Heat-treatment-free recycled aluminum-based die-cast aluminum alloy and method of making, structural member

Abstract

The application provides a preparation method of a heat treatment-free recycled aluminum-based die-casting aluminum alloy, comprising the following steps: testing a recycled aluminum liquid; calculating the adding amount of Si, Cu, Mn, Mg, Zn, Ti, RE, Sr and B; adding Si, Cu, Mn, Mg, Zn, Ti and B into the recycled aluminum liquid to obtain an alloy liquid; performing refining, electromagnetic stirring, slag skimming and die-casting treatment to obtain an aluminum alloy part; and performing low-temperature quenching treatment to obtain an aluminum alloy containing 6-9wt% of Si, 0.1-0.6wt% of Fe, 0.01-0.4wt% of Cu, 0.01-0.8wt% of Mn, 0.01-0.5wt% of Mg, 0.01-0.5wt% of Zn, 0.01-0.2wt% of Ti, 0-0.1wt% of RE, 0-0.05wt% of Sr and 0-0.01wt% of B, wherein the temperature of the low-temperature quenching treatment is-150-0°C, and the time is 0.1-10h. The application also provides the aluminum alloy and a structural part prepared by the method.

Description

[0001] This invention is a divisional application. The original application number is 202410672817.7, the application date is May 28, 2024, and the title is "Heat-free die-cast aluminum alloy based on recycled aluminum and its preparation method and structural parts". Technical Field

[0002] This invention relates to the field of aluminum alloy technology, and in particular to a method for preparing a heat-free die-cast aluminum alloy based on recycled aluminum, the heat-free die-cast aluminum alloy obtained by the method, and structural components. Background Technology

[0003] To improve demolding performance, Fe needs to be added to heat-free die-casting aluminum alloys (such as Al-Si heat-free die-casting aluminum alloys). The amount of Fe added needs to be greater than 0.6 wt%. However, excessive Fe easily forms needle-like or plate-like β-AlFeSi phases, leading to a decrease in the plasticity of the aluminum alloy. When reducing the amount of Fe added, an appropriate amount of Mn can be added to ensure that the aluminum alloy has good anti-sticking properties while avoiding the formation of needle-like or plate-like β-AlFeSi phases. Due to the requirement for low Fe content, the industry currently mainly uses electrolytic aluminum ingots to directly formulate heat-free die-casting aluminum alloys, and recycled aluminum (with high Fe content) cannot be used, which results in higher costs.

[0004] Therefore, there is an urgent need to develop a heat-free die-cast aluminum alloy with low cost, excellent tensile strength, yield strength, and elongation. Summary of the Invention

[0005] In view of the above-mentioned defects of the prior art, the present invention provides a heat-free die-cast aluminum alloy based on recycled aluminum, which aims to ensure that the heat-free die-cast aluminum alloy based on recycled aluminum has a lower cost and better tensile strength, yield strength and elongation.

[0006] This invention also provides a method for preparing a heat-free die-cast aluminum alloy based on recycled aluminum, comprising the following steps:

[0007] Provide recycled aluminum;

[0008] The recycled aluminum is heated to obtain molten recycled aluminum;

[0009] The recycled aluminum liquid was analyzed to obtain the elements and their contents.

[0010] Based on the elements and content of the recycled aluminum liquid and the preset elements and content of the heat-free die-cast aluminum alloy based on recycled aluminum, calculate the amounts of Si, Cu, Mn, Mg, Zn, Ti, Sr, RE and B to be added to the recycled aluminum liquid.

[0011] Si, Cu, Mn, Mg, Zn, Ti, Sr, RE and B are added to the recycled aluminum liquid, and a second heat treatment is performed to obtain an alloy liquid;

[0012] The alloy liquid is subjected to refining, electromagnetic stirring, slag removal, and die casting to obtain aluminum alloy parts; and

[0013] The aluminum alloy parts are subjected to low-temperature quenching treatment to obtain the heat-free die-cast aluminum alloy based on recycled aluminum. The heat-free die-cast aluminum alloy based on recycled aluminum contains Al, and also contains 6-9% Si, 0.1-0.6% Fe, 0.01-0.4% Cu, 0.01-0.8% Mn, 0.01-0.5% Mg, 0.01-0.5% Zn, 0.01-0.2% Ti, 0-0.1% RE, 0-0.05% Sr, and 0-0.01% B. The low-temperature quenching treatment is performed at a temperature of -150~0°C for 0.1~10h.

[0014] Furthermore, the low-temperature quenching treatment is performed at a temperature of -140 to 0°C for a time of 0.1 to 10 hours.

[0015] Furthermore, the heat-free die-cast aluminum alloy based on recycled aluminum contains 7-9% Si, 0.2-0.5% Fe, 0.1-0.3% Cu, 0.3-0.7% Mn, 0.2-0.4% Mg, 0.2-0.4% Zn, 0.1-0.2% Ti, 0-0.1% RE, 0.005-0.05% Sr, and 0.005-0.01% B by mass.

[0016] Furthermore, in the recycled aluminum liquid, the mass ratio of Mn to Fe is 0.5-2:1.

[0017] Furthermore, the preparation method further includes the step of adding at least one of Co, Be, and Ca to the recycled aluminum liquid, wherein at least one of the following conditions is met:

[0018] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Co is 0-0.1%.

[0019] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Be is 0-0.1%;

[0020] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Ca is 0-0.1%.

[0021] Furthermore, in the recycled aluminum liquid, the mass ratio of Co to Fe is 0.2-1:1.

[0022] Furthermore, the preparation method further includes the step of adding C to the recycled aluminum liquid, wherein the mass percentage content of C in the heat-free die-cast aluminum alloy based on recycled aluminum is 0-0.05%.

[0023] Furthermore, the preparation method further includes the step of adding at least one of Nb, Ni, Te, In, Mo, Ag, Cd, V, Sn, Zr, Sb, and Bi to the recycled aluminum liquid, wherein at least one of the following conditions is satisfied:

[0024] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Nb is 0-0.1%.

[0025] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Ni is 0-0.2%.

[0026] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Te is 0-0.1%;

[0027] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of In is 0-0.1%;

[0028] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Mo is 0-0.2%.

[0029] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Ag is 0-0.1%.

[0030] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the Cd content is 0-0.05% by mass.

[0031] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of V is 0-0.2%.

[0032] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Sn is 0-0.08%.

[0033] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the Zr content is 0-0.2% by mass.

[0034] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the Sb mass percentage content is 0-0.2%;

[0035] In the heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Bi is 0-0.2%.

[0036] This invention provides a heat-free die-cast aluminum alloy based on recycled aluminum, prepared by the aforementioned method.

[0037] The present invention also provides a structural component, at least a portion of which is made of the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum.

[0038] In this invention, the method for preparing a heat-free die-cast aluminum alloy based on recycled aluminum uses recycled aluminum as raw material to reduce costs. Unlike primary aluminum, recycled aluminum has a wider range of Fe content, a greater variety of impurity elements, and higher content. To improve the utilization rate of recycled aluminum, on the one hand, it needs to be more tolerant of high Fe content; higher Fe content leads to poorer overall performance, so the Fe content / Fe morphology must be controlled to reduce Fe's harmful effects. On the other hand, it also needs to be highly tolerant of the characteristics of recycled aluminum alloys, which have a wide variety of impurity elements and a high range of impurity element composition, to reduce the impact of impurity elements on alloy performance.

[0039] The addition of Si, Cu, Mn, Mg, Zn, Ti, Sr, and B to recycled aluminum melt, with their mutual influence and interaction, solves the shortcomings of recycled aluminum such as high Fe content and a large variety and content of impurity elements. This results in a heat-free die-cast aluminum alloy with tensile strength greater than 260 MPa, yield strength greater than 120 MPa, and elongation greater than 10%. This heat-free die-cast aluminum alloy based on recycled aluminum contains 6-9% Si, 0.1-0.6% Fe, 0.01-0.4% Cu, 0.01-0.8% Mn, 0.01-0.5% Mg, 0.01-0.5% Zn, 0.01-0.2% Ti, 0-0.05% Sr, and 0-0.01% B. Specifically:

[0040] (1) Si can improve the process flow properties of aluminum alloys, but if the content is too high, it will reduce the elongation. Si can also react with Al, Fe, Mg, Cu, B and other substances to generate second phases such as Mg2Si, AlFeSi, AlFeSiCu, AlFeMgSi, AlCuMgSi, AlFeSiB, which can improve the tensile strength and yield strength of aluminum alloys.

[0041] (2) Mg can react with Al, Fe, Si, Cu, Zn and other elements to form second phases such as AlFeMgSi, (CuMg)Al2, AlCuMgSi, Mg2Si, Mg2Zn, and Mg2SiZn, which can improve the tensile strength and yield strength of aluminum alloys. Among them, when Mg is dissolved in CuAl2 and AlFeSi phases, it forms (CuMg)Al2 and AlFeSiMg phases.

[0042] (3) Cu can react with Al, Fe, Si, Mg, Zn and other substances to form second phases such as CuAl2, AlFeSiCu, AlCuMgSi, Al2CuZn, (CuMg)Al2, which can improve the tensile strength and yield strength of aluminum alloys. It can also promote the precipitation of second phases such as Mg2Si, Mg2Zn, and Mg2SiZn, and increase the volume fraction and dispersion of precipitated phases. Subsequent natural aging treatment or vehicle painting and baking heat treatment (referred to as T85 treatment) can further improve the aging strengthening effect of Cu and Mg.

[0043] (4) Zn can react with Al, Mg, Cu and Si to form second phases such as MgZn2, Mg2SiZn and Al2CuZn, which can improve the tensile strength and yield strength of aluminum alloys. Zn can eliminate elemental Si to reduce the influence of Si on the properties of aluminum alloys. It can also promote the precipitation of phases such as Mg2Si, Mg2Zn, Mg2SiZn and Al2Cu, and increase the volume fraction and dispersion of precipitated phases.

[0044] (5) Fe can improve the demolding performance and can also react with Al, Si, Mg, Cu and B to generate second phases such as Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu and AlFeSiB, which can improve the tensile strength and yield strength of aluminum alloys. However, the Fe content and / or Fe morphology need to be controlled.

[0045] (6) Mn can react with Al, Fe, Si, and Cu to form MnAl2, MnAl6, α-(Fe,Mn)Al6, and Al. 12 CuMn2, α-Al(FeMn)Si, τ(Cu2Mn3Al 20Mn can improve the tensile strength and yield strength of aluminum alloys by forming second phases such as α-Al(Fe,Mn)Si. Mn can significantly refine grain size through lattice distortion caused by solid solution in the matrix and the MnAl6 dispersed particles produced by its reaction with Al, thereby improving elongation. MnAl6 can also dissolve Fe to form α-(Fe,Mn)Al6 phase, reducing Fe content and mitigating Fe hazard. Mn reacts with Al, Fe, Mn, and Si to form spherical or granular AlFeMnSi composite phases, avoiding the formation of long needle-like Fe phases and thus reducing Fe hazard. This improves the mold release properties of aluminum alloys while increasing their tensile strength and yield strength. Mn can transform coarse needle-like β-AlFeSi phases into small granular α-Al(FeMn)Si phase dispersed particles, improving Fe morphology and eliminating Fe hazard. Specifically, Mn can replace some of the Fe in the coarse needle-like β-AlFeSi phase, generating small granular dispersed β-Al(Fe,Mn)Si phases. The formation and growth shape of the Al(FeMn)Si phase and β phase are improved, thereby reducing the harm of Fe. Mn can also promote the transformation of the needle-like β-Al(FeMn)Si phase into the small-particle α-Al(FeMn)Si dispersed phase. The generated α-Al(FeMn)Si dispersed particles are distributed in the aluminum matrix and strongly pinned to the subgrain boundaries of the aluminum alloy. This is mainly because the Mn-containing α-phase dispersed particles in the aluminum alloy can act as non-uniform nucleation sites during the aging process of the β′ phase, thus inducing its nucleation and accelerating the precipitation of the β′ phase. Mn can also react with impurity phases in the recycled aluminum liquid to form Al-Mn-X phase (X is an impurity element, including but not limited to transition metal elements such as Fe, Cr, Sn, Pb, Cd, etc.), which can purify the recycled aluminum liquid. These phases can act as grain nucleation sites to increase the nucleation rate and refine the grains. Purification can improve the tensile strength, yield strength, elongation and fluidity of the alloy.

[0046] (7) Sr preferentially combines with Fe to form dispersion strengthening, reducing the solid solubility of Fe in recycled aluminum, thereby improving the yield strength and tensile strength of aluminum alloys; Sr can change the behavior of intermetallic compound phases in crystallography, and can be used as a modifier to refine the grains and second phase of aluminum alloys through heterogeneous nucleation theory or twin valley mechanism. For example, Sr can change the morphology of eutectic silicon phase through modification, thereby improving the elongation of aluminum alloys and reducing the tendency of sticking to the mold during die casting; Sr can transform the coarse needle-like β-AlFeSi and β-AlFeMnSi phases in the ingot into small granular Chinese character-shaped α-AlFeSi and α-Al(FeMn)Si phases, reducing the homogenization time of the ingot, and improving the yield strength, tensile strength and elongation of aluminum alloys;

[0047] (8) The TiAl2 phase generated by the reaction of Ti and Al, as a non-spontaneous nucleus during crystallization, can refine the grains, second phase and precipitated phase, thereby improving the tensile strength, yield strength and elongation of aluminum alloys;

[0048] (9) B can undergo borylation reaction with transition metal elements (including transition metal elements such as Fe) to generate compounds such as ferroboron compounds that can be separated from recycled aluminum liquid, thereby reducing the content of transition metal elements such as Fe and purifying recycled aluminum liquid; B is easily adsorbed on the surface of iron-rich phase, inhibiting the growth of iron-rich phase and playing a role in controlling the size of iron-rich phase, and can also prevent the formation of iron-rich phase in recycled aluminum liquid; B can inhibit the segregation of Ti3Al, therefore, the effect is better when Ti and B are used together; B can also refine grains and the second phase to improve the elongation of aluminum alloy.

[0049] The combination of B, Mn, and Sr within the aforementioned content range can regulate Fe content and improve Fe morphology, thereby eliminating Fe hazards and overcoming the defect of a wide and high Fe content range in recycled aluminum. The combined effect of Si, Cu, Mn, Mg, Zn, Ti, Sr, and Fe within the aforementioned content range can improve the tensile strength and yield strength of aluminum alloys. The combined effect of Mn, B, Ti, and Sr within the aforementioned content range can refine grains, second phases, and precipitated phases, thereby improving the elongation of aluminum alloys. Cu and Zn within the aforementioned content range can promote the precipitation of second phases, increase the volume fraction and dispersion of precipitated phases, and further improve the tensile strength, yield strength, and elongation of aluminum alloys. B and Mn within the aforementioned content range can also purify recycled aluminum liquid, remove impurity elements, and, in conjunction with refining and slag removal processes, remove as many impurity elements as possible. Furthermore, this invention maximizes the range of Mn and Ti content. The combination of Mn, B, and Ti can effectively control Fe, purify the recycled aluminum liquid, promote the precipitation of precipitated phases, and refine the grains, second phase, and precipitated phases. To improve the raw material source for alloy smelting and make full use of recycled aluminum resources, the content range of at least one of the main elements Fe, Cu, Mn, Mg, Zn, and Ti has been increased. Through the reasonable proportion of these elements, even if the recycled aluminum alloy contains too many types and too high contents of impurity elements, a high-performance heat-treatable die-cast aluminum alloy can be obtained through the synergistic effect of these elements.

[0050] This invention uses recycled aluminum as raw material. Recycled aluminum has significant advantages in "energy saving and emission reduction," with production energy consumption only 4.9% and carbon emissions only 4.2% of that of primary aluminum. Compared to using primary aluminum as raw material, this invention has a lower cost. Moreover, under the combined effect of Si, Cu, Mn, Mg, Zn, Ti, Sr, Fe, and B within the aforementioned content range, combined with refining, electromagnetic stirring, and slag removal, the Fe content and Fe morphology in recycled aluminum are effectively controlled, and the types and content range of impurity elements are expanded, resulting in a heat-free die-cast aluminum alloy with excellent comprehensive performance. In addition, the prices of Si, Cu, Mn, Mg, Zn, Ti, Sr, and B are all low, and the Si content is no more than 9%, which can further reduce costs.

[0051] Since the mechanical properties of heat-free die-cast aluminum alloys cannot be improved by aging heat treatment, most of the solute atoms in the heat-free die-cast aluminum alloy based on recycled aluminum of the present invention exist in the aluminum matrix in solid solution form. In addition to fine grain strengthening, the strength increase of the heat-free die-cast aluminum alloy mainly comes from the pinning of dislocations by lattice volume mismatch and elastic mismatch caused by solid solution atoms, i.e. solid solution strengthening.

[0052] During storage and transportation after die casting, heat-free die-cast aluminum alloys undergo natural aging, meaning their strength increases with prolonged storage time. This natural aging is attributed to the aggregation effect of solute atoms in the aluminum alloy, forming solute atom clusters. These clusters are disordered aggregations of solute atoms within the aluminum matrix, typically ranging in size from a few nanometers and composed of several to dozens of randomly distributed atoms without a defined crystal structure.

[0053] The strength variation of heat-free die-cast aluminum alloys is mainly related to the size and volume fraction of solute atomic clusters. During natural aging, the formation and growth of clusters are closely linked to changes in the concentration of supersaturated quenching vacancies. Vacancies are thermal defects, and their concentration has an exponential relationship with temperature. This invention performs low-temperature quenching on aluminum alloy parts after die casting to generate supersaturated vacancies, thereby improving the mechanical properties of heat-free die-cast aluminum alloys. Specifically, during die casting, the equilibrium vacancy concentration is relatively high; during subsequent quenching, some vacancies at high temperatures are retained, resulting in supersaturated vacancies. Furthermore, the low-temperature quenching also causes the aluminum alloy to shrink, producing plastic deformation, reducing the solubility of elements in aluminum, increasing the nucleation sites of clusters, and refining the α-Al phase and eutectic Si phase structure, thereby improving the yield strength, tensile strength, and elongation of the heat-free die-cast aluminum alloy.

[0054] The addition of Cu, Mn, Mg, Zn, Ti, Sr, Fe, and B can also regulate the behavior of solute atom clusters in aluminum alloys, such as influencing the formation of existing clusters and the formation of new clusters by adjusting vacancies. In the recycled aluminum liquid of this invention, the addition of Mg (0.01-0.5 wt%) and Cu (0.01-0.4 wt%) within a certain content range activates vacancy diffusion and promotes the formation of Mg-Si and Cu-Mg clusters, significantly strengthening the clusters. Mn and Sr have much larger atomic radii than Al. The Mn and Sr atoms within the aforementioned content range form lattice distortions in the aluminum matrix. Combined with the pinned vacancies and Mg-Si and Cu-Mg clusters added to the heat-free aluminum alloy, and the promotion of cluster growth, further enhance the natural aging effect, thereby improving the yield strength, tensile strength, and elongation of the heat-free aluminum alloy.

[0055] In summary, under the combined effects of Si, Cu, Mn, Mg, Zn, Ti, Sr, Fe and B within the above-mentioned content range, a heat-free die-casting aluminum alloy based on recycled aluminum with excellent demolding performance, tensile strength, yield strength and elongation is obtained. Detailed Implementation

[0056] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0057] This invention provides a method for preparing a heat-free die-cast aluminum alloy based on recycled aluminum, comprising the following steps:

[0058] Provide recycled aluminum;

[0059] The recycled aluminum is heated at a temperature of 680-720°C to obtain molten recycled aluminum.

[0060] The recycled aluminum liquid was analyzed to obtain the elements and their contents.

[0061] Based on the elements and content of the recycled aluminum liquid and the preset elements and content of the heat-free die-cast aluminum alloy based on recycled aluminum, the amounts of Si, Cu, Mn, Mg, Zn, Ti and B to be added to the recycled aluminum liquid are designed.

[0062] B is added to the recycled aluminum liquid at a temperature of 710-740°C, and the mixture is stirred electromagnetically.

[0063] Si, Cu, Mn, Mg, Zn, and Ti are added to the recycled aluminum liquid at a temperature of 740-780°C, followed by heat treatment and electromagnetic stirring to obtain an alloy liquid; and

[0064] The alloy liquid is subjected to refining, electromagnetic stirring, slag removal, and die casting to obtain aluminum alloy parts; and

[0065] The aluminum alloy parts are subjected to low-temperature quenching treatment to obtain the heat-free die-cast aluminum alloy based on recycled aluminum. The heat-free die-cast aluminum alloy based on recycled aluminum contains Al, and also contains 6-9% Si, 0.1-0.6% Fe, 0.01-0.4% Cu, 0.01-0.8% Mn, 0.01-0.5% Mg, 0.01-0.5% Zn, 0.01-0.2% Ti, 0-0.05% Sr, 0-0.01% B, and unavoidable impurities.

[0066] Recycled aluminum is aluminum alloy obtained by remelting scrap aluminum, scrap aluminum alloys, or aluminum-containing waste.

[0067] Understandably, the pre-designed heat-free die-cast aluminum alloy based on recycled aluminum contains 6-9% Si, 0.1-0.6% Fe, 0.01-0.4% Cu, 0.01-0.8% Mn, 0.01-0.5% Mg, 0.01-0.5% Zn, 0.01-0.2% Ti, 0-0.05% Sr, 0-0.01% B, and unavoidable impurities. After refining, electromagnetic stirring, and slag removal of the alloy liquid, the elemental composition and content of the alloy liquid can be tested again. If the tested elemental composition and content of the alloy liquid are inconsistent with those of the pre-designed heat-free die-cast aluminum alloy based on recycled aluminum, a certain amount of the corresponding element is added; if they are consistent, die casting is performed.

[0068] In one embodiment, the heat-free die-cast aluminum alloy based on recycled aluminum contains 7-9% Si, 0.2-0.5% Fe, 0.1-0.3% Cu, 0.3-0.7% Mn, 0.2-0.4% Mg, 0.2-0.4% Zn, 0.1-0.2% Ti, 0.005-0.05% Sr, and 0.005-0.01% B by mass.

[0069] Low-temperature quenching can be performed using ice water or liquid nitrogen. The temperature of the low-temperature quenching treatment is -200~0°C, specifically -200°C, -190°C, -180°C, -170°C, -160°C, -150°C, -140°C, -130°C, -120°C, -110°C, -100°C, -90°C, -80°C, -70°C, -60°C, -50°C, -40°C, -30°C, -20°C, -10°C, -9°C, -8°C, -7°C, -6°C, -5°C, -4°C, -3°C, -2°C, -1°C, or 0°C. The cryogenic quenching treatment time is 0.1~10h, specifically 0.1h, 0.5h, 1h, 5h, or 10h. It is understood that ice / ice water and liquid nitrogen can be added in a timely manner to maintain the cryogenic quenching temperature below 0°C, preserving as many vacancies as possible and ensuring the generation of supersaturated vacancies.

[0070] Electromagnetic stirring accelerates the dissolution of Mn and allows more elements, such as Mn and Fe, to react uniformly, generating a more dispersed and finer α-Al(FeMn)Si phase, thus improving the effect of Fe modification. The electromagnetic stirring frequency is 10 to 30 Hz, and the time is 1 to 10 minutes. This electromagnetic stirring treatment can refine the grains and also change the morphology of the Fe phase (e.g., it can transform long needle-like or blocky Al(FeMn)Si phase into a dispersed nanoscale spherical Al(MnFe)Cu phase).

[0071] Before the first heat treatment of the recycled aluminum, the recycled aluminum material can be pretreated, such as sorting, crushing, magnetic separation for iron removal, and washing. The composition and content of the recycled aluminum can also be tested for the first time using a photoelectric direct-reading spectrometer or chemical analysis method. This allows recycled aluminum with similar compositions and contents to be mixed together based on the test results, avoiding situations where the mixed recycled aluminum has an overly complex composition, excessive levels of certain elements, or insufficient levels of certain elements. Before testing the recycled aluminum liquid, it can also be refined to remove surface slag and other impurities.

[0072] In one embodiment, the refining process is carried out at a temperature of 690-750°C for 10-20 minutes. The refining agent may include the following raw materials in parts by weight: 60-70 parts KF, 150-60 parts NaC, 40-60 parts LiCl, 20-25 parts cryolite, 10-25 parts AlF3, 10-15 parts CaF2, 5-10 parts light calcium carbonate, 15-20 parts graphite powder, 10-20 parts talc powder, 20-30 parts MgCl2, and 10-30 parts rare earth salts. The rare earth salts may be a mixture of one or more of light rare earth chlorides, fluorides, and nitrates. The rare earth salts may be a mixture of one or more of heavy rare earth chlorides, fluorides, and nitrates. The mass ratio of the refining agent to the recycled aluminum liquid is 0.0013-0.0018:1.

[0073] In another embodiment, the alloy liquid is refined at a temperature of 710~735ºC for 10~30 min, wherein the mass ratio of refining agent to alloy liquid is 0.01~0.05:1, and the refining agent comprises a metal salt and hexachloroethane in a mass ratio of 0.5~1.5:1, wherein the metal salt is at least one selected from aluminum fluoride, sodium fluoride, sodium nitrate, aluminum nitrate, manganese chloride, zinc chloride, and sodium chloride. In one embodiment, the mass ratio of fluoride salt, nitrate salt, and chloride salt is 1:0.5~1.5:0.5~1.5.

[0074] The alloy molten material is die-cast at a temperature of 660-700ºC, wherein the die-casting speed of the die-casting machine is 0.23-2.5 m / s. It is understood that the die-casting process of this invention is a conventional die-casting process; vacuum die-casting can also be used to die-cast the alloy molten material. The strength (e.g., yield strength and tensile strength) and elongation of the aluminum alloy after vacuum die-casting are higher than those of the aluminum alloy after conventional die-casting.

[0075] In both the recycled aluminum melt and the alloy melt, the mass ratio of Mn to Fe can be 0.5-2:1, preferably 0.6-1.5:1, specifically 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, 1.14:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, or 2:1. During the die-casting process, the cooling rate is relatively high, and Fe will form fine, short rod-shaped or blocky Al-Fe or Al-Fe-Si phases, thus preventing Fe from affecting the elongation.

[0076] The mass percentage content of Si can be 6%, 6.2%, 6.4%, 6.6%, 6.7%, 6.8%, 6.9%, 7%, 7.2%, 7.4%, 7.6%, 7.8%, 8%, 8.2%, 8.4%, 8.6%, 8.8%, or 9%. The mass percentage content of Fe can be 0.1%, 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%, 0.42%, 0.44%, 0.46%, 0.48%, 0.5%, 0.52%, 0.54%, 0.56%, 0.58%, or 0.6%. The specific percentage content of Cu by mass can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.22%, 0.24%, 0.26%, 0.28%, 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, or 0.4%. The specific mass percentage content of Mn 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%, 0.2%. 9%, 0.3%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 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 specific percentage content of Mg by mass can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 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%, 0.42%, 0.44%, 0.46%, 0.48%, or 0.5%. The specific percentage content of Zn by mass can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 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%, 0.42%, 0.44%, 0.46%, 0.48%, or 0.5%. The mass percentage content of Ti can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 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 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%. Si, Cu, Mn, Mg, Zn, Ti, Sr, and B can be added in elemental or alloy form. The intermediate alloy has good dispersibility and is easily dissolved in recycled aluminum liquid. In the heat-free die-cast aluminum alloy based on recycled aluminum, the content of a single impurity does not exceed 0.05%, and the total impurity content does not exceed 0.15%.

[0077] When the Si content is high (>7%), the fluidity of the aluminum alloy melt is significantly improved, and the hardness and strength of the alloy are also correspondingly increased. However, a high Si content will severely reduce the plasticity of the alloy. The form and microstructure of Si in the matrix have a significant impact on the alloy's properties. Through the combined application of elemental modification and electromagnetic stirring, the morphology and distribution of the Si phase can be significantly improved, minimizing the damage of Si to the alloy's properties. The main role of Si is to increase the fluidity of aluminum alloys, while also improving their strength within a certain range.

[0078] The strengthening effect of Mg on Al is significant. When added together with less than 1% Mn, a combined strengthening effect can occur. Therefore, adding Mn can reduce the Mg content and decrease the tendency for hot cracking. Furthermore, Mn can precipitate Mg5Al8 compounds, improving corrosion resistance and weldability. When the Mg content is below 0.5 wt.%, the yield strength is linearly related to the increase in Mg content. When the Mg content is greater than 0.5 wt.%, the linear relationship is broken, and the strengthening response of the Al-Si-Mg alloy is reduced. This is related to the fact that the formation of the AlFeMgSi phase occupies a large number of Mg atoms, making precipitation strengthening difficult.

[0079] Adding a small amount of Zn can produce a strong solid solution strengthening effect, significantly improving the strength of aluminum alloys. Zn can promote the precipitation of primary Si, reduce the solid solubility of Si in Al, enhance the precipitation strengthening effect of aluminum alloys, promote the aging precipitation kinetics of aluminum alloys, and increase the density of precipitated phases in the matrix. In die-cast aluminum alloys, Zn can improve fluidity, increase hot brittleness, and reduce corrosion resistance.

[0080] In this invention, the method for preparing a heat-free die-cast aluminum alloy based on recycled aluminum uses recycled aluminum as raw material to reduce costs. Unlike primary aluminum, recycled aluminum has a wider range of Fe content, a greater variety of impurity elements, and higher content. To improve the utilization rate of recycled aluminum, on the one hand, it needs to be more tolerant of high Fe content; higher Fe content leads to poorer overall performance, so the Fe content / Fe morphology must be controlled to reduce Fe's harmful effects. On the other hand, it also needs to be highly tolerant of the characteristics of recycled aluminum alloys, which have a wide variety of impurity elements and a high range of impurity element composition, to reduce the impact of impurity elements on alloy performance.

[0081] The addition of Si, Cu, Mn, Mg, Zn, Ti, Sr, and B to recycled aluminum melt, with their mutual influence and interaction, solves the shortcomings of recycled aluminum such as high Fe content and a large variety and content of impurity elements. This results in a heat-free die-cast aluminum alloy with tensile strength greater than 260 MPa, yield strength greater than 120 MPa, and elongation greater than 10%. This heat-free die-cast aluminum alloy based on recycled aluminum contains 6-9% Si, 0.1-0.6% Fe, 0.01-0.4% Cu, 0.01-0.8% Mn, 0.01-0.5% Mg, 0.01-0.5% Zn, 0.01-0.2% Ti, 0-0.05% Sr, and 0-0.01% B. Specifically:

[0082] (1) Si can improve the process flow properties of aluminum alloys, but if the content is too high, it will reduce the elongation. Si can also react with Al, Fe, Mg, Cu, B and other substances to generate second phases such as Mg2Si, AlFeSi, AlFeSiCu, AlFeMgSi, AlCuMgSi, AlFeSiB, which can improve the tensile strength and yield strength of aluminum alloys.

[0083] (2) Mg can react with Al, Fe, Si, Cu, Zn and other elements to form second phases such as AlFeMgSi, (CuMg)Al2, AlCuMgSi, Mg2Si, Mg2Zn, and Mg2SiZn, which can improve the tensile strength and yield strength of aluminum alloys. Among them, when Mg is dissolved in CuAl2 and AlFeSi phases, it forms (CuMg)Al2 and AlFeSiMg phases.

[0084] (3) Cu can react with Al, Fe, Si, Mg, Zn and other substances to form second phases such as CuAl2, AlFeSiCu, AlCuMgSi, Al2CuZn, (CuMg)Al2, which can improve the tensile strength and yield strength of aluminum alloys. It can also promote the precipitation of second phases such as Mg2Si, Mg2Zn, and Mg2SiZn, and increase the volume fraction and dispersion of precipitated phases. Subsequent natural aging treatment or vehicle painting and baking heat treatment (referred to as T85 treatment) can further improve the aging strengthening effect of Cu and Mg.

[0085] (4) Zn can react with Al, Mg, Cu and Si to form second phases such as MgZn2, Mg2SiZn and Al2CuZn, which can improve the tensile strength and yield strength of aluminum alloys. Zn can eliminate elemental Si to reduce the influence of Si on the properties of aluminum alloys. It can also promote the precipitation of phases such as Mg2Si, Mg2Zn, Mg2SiZn and Al2Cu, and increase the volume fraction and dispersion of precipitated phases.

[0086] (5) Fe can improve the demolding performance and can also react with Al, Si, Mg, Cu and B to generate second phases such as Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu and AlFeSiB, which can improve the tensile strength and yield strength of aluminum alloys. However, the Fe content and / or Fe morphology need to be controlled.

[0087] (6) Mn can react with Al, Fe, Si, and Cu to form MnAl2, MnAl6, α-(Fe,Mn)Al6, and Al. 12 CuMn2, α-Al(FeMn)Si, τ(Cu2Mn3Al 20Mn can improve the tensile strength and yield strength of aluminum alloys by forming second phases such as α-Al(Fe,Mn)Si. Mn can significantly refine grain size through lattice distortion caused by solid solution in the matrix and the MnAl6 dispersed particles produced by its reaction with Al, thereby improving elongation. MnAl6 can also dissolve Fe to form α-(Fe,Mn)Al6 phase, reducing Fe content and mitigating Fe hazard. Mn reacts with Al, Fe, Mn, and Si to form spherical or granular AlFeMnSi composite phases, avoiding the formation of long needle-like Fe phases and thus reducing Fe hazard. This improves the mold release properties of aluminum alloys while increasing their tensile strength and yield strength. Mn can transform coarse needle-like β-AlFeSi phases into small granular α-Al(FeMn)Si phase dispersed particles, improving Fe morphology and eliminating Fe hazard. Specifically, Mn can replace some of the Fe in the coarse needle-like β-AlFeSi phase, generating small granular dispersed β-Al(Fe,Mn)Si phases. The formation and growth shape of the Al(FeMn)Si phase and β phase are improved, thereby reducing the harm of Fe. Mn can also promote the transformation of the needle-like β-Al(FeMn)Si phase into the small-particle α-Al(FeMn)Si dispersed phase. The generated α-Al(FeMn)Si dispersed particles are distributed in the aluminum matrix and strongly pinned to the subgrain boundaries of the aluminum alloy. This is mainly because the Mn-containing α-phase dispersed particles in the aluminum alloy can act as non-uniform nucleation sites during the aging process of the β′ phase, thus inducing its nucleation and accelerating the precipitation of the β′ phase. Mn can also react with impurity phases in the recycled aluminum liquid to form Al-Mn-X phase (X is an impurity element, including but not limited to transition metal elements such as Fe, Cr, Sn, Pb, Cd, etc.), which can purify the recycled aluminum liquid. These phases can act as grain nucleation sites to increase the nucleation rate and refine the grains. Purification can improve the tensile strength, yield strength, elongation and fluidity of the alloy.

[0088] (7) Sr preferentially combines with Fe to form dispersion strengthening, reducing the solid solubility of Fe in recycled aluminum, thereby improving the yield strength and tensile strength of aluminum alloys; Sr can change the behavior of intermetallic compound phases in crystallography, and can be used as a modifier to refine the grains and second phase of aluminum alloys through heterogeneous nucleation theory or twin valley mechanism. For example, Sr can change the morphology of eutectic silicon phase through modification, thereby improving the elongation of aluminum alloys and reducing the tendency of sticking to the mold during die casting; Sr can transform the coarse needle-like β-AlFeSi and β-AlFeMnSi phases in the ingot into small granular Chinese character-shaped α-AlFeSi and α-Al(FeMn)Si phases, reducing the homogenization time of the ingot, and improving the yield strength, tensile strength and elongation of aluminum alloys;

[0089] (8) The TiAl2 phase generated by the reaction of Ti and Al, as a non-spontaneous nucleus during crystallization, can refine the grains, second phase and precipitated phase, thereby improving the tensile strength, yield strength and elongation of aluminum alloys;

[0090] (9) B can undergo borylation reaction with transition metal elements (including transition metal elements such as Fe) to generate compounds such as ferroboron compounds that can be separated from recycled aluminum liquid, thereby reducing the content of transition metal elements such as Fe and purifying recycled aluminum liquid; B is easily adsorbed on the surface of iron-rich phase, inhibiting the growth of iron-rich phase and playing a role in controlling the size of iron-rich phase, and can also prevent the formation of iron-rich phase in recycled aluminum liquid; B can inhibit the segregation of Ti3Al, therefore, the effect is better when Ti and B are used together; B can also refine grains and the second phase to improve the elongation of aluminum alloy.

[0091] The combination of B, Mn, and Sr within the aforementioned content range can regulate Fe content and improve Fe morphology, thereby eliminating Fe hazards and overcoming the defect of a wide and high Fe content range in recycled aluminum. The combined effect of Si, Cu, Mn, Mg, Zn, Ti, Sr, and Fe within the aforementioned content range can improve the tensile strength and yield strength of aluminum alloys. The combined effect of Mn, B, Ti, and Sr within the aforementioned content range can refine grains, second phases, and precipitated phases, thereby improving the elongation of aluminum alloys. Cu and Zn within the aforementioned content range can promote the precipitation of second phases, increase the volume fraction and dispersion of precipitated phases, and further improve the tensile strength, yield strength, and elongation of aluminum alloys. B and Mn within the aforementioned content range can also purify recycled aluminum liquid, remove impurity elements, and, in conjunction with refining and slag removal processes, remove as many impurity elements as possible. Furthermore, this invention maximizes the range of Mn and Ti content. The combination of Mn, B, and Ti can effectively control Fe, purify the recycled aluminum liquid, promote the precipitation of precipitated phases, and refine the grains, second phase, and precipitated phases. To improve the raw material source for alloy smelting and make full use of recycled aluminum resources, the content range of at least one of the main elements Fe, Cu, Mn, Mg, Zn, and Ti has been increased. Through the reasonable proportion of these elements, even if the recycled aluminum alloy contains too many types and too high contents of impurity elements, a high-performance heat-treatable die-cast aluminum alloy can be obtained through the synergistic effect of these elements.

[0092] This invention uses recycled aluminum as raw material. Recycled aluminum has significant advantages in "energy saving and emission reduction," with production energy consumption only 4.9% and carbon emissions only 4.2% of that of primary aluminum. Compared to using primary aluminum as raw material, this invention has a lower cost. Moreover, under the combined effect of Si, Cu, Mn, Mg, Zn, Ti, Sr, Fe, and B within the aforementioned content range, combined with refining, electromagnetic stirring, and slag removal, the Fe content and Fe morphology in recycled aluminum are effectively controlled, and the types and content range of impurity elements are expanded, resulting in a heat-free die-cast aluminum alloy with excellent comprehensive performance. In addition, the prices of Si, Cu, Mn, Mg, Zn, Ti, Sr, and B are all low, and the Si content is no more than 9%, which can further reduce costs.

[0093] Since the mechanical properties of heat-free die-cast aluminum alloys cannot be improved by aging heat treatment, most of the solute atoms in the heat-free die-cast aluminum alloy based on recycled aluminum of the present invention exist in the aluminum matrix in solid solution form. In addition to fine grain strengthening, the strength increase of the heat-free die-cast aluminum alloy mainly comes from the pinning of dislocations by lattice volume mismatch and elastic mismatch caused by solid solution atoms, i.e. solid solution strengthening.

[0094] During storage and transportation after die casting, heat-free die-cast aluminum alloys undergo natural aging, meaning their strength increases with prolonged storage time. This natural aging is attributed to the aggregation effect of solute atoms in the aluminum alloy, forming solute atom clusters. These clusters are disordered aggregations of solute atoms within the aluminum matrix, typically ranging in size from a few nanometers and composed of several to dozens of randomly distributed atoms without a defined crystal structure.

[0095] The strength variation of heat-free die-cast aluminum alloys is mainly related to the size and volume fraction of solute atomic clusters. During natural aging, the formation and growth of clusters are closely linked to changes in the concentration of supersaturated quenching vacancies. Vacancies are thermal defects, and their concentration has an exponential relationship with temperature. This invention performs low-temperature quenching on aluminum alloy parts after die casting to generate supersaturated vacancies, thereby improving the mechanical properties of heat-free die-cast aluminum alloys. Specifically, during die casting, the equilibrium vacancy concentration is relatively high; during subsequent quenching, some vacancies at high temperatures are retained, resulting in supersaturated vacancies. Furthermore, the low-temperature quenching also causes the aluminum alloy to shrink, producing plastic deformation, reducing the solubility of elements in aluminum, increasing the nucleation sites of clusters, and refining the α-Al phase and eutectic Si phase structure, thereby improving the yield strength, tensile strength, and elongation of the heat-free die-cast aluminum alloy.

[0096] The addition of Cu, Mn, Mg, Zn, Ti, Sr, Fe, and B can also regulate the behavior of solute atom clusters in aluminum alloys, such as influencing the formation of existing clusters and the formation of new clusters by adjusting vacancies. In the recycled aluminum liquid of this invention, the addition of Mg (0.01-0.5 wt%) and Cu (0.01-0.4 wt%) within a certain content range activates vacancy diffusion and promotes the formation of Mg-Si and Cu-Mg clusters, significantly strengthening the clusters. Mn and Sr have much larger atomic radii than Al. The Mn and Sr atoms within the aforementioned content range form lattice distortions in the aluminum matrix. Combined with the pinned vacancies and Mg-Si and Cu-Mg clusters added to the heat-free aluminum alloy, and the promotion of cluster growth, further enhance the natural aging effect, thereby improving the yield strength, tensile strength, and elongation of the heat-free aluminum alloy.

[0097] In summary, under the combined effects of Si, Cu, Mn, Mg, Zn, Ti, Sr, Fe and B within the above-mentioned content range, a heat-free die-casting aluminum alloy based on recycled aluminum with excellent demolding performance, tensile strength, yield strength and elongation is obtained.

[0098] When adding Mn to the recycled aluminum liquid, at least one of Cr, RE, Co, Be and Ca can be added simultaneously, followed by electromagnetic stirring.

[0099] Electromagnetic stirring accelerates the dispersion of elements such as Cr, RE, Co, Be, and Ca in the solution, making them less prone to aggregation and growth. It also allows more elements, such as Cr, RE, Co, Be, Ca, and Fe, to participate in the reaction more uniformly, generating finer and more dispersed α-Al(FeMn)Si second phases, thus improving the effect of Fe modification and refining the second phase. The electromagnetic stirring frequency is 20 to 40 Hz, and the time is 5-15 minutes. This electromagnetic stirring treatment can refine the grains and also change the morphology of the Fe phase (e.g., transforming long needle-like or blocky Al(FeMn)Si phases into dispersed nanoscale spherical Al(MnFe)Cu phases).

[0100] After adding Mn to the recycled aluminum liquid, at least one of C, Nb, Ni, Te, In, Mo, Ag, Cd, V, Sn, Zr, Sb and Bi can be added to the recycled aluminum liquid at a temperature of 700-760°C, and the mixture is then stirred electromagnetically.

[0101] Electromagnetic stirring accelerates the dispersion of elements such as C, Nb, Ni, Te, In, Mo, Ag, Cd, V, Sn, Zr, Sb, and Bi in the solution, making them less prone to aggregation and growth. Furthermore, it allows more elements, including C, Nb, Ni, Te, In, Mo, Ag, Cd, V, Sn, Zr, Sb, In, Bi, Cr, RE, Co, Be, Ca, and Fe, to participate in the reaction more uniformly, generating a more dispersed and finer second phase, improving the effect of Fe modification, and refining the second phase. The electromagnetic stirring frequency is 20 to 40 Hz, and the time is 5-15 minutes. This electromagnetic stirring treatment can refine the grains and also change the morphology of the Fe phase (e.g., transforming long needle-like or blocky Al(FeMn)Si phase into dispersed nanoscale spherical Al(MnFe)Cu phase).

[0102] Cr, RE, Co, Be, Ca, C, Nb, Ni, Te, In, Mo, Ag, Cd, V, Sn, Zr, Sb, and Bi can be added in elemental or alloy form. The intermediate alloy exhibits good dispersibility and is easily dissolved in the recycled aluminum molten metal. Of course, the amounts of Cr, RE, Co, Be, Ca, C, Nb, Ni, Te, In, Mo, Ag, Cd, V, Sn, Zr, Sb, and Bi to be added to the recycled aluminum molten metal can be calculated based on the elements and content of the recycled aluminum molten metal and the elements and content of a pre-set heat-free die-casting aluminum alloy based on recycled aluminum.

[0103] In the heat-free die-cast aluminum alloy based on recycled aluminum, the total mass percentage content of at least one element selected from Cr, RE, Co, Be, Ca, C, Nb, Ni, Te, In, Mo, Ag, Cd, V, Sn, Zr, Sb, and Bi is not greater than 0.4%, preferably not greater than 0.3%, and can specifically be 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, or 0.4%.

[0104] RE is at least one of La, Ce, Pr, Nd, Er, Sm, Y, Gd, and Sc. In one embodiment, RE is La, Y, and Sm, with a ratio of 0.01-0.03:0.02-0.05:1. In another embodiment, RE is Pr, Er, and Nd, with a ratio of 0.02-0.05:0.03-0.08:1. In yet another embodiment, RE is Sm, Y, and Gd, with a ratio of 0.06-0.08:0.1-0.2:1. Adding multiple rare earth elements in combination achieves a better refining effect.

[0105] In the recycled aluminum liquid and aluminum alloy liquid, the mass ratio of Cr to Fe is 0.2-1:1, preferably 0.5-1:1, and can specifically be 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.

[0106] In the recycled aluminum liquid and aluminum alloy liquid, the mass ratio of Co to Fe is 0.2-1:1, preferably 0.5-1:1, and can specifically be 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.

[0107] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Cr is 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 transform the acicular β-Fe phase into the α-Fe phase to improve the Fe morphology and eliminate the harmful effects of Fe. It also readily forms a dispersed phase with Fe to reduce the Fe content and mitigate the harmful effects of Fe. Cr forms (CrFe)Al7 and (CrMn)Al in the recycled aluminum melt. 12 Intermetallic compounds can hinder the nucleation and growth processes of recrystallization, thereby improving the tensile strength, yield strength, and elongation of aluminum alloys and reducing their susceptibility to stress corrosion cracking. Various fine chromium-containing compounds formed by Cr in aluminum alloys can redissolve in the α-phase during the solid solution stage, and then disperse and precipitate various Cr-containing phases, such as the α-AlCrSi dispersed phase, during the aging stage. These Cr-containing phases can act as nuclei for the heterogeneous nucleation of β" and θ" phases, accelerating their formation and thus improving the tensile strength and yield strength of the aluminum alloy. Simultaneously, the dispersed precipitation of Cr-containing phases in the matrix inevitably delays the formation of the θ′ phase at grain boundaries. Furthermore, Mn and Cr can form dispersed α-Al(FeMnCr)Si phases with Fe and Si. The high bulk density and strong thermal stability of the α-Al(FeMnCr)Si phase can effectively control the grain growth process of recycled aluminum by pinning grain boundaries, thereby controlling grain size. When Cr and Mo are added together, a multi-phase complex rich in Cr and Mo can be generated, which significantly improves the tensile strength of aluminum alloys.

[0108] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of RE is 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%. RE is distributed in the same region as the Fe phase and can form a rare earth active film on the surface of the iron-containing phase or combine with Al, Fe, Ti, and other atoms to form rare earth compounds such as AlFeRE. This prevents the formation of hard and brittle β-AlFeSi phases at grain boundaries, effectively reducing the solid solution of harmful elements in the aluminum matrix, thereby improving the tensile strength and yield strength of the aluminum alloy. RE can transform the elongated β-Fe phase into a spherical α-Fe phase and modify elemental Si. RE can also promote the precipitation of dispersed phases such as CuAl2 and (CuMg)Al2, further improving the tensile strength and yield strength of the aluminum alloy. Resin (RE) is a surface-active element with a radius larger than that of Al. It cannot enter the α-Al lattice but can segregate at grain boundaries or adsorb at the solid-liquid interface, forming supercooling. This increases the chance of dendrite melting, thereby refining the grains, the second phase, and precipitated phases (e.g., refining Al3Fe, Al3ScZr, AlSiMo, and Mg2Si phases), further improving the tensile strength, yield strength, and elongation of aluminum alloys. The combination of Ca and RE phases can significantly refine the grains and the second phase, thereby improving tensile strength, yield strength, and elongation.

[0109] When RE (0-0.1wt%) and Zr (0-0.2wt%) are added to recycled aluminum liquid within a certain range, and the mass ratio of RE to Zr is 0.1-1:1, the highly distorted coherent solid solution elements can promote the formation of atomic clusters such as high-density Mg-Si clusters and Cu-Mg clusters, and significantly inhibit the diffusion of atoms in the atomic clusters, thereby improving the stability of the atomic clusters and thus improving the yield strength, tensile strength and elongation of the aluminum alloy.

[0110] The mass ratio of RE to Zr is 0.1-1:1, preferably 0.5-1:1, and can specifically be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, or 1:1.

[0111] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Co is 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 promote the formation of Fe spheroidal phases, generating small-particle-size Al3(Fe,Co) phases that improve the mechanical properties of aluminum alloys. It can also transform coarse needle-like and lamellar Al3Fe phases into α-Al. 15(Fe,Co)3Si2 (which can be granular, flower-like, or fine strip-like) has a refining effect on the Al3Fe phase, further improving the tensile strength, yield strength, and elongation of aluminum alloys. The addition of Ce and Co not only improves the thermal stability of recycled aluminum but also promotes… <001> and <111> Orientation formation is used to improve the mechanical properties of aluminum alloys.

[0112] In the heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Be is 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, thereby improving the tensile strength and yield strength of aluminum alloys. It can refine the Si phase by transforming the eutectic Si phase from a lamellar phase to a finer phase, thus reducing or eliminating the adverse effects of Si on the properties of aluminum alloys. It can also transform the plate-like β-mezzanine phase into the relatively harmless Chinese character-shaped Be-Fe (Al8Fe2SiBe) phase and prevent the formation of the acicular β-Fe phase, thereby reducing or eliminating the adverse effects of Fe on the properties of aluminum alloys. Furthermore, it can promote the formation and precipitation of phases such as Mg2Si, Mg2Zn, Mg2SiZn, and Al2Cu, thereby reducing the solid solubility of these elements in the aluminum matrix. Be can also form an active film on the surface of impurity element phases such as Fe, preventing the growth of impurity elements. It can also segregate at grain boundaries or adsorb at the solid-liquid interface, forming a supercooling effect that increases the chance of dendrite melting, thus refining the grains. The refining effect of Be increases with increasing Be content.

[0113] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Ca is 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%. Ca can improve the β-Fe phase to reduce the harmful effects of Fe, and can also react with Al, Cu, Zn, and Si to form second phases such as Al4Ca, Al2Ca3, AlCa2, AlCaCu, CaZn, CaAlZn, and Al2CaSi2, thereby improving 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 alloys.

[0114] The addition of elements such as Cr, RE, Co, Be, and Sr not only further promotes the reaction between Mn and Fe by reducing their maximum solid solubility in the matrix, but also occupies the positions of Mn and Fe elements in the second phase. By controlling the structure of the second phase, the Fe-containing phase becomes more dispersed and fine, further promoting the effect of Fe modification. Therefore, when the mass ratio of Mn to Fe is greater than 1.2:1, the α-Al(MnFeX)Si phase (where X is any one or more of Cr, RE, Co, Be, Sr, etc.) can still remain fine and dispersed, and there is no excess Mn reacting with Al to form a coarse AlMn phase.

[0115] When Ti, B, and RE are used together, the effective action time of Ti and B can be extended. This is because RE improves the wettability of aluminum alloy liquid to borides, making it less likely for TiB2 to agglomerate and precipitate, thus ensuring an effective amount of TiB2.

[0116] The combined action of Mn, Cr, and RE effectively improves the morphology of Fe, reduces the Fe content, and refines and controls the grain size, resulting in aluminum alloys with better tensile strength, yield strength, and elongation. Specifically, Mn can significantly refine recrystallized grains and the second phase, effectively transforming the coarse needle-like or plate-like β-AlFeSi phase into small granular α-Al(FeMn)Si dispersed particles to improve the Fe morphology. It can also react with Fe to form the α-(Fe,Mn)Al6 phase to reduce the Fe content. Clearly, Mn can reduce the Fe content, improve the Fe morphology, and refine the grains and the second phase. Cr can effectively transform the needle-like β-Fe phase into the α-Fe phase to improve the Fe morphology, and it can also react with Fe to form (CrFe)Al7 and (CrMn)Al6 phases. 12The presence of dispersed phases reduces the Fe content and reacts with Al, Si, and Mg to form dispersed phases such as AlCrSi and Mg2(SiCr), increasing the precipitation volume fraction and uniformity of the dispersed phases. Cr can also hinder grain growth, refine grains and the second phase, thereby increasing the alloy's tensile strength, yield strength, and elongation. The distribution area of ​​RE is consistent with that of the Fe phase, which can form a rare earth active film on the Fe phase surface, preventing the formation of a hard and brittle β-AlFeSi phase at the grain boundaries. When Mn, Cr, and RE are added together, they can effectively improve the Fe morphology. When Mn and Cr are added together, they can form dispersed α-Al(FeMnCr)Si and α-Al(FeMnCr)Si phases with Fe and Si. These phases have high density and strong thermal stability. With prolonged standing time, some of these phases settle to the bottom, while others pin the grain boundaries, effectively refining and controlling the grain size. Mn, Cr, and RE can react with trace impurities in recycled aluminum to form Al-Cr-X, Al-Mn-X, and Al-RE-X phases (where X is an impurity element, including but not limited to transition metals such as Fe, Cr, Sn, Pb, and Cd). These phases purify the aluminum alloy and improve its elongation. They can also act as grain nucleation sites, increasing the nucleation rate and refining the grains, thereby improving the alloy's tensile strength, yield strength, and fluidity. In summary, the synergistic effect of Mn, Cr, and RE within the aforementioned content ranges improves the Fe morphology and reduces the Fe content while refining the grains, resulting in an aluminum alloy with excellent overall performance.

[0117] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of C is 0-0.05%, specifically 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%. C acts as a grain refiner, significantly refining the grain size and second phase to improve the elongation of the aluminum alloy. It also acts as a highly efficient modifier, reacting with Fe during heat treatment to form carbides, thereby increasing the tensile strength and yield strength of the aluminum alloy.

[0118] The combined action of Ti, C, B, and Sr can effectively refine grains and the second phase. Specifically, B can inhibit the segregation of Ti3Al; when Ti and B are used together, they can effectively reduce the Fe content and refine the grains and the second phase. When RE, Ti, and B are combined, TiB2 is less likely to agglomerate and precipitate, ensuring an effective amount of TiB2. The TiAl3 phase formed by the reaction of Ti and Al can act as a non-spontaneous nucleus during crystallization, refining the grains and the second phase. Sr, as a modifier, can refine the grains and the second phase, and can also transform coarse needle-like β-AlFeSi and β-AlFeMnSi phases into small granular, Chinese character-shaped α-AlFeSi and α-Al(FeMn)Si phases. When these four are used in combination, they can effectively reduce the Fe content, improve the Fe morphology, and refine the grains and the second phase.

[0119] When B, Mn, Cr, and RE are combined, they can prevent the formation of iron-rich phases. This allows for the pre-calculation of the amounts of B, Mn, Cr, or RE to be added to the recycled aluminum melt based on the Fe content in the recycled aluminum, eliminating concerns about the difficulty in effectively removing the β-Fe phase due to the continuous formation of iron-rich phases in the recycled aluminum. At least one of Ti, C, and Sr can assist B, Mn, Cr, and RE in further refining the grains and the second phase, further reducing the size of the α-Fe phase. Specifically, Sr can preferentially combine with elements such as Fe, Cu, and Si to form dispersion strengthening, reducing the distribution of Cr, Mn, and Cu towards grain boundaries and decreasing their solid solubility in the alloy, thereby improving the overall performance of the alloy. The synergistic effect of Mn, Cr, RE, B, Ti, C, and Sr within the aforementioned content range improves the Fe morphology and reduces the Fe content while refining the grains and the second phase, resulting in an aluminum alloy with excellent overall performance.

[0120] In the heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Nb 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%. Nb can react with Al and B to form high-temperature strengthening metal compounds such as AlNb3, AlNb, Al3Nb, and NbB2; some Nb can be dispersed in the matrix grain boundaries, which can significantly improve the yield strength and tensile strength of the aluminum alloy; Nb can refine the grains and the second phase to improve the elongation of the aluminum alloy; the lattice mismatch constant between NbB2 and Al (30.6%) is smaller than that between TiB2 and Al (34.0%), and considering only the interaction with Al, NbB2 is more likely to be a potential heterogeneous nucleation site than TiB2.

[0121] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Ni is 0-0.02%, specifically 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, or 0.02%. Ni can refine grains, promote the precipitation of the second phase, increase the volume fraction and dispersion of the precipitated phase, and can also react with Al, Fe, Mg, Si, etc. to form second phases such as AlFeSiNi, AlFeMgSiNi, and FeNiAl9, thereby reducing the Fe content.

[0122] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Te 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%. Te can narrow the solidification temperature range of the aluminum alloy, forming fine petal-shaped rather than dendritic primary crystals, reducing or eliminating micro-shrinkage porosity, thereby improving the mechanical and thermal properties of the aluminum alloy. When Sb is added in combination with Te, fine petal-shaped primary crystals can be formed to improve the tensile strength and elongation of the aluminum alloy.

[0123] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Ag 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%. Ag can promote the precipitation of second phases (such as Al2Cu, Mg2Si, Mg3Sb2, and Mg3Bi2), refine the precipitated phases and increase the density of the precipitated phases, thereby enhancing the precipitation strengthening effect of the aluminum alloy and improving the tensile strength, yield strength, and elongation of the aluminum alloy.

[0124] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of In 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%. 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 of the aluminum alloy. Ag, In, and Nb work together to promote the precipitation of the second phase and refine the grains and precipitated phases. Specifically, In can react with Al and Cu to form second phases such as AlIn and CuIn; Nb, Ti and Al can form TiAl-Nb phase; Ag can promote the precipitation of the second phase and refine the precipitated phase; Nb and In can also refine the grains and the second phase, thus simultaneously improving the tensile strength, yield strength and elongation of aluminum alloys.

[0125] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Mo is 0-0.02%, specifically 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, or 0.02%. Mo can also react with Al, Si, Fe, etc., to form second phases such as AlMo, AlSiMo, and AlSiFeMo, which are dispersed in the grain boundaries of the aluminum matrix. Mo can also refine the grains, improve the morphology of Fe-containing intermetallic compounds, and further improve the tensile strength, yield strength, and elongation of the aluminum alloy.

[0126] In the heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Cd is 0-0.05%, specifically 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%. 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, thereby improving the tensile strength and yield strength of aluminum alloys and reducing the Fe content. During the aging stage, Cd will form a large number of Cd-vacancy clusters, which will promote and accelerate the precipitation of CuAl2 phase, thereby reducing the solid solubility of the above elements in the aluminum matrix.

[0127] In the heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of V is 0-0.02%, specifically 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, or 0.02%. V can react with Al to form VAl. 11 Refractory compounds such as Al3V play a role in refining grains during the casting process. V can also refine the recrystallization structure and increase the recrystallization temperature, thereby improving the tensile strength, yield strength and elongation of aluminum alloys. During the die casting process, the temperature cooling rate is relatively large. The unstable 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. This can prevent dislocation movement and recrystallization nucleation and growth, and significantly improve the tensile strength and yield strength of aluminum alloys.

[0128] In the heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Sn is 0-0.08%, specifically 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%, 0.05%, 0.06%, 0.07%, or 0.08%. Sn can react with Al, Mg, Sc, etc. to form second phases such as Al9Sn7, Al6Sn5, Al5Sn2, Al3Sn4, Mg2Sn, and Mg2ScSn, thereby improving the tensile strength and yield strength of aluminum alloys. Sn can also promote the precipitation of second phases such as Mg2Si, Mg2Zn, Mg2SiZn, and Al2Cu, thereby reducing the solid solubility of these elements in the aluminum matrix. Sn can also effectively inhibit the growth of the MgSi2 phase and promote its dispersed distribution, thereby improving the tensile strength and yield strength of the alloy.

[0129] In the heat-free die-cast aluminum alloy based on recycled aluminum, the Zr content is 0-0.02% by mass, specifically 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, or 0.02%. 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 aluminum alloys. Zr can also promote the precipitation of phases such as Mg2Sn, Mg2Si, Mg3Sb2 and CuAl2, thereby reducing the solid solubility of these elements in the aluminum matrix. Zr can also refine the grains, further improving the elongation of aluminum alloys. The addition of B can transform Zr from a solid solution state to a precipitated state, existing in the form of fine plate-like second phase particles inside the grains and at the grain boundaries, reducing lattice distortion, improving the orderliness of the aluminum matrix, and enhancing the tensile strength and yield strength of aluminum alloys. The combined effect of Er and Zr can promote the precipitation of the β″ phase and make the β″ phase finer and more dispersed. The synergistic effect of Er and Zr can significantly inhibit the recrystallization of Al-Fe alloys.

[0130] The mass ratio of Er to Zr can be 0.5-5:1, preferably 1-3:1, specifically 0.5:1, 1:1, 2:1, 3:1, 4:1, or 5:1.

[0131] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Sb is 0-0.02%, specifically 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, or 0.02%. Sb can react with Mg to form second phases such as Mg3Sb2, which can improve the tensile strength and yield strength of the aluminum alloy. When Sb is added in combination with Te, it can form fine petal-shaped primary crystals, thereby improving the tensile strength and elongation of the aluminum alloy.

[0132] In the aforementioned heat-free die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Bi is 0-0.02%, specifically 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, or 0.02%. Bi can react with Mg and Cd to form second phases such as Mg3Bi2 and Mg3(BiCd)2, which can improve the tensile strength and yield strength of the aluminum alloy.

[0133] The present invention also provides a structural component, at least a portion of which is made of the aforementioned heat-treatable die-cast aluminum alloy based on recycled aluminum or a heat-treatable die-cast aluminum alloy based on recycled aluminum prepared by the aforementioned method. This structural component can be applied in new energy vehicles as an automotive structural component, such as the entire vehicle body, rear wheel arch inner panel, rear longitudinal beam, floor connecting plate, rear floor plate, beam inner reinforcing plate, hood, mudguards, doors, rear cargo box, and roof, etc.

[0134] Of course, the structural components of this invention can also be used in other fields, such as aerospace, high-speed rail, shipbuilding, mobile devices, home appliances, chemical industry, daily necessities, and construction.

[0135] Examples and Comparative Examples

[0136] Please refer to Table 1 for the composition and content of the heat-free die-cast aluminum alloys based on recycled aluminum in Examples 1 to 5 and Comparative Examples 1 to 2, and please refer to Table 2 for the performance test results.

[0137] Table 1. Composition and content of aluminum alloys in Examples 1 to 5 and Comparative Examples 1 to 2

[0138]

[0139] For the sake of simplicity, the content of trace elements such as impurities in the comparative examples and embodiments is not shown.

[0140] A domestically produced CSS-44100 electronic universal tensile testing machine was used to process and test the specimens according to the specifications of the "Metallic Materials - Tensile Testing at Room Temperature" (GB / T228-2002) and the "Metallic Materials - Tensile Testing at High Temperature" (GB4338-2006-T). The processed specimens were polished using 800# and 1500# wet sandpaper. The tensile force of the machine was 2 kN, and the tensile speed was 2 mm / min. Three specimens were tested under the same conditions, and the average value was taken.

[0141] Table 2 shows the performance test results of the aluminum alloys in Examples 1 to 5 and Comparative Examples 1 to 2.

[0142]

[0143] The tensile strength, yield strength, and elongation of the heat-free die-cast aluminum alloys based on recycled aluminum in Examples 1 to 5 are significantly greater than those in Comparative Examples 1 to 2. This indicates that the heat-free die-cast aluminum alloys based on recycled aluminum of the present invention have superior properties. Specifically, the Mn content in Examples 1 to 5 is higher than that in Comparative Examples 1 to 2, the Zn content in Examples 1 to 5 is higher than that in Comparative Examples 1 to 2, and the Ti content in Examples 1 to 5 is higher than that in Comparative Examples 1 to 2. This demonstrates that increasing the Mn, Zn, and Ti content in Examples 1 to 5 allows for the interaction of these elements, resulting in heat-free die-cast aluminum alloys based on recycled aluminum with superior performance.

[0144] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the content of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing a heat-treatment-free recycled-aluminum-based die-casting aluminum alloy, comprising the following steps: providing recycled aluminum; performing a heating treatment on the recycled aluminum to obtain a recycled aluminum liquid; performing an assay on the recycled aluminum liquid to obtain elements and contents of the recycled aluminum liquid; calculating amounts of Si, Cu, Mn, Mg, Zn, Ti, Sr, RE and B to be added to the recycled aluminum liquid according to the elements and contents of the recycled aluminum liquid and preset elements and contents of the heat-treatment-free recycled-aluminum-based die-casting aluminum alloy; adding Si, Cu, Mn, Mg, Zn, Ti, Sr, RE and B to the recycled aluminum liquid to perform a second heating treatment to obtain an alloy liquid; performing a refining treatment, electromagnetic stirring, skimming treatment and die-casting treatment on the alloy liquid to obtain an aluminum alloy part; and performing a low-temperature quenching treatment on the aluminum alloy part to obtain the heat-treatment-free recycled-aluminum-based die-casting aluminum alloy, wherein the heat-treatment-free recycled-aluminum-based die-casting aluminum alloy contains Al, and further contains Si with a mass percentage of 6-9%, Fe with a mass percentage of 0.3-0.6%, Cu with a mass percentage of 0.01-0.4%, Mn with a mass percentage of 0.01-0.8%, Mg with a mass percentage of 0.01-0.5%, Zn with a mass percentage of 0.01-0.5%, Ti with a mass percentage of 0.01-0.2%, RE with a mass percentage of 0-0.1%, Sr with a mass percentage of 0-0.05% and B with a mass percentage of 0-0.01%, the low-temperature quenching treatment is performed at a temperature of -150-0°C for a time of 0.1-10h. The low-temperature quenching treatment is performed at a temperature of -140-0°C for a time of 0.1-10h. The heat-treatment-free recycled-aluminum-based die-casting aluminum alloy contains Si with a mass percentage of 7-9%, Fe with a mass percentage of 0.3-0.5%, Cu with a mass percentage of 0.1-0.3%, Mn with a mass percentage of 0.3-0.7%, Mg with a mass percentage of 0.2-0.4%, Zn with a mass percentage of 0.2-0.4%, Ti with a mass percentage of 0.1-0.2%, RE with a mass percentage of 0-0.1%, Sr with a mass percentage of 0.005-0.05% and B with a mass percentage of 0.005-0.01%. In the recycled aluminum liquid, the mass ratio of Mn to Fe is 0.5-2:

1. The method further comprises a step of adding at least one of Co, Be and Ca to the recycled aluminum liquid, wherein at least one of the following conditions is met: the mass percentage of Co in the heat-treatment-free recycled-aluminum-based die-casting aluminum alloy is 0-0.1%; the mass percentage of Be in the heat-treatment-free recycled-aluminum-based die-casting aluminum alloy is 0-0.1%; and the mass percentage of Ca in the heat-treatment-free recycled-aluminum-based die-casting aluminum alloy is 0-0.1%. ​ ​ ​ 2. The method of producing a heat-treatment-free pressure die cast aluminium alloy based on secondary aluminium according to claim 1, characterized in that, ​ 3. The method of producing a heat-treat-free pressure die cast aluminium alloy based on secondary aluminium according to claim 1, characterized in that, ​ 4. The method of producing a heat-treat-free pressure die cast aluminium alloy based on secondary aluminium according to claim 1, characterized in that, ​ 5. The method of producing a heat-treat-free pressure die cast aluminium alloy based on secondary aluminium according to claim 1, characterized in that, ​ ​ ​ ​ 6. The method of producing a heat-treatable die casting aluminium alloy based on secondary aluminium according to claim 5, characterized in that The mass ratio of Co to Fe in the recycled aluminum liquid is 0.2-1:

1.

7. The method of producing a heat-treat-free pressure die cast aluminium alloy based on secondary aluminium according to claim 1, characterized in that, The method further comprises a step of adding C to the recycled aluminum liquid, wherein the content of C in the recycled aluminum-based heat-treatment-free die-casting aluminum alloy is 0-0.05% by mass.

8. Process for the production of a heat-treatment-free, reground aluminium-based die-casting aluminium alloy according to any one of claims 1 to 7, characterized in that, The method further comprises a step of adding at least one of Nb, Ni, Te, In, Mo, Ag, Cd, V, Sn, Zr, Sb, and Bi to the recycled aluminum liquid, wherein at least one of the following conditions is satisfied: The content of Nb in the recycled aluminum-based heat-treatment-free die-casting aluminum alloy is 0-0.1% by mass; The content of Ni in the recycled aluminum-based heat-treatment-free die-casting aluminum alloy is 0-0.2% by mass; The content of Te in the recycled aluminum-based heat-treatment-free die-casting aluminum alloy is 0-0.1% by mass; The content of In in the recycled aluminum-based heat-treatment-free die-casting aluminum alloy is 0-0.1% by mass; The content of Mo in the recycled aluminum-based heat-treatment-free die-casting aluminum alloy is 0-0.2% by mass; The content of Ag in the recycled aluminum-based heat-treatment-free die-casting aluminum alloy is 0-0.1% by mass; The content of Cd in the recycled aluminum-based heat-treatment-free die-casting aluminum alloy is 0-0.05% by mass; The content of V in the recycled aluminum-based heat-treatment-free die-casting aluminum alloy is 0-0.2% by mass; The content of Sn in the recycled aluminum-based heat-treatment-free die-casting aluminum alloy is 0-0.08% by mass; The content of Zr in the recycled aluminum-based heat-treatment-free die-casting aluminum alloy is 0-0.2% by mass; The content of Sb in the recycled aluminum-based heat-treatment-free die-casting aluminum alloy is 0-0.2% by mass; The content of Bi in the recycled aluminum-based heat-treatment-free die-casting aluminum alloy is 0-0.2% by mass.

9. A recycled aluminum-based heat-treatment-free die-casting aluminum alloy prepared by the method of any one of claims 1 to 8.

10. A structural member, characterized by At least part of the structural member is made of the recycled aluminum-based heat-treatment-free die-casting aluminum alloy prepared by the method of any one of claims 1 to 8 or the recycled aluminum-based heat-treatment-free die-casting aluminum alloy of claim 9.

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