heat treatment-free aluminum alloy has excellent fluidity, demolding performance, tensile strength, yield strength, and elongation.

[0057] The high-fluidity heat treatment-free die-casting aluminum alloy also contains C in a mass percentage of 0-0.1%, 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%. C can significantly reduce the surface tension of the molten aluminum alloy, can reduce or even eliminate the influence of the surface tension of the surface oxide film of the aluminum alloy, and can improve the fluidity of the aluminum alloy. Ti, C, and B can work together to significantly improve the fluidity of the aluminum alloy, have a certain feeding effect on the interdendritic liquid phase, can enable the stress concentration position of the alloy to withstand a larger deformation amount, and can avoid the generation of thermal cracks; secondly, the smaller the grain size, the more the number of grains, and the number of grain boundaries also increases, which increases the hindering effect of the grain boundaries on the movement of dislocations, delays the generation and continuous growth of cracks in the stretching process due to the more compact structure, and the deformation between alloy grains is more dispersed, and the alloy can withstand a larger deformation amount, so the tensile strength, yield strength, and elongation of the aluminum alloy are also improved.

[0058] The high-fluidity heat treatment-free die-casting aluminum alloy also contains Li in a mass percentage of 0-0.1%, 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%. Li can react with Al to form high-temperature strengthening phases such as Al2Li3, AlLi2, and AlLi5, which can improve the tensile strength and yield strength of the aluminum alloy. Li can also significantly reduce the surface tension of the molten aluminum alloy, can reduce or even eliminate the influence of the surface tension of the surface oxide film of the aluminum alloy, and can improve the fluidity of the aluminum alloy.

[0059] The high-fluidity heat treatment-free die-casting aluminum alloy also contains Pb in a mass percentage of 0-0.1%, 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%. Pb can react with Al to form high-temperature strengthening phases such as Al9Pb7, Al6Pb5, Al5Pb3, and Al3Pb4, which can improve the tensile strength and yield strength of the aluminum alloy. Pb can also significantly reduce the surface tension of the molten aluminum alloy, can reduce or even eliminate the influence of the surface tension of the surface oxide film of the aluminum alloy, and can improve the fluidity of the aluminum alloy.

[0060] The high-fluidity heat-treatment-free die-casting aluminum alloy also contains Ca in a mass percentage of 0-0.1%, specifically 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, or 0.06%. The high-fluidity heat-treatment-free die-casting aluminum alloy also contains Sn in a mass percentage of 0-0.1%, 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%. Ca can improve the β-Fe phase to reduce Fe hazards, and can also react with Al, Cu, Zn, Si to form Al4Ca, Al2Ca3, AlCa2, AlCaCu, CaZn, CaAlZn, Al2CaSi2, etc. second phases to improve the tensile strength and yield strength of the aluminum alloy; Ca can also refine the eutectic structure, improve the β-Fe phase, and has a modifying effect on Al-Si series alloys, which can refine the Si phase; Sn can react with Al, Mg, Sc, etc. to form Al9Sn7, Al6Sn5, Al5Sn2, Al3Sn4, Mg2Sn, Mg2ScSn, etc. second phases to improve the tensile strength and yield strength of the aluminum alloy; Sn can promote the precipitation of Mg2Si, Mg2Zn, Mg2SiZn, Al2Cu, etc. second phases to reduce the solid solubility of the above elements in the aluminum matrix; Ca and Sn can also significantly reduce the surface tension of the molten aluminum alloy, which can reduce or even eliminate the influence of the surface tension of the aluminum alloy surface oxide film to improve the fluidity of the aluminum alloy. Ca and RE can significantly refine the grains and second phases to improve the tensile strength, yield strength, fluidity, and elongation.

[0061] The mass ratio of Ca, Sn, and RE is 0.01-1:0.01-1:1, preferably 0.05-5:0.05-1:1. Specifically, it can be 0.01:0.01:1, 0.01:0.05:1, 0.01:0.1:1, 0.01:0.5:1, 0.01:1:1, 0.05:0.01:1, 0.05:0.05:1, 0.05:0.1:1, 0.05:0.5:1, 0.05:1:1, 0.1:0.01:1, 0.1:0.05:1, 0.1:0.1:1, 0.1:0.5:1, 0.1:1:1, 0.5:0.01:1, 0.5:0.05:1, 0.5:0.1:1, 0.5:0.5:1, 0.5:1:1, 1:0.01:1, 1:0.05:1, 1:0.1:1, 1:0.5:1, or 1:1:1.

[0062] The high-fluidity heat-treatment-free die-casting aluminum alloy also contains Co in a mass percentage of 0-0.1%, specifically 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. Co can react with Al, Fe, Si, etc. to form second phases such as Al3Fe, (Fe, Co)3Si2, Al3(Fe, Co), etc. Co has a refining effect on the Al3Fe phase and can also convert the Al3Fe phase into α-Al 15 (Fe, Co)3Si2, Al3(Fe, Co), etc. Co has a refining effect on the Al3Fe phase and can also convert the Al3Fe phase into α-Al 15 (Fe, Co)3Si2, Al3(Fe, Co), etc. Co has a refining effect on the Al3Fe phase and can also convert the Al3Fe phase into α-Al

[0063] The high-fluidity heat-treatment-free die-casting aluminum alloy also contains Be in a mass percentage of 0-0.1%, specifically 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. Be can react with Al, Fe, Si, etc. to form second phases such as Be-Fe(Al8Fe2SiBe)2, etc., to improve the tensile strength and yield strength of the aluminum alloy. Be can refine the eutectic Si phase from flaky to fine phase to reduce or eliminate the adverse effects of Si on the performance of the aluminum alloy. Be can convert the plate-shaped β intermediate phase into relatively harmless Chinese-character-shaped Be-Fe(Al8Fe2SiBe) phase to reduce or eliminate the adverse effects of Fe on the performance of the aluminum alloy. Be can also promote the precipitation of phases such as Mg2Si, Mg2Zn, Mg2SiZn, Al2Cu, etc., to reduce the solid solubility of the above elements in the aluminum matrix. Be can also form an active film on the surface of impurity element phases such as Fe, preventing the growth of impurity elements and allowing them to segregate on the grain boundaries or adsorb on the solid-liquid interface, forming supercooling and increasing the chances of dendrite melting, thereby refining the grains and improving the fluidity and elongation of the aluminum alloy. The combination of Be and Sc can also improve the morphology of needle-shaped Fe-containing phases and improve the yield strength, tensile strength, and elongation of the aluminum alloy.

[0064] The mass ratio of Co, Be and Fe is 0.01-1:0.01-1:1, preferably 0.1-1:0.05-0.2:1, and specifically can be 0.01:0.01:1, 0.01:0.05:1, 0.01:0.1:1, 0.01:0.5:1, 0.01:1:1, 0.05:0.01:1, 0.05:0.05:1, 0.05:0.1:1, 0.05:0.5:1, 0.05:1:1, 0.1:0.01:1, 0.1:0.05:1, 0.1:0.1:1, 0.1:0.5:1, 0.1:1:1, 0.5:0.01:1, 0.5:0.05:1, 0.5:0.1:1, 0.5:0.5:1, 0.5:1:1, 1:0.01:1, 1:0.05:1, 1:0.1:1, 1:0.5:1, or 1:1:1.

[0065] The high-fluidity heat-treatment-free die-casting aluminum alloy also contains Zr in a mass percentage of 0-0.2%, and specifically 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%. Zr can react with Al, RE, etc. to form second phases such as Al3ScZr and (Zr, RE)Al3, thereby improving the tensile strength and yield strength of the aluminum alloy. Zr can also promote the precipitation of phases such as Mg2Sn, Mg2Si, MgZnCu, Mg3Sb2 and CuAl2, thereby reducing the solid solubility of the above elements in the aluminum matrix. Zr can also refine the grains, further improving the elongation and fluidity of the aluminum alloy. The combination of Er and Zr can promote the precipitation of β" phases and make the β" phases more fine and dispersed. The synergistic effect of Zr and Er can significantly inhibit the recrystallization of Al-0.4Fe alloy.

[0066] The mass ratio of RE and 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.

[0067] The mass ratio of (Mn+RE) to Fe is 0.1-3:1 (i.e., the mass ratio of the mass sum of Mn and RE to the mass of Fe), and specifically can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, or 3:1. The mass ratio of (Mn+RE+Zr) to Fe is 0.16-1.5:1 (i.e., the mass ratio of the mass sum of Mn, RE, and Zr to the mass of Fe), and specifically can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, or 3:1.

[0068] During the process of die casting, the temperature cooling rate is large, and when the Fe content is 0.01-0.4% and the mass ratio of (Mn+RE) to Fe is 0.1-0.6:1, Fe basically forms fine short rod-shaped or block-shaped Al-Fe phases or Al-Fe-Si phases, and it is not necessary to add a large amount of Mn to reduce the influence of Fe on the flowability and elongation of the aluminum alloy, and RE can round the fine short rod-shaped or block-shaped Al-Fe phases or Al-Fe-Si phases to improve the elongation and flowability; RE cooperates with Zr to significantly round the fine short rod-shaped or block-shaped Al-Fe phases or Al-Fe-Si phases to improve the elongation and flowability. When the mass ratio of Mn to Fe is 0.6-3:1, due to the large temperature cooling rate during the process of die casting, part of Fe will form fine short rod-shaped or block-shaped Al-Fe phases or Al-Fe-Si phases, and Mn can reduce the influence of Fe on the elongation of the aluminum alloy; Mn can also generate a second phase with a plurality of elements to improve the tensile strength and yield strength of the aluminum alloy, and avoid the adverse effects caused by excessive Mn content; the addition of elements such as Cr, RE, Co, Be, and Sr can not only further promote the reaction of Mn and Fe by reducing the maximum solid solubility in the matrix, but also can occupy the positions of Mn and Fe elements in the second phase, control the structure of the second phase, make the Fe-containing phase more dispersed and fine, and further promote the effect of modifying Fe; and when the mass ratio is greater than 0.6:1, especially greater than 1.2:1, the α-Al(MnFeX)Si phase (X can be Cr, RE, Co, Be, or Sr) can still remain fine and dispersed, and there is no excessive Mn and Al to generate coarse AlMn phases; in addition, electromagnetic stirring can accelerate the dissolution of Mn and other alloy elements on one hand, and on the other hand, can make more Mn and Fe participate in the reaction to generate more dispersed and fine α-Al(FeMn)Si phases, and improve the effect of modifying Fe.

[0069] The high-fluidity heat-treatment-free die-casting aluminum alloy also contains Cd in a mass percentage of 0-0.1%, specifically 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. Cd can refine α-Al, react with Al, RE, Cu, Mg, Si, Fe, Sb, Bi, etc. in the melt to form REAl2Cd3, Al3Cd, Al2Cd3, (CuCd)Al2, Mg2(SiCdREFe), Mg3(SbCd)2, Mg3(BiCd)2, etc. strengthening phases, to improve the tensile strength and yield strength of the aluminum alloy; Cd can form a large number of Cd-vacancy clusters in the aging stage, to promote and accelerate the precipitation of CuAl2 phase, to reduce the solid solubility of the above elements in the aluminum matrix.

[0070] The mass ratio of Bi, Cd, and Mg is 0.1-2:0.01-1:1, preferably 0.5-1:0.1-0.5:1, 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, 0.5:0.01:1, 0.5:0.05:1, 0.5:0.1:1, 0.5:0.5:1, 0.5:1:1, 1:0.01:1, 1:0.05:1, 1:0.1:1, 1:0.5:1, 1:1:1, 2:0.01:1, 2:0.05:1, 2:0.1:1, 2:0.5:1, or 2:1:1.

[0071] The high-fluidity heat-treatment-free die-casting aluminum alloy also contains Ni in a mass percentage of 0-0.4%, 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%, 0.22%, 0.24%, 0.26%, 0.28%, 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, or 0.4%. Ni can refine grains, promote the precipitation of second phases to increase the volume fraction and dispersion degree of precipitates, and also react with Al, Fe, Mg, Si, etc. to form second phases such as Al3Ni, AlFeSiNi, AlFeMgSiNi, FeNiAl9, etc. to reduce the Fe content. With the increase of the Ni content, the shrinkage of the aluminum alloy decreases and the fluidity increases, because when the shrinkage of the Ni element is significantly lower than that of the Al element, a stable Al3Ni eutectic phase is formed when the content is 0-0.4%, more specifically 0.006-0.4%, the Al3Ni eutectic phase is a strengthening phase, and its linear shrinkage coefficient is also lower than that of pure aluminum, thus reducing the shrinkage of the aluminum alloy and improving the fluidity of the aluminum alloy. The shrinkage of the FeNi phase is also significantly lower than that of the Al element, so the FeNi phase can also improve the fluidity of the aluminum alloy. Ni can further promote the formation of Cu-Mg-Zn clusters, Mg-Si-Zn clusters, and Mg-Si-Cu-Zn clusters, significantly strengthening the clusters.

[0072] The mass ratio of Ni to Fe is 0.1-4:1, preferably 0.1-1:1, 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, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, 3.1:1, 3.2:1, 3.3:1, 3.4:1, 3.5:1, 3.6:1, 3.7:1, 3.8:1, 3.9:1, or 4:1.

[0073] The high-fluidity heat-treatment-free die-casting aluminum alloy also contains Cr in a mass percentage of 0-0.1%, specifically 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. Cr can react with Al, Fe, Mn, etc. to form (CrFe)Al7 and (CrMn)Al 12 intermetallic compounds, which can hinder the nucleation and growth of recrystallization to improve the tensile strength, yield strength, and elongation of the aluminum alloy. Cr can also convert needle-like β-Fe phase into α-Fe phase.

[0074] Mn, Cr, and RE jointly act to effectively improve the Fe morphology, reduce the Fe content, and refine the grain size, so that the aluminum alloy has better comprehensive performance. Specifically, when Mn and Cr are jointly added, they can form the α-Al(FeMnCr)Si phase that is dispersedly distributed, has high bulk density, and is highly thermally stable. With the extension of the standing time, part of the phase sinks to the bottom, and part of the phase pins the grain boundaries, which can effectively refine and control the grain size. Mn, Cr, and RE can also react with the trace impurities in the secondary aluminum to form Al-Cr-X and Al-Mn-X, Al-RE-X (X is an impurity element) phases. These phases can serve as grain nucleation points to improve the nucleation rate, refine the grains, and improve the tensile strength, yield strength, and fluidity of the alloy. In addition, the purity of the secondary aluminum can be improved, and the elongation and fluidity of the alloy can be improved.

[0075] The high-fluidity heat-treatment-free die-casting aluminum alloy also contains V in a mass percentage of 0-0.2%, 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%. V can react with Al to form VAl 11 refractory compounds during the melting and casting process, which can refine the grains, improve the recrystallization structure and recrystallization temperature, and improve the tensile strength, yield strength, and elongation of the aluminum alloy. During the die-casting process, the temperature cooling rate is large, and the non-steady-state phase Al3V obtained by fast cooling can 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.

[0076] The mass ratio of Cr to V is 0.1-5:1, preferably 0.5-5:1, and specifically can be 0.1:1, 0.5:1, 1:1, 2:1, 3:1, 4:1, or 5:1.

[0077] The high-fluidity heat-treatment-free die-casting aluminum alloy also contains 0-0.2% of Sb in terms of mass percentage, and specifically 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%. Sb can react with Mg and the like to form secondary phases such as Mg3Sb2, thereby improving the tensile strength and yield strength of the aluminum alloy. Sb can significantly reduce the surface tension of the molten aluminum alloy, and can reduce or even eliminate the influence of the surface tension of the surface oxide film of the aluminum alloy to improve the fluidity of the aluminum alloy. Sb can also refine the Si phase to improve the fluidity of the aluminum alloy.

[0078] The mass ratio of Mg to Sb is 0.5-20:1, preferably 5-15:1, and further preferably 5-10:1, and specifically can be 0.5:1, 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.

[0079] In an embodiment, the high-fluidity heat-treatment-free die-casting aluminum alloy also contains 0-0.1% of Te in terms of mass percentage, and specifically can be 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. Te has a modifying effect to refine the Si phase, thereby improving the fluidity and elongation of the aluminum alloy; when Sb and Te are added in combination, fine petal-shaped primary crystals can be formed, thereby improving the tensile strength, fluidity, and elongation of the aluminum alloy.

[0080] The high-fluidity heat-treatment-free die-casting aluminum alloy also contains 0-0.1% of Ag in terms of mass percentage, and specifically can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. Ag can promote the precipitation of secondary phases such as Al2Cu, Mg2Si, Mg3Sb2, MgZnCu, 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 improving the tensile strength, yield strength, fluidity, and elongation of the aluminum alloy.

[0081] The mass ratio of Mg to Ag is 1-30:1, preferably 5-25:1, further preferably 10-15:1, 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, 20:1, 21:1, 22:1, 23:1, 24:1, 25:1, 26:1, 27:1, 28:1, 29:1, or 30:1.

[0082] The high-fluidity heat-treatment-free die-casting aluminum alloy further contains 0-0.1% of Nb in terms of mass percentage, and specifically can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. Nb can form strengthening metallic compounds such as AlNb3, AlNb, and Al3Nb in the melt, and part of the Nb can be distributed in the form of a dispersed phase at the grain boundaries of the matrix, which can significantly improve the yield strength and tensile strength of the aluminum alloy. Nb can refine the grains and the second phase, thereby improving the elongation and fluidity of the aluminum alloy.

[0083] The mass ratio of Mg to Nb is 1-25:1, preferably 5-20:1, and specifically can be 1:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 21:1, 22:1, 23:1, 24:1, or 25:1.

[0084] The high-fluidity heat-treatment-free die-casting aluminum alloy further contains 0-0.2% of In in terms of mass percentage, and specifically 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%. In can react with Al and Cu to form second phases such as AlIn and CuIn, thereby improving the tensile strength and yield strength of the aluminum alloy; In can also refine the grains, thereby improving the elongation and fluidity of the aluminum alloy. Ag, In, and Nb can cooperate with each other to significantly promote the precipitation of the second phase and refine the grains and the precipitated phase. Specifically, In can react with Al and Cu to form second phases such as AlIn and CuIn; Nb, Ti, and Al can form second phases such as TiAl-Nb; Ag can promote the precipitation of the second phase and refine the precipitated phase; and Nb and In can further refine the grains and the second phase, thereby achieving the purposes of improving the tensile strength, yield strength, and elongation of the aluminum alloy.

[0085] The mass ratio of Cu to In is 2-35:1, preferably 10-30:1, and specifically can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 21:1, 22:1, 23:1, 24:1, 25:1, 26:1, 27:1, 28:1, 29:1, 30:1, 31:1, 32:1, 33:1, 34:1, or 35:1.

[0086] The high-fluidity heat-treatment-free die-casting aluminum alloy further contains Mo at a mass percentage of 0-0.2%, and specifically 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%. Mo can also react with Al, Si, Fe, etc. to form second phases such as AlMo, AlSiMo, AlSiFeMo, etc., which are distributed in the grain boundaries of the aluminum matrix in the form of dispersed phases; Mo can also refine the grains, improve the morphology of the Fe-containing intermetallic compounds, and further improve the tensile strength, yield strength, fluidity, and elongation of the aluminum alloy; when Cr and Mo are added together, Cr-rich and Mo-rich multi-element phases can be generated, which can significantly improve the tensile strength of the aluminum alloy;

[0087] The mass ratio of Fe to Mo is 1-30:1, preferably 5-15:1, and specifically can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 15:1, 20:1, 25:1, or 30:1.

[0088] The high-fluidity heat-treatment-free die-casting aluminum alloy further contains Ge at a mass percentage of 0-0.1%, and specifically can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. Ge can react with Al and Si to form second phases such as Al9Ge7, Al6Ge5, Al5Ge2, Al3Ge4, and SiGe; Ge can promote the precipitation of second phases such as Mg2Si and CuAl2, thereby reducing the solid solubility of the above elements in the aluminum matrix; Ge also has a modification effect to refine the Si phase. In this way, Ge can improve the tensile strength, yield strength, fluidity, and elongation of the aluminum alloy.

[0089] The mass ratio of Mg to Ge is 1-40:1, preferably 5-20:1, preferably 10-15:1, 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, 20:1, 21:1, 22:1, 23:1, 24:1, 25:1, 26:1, 27:1, 28:1, 29:1, 30:1, 35:1, or 40:1.

[0090] In one embodiment of the present application, the high-fluidity heat-treatment-free die-casting aluminum alloy contains Si at a mass percentage of 10-11.5%, Fe at a mass percentage of 0.01-0.6%, Cu at a mass percentage of 0.2-0.8%, Mn at a mass percentage of 0.01-1%, Mg at a mass percentage of 0.1-0.5%, Zn at a mass percentage of 0.2-1%, B at a mass percentage of 0-0.01%, Sr at a mass percentage of 0-0.05%, RE at a mass percentage of 0-0.2%, Bi at a mass percentage of 0-0.3%, Ti at a mass percentage of 0.01-0.3%, Co at a mass percentage of 0.01-0.05%, Be at a mass percentage of 0.01-0.05%, Cr at a mass percentage of 0.01-0.05%, V at a mass percentage of 0.05-0.1%, and Zr at a mass percentage of 0.01-0.1%.

[0091] In another embodiment of the present application, the high-fluidity heat-treatment-free die-casting aluminum alloy contains Si at a mass percentage of 10-11.5%, Fe at a mass percentage of 0.01-0.6%, Cu at a mass percentage of 0.2-0.8%, Mn at a mass percentage of 0.01-1%, Mg at a mass percentage of 0.1-0.5%, Zn at a mass percentage of 0.2-1%, B at a mass percentage of 0-0.01%, Sr at a mass percentage of 0-0.05%, RE at a mass percentage of 0-0.2%, Bi at a mass percentage of 0-0.3%, Ti at a mass percentage of 0.01-0.3%, Li at a mass percentage of 0.1-0.3%, Sb at a mass percentage of 0.01-0.1%, Sn at a mass percentage of 0.01-0.1%, Te at a mass percentage of 0.01-0.05%, Ni at a mass percentage of 0.01-0.3%, Cd at a mass percentage of 0.01-0.05%, Mo at a mass percentage of 0.1-0.3%, and Ge at a mass percentage of 0.01-0.05%.

[0092] In another embodiment of the present application, the high-fluidity heat-treatment-free die-casting aluminum alloy contains 10-11.5% of Si, 0.01-0.6% of Fe, 0.2-0.8% of Cu, 0.01-1% of Mn, 0.1-0.5% of Mg, 0.2-1% of Zn, 0-0.01% of B, 0-0.05% of Sr, 0-0.2% of RE, 0-0.3% of Bi, 0.01-0.3% of Ti, 0.01-0.05% of Pb, 0.01-0.1% of C, 0.01-0.06% of Ca, 0.01-0.1% of Nb, 0.01-0.02% of Ag, and 0.01-0.1% of In.

[0093] The present application also provides a method for preparing a high-fluidity heat-treatment-free die-casting aluminum alloy, comprising the following steps:

[0094] firstly heating an Al source (preferably virgin aluminum, specifically electrolytic aluminum) to 750-830°C to obtain aluminum liquid;

[0095] adding a Si source, a Fe source, a Cu source, a Mn source, a Mg source, a Zn source, a B source, a Sr source, a RE source, a Ni source, and a Ti source into the aluminum liquid, and secondly heating to obtain alloy liquid; and

[0096] refining, skimming, and die-casting the alloy liquid to obtain aluminum alloy parts; and

[0097] low-temperature quenching the aluminum alloy parts to obtain a high-fluidity heat-treatment-free die-casting aluminum alloy containing Al, 10-11.5% of Si, 0.01-0.6% of Fe, 0.2-0.8% of Cu, 0.01-1% of Mn, 0.1-0.5% of Mg, 0.2-1% of Zn, 0-0.01% of B, 0-0.05% of Sr, 0-0.2% of RE, 0-0.3% of Bi, and 0.01-0.3% of Ti.

[0098] The Si source, Fe source, Cu source, Mn source, Mg source, Zn source, B source, Sr source, RE source, Bi source, and Ti source can be added in elemental or alloy form. The Al source can be primary aluminum, or recycled aluminum. When recycled aluminum is used, the composition and content of the molten recycled aluminum liquid are detected, and the content of the elements added to the recycled aluminum industry is calculated according to the detection results to obtain the high-fluidity heat-treatment-free die-casting aluminum alloy of the present application.

[0099] The low-temperature quenching treatment can be performed using ice water or liquid nitrogen. The temperature of the low-temperature quenching treatment is -200 to 0°C, and can be specifically -200°C, -150°C, -100°C, -50°C, -10°C, or 0°C. The time of the low-temperature quenching treatment is 0.1 to 10 h, and can be specifically 0.1 h, 0.5 h, 1 h, 5 h, or 10 h. It can be understood that ice / ice water can be added in time, and liquid nitrogen can be supplemented in time to maintain the temperature of the low-temperature quenching treatment at no more than 0°C, to retain as many vacancies as possible, and to ensure the generation of supersaturated vacancies.

[0100] The alloy liquid is subjected to a refining treatment at a temperature of 710 to 735°C for 10 to 30 min, wherein the mass ratio of the refining agent to the alloy liquid is 0.01 to 0.05:1, and the refining agent comprises metal salts and hexachloroethane in a mass ratio of 0.5 to 1.5:1, and the metal salts are at least one of aluminum fluoride, sodium fluoride, sodium nitrate, aluminum nitrate, manganese chloride, zinc chloride, and sodium chloride. In an embodiment, the mass ratio of the fluoride salt, the nitrate salt, and the chloride salt is 1:0.5 to 1.5:0.5 to 1.5.

[0101] The alloy liquid is subjected to a die-casting treatment at a temperature of 660 to 700°C, wherein the die-casting speed of the die-casting machine is 0.23 to 2.5 m / s. It can be understood that the die-casting treatment of the present application is a normal die-casting treatment, and the alloy liquid can also be subjected to a vacuum die-casting treatment, and the strength (such as yield strength and tensile strength) and elongation of the aluminum alloy after the vacuum die-casting treatment are higher than those of the aluminum alloy after the normal die-casting treatment. The cooling rate in the die-casting treatment can be 10 to 60 K / S, and can be 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.

[0102] The preparation method of the high-fluidity heat-treatment-free die-casting aluminum alloy further comprises the step of adding at least one of C source, Li source, Pb source, Sb source, Sn source, Ca source, Co source, Cd source, Be source, Ni source, Nb source, Te source, Ag source, In source, Zr source, Mo source, Cr source, Ge source, and V source in the form of an element or an alloy to the molten aluminum. The total mass percentage content of the elements selected from at least one of C source, Li source, Pb source, Sb source, Sn source, Ca source, Co source, Cd source, Be source, Ni source, Nb source, Te source, Ag source, In source, Zr source, Mo source, Cr source, Ge source, and V source is not more than 0.7%, preferably not more than 0.5%, more preferably not more than 0.2%, and specifically can be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, or 0.7%. The content of a single impurity in the high-fluidity heat-treatment-free die-casting aluminum alloy is not more than 0.05%, and the total impurity content is not more than 0.15%.

[0103] The application further provides a structural member, at least part of which is made of the high-elongation heat-treatment-free aluminum alloy. The structural member can be applied to a new energy vehicle and is used as a vehicle structural member, such as a whole vehicle body, a rear wheel cover inner plate, a rear longitudinal beam, a bottom plate connecting plate, a rear bottom plate, a beam inner reinforcing plate, an engine cover, a fender, a door, a rear compartment, and a roof, etc. Of course, the structural member can also be used in other aspects, such as aerospace, high-speed rail, ship, mobile device, household appliance, chemical industry, daily necessities, building, etc.

[0104] Examples and comparative examples

[0105] 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.

[0106] Table 1 Components and contents of the aluminum alloys of Examples 1 to 5 and Comparative Examples 1 to 2

[0107]

[0108] For simplicity of expression, the contents of impurities and other trace elements in the comparative examples and examples are not shown.

[0109] A domestic CSS-44100 electronic universal tensile testing machine is used to process and test the samples according to the provisions of the metal material room temperature tensile test method (GB / T228-2002) and the metal material high temperature tensile test method (GB4338-2006-T). The processed samples are polished using 800# and 1500# water sandpaper, the tensile force of the tensile testing machine is 2kN, the tensile speed is 2mm / min, three samples are tested under the same condition, and the average value is taken.

[0110] The fluidity of the aluminum alloy corresponding to the examples and the comparative examples is determined by the screw sample method using a spiral fluidity testing device. During the test, the ambient temperature is 20-30℃, the upper and lower molds are kept consistent, the pouring temperature is controlled to be above the liquidus of the alloy (which can be 50-90℃), when the temperature reaches the requirement, pouring is performed, the pouring liquid flow is kept stable, after pouring is completed, 30min is waited for shakeout treatment, and then the screw sample length is determined. Three samples are tested under the same condition, and the average value is taken.

[0111] The fluidity of the aluminum alloy is tested using a single spiral fluidity testing device. During the test, the ambient temperature is about 30℃, the pouring temperature is about 60℃, after pouring is completed, about 30min is waited for shakeout treatment, and then the screw sample length is tested, and the fluidity of the aluminum alloy is determined according to the tested sample length and the temperature at the time of pouring.

[0112] Table 2: Performance test results of the aluminum alloys of examples 1-5 and comparative examples 1-2

[0113]

[0114] The tensile strength, yield strength, fluidity and elongation of the high-fluidity heat-treatment-free die-casting aluminum alloys of examples 1-5 are all significantly greater than those of the high-fluidity heat-treatment-free die-casting aluminum alloys of comparative examples 1-2. Moreover, the fluidity of examples 1-5 is greater than that of the ADC12 aluminum alloy (about 1936mm) and that of the C611 aluminum alloy (about 1550mm). It is shown that the high-fluidity heat-treatment-free die-casting aluminum alloys of the present application have good performance.

[0115] The above description is merely preferred embodiments of the present application, and is not intended to limit the patent scope of the present application. Any equivalent structural transformation made according to the content of the present application specification, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present application.

Claims

1. A high fluidity heat-treatable die cast aluminium alloy characterised in that, The high-fluidity heat-treatment-free die-casting aluminum alloy further contains Si in a mass percentage of 10-11.5%, Fe in a mass percentage of 0.01-0.6%, Cu in a mass percentage of 0.2-0.8%, Mn in a mass percentage of 0.01-1%, Mg in a mass percentage of 0.1-0.5%, Zn in a mass percentage of 0.2-1%, B in a mass percentage of 0-0.01%, Sr in a mass percentage of 0-0.05%, RE in a mass percentage of 0-0.2%, Bi in a mass percentage of 0-0.3%, and Ti in a mass percentage of 0.01-0.3%, with the balance being Al, and is subjected to die-casting treatment at a temperature of 660-700°C and a speed of 0.23-2.5 m / s and low-temperature quenching treatment at a temperature of -150-0°C for 0.1-10 h.

2. The high-fluidity heat-treatment-free die-casting aluminum alloy according to claim 1, characterized in that: the mass ratio of Ti to B is 1-50:1; the mass ratio of Mn to Fe is 0.1-3:1; the mass ratio of (Mn+RE) to Fe is 0.1-3:1; the sum of the mass percentages of Mn and Fe is 0.25-1.2%; and RE is at least one of La, Ce, Pr, Nd, Er, Sm, Y, Gd, and Sc.

3. The high fluidity heat treatment free die casting aluminium alloy as claimed in claim 1, wherein, the mass percentage of Fe is 0.55-0.6%.

4. The high fluidity heat-treatable die casting aluminium alloy according to any one of claims 1 to 3, characterised in that, at least one of the following conditions is satisfied: the high-fluidity heat-treatment-free die-casting aluminum alloy further contains C in a mass percentage of 0.001-0.1%; the high-fluidity heat-treatment-free die-casting aluminum alloy further contains Li in a mass percentage of 0.001-0.1%; the high-fluidity heat-treatment-free die-casting aluminum alloy further contains Sb in a mass percentage of 0.01-0.2%; the high-fluidity heat-treatment-free die-casting aluminum alloy further contains Co in a mass percentage of 0.01-0.1%; the high-fluidity heat-treatment-free die-casting aluminum alloy further contains Cd in a mass percentage of 0.01-0.1%; the high-fluidity heat-treatment-free die-casting aluminum alloy further contains Be in a mass percentage of 0.01-0.1%; the high-fluidity heat-treatment-free die-casting aluminum alloy further contains Nb in a mass percentage of 0.01-0.1%; the high-fluidity heat-treatment-free die-casting aluminum alloy further contains Ag in a mass percentage of 0.01-0.1%; the high-fluidity heat-treatment-free die-casting aluminum alloy further contains Zr in a mass percentage of 0.01-0.2%.

5. The high fluidity heat-treatable die casting aluminium alloy as claimed in claim 4, wherein, at least one of the following conditions is satisfied: when the high-fluidity heat-treatment-free die-casting aluminum alloy further contains Sb and Nb, the mass ratio of Mg to Sb is 0.5-20:1, and the mass ratio of Mg to Nb is 1-25:

1. When the high-fluidity heat-treatment-free die-casting aluminum alloy further contains Ag, the mass ratio of Mg to Ag is 1-30:1; When the high-fluidity heat-treatment-free die-casting aluminum alloy further contains Zr, the mass ratio of RE to Zr is 0.1-1:1; When the high-fluidity heat-treatment-free die-casting aluminum alloy further contains Cd, the mass ratio of Bi, Cd and Mg is 0.1-2:0.01-1:1; When the high-fluidity heat-treatment-free die-casting aluminum alloy further contains Co and Be, the mass ratio of Co, Be and Fe is 0.01-1:0.01-1:1; When the high-fluidity heat-treatment-free die-casting aluminum alloy further contains Zr, the mass ratio of (Mn+RE+Zr) to Fe is 0.1-3:

1.

6. A preparation method of a high-fluidity heat-treatment-free die-casting aluminum alloy, comprising the following steps: performing first heating treatment on an Al source to obtain an 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, an RE source, a Bi source, and a Ti source into the aluminum liquid to perform second heating treatment to obtain an alloy liquid; and performing refining treatment, skimming treatment, and die-casting treatment on the alloy liquid to obtain an aluminum alloy part, the temperature of the die-casting treatment is 660-700ºC, the speed is 0.23-2.5 m / s, and the cooling rate in the die-casting treatment is 10-60 K / s; and performing low-temperature quenching treatment on the aluminum alloy part to obtain a high-fluidity heat-treatment-free die-casting aluminum alloy, the temperature of the low-temperature quenching treatment is -150-0ºC, and the time is 0.1-10 h, the high-fluidity heat-treatment-free die-casting aluminum alloy contains Si at a mass percentage of 10-11.5%, Fe at a mass percentage of 0.01-0.6%, Cu at a mass percentage of 0.2-0.8%, Mn at a mass percentage of 0.01-1%, Mg at a mass percentage of 0.1-0.5%, Zn at a mass percentage of 0.2-1%, B at a mass percentage of 0-0.01%, Sr at a mass percentage of 0-0.05%, RE at a mass percentage of 0-0.2%, Bi at a mass percentage of 0-0.3%, and Ti at a mass percentage of 0.01-0.3%, and the balance is Al.

7. A structural member, characterized by At least part of the structural member is made of the high-elongation heat-treatment-free aluminum alloy according to any one of claims 1-5 or the high-elongation heat-treatment-free aluminum alloy prepared by the preparation method according to claim 6.

Images