High-strength Al-Si-Mg series die-casting aluminum alloy and preparation method and structural part thereof

Abstract

The invention provides a high-strength Al-Si-Mg series die-casting aluminum alloy, a preparation method thereof and a structural part. The high-strength Al-Si-Mg series die-casting aluminum alloy contains Al, the high-strength aluminum alloy material is characterized by further comprising, by mass, 6%-8% of Si, 1.2%-1.8% of Mg, 0.01%-2.5% of Ni, 0.01%-0.4% of Fe, 0.01%-0.5% of Cr, 0.06%-0.25% of Ti, 0%-0.05% of Sr, 0%-0.3% of Zr and 0%-0.1% of Cu. The tensile strength of the high-strength Al-Si-Mg series die-casting aluminum alloy is not lower than 400 MPa, the yield strength is not lower than 310 MPa, and the elongation is not lower than 4%.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and particularly to a high-strength Al-Si-Mg series die-casting aluminum alloy, a preparation method thereof, and a structural member. Background Art

[0002] Die-casting aluminum alloys have good comprehensive properties, such as high strength, low density, excellent mechanical properties, easy machining and cutting, etc., and are widely used in the fields of aerospace and military industry, new energy vehicles, consumer electronic products, household and industrial electrical appliances, and high-rise buildings.

[0003] For aluminum-silicon series die-casting aluminum alloys, with the increase of the silicon element content, the fluidity and density of the aluminum alloy gradually increase, and the forming performance and mechanical properties gradually improve. However, the addition of the silicon element does not greatly improve the strength of the die-casting aluminum alloy, resulting in the strength of the existing aluminum-silicon series die-casting aluminum alloys being difficult to meet the requirements. Summary of the Invention

[0004] In view of the above-mentioned defects of the prior art, the present invention provides a high-strength Al-Si-Mg series die-casting aluminum alloy.

[0005] The present invention provides a high-strength Al-Si-Mg series die-casting aluminum alloy, which contains Al, and also contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Ni with a mass percentage content of 0.01-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.01-0.5%, Ti with a mass percentage content of 0.06-0.25%, Sr with a mass percentage content of 0-0.05%, Zr with a mass percentage content of 0-0.3%, SiC with a mass percentage content of 0-35%, and Cu with a mass percentage content of 0-0.1%.

[0006] Further, the high-strength Al-Si-Mg series die-casting aluminum alloy also contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Ni with a mass percentage content of 0.1-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.01-0.5%, Ti with a mass percentage content of 0.06-0.25%, Sr with a mass percentage content of 0.01-0.05%, Zr with a mass percentage content of 0.01-0.3%, SiC with a mass percentage content of 1-15%, and Cu with a mass percentage content of 0.001-0.1%.

[0007] Further, the high-strength Al-Si-Mg series die-casting aluminum alloy further contains Co with a mass percentage content of 0.01-0.5% and Mn with a mass percentage content of 0.01-0.5%. Among them, the sum of the mass percentage contents of Fe, Cr, Co and Mn is 0.04-1%.

[0008] Further, the high-strength Al-Si-Mg series die-casting aluminum alloy further contains Sn with a mass percentage content of 0.01-0.3%, Sb with a mass percentage content of 0.01-0.3%, Zn with a mass percentage content of 0.01-0.6%, and Bi with a mass percentage content of 0.01-0.3%. The sum of the mass percentage contents of Sn, Sb, Zn, Fe and Bi is 0.05-1.2%, and the mass ratio of the sum of the mass percentage contents of Sn, Sb, Zn, Fe and Bi to the mass percentage content of Mg is 0.1-1:1.

[0009] Further, the high-strength Al-Si-Mg series die-casting aluminum alloy further contains at least one of Cd, Ca, Be, V, B, RE, Ge, Mo, Nb, Te, Ag, In, AlTiB, BN, and AlTiC. Among them, the mass percentage content of Cd is 0-0.2%, the mass percentage content of Ca is 0-0.2%, the mass percentage content of Be is 0-0.2%, the mass percentage content of V is 0-0.2%, the mass percentage content of B is 0-0.1%, the mass percentage content of RE is 0-0.2%, the mass percentage content of Ge is 0-0.1%, the mass percentage content of Mo is 0-0.2%, the mass percentage content of Nb is 0-0.1%, the mass percentage content of Te is 0-0.1%, the mass percentage content of Ag is 0-0.1%, the mass percentage content of In is 0-0.2%, the mass percentage content of AlTB is 0-1%, the mass percentage content of BN is 0-1%, and the mass percentage content of AlTiC is 0-1%.

[0010] The present invention also provides a preparation method of a high-strength Al-Si-Mg series die-casting aluminum alloy, comprising the following steps: Providing a Si source, a Mg source, a Ni source, an Fe source, a Cr source, a Ti source, a Sr source, a Zr source, a SiC source, a Cu source, and an Al source; Performing a heat treatment on the Al source to obtain molten aluminum; Adding the Si source, the Mg source, the Ni source, the Fe source, the Cr source, the Ti source, the Sr source, the Zr source, the SiC source, and the Cu source to the molten aluminum to obtain a mixed liquid; and The mixed solution is subjected to die-casting treatment and aging treatment to obtain the high-strength Al-Si-Mg series die-casting aluminum alloy. Among them, the high-strength Al-Si-Mg series die-casting aluminum alloy contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Ni with a mass percentage content of 0.01-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.01-0.5%, Ti with a mass percentage content of 0.06-0.25%, Sr with a mass percentage content of 0-0.05%, Zr with a mass percentage content of 0-0.3%, SiC with a mass percentage content of 0-35%, and Cu with a mass percentage content of 0-0.1%.

[0011] Further, the die-casting treatment is high-pressure casting. In the high-pressure casting, the temperature is 600-670 °C, the low-speed injection speed is 0.23-0.3 m / s, and the high-speed injection speed is 2-2.5 m / s; or The die-casting treatment is semi-solid die-casting treatment. In the semi-solid die-casting treatment, the temperature of the mixed solution is 580-610 °C, the stirring speed is 550-700 r / min, the stirring duration is 4-10 min, the solid fraction is 35-50%, the injection speed is 0.4-1.5 m / s, the mold temperature is 220-240 °C, and the air pressure in the mold cavity is 30-50 kPa.

[0012] Further, the temperature of the aging treatment is 170-250 °C, and the time is 0.05-30 h; or The aging treatment includes the first-stage aging treatment, the second-stage aging treatment, the third-stage aging treatment, and the fourth-stage aging treatment. The temperature of the first-stage aging treatment is 80-120 °C, and the time is 3-20 h; the temperature of the second-stage aging treatment is -200~-100 °C, and the time is 0.5~10 h; the temperature of the third-stage aging treatment is 170-250 °C, and the time is 0.05-5 h. After the second-stage aging treatment, the temperature is adjusted to 170-250 °C within 1-5 min; the fourth-stage aging treatment is natural aging treatment or water-cooling aging treatment; or The aging treatment includes the first-stage low-temperature electric field aging treatment and the second-stage high-temperature aging treatment. Among them, the temperature of the first-stage low-temperature electric field aging treatment is 50-130 °C, the time is 0.1-100 h, and the electric field strength is 2-50 kV / cm; the temperature of the second-stage high-temperature aging treatment is 170-250 °C, and the time is 0.05-30 h.

[0013] Further, the preparation method of the high-strength Al-Si-Mg series die-casting aluminum alloy further includes the step of adding at least one of Co source, Mn source, Sn source, Sb source, Zn source, Fe source, Bi source, Cd source, Ca source, Be source, V source, B source, RE source, Ge source, Mo source, Nb source, Te source, Ag source, In source, AlTiB source, BN source, and AlTiC source to the aluminum liquid. Among them, the mass percentage content of Co is 0.01-0.5%, the mass percentage content of Mn is 0.01-0.5%, the mass percentage content of Sn is 0.01-0.5%, the mass percentage content of Sb is 0.01-0.5%, the mass percentage content of Zn is 0.01-0.6%, the mass percentage content of Bi is 0.01-0.5%, the mass percentage content of Cd is 0-0.2%, the mass percentage content of Ca is 0-0.2%, the mass percentage content of Be is 0-0.2%, the mass percentage content of V is 0-0.2%, the mass percentage content of B is 0-0.1%, the mass percentage content of RE is 0-0.2%, the mass percentage content of Ge is 0-0.1%, the mass percentage content of Mo is 0-0.2%, the mass percentage content of Nb is 0-0.1%, the mass percentage content of Te is 0-0.1%, the mass percentage content of Ag is 0-0.1%, the mass percentage content of In is 0-0.2%, the mass percentage content of AlTB is 0-1%, the mass percentage content of BN is 0-1%, and the mass percentage content of AlTiC is 0-1%.

[0014] The present invention also provides a structural member, the material of which is the high-strength Al-Si-Mg series die-casting aluminum alloy, or the high-strength Al-Si-Mg series die-casting aluminum alloy prepared by the preparation method of the high-strength Al-Si-Mg series die-casting aluminum alloy.

[0015] In the technical solution of the present invention, the high-strength Al-Si-Mg series die-casting aluminum alloy contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Ni with a mass percentage content of 0.01-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.01-0.5%, Ti with a mass percentage content of 0.06-0.25%, Sr with a mass percentage content of 0-0.05%, Zr with a mass percentage content of 0-0.3%, SiC with a mass percentage content of 0-35%, and Cu with a mass percentage content of 0-0.1%. The elements with the above contents interact with each other and affect each other, so that the high-strength Al-Si-Mg series die-casting aluminum alloy has both better yield strength and tensile strength. The tensile strength of the high-strength Al-Si-Mg series die-casting aluminum alloy is not lower than 400 MPa, the yield strength is not lower than 310 MPa, and the elongation is not lower than 4%. Detailed implementation mode

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0017] An embodiment of the present invention provides a high-strength Al-Si-Mg series die-casting aluminum alloy. The high-strength Al-Si-Mg series die-casting aluminum alloy has better tensile strength and yield strength and is suitable for being made into structural parts with higher strength requirements.

[0018] The high-strength Al-Si-Mg series die-casting aluminum alloy contains Al, and also contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Ni with a mass percentage content of 0.01-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.01-0.5%, Ti with a mass percentage content of 0.06-0.25%, Sr with a mass percentage content of 0-0.05%, Zr with a mass percentage content of 0-0.3%, SiC with a mass percentage content of 0-35%, and Cu with a mass percentage content of 0-0.1%.

[0019] The mass percentage content of Si can specifically be 6%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9%, or 8%.

[0020] The mass percentage content of Mg can specifically be 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, or 1.8%.

[0021] The mass percentage content of Ni can specifically be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 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%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, or 2.5%.

[0022] The mass percentage content of Fe can specifically be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 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%, or 0.4%.

[0023] The mass percentage content of Cr can specifically be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 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%, or 0.5%.

[0024] The mass percentage content of Ti can specifically be 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, or 0.25%.

[0025] The mass percentage content of Sr can specifically 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%.

[0026] The mass percentage content of Zr can specifically be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, or 0.3%.

[0027] The mass percentage content of SiC can specifically be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, 20.5%, 21%, 21.5%, 22%, 22.5%, 23%, 23.5%, 24%, 24.5%, 25%, 25.5%, 26%, 26.5%, 27%, 27.5%, 28%, 28.5%, 29%, 29.5%, 30%, 30.5%, 31%, 31.5%, 32%, 32.5%, 33%, 33.5%, 34%, 34.5%, or 35%.

[0028] The mass percentage content of Cu may specifically 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%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%.

[0029] In an embodiment, the high-strength Al-Si-Mg series die-casting aluminum alloy further contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Ni with a mass percentage content of 0.1-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.01-0.5%, Ti with a mass percentage content of 0.06-0.25%, Sr with a mass percentage content of 0.01-0.05%, Zr with a mass percentage content of 0.01-0.3%, SiC with a mass percentage content of 1-15%, and Cu with a mass percentage content of 0.001-0.1%.

[0030] It can be understood that the Al-Si-Mg series die-casting aluminum alloy further contains impurities, where the mass percentage content of a single impurity is less than 0.02%, and the sum of the mass percentage contents of the impurities is less than 0.1%.

[0031] In the technical solution of the present invention, the Al-Si-Mg series high thermal conductivity aluminum alloy contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Ni with a mass percentage content of 0.01-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.01-0.5%, Ti with a mass percentage content of 0.06-0.25%, Sr with a mass percentage content of 0-0.05%, Zr with a mass percentage content of 0-0.3%, SiC with a mass percentage content of 0-35%, and Cu with a mass percentage content of 0-0.1%. Si, Mg, Ni, Fe, Cr, Ti, Sr, Zr, SiC, and Cu within the above content ranges interact with each other as a whole, ensuring that the Al-Si-Mg series has better yield strength and tensile strength. Specifically as follows: (1) When the mass percentage content of Si is 6-8%, Si can improve the fluidity and density of the aluminum alloy, thereby improving the forming performance and mechanical properties of the aluminum alloy. When the mass percentage content of Si is 6-8%, the improvement of strength is not obvious; when the Si content exceeds 8%, coarse elemental Si will appear, sharply reducing the elongation rate of the aluminum alloy; (2) The mass percentage content of Mg is 1.2 - 1.8%. Mg can significantly improve the mechanical properties of aluminum alloys. Mg can react with other elements to form secondary phases, avoiding adverse effects on the elongation rate of aluminum alloys. Mg can react with Al, Fe, Si, Cu, Zn, B, Ni, etc. to form secondary phases such as MgB, Mg2Si, Mg2Zn, Mg2SiZn, (CuMg)Al2, AlFeMgSi, AlFeMgSiNi, etc. However, Mg with a mass percentage content of 1.2 - 1.8% will sharply reduce the elongation rate of aluminum alloys. (3) The mass percentage content of Ni is 0.01 - 2.5%. Ni can refine grains, secondary phases and precipitation phases to improve the elongation rate of aluminum alloys. Ni can react with other elements to form secondary phases to avoid adverse effects on the elongation rate of aluminum alloys when the content of Ni dissolved in the aluminum matrix is relatively high. Specifically, Ni can react with Al, Fe, Mg, Si, etc. to form secondary phases such as Al3Ni, AlFeSiNi, AlFeMgSiNi, FeNiAl9, etc., avoiding adverse effects on the elongation rate when the contents of Mg and Ni are too high. Ni can also promote the precipitation of phases such as CuAl2, Mg2Si, (CuMg)Al2, etc., increasing the volume fraction and dispersion degree of the precipitation phases, reducing the solid solubility of alloying elements in the aluminum matrix to improve the elongation rate of aluminum alloys. Ni and Cu and Mg can promote each other's precipitation to improve the strength and elongation rate of aluminum alloys. The content of Mg and the content of Ni can be proportional. When the content of Mg is high, the content of Ni can also be set relatively high to form more AlFeMgSiNi secondary phases with a dispersed distribution, significantly improving the strength of aluminum alloys. (4) The mass percentage content of Fe is 0.01 - 0.4%. On the one hand, Fe can reduce the mold sticking tendency of aluminum alloy castings and improve the mechanical properties of aluminum alloys. On the other hand, Fe can react with other elements as much as possible to form secondary phases to avoid adverse effects on the elongation rate of aluminum alloys caused by Fe dissolved in the aluminum matrix. Specifically, Fe can react with Al, Si, Mg, Cu, Mn, Ni, etc. to form secondary phases such as Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu, AlFeSiNi, AlFeMgSiNi, AlFeMnSi, (CrFe)Al7, (CrMn)Al 12 and AlFeSiB, FeNiAl9, etc. (5) The mass percentage content of Cr is 0.01 - 0.5%. Cr can form (CrFe)Al7 and (CrMn)Al in aluminum 12Intermetallic compounds such as these have a certain strengthening effect on aluminum alloys; Cr can also improve the toughness of aluminum alloys and reduce the sensitivity to stress corrosion cracking; Cr can also improve the morphology of Fe, transform the β-Fe phase into the α-Fe phase, and reduce the splitting effect of the β-Fe phase on the aluminum matrix when it cannot be dissolved, thereby increasing the elongation of the aluminum alloy; an appropriate amount of Cr forms various fine chromium-containing compounds in as-cast aluminum alloys, which can dissolve in the α phase during the die-casting stage and can precipitate various Cr-containing phases during the aging stage. These Cr-containing phases can serve as the nuclei for the heterogeneous nucleation of the β" phase, thereby accelerating the formation of the β" phase. The precipitation of these Cr-containing phases in the aluminum matrix will necessarily have a certain delaying effect on the formation of metastable phases precipitated at the grain boundaries, thereby increasing the elongation of the aluminum alloy; Cr can also significantly improve the microstructure and phase distribution of the original alloy, forming some Cr-rich multi-phases. The changes and distribution of these phases can increase the strength of the aluminum alloy; (6)The mass percentage content of Ti is 0.06 - 0.25%. Ti can increase the strength and elongation of aluminum alloys. Specifically, the TiAl3 phase formed by the reaction of Ti and Al can serve as a non-spontaneous nucleus during crystallization, refine the grains, secondary phases, and precipitation phases, thereby increasing the strength and elongation of aluminum alloys; (7)The mass percentage content of Sr is 0 - 0.05%. Sr can be used for modification treatment through the heterogeneous nucleation theory or the twin trough mechanism to refine secondary phases such as eutectic silicon and increase the strength and elongation of aluminum alloys; Sr can also transform the β-Fe phase in the ingot into the α-Fe phase to reduce the splitting effect of the β-Fe phase on the aluminum matrix when it cannot be dissolved, thereby increasing the elongation of the aluminum alloy; Sr can preferentially combine with elements such as Fe, Cu, Mn, Cr, and Si to form dispersion strengthening to avoid the adverse effect of Sr dissolved in the aluminum matrix on the elongation of aluminum alloys; Sr can also promote the precipitation of phases such as CuAl2, AlFeSi, AlFeSiNi, and Mg2Si to reduce the solid solubility of these alloying elements in the aluminum matrix to increase the elongation of aluminum alloys; (8)The mass percentage content of Zr is 0 - 0.3%. Zr can increase the strength of aluminum alloys; Zr can also form the Al3Zr phase in aluminum alloys. The Al3Zr phase can refine the grains, secondary phases, and precipitation phases, thereby increasing the elongation of aluminum alloys; (9)The mass percentage content of SiC is 0 - 35%. SiC can form a dispersed phase in aluminum alloys and form a strong interfacial bond with the aluminum matrix, thereby effectively increasing the strength and elongation of the alloy; SiC also has a better refining effect, further increasing the elongation of aluminum alloys; The mass percentage content of Cu is 0 - 0.1%. The solution strengthening of Cu in the aluminum matrix can improve the strength of the aluminum alloy; when the mass percentage content of Cu is not more than 0.1%, the elongation rate of the aluminum alloy can be significantly improved; trace Cu can also reduce the natural aging rate, thereby reducing the adverse effects of the parking effect on the alloy.

[0032] In order to avoid the adverse effect of Si on the elongation, the mass percentage content of Si is set to 6-8% (preferably 6-7.5%) in the present invention, but the mass percentage content of Si of 6-8% does not significantly improve the strength of the aluminum alloy; the mass percentage content of Mg is correspondingly set to 1.2-1.8% (preferably 1.4-1.6%), the mass percentage content of Ni is set to 0.01-2.5% (preferably 0.5-2%), the mass percentage content of Zr is 0-0.3%, and the mass percentage content of SiC is 0-35%, and the strength of the aluminum alloy is greatly improved by Mg, Ni, Zr, and SiC, but the mass percentage content of Mg is set to 1.2-1.8%, which will greatly reduce the elongation of the aluminum alloy; in order to improve the elongation of the aluminum alloy, the mass percentage content of Fe and Cu is set to be relatively low, 0.01-0.4% (preferably 0.1-0.2%) and 0-0.1% (preferably 0.001-0.05%), respectively, to avoid high The Fe content affects the elongation of the aluminum alloy, and the elongation of the aluminum alloy is improved by a low content of Cu; the present invention also comprises 0.01-0.5% by mass Cr, 0.06-0.25% by mass Ti, 0.01-2.5% by mass Ni, 0-0.3% by mass Zr, 0-35% by mass SiC, and 0-0.05% by mass Sr (preferably 0.01-0. 05%), can refine the grains, second phase and precipitation phase to improve the strength and elongation of aluminum alloy; when the Fe content is not high, Cr with a mass percentage of 0.01-0.5% can also improve the demolding performance of aluminum alloy; Zn, Cr, Ni, Sr can also promote the precipitation of Mg2Si, MgZn2, Mg2SiZn, Al2Cu, etc., further improving the elongation and mechanical properties of aluminum alloy; the above elements can also react with each other to form a second phase to avoid solid solution in the aluminum matrix to affect the elongation of aluminum alloy. In this way, Si, Mg, Ni, Fe, Cr, Ti, Sr, Zr, SiC, and Cu in the above content range interact with each other as a whole, which can make the aluminum alloy elements have better strength, elongation, and demolding performance. Moreover, under the further action of subsequent refining treatment, aging treatment and die-casting treatment, the solid solubility of each element in the aluminum matrix of Si, Mg, Zn, Fe, Cr, Ti, Sr, and Cu within the above-mentioned content range is further reduced, and the impurity elements are also further reduced, which can eliminate the adverse effects of alloy elements and impurity elements on the strength and elongation of the aluminum alloy as much as possible, and the second phase (such as Al3Fe, Mg2Si, Al2Cu, AlFeSiNi, AlMnSi phases, etc.) can also be refined in the aluminum matrix and at the grain boundaries or within the grain boundaries, thereby greatly improving the strength and elongation of the aluminum alloy.

[0033] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains Co with a mass percentage content of 0.01-0.5% and Mn with a mass percentage content of 0.01-0.5%. Among them, the sum of the mass percentage contents of Fe, Cr, Co and Mn is 0.04-1%, specifically, it can be 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%.

[0034] The mass percentage contents of Co and Mn can specifically be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 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%, or 0.5%.

[0035] The sum of the mass percentage contents of Fe, Cr, Co and Mn can specifically be 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 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% or 1%.

[0036] Co can refine grains to improve the mechanical properties of aluminum alloy; Co can also react with other elements as much as possible to generate the second phase to improve the mechanical properties of aluminum alloy. Specifically, Co can react with Al, Fe, Si, etc. to generate second phases such as Al 15 (Fe,Co)3Si2, Al3(Fe,Co), etc.; The refinement effect of Co on the Al3Fe phase can transform the coarse needle-like and flaky β-Al3Fe phase into small flower-like and fine strip-like α-Al 15 (Fe,Co)3Si2 phase, and can also promote the precipitation of α-Al 15 (Fe,Co)3Si2 phase, further improving the mechanical properties of aluminum alloy.

[0037] Mn can react with Fe to form fine and dispersed α-Al(FeMn)Si phases, thereby improving and regulating the β-Fe-rich phase; Mn can significantly refine the 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 and enhance the strength and elongation of the aluminum alloy. Mn can form independent Mn-rich hardening phases of Al6Mn and Al6FeMn in the aluminum alloy. The Mn-rich phases are distributed at or near the grain boundaries to pin the grain boundaries. Although the coherence between the Mn-rich phases and the Al matrix is relatively low and their sizes are relatively large, and the ability to pin dislocations is weak, the combined addition of Mn and Zr can not only reduce the usage amounts of each alloying element, but also promote the mutual precipitation to form more amounts of Al6(Mn,Zr) phases, Al3(Zr,Mn) phases and Al6(FeMnZr) phases, and the strengthening effect is much greater than that when Mn or Zr is added alone.

[0038] To avoid the influence of Fe on the elongation of the aluminum alloy, the mass percentage content of Fe can be set relatively low. To ensure the demolding performance of the aluminum alloy, the sum of the mass percentage contents of Fe, Cr, Co and Mn can be 0.04 - 1%, preferably 0.3 - 0.6%. When the contents of Fe and / or Cr are relatively low, smooth demolding can also be achieved. When the surface of the mold is treated to form a boron carbide layer on the parting surface of the mold, the mass percentage content of Fe can be 0.01 - 0.1% (preferably 0.01 - 0.06%), and the sum of the mass percentage contents of Fe and Mn can be 0.02 - 0.1%, specifically 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09% or 0.1%.

[0039] When the surface of the mold is treated to form a boron carbide layer on the parting surface of the mold, if Co and Mn are further combined, the demolding performance of the aluminum alloy can be further improved. At this time, the sum of the mass percentage contents of Fe, Cr, Co and Mn is 0.04 - 0.5%, preferably 0.05 - 0.3%, and further preferably 0.05 - 0.1%. In this way, better demolding performance can be achieved, and the influence of excessive element addition on the elongation can be avoided.

[0040] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains Sn with a mass percentage content of 0.01-0.3%, Sb with a mass percentage content of 0.01-0.3%, Zn with a mass percentage content of 0.01-0.6%, and Bi with a mass percentage content of 0.01-0.3%. The sum of the mass percentage contents of Sn, Sb, Zn, Fe, and Bi is 0.05-1.2%, and the mass ratio of the sum of the mass percentage contents of Sn, Sb, Zn, Fe, and Bi to the mass percentage content of Mg is 0.1-1:1.

[0041] The mass percentage contents of Sn, Sb, and Bi can specifically be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 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 mass percentage content of Zn can specifically be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 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%.

[0043] The sum of the mass percentage contents of Sn, Sb, Zn, Fe and Bi can specifically be 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 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%.

[0044] The mass ratio of the sum of the mass percentage contents of Sn, Sb, Zn, Fe and Bi to the mass percentage content of Mg 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.

[0045] Sn, Sb, Zn, Fe and Bi can all react with Mg to form the second phase. Mg preferentially reacts with Si to form the Mg2Si phase, and then reacts with Sn, Sb, Zn, Fe and Bi to form second phases such as Mg2Sn, AlFeMgSiNi, Mg3Sb2, MgZn2, Mg2ZnSi, Mg3Bi2, etc., which can avoid the adverse effect of Mg dissolved in the aluminum matrix on the elongation of the aluminum alloy. When the sum of the mass percentage contents of Sn, Sb, Zn, Fe and Bi is 0.05 - 1.2%, and the mass ratio of the sum of the mass percentage contents of Sn, Sb, Zn, Fe and Bi to the mass percentage content of Mg is 0.1 - 1:1, it can ensure that all or nearly all of Mg reacts with other alloying elements to form the second phase, avoiding the existence of Mg dissolved in the aluminum matrix, and at the same time avoiding the influence of the addition of too many elements on the elongation of the aluminum alloy. Specifically: Sn can react with Mg to form round spherical and dispersed Mg2Sn strengthening phases, which can reduce the solid solubility of Mg and Sn in the aluminum matrix. Sn can also react with other elements to form the second phase, thereby improving the mechanical properties of the aluminum alloy. Sn can specifically form various high-temperature strengthening phases such as Al9Sn7, Al6Sn5, Al5Sn2, Al3Sn4, etc. with Al.

[0046] Sb can be used as a modifier in aluminum alloys, effectively reducing the size of eutectic silicon lamellae, greatly reducing the possibility of Si splitting the matrix, and improving the mechanical properties of the alloy; Sb can react with other elements such as Mg to form the second phase Mg3Sb2, further improving the mechanical properties of the alloy; in addition, the addition of Sb can also improve the mutual precipitation of elements such as Cu, Zn, Ni, etc. with large solid solubility in the alloy matrix, further improving the mechanical properties of the alloy.

[0047] Bi expands during solidification, which is beneficial for feeding. It can form strengthening phases such as Mg3Bi2 and Mg3(BiCd)2 with Mg and Cd, etc., to improve the mechanical properties of the alloy.

[0048] Zn can be dissolved in the aluminum matrix to significantly improve the strength of the aluminum alloy through solid solution strengthening. After aging treatment, the precipitated elemental Zn can further enhance the strength of the aluminum alloy; moreover, elemental Zn is a non-brittle phase between grain boundaries, which can increase the elongation of the aluminum alloy; Zn can increase the eutectic structure of the aluminum alloy and improve its fluidity, making the aluminum alloy suitable for die-casting; Zn can eliminate elemental Si to reduce the adverse effects of elemental Si on the properties of the aluminum alloy. Zn can also promote the precipitation of phases such as Mg2Si and Al2Cu, improving the mechanical properties; in addition, Zn can react with other elements to form a second phase to avoid the adverse effects of Zn dissolved in the aluminum matrix on the elongation of the aluminum alloy. Specifically, Zn can react with Al, Mg, Cu, and Si, etc., to form second phases such as MgZn2, Mg2SiZn, and Al2CuZn.

[0049] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains RE with a mass percentage content of 0 - 0.2%, Mo with a mass percentage content of 0 - 0.2%, and Be with a mass percentage content of 0 - 0.2%. RE is at least one of La, Ce, Pr, Nd, Er, Sm, Y, and Gd.

[0050] The specific mass percentage contents of RE, Mo, and Be 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%, 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%.

[0051] The elements Mn, Cr, RE, Mo, Co, Be, and Sr cooperate with each other, which can not only reduce their maximum solid solubility in the aluminum matrix to improve the mechanical properties, but also promote the reaction between Mn and Fe. Mn can occupy the position of Fe element in the second phase, making the Fe-containing phase more dispersed and fine, and promoting the effect of modifying Fe. Between the elements Mn, Cr, RE, Mo, Co, Be, and Sr, a fine and dispersed ɑ-Al(MnFeX)Si phase (where X is at least one of Cr, RE, Mo, Co, Be, and Sr) can also be formed to increase the elongation of the aluminum alloy.

[0052] Combining Cu with a mass percentage content of 0.001 - 0.04%, RE with a mass percentage content of 0.001 - 0.2%, and Zr with a mass percentage content of 0.001 - 0.3% can significantly improve the degree of dispersion distribution of Mg2Si, and at the same time prevent the formation of coarse phases such as AlSiFe, Mg3Sb2, Mg2Sn, MgZn2, Mg2SiZn, and Al3Zr, and reduce the solid solubility of various elements in the matrix, ensuring uniform precipitation during the solidification of the alloy; the addition of trace Cu can also reduce the anisotropy that appears after adding Mn to the alloy.

[0053] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains Cd with a mass percentage content of 0 - 0.2%. The mass percentage content of Cd can specifically 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%, 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%. Cd can improve the strength of the aluminum alloy; Cd can also refine grains, secondary phases, and precipitation phases to improve the elongation of the aluminum alloy. Cd can refine α-Al and can also form strengthening phases such as REAl2Cd3, Al3Cd, Al2Cd3, (CuCd)Al2, Mg2(SiCdREFe), and Mg3(BiCd)2 with Al, RE, Cu, Mg, Si, Fe, and Bi to reduce their solid solubility in the aluminum matrix and increase the volume fraction of the precipitation phase, thereby improving the strength and mechanical properties of the aluminum alloy. In addition, a large number of Cd-vacancy clusters will be formed during the aging stage of Cd, promoting and accelerating the precipitation of phases such as CuAl2 and Mg2Si, reducing the solid solubility of the above elements in the aluminum matrix, and further improving the strength and mechanical properties of the aluminum alloy.

[0054] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains Ca with a mass percentage of 0-0.2%. The specific mass percentage content of Ca 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%, 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%. Ca can refine the eutectic structure, improve the β-Fe phase, improve the heat treatment performance of the alloy while increasing the alloy strength, and can also form strengthening phases such as Al4Ca, Al2Ca3, AlCa2, and AlCaCu with Cu and Al, significantly increasing the strength, heat resistance, and fatigue resistance of the aluminum alloy.

[0055] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains V with a mass percentage of 0-0.2%. The specific mass percentage content of V 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%, 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 refine grains, second phases, and precipitation phases to reduce the grain boundary area and the corrosion sensitivity at the grain boundaries, thereby improving the corrosion resistance and elongation of the aluminum alloy.

[0056] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains In with a mass percentage of 0-0.2%. The specific mass percentage content of In 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%, 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 increase the strength of the aluminum alloy; In can also refine grains, second phases, and precipitation phases to increase the elongation of the aluminum alloy.

[0057] The high-strength Al-Si-Mg series die-casting aluminum alloy further contains B with a mass percentage of 0-0.1%. The specific mass percentage content of B 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%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. B can refine grains, second phases, and precipitation phases to improve the elongation of the aluminum alloy; B can react with Al, Fe, Si, Mg, Cu, etc. to form second phases such as AlFeSiB, MgB, CuB, etc., which can not only reduce the solid solubility of the above elements in the matrix and reduce the adverse effects of the above elements on elongation and thermal conductivity; in addition, B can also refine grains, modify and refine elemental Si to reduce the adverse effects of coarse elemental Si on the properties of the aluminum alloy, and can also transform the β-AlFeSi phase into the Chinese character-shaped α-AlFeSi phase to eliminate the adverse effects of the iron-rich phase on the properties of the aluminum alloy, and can inhibit the segregation of TiAl3. Therefore, the effect is better when Ti and B are used together; the boronization effect of B can also purify the aluminum alloy liquid and further improve the strength and elongation of the aluminum alloy.

[0058] The high-strength Al-Si-Mg series die-casting aluminum alloy further contains Ge with a mass percentage of 0-0.1%. The specific mass percentage content of Ge 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%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. Ge can improve the mechanical properties of the aluminum alloy; Ge can react with other elements to form second phases and improve the mechanical properties of the alloy. Specifically, Ge can react with Al and Si, etc. to form second phases such as Al9Ge7, Al6Ge5, Al5Ge2, Al3Ge4, SiGe. In addition, Ge can promote the precipitation of second phases such as Mg2Si and CuAl2, refine the precipitation phases, and reduce the solid solubility of the above elements in the aluminum matrix. Ge can also replace some Si atoms in the metastable precipitation phases, and the Si-Ge phase precipitated in the initial stage of aging provides a nucleation site for the main precipitation phases such as β" and θ", increasing the density of phases such as β" and θ" to further improve the mechanical properties of the aluminum alloy.

[0059] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains Nb with a mass percentage content of 0-0.1%. The specific mass percentage content of Nb 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%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. Nb can improve the strength of the aluminum alloy; Nb can also refine grains, secondary phases, and precipitation phases to improve the elongation rate of the aluminum alloy. When the high-strength Al-Si-Mg series die-casting aluminum alloy contains both Nb and B, strengthening metal compounds such as AlNb3, AlNb, Al3Nb, and NbB2 can be formed, significantly improving the strength of the aluminum alloy.

[0060] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains Te with a mass percentage content of 0-0.1%. The specific mass percentage content of Te 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%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. Te can modify eutectic silicon, shortening the eutectic silicon along the length direction to improve the elongation rate of the aluminum alloy; when the aluminum alloy contains both Sb and Te, fine petal-shaped primary crystals can be formed, further improving the strength and elongation rate of the aluminum alloy.

[0061] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains Ag with a mass percentage content of 0-0.1%. The specific mass percentage content of Ag 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%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. Ag can refine the secondary phase to improve the elongation rate of the aluminum alloy. Ag can promote the precipitation of secondary phases (such as Al2Cu, Mg2Si, Mg2Sb, MgZn2, Mg3Sn2, and Mg3Bi2, etc.), refine the precipitation phases and increase the precipitation phase density, enhancing the precipitation strengthening effect of the aluminum alloy, and can also refine the secondary phase to improve the elongation rate, strength, and mechanical properties of the aluminum alloy.

[0062] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains AlTiB with a mass percentage content of 0-1%, BN with a mass percentage content of 0-1%, and AlTiC with a mass percentage content of 0-1%.

[0063] The mass percentage contents of AlTiB, BN, and AlTiC can specifically be 0.1%, 0.15%, 0.2%, 0.25%, 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%, or 1%.

[0064] When AlTiB and SiC are used in combination, the mass percentage content of SiC can be reduced to 4 - 10%, thereby reducing costs. In a preferred embodiment, the mass percentage content of AlTiB is 0.3 - 0.8% of AlTiB, and the mass percentage content of SiC is 5 - 8%. Specifically, when AlTiB and SiC are used in combination, a C-TiB2 particle complex is formed at the SiC-Al interface. The C atoms in SiC tend to enhance the adhesion energy of the C-TiB2 / Al interface, causing the originally elongated TiAl3 to break and shorten, so as to avoid the enrichment and growth of TiAl3, greatly enhancing the composite refinement effect. And through multiple experimental verifications: when the mass percentage content of AlTiB is 0.1 - 0.5% and the mass percentage content of SiC is 4 - 10% are combined with each other, the strength, elongation, wear resistance, corrosion resistance, and thermal stability of the aluminum alloy can be greatly improved.

[0065] AlTiB, SiC, AlTiC, and BN all have good refinement effects. When used in combination, the respective contents can be reduced to achieve a good refinement effect. When SiC is used in combination with Ti and B, a C-TiB2 particle complex is formed at the SiC-Al interface. The C atoms in SiC tend to enhance the adhesion energy of the C-TiB2 / Al interface, causing the originally elongated TiAl3 to break and shorten, so as to avoid the enrichment and growth of TiAl3, greatly enhancing the composite refinement effect; BN is diffusely distributed with AlB2 and AlN nanonucleation at the aluminum matrix interface and grain boundaries, which can refine the grains and promote the uniform nucleation of grains to improve the elongation of the aluminum alloy; under the action of SiC, Ti, B, and BN, AlTiC is not easy to aggregate and has a good effect of fine grain strengthening.

[0066] The present invention also provides a method for preparing a high-strength Al-Si-Mg series die-casting aluminum alloy, comprising the following steps: Providing a Si source, a Mg source, a Ni source, a Fe source, a Cr source, a Ti source, a Sr source, a Zr source, a SiC source, a Cu source, and an Al source; Performing a heat treatment on the Al source to obtain molten aluminum; Adjusting the temperature of the molten aluminum to 750 - 820 °C, and adding the Si source to the molten aluminum to obtain a first mixed solution; Adjust the temperature of the first mixed solution to 720 - 740 °C, and add Si source, Mg source, Ni source, Fe source, Cr source, Ti source, Sr source, Zr source, SiC source, and Cu source to the first mixed solution to obtain a second mixed solution; Perform degassing treatment, refining treatment, and die-casting treatment on the second mixed solution to obtain an aluminum alloy part; and Perform aging treatment on the aluminum alloy part to obtain the high-strength Al-Si-Mg series die-cast aluminum alloy, wherein the high-strength Al-Si-Mg series die-cast aluminum alloy contains Si with a mass percentage content of 6 - 8%, Mg with a mass percentage content of 1.2 - 1.8%, Ni with a mass percentage content of 0.01 - 2.5%, Fe with a mass percentage content of 0.01 - 0.4%, Cr with a mass percentage content of 0.01 - 0.5%, Ti with a mass percentage content of 0.06 - 0.25%, Sr with a mass percentage content of 0 - 0.05%, SiC with a mass percentage content of 0 - 35%, Zr with a mass percentage content of 0 - 0.3%, and Cu with a mass percentage content of 0 - 0.1%.

[0067] The Si source, Mg source, Ni source, Fe source, Cr source, Ti source, Sr source, Zr source, SiC source, and Cu source can be aluminum master alloys.

[0068] In one embodiment, the die-casting treatment can be high-pressure casting, with a temperature of 600 - 670 °C, a low-speed injection speed of 0.23 - 0.3 m / s, and a high-speed injection speed of 2 - 2.5 m / s. The temperature of the die-casting treatment of the existing die-cast aluminum alloy is about 680 °C, which is relatively high. When the mixed solution is placed in the mold at this temperature, the erosion of the mold by the mixed solution is extremely large, resulting in a short service life of the mold. The melting point of the Al-Si-Mg series die-cast aluminum alloy of the present invention is relatively low, so that the temperature of the die-casting treatment of the present invention can be set relatively low, with less erosion of the mold, and the service life of the mold can be improved.

[0069] In another embodiment, the die-casting treatment can be semi-solid die-casting treatment to obtain a semi-solid die-cast aluminum alloy. In the semi-solid die-casting treatment, a device that can increase "flow + stirring" is used to improve the uniformity of the second mixed solution to obtain a semi-solid slurry. Combining with vacuum-assisted technology, the air pressure in the mold cavity is reduced to 30 - 50 kPa, and then the semi-solid slurry is injected into the mold for semi-solid die-casting forming. The temperature of the second mixed solution in the semi-solid die-casting treatment is 580 - 610 °C, the stirring speed is 550 - 700 r / min, the stirring duration is 4 - 10 min, the solid fraction is controlled at 35 - 50%, the injection speed is 0.4 - 1.5 m / s, and the mold temperature is 220 - 240 °C.

[0070] When the die-casting process is a semi-solid die-casting process, the refining process can be as follows: Mix potassium titanate whiskers and aluminum powder to obtain a mixture; Under an argon protective atmosphere, use a low-energy ball mill to crush the mixture; When mechanically stirring or electromagnetically stirring the second mixed liquid, add the mixture of potassium titanate whiskers and aluminum powder to the second mixed liquid. The addition of aluminum powder can improve the wettability of the mixture and the aluminum melt and avoid agglomeration. During the crushing process, the ball-to-material ratio is 6:1, the ball milling time is 30 - 100 minutes, and the rotation speed is 150 - 300 rpm. The addition ratio of the mixture is 3 - 10% of the mass of the second mixed liquid, specifically 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. Utilize the crystallographic orientation relationship between potassium titanate whiskers and α-Al, and by controlling the temperature and holding time of the second mixed liquid, form a titanium-rich transition layer on the surface of the potassium titanate whiskers, reduce the interfacial misfit degree, and enhance the heterogeneous nucleation ability. Potassium titanate whiskers, as a heterogeneous nucleation substrate, preferentially induce the nucleation of α-Al grains during the solidification process of aluminum alloy, significantly increasing the nucleation rate, thereby refining the grains. Potassium titanate whiskers can also inhibit grain growth. The dispersed potassium titanate whiskers limit the abnormal growth of grains through physical hindrance, and at the same time reduce the dendrite spacing, improving the uniformity of the aluminum alloy microstructure. In this way, the strength, wear resistance, and machinability of the aluminum alloy can be improved, and it is suitable for manufacturing precision components such as engine cylinder liners and bearings.

[0071] In the high-pressure die-casting or semi-solid die-casting process, the used mold includes a moving mold and a fixed mold. Both the moving mold and the fixed mold are formed with parting surfaces, and the two parting surfaces together form a cavity for accommodating the mixed melt to mold an aluminum alloy product with a certain shape. Before the die-casting process, both parting surfaces can undergo surface treatment, and the surface treatment is to form a boron carbide layer on the parting surface. The boron carbide layer can not only improve the demolding performance, but also improve the wear resistance of the mold, and can further resist the erosion of chemical substances such as acids, alkalis, and salts and the thermal erosion of aluminum alloy, thereby extending the service life of the mold. The thickness of the boron carbide layer can be 1 - 10 mm, specifically 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, or 10 mm. Through the surface treatment, the Fe content, the sum of the mass percentage contents of Fe and Cr, or the sum of the mass percentage contents of Fe, Cr, Co, and Mn can be set to be relatively low.

[0072] The surface treatment may be as follows: Mix a boron-containing gas (such as BCl3) with a carbon-containing gas (such as CH4) to obtain a mixed gas; introduce the mixed gas into the cavity, and through chemical vapor deposition, the boron-containing gas and the carbon-containing gas chemically react and deposit on the parting surface to form a boron carbide layer. The temperature of the chemical vapor deposition method is 900 - 1200 °C, the deposition pressure is 200 - 500 Pa, and the carrier gas flow rate is 100 - 200 sccm. The boron carbide layer can make the hardness of the die steel reach 3000 - 4000 Hv; the boron carbide layer can reduce the affinity of the mixed melt to the die surface, improve the demolding performance of the aluminum alloy, and smooth demolding can also be achieved even with a low content of Fe, Cr, Co, or Mn, greatly improving the elongation rate of the aluminum alloy; the boron carbide layer can resist the erosion of chemical substances such as acids, alkalis, and salts, and can improve the corrosion resistance of the aluminum alloy; the boron carbide layer can still maintain good physical and chemical properties in a high-temperature environment, and can improve the thermal stability of the aluminum alloy; the boron carbide layer has an extremely low friction coefficient, improves the surface smoothness of the aluminum alloy, and can significantly reduce the wear and energy consumption generated by mechanical friction of the aluminum alloy product; the boron carbide layer also has high heat transfer performance. At the moment when the aluminum alloy is formed, the boron carbide layer can quickly conduct away heat, improve the heat transfer speed of the die, and the heat transfer speed is 2 - 4 times that of an ordinary die, enabling the formed aluminum alloy to cool faster and the structure to be more refined, thereby improving the strength and elongation rate of the aluminum alloy.

[0073] The degassing treatment is as follows: Adjust the temperature of the second mixed liquid to 700 - 740 °C, and introduce an inert gas such as argon into the second mixed liquid using a degasser. The temperature of the degassing treatment may specifically be 700 °C, 710 °C, 720 °C, 730 °C, or 740 °C. The time of the degassing treatment is 10 - 30 min, and may specifically be 10 min, 15 min, 20 min, 25 min, or 30 min.

[0074] In another embodiment, the refining treatment is as follows: when introducing an inert gas such as argon into the second mixture by means of a degassing machine, a grain refiner can be added simultaneously. The eddy current formed by the rotating disk of the degassing machine in the second mixture can evenly disperse the grain refiner and mix it into the second mixture. The grain refiner can refine the alloy structure to improve the strength and elongation of the aluminum alloy, and has the advantages of good dispersibility and low cost. The time of the refining treatment is 10 - 30 min, specifically it can be 10 min, 15 min, 20 min, 25 min, or 30 min, and the temperature of the refining treatment is 700 - 740 °C, specifically it can be 700 °C, 710 °C, 720 °C, 730 °C, or 740 °C. The grain refiner contains: 5 - 10 parts of potassium hexafluoroaluminate, 6 - 20 parts of AlTi5B1 metal powder, 8 - 25 parts of potassium titanate whisker powder, 20 - 40 parts of sodium chloride + potassium chloride, 5 - 10 parts of potassium nitrate, 5 - 10 parts of potassium carbonate, and 0.5 - 3 parts of potassium silicate. It can be understood that this refining treatment is applicable to semi-solid die casting and high-pressure casting.

[0075] In one embodiment, the temperature of the aging treatment is 170 - 250 °C and the time is 0.05 - 30 h. The temperature of the aging treatment can specifically be 170 °C, 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, or 250 °C, and the time can specifically be 0.05 h, 1 h, 5 h, 10 h, 15 h, 20 h, 25 h, or 30 h.

[0076] In another embodiment, the aging treatment includes a first-stage aging treatment, a second-stage aging treatment, and a third-stage aging treatment. The temperature of the first-stage aging treatment is 80 - 120 °C, specifically it can be 80 °C, 85 °C, 90 °C, 95 °C, 100 °C, 105 °C, 110 °C, 115 °C, or 120 °C, and the time is 3 - 20 h, specifically it can be 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, or 20 h; the temperature of the second-stage aging treatment is -200 to -100 °C, specifically it can be -200 °C, -190 °C, -180 °C, -170 °C, -160 °C, -150 °C, -140 °C, -130 °C, -120 °C, -110 °C, or -100 °C, and the time is 0.5 - 10 h, specifically it can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, or 10 h; the temperature of the third-stage aging treatment is 170 - 250 °C, specifically it can be 170 °C, 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, or 250 °C, and the time is 0.05 - 5 h, specifically it can be 0.05 h, 0.1 h, 0.2 h, 0.3 h, 0.4 h, 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1 h, 2 h, 3 h, 4 h, or 5 h. The temperature of the first-stage aging treatment is relatively low. In the first-stage aging treatment, the atoms in the die-cast aluminum alloy parts are stabilized, and a dense GP zone is formed, while avoiding the rapid precipitation of unsaturated Ni. Thus, the Ni content can be set relatively high.During the second-stage aging treatment, there is a sharp volume shrinkage, generating a considerable amount of stress, which in turn produces a large number of dislocations. These dislocations interact with the stress in the alloy, the grain boundaries, and entangle with each other to increase the yield strength, tensile strength, and elongation of the alloy; during this second-stage aging treatment, the crystal structure of the material changes, and recovery recrystallization occurs during the cryogenic recovery process, resulting in grain rotation and the formation of a recrystallization texture by preferred orientation, increasing the tensile strength and yield strength of the aluminum alloy; a large number of supersaturated point defects (such as vacancies) and dislocations obtained by the aluminum alloy during this second-stage aging treatment can further promote the segregation of solute atoms such as Si, Mg, Ni, Fe, Cr, Ti, Sr, Zr, Cu, significantly increasing the GP zone range, increasing the nucleation rate during the third-stage aging treatment, and promoting the more complete precipitation of alloying elements; after the second-stage aging treatment is completed, the temperature is adjusted to 170 - 250 °C within 1 - 5 minutes to ensure that the supersaturated point defects (such as vacancies) and dislocations formed during the second-stage aging treatment can be all or nearly all retained until the third-stage aging treatment. At this time, the GP zones gradually transform into precipitates with smaller size but larger volume fraction, precipitating all or nearly all of the alloying elements dissolved in the alloy interior, increasing the pinning effect on dislocations, and greatly increasing the strength and elongation of the aluminum alloy. The aging treatment may further include a fourth-stage aging treatment, and the fourth-stage aging treatment can be natural aging treatment or water-cooled aging treatment. After the fourth-stage aging treatment, the elongation of the aluminum alloy is further increased, but the strength decreases. The natural aging treatment is to place the aluminum alloy parts after the third-stage aging treatment at room temperature for 0.5 - 5 h, specifically 0.5 h, 1 h, 2 h, 3 h, 4 h, or 5 h. The water-cooled aging treatment is to place the aluminum alloy parts after the third-stage aging treatment in normal-temperature water for 0.5 - 5 h, specifically 0.5 h, 1 h, 2 h, 3 h, 4 h, or 5 h. During the natural aging treatment process, the temperature of the aluminum alloy parts will drop rapidly, and fine strengthening phases continue to precipitate but the precipitation rate also decreases, further increasing the strength and elongation of the aluminum alloy. During the water-cooled aging treatment process, the temperature of the aluminum alloy parts will drop even more rapidly, and fine strengthening phases continue to precipitate but the precipitation rate decreases even faster, further increasing the strength and elongation of the aluminum alloy. The strength and elongation of the aluminum alloy after the water-cooled aging treatment are greater than those of the aluminum alloy after the natural aging treatment. The combined addition of Si, Mg, Ni, Fe, Cr, Ti, Sr, Zr, Cu enables the alloy to disperse and precipitate a variety of dispersion phases containing Si, Mg, Ni, Fe, Cr, Ti, Sr, Zr, Cu during the aging stage. These dispersion phases themselves can refine the grains, increasing the alloy strength and elongation; they can also serve as the core for the heterogeneous nucleation of the β" phase, thereby accelerating the formation of the β" phase, further increasing the strength and elongation.

[0077] In another embodiment, the aging treatment includes a first-stage low-temperature electric-field aging treatment and a second-stage high-temperature aging treatment. The temperature of the first-stage low-temperature electric-field aging treatment is 50 - 130 °C, the time is 0.1 - 100 h, and the electric-field strength is 2 - 50 kV / cm. The temperature of the first-stage low-temperature electric-field aging treatment can specifically be 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, 95 °C, 100 °C, 105 °C, 110 °C, 115 °C, 120 °C, 125 °C, or 130 °C, the time can specifically be 0.1 h, 0.5 h, 1 h, 5 h, 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h, 50 h, 55 h, 60 h, 65 h, 70 h, 75 h, 80 h, 85 h, 90 h, 95 h, or 100 h, and the electric-field strength can specifically be 2 kV / cm, 5 kV / cm, 10 kV / cm, 15 kV / cm, 20 kV / cm, 25 kV / cm, 30 kV / cm, 35 kV / cm, 40 kV / cm, 45 kV / cm, or 50 kV / cm. The second-stage high-temperature aging treatment has no electric-field effect, its temperature is 170 - 250 °C, and the time is 0.05 - 30 h. The temperature of the second-stage high-temperature aging treatment can specifically be 170 °C, 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, or 250 °C, and the time can specifically be 0.05 h, 0.1 h, 0.5 h, 1 h, 5 h, 10 h, 15 h, 20 h, 25 h, or 30 h. During the first-stage low-temperature electric-field aging treatment, the low temperature of 50 - 130 °C can inhibit the segregation of atoms such as Si, Mg, Ni, Fe, Cr, Ti, Sr, Zr, and Cu, and at the same time make the alloy have a greater degree of supercooling, significantly increasing the range of GP zones, facilitating the increase in the nucleation rate during the subsequent high-temperature process, and enabling the alloying elements to precipitate more fully. Secondly, since applying an electric field at low temperature reduces the precipitation activation energy of the phases in the alloy, low-temperature electric-field aging can accelerate the precipitation nucleation rate of the precipitate phases during aging, and increase the volume fraction of nucleation sites. The hardness of the alloy increases significantly at the initial stage of electric-field aging. During the subsequent second-stage high-temperature aging treatment, the time required for the alloy to reach the peak hardness is shortened, the volume fraction of the precipitate phases is increased, and the size of the precipitate phases is refined. As the electric-field strength increases during the first-stage low-temperature electric-field aging treatment, the number of nucleation sites of the strengthening phases precipitated in the alloy increases sharply, indicating that increasing the electric-field strength can increase the nucleation and precipitation rate of the precipitate phases, and has no obvious effect on the growth of the second-stage high-temperature aging phases without an electric-field effect, and no coarsening of the size will occur, thereby increasing the elongation of the aluminum alloy.

[0078] In the technical solution of the present invention, the high-strength Al-Si-Mg series die-casting aluminum alloy contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Ni with a mass percentage content of 0.01-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.01-0.5%, Ti with a mass percentage content of 0.06-0.25%, Sr with a mass percentage content of 0-0.05%, Zr with a mass percentage content of 0-0.3%, SiC with a mass percentage content of 0-35%, and Cu with a mass percentage content of 0-0.1%. The elements with the above contents interact with each other and influence each other, so that the high-strength Al-Si-Mg series die-casting aluminum alloy has both better yield strength and tensile strength.

[0079] In the technical solution of the present invention, in order to avoid the adverse effect of Si on the elongation, the mass percentage content of Si is set to 6-8% (preferably 6-7.5%), but the mass percentage content of Si of 6-8% does not improve the strength of the aluminum alloy much; the mass percentage content of Mg is correspondingly set to 1.2-1.8% (preferably 1.4-1.6%), the mass percentage content of Ni is set to 0.01-2.5% (preferably 0.5-2%), the mass percentage content of Zr is 0-0.3%, and the mass percentage content of SiC is 0-35%. The strength of the aluminum alloy is greatly improved by Mg, Ni, Zr, and SiC, but the mass percentage content of Mg is set to 1.2-1.8%, which greatly reduces the elongation of the aluminum alloy; in order to improve the elongation of the aluminum alloy, the mass percentage content of Fe and Cu is set to be relatively low, 0.01-0.4% (preferably 0.1-0.2%) and 0-0.1% (preferably 0.001-0.05%) respectively. , avoiding the influence of high content of Fe on the elongation of aluminum alloy, and improving the elongation of aluminum alloy by low content of Cu; the present invention also adopts 0.01-0.5% by mass Cr, 0.06-0.25% by mass Ti, 0.01-2.5% by mass Ni, 0-0.3% by mass Zr, 0-35% by mass SiC, and 0-0.05% by mass Sr (preferably 0.01- 0.05%), can refine the grains, second phase and precipitation phase to improve the strength and elongation of aluminum alloy; when the Fe content is not high, Cr with a mass percentage of 0.01-0.5% can also improve the demolding performance of aluminum alloy; Zn, Cr, Ni, Sr can also promote the precipitation of Mg2Si, MgZn2, Mg2SiZn, Al2Cu, etc., further improving the elongation and mechanical properties of aluminum alloy; the above elements can also react with each other to form a second phase to avoid solid solution in the aluminum matrix to affect the elongation of aluminum alloy. In this way, Si, Mg, Ni, Fe, Cr, Ti, Sr, Zr, SiC, and Cu in the above content range interact with each other as a whole, which can make the aluminum alloy elements have better strength, elongation, and demolding performance. Moreover, under the further action of subsequent refining treatment, aging treatment and die-casting treatment, the solid solubility of each element in the aluminum matrix of Si, Mg, Zn, Fe, Cr, Ti, Sr, and Cu within the above-mentioned content range is further reduced, and the impurity elements are also further reduced, which can eliminate the adverse effects of alloy elements and impurity elements on the strength and elongation of the aluminum alloy as much as possible, and the second phase (such as Al3Fe, Mg2Si, Al2Cu, AlFeSiNi, AlMnSi phases, etc.) can also be refined in the aluminum matrix and at the grain boundaries or within the grain boundaries, thereby greatly improving the strength and elongation of the aluminum alloy.

[0080] The preparation method of the high-strength Al-Si-Mg series die-casting aluminum alloy further includes the step of adding at least one of Co source, Mn source, Sn source, Sb source, Ni source, Fe source, Bi source, Cd source, Ca source, Be source, V source, B source, RE source, Ge source, Mo source, Nb source, Te source, Ag source, In source, Zn source, AlTiB source, BN source, and AlTiC source to the first mixed solution. The above elements can be used to improve the strength and elongation rate of the aluminum alloy at least, so as to obtain a high-strength Al-Si-Mg series die-casting aluminum alloy with more excellent performance. The raw materials of the above alloying elements can be aluminum master alloys. For example, the RE source can be an Al-RE alloy.

[0081] Examples For the components and contents of the aluminum alloys in Examples 1 to 10, please refer to Table 1, and for the performance test results, please refer to Table 2.

[0082] Table 1 Components and contents of the aluminum alloys in Examples 1 to 10 For simplicity of expression, all impurity elements and their contents are not shown.

[0083] Table 2 Performance test results of the aluminum alloys in Examples 1 to 10 The aluminum alloys in Examples 1 to 10 are made into structural parts, and the tensile strength, yield strength, and elongation rate of the structural parts are tested. The test results are shown in Table 2. Among them, during the production process of Examples 6 to 10, the surface of the mold was treated, and a 2-mm boron carbide layer was formed on the parting surface of the mold.

[0084] Table 2 shows that: the aluminum alloys in Examples 1 to 10 of the present embodiment have better tensile strength, yield strength, and elongation rate. Specifically, the tensile strength of the aluminum alloys in Examples 1 to 10 of the present embodiment is not lower than 400 MPa, the yield strength is not lower than 310 MPa, and the elongation rate is not lower than 4%.

[0085] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made using the content of the specification of the present invention under the inventive concept of the present invention, or any direct / indirect application in other related technical fields is included in the patent protection scope of the present invention.

Claims

1. A high-strength Al-Si-Mg series die-casting aluminum alloy contains Al, and is characterized in that, The high-strength Al-Si-Mg series die-casting aluminum alloy also contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Ni with a mass percentage content of 0.01-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.01-0.5%, Ti with a mass percentage content of 0.06-0.25%, Sr with a mass percentage content of 0-0.05%, Zr with a mass percentage content of 0-0.3%, SiC with a mass percentage content of 0-35%, and Cu with a mass percentage content of 0-0.1%.

2. The high-strength Al-Si-Mg series die-casting aluminum alloy according to claim 1, characterized in that, The high-strength Al-Si-Mg series die-casting aluminum alloy also contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Ni with a mass percentage content of 0.1-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.01-0.5%, Ti with a mass percentage content of 0.06-0.25%, Sr with a mass percentage content of 0.01-0.05%, Zr with a mass percentage content of 0.01-0.3%, SiC with a mass percentage content of 1-15%, and Cu with a mass percentage content of 0.001-0.1%.

3. The high-strength Al-Si-Mg series die-casting aluminum alloy according to claim 1, characterized in that, The high-strength Al-Si-Mg series die-casting aluminum alloy also contains Co with a mass percentage content of 0.01-0.5% and Mn with a mass percentage content of 0.01-0.5%. Among them, the sum of the mass percentage contents of Fe, Cr, Co, and Mn is 0.04-1%.

4. The high-strength Al-Si-Mg series die-casting aluminum alloy according to claim 1, characterized in that, The high-strength Al-Si-Mg series die-casting aluminum alloy also contains Sn with a mass percentage content of 0.01-0.3%, Sb with a mass percentage content of 0.01-0.3%, Zn with a mass percentage content of 0.01-0.6%, and Bi with a mass percentage content of 0.01-0.3%. The sum of the mass percentage contents of Sn, Sb, Zn, Fe, and Bi is 0.05-1.2%. The mass ratio of the sum of the mass percentage contents of Sn, Sb, Zn, Fe, and Bi to the mass percentage content of Mg is 0.1-1:

1.

5. The high-strength Al-Si-Mg series die-casting aluminum alloy according to claim 1, characterized in that, The high-strength Al-Si-Mg series die-casting aluminum alloy further contains at least one of Cd, Ca, Be, V, B, RE, Ge, Mo, Nb, Te, Ag, In, AlTiB, BN, and AlTiC. Among them, the mass percentage content of Cd is 0-0.2%, the mass percentage content of Ca is 0-0.2%, the mass percentage content of Be is 0-0.2%, the mass percentage content of V is 0-0.2%, the mass percentage content of B is 0-0.1%, the mass percentage content of RE is 0-0.2%, the mass percentage content of Ge is 0-0.1%, the mass percentage content of Mo is 0-0.2%, the mass percentage content of Nb is 0-0.1%, the mass percentage content of Te is 0-0.1%, the mass percentage content of Ag is 0-0.1%, the mass percentage content of In is 0-0.2%, the mass percentage content of AlTB is 0-1%, the mass percentage content of BN is 0-1%, and the mass percentage content of AlTiC is 0-1%.

6. A preparation method of a high-strength Al-Si-Mg series die-casting aluminum alloy, comprising the following steps: Providing a Si source, a Mg source, a Ni source, a Fe source, a Cr source, a Ti source, a Sr source, a Zr source, a SiC source, a Cu source, and an Al source; Performing a heat treatment on the Al source to obtain molten aluminum; Adding the Si source, the Mg source, the Ni source, the Fe source, the Cr source, the Ti source, the Sr source, the Zr source, the SiC source, and the Cu source to the molten aluminum to obtain a mixed solution; and Performing die-casting treatment and aging treatment on the mixed solution to obtain the high-strength Al-Si-Mg series die-casting aluminum alloy, wherein the high-strength Al-Si-Mg series die-casting aluminum alloy contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Ni with a mass percentage content of 0.01-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.01-0.5%, Ti with a mass percentage content of 0.06-0.25%, Sr with a mass percentage content of 0-0.05%, Zr with a mass percentage content of 0-0.3%, SiC with a mass percentage content of 0-35%, and Cu with a mass percentage content of 0-0.1%.

7. The preparation method of the high-strength Al-Si-Mg series die-casting aluminum alloy according to claim 6, wherein The temperature of the aging treatment is 170-250°C, and the time is 0.05-30h; or The aging treatment includes a first-stage aging treatment, a second-stage aging treatment, a third-stage aging treatment, and a fourth-stage aging treatment. The temperature of the first-stage aging treatment is 80 - 120°C, and the time is 3 - 20 h; the temperature of the second-stage aging treatment is -200 to -100°C, and the time is 0.5 - 10 h; the temperature of the third-stage aging treatment is 170 - 250°C, and the time is 0.05 - 5 h. After the second-stage aging treatment, the temperature is adjusted to 170 - 250°C within 1 - 5 min; the fourth-stage aging treatment is natural aging treatment or water-cooling aging treatment; or The aging treatment includes a first-stage low-temperature electric-field aging treatment and a second-stage high-temperature aging treatment. Among them, the temperature of the first-stage low-temperature electric-field aging treatment is 50 - 130°C, the time is 0.1 - 100 h, and the electric field strength is 2 - 50 kV / cm; the temperature of the second-stage high-temperature aging treatment is 170 - 250°C, and the time is 0.05 - 30 h.

8. The preparation method of the high-strength Al-Si-Mg series die-casting aluminum alloy according to claim 6, characterized in that, The die-casting treatment is high-pressure die-casting. In the high-pressure die-casting, the temperature is 600 - 670ºC, the low-speed injection speed is 0.23 - 0.3 m / s, and the high-speed injection speed is 2 - 2.5 m / s; or The die-casting treatment is semi-solid die-casting. In the semi-solid die-casting, the temperature of the mixed liquid is 580 - 610°C, the stirring speed is 550 - 700 r / min, the stirring duration is 4 - 10 min, the solid fraction is 35 - 50%, the injection speed is 0.4 - 1.5 m / s, the mold temperature is 220 - 240°C, and the air pressure in the mold cavity is 30 - 50 kPa.

9. The preparation method of the high-strength Al-Si-Mg series die-casting aluminum alloy according to claim 6, characterized in that, The preparation method of the high-strength Al-Si-Mg series die-casting aluminum alloy further includes the step of adding at least one of Co source, Mn source, Sn source, Sb source, Zn source, Fe source, Bi source, Cd source, Ca source, Be source, V source, B source, RE source, Ge source, Mo source, Nb source, Te source, Ag source, In source, AlTiB source, BN source, and AlTiC source to the aluminum liquid, wherein the mass percentage content of Co is 0.01-0.5%, the mass percentage content of Mn is 0.01-0.5%, the mass percentage content of Sn is 0.01-0.5%, the mass percentage content of Sb is 0.01-0.5%, the mass percentage content of Zn is 0.01-0.6%, the mass percentage content of Bi is 0.01-0.5%, the mass percentage content of Cd is 0-0.2%, the mass percentage content of Ca is 0-0.2%, the mass percentage content of Be is 0-0.2%, the mass percentage content of V is 0-0.2%, the mass percentage content of B is 0-0.1%, the mass percentage content of RE is 0-0.2%, the mass percentage content of Ge is 0-0.1%, the mass percentage content of Mo is 0-0.2%, the mass percentage content of Nb is 0-0.1%, the mass percentage content of Te is 0-0.1%, the mass percentage content of Ag is 0-0.1%, the mass percentage content of In is 0-0.2%, the mass percentage content of AlTB is 0-1%, the mass percentage content of BN is 0-1%, and the mass percentage content of AlTiC is 0-1%.

10. A structural member, characterized in that, The material of the structural member is the high-strength Al-Si-Mg series die-casting aluminum alloy according to any one of claims 1-5, or the high-strength Al-Si-Mg series die-casting aluminum alloy prepared by the preparation method of the high-strength Al-Si-Mg series die-casting aluminum alloy according to any one of claims 6-9.

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