High-strength al-si-mg series die-casting aluminum alloy, preparation method thereof and structural member

Abstract

The application provides a high-strength Al-Si-Mg series die-casting aluminum alloy and a preparation method and a structural member thereof. The high-strength Al-Si-Mg series die-casting aluminum alloy contains Al, and also contains Si with a mass percentage of 6-8%, Mg with a mass percentage of 1.2-1.8%, Ni with a mass percentage of 0.01-2.5%, Fe with a mass percentage of 0.01-0.4%, Cr with a mass percentage of 0.01-0.5%, Ti with a mass percentage of 0.06-0.25%, Sr with a mass percentage of 0-0.05%, Zr with a mass percentage of 0-0.3%, and Cu with a mass percentage of 0-0.1%. The high-strength Al-Si-Mg series die-casting aluminum alloy has a tensile strength of not less than 400 MPa, a yield strength of not less than 310 MPa, and an elongation of not less than 4%.

Description

TECHNICAL FIELD

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

[0002] The die-casting aluminum alloy has good comprehensive performance, high strength, small density, good mechanical properties, easy processing and cutting, and is widely used in the fields of aerospace, new energy vehicles, consumer electronics, household and industrial electrical appliances, and high-rise buildings.

[0003] With the increase of the content of silicon element, the flowability and compactness of the aluminum alloy gradually increase, and the forming performance and mechanical properties gradually improve. However, the addition of silicon element does not greatly improve the strength of the die-casting aluminum alloy, so that the strength of the existing Al-Si series die-casting aluminum alloy cannot meet the demand. SUMMARY

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

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

[0006] Further, the high-strength Al-Si-Mg series die-casting aluminum alloy further contains Si with a mass percentage of 6-8%, Mg with a mass percentage of 1.2-1.8%, Ni with a mass percentage of 0.1-2.5%, Fe with a mass percentage of 0.01-0.4%, Cr with a mass percentage of 0.01-0.5%, Ti with a mass percentage of 0.06-0.25%, Sr with a mass percentage of 0.01-0.05%, Zr with a mass percentage of 0.01-0.3%, SiC with a mass percentage of 1-15%, and Cu with a mass percentage 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 of 0.01-0.5% and Mn with a mass percentage of 0.01-0.5%, wherein the sum of the mass percentages 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 of 0.01-0.3%, Sb with a mass percentage of 0.01-0.3%, Zn with a mass percentage of 0.01-0.6%, and Bi with a mass percentage of 0.01-0.3%, wherein the sum of the mass percentages of Sn, Sb, Zn and Bi is 0.05-1.2%, and the mass ratio of the sum of the mass percentages of Sn, Sb, Zn and Bi to the mass percentage 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, wherein the mass percentage of Cd is 0-0.2%, the mass percentage of Ca is 0-0.2%, the mass percentage of Be is 0-0.2%, the mass percentage of V is 0-0.2%, the mass percentage of B is 0-0.1%, the mass percentage of RE is 0-0.2%, the mass percentage of Ge is 0-0.1%, the mass percentage of Mo is 0-0.2%, the mass percentage of Nb is 0-0.1%, the mass percentage of Te is 0-0.1%, the mass percentage of Ag is 0-0.1%, the mass percentage of In is 0-0.2%, the mass percentage of AlTB is 0-1%, the mass percentage of BN is 0-1%, and the mass percentage of AlTiC is 0-1%.

[0010] The application further provides a preparation method of the high-strength Al-Si-Mg series die-casting aluminum alloy, comprising the following steps:

[0011] 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;

[0012] subjecting the Al source to a heating treatment to obtain aluminum liquid;

[0013] 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 into the aluminum liquid to obtain a mixed liquid; and

[0014] 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, wherein the high-strength Al-Si-Mg series die casting aluminum alloy contains Si with a mass percentage of 6-8%, Mg with a mass percentage of 1.2-1.8%, Ni with a mass percentage of 0.01-2.5%, Fe with a mass percentage of 0.01-0.4%, Cr with a mass percentage of 0.01-0.5%, Ti with a mass percentage of 0.06-0.25%, Sr with a mass percentage of 0-0.05%, Zr with a mass percentage of 0-0.3%, SiC with a mass percentage of 0-35%, and Cu with a mass percentage of 0-0.1%.

[0015] Further, the die casting treatment is high-pressure casting, wherein 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

[0016] The die casting treatment is semi-solid die casting treatment, wherein the temperature of the mixed solution is 580-610°C, the stirring speed is 550-700 r / min, the stirring time is 4-10 min, the solid phase rate is 35-50%, the injection speed is 0.4-1.5 m / s, the mold temperature is 220-240°C, and the air pressure of the mold cavity is 30-50 kPa.

[0017] Further, the temperature of the aging treatment is 170-250°C, and the time is 0.05-30 h; or

[0018] The aging treatment includes first-stage aging treatment, second-stage aging treatment, third-stage aging treatment, and fourth-stage aging treatment, wherein 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; the temperature is adjusted to 170-250°C within 1-5 min after the second-stage aging treatment; and the fourth-stage aging treatment is natural aging treatment or water cooling aging treatment; or

[0019] The aging treatment includes first-stage low-temperature electric field aging treatment and second-stage high-temperature aging treatment, wherein 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; and the temperature of the second-stage high-temperature aging treatment is 170-250°C, and the time is 0.05-30 h.

[0020] Further, the preparation method of the high-strength Al-Si-Mg series die-casting aluminum alloy further comprises 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 into 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%.

[0021] The application further provides a structural member made of the high-strength Al-Si-Mg series die-casting aluminum alloy or prepared by the preparation method of the high-strength Al-Si-Mg series die-casting aluminum alloy.

[0022] In the technical scheme, 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 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. The tensile strength of the high-strength Al-Si-Mg series die-casting aluminum alloy is not less than 400 MPa, the yield strength is not less than 310 MPa, and the elongation is not less than 4%. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work, fall within the protection scope of the present application.

[0024] An embodiment of the present application 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 high strength requirements.

[0025] The high-strength Al-Si-Mg series die-casting aluminum alloy contains Al, and further contains Si with a mass percentage of 6-8%, Mg with a mass percentage of 1.2-1.8%, Ni with a mass percentage of 0.01-2.5%, Fe with a mass percentage of 0.01-0.4%, Cr with a mass percentage of 0.01-0.5%, Ti with a mass percentage of 0.06-0.25%, Sr with a mass percentage of 0-0.05%, Zr with a mass percentage of 0-0.3%, SiC with a mass percentage of 0-35%, and Cu with a mass percentage of 0-0.1%.

[0026] The mass percentage of Si can be specifically 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%.

[0027] The mass percentage of Mg can be specifically 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, or 1.8%.

[0028] The mass percent 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%.

[0029] The mass percent 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%.

[0030] The mass percent 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%.

[0031] The mass percent 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%.

[0032] The mass percent 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%.

[0033] The mass percent 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%.

[0034] The mass percent 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%.

[0035] The specific percentage content of Cu by mass 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%.

[0036] In one embodiment, the high-strength Al-Si-Mg die-cast aluminum alloy further comprises 6-8% Si, 1.2-1.8% Mg, 0.1-2.5% Ni, 0.01-0.4% Fe, 0.01-0.5% Cr, 0.06-0.25% Ti, 0.01-0.05% Sr, 0.01-0.3% Zr, 1-15% SiC, and 0.001-0.1% Cu by mass.

[0037] It is understood that the Al-Si-Mg series die-cast aluminum alloy also contains impurities, wherein 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%.

[0038] In the technical solution of this invention, the Al-Si-Mg system high thermal conductivity aluminum alloy contains 6-8% Si, 1.2-1.8% Mg, 0.01-2.5% Ni, 0.01-0.4% Fe, 0.01-0.5% Cr, 0.06-0.25% Ti, 0-0.05% Sr, 0-0.3% Zr, 0-35% SiC, and 0-0.1% Cu by mass. The Si, Mg, Ni, Fe, Cr, Ti, Sr, Zr, SiC, and Cu within the above content ranges act as a whole, interacting and influencing each other to ensure that the Al-Si-Mg system possesses superior yield strength and tensile strength. Specifically:

[0039] (1) When the mass percentage content of Si is 6-8%, Si can improve the fluidity and density of aluminum alloy, thereby improving the forming performance and mechanical properties of 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, which will drastically reduce the elongation of aluminum alloy.

[0040] (2) the mass percentage content of Mg is 1.2-1.8%, Mg can greatly improve the mechanical properties of the aluminum alloy; Mg can react with other elements to generate a second phase, avoiding the adverse effect on the elongation of the aluminum alloy, Mg can react with Al, Fe, Si, Cu, Zn, B, Ni and the like to generate a second phase of MgB, Mg2Si, Mg2Zn, Mg2SiZn, (CuMg)Al2, AlFeMgSi, AlFeMgSiNi and the like; but the mass percentage content of 1.2-1.8% of Mg can sharply reduce the elongation of the aluminum alloy;

[0041] (3) the mass percentage content of Ni is 0.01-2.5%, Ni can refine grains, second phases and precipitated phases to improve the elongation of the aluminum alloy; Ni can react with other elements to generate a second phase, avoiding the adverse effect on the elongation of the aluminum alloy when the content of Ni dissolved in the aluminum matrix is high, specifically, Ni can react with Al, Fe, Mg, Si and the like to generate a second phase of Al3Ni, AlFeSiNi, AlFeMgSiNi, FeNiAl9 and the like, avoiding the adverse effect on the elongation when the contents of Mg and Ni are too high; Ni can also promote the precipitation of phases of CuAl2, Mg2Si, (CuMg)Al2 and the like, improving the volume fraction and dispersion degree of the precipitated phases and reducing the solid solubility of alloy elements in the aluminum matrix to improve the elongation of the aluminum alloy; Ni and Mg can promote the precipitation of each other to improve the strength and elongation of the aluminum alloy; 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 to be high to generate more second phases of AlFeMgSiNi dispersedly distributed to greatly improve the strength of the aluminum alloy;

[0042] (4) the mass percentage content of Fe is 0.01-0.4%, on the one hand, Fe can reduce the sticking tendency of the aluminum alloy castings and improve the mechanical properties of the aluminum alloy, on the other hand, Fe can react with other elements to generate a second phase as much as possible to avoid the adverse effect on the elongation of the aluminum alloy caused by Fe dissolved in the aluminum matrix, specifically, Fe can react with Al, Si, Mg, Cu, Mn, Ni and the like to generate a second phase of Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu, AlFeSiNi, AlFeMgSiNi, AlFeMnSi, (CrFe)Al7, (CrMn)Al 12 , AlFeSiB, FeNiAl9 and the like;

[0043] (5) the mass percentage content of Cr is 0.01-0.5%, Cr can form (CrFe)Al7 and (CrMn)Al 12The intermetallic compound has certain strengthening effect on the aluminum alloy; Cr can improve the toughness of the aluminum alloy and reduce the stress corrosion cracking sensitivity; Cr can also improve the Fe morphology, change the β-Fe phase into the α-Fe phase, reduce the cutting effect of the β-Fe phase on the aluminum matrix when the β-Fe phase cannot be dissolved, and improve the elongation of the aluminum alloy; a proper amount of Cr can form various fine Cr-containing compounds in the as-cast aluminum alloy, which can be dissolved in the α phase during the die casting stage and can be dispersedly precipitated in various Cr-containing phases during the aging stage, the Cr-containing phases can act as the core of the non-uniform nucleation of the β" phase, and then the formation of the β" phase is accelerated, and the dispersed precipitation of the Cr-containing phases in the aluminum matrix can certainly delay the formation of the metastable phase precipitated at the grain boundary, thereby improving the elongation of the aluminum alloy; Cr can also significantly improve the original alloy organization morphology and phase distribution, and form some Cr-rich multi-phase, and the change and distribution of the phases can improve the strength of the aluminum alloy;

[0044] (6) The mass percentage content of Ti is 0.06-0.25%, and Ti can improve the strength and elongation of the aluminum alloy; specifically, the TiAl3 phase generated by the reaction of Ti and Al can act as a non-spontaneous core during crystallization, can refine the grains, the second phase and the precipitated phase, and can improve the strength and elongation of the aluminum alloy;

[0045] (7) The mass percentage content of Sr is 0-0.05%, and Sr can be modified by the heterogeneous nucleation theory or the twin valley mechanism to refine the second phase such as eutectic silicon, improve the strength and elongation of the aluminum alloy, change the β-Fe phase into the α-Fe phase in the ingot to reduce the cutting effect of the β-Fe phase on the aluminum matrix when the β-Fe phase cannot be dissolved, improve the elongation of the aluminum alloy, preferentially combine with Fe, Cu, Mn, Cr, Si and other elements to form dispersion strengthening, avoid the adverse effect of Sr dissolved in the aluminum matrix on the elongation of the aluminum alloy, and promote the precipitation of CuAl2, AlFeSi, AlFeSiNi, Mg2Si and other phases to reduce the solid solubility of these alloy elements in the aluminum matrix to improve the elongation of the aluminum alloy;

[0046] (8) The mass percentage content of Zr is 0-0.3%, and Zr can improve the strength of the aluminum alloy; Zr can also form the Al3Zr phase in the aluminum alloy, the Al3Zr phase can refine the grains, the second phase and the precipitated phase, and can improve the elongation of the aluminum alloy;

[0047] (9) The mass percentage content of SiC is 0-35%, and SiC can form a dispersed phase in the aluminum alloy, form a strong interface with the aluminum matrix, and thus effectively improve the strength and elongation of the alloy; SiC also has a good refining effect, and further improves the elongation of the aluminum alloy;

[0048] (10) The mass percentage content of Cu is 0-0.1%, and the solid 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 of the aluminum alloy can be significantly improved; and trace Cu can also reduce the natural aging speed, thereby reducing the adverse effects of the parking effect on the alloy.

[0049] 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 application, but the Si with the mass percentage content of 6-8% does not greatly improve the strength of the aluminum alloy; the mass percentage content of Mg is set to 1.2-1.8% (preferably 1.4-1.6%) in the present application, the mass percentage content of Ni is set to 0.01-2.5% (preferably 0.5-2%), the mass percentage content of Zr is set to 0-0.3%, and the mass percentage content of SiC is set to 0-35%, so that the strength of the aluminum alloy is greatly improved by Mg, Ni, Zr, and SiC, but the Mg with the mass percentage content of 1.2-1.8% greatly reduces the elongation of the aluminum alloy; to improve the elongation of the aluminum alloy, the mass percentage contents of Fe and Cu are set to be relatively low, i.e. 0.01-0.4% (preferably 0.1-0.2%) and 0-0.1% (preferably 0.001-0.05%) respectively, so as to avoid the high content of Fe from affecting the elongation of the aluminum alloy, and to improve the elongation of the aluminum alloy by the low content of Cu; the present application also uses Cr with the mass percentage content of 0.01-0.5%, Ti with the mass percentage content of 0.06-0.25%, Ni with the mass percentage content of 0.01-2.5%, Zr with the mass percentage content of 0-0.3%, SiC with the mass percentage content of 0-35%, and Sr with the mass percentage content of 0-0.05% (preferably 0.01-0.05%) to refine the grains, the second phase, and the precipitated phase, so as to improve the strength and the elongation of the aluminum alloy; when the content of Fe is not high, the Cr with the mass percentage content of 0.01-0.5% can also improve the demolding performance of the aluminum alloy; Zn, Cr, Ni, and Sr can also promote the precipitation of Mg2Si, MgZn2, Mg2SiZn, Al2Cu, etc., so as to further improve the elongation and the mechanical properties of the aluminum alloy; the above elements can also react with each other to form the second phase, so as to avoid the solid solution in the aluminum matrix from affecting the elongation of the aluminum alloy. In this way, the Si, Mg, Ni, Fe, Cr, Ti, Sr, Zr, SiC, and Cu in the above content range interact with and affect each other as a whole, so that the aluminum alloy elements have better strength, elongation, and demolding performance. Moreover, the Si, Mg, Zn, Fe, Cr, Ti, Sr, and Cu in the above content range are further affected by the subsequent refining treatment, aging treatment, and die casting treatment, the solid solubility of each element in the aluminum matrix is further reduced, the impurity elements are also further reduced, the adverse effects of the alloy elements and the impurity elements on the strength and the elongation of the aluminum alloy are eliminated as much as possible, the second phase (such as Al3Fe, Mg2Si, Al2Cu, AlFeSiNi, AlMnSi phase, etc.) can also be refined in the aluminum matrix and at or in the grain boundaries, so that the strength and the elongation of the aluminum alloy are greatly improved.

[0050] The high-strength Al-Si-Mg series die-casting aluminum alloy further comprises Co in a mass percentage of 0.01-0.5% and Mn in a mass percentage of 0.01-0.5%, wherein the sum of the mass percentages of Fe, Cr, Co and Mn is 0.04-1%, and specifically 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%.

[0051] The mass percentage of Co and Mn specifically can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 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%.

[0052] The sum of the mass percentages of Fe, Cr, Co and Mn specifically can 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%.

[0053] Co can refine grains to improve the mechanical properties of the aluminum alloy; Co can also react with other elements as much as possible to generate a second phase to improve the mechanical properties of the aluminum alloy, specifically, Co can react with Al, Fe, Si, etc. to generate Al 15 (Fe,Co)3Si2, Al3(Fe,Co) and other second phases; the refining effect of Co on Al3Fe phase can convert coarse needle-shaped and flaky β-Al3Fe phase into small flower-shaped and fine strip-shaped 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 the aluminum alloy.

[0054] Mn can react with Fe to form fine dispersed α-Al(FeMn)Si phase to improve the regulation of β-Fe-rich phase; Mn can significantly refine the recrystallized grains and second phase, effectively convert the coarse needle-like or flaky β-AlFeSi phase into small granular α-Al(FeMn)Si dispersed particles to improve the Fe morphology, thereby improving the strength and elongation of the aluminum alloy. Mn can form independent Al6Mn and Al6FeMn hardening phases in the aluminum alloy, and the Mn-rich phase is distributed at the grain boundary or near the grain boundary to pin the grain boundary. Although the Mn-rich phase has low coherence with the Al matrix and its size is large, the ability to pin dislocations is weak, but the combined addition of Mn and Zr not only reduces the use amount of each alloying element, but also promotes mutual precipitation to form more Al6(Mn,Zr) phase, Al3(Zr,Mn) phase and Al6(FeMnZr) phase, and the strengthening effect is much greater than that when Mn or Zr is added alone.

[0055] In order to avoid the influence of Fe on the elongation of the aluminum alloy, the mass percentage content of Fe can be set lower. In order to ensure the demolding performance of the aluminum alloy, the sum of the mass percentage contents of Fe, Cr, Co and Mn is 0.04-1%, preferably 0.3-0.6%. When the mold is surface 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%.

[0056] When the mold is surface 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 more preferably 0.05-0.1%. In this way, better demolding performance can be achieved, and the addition of too many elements to affect the elongation can be avoided.

[0057] The high-strength Al-Si-Mg series die-casting aluminum alloy further contains Sn in a mass percentage of 0.01-0.3%, Sb in a mass percentage of 0.01-0.3%, Zn in a mass percentage of 0.01-0.6%, Bi in a mass percentage of 0.01-0.3%, the sum of mass percentages of Sn, Sb, Zn, Fe and Bi being 0.05-1.2%, and the mass ratio of the sum of mass percentages of Sn, Sb, Zn, Fe and Bi to the mass percentage of Mg being 0.1:1-1:1.

[0058] The mass percentage of Sn, Sb and Bi can be specifically 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, or 0.3%.

[0059] The mass percentage of Zn can be specifically 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 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%.

[0060] The sum of the mass percentage contents of Sn, Sb, Zn, Fe and Bi can be specifically 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%.

[0061] 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 be specifically 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, or 1:1.

[0062] Sn, Sb, Zn, Fe and Bi can all react with Mg to form a second phase. Mg preferentially reacts with Si to form a Mg2Si phase, and then reacts with Sn, Sb, Zn, Fe and Bi to form Mg2Sn, AlFeMgSiNi, Mg3Sb2, MgZn2, Mg2ZnSi, Mg3Bi2 and other second phases, which can avoid the adverse effects of Mg solid-solved 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 be ensured that Mg is all or almost all reacted with other alloying elements to form a second phase, avoiding the presence of Mg solid-solved in the aluminum matrix, and also avoiding the addition of too many elements to affect the elongation of the aluminum alloy. Specifically:

[0063] Sn can react with Mg to form a round and spherical dispersed Mg2Sn strengthening phase, which can reduce the solid solubility of Mg and Sn in the aluminum matrix. Sn can also react with other elements to form a second phase, thereby improving the mechanical properties of the aluminum alloy. Sn can specifically form Al9Sn7, Al6Sn5, Al5Sn2, Al3Sn4 and other high-temperature strengthening phases with Al.

[0064] Sb can be used as a modifier in the aluminum alloy, effectively reducing the size of the eutectic silicon lamella and greatly reducing the possibility of Si cutting the matrix, thereby improving the mechanical properties of the alloy. Sb can react with Mg and other elements to form a 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 and Ni in the alloy matrix, further improving the mechanical properties of the alloy.

[0065] Bi expands during solidification, which is beneficial to feeding, and can form Mg3Bi2, Mg3(BiCd)2 strengthening phase with Mg and Cd, etc., to improve the mechanical properties of the alloy.

[0066] Zn can be dissolved in the aluminum matrix to greatly improve the strength of the aluminum alloy through solid solution strengthening, and after aging treatment, the precipitated elemental Zn can further improve the strength of the aluminum alloy; and the elemental Zn is a non-brittle phase between grain boundaries, which can improve the elongation of the aluminum alloy; Zn can increase the eutectic structure of the aluminum alloy to improve the flowability of the aluminum alloy, so that the aluminum alloy is suitable for die casting; Zn can eliminate elemental Si to reduce the adverse effects of elemental Si on the performance of the aluminum alloy, and Zn can also promote the precipitation of phases such as Mg2Si and Al2Cu to improve the mechanical properties; in addition, Zn can also 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 to form second phases such as MgZn2, Mg2SiZn and Al2CuZn.

[0067] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains RE with a mass percentage of 0-0.2%, Mo with a mass percentage of 0-0.2%, and Be with a mass percentage of 0-0.2%. The RE is at least one of La, Ce, Pr, Nd, Er, Sm, Y, and Gd.

[0068] The mass percentage of RE, Mo and Be can be 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%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%.

[0069] The mutual cooperation of Mn, Cr, RE, Mo, Co, Be, and Sr elements not only reduces the maximum solid solubility of each other in the aluminum matrix to improve the mechanical properties, but also promotes the reaction of Mn and Fe, and Mn can occupy the position of Fe elements in the second phase, making the Fe-containing phase more dispersed and fine, and promoting the effect of modifying Fe. The elements of Mn, Cr, RE, Mo, Co, Be, and Sr can also form a fine and dispersed a-Al(MnFeX)Si phase (wherein X is at least one of Cr, RE, Mo, Co, Be, and Sr), to improve the elongation of the aluminum alloy.

[0070] The Cu with the mass percentage content of 0.001-0.04% in combination with the RE with the mass percentage content of 0.001-0.2% and the Zr with the mass percentage content of 0.001-0.3% can significantly improve the dispersion distribution degree of Mg2Si, and can prevent the formation of coarse AlSiFe, Mg3Sb2, Mg2Sn, MgZn2, Mg2SiZn, Al3Zr and the like, and can reduce the solid solubility of various elements in the matrix, and ensure the uniform precipitation of the alloy during the solidification process; the addition of trace Cu can also reduce the anisotropy after the addition of Mn in the alloy.

[0071] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains Cd with the mass percentage content of 0-0.2%. The mass percentage content of Cd 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%. Cd can improve the strength of the aluminum alloy; Cd can also refine the grains, the second phase and the precipitated phase to improve the elongation of the aluminum alloy. Cd can refine α-Al, and can also form REAl2Cd3, Al3Cd, Al2Cd3, (CuCd)Al2, Mg2(SiCdREFe), Mg3(BiCd)2 and the like to reduce the solid solubility of each other in the aluminum matrix and improve the volume fraction of the precipitated phase, thereby improving the strength and mechanical properties of the aluminum alloy. In addition, Cd can form a large number of Cd-vacancy clusters during the aging stage, promote and accelerate the precipitation of CuAl2, Mg2Si and the like, thereby reducing the solid solubility of the above elements in the aluminum matrix, and further improving the strength and mechanical properties of the aluminum alloy.

[0072] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains Ca in a mass percentage of 0-0.2%. The mass percentage 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 improving the strength of the alloy, and can also form Al4Ca, Al2Ca3, AlCa2, AlCaCu strengthening phases with Cu and Al, significantly improving the strength, heat resistance, and fatigue resistance of the aluminum alloy.

[0073] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains V in a mass percentage of 0-0.2%. The mass percentage 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 the grains, second phases, and precipitated phases, reduce the grain boundary area, and reduce the corrosion sensitivity at the grain boundary, thereby improving the corrosion resistance and elongation of the aluminum alloy.

[0074] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains In in a mass percentage of 0-0.2%. The mass percentage 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 improve the strength of the aluminum alloy; In can also refine the grains, second phases, and precipitated phases, thereby improving the elongation of the aluminum alloy.

[0075] The high-strength Al-Si-Mg series die-casting aluminum alloy further contains B in a mass percentage of 0-0.1%. The mass percentage 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 precipitated 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, and CuB, which can reduce the solid solubility of the above elements in the matrix and reduce the adverse effects of the above elements on the elongation and thermal conductivity; in addition, B can refine grains, modify elemental Si to reduce the adverse effects of coarse elemental Si on the performance of the aluminum alloy, and can change the β-AlFeSi phase into a Chinese character-shaped α-AlFeSi phase to eliminate the adverse effects of the iron-rich phase on the performance of the aluminum alloy, and can inhibit the segregation of TiAl3, so that Ti and B have a good effect when used together; the boronization of B can also purify the aluminum alloy liquid, further improving the strength and elongation of the aluminum alloy.

[0076] The high-strength Al-Si-Mg series die-casting aluminum alloy further contains Ge in a mass percentage of 0-0.1%. The mass percentage 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 to improve the mechanical properties of the alloy. Specifically, Ge can react with Al and Si to form second phases such as Al9Ge7, Al6Ge5, Al5Ge2, Al3Ge4, and SiGe. In addition, Ge can promote the precipitation of second phases such as Mg2Si and CuAl2, refine the precipitated phases, reduce the solid solubility of the above elements in the aluminum matrix, and Ge can also replace part of the Si atoms in the metastable precipitated phase, providing nucleation sites for the main precipitated phases β" and θ" at the early stage of aging, increasing the density of the β" and θ" phases, and further improving the mechanical properties of the aluminum alloy.

[0077] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains 0-0.1% of Nb in terms of mass percentage. The mass percentage 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 the grains, the second phase, and the precipitated phase, thereby improving the elongation 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, thereby significantly improving the strength of the aluminum alloy.

[0078] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains 0-0.1% of Te in terms of mass percentage. The mass percentage 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 the eutectic silicon, shorten the length of the eutectic silicon, and improve the elongation of the aluminum alloy; when the aluminum alloy contains both Sb and Te, fine petal-shaped primary crystals can be formed, thereby further improving the strength and elongation of the aluminum alloy.

[0079] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains 0-0.1% of Ag in terms of mass percentage. The mass percentage 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 second phase, thereby improving the elongation of the aluminum alloy. Ag can promote the precipitation of the second phase (such as Al2Cu, Mg2Si, Mg2Sb, MgZn2, Mg3Sn2, and Mg3Bi2), refine the precipitated phase, and improve the density of the precipitated phase, thereby improving the precipitation strengthening effect of the aluminum alloy, and Ag can also refine the second phase, thereby improving the elongation, strength, and mechanical properties of the aluminum alloy.

[0080] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains 0-1% of AlTiB, 0-1% of BN, and 0-1% of AlTiC in terms of mass percentage.

[0081] The mass percentage content of AlTiB, BN and AlTiC can 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%.

[0082] When AlTiB and SiC are used in combination, the mass percentage content of SiC can be reduced to 4-10%, thus reducing the cost. 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 have a tendency to enhance the adhesion energy of the C-TiB2 / Al interface, the originally long strip-shaped TiAl3 is broken and shortened, so as to avoid the enrichment and growth of TiAl3, and the composite refining effect is greatly enhanced. And it has been verified through multiple experiments that when the mass percentage content of AlTiB is 0.1-0.5% and the mass percentage content of SiC is 4-10%, the strength, elongation, wear resistance, corrosion resistance and thermal stability of the aluminum alloy can be greatly improved.

[0083] AlTiB, SiC, AlTiC and BN all have good refining effect, and when used in combination, the content of each can be reduced to achieve a good refining 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 have a tendency to enhance the adhesion energy of the C-TiB2 / Al interface, the originally long strip-shaped TiAl3 is broken and shortened, so as to avoid the enrichment and growth of TiAl3, and the composite refining effect is greatly enhanced; BN is dispersedly distributed at the interface and grain boundary of the aluminum matrix to form AlB2 and AlN nano-nuclei, which can refine the grains and promote the uniform nucleation of the 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 fine-grain strengthening effect.

[0084] The application also provides a preparation method of the high-strength Al-Si-Mg series die-casting aluminum alloy.

[0085] Si source, Mg source, Ni source, Fe source, Cr source, Ti source, Sr source, Zr source, SiC source, Cu source and Al source are provided.

[0086] The Al source is subjected to a heating treatment to obtain aluminum liquid.

[0087] adjusting a temperature of the molten aluminum to be 750-820ºC, adding a Si source into the molten aluminum to obtain a first mixed liquid;

[0088] adjusting a temperature of the first mixed liquid to be 720-740ºC, adding 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, and a Cu source into the first mixed liquid to obtain a second mixed liquid;

[0089] performing degassing treatment, refining treatment, and die casting treatment on the second mixed liquid to obtain an aluminum alloy part; and

[0090] performing aging treatment on the aluminum alloy part 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 of 6-8%, Mg with a mass percentage of 1.2-1.8%, Ni with a mass percentage of 0.01-2.5%, Fe with a mass percentage of 0.01-0.4%, Cr with a mass percentage of 0.01-0.5%, Ti with a mass percentage of 0.06-0.25%, Sr with a mass percentage of 0-0.05%, SiC with a mass percentage of 0-35%, Zr with a mass percentage of 0-0.3%, and Cu with a mass percentage of 0-0.1%.

[0091] 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 can be aluminum intermediate alloy.

[0092] In an embodiment, the die casting treatment can be high-pressure casting, the temperature is 600-670ºC, the low-speed injection speed is 0.23-0.3m / s, and the high-speed injection speed is 2-2.5m / s. The temperature of the existing die-casting aluminum alloy is about 680ºC, which is relatively high. When the mixed liquid is placed in the mold at this temperature, the erosion of the mixed liquid to the mold is extremely large, which can cause the service life of the mold to be relatively short. The melting point of the Al-Si-Mg series die-casting aluminum alloy of the present application is relatively low, so that the temperature of the die casting treatment of the present application can be set to be relatively low, the erosion to the mold is relatively small, and the service life of the mold can be improved.

[0093] In another embodiment, the die casting process can be a semi-solid die casting process to produce a semi-solid die casting aluminum alloy. In the semi-solid die casting process, a device that can increase "flow + stirring" is used to improve the uniformity of the second mixture to obtain a semi-solid slurry, and a vacuum-assisted technique is used to reduce the air pressure in the mold cavity to 30-50 kPa, and then the semi-solid slurry is injected into the mold for semi-solid die casting forming. In the semi-solid die casting process, the temperature of the second mixture is 580-610°C, the stirring speed is 550-700 r / min, the stirring time is 4-10 min, the solid phase rate is controlled at 35-50%, the injection speed is 0.4-1.5 m / s, and the mold temperature is 220-240°C.

[0094] When the die casting process is a semi-solid die casting process, the refining process can be: mixing potassium titanate whiskers and aluminum powder to obtain a mixture; using a low-energy ball mill to crush the mixture under an argon protective atmosphere; and adding the mixture of potassium titanate whiskers and aluminum powder to the second mixture while mechanically stirring or electromagnetically stirring the second mixture. 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 to the mass of the second mixture is 3-10%, specifically 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. By controlling the temperature and holding time of the second mixture, a titanium-rich transition layer is formed on the surface of the potassium titanate whiskers based on the crystallographic orientation relationship between potassium titanate whiskers and α-Al, which reduces the interface mismatch degree and enhances the heterogeneous nucleation ability. The potassium titanate whiskers act as a non-uniform nucleation substrate and preferentially induce the nucleation of α-Al grains during the solidification process of the aluminum alloy, significantly increasing the nucleation rate and thereby refining the grains. The potassium titanate whiskers can also inhibit grain growth. The dispersed potassium titanate whiskers limit the abnormal growth of grains through physical hindering and reduce the interdendritic spacing, thereby improving the uniformity of the aluminum alloy structure. In this way, the strength, wear resistance, and cutting machinability of the aluminum alloy can be improved, making it suitable for manufacturing precision components such as engine cylinder sleeves and bearings.

[0095] The high-pressure casting or semi-solid die casting process uses a mold including a movable mold and a fixed mold, both of which are formed with parting surfaces that together form a cavity for receiving the mixed melt to form an aluminum alloy product with a certain shape. Before the die casting process, both parting surfaces can be subjected to a surface treatment, which is forming a boron carbide layer on the parting surfaces. The boron carbide layer not only improves the demolding performance, but also improves the wear resistance of the mold, and can resist the corrosion of chemical substances such as acid, alkali, and salt, and the thermal erosion of aluminum alloy, thereby prolonging the service life of the mold. The thickness of the boron carbide layer can be 1-10 mm, and specifically can be 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 content of Fe, the sum of the mass percentages of Fe and Cr, or the sum of the mass percentages of Fe, Cr, Co, and Mn can be set lower.

[0096] The surface treatment can be mixing a boron-containing gas (such as BCl3) with a carbon-containing gas (such as CH4) to obtain a mixed gas, introducing the mixed gas into the cavity, and depositing a boron carbide layer on the parting surfaces by chemical vapor deposition, in which the boron-containing gas and the carbon-containing gas chemically react. The temperature of the chemical vapor deposition 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 mold steel reach 3000-4000 Hv; the boron carbide layer can reduce the affinity of the mixed melt to the surface of the mold, improve the demolding performance of the aluminum alloy, and enable smooth demolding even with a lower content of Fe, Cr, Co, or Mn, thereby greatly improving the elongation of the aluminum alloy; the boron carbide layer can resist the corrosion of chemical substances such as acid, alkali, and salt, and can improve the corrosion resistance of the aluminum alloy; the boron carbide layer can 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 a very low friction coefficient, and can improve the smoothness of the surface of the aluminum alloy, thereby significantly reducing the wear and energy consumption of the aluminum alloy product caused by mechanical friction; and the boron carbide layer also has high heat transfer properties, and can quickly conduct heat away at the moment of forming the aluminum alloy, thereby improving the heat transfer speed of the mold, which is 2-4 times that of an ordinary mold, allowing the formed aluminum alloy to cool faster and the structure to be more refined, thereby improving the strength and elongation of the aluminum alloy.

[0097] The degassing treatment adjusts the temperature of the second mixed solution to 700-740°C, and uses a degassing machine to introduce an inert gas such as argon into the second mixed solution. The temperature of the degassing treatment can be specifically 700°C, 710°C, 720°C, 730°C, or 740°C. The time of the degassing treatment is 10-30 min, and can be specifically 10 min, 15 min, 20 min, 25 min, or 30 min.

[0098] In another embodiment, the refining treatment is that when the argon or other inert gas is introduced into the second mixed solution by the degassing machine, the refining agent can be added at the same time. The vortex formed by the rotating disc of the degassing machine in the second mixed solution can make the refining agent uniformly dispersed and mixed into the second mixed solution. The refining agent 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 refining treatment time is 10-30 min, specifically 10 min, 15 min, 20 min, 25 min, or 30 min. The refining treatment temperature is 700-740℃, specifically 700℃, 710℃, 720℃, 730℃, or 740℃. The refining agent contains: potassium fluoroaluminate 5-10 parts, AlTi5B1 metal powder 6-20 parts, potassium titanate whisker powder 8-25 parts, sodium chloride + potassium chloride 20-40 parts, potassium nitrate 5-10 parts, potassium carbonate 5-10 parts, and potassium silicate 0.5-3 parts. It can be understood that the refining treatment is suitable for semi-solid die casting treatment and high-pressure casting.

[0099] In an embodiment, the aging treatment temperature is 170-250℃, and the aging treatment time is 0.05-30h. The aging treatment temperature can be specifically 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, or 250℃, and the aging treatment time can be specifically 0.05h, 1h, 5h, 10h, 15h, 20h, 25h, or 30h.

[0100] In another embodiment, the aging treatment comprises a first stage aging treatment, a second stage aging treatment, and a third stage aging treatment. The first stage aging treatment has a temperature of 80-120°C, specifically 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, or 120°C, and a time of 3-20h, specifically 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, or 20h; the second stage aging treatment has a temperature of -200~-100°C, specifically -200°C, -190°C, -180°C, -170°C, -160°C, -150°C, -140°C, -130°C, -120°C, -110°C, or -100°C, and a time of 0.5~10h, specifically 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, or 10h; and the third stage aging treatment has a temperature of 170-250°C, specifically 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, or 250°C, and a time of 0.05-5h, specifically 0.05h, 0.1h, 0.2h, 0.3h, 0.4h, 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1h, 2h, 3h, 4h, or 5h. The first stage aging treatment has a lower temperature, in which the atoms in the aluminum alloy part obtained by die casting are stabilized and dense GP zones are formed, while avoiding the rapid precipitation of unsaturated Ni, so that the content of Ni can be set higher.In the second aging treatment, the volume shrinks sharply, which generates considerable stress, and in turn generates a large number of dislocations. The dislocations interact with the stress and grain boundaries in the alloy and entangle with each other, which increases the yield strength, tensile strength, and elongation of the alloy. During the second aging treatment, the crystal structure of the material changes, and recovery recrystallization occurs during the cryogenic recovery process, which causes the grains to rotate and form recrystallization texture, thereby increasing the tensile strength and yield strength of the aluminum alloy. The large number of supersaturated point defects (such as vacancies) and dislocations obtained by the aluminum alloy during the second aging treatment can further promote the segregation of solute atoms such as Si, Mg, Ni, Fe, Cr, Ti, Sr, Zr, and Cu, significantly increase the GP zone range, increase the nucleation rate during the third aging treatment, and promote the full precipitation of alloying elements. After the second aging treatment, the temperature is adjusted to 170-250°C within 1-5 min to ensure that the supersaturated point defects (such as vacancies) and dislocations formed during the second aging treatment are retained in the third aging treatment. At this time, the GP zone gradually changes into smaller but larger volume fraction precipitates, which fully or nearly fully precipitate the alloying elements dissolved in the alloy, increase the pinning effect on dislocations, and greatly increase the strength and elongation of the aluminum alloy. The aging treatment can further include a fourth aging treatment, which can be natural aging treatment or water cooling aging treatment. After the fourth aging treatment, the elongation of the aluminum alloy is further improved, but the strength decreases. The natural aging treatment is to place the aluminum alloy parts after the third 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 cooling aging treatment is to place the aluminum alloy parts after the third 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, the temperature of the aluminum alloy parts decreases rapidly, and the fine strengthening phase continues to precipitate but the precipitation rate decreases, which further improves the strength and elongation of the aluminum alloy. During the water cooling aging treatment, the temperature of the aluminum alloy parts decreases more rapidly, and the fine strengthening phase continues to precipitate but the precipitation rate decreases more rapidly, which further improves the strength and elongation of the aluminum alloy. The strength and elongation of the aluminum alloy after the water cooling 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, and Cu allows the alloy to precipitate a variety of Si, Mg, Ni, Fe, Cr, Ti, Sr, Zr, and Cu-containing dispersoids during the aging stage. These dispersoids can themselves refine the grains, increase the strength and elongation of the alloy, and serve as the core for the heterogeneous nucleation of β" phase, thereby further increasing the strength and elongation.

[0101] In another embodiment, the aging treatment comprises a first low-temperature electric field aging treatment and a second high-temperature aging treatment. The first low-temperature electric field aging treatment has a temperature of 50-130°C, a time of 0.1-100h, and an electric field strength of 2-50kV / cm. The temperature of the first low-temperature electric field aging treatment can be specifically 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 be specifically 0.1h, 0.5h, 1h, 5h, 10h, 15h, 20h, 25h, 30h, 35h, 40h, 45h, 50h, 55h, 60h, 65h, 70h, 75h, 80h, 85h, 90h, 95h, or 100h, and the electric field strength can be specifically 2kV / cm, 5kV / cm, 10kV / cm, 15kV / cm, 20kV / cm, 25kV / cm, 30kV / cm, 35kV / cm, 40kV / cm, 45kV / cm, or 50kV / cm. The second high-temperature aging treatment has no electric field effect, has a temperature of 170-250°C, and has a time of 0.05-30h. The temperature of the second high-temperature aging treatment can be specifically 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, or 250°C, and the time can be specifically 0.05h, 0.1h, 0.5h, 1h, 5h, 10h, 15h, 20h, 25h, or 30h. During the first low-temperature electric field aging treatment, the low temperature of 50-130°C can inhibit the atomic segregation of Si, Mg, Ni, Fe, Cr, Ti, Sr, Zr, Cu, etc., and at the same time, can make the alloy have a greater undercooling degree, significantly increase the GP zone range, facilitate the increase of the nucleation rate in the subsequent high-temperature process, and enable the alloy elements to be more fully precipitated. Secondly, the application of an electric field at a low temperature can reduce the precipitation activation energy of the phases in the alloy, can accelerate the precipitation nucleation rate of the precipitated phases in the aging process, and can increase the volume fraction of the nucleation points. The hardness of the alloy increases significantly at the initial stage of the electric field aging, and in the subsequent second high-temperature aging treatment, the time required for the alloy to reach the peak hardness is shortened, the volume fraction of the precipitated phases is increased, and the precipitated phase size is refined. With the increase of the electric field strength in the first low-temperature electric field aging treatment, the number of nucleation points of the strengthening phases precipitated in the alloy increases sharply, which indicates that increasing the electric field strength can increase the nucleation and precipitation rate of the precipitated phases, and does not have a significant effect on the growth of the second high-temperature aging phases without electric field effect, and does not cause size coarsening, thereby improving the elongation of the aluminum alloy.

[0102] The high-strength Al-Si-Mg series die-casting aluminum alloy contains 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, 0-35% of SiC and 0-0.1% of Cu in terms of mass percentage. The elements interact with each other and affect each other, so that the high-strength Al-Si-Mg series die-casting aluminum alloy has better yield strength and tensile strength.

[0103] In the technical scheme of the present application, 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 strength of the aluminum alloy is not improved much when the mass percentage content of Si is 6-8%; correspondingly, the mass percentage content of Mg is 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%, so that the strength of the aluminum alloy is greatly improved by Mg, Ni, Zr, and SiC, but the elongation of the aluminum alloy is greatly reduced when the mass percentage content of Mg is 1.2-1.8%; in order to improve the elongation of the aluminum alloy, the mass percentage contents of Fe and Cu are set to be relatively low, i.e. 0.01-0.4% (preferably 0.1-0.2%) and 0-0.1% (preferably 0.001-0.05%) respectively, so as to avoid the influence of high content of Fe on the elongation of the aluminum alloy, and at the same time, the elongation of the aluminum alloy is improved by low content of Cu; the present application also uses Cr with a mass percentage content of 0.01-0.5%, Ti with a mass percentage content of 0.06-0.25%, Ni with a mass percentage content of 0.01-2.5%, Zr with a mass percentage content of 0-0.3%, SiC with a mass percentage content of 0-35%, and Sr with a mass percentage content of 0-0.05% (preferably 0.01-0.05%) to refine the grains, the second phase and the precipitated phase, so as to improve the strength and the elongation of the aluminum alloy; when the content of Fe is not high, the Cr with a mass percentage content of 0.01-0.5% can also improve the demolding performance of the aluminum alloy; Zn, Cr, Ni, and Sr can also promote the precipitation of Mg2Si, MgZn2, Mg2SiZn, Al2Cu, etc., so as to further improve the elongation and the mechanical properties of the aluminum alloy; the above-mentioned elements can also react with each other to form the second phase, so as to avoid the influence of solid solution in the aluminum matrix on the elongation of the aluminum alloy. In this way, the Si, Mg, Ni, Fe, Cr, Ti, Sr, Zr, SiC, and Cu in the above-mentioned content range interact with and affect each other as a whole, so that the aluminum alloy elements have better strength, elongation, and demolding performance. Moreover, under the further action of the above-mentioned content range of Si, Mg, Zn, Fe, Cr, Ti, Sr, and Cu in the subsequent refining treatment, aging treatment, and die casting treatment, the solid solubility of each element in the aluminum matrix is further reduced, and the impurity elements are also further reduced, so as to 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 phase, etc.) can also be refined in the aluminum matrix and at or in the grain boundaries, so as to greatly improve the strength and the elongation of the aluminum alloy.

[0104] The preparation method of the high-strength Al-Si-Mg series die-casting aluminum alloy further comprises 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 into the first mixed solution. The above elements can at least be used to improve the strength and elongation of the aluminum alloy, so as to obtain a high-strength Al-Si-Mg series die-casting aluminum alloy with more excellent performance. The raw material of the above alloying elements can be aluminum master alloy. For example, the RE source can be Al-RE alloy.

[0105] Embodiment

[0106] The components and contents of the aluminum alloys of examples one to ten are shown in Table 1, and the performance test results are shown in Table 2.

[0107] Table 1 Components and contents of the aluminum alloys of examples one to ten

[0108]

[0109]

[0110] For simplicity, all impurity elements and contents are not shown.

[0111] Table 2 Performance test results of the aluminum alloys of examples one to ten

[0112]

[0113] The aluminum alloys of examples one to ten are made into structural parts, and the tensile strength, yield strength, and elongation of the structural parts are tested. The test results are shown in Table 2. Among them, the molds are surface treated during the production process of examples six to ten, and a 2mm boron carbide layer is formed on the parting surface of the mold.

[0114] Table 2 shows that the aluminum alloys of examples one to ten have better tensile strength, yield strength, and elongation. Specifically, the tensile strength of the aluminum alloys of examples one to ten is not less than 400MPa, the yield strength is not less than 310MPa, and the elongation is not less than 4%.

[0115] The above only describes the preferred embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent structural transformation based on the content of the present application, or direct / indirect application in other related technical fields is included in the patent protection scope of the present application.

Claims

1. A high-strength Al-Si-Mg die-cast aluminum alloy, containing Al, characterized in that, The high-strength Al-Si-Mg die-cast aluminum alloy further contains 6-8% Si, 1.2-1.8% Mg, 0.01-2.5% Ni, 0.01-0.4% Fe, 0.01-0.5% Cr, 0.06-0.25% Ti, 0-0.05% Sr, 0-0.3% Zr, 0-35% SiC, and 0-0.1% Cu by mass. The preparation method of the high-strength Al-Si-Mg die-cast aluminum alloy includes the following steps: It provides Si, Mg, Ni, Fe, Cr, Ti, Sr, Zr, SiC, Cu, and Al sources; The Al source is heated to obtain molten aluminum; Adding Si, Mg, Ni, Fe, Cr, Ti, Sr, Zr, SiC, and Cu sources to the molten aluminum yields a mixed solution; and The mixture is subjected to die casting and aging treatment to obtain the high-strength Al-Si-Mg die-cast aluminum alloy. 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 hours. The temperature of the second-stage aging treatment is -200 to -100°C, and the time is 0.5 to 10 hours. The temperature of the third-stage aging treatment is 170-250°C, and the time is 0.05 to 5 hours. After the second-stage aging treatment is completed, the temperature is adjusted to 170-250°C within 1-5 minutes. The fourth-stage aging treatment is either natural aging treatment or water-cooled aging treatment. The natural aging treatment involves placing the aluminum alloy parts that have undergone the third-stage aging treatment at room temperature for 0.5-5 hours. The water-cooled aging treatment involves placing the aluminum alloy parts that have undergone the third-stage aging treatment in room temperature water for 0.5-5 hours.

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

3. The high-strength Al-Si-Mg die-cast aluminum alloy according to claim 1, characterized in that, The high-strength Al-Si-Mg die-cast aluminum alloy further contains 0.01-0.5% Co and 0.01-0.5% Mn by mass, wherein the sum of the mass percentages of Fe, Cr, Co and Mn is 0.04-1%.

4. The high-strength Al-Si-Mg die-cast aluminum alloy according to claim 1, characterized in that, The high-strength Al-Si-Mg die-cast aluminum alloy further contains 0.01-0.3% Sn, 0.01-0.3% Sb, 0.01-0.6% Zn, and 0.01-0.3% Bi by mass. The sum of the mass percentages of Sn, Sb, Zn, Fe, and Bi is 0.05-1.2%, and the mass ratio of the sum of the mass percentages of Sn, Sb, Zn, Fe, and Bi to the mass percentage of Mg is 0.1-1:

1.

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

6. A method for preparing a high-strength Al-Si-Mg die-cast aluminum alloy, comprising the following steps: It provides Si, Mg, Ni, Fe, Cr, Ti, Sr, Zr, SiC, Cu, and Al sources; The Al source is heated to obtain molten aluminum; Adding Si, Mg, Ni, Fe, Cr, Ti, Sr, Zr, SiC, and Cu sources to the molten aluminum yields a mixed solution; and The mixture is subjected to die casting and aging treatment to obtain the high-strength Al-Si-Mg die-cast aluminum alloy. The high-strength Al-Si-Mg die-cast aluminum alloy contains 6-8% Si, 1.2-1.8% Mg, 0.01-2.5% Ni, 0.01-0.4% Fe, 0.01-0.5% Cr, 0.06-0.25% Ti, 0-0.05% Sr, 0-0.3% Zr, 0-35% SiC, and 0-0.1% Cu by mass. The aging treatment includes... The process includes a first-stage aging treatment, a second-stage aging treatment, a third-stage aging treatment, and a fourth-stage aging treatment. The first-stage aging treatment is carried out at a temperature of 80-120°C for 3-20 hours. The second-stage aging treatment is carried out at a temperature of -200 to -100°C for 0.5 to 10 hours. The third-stage aging treatment is carried out at a temperature of 170-250°C for 0.05 to 5 hours. After the second-stage aging treatment is completed, the temperature is adjusted to 170-250°C within 1-5 minutes. The fourth-stage aging treatment is either a natural aging treatment or a water-cooled aging treatment. The natural aging treatment involves placing the aluminum alloy parts that have undergone the third-stage aging treatment at room temperature for 0.5-5 hours. The water-cooled aging treatment involves placing the aluminum alloy parts that have undergone the third-stage aging treatment in room temperature water for 0.5-5 hours.

7. The method for preparing high-strength Al-Si-Mg die-cast aluminum alloy according to claim 6, characterized in that, The die-casting process is high-pressure casting, in which the temperature is 600-670ºC, the low-speed injection velocity is 0.23-0.3m / s, and the high-speed injection velocity is 2-2.5m / s; or The die casting process is a semi-solid die casting process. In the semi-solid die casting process, the temperature of the mixture is 580-610℃, the stirring speed is 550-700 r / min, the stirring time is 4-10min, the solid phase rate is 35-50%, the injection speed is 0.4-1.5m / s, the mold temperature is 220-240℃, and the air pressure in the mold cavity is 30-50kPa.

8. The method for preparing high-strength Al-Si-Mg die-cast aluminum alloy according to claim 6, characterized in that, The preparation method of the high-strength Al-Si-Mg die-cast aluminum alloy further includes the step of adding at least one of the following sources to the molten aluminum: Co source, Mn source, Sn source, Sb source, Zn 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, 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 0.01-0.3%, the mass percentage content of Sb is 0.01-0.3%, the mass percentage content of Zn is 0.01-0.6%, and the mass percentage content of Bi is 0.01-0.5%. 0.3%, Cd mass percentage is 0-0.2%, Ca mass percentage is 0-0.2%, Be mass percentage is 0-0.2%, V mass percentage is 0-0.2%, B mass percentage is 0-0.1%, RE mass percentage is 0-0.2%, Ge mass percentage is 0-0.1%, Mo mass percentage is 0-0.2%, Nb mass percentage is 0-0.1%, Te mass percentage is 0-0.1%, Ag mass percentage is 0-0.1%, In mass percentage is 0-0.2%, AlTiB mass percentage is 0-1%, BN mass percentage is 0-1%, AlTiC mass percentage is 0-1%.

9. A structural component, characterized in that, The material of the structural component is the high-strength Al-Si-Mg die-cast aluminum alloy as described in any one of claims 1-5, or the high-strength Al-Si-Mg die-cast aluminum alloy prepared by the preparation method of the high-strength Al-Si-Mg die-cast aluminum alloy as described in any one of claims 6-8.

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