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

Abstract

The application provides a high-strength high-elongation Al-Si-Mg series die-casting aluminum alloy and a preparation method and a structural member thereof. The high-strength high-elongation 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%, Zn with a mass percentage of 0.001-2.5%, Fe with a mass percentage of 0.01-0.4%, Cr with a mass percentage of 0.001-0.5%, Ti with a mass percentage of 0.001-0.15%, Sr with a mass percentage of 0-0.05%, Mn with a mass percentage of 0-0.3%, Zr with a mass percentage of 0-0.3%, Li with a mass percentage of 0-0.5%, and Cu with a mass percentage of 0-0.1%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum alloy, and particularly relates to a high-strength high-elongation 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, has the advantages of high strength, small density, good mechanical properties, easy machining and cutting, and is widely applied in the fields of aerospace military industry, new energy vehicles, consumer electronics, household and industrial electrical appliances and high-rise buildings. For the Al-Si series die-casting aluminum alloy, the addition of silicon element does not greatly improve the strength of the die-casting aluminum alloy, and it is necessary to add alloy elements such as Mg element which can improve the strength. However, the addition of Mg element sharply reduces the elongation of the Al-Si series die-casting aluminum alloy. Therefore, it is urgent to provide an Al-Si series die-casting aluminum alloy which has better tensile strength, yield strength and elongation. SUMMARY

[0003] In view of the above defects of the prior art, the present application provides a high-strength high-elongation Al-Si-Mg series die-casting aluminum alloy which has better tensile strength, yield strength and elongation.

[0004] The present application provides a high-strength high-elongation Al-Si-Mg series die-casting aluminum alloy which contains Al, and further contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Zn with a mass percentage content of 0.001-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.001-0.5%, Ti with a mass percentage content of 0.001-0.15%, Sr with a mass percentage content of 0-0.05%, Mn with a mass percentage content of 0-0.3%, Zr with a mass percentage content of 0-0.3%, Li with a mass percentage content of 0-0.5%, and Cu with a mass percentage content of 0-0.1%.

[0005] Further, the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy further contains Si with a mass percentage of -8%, Mg with a mass percentage of 1.2-1.8%, Zn with a mass percentage of 0.001-2%, Fe with a mass percentage of 0.01-0.4%, Cr with a mass percentage of 0.001-0.5%, Ti with a mass percentage of 0.001-0.15%, Sr with a mass percentage of 0.001-0.05%, Mn with a mass percentage of 0.001-0.3%, Zr with a mass percentage of 0.001-0.3%, Li with a mass percentage of 0.001-0.5%, and Cu with a mass percentage of 0.001-0.1%.

[0006] Further, the mass ratio of Mg to Zn is 0.1-10:1.

[0007] Further, the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy further contains at least one of Sb, Sn, Co, Bi, Ca, Be, V, Ge, Mo, Nb, Te, Ag, In, AlTiB, SiC, BN, and AlTiC, wherein the mass percentage of Sb is 0-0.3%, the mass percentage of Sn is 0-0.3%, the mass percentage of Co is 0-0.3%, the mass percentage of Bi is 0-0.3%, 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 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 SiC is 0-35%, the mass percentage of BN is 0-1%, and the mass percentage of AlTiC is 0-1%.

[0008] The application further provides a preparation method of the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy, comprising the following steps:

[0009] providing a Si source, a Mg source, a Zn source, a Fe source, a Cr source, a Ti source, a Sr source, a Mn source, a Li source, a Zr source, a Cu source, and an Al source;

[0010] heating the Al source to obtain aluminum liquid;

[0011] adding a Si source, a Mg source, a Zn source, a Fe source, a Cr source, a Ti source, a Sr source, a Mn source, a Li source, a Zr source, and a Cu source into the molten aluminum to obtain a mixed liquid; and

[0012] subjecting the mixed liquid to a die casting treatment and an aging treatment to obtain the high-strength and high-elongation Al-Si-Mg series die casting aluminum alloy, wherein the high-strength and high-elongation Al-Si-Mg series die casting aluminum alloy contains Si in a mass percentage of 6-8%, Mg in a mass percentage of 1.2-1.8%, Zn in a mass percentage of 0.001-2.5%, Fe in a mass percentage of 0.01-0.4%, Cr in a mass percentage of 0.001-0.5%, Ti in a mass percentage of 0.001-0.15%, Sr in a mass percentage of 0-0.05%, Mn in a mass percentage of 0-0.3%, Zr in a mass percentage of 0-0.3%, Li in a mass percentage of 0-0.5%, and Cu in a mass percentage of 0-0.1%.

[0013] Further, the method for preparing the high-strength and high-elongation Al-Si-Mg series die casting aluminum alloy further comprises a step of subjecting the mold to surface treatment, wherein the surface treatment is forming a boron carbide layer on the parting surface of the mold.

[0014] Further, the die casting treatment is high-pressure casting, wherein 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

[0015] the die casting treatment is semi-solid die casting treatment, wherein the temperature of the mixed liquid is 580-610ºC, 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 220-240ºC, and the air pressure of the mold cavity is 30-50 kPa.

[0016] Further, the temperature of the aging treatment is 170-250ºC, and the time is 0.05-30 h; or

[0017] The aging treatment comprises 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 has a temperature of 80-120 DEG C and a time of 3-20 h, the second-stage aging treatment has a temperature of -200 to -100 DEG C and a time of 0.5-10 h, the third-stage aging treatment has a temperature of 170-250 DEG C and a time of 0.05-5 h, the temperature is adjusted to 170-250 DEG 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.

[0018] The aging treatment comprises 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 has a temperature of 80-120 DEG C and a time of 3-20 h, the second-stage aging treatment has a temperature of -200 to -100 DEG C and a time of 0.5-10 h, the third-stage aging treatment has a temperature of 170-250 DEG C and a time of 0.05-5 h, the temperature is adjusted to 170-250 DEG 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.

[0019] Further, the preparation method of the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy further comprises the step of adding at least one of Sb source, Sn source, Co source, Bi source, Ca source, Be source, V source, Ge source, Mo source, Nb source, Te source, Ag source, In source, AlTiB source, SiC source, BN source and AlTiC source into the aluminum liquid, wherein the mass percentage content of Sb is 0-0.3%, the mass percentage content of Sn is 0-0.3%, the mass percentage content of Co is 0-0.3%, the mass percentage content of Bi is 0-0.3%, 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 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 AlTiB is 0-1%, the mass percentage content of SiC is 0-35%, the mass percentage content of BN is 0-1%, and the mass percentage content of AlTiC is 0-1%.

[0020] The application further provides a structural member made of the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy or prepared by the preparation method of the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy.

[0021] The high-strength high-elongation Al-Si-Mg series die-casting aluminum alloy contains 6-8% of Si, 1.2-1.8% of Mg, 0.001-2.5% of Zn, 0.01-0.4% of Fe, 0.001-0.5% of Cr, 0.001-0.15% of Ti, 0-0.05% of Sr, 0-0.3% of Mn, 0-0.3% of Zr 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 high-elongation Al-Si-Mg series die-casting aluminum alloy has better yield strength, tensile strength and elongation. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0023] An embodiment of the present application provides a high-strength high-elongation Al-Si-Mg series die-casting aluminum alloy. The high-strength high-elongation Al-Si-Mg series die-casting aluminum alloy has better tensile strength, yield strength and elongation, and is suitable for being made into various structural parts. The thickness of the structural part can be 1.5-15 mm, and specifically can be 1.5 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm or 15 mm.

[0024] The high-strength high-elongation Al-Si-Mg series die-casting aluminum alloy contains Al, and further contains 6-8% of Si, 1.2-1.8% of Mg, 0.001-2.5% of Zn, 0.01-0.4% of Fe, 0.001-0.5% of Cr, 0.001-0.15% of Ti, 0-0.05% of Sr, 0-0.3% of Mn, 0-0.3% of Zr, 0-0.5% of Li and 0-0.1% of Cu in terms of mass percentage.

[0025] The mass percentage content 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%.

[0026] The mass percentage content of Mg can be specifically 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, or 1.8%.

[0027] The mass percentage content of Zn 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%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.45%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.78%, 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%. The mass percentage content of Mg and the mass percentage content of Zn can be proportional, and when the content of Mg is high, the content of Zn can also be set to be high, so as to generate more MgZn2 dispersed second phase, thereby greatly improving the strength of the aluminum alloy. The mass ratio of Mg to Zn is 0.1-10:1, and can be specifically 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1.

[0028] The mass percentage content of Fe 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%, or 0.4%.

[0029] The mass percent content of Cr and Li 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%, 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%.

[0030] The mass percent content of Ti 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%, or 0.15%.

[0031] The mass percent content of Mn and Zr 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%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, or 0.3%.

[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 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%.

[0034] In one embodiment, the high-strength, high-elongation Al-Si-Mg die-cast aluminum alloy further comprises 6-8% Si, 1.2-1.8% Mg, 0.001-2% Zn, 0.01-0.4% Fe, 0.001-0.5% Cr, 0.001-0.15% Ti, 0.001-0.05% Sr, 0.001-0.3% Mn, 0.001-0.3% Zr, and 0.001-0.1% Cu.

[0035] 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%.

[0036] 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, 0.001-2.5% Zn, 0.01-0.4% Fe, 0.001-0.5% Cr, 0.001-0.15% Ti, 0-0.05% Sr, 0-0.3% Mn, 0-0.3% Zr, and 0-0.1% Cu by mass. The Si, Mg, Zn, Fe, Cr, Ti, Sr, Mn, Li, Zr, and Cu within the above content ranges act as a whole, interacting and influencing each other to ensure that the Al-Si-Mg system has a better elongation. Specifically:

[0037] (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.

[0038] (2) The mass percentage content of Mg is 1.2-1.8%, and Mg can greatly improve the mechanical properties of the aluminum alloy; Mg can react with other elements to form a second phase, thereby avoiding adverse effects on the elongation of the aluminum alloy; Mg can react with Al, Fe, Si, Cu, Zn, B, Ni and the like to form MgB, Mg2Sn, 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;

[0039] (3) The mass percentage content of Zn is 0.01-2.5%, and Zn can be dissolved in the aluminum matrix to greatly improve the strength of the aluminum alloy through solid solution strengthening; 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, thereby improving 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; Zn can also promote the precipitation of phases such as Mg2Si and Al2Cu, thereby improving the mechanical properties; in addition, Zn can react with other elements to form a second phase, thereby avoiding 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 and the like to form MgZn2, Mg2SiZn, Al2CuZn and the like;

[0040] (4) The mass percentage content of Fe is 0.01-0.4%, on the one hand, Fe can reduce the die sticking tendency of the aluminum alloy casting and improve the mechanical properties of the aluminum alloy; on the other hand, Fe can react with other elements to form a second phase as much as possible, thereby avoiding adverse effects of Fe dissolved in the aluminum matrix on the elongation of the aluminum alloy; specifically, Fe can react with Al, Si, Mg, Cu, Mn, Ni and the like to form Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu, AlFeSiNi, AlFeMgSiNi, AlFeMnSi, (CrFe)Al7, (CrMn)Al 12 , AlFeSiB, FeNiAl9 and the like;

[0041] (5) The mass percentage content of Cr is 0.001-0.5%, and Cr can form (CrFe)Al7 and (CrMn)Al 12The intermetallic compound has certain strengthening effect on the aluminum alloy; Cr can also 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; the appropriate amount of Cr forms a plurality of fine compounds containing Cr 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 a plurality of 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;

[0042] (6) The mass percentage content of Ti is 0.001-0.15%, 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;

[0043] (7) The mass percentage content of Sr is 0-0.05%, 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; Sr can also 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, thereby improving the elongation of the aluminum alloy; Sr can preferentially combine with Fe, Cu, Mn, Cr, Si and other elements to form dispersion strengthening, thereby avoiding the adverse effect of Sr solid-solved in the aluminum matrix on the elongation of the aluminum alloy; Sr can also promote the precipitation of CuAl2, Mg2Si and other phases to reduce the solid solubility of these alloying elements in the aluminum matrix to improve the elongation of the aluminum alloy;

[0044] (8) The mass percentage content of Mn is 0-0.3%, the mass percentage content of Mn is 0.001-0.3%, Mn reacts with Fe to generate a dispersed and fine α-Al(FeMn)Si phase, which can improve the regulation and control of the β-Fe-rich phase; Mn can significantly refine the recrystallized grains and the second phase, effectively change the coarse needle-shaped or flaky β-AlFeSi phase into small particle-shaped α-Al(FeMn)Si dispersion particles to improve the Fe morphology, thereby improving the strength and elongation of the aluminum alloy;

[0045] (9) The mass percentage content of Zr is 0-0.3%, and Zr can improve the strength of the aluminum alloy; Zr can also form Al3Zr phase in the aluminum alloy, and the Al3Zr phase can refine the grains, the second phase and the precipitated phase, so as to improve the elongation of the aluminum alloy; Mn can form independent Al6Mn and Al6FeMn hardening phases in the aluminum alloy, and the Mn-rich phases are distributed in the grain boundaries or near the grain boundaries to pin the grain boundaries; although the Mn-rich phases have low coherence with the Al matrix and have large sizes, the ability of pinning dislocations is weak, but the combined addition of Mn and Zr can not only reduce the usage amount of each alloying element, but also promote the precipitation of each other to form more Al6(Mn,Zr) and Al6(FeMnZr) phases, and the strengthening effect is much greater than that when Mn or Zr is added alone; 3( Zr,Mn) phase and Al6(FeMnZr) phase;

[0046] (10) The mass percentage content of Li is 0-0.5%, and the solid solution strengthening of Li in the aluminum matrix can improve the strength of the aluminum alloy; and the fraction of the aging precipitated phase δ' phase (Al3Li) is increased to improve the precipitated strengthening effect; in addition, the addition of Li greatly reduces the maximum solubility of elements such as Mg, Cu and Zr in the Al solid solution, reduces the stacking fault energy, promotes the formation of {111} Al stacking defects, and the {111} Al stacking defects are beneficial for nucleation; the high-angle grain boundaries and the low-angle grain boundaries are beneficial for the generation of the lamellar T1 phase (Al2CuLi); vacancies or vacancy groups can provide nucleation sites to form phases such as Mg2Si to pin the grain boundaries, so as to improve the strength and elongation of the aluminum alloy;

[0047] (11) 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 greater than 0.1%, the elongation of the aluminum alloy can be significantly improved; a small amount of Cu can also reduce the natural aging speed, so as to reduce the adverse effects of the parking effect on the alloy.

[0048] In order to avoid the adverse effect of Si on elongation, the mass percentage content of Si is set to 6-8% (preferably 6-7.5%) in the application, but the Si with the mass percentage content of 6-8% does not have a high improvement on 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 application, the mass percentage content of Zn is set to 0.01-2.5% (preferably 0.5-2%), and the mass percentage content of Li is set to 0-0.5% (preferably 0.1-0.5%), so as to greatly improve the strength of the aluminum alloy by Mg, Zn and Li, but the Mg with the mass percentage content of 1.2-1.8% can greatly reduce the elongation of the aluminum alloy, and Zn and Li can reduce the reduction of the elongation of the aluminum alloy caused by high content of Mg; 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 0.05-0.2%) 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; the application also adds Cr with the mass percentage content of 0.001-0.5% (preferably 0.01-0.2%) and Mn with the mass percentage content of 0-0.3% (preferably 0.01-0.2%), so as to compensate for the influence of low content of Fe on the demolding performance, thereby ensuring the demolding performance of the aluminum alloy, and the cooperation of Cr, Mn and Li can also improve the strength and elongation of the aluminum alloy; the application also adds Zr with the mass percentage content of 0-0.3% (preferably 0.01-0.2%), and the composite addition of Mn and Zr can not only reduce the usage amount of each alloying element, but also promote the mutual precipitation, thereby further improving the high-strengthening effect; the application also adds Ti with the mass percentage content of 0.001-0.15% (preferably 0.01-0.1%) and Sr with the mass percentage content of 0-0.05% (preferably 0.01-0.05%), so as to refine the grains, the second phase and the precipitated phase, thereby improving the strength and elongation of the aluminum alloy; Sr and Zr can also promote the precipitation of Mg2Si, MgB, (CuMg)Al2 and the like, thereby further improving the elongation of the aluminum alloy; the above-mentioned elements can also react with each other to form a second phase, thereby avoiding the influence of solid solution in the aluminum matrix on the elongation of the aluminum alloy. In this way, the Si, Mg, Zn, Fe, Cr, Ti, Sr, Mn, Li, Zr and Cu in the above-mentioned content range interact with and influence each other as a whole, so as to make the aluminum alloy elements have better strength, elongation and demolding performance.Moreover, the Si, Mg, Zn, Fe, Cr, Ti, Sr, Mn, Li, Zr, and Cu in the above content range further reduce the solid solubility of each element in the aluminum matrix and further reduce impurities under the further action of subsequent refining treatment, aging treatment, and die casting treatment, so as to eliminate the adverse effects of alloying elements and impurities on the elongation of the aluminum alloy as much as possible, and the second phase (such as Al3Fe, Mg2Si, Al2Cu, MgZn2, AlMnSi phase, etc.) can also be refined in the aluminum matrix and at or in the grain boundary, greatly improving the strength and elongation of the aluminum alloy.

[0049] The high-strength high-elongation Al-Si-Mg series die-casting aluminum alloy also contains 0.01-0.3% of Sb by mass percentage, 0.01-0.3% of Sn by mass percentage, 0.01-0.5% of Ni by mass percentage, and 0.01-0.3% of Bi by mass percentage.

[0050] The mass percentage of Sb, Sn, 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%.

[0051] The mass percentage of Ni 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%, or 0.5%.

[0052] The sum of the mass percentage contents of Sn, Sb, Ni, Fe and Bi is 0.05-1%. Specifically, the sum of the mass percentage contents of Sn, Sb, Ni, Fe and Bi can 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% or 1%.

[0053] The mass ratio of the sum of the mass percentage contents of Sn, Sb, Fe and Bi to the mass percentage content of Mg is 0.05-1:1. Specifically, the mass ratio of the sum of the mass percentage contents of Sn, Sb, Fe and Bi to the mass percentage content of Mg can be 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1.

[0054] Sn, Sb, 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, Fe and Bi to form Mg2Sn, AlFeMgSiNi, Mg3Sb2, 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. The sum of the mass percentage contents of Sn, Sb, Ni, Fe and Bi is 0.05-1%, and the mass ratio of the sum of the mass percentage contents of Sn, Sb, Ni, Fe and Bi to the mass percentage content of Mg is 0.05-1:1, which can ensure that Mg is entirely or almost entirely reacted with other alloying elements to form a second phase, avoid the presence of Mg solid-solved in the aluminum matrix, and also avoid the addition of too many elements to affect the elongation of the aluminum alloy. Specifically:

[0055] Fe can as much as possible react with other elements to form a second phase to avoid the adverse effects of Fe solid-solved in the aluminum matrix on the elongation of the aluminum alloy. Specifically, Fe can react with Al, Si, Mg, Cu, Mn, Ni and other elements to form Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu, AlFeSiNi, AlFeMgSiNi, AlFeMnSi, (CrFe)Al7, (CrMn)Al 12 , AlFeSiB, FeNiAl9 and other second phases.

[0056] Sb can be used as a modifier in aluminum alloy, effectively reducing the size of eutectic silicon layer, greatly reducing the possibility of Si cutting the matrix, to improve the mechanical properties of the alloy; Sb can react with other elements such as Mg to form second phase Mg3Sb2, to improve the mechanical properties of the alloy; in addition, the addition of Sb can also increase the mutual precipitation of elements such as Cu, Zn, Ni, etc. with a large solid solubility in the alloy matrix, further improving the mechanical properties of the alloy.

[0057] Sn can react with Mg to form 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 second phases, 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.

[0058] Bi expands during solidification, which is beneficial for feeding, and can form strengthening phases such as Mg3Bi2 and Mg3(BiCd)2 with Mg and Cd, thereby improving the mechanical properties of the alloy.

[0059] Ni can improve the mechanical properties of the aluminum alloy. Ni can also react with other elements to form second phases, thereby avoiding the adverse effects of Ni solid-solubilized in the aluminum matrix on the elongation of the aluminum alloy. Specifically, Ni can react with Al, Fe, Mg, Si, etc. to form second phases such as Al3Ni, AlFeSiNi, AlFeMgSiNi, and FeNiAl9, thereby promoting the precipitation of elements such as Cu, Mg, Zn, Si, and Fe that are solid-solubilized in the alloy. Ni can also refine the grains and promote the precipitation of strengthening phases such as CuAl2, (CuMg)Al2, and Mg2Si, thereby reducing the solid solubility of alloying elements in the aluminum matrix. Cu with a mass percentage content of 0-0.1% can cooperate with Mg with a mass percentage content of 1.2-1.8% and Ni with a mass percentage content of 0.01-0.5% to produce a composite strengthening effect, thereby reducing the solid solubility of each other in the matrix and improving the mechanical strength and elongation of the aluminum alloy.

[0060] The high-strength and high-elongation 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%, Co with a mass percentage content of 0-0.3%, 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.

[0061] The specific percentage content of RE, Mo, and Be 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%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%.

[0062] Co can react with other elements to form a second phase, thereby improving the mechanical properties of aluminum alloys. Specifically, Co can react with Al, Fe, Si, etc., to form Al. 15 Secondary phases include (Fe,Co)3Si2 and Al3(Fe,Co); Co can refine grains and also refine the Al3Fe phase, transforming coarse needle-like and plate-like β-Al3Fe phases into small flower-like and fine strip-like α-Al3Fe phases. 15 The (Fe,Co)3Si2 phase, with Co also promoting α-Al 15 The precipitation of the (Fe,Co)3Si2 phase further improves the strength and elongation of the aluminum alloy.

[0063] To avoid the influence of Fe on the elongation of aluminum alloys, the mass percentage content of Fe can be set relatively low. To ensure the demolding performance of aluminum alloys, the sum of the mass percentage contents of Fe, Cr, Co, and Mn should be 0.04-1%, specifically 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%. When the mold undergoes surface treatment to form a boron carbide layer on the parting surface, 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%; the sum of the mass percentage contents of Fe, Cr, and Mn can be 0.04-0.1%, specifically 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%; the sum of the mass percentage contents of Fe, Cr, Co, and Mn can be 0.04-0.5%, preferably 0.05-0.3%, and more preferably 0.05-0.1%. This achieves better demolding performance and avoids the impact of excessive element addition on elongation.

[0064] The elements of Mn, Cr, RE, Mo, Co, Be and Sr can not only reduce the maximum solid solubility of each other in the aluminum matrix to improve the elongation, but also promote the reaction of Mn and Fe, and Mn can occupy the position of Fe element in the second phase, so that the Fe-containing phase is more dispersed and fine, and the effect of modifying Fe is promoted. The elements of Mn, Cr, RE, Mo, Co, Be and Sr can also generate a-Al(MnFeX)Si phase (wherein X is at least one of Cr, RE, Mo, Co, Be and Sr) in a fine and dispersed state to improve the elongation of the aluminum alloy.

[0065] The combined addition of Ni with a mass percentage content of 0.01-0.5% and Co with a mass percentage content of 0.01-0.5% can effectively modify Fe and convert free Fe into a second phase to improve the mechanical properties of the aluminum alloy. The combination of 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 dispersion distribution degree of Mg2Si, while preventing the formation of coarse AlSiFe, Mg3Sb2, Mg2Si, Al3Zr and other phases, and reducing the solid solubility of various elements in the matrix to ensure uniform precipitation of the alloy during solidification; the addition of trace Cu can also reduce the anisotropy of the alloy after the addition of Mn.

[0066] The high-strength high-elongation Al-Si-Mg series die-casting aluminum alloy also contains Ca with a mass percentage content of 0-0.2%. The mass percentage content of Ca 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%. Ca can refine the eutectic structure, improve the β-Fe phase, improve the strength of the alloy while improving the heat treatment performance of the alloy, and also generate Al4Ca, Al2Ca3, AlCa2, AlCaCu strengthening phases with Cu and Al, significantly improving the strength, heat resistance and fatigue resistance of the aluminum alloy.

[0067] The high-strength and high-elongation 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 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%. V can refine the grains, the second phase and the precipitated phase, so as to reduce the grain boundary area and the corrosion sensitivity at the grain boundary, thereby improving the corrosion resistance and the elongation of the aluminum alloy.

[0068] The high-strength and high-elongation 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 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%. In can improve the strength of the aluminum alloy; In can also refine the grains, the second phase and the precipitated phase, so as to improve the elongation of the aluminum alloy.

[0069] The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy also 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 a second phase, thereby improving the mechanical properties of the alloy. Specifically, Ge can react with Al and Si to form Al9Ge7, Al6Ge5, Al5Ge2, Al3Ge4, SiGe, and other second phases. In addition, Ge can promote the precipitation of Mg2Si, CuAl2, and other second phases, refine the precipitated phases, and reduce the solid solubility of the above elements in the aluminum matrix. Ge can also replace part of the Si atoms in the metastable precipitated phase, provide nucleation sites for the Si-Ge phase that is precipitated at the early stage of aging, increase the density of the β", θ", and other phases, and further improve the mechanical properties of the aluminum alloy.

[0070] The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy also contains Nb in a mass percentage of 0-0.1%. 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, second phases, and precipitated phases, thereby improving the elongation of the aluminum alloy. When the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy contains both Nb and B, it can form AlNb3, AlNb, Al3Nb, NbB2, and other strengthening metallic compounds, thereby significantly improving the strength of the aluminum alloy.

[0071] The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy also contains Te in a mass percentage of 0-0.1%. 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 eutectic silicon in the length direction, 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, further improving the strength and elongation of the aluminum alloy.

[0072] The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy also contains Ag in a mass percentage of 0-0.1%. 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, improving the elongation of the aluminum alloy. Ag can promote the precipitation of the second phase (such as Al2Cu, Mg2Si, Mg2Sb, Mg3Sn2, and Mg3Bi2, etc.), refine the precipitated phase and improve the precipitated phase density, improve the precipitation strengthening effect of the aluminum alloy, and also refine the second phase, improving the elongation and strength of the aluminum alloy.

[0073] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains Cd in a mass percentage of 0-0.2%. The mass percentage 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 increase the strength of the aluminum alloy; Cd can also refine the grains, the second phase, and the precipitated phase to increase the elongation of the aluminum alloy. Cd can refine α-Al and also form REAl2Cd3, Al3Cd, Al2Cd3, (CuCd)Al2, Mg2(SiCdREFe), Mg3(BiCd)2, and other strengthening phases with Al, RE, Cu, Mg, Si, Fe, and Bi to reduce the solid solubility of each other in the aluminum matrix and increase the volume fraction of the precipitated phase, thereby increasing the strength 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 other phases, reduce the solid solubility of the above elements in the aluminum matrix, and further increase the strength of the aluminum alloy.

[0074] The high-strength Al-Si-Mg series die-casting aluminum alloy also 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 the grains, the second phase, and the precipitated phase to increase the elongation of the aluminum alloy; B can react with Al, Fe, Si, Mg, Cu, and other elements to form AlFeSiB, MgB, CuB, and other second phases, 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 performance. In addition, B can also refine the grains, modify the elemental Si to reduce the adverse effects of coarse elemental Si on the performance of the aluminum alloy, 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 inhibit the segregation of TiAl3. Therefore, Ti and B have a good effect when used together. The boronization of B can also purify the aluminum alloy liquid, further increasing the strength and elongation of the aluminum alloy.

[0075] The high-strength high-elongation Al-Si-Mg series die-casting aluminum alloy further contains 0-1% of AlTiB, 0-35% of SiC, 0-1% of BN, and 0-1% of AlTiC in terms of mass percentage.

[0076] The mass percentage of AlTiB, BN, and AlTiC can be specifically 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%.

[0077] The mass percentage of SiC can be specifically 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%.

[0078] When AlTiB and SiC are used in combination, the mass percentage of SiC can be reduced to 4-10%, which can reduce the cost. In a preferred embodiment, the mass percentage of AlTiB is 0.3-0.8% of AlTiB, and the mass percentage 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 refinement effect of the combination is greatly enhanced. And it has been verified through multiple experiments that when the mass percentage of AlTiB is 0.1-0.5% and the mass percentage of SiC is 4-10%, the strength, elongation, wear resistance, corrosion resistance, and thermal stability of the aluminum alloy can be greatly improved.

[0079] AlTiB, SiC, AlTiC, and BN all have good refining effect, and when used in combination, the content of each can be reduced to achieve good refining effect. When SiC is used in combination with Ti and B, C-TiB2 particle complexes are 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, so that the originally long strip-shaped TiAl3 is broken and shortened, thereby avoiding the enrichment and growth of TiAl3, and greatly enhancing the composite refining effect; 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 uniform nucleation of the grains, so as 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 good fine-grain strengthening effect.

[0080] The application also provides a preparation method of the high-strength high-elongation Al-Si-Mg series die-casting aluminum alloy.

[0081] Si source, Mg source, Zn source, Fe source, Cr source, Ti source, Sr source, Mn source, Li source, Zr source, Cu source, and Al source are provided.

[0082] The Al source is subjected to heating treatment to obtain aluminum liquid.

[0083] The temperature of the aluminum liquid is adjusted to 750-820°C, the Si source is added to the aluminum liquid to obtain a first mixed liquid.

[0084] The temperature of the first mixed liquid is adjusted to 720-740°C, the Si source, Mg source, Zn source, Fe source, Cr source, Ti source, Sr source, Mn source, Li source, Zr source, and Cu source are added to the first mixed liquid to obtain a second mixed liquid.

[0085] The second mixed liquid is subjected to degassing treatment, refining treatment, and die-casting treatment to obtain an aluminum alloy part.

[0086] The aluminum alloy part is subjected to aging treatment to obtain the high-strength high-elongation Al-Si-Mg series die-casting aluminum alloy, wherein the high-strength high-elongation 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%, Zn with a mass percentage content of 0.001-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.001-0.5%, Ti with a mass percentage content of 0.001-0.15%, Sr with a mass percentage content of 0-0.05%, Mn with a mass percentage content of 0-0.3%, Zr with a mass percentage content of 0-0.3%, Li with a mass percentage content of 0-0.5%, and Cu with a mass percentage content of 0-0.1%.

[0087] The Si source, Mg source, Zn source, Fe source, Cr source, Ti source, Sr source, Mn source, Li source, Zr source, and Cu source can be aluminum intermediate alloy.

[0088] In an embodiment, the die casting process can be 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. The temperature of the existing die casting aluminum alloy is about 680°C, 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 great, which can cause the service life of the mold to be short. The melting point of the Al-Si-Mg series die casting aluminum alloy of the present application is relatively low, so the temperature of the die casting process of the present application can be set to be relatively low, the erosion to the mold is small, and the service life of the mold can be improved.

[0089] In another embodiment, the die casting process can be a semi-solid die casting process to obtain 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 mixed liquid to obtain a semi-solid slurry. The air pressure in the mold cavity is reduced to 30-50 kPa by vacuum assisted technology, 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 mixed liquid 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.

[0090] 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; crushing the mixture under an argon protective atmosphere using a low-energy ball mill; and adding the mixture of potassium titanate whiskers and aluminum powder to the second mixed solution while mechanically stirring or electromagnetically stirring the second mixed solution. The addition of aluminum powder can improve the wettability of the mixture with 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 proportion of the mixture is 3-10% of the mass of the second mixed solution, and can be specifically 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. By controlling the temperature and holding time of the second mixed solution, a titanium-rich transition layer is formed on the surface of the potassium titanate whiskers based on the crystallographic orientation relationship between the potassium titanate whiskers and the α-Al, thereby reducing the interface mismatch degree and enhancing the heterogeneous nucleation ability. The potassium titanate whiskers act as a non-uniform nucleation substrate to 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, while reducing the interdendritic spacing and 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 use as a precision component such as an engine cylinder liner or bearing.

[0091] In the high-pressure casting or semi-solid die casting process, the mold used includes a moving mold and a stationary mold, both of which are formed with parting surfaces that together form a cavity for containing 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 surface treatment, which is forming a boron carbide layer on the parting surface. 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 chemicals such as acids, bases, and salts, and the thermal erosion of aluminum alloys, thereby prolonging 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 content of Fe, the sum of the mass percentages of Fe and Cr, or the sum of the mass percentages of Fe, Cr, and Mn, or the sum of the mass percentages of Fe, Cr, Co, and Mn can be set lower.

[0092] 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 a 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 is 900-1200°C, the deposition pressure is 200-500pa, and the carrier gas flow is 100-200sccm. The boron carbide layer can make the hardness of the mold steel reach 3000-4000Hv; the boron carbide layer can reduce the affinity of the mixed melt to the mold surface, improve the demolding performance of the aluminum alloy, and the aluminum alloy can be smoothly demolded even if the content of Fe, Cr, Co, or Mn is low, greatly improving the elongation of the aluminum alloy; the boron carbide layer can resist the corrosion of chemicals such as acid, alkali, and salt, 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 a very low friction coefficient, improves the smoothness of the surface of the aluminum alloy, and can significantly reduce the wear and energy consumption of the aluminum alloy product caused by mechanical friction; the boron carbide layer also has high heat conductivity, and at the moment of forming the aluminum alloy, the boron carbide layer can quickly conduct heat away, improve the heat transfer speed of the mold, and the heat transfer speed is 2-4 times that of the ordinary mold, so that the formed aluminum alloy can be cooled faster, the organization is more refined, and the strength and elongation of the aluminum alloy are improved.

[0093] The degassing treatment is: adjusting the temperature of the second mixed solution to 700-740°C, and using 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 10-30min, and can be specifically 10min, 15min, 20min, 25min, or 30min.

[0094] In another embodiment, the refining treatment is that when the inert gas such as argon is introduced into the second mixed liquid by the degassing machine, the refining agent can be added at the same time, and the vortex formed by the rotating disc of the degassing machine in the second mixed liquid can make the refining agent uniformly dispersed and mixed into the second mixed liquid. 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, and 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.

[0095] 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.

[0096] 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, 0.5h, 1h, 5h, 10h, 15h, 20h, 25h, or 30h. The first stage aging treatment has a lower temperature, in which solute 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 Zn, so that the Zn content 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 to increase 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 by preferred orientation, 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 in the second aging treatment can further promote the segregation of solute atoms such as Si, Mg, Zn, Fe, Cr, Li, Ti, Sr, Mn, and Zr, 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 a precipitate phase with smaller size but larger volume fraction, which fully or nearly fully precipitates the alloying elements dissolved in the alloy, increases the pinning effect on dislocations, and greatly increases the strength and elongation of the aluminum alloy. The combined addition of Si, Mg, Zn, Fe, Cr, Li, Ti, Sr, Mn, and Zr allows the alloy to precipitate a variety of Si, Mg, Zn, Fe, Cr, Li, Ti, Sr, Mn, and Zr-containing dispersed phases during the aging stage. These dispersed phases themselves can refine the grains and increase the strength and elongation of the alloy. They can also act as the core of non-uniform nucleation of β" phase, thereby accelerating the formation of β" phase and further increasing the strength and elongation. 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 increased, but the strength is decreased. 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, thereby further increasing 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, thereby further increasing 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.

[0097] 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, Zn, Fe, Cr, Li, Ti, Sr, Mn, Zr, etc., and at the same time, can make the alloy have a greater undercooling degree, significantly improve 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 reduces the precipitation activation energy of the phases in the alloy, and the low-temperature electric field aging can accelerate the precipitation nucleation rate of the precipitated phases in the aging process and improve 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 precipitated strengthening phases in the alloy increases sharply, indicating that increasing the electric field strength can improve 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.

[0098] The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy contains 6-8% of Si, 1.2-1.8% of Mg, 0.001-2.5% of Zn, 0.01-0.4% of Fe, 0.001-0.5% of Cr, 0.001-0.15% of Ti, 0-0.05% of Sr, 0-0.3% of Mn, 0-0.3% of Zr, 0-0.5% of Li and 0-0.1% of Cu, by mass percentage. The elements interact with each other and affect each other, so that the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy has better yield strength, tensile strength and elongation.

[0099] In the technical scheme of the present application, in order to avoid the adverse effect of Si on 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 Zn is set to 0.01-2.5% (preferably 0.5-2%), and the mass percentage content of Li is set to 0-0.5% (preferably 0.1-0.5%), so as to greatly improve the strength of the aluminum alloy, but the elongation of the aluminum alloy is greatly reduced when the mass percentage content of Mg is 1.2-1.8%, and Zn and Li can reduce the reduction of the elongation of the aluminum alloy caused by high content of Mg; 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 0.05-0.2%) 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; the present application further adds Cr with a mass percentage content of 0.001-0.5% (preferably 0.01-0.2%) and Mn with a mass percentage content of 0-0.3% (preferably 0.01-0.2%), so as to compensate for the influence of low content of Fe on the demolding performance, thereby ensuring the demolding performance of the aluminum alloy, and Cr, Mn and Li can also improve the strength and elongation of the aluminum alloy simultaneously; the present application further adds Zr with a mass percentage content of 0-0.3% (preferably 0.01-0.2%), and the composite addition of Mn and Zr can not only reduce the usage amount of each alloying element, but also promote the mutual precipitation, thereby further improving the strengthening effect; the present application further adds Ti with a mass percentage content of 0.001-0.15% (preferably 0.01-0.1%) and Sr with a mass percentage content of 0-0.05% (preferably 0.01-0.05%), so as to refine the grains, the second phase and the precipitated phase, thereby improving the strength and elongation of the aluminum alloy; Sr and Zr can also promote the precipitation of Mg2Si, MgB, (CuMg)Al2 and the like, thereby further improving the elongation of the aluminum alloy; the above-mentioned elements can also react with each other to form a second phase, thereby avoiding the influence of solid solution in the aluminum matrix on the elongation of the aluminum alloy. In this way, Si, Mg, Zn, Fe, Cr, Ti, Sr, Mn, Li, Zr and Cu in the above-mentioned content range interact with and influence each other as a whole, so as to make the aluminum alloy elements have better strength, elongation and demolding performance.Moreover, under the further action of the Si, Mg, Zn, Fe, Cr, Ti, Sr, Mn, Li, Zr, and Cu in the above content range in 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 further reduced, the adverse effects of the alloying elements and the impurity elements on the elongation of the aluminum alloy are eliminated as much as possible, the second phase (such as Al3Fe, Mg2Si, Al2Cu, MgZn2, AlMnSi phase, etc.) in the aluminum matrix and at or in the grain boundary can also be refined, and the strength and elongation of the aluminum alloy are greatly improved.

[0100] The preparation method of the high-strength high-elongation Al-Si-Mg series die-casting aluminum alloy further comprises the step of adding at least one of a Sb source, a Sn source, a Bi source, a Ni source, an RE source, a Mo source, a Be source, a Ca source, a V source, an In source, a Ge source, a Nb source, a Te source, an Ag source, a Co source, a Cd source, a B source, an AlTiB source, a SiC source, a BN source, and an AlTiC source into the first mixed solution. The above elements can at least be used to improve the strength or elongation of the aluminum alloy, and a high-strength high-elongation Al-Si-Mg series die-casting aluminum alloy with more excellent performance is obtained. The raw materials of the above alloying elements can be aluminum intermediate alloy. For example, the RE source can be an Al-RE alloy.

[0101] Embodiment

[0102] The components and contents of the aluminum alloys of Examples 1 to 10 are shown in Table 1, and the performance test results are shown in Table 2.

[0103] Table 1 Components and contents of the aluminum alloys of Examples 1 to 10

[0104]

[0105]

[0106] For simplicity, all impurity elements and contents are not shown.

[0107] Table 2 Performance test results of the aluminum alloys of Examples 1 to 10

[0108]

[0109] The aluminum alloys of Examples 1 to 10 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. In the manufacturing process of Examples 6 to 10, the mold is surface treated to form a 2mm boron carbide layer on the parting surface of the mold.

[0110] Table 2 shows that the aluminum alloys of Examples 1-10 have better tensile strength, yield strength, and elongation. Specifically, the tensile strength of the aluminum alloys of Examples 1-10 is not less than 400 MPa, the yield strength is not less than 310 MPa, and the elongation is not less than 5%.

[0111] The above merely provides the preferred embodiments of the present application, but does not limit the patent scope of the present application. Any equivalent structure transformation based on the content of the present application, or direct / indirect application in other related technical fields, falls within the patent protection scope of the present application.

Claims

1. A high-strength, high-elongation Al-Si-Mg die-cast aluminum alloy, containing Al, characterized in that, The high-strength, high-elongation Al-Si-Mg die-cast aluminum alloy also contains 6-8% Si, 1.2-1.8% Mg, 0.001-2.5% Zn, 0.01-0.4% Fe, 0.001-0.5% Cr, 0.001-0.15% Ti, 0.001-0.05% Sr, 0.001-0.3% Mn, 0.001-0.3% Zr, 0.001-0.5% Li, and other components by mass percentage. The high-strength, high-elongation Al-Si-Mg die-cast aluminum alloy, containing 0.001-0.1% Cu, underwent aging treatment after die-casting. The aging treatment included 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 was performed at 80-120°C for 3-20 hours; the second-stage aging treatment was performed at -200 to -100°C for 0.5-10 hours; the third-stage aging treatment was performed at 170-250°C for 0.05-5 hours. After the second-stage aging treatment, the temperature was adjusted to 170-250°C within 1-5 minutes. The fourth-stage aging treatment was a natural aging treatment.

2. The high-strength, high-elongation Al-Si-Mg die-cast aluminum alloy according to claim 1, characterized in that, The high-strength, high-elongation Al-Si-Mg die-cast aluminum alloy also contains 6-8% Si, 1.2-1.8% Mg, 0.001-2% Zn, 0.01-0.4% Fe, 0.001-0.5% Cr, 0.001-0.15% Ti, 0.001-0.05% Sr, 0.001-0.3% Mn, 0.001-0.3% Zr, 0.001-0.5% Li, and 0.001-0.1% Cu.

3. The high-strength, high-elongation Al-Si-Mg die-cast aluminum alloy according to claim 1, characterized in that, The mass ratio of Mg to Zn is 0.72-10:

1.

4. The high-strength, high-elongation Al-Si-Mg die-cast aluminum alloy according to claim 3, characterized in that, The mass percentage content of Mg is 1.2-1.8%, the mass percentage content of Zn is 0.5-2%, and the mass percentage content of Li is 0.1-0.5%.

5. The high-strength, high-elongation Al-Si-Mg die-cast aluminum alloy according to claim 1, characterized in that, The high-strength, high-elongation Al-Si-Mg die-cast aluminum alloy further contains at least one of Sb, Sn, Co, Bi, Ca, Be, V, Ge, Mo, Nb, Te, Ag, In, AlTiB, SiC, BN, and AlTiC, wherein the mass percentage content of Sb is 0-0.3%, the mass percentage content of Sn is 0-0.3%, the mass percentage content of Co is 0-0.3%, the mass percentage content of Bi is 0-0.3%, the mass percentage content of Ca is 0-0.2%, and the mass percentage content of Be is 0-0.2%. The mass percentage content of V is 0-0.2%, Ge is 0-0.1%, Mo is 0-0.2%, Nb is 0-0.1%, Te is 0-0.1%, Ag is 0-0.1%, In is 0-0.2%, AlTiB is 0-1%, SiC is 0-35%, BN is 0-1%, and AlTiC is 0-1%.

6. A method for preparing a high-strength, high-elongation Al-Si-Mg die-cast aluminum alloy, comprising the following steps: It provides Si, Mg, Zn, Fe, Cr, Ti, Sr, Mn, Li, Zr, Cu, and Al sources; The Al source is heated to obtain molten aluminum; Adding Si, Mg, Zn, Fe, Cr, Ti, Sr, Mn, Li, Zr, 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, high-elongation Al-Si-Mg die-cast aluminum alloy. The high-strength, high-elongation Al-Si-Mg die-cast aluminum alloy contains, by mass percentage: 6-8% Si, 1.2-1.8% Mg, 0.001-2.5% Zn, 0.01-0.4% Fe, 0.001-0.5% Cr, 0.001-0.15% Ti, 0.001-0.05% Sr, 0.001-0.3% Mn, and [other components not specified in the original text]. The aging treatment comprises 0.001-0.3% Zr, 0.001-0.5% Li (by mass), and 0.001-0.1% Cu (by mass). 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 first-stage aging treatment is performed at a temperature of 80-120°C for 3-20 hours; the second-stage aging treatment is performed at a temperature of -200 to -100°C for 0.5 to 10 hours; the third-stage aging treatment is performed at a temperature of 170-250°C for 0.05-5 hours. After the second-stage aging treatment, the temperature is adjusted to 170-250°C within 1-5 minutes. The fourth-stage aging treatment is a natural aging treatment.

7. The method for preparing high-strength, high-elongation Al-Si-Mg die-cast aluminum alloy according to claim 6, characterized in that, The preparation method of the high-strength, high-elongation Al-Si-Mg die-cast aluminum alloy further includes a step of surface treatment of the mold, wherein the surface treatment is to form a boron carbide layer on the parting surface of the mold.

8. The method for preparing high-strength, high-elongation 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.

9. The method for preparing high-strength, high-elongation Al-Si-Mg die-cast aluminum alloy according to claim 6, characterized in that, The preparation method of the high-strength, high-elongation Al-Si-Mg die-cast aluminum alloy further includes the step of adding at least one of the following sources to the molten aluminum: Sb source, Sn source, Co source, Bi source, Ca source, Be source, V source, Ge source, Mo source, Nb source, Te source, Ag source, In source, AlTiB source, SiC source, BN source, and AlTiC source. The mass percentage content of Sb is 0-0.3%, the mass percentage content of Sn is 0-0.3%, the mass percentage content of Co is 0-0.3%, the mass percentage content of Bi is 0-0.3%, and the mass percentage content of Ca is 0-0.2%. The mass percentage content of Be is 0-0.2%, V is 0-0.2%, Ge is 0-0.1%, Mo is 0-0.2%, Nb is 0-0.1%, Te is 0-0.1%, Ag is 0-0.1%, In is 0-0.2%, AlTiB is 0-1%, SiC is 0-35%, BN is 0-1%, and AlTiC is 0-1%.

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

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